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SYSTEM
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CHEMISTRY. 
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                           A

        S     Y     S     T      E     M

                          O F

CHEMISTRY:

                COMPREHENDING THE

 HISTORY, THEORY,  and PRACTICE
                       OP  T H 1

       SCI    E    N    C    E,
   ACCORDING TO THE LATEST DISCOVERIES AND IMPROVEMENTS.
ILLUSTRATED WITH COPPERPLATES.
      EXTRACTED trom the AMERICAN EDITION of the ENCYCLOPEDIA;
                  NOW PUBLISHING,
By T. DOBSON, at the Stone-Houfe, in Second-Street, Philadelphia.
                        M,DCC,XCI; 
 
HISTORY    of
    i     S^ HEMISTB.Y may be defined,  The ftudy of fuch
 Definition. \^> phenomena or properties of bodies as are difcovered
          by  varioufly mixing them together, and by  expoling
          them to different degrees of heat,  alone, or in mix-
          ture, with a view to  the  enlargement of our know-
          ledge in nature, and to the improvement of the ufeful
          arts : or,  It is the ftudy of the  effects of heat and mix-
          ture upon all bodies, whether natural or artificial, with
          a view to  the improvement of arts and natural know-
    %     ledge.
Antiquity.   The fcience of chemiftry is undoubtedly of very
          high antiquity ; and, like mod other fciences, its origin
          cannot  be traced.  In fcripture, Tubal Cain, the 8th
          from Adam,  is mentioned as  the father or inftruct.or
          of every artificer in  brafs or iron.  This, however,
          does not conftitute him a chemift, any more than a
          founder or blackfmith among  us has  a right to that
          title.  The name of chemift could only belong to him,
         whoever he was, who firft difcovered the method of
          extracting metals from their ores; and  this perfon
         muft neceifarily have lived before Tubal Cain, as eve-
         ry blackfmith or founder muft have metals ready pre-
         pared  to  his  hand.   Neverthelefs,   as Tubal Cain
         lived before the  flood, and the fcience of chemiflry
         muft have exifted before  his  time, fome have con-
         jectured, that the metallurgic  part, on account of its
         extreme ufefulnefs to  mankind, was revealed to Adam
    ,     by God himfelf.
Science      Be this as it will, Siphoas, an Egyptian, is confider-
founded.  ed  by  the chemifls as the founder of their fcience.
         He  was known by the Greeks under the  name of
         Hermes, or Mercurius Trifmegiftus;  and is fuppofed
         to have lived  more than 1900 years before the Chri-
         ftian sera.  A numerous lift of this philofopher's works
         is given by Clemens Alexandi inus ; but none of them
         are  now to be  found, nor do any of them appear to
         have been written profefTedly on chemiflry.
           Two illuftrious Egyptians, of the name of Hermes,
         are  recorded by ancient authors.  The elder fuppofed
         to be the fame with Mizrahn, the grandfon of Noah,
         the  Hermes of the Greeks, and Mercury of the Ro-
         mans.   The younger Hermes  lived a thoufand years
         afterwards ; and is fuppofed to have reftored the fci-
         ences after they had fallen into oblivion,  in confe-
         rence of an inundation of the Nile.   No lefs than
CHEMISTRY.
36,000 books are faid to have been written under the
name of Hermes ; but, according to Jamblichus, a cu-
flom prevailed of inferibing all  books of fcience with
the name of Hermes.   Some authors deny the exift-
ence of Hermes, and maintain that his hiflory is alle-
gorical.                                              4
   As the fcience of chemiflry is fuppofed to have been M°fes top-
well known to the Egyptians, Mofes, who was fkilled j^n^ be
in their wifdom, is thence ranked among the number chgmiftrv:
of chemifls ;  a proof of whofe fkill in this fcience is
thought to  be, his diffolving the golden calf made  by
the Ifraelites, fo as to render it potable.
   Of all the Greeks who travelled into Egypt in or-
der to acquire knowledge, Democritus alone was  ad-
mitted into their myfleries.   The Egyptian priefls are
faid to have taught him many chemical operations;
among which were the arts of foftening ivory, of vi-
trifying flints,  and of imitating precious ftones.   Dr
Black, however, is of opinion, that Democritus knew
nothing more of thefe arts than that of making a coarfc
kind of glafs, as no mention is particularly made of his
imitating any other precious flone  than the emerald,
whofe colour is green ; and  the coarfer the glafs  the
greener it is.
  After the time of Democritus, we may know that
conliderable improvements were made in chemiftry, as
phyficians began to make ufe of metallic preparations,
as cerufe, verdegris, litharge,  &c.   Diofcorides,de~
fcribesthe diflillationof mercury from cinnabar by means    5
of an evibic,  from  which, by adding the Arabic Al, Derivation,.
comes the, term AIe?nbic.   The art of diftillation, how- of,the,T"^
ever,  at that  time was in a very rude ftate ; the ope-  cmbic-
ration being performed chiefly by feparating the air,
and more fubtle part of tar, from the reft of the matter.    6
This was done by putting the matter to be diflilled in- Original
to a veffel, the mouth of which was covered  with a method of
wet cloth ; and by this  the fleams of  afcending va- dl^'llin£'
pour were condenfed, which were afterwards procured
by wringing out the cloth.   No other diftillation,  be-
fides this kind, is mentioned by Galen, Oribafius, JEM~
an, or Paulus iEgineta.
  The precife time is not known when the three mine-
ral acids were firft difcovered ; though, as no mention is
made of them by Geber, Avicenna, or Roger Bacon, it
is probable  that they were not known in the 12th cen-
                                            tury. 
CHEMISTRY.
Hiflory
    7
Piny i ..:■
count of
I he origiu
..f gUl*.
making.
    8
Alchemy
firft men-
tioned by
Finnioui
Maternui.
Origin of
the f.ible
the Argo-
nauts.
Alchemy
f.r^ fuppo
1. .1 to he
lie. JVC.'
i. in the
Ai.Iium.
wry.  Haytnond Lally gives fome hints of his being
.;• .painted with the  marine acid ; whence it  is pro-
bable, that it was difcovered towards the end of the
 iVih, or beginning of the 14th century.
   Several chemical facts are related by i'lir.y, particu-
larly the making of glafs  which ht afcribes to the fol-
''<v. nig accident. " Some merchants in the Levant, who
had  nitre on board their (hip,  having occalion  to land,
lighted a lire on the land in order to prepare their food.
To fupport their veflels they took lome of the lumps
of nitre with which  their iriip was loaded: and the fire
acting on thefc, melted part of them along with the
 land, and thus formed the tranfparent fubftance called
 g'afs, to the great furprife of the  beholders."  But it
 is jo.lv.Hc,  that the art of glafs-making was known
 long before ;  and it is by no means likely that it took
 its rife from fuch an accident.
   The next traces we find of chemiftry are to be ex-
 tracted from the extravagant purfuits of the Alchemifts t
 who imagined  it pollible to convert the bafer metals
 into gold or filver.  The firft mention we find of this
 ftudy is by Julius Kirmicus Maternus, who lived in the
 beginning of the fourth century,  and fpeaks of it as a
 well known  purfuit  in his time.   /Eneas Blafius, who
 lived in the fifth century,  likewife fpeaks of it; and
 Suidas explains the term by telling us, that it is the art
 of making gold and  filver.   He tells us,  that Diocle-
 lian, when perfecuting the Chriftians, forbad all che-
 mical operations, left his fubjects fhould difcover the art
 of making gold, and thus be induced to rebel againft
 him.   He  fuppofes  alfo,  that  the  Argonautic  expe-
 dition was only an attempt  to procure a fkin or parch-
 ment, on which was written the recipe for making
 gold.  It  is a common practice, however,  in  fome
 places where gold is waflied down in Imall particles by
 brooks and rivulets  from  the mountains,  to fufpend in
 the water the fkins of animals having wool or hair upon
 them,  in order to detain  the  heavier panicles which
 contain the gold ; and this probably gave rife to the fable
 of the golden fleece.  Suidas, however,  who lived  as
 late as the tenth century, defcrves  very little credit,
 tipecially as alchemy is not mentioned by any ancient
 author.—The Arabian phyficians  afford the moft clear
 and diftinct  evidence concerning alchemy.   Avicenna,
 who lived in the tenth  century, is faid by a difeiple of
 his to  have  wrote  upon alchemy ; he mentions alfo
 roic-v.ater, and fome other chemical preparations; and
 i'i the  12J1 century we find phyficians advifed to cui-
 us.ue an acquaintance with the chemills ; and another
 of  the Arabian writers fay, that  the method of pre-
 wiring rofe water, &c. was then well known.—From
• tins evidence of the exifter.ee of  alchemy among the
 Arabians,  with the  prefatory article A/,  to denote
 rhe greatnefs of the f'.icuee, it  has  been conjectured,
 tint the doctrine  of the  tranfmutation of metals fin:
 :■' >k its rife  among  the Arabians,  and was introduced
 into Europe  bv means of »the Cn fades,  and by the ra-
 pid conn its'of the Arabians  themfelves  in Europe
 r.s  well as in Alia and Africa.   Eunpe  at that time
 had been in  a liate of ih< gr.ateft barbarity from the
 reunions of the northern nations ;  but  the  Arabians
 louributrd to revive fone of the faiences,  and  ir.tro-
  '^:ed a'-.hem? among the  reft, which co-tinued till
 ii,c  middle of the 17-h  ce:::;iry  ; at which  time the
extravagance of  its profclTors rofe  to the  gmteft
height.                                                ir
  Though the pretenlions of the  alchemifts are now No credit
univerfally refuted, yet from fome of the difcoverks due t< the
which have  been  made in chemiftry, we are even yet docM  • •  >>t
in danger of giving fome credit  to  the  poflibility of ,I'l,niiUta~
the procefs of tranfmutation.   W hen we conlidcr that
the metals are bodies compounded of parts  which we
can take  away and reftore,  and  that they  are clofely
allied to one another in their external appearance, we
may be inclined to think favourably even of the pro-
jects of the  alchemifts.   The very feparation of the
metals from their  ores, the depriving them  of their
ductility and malleability, and the reftoration of thefe
properties to them at pleafure,  will  appear very fur-
priling to thofe who are unacquainted with  chemiftry.
There are alfo proceffes of the more  difficult kind,  by    I2
which quickfilver may be produced  from metals that QuickGIvor
are commonly folid, as from lead.  Some of thefe we produced
find in Boerhaave,  Boyle, &c. authors of the greateft frol»i  lead.
credit, who both fpeak  of the operation and product
as realities of which they were convinced by their own
experience.   Thefe have been urged, not without fome
plaulibility,  in favour of the tranfmutation  of the im-
perfect metals into gold;  and hence the delulions of
alchemy were not confined to the vain, the ignorant,
and the ambitious part of mankind ;  but many ingeni-
ous and learned men, who took pleafure in the ftudy
of nature, have been feduced into this  unhappy pur-
fuit.  This  happened chiefly in Germany,  where the
variety of mines naturally turned  the thoughts of che-
mifls principally towards the metals, though the nu-
merous failures of thofe who had attempted this art
ought to have taught them better.
   About the beginning of the 16th century,  the pre-
tenders to alchemy were very numerous, and a multi-
tude of knaves, who had beggared  themfelves in the at-
tempt, now went about to enfnare others, performing
legerdemain tricks, and  caufing people believe that
they could actually make gold and filver.  A number
of the tricks they  made ufe of are to be met with in Le-
mery.  Many books, with the fame defign of impofing
upon mankind, were written upon the fubject  of al-
chemy.   They aiTumed fictitious names of the greateft
antiquity, and contained rules for preparing the philo-
fopher's flone ; afmall quantity of which thrown into
a bafe metal fhould convert the whole into gold. They
are wrote in a myfterious ftyle,  without any diftinct
meaning ; and  though fometimes proceffes  are clearly
enough defcribed, they are found  to be falfe  and deceit-
ful upon trial, the products not anfwering the preten-
lions of the  authors.  Their excufe  was, that it  was
vain to expect plain accounts of thefe matters, or  that
the books on thefe fubjects fhould  be  written diftinctly
and clearly  ; that the value  of gold was in  proportion
to its fcarcity,  and that it might  be  employed to bad
purpofes : they wrote only for the laborious and judi-
cious chemifls, who would underftand them provided
they made  themfelves acquainted \\ ith the metals by
ftudy and experience.   But in fact,  no diftinct mean-
ing has ever been obtained, and  the books have only
ferved to  delude and betray  a great number of others
into the lofs of their lives.
   But though the alchemifts failed in the execution of
                                              tUcir 
 Hiftoty.                           C    H    K   M
    13     their grand proj eft, We mull: ftill own ourfelves indebt-
 Chemiftry  ecj t0  them for many difcoveries brought to light du-
 denvcd    y-m^ tjie t\me ^y- Vainly fpent their labour in the ex-
  ritaee"   petition of making gold.   Some of thefe are the me-
 from the   thods of preparing fpirit of wine, aquafortis, volatile
 labours of  alkali, vitriolic acid,  and gun-powder.   Medicine too
 the akhe-  was indebted  to them for ieveral  valuable remedies ;
 mifts.     whence alfo it appears that many, who had wafted their
          time in the vain parfuit of  the  philofoper's  ftone,
          thought of trying fome of  their molt elaborate  prepa-
          rations in the cure of difeafes ; and meeting with fome
          fuccefs,  they prefumed  that difeafes were only to be
          cured  by the aulftance of chemiftry ; and that the moft
          elaborate of all its preparations, the philofopher's ftone,
          would cure all difeafes.  Some cares they performed
          did indeed awaken the  atttention  of phyficians ; and
          they introduced the ufe of opium, which had formerly
          been accounted poifonous. They fucceeded alfo in the
          cure of the venereal difeafe, which had lately made its
          appearance,  and baffled the  regular phyficians; but
          the chemifts, by giving mercury, put a flop to its ra-
          vages, and thus introduced this valuable article into the
    I4     materia medica.
 •f Paracel-   The mofHamous of the chemical profeffors was Pa-
 fu«.       racelfus, well known for his arrogance, abfurdity, and
          profligacy.   He was  bred  to  the  ftudy of medicine ;
          but becoming acquainted with  the alchemifts, travelled
          about in the character of a phyfician, and was at great
          pains to collect powerful medicines from all quarters.
          Thefe he ufed with great freedom and boldnefs.  His
          fuccefs in fome cafes operated  fo upon the natural ar-
          rogance and felf-fufiiciency of his difpofition,  that he
          formed a delign  of  overturning the whole fyftem of
          medicine,  and fupplying a new one from chemiftry  :
          and indeed he found but very  weak adverfaries in the
          fubtle theories of Galen with the refinements of the A-
          rabian phyficians, which only prevailed in his time ;
          and he no doubt had  fome fhare in banifhing that ve-
          neration which had been fo long entertained for thefe
    15   "celebrated perfonages.
 Hiftory of  <  From the time of Paracelfus, chemiftry began eve-
 chemiftry  Yy where to afTume a new face.  In Great Britain,
fincethe   Lord  Verulam amufed  himfelf at his  leifure  hours
 pmC °lfus  w*^ f°rming plans for promoting the fciences in ge-
    jg   ' neral, efpecially thofe which  related to the ftudy of
Thefcience nature.  He  foon  found that chemiftry might turn
ftudied by  out one of the  moft ufeful and  comprehenfive branches
Lord Ve-   of natural philofophy, and pointed out the means of its
rulam;     improvement.  A number of experiments were propo-
          fed by him ;  but he obferved,  that the views of che-
          mifts were as yet only adapted to explain their parti-
          cular operations  on metals ;  and  he obferved, that,
          inftead of  the abftrufe and barren philofophy of the
          times, it  was  neceffary to make a very large collec-
          tion of facts,  and  to compare them with each other
          very maturely and cautioully,  in order to difcover the
          common caufes and circumftances of connection up-
          on which they all depend.   He  did not,  however,
          make any considerable difcoveries, and  his works are
    j-     tedious and difagreeable to the reader.
And by Mr   A fuperior genius to Lord Verulam was Mr Boyle,
Boyle.     who was born the very day that the former died.  His
          circumftances were opulent, his manners agreeable; he
          was endowed by nature with a goodnefs  of heart; and
          bis inclination  led him entirely to the ftudy of nature,
I   S   T   R    Y.                                    7
 which he was beft pleafed with cultivating in the way
 of experiment. He confidered the weight, fpring, and
 qualities of the air ;  and wrote on  hydroftatics and
 other fubjects ; and was  poflefled of that happy pene-
 tration  and ingenuity fb well fuitcd to the  making of
 experiments in philofophy, which ferves to deduce the
 moft ufeful truths  from the moft  fimple and femingly
 infignificant facts.   As chemiftry was  his  favourite
 fcience, he fpared no pains to procure from chemifts of
 greatefl note the knowledge of curious experiments,
 and entertained a number of operators conftantly about
 him.  His difcoveries are related in an eafy ftyle : and
 though rather copious, fuited to the tafte of the times
 in which he lived, and free from that abfurd and my-
 fterious air which formerly prevailed in chemical wri-
 tings : nor does he betray a defign of concealing any
 thing except fome  particulars which were communica-
 ted to him under the notion of fecrecy, or the know-
 ledge of which might do more harm than good.  It
 is objected indeed,  that he betrays a good deal of cre-
 dulity with regard  to facts which  are given on  the
 faith of others, and which may feem incredible ; but
 this  proceeded from his  candour, and his being little
 difpofed to fufpect  others.   He fhowed the neceflary
 connection between philofophy and the arts ; and  faid,
 that by attending the fhop of a workman, he learned
 more philofophy than he had done in the fchools for a
 long time  Thus  his writings fhowed  an  univerfal
 tafte for the ftudy  of nature, which had now made
 fome advances in the other parts of the world.           jg
   Agricola is  one of the firft and beft authors on the Chemiflry
 fubject of metallurgy. Being born in a village in Mif- emerges
 nia, a country abounding in mines and  metallurgic fron;its °^
 works, he defcribed them exactly  and  copioufly.  He fcurity*
 was a phyfician, and cotemporary with Paracelfus, but
 of a  character very different.  His writings are clear
 and inltructive, as  thofe of Paracelfus are obfeure and
 ufelefs.   Lazarus Erker, Schinder, Schlutter, Henkel,
 &c. have  alfo written on metallurgy, and  defcribed
 the art of affaying metals.   Anthony Neri,  Dr Mer-
 ret, and the famous Kunckel (who  difcovered the phof-
 phorus of urine), have defcribed very fully the arts of
 making glafs,  enamels, imitations of precious ftones,
 &c.:  but their writings, as well as thofe of fucceeding
 chemifts,  are not free from the illufionsof alchemy ; fo
 true  it is, that an obftinate and inveterate malady ne-
 ver difappears at once, without leaving traces behind.
 In a fliort time, however,  the alchemical phrenzy was
 attacked by many powerful antagonifts,  who contri-
 buted  to refcue the fcience of chemiftry from an evil,
 which at once  difgraced it and retarded its progrefs.
 Among thefe,  the moft diftinguifhed are Kircher a Je-
 fuit, and Conringius a phyfician, who wrote with much
 fuccefs and reputation.                                 x
   About the year 1650 the Royal Society was form- Royal^Sr>
 ed by a number of gentlemen who were unwilling to ciety ho-w
 engage in the civil  wars ; and being ftruck with the founded,
 extenfive views of Lord Verulam and Mr Boyle,  con-
 tributed to the expence of coftly experiments.   This
 example  appeared  fo noble, and  the defign fo good,
 that it has been followed by all  the civilized ftates of
 Europe, and has met with the protection of their re-
 fpective fovereigns;  and from thefe chemiftry has re-
 ceived confiderable improvements.   In France, Geof-
 froy,  Lemery, Reaumur,  &c. came to be diftinguifh-
                                               ed s 
%                                   C   H    E   M
         ed ;  tr.d in Germany Margraaf, Pott, and others, have
         made a confiderable figure  in  thofe focieties.  Kunc-
         kel, Begar, Suhl, and Hoffman,  &c. have done great
         fervice to fociery, by introducing new arts, and the nu-
    io    mcrous improvements they have made.
Of the im-   The chemifts who have  made a figure  in  Germany
\ rove-    and France are more in number than thofe whom Bri-
mrntsmade lajn j,as  produced.   In France,  the fociety was en-
 Yt »<rCnt couragco< by lnc f°vereign ; and in it they have diveft-
ckcmiftry. c^ themfelves of that myfterious air which was affect-
         ed in former ages.  In Germany, the richncfs of the
         r ountry,  and the great variety of mines, by turning the
         attention of chemifts  to the metals, have given  that
         alchymiftical air to their writings which we obferve in
         them.  The number of thofe who have applied them-
   S   T    R   Y.                          Theory-
felves to chemiftry is very fmall in England, owing to
the great improvements made by Sir Ifaac Newton in
the iciences of aftronomy and optics ; which, by turn-
ing the general attention that way, has occafioned what
may be called a neglect of chemiftry.  But  if their
number be inconfiderablc,  they are by no means infe-
rior in merit and fame.  The name of Boyle has alwayt
been held in the higheft efteem, as well as that of Hales,
for the analyfis he  has made of the air.   Sir Ifaac
Newton alone has done more to the eftablifhing a ra-
tional chemical theory than ever was done before.  Of
late, the tafte for the ftudy has became more general,
and many ufeful books have appeared ; fo that it is to
be hoped they will foon excel in this branch of fcience^
as they have done in all the reft.
THEOKi 
THEORY    of
                                              PAR


    zi     A  Ccording to the definition we have given of this
 Perfe<*    x\ fcience,  the theory  of it ought to  confift in a
 Theory,   thorough knowledge of all the phenomena which refult
 w ut#     from every poflible combination of its objects with one
          another, or from expofing them in all poffible ways to
          thofe fubftances which chemifts have  found to be the
          moft active in producing a change.  So various, how-
          ever, and fo widely extended  are the objects of che-
          miftry (comprehending all terreftrial bodies whatever),
          that a knowledge of this kind is utterly unattainable by
          man.  The utmoft that can be done in this cafe is,  to
          give fome account of the phenomena which accompany
          the mixtures of particular fubftances,  or the  appearan-
          ces they put on when expofed  to heat; and thefe have
          been already fo well afcertained, that they may now be
          laid down as  rules, whereby we may, with a good
          deal of certainty, judge of the event  of  our  experi-
    a2,    ments,  even before they are made.
 Objects of    Here  we muft obferve, that though the objects of
 Chemiftry, chemiftry are  as various as there are different fubftan-
 what.     ces in the whole fyftem of nature, yet they  cannot all
          be examined  with equal  eafe.   Some of thefe fub-
          ftances act upon others with great violence ;  and the
          greater their  activity, the more  difficultly are they
          themfelves fubjected to a chemical examination. Thus,
          fire,  which  is the moft active body in nature, is fo
          little the fubjedt  of examination,  that  it hath hi-
          therto baffled  the ingenuity  of the greateft philofo-
          phers to underftand its compofition.   This fubftance,
          therefore, though it be the principal, if not the only
          agent in chemiftry, is not properly an objefi  of it, be-
          caufe it cannot be made a fubject of any chemical ope-
   .aj     ration.
Suppofition   It hath been cuftomary to confider all bodies as com-
of element* pofed of certain permanent and  unchangeable parts
the origin  ca]iej elements; and that the end of chemiftry was to
of alchemy. rep0jve bodies  into thefe elements, and to recompofe
          them again by a proper mixture  of the  elements
          when fo feparated.  Upon this fuppofition the  alche-
          mifts went; who, fuppofing that all bodies were com-
          pofed of fait, fulphur,  and mercury, endeavoured to
          rind  out the proportions in which thefe exifted in gold,
          and then to form that metal by combining them in a
          iimilar manner.  Had they taken care to afcertain the
          real  exiftence  of their elements, and, by mixing them
          together, compofed any one metal whatever,  though
CHEMISTRY.
  T      I.


but a grain of lead, the leaft valuable of them all ;
their pretenfions would  have been very rational and
well founded; but as they never afcertained the exift-
ence of fuch elementary bodies, it is no wonder that
their labours were never attended with fuccefs.          24
   Another fet of elements  which were as generally Mr lSoyle'a
received,  and indeed continue to be fo in  fome mea- opinion.
fure to this day, are fire,  air, earth,  and water.—
This doctrine  of elements was ftrenuoufly oppofed by
Mr Boyle ; who endeavoured to prove, that  fire was
not an element per fet  but generated merely from the
motion of the particles of terreftrial bodies among one
another ; that air was generally produced from the fub-
ftance of folid bodies; and that water, by a great num-
ber of diftillations, was converted into earth.   His ar-
guments, however, concerning fire were not at all con-
clufive ; nor does the expulfion of air from fixed bo-
dies prove that any of their folid  parts were  emjiloy-
ed in the compofition of that air; as later  difcoveries
have fhown that air may be abforbed from the  external
atmofphere, and fixed in a great number of folid fub-
ftances. His afTertion concerning water deferves muclt
confideration, and  the  experiment is well worth re-
peating ; but it does not appear that he, or any other
perfon,  ought to  have relied upon the experiment
which was intended to prove this tranfmutation.  The
fact  was this.   Having defigned to try the poflibility
of reducing water  to earth by repeated diftillations,
he diftilled an ounce of water three times over himfelf,
and found  a fmall quantity of earth always remaining.
He then gave it to another, who diftilled it  197 times.
The amount of earth from the whole diftillations was
fix drams, or |ths of the quantity of water employed ;
and this earth was fixed, white, and infoluble in wa-
ter.—Here it  is  evident, that great fufpicions muil
lie againft the fidelity of the unknown operator, who
no doubt would be wearied  out with fuch  a  number
of diftillations^   The affair  might  appear trivial  to
him ;  and as he would perhaps know to which fide Mr.
Boyle's opinion inclined, he might favour it, by mix-
ing fome white earth with the water.   Had the ex-
periment been tried by Mr Boyle's own  hand, his
known character would have put the matter beyond a
doubt.
  The decompofition of water, however,  in another
way,  by the combination of one part of it with the
                        B                  phlo- 
ic             ,                     C    H   E'  M
         pMogiftit, and another with the earthy part of a metal,
         is now well af.ertaincd,  and the experiments which
         led to the difcovery arc treated of under the  articles
   ts    Aerology and Water.
TviftcDce     Even the cxiftencc of  earth as an  element appears
rf elements as dubious as that of the others ;  for  it is certain that
ihfpntcd.  there is no fuecies of earth wiutcver, from which we
         can  produce two diilimilar bodies, by adding their o-
         ther component parts.—Thus,  the earth of alum has
         all the characters of fimplicity which we can defirein
         any terreftrial fubftance.  It is white, infipid, inodo-
         rous, and perfectly fixed in the fire ; nevertheleis, it
         feems to be only an element of  that particular body
         called alum ; for though alum is compofed of a pure
         earth and vitriolic acid joined together, and Epfom fait
         and  fclenite are both compofed of a pure earth  com-
         bined with the fame acid ;  yet by adding oil of vitriol
         to the earth of alum,  in any poffible way, we lhall  ne-
         ver be able to form either Epfom fait or felenite.  In
         like manner, though all  the imperfect metals are com-
         pofed  of inflammable matter joined with an earthy ba-
         fis ; yet by adding to earth of alum any proportion
         we pleafe of inflammable matter, we (hall  never pro-
         duce a metal; and what is  ftill  more mortifying,  we
         can  never make the earthy  balls  of one  metallic fub-
         ftance produce any other metal than that which it ori-
    26   ginally compofed.
Elenmt*     A little confidcration upon  the fubject of  elements
necefiarily will convince us, not only that no fuch bodies have ever
invifible.  vet Deeu difcovered, but  that they never will; and for
         this plain reafon, that they muft be in their own nature
         invifible.—The component  parts of any fubftance may
         with propriety enough be called  the elements of that
         fubftance, as.long as we propofe carrying the decom-
         pofition no farther ; but thefe elements have  not  the
         leaft property  refembling any fubftance which  they
          rompofe.  Thus, it is found that  the  compound fait
         called/*/ amvioniac, is formed by the union of an acid
          and an alkali:  we may therefore properly enough call
          thefe two the elements offal ammoniac ; but,  taken fe-
          parately, they have not  the lead refcmblance to  the
          compound,  which is  formed out of  them.   Both the
          acid and alkali are by themfelves fo  volatile  as  to be
          capable of diflipation  into an invifible vapour by  the
          heat of one's hand ; whereas, when joined together,
          they are fo fixed as almoft to endure  a red  heat  with-
          out going off.  If, again, we were to feek  for the ele-
          ments of the acid and alkali, we muft not expect to
          ii nd them have any properties refembling either an acid
          or an alkali, but others quite different.  Any com-
          mon clement of all bodies muft therefore be a fubftance
          which has no property fimilar to any other in the whole
          fyftem of nature, and confequently muft be impercep-
    a7    tible.
 Sappofiticn   To the  abovementioned  four elements, viz. fire,
 concerning air, earth, and water, a kind of fifth element has ge-
 j.idoglfton. nerally been added, but not  ufually  diftinguifhed by
          that name, though it has apparently an equal, if not
          a greater, right to the title of an element than any of
          the others.  This fubftance is called the phlogifton, or
          inflammable principle ;  on  which the ignition  of all
          bodies depend . The exiftence of this element was firft
          anerted  bv Stahl, and from him the opinion has been
          derived  to other chemifts:  but of late a new  doctrine
          was broached by M. Lavoilier,  who  denies the exilt-
   S   T   R   Y.                            Theory.
ence of phlogifton altogether.  Though none of thefe Of the
iubftanccs therefore arc  properly  the  objects of chc- Element
miltry, yet as they  have fo much ingrollcd the attcn- ? tlT*' ^
tion of modern  chemifts, wc fhall here give an ac-
count of the moft remarkable theories that have ap-
peared concerning them.

          Sect. I. Of the Element of Fire.

  The opinions concerning the element of fire may
be divided into two general dalles; the one confidering    2g
it as an effect, the other as a  caufe.   The former  is Two gent-
maintained by Lord Bacon,  Mr  Boyle,  and Sir Ifaac ral theori«j
Newton ;  whofe refpectable names for a long time gave °f beat.
fuch a fanction to this theory, that  it  was generally
looked upon  as  an eftabliihed truth.   Some  learned
men, however, among whom was the great Dr Boer-
haave, always diflented,  and infiftcd that fire W7as a fluid
univerfally diffufed, and equally pi cfent in the frozen
regions of Nova Zcmbla as in a glafs-houfe furnace,
only that in the  latter its motion made.it confpicuous ;
and by fetting it in motion in the coldeft parts of the
world, its previous exiftence there would be  equally
demonftrable as in the furnace abovementioned.
  Lord Bacon defines heat, which he ufes as a fynony- j_,ord fa-
mous term with fire, to be an expanfive undulatory mo- con's de-
tion in the particles of a body, whereby they tend with finition of
fome  rapidity towards  the circumference, and alfo a beat.
little  upwards.   Hence, if in any natural body you
can excite a motion whereby it fhall expand or dilate
itfelf, and can reprefs and direct this motion upon it-
felf in fuch a manner that the motion fhall not proceed
uniformly, but obtain in fome parts and be checked in
others, you will generate heat or fire.
  The fame opinion is  fupported by Mr Boyle in the j^T Joyic'8
following manner : " The production of heat difcovcrs opinion
nothing, either in the agent or patient, but motion, and
its natural effects.   When a fmith brifkly hammers a
fmall piece of iron, the metal thereby becomes exceed-
ingly hot: yet there is  nothing to make it fo, except
the motion of the hammer imprefling a vehement and
var-iouily  determined  agitation on the fmall parts of
the iron ;  which, being  a cold body before, grows hot
by that fuperinduced motion of its fmall parts : firft, in
a more loofe acceptation of  the word, with regard  to
fome  other bodies, in comparifon of which it was cold
before ; then fenfibly hot, becaufe the motion in the
parts of the iron is greater than  that in the parts of
our fingers; at the fame time that the hammer and an-
vil, by which the percuffion is communicated, may, on
account of their magnitude, remain  cold.  It is not
neceifary, therefore, that a  body fhould itfelf be hot
in order to communicate heat to another."
  The arguments made ufe  of by Sir Ifaac  Newton ScntuLnts
are not intended polltively to eftablilh any kind of the- of Sir Ifaac
ory relating to fire, but  are to be found in a conjedture, Newton.
publifhed  at the end of his Trcatife  on Optics, con-
cerning the nature of the fun and flars.   " Large bo-
dies (he obferves) preferve ihtir heat thelongeft, their
parts heating one another;  and why  may not great,
denfe, and fixed bodies, when heated beyond a certain
degree, emit light fo copioufly, as, by the emiffion and
reaction of it, and the reflections and refractions with-
in the pores, to grow continually hotitr, till they arrive
at fuch a period of heat as  ii, that of  the fun ? Their
                                             parts
/ 
Theory.
CHEMISTRY.
11
Of the
Element
of Fire.
   32
Fire now
generally
           parts may be further preferved from fuming away,  not
           only bytheir fixity, but by the vaft weight and denfity
           of  the atmofphere.incumbent  on them, ftrongly com-
           preffing them, and condenfing the vapours exhaled from
           them.  Thus we fee, that warm water, in an exhaufted
           receiver,  fhall boil as vehemently as the hotteft water
           expofed to the air: the weight of the incumbent atmo-
           fphere in this latter  cafe  keeping down the vapours,
           and hindering  the ebullition till it has received its ut-
           moft degree of heat.   Thus alfo  a  mixture  of tin and
           lead, put  on a red hot iron in  pacuo, emits a fume and
           fiame : but the fame  mixture in the open air, by reafon
           of the incumbent atmofphere, does not emit the leaft fen-
           fible flame." In confequence of thefe experiments, Sir
           Ifaac conjectures, that there is no effential  diftinction
           betwixt fire and grofs  bodies ; but that they may be
           converted into one another.  " Fire  (he fays) is a body
           heated fo hot as  to emit  light  copiouflyj  for what
           (fays he)  is a red hot iron but fire  ?"
            The hypothefes of  thefe great men produced long
           and violent difputes,  which were never decifively fet-
 allowed to  tied : The difcoveries in electricity,  however furnifhed
 be  an ele-  fuch additional ftrength  to the followers of Dr Boer-
 went/trfe.  ]laaYC) that fire is now believed to be  an elemenband
         "  fluid diftinct from all others, by at leaft as many as e-
           fpoufe the contrary fyflem ; but the queflion is not de-
           cided,  Whether the fire itfelf is to be confidered as the
        ,  agent ?  or,  Whether  its action is to be derived from
          the  principles  of attraction and  repulfion, the na-
    ,.     tural agents fuppofed  to influence  other  material
 Two other fubftances ?  This has produced  two  other  fyftems
 theories in- of a kind of mixed  nature, in  which  heat or fire
 ftiuted..   is  confidered as a fubftance diftinct from all others,
          but  which  acts  in  other  bodies  according to  its
          quantity.  Thefe fyftems have been  promulgated by
          Dr  Black of Edinburgh and Dr Irvine of Glafgow.
          They differ from the opinions of Mr Boyle, Lord Ba-
          con-, and Sir  Ifaac Newton, in fuppofing heat to be,a
          fluid diftinct from all  other material fubftances ; and
          they alfo differ from the hypothefis of Dr Boerhaave,
          Lemery, and others, in fuppofing different terreftrial
          fubftances to be hot according  to the quantity of fluid
          contained, and  not according to the force with which
          it moves in them.
            Dr Black is  of opinion that  heat, which  he  feems
account of to make iynonymous with fire, exifts in two  different
Dr  Black's ftates ;  in' one-of"'which it affects our fenfes and the
and Dr ir- thermometer, in  the "other it  does not.  The former
vine's the- therefore he calls fenjible heat, the later latent heat. On
ones.     thek principlesJie gives the only fatisfactory explana-
         tion of  the phenomena of evaporation and fluidity that
         has  yet appeared, as  fhall afterwards  be more fully
         explained.  At prefent we fhall only obferve, that, ac-
         cording to the  theory of Dr Black,  heat or fire it-
         felf feems to be the agent;  but, according to that  of
         Dr Irvine, as far as we can gather it from the treatifes
         of Dr Crawford and others, the principles of attrac-
         tion and repulfion are the agents by  which heat,  as
         well as other bodies, is influenced. Thus, on the princi-
         ples of Dr  Black, we fay, that water is  converted into
         vapour .by  a quantity  of heat entering  into it in a la-
         tent  ftate, and thereby rendering it fpecifically lighter
         than the atmofphere ;  according to the principles  of
         Dr Irvine, we fay, that water is converted into vapour
         by having its capacity  for attracting  heat from the
   34
In what
they dif-
fer fro m
the for-
   35
General
 atmofphere increafed. So that, according to the former, Of the
 the abforption of heat is the caufe ;  according to  the Element
 latter, th.tcffetl, of its converfion into vapour.       of Fire.
    Dr Crawford,  in his  Treatife  on Heat, jpublifh-   ~~^
 ed  in 1788,  informs  us,  that  heat, in  the philo-Dr Irvine'?
 fophical  fenfe  of the word,  has been  ufed to  ex- thtory ex-
 prefs what is  frequently called the element of fire,  in plained b)'
 the abftrad,  without regard  to  the peculiar  effectsDr Craw-
 which  it may produce in relation  to  other bodies.
 This, with Dr Irvine, he  calls abfolute heat ;  and  the Abfolutc
 external caufe, as having a relation to the effects it heat de-
 producos, he calls relative heat. "From this view of fined.
 the matter (fays he), it appears, that abfolute heat ex-
 preffes, in the abftract,  that power or element which,
 when it is prefent to a certain degree, excites' in all ani-    a.
 mals the  fenfationof heat; and relative heat exprefles Relative
 the fame power,  confidered  as having a relation to heat,.
 the effects by which it is known and meafured.
   "  The effects by which heat is  known and meafu- How di-
 red are three; and therefore relative heat may admit of vided.
 three fubdivifions.  1. This principle is known by the
 peculiar fenfations  which  it excites in animals. Con-
 fidered as exciting  thofe fenfations, it is called fenfible,
 heat.  2. It is known by the effect which it produces
 upon an inftrument that has been employed to meafure
 it, termed a thermometer. This is called the temperature
 of heat in bodies. 3.. It has been found by experiment,
 that in bodies of different  kinds the  quantities of ab-
 folute heat may be  unequal, though the temperatures
 and weights be the fame. When the principle of heat
 is confidered  relatively  to the  whole quantity of it
 contained in bodies of different kinds, but which have
 equal  weights and temperatures,  I fhall term it com- Compara-
 parative heat.   If, for example, the temperatures and tive heat
 weights being the fame, the whole quantity of heat in defined.
 water be four  times as great as  that of antimony, the
 comparative heats of thefe fubftances  are faid to be  as
 four to one."
   In order  to  haye a proper  conception of what is Experi-
 meant by  a difference in abfolute heat, when the tern- ments by
 peratures are  the fame, it  will be neceffary to relate wnich  Dr
 fome experiments, by which Dr Black was firft led  to Black wa*
 the difcovery of latent heat.  He obferves, that when Clover &
 two equal mafles of the fame matter,  heated to diffe- ef latent*
 rent degrees, are mixed together, the  heat of the mix- heat.
 ture ought to be an arithmetical mean  betwixt the two
 extremes. This, however,  only takes place on mixing
 hot and cold water together; but  if  inftead of cold
 water we take ice,  the cafe is  remarkably  different.   4&
 Here the temperature of  the mixture is much below A 1uantIty
 the arthmetical  mean, and a quantity of heat is ap- ?f ^cat 'j*
 parently loft.   Now we know that the temperature  of J"*  oficcf
 ice newly frozen is generally  32  degrees of Fahren-
 heit ; fuppofing therefore  the temperature of the water
 which diflblres it to be 120, the arithmetical mean  is
 7i; but if the mixture indicates a temperature only of
 6o°, then we  muft  fuppofe that the ice  contained n"
 of heat lefs than was indicated by the thermometer ;
 and confequently, that water at 3a0 contains  n° more
of abfolute heat than ice at 320.                        43
   The fame thing is madeftill more evident from the Great
condenfatiou of vapour. The fluid of  water  is not ca- quantitT
pable  of fuftaining a great  degree  of  heat ;  and 2120 ofh"fc  .
of Fahrenheit  is the utmoft it can be made to bear, by°thec6n-
vvithout an extraordinary degree of prefTure, as in Pa- dc»fation  '
                          B 2                 pin's of vapour. 
CHEMISTRY.
   44
Dr Black'*
method of
         pin'sdigfHe:, or the admixture of faline fubftances :
         the temperature of the IK am emitted by it therefore
         never can exceed 212°, except in the cafes juft men-
         tioned ;  and it is often capable of bearing a great de-
         gree of cold without being condenfed.  When the con-
         denfation takes place  at  laft, however, a very confi-
         ilcrablc dcgr<^ of heat is always produced; and Dr
         Black has fhown, that, in the con den fat ion of fteam
         by  the refrigeratory of a common ftill, as  much heat
         is communicated to the water in the refrigeratory as
         would be fulficient to  make  the water which  comes
         over as hot as red hot-iron, were it all to exift in a fen-
         fible ftate.   His method of making the calculation is
         very eafy.   For, fuppofing the refrigeratory  to con-
calculating tain ico pounds of water, and that one pound has been
"•       diftilled  ; if the water in the refrigeratory has received
         10 degrees of heat, we know that the diftilled pound
         has parted with iooo.  If in paffing through the worm
         of the refrigeratory, it has been reduced to the tempera-
         ture of 500 of Fahrenheit, having been at 212°  when it
         entered it, then it has loft only 1620 of fenfible heat;
         all the reft  communicated to the water of the refrige-
         ratory amounting to more than 8oo°, having been con-
    4_y    tained in a  latent ftate, and  fuch as could not then  af-
Mr Watt's feci the thermometer.   This experiment was tried by
1 xpcriment Mr Watt in a manner ftill more ftriking, by a diftilla-
on the di- tj0n Qf  water /;; vacuo.  Thus the fteam, freed from
fhllatioii of tjK. prcn;Ui.e 0f the atmofphere, could not conceive fuch
vm" '"  a degree of fenfible heat as in the common method of di-
         ftilling.  It  came  over therefore with a very gentle
         warmth, fcarcc more  than what the hand could bear  ;
         neverthelefs it had abforbed  as much heat  as  though
         the diftillation had been performed  in the common
         way ;  for the refrigeratory  had 1000 degrees of heat
    46   communicated to it.
Difference    The difference of abfolute heat is likewife  percep-
of abfolute tible betwixt any two bodies  of different denfity, water
heat in dif- anci mercury for inftance :  and in comparing thefe, it
         will always  be found that the thinneft fluids  contain
         the greateft quantity of abfolute  heat ; as water more
         than mercury,  fpirit of wine, more than water, ether
         more than fpirit  of wine, and  air more than any of
         them. Dr Black having bronght equal bulksof mercury
         and water,  the former to a temperature of  50 degrees
         higher  than the latter, found that, on mixture, there
         was a gain of only 20 degrees above the original ; but on
         reverling the experiment,  and heating the water 50
         degrees above the mercury, there was a gain of 30 de-
         grees on the whole. " Hence (faysDr Cleghorn in his
Theory.
farent
fluids.
    47
Thinneft
fluid* con
tain the
created
quantity
•tf heat.
   48
Great dif-
 ference be- thefis de Igne) it appears, that the quantity of heat in
 twixt the  water is to that in mercury, when both are of equal
 filiations rempenmirCs, as 3 to 2." Dr Crawford, however, tells
 horn and   us» that "  the  fame quantity of heat which raifes a
 Crawford,  pound of water one degree, will raife a pound of mer-
          cury 28 degrees ; whence it follows, that the compa-
          rative heat of water is to that of mercury  as 28 to 1 :
          and confequcntly, the alterations which a^e produced
          in the temperatures of bodies by given  quantities  of
          abfolnte heat,  may properly be applied as a meafureof
          their comparative heats ; the alterations of tempera-
          ture  and  the comparative  heats being reciprocally
          proportional to one another.
t rawford »   " Senfible heat (continuesDr Crawford) depends part-
account of ly on the ftate of the temperature, and partly on that of
frn&bk
heat.
the organ of feeling ; and therefore if a variation be pro- Of the
duccd in the latter,  the fenfible bent will be dilltrent, lament
though the temperature continue the fame.  Thus water °J Yir''  _.
at  the temperature of 620 of Fabrenheit appears cold 10
a warm hand immerfed in it; but on the contrary, that
fluid will appear warm if a hand be applied to it which
has a lower degree  of heat than62°.  For this rcafon,
the thermometer is a much more accurate mcafurc of
heat than the fenfes of  animals.   As long, however,
as  the organs remain unchanged, the fenfible heat is in
proportion to  the  temperature ; and therefore thofe
terms have generally been confidered as Iynonymous.    so
On this fubjectDr Reid obferves,  that until the ratio Dr Reid'i
between one temperature and another be afcertained by oburwtion
experiment and induction, we ought to confider tern- concerning
perature  as a meafure which admits of degrees, but not ttn,Pcra"
of ratios  ; and  consequently ought not to  conclude,
that the  temperature of one body is double or triple to
that of another, unlefs the ratio of different tempera-
tures were determined.   Nor  ought we to  ufc the ex-
preflions  of a double or triple temperature, thofe  being
expreffions which  convey no diftinct meaning until
the ratio of different temperatures  be determined."       51
   In making experiments on the comparative quanti- Difference
ties  of heat in different bodies, our author choofes ra- betwixt
ther to ufe equal weights than   equal bulks  of the fub- *!" cal^a"
fiances to be  compared.  Thus he found the compa- t">mo  n
      ,     r     *   ,     ■,     r             r?   Lrawrora
rative heat of water to be to that of mercury as 28 to aU(j iu.ack.
1 by weight,  and 2 to 1  by bulk ; which  differs very
confidcrably from the  conclufion of  Dr  Black, who
makes it only  as 3 to 2, as has  been already men-
tioned.                                                 .%
   From the differences obferved in  the  quantities of Capacities
abfolute heat contained in  different bodies, our author for contain-
concludes, that " there muft be certain efTential difte- ing beat
rences in  the  nature of bodies ;*  in confequence of exPlained<
which, fome have the power of collecting and retaining
that element in greater quantity than  others."  Thefe
different powers he calls the capacities for  containing
heat.  Thus, if we find by experiment that a pound
of water contains four times as much abfolute heat as
diaphoretic antimony, when at the fame  temperature,
the capacity of  water for containing heat is faid to be
to that of animony as 4 to  1.                             .«
   " The temperature, the capacity for containing heat, How the
and  the abfolnte heat contained, may  be  diftinguifhed capacity,
from each other in the following manner.            tempera-
   " The capacity for  containing heat, and theabfo- t"e' and
lute heat contained,  are diftinguifhed as a  force diftinft Jeat aVe
from the fubject upon which it operates.  When we to be di-
fpeak ©f the capacity, we mean a  power inherent in ftinguifhed.
the heated body; when we fpeak of the abfolute heat,
we mean an unknown principle which is  retained in
the body by the operation of  this power ;  and  when
we fpeak of the temperature, we confider the unknown
principle as producing certain  effects  upon the ther-
mometer.
   " The capacity for containing  heat may  continue
unchanged, while the abfolute  heat is  varied without
end.  If a poand of ice,  for example, be  fuppofed to
retain its  folid form, the quantity of its abfolute heat
will be altered by every increafe or diminution of  its
fenfible heat: but  as long as its  form continues the
fame, its capacity for receiving beat is not  affected by
                                               an 
Theory.
CHEMISTRY,
»3
Of the
Element
of Fire
54
           an alteration of temperature, and would remain un-
           changed though the body were wholly deprived of its
           heat."
             In the courfe of his work,  Dr Crawford obferves,
  Crawford's that " he has not entered into the inquiry  which has
  opinion    been fo much agitated among the Englifh, the French,
  heatin"^ and the German philofophers,  Whether heat be afub-
  abftradt* ' flance or a Quality ? In fome places indeed he has ufed
           exprelfions which feem to favour the former opinion ;
           but his fole motive for adopting thefe  was, becaufe the
           language feemed to be more fimple and natural, and
           more confonant to the facts  which had been eftablifhed
           by experiment.  At the fame time, he is  perfuaded
           that  it would be a very difficult  matter to  reconcile
           many of the phenomena with  the fuppofition that heat
           is a  quality.   It is  not eafy  to conceive,  upon this hy-
           pothefis,  how heat can be abforbed in the proceffes of
           fufion, evaporation, combuflion ;  how the quantity of
           heat  in the  air can  be diminifhed,  and that in the
           blood increafed, by refpiration, though no fenfible heat
           or cold be produced.
             " Whereas,  if we adopt the opinion that heat is a di-
           ftinct fubftance, or anelementfui generis, the phenome-
          na will be found to admit of a fimple and obvious in-
           terpretation.
             " Fire will be confidered as a principle;  which is
           diftributed in various proportions throughout the dif-
          ferent  kingdoms of nature.   The mode of its union
          with bodies  will  refemble  that particular  fpecies of
          union,  wherein the elements are combined by the joint
          forces of preffure and attraction.   Of this kind is the
          combination of f tied air and water;  for fixed  air is
          retained in water partly by its  attraction  for that fluid,
 by the pref-and partly by the preffure of the external air ;  and if
 fure °^,tlle either of thefe forces be diminiflied,  a portion of the
          fixed air efcapes.  In like manner, it  may be con-
          ceived that elementary fire is retained in bodies, partly
          by its attraction to  thefe bodies, and partly by the
          action of the furrounding lieat; and  in that  cafe a
          portion of it will be difengaged, either by diminifhing
          the attractive force, or by leffening the temperature of
          the circumambient medium.   If, however, fire be a
          fubftance  which is fubject to  the  laws of attraction,
          the mode of its union with  bodies feems to be diffe-
          rent  from  that  which takes place in chemical combi-
          nation : for, in chemical combination, the elements ac-
          quire new properties, and either wholly  or in part lofe
          thofe  by which they  v.rere formerly characterized.
          But we have  no fuflicient evidence for believing that
          fire,  in confequence  of its  union  with  bodies,  does,
          in any inftance, lofe its diftinguifhing  properties."
            Dr Berkenhout,  in  his firft Lines  of the  Theory
hout'Vopi-and Practice of Philofophical Chemiftry, informs us,
nion con-  that " heat, or the  matter of heat, is by Scheele and
cerning the Bergman fubftituted for fire, which they believe to be
nature of  t]ie ac^ion 0f heat when increafed to a certain degree.
heat.      ,p|ie £rfl. Q£ ^jfe celebrated chemifts believed this mat-
          ter of heat to  be a compound of phlogifton  and pure
          air.  He was certainly miftaken.   It feems more phi-
          lofophical to confider heat as an effect, of which fire is
          the fole caufe.
Hisdivl-     "  Heat * confider not as a diftinct fubftance, but as
fionoffire  an effect of fire, fixed or volatile ;  in both which ftates
into fixed   fire feems to exift in all bodies, folid and fluid.  Fixed
and vola-   fire I  believe to  be  a  conftituent part of all bodies,
tile.
    55
Fire con-
tained in
bodiespart-
ly by its
attraction
to them,
and partly
external
fluid.
   5°
Dr Kerken
 and their fpecific heat to depend on the  quantity  of Of the
 fixed fire in each.   This fixed, this latent fire, cannot Element
 be feparated  from the other  conftituent parts  of bo- °f Fire'  ^
 dies but by their decompolition :  it then becomes vo-
 latile and incoercible.   If this hypothefis  be true, fire
 exifts,  in all natural bodies  that contain phlogifton,  in
 three different ftates : i. In that volatile ftate in which
 it  perpetually fluctuates between one  body and an-
 other.   2.  Combined  with an acid, probably in the
 form of fixed inflammable air or phlogifton.  3. Un-
 combined and fixed, as a conftituent principle, deter-
 mining the fpecific heat of bodies.                       58
   << Pure (or volatile) fire is diftinguifhed by the fol- Pnreorve-
 lowing properties.   1. It is effentially fluid, invifible, lat*le fire
 and without weight.  2. It is  the immediate caufe  0fdefincd*
 all fluidity.  3.  It  penetrates  and pervades all bodies
 on the furface of the earth, and as far beneath the fur-
 face as hath hitherto been explored.  Water hath ne-
 ver been found  in  a congealed ftate in the deepeft
 mines.   4. It  has a eonftant tendency to diffufe  itfelf
 equally through all bodies, howfoever different in  point
 of denfity.  A marble flab,  a plate of iron,  a decanter
 of water, and a lady's muff,  at the fame diftance  from
 the fire, and other external circumftances, being equal,
 poffefs an equal degree of heat,  which is precifely that
 of the atmofphere in which they  ftand.   5. It is per-
 petually in motion from one body to  another, and
 from different pans of the fame body, becaufe external
 circumftances are continually varying.   6.  In fluctu-
 ating from one body to another, it produces a eonftant
 vibration of their conftituent parts ;  for all  bodies ex-
 pand  and  contract in  proportion  to  the  quantity  of
 fire they  contain.   7. Accumulated  beyond a certain
 quantity, it effects the difMntion of bodies,  by forcing
 their conftituent parts  beyond the fphere of mutual
 attraction, called the attraction of'cohefton, which is the
 caufe of folidity.  Hence the foyeriegn agency of fire
 in chemical operations."
   Dr Crawford, befides the opinions already quoted, Dr Craw-
 tells us, that  fire,  in the  vulgar acceptation of the ford's de-
 word,  expreffes a certain degree of heat accompanied fiction of
 with light; and is  particularly applied  to that heatfire'
 and light  which  are produced by  the inflammation of
 combaftible  bodies.  But as heat, when  accumulated
 in a fufficient quantity, h conftantly accompanied  with
 light; or, in other words,  as fire is always produced
 by the  increafe of heat, philofophers have generally
 confidered  thefe  phenomena as proceeding from the
 fame caufe : and have therefore ufed the word fire to
 exprefs that unknown principle, which, when it is pre-
 fent to a certain degree, excites the  fenfation of  heat
 alone; but,  when accumulated to a greater  degree,
 renders itfelf obvious both to the  fight  and touch, or
 produces heat accompanied with light.  In  this fenfe,
 the element of fire fignifies the fame thing with abfo-
 lute heat.
  Having premifed  thefe general  definitions and re-
marks,  he gives the  properties of heat in the following
words :                                    '            6
  " I. Heat has a eonftant tendency to diffufe itfelf over Heat ha»a
all bodies  till  they are brought to the fame tempera- tendency
ture.  Thus it is found  by the thermometer, that  if to diffufe
two bodies of different  temperatures  are  mixed  toge-itfelf c"
ther, or placed contiguous,  the heat pafles  from the ?™^ly <mr
one to the other till their temperatures become equal;
                                               and 
C   H   E   M    I   S    T   R    Y.
Theory.
It is con-
tained in
consider-
able quan-
tity in all
bodies.
   6x
Great de-
gree of cold
at lilaf-
g°w,
   63
In Siberia,
and at
Hudfon's
bay.
   64
Quantity
of heat li-
mited in
all bodies.
Todies uni-
\rn~ally ex-
panded by
beat.
and thitall inanimate bodies, wlicn heated and placed
in a cold medium,  continually lolc hesn, till in proccls
of time they arc brought to the ftate of the (urrouud-
ing medium.
  *« From this property of heat it follows, that the va-
rious dalle? nt bodies throughout the earth, if they were
not acted upon by external  caul'es,  would  at length,
arrive at a common temperature when  the heat would
become quiefcent ; in like manner as the waters of the
ocean, if not prevented by the  winds and by the  at-
tractions of the fun and moon, would come to an equi-
librium, and would remain in a ftate of reft.  But as
caufes continually occur in nature to difturb the balance
of heat as well as that of the waters of the ocean,  thofe
elements arc kept in a eonftant fluctuation.
  "  II. Heat is contained in confiderable quantities in
all bodies when at the common temperature of the at-
mofphere.
  " Fromthc intcrefting experimentswhichwerc made
on cold by Mr Wilfon, we learn, that  at Glafgow, in
the winter of the year 1780, the thermometer on the
furface of fnow funk 25  degrees below the beginning
of Fahrenheit's fcale.
  "  Wc are told  by Dr Pallas,  that in the deferts of
Siberia, during a very intenfe froft, the mercury was
found congealed in thermometers expofed to the atmo-
fphere, and a quantity of that  fluid in an open  bowl
placed in a fimilar lituation,  at the fame time became
folid.   The decifivc experiments of Mr Hmchins at
Hudfon's Bay prove, that the freezing point ofrnc---
cury is very nearly 400 below the zero  (or o°) of Fah-
renheit.  From which it follows, that at the time of
Dr Pallas's obfervation,  the atmofphere in Siberia muft
have   been  cooled to minus 40.  1'y  a paper lately
tranfmitted  to  the Royal Society we are in'ormed,
that the fpirit-of-winc thermometer, in the open  v'.r at
Hudfon's Bay fell to—42  in  the winter of  1735 ;
and from the fame communication we  learn, that by  a
mixture of fnow  and vitriolic :icld, the heat Tv~s fi
much diminilhed, that the fpirit of wine funk to — 80,
which is 112 below the freezing point  of water.
   "  Hence it is manifect,  that heat .is cont.lined in
confiderable quantities in all  bodies when rt the com-
mon  temperature of the atmofphere..  It is p'.ain,  how-
ever,  that the .mmuity  inherent in each individual
body  is limited.   This, I think, muft be admitted,
whatever be the hypothefis which wc adopt concerning
the nature of heat ; whether we conceive it to be  a
force or power belonging to bodies, or an element-try
principle contained in them.  For thofe who confider
heat  as an clement, will not  fuppofe that an  unli-
mited quantity of it can Se contained in a finite body ;
and if heat be confidered as  a force or power, the fup-
pofition that  finite  bodies are actuated by forces or
powers which are infinite is evilly inadmiflible.
   "  To place this in another ';ght, we know that bo-
dies are univerfally expanded by heat, excepting in a
very  few inftances, which do not,afford a juft objection
to the general fact; becaufe,  in thofe inftances,  by the
action of heat a fluid is extricated that  previoully fepa-
rated the particles from each other.   Since, therefore,
heat is found to expand bodies  in  the temperatures
which fall within the reach of our obfervation, we may
conclude that the fame thing  takes place in all tempe-
ratures."
  Onr author,  by a fet of very accurate and laborious
experiments, determines that thccxpanlions in mercury
and fome other fluids are proportionable to the quan-
tities of heat applied; " from which  (fays he) it  is
ma:.ifeft, that the quantities of heat in bodies arc limi-
ted, becaufe an infinite heat would produce an infinite
expanlion.
  "  It is manifeft, that the number of degrees of fen-
fible heat, as mcafured by the thermometer, and cfti-
mated from  the  beginning 0/ the fcale, muft be the
fame in all bodies which have a common temperature ;
for by the firft general fact it is proved, that heat has
a eonftant  tendency  to  diffufe itfelf  uniformly over
bodies  till their  temperatures become equal.  From
which it may be inferred, that if a quantity of heat
were added to bodies abfohuely cold, the fame uniform
diffulion would take place ; and that if  a thermometer,
altogether deprived of its heat, were  applied to fuch
bodies,  it would bs equally expanded by them, thewholc
of the fenfible heat which they had acquired being in-
dicated by that  expanfion.
  " III. If the  parts of the  fame  homogeneous fub-
ftance have z common temperature, the  cuautity  of
abfolute heat will be proportional to the bulk or quan-
tity of matter.   Thus the quantity of abfolute heat in
t\\ o pounds of water is double that which is contained
in one pound when at the fame temperature.
  " IV. The dilatations and contractions of the fluid
in the mercurial  thermometer are nearly proportional
to the quantities of abfolute heat which are communi-
cated to the  fame homogeneous bodies, or feparated
from th:i.i,  as long as they retain the fame form. Thus
the quantity of heat required  to raife a body four de-
grees in temperature  by the mercurial thermometer, is
nearly double that which is   required to raife it two
degrees, four times that required to raife it one degree,
and fo in proportion.''
  Thus we fine',  that Dr Black, Dr Irvine, Dr Craw-
ford,  and Dr Bcrkcnhout,  agree in fpeaking of fire or
heat as  a nuid fubftance diftinct from all other bodies*
Mr lOrwo , inhisTreatife of Phlogifton, agrees in the
fame opinion.  (< Some (fays he)  have thought,  that
I fncnld have included the matter of heat, or elemen-
tary fire,  in the definition of inflammable air ; but as
fire is contained in ail corporeal fubftances, to mention
it is perfectly ueedlefs, except where bodies differ from
c.ich other in  the quantity of it they  contain."  On
the other hand,  Mr  Cavendiih,  Phil. Tranf. lxxiv.
P.  141. tells us, that " he thinks it more likely that
there is no fuch thing as elementary heat :" but, as he
gives no reafon for this opinion, it feems probable that
the greater  part of philofophers either pofitively  be-
lieve that heat is an elementary fluid diftinct from  all
others,  or find themfelves  obliged to adopt a language
which neceflarily implies it. The only  difficulty which
now remains therefore is, to affix a proper idea to the
phrafe quantity of heat, which we find univerfally made
ufe of,  without  any  thing to determine our opinions
concerning it.
  That we cannot fpeak of a quantity of fire or heat in
the fame fenfe  as we  fpeak  of a quantity of water  or
any other fluid  is evident, becaufe we can take away
the quantity of water which  any  fubftance contains
but cannot do fo with heat.  Nay, in  many cafes wc
arc fure, ih„r a fubftance very cold to the touch docs
                                                yet
Of the
Element
of Fire,

   66
 Expanfion
ofmcrcury,
&c. propor-
tionable to
the degrees
of heat.
    6j
Homoge-
neous bo-
dies of the
fame tem-
perature,
contain
quantities
of heatpro-i
portionable
to thofe of
their mat-
ter.
   68
Mr Kir-
wan's opi-
nion con-
cerning
fire.

   69
Mr Caven-
difli's opi-
nion that
it is not a
diftinct
fubftance.
    70
Difficulty
in defining
the phrafe
quantity of
beat.
    If
Thisphrale
cannot be
ufed in the
common
acceptation
of the word
with regard
to fire. 
  Theory.                          C   H   E   M
 Of the    yet contain a very confiderable quantity of heat.  The
 Element  vapour of water, for inflance, may be made much colder
 «f Fire    than the ufual temperature of the atmofphere without
 "   g—"~' being condenfed, wnen at the fame time we are certain
          that it  contains  a great  quantity of heat;  and the
          fame may be faid of water, which, in the act of freez-
          ing, throws out a great quantity of heat without be-
          coming colder;  and in the act of melting abforbs as
          much without becoming warmer.  It is  not therefore
          by the mere prefence or abfence of this fluid  that wc
          can determine the real quantity of this fluid; nor does
          it appear that the word quantity can be at all accurate-
          ly applied to the  element itfelf, becaufe  we have' no
     y%    method of meafuring it.
 Dr Cleg-     Dr Cleghorn, in his inaugural differtation De  Igne
 horn's opi- throws fome  light on this  fubject, by observing, that
 ition.     « the thermometer fliows only the quantity of heat
          going out of a body, not that which is really contained
          in it:"  and he alfo infifts, that " we can neither affent
          to the opinion  of Dr  Boerhaave, who  fuppofed that
          heat  was diftributed among bodies  in  proportion to
          their bulks;  nor to  the  hypothefis  of others,  who
          imagined that they were heated in proportion to their
          denfities."   But in what proportion, then,  are they
          heated ; or how are we to meafure the quantity which
          they really contain, feeing the thermometer informs us
     73    only of what they part with ?
 The latent    As this point is by no means  afcertained, wc cannot
 heat of bo- form a direct idea concerning the abfolute quantity of
 dies cannot jieat contained in any body; and therefore when we
 be mcafu- fpeak 0f quantities of this fluid, we muft in fact, if we
          mean any thing, think of the fenfible quantity flowing
          out of them ; and though we fhould fuppofe the whole
          of this fenfible heat to be removed, it would  ftill  be
    74    impoffible for us .to know how much remained in a la-
 Dr Cleg-  tent ftate, and could not be diflipated.   This difficulty
 horn's hy- will ftill appear the greater, if  with Dr  Cleghorn and
 pothefis   others we fuppofe  the fluid of heat to be  fubject to'the
 concerning jaws 0f  attra&ion and repulfion.  This gentleman
 *"'      fuppofes, that the particles of heat (like the particles
          of electric fluid accordingto theFranklinianhypathefis)
          are repulfive of one another, but attracted by all other
          fubftances.   " If any body (fays he), heated  beyond
          the common temperature of the air,  is expofed to  it,
          the heat flows out from it into the atmofphere, and
          diffufes itfelf equally all around till the air becomes of
          the fame temperature with itfelf.  The fame happens
          to bodies fufpended in vacuo.  Hence it is juftly con-
          cluded,  that there exifts between the particles  of heat
          a repulfive power, by which they mutually recede from
          each  other.   Notwithftanding this repulfive  power,
          however, the quantities of heat contained in different
          fubftances, even of the fame temperature, arc found to
          be altogether different; and from Dr Black's experi-
          ments it now  appears, that the quantity of heat is
          fcarce ever the fame in any two different bodies : and
          hence we may conclude, that terreftrial  bodies have a
          power of attracting heat, and that this power is differ-
          ent in different fubftances.—From thefe principles It
          evidently follows, that heat is diftributed among bodies
          directly in proportion  to their attracting powers, and
v   ?.■?    inverfely according to- the repulfive power between the
 bnum'of  particles of heat themfelves.  Such is the diftribution
 heat dc-   °f neat  among  bodies  in the neighbourhood  of each
 fined.     other; and which is called the equilibrium of heat > be-
I   S   T   R   Y.
*5
 caufe the thermometer fliows no difference of tempera- Of the
 ture among them.  For feeing the heat is diftributed Element
 according  to the attracting power of each,  the ther-    '"•. t
 mometer having  alfo  a proper attraction of its own,
 can fhow no difference in the attracting power of each;
 for which  reafon all  bodies in the neighbourhood of
 each  other are  foon  reduced to the  fame  tempera-
 ture."                                                7g
   If we affent to  Dr Cleghorn's hypothefis,  the quan- The quan-
 tity of heat contained  in any fubftance depends, in the tity of heat
 firft place, on the attracting power of that fubftance, cannot be
 which is altogether unknown ;  and,  in  the  fecond determind
 place, on the repulfive powers of  the particles of heat pythefiS¥ *"
 themfelves, which are equally unknown.  To deter- *
 mine the quantity, therefore, muft be impoffible. Nei-
 ther will the mixture  of two different fluids,  as in Dr
 Black's experiments,  affift us in the leaft ; for though
 water,  heated  more  than mercury, communicates  a
 greater heat to that fluid than the latter does  to water ;
 this only  fhows that  water more  readily  parts with
 fome  part of the heat  if contains  than mercury does,
 but has hot the leaft tendency to difcover the quantity
 contained in either.
  ' Dr Crawford, as we have already feen, calls  the de-
gree,  or,  if we may vary the phrafe, the qua?itity of
power or element (fluid, if we may fubftitute a fynony-
 mous word) exifting or prefent in any body, its abfo-
 lute heat;  and  lays down a rule for determining the    7_
 proportional quantities of heat in different bodies. u It Dr Oaw-
 will  appear (fays  he)  from the  experiments after- ford's me-
 wards recited;  that if a pound of water and a pound thod of de-
 of diaphoretic antimony have a common temperature, termining
 the quantity of  abfolute  heat contained in  the for- . e ProPor"
 mer is nearly four times that contained in the latter."  '?"*.;.:,,,
   rr-*1           •   1*11  ...         ..            II lid IIII tlC5>
 —The  manner m which he llluftrates this is as fol- Qf heat*
 lows.
   " If four pounds of diaphoretic antimony at 20 be
 mixed with one pound of  ice at  32,  the temperature
 will be nearly 26 :  the ice will be cooled fix  degrees,
 and the antimony heated fix.  If we reverfe the expe-
 riment, the effect will be the fame.  Thjfek, if we
 take fix degrees of heat from four pounds oW^imony,.
 and add it to a pound  of ice, the latter willbeneated
 fix degrees.  The fame quantity  of heat, therefore,
 which raifes a pound of ice fix degrees, will raife four
 pounds of antimony fix degrees.
   " If this experiment be made at different  tempera-
 tures, we fhall have a fimilar refult.  If, for  example,,
 the antimony at ic, or at  any given degree below the
 freezing point, be mixed with the ice at 32, the heat
 of the mixture will be the arithmetical mean between
 that of the warmer and colder fubftance.  And fince
 the capacities of bodies are permanent as long as they
retain the fame form,  we infer, that the refult would
be the fame if  the  antimony were deprived of all its
 heat,  and were mixed with the ice at 32.   But it is
 evident,  that in this cafe the ice would communicate
 to the antimony the half of its abfolute  heat.  For if
 200 below  froft be conceived to be the point of  total
 privation, the antimony will he wholly deprived of its
heat when cooled to 200 degrees  below 32, and  the
heat contained in  the ice when at 32 will be 200
 degrees.   If we  now fuppofe them to be mixed toge-
ther,  the temperature of the mixture will be half the
 excefs of the hotter above  the  colder,  or the ice will
                                                be 
CHEMISTRY.
His me
         1< ,-mled too degrees and the antimony heated ioo.
         The one half <>f the heat, therefore, which was con-
         tamed in the ice pre\ious to the mixture will be com-
         municated to the antimony ; from which it is maiitcn,
         that after the mixture the ice and antimony mull con-
         tain equal quantities of abfolute heat.
            " To place this in another light, it has been proved,
         that the fame quantity of heat which raifes a pound of
         ice fix degrees will raife four pound of antimony fix
         degrees.  And as the capacities of bodies, while they
         retain  the fame form, are not altered by a change of
         temperature ; it follows, that the fame quantity of heat
         which raifes the ice 200 degrees, or any given number
         nf degrees, will raife the  antimony an equal number of
         degrees.
            " A pound  of ice, therefore, and  four pounds of
         antimony,   when  at the fame  temperature, contain
         equal quantities of abfolute heat.  But  it appears from
         the third general fact (n°  67.), that four  pounds of
         antimony contain four times as much abfolute heat as
         one pound  of antimony; and hence the  quantity of
         abfolute heat in a pound of ice is to that in a pound of
         antimony as four to one."
            From this quotation  it is evident,  that, notwith-
thod infuf- ftanding all  the  diftinctions which Dr Crawford has
ficient.    laid down betwixt abfolute heat and temperature, it is
         only the quantity of the  latter that can be mcafured  ;
         and all  that we can fay concerning the  matter is, that
         when certain bodies are mixed together, fome of them
         part with a greater quantity of heat than others ; but
         how much  they contain muft  remain for ever un-
         known, unlefs we can fall on fome method of meafu-
         ring the quantity of heat as we do that of  any other
         fluid.
Nicholfon's   *Ir  N'icholfon, who has collected the principal opi-
* count of nions on the fubject of heat, feems undetermined whe-
thr theories ther to believe the doctrine of Boyle or of Boerhave
of heat.   on the fubject.   " There are two opinions (fays he)
         concerning  heat.  According  to  one opinion, heat
         conlifts in a vibratory motion of the parts  of  bodies
         among each other,  whofe greater or lefs intenfity oc-
         caiions the increafe or diminution of temperature.  Ac-
         cording to the other opinion,  heat is a fubtile fluid that
         eaiily pervades the pores of all bodies, cauling them
         to expand by means of its elaftkity or otherwife.  Each
         of thefe opinions is attended with its peculiar difficul-
         ties.  The phenomena of  heat may be accounted fin-
         by either of them,  provided certain fuppoiitions be al-
         lowed  to each reflectively;  but the want of proof of
         the truth of fuch fuppofitions renders it very difficult,
         if not impoffible, to decide as yet whether heat confifts
         merely in  motion or in fome peculiar matter.  The
         word quantity, applied to heat, will therefore  denote
         cither  motion  or matter,  according  to the opinion
         made ufe of, and may be ufed indefinitely  without de-
         termining which.
            <• The chief advantage which the opinion that heat
         iscaufed by mere vibration ponenes, is its great fimpli-
         city.   It is highly  probable, that all heated  bodies
         have an intcftine motion, or vibration  of their  parts;
         and it is certain that perculfion, friction, and other
         methods of agitating the minute parts  of bodies, will
         likewife increafe their temperature.   Why,  then, it is
         demanded,   fhould wc multiply caufes, by  fuppofing
         the ...:.. n;c of an  unknown fluid, when the mere vi-
Theory.
    80
 Advanta-
1 ge* of the
 doctrine
 chat heat
 is cauf: I
 by vibra-
bration of parts which is known to obtain may be ap-
plied to explain the phenomena :''
  To this the reply is  obvious,  that the vibration of
parts is an effect; n>r matter will not begin to move of
itfelf:  and if it is an effect,  we muft fuppofe a caufe for
it; which, though we fhould not call it a fluid, would
be equally unknown and inexplicable with that whofe
exiftence  is aliened by thofe who maintain that fire is
a fluid per fe.  Dr Cleghorn, however, in the diflcrta-
tion already quoted, aflerts, that " heat  is occafioned
by a certain fluid, and not by motion  alone, as fome
eminent writers  have imagined :  becaufe,  1. Thofe
who have adopted the hypothefis  of motion could
never even prove the exiftence  of that motion for
which  they  contended ; and though  it  fhould  be
granted,   the  phenomena could  not be explained by
it.  2. If  heat depended on motion, it would inftan-
taneoufly  pafs through  an  elaftic  body; but  we fee
that  heat  pafles  through bodies  flowly  like a fluid.
3.  If  heat depended on vibration,  it ought to be com-
municated from a given vibration  in proportion to the
quantity of matter; which  is found not  to  hold true
in fact. On the other hand,  there are numberlefs argu-
ments in favour of the opinion that heat proceeds from
elementary fire.   1. Mr Locke  hath obferved,  that
when we perceive a number of qualities always exifting
together, we may gather from thence that there really
is fome fubftance which produces thefe qualities. 2. The
hypothefis of elementary fire is fimple and agreeable to
the phenomena.   3. From  fome experiments made by
Sir Ifaac Newton, it appears, that bodies acquire heat
and cold /;: vacuo, until they become of the fame tem-
perature with the  atmofphere; fo  that heat cxifts in
the abfence of all  other matter, and is therefore a fub-
ftance by itfelf."
  But though thefe and other arguments fcem clearly
to cftablifh the point that fire or heat is a diftinct fluid,
we are ftill involved in very great difficulties concern-
ing its nature and properties.  If it be fuppofed  a
fluid, it is impoffible to affign any limits to its extent;
and we muft  of neceffity likewife fuppofe that it per-
vades  the  whole creation, and confeqnently cdnftitutes
an abfolute plenum, contrary to a fundamental princi-
ple of the  received fyftem of natural philofophy.   But
if this is the cafe, it is vain to talk of its being abforb-
ed,  accumulated,  collected, or attracted by different
bodies, fince it is already prefent in all points of fpace;
and we can conceive of terreftrial bodies  no  otherwife
than as fponges thrown into the ocean, each of which
will be as full of fluid as it can hold.  The different capa-
cities will then be fimilar to the differences between bits
of wood,   fponge, porous ftones,  &c.  for containing
water ; all of which depend entirely on the ftructure of
the bodies themfelves, and which,  unlefs we could fe-
parate the water  by prcfliire, or by evaporation, would
be forever unknown.   Suppofing   it were  impoffible
to collect this water in the manner we fpeak of  we
could only judge of the quantity they contained by the
degree to which they fwelled by being immerfed in it.
ft  is  eafy to fee, however,  that  fuch  a method of
judging would be very inadequate to the purpofe  as
fubftances might  contain internal  cavities or pores in
which water could lodge without augmenting the  ex-
ternal  bulk.   This would fuggeft  another method
of judging of the quantity, namely, the fpecific gra-
                                            vity ;
Of the
Element
of Fire.
»-----.✓——'
    81
Anfwcr t«
Mr Nichol-
fon's argu-
ment.
    8x
Dr Cleg-
horn's
proof that
heat is oc-
cafioned by
a fluid.
   35
Difficulties
concerning
the nature
and proper-
ties of Fire. 
Theory>
CHEMISTRY.
17
Element
of Fire.
   84
Difficulty
arifing
from
heat diffu-
fes itfelf
equally.
          vity ; and we might reafonably fuppofe, that fubftan-
          ces  of the greateft fpecific gravity would contain  the
          fmalleft quantity of water, though ftill we could by
          no means determine  what quantity they did contain,
          unlefs we could lay hold of the element itfelf.
            This  feems to be very much the cafe with elemen-
          tary fire, if  we fuppofe it to be  a fluid per fe.  We
          judge of its prefence by the degree of expanfion which
          one heated  body communicates to  another : but this is
          only fimilar to the calculation  of the quantity of moi-
          fture a fponge or  any  other body contains, by what
          it communicates  to wood when it comes into contact
          with it  ; which never  could be fuppofed to  carry  the
          leaft pretentions to accuracy,  though we fhould afcer-
          tain it with all  imaginable exactnefs.   It is likewife
          probable, that the moft denfe bodies contain the fmalleft
          quantity of  fire,  as they generally communicate lefs
          when heated to an equal temperature than thofe which
          are more rare, though we are far from having any per-
          fect knowledge in this refpect.
            But the greateft difficulty of all will be, on the fup-
          pofition that  heat is a fluid, and an omniprefent one
          (which it muft  be,  or  there would be fome  places
the fuppo-  where bodies could  not  be heated),  to anfwer  the
fition that  queftion, Why are not  all bodies of an equal tempera-
          ture, excepting only the differences arifing from their
          fpecific denfities,  wrhich  render fome capable of
          containing a greater quantity than others?—The dif-
          ficulty will  not be leflened, though the omniprefence
          of theiluid  fhould  be given up, if wefuppofe, as is
          generally done, that heat has  a tendency to diffufe it-
          felf equably every way. If it has this tendency, what
          hinders  it from doing fo ?  Why doth not the heat
          from the burning regions of the torrid zone diffufe it-
          felf equally all over the globe, and reduce the earth to
          one common temperature ?  This indeed might require
          time ; but the experience of all ages  has fhown that
          there is not the  leaft advance  towards an equality of
          temperature.  The middle regions of the  earth con-
          tinue as hot, and the polar ones as cold, as we have any
          reafon to believe they were  at  the creation of the
          world, or as we have any reafon to believe they will be
          while the world remains.   This indeed is one of the
          many inftances of the impropriety of eftablifhing gene-
          ral laws from the trifling experiments we are capable
          of making, and which  hold good only on the narrow
          fcales on which we can  make them, but are utterly in-
          fufficient to folve  the  phenomena  of the great fyflem
          of nature, and which  can be folved only  by obferving
          other phenomena of  the fame  fyflem undifturbed  by
          any manoeuvres of our own.
           Again, fuppofing the objection already made could
         be got over,  and fatisfactery reafons fhould  be given
         why an equilibrium of temperature  in the earth and its
         atmofphere fhould never be obtained,  it will by no
         means be eafy  to tell what becomes of the heat which
         is  communicated  to  the earth at. certain times of the
         year. TJiis difficulty, or fomethingfimilar, Dr Craw
   85
Another
from the
feeming
difappear-
ance of the
heat.
   86
Dr Craw
ford's folu- ford feems to have had in view when treating of the
lion.     effects of the evolution and abforption of heat.   Thus,
         fays he, " the Deity has guarded againft fudden viciffi-
         tudes of heat and cold upon the furface of the earth.
            iC For if heat, were not evolved by the procefs of
         congelation, all the waters which  were expofed to the
         influence  of the external air, when its temperature was
 reduced below 320, would fpeedily become folid ; and,  Element
 at the moment of congelation, the progrefs of cooling of Flre-
 would be as rapid at it was Lefore the air had arri- "" "~^
 ved at its freezing point.
   " This is manifeft from what was formerly obferved
 refpecting the congelation of different fluids.   It was
 fhown, that if the velocities of the feparation of heat
 were equal, the times of the  congelation  would be in
 proportion to  the quantities of heat which the fluids
 gave off from  an iniernal fource  in the freezing pro-
 cefs.   Whence  it follows, that if no heat were evol-
 ved, the congelation fhould be inftantaneous.
   " In the  prefent ftate  of things, as foon as the at-
 mofphere is cooled below 320, the  waters  begin to
 freeze, and at the fame time to evolve heat ;  in con-
 fequence of  which, whatever may be the degree of cold
 in die external air, the freezing  mafs remains at 320,
 until  the whole is congealed ;  and as the quantity of
 heat extricated in the freezing of wateris confiderable,
 the pr»grcfs of congelation  in large  mafTes is  very
 flow.—That the abforption and extrication of heat in
 the melting and freezing of bodies has a  tendency to
 retard the progrefs of thefe proceffes, is remarked by
 Mr Wilkie  in  his effay  on latent Heat.—The fame
 doctrine is likewife taught by Dr Black  in his lec-
 tures,                                                 g
   " In the northern and  fbuthern regions, therefore, Severity of
 upon the  approach of winter, a quantity of elementary the cold in
 fire is extricated from the waters, proportional  to the the north-
 degree of cold that prevails in the atmofphere.  Thus e*'n re" . .
 the feverity of the froft is mitigated, and its progrefs &wns m'u"
 retarded ; and it would feem that, during this retarda- f^  ro-
 tion of the cooling procefs, the various tribes of animals dua^nof
 and vegetables which inhabit the  circumpolar regions icc.     '
 gradually acquire power of refitting its influence.         g8
   " On the contrary, if, in the melting of ice, aquan- inuudati-
 tity of  heat were not abforbed, and rendered infen- ons prc-
 fible, that fubftance, when it was expofed to a medium vented by
 warmer than 320, would fpeedily become fluid, and the the fl?w"
 procefs of heating  would be as rapid as if no alteration ne/. ™ith
 in its form  had taken place. If things were thus con- W„\edw*!
 ftituted, the vaft mafTes of ice and fnow which are col- fe^ melts.*"
 lectedin the frigid zones would, upon the approach of
 fummer, fuddenly dillblve,  and great inundations would
 annually overflow  the regions  near to the poles.
   " But by the operation  of  the law of the abforp-
 tion of heat, when the ice and fnow upon the returnof
 fpring have arrived at 320, they begin to melt, and at
 the fame time to imbibe heat :  during this procefs, a
large quantity of elementary fire becomes  infenfible ;
in confequence of which   the earth is flowly  heated,
and  thofe gradual changes are produced which  are
euential to the prefervationof the animal and vegetable
kingdoms.                                           «
   " We may  remark,  in  the laft place, that this law Equaldi-
 not only refills hidden changes of  temperature,  but ftribution
 that it likewife  contributes  to  a  more  equal diftribu- of heat prg^.
 tion of the  principle of heat  throughout the various mo,:ed h7
parts of the  earth,  in different feafons and climates. **" :,bf°J"
 Thus the diurnal heats are moderated by the evapora- evolutiou.
 tion of tfje water.,  on the earth's furface, a portion of
 the fire derived from the fun being abforbed and  ex- /
 tinguiihed by the  vapours at the moment of their af-
 cent.  On the approach of night the vapours are again
 condenfed, and falling in the form of dew, communicate
                        C                       to 
IS
CHEMISTRY.
F.k-mt'
"i Kirr
   90
Hrar of tf
thus miti-
gated.
          10 the air and to the earth the fire which they had ini-
          I'iUr.l during the d..y.
            "  It wa. before ;.: >\vn, tha*, in the regions near to
          the p ties, when the vernal and fuminer heats prevail,
          pn>\ ifionis made for tenipcringthe fevcrity of the win-
          ter odd,  a quantity of elementary fire, upon  the dif-
          lolution of the ice and l'm>w,  being abforbed by  the
          waters, and d'-poiited, as.  it were, in a great magazine
          t\<r the parn.>fc of mitigating the intentny of the cold
          when the Lot returns.
            '• From the experiments of Hales, Hallcy, and Wat-
t.irrid rone fbi^ jt t-ppc\ rs, that vaft quantities of water arc conti-
          nually converted into vapour by the action of the folar
          rays  upon the portion of the earth's furface which is
          expifcd to the light; and  by the celebrated difcovery of
          Dr Black, it is proved, that, in the procefs of evapora-
          tion,  much elementary fire is abforbed. It is inanifeft,
          that this caufe will have a powerful influence in  miti-
          gating  the intenlity of the heat in the torrid zone, and
          in promoting a more equal diffulion of it through the
          earth.  For a  confiderable portion of the heat, which
          is excited by theaction of the folar rays upon.the earth's
          firfacc within the tropics, is abforbed by  the aqueous
          v .ijionrs, which being collected in the form of clouds, are
          fpread like a canopy over the horizon,  to defend the
          fubjaccnt regions  from the direct rays  of  the  fun.  A
          great quantity of  elementary fire is thus  rendered in-
          fenlible in the torrid zone, and is carried by  the  dif-
          perlion of the vapours to the north and to the fouth,
          where it  is gradually communicated to the earth when
          the vapours  are coudenfed."
Th:s folu     That all this takes place, as the Doctor has advanced,
tion totally cannot  be denied ; but, by allowing it, the difficulty is
infufficient not removed in the fmalleft degree, as will appear from
to remove a die conii leration of the phenomena which he  him-
thaJifficul- fcif ]ias mentioned.  He owns that the fun communi-
tJ-        cates lire to the earth : the queftion is, What becomes
          of  it, feeing  the   emillion is  continual  ?  In funnier,
          the air,  the  earth; and the w-ater, are heated to a
          certain degree.   On the  fun's  declining fouthward,
          the air firft  lofes its heat.  Whither docs it go ?  It
          does  not afcend ir.to the higher regions of the atmo-
          fphere, for thefe are conftantly found colder than the
          pins below. It does not defcend to the earth and water  ;
          . >r ih fe ; i ve out the quantity they had abforbed, as Dr
          Cr.i'vn.rd'obferves. Neither  does it go laterally to the
          fouthern  regions  ; for they  are conftantly very  hot,
          mid ought to impart their heat to thofe farther north,
          inftead of receiving any from  them.   Ho w comes it
          then, that the atmolphere feems perpetually to receive
          heat  without ever being fatiated ? or if the heat cannot
          be  found  going off either upv. a>-u>,  downwards, or
          fideways, how  are wc  to  account for its diiappear-
9*
( f()lu-
  This qncflion fcem< to be altogether unanfwerable
on the fupp.'lition that heat is occaliontd by the mere
    91 rt
Heat moft
the aciion prefence of  a  fluid ; but if we fuppofe it to be only a
of an om-  particular mode of action of an onuiiprefcnt fluid, the
t   -icfcnt   v. liolc  difficulty vanilhes at once.—On this 1. pp  iition
il iid.      indeed the  queftion will natni ally arife, \\ hence does
          this motion proceed, or by what is its action m general
F!r  Lm*  htermired?  Dr Berkerdiout,  in enumerating the
deit •  te of prop* rtics of  :"..::a, exempts fire from two of thofe
gravity and ufUi4i!.,  afcribed  to  other  material  fubftar.ces,  viz
™» **»"— irraMuao:: and the lis u.i-.rtix,   " According to the
                                                 Theory.
philofophcrs (fays he), matter cannot move without be- Element
ing cither  impelled or attracted. I doubt much whe- <»f *irc-
ther this be true of lire, and whether, when  uacom- v~^/
bined, motion be not one  of its c hernial  properties.—
Gravitation feems alfo to be no property of fire, which
moves with equal facility in all directions, and may be
accumulated in hard  bodies to any degree without in-
creafing their weight.   Fire,  being the caufe of vola-
tility,  feems  rather to be in eonftant countcracliou to
gravity."
  But however effential we may fuppofe the motion of
fire to be to it, there cannot be  any filf-exiftent mo-
bility in its parts,  otherwife it would loon be diffufed
equally throughout the univerie, and the temperature of
the whole reduced to an equilibrium.   According to r);Urn,u_
the prefent conflitution of nature, we fee that the diltri- tion of heat
bution of  heat  is  principally owing to the fun ;  and owing to
what" we call its quantity, depends on thepoiition of the tJlc fun.
fun with regard to  terreftrial objects and the length of    oj
time they arecxpondto  his  rays.   Heat is  i,ot pro- How heat
duced while the rays have a direct pafiage ; and there- '8 produced
fore fluids  through which they pals calily, as  air, are y  c   '
not heated by the  rays of the fun. But when the rays r*^*'
are impeded  in their courfe, and reflected in confide-
rable quantity, a degree oi heat takes place,  which is
always greater or  lefs in proportion to  theintenfity of
the ray:,.—In the reflecting lubftance, the heat will be
comparatively greater in proportion to  the quantity of
rays  which are aoibrbcd or flopped in their courfe by
it : but in any lubftance interpofed betwixt the fun and
the reflecting body, the heat is proportional  to  the
quantity of rays reflected.—Now it  is plain, that when
the particles  of light fall upon any  opaque fubftance,
and enter  its pores, which by their extreme fubtilty
they are well calculated to  do, they  muft make an at-
tempt topafs directly through it in their natural courfe  ;
but as this cannot  be done,  they will  pufh  laterally,
and in all directions, in confequence of  being perpe-
tually urged by the impulfe of the light coming from
the fun : and thus  an action will be  propagated in all
directions  as radii from a centre towards a circumfe-
rence, which when it  takes place in that fubtile fluid
always produces what we call heat.                      ^
  In completing the  fyflem of  nature,  we  perceive proofs ef
three kinds  of fluids of extreme fubtilty,  and very tht identity
much refembling one another,  viz. fire, light, and elec- °f nrc>
tricity.  That  it fhould be agreeable to  vulgar  con- bght^and
ceptions to fuppofe thefe all to be ultimately  the fame, clc"natJ*
is  not furpriling ;  and on examining the evidence of
their identity, it will certainly be found exceedingly
firong.   They all agree  in  the property of exciting
the feufacion of heat in certain  circumftances, and in
not doing fo  in others.   Fire, we know, in the com-
mon  acceptation of the  word,  always does  fo ;  but
when it aliiunco the latent and invifible ftate, as in the
formation  of vapour, it lays afidc this fee iringly effen-
tial property, and  the vapour is cold  to the touch___
Light,  when collected in a focui by a burning glafs,
i. e. when  us rav ; converge towards a  centre, and di-
verge or attempt to diverge from ore, p: oduc es heat al-
fo : and fo  docs the electric fluid; for it has been found
that the aura converging from a very la: ge conductor to
thepoint of a needle, is capable of fcttingon fire a r. .!]
cartridge of gunpov. d( r, or a quantity of tinder furroud-
ing it *.  There fccuis  alfo to  be a coiir.ectiuii  betwixt. Ste  ,.
                                                fire tricit3. 
Theory.
CHEMISTRY.
Element
•f Fire.
          fire and electricity in another way ; for in proportion as
          heat is diminifhed, or the bodies are cooled, electricity
          fucceeds in its place.  Thus all electric bodies by heat
          become conductors of electricity, and  cannot be ex-
on between cited  or made to fhow  any figns of containing that
fire or heat {{u\d .  but as f00u as th.e heat is removed, their electric
          property returns.  Water  is naturally a conducting
          fubftance : by being frozen its conducting power is lef-
          fened,  which fhows  an approach to  electricity; and,.
          by being cooled down to 200 below  o of Fahrenheit,
          the ice actually becomes electric, and will emit fparks
* See Elec- by friction like  glafs*.   The atmofphere is a natural
   97
Connecti-
>ud electri-
city
trieity.


    98
Exceffive
electricity
99
Heat
           electric : but by a certain degree of heat it lofes this
           property, and becomes a conductor; nor  is there any
           doubt that its electric properties are increafed in pro-
           portion to the degree of cold imparted  to it.   In the
           winter time, therefore, we muft confider the frozen fur-
  o   epo ar face Q£ ^ eartj^  t]ie water> anc[ the atmofphere of the
  winter.    polarrcgions, as forming one electrical machine of enor-
           mous magnitude ;  for the natural cold of thefe countries
           is often fuflicient  to  cool the water to more than 200
           below o, and  confequently to  render it  an  electric.
           That this is really the cafe, appears from the exceffive-
           ly bright aurora borealis  and other electric appear-
           ances,  far exceeding any thing obferved in this coun-
           try.  In the fummer time, however, no  fuch appear-
           ances are to be feen,  nor any thing remarkable except
           an exceffive heat from the long continuance of the fun
           above the horizon.   This quantity of heat then being
 fummerbe- fucceeded by a proportionable quantity of electricity
 comes elec- jn winter, it is impoffible to avoid concluding that the
 trie fluid in ^eat m furnmer becomes electric fluid in winter, which,
          going off through the celeftial expanfe, returns again
          to the grand fource of light and heat from which  it
          originally came ; thus making roomfor the fucceeding
          quantities which are to enliven the earth during the fol-
          lowing fummer.
            Thus the difappearance of heat in winter,  and of
    I00    electricity in fummer, in thefe countries,  will be very
 Why thun- naturally and eafily accounted for.   It is true, that the
 derand    phenomena of thunder and lightning fhow the  exift-
          ence of this fluid in vaft quantities during the fummer
          feafon : but thefe  phenomena arc only  partial,  and
          though formidable  to us, are trifling in comparifon with
          the vaft quantities of electric matter difcharged by the
          continual flafhing  of  the aurora borealis, not to men-
          tion the fire-balls and meteors called falling ftars, which
          are very often to be feen in the northern countries. In
          the fummer-time, the air which is an electric, heated by
          the  rays of the fun, is excited or made to  part with
          the fluid to the vapours  contained in it; and it  is  the
          unequal or oppofite electricity of the  clouds to  one
          another, or to the earth,  which produces the lightning.
          But in winter, when the air, earth, and vapours,  all be-
          come electric, they cannot difcharge fparks from one to
          another as before ;  but the whole, as one connected  and
          vaft electrified  apparatus, difcharges the matter almoft
   101    in a continued ftream for many months.
Heat.light,   From a confideration of  thefe and other phenomena
cold, and  of nature, as well  as of the beft experiments which
 ll^ff'/*'  nave  hitnert0 Deen  made, we muft confider  fire in  the
1 fe  c  .  ?  abftract as an omniprefent  fluid,  of fuch fubtilty as to
verfal fluid prevade all terreftrial fubftances. When by any means it
          is made to diverge every way as from a centre, there it
          operates as heat; expands, rarefies, or burns, according
lightning
take place
in fummer
and not in
winter.
  to the intenfity of its action.  Proceeding in ftraight Nature  of
  and parallel lines, or fuch as diverge but little,  it acts ^eat-____
  as light, and fhows none of that power difcoverable in     *
  the former cafe,  though this  is eafily difcoverable by
  making it converge into a focus.  In a quiefcent ftate,
  or where the motion is but little, it preffes on the fur-
  faces  of bodies, contracts and diminifhes them  every
  way in  bulk, forces  out the expanding  fluid within
  their  pores, and then acts as cold.   In this cafe alfo,
  being obliged to fuftain the  vehement action of that
  part of the fluid which is in motion, it flies with violence
  to every place where the preffure is leffened,  and pro-
  duces all the phenomena of El e c t r i c i t y .

             § I.  Of the  Nature of  Heat.
                      .                                 I0%   *
    The manner in which the phenomena of heat m:iv Particular-
  be folved,  and its  nature underftood, will appear  from f«Iution of
  the following propofitions.                           t,le Pheno-
    1. It is in all cafes  obferved,  that when light pro- !"ena °
  ceeds in confiderable quantity from a point, diverging
  as the radii of a circle from its centre, there a confi-
  derable degree of heat  is found to exift, if an  opaque
  body, having no great reflective power, is brought near
  that point.
    2.  This action  of the light, therefore, may be ac-
  counted the ultimate caufe of heat, without having re-
  courfe to any  farther fuppofitions ; becaufe nothing
  elfe befides this action is evident to our fenfes.
    3. If the  point from which the rays are emitted is
 placed in a tranfparent medium, fuch as air or water,
 that medium, without the  prefence of an opaepie body,
 will not be heated.
   4. Another caufe of  heat, therefore, is the refift-
 ance of the parts of that body on which the light falls,
 to the action mentioned in  Prop. 1. Where this refin-
 ance is weak, as in the cafes juft mentioned, the heat ii
 either nothing, or  very little.
   c. If a body capable of reflecting light  very  co-
 pioufiy is brought near the lucid point, it will not be
 heated*.                                             * See
   6. A penetration of the light, therefore, into the the article
 fubftance of the body,  and likewife a confiderable de- v?r'["'j>-
 gree of refiftance on the part of that body to the action GU^'
 of the light,  are the requifites to produce heat.
   7. Thofe bodies  ought to conceive the greateft  de-
 grees of heat into whofe fubftance the light can beft
 penetrate, i. e. which have the leaft reflective  power,
 and which moft ftrongly refift  its action ; which is  evi-
 dently  the cafe with black  and folid fubftances.
   8. By  heat all bodies are expanded in their dimen-
 fions every way, and that in proportion to  their bulk
 and the quantity of heat communicated to them.
  9. This expanfion takes place not only by an addi-
 tion of fenfible heat, but likewife of that which is latent.
 Of this laft we have a remarkable inftance in the  cafe
 of  fnow mixed with fpirit of nitre.   The fpirit of
 nitre contains a certain quantity of latent heat, which
 cannot be feparated  from it without effecting a change-
 on the fpirit  itfelf;  fo that, if deprived of  this heat,
 it would no longer be fpirit of nitre.—Befides this,  it
 contains a quantity of fenfible heat, of a great part of
which it may be deprived, and yet retain its character-
ise properties as  nitrous  acid.  When it is poured
upon fnow, the latter is immediately melted by the ac-
tion of the latent heat in the acid.   The fnow  cannot
                          C a                    be 
10
C   H   E    M    I   S   T    R   Y.
Theory.
K.MTfof be melte ! or converted into water, without imbibing a
Meat.___ quantity of latent beat, which it receives immediately
       "* limi  the  acid which melts it.   lhn  the acid cannot
         pirt with  the heat without dccompolition ;  to prevent
         which,  its  fenliblc heat occupies the  place of  that
         which has entered the fnow and liquefied it. The mix-
         ture then  becomes  exceedingly cold,  and the heat
         forces into it from all the  bodies in the neighbour-
         hood ; fo that, by the time it has recovered that quan-
         tity of fenfible heat which was loft,  or arrived  at the
         temperature of the atmofphere around it,  it will con-
         tain a confiderably larger quantity of heat  than it o-
         riginally did, and is therefore obferved to be expand-
         ed in bulk.   Another inftance of this expanfive power
         of Jaunt heat is  in the  cafe of fteam, which always
         occupies a much larger fpace than the fubftance from
         which it was produced ; and this whether its tempe-
         rature is greater  or  lefs than the furrounding atmo-
         fphere.
            ro. The difference between latent and fenfible heat,
         then,' as far as we can conceive,  is, that the expanfive
         power of the former is directed only againft the particles
         of which the body is  compofed ; but that of the latter
         is directed alfo againft other bodies. Neither doth there
         feem to be any difference at all between them farther
         than  in quantity.   If water,  for inftance, hath but a
         fmall quantity of heat, its parts are  brought near each
         other, it contracts in bulk,  and feels cold.  Still,  how-
         ever, fome part  of the heat is detained among the a-
         qucous particles,  which  prevents the fluid from con-
         gealing into a folid  mats.  But, by a continuation of
         the contracting power of the cold, the particles of wa-
         ter are at laft brought fo  near each other that the in-
         ternal or latent heat is forced  out.  By this discharge
         a quantity of air is alfo  produced,  the  water is con-
         gealed,  and the  ice occupies a greater fpace  than the
         water did ;  but then it is full of air-bubbles, which are
         evidently the caufe of its expanfion.  The  heat then
         becomes fenfible, or,  as it were,  lies on the outfide of
         the matter; and consequently is eafily  diffipated into
         the air, or Communicated  to  other bodies.   Another
         way in which the latent heat may be extricated is by a
         eonftant addition of fenfible heat.  In this cafe the bo-
         dy is firft railed  into vapour, which for fome time car-
         ries off the redundant quantity of heat.   But as the
         quantity of this  heat-is continually increafed, the tex-
         ture of the vapour itfelf is at laft totally deftroyed.  It
         hevomes  too  much  expanded to contain the  heat,
         which is therefore violently thrown out on all fides into
         the atmofphere,  and the body  is faid to burn, or be on
         fire.  See Combustion, Flame, and  Icnition.
            ii. Hence it follows,  that thofe bodies which have
         ihe leaft fharc  of latent  heat,  appear  to  have the
         greateft quantity of fenfible heat; but this  !^ only in
         appearance, for  the  great  quantity they feem to con-
         tain is  ow ing really to  their  inability to contain it.
         Thus, if we can fuppofe a fubftance capable of tranf-
         mitting heat through it as fall as it received it;  if fuch
         a fubftance  was  fet over a fire, it would be  as hot as
         the fire  itfelf, and yet the moment it was taken off,  it
         \ otild be perfectly cool, on account of its incapacity
         to detain the heat among the particles of which it was
         compofed.
            \2. The heat, therefore, in all bodies confifts in a
         ferula  siA.rn tuiion of the  elementary  fire within
them tending from a centre to a circumference,  and Nature of
thus making an effort to feparatc  the particles of Heat.
the body from each other, and  thereby to  change its >"~~*
form or mode of exiftence.  When this change is ef-
fected, bodies are faid to be diflipatcd in vapour,  cal-
cined,  vitrified, or burnt, according to  their different
natures.
   13.  Inflammable bodies are fuch as arc eafily raifed
in vapours; that is, the fire calily  penetrates  their
parts,  and combines with them in Inch quantity, that,
becoming exceedingly  light,  they arc  carried up by
the atmofphere.   Every fucceeding addition of heat
to the  body increafes alio the quantity of lattnt  heat
in the vapour, till at laft, being unable to rclifl its ac-
tion, the heat breaks out all at once,  the vapour is con-
verted into flame,  and is totally decompofed.   Sec the
article Flame,  and Prop. 10.
   14.  Uninflammable bodies are thofe w hichhave their
parts more firmly connected, or otherwife difpofed in
fuch a  manner,  that the particles of heat cannot eafily
combine with them or raife them into vapour.
   15.  Heat therefore  being only a certain  mode of
the action of elementary fire, it follows, that the ca-
pacity  of a bedy for containing it,  is  only a certain
conflitution of the body itfelf, or a difpolition of'its
parts,  which can allow the elementary fire contained in
it to exert its expanfive power upon them without be-
ing diflipatcd  on  other  bodies.   Thofe  fubftances
which allow the expanfive power of the fire to operate
on their own particles  are faia  to contain a great deal
of heat; but thofe which throw it  away from them-
felves upon other bodies, though they feel very hot, yet
philofophically fpeaking they contain very little heat.
   16.  What is called the quantity of heat contained in
any fubftance,  if  we would  fpeak  with the ftrictefl
propriety, is only the  apparent force of its action, ei-
ther upon the parts of the body itfelf, or upon other
bodies in  its neighbourhood.   The  expanfive force of
the elementary fire contained  in any body upon  the
parts of that body, is the quantity of latent heat contained
in it;  and the expanfive force of the fire exerted upon
other bodies which touch or come near it, is the quan-
tity offenfibleJieat it contains.
   17.  If  what  we call heat confifts only in  a certain
action of that fluid called elementary fire, namely, its
expanfion, or acting from a centre to a circumference,
it follows, that if the  fame fluid act in a manner di-
rectly  oppofite to the  former, or prefs upon the par-
ticles of a body  as from a circumference to a centre,
it will then produce effects directly oppofite to thofe
of heat, i. e. it will then be abfolute cold, andproduceall
the effects already attributed to Cold. See that article.
   18.  If heat and cold then are only two  different
modifications of the fame fluid,  it follows, that if a hot
body  and  a cold one are fuddenly brought near each
other, the heat of the one ought to drive before it  a
part of the cold contained in the other,  i. e.  the  two
portions of elementary fire acting in two oppofite ways,
ought  in fome meafurc to operate updh one another
as any two different bodies would when  driven againft
each  other.  When  a hot  and a cold body therefore
are brought  near each  other,  that  part of the  cold
body  fartheft from the hot one  ought  to become colder
than before, and that part of the hot body fartheft from
the cold one ought to become hotter  than be/orc 
Theory.
CHEMISTRY.
General      19. For the fame reafon, the greateft degree of cold
Effects of  in  any body ought  to be no obftacle, or at leaft very
Heat.     little, to  its conceiving  heat, when put in a proper
'   *~mmm' fituation.   Cold air, cold fuel, &c. ought  to become
          as intenfely heated, and nearly as foon, as that which
          is hotter.
            The two laft propofitions are  of great importance.
          When  the  firft of them is thoroughly eft^lifhed,  it
          will confirm beyond a doubt,  that cold is a pofitive, as
          well as heat;  and that each of them has a feparate and
          diftinct power,  of  which the action of its antagonift
          is the only proper limit; i. e. that heat can only limit
          the power of cold,  and vice verfa.  A ftrong confir-
          mation of this propofition is the experiment related by
          M. Geoffroy ; an account of which is given under the
          article  Cold.   Another,  but not  fo well authen-
          ticated, is related under the article Congelation.
          -^De  Luc's  obfervation  alfo,  mentioned  by Dr
          Cleghorn, affords a pretty ftrong  proof of it;  for  if
          the  lower parts of the atmofphere are cooled by the
          paffage of the fun's rays  at fome diftance above, and
          it hath been already  fhown  that they do not attract
          the  heat from the  lower parts, it follows, that they
          muft expel part of the cold from the upper regions.—
          The  other  propofition,  when fully eftablifhed, will
          prove,  that  heat and  cold are really convertible into
          one another; which indeed  feems not improbable, as
          we fee that fires will burn with the greateft fiercenefs
          during the time of intenfe frofts, when the coldeft air
          is admitted to them ;  and even in thofe difrnal regions
          of Siberia, when the intenfe cold of the atmofphere is
          fufficient to  congeal quickfilver,  it cannot be doubted
          that fires will burn  as well as in this country*; which
          could not happen if heat was a fluid per fe, and capable
          of being carried off, or abfolutely diminilhed in quan-
          tity,  either  in any part of the atmofphere itfelf,  or in
          fuch terreftrial bodies as are ufed for fuel.

              •   § 2.  Of the general Effects of Heat*

            Having  faid thus much  concerning.the nature of
          heat in general,  we come now to a particular explana-
          tion of its feveral effects, which indeed conftitute the
          whole of the active part of chemiftry.—Thefe are,
            I.  Expanfion, or increafe of bulk in every direction.
          This  is  a  neceffary confequence of  the  endeavour
          which the fluid makes to efcape in all directions, when
          made to converge into a focus.  The degree of expan-
          fion is unequal in  different  bodies, but in  the  fame
   iqx     body is always proportionable to  the degree of heat
hrftru-     applied.   There are two different inftruments  in ufe
ments for   for afcertaining the degrees of expanfion ;  and as we
meafunng  have aiready fhown, that the degree of heat can only
the cxpan- ^ known by the expanfion, thefe effects of heat  upon
dies' °  °~ t^ie nl^-ruinent are nfually taken  for the degrees of
          heat  themfelves.  Thefe inftruments  are called the
          Thermometer and Pyrometer.   The former is
          compofed of a glafs tube,  with a globe or rather oval
          tube at one end, and exactly clofed at the other : it is
          moft ufually filled with mercury or  fpirit of wine ; but
          mercury is generally preferred on account  of its ex-
          panfions being more equable than thofe of any other
          fluid.   It  has the  difadvantage, however,  of being
          fubject to congelation; which is not the cafe with fpi-
          rit of wine, whenyery highly rectified.  Spirit-of-wine
                                                        21
thermometers,  therefore  ought not to be entirely dif- General
ufed, but feem rather a neceffary part of  the chemi- Effects of
cal apparatus, as well as thofe made of mercury.      Heat-
   As no thermometer  made with any  fluid can mea-    I04
fure either  the degrees of heat about the  point at Wedge-
which it boils,  or the degree of cold bedow  which it wood's im-
congeals, inftruments  have been contrived by which provemenc
the  expanfion  of folid bodies,  though much lefs than «f the ther-
what is occafioned by  an equal degree of heat in a momeU
fluid, may become vilible.   Thefe were ufually called
Pyrometer*; but Mr Wedgewood has lately contrived
a  method of connecting the two together, in which
the higheft degree of heat,  exceeding even  that of a
glafs-houfe furnace,  may be meafured as accurately as
the more moderate degrees by the common mercurial
thermometer.   See Thermometer.                   io^
   Expanfion in fome cafes does not appear to be the inftances
effect of heat,  of which we have two remarkable in- of bodies
fiances,  viz. of iron, which always expands in cool- expanding
ing after it has  been melted ; and of water, which ex- ^y  co^d*
pands with  prodigious force in the  act of freezing.
The power with which iron expands in the  act of
palling  from a  fluid to a folid  ftate, has never  been
meafured, nor indeed does it feem eafy to  do fo; but
that of  freezing water has been accurately computed.    ro6
This was done  by the Florentine Academicians, who Prodigious
having filled an hollow brafs ball of an inch diameter, force exert-
with water, expofed it to a mixture of fnow and fait, eJ bX wa-
in order to congeal the water, and try whether its force te.r  m   ~
was fufficient to burft the ball or not.  The ball, being Zins'
made very ftrong,  refitted the expanding force of the
water twice, even though  a confiderable  part of its
thirknefs had been  pared off when it was perceived
too ftrong at firft.   At the third time it burft  ; and by
a  calculation founded on the thicknefs  of the globe
and  the tenacity of  the metal, it was found  that the
expanfive power of a fpherule of water only one inch
in diameter, was  fufficient to overcome a refiftance of
more than 27,000 pounds, or 13 tons and an  half.        xoj
   A power of expanfion fo prodigious, little  lefs than Ufed as an
double that of the moft powerful fleam-engines, and argument
exerted in fo fmall a body,  feemingly by the  force of for tne ex""
cold, was thought to be a very  powerful argument in lfte"ce of
favour of thofe  who fuppofe  cold to be a pofitive fub- D°rltivSe
fiance as well as heat; and  indeed contributed  not a fubftance.
little to  embarrafs  the  oppofite party.   Dr  Black's    108
difcovery of latent heat, however, has  now afforded Explained
a very eafy and natural  explication of this phenome- bv Dr,
non.  He has fhown, that,  in the act of congelation, Black'sthe—
water is not cooled more than it was before, but ra- 0I
ther grows warmer : that as much heat is discharged,
and paffes from a latent to a fenfible ftate, as, had it
been applied to w7ater in its fluid  ftate, would have
heated  it to 1350.  In  this procefs the expanfion is The*exp
occafioned by a great number of minute bubbles fud- fion produ-*
denly produced.   Thefe were formerly fuppofed to be ced  by the
formed  of cold  in the abftract; and to be fo fubtile, extrication
that, inlinuatmg themfelves into the fubftances of the
fluid, they augmented its bulk,  at the fame time that,
by impeding the  motion of  its particles  upon each
other, they  changed it  from a fluid to  a  folid.  Dr
Black, however, has demonftrated, that thefe  are only
air extricated during the congelation ; and to  the ex-
trication of this air he very juftly attributes the prodi-
gious expanfive force exerted by freezing water.  The
                                             "enly
ory
tent heat.
109
of air-bub-
bles. 
£2
General
i flva* of
Heat.
                                      C    H    E    M
          only q icftion, therefore,  whichnow remains  is, By
          wh.u means this air comes to be extricated, and  to take
          up more room than it naturally doo in the fluid ? To
          this  wc can fcarcc give any other anfwer, than that
          pan of the heat which is difcharged from the freezing
          water combines with the air in its unclaliic ftate, and,
          by rcftsring its elasticity, gives  it that extraordinary
          force, as wc fee alfo in the cafe of air fuddenly extri-
          cated in the  e xplofion of gunpowder.  Thus  expan-
          fion, even in the cafe of freezing, is propenv an effect
          of heat ; and muft therefore be con'"     :  ?s a  pheno-
          menon unifbrmly and certainly attending .'. c ry,; n of
    m   he it, and in all cafes to be afcribed to it.
 Capacity of   The only way in which the element or  fluid of fire
 • body for can be fuppofed to act,  and  the ttay in which we can
 f"nta,mng have a rational idea of its being  able to produce both
 f"!' with 'lcat ancJ col(* accor(hng to the  diverlity of its  action,
 theadion  has  been already  explained  fo fully,  that it is needlefs
 of heat up- at prefent to enter into any further difcutlion  of the
 on that bo- fubject.  It will  eafily appear, that  the  capacity for
 dy.       containing  heat  is  nothing  different  from the  action
          of heat upon that body in expanding, and at laft alter-
          ing its form in fuch a manner, as cither to be able to
          infinuate itfelf among the particles in much greater
          quantity than before,  ftill  retaining its internal ac-
          tion, though the external one becomes imperceptible;
          or fcattcring  them  in  fuch  a manner, that it  breaks
          forth in great quantity in its peculiar appearances of
          fire and light; in the former cafe producing vapour or
    IX1    f:uoke,_ and in the latter flame, as (hall afterwards be
 tmpoffihili- more fhlly explained.   It muft likewife appear,  that
 ty of deter- to determine  the  quantity  of  heat  in any body is
 mining the altogether  impoflible :  and with regard  to  xhe  lowcft
 quantity of je-rec Qf j)Cat  of touj  cxpulfion  of  that ih.iid,  fo
 [Rilt 3I1V
 body con-  ^"ar *"lom being able to determine  what it is,  the pro-
          bability muft  be,  that  nature docs  not admit of any
          fuch  thing ;  for if heat confifts in the expanfive ac-
          tion  of a certain  fluid, and cold* in its oppofite or
          contractile  action,  there is very  little reafon to  fup-
          p.ife  that the  conflitution of  nature will allow anyone
          of thefe actions  intircly to  ceafe, as it ih es not ap-
          pear  by what means it could again be renew ed.  Cold,
          as wc have  already feen, always tends to produce elec-
          tricity ; and the connexion  betwixt that mid fire is fo
          ltron;,  that we cannot  fuppofe the former to be car-
          ried  to any great extreme without .producing the lat-
          ter.   Whatever we may therefore fuppofe concerning
          the capacities  of different bodies  for containing heat,
          or concerning the point of total privation of heat, muft
          Ik- altogether void  of foundation.  A rule, however,
          has been given by Mr Kirwan for finding the point of
          to:al  privation, v\ hich, together  with its  demcmilra-
          tion, wc fhall fubjoin ;  and  as it  is  neceffary for the
          better  underftanding of this, to call to remembrance
          what Ins been faid concerning the difference between
          the temperatures and fpecific heats of bodies,  we  fhall
          infert an epitome of the  doctrine frmn Mr Nicholfon.
            <'  If two eqtu.l  bodies of  different kinds and tem-
          peratures be brought into conrr.ct, the  common tem-
          perature, will feldom, ,:f ever, be the mean betwixt the
          tuo original temperatures; that is t> l"  y,  the furplus
          of heat in the hotter body will be  unequally divided
containing  between ther.., and the proportion of this furplus re-
hr'-t, &c.   tained by e..Ji body will exprefs  their  refpective dii-
          po:;tions, a.5ni:ics, or capacities,  lhr he.it.—if,  there
I   S   T    R   Y.
Theory.
taint.
M:Ni-:.o
Con's ac-
count o£

tieso! Wei-
ll, es for
 fore, a given fubftance, as for example fluid water, be emend
 taken as the itandard of companion,  and its capacity F.iifci-. of
 for  heat be called one, or unity,  the refpeetive capa- Heat.
 cities of their bodies  may be determined by cxperi- v~~v
 mem,  and exprcllcd in numbers in the fame manner
 as lpceific gravities ufually  are.  And  becaufe  it  is
 cftabliihed as well from reafon as experiment, that the
 fame cap.:  ity for heat obtains in all  temperatures of a
 piven body, fo long as its ftate of folidity,  fluidity, or
 vapour is not changed, it v\ ill follow, that the whole
 quantities oi   ' i in equal bodies of a given temperature
 will be  as thofe cax  ••..es.  And as  the  rcipcctivc
 quantities of matter, in bodies of equal volume,  give
 the  proportions  of their  fpecific gravities,  fo the re-
 fpeetive quantities of heat in bodies of equal weight and
 temperature give the proportions of their fpecific heats.
   " A greater capacity  for  heat, or greater fpecific
 heat, in a given body, anfwers the fame purpofc  with
 refpect  to  temperature as an increafe  of the mafs;
 or  the  quantity of  heat  required to  be  added  or
 fubductvd, in order to bring a body to  a given tempe-
 rature, will be as its capacity or fpecific heat.
   " The capacities not only differ in various bodies,
 'mt avP in the fame body, according as it is either
 in a { lid, fluid, or vaporous il.uc.   All the experi-
ments  hitherto made confpire to fhow,  that the  capa-
 city, and coufequently the fpecific heat, is greateft
in the vaporous, lefs in the fluid," and leaft  in the fo-
lid ftate.
  " The quantity of heat that conftitutes the difference
between  the feveraLftatcs,  may be found in degrees of
the  thernic cter   Thus if  equal quantities of water
at 1620 and ice at 320 of temperature be mixed, the
ice melts, and the common temperature becomes 320 ;
or otherwife, if equal quantities of frozen or fluid wa-
ter, both at 320, be placed in a like fituation to acquire
heat from a fire,  the water will become heated to 1620,
while the ice melts without acquiringany increafe of tem-
perature.   In either cafe the ice acquires  1300 of heat,
which produces no other effect than rendering it fluid.
Fluid water, therefore, contains not only as much more
heat than  ice,  as is indicated by the  thermometer,
but  alfo  1300,  thar  is in fome  manner or  other cm-
ployed  in giving it  fluidity.  And as fluid water can-
not become ice without parting with 130° of heat be-
fides what it had above 320 in its temperature ; fo al-
fo fteam cannot  become condenfed  into water with-
out imparting  much more heat  to the matters  it  is
cooled  by, than  water at the fame temperature would
have done.
   " The heat employed in maintaining the fluid  or
vaporous form of a body,  has been called latent heat
becaufe it does not affect the thermometer.
  " From the confidcration of  the fpecific heats  of^i-Kir-
 the fame body  in the two ftates of fluidity and folidi- wan'stheo-
 ty, and the difference between thofe fpecific heats,  is rem for
 deduced a  method of finding the number of  ih <.-c, s finding the
 which  denote the temperature of any lx>dy immcc'i;■•<:- roilltofto-
 ly after congelation, reckoned from  the natural /fro, tal rrifva"
 or abfolute privation of heat.  The rule is; multiply h° t
 the  degrees of heat required to ree'uee  any folid to a
 fluid ftate, by the number expreffing  the fpecific heat
 of the fluid : divide  this product 1  . the difference I e-
 tv.een  the  numbers expreffing the  l\ < cific heat of the
 body in each ftate :  the q> y.;e..t v, iil  be the number
                                                 of 
 Theory.
          of degrees of temperature, reckoned from an  abfolute
          privation of heat.
            " This theorem is Mr Kirwan's, and maybe proved
          thus.   Let s reprefent the required temperature of the
          body'j uft congealed, /=the  number of degrees that
          exprefs the heat required to reduce it to fluidity, n —
          the  fpecific heat of  the folid, and m — the fpecific
          heat of the fluid.  Then s+l : s r: m : n.   Whence
                In
          s —_______=: the temperature from the natural zero
              m—n
          in ther mom etrical degrees of the  fluid.   But becaufe
          the  actual fall of the thermometer is to be produced
          by cooling the folid, we muft pay attention to its capa-
          city.  The  quantity of  heat required to  produce  a
          given change of temperature in  a  body is as its  capa-
          city ;  and consequently the  changes  of temperature,
          when the quantity of heat  is given, will be inverfely
             ,       . .      ,    c               In    In
          as the capacities : therefore, /; : m : :-----------■ — s.
                                             ?n—n :m—u
          which is the rule abovementioned.
            " If the data /, m, and n, be  accurately obtained
          by experiment,  in any one inftance, and the difference
          between the zero of Fahrenheit's fcale and the natural
          zero he thence found  in  degrees of  that  fcale, this
          difference will ferve  to reduce all temperatures to the
          numeration which commences at the natural o.  So
          that i being known  in all cafes, if any two of the
          quantities /, m, or /;, be given in any body, the other
          may be likewife had.   For /= Jy/~—; and m = -ii-
                                        m              s—/
          ~n i   ^.sm-—Im
          and n —_______.

            " To give an example of this curious rule, let it be
          required to determine how many degrees of refrigera-
          tion would  abfolutely deprive ice of all its heat ?  The
          degrees of heat  neceflary to melt ice are 130 ; and the
          fpecific heats of ice and water are as 9  to  10.   The
          number 130 multiplied by 10, produces  1300, and
          divided  by the  difference  between 9  and  10 quotes
          1300 :  therefore if ice  were cooled 1300 degrees be-
          low 320, or to—1268 of Fahrenheit's fcale, it would
          retain no more  heat."
            II.  Fluidity is another effect of heat, and is capable
          of taking place in all bodies hitherto known,  when
          the  fire is carried  to a certain pitch.  Theories have
          been invented,  by which fluidity was afcribed to the
          fmoothnefs  and  round figure of the particles whereof
          bodies were compofed,  and folidity to  an angular or
          irregular figure.   It has alfo been afcribed to a ftrong-
          er degree  of attraction between the parts of  folids
Fluidity to than of fluids.   Dr Black, however,  has fhown, that
be afcribed jn the cafe of melting ice, we are certainly to afcribe
to the ah-  tj,e aCqL1jred fluidity of the water to the abforption of
 orp ion o  jieat<   This was determined by a decifive experiment,
          in which he expofed a  Florence-flafk full of water to
          the atmofphere  in a warm room,  when he found that
          the heat in the  air evidently  left it, to flow  into the
          ice in the bottle, and reduced it to fluidity.  The air
          thus deprived of its heat,  he felt fenfibly defcending
          like a cold hlaft  from the bottle, and continuing to do
          fo as long as any of the ice remained unthawed; yet
          after it wis all  melted, the temperature  of the fluid
          was  no more than 320.  Different degrees of heat are
          requilite for converting different folids into fluids, for
          winch fee the Table of Degrees of Heat.
CHEMISTRY.
23
"5
   This theory receives an additional confirmation from General
the quantity of heat which is always known to be produ- KffeA of
ced by the converfion of a fluid into a folid.  And that t  eat^
this is really the cafe appears,  1. From what happens in    u6
the congelation of waters, it appears that ice is formed Senfible
very llowly, and with feveral circumftances which fup- heat pro Ju-
port the theory.—Thus, if we fuppofe equal quantities ce(1 b/ thc
rr          , J   .     1 • 1  •     1       11   r__a  conversion
of water to the  air, which is perhaps 10 below irolt, 0f agui(j
and add to  one  of thefe a fmall quantity of fait °r int0 a folid.
fpirit  of wine,  and obftrve the  cooling of each, we
fhall find them both grow gradually colder, until they
arrive at the temperature of froft : after which the wa-
ter containing the fait will continue to grow colder,
until it has arrived at  the temperature  of the air, at
the fame time that only a fmall quantity of the other
water  is converted into ice!   "Yet were the common
opinion juft, it ought all to have been congealed by this
time;  inftead of which,  it is  fcarce  grown a degree
colder during the whole time.  Its remaining at the
fame temperature for fo long a time, fliows that it has
been communicating heat to the atmofphere ; for it is
impoffible  that any boely can remain in contact with an-
other that is colder, without communicating heat to it.
Whence then comes this heat ?  There  muft be fome
fource adding to the fenfible heat of the water, fo as to
keep  its temperature to the freezing point: and  this
fource of heat muft be very confiderable ; for it wiD
continue to act for a very long time before  the  water
is changed into ice ; during all which time, even to the
laft drop,  the water is not a degree colder than 320 of
Fahrenheit's thermometer.   This, therefore, is the
latent heat of the water, which had formerly entered
into it during its tranfition from ice to a fluid ftate.
   A ftill ftronger argument is derived  from the  fol- Argument
lowing experiment;  which evinces that the fluidity of in fupport
water really  depends upon its latent heat, and that of thetheo-
the fenfible heat is only a mean or condition to its T from
containing the latent heat. This experiment confifts wa!f* re"
in expoling water contained in a covered beer-pdafs to U1*1]"1!?.
 ,   •/-      ijj-/-l   -i       11      ,&      fluid tho
the air of  a cold frofty night ; and when the atmo- cooiea Dc-
fphere is at the temperature of perhaps io° or 120 be- low 3a0.
low froft,  the  water  will acquire that temperature
without freezing: fo  that the fluidity  of the  water
does not altogether  depend on the quantity of fen-
fible heat contained in it.  The congelation, however,
may be  brought on by touching it  with  a bit  of  ice,
with the extremity of a wire, by a Ihock upon the
board, or  otherwife dillurbing it; and we then fiml
the temperature  fuddenly raifed up to 320.   This
fhows plainly, that the water has a difpofition to re-
tain the quantity of latent heat,  upon which its  flui-
dity muft immediately and neceflarily depend ; and it
retains it with a certain degree of force, fo as to keep
the water fluid in a temperature below that in which
it ufually parts with the latent heat and congeals.  By
difturbing it, however, we inftantly bring on the con-
gelation, which  cannot take place without an extri-
cation of the latent heat;  which  then, being changed
into the ordinary or moveable heat, raifes the thermo-
meter as ufual.   The quantity of heat difcharged from
the firft fmall portion of ice formed  in  the water is
fufficient to prevent any more  latent  heat from fepa-
rating,  and confequently from any  more ice  being
produced till more  of  the fenfible heat is abftracted.
  This doctrine extends not only to fuch bodies as
are actually converted from a folid to a fluid, or from 
n
CHEMISTRY.
<: n ral
k.SccU of
Hear


H.-Mthe
laulcot the
f 'ftncft of
bodice ap-
p aching
to fluidity.
   Tt9
AM..r;> •.;,.!,
of heat the
onivcrfjl
caufe of
fluidity.
   110
Vapour
formed by
the .lbforp-
rion of la-
rrnt heat.
   Ill
^"tp-.ri-
mentJ by
Dr lUack
on the con
wrfion of
water into
vapour.
a fluid to a f>!id ftate, k:: to fuch as arc in a kind of
middle (late betwixt folidity  and fluidity; for every
degree oi  ib ft nets depends on a certain degree ot heat
con: lined  in  the bod),  Thm, for inftance, melted
Wi\, allowed to cool flowly,  fi>on hecomes opaque and
coniutcnt ; but it malt be colder ftill before it attains
itb utmoft  degree of hardnefs.   Tiure  is therefore a
certain degree o( heat below which every body is folid,
and above  which every one is fluid ; the former being
called thecouge.t//;;g,  and the latter  the ;.'.:U;/:g, point
of bodies.
   By nuking experiments upon different fubftances,
the  Doctor was convinced that latent heat is  the uni-
vcrf.il caufe of fluidity ; and the doctrine holds good in
all the experiments that have hitherto been made upon
Ipermacea, bees-wax, and fome of the  metals.  If
they are melted, allowed to cool  flowly, and a thermo-
meter be immerfed into them, we find, that as long as
they continue fluid, their fenfible heat diminifhes very
faft ; but as foon as they begin to grow folid, the fen-
fible heat  continues greater than that of the air to
which they are expofed ; and during all this time it is
coiinu uniting heat to the air, without having its fen-
fible heat  diminilhed ; for the  latent heat within  the
fluid gradually receives a fenfible form, and  keeps up
the temperature, proving  a fource of fenfible hear,
which is communicated to the neighbouring bodies as
well as the furroundingair.  The foftnefs and ductility
of bodies depend on this alfo.
   III. Evaporation.   A  third effect of the action of
heat is that of converting bodies into vapour, by which
they are rendered fpccifically lighter than the furround-
ing atmofphere, and enabled to rife in it.  To account
for  this many theories have been invented ; but that of
DfcBl;; h, who accounts for it, as well ijs fluidity from
the abforption of latent  heat, is now univerfally  re-
ceived.  The circumftances by which he proves and il-
lullrates his doctrine  arc the following :
   i. When we attend to the phenomena of boiling wa-
ter, in a tea kettle  for inftance,  it may, when firft put
upon the fire, be about the temperature of 48" or 500.
In a quarter of an hour it will become heated to 2120.
It then begins to boil, and has gained 1620 of vapour in
that time.  Now, if the converlion of it into vapour  de-
pended on the quantity of fenfible heat introduced, we
may afk how long it  wiU be  neceffary to raife it all in
vapour ? Surely another quarter of  an hour fhould be
 fufficient; but this is far  from being the. cr.ie.   Dr
 Bl'ck made fome experiments  upon this fubject in
 conjunction with another gentleman.  Having the op-
■ portunity  of what is called a kitchen-table or a thick
 plate of call iron,  one end of which  was made fenliWy
 red-hot,  they fet upon this fome iron veffels with cir-
 c.ihir flat  bottoms,  of about four inches diameter,  and
 which contained a quantity of v. iter.  The  tempera-
 ture of the water was :.^i, as alfo when it began to
boil;  and when the whole of it was boiled away, it was
found, that  when fet on the table its temperature  had
been SA° ' i" f°ur minutes ll begm to boil, and in that
fpace of time received iy8° degrees of heat.   H;J  the
evaporation, therefore, depended merely on the quan-
tity of fenfible heat introduced, it ought to h^ve been
diflipated entirely in  a fingle minute more.   It was,
however,  ii minutes In dimpating ;  and therefore  had
•^ccivcd^Jo?. degrees of heat before i*. viai  all cvapo-
                                           1
Theory.
rated.   All this time, therefore, while the water con-
tinued to boil, it was receiving a great quanta) of luat,
which muft have been  flowing  equally fait out ol it ;
for the veil'el.was no hotter, and the iron plate  conti-
nued equally hot, the whole time.   The veilcls were
of different lhapo, fome of them cylindrical, fome co-
nical, others \\ idening upwards ; one of the dcligns of
the experiment berhg to fhow how far the evaporation
was retarded by the particular form of the veflels.  By
fufpending a thermometer in the mouth of one of the
evaporating veffels, the heat of the fteam was found to
be exactly 212°;  fo  that  as  the great quantity  of
heat abforbed was found neither to have  remained in
the water, nor to have been carried away by the fteam
in a fenfible maimer, we have nothing left  to fuppofe,
but that it flew off as one of the component  parts  of
the fteam in a latent ftate.
   2. In an experiment to fhow the fixednefs of the
boiling point of water, Dr Black inclofed fome of that
fluid in  a ftrong vial having a thermometer in it, and
flopped clofe with a cork.  By  the application of heat
he hoped now to be able to raife the thermometer fome
degrees above the boiling point, which would be the
natural confequence of the confinement of  the fleam.
When this was done, he pulled out the cork, and fup-
pofed that the water would now all fly out in  vapour :
but in this he was totally difappointed ; a fudden and
very tumultuous boiling enfued, which threw out fome
of the water ; but though fome quantity of fteam like-
wife iflued, the quantity of water was not confiderably
diminiflied.  The  vial had  been heated to 200 above
the. boiling point,"but almoft inftantly cooled down to
2120, when the cork was taken out.
   3. Mr Watt,  in  making  fome experiments  on the
force of fleam, had occafion  to  ufe Papin's digefter,
with a  pipe proceeding from its fide; the orifice  of
which was fhut with a valve preiled down by one end
of a lever.  Thus he heated fteam to 4000 of Fahren-
heit ; after which, having fuddenly ftruck off the lever,
a quantity of fteam  flew out with cortfideiable noife,
and with fuch violence as to make an imprellion on the
ceiling of the room ;  but this noife  gradually diminifli-
ed, and  after ten minutes it ceafed entirely ; and upon
opening the machine, he found the greateft part of the
water ftill remaining.
   4. The change  of fenfible into latent heat in the
formation of vapour, appears ftill more evident  in the
boiling of water in vacuo.   Mr Boyle took a quantity
of water which had been previonfly boiled  to purge it
of its air,  and put it whilft hot under the receiver of an
air-pump. In confeepnence of this it began again to boil,
and continued boiling till it was only lukewarm, and it
foon arrived at this temperature;  fo that in this tafe
alfo the heat had difappeared during the converfion  of
the fluid into vapour.   Others have repeated the ex-
periment, as Boerhaave, Mufchenbroek; andRobinfon,
who lectures on chemiftry in Glafgow,  fays that the
heat diminiflies very fall till it  comes to  900 or 950
which feems to be the boiling point of water in vacuo.
As a confiderable p .1 ■ of the heat thus difappet.rs, aid
is to be difcovered m ither in the water nor in the va-
pour, we muft conclude that it enters the latter as part
of its compoliticn..
   ;. Thus alfo we may understand Ibme curious expe-
riments made V: Dr Cullen upon ether and other vo-
                                             htlih;
   122
Boiling
point of
water in
vacuo de-
termined
by Mr
Lcryle.
   1*3
And by
Mr Robin-
fon of Glaf-
gow.
* 
General
Effects of
Heat.

   124
fation of
vapour
 T heory.
          Utile fluids.  He employed fome perfons to make ex-
          periments upon  the cold produced  by evaporation;
          and willing to repeat them himfelf /';; vacuo,  he put
          fome of the moft volatile liquors under  the receiver
DrCulien's°f an air-pump.   One  of thefe was ether.   It was
experi-    contained  in  a glafs,  in which there was alfo placed
ments on   fome water.  When the air was extracted, the ether
coldprodu- Degan. to boil,  and to be converted  into vapour, till it
red >y eva- became p0 yeYy coi^ t^at it froze the water contained
          in the velfel,  though the temperature of the room was
          about  500.   Here  therefore there was  a quantity of
          heat which difappeared  all of a hidden ;  which it is
          plain could not be owing to its having any communi-
          cation with that of the atmofphere or other cold bo-
          dies, as they could not render it colder than they were
          themfelves.   Ether therefore  is to be confidered as a
          fluid fo volatile, that were it not for the preffure of the
          atmofphere it would be perpetually in the ftate of va-
    ia5    Pour-
Heatexpel-   6. That this heat which enters into the vapour is
led in great not deftroyed,  but  remains  in  a  latent  ftate,   is
quantity by eafily  proved; for we  find  that a great  quantity of
theconden- jjeat js expelled from vapour when it is condenfed again
r.i..Vn  ~F           111-     *  r 1    • •   11     _,, .  . °
          to  form the body it compofed originally.   This is ea-
          fily afcertained by obferving the quantity of heat com-
          municated to  the water  in the refrigeratory of a ftill
          by any given  quantity of liquid which  comes over.
          Thus,  if  the refrigeratory contain  100 pounds of
          water,  and the diftillation be continued  till only one
          pound has come over, fuppofing the water in the refri-
          geratory to have received 8° of heat; it is plain, that
          if  the whole of the  quantity thus  received could  be
          thrown into one pound of water, the latter would  be
          heated to  8000 ; which is fufficient to make an equal
          fpace of iron red-hot.   But that this quantity of heat
          is  received by the water in the refrigeratory has ap-
          peared from feveral experiments, which fhow that wa-
          ter, by being converted  into vapour,  abforbs between
    I26    8000 and 9000 of heat.
Mr Watt's   On this principle we may  explain  fome curious
experi-    experiments made  by Mr Watt with regard to the
ments  on   evaporation of fluids  in vacuo.   That gentleman had
the evapo-  forme(j a defign of converting water  into  fteam with
fahkin va- ^s exPence  °f  fuel> which  he imagined might  be
CU9t '      done by removing the preflure of the  air from the
          water, which he  thought would thus require a much
          fmaller quantity of fuel to convert it into vapour.   Dr
          Black, however,  perceiving that only the fmall quan-
          tity of fenfible heat the fteam  poffeffed could  thus  be
          carried off, informed him beforehand that his project
          would diot be found attended with  the advantages  he
          imagined.. aThe  experiment,  however, was made in
          the following  manner : A ftill was procured of tinned
          iron, the bedy of which refcmbled that of a  retort,
          with a veflel ferving as a condenfer ;  the whole appa-
          ratus b«[iig clofe,  excepting a little hole in the extre-
          mity of^th'e condenfing velfel.   He firft exhaufted this
          veflel of*air by holding the condenfer over the retort,
          in which fome boiling waterifas contained, until it was
          entirely converted  into  fteam.    He then fuddenly
          flopped the little hole, ana 1 emoved  the veffels from
          the fire ;  when, after they were aftoled,  there was a
          pretty perfect vacuum formed "try the  condemnation of
          the fteam.  The retort was then jsut  ™> the fire, and
          turn* d fo that the  pipe  and yConden/hig' vcncl fhould
CHEMISTRY.
25
 hang downward ; and plunging them into cold water, General
 heat was applied to the  ftill till  the water  boiled, as Effects of
 could be  known by the noife.  It was kept  boiling, Heat.
 till a quantity of fteam was pufhed over and condenfed
 with a very gentle heat,  the ftill feeling little warmer
 than  his hand.  After a certain  quantity had been
 diftilled, the apparatus was removed, and he had noted
 the heat of the water in the refrigeratory ;  but though
 the fteam all along came over with fo gentle a heat,
 he found the quantity communicated to the water in
 the refrigeratory to be furprifingly great, not lefs than
 rooo° ; fo that it would have been more than fufficient
 to heat the quantity of liquor which came over red-hot.   I2-
   IV. Ignition, or the caufing bodies to fliine or emit ignition a
 light  in  the  dark.   This may be confidered as a fpe- conflanr
 cies of inflammation, and fhall therefore be explained and ftcady
 under that head: here we fhall only obferve,  that ig- ^ffe<a of
 nition is a more Heady and eonftant effect of heat than ieat* g
 either the production  of fluidity or vapour ; and  ap- Au ignited
 pears not only to be the fame  degree with  regard to bodies e-
 any particular body, but the fame with regard to all qually hot.
 kinds of matter.  Dr Martin imagines,  that a red-hot
 piece of iron is hotter than a red-hot piece of ftone;  but
 if you put into a crucible an hundred different kinds of
 matter, as metals, glafs, &c. that are capable of bearing
 a red heat, they will all begin to appear luminous about
 the fame time, and their brightnefs will increafe equal-
 ly as their heat increafes.   But it is difficult to know
 at what point this begins, as we have no way of afcer ■
 taining the beginning or loweft degree of ignition  but
 by the effect  it produces on  our fight, and we cannot
 be fure  that we perceive the loweft degree of light;
 for we know that other animals fee objects with fuch
 light  as  appears perfect darknefs to us.   Sir  Ifaac
 Newton's method of determining this has been already
 mentioned.
   Dr Boerhaave entertained a  notion,  that  fome Metals
 metals,  after being once brought into a ftate of  fu- may be-
 fion, could be made no hotter ; and propofes  the pof- c°me vaft-
 fibility of this as a queftion,  " Whether the  heat of1? better
 metals can be increafed after they are melted ?" There afte5 the^
 is  not, however, the leaft doubt but that their heat may ^0 f^on;
 be vaftly increafed after they are melted;  and we know
 certainly that  fuch  as   are  of eafy fulion  may  be
 heated to  a vaftly greater degree after being melted;
 and why may not thofe requiring ftronger heats be the
 fame ?  We are fure that this is the cafe with filver,
which, after being melted, may be brought to fuch a
heat as to become too dazzling for the eye to bear  it.
 If Boerhaave's opinion were  juft,  it would be impoffi-
ble to caft any  metal into moulds,  becaufe it muft lofe
a little heat in being removed from the fire and in en-
 tering  the mould;  nor  would they receive a proper
impreifion if they did not contain a greater quantity
of heat than  was neceffary for their fulion.              T
   Ignition appears to be univerfal; and all bodies  ca- ignition an
 pable of fupportiug it without being converted into an univerfnl
 elaftic vapour that  cannot  be confined,  are  affected effe<a of
 the fame  way.  Water, which in its ordinary ftate ^rc#
feems very little capable of enduring this heat,  may be w r31
confined  in  ftrong veffels fo  as to  become capable of bTmacT^
melting lead, which is more than  halfway betwixt a fufikiently
red heat and that of boiling water.   Experiments with hot to melt
 the eolipile fnow alfo that  it can be made red-hot; lead;
 for when the fteam pafles through burning fuel, it can-
                         D                 '   no 
zh
CHEMISTRY.
Theory.
f icneral
l.Se&% of
Heat
   *3«
Diff.rcnce
nition ai.
inflamma
tion.
   I3>
Inflamma
tion de-
         not mils of being  nude  red hot.   Dr Black  has  alfo
         frequently feen the \apo ir of water healed hy throw-
         ing it  i .to the alh-pit of a furnace, fo as to produce a
         very large and tranfparent flame in riling up  through
         the vet:.  There is reafon therefore to conclude,  that
         ignitbm is one of the more general  effects of heat, only
         that fome bodies arc incapable of  it  until they be re-
         duced  to a ftate of vapour.
            V.  The laft of the  t heels of heat here to  be taken
         notice of is .  .fi./;■.;:.-.;:.',;:.  It differs from ignition in
betwm i}i- [i,|S) t}iat t]lc  bodies iubject to the latter gradually grow
         cooler as foon as  they  are taken out of the fire, with-
         out undergoing any confiderable change ; while thofe
         fubject to inflammation become continually hotter and
         hotter, communicating a vaft quantity of heat toothers,
         and undergoing a kind of decompoiition themfelves,
         infomuch, that by this means  they  have beeen thought
         to be  reduced to  their  cemltituent principles or  ele-
         ments.  Some fubftances indeed  feem to  be an excep-
         tion to this, as in  the open air they burn  totally away,
compounds wjt]10llt icaving any refiduum or producing  any  foot.
■lot deftroy Thefe are fpirit of wine, fulphur, and efpecially inflam-
hodics.    mablc air ; which laft, by a  proper mixture  with  de-
         phlo Mfticated air, may be  fo totally confumed,  that
         fcarce  a fiftieth part of the  two will remain.  On a
         careful examination of thefe  fubftances,  however, we
         find that there is by no means a total confumption,  or
         indeed, properly  fpeaking, any  confumption  at all, at
   j     leaft if we meafure the quantity of matter by the weight
Spirit of  0*  tne fiibftance employed.   Thus, if we are at pains
wine yield* to collect the  vapour of burning fpirit of \\ ine, we  will
a great   find,  that an acpieous  dew is collected,  which fome-
quantity of times  equals the fpirit of wine itfelf in weight. With
water by  rCtrard to fulphur,  the cafe is ftill more  evident ;  for
 >emg  urn- ^c vapour 0f this, when collected, not only equals
          but greatly exceeds the weight of the fulphur employ-
          ed ;  and  o i burning  dephlogifticatcd  aud inflam-
   i,{    mable air together, as much  water is found to be  pro-
Water pro- diced  as  nearly equals the weight of both airs.   In
iluccdby   like manner, when we collect the aflies, water, foot,
:hu deda-  ailj 0[]^  procured by burning any  of the common in-
Loa,hT" T  ^amuu^c  fubftances, we will find, that they in  ge-
ticateJSand nera^  c^cecd  the weight of the matter employ  ed.  The
iniLmma- great  walle of bodies by fire, therefore, is o\\ ing to the
rk air.    dihipation of the volatile principles they contain, which
          are carried off and rendered  invifible by being mixed
   j-6    with the atmofphere.
of ti:e ex-   The procefs of inflammation has long been explain-
v/t.nce of  ed from the preience of a fubftance cr.ilcd fl/cgiftcn in
phlo^nion. thofe  bodies which are fubject to it, and which is fup-
          p< fed to be the fame  in all  bodies belonging  to this
   1^7    chtfs ;  the differences between them arifing  from the
Dvniid by principles with which it is combined.  This doctrine,
          '.\hieh was firft introduced by Stahl, has given occa-
          iion to fuch various and difcord.int thenks, that the
          exiftence of  phlogifton has been lately denied  altoge-
          ther by.M. Lavoiuer,  who brought  in a new metho.l
          of folving the phenomena of fire,  hem,  and  ignition,
          without any affiftance from this  principle.
            The f  nidation of  M. Lavoilier's doctrine is  the
          ir  r   ^ of weight in met: Is by calcination.   This in-
          creafe he finds to  be pr.ciftly, or very nearly fo,  pro-
          \\ rtionable to the  dccrcule  of  weigh:  in the air in
          which :hcy are calcined.  His theory,  therefore, is,
          that in the a.-, of  calcination, the pure part of the air,
M.  1
lur.
.\	13* . jmc.ts
	n:'t it wn
f-cir. ;be	
1 •'. L" » i in.	rciici ight of t .hv
C.J	„ j.att-n.
which he calls  the lui.lify'fg or oviyv/.c.vj principle,
unites with the metal, aiu'l converts it into a calx.   In
like manner, in  fubftances truly inflammable, the heat
ami flame are fuppofed to proceed from the union of
the pure air, or the oxygenous principle, with the fub-
ftance,  and  converting  it into thofe principles which
are found to remain after inflammation.   Thus the in-
creafed weight of the fubftance is eafily  accounted for ;
while the inflammation, in his opinion, is nothing more
than  a  combination of  the  inflammable  body  it-
felf with pure air, which  has an attraction lor it :
and in confirmation of that it is urged, that when coin-
bullion is performed in empyreal or dephlogifticatcd
air, the whole of the latter is abforbed ;  but in com-
mon atmofpherical air only one-fourth, being the quan-
tity of pure  air contained in it.
   Other arguments in favour of this opinion are, that
the calces of the perfect metals may be reduced v\ ithout
addition by the mere emiffion of the oxygenous principle,
(dephlogilticated air) ; by an union w ith which they af-
furne  the form  of a  calx.    Thus he  evades a very
ftrong argument ufed by the oppofite party ; who ad-
duced,  as a  proof of the exiftence of phlogifton, the
ufe of charcoal in the reduction of metals to their pro-
per form.  A difpute indeed took place betwixt M.
Lavoifier and Dr Prieftleyjconceming the reduction of
the w hole  of a mercurial  calx  formed by an  union
with  the nitrous acid without  addition;  the Doctor
maintaining  that the whole could  not  be  reduced  by
mere  heat,  but  that  a very perceptible quantity was
always loft:  but on a thorough examination of the
fubject,  the  truth feemed rather to lie on M.  Lavoi-
fier's  fide.  Sec Aerology.
   Another theory, fomewhat  fimilar to that of Lavoi-
fier's, has been publifhed by Dr Lubbock, in an Inau-
gural Difiertation in  1784.   In this  he fuppofes  two
kinds of matter to exift in  the univerfe; one he calls
the principhmi• proprium, the other theprincipiumfor-
bile;  and it is this latter, which, according to our au-
thor,  is the principle of mutability,  or which by be-
ing united in various proportions with the other, forms
bodies of all the different kinds we fee  in  nature.   It
is this principle, therefore, which he fuppofes to be ab-
forbed in the calcination of metals, and not empyreal
air, as .M. La\ oilier fuppofes; and he contends, that
this lhme principle extends  throughout the whole fy-
flem  of nature,  even to the utmoft celeftial bounds.
   I: would exceed the limits of this treatife to i;ive an
account of the various theories which have been invent-
ed, and the arguments ufed  for and againft them ;  nor
indeed is there any occafion  for doing fo, as latf^pe-
riments  have reduced the difpute into a mu|h narrow-
er compafs than before, and furnifhed  thBfynoft tieci-
l.vt arguments in favour of the exiftence < f phlogifton.
   The greateft objection to the belief ofyhju; prin-
ciple  wa^, that it could neither be feen nor {elf, by yut
fenfes directly,  nor  difcover itfelf indireclfafry tfce
weight  it ^jimunicated to the  bodies withffljich it
was united ;^^ the conti:n  ,  the latter alwaysDecame
lighter in j^ponicm £> th<- "piar.tity they contained  :
fo that it was ima^fd, ?r«fiesd of lx ing  poffefled of
any fpecific  £]-$!["> oI" *'-'• ",V11< tu ,,e a principle  of po-
fitive levity, fichus tb;v    heat or light may be rea-
fon. \]y fuppofed  yrhb of lection, however, h, ]ow
imh-ly  removed;  and ; * Vgrfton  in  the  ..Iftr.-n'r  is
                                              four. (I
   140
Arguments
for the
non-exift-
ence of
phlogifton,
from the
reduction
of the cal-
ces of per-
fect metals
without
addition.
   141
Difpute be-
twixt La-
voifier and
Prieftley.
   142
Dr Lub-
bock's the-
ory.
   143
Difputtb
concerning
phlogifton
now entire-
ly decided.
   144
Objections
againft  the
exiftence of
phlcgilton
from its iii-
v,l,l,,Kty
and ii.ji] fi-
led want of
giavity.
tf 
Theory.
CHEMISTRY.
27
Heat.

   145
Common
charcoal
and phlo-
gifton the
fame.
   146
Decifive
proofs of
Spirit of
wine and
 General    found to be no fubtile principle capable of eluding our
 Effects of  refearches, but one very common, and eafily met with,
           being no other than common charcoal.   In the laft
           edition of this work, under the article Phlogiston,
           it was fhown, that inflammable air, deprived of its ela-
           fticity, and combined with metallic fubftances, is real-
           ly their phlogifton ; and that in the inflammable bo-
           dies commonly  ufed, what we  call their phlogifton,
           is really their oil; and that which exifts in charcoal, and
           cannot be driven off by diftillation, is part of the em-
           pyreumatic or burnt oil of the fubject which adheres fo
          obftinately.  A limilar doctrine  foon after appeared in
           the Philosophical Tranfaitions for 1782, and  the iden-
           tity of phlogifton and inflammable air was  clearly pro-
          ved by Mr Kirwan.  Still, however, it was infilled by
          the French philofophers and others, that  no facts had
          been adduced againft  M.  Lavoilier, nor any  decifive
 this identi- proofs appeared of the exiftence of phlogifton as a fiib-
 D SpV^nftby ^ance Per fe-   Facts °f this kind, however,'have now
 ley.'1'6  " ^een difcovered by  Dr Prieftley, and are related under
          the articles  Aerology, Charcoal, Phlogiston,
          &c.   It is  fufficient at prefent  to mention,  that he
          has been able to convert the pureft fpirit  of wine,
          and one of the  hardeft  metals,  viz.  copper, as  well
          as feveral   others,  into  a  fubftance  entirely  refem-
 metals con- bling charcoal;  that by means of the heat of a burn-
 vemble in- ^ ^^ -m vacuo? ne nas diflipnted this metallic char-
    148   ' coa^ as we^ as tne  common kind, entirely  intoinflam-
 Charcoal   mable  air,  with the afliftance only of a little  water,
 entirelydif- which feems neceffary  to make  it aflume, the aerial
 fipated by form,  and perhaps  is the true folvent of it; and by a
 heat into   combination with the element of heat, with the aid of
 uiflamma- tjie cnarcoai^ [s enabled  to  refill condenfation  in the
 * See  Elaf- common way.* This inflammable air, when abforbed by
 tic Vapour, metallic calces, again reduces them to  their  metallic
          form :  fo that here is one fact by  which  the phlogifton
          not only appears to  our fenfes, but we are able to af-
          ccrtain its quantity with the utmoft precilion.  Nor can
          it here be  any objection, that the reduced metal is
          lighter than the  calx;  for this only proves that the
          metallic earth, while a calx, is united to a heavy ingre-
          dient  (the  bafis of dephlogifticated air),  and in the
          latter  to a light one, viz. charcoal, the bafis of inflam-
          mable air.
            Another  cafe in which the exiftence  of phlogifton
          is made equally evident to our fenfes, and where no
          fuch objection can occur, is  related  under the article
          Aerology, n° 112.  It is there fhown,  that " by the
          lofs of one grain  of charcoal of copper (formed by the
Dephlogif- union of fpirit of wine with the metal), and which like
       r  common charcoal was confumed  without having  any
          refiduum, he reduced four ounce-meafures  of dephlo-
          gifticated air till only one-ninth remained  unabforbed
          by water ;  and, again, with the lofs of one grain and a
          half" of charcoal,  fix and an half meafures of dephlogi-
          fticated air were reduced till  five and an half meafures
          were pure fixed air."—Here, then, is an abfolute and
          undenialjfle evidence, that fixed air is compofed of de-
          phlogifticated air,  and charcoal or phlogifton, and ele-
          mentary fire.   There were no other ingredients pre-
          fent, and the charcoal muft either have been annihila-
          ted or  difpofed  of in the  manner juft mentioned :  but
          the fuperior  weight  of the fixed  air evidently  fliows
          that fome ingredient had been added to  the dephlogi-
          fticated air;  and which increafe was more than we  can
   M9
Metallic
calces re-
duced by.
inflamma-
ble air.
   150
Why me-
tals are
lighter in
their  me-
tallic  than
in their
calcined
ftate.
   f$f
converted
into aerial
acid by
charcoal.
  fuppofe to arife from the condenfation  of the dephlo- General
  giiticated air during the operation, for this fome times Effects of
  amounted to no more than one-thirtieth part.         . cat'
    The ftrongeft objection which can be made  againft    i5z
  the doctrine of phlogifton may be drawn from the to- Objections
  tal confumption of pure air in certain cafes of combu- drawnfrom
  ftion, for inftance, in that of phofphorus, inflammable tne *ot*!
  air,  and iron.   It muft be obferved, however,  that in ^™c uM™n
  no cafe  whatever is  the air totally confumed ; and gifticated
  in that of inflammable air water is produced by the air in fome
  union  of the bafis  of the  latter,  that is charcoal, cafes.
  with the bafis  of dephlogifticated air,  the oxygenous
  principle  of M.  Lavoilier, and which  appears  to be
  one of the component parts of Water,   in die cafe
  of phofphorus, the latter is converted  into an  acid;
  and in all probability a quantity of water is alfo pro-
  duced, by which part of it is converted into cryftalline   ij-
  flowers.   The cafe of the iron,  therefore, alone re- Littlephlo-
  mains to be confidered.   Dr Prieftley's experiments g'fton ex-
  on this fubject are related at length under the article pellcdfrom
  Aerology, n° 67 etfeq.   In  them the  iron  burnt •n°n^nt;e"
  brifkiy in dephlogifticated air,  which,  according to jn dephTo^
  the common theory, fhould have indicated  the expul- giftkated
 fion of a great quantity of phlogifton ;  yet the whole air.
 refiduum, of which the fixed air, produced by the fup-
 pofed union  of the phlogifton or principle of inflamma-
 bility, Was only a  part,  fcarce amounted  fometimes to
 one-fourteenth of the air originally employed.           z..
   The argument, however, inftead of contradicting The  objec-
 the exiftence of phlogifton,  only fliows,  that in fome t>f),i  incon-
 cafes the diffipation of a very fmall  quantity of phlo- cIufive.
 gifton is neceflary to inflammation ;  or that the  aerial
 principle may  combine with  the iron in its metallic
 ftate.   In this cafe only  a  very  little  quantity- of
 the phlogifton  of the  iron was dillipated ;  for it was   u,
 not reduced to a calx,  but to that kind  of  fcoriae Iron is not
 which flies off in  fcales by beating the  metal  when reduced to
 red-hot  with an hammer.  A decifive  proof of this a "^ by
 was had by uniting  iron thus combined with the Jjur?!ngTin
 bafis  of  dephlogifticated  air  with  inflammable air. ticatedgair.
 By this  the metal was  indeed reduced to perfect   156   "
 iron again ; but water  was produced at the fame  time Water pro-
 froni the union of the bafis of the two airs, that of the ducedinthe
 inflammable air being capable of furnifhing a fuperflu- redu,ftion
 ous quantity, which united with the other into the „f u bV,n"
 form of a fluid.                                     flammable
   The exiftence of phlogifton being thus proved, and  "\Sy
 its nature afcertained, we may now proceed  to deter- Heat  pro-
 mine  the queftion, Whether the great quantity of heat duced in
 produced  by the combuftion of inflammable bodiesthe 5om"
 proceeds from the bodies themfelves, or  from the air b"?lon of
 which muft be admitted to them in order to make them y ^d"'*"
 burn ?  That the  heat  in  this  cafe  proceeds  from derived
 the atmofphere is  evident; becaufe in   all  cafes of from the
 combuftion there is a  certain diminution undoubted- air.
 ly takes place by means of the converfion of the de-
 phlogifticated part of the atmofphere into fixed air.
 It is proved, under  the article Elastic Vapours,  that
 elementary fire is the univerfal caufe of  elafticity in
 fluids.   By uniting a certain quantity of it with any
fubftance, the latter at length aflumes an aerial or va-
porous form ; and it is this vapour alone which is in-
flammable*.  Different vapours no doubt  contain dif- * See-the
ferent quantities of thefe ingredients ;  but in all cafes articIc
the bafis of the dephlogifticated part of the atmofphere"^"''
                       D  2                  muft 
C   H    K   M    I    S   T   R   Y.
of air has
the fame
effea.
         muft  unite  with the  ph'm-ifton of the inflammable
         body, or with fomcthing elle, fo that a decompolition
         may enfuc :  and it is this decompolition which produces
         the heat and light; l<>r then the fire contained in the
         atm<>tt>!icrc  having no longer any thing  to abforb it,
         inuft appear in  its  proper form.  But  in thofe cafes
l  i-.jifton where there is a great quantity of phlogifton, and con-
f™v",:*   fcquciuly much  fixed air produced,  the latter abforbs
fmm bein" *'' nv,cn '1C l! in  a  latent  ftate, that  the  quantity
intenfe.  " communicated to furrounding  bodies muft  be greatly
         diniiniihed; and if an excels of this ingredient, not
         only fixed air, but the phlogifticated kind and grofs
         fmoke be alfo produced, this diminifhes the heat ftill
         farther by the great abforption,  and will even deftroy
         it altogether.   The  remedy for  this is either to dimi-
         nilli  the quantity of phlogifton, or to  augment the
         quantity of air ; which, by furnifhing a greater quan-
    IT«   tity of dephlogifticated balls, affords  an opportunity
TYo great for the evolution of a greater quantity of heat.  On
aq'.iantity the  other hand, when the quantity  of air is too great,
         the  phlogiftic matter cannot combine with  the balls of
         the  pure air in fufficient quantity to effect a decompo-
         fition;  and therefore the heat is abforbed in a latent
         ftate, and the fire goes out.
            Km n this theory, which is farther illuftrated under
          the articles Fire, Flame, Heat, Phlogiston, &c.
          we  may not only have a rational idea of the manner in
          which  inflammation is generally accomplilhcd, but fee
          why a  fire  may be put out both  by  too great  a quan-
          tity of fuel, and by too great a quantity of air.  We
          may alfo fee why the folar beams  and electric fluid,
 and that ?f-vvliicli  contain  no  phlogiftic matter,  excite a much
  eancity. ^rc powerful heat  than any we can raife in our hot-
          tcft furnaces.   The  difference  between ignition and
          inflammation will  now likewife appear ; fuch  bodies
          a* arc  capable only of ignition containing  little or no
          phU>gifton, but inflammable bodies a great deal.
           ' The following table lhows the moft remarkable de-
 the various grees of heat from the congelation of mercury to that
 •V>;rces of of Mr  Wedge wood's hottcft furnace.
 beat.          Mercury freezes at
               Weak fpirit e>f wine
               Brandy at        ...
               Cold produced  by fnow and fait mixed
               Strong wine freezes at
               Vinegar freezes at
               Water freezes at
               Temperature of fpring and autumn
               Ordinary  fummer weather
               Saltry heat
               Heat  of human blood
               Feverifh heat
               Bees  wax melts
               Scram coagulates
               Spirit of wine boils
               Water boils      -
                i •. melts    -
               Bifmuth melts
               Oil of \itriol boils
               Oil ef turpentine boils
               Lead melts
               • biickfilver and linfeed-oil boil
               Iron begins to fhine in the dark
               Iron Alices brifkly in the dark
               Iron Unties in the twilight
   160
Why the
fohr her.t
are fo il
t,. ul'e.
 16 1
.Lie of
      40
      32
      10
       o
      20
      27
      32
      50
      65
      75
97 to 100
     108
     142
     156
     174
     212
     408
     460
     550
     Soi
     535
     600
     635
     7io
Iroii red-hot from a common firr
Rcd heat fully  viliblc in  day light ac-
  cording to Mr \\ edgewood
Heat  by which his enamel  colours are
  burnt on
Brafs melts        -
Sv. edilh copper melts
Fine filver melts
Fine gold melts
Leaft welding heat of iron
Grtytclt ditto
Greateft heat of  a common fmith's
  forge        ...
Call iron melts
Greateft heat  of Wedgewood's  fmall
  air-furnace      -
Extremity of the fcale of his thermo-
  meter      ...
    Theory.
 IOJO  Elective
      Attraelii'ji.
 1077 '    "

 l8>7
 ;8u7
 4587
 4717
 52? 7
12777
r?42 7

17^7
17977

21877

32277
Sect. II.   Of the Doctrine of Elective Attraction, and
        of the different Objects of Chemiftry.
162
  Before we proceed to give a general theory of the Chemical
changes which happen upon the mixtures of different attraction.
bodies together,  or expoling them fingly to heat, wc
muft obferve, that  all depend on certain qualities
in bodies, by which  fome  of them are apt  to join
together, and to  remain united while they have an op-
portunity.  The caufe of thefe qualities is totally un-
known ;  and therefore philofophers, after the example
of Sir Ifaac Newton, have  expreffed the apparent ef-
fect  of this unknown caufe by the  word  attraction.
From them the  word has  been adopted by the che-
mifts, and  is now generally ufed in fpeaking of the
phenomena which are obferved in the mixture of dif-
ferent fubftances; but to diflinguifh it from other kinds,
it is  ufually called Elective.
  This attraction is not equally ftrong between all fub-
ftances ;  in confequence of which, if any body is com-
pounded of two others,  and another is prefented to it
which has a greater attraction  for one  of the  compo-
nent parts than they have for one  another, the fub-
ftance v. ill  be c,'-:c*>>;; '.undid.  A new compound is then
formed by the union of that third fubftance with one of
the component parts or  elevients (if we pleafe to call
them fo) of the  firft.   If the attraction between the
body fuperadded  and cither of the component parts of
the other is not  fo ftrong as that  between themfelves,
no decompofition will er.fue ; or if the  third fubftance
is attracted by both the others, a new compofition will
take place by the union of all the three.                 ,63
  The objects  of chemiftry,  as wc  have already ob- Objefis of
ferved,  are fo various,  that an enumeration of them chemiftry
all is impoffible.   To cafe the  mind, therefore,  when how claf"
fpeaking of them, and render more  ufeful  any  thing fcd"
that is find or wrote on chemiftry,  it  is neceffary  to
divide them into different  clafles, comprehending in
each clafs thofe bodies which have the  greateft refem-
blance to one another, and  to which one common rule
applies pretty generally.—The divifionformerly ufed,
was that  of vegetables, animals, and  minerals ; but
this has  been thought improper, as there are  many
fubftances in each of thofe kingdoms which differ \ ery
w ide'.;, from one another, and which are by no means
fubject  to  the  fame  lav.:.  The moft approved me-
                                              thod, 
Theory.
CHEMISTRY.
29
   Salts,   thod,  at prefent, of arranging the objects of chemiftry,
 *—-v----' is into falts, earths,   metals, inflammable fubftances,
          waters,  animal and vegetable fubftances.
                          Sect. III.  Salts.

  silts.      Salts are cither fuftble,  that is, capable of abiding
          the fire, and melting in a ftrong  heat, without  being
          diflipated ; or volatile, that is, being difperfed in va-
          pour with a fmall heat.   Their  other properties are,
          that they are folublc in water : not inflammable, unlefs
          by certain  additions;  and give a fenfation  of  tafte
          when  applied to the tongue.
            The moft general cbaracteriftic of falts is, that they
          are all foluble in water, though fome of them with much
          more difficulty than others.  Moft of them have like-
          wife the property of forming themfelves, in certain
          circumftances, into  folid tranfparent manes of regular
          figures,  different according to the  different fait made
          ufe of, and which are termed cryftals of that fait.   In
          this ftate they always contain a quantity of water;  and
          therefore the utmoft  degree of purity in  which a fiilt
          can be procured, is when it has been well cryftallized,
          and the cryftals are freed of their fuperfluous moifture
          by a gentle heat.  They generally appear then in the
    6     form of a white powder.
Phenome-    In tne folntion of falts  in water, the firft thing ob-
na attend-  fervable is,  that the water parts  with the air  contain-
ingtheirfo- ed in it;  which  immediately rifes to the top in  the
lution.     form of bubbles.  This, however,  is moft remarkable
          when  the fait is in the dry form we have jufl now men-
          tioned, becaufe there is always a quantity of air  en-
          tangled among the interflices of the powder, which ri-
          fes along with the  reft ; and this difcharge  of air is
          fometimes fo great,  as to be miftaken for an effervef-
          cence.   From this, however, it is elfentially different.
          See Effervescence.
            Another thing obfervable in the folution of falts is,
          that a confiderable change happens in the temperature
          of the water in which they  are diffolved ;  the  mixture
          becoming either a good deal warmer or colder than ei-
          ther the fait or the water were  before.  In  general,
          however, there is an increafe of cold, and fcarce any
          fait  produces heat, except  when  it has been  made
          very dry, and deprived of that moifture which  it na-
          turally requires ; and thus the heating  of falts by be-
          ing mixed with water maybe explained  on the fame
          principle with the heat produced by  quicklime.   See
          pUICKLIME.
          ""After fait  has been diffolved in  a  certain  quantity
          by water, no more of that fait will be taken up unlefs
          the water is heated ;  and  as long  as the heaf continues
      •    to increafe,  the fait will be  diffolved.   When the wa-
          ter boils, at  which  time it has  attained its  greateft
          heat,  and will take  up no more fait,  it is then faid to
          be faturated with that fait.   This,  however,  does not
          prevent it from taking up a  certain quantity of another
          fait, and after that perhaps of a third, or fourth,  with-
          out lettfhg go any of  the firft which it had diffolved.
          How far this property  of water  extends, has not yet
          been afcertained  by  experiments.
            To  the above rule  there is  only one  exception
          known as yet;  namely,  common fca-falt : for water
          diffolves it in the very fame quantity  when cold as
          when  boiling hot.   It has been  faid by fome, that all
          deliquefcent falts, or thofe which grow  moift on being
Salts.
166
167
of falts.
   16?,
Salts de-
expofed to the air, had the fame property:- but this is
found to be a miftake.
  This property of folubility, which all the falts pof- ^'mi.
fefs in common, renders them eafily mifcible together; andfepara-
and the property by  which moft of them flioot in- tion of fait*
to cryftals, renders thofe eafily feparable again which
have no particular attraction for one another.   This is
likewife rendered  ftill more  eafy by their requiring
different proportions  of water, and different degrees
of heat, to fufpend them; for by this they cryftallize
at different  times, and we  have not  the trouble of
picking the cryftals  of one out among thofe  of the
other.
  The manner in which the folution of falts in water Hypothefis
is effected, is  equally unaccountable with moft of the concerning
other operations  of  nature.   Sir Ifaac Newton fup- tnefo
pofed that the particles of water got  between  thofe
of the fait, and arranged them all at an equal diftance
from one another: and from this he alfo accounts for
the regular figures they affume on palling  into a cry-
flalline  form ; becaufe,  having been once arranged in
an orderly manner,  they could not come  together in
diforder, unlefs fomething was to difturb the water in
which they were fufpended ; and if any fuch difturb-
ance is given,  we find the cryftals are by no means fo
regular as otherwife they would have proved.  Others
have thought that thefe figures depend on a certain po-
larity in the very fmall particles  into which the fait is
refolved when in a ftate of folution.   Thefe things,
however, are merely conjectural;  neither is it a matter
of any confequence to a chemift'whether they are right
or wrong.
  Though folution is that operation which falts un-
dergo the moft eafily, and which fhould feem to  affect ftru&ible
them the leaft of any, a repetition of it proves never- byfepeated
thelefs very injurious to them, efpecially if it is fol- foluUons-
lowed by  quick evaporation ;  and the  fait, inftead of
being cryftallized, is  dried with a pretty ftrong heat.
Newman relates, that a pound of fea-falt was reduced,
by 13 folutions and exficcations, to half an ounce ; and
even that was  moftly earth.   Where folution is requi-
red, therefore, it ought always to be done in clofe vef-
fels, in which  alfo the fubfequent evaporation fhould
be performed,  (fee  Evaporation);  and in all cafes
where cryftallization is practicable,  it ought to be pre-
ferred to violent exficcation.
  The two great divifions of falts are into acids and
alkalies. The former of thefe are known by their pecu-
liar tafte,  which is called acid or Jour.   They are not
found in a folid form ;  neither are any of them, except
the acids of vitriol, of tartar, of phofphorus, and of
borax, capable of being reduced  to folidity.  The o-
thers, when highly  concentrated, that is,  brought 10
the utmoft degree of ftrength of which they are ca-
pable, always become an invifible vapour, permanently
elaftic,  until it conies in contact with water, or fome
other fubftance with  which they are capable of uni-
ting.   For fitch acids the name of falts feems lefs pro-
per, as we can fcarcely fay that a vapour,  which is al-
ready much  more fluid than  water,  can be  diffolved in
that element.
  The  acids are divided into the mineral, the vege-
table, and the animal; exprelfing their different ori-
gin, or where  they  are moft commonly to be found.
The mineral acids are commonly reckoned three ; the
                                                vi-
 169
Acids. 
C    H   E    M    I   S   T    R   Y.
Theory.
  170
Alkalies.
Different
action of
vitriolic,  the nitrous,  and the marine.   1 "■'  this  the
acid of  borax ought  to be added ;  bat  its  wcaknefs
m.-.NC* it much lets taken  notice of as an acid than the
others.   A Swcdilh themift, however, Mr  Schcelc,
hath lately added Lveral other >, which  arc afterwards
laken notice of.
   The  vegetable kingdom affords only two diftinct fpe-
cics of  acm>, at leaft without the afliftancc of fome
chemical operation.  The one appears fluid, and when
concentrated to the utmoft degree becomes an invifible
v.!j"ir,   This is  produced  from fermented liquors,
under the name of vinegar.   An acid fimilar to this,
and which is thought not to be effentially different from
it,  is extracted  from moft  vegetables  by diftillation
with a  ftrong  fire.   The other is likewife a confe-
quence  of  fermentation; and  crufts on the  bottom
and fides  of cafks in  which wine is put to depurate
itfelf.   In its crude ftate it is called tartar;  and when
afterwards purified,  is called the cream,  or cryftals, of
tartar.  As for the various acids produced in the  dif-
ferent chemical proceffes to be afterwards related, we
forbear to  mention  them at prefent, it  being  juftly
fufpeetcd  that fome of them are artificial.
   The  animal acids, which  have hitherto been difco-
vered,  are  only  two; the acid of  ants,  and that of
urine, which is alfo the acid of phofphorus.  The  firft
of thefe is volatile ; and consequently muft be fuppofed
a vapour when in its ftrongeft ftate : the  other  is ex-
ceedingly  fixed;  and will rather melt  into glafs than
rife in vapours.  Befides thefe,  it is laid an acid is con-
tained in  blood, in wafps, bees, &c. :  but no experi-
ments have as yet been  made on  thefe to  determine
this matter with any degree  of precilion.
   The  alkalies are of two kinds ;  fixed and volatile.
The  fixed kind are fubdivided into two;  the vege-
table, and  mineral or fulfil alkali.   The  vegetable is
fo called, becaufe it is procured from the aflies of burnt
vegetables; the  foflile, becaufe it  is found native in
fome places of  the  earth, and is the bafis of lea-fait,
whie'h in fome places is dugout of mines in vaft quan-
tity.   They are called  fixed,  becaufe  they endure a
very intenfe degree of heat without being dilfipated in
vapour, fo  as even  to form a part of the compofition
of glut*.  The volatile alkali is generally obtained by
diftillation from animal fubftances.    In its pure ftate
this alkali is perfectly invifible ; but affects  the fenfe
of fmelling to fuch a degree, as not to be approached
with fafety.
   The acids and alkalies are generally thought to be
entirely oppofite  in their  natures  to one anotlier.
alkalies and Some, however, imagine them to  be extremely fimi-
ia^-      lar, and to  be as it were parts of one fubftance vio-
          lently taken from each ether.  Certain ic is, that when
          fcparated,  they appear as oppofite  to  one another as
          heat ;: id cold.   Their oppofite aclion indeed very much
          refcmbles that of heat  and cold, even when applied to
          the tongue;  for the alkali has a he:, bitter,  burning
          t-fte, while the acid, if not conliderably concentrated,
          alwa»i  gives a fenfation of coldnefs.  In  their aclion
          too f'pon animal fubftance-,  the alkali diflol.e
          reduces the part to a mucilage ; while the  acid,
,  and
if not
   1;*
Neutral
(alts.
very much concentrated, tends to  prci'erve it  uncor
ruptcd.
   If an alkaline fait,  and
lio'.fiJ ftate, Lcr.ixcd tuge
moderately ftrong acid in a
her, they will immediately
unite ; and, pnnided the alkali Ins not  been depri-
ved of its i ;ed air, their union will be attended with
a very confiderable eflervcfccnce : (fee A v r o j co \.)
If the alkali has been deprived of air, no ttfervefcence
will enfue, but they  will quietly mix together ;  but
if a due proportion of each  has  been added, the li-
quor will  neither  have  the properties of an acid  nor
an alkali, but \\ ill be what is called neutral. The bring-
ing the liquor into this ftate, is  called fatnrati s' the
acid or alkali,  or  combining them to  the point of fa-
turation.
   If the liquor after  fuch a faturation be gently eva-
porated, a laline mafs will be left,  which is neither an
acid nor an alkali, but a new compound formed by
the union of the two,  and which is called ap:rf:ii neu-
tral fait.   The epithet perfect is gi\en  it, to make a
diftinction between the falts  formed by the  union of
an acid  and an alkali, and thofe formed by the union
of acids, with earthy or metallic fubftances ; for thefe will
likewife unite with acids, and fome  of the compounds
will cryftallizeinto regular figures ; but, becaufe of their
weaker union with thefe fubftances, the falts refultiug
from combinations of this kind are called imperfect.
   All  acids, the  volatile Sulphureous one excepted,
change the blue infulions of vegetables, fuch as  vio-
lets, to a  red; and alkalies, as  well as fome of the
imperfect neutrals, change them to green. This is the
niceft  teft of an acid or alkali abounding in any fub-
ftance, and feems  the moft proper method of determi-
ning whether a folution  intended to be  neutral really
is fo or not.
   Though between every acid and alkali there  is a
\ery ftrong attraction, yet this is far from being the
fame in all;  neither is it the fame  between the fame
acid and alkali in different  circumftances of the acid.
When  the acids are in a liquid  ftate, and as free as
poifible of inflammable matter, between  which  and
the  nitrous and vitriolic acids there is a veiy  ftrong
attraction, the   vitriolic  will expel any of the  reft
from an alkaline bafis, and take its  place.  Thus, if
you combine the acid  of  fea-falt,  or marine  acid, to
the point of Saturation,  with the foffil alkali, a neu-
tral fait will be formed,  which has  every property of
common fait: but, if you pour on  a  certain propor-
tion of the vitriolic acid,  the acid  of fea-falt will im-
mediately be expelled ;  and the liquor, upon being e-
vaporated, will contain not the neutral fait formed by
an union of the marine acid with the alkali, but ano-
ther confuting of the vitriolic acid joined with that al-
kali, and which has quite different properties from the
former.    „
   When the acids and alkalies are applied to one ano-
ther in a liquid ftate, the vitriolic acid  always fliows
itfelf to be the  moft powerful; but when  applied  in a
folid form, and urged with a violent heat,  the  cafe is
very much altered.   Thus,  the acid  of borax, com-
monly called fal fedativus, is fo weak as to be difen-
gaged  from its  bafis by every acid applied in a liquid
form,  that of tartar alone excepted;  but  if even  the
vitriolic acid combined with an alkali be mixed with
this weak  acid, then exficcated, and  at  laft  urged
with a vehement fire, the vitriolic acid will be  difen-
gaged  from  its balls, and  rife in  vapours,   leaving
the weaker acid in poifeflion of the alkali.   The fame
thing happens  on adding the phofphorine  or urinous
                                               acid,
ills.
   173
Vegetable
colours
changed by
acids and
alkalies.
   174
Differences
in the de-
grees of at-
traction be-
tween acids
and alkalies 
Theory.
CHEMISTRY.
3*
Salts.
  ,175 .
Acids unite
with phlo-
gifton.
   176
With me-
tals and
earth.

   177
Electiye
attractions.
acid, or the acid of arfenic,  &c. to combinations of
the vitriolic or other acids with alkaline falts.—When
the acids are in a liquid ftate, therefore the moft power-
ful is the vitriolic ; next the nitrous ; then the ma-
rine ;  then vinegar ; acid of  ants ; and laftly the fal
fedativus and tartar, which feem to be nearly equal in
this refpect.—If they are applied in a folid form, the
moft powerful are  the fal fedativus and phofphorine
acid ;  then the vitriolic, nitrous, marine, and vegetable
acids.
   When they are reduced to  vapour,  the cafe is ex-
ceedingly  different ;  for then the marine acid appears
to be the moft powerful, and  the vitriolic the leaft fo
of  any.  It   is impoffible, however,  to preferve the
vitriolic acid in the form of vapour, without combin-
ing it  with a certain quantity of inflammable matter,
which muft neceflarily deftroy its ftrength.  Dr Prieft-
ley found,  that the marine acid, when reduced to va-
pour,  was  capable of difuniting  the nitrous acid  from
a fixed alkali.
   Though the vitriolic acid Sometimes  affumes a Solid
form,  it is by no means eafy to  reduce it to this ftate
by mere concentration, without the affiftance of  ni-
trous  acid.  Baldafart,  however,   pretends  that  he
difcovered, in the neighbourhood of a volcano, a pure
and  icy oil of vitriol, from  which nothing could be
precipitated  by alkaline falts ; though there is cer-
tainly very great reafon to  doubt the accuracy  of this
obfervation.   Of  late  the nitrous acid has alfo been
found  capable of afluming a folid form.   This was
firft obferved by M. Bernhard in diftilling a very large
quantity of  the acid.  At that time  he perceived a
white fait adhering to the infideof the receiver, which
on examination proved to be the acid of nitre in a con-
crete  form ;  being  extremely corrofive, emitting red
vapours copioufly on being expofed to the air, and at
length totally evaporating in  it.   Its fpecific gravity,
however,  was far inferior to that of the glacial oil of
vitriol.
   The acids  have  the property  of uniting themfelves
to many other  fubftances  befides fixed alkalies,  and
forming neutral compounds  with  them.   Of  thefe
the  chief is  the principle  of inflammability or phlo-
gifton.  In the vitriolic, nitrous,  and phofphorine a-
cids, the attraction for this principle is very ftrong ;
fo great, that the two former  will  even leave a  fixed
alkali  to unite with  it.   In the marine acid it is lefs
perceptible ; in the liquid vegetable or animal acid
ftill  lefs ;  and in the acid of  tartar, and fal fedativus,
not  at all.
   Belides this, all acids will diflblve metalMfc and ear-
thy  fubftances : with  thefe,  however, they do not in
general unite So firmly with alkaline Salts ; nor do they
unite So Strongly with metals  as with earths.
   In general, therefore, we may  expect;, that after ha-
ving dilfolved a metal in any acid whatever, if we add
an earthy Subftar.ce to that Solution, the acid will quit
the metal,  which it had before diffolved, to unite with
the earth.   In this cafe the folution will not be clear
as before, but will  remain muddy,  and  a  quantity of
powder will fall to the bottom.   This powder is  the
metalline fubftance  itfelf, but  deprived of one of its
component  parts ; and in this cafe  it is Said to precipitate
in the  form of a calx.
  If to this new folution of the earthy fubftance in  an
acid liquor, a volatile alkaline Salt, not  deprived of its
Salts.
 fixed air,  is added, the acid will quit the  earth, and
 unite  wi th the alkaline  fait.  The earth thus dif- "
 engaged will again precipitate, and lie at the bottom in
 fine powder, while  the volatile  alkali  and acid re-
 main combined together, and the liquor again becomes
 clear.
   The attraction between volatile alkalies and acids is
 confiderably lefs  than between fixed alkalies and the.
 fame acids. If, therefore,  a fixed alkali be now add-
 ed to the liquor, the volatile alkali will  be  Separated,
 and the acid will unite with the fixed alkali.  The vo-
 latile alkali indeed,  being  perfectly foluble in water,
 cannot precipitate, but will difcover its Separation by
 the pungent Smell of the mixture ; and upon evapora-
 ting the liquor, the volatile alkali will be diffipated, and
 a faline mafs, confifting of the acid and fixed alkali,
 will remain.                                           I7g
   Laftly, If the acid employed was the nitrous, which Detonation
 has a ftrong attraction for the principle of inflamma- of nitre.
 bility, if the faline  mafs be  mixed  with  a proper
 quantity  of inflammable  matter,  and expofed  to  a
 ftrong heat, the acid will leave the alkali with vaft ra-
 pidity, combine with the inflammable matter, and be
 deftroyed in flame in a moment, leaving the alkali quite
 pure.                                                  I70
   Though the  abovementioned effects generally  hap- Exceptions
 pen, yet we are not to  expect that they will invari- totheabov^
 ably  prove the fame whatever acid is made ufe of; rules"
 or even that they will be  the fame  in all poflible va-
 riety of circumftances in which the  fame acid can be
 ufed.—The acid  of tartar is one exception, where the
 general rule is in a manner reverfed ;  for this acid will
 quit a  fixed alkali for an earth,  eSpecially if calcined,
 and even for iron. If lead, mercury or  filver, are dif-
 folved in  the nitrous acid, and a fmall quantity of the
 marine acid is added, it will  Separate the Stronger ni-
 trous acid, and  fall to the bottom with the metals in
 form of a white powder—The  vitriolic acid, by it-
 felf, has a  greater attraction  for earthy  fubftances
 than for  metals; and greater ftill for fixed  alkaline
 falts than for either of thefe : but if quickfilver is dif-
 folved in the nitrous acid, and this folution is poured
 into a  combination of vitriolic  acid with fixed alkali,
 the vitriolic acid will quit the alkali to unite with the
 quickfilver.  Yet quickfilver by itfelf cannot eafily be
 united with this acid. The reafon of all thefe anoma-
 lies, however,  is fully explained in the following Sec-
 tion.

   \  I.  Of the Operations of Solution and Precipitation.

   The chemical Solution of folid bodies in acid or other
 menftrua, is a phenomenon which, though our familia-
 rity with it has now taken off" our furpriSe,  muft un-
 doubtedly have occafioned the greateft admiration and
 aftonifhment in thcSe who firft obferved it.   It would
 far exceed the  limits of this treatife to  fpeak particu-
 larly of all the  various  circumftances  attending the
 folution of-different fubftances in every poflible  men-
 ftruum.  The following are. the moft remarkable, col-
 lected  from  Mr Bergman's Differtion  on Metallic
 Precipitates.                                           xg0,
   I. On putting  a fmall piece of metal into any  acid, Phenome-
it is diffolved fometimeswith violence, fometimes gent- "a  atten-
ly,  according to the nature of the menftruum and 0fdin£the
the metal to be  diffolved.                             folution
  2. The nitrous acid is the moft powerful in its ac-    a met*k
                                                tion 
CHEMISTRY.
3-
MuHm   n •. ,ga ; etallic jubilances,  when unaffiftcd by heat.
i..U l'rtci- v,,, great  indeed is the violence with whicli  this acid
1  titton.  ^ Sometimes acts, that the metal, inftcad of being diilbl-
   i .-* i    ved, Separates inftantaneoufly from it in  the  form of a
N'tmu»  a-calx or powiicr  fcarce folublc  in  any i-'euftrmnn, at
cid the mod thc fame time that the heat, ctfcrvefcencc, and noxious
violent in VSp(rars iifu'mg from the mixture,  r.mier it abSolunl;
t  on**™" neccilary to moderate the  action  of the menftrt: un,
          either ■y  dilution or <Vl, or both.  I p. other  cafes,
          however,  as when put  to gold or platint,  the ni-
          trous acid has no cried until it  be united with the ma-
          rine, when the mixture acts upon thofe metals, which
    tgj    neither of the acids Singly would touch.
Vitriolic     ?• The action of  the  vitriolic acid,  though  in the
acid acts   higeft degree of concentration, is more weak.  It does
more weak-not readily attack filver or mercury  unlefs alfifted by
•y*        a boiling heat, nor will even that be fufficient to make
    18j    it act upon gold or platina.
Marino a-   4. The action of marine acid, unlefs on fome particu-
cidgeneral-iar fobftame-, is ftill  more weak ; but  when deptd■>.
 • mi°rti   gifticated, or deprived of part of the phlogifton eftennal
either ex- t0 *ts conflitution as an acid, it  acts much more powcr-
cept when Sully, and diflblves all the metals  completely.
dephl.^iiti-    5. The  other acids, as  thofe of  fluor, borax, with
catcd.     fuch as are obtained  from the animal and  vegetable
    '84    kingdoms, arc much inferior  in their powers as fol-
th   "d   vents> unlefs in very few inftances.
 niuch       6.   Metals vary very much  in their degrees of Solu-
weakcrltill. bility ;  fome yielding to almoft eveiy menftruum, and
    185    others, as has been already obferved, being Scarce ac-
Di.Tcrcm  u'd liu.hi by the moft  powerful.
degree* of    ^ V.\\\c ami  jroll are Q( tnc formcr kind, and gold
mcuii"7"1 aml ll,vcr ot tllc ,atter> cluJin£ thc marine ;  and gold,
    rg^    unlefs in one particular cafe, viz. when affifted by heat
Solution   i" a clofc  veiled, the action of the nitrious acid alio.
 fometimei Thefe metals, howe\er, which in theirperfect ftate re-
 promoted fin the action of the moft powerful menftrua, may be
by  abftrac- diffolved much more readily when deprived of a cer-
 tingacer- ta-n quantity 0f their  inflammable  prin nde.   But
 portion of though the  Separation of this principle in fome degree
 phlogifton. renders metals more foluble, the abftraction of too much
    187    of it, particularly in the cafe of iron and tin, renders
Tut is to-  thefe metals almoft entirely infoluble. Manganefe is the
tally  pre- ln0ft. remarkable  inftance of  this power of  the phlo-
ventedby g^jc principle, in depriving metals of their Solubility
 v'ivToo"  ty its abfence, or reftoring it to them by its preSence;
 much :    for this fubftance, when reduced  to blackneSs, cannot
 exemplified be  didblved by any  acid  without  the addition of
 in manga-  fome inflammable matter ; but when by the addition of
 r.efe.      phlogifton it has become white,  may be didblved in
    lgg    any acid.
 Solution of    8. The diflblution of metals by acids, even to their
 metals at- very laft particle, is attended by a vifibleeffervefcence :
 tended    this is more perceptible  according  to the quicknefs of
 with anef-  tb.c folution ;  b-.it more obScnre, and Scarcely to be feen
 fervef-    at aj^  when the Solution proceeds flow ly.
 cencCo        9.  The  elaftic fluids extricated: by thefe folutions
 Various    arc various, according to the nature of the acid  and of
 kinds-»fe-  the metal employed.  With the nitn.-H, the fuid pro-
 laftic fluids duced is coi -nonly that called nitrous air;  with vitrio-
 cxtricated. ]jc ar,j marine acids the  produce is fomeiimcs inflarn-
          mbleair,  fomeiimrs otherwife, acccordingto the na-
           ture of the  meul acted upon.
             10.  licit in a greater or  fmalier degree is always
          nrodr.ccd during the dinhhttion of meuls;  and the de-
                                                        1
Theory.
gree of it is in  proportion to the quantity of the mat- Folution
tcr and the quicknefs of the folution ;  «rd hence, in -™d Preci-
fmall quantities  of  metal,  and when the folution  pro- rta  °"'  .
cctds very llowly, the temperature of the mafs is fcarce-
ly altered.                                             ,90
   11.  The  calces of  metals cither yield no air  at all, Heat pro-
or only the aerial r.cki, unlets when urged by a violent duced du-
heat alnmit to ignition ; when, by means of vitriolic or ring the
nitrous acid, they yield a quantity of pure air, after d'"°'utj°"
other elaftic fluids *hch as \itriolic, nitrous, or phlo- ° "—j**
gifticated air.   None of  the dephlogifticated  air  is Littje a;r
ufually produced by  the marine  acid in conjunction can be ob-
with metallic calces.                                 tamed from
   1 2.  The  Solutions  oS Some metals are coloured, 0- metals
thers are not.  The colour of the former is only that ^he" caI"
which is proper to the calx, but rendered more vivid cine  "
by the  moifture.  Thus  folutions oS gold and  platina various
are yellow ;  thoSe oS copper, blue or  green ;  Solutions colours of
of nickel of a  bright green ;  but thofe of cobalt are metallic
red, although the calx is black.   We may obferve that calces.
even this red colour may be heightened  to  blacknefs.
Iron moderately calcined is green ; but this rarely con-
tinues upon further  dephlogiftication.   The  white
calces of filver,  lead, tin, bifmuth, arfenic, antimony,
and manganefe, are diffolved without  colour ;  but fo-
lutions of lead, tin, and  antimony, are fomewhat  yel-
low, unlefs fufficiently diluted.   Mercury,  however,
forms a Singular exception to this rule ; for the orange-
coloured calx of this metal forms a colourlefs foiution.
The metals  yielding coloured folutions  are gold,  pla-
tina, copper, iron, tin, nickel, and cobalt; the reft, if
properly depurated, give no tinge.  A  folution of fil-
ver  is Sometimes of a blue or green colour at firft, al-
though there be no copper prefent; the vitriolic  acid
becomes blue with copper ; the nitrous may be  made
either blue or green at pleafiire ;  the marine varies ac-
cording to the quantity of  water with which it is di-
luted.   Manganefe, when too much  dephlogifticatcd,
renders both the vitriolic and marine acids purple.        I0.
   With regard to the caufeof  chemical folutions,  our l'ergman'i
author obferves, that  though attraction  muft be look- account of
ed upon as  the  fundamental caufe,  yet  we may alfo the caufe 0f
lay  it down  as a maxim,  that no metal can be taken chemical
up by an acid, and at the fame timepreferve  the whole folutJon'
quantity of phlogifton which was neceffary to it in its
metallic ftate.   A certain proportion of the principle of s0lu^4
inflammability therefore maybe confidered as an  ob- impeded by
ftacle  which muft  be removed  before a folution  can too great a
take place.   Thus, of all the acids, the nitrous attracts quantity of
phlogifton the moft powerfully,  and feparates it even phlogifton.
from the vitriolic.   A proof of this  may be  had  by     J59
boiling  fulphur  flowly in concentrated  nitrous acid. 4" jj-f
At length all its phlogifton may be feparated, and the tkatedUy
vitriolic acid will remain, deprived of its  principle of nitrous
inflammability.   The extraordinary lolvent powers of acid.
this acid, therefore, is conformed to thepeculiarity of
its nature in this rcipcct.  For this menftruum diflblves
met ils for fomtion v.dth the greateft eafe, moft com-     196
monly without any afliftance from external heat; wliich <'aki> of
in fome inftances would be  hurtful,  by  feparating too fomc mct-
much  of phlogifton, as appears in the cr.fe of iron,  tin aJs PrePa;
and antimony ;  all of which maybefo frr dtphlooifti! rcd Ly r:l~
     11   1    •         -i      1*     j   j     "    trous acid
cated by  the nnrons  acid, as to be rendered extremely ajn (,jt •
 tiifficult of Sh.uion :  for this reafon it  i-  very often foluble e-
 ncceflary, as has .d/'.ady been obferved, to t mrerthe v«" after-
                                            activity war»b. 
Theory.
CHEMISTRY.
33
   197
Why the
adt on
lead, fil-
ver, &c.
without a
boiling
heat.
   198
Why ma-
rine acid
acts on
fome me-
 Solution   activity of this menftruum  by water.  The vitriolic
 and preci-  acid requires a boiling heat before it can  act upon fif-
 pitation. ^ ver or mercury. J  The reafon of this is, that by means
           of the heat, the watery part of the menftruum is dimi-
           niflied, its power is thereby increafed, and the connec-
 vitriolic a- tion of the metallic earths with the inflammable prin-
 cid cannot  ciple diminished.   Marine acid,  which contains phlo-
           gifton as one of its conftituent principles,  muft necef-
           f mily have little or no effect on thoSe metals  which re-
           tain their principle of inflammability very obftinately.
           But its watery part being diminiflied by boiling, it
           ailumes an aerial form, and powerfully attracts a lar-
           ger quantity of phlogifton than before ; fo that in a va-
           porous ftate it will  diflblve metals, particularly filver
           and mercury, which in its liquid form it would fcarce
           be brought to touch.  When dephlogifticated as much
 tals and not as poflible, it attracts phlogifton with prodigious avi-
 on others,   dity,  diffolving all  metals by its  attraction  for their
           phlogifton,  and, uniting the inflammable  principle to
           itfelf, refumes the ordinary form of marine acid.  When
           dephlogifticated by means of nitrous acid  in aqua  re-
           gis, it diflblves gold and  platina.   On the fame prin-
           ciples may we  account for its inferiority in power to
    150    the other acids.
 Why fome    It has already been obferved that the metals differ
 metals are  much in their degrees of folubility, which is owftng to
 m?Fe f""   the various, degrees of force with which they retain
 •then1      their Phlogifton-  Thoi'e called perfect metals  effec-
           tually refift calcination in the dry way.   In this opera-
           tion,  the fire  on the one hand,  the great  caufe of the
           volatility of bodies,  ftrenuoufly endeavours to expel the
          phlogifton ;  on the other hand, the bafis of the dephlo-
          gifticated part of the atmofphere (the acidifying prin-
          ciple of M. Lavoilier, and the principi;t7i> fovbile of Dr
           Lubbock) attracts   the  calx ftrongly.   Experience,
           however, fhows, that thefe two forces united, cannot
           decompofe gold, filver,  or  platina to any confiderable
           degree.  All the  other metals  yield to  thefe  forces
          when  united,  but  not Singly.   Iron and zinc retain
          their inflammable  principle fo flightly, that  any  acid
          immediately acts upon them ; but if the other metals h:
          properly prepared  for folution by being calcined to a
          certain degree, the acid will immediately take them no.
          Any further privation,  however, would be  injurious,
          and precipitate  what was before diflblved.   Thus the
P-'=C!P>tates nitrous acid,  when added  to a folution of tin or anti-
a folution        .     '.       ....          ,.          _.
of tin or   mony in marine acid, by its extraordinary  attraction
          for phlogifton  carries off fuch a quantity  of it,  that
          the calces of the metals are immediately precipitated.
             The various  elaftic fluids  which reftmible air, and
          which are produced in plenty during the diffolution of
          metals,  may be reduced to the following, viz. thofe ex-
          tricated by  the  vitriolic, nitrous,  and marine  rchls,
          fluor acid, vinegar,  alkaline Salts, and heparfulphuns.
            Pure  vitriolic acid expoSed to a violent  heat, is in-
          deed reSolved into vapours,  but of fuch a nature,  that
          when the heat is gone, they condenfc again into an a-
          cid liquor of the fane  nature as before,   Bm if  any
be reduced  fubftance be added  which contains phlogifton in a Se-
into an ae-  parable flute, an elaftic fluid is prochved by  means of
rial form  fire, which is Scarcely condenfible by"the m T" xtreme
          cold, unlefs  it coxites in contact with v/ate  y   This is
          called the volatile  fuli hureous  acid,  or \ hriolic acid
          air, which may be   .ctdiy abforbed by wat; c.  In this
          cafe the bond of union  betwixt it and  the phlogifton
   400
Why ni-
trous acid
antimony.
   301
Different
kinds of
air produ-
ced during
the diffo-
lution of
metals.
   20Z
Pure* Vi-
triolic a-
cid cannot
but by a
combina-
tion with
phlojjiH on
 is fo weak, that the latter foon flies  off totally, and Solution
 common vitriolic acid is regenerated.                 and F«ei-
    The nitrous acid undergoes  a fimilar  change in a Pltatl°m „
 more obvious  manner.   Let a piece of iiiver, for in-    203
 ftance be  put  into a dilute nitrous acid, and  the  fur- Nitrous a-
 face of the metal will inftantly be covered with in- cidmore
 numerable bubbles, which arifing to the top of the Ii- obvioufly
 quor, there burft ; and if collected, are found to be ni-c iangc  '
 trous air.   The nitrous acid faturates itfelf with phlc- y^ n;_
 gifton more completely than  the vitriolic; therefore trous air
 the elaftic fluid produced, or nitrous air, does not unite does not u-
 with water, and fcarce retains any veftige of an acid nite with
 nature.  The vitriolic acid, however,  differs from the watcr,«
 nitrous in this refpect, that the phlogifton is abforbed
 by the latter even beyond the point neceffary to  obli-
 terate  its acid nature.  In proof of this, our author
 adduces the decomposition of  hepatic  by means of ni-
 trous air.                                               205
   The marine acid   exhibits  different phenomena. Phenome-
 It naturally  contains  phlogifton, and therefore canlia exhibit-
 by  its means be refolved into a kind of air Somewhat ed by the
 Similar to that produced by  the vitriolic acid when ar- n?*rme a"
 tificially united to the fame principle,  and which has
 the fame property, viz. that of remaining permanent-
 ly elaftic as long as it is kept  from the contact of wa-
 ter.   But as the  acid  we fpeak of naturally contains
 phlogifton, there is no neceflity of adding more to
 produce this effect.   In the mean time, the marine as
 well as nitrous air, when in its expanded ftate,_attracts
 phlogifton, and that with wonderful avidity.             2C^
   When the marine  acid is dephlogifticated, it yields  Of  the
 another elaftic fluid of a reddiih brown colour,  having dephlogif-
 an odour like that  of warm aqua regia.   This  does ticateel
 not unite with water, or only  in very  fmall quantity:  n™nne  a"
 and by the addition of a proper proportion  of phlogiS-
 ton may be reduced again to common marine acid.  It
 is  Said that the marine  acid maybe  dephlogifticated
 by lead as well as by manganefe,  the nitrous acid, and
 arfenic.                           #                -   ao?
   The fluor acid abounds with phlogifton,  and  there- ofthe fluor
 fore may, without any adventitious matter,  be  reduced acid.
 to an  elaftic fluid.   This air is eafily diftinguifhed
 from all others by its corrofion of glafs whilft hot.        2o8
   Vinegar alSo contains phlogifton ; and for that rea- Why vine-
 fon, when well dephlegmated, may be reduced  without gar may be
 addition into a permanently elaftic fluid, called acetous reduccd.m"
 •            r         J                           toairwith-
   A1I thefe fluids feem to be nothing  elfe, according tion-
 to Mr Bergman,  than the acids themfelves expanded    209
 by phlogifton.  " Perhaps  (fays  he) the matter of Heat and
 heat alfo enters their compofition."  The experiments not phlo-
 lately made on  theSe Subjects, however, have put it be- g'^on th«
 yond all  doubt, that  the expanfive principle  is not ^"wi^
 phlogifton but iiea1 ;  nevertheless, it Seems highly pro- cjty%
 bable, that theSe elaftic fluids  do really confift ofthe
 acid united to phlogifton, and expanded by "heat.   This
 is  alfo  the cafe with the cauftic volatile alkali,  now
 called alkaline  air.                                      2IO
   In the hepatic air, it has been fhown by Mr Berg- Sulphur
 man, that fulphur exifts which contains phlogifton; and exifls in
 there  ic little reaf'011  to  doubt  that  the  expanfive hepatic air.
power here is the fame as in other cafes.   See Hepa-
 tic Air.
   The heat generated during the folution of metals is
by  Sir Bergman fuppofed  to  be owing to  the matter
                        E                       of 
34
Polu'.on
and Preci-
pitation.

   ait
Heat in l>-
lution molt
probably
jTocced*
liom the
fblvcnt li-
quor.
Solid bo-
dies do not
part with
fo much
heat as
fluids.
   **3
Why little
nr no ela-
ftic fluid is
obtained
from n.t-
tallic cal-
ces.
   114
Me-allic
folutions
contain a
calx of the
nut.-.! with
various i!e-
gTees of
phlogifton.
                            C    II   E    M   I
of lie:.t which had  been fixed in  the  metals ; but it
may with much  more rcaloa be fuppofed 10 proceed
from the acii:.   Dr  Black has demo, n.ateu,  tinn heat
is univerfally the principle of nuu.n; ; and aft nuid*,
whether acid  or not, arc   found  to contain a great
quantity of it.  It is not probable that lolieih,  even tne
moft inflammable, contain an equal quantity ; for it is
;:ivays obferved,  that bodies in becoming ltuid r.Lnorb
heat, and throw it out again  onbtconui.gSolid.  Acids
in all probability  contain a much greater quantity than
what is neceflary to their fluidity ;  for we lee that the
nitrous acid,  when poured upon fnow, parts with as
much heat as is neceflary to  diflblve the i\«nv,  at the
Same time that  it  ftill retains  its fluidity.  The cafe is
not So with common  Salt, which is a Solid : Sor thougn,
in a mixture of  fait and  Snow, the latter, ah (orbs as
much heat from the  Salt as is neceflary  for its own li-
quefaction ;  \ct the  fait could  not be held in folution
by  a liquid of  this  temperature, were.it not that an
additional  quantity  is perpetually  abforbed  from the
adjacent bodies,  particularly  the  atmoSphere.   But
were it pollible to prevent this  adventitious increafe of
heat, there is not the leaft reafon  to believe  that the
fait would be diflblved ; for the ftrongeft brine,  when
reduced  to  the temperature of o  of Fahrenheit,  is
decompofed, the  fait falling to the  bottom in pow-
der, and the water being converted into ice.  Add to
this alfo, that the cold produc«d by fpirit of nitre and
fnow is much more intenfe than that produced by com-
mon fait and fnow ;  which undoubtedly fhows,  that a
folid does not readily part with  as much  heat as a fluid,
and  consequently cannot be fuppofed  to  contain as
much.  The folution of metals in acids alfo demon -
ftratcs, that the folid fubftance has not parted  with
heat, but abforbed it ;  for as  foon as  the folution be-
comes folid again, /.  e. when it cryftallizes,  the tem-
perature becomes higher  than before.
   The calces of metals have  not that quantity of phlo-
gifton that is neceflary for their metallic ftate, but yet
are not entirely deftitute of it;  therefore, in their fo-
lution, learcc any elaftic  fluid is genery.ed, unlefs the
fire  be continued after cxliccation.  buch as contain
aerial acid, diScharge it immediately in the Same form
as they had received it   It is remarkable, that Dr
Prieftley mentions a calx of lead, which, withtheacid
ofpholphorous, produced an inflammable air. By means
ol the nitrous acid and  evaporation  to drynefs, a pure
air is produced.  Sometimes a fmall portion of vitriolic
acid  air is obtained by means of a proper degree of
fire  from vitriolic acid,  but a  far greater  quantity of
pure air.
  The folutions made  by  the menftrua abovemen-
tioned, contain a metallic calx  intimately united with
the  acid, the quantity of phlogifton  left being  va-
rious according to the difference of the menftrua and
of the temperature;  but the performance of the opera-
tion either with or without intenfe her.t,  frequently oc-
calions a remarkable dirrerer.ee.  That metals are leSs
calcined by the marine th.n by the nitrous acid, ap-
pe.irs from pairing concentrated nitrous acid^ on tin or
antimony; h n  the difference,  if it actually does take
place, is lefs vilible in other mcn.K
  Some modern chemifls have denied this calcination
of metals by fi•'. :hm.   They have infifted,  that  the
pcrfcet metals ought to be excepted,  as they do  not
  S   T    R   Y.
yield to the moft i.ncnfc fire.
c\ci-,  it may be obferved, i.
Theory.
                              On this fill jecl, how- Solu ion
                            that uiiiing iheii  iclu- »«*»  »•«■«*!-
tion nitrous air is always generated, and that ol a \ciy r'tiu'"n-  ,
perfect  kind, which cannot happen w hhm.i phlogi-    uj
lion ; but in this cale there is i.enlih.ir puknt which Realm.t
can yield  phlogifton except  the n.ciuN.   i hcrclore, for l»-lic-
2.  1 he metals,  when piecipitaicd liom their irei-itrua vin?ithat
by  fixed alkalis, both  with  reipcd.10  their external "
appearance and  internal properto, appear to  be cal
cined.   rl hus the precipitate of  gold ret ufe s to unite
metals arc
calcineu by
1 hlogifloa.
with mcrcum, ana may be dinolvedby marine acid and
other im pie menftrua, and that without the produc-
tion of any  elaftic f'.uid.    2. Glafs may be ftaincd by
thefe  edccs;  but no metal in  its perfect ftate can be
taken up by glafs.     _                                 2l6
   The common  objection m,  that the  calces of the why the
perfect metals may  be reduced  by heat alone without calces of
the addition of charcoal.   Many  theories have been the perfect
invented to fblve  this phenomenon.   Some have  fup- meta'»
pofed,  that the matter of heat  and light are  the fame jiayj)cre"
with the phhgifton, and that thus the calces are redu- w;tb0utad-
ced in  the fame  manner  as by charcoal or other fub- dition.
fiances ufually termed //.'"  '.' t.  But in this cafe wc
ought  to find  the calces  n the imperfect metals alio
reduced by  a  long continuance of heat, as well  as the
more perfect ; which, however, has never  yet been
known to take place.  Some,  among whofe number
is Dr Lewis,  have  imagined,  that the  porofity  of the
vcflels, particularly thofe made of earthen ware,  may
be fuch as to  admit the paifagc of phlogiftic \apours
thro ■ h them  ; and he inftances the revival of globules
of led in the middle of pieces of glafs upwards of
an inch in thickimfs, and that where there was not the
leaft appearance of a crack.  But from  an experiment
of Mr Kirwan's to be afterwards related, it is much
more probable that the reduction is effected by means
of the phlogifton  contained in one part  of the calx at-
tracted by another ;  by which  means the latter is re-
duced to a perfect metal, while the  former becomes
fomewhat more dephlogifticated.   In confequence of
this it  appears, that the calx of the perfect  metals is
never totally  reduced:  for if  the operation be  per-
formed  in a glafs retort,  the   bottom of it is always
ftained ; which indicates  the  exiftence of a calx, in
however little quantity.                                  ai«
   The  following fact,  Mr Bergman fays,  has been Difficulty
propofed to him as an inextricable dilemma.  "  Silver concerning
cannot amalgamate  with mercury  except when in 'ts tnearnal-
metallic ftate,  yet both  falited   and nitrated  filver are S*™UoH
taken up by mercury ; it is therefore not calcined by f0iv'cdby
the acids, but adheres to them in its metallic form." Bergman.
This, however, may be eafily  folved  in the following
manner.  It is well known that the calx of copper,
diflblved in the vitriolic acid, is precipitated in its me-
tallic form on  the addition of iron, and that by means
of a double elective attraction ;  for the iron, diffolving
in the  acid, would  form  an  inr'an n able air by its
phlogifton, were  not the copper prefent which takes
it up,  and thereby becomes infoluble  as long as it re-
tains it; but  mercury has  a  ftronger  attraction for
acids than filver: if therefore  falited or nitrated filver
be triturated with me ret ry, the filver  muft  be preci-
pitated in a metallic ftate,  and the mercury be calcined
by being diflbhed.   This alfo tak< , lb',  provided
there be moifture fufficient tofuficr the cituivc attrac-
                                              tions 
Theory.
CHEMISTRY.
35
   ai8
Phlogifton
the caufe
of colour
in metal-
lic folu-
tions.
Solution   tions to  operate. The fuperabundant mercury greedi-
and Preci- ly takes up the comminuted filver precipitate ; and the
pitation.   arbores Diana are nothing more than fuch an amalgam
          cryftallized.   But although the acids cannot take up
          any metal while it retains its full proportion of phlo-
          gifton, various metallic falts are able to effect that fo-
          lution.   Thus  nitrated or falited  mercury, boiled in
          water together with the crude  metal, can take up a
          certain portion of it  without dephlogiftication;  and
          the latter of thefe falts, even in the via ftcca, becomes
          a'mercurius  dulcis, which contains at the fame time a
          crude and  a calcined mercury.
           Perfect folutions fhould  in general be  transparent;
          but fome, as  has been already mentioned, are diftin-
          guilhed by  a peculiar colour.  That phlogifton is the
          chief caufe of colour  appears from  hence,  that  the
          black clax of manganefe tinges vitriolic acid of a red
          colour ;  but on the addition of Sugar the tinge is en-
          tirely deftroyed.   Nitrous acid  is  rendered blue by
          copper;  but  when the metal is atlded in confiderable
          quantity, it becomes of a very deep green. The  ma-
          rine acid,  which dephlogifticates the copper leSs, is
          yet made  green; but by  dephlegmation  may  be So
          condenSed  as  -to become brown.  Mr  Bergman  has
          fometimes Seen a Solution of filver green,  without the
         preSence of the fmalleft particle of copper. This de-
         pends on the abforption of nitrous air : for let fmoking
         nitrous acid be  diluted, on  the addition  of a  certain
         quantity of water it will be  of  a  deep green ;  by a
         greater, blue ;  and upon a  ftill greater, becomes lim-
         pid.   By  means of the water, the nitrousv  air is ex-
         tended to a greater fpace; and this  attenuation gradu-
         ally increafed  varies the colours.  Hence  we fee why
         nitrous  acid is  made  green by  a  large  quantity of
          copper.
           Metals dephlogifticated  by acid Solvents powerfully
          attract phlogifton;  nay, nitrated filver and mercury,
   219
Attraction
of phlo- j
 gifton the  and falited antimony, corrode animal fubftances, in or-
 caufe of   der, as our author fuppoSes, to  extract  it.   "This
 eauftiaty.  metallic caufticity (Says he), which is only to be  mo-
          derated by phlogifton, ought to  be carefully  diftin-
          gufhed from the acid  caufticity, which is reprefled by
          alkalies,  and the alkaline, which is mitigated by acids.
          Colours vary according  to the quantity of phlogifton
          prefent;  and  fome experiments fhow, that by  a Suffi-
   i20    cient quantity all colour is entirely deftroyed.
 Phenome-    All metals may be precipitated  by alkaline  falts;
 na attend-  which, by their fuperior power of attraction, feparate
 ing the    therri  from their menftrua ; but their difference with
 precipita-  regard to their nature and preparation alters the  na-
 uM  T" mre °^ t^ie Precipltate-   With  the cauftic fixed alkali
kahneTatts.tne ca^ces fall almoft entirely pure,  but  loaded with
        ' water.  The weight is  found to  be increafed  by  the
          water, and perhaps (fays Mr Bergman) by the  matter
          of heat ; but yet leSs  than by the  aerial  acid.  With
          the aerated fixed alkali,  by means  of a double decom-
          pofition, the  aerial  acid unites to moft cakes   The vo-
          latile alkali, which naturally contains phlogifton, fome-
          times phlo^ifticates the  precipitate.  It throws down
          a black or white precipitate ofmercury ; nay, it makes
          the orange-coloured precipitate white.  Gold receives
          its fulminating quality from this precipitant, as is af-
          terwards  to  be explained.  The alkali, which is com-
          monly called phiogiflicated, generally precipitates metals
          with an increafe of weight.
    The acids frequently occasion precipitates, and that Solution
 for various reafons.  By means of elective attraction, and Freci-
 mercury, filver, and lead, are taken from  the  nitrous Pltatlon»  ^
 acid by the addition ofthe marine or vitriolic.   Thefe    22I
 acids form with the metals new compounds which are Precipi-
 difficult of folution in water  ;  they are therefore pre- rates
 cipitated in greater or lefler quantity  according to cir- occafioned
 omittances.  The nitrous  acid is capable of  decom-  yHaciT.s'.
 pounding falited  tin and  antimony by  dephlogiftica-     w ''
 ting the calx of the metals too much  ; for when thefe
 are too much calcined, they cannot be diflblved in any
 menftruum, as has been already obferved.                222
    Metallic folutions are fometimes difturbed  by the By the per-
 neutral falts formed by an union of alkalies with acids. ie& neutral
 Thofe which contain the  vitriolic or  marine acids de- fa*ts;
 compofe folutions of filver,  mercury, or lead, 'in ni-    22,
 trous  acid, and precipitate the  metals.  By forming a By a triple
 triple combination, the vegetable as well as  the vola- ccmbinati-
 tilc alkali, though Saturated with vitriolic,  nitrous, or on-
 marine acid, precipitate platina from aqua  regia ; but
 when the bafis is mineral alkali, the fait has no power    234
 of this  kind.  Some  metallic  falts  can  decompofe Some me-
 others,  and precipitate  their bafes ; which may hap- tabic falts
 pen whether the  acid be different in  the two falts or decompofe
 not.   Solution of gold affords  an  example  of each of otners-
 thefe cafes.  This  is precipitated by  martial vitriol ; wh22/j,
 the reafon of which will appear from considering the ti01/of° U"
 nature of the precipitate : for this, when well waflied gold is pre-
 and dried, not only fhows many Shining gold-coloured cipitated
 particles,  but alSo unites with mercury by trituration, by green
 diflblves in aqua regia, but not in marine acid alone, to- vitno1:
 gether with other circumftances which evince a complete
 refufcitation of the gold. Martial vitrol,  in its ordina-
 ry ftate, contains phlogifcon, but veryloofely adhering ;
 fo that the clax of  gold may eafily take it from the
 folution to fupply the lofs it  had fuftained  during the   2z6
 folution.   That this is the true foundation ofthe pro- But not by
 cefs, appears alfo from the following circumftances, this fait
 that the weight of  the gold is exactly recovered, and when de."
 that  dephlogifticated vitriol  will  not precipitate this Phlog^i-
 metal.   The  reafon that  the Surrounding aqua regia cate "
 leaves this precipitate untouched is,  that  the  men-
 ftruum is diluted and weakened  by  a large quantity of
 water; for upon  boiling it gently, fo as to expel part
 of the water, the menftruum recovers its folvent  pow-
 er, and  takes up the precipitate again.                  227
   It is Somewhat more difficult to explain the reaSon Why folu-
 why the Solution of gold in aqua regia  fhould be preci- tion of
 pitated by a Solution of tin in  the fame menftruum. gold 1S rre"
 Here Mr Bergman firft fuppofed  that the the tin had at-
 tracted a fuperabundance of acid,  and  taken it from
 the gold ; which  being  therefore deftitute  el  its pro-
 per quantity, muft fall to the  bottom :  but on employ
 ing a Solution containing a  Superabundant  aqua  regia,
 the Same precipitation took place. The cauSe is thereSore
 not in the menftruum.   On examining the precipitate
 itfelf,  we find nothing like  the metallic Splendor  of   218
 gold, but that it entirely refembles  a calx.  It is eafily This pro-
 found by its weight, indeed,  that it cannot confift en- cipitate
 tirely  of gold ;  and in  fact  chemical  examination confifts
 fhows that it confifts partly of tin.   It cannot  be dif-purtly of
folved by the marine acid alone, but is  eafily taken up
by the addition of a little  nitrous  acid.   It Scarcely
unites with mercury by trituration.   Thefe  properties
feem to indicate, that the gold  has fo far received phlo-
                       E  2                   gifton
cipitated by
folution of
tin. 
   129
Preeijita-
tion r>i :'.k
tal
anol
36                                   CHE   M    I
Soluti n    gifton as torcfift the marine acid until it receive the
:.ni Preci- ahiflancc of  the nitrous ;  but  its earthy  appearance,
i'llut'":i-   and difficulty of uniting with mercury, evince that u is
        "'not in its  complete  metallic  form.   The following
          therefore, according to our author, feems to be  the
          moft etify and rational  explanation.  The folution o;
          tin  ncceii.ny fur this  opera ion  muft retain as  much
          phlogifton as it po.iuly can, in a confiftcncc with foh;-
          bilitv.   1 4lis is  dropped  into a folution of gold very
          mach diluicd ; by v. iiich means the phlogifton remain-
          ing in  the tin is more loofened, and of con Sequence
          morecalily attracted by the gold c. lx, which is there-
          by  brought  to a ltate approximating to completion,  So
          that it can no longer  be retained by the menftruum ;
          and the Same happens to the tin, by means oS the dc-
          phlogiftication ; they  muft both therefore fall to the
          bottom  mixed  intimately  with  one another.  It  is
          probable, Says he,  that in thi. cale it is the tin which
          prevent.* the. matter  Sroni uniting with mercury.
            The metals precipitate onea nother after a certain or-
         - der, which is the Same in all acid menftrur.. This  pre-
    by ouecipi[ation is oecaiioncd by a double elective attra-;  ion ;
    lu""'   Sor the metal to be precipitated exifts in the Solution in
double c- * a  calciaed flatc ; but bcinS reduced by the phlogifton
Ucliveat- °f lne precipitant falls to the bottom, while at the fame
taction,  time the precipitant  becomes foluble  by  calcination:
          but if the precipitant has been  calcined fo  that  a part
          of"it being inSolublc  is mixed with  the precipitate, the
          metallic Splendor is wanting,  and it puts on an earthy
          appearance.   A pure precipitate is oS the Same weight
          with the metal before Solution.  The nhxed precipi-
          tates are lefs frequently met with, yet gold precipitated
    a„0    b/  tin exhibits one oSthat kind.
 variations    Though  the ord-.-r  in which the metals precipitate
 in the or- one .mother is eonftant and never  inverted, yet there
 der in    are many anomalous circumftances which occur in the
 w huh the mattcr.   Thus zinc  conftantly  prevails  over iron;
 metals pre- jrQa Qvcr 1caj  . jea(i over tjn . tjn over COrncr ;  c  n-

anothcr°ne Pcr ovcr fllvcr ;  lilvCV °Vei" mercul7»  4i'c' Zct n i"oni;:"
          times  happens, that a metal which, according to the
          general rule, precipitates  another  in its metallic  fta.te
          from one menftruum,  precipitates it from another  in
          form of a calx, and not at  all from a third. Thus zinc
          precipitates iron from marine acid in its metallic ftate,
          but from the nitrous  only in form of a chx.  Tin is
          precipated by lead from the marine acid in its metal-
          lic ftate,  but is not  thrown down from the nitrous
          acid ; and from the acetous is precipitated even by iron
          and zinc in form of a clax ; folution of lead in vinegar
          is  not  precipitated by iron.
             In  Mr Bergman's  experiments on this fubject  he
          employed the mineral alkali, as the degree of its  fatu-
          rati-m with fixed air was more  eonftant.  When  he
          had occauon fin a  cauftic alkali, h • prepared it  by a
          fmall rmamity of burned lime kept in a  eh ;e bottle;
          and the goodnefs of  it was proved by its occafioning
          n . precipTtation in lime water.   Phlogifticated  alkali,
          or that by which PrvMfian blue  is prepared, was alfo
          made ufe of.  With ihafe he made the following ob-
          servations.   Gold diffolved in aqua regia is preci] hated
          bv cauftic alkali almoft black; by  the aerated, yellow,
          as  well a> by  the phlogifticated, unlefs  fome iron  be
          prefent, which frequently u ippens ; but  the whole of
S    T    R   Y.
Neither the cauftic nor
'."ii
Mir.
kali why
preferred
; s a prcei-
j itant by
Mr Bcr--
m..n.
   232
H >■*• We
prepared
his cauftic
a'kali.
   - >1
Various
rre ipitates
*." gold.
the gold ia Scarce c .<.   ^
cannot be afcertained.
ecipi...t'-\!, fo that the weight   1
                                                  Theory.
                          crated miner.d alkali pre- Solution
cipitate one half of platina uinolvcd in  aqua regia ; the and l>r«'-
preeipitatc is of an orange colour, which on d)ing be- Plta"^"- ,
comes  brown.   An ovcr-p.oportion ot  alkali  rcdif-    1-4
loi.es  the precip'taie, and  the liquor becomes  more Mineral
dark;  nay, the  precipitation is fo impelled, that 1 he alkalies
mattcr  ftcms to  be  diflblved  e\en-by  neutral  Silt'. i>'-e'pitate
The p'. togifticated alkali  docs  not  piccijdtate the P^'jJJ]'"1"
depurated  folathm,  nor even  make it  turbid,  but1   c  7'
heightens  the colour in the Same manner as an excels
of aRili-           .    .        .                .235
   Solution of liver in  nitrons acid lets fall a white prccipi-
precipitiue by the aerated alkali;  brown by the cau-tatcs
itic, and oS an  obfenre  yellow.   Ly  the ni.rous and of filver.
marine acids it  lets fall a white precipitate, which
with the former confifts  en"  more diftinct particles,
which grow black more flowly with the light of the
fun-                                                    2^6
   falited mercury lets fall a red precipitate, or  ra-of mer-
ther one  of a  ferruginous  colour, by aerated alkali ; cury.
but of a  more ycllowilh  or orange colour by the cau-
ftic.   Nitrated mercury prepared without heat, 3 iehis
a ferrugiimns precipitate with  mineral alkali ; a 1 r - ];
with cauftic : and  when prepared with  heat, ityieltls
to cauftic alkali an orange  or reddifh yellow precipi-
tate.   By  phlogifticated alkali it is precipitated from
all acids  of  a white colour ;  but turns  of a browniih
yellow when dry.   Salited mercury is very Sparingly
precipitated by this alkali.   The precipitate by  phlo-
gifticated alkali m  again diflblved, if too much of the
precipitant be made ufe or.—Corrofive Sublimate muft
be very cautioufly precipitated by cauftic,  as well  as
aerated fixed alkali; for the part Separated may  again
be diflblved by a large quantity of water.   When too
much  alkali is ufed, a  new compound  arifes of a pe-
culiar  nature.                                           t^
   Solution of lead in fpirit of nitre is precipitated  down Prccipi-
white  by  aerated, cauftic, or phlogifticated alkali, tatcs
By ufing  too much alkali, the  precipitate by the  phlo- °f hi.d.
gifticated kind is dilfo'ved with a brownifh yellow  co-
loir .  Vitriol of lead  and folution of lead in marine
acid are precipitated  white.                              a,g
   Blue folution of copper in fpirit of nitre is precipi- of copper;
tated of a bright green by aerated fixed  alkali; by the
cauftic of agreyifh brown, which grows reddifh by age.
By phlogifticated  alkali copper is precipitated  of a
greenifh colour, which grows afterwards of a brownifh
red, and  upon exficcation almoft black.   The  aerial
acid takes up a  Small quantity of copper during  the
precipitation, which is  again  elcpotited  by the heat of
boiling.
   Aerated fixed alkali precipitates iron  of a green co- of  -a*".
lour from vitriolic and marine acid ; but  the precipi-        '
tate becomes of a brownifh yellow, especially on  ex-
ficcation ;  with the cauftic alkali  it approaches more
to black.   In the  precipitation  fome part is held in
folution  by  the  aerial-acid,  when  the  mild alkali
Unfed.   With phlogifticated  alkali a Pruflian blue is
formed.
   Tin is precipitated of a white colour  by every alka- of ti
line fait,  even   by the  phlogifticvted  kind ;  bi t at
length Some blue particles appear in the  mixture: fo
that the  whole, when collected and dried, appeal sofa
   in bine colour.  That theft Hue particles are c--.:-
fioncdby iron appears by calcination ;  for * j . y become
                                              ferru-
24c 
Theory.
CHEMISTRY.
37
meith :

   24a
Of nickel
   243
Of arfenic;
Solution   ferruginous, and obey the magnet. Our author has al-
and Preci-  ways found a proportion of iron in tin.
pitation.     iiiimuth is thrown down of a fine white by water
   ^x    and alkalies, particularly the former; phlogifticated al-
Precipi-    kali throws down a yellow powder, whicli being mix-
tatesof bif- ed with blue partrsles occafioned by iron, at length ap-
          pears green.  This yellow Sediment caiily diiiolves in
          nitrous acid.
            Nickel  is precipitated of a whitifh green  by fixed
          alkalies ;  by the phlogifticated alkali of  a  yellow;
          and by exficcation it is condenfed into a dark brown
          mafs.
            Arfenic diffolved in acids, which prevent too great
          dephlogiftication, may, to a certain degree, be precipi-
          tated white by the fixed alkali, even when phlogifti-
          cated,  but the fediment  is  found foluble  in water;
          yet nitrous acid,  either alone,  or joined  with the ma-
          rine, generally dephlogifticates the arfenical acid, which
          thereby becomes  unfit for fepa^ation.  Arfenic  dif-
          folved  in  marine acid,  with the  afliftance  of a little
          nitrous acid, depofited a white fediment on the addi-
          tion of  a large quantity of phlogifticated alkali.   The
          Sediment was  mixed  with  Pruflian blue.   This  was
          diifolved in water, and freed by frequent filtration from
          the blue particles ; and at length, on evaporating to
          drynefs, yielded a SemipellucidmaSs.
           Cobalt diflblved in  acids is thrown down by fixed
          alkali,  whether aerated or cauftic, of a  reddifh blue,
          which grows darker on exficcation, efpecially when the
          former  alkali has been  ufed.  Phlogifticated alkali
          throws  down a  powder  of almoft  the  fame colour,
         which,  upon exficcation, becomes of a reddifh brown.
           Zinc is precipitated white by  aerated and cauftic
         fixed alkalies,  as  alfo by the phlogifticated alkali;  but
          this  laft becomes  of a citron colour on exficcation : a
          fmall portion of aerial acid may eafily efcape during
          the precipitation.
           Antimony is precipitated white by alkalies.  When
         the phlogifticated alkali is uSed,  Some blue  particles
         are almoft always  precipitated at the Same time, though
         the regulus had been prepared without any iron.  This
         operation  fhould  be  cautioufly conducted,  left  fome
         part  be  taken up by the alkaline Salt.
           Manganefe  procured by  reduction from  common
         magnefia  nigra, generally renders  menftrua brown,
         and with aerated alkali yields a yellowilh brown fedi-
         ment; with the cauftic, one ftill darker ; with the phlo-
         gifticated, firft a blue,  then a white, powder is Separa-
         ted,  the  mixture  of which  renders the maSs a black
         green.   To obtain a pure  and white calx of manga-
         nefe, we muft diflblve in pure vinegar the precipitate
         thrown  down by cauftic alkali ; for there ftill remains
         a quantity of iron  which is taken up by the aerial a-
         cid.  This acetous folution contains little or nothing
         of iron.   That metal  may alfo at firft be  Separated by
         a fmall  quantity of volatile alkali.
           The  common folution of the regulus  is  not  per-
         fectly precipitated by  the aerated alkali;  and upon e-
         vaporating  the remaining liquor fpontaneonfly to dry-
         nefs, grains of a  metallic  Splendor,  and not unlike
         copper,  are depofited on the glaSs.   The nitrous  acid
         attracts  theSe readily, though they are only partially
   244
Of cobalt
   245
Of zine:
   246
Of anti-
mony ;
   247
Of man-
ganefe.
 diflblved by  it; but on the addition of zinc,  nothing Solution
 falls befides the manganefe, though at firft it is a lit- an£* f'1'--"'
 tie reddifh.   Vv ith phlogifticated  alkali,  we  obtain a flta^rn- _
 yellow precipitate like pure manganefe,  provided the
 iolution has  depofited the iron when too  lmn.h  de-
 phlogifticated by age.  But the new folution yields  a
 precipitate almoft like that which is obtained from com-
 mon regulus.   The yellow fediment may be diflblved
 in water.                                              a/^
   The following is Mr Bergman's table of  the quan- On the
 tities of precipitate  of different metals, thrown down came of
 from various menftrua by the different alkalies. " On fuci? £reat'
 comparing  the weights (fays  he),  a  queftion occurs yanatKlls
 concerning the  caufe of fuch enormous  difiti enccs; '"„,  vt of
 and it  is plain, that this  caufe muft be Sought for ir. p^Xi.
 the precipitates themfelves—The fixed alkali fatura- tates.
 ted with aerial acid, when added  to  the  folution, is
 taken up  by the more powerful menftruum ; and the
 weaker is of  courfe  expelled,  and is abforbed by the
 calx as it falls, in greater or lelfer quantity according
 to  circumftances.  That  this  is  actually  the  caSe is
 eafily demonstrated :—Let a bottle containing a quan-
 tity of nitrous acid be accurately weighed.   Let there
 be put into it,  for inftance, 132 parts oS lead precipi-
 tated by aerated alkali; and not only an  efferveScence
 will be obServed, which continues until the very laft
 particle is diflblved, but when  the folution is finifhed,
 a  deficiency oS weight is  discovered,  which amounts
 nearly to 21,  and which is undoubtedly owing to the
 extrication  of aerial acid.   But  132—21=111 ;  a
 weight  which  ftill  confiderably exceeds  that  of  the
 metal.  Upon  diftillation  nearly eight oS water  are
 discovered.  There yet remain  therefore three, which
 by violent heat are increafed by Seven ; for 132 of the
 calx wTell calcined yield no.   The whole increment
 of weight then does not depend  on the water and aerial
 acid.   The fame thing is  evinced by  confidering the
 precipitate oS lead by the cauftic alkali; in  whicli cafe
 there can be no aerial acid, nor does any efferveScence
 accompany the Solution.   If wc fuppofe the  quantity
 of water equal in both cafes, yet even on  this Suppo-
 sition the whole exceSs of weight is  not accounted
 for;  for  116—8=108.   It  is  therefore probable,
 that the matter of heat is attached to the calx (a).—In
 proof of this opinion, and  that cauftic alkalies contain
 the matter of heat,  our author adduces feveral argu-   249
 ments, of which the following is the ftrongeft.—" Let Argument
 the heat occafioned  by the mixture of any acid and in favour
 cauftic  alkali  be determined by a  thermometer;  let ofthe
 then an equal portion of the fame menftruum be fatu- weight  of
 rated with a metal;  afterwards, on the addition of an Prec'P'-
 equal quantity of cauftic alkali, it  will he  found,  ei- atesbenS
 ther tnat no heat is generated,  or a degree very much hythemat-
 lefs than before.—Some of the matter  of heat  there- terof heat,
 fore is taken up and fixed, which alfo generally makes
 the colours of the precipitates  more obfeure ; and  in
 diftillation with Sal-ammoniac, communicates to the vo-
latile alkali the quantity that had been taken away."
  In this inftance alfo, however, our author Seems to Tnfufly°ent
have been deceived.  It  has  already been obferved,
that in all folutions  generating heat, it moft  probably
comes from the fluid.  Acids  contain a quantity fuf-
                                             ficient
(a) This increafe of weight is with more probability to be afcribed to a remainder of the acid. 
»5'
                            CHE   M    I
ficicnt not  only St  their  own  fluidity, but  for ren-
dering folid  bodies  fluid alfo.   After they have dif-
lolvcd the  metal,  however,  this Superfluous  quantity
is employed;  ami when the cauftic alkali is added,  if
in a folid form, it is again employed in giving fluidity
to the alkali;  or if the alkali be .heady  didblved, the
increafed  quaniby of fluid makes the heat extricated
lef •• Srcepfude.
  " What nas been Said of lead (continues our author),
is   alfo true of  the  other metals,   a few excepted,
which feem to take np little or no aerial acid ; fuch
arc ti-,, antimony, gold and platina.—But fome pre-
cipitates retain alio  a  quantity of  the menftruum
S    T   R   Y.
Theory.
rained by
l>me pre-
cipitates.
*5»
A quantity Thus,  corrofive mercury,  precipitated' by aerated al-
oi the met:- J<.ali, retains a portion of marine acid,  which  cannot
        -  be wafhed off by water ; but, by cauftic  alkali, the
          precipitate may be obtained, either  free of the acid
          altogether, or in a great meafure.   In this cafe,  as in
          many others,  the aerial acid feems to generate a triple
          fait,  fcarce at all Soluble.   The preSence of the marine
          acid  is  eafily difcovered by folution of filver in ni-
nifP.r.nce  trous acid, iS the menftruum  has  been pure.   Hence
in the pre-  we obServe another difference  in mercury precipitated
cipitates  of froin marine add,  according as we employ the aerated
mercury.  or caunjc  ai]caif . tjie latter, well wafhed,  and put in-
          to volatile alkali, is  Scarcely changed  in  colour ; but
          the former inftantty grows white, generating a fpe-
          cics  of fal-alembroth, but  containing fo little marine
          aciel  as  not to be eafily Soluble in water.   The calces
          which retain any oS their former menftruum, generally
          give over  on diftillation a Small portion of  Sublimate.
          The mercurial calx juft mentioned,  expoSed to  a Suf-
          ficient degree of heat,  is partly reduced to  crude mer-
          cury, partly to mercurius dulcis, by means of its re-
          maining marine acid.  This mercurius dulcis did not
          exift in the precipitate ; for in that cafe it would be
          eafily difcovered by  acids in whicli  it  is not  foluble,
          and would grow black with cauftic alkali,  neither of
          which  take place,  fo that it muft be  generated during
          the diftillation."
            Mr Bergman concludes his  differtation,  with an e-
          numeration of the advantages  refill ting from the care-
          ful examination  of metallic precipitates.—Thefe are
          i. That thus the theory of the operation will be more
          perfectly underftood.   2. We may difcover the more
          ufe fill and remarkable properties.  3. A foundation is
          thereby laid for effaying in  the moift way, from  the
          bare knowledge of the weights.  "  It  may be objec-
          ted (fays he),  that the doctrine ofthe weights is very
          fallacious ; that  they vary  in different precipitates;
          that  by imperfect  precipitation  fomething remains
          in the liquor ; and that fometimes extraneous matters
          remain in  them.  All this is true ; but  if the mode of
          operation be the fame, the  refults of the experiments
          will be e\]  t.-rlly eonftant.   Thus,  let us fippofe  that
          a  certain quantity of  metal a, precipitated in a certain
          manner, makes a weight^,- if that  fame  manner be
          ex n :!y emploved, we may fairly conclude, that a quan-
          tity of precipitate nb,  occurring in any cale, is corre-
          fpondent to a quantity of perfect metal na ; though,
          in the fundamental experiment, the preripitationis either
          incomplete, or Some extraneous matter may  be prefent.
          4. The  nature of metals is thus illuftrated.  Platina,
         nickel,  cobalt, and manganefe,  a^e fuppofed by fome to
         derive their origin from a mixnire of other metals. But
         if iron ::cc charily enters into the compofition of platina,
   «53
Ad van:.1-
   to be
mr;v,d
from the
examina-
tion of me
tallic prc-
' ipitates.
when the lattcT is diflblved in aqua regit, it ought  to Solution
yield a Pruflian blue on the addition ot  phlogifticated anJ Prcei-
alkali ;  which indeed is the cafe when common platina V" >tl0n-  j
is employed, but not with that which is well depurated.   ^4
In like manner, if iron,  adhering very obltinately  to Platiiu it
nickel,  formed a great port of the latter, the precipi- 'tt comp«-
tates  obtained from it by alkalies  could  not  differ I'-J.Part'y
from martial precipitates fo much as they do in colour,   ,ron ■
weight, and  other properties.  The  fame  holds true Nor **
of cobalt and manganefe.   The regulus  obtained from ]u, 0f  njc.
the latter contains about  0.08  of iron,  which  affects kcl;
the mixture in  the  following  manner.   An  hundred   256
pounds  diflblved in an acid menftruum, yields,  by Cobalt or
treatment with phlogifticated alkali, a powder confining nil'nsaucfe
partly of blue,  partly of brownifh yellow particles, Quanth
equal in weight to  150 pounds;  but eight pounds of 0f procipi-
iron yield 48 of Pruflian blue, nearly ', of the whole mafs tate ob-
of piecipitare : whence it follows, that 100 parts of pure taincd
manganefe yield to phlogifticated alkali Scarcely  111; from m^n-
i. e. nearly fix  timeslcfs than an equal weight of iron. £an .J3*
  " Laftly, by this method of examining precipitates, p  °?' ,l~
it may perhaps be  poflible to determine the  unequal kaij
quantities of phlogifton in  different metals ; for a given    2^8
weight of precipitating metal does not yield an  equal Metals
quantity  of precipitate: thus,  for inftance, copper  is contain dis-
able to  precipitate  from  nitrous  acid  four times its ^ercnl
                                                    quantities
                                                    of phlogif-
                                             Yielded ton.
                                          dry precip.
weight of filver."
f  Gold,
Platina,
Silver,
Mercury,
o
Lead,
Copper,
Iron,
Tin,
BiSmuth,
Nickel,
Arfenic, _
r.*i
&H
"aerated mineral alkali
 cauftic
 phlogifticated
 martial vitriol
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 falited
 vitriolated
 aerated mineral alkali
 cauftic
 phlogifticated
 vitriolated
 aerated mineral alkali
 cauftic
 phlogifticated
 vitriolated.
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 pure water
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
       *S9
106 Table of
j IO different
 __precipi-
iootatc*'
 34
 36

129
112
MS
133
134
no
104

119
132
116

M3
194
158
530
225
170
590
131
130
250
130
125
180
113
135
128
250
Arfenic, 
Theory.
CHEMISTRY.
39
^ ArSenic,

  Cobalt,
Zinc,
<
   260
Kirwan's
definition
of chemi-
cal attrac-
tion.
Antimony
'G I
 <u 1
Mang.
■J
'cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
 aerated mineral alkali
 cauftic
 phlogifticated
   Yielded
dry prccip.

     180
     160
     140
     142
     193
     161
     495
     140
     138
     138
     180
     168
     150
   261
Difference
betwixt
chemical
attraction
and that
of cohe-
fion.
   262
Geoffroy's
rule for de-
termining
the degree
of chemi-
cal attrac-
tion.
   263
Chemical
decompo-
fitiuns, tho'
feemingly
fingle are
©ften dou-
ble.
   264
Force of
the attrac-
tive pow-
ers to be
determined
by num-
bers.
   265
True me-
thod of in-
vestigating
the quanti-
ty of at-
traction
each of the
acids has
for its dif-
ferent ba-
les.
   Mr Kir wan has  made  a great  number of experi-
 ments on the attractive powers of the mineral acids to
 various fubftances, and  greatly illuftrated the opera-
 tions of both folution and precipitation.   Chemical at-
 traction,  he obferves, t( is that power  by which the
 invifible particles of different bodies intermix and u-
 nite with each other fo intimately, as  to be infeparable
 by mere mechanical means." Thus it differs from the
 attraction  of cohefion, as well as from  that of mag-
 netiSm and electricity,  as  not acting  with  the indif-
 ference obServed to  take  place in theSe pow7ers, but
 cauiing a body already  united to another to quit that
 and unite with a third ; whence it is called elective
 attraction.  Hence attraction of cohefion often  takes
 place betwixt bodies that have  no  chemical attraction
 for each other;  as for  inftance, bifmuth and regulus
 of cobalt, which cannot be made to unite together by
 fufion, though they cohere with each other fo Strong-
 ly, that they cannot be Separated  but by the blow of
 a  hammer.
   To determine  the degrees of attraction betwixt dif-
 ferent fubftances, M. Geoffroy laid it down as a gene-
 ral rule,  that when two  fubftances  are united, and
 either quits the other to unite with a third, that which
 thus unites to the third  muft be fai'd to have a greater
 affinity to it than to the  fubftance it has quitted.  In
 many  caSes, however, the Seemingly  fingle decompo-
 sition  is in  truth a double one.  Thus,  when the vi-
 triolic acid expels the air from a fixed alkali, it  does
 not neceflarily follow, that the acid is more attracted
 by the alkali  than the fixed air ; for here though the
 latter refigns its place to the  acid,  yet the acid  gives
 out its fire to the air ; whence a decompofition might
 take place, even though the attractive powers of both"
 the vitriolic and aerial acid to the alkali were equal.
   To attain to any certainty in this matter, therefore,
 it  is neceffary to  determine the quantity  and force of
 each of the attractive powers, and denote it by num-
bers.   The neceflity of this has been  obferved by Mr
 Morveau and Mr Wenzel,  who have both propofed
methods for anfwering  the purpofe ;  but Mr Kirwan
has fhowed  that  both are defective : and he tells us,
that the difcovery ofthe quantity of real acid in  each
of the mineral acid liquors, with the proportion of real
 acid taken up  by  a given quantity of each bafis at the
 point  of Saturation, led him unexpectedly to what
 Seems  the true method of invefti-miiag the quantity of
 attra tion which  each acid bears to the Several bafes to
 which it is capable of uniting : « for it was impoffible
 (fays he) not to perceive, 1. That the quantity of real Solution
 acid neceflary to laturate a given weight of each bafis and Preci-
 i's inverfely  as the affinity of each  bafis to fuch acid. P1 atlon-  t
 2. That the quantity of each bafis requifite to faturate
 a given quantity of each acid is directly as the affinity
 of fuch a  id  to each bafis.   Thus  100 grains of each of
 the acids  require for their faturation a greater quantity
 of fixed alkali than of calcareous earths, more of this
 earth than of volatile alkali, more of this alkali than
 of magnefia,  and more of magnefia  than  of earth of
 alum.
   '• If an acid be  united  to lefs  of any bafis than is
 requifite for its faturation, its affinity to the  deficient
 part of its bafis is as the ratio which that deficient part
 bears to the whole of what the acid can faturate.  Thus,
 if 100 grains of" vitriolic acid, wdiich can faturate  no
 of calcareous earth, be united only to §5,  its affinity
 to the  deficient 55 parts fhould  be eftimated one half
 of its  whole affinity ; but its affinity to the  retained
 part is as  its whole affinity."                            2gg
   To explain the decompositions in which  thefe acids Method of
 are  concerned, we mult confider, firft,  the powers explaining
 which refill  any decompofition,  and tend to keep  the the t,ecom-
 bodies in their preSent ftate ; and, Secondly, the pow-ers p2-fi«0'Js>.
 which tend  to effect a decompofition and new union ; „.;V!ii„„/
 the former our author calls quiefcent c.fj. nities, the latter   a67
 divellent.   A decompofition will therefore always take Qu^fcent
 place when the fum of the divellent affinities is greater and divel-
 than the quieScent; and, on the contrary,  no  decom- 1'~nt &^lli'
 pofition will  happen when the fum of the quieScentties'
 affinities is greater  than that ofthe divellent.   All we
 have to do therefore is to compare  the Sums of each
 of thefe powers.   The method our author takes to
 compare  the affinities together is by  the following
 table;  in  which the quantity of alkali,  earth, &c. fa-
 turated by 100 grains of each ofthe mineral acids, is
 flated.
                                                       268
             Veg. fixed Mineral Calcar,  Vol. Mag-Earth of Quantity
              alkali.   alkali.   earth,   alk. nefia.  alum,  of acid ta-
 Vitriolic acid  215    16c   no    90   80     75
 Nitrous acid   215    16c     96    87   75    65
 Marine acid    215    158     89    79   71    55
  Thefe numbers he confiders as  adequate expreffions
 ofthe quanity of each ofthe affinities.  Thus the af-
 finity of the vitriolic acid to fixed vegetable alkali is
 to the affinity with which it  adheres  to  calcareous
 earth as 215  to no; and to that which the  nitrous
 acid bears to calcareous earth as 215 to 96, &c.  Fence rxpreflive
 we fum up the powers of affinity betwixt any number of the
of different  fubftances, and account for their derom- quantity of
pofitions,  as  in the following example  of the doubleattra<aion
decompofition, which  takes place when a folution of I ^.  ?ve
vitriolated tartar and folution of lime or chalk in  ni- 0f thefe
trous acid are mixed together.                        bafes.
ken up by
various ba-
fes.
269
   Qr/iefcent Affinities.
Vitriolic acid to vege-
  table fixed alkali,  215
Nitrous acid to  calca-
  reous earth,         96

  Sum of quiefcent ">
     affinities      C
   Divellent Affinities.
Vitriolic acid to calca-
  reous earth,        nc
Nitrous a- id to vege-
  table alkali,      '  2iclolidon-of
                    -----calcareous
  Sum of divellent 1      c-rth
   270
Decompa-
ction of
vitriolated
tartar by
affinities
■25 piained.
  Hence we fee that a double decompofition muft enfue.
The fame will be  produced,  if inftead of vitriolated
tartar w7e make ufe of Glauber's fait; for the fum of
                                                 the 
4°
CHEMIST    R    Y.
Theory.
Solution
«:.J l'rcci
pitation.
Coinci-
dence t>f
the aboTe
tabic with
experience
*T-
         the q/..'-rent a".;, nies  is  261,  oi" the eiivcllcnt 275 ;
         with  vitriolic anv.rumiac the  Sum of the  quiefcent  is
         l-'., of the dii.ei'. n  io>,  :■:<:.   In mixing vitriolated
         tat.ur with folution of  maxnclia in nitrous or  marine
         acids,  a double dccompoiitiou  takes place though in-
         visibly, u,s the vitriolic jLpfmnfak is very foluble in wa-
         ter, and therefore cannot be precipitated like felenite.
         In  the former cafe  the fun ot the quieScent powers is
         :g.,  of the  divellent 2<jS; in the  Second 2i.6  and

            Other decompofitions take place in the Same manner;
         and from all the ia.u which  our author had occalioii
         to obferve,  he concludes, that the quaiuity of each at-
         fiuity, asdctermi;ied in the above tabic, coincides ex-
         actly v. hh experience ; and that thefe decompositions
         are perfectly couiiftent with the Superior affinity which
         has been hitherto obferved iu the vitriolic and nitrous
         a. ids with fixed alkalies  over the calcareous  earths;
         nor do they iniiinge  in the leaft the known laws  of
         affinity,  as  has been  iniiuuated by  fome  chemifts.
Miftakc of One tact only, mentioned in Dr Ci ell's Journal, feems
I>r Cre-ll  to be repugnant to what is here  advanced ; and that is,
corrected. tjut [f folutions of one part of  alum and two of com-
         mon  fait be  mixed  together,  evapormed, and fet  to
         cryiL.tHi/e, a Glauber's Salt will be  formed; though,
         in  this cafe, the Sum of* the quieScent affinities is 21?,
         and that of the divellent only 223.   Mr  Kirwan re-
         peated this experiment without fuccefs; and Dr Crell
         himfelS  owns that it will not Succeed but in the moft
         intenfe cold.   Ii it does fucceed at all, he lays the de-
         compofition muft arife from a large excefs of acid  in
         the alum,  which acted upon and decomposed the com-
         mon Salt:  and this explanation  is  confirmed  by  the
         fmall proportion of Gla.bar's fait faid to  be obtained
         by this  procefs; for from  ;olb. of common fait  and
          16 of af.im, only 15 lb. of Ghmbcr's fait were  produ-
         ced ; whereas,  if the whole of the alum  had been de-
         compofed, there lhould have  been formed,  according
         to  Mr Kirwau's computation of the  quantity of acid
         i:i  the different film, 2o;lb, or, according to Mr B.rg-
   i-}   man's,  22lh. of Glauber's fait.
Formation   h\ fome cafes, the neutral falts have  a power  of
i;:'tripL"  uniting, without  any  decompofition, or with  only a
and cpia-   very fma\\ onC) to a third  fubftance; thus forming
crulllefalts"triple falts, and fometimes quadruple;  which  often
   1-4   caufes anomalies thr.t have not yet been fufficiently in-
Volatile al- veftigatcd.  Volatile alkalies in particular are pollefled
kalics par- 0f  tne power of uniting with  neutral falts in this man-
t ularly  ner_   Hence they feem to precipitate magnefia from
          Epfom fait, even when perfectly cauftic ;  hat  this is
         owing to their  combimnion with that Silt,  and form-
         ing a triple ore, which is infolul le in water.
             It  feems extraordinary that,  according to Mr  Kir-
          wans table,  the three miner.'  acids fK-.dd have the
          fame affinity*to vegetable fixed a'kalies, when it is well
         kr. m;i  that the vitriolic will expel either ofthe other
         two from an alkaline  b.^is.   In explication of  tlfts,
          Mr Kirwan obferves, that nitre is decompofed by the
         marine acid ; mid that  Glauber's fait and vitriolic mn-
         monitc  are decompofed  by  that  of nitre ; and  that
f> mi laits
»f tl'.S
kiuel.
    -75
Yiviol.C
{.  i dc-
C DP'pofed
by the iii-
r 1....... and
marine a-
cidt.

Thefe Jc.-
cumpoG-
tioii»fu p-
pofod to a
rile from
con: pound
the
   fe falts. as well as cubic ni.r*  and nitrous  ammo-
nia:, are decompofed by the m trine acid.
  Mr Kirwan is of opiiioi,  that thefe decompofitions
are  the  effect of a double  . ii.ity,  or at kali of com-
pc.:d  iV.-^e..  lit fifty.cLcd that  they arofc from the
different capacities of the acids for elementary  fire ;
and to determine this matter, he  made  the following
experiments, in  which  the decompofitions were not
difcovered by cryftallization,  but  b> tefts.
   1.  Having procured a quantity oS each oS the  three
mineral  acks  containing  the Same proportion of real
acid,  and reduced them to  the temperature of 68°  of
Fahrenheit, ico grains of vitriolic  acid, containing
26.6 of re... acid, was projected upon 480 grains of oil
of tartar at the fame temperature, by which the ther-
mometer was railed  to 1 ;8°.
   2.  An hundred grains of Spirit of nitre, containing
alio 26.6, projected on 480 grains of oil of tartar, pro-
duced o::iy 120"  of lie; t.
   ;.  An humired grains of fpirit of fait, the  fpecific
gravity of which was 1220, and which contained the
ufttal  proportion of real acid, raifed the thermometer
from  69 to 129.
   "  Hence (lays he) it follows, that the vitriolic acid
contains more ipecific fire,  or at  leaft gives out more
by uniting with fixed alkalies, than cither the nitrous
or marine; and therefore when the vitriolic acid comes
in contact with either nitre or fait of Sylvius, its fire
paffes into thefe acids, whicli are  thereby rarefied to a
great degree,  and are thus  expelled from their  alka-
line bafis, which is then Seized on by the vitriolic."—
On this, however,  it is obvious to remark,  that, ac-
cording to Mr Kirwan's explanation, the marine acid,
as giving out more Specific  heat, ought to expel the
nitrous from an alkaline bafis ; which, however, is not
the caSe.   Something elie, therefore, befides the mere
quantity of fpecific heat, muft here be taken into confi-
deration.  Mr Kirwan, however, goes on to prove the
truth of his theory by the following experiments.
   4.  To 400  grains of vitriolic  acid,  whofe  fpecific
gravity w as 1.362, fixty grains of nitre were added ; on
which the thermometer fell from 68° to 6o°.   During
the time of this deScent, the  nitrous acid was  not ex-
pelled ;  for fome filings  of  copper,  put  into the mix-
ture,  were not acted  upon in the leaft ;  but  in five
minutes  afterwards  they vifibly efferveSeed,  which
fhowed that the nitrous  acid began to be expelled ; Sor
the vitriolic acid does not  act upon copper but by  a
boiling heat.
   5.  Sixty grains oS nitre  were  put to 400 of oil  of
vitriol, whofe fpecific gravity wt-.s  1.870; the  ther-
mometer inftantly roSe from 68° to 1050,  and the ni-
trous  acid was expelled in a vifible fume.—<< TheSe
experiments (Says Mr Kirwan) prove, 1. That  neu-
tral Salts are not decomposed  by mere  Solution in an
aci^  different from  their own.   2. That the nitrous
r.cid,   being  converted  into  vapour,  had imbibed  a
large quantity of fire.   Eut  as the vitriolic acid,  in
both thefe experiments, was uSedin much larger quan-
tity than was neceflary to  faturate the alkali of the
nitre, fixty grains oS the latter were put into 64  of
the ahovemtntioned dilute Spirit  of vitriol, which  con-
tained the fame quantity cf real vitriolic acid that the
6c grains of nitre did oS the nitrous ;  with the  addi-
tion of 40 grains of water  and a few  ccrptr-filings.
In leSs  than two hours the  copper was ac'td upon
and confequemly the nitrous acid was expelled.
   6.  To  400 ; :..i::s of oil of vitriol,  of the  fpe-
cific^gran".  or   \.r)n-.f   ico  grains of  conmon  fait
were  ad.:.el.   /ui cfitrvefcence  immediately  enfued,
                                                «nd
Solution
and I'reci-
pitation.

   »77
Kxpcri-
rcu nts to
determinr
this by the
various  de-
grees of
heat ex-
cited  by
mixtures.
  . 2?f
Vitriolic
acid con-
tains mote
fire than
the nitrous
and ma-
rine.
   2/9
Difficulty
in the theo-
ry •
   a8o
On the ex-
pulfion of
the nitroui
acid by the
vitriolic di-
luted.
   a8l
By the fame
acid con-
centrated.
With a
fmall quan-
tity of di-
luted vitri-
olic acid.
   283
On the ex-
pulfion of
narine a-
cid by  the
concentra-
ted vitrio-
lic. 
Th
eory.
C   H   E    M   T    S   T   R    Y.
   284
Both the
marine a-
cids re-
eeive fire
from the
vitriolic
during
their
Solution,   and the marine acid rofe in white  vapours.   A ther-
and Preci- mometer held in the liquor rofe only  4 degrees, but
pitation.  ^ in the froth it  aScended to  io°, and fell again  upmi
          being replaced in the liquor.  Hence Mr Kirwan con-
          cludes, that the vitriolic acid gives out  its fire to the
nitrous and marine ;  and that this latter received  more than  it
          could abSorb even in the ftate oS vapour, and therefore
          communicated heat to the contiguous liquor,   it ap-
          pears to  him alfo, that  the nitrous and marine acids
          receive fire from the vitriolic,  ami  are  throwm into a
          vaporous ftate, or  at leaft rarefied to Such  a degree as
          to be expelled from their alkaline bafis, though  their
expulfion.  affinity with that bafis may  be  equally ftrong with the
   af>     vitriolic.
On the de-   7-  To aScertain the manner in which vitriolated
compo-    tartar and  Glauber's Salt are decompoSed by  fpirit of
fition of    nitre, 60 grains oS powdered tartar of vitriol were
vitriolated p,in jIlto ^0O 0f nicrous SiCid>  whole Specific gravity
tartar by   was r.a55, and which contained  about  105 grains of
nitrous 3.™        -^ -* ^ /                             ^./£3       -
fid>       real acid.  The thermometer was not affected by the
          mixture ; but in 24 hours the vitriolic acid was in part
          difengaged, as appeared by the acid mixture acting up-
          on regulus  of  antimony, which neither pure vitriolic
          nor pure  nitrous acid will do by themfelves.  On pat-
          ting the fame quantity of vitriolated  tartar  into 400
          grains  of  fpirit of nitre whofe fpecific gravity was
          1.4780, the thermometer rofe from 670 to 790 :  the vi-
          triolated tartar was quickly diflblved, and the regulus
   286    °f antimony ihowed that the vitriolic acid, was  difen-
Acidsunite gaged.  Hence it  appeared  that the nitrous  acid, ha-
to alkalies  ving the  Same affinity with the bails oS vitriolated tar-
by giving  tar as j-^g variolic, km giving  out, during the  Solu-
          tion, more fire than was neceffary to perform the folu-
          tion, the vitriolic, receiving this fire, was difengaged :
          for as it  cannot unite  to alkalies  without giving out
          fire  ; fo when it receives back that fire, it muft quit
          them.  The reafon why the nitrous acid, which Spe-
          cifically contains leSs fire than  the vitriolic,  gives out
          So much is, that  its quantity  in both  theSe  experi-
          ments is far greater than that of the  vitriolic;  it  be-
          ing in the firft as 105 to 17, and in the laft as 158 to
          17.
            8.  To  60 grains of fpirit of nitre,  whofe fpecific
          gravity was 1.355,  Mr Kirwan added 1000 grains of
         water ; and into this dilute acid put 60 grains of vitrio-
         lated tartar, containing exactly the fame quantity of real
         acid-that  the 60 grains of nitrous acid did.   In eight
         days the vitriolated tartar was almoft entirely diflblved,
         and  without any Sign of its  decompofition  ; and no
         nitre was found  upon  evaporating  the liquor.. Hence
         he concludes, that the nitrous acid  can  never decom-
         pose vitriolated tartar,  without  the afliftance  of heat,
         but when its quantity is fo great that it  contains  con-
         fiderably more fire, and by the act of Solution  is  de-
         termined  to give out  this fire.  This Salt is alSo de-
         composed, in Similar circumftances,  by  the marine a-
         cid ;  though ftill more flowly and with more difficulty
         than by the nitrous, as appears by the  following ex-
         periments.
            9.  Into 400 grains of Spirit of fait, whofe  Specific
         gravity was 1.220, were put 60 grains  of  vitriolated
         tartar. The thermometer was not affected in the leaft,
         and  the  fait didblved very  flowly.   Some pulverized
         bifmuth was added to  try whether the  vitriolic  acid
         was difengaged ;  and in 12 hours part of it was diS*
out fire,
and quit
them by
receiving
it.
   «87
Vitriolated
tartar can-
not be de-
compofed
by diluted
nitrous a-
«id.
   288
Decompo-
fition of
vitriolated
tartar by
marine a-
cid.
                                                           4*
 .blvea, fo fmi: it could not be precipitated  by water. Solution
 Tift's  ihowed, that part of the vitriolic acid was dif- and Pred-
 ion:,:  1 ; for this, femi-metal cannot be kept in foluiion Pltat">n-  t
 w-htii much diluted with water,  excepting by -a  mix-
 ture of marine and vitriolic acids.                      289
   In this expei iment the quantity of marine acid was Requifitcs
 im: h greater than that ofthe vitriolic; and therefore for the fire-
 it was capable of di dodging ft.   'I his circumftance a cefs oftnis-'-
 lone, however, is not Sufficient ;  the acid muft be dif- m^51"
 pofed  to  give out  by Solution  that  quantity  of fire
 which it is neceflary the vitriolic fhould receive in or-
 der to its quitting the bafis to which it is united ;  and
 therefore when Mr  Cornette added two ounces of Spi-
 rit oS  Salt to half an ounce of vitriolated tartar already vitriohtcef.
 diflblved, in water, no decompofition  took place.  The tartar dif-
 r.eaSonof this was, that as the vitriolated tartar was-al- folved in
 ready  diflblved,  no cold  nor heat  was generated by water can-
 the mixture ; and therefore the Spirit  of fait could not notbe de-
 give out any fire. Glauber's fait is more eafily decompo- £omP01f
 0        J                              /jr    f)y marine
 Std by marine  acid  then vitriolated tartar, on account ffi^& an^
 of its being more eafily Soluble in Spirit  of  fait;  and why.
 likewife becauSe its alkaline bafis  takes  up  an equal
 quantity of both acids : consequently the marine gives
 out more fire in uniting to  the bafis of Glauber's  Salt
 than on being united to that of vitriolated tartar.  Vi-
 triolic ammoniac is alSo decompofed by means of ma-   2gt
 rine acid ;  but in all thefe caSes, the quantity of ma- Decompo-
 rine acid muft greatly  exceed   that  of  the vitriolic fition of
 contained in the fait to be  decompofed ; and it muft vitriolic
 be remarked, that according to the observations of Mr- aniniGnia^
 Bergman,  the decompofition of  Glauber's fait or vi- f".. f a,""
 triolic ammoniac by this acid is never complete.      ^ marine
   On  the fame principles the marine acid decompofes acid never
 falts which have the nitrous acid for their bafis.  Mr complete.
 Cornette found,  that cubic nitre was more  eafily de-    a9a
 compofed by it than that which  has  vegetable alkali NltroUs
 for- its bails.  Accordingly, during   the  Solution of  sdef"
 prifmatic nitre, only three degrees  of  cold were  pro- by^narLc.-
 duced  ; but fix by the folution of cubic  nitre ;  which acid.
 fhows  that the  fpirit of fait gave out more fire in  the
 latter cafe than in the former ;  and its quantity muft
 always be greater than that of  the nitrous  acid con-
 tained in the mineral alkaline bafis ; becauSe  this' bafis
 requires for its Saturation more oS the  marine  than of
 the nitrous acid.   The nitrous acid, however, in  its
 turn decompoSes Salt of Sylvius and common  fait ;  but
it muft always be in greater quantity than the  marine
to produce  that effect.
   10.  Sixty grains  of  common  fait being  added to Marine
 400 of colourleSs fpirit of  nitre, whofe  fpecific  gra- falts de-
vity was 1.478,  the mixture quickly  efferveSced  and compofed
grew red, yet the thermometer roSe but two  degrees ; ^ the ni~
which fhowed  that the marine acid had  abSorbed the trous acu1*-
greater part of the firft given  out by that  of nitre;
the decompofition was likewiSe haftened by  the Supe-
rior affinity ofthe nitrous acid to the alkaline bafis of
the Sea-Salt:  hence  the decompofition of fea-Salt by
means  of nitre  takes place without any  folution ;  but
fpirit  of fait will not decompofe cubic  nitre until it has
firft diflblved it.  This  mutual expulfion  oS  the  ni-
trous and marine acids by each other, is the reafon why
aqua-regia  may be  made  by  adding nitre or nitrous^
ammoniac to fpirit of  fait, as well as by adding com-.
mon fait or Sal ammoniac to Spirit of nitre.
   Selenite  cannot be decompoSed either by nitrous or
                            F                marine 
4*
CHEMISTRY.
Theory.
          nut-ire acid ;  becaufe it cannot be  diflblved  in  either
          wiiuoui the affiltancc of foreign heat.   It muft like-
          wife Ik obferved,  that  in all  decompositions of this
          kiml, when the liquor has been evaporated to a cer-
          tain degree, the vitriolic acid expels in its turn the ni-
          trous or marine acid to which  it had already yielded
          its bails.  The  reafon of this is, that the free part of
          the weaker acids being evaporated, the neutral  falts
          begin to cryftallize,  and then giving out heat, the vi-
          triolic abforbs it ;  and thus reacting upon them  expels
          them from the alkali or earth to whicli they arc  united.
            Mr  Kirwan  found much more  difficulty in  deter-
          mining the attractive powers ofthe different acids to
          the metals than to alkaline falts  or earths.   Some of
          the difficulties met with in this cafe arofe from the na-
          ture of metallic fubftances themfelves.   Their  calces
          when formed by fire always contain a quantity of air,
Difficultiei which  cannot be  extracted from them without  great
m deter-   difficulty, and is very foon re-abforbed ;  and if formed
mining the ^ folution, they as  conftantly retain a  part of their
powers of  f°lvcnt or precipitant ; fo that the precife weight of the
the acid*   metalline part  can fcarce be difcovered. Our author,
          therefore, and becaufe metallic calces arc generally in-
          foluble  in acids, chofe  to have  the metals in  their
          perfect ftate : and even here they muft  lofe a part of
          their phlogifton before they can  be diflblved in acids,
          and a confiderable part remains in the  folution of the
          acid and calx ;  which laft quantity he endeavoured to
          determine.
             A new difficulty now occurred,  arifing  from the
          impofiibility  of finding the real quantity  of acid ne-
          ceflary to faturate  the metal,  for all metallic folutions
          contain an excefs  of acid : the reafon  of  which is,
          that the falts formed by a due  proportion of acid and
          calx are infoluble in water without a further quantity
          of acid; and in fome cafes this  quantity, and even its
          proportion to the aqueous part of the  liquor, muft be
          very confiderable, as in folutions of bifmuth.   It was
   398
 Quantities 100 grains of    Iron.   Copper
                                 260
   -94
S--lcnif .■»
uinnot bf
dec«mpo-
i'-d by ma
rine acid.
    -)5
Why the
vitriolic
acid al-
fumes on
evapora-
tion the
bafes it
had loft.
   296
to metals.
   497
Metallic
falts info-
hible in
water
without an
excefs of
acids.
r>f the dif-
ferent me-
tals taken
up by a-
cid.
Vitriolic
  acid
Nitrous
  acid
Marine
  acid
in vain  mtempted to deprive thoCc folutions of their
excefs of acid by  means  of cauftic alkalies and  lime-
water  ; for  when deprived of only part of it, many of
the metals were precipitated, and all of them would be
fo if deprived ofthe whole.  As the folution of filver,
however, can be  very  much faturatcd, Mr  Kirwan
began  with it and  found that 657  grains of  this folu-
tion contained 100 grains of filver,  and 31.38 grains
of real acid,  after making the  proper allowance  for
the quantity  diflipated in  nitrous air.  Nine grains of
this folution tinged an equal quantity of folution  of
litmus as red as T%. of a grain of real acid of fpirit of
nitre would have done;  whence our author  concluded
that 9 grains of his folution of filver contained an  ex-
cefs  of  -,%.  of  a  grain  of real filver : according to
which calculation, the whole quantity ought to have
contained 5.6  grains ;  which  deducted from  31.38,
leaves 25.78 grains for the quantity of acid faturatcd
by 100 grains of filver.
   As  the vitriolic folutions of  tin, bifmuth,  regulus
of  antimony, nickel, and regulus of  arfenic,  con-
tain a  large excefs of acid,  Mr  Kirwan Saturated
part of it with  cauftic volatile alkali  before  he tried
them with the infulion of litmus ; and the fame me
thod was ufed with folutions of  iron, lead, tin,  and
regulus of antimony in the nitrous  and marine  acids.
The proportion of vitriolic and marine acid taken up
by lead, filver, and mercury, were determined  by com-
puting the quautity of  real acid neceflary to precipi-
tate thefe metals from their folutions in the nitrous a-
eid ;  which  Seemed  to be the  moft  exact method of
determining this  point.   The  refult of all the  expe-
riments was,  that 100  grains  of each of thefe acids
take up at the point of faturation of each metallic fub-
ftance, dephlogifticated  fuch a  degree as  is neceflary
for its folution in  each  acid,  the quantities marked
in the following table.
Tin.    Lead.  Silver.   Merc.  Zi«c. Kifmuth. Nickel. Cobalt.  Reg. of ant. Reg. of arfen.
Solution
and Preci-
pitation.
270
2H    255
138    412    390
120
305
i75
265    265    130    400    420
432	318	250 310	320
416	304	290	300
438	312	2 CO 320	275 310
360
350
370
200
I94

I98
260
220
290
            Though from this table, compared with the former,
          wc  might fuppofe that metals, having a greater at-
          traction for acids than alkalies, could not be  precipi-
          tated by them, yet Mr Kirwan obferves, that the com-
          mon tables, which  poftpone metallic fubftances to al-
          kaline falts, are in reality juft, though there can fcarce
          be any room to  doubt that almoft all metallic fubftan-
          ces have a greater affinity with acids than alkalies have.
          The common tables, he Say;, are tables of precipitation
          rather than of affinity, as far as they relate  to metallic
greater af- fubftances.  Thefe precipitations, however, are  con-
fin-ty with ^aiujy. t^c refult of a double affinity  and  decompofi-
-cidij than  t.Qn _  thc prec}p;tarjng metal yielding its phlogifton to
a Italics.           . ■».___,  ___  ...lm- ,i.„  «_«^-;„;.«.^j  „^.„i
   '-99
Me: a
have a
   300
Why alka.
l»e> preci-
piure the
luctals.
the  precipitated  one,  while the  precipitated metal
yields its acid to the other.  Thus, though copper in
its metallic form precipitates filver and  mercury  from
rhe  nitrous  acid, yet  the calx  will precipitate nei-
ther.
  The Superior attraction the n?tro»:s acid has to fnver
rather than fixed alkali, appears from the following ex-
periment.   If a  Solution of  filver in  nitrous acid be
poured into  a  mixed  folution of  alkali and fea-falt,
the filver will be precipitated by the Sea-Salt into a luna
cornea, and not by  the looSe alkali contained in the
liquor.   " Now (Says  Mr Kirwan), if the  nitrous
acid had a greater affinity to the  free alkali than  to
the filver, it is evident that the filver would be preci-
pitated  pure,  and not in the ftate of luna cornea ; but
from its being precipitated  in this ftate, it is  plain,
that the precipitation was not accomplifhed by a fingle
but by adouble affinity.   Hence alfo the marine acid
appears to  have a greater attraction to  filver than the
nitrous has to fixed  alkalies.   The refult is limilaT
when we make ufe of folutions of lead or  mercury  in
the nitrous  acid.  Mr Bayen has alfo fhown, that vi-
triol of  lead and corrofive Sublimate mercury cannot
be deprived of more that: half their .-.cid, even by cau-
ftic fixed mkalies.
                                              \Vn>
   301
Nitrous a-
cid at traces
filver more
than fixed
alkali. 
Theory.
CHEMISTRY.
pitation.

   3°a
Sea-falt de
compofed
in various
ways by
means of
lead.
Solution     With regard to lead, if perfectly dry fait be projedt-
and Preci- ed 0n this metal heated to ignition, the Common fait will
          be decompofed, and plumbum corneum formed.   Nor
          can we attribute this to the volatilization of the alkali
          by heat ;  for the alkali is as fixed as the lead, and
          muft therefore be caufed by  the fuperior attraction
          which the calx of this metal, even when dephlogifti-
          cated,  has for the marine acid.   Mr Scheele  informs
          us,  that if a folution of comrnon fait  be digefted with
          litharge,  the common fait  will be  decompofed, and a
          cauftic alkali produced.   It  may alfo be decompofed
          limply by  letting  its folution pafs flowly through a fun-
          nel filled  with litharge ; and the fame thing happens
          to a. folution of calcareous earth in marine acid ; which
          fhows that the decompofition takes place merely by the
          fuperior degree of attraction betwixt  the acid and  me-
          tallic calx (a).
            That acids  have a greater attraction for  metallic
          earths than volatile alkalies, is ftill more evident. Luna
talric earth cornca \s foluble in volatile alkalies ; but if this folution
more
ftrongly
than vola-
tile alkali.
   303
Acids at
traiil me
          be triturated with four times its weightof quickfilver, a
          mercurius dulcis, and not fal ammoniac, is formed.  The
          reafon why alkalies andearthsprecipitateall metallicfo-
          lutions is, that the metalsare  held in folution by an ex-
          cefs of acid.   Even  if the alkaline and earthy fubftance
          did no more than abforb this excefs of acid,  a precipi-
          tation muft neceflarily enfue ;  but they not only take up
          this fuperabnndant acid,  but  alfo the greater part of
          that which is neceflary to faturate the metallic earth.
          This they are enabled to do by  means of a double af-
          finity ; for during the folution of metals, only a fmall
          part of the phlogifton,  comparatively fpeaking, efcapes,
          the remainder being retained by the compound of acid
          and calx.  When therefore an alkali or earth is added
          to fuch a folution, the phlogifton quits  the acid, and
          joins with the calx, while the greater part of the acid
          reunites  to the precipitate. Notwithftanding this great
          affinity,  however, of metallic  earths to acids, there are
          but few inftances of their  decompoling thofe  falts
          which have an alkali, or an earth for their bafis, by rea-
          fon ofthe inability of the acids, while combined with
          thefe bafes, and thereby deprived  of a great part of
earth oral- their fpecific  fire, to volatilize the phlogifton combi-
kali for    ned with the  metallic earths, which muft neceflarily
their bafis. he expelled before an acid can combine with them : and
          as to the metallic calces,  they are generally combined
          with fixed air, which muft alfo be partly expelled ; but
          ammoniacal falts (containing much more fire, for they
          abforb it during their formation) for that reafonact much
          more powerfully on metals.  Allowing then the affini-
          ties ofthe mineral acids with metallic fubftances to be
          as above,  all double decompofitions,  in which only  falts
          containing  thefe acids united to alkaline,  terrene, or
          metallic bafes, areconcerned, admitof aneafy explana-
          tion ;  nay, fays Mr  Kirwan,  I am bold to fay, they
          cannot otherwife be explained.   Thus,  if a  folution
       of of tartar vitriolate, and of filver in the nitrous acid, be
       ,   mixedinproperplfoportion, nitreandvitrioloffilverwill
          be formed ; and this latter for the moft part precipitated.
   304
Why the
metallic
earths fel-
dom de-
compofe
falts ha-
ving an
   3°S
Decompo-
fition of
vitriolated
tartar by
folution
filver ex-
plained ;
   Quiefcent Affinities
Nitrous acid to filver, 375
Vitriolic acid to ve- 7
  getable alkali,  3

                     590
                                43
   Divellent Affinities.    Solution
Nitrous acid to ve- 7     . and PrccI-
  getable alkali,  C  aI* pitation.  ,
Vitriolic acid to filver, 390

                     605   306
   Thus alfo, if,  inftead of a folution of tartar vitrio- And of ^
 late, that of Glauber's fait,  or of vitriolic fal ammo- J?laub.er's~
 niac, felenite,  Epfom fait, or alum,  be ufed,  the ba- if^mmot"
 lance is conftantly in favour ofthe divellent powers ; and n-"ac  ^c
 a precipitation  is  the confequence,  though but flight
 when felenite or alum are ufed.                         307
   Solution of filver is alfo precipitated by the vitriolic In whatca-
 folutions of iron,  copper, tin, and probably  by many fes folution
 other folutions of metals  in the vitriolic acid : for this   filyer- is
 reafon, among others  undoubtedly,  that they con tain J^"^1^
 an excefs  of acid: but if a faturated folution of filver tncr me-
 be mixed  with a very faturated folution of leadormer- tals.
 cury in the vitriolic acid, the filver will not  be preci-
 pitated ; and in both cafes the balance is in favour of
 the quiefcent affinities.                                 308
   All the  marine neutral  falts, whether the bafis be al- Conftantly
 kaline, terrene, or metallic, decompofe the nitrous folu- decompo-
 tion of filver ; and thefe decompofitions are conftantly f?d y  ma~
 indicated  by the balance  of affinities already deScribed.        *
 The Same thing alSo takes place with Solution of filver
 in the vitriolic acid, as is indicated alfo by  the fame    300
 table.  The  nitrous  Solution of lead is alfo decompo- As alfo As-
 fed, and the metal for the moft part precipitated, tin- lution or
 lefs the Solution be very dilute in the form  of vitriol of lead.
 lead, by all the neutral falts  containing either the  vi-
 triolic or marine acid, excepting only the combination
 of filver with marine acid, which precipitates it in no
 other way than by its excefs of acid.                     310
   Solution of lead in marine  acid is decompofed by all Solution eff
 the  neutral falts containing the vitriolic acid, excepting lead m
 only felenite and folution ofnickelin oil of vitriol.  Thefe rna"ne'a'
 can only precipitate it by virtue of an excefs of acid. p0re<j^la"'
   Nitrous folution of mercury is decompofed by all the vitriolic
 neutral falts containing the vitriolic acid, except vitrio] falts;
 of lead, which only decompofes it by an excefs of acid.   3*1
   All the  falts containing marine acid decompofe the Au~° m"
 nitrous folution of mercury, excepting the combina- t.ous  f
 tions of marine acid with filver and lead,  which decom- "^cJL..
 pofe it by  excefs of acid.                                ^iz
   Thefe falts alio decompofe vitriol of mercury, tho'Andby
 a precipitation does not always appear,  owing, as Mr the falts
 Kirwan fuppofes, to the facility with which a fmall quan- containing
 tity of the  marine fait of mercury is foluble in an excefs nJaniiea-
 ofacid. MarineSaltoSfilver, however, decomposes vitriol C1 '
 of mercury only through its exceSs of acid.  Kence we vitriol of
 fee why luna cornea can  never be reduced by fixed al- mercury
 kalies without lofs ; and  were it not that the action of decompo-
 the alkali is affifted by heat,  it never could be reduced feJ bylna"
 by them at all.                                      fine acid..
   When oil of vitriol is  mixed with a folution of cor- ■whylun*
 rofive fublimate,  a precipitate falls; but this, as Mr COrnea
 Bergman remarks, does  not  proceed from  a decompo- cannot be
                         F  2                 fltion reduced
                                                     without
---------------_---------------------'-------------- lofs by
                                                     alkaline
   (a)  Thefe experiments have been repeated4>y many other chemifts without fuccefs ;  and  Mr WieglebfaltK
informs, that none of thofe who have attempted to decompofe fea-falt by means of lead, ever found their  me-
thods anfwer the jpurpofc.. 
44
 Solution
 and 1 rrci-
 | itatio:-..
r.-c-.i}o i-
t on of cor-
ro five mer-
cury  by
oil of n-
triol ex-
plained.
    U6
Tabic of
the affini-
ties to the
different
i ctuU ex-
I o.jied.
   317
Ofthe
(}:: ilitity of
]  1. -gifton
iont..i:: jd
in  the dif-
ferent me-
tals.
   318
Motio>.l of
c.ileul.it.ing
this quan-
tity exem-
plified in
r-.m.xof
arlenic.
C   H   E    M   I    S   T.   R   Y.
Theory.
fiiion of the mercurial fait, kit  from an abflraclion of
the water nccciiary to keep the fublimatc diiiulved.
   In the foregoing table two different affiniticb arc af-
figncd  to  tin-  vitriolic  acid  with regard  to  bif-
r. ith and nickel ; one  lhowing  the aftiniiy  which
thefe acids  bear to the  metals when  dcplilogiftici-
tcd only  by  folution  in the acids; the  other that
which  the acids bear to them when  more  dephlo-
gifticated, as  when they arc diflblved  in the  nitrous
acid.   On the other hand, all the acids have lefs affi-
nity with the  calces of iron,  zinc, tin,  and antimony,
when they arc dephlogifticated  to a certain degree ;
but our author  found himfelf unable to give any cer-
tain criteria of this dephlogiflication.
   The  moft difficult point to be fettled was the pre-
cipitation of metals  by each other from  the  mineral
acid>.   To determine this it was neceflary to find the
quantity  of phlogifton in  each  of them, not  only in
their natural ftate, but  according  to their various de-
grees of dephlogiflication by each  of the acids.  The
fubftance  he chofc for determining the  abfolute quan-
tity of phlogifton in a metallic fubftance was regulus of
arfenic.   An  hundred grains of this femimetal diflbl-
ved in dilute nitrous acid yielded 102.4 cubic inches of
nitrous air ; which, according to his calculations on that
Subject, contain 6.86 grains oS phlogifton : and hence
he concluded that 100 grains of regulus  oSarSenic con-
tain 6.86  grains of phlogifton.   from this  experi-
mem,  three times repeated with the fame fuccefs, our
author  proceeded  to form,  by  calculation, a table of
the abfolute quantity of phlogifton  contained  in me-
tals, the  relative  quantity having been computed by
Mr Bergman  and his calculations adopted by  our au-
319	inor. 1 neic epiauiuics	are as ioiio>	v.
Table of		Relative	Abfolute
the quanti-		Quantity.	Quantity
ties of phlo-	ioo grains Gold	394	24.82
gifton in	Copper	:i2	19.65
different	Cobalt	270	17.01
rie'.ab.	Iron	2^3	14.67
	Zinc	182	II.46
	Nickel	156	9.82
	Regulus of"	► 120	7.56
	antiinonv	\	
	Tin	114	7.l8
	Regulus of"	► 1C-9	6.S6
	arfenic		
	Silver	100	6.30
	- _. Mercury	"4	4.56
	Bifuuuh	57	3-59
	Lead	43	2.70
   3"
Exp;r;-
rients ex-
pla^'.ii'*;
th- redac-
tion ot
filver per
  This point he likewife endeavoured to afcertain by
other experiments. As Silver iofe-s a  certain quantity
ofp'ilogillon,  winch  efcapesand Separates from it du-
ring its fiflution in nitrous acid, he concluded, that if
the folution wis  expofed to nothing from  which it
could reobmin phlogifton, and this was diftilled to dry-
nefs,  ami entirely  Separated Srom the acid, as much fil-
ver hvuld remain  unreduced as  correfponded with the
quantity of phlogifton ^ft by it; and if this quantity
com.rp.mdcd w ith that in the above table, he then had
goe>d rer.fjn tj conclude that the table was jail.
  Kor this pjrpoft 1 20 grains of Standard filver were
ehflblvcd in dephlogilVictrcd nitrous acid diluted  with
water,  and he obtained from it 24 cubic  inches of ni-
trous  air.  This  Solution was  gently  evaporated  to
drynefs; and he found that,  during the evaporation, ;<U tion
about a quarter of a grain ofthe ilhcr had beet, volaii- "^ l'r*<"»-
lizcd. The dry refiduum was then uiliilftd,  jud kept 1,"■'"'■'"•  __
an hour in a coated grccn-glafs icmrt S.t.utd  aln.olt to
a white heat.   Abundance of  nitrous acid  palitd oft
during the operation, and a green and white  lub.imaic
rofe into the neck of the retort, fome of it even  pal-
ling over into the receiver.  On breaking the retort, the
inlide was penetrated with  ayellow and red tinge, and
partly covered over with an exceedingly line Silver pow-
der, which could  Scarcely  be feraped eft.   i he re-
mainder of the  Silver was  white, and perSeclly  free
from acid, but  not melted into a button.  On being
collected, it weighed 94 grains ; consequently 26 grains
had been  loft either  by  Sublimation  or \ itrification ;
but of thefe 26 grains 9  were copper ; for too grains
of itandard filver contain 71, oS copper, therefore only
1 7 grains of pure filver remained unreduced,  being ci-   32J
ther volatilized or  \iuified.   The whole quantity of Quantity  ■
pure filver in 120 grains of Standard filver amounts to of pure ma-
in grains;  then it" in  grains of pure  filver lofe i7ta\con".
by being deprived of its  phlogifton, ico grains of the !a,ne. T
fame fhould lofe  15.3;  and by  the above table 15-3 filver.
grains of filver fhould  contain 0.945  of a  grain of
phlogifton.   Now, 100  grains of pure filver : fiord
14 cubic inches of nitrous air, which, according to our
authtir's  calculation,  contain  0.938  of a  grain of
phlogifton;  and this differs from 0.945 only by .C07
of a grain.  "  In this experiment (fays Mr Kirwan)
only as much of the filver Sublimed as could not regain
phlogifton ;  the remainder regained it from the nitrous
air abforbed by the folution, and by that which remain-
ed in the acid and calx.  If this were not fo, I do not
fee why the whole of the filver would not Sublime."     ,2a
   Dr Prieftley having Several times diffolved mercury Pxamina.
in the nitrous acid, and revivified it by diftilling over tion  of Dr
that acid, conftantly Sound a  confiderable portion oS it f'riiftley's
unreduced.   To  try whether that  proportion corre- ciPcruncnt
fponded  with his  calculation, Mr  Kirwan  examined ^""""v"*
Dr Prieftley's experiment, viz.  that having diflblved ,,f mcr.
17 penny-weights 13 grains  (321 grains) of mercury cury.
in nitrous acid,  36 grains  remained unreduced.   Ac-
cording to Mr Kirwan's calculation  56 grains fhould
have remained  unreduced ; for ico grains of mercury
afford 12  cubic  inches of nitrous air ; of confequence
321 grains lhould  afford 38.52, which contain 2.58
of phlogifton :  and if, as according to the table,  4.56
grains of phlogiftion be  neceflary  to  metallize  100
grains of mercury, 2.58 grains  will be neceflary to
metallize 56 grains of the Same metal ; and our author
is Satisfied Srom his own  trials, that  more than 50
grains would have remained unreduced, if dephlogifti-
cated nitrous acid had been ufed in diflolving the mer-
cury, and  the Solution  performed  with heat  and a    ,,,
ftrong acid:  but  tint which the  Doctor tiled was of why fo
thefmoking kind,  and consequently contained a  con-much of
fiderable  quantity  of phlogifton  already,  which un-tben-.e-al
doubtedly conuilued to  revive  more  of  the  metalwas!'vi"
than wotdd otheruiie have  been dm e.  It  is true, p(ddn , e
Dr Prief ley afterwards revived a great part of what ^'^V['
had originally remained -unreduced ," tut this happened menu.
alter it had  been  Some  time  cxpo':d to the f'<c air,
Srom which  the calces of metals always attract'phlc.if-
tou  ; as is evident in luna cornea, which blackens on be-
ing expofe fi to the air.
   By mmthcr experiment  of Dr Prieftley's, it was
                                               found 
\Theoty.
C   H
M   'I    S    T   R    Y.
45
   3*4
Of the re-
vival of
leud from
minium by
inflamma-
ble air.
   325
Mr Kir-
wan's re-
marks on
the expe-
riments of
Dr Prieft-
ley.


   326
Of the at-
 Solutipn   fpund,  that nearly five pennyweights of minium, from
 and Preci-  whence all its air was  extracted, that is, about 118
 pitation. ^ grains, abforbed  40 ouncc-meafures,  or  75.8  cubic
           inches of inflammable air, containing  2.65 grains  of
           phlogifton, by which they were reduced. An hundred
           grains of minium, therefore, require for their reduc-
           tion nearly  2.25 grains of phlogifton.   In another
           experiment made with more care, he found, that 480
           grains of minium abforbed 108 ounce-meafures of in-
           flammable air; fo that,  according to this, 100 grains
           of minium require for their reduction  1.49 grains  of
           phlogifton ;  and  in two  fucceeding experiments he
           found the quantity ftill lefs.   On this Mr Kirwan re-
           marks,  1. That the whole of the minium was not de-
           phlogifticated ; for it is never  equally calcined, and
           befides much of it muft have been reduced during the
           expulfion of its air.   2.  The quantity of phlogifton  in
           the inflammable air may  have  been greater,  as this
           varies with its temperature and the weight of the at-
           mofphere : fo that on the whole thefe experiments con-
           firm the refults exprefled in the table.
            Mr Kirwan next proceeds to confider the attraction
 tracftion of of metallic calces  to  phlogifton.   Inflammable  air,
 metallic   when condenfed into a folid fubftance, he fuppofes not
 cakes to   only equal, but much fuperior, to any metallic calx  in
 phlogifton. fpecific gravity ;  and therefore, if we  could find the
          fpecific  gravity of any calx free both  from  phlog§fcm
          and fixed  air, we  would thus know the denfity which
 Of finding phlogifton acquires by its  union with  fuch calx.   It
 the fpecific has, however, hitherto  proved impoffible to  procure
 gravity of calces in fuch a ftate ;  as,  during their dephlogiflica-
          tion, they combine with fixed air or fome particles  of
          the menftruum,  whence their abfolute  weight is in-
          creafed, and their  Specific gravity diminiflied.   Kence
          it appears, that the Specific gravity of the calces differs
          much lefs from that of their refpeetive metals, than the
          fpecific  gravity which the phlogifton acquires by its
          union with thofe calces from that which it poffeffes in
          its uncombhied ftate.  Hence,  inftead of deducing the
          quantity of affinity betwixt phlogifton and metallic cal-
          ces front the following propofition, that " the  affinity
          of metallic calces to phlogifton is  in a compound ratio
          of its quantity and denfity in each metal," he is obliged
          to deduce it from this other,  that " the  affinity of me-
          tallic  calces to phlogifton is directly as the fpecific
          gravity ofthe respective  metals, and inverSely as the
greesof af- quantity of calx contained in a given weight of theSe
fin it y to    metals."   This latter propofition is an  approximation
phlogifton     he former  f0arided on this truth, that " the larger
may be dc-             '                    to
the differ-
ent me-
tallic cal
ces.
   3l8
Whence
their va-
rious At-
the quantity of phlogifton in any metal is,  the Smaller Solution
is the quantity of calx in a given weight  of that me- al, d I'reci-
tal;" and, that " the denfity which the phlogifton ac- Pltati°n-  j
quires is as the fpecific gravity of the metal."   This
latter propofition, however, is  not ftrictly  true, for
this denfity is much greater ; but its defect  is only fen-
fible with  regard  to  thofe metals which contain a
confiderable quantity of phlogifton, as gold, copper,
cobalt, and iron.   With regard to the reft, it is of 110
importance.  The fpecific gravity of the different me-
tals, then, being as represented in the firft column of
the following table, the affinity of their calces to phlo-
gifton will  be as in rhe fecond;  and  the third ex-
prefles the affinities in numbers homogeneous  with
thofe whicli exprefs the affinities of acids  with their
bafis.                                                  330
                        Proportionable  Real Affinities cf Table of
                          Affinities.    Calx to Phlogift. the pro-
Gold
Mercury
Silver .
Lead
Copper
Bifmuth
Cobalt
Iron
Regulus  of ">
Arfenic    3
Zinc
Tin
Regulus  of"?
Antimony  3
 Specific
 Gravity.
 l9
 M
 11.091
 n-33
   8.8
  9.6
   7-7
   7-7

I  8.31
   7.24
   7
   6.86
0.25
0.147
0.118
0.116
0.109
0.099
0.092
0.090
0.089
0.0812
0.075
0.074
1041
 612
 491
 483
 454
 412
 383
 375
 370

 338
 312
 308
portional
affinities of
metallic
calces to
phlogifton.
331
   From  this table we may fee why lead is ufeful in Why lead
cupellation ;  namely, becaufe it has a  greater affinity is ufeful in
with phlogifton than  the calces of any of the  other cupellation.
imperfect metals ;  consequently after it has loft its
own phlogifton, it attracts that oS the  other metals
with which it is mixed, and thus promotes their  calci-
nation and vitrification.                                ,,a
   The third point neceflary for the explanation of the Quantityof
phenomena attending  the folution oS metals, and their phlogifton
precipitation by each  other, is to determine  the pro- loft ky rne-
portion oS phlogifton which they loSe by Solution in tajs.dur.ing
each oS the acids, and the affinity  wdiich their calcesCa anatIon'
bear to the part So loft.   Though our  author was not
able to determine this by any  direct experiment,  yet
Srom  various considerations he was  led to believe that
it was as follows :
may
tcrmined.
                    Quantity of Phlogifton Separated
From Iron, Copper, Tin, Lead, Silver, Mercury, Zinc, Bifmuth, Cobalt, Nickel, Reg. of Ant. Reg. of Arf.
          By the vitriolic ,                        .  £  d
            acid         5
          By nitrous "acid      *      -/Vo-   V-r  t'A Entire
          By m arine acid     T4vy    • T%7^   tV  --?**■-----   -
Ofthe       The affinity of  the-  calces to the deficient part of
affinity of  their  phlogifton 'may  now be  eafily  calculated ; for
calces to  ,  they may be eonfiehmed as acids, whofe affinity  to the
thedefi-i-  deficient part of  their hifis is as the ratio which that
c£t part of part  b,ears- t0 the.whole.  Thus the affinity of iron,
e^oiif1 °" tnoroughly deprived of it's phlogifton,  being 375, as it
          lbfes two-thirds  of its phlogifton by  folution  in the
          vitriolic acid, the af^nit'y'of  iron to  thefe  is  two-
          thirds of its whole affinity ;' that is, two-thirds of 375.,
          or 250. '
TVV   -\\   Entire    TYT

-iVs-   Entire Entire   Entire
333
  Thus we may eafily conftruct a table of the affinities Ufe of
of the phlogifton of different metals for .their  cal- thefe cal-
ces ; and from this and  that formerly given, by which culations
the affinities of the acids to the metallic calces was ex- Jnd tatles
preffed, we may gueSs what will happen on putting one ™ ??™~
metal in the Solution of another.  Thus iS a piece of flri thephe-
copper be put  into a faturated Solution of filver, the nomena of
filver will be precipitated ;  for the  balance is in fa- precipita-
vour of the divellent powers, as appears from the fol- tion«
lowing calculation.
                                           Quiefcent 
46
CHEMISTRY.
'ilution
u i Hreci-
   334
Of the ex-
*.ch of a-
   QjufctLt Affitr.ti:.
Nitrous acid to Silver
Calx  of  copper to }
  phlogifton      5
Sum of the quief- /
  cent affinities   3
Theory,
375
363
7; 8
   Divellent Affinities.
Nitrons acid to copper 255
Calx  of filver  to 7
  phlogifton      3  49
Suni of the divel-
lent
\  746
lution.
   336
Why cop-
per is dif-
folved by
   337
Iron and
Zincthe
            In making thefe  experiments the  folutions muft be
          nearly,  though not entirely,  faturated.  If much fu-
ci  in ou-perp4llOLls acid be left, a large quantity of the added
tiom pro-  •»    ,   ....   j-,-r  1   J  1   r             ■•
ncr for ma-,ncu^ Wl'* "c diflolved, before any  precipitation can
king thefe  oC made to appear ; and when the folution is perfect -
experi-    ly faturated, the attraction of the calces for one another
menu.    begins to  appear ; a power  which  fometimes takes
   335    place, and which has not  yet been fully inveftigated.
Why the     In this  way the precipitating metals  are  more de-
nietaUare  phlogifticated than by direct  folution  in  their re-
"hi" ,(ft"   CPC<^'VC menftrua; and are even  diflblved by men-
cate-dby"  ^rua which  would not otherwife  affect them.  The
mutual    reafon of this is,  that  their phlogifton is acted upon by
precipitati- two powers inftead  of one :  and hence, though copper
on than by be directly foluble  in the vitriolic acid  only when in
direct, fo-  iK concentrated  ftate,  and  heated to  a great degree ;
          yet if a  piece of copper be put into a  folution of filver,
          mercury,  or  even iron, though dilute and cold,  and
          expofed to the air, it will be diflblved ; a circumftance
          which has juftly excited the admiration of Several enii-
folution of nent chemifts,  and which is inexplicable on any otdier
filver, mer- principles than thoSe  juft now laid down.  From this
cury, or 1-  circumftance  wc may  See the reaSon why vitriol oS cop-
          per, when formed by nature,  always  contains iron.
            Mr  Kirwan  now  proceeds to  confider  the  folu-
          tions of metallic fubftances in all the  different acids.
            Vitriolic acid, he obferves, diflblves  only iron and
          zinc of all the metallic fubftances, becaufe its affinity
°m/mc*  s to their calces is  greater than that which they bear to
b'y vitriolic t^ie phlogifton they  muft  lofe before they can unite
acid.      with it.
   338       Nitrous acid has lefs affinity with  all metallic  Sub-
Nitrous a- ftances than  either the vitriolic or marine ; yet it dif-
ciddifl*olvesf0ives them  all,  gold, Silver, and platina excepted,
aJ* m^ls, though  it  has even leSs affinity w ith them than they
h °s\{ 'af- niyc with that  portion of  phlogifton which muft be
fmity with hflh before they can diffolve in any acid.   The reafon
them than  of this is, that it unites with phlogifton, unlefs when in
the vitrio- too diluted a  ftate ;  and the heat produced by its union
lie or ma-  wjth phlogifton is  fufficient to promote the folution of
,mc*      the metal.  On the other  hand, when  very concen-
Wh^'    trated, it cannot diflblve them : becaufe the acid does
rannot dif-not r^ea  contain fire  enough to throw the phlogi-
folve them lion into an aerial form, and  reduce  the folid to a li-
whenmuch quiel.
concentra-    Tne marine acid dephlogifticates metals lefs power-
ecJ"       fully than any other.    It can  make no folution, or  at
          leaft can operate but very flowly, without heat, in thofe
          cafes where  the metallic calx has  a  ftronger  affinity
          with that portion of the phlogifton which muft be loft,
cid can dif- than the acid : nor can it  operate brifkly even where
foNe  me-  tne attraction is ftronger,  provided, the quantity of
 tal*, and  aci(j ^e  fmaij . becaufe fuch  a little  quantity  of  acid
          does not contain fire  enough  to volatilize the phlogif-
          ton : and hence heat  is neceflary  to  aflift the  marine
          acid in dniohing leacL When dephlogifticated, k acts
          more powerfully.
             It has been obferved, that  copper  and iron mutual-
          ly precipitate one another.   If a  piece  of copper be
In what
cafes the
marine a-
wheu it
sanuot.
put into a faturated folution of iron  frefh  made, no
precipitation will enfue tor 12 hours,  or even longer,
if the liquor be kept clofc from the air;  but it  the li-
quor be expofed to the open air, the addition of vo-
latile alkali  will fhow,  in  24 hours, that fome of the
copper has been  didblved,  or  Sooner,  if heat  be ap-
plied, and a calx of iron is precipitated.  The reafon
of this w ill  be underftood from the  following flatc of
the affinities.
Solution
and Preci-
pitation.

   341
Why cop-
per and i.
ron preci-
pitate one
another.
        Quiefcent.
Vitriolic acid to calx of
  iron     -    -    270
Copper to  its phlogi-
  lton     -    -    360

                     560
        Divellent.
Vitriolic acid to cop-
  per     -     -     260
Calx of iron to phlo-
  gifton      -    -    250

                     510
  In  this  cafe no  decompofition can take place,  be-
caufe  the fum of the divellent affinities is lefs than that
of the quiefcent; but in the Second, when  much of
the phlogifton of the iron has efcaped,  the affinity  of
the calx of iron to the acid is greatly  diminiflied, at
the fame time that the affinity of the calx to  phlogi-
fton is augmented.  The  ftate  of the affinities may
therefore be fuppofed as follows.
        Quiefcent.
Vitriolic acid to calx
  of iron     -      240
Copper to  its  phlo-
  gifton      -      360
        Divellent.
Vitriolic acid to cop-
  per        -       260
Calx of iron to phlo-
  gifton     -       3 70
                     600                        630
  The increafe of affinity of the calx of iron to  phlo-
gifton is not a  mere fuppolition ; for if we put fome
frefh iron to a folution of the metal fo far dephlogifti-
cated as to refufe to cryftallize, fo much of the  phlo-
gifton will be regained that the impoverifhed folution
will now yield cryftals. The reafon why the increafed
quantity of phlogifton does  not  enable the acid to re-
act  upon the metal is,  becaufe it is neither Sufficiently
large, nor attracted  with a  fufficient degree of force,
to which  the accefs of air and heat employed contri-
bute considerably.   The diminution  of attraction in
calces of iron for acids is evident, not only from this
but many  other experiments ; and particularly from
the neceffity of adding more acid to a turbid folution
of iron in order to re-eftablifh its transparency.
  A dephlogifticated folution of iron  is alfo precipita-
ted by the calces of copper.   The fame thing happens
to a folution of iron in nitrous acid ;  only as  the acid
predominates greatly in this folution,  fome of the cop-
per is diffolved before any of the iron is  precipitated.
Copper precipitates nothing from folution  of iron in
the marine acid, though expofed to the  open air for
24 hours.
  Solution of copper in the vitriolic  acid is inftantly
precipitated by iron ; the reafon of which is plain from
the common  table of affinities :  and hence the  foun-
dation of  the method of extracting copper, by means
of iron, from fome mineral waters.  The precipitated
folution affords a vitriol of iron,  but  of a paler  kind
than that commonly met with,  and leis fit for dyeing,
as being more dcphlogiflicated:  the  reafon  of which
is,  that  copper contains more phlogifton than iran :
old iron is alfo ufed  which  has partly  loft its  phlo-
                                             gifloa.
   342
Increafe of
the attrac-
tion of
calx of iron
to phlogi-
fton de-
monftra-
ted.
   343
Calces o
copper pre-
cipitate de-
phlogifti-
cated folu-
tions of i-
ron.
   344
Martial Ti-
triol procu-
red by pre-
cipitation
of copper
lefs fit for
dyeingthaa.
the com-
mon. 
Theory*
Solution
and Preci-
pitation.

   345
Solution of
copper
fcarcely de-
compofed
by calt i-
   346
Why a fa-
turated fo-
lution of
filver can
fcarce be
precipita-
ted by iron.
   347
Of the pre-
cipitation
ni zinc and
iron by one
another.
   348
Why cop-
per fome-
times can-
not preci-
pitate fil-
ver.
   349
Blue vitri-
ol cannot
be formed
by boiling
a folution
of alum
with cop-
per filings.
   350
Why tin
cannot be
precipita-
ted in its
metallic
form-.
                             CHEMI
gifton.   Hence the iron is more  dephlogifticated  by
precipitating copper than by mere diflblution in the
vitriolic acid ; and  hence caft iron, according to the
observations of Mr Schlutter, will fcarcely precipitate
a folution of copper ;  becaufe  it  contains  lefs phlo-
gifton than bar-iron, as Mr Bergman has informed us.
  Mr  Kirwan  always found filver eafily precipitated
by means of  iron  from its folution in nitrous acid ;
though Bergman had obferved that a faturated folution
of filver could  not be thus  precipitated without great
difficulty, even though the Solution were diluted and
and an exceSs of acid added to it.   What precipitation
took place could only be accomplifhed by fome kinds
of iron.   The reaSon of this Mr  Kirwan SuppoSes to
be,  that the Solution, even after it is Saturated, takes
up Some  of the filver in its metallic form ; which Mr
Scheele has alSo obServed to take place in quickfilver.
The laft portions  of both theSe metals when diflblved
in ftrong nitrous acid,  afford no air, and consequently
are  not  dephlogifticated.  This compound  of calx,
therefore, and of filver in its metallic ftate, it may rea-
fonably be fuppofed cannot be  precipitated by  iron,
as the filver in its  metallic form prevents the calx from
coming into contact with the iron,  and extracting the
phlogifton from it ; and for  the fame  reafon iron has
been obferved not to precipitate a  folution of mercury
in the nitrous  acid.
  Zinc cannot precipitate iron, as Mr Bergman has
fhown, until  the folution of the latter lofes part of  its
phlogifton.   Hence  we may underftand why Newmann
denied that iron can be precipitated by means of zinc.
Mr Kirwan,  however, has found, that zinc does not
precipitate iron from  the nitrous  acid;  but  on the
contrary, that iron  precipitates zinc.  In a fhort time
the acid  rediflblves the  zinc and lets fall  the iron,
owing to the calx of iron being too much dephlogifti-
cated.   Iron, however, will not precipitate zinc either
from the vitriolic or marine  acids.  Moft of the me-
tallic fubftances ^precipitated  by iron from  the nitrous
acid are in fome meafure redilfolved fliortly after ; be-
caufe the nitrous acid foon dephlogifticates the iron too
much, then lets it fall, reacts on the other metals, and
diflblves them.
  Dr Lewis obferves, that filver is fometimes not pre-
cipitated by copper from the nitrous acid;  which hap-
pens either when  the acid is fuperfaturated with filver
by taking up fome in its metallic form, or  when the
filver is  not much dephlogifticated.  In this cafe, the
remedy is to heat the folution  and add a little more acid,
which dephlogifticates it further ;  but the nitrous acid
always retains  a little filver.
  It has commonly been related by chemical authors,
that blue  vitriol  will  be  formed  by adding filings
of copper to a boiling folution of alum.  Mr Kirwan,
however, has  fhowed  this to be  an error ; for after
boiling  a folution of alum for 20 hours with copper
filings,  not a particle of the  metal was diffolved ; the
liquor Handing even the teft of the volatile alkali.  The
alum indeed was precipitated  from the  liquor, but ftill
retained its  faline  form;  fo that the precipitation
was occafioned only  by the diffipation of the fuperflu-
ous acid.
  No metal is  capable  of precipitating tin  in its me-
tallic  form ;  the  reafon  of which, according  to Mr
Kirwan,  is, becaufe the  precipitation is not the effect
  S   T   R    Y.                                    47
of a double  affinity, but of the fingle greater affinity Solution
of  its menftruum  to every other metallic earth.   Me- and Preci-
tals precipitated from the nitrous acid  by tin are af- P'tat'Qn-  y
terwards redilfolved, becaufe  the  acid  foon quits the   35I
tin  by  reafon of  its becoming  too  much dephlogi- Why me-
fticated.                                             tJ|ls Pr">-
  Lead precipitates metallic folutions in the  vitriolic PItated by
and marine acids but flowly,  becaufe the firft  portions J^"ds '
of lead taken up form falts very difficult  of folution, re(jifr0[vefj
which cover its furface,  and protect it from the  fur-   3^2
ther action of the acid; at the fame time it contains Precipita-
fo little phlogifton, that a great quantity of it muft be tions by
diflblved before it  will diflblve other metals.  A folu- lead-
tion of lead very much faturated  cannot be precipita-
ted  by iron but with difficulty, if at all.   Mr  Kirwan
conjectures  that this may arife from fome ofthe  lead
alfo being taken up in its metallic form,  as is the cafe
with  mercury and filver.  Iron will not  precipitate
lead from marine  acid ;  for  though  a precipitate ap-
pears  the acid is ftill adhering to the metal.  On the
contrary,  iron is precipitated from its folution in this
acid by lead, though very flowly.                       353
  Mercury  is quickly precipitated from the vitriolic Precipita-
acid by copper, though the difference between the fum tions of
of  the quiefcent  and divellent affinities is but very mercuryby
fmall. The precipitation, however,  takes place, be- C0PPer*
caufe  the calx of  mercury has a ftrong  attraction  for
phlogifton ;  and a very fmall portion of what  is con-
tained in copper is fufficient  to revive it.                3j4
  Silver,  however, is not able to precipitate mercury It cannot
from  the vitriolic acid, unlefs it contains  copper ; in be precipi-
which cafe a precipitation will enfue : but on diftilling tatcdbyfil-
filver and turpeth  mineral, the mercury will pafs over v.r. rj.m
in its metallic form; which fhows that  the affinity ofaci(j.
the calx of mercury to phlogifton is increafed by heat,
though the difference betwixt the divellent and quief-
cent powers is very fmall.                              2SS
  Mercury appeared  to be precipitated by filver from Why mer-
the nitrous  acid, though very flowly;  but when  the cury and
folution was made  without heat, it was not at all pre-fi. v.er Pre"
cipitated.   On the other  hand, mercury  precipitates cipitfteone
filver from this  acid, not  by virtue of the fuperiority from thc
of the ufual  divellent powers, but by reafon of the at- nitrous a-
traction of mercury and filver for each other ; for they cid.
form  partly an amalgam and partly  a  vegetation,
fcarcely any thing of either remaining in the folu-   3S&
tion.                                                Corrofive
  Silver does not  precipitate mercury from the folu- fublimate
tion of corrofive  fublimate  ;  but,  on  the contrary, „r"cipita.-
merenry precipitates filver from the* marine acid : and ted by fil-
if a folution of lutia cornea in volatile alkali be tritura- ver; but
ted  with mercury, calomel will be formed ; yet on di- luna cornea
ftilling calomel and filver  together, the mercury willmav nc de"
pafs in its metallic form, and luna cornea will be form- comPofcd
ed.    The fame  thing happens  on diftilling filver and y '^if'b.
corrofive fublimate, the affinity of calx of mercury toiJn'iate by
phlogifton increafing with heat.                      filver, in
  Bifmuth precipitates nothing from vitriol of copper the dry
in 16  hours  ;  nor  does copper from vitriol of bifmuth. W*T-
The two metallic fubftances, however,alternately pre-   $P.
cipitate one  another from the nitrous acid, which pro- f-reQlffyr
ceed  from their different degrees of dephlogiflication. muth
  Nickel will fcarcely precipitate any metal except it   358
be  reduced  to powder.  A black powder as precipi-Nickel
tated  by means of zinc  from the folution of nickel precipita-
                                                  •m ted by zinc. 
4»
Iron an 1
eiAtUv.ll
I  ircely
precipitate
one i.i<>-
ther.
   360
Precip r.:
tion of ca
per, 1
and 1m,-
nuth by
r.ekd.
Folution   in  the vitriolic and  t.itr   s  aci.^,  which has  been
*°«* Preci- ,ho\vn by lw guun to comift of anc;,:.c, nickel, and a
1 nation.   ijujc 0p tac /.mc'hfclf.   The latter, however,  prccipi-
    v-,,    tatcs nickel from the marine acu:.
            The  loiiuionsei  iron a.id nickel in the vitriolic acid
          muttully .tet up >n thele metals ; b..t  neither of  them
          will prejipit.ue the  other  in 24 houm,  though on re-
          maining longer at  reft iron Seems to o.:\ e tne advan-
          tage.   Irum ho.vever,  evidently p ecipitates nickel
          from  the  nitrous  acid ; and thougn  nickel Seems to
          precipitate iron, yet this ariSes only  from the gradual
          dcphlogiiti  atiou of the iron.
            Copper is p. e cipitated in its  mctalic  form from the
          vitriooj, nfroiu,  andnmrine  acieis, by niekcl.  The
          vitriolic and nitrous Solutions of lead Seem to act upon
          it without any decompofition, the  calces uniting to
          each other.  Lead Seems  tor  Some  time  to  be  acted
          upon in the Same manner by the vitriolic and nitrous
          Solutions of iu.'L;, but at laft nickel Seems to have the
          advantage ; but a black precipitate appears which ever
          of them is  put  into the Solution ofthe  other.   How-
          ever, nickel readily precipitates vitriolic  and nitrous
          folutions of bifmuth;  but in   the  marine  acid  both
          thefe fernimetals are foluble in  the  folutions of each
          other: yet nickel preeipitatesbifmuth very flowly, and
          only in part ;  while bilmuth precipitates a red  powder,
          fuppofed by Mr Kirwan to be ochre, from the folution
          of nickel.
            Cobalt  is not  precipinttcd by zinc either from the
          vitriolic or nitrous acift, though it  feems  to  have
          fome effect  upon it when ditiblved in that of fea-falt.
            Iron  precipitates cobalt from all  the three  acids,
          yet much of the femimetal  is retained in  the  vitriolic
          and  nitrous Solutions  oS it, particularly  the  latter ;
          which, alter letting fall the cobalt,  takes it up again,
    363    and  lets fall a dephlogifticatcd calx  of  iron.   Nickel
Nickel pre-alfo,  though it docs not  precipitate ceibalt itfelf, as
ci^tur^   appears by the remaining rednefs of the folution, yet
fome hctc- COU(i;antly precipitates fome heterogeneous mattcr Srom
          it.   Solution oS cobalt  in the marine acid becomes co-
          lourlefs by the addition of nickel.  Bifmuth is foluble
          in the  vitriolic ami nitrous folutions of  cobalt,  and
          throws down  a fmall white  precipitate, but does not
          affect the metallic part.  Nor  can we attribute  thefe
          folutions in vitriolic acid to any excefs  in that  acid, as
jh,tcP0^" they are dilute and made without beat.  Copper alfo
addition of precipitates Srom the Solution of cobalt a white powder
bum-.ith or fuppofed to be arfenic.
i..p,ier.      The regulus of  ir.ttt .  \  has no effect on  folution
          of copper  in  \ . ;.»lic ac  :,  nor  is  precipitated  by it
          from the fame acid ; but it didolves ft.wly in vitriol of
          antimony.   With folution of vitriol of lead it becomes
          red in  16 hours, but is  fcarcely precipitated by lead
          from  the vitriolic acid.   Powdered regulus alfo preci-
          pitates vitriol of mercury very llightly.   Eifmuth nei-
          ther precipitates nor is  precipitated  by the regulus in
          24 hours from  the vitriolic acid.   Tin precipitates the
          rectus from  the nitrous acid ; but  if regulus  be put
          into a folution of tin in the fame acid, neither ofthe
          metals will be  found in the liquid in 16 hours, either
          by reafon ofthe dephlogifticationor of the union of the
fait formed ca]ccs lo each u:iur.
by iron,re-  jron docs not precipitate  regulus  of antimony en-
eulusofan- .  .         ,  *   .r     . ,  °. .  r      .  r'
timouy,   tircly  lru:n inc  mannc  aci"J but  "-'cms to form a
and marine triple  fait,  confifting  of  the   acid  and both  calces.
 ' 361
Zinc can-
not preci-
pitate co-
balt.
   36 a
Cobalt pre-
cipitated
by iron
rogeneous
mattcr
from it.
   364
folutiom
of cobalt
let fill a
   36J
Precipita-
tions of
and by rc-
gulut of
antimony.
A triple
CHEMISTRY.
                          The regulus may alio Le diffolved  by  marine fait ot
                          iron.
                             C <pper  docs not  precipitate regulus of antimon)
                          liom marine  acid in. 16 hours j  and if the rcRulir be
                          put into marine fait  of copper, it will be  eh.solved.
                          and volatile alkalies w ill not g; ve a blue, but a ye llou •
                          ifh white precipitate ; fb tlmt  here  alfo a trifle fall is
                          tenm.Ce'.
                             bolution of arfenic  in vitriolic acid  acts upon iron,
                          lead,  copper, nickel,  and  zinc ;  but  Scarce  five any
                          preapiute :   neither  is  arfenic piceiphatcd  by  iron
                          1101:1  the  nitrous acid,  though it  is  by copper, and
                          even lilver gives  a ili^lit white precipitate.   Regulus
                          of arfenic, however,  precipitates filver completely in
                          16 hours: whence the  former precipitate feems to be
                          a triple fait.   Mercury alfo llightly pre. ipitates arScnic
                          from  the  nitrous acid,  and  fceins to  unite  with it,
                          though it is itfelf precipitated ty regulus ot arfenic in
                          24 hours.
                             bilmuth Slightly prcupimtcs  arfenic from  fpirit of
                          nitre,  but regulus of  arfenic  forms a copious precipi-
                          tate  in the nitrous fplution of  bifmuth ;  fb  that  Mi
                          Kirwan is of opinion  thm the calces unite.   It is  not
                          precipitated  from this acid by nickel,  but the  calces
                          unite.   Though regulus of arfenic produces a copious
                          precipitate in the folution of nickel in nitrous acid,  yet
                          the liepior remains green ; fo that the nickel is certainly
                          not precipitated.   J he  white  precipitate in  this cafe
                          feems  to be  arfenic flightly dephlogifticated.  Regu-
                          lus of  arfenic alio produces a  white  precipitate in  the
                          nitrous Solution of cobalt, but  the liquor ftill continues
                          red.
                             Regulus of arfenic  is precipitated from the marine
                          acid by copper;  but  the precipitate does not ftrike  a
                          blue colour with volatile alkali,  becaufe the  metal
                          unites  with the arfenic.   The arfenic  is  alfo precipi-
                          tated by iron.  Tin is foluble  in marine folution of ar-
                          fenic,  but Mr Kirwan could  not obferve any precipi-
                          tation ; nor  does regulus of  arfenic  precipitate tin.
                          Neither bifmuth nor regulus of arfenic  precipitate each
                          other from marine acid  in 16  hours.   Regulus of an-
                          timouy is alfo acted upon by the marine folution of ar-
                          fenic,  though it  caufes  no  precipitate, nor  does  the
                          regulus of arfenic precipitate it.
heory.
.k'i artion
..no lieci-
pitoi< ti-

~7^
Another
Ii in.nl by
tqi U» of ■
autuiH>ny,
iiarinc a-
ei  , arid
U-PJ.T.
   368
l'rccipita-
tionsof and
Ly arfenic.
   3*9
Regulus of
arlcuic pre-
cipitated
by bifmuth
from the
nitrous a-
cid ;
   370
And by
copper
from the
marine »
cid.
§•■ 2.  Ofthe Quantities of Acid,  Alkali,  &c. contained
  in different Salts, with the Specific Gravity cf the In-
  gredients.

  It  is  a problem by which the attention of the beft
modern chemifts has been engaged, to determine the-
quantity of acid exifling in  a  dry ftate in the  various
compound falts, refilling from the union of acid w ith
alkaline, earthy, and metallic fubftances.  In this way
Mr Kirwan has greatly excelled all others,  and deter-
mined the matter with an accuracy and precifion alto-
gether unbooked Sor.  His decifions are founded on the
following principles.
  1. That the fpecific gravity of bodies is their weight Specific
divided by an  equal  bulk of rain or diftilled water ; the gravity of
latter being the ftandard with which every other body bodies ho-w
is compared.                                         found.
  2. That if  bodies fpecifically heavier than water be
weighed in air and in water,  they lefe in water part
of the weight which they were found  to have  in air ;
                                                 and 
Theory.
CHEMIST
R    V.
49
Contents,
fee. of the
Salts.
   37*
To find the
Weight of
an equal
bulk of wa-
ter where
tke fpecific
gravity is
known.
   373
Mathema-
tical fpeci-
fic gravity
explained.
   374
Increafed
denfity of
mixtures
accounted
for.
   575
Weights of
different
kinds of air
   376
Method of
finding the
quantity of
pure acid
contained
in fpirit of
fait.
and that the weight fo loft is juft the fame as  that of
an equal bulk of water ; a^nd confequently, that their
fpecific gravity is equal to their weight in air,  or ab-
folute  weight divided   by their lofs  of  weight  in
water.
   3.  That if a folid, fpecifically heavier than a liquid,
be weighed firft in  air  and then in that  liquid, the
weight it lofes is equal to  the weight of an equal vo-
lume of that  liquid; and  confequently, if fuch folid
be weighed firft in air,  then in water, and afterwards
in any other liquid, the fpecific gravity will be as the
weight loft in it by fuch folid, divided by the lofs of
weight of the fame folid  in water.   This  method of
finding the fpecific gravity of liquids, our author found
more exact  than that by the aerometer, or the coinpa-
rifons of the weights of equal meafures of fuch liquids
and water,  both of which are fubject to feveral  inaccu-
racies.
   4.  That where the fpecific gravity of bodies is al-
ready known, we  may find  the  weight of an equal
bulk of water ;  it being as the quotient of their abfo-
lute weight divided by their fpecific gravities : and this
he calls their lofs of weight in water.
   Thus where the fpecific gravity and abfolnte weight
of  the ingredients of any  compound are  known, the
fpecific gravity of fuch compound may eafily be calcu-
lated ; as it ought  to be intermediate betwixt that of
the lighter and that of the heavier, according to their
feveral proportions: and this Mr  Kirwan calls the ma-
thematical  fpecific  gravity.  But in  fact the  fpecific
gravity of compounds,  found  by actual experiment,
Seldom agrees with  that found by calculation;  but is
often greater, without any diminution of  the  lighter
ingredient.   This increafe of denfity, then, Mr Kirwan
fuppofes to arife from a clofer union of the component
parts to each other  than either had feparately  with its
own integrant parts ; and  this  more intimate union
muft, he thinks, proceed from the attraction  of thefe
parts to each  other: for  which  reafon he fuppofed,
that this attraction might be eftimated by the increafe
of denfity or  fpecific gravity,  and was  proportionable
to it;  but foon found that he was  miftaken in this
point.
   With regard to the abfolute weights of feveral forts
of air, our author adheres to the  computations  of Mr
Fontana, at whofe  experiments he was prefent ;  the
thermometer being at 550, and the  barometer at 29;
inches, or nearly fo.  Thefe weights were as follow:
       Cubic  inch  of common  air,     -     0.3S5
                     fixed air,        -      0.570
                     marine acid air,       0.654
                     nitrous air,     -     0.399
                     Vitriolic acid air,      0.778
                     alkaline air,     -     0.2
                     inflammable air,       0.03
  Mr Kirwan begins his iiiveftigations with the marine
acid ; endeavouring firft to find the exact  quantity of
pure acid it contains at any  given  fpecific gravity, and
then by means of it  determining  the  weight  of acid
contained in all other acids.  For if a given quantity
of pure fixed alkali were faturated, firft by a  certain
quantity of fpirit  of fait, and  then  by determined
quantities of the other acids, he concluded, that each of
thefe quantities of acid liquor inuft contain the fame
quantity of acid; and this being known, the remain-
der, being  the  aqueous part, muft alfo be  known* Contents,
This conclufion, however, refltd entirely on the  fup- ^c- otthc
polition  that the fame  quantity of all  the  acids was ?
requifite for the faturation of a given quantity of fixed
alkali;  for if fuch given quantity of fixed alkali might
be faturated by a Smaller quantity of one acid than  of
another,  the conclufion  fell  to  the  ground.   The
weight of the neutral falts produced might indeed de-
termine this point in Some meafnre; but ftill a Source
of inaccuracy remained ; to obviate which he ufed the
following expedient.   1.  He fuppofed the  quantities-
of nitrous and vitriolic acids  neceffary to  Saturate  u
given quantity of fixed alkali exactly the fame as that
of marine acid,  whofe  quantity he had determined;
and  to prove the truth of this fuppofition, he obServed
the Specific  gravity of the  fpirit of nitre and oil of vi-
triol he employed,  and in which he  fuppofed, from
the trial with alkalies, a certain proportion of acid and
water.   He then added to thefe more acid and water,
and calculated what the fpecific  gravity fhould be on
the above fuppofition ;  and finding the  refult agreeable
with the fuppofition,  he concluded the  latter to be
exact.   The following  experiments were made on the
marine acid.                                          377
   Two bottles were filled nearly to the top with di- Method of
ftilled water, of which  they contained  in all 1399.9 finding the
grains, and fucceffively introduced into two cylinders fpecl.nc
filled with marine air ;  and the procefs was renewed, f—I^f0
until the water had imbibed, in  18 days, about  794 fah.
cubic inches of the marine air.  The thermometer did
not rife all this time above 550; nor fink, unlefs perhaps
at night, above 500 ; the barometer  ftanding betw-ecn
29  and 30  inches.  This dilute fpirit of fait  then
weighed 1920 grains ; that is, 520.1 more than before;
the weight  of  the quantity  of marine air abforbed.
The fpecific gravity of the  liquor was  found to be
1.225. Its lofs of weight in water (that is, the weight
of an equal  bulk of water) fhould then be 1567.346
nearly ; but it contained only,  as v/e have feen, 1399.9
grains of  water :  Subtracting this  therefore  from.
1567.346, the remainder (that is, 167.446) muft be
the  lofs of  520.1  grains of marine  acid ; and confe-
quently the  Specific gravity of the pure marine acid,
in fuch a condenfed ftate as when  it is united to water,
muft be -,}*.°'t:-g, or 3.100.
  Still, however,  it might be fufpected, that the  den-'
fity of this  Spirit  did not  entirely proceed Srom the
mere denfity of the marine acid, but in part alfo from
the attraction of this acid to water ; and though the
length of time requifite to make the water imbibe this ■
quantity of marine acid  air, naturally led to  the fuppo-
fition that the attraction was not very confiderable, yet
the following experiment was more fatisfactory.   He
expofed 1440 grains of this fpirit  of fait to marine acid
air for five days, the thermometer being at 50°, or be-
low ; and then found that it weighed 1562 grains, and
confequently had imbibed 122 grains more.   Its fpeci-
fic gravity was then 1.253, which was precifely what
it fhould have been by calculation.                       ..g
  Being now fatisfied that the proportion of acid in To find the
fpirit of fait was discovered, our author determined to proportion
find  it  in other acids alSo.  For  this purpofe he  took ?f Pure air
180 grains of very ftrong oil of tartar per d. ii^niuv:, and ".'°.t.hcr a*
found that  it was  faturated  by  180 grains of fpirit C1   1<luor!*
of fait, whofe  fpecific gravity was 1.225 ; and  by
                        G               calculation 
   3'?.
Q; antiti-.'s
' t  icid. wa
tcr,
kali
■ -:!;xeialt
50                                   CHEMI
ront.-nM. c.lculati * it appeare d, tlut 180 grains  of this fpirit
'  «fth« conuineJ 48.7 grains of  acid, a:..I  131.3 of  w.ter.
v'lt<      Hence lie drew up a tatflc of the  tpecific gravities of
         acid liquors containing ^'.7 grains  of p.irc  acid, with
         di fcrciit proportions of w-..ten, from 50  10410  parts;
         the  liquor wk!i  the firft proportion having a fpecific
         gravity of 1.49"%  and the latter weighing only 1.074.
          Mr ft.urmc  had determined the fpecific  gravity of the
         ftrongeft f;>irit of fait made in the  common manner to
          1. i'* 7, ant in gmau r.190 ;  but  we arc told  in the
          Pari,  Memoirs for 1700, that Mr  Homberg  had pro-
          duced a fpirit whofe fpecific gravity  was  1.300 ; and
          fiat made by  Dr Prieftley, by faturating water with
          marine acid air,  muft have been about   1.500.   The
          f,nrit  of fait, therefore, whole fpecific gravity is 1.261,
          has but little attraction for water, and  therefore at-
          tracts none  from the air ; for which reafon alio it docs
          not heat the ball  of a thermometer,  as the  vitriolic
          ;.il nitrous acids do ;  though  Mr Cavallo  found that
          this all" j had Some effect upon  the thermometer.   Com-
          mon Spirit of f tit,  Mr Kirwan informs  u, is  always
          adulterated with vitriolic acid, and therefore  unfit for
          thefe  trials.
            Mr Kirwan now  fet about inveftigating the quanti-
          ty of acid, water, and fixed alkali, indigeftive fait,  or
     11  al-a combination of the ma:i.:c  acid  with  vegetable al-
     ii di- k li.   For  tiis p trpofe he took 100  grains of  a folu-
          tion of tolerably p ire vegetable alkali,  that had been
          three  times calcined to enutcnefs,  the fpecific gravity
          of which was  1.097;  diluting alfo the fpiiit  of fidt
          with di tie rem portions of  water ;  the fpecific gravity
          of one fort  being  1.015,  and of  another  1.09".   He
          then found  that the above quantity of  folulion 0/ the
          vegetable  alkali required for  its  faturation 27 grains
          of that fpirit of fait whofe fpecific gravity was 1x93,
          and 23.35  grains  of that  whofe fpecific gravity was
          1.115. Now, 27 grains of fpirit  of  alt, whofe fpe-
          cifiv. gravity is 1.09?, contain 3.55 grains of  marine
          acid,  as appears  by calculation.   The principles on
          which calculations of this kind are founded, our author
          gives in the words of Mr Cotes.
            " The data requifite are the Specific gravities ofthe
          m'.xt'Tc  and of  the  two ingredi*. ns.   Then, as the
          difference of the fpecific  gravities  of the mixture and
jrravitie* of the lighter ingredient is to the different of the fpe-
:he diffe-  Cli\c rrravitics of the mixture and the heavier ingreui-
rent  niv.il.- em . ^o js tnc mag11itU(jc 0f tae heavier to the  magni-
          tude of the lighter ingredient.  Then, as the  magni-
          tude of the hca\ier, multiplied into its fpecific gravity,
          is to  the mag nit tele of the lighter multiplied into its
          fpecific gravity ;  fo is the weight ofthe heavier to the
          weight of  the  lighter.  Then, as  the fum of thefe
          \m; ,'i> is  to the weight of either ingredient; (bis the
          weight given to the weight ofthe  ingredient fought."
          Tims, in the prefent cafe, 1.098—1.000^x98 is the
          magnitude  of the heavier ingredient, viz. the  marine
          acid,  and .afxi. 100=0.3038 the weight of the ma-
          rine acid; aai it the other handx3.100—1.09^2.002,
          the magnitude ofthe water;  and 2.002x1.000=2.002
          its  weight  ; the fum of thefe weights is 2.3058 : then
          if  2.3053 parts >>S  Spirit of fait contain o.^o^ parts
          acid,  27 crams of this fpiiit  of fait  will contain ^.55
          acid.   In the fine manner  it will  be  found, that
          2:.;5  grains of fpirit of 'alt,  whofe fpecific giv.wtv is
          1.115, contains  :.,->-grains acid.
            O.t: u.tho: Jd-ibci very particularly his method of
C01, tents.
&c. oi the
   380
How to
find the
FJ'l. ific
   S    T   R    Y.                            Theory.
making the faturation  of the alkali with  ihe.-ui
which,  as it is always difficult to hit w ith preciiion, w e  *c- v
fliall here t ran Scribe.   "  It was performed by putting  ?alt8,
the glafs cylinder which contained  the alkaline  folu-    381
tion on the Scale of a very fenfible balance, and at the  Mr Kir-
San e time weighing the acid liquor in another pair oS  «an'i n>e-
fcalcs ;  w hen the loSs of weight indicated the eleape oftnt)l1 of fa"
nearly  equal  quantities of fixed air contained in the  |}^"-j
fohnion.  Then the acid was gradually added by dip-  and alka]j
ping a glals rod in it, to the top of which a fmall drop  ^;th 8Cci-
of acid adhered.  With this the folution  was ftirred,  raey.
and very  Small drops taken up and laid  upon bits of
paper itained blue with radifh juice.   As loon as the
paper was in  the  leaft reddened,  the operation  was
completed ;  fo-that there was always a very fmall ex-
cefs of acid, for which half a grain  was  conftainly al-
lowed ; but no allowance was made for the fixed air,
which always remains in the folution.   But as on this
account only a fmall quantity of the alkaline folution
was ufed, this proportion of fixed air nnift have been
incomidcrable.  If one ounce of the folution had been,
employed,  this inappretiable portion of fixed air, would
be fufficient to caufe a fenfible error; for the quantity
of fixed air loft by the difference betwixt the weight
added to the 100  grains  and the actual  weight of the
compound was judged of; and when this  difference
amounted to 2.2 grains, the whole of the fixed air was
judged to be cxjK-'lcd :  and it was  found to be fo; as
100 grains of  the  alkaline fohui.m, being evaporated
to da.an is, in the heat of 300°, left a relidmim which
amounted to  io; grains, which contained 2.2 grains
of fixed air."                                           ,ga
   The refult of this experiment was, that 8.3 grains  Quantity
of pure vegetable alkali, freed from fixed  air and water,  ofmild and
or 10.5 of mild fixed alkali, were faturated by 3.55  cauftic
grains of pure marine acid ;  and confequently the re-  v.t.8C.t.a^
fulting  neutral fait fhould, if it contained no water,  ^."j i,!!*"
wegh 11.85 grains :  but the  falts refill ting from  this  „jven
union (the folution being evaporated  to perfect dry-  weight of
nefs in a heat of 160 degrees, kept up for four hours)  marine
weighed at a  medium 12.66  grains.  Of this 11.85  acid.
grains were acid and  alkali; therefore the remainder,
viz. 0.81 grains, were water.  An hundred grains of
perfectly  dry  digeftive  fait  contain 28 grains  acitl,
6.55 of wafer,  and 65.4 of fixed alkali.
   in his experiments on the nitrous acid, Mr Kirwan
made ufe only ofthe dephlogifticated kind, which ap-     ,g-
prari j.ne and colcurlefs as water.   " This  pure acid Nitrous
(r.;v s he) cannot be made to exift in the form of air, as acid, when
Dr Prieftley has fhown ; for when it  is deprived of pure, can-
water and phlogifton, and furnifhed with a due pro-notbe
portion of elementary fire, it ceafes  to have the pro- "i:aae.to
        c      ■ 1    j  l       j   -Li   -n-     1  •   txift in an
P'.rnesof an acid, and  becomes dephlogifticated air. aer:al
Its proportion therefore  could not be determined inform.
fpirit of nitre as the  marine acid had  been in fpirit of
fait in the laft experiment."—To determine the mat-
ter, the following  experiments were made.              -g.
   1.  To 1963.25 grains of  dephlogifticated fpirit of Howtod«-
nitvc,  whofe fpecific gravity was 1.419,  he gradually  tcrmine
added  179.5 grains  <f diftilled water; and when jttbequanti-
cooled,  l!;e
to be i.'»E'9.
  2. To : 9
then ad.'. -.!,
found to be
  :. An In,
   die gravity of the mixture was found ly°f Pur«
      b     J                         acid eon-
    ,  , .     «           e            taincd ia
 .5 of this 170.75 grains of water v.erefpirit 0j
md the five:fie gravity of the mixtureuitr«.
 :6a.
.'.red grains of a ioimicm of fixed vegc-^
                                 tabic 
Theory.
CHEMISTRY.
5*
Contents,
&c. of the
Salt*.
   3*5
Proportion
of acid in
fpirit of ni-
tre to
           table alkali, Whofe fpecific gravity was 1.097, the Same
           that had been Sormerly uSed in the experiments with
           Spirit of fait, was  found  to be faturated by 11  grains
          of the fpirit of nitre, whofe fpecific gravity was 1.419,
          by 12 of that whofe fpecific gravity was 1.389, and by
           13.08 of that whofe Specific gravity was 1.362.   TheSe
          quantities were the medium of five experiments ;  and
          it was found neceffary to dilute the acid with  a fmall
          quantity of water.   When this was neglected,  part of
          the acid was phlogifticated,  and flew olf with the fixed
          air.   Ten minutes  were alfo  allowed after each affu-
          fion for the matters  to unite ;  a precaution which was
          likewife found to be abfolutely neceflary.
            Upon the fuppofition, therefore,  that a given quan-
          tity of vegetable fixed alkali  is faturated by the fame
     that" weignt°f both acids, we fee that ir grains of fpirit of
jn rp;rit 0f nitre,  whofe  fpecific gravity  is 1.419,  contain  the
fait.       fame quantity of acid with 27 grains of fpirit of fait,
          whofe fpecific gravity is 1.098,  or 3.55 grains.   The
          remainder of  11  grains, or 7.45 grains, is therefore
          mere water ; and of confequence, if the denfity of the
          acid and water had not been increafed by  their  union,
   3gg    the fpecific gravity of the pure nitrous acid fhould be
To find the H.8729.   But the  fpecific gravity of the nitrous,  as
fpecifkgra- well as  of the vitriolic acid, is augmented by its union
vity of the with water ; and therefore the lofs of its weight in
pure m-   water js not exactly, as  it would appear by calculation
rou*g" '  from the above  premifes, according to the rules al-
How to de- ready laid down.  To  determine  therefore the real
terminethe fpecific  gravity of the  acid in  its  natural ftate, the
accrued    quantity of accrued denfity muft be  found,  and fub-
denfity on.  tracted from the  fpeciffc gravity ofthe fpirit of nitre,
?V"c ?:fpi" wm°fe  trae mathematical  fpecific  gravity will then
          appear.   This   our  author   endeavoured  to   effect
          by mixing  different portions of fpirit of nitre and
          water, remarking the degree of diminution they fuf-
          tained by fuch union; but was never  able to attain a
          fufficient degree  of exactnefs in the experiment.  He
          had recourSe therefore to the following method,  as af-
          fording more fatisfaction,  though not altogether accu-
          rate.  Twelve grains ofthe fpirit of nitre, whoSe Spe-
          cific  gravity by observation was  1.389, contained, as
          our author fuppofed from the former experiment, 3.55
          grains  of real acid,  and 8.45 of water:  then  if the
          fpecific gravity of the pure nitrous acid were 11.872, that
          of this compound  acid and water fhould be 1.3 71 ; for
          the lofs of 3.55 fhould be 0.299,  ana< tne l°**s 0T~tnc water
          8.45, the fum ofthe loffes 8.749. Now,-^-11-= 1.371
rit of nitre
with wa-
ter.
                                               8.749
          but the  fpecific  gravity,  as already  mentioned, was
          1.389 :  therefore the accrued denfity was at leaft 0.18.
          the difference betwixt  1.389 and 1.3 71.   This calcu-
          lation indeed is  not  altogether exact  : but our author
          concludes, that 0.18  is certainly a near approximation
          to the degree of denfity that accrues to 3.55  grains of
          acid by  their union to 7.45 grains of water: there-
          fore, fubtracting this from 1.419, we have nearly the
          mathematical fpecific gravity  of that proportion of
          acid and water,  namely,  1.401.
            Again, Since 11 grains of this fpirit of nitre  contain
          3.55 grains acid, and 7.45 of water, its loSs of weight
          fhould beJJ—=7.855 ; and fubtracting  the  lofs of
                  1.401
•fthiacid the aqurous part from this, the remainder 0.45 is the
   388
To deter-
mine the
mathema-
tical Speci-
fic gravity
lofs ofthe 3.55 grainsacid;  and confequently the tine Contents,
fpecific gravity ofthe pure  and mere  nitrous  acid is &c. ofthe
 2 CC                                               Salts.
_!22_=8.7654. This being fettled, the mathematical '----«---'
0.405
fpecific gravity and true increafe  of denfity  of  the
above mixtures will be found.  Thus the mathematical
fpecific gravity of 12 grains of that fpirit  of nitre,
whofe fpecific gravity, byobfervation,was 1.389, muft
be 1.355 ;  fuppofing it  tp  contain 3.55  grains  acid
and 8.45 of water.   For the lofs of 3.55' grains  acid

is -L—0.405,  and the  lofs  of water  8.45 ;

fum of thefe loffes is 8.855.  Then-
the
12
=1.355; and
                                  8.855
 confequently the accrued denfity is 1.389—1.355—034.
 In the fame manner it will be found that the mathe-
 matical fpecific gravity of  13.08 grains of that fpirit
 of nitre, whofe, fpecific gravity by obfervation was
 1.362, muft  be 1.315; and  confequently its  accrued
 denfity .047.                                          3%f
   The whole of this, however,  ftill refts on the fup- Experi-
 pofition that each  of thefe portions  of fpirit of nitre rnent to de-
 contain 3.55 grains of acid.   To verify this fuppofi-tcrm,ne
 tion, our author examined the mathematical fpecific gra-  .  (f"an",
 vities of the firft mixture he had  made of fpirit of nitre acidin fpt-
 and water in large quantities; for if the mathematical rjt 0f nitre.
 fpecific gravities of thefe agreed exactly with thofe of
 the  quantities he  had fuppofed in Smaller portions of
 each, he could not but conclude that the Suppositions of
 fuch proportions of acid and water, as he had deter-
 mined in each, were juft.                               300
   This being determined by proper  calculations, Mr Table of
 Kirwan next proceeded to construct another table of fpecificgra-
 fpecific gravities, continuing his mixtures, till the ma- V1^ for
 thematical  fpecific gravities  found  by obfervation f?int °/
 nearly coincided with thofe made by calculation.   In conftru<>W
 this table the  fpirit of nitre was mixed with water in ted.
 various proportions, but after a different manner from
 that  obferved with the fpirit of fait.   Nine grains of
 the  fpirit  containing 3.55 grains of pure acid were
 mixed with 5.45 of water ;  the accrued denfity ofthe
 mixture was  found to be nothing,  the mathematical
 fpecific gravity 1.537, and the fpecific gravity by ob-
 fervation was found  the  fame.  When  10 grains of
 fpirit were mixed with 6.45 of water,  the accrued den-
 fity  Was  0.009,  tne niathematical  fpecific  gravity
 1.458, and the fpecific gravity by obfervation  1.467.
 In this  manner he proceeded  until  38.90 grains of
 water were mixed  with  42.45 of fpirit.  In this cafe
 the accrued denfity was found to be 0.002, the mathe-
 matical fpecific gravity 1.080, and the fpecific gravity
 by obfervation  1.082.
  The intermediate fpecific gravities, in a table of this
 kind, may be found by taking an arithmetical mean be-
 twixt the fpecific gravities,byobfervation,betwixt which
the defired Specific gravity lies,  and noting how much it   / .
exceeds or Sails. Short of Such arithmetical mean ; and
 then taking alSo an  arithmetical mean betwixt the ma-
thematical Specific gravities betwixt which that Sought
for muft lie, and a proportionate excefs  or defect.
  The  fpecific gravity of the ftrongeft Spirit of nitre
yet made, is,  according to Mr Baume, 1.500, and ac-
cording to Mr Bergman 1.586.
  Our author next proceeded to examine the propor-
                       G  2                    tion 
CHEMISTRY.
Theory.
   394
 Mr Kir-
wan's ex-
periments
confirmed
by one of
lontina.
!;"-t of acil, water, and fixed alkali in nitre, in a man-
 cr Simihu- to what he had already done with digcltivc
l.dt; aim i mud that 100 grains of perfectly d.^ nitre
coitai*ud 2^.48 grains of amd, 5.2 ot water,  ami 66.32
jt fixed alkali.
   borne  experiments ofthe fame kind had been made
by M.  Homberg; the relults of which our author com-
pared wiui tiuk  of his ou::.   The  -peeific gravity of
the spirit of nitre which M.  Homberg  made  ufe of
was 1.549;  a'1^ °f this, he fays, one  ounce  two
drachm-, and 36 grains, or 621 troy  graft's,  are requi-
red to  faturate one  French ounce  ^-2.)  troy) of dry
Salt  or  tartar.   According to   Mr Kiruan's computa-
tion, however, 613 grains are Sufficient; lor the lpeci-
lu gravity lies between the Specific gravities by obser-
vation 1.362 and 1.537, and is nearly an  arithmeti-
cal mean between them.   The corresponding  mathe-
matical  Specific  gravity  lies between the quantities
marked  in Mr KhuaiTs table 1.315 and 1.286, being
nearly 1.300.  Now the preiportion oSacid  and water in
this is 2.629 of acid and 7.465 oS water ;  for 8.765—
1.300=7.465  of water,   and 8.765X-3°o=2.629 of
acid;  and the fum of both is 10.044.  Now, fince
■10. c grain* ofmild vegetable alkali require 3.53 grains
of acid for their  faturation, 472.5 will require  159.7 ;
therefore  if   10.044  grains  of nitre contain  2.629
grains  acid, the quantity  of this fpirit of nitre requi-
fite to give 159.7  will be 613.2 nearly,  and thus the
difference with M. Homberg is only  about  eight grains.
   M.  Homberg  fays he found  his  fait,  when evapo-
 rated to drynefs, to weigh 186 grains more than be-
 fore,  but  by  Mr  Kirwan's  experiment, it   iliould
 weigh but 92.8 grains more than at firft ; the caufe of
 which difference will  be mentioned in treating of vi-
 triolated tartar,  as it cannot be entirely  attributed  to
the difference of evaporation.
   He alfo afferts, that one ounce (472.5 Troy  grains)
of this fpirit of  nitre  contains 141  grains of Troy of
 real acid.  According to Mr Kirwan's  computation,
 however, it contains  only 123.08 grains of real acid.
 But this difference evidently proceeds from his neglect-
 ing the quantity of water that certainly enters  into
 the compofition  of nitre ;  for he proceeds on this ana-
 logy,  621 :  186.6 : : 472.5 : 141.
    Our author obferves, that  the proportion of fixed
 alkali affigned by him to nitre is fully confirmed by an
 experiment of Sir Fontana's infertedin Rozier's Jour-
 nal Sor 1773.  He decompoSed two ounces of nitre by
 diftilling it with a ftrong heat for 18 hours.  After the
 diftillation there remained in  the  retort a fubftance
 purely alkaline,  amounting to 10 French drachms and
 22  grains.   Now  two French ounces  contain  945
 grains  Troy, and  the alkaline matter 6o7 grains of
 the fimc kind  :  according  to Mr  Kirwan's com-
 putation the two ounces of nitre ought to contain 625
 grains of alkali.  Such a fmall difference he fuppofes
 to proceed from  the lofs in transferring from one vef-
 fel to  another, weighing, filtering, evaporating, ire.
 Mr Kirwan  alfo  fhows  in a very particular manner the
 agreement of his calculations with the experiments of
 r I. Lavoilier on  mercury didblved in fpirit of nitre; but
 u ir limits will not allow us to infert an account of them.
   When  finding  the quantity of pure acid contained
 in oil  of vitr'ol, our author  made  ufe of fuch as was
 ;.».: dephlogiiticitcd ; but, though pale, yet a little in-
clining to red.   It contained fome whitilh mattcr, asCoutcnu,
he prtccived by  its growing milky on the aftufion ot **«.. u'ibe
pure diftilled water ; but he imagines ii was  as pure as » u'
the kind ufed in all experiments.                       ,0j
  To 2519.75 grains of this oil of vitriol, whofe fpc- ExrVri-
cific gravity was 1.819, he gradually added  180 grains incuts on
of diftilled  water, and lix hours  after  found its fipeci- 0,j oi vi_'
fie  gravity to be 1.771.—To  this mixture he  again*   '
added  178.7c grains of water, and  found its  fpecific
gravity,  w hen cooled to the temperature of  the atmo-
lpietc,  to be 1.719, at which time it was milky.  The
fame quantity of the oil of tartar abovementioned was
then faturated with each of thefe kinds of oil of vitriol
in the manner already  defcribed.  The faturation was
eftected (taking a medium of five experiments) by 6.5
grains of that whole Specific giavity was 1.819, by 6.96
grains of that wlmit. Sped;.c gravity was 1.771, and
by  7.41 of that whofe  fpeenic giavity was 1.719.        396
   It was found neceliam to add a certain  pioportion Dilution of
of  water to each of thefe forts of oil of vitriol ; for *>\l if vi-
when  they  were not  diluted, part ofthe acid was t,io1 wn7
phlogifticated, and went off with the fixed air;  but n«effarym
know ing the quantity  of water that was adued, it was p-ji^ou!"
eafy to  rind by  the rule of proportion  the quantity  of
each fort of vitriol that was  taken  up  by  the alkali.
Hence it was fuppofed, that each of  thefe quantities
of oil of vitriol of different denfities  contained  3.55
grains of acid ; as they faturated the fame quantity of
vegetable fixed alkali with 11 grains of fpiiit of nitre,
which contained that quantity of acid.                    .^
   It was next attempted to find the fpecific  gravity To find th«
ofthe pure vitriolic acid in a manner fimilar to that fpecific gra-
by which the gravity of the nitrous acid was found ; vityofpure
as  it cannot be had in the fhape of air, unlefs  whenvIt.no^'
united w ithfuch aquantity ofphlogifton as quite alters its a
properties.  The lofs of 6.5 grains of oil of vitriol, whofe
but
as
fpecific gravity is 1.819, is___—- =: 3.572

thefe 6.5 grains contained, befides 3.55 of acid, 2.95
of water, the lofs of this muft be fubtracted from the
entire lofs;  and then the remainder, or 0.622, is the3
lofs of the  pure acid  part in that ftate  or denfity to
which it is reduced by its union with water.  The fpe-
cific gravity, therefore, of the pure vitriolic acid,  in
this ftate of denfity, is  ^'SL — 5.707.   But  to find
                       0.622
its  natural fpecific gravity, we muft  find how  mnch
its denfity is increafed by its union with this quantity
of water : and in order to obferve this, he  proceeded
as before with the nitrous acid.  6.96 grains of  oil of
vitriol,  whofe fpecific  gravity was  1.771,  contained
3.55 of acid and 3.41  of water ; then its Specific gra-
vity by  calculation  fhould  be 1.726;  for  the lofs of
3.5 5 grains of acid is _LL5_ = 0.622; the lofs of 2.41
                    5-707
grainsofwateris3-4i ;  the fum of theloffes 4.032 : then
———= 17-16; therefore the accrued denfity  is  1.771
 4.032
—1.726=0.45.  Taking this therefore  from 1.819,
its mathematical fpecific gravity will be 1.774.    Then
the lofs of 6.5  grains of oil  of vitriol, whofe  fpecific
gravity by obfervation  is 1.819, will be found  to  be
—li_ = 4.663 ; but of this,  2.95  grains are  the lofs
 1-774
                                                 ©f 
Theory.
CHEMIST&Y.
S3
Contents,
&c. of the
Salts.
3?8
  . 399
Difference
with Mr
           of the water it contains, and the remainder 0.714 are
           the lofs of the mere acid part.   Then _?__££„ is near-
                                               0.714
           ly the true fpecific gravity of the pure vitriolic acid.
           The fpecific gravity of the moft concentrated oil  of
           vitriol yet made, is, according to M. Baume and iierg-
           man, 2.125.
             Mr Kirwan  now conftructed  a table of  the fpecific
           gravities of vitriolic acids, of different ftrengths, in  a
           manner fimilar to thofe  conftructed for fpirit  of fait
           and fpirit of nitre ; but for which, as well as the others,
 Quantity of we muft  refer to Phil. Tranf. vol. 71.   He then pro-
 acid, alkali, ceeded to find the proportion of  acid, wrater,  and fix-
 and water, ed alkali, in  vitriolated  tartar as he had before done
 mvitnola- -m ^ Jireftivus and  nitre.—He found the falts re-
 i«crniined ^""i fr°m the faturation of the fame oil of tartar,
        .  with portions of oil of vitriol, of different Specific gra-
           vities, to weigh at a  medium 12,4.5 grains.  Of this
           weight only 11.85 grains were alkali and acid.  The
           remainder, therefore, was water, viz 0.6 of a grain.
           Confequently 100 grains of perfectly dry tartar vitrio-
           late contain  21.58 grains acid, 4.82 of water, and
           66.67 °f fixed vegetable alkali.—In drying this fait, a
          heat of 240  degrees was made  ufe  of,  to expel the
          adhering acid  more thoroughly.  It was kept in this
           heat for a quarter of an hour.
             According to Mr Homberg, one French  ounce, or
           472.5 grains troy, of dry fait  of tartar, required 297.5
 Homberg grains troy, of oil  of vitriol, whofe fpecific gravity
 accounted  was 1.674 to faturate  it : but by Mr Kirwan's  calcu-
 f*r-      lation, this quantity of fixed alkali would require 325
          grains ; a difference which,  confidering the different
          methods  they made ufe of for determining the fpeci-
          fic gravities   (Homberg's method by  menfuration,
          giving it  always lefs than Mr Kirwan's) the different
          deficcation of their alkalies, &c.  may be accounted in-
          confiderable.
             The Salt  produced, according  to Mr  Homberg,
          weighed 182 grains troy above the original  weight of
          the fixed alkali; but by Kirwan's experiment, it fhould
          weigh but 87.7 grains more.  " It is hard to fay (adds
          Mr Kirwan) how Mr  Homberg could find  this great
          excefs of weight, both in nitre and tartar  vitriolate;
          unlefs he  meant by the weight ofthe fait of tartar the
          weight of the mere alkaline part  diftinct from the fix-
          ed air it contained : and indeed one would be tempted
          to  think he did make the  diftinction ; for in that cafe
          the excefs of weight would be nearly fuch as he  de-
          termined  it."
             From Mr Homberg's calculations, he inferred that
          one ounce (472.5 grains) of oil of vitriol contains
          291.7 grains of acid.   Mr Kirwan computes the  acid
          only at 213.3 grains ; but Homberg made no allowance
          for the water contained in tartar  vitriolate ; and ima-
          gined  the  whole increafe of weight proceeded from the
          acid that is united in it  to the fixed alkali.  Now the a-
          queous part in 560 grains of tartar vitriolate amounts
          to  56 grains ;  the remaining  difference may he attri-
   400    buted  to the different degrees  of deficcation, &c.
Specific       On  the acetous acid Mr Kirwan  did not make any
grav.tyof  experiment;  but by calculating from thofe of Hom-
the ..cetous berg,  he finds  that  the fpecific  gravity of the pure
8         acetous acid, free from  fuperfluous  water, fliould  be
          2.;o.  " It is  probable (fays  Mr Kirwan), that its
          affinity to  water is not ftrong enough to caufe any ir-
          regular increafe in its denfity j at leaft what  can be
401
  expreffed by three decimals : and hence its proportion Contents,
  of acid and water may always  be  calculated from its &c- <»fthe
  fpecific quantity and abfolute weight."               Salts-
    An hundred  parts  of  foliated  tartar, or,  as  it
  fhould rather be  called, acetous tartar, contain,  when
  well dried, 32 of fixed alkali, 19 of  acid, and 49 parts
  of water.—The  fpecific gravity of the ftrongeft  con-
  centrated vinegar yet made is  1.069.—It is more  dif- Specific
  ficult to rind the point of faturation with the vegetable grav»ty °f
  than with the mineral acids, becaufe theycontaina muci- ftrong Vi"
  lage that prevents their immediate union with alkalies ; neSar'
  and hence they are commonly  ufed  in too great quan-
  tity :  they fhould be ufed moderately hot,  and fuffi-
  cient  time allowed them to unite.                       4oa
   From all the experiments above  related, Mr Kirwan Vegetable
  concludes, 1. That the  fixed vegetable alkali takes up fixed alka-
  an equal quantity of the three  mineral acids, and pro- h takes UP
  bably of  all pure acids; for we  have feen  that  8.5aneq"al  f
  grains of pure vegetable alkali,  that is,  free from fix"- STthTni?-
  ed air, take up 3.55 grains of each  of thefe acids ; and nerai acids.
  confequently too parts  of cauftic  fixed  alkali would
 require 42.4 parts of acid  to faturate them.  But  Mr
  Bergman has found that 100 parts of cauftic fixed  ve-
 getable alkali take up 47 parts ofthe aerial acid ; which,
 confidering that his alkali might contain fome water,
 ditters but  little from that  already given.  It fhould
 feem,  therefore, that  alkalies  have  a certain  deter-
 mined capacity of uniting to acids, that is, to agiven
 weight of acids ;  and that this capacity is  equally  fa-
 tiated  by a given weight of any pure acid indiscrimi-
 nately.  This weight is about 2.35 of  the  vegetable
 alkali.
                                                      403
   2.  That the three mineral acids,  and  probably  all Quantity of
 pure acids,  take up  2.253 times  their own weight of the alkali
 pure vegetable alkali,  that is, are  faturated by  that neceffary to
 quantity.                                     •      faturate the
   3. That  the denfity  accruing  to compound  fub-aci s"
 fiances, from the  union  of their compound  pans, and incrtafe of
 exceeding its mathematical ratio, increaSes  from a mi- denfity in
 ?iimum, when the quantity of one of them is very fmall compound
 in proportion to that ofthe other  ; to a  maximum, when fubftances..
 their qualities differ lefs :  but that the attraction,  on
 the  contrary, of  that  part which  is in  the fmalleft
 quantity to that which is in the greater, is at its maxi-   40.
 111 ism when the accrued denfity is at its minimum  ; but Why de-
 not reciprocally  :  and  hence the point of faturation is compofi-
 probably the maximum of denfity and  the minimum  of tioils are
 fenfible attraction of one of the parts.   Hence no de- *yme"
 compofition operated by means of a  fubftance that has times :n"
 a greater afliuity with one partof a compound than with and other-
 the other, and than thefe parts have wfttb  each other, wife.
 can be complete,  unlefs the minimum affinity of this   406
 third   fubftance be greater than  the maximum affinity w,iy the
 of the parts already united.   Hence alfo few decom- laftPor^o»*
 pofitions arc complete, unlefs a  double affinity inter- « 8   ,
          1 l '     1   1 n.      •     r 1    r       i «ance ob-
 venes ; and hence the laft  portions  of the feparated fti„atelv
 fubftance adhere fo  obftfiately  to  that with which adhere to
 it was firft united, as all chemifts  have obferved.— that with
 Thus,  though  acids have  a greater  affinity to phlo- which it
gifton  than  the earths of the different metals have  to wasunite^*
it, yet  they can never  totally  dephlogifticate  thefe .  -1°7
 earths  but only to  a certain degree ;  fo,  though  at- nevertotaW
 mofpheric air, and particularly dephlogifticated air, at- lydephlo-
 tracts  phlogifton more fir on gly  than  the nitrous acid giuicate
 does, yet not even  dephlogifticated air can deprive the metallic
 nitrous acid totally of its phlogifton  ; as is evident from tvt&*
                                                 th<i 
54
CHEMISTRY.
Theory.
Content i,
*c. of the
Suit*.
r.v rcury
and alum
tetain part
ot the aciJ

Alkali *
p!  ogifli-
cate  em>
centraied
a.uis.
   4IO
t>.e red colour of the nitrous acid, when nitrous air and
dcpiiloginicuicd air arc 1 Mixed together.  Hence mer-
cury prce ipitatcd  from im  l<» ution in . uy  acid, even
by fixtd ^lki'.e,,  conftantly retains a portion of the
acid  to winch u  was originally  united,  as Mr Haven
°f has lhown.  Thus alio the earth of alum,  wheu preci
 411
vific
          i'it.ucd iu like manner from its folution,  retains turt
          of tbc acid ;  and thus feveral anomalous decouipofi-
          tious may  be explained.
            4. That concentrated acids are in fome meafure phlo-
          gi,netted,  and evaporate by union with fixed alkalies.
            5. That, knowing  the quantity  of fixed alkali in
          oil of tartar,  wc may determine the  quantity  of real
          pure acid in any other acid fubftance that  is difficult-
          ly decompofed ; as the Sedative acid, and thofe in ve-
n<>\vto Je- gctables and animals.  For  10.5  grains  of the mild
tenminethe alkali will  always be faturated by 3.55  grains  of reft
quantity of acjj . anj  reciprocally,  the quantity of  acid  in any
pure acid  acj<j ijqllor Deing known,  the quantity of real alkali
flmaL  """ *u iny vegctaDlc alkaline liquor may be found.
            Having thus determined the quantity  of acid con-
          tained in the liquids of  that kind ufually  employed in
          chemiftry,  as well as  the  fpecific gravities of the acids
          themfelves, Mr  Kirwan became delirous  of inveftiga-
          ting the gravity of fixed and volatile alkalies.   But as
gravity of  thefe fubftances are not eafily  preferved  from  uniting
tixid air   themfelves with fixed air, he was led to  confider the
ued""11"   Kravfty °f this in its fixed ftate, as an element necef-
   412    ^r>' f°r lllG calculation ofthe quantities of the alkalies.
Specific       To find  the fpecific gravity  of  the fixed vegetable
jravity of  alicali, our author proceeded in a manner funilar to that
fixed vege- already defcribed, excepting  that  he weighed it  in
vdftc alka- €t|lcr jnftead of fpirit of wine.  The refultSOfhisexpc-
u inveftt-                  *                               *
eated.     ninents are.
    .l3       1. That 100 grains of  this  alkali contain about 6.7
QnJntityof grains of earth ; which, according to Mr  Bergman, is
earth con- ffliceous.   It palfes the filter along  with it when  the
*ainedjn it. alkali is not faturated with fixed air ;  fo that it feems
          to be held  iu folution in the fame manner as in the Ii-
   414    QM>r fil;e.,>Ji.
Quantity♦!    2.  The  quantity of fixed air in oil of tartar and dry
fixed air in vegetable fixed alkali is various at  various times, and
oil of tartar in various parcels of the fame  fait ; but in  thepurer al-
ind^y!c*kaiies  it may  be reckoned at a medium 21 grains in
          100 ; and hence  the quantity of this alkali may very
          nearly be gucftcd at iiiiaay folution,  by adding a  known
          wcigtu of any dilute acid  to a given weight of fuch a
          Solution,  and then weighing  it again;  for as  21 is to
          100, fo is the weight  loft  to the weight of mild alkali
          in fuch folution. The fpecific  gravity ofmild and per-
          fectly dry vegetable fixed alkali, four  times calcined,
         free from iiliceous earth, and containing 21 per  cent, of
         6\cd aj.r, was found" to-be 5.0527.  When it contains
          more fixed ajr the gravity is probably  higher,  except
         when it is  not perfectly dry ;  and  hence the  fpeciiic
         gravity of this alkali, whencaoftic, was fuppofed by Mr
          Kirwan to be 4.2:4. For this reafon the fixed alkalies,
          when united to aerial acid, arc Specifically  heavier than
         when united either to the  vitriolic or nitrous.   Thus
          Mr R. \S ati'on, in the PhilofophicalTmnft.e:ftm«;  for
          1770, i"ft»rms '..>, that, he found the fpecific gravity of
          d'y fdt of tartar, including the Siliceous earth  it nam-
         raliy contains, to be 2.761 ; whereas the fpecific gravity
         of viiriolawd  tartar  was only 2.636, and that of niire
         1.0;?.   The reafpafrhy nitf is fo much lighter than
getable fix
«d alkali.
 Mr Wat-
ton's ac-
cour.: of
the fpeef c
gravity,o(:
ialt of tAI-
•wr, &c.
• .-"..ir vitriolate is,  that it contains much more water,
a.id the uiion'u the acid with the water is lei's intimate.
   Impure v e ge. iblc tixedidkalics, fuch as pearl -alh, pot-
afhe^ekc.  com ft u more fixed air than the  purer kind.
According to Mr Cavendifh, jnarl-alh  contains  2^.4
or 20.7per c;n:. of fixedair. i  eiicc in  'ye > made from
thefe falts, of equ.u Specific  gravities  with  thofe  of a
purer alkaii, the quamity  of faline matter will  proba-
bly be in the ratio of 28.4 or 2S.7 to 21 ; but this ad-
ditional weight is onlv fixedair.  Much alfo  defends
on their age;  the oldel't contai.in^ moft fixed an. Our
author alfo gives a table of the ipcciSc gravities of differ-
ent Solutions of vegetable fixedalkali, in a manner fnuilar
to w hat  he  had done before with the acids.  He  begins
with 64.02  grains of a folution containing  26.25
grains of fait, and 38.67  of water. The accrued  den-
fity he finds to be .050, the mathematical fpecific gra-
vity r.445,  and the  fpecific  gravity  by  obfervation
1.495.  By continually diluting the  folution  contain-
ing the fame quantity of  fait,  he brings the  abfolute
weight of it at laft-to 341.94 grains, of which 317-49
are water ;  the  accrued  denfity 0.01,  the mathema-
tical fpecific gravity 1.061,  and the fpeciiic gravity by
obfervation 1.062.
   In a fubfequent paper on lifts  fubject, Philofophical
Transactions, vol. 72, p.  179, our author corrects a
fmall miftakc concerning  the quantity of acid taken up
by 10.5 grains of mild vegetable alkali.  In his former
computations he had made no allowance for the  fmall
quantity of earth contained  in this quantity of alkali ;
which, tfiough inconfidcrable in  it, becomes of  confe-
quence where the epiantities are large. The error, how-
ever, occafioned by this omifliou,is Senfiblein his calcula-
tions concerning the quantities of acid alkali, &c.  con-
tained in the neutral Salts, as well as in that concerning
the vegetable alkali.  When  the  correction h properly
made, lie Says, it will be Sound that 100 grains of fuch al-
kali, free from earth, water, and fixed air, takeup 46.77
of the mineral acids, that is, ofthe mere acid part; and
100 grains of common mild vegetable  alkali  take up
36.23 grains of real acid.   An hundred grains of per-
fectly dry tartar vitriolate contain  30.21 of  real  acid,
64.61 of fixed alkali, and 5.18 of water.  Cryftallized
tartar vitriolate lofcs only one percent, of water in a heat
iu which its acid is not Separated in any degree ; and
therefore contains 6.18 of water.   An hundred grains
of nitre, perfectly dry, contain 30.86 of acid, 66 of al-
kali, and 3.14 of water ;  but in cryftallized nitre the
proportion of  water  is fomewhat  greater ;  for 100
grains of thofe cryftals being expofed  to a  heat of
1 So0 for two hours, loft three grains of their  weight
without exhaling any acid frnell  ,• but when expofed to
a heat of 200 degrees, the Smell  oS the nitrous  acid is
diftinctly perceived.  Hence 100 grains of cryftallized
nitre contain 29.S9 of mere  acid, 63.97 of alkali,  and
6.14 of water.  An hundred grains of digeftrve  fait
perfectly dry, contain 29.68 of marine acid, 63.47 of
alkali, and 6.85 of  water.  One  hundred grains of
cryftallized digeftivcfalt lofe but one grain of their
weight before the fmcllof the marine acid is perceived ;
and hence they contain 7.85  grains (ft water.
   Another rnifUke, more  difficult: to be corrected,  was
Ms f tppofing the mixtures of oil of vitriol and water,
and fpirit of nitre and water, had attained  tlieir  maxi-
mum of denfuy when they had cooled to the tempera-
                                               ture
Content*,
&c. of the
Salts.

   416
Why nitre
is fo much
lighterth; u
vitrii l.'.iul
tartar.
   417
Quantity of
fixtd air in
pure vege-
table alka-
lies, eii tcr-
mined by
Mr t avcn-
difh.
   418
Quantityof
acid taken
up by mild
fixed alkali
exactly de-
termined.
   419
Ofthe
quantity of
ingredients
in vitrio-
lated tar-
tar;
   420
Fn nitre,
   4"
In digoAive
fait. 
Theory.
CHEMISTRY.
£S
Contents,
&c  ofthe
Salts.

   42Z
Time re-
quired by
mixtures
of mineral
acids and
water to ac-
quire their
utmoft
denfity.
   4*3
Alteration
of the den-
fity of acids
by various
degrees of
heat.
 tnre of the atmofphere ;  which at the time he made the
 experiment was between 500 and 6o° of Fahrenheit.
 The mixture with oil of vitriol had been fuffered to ftand
 fix hours; but when the acid was  fo much diluted as
 to occafion little or no heat, it was allowed to ftand on-
 ly for a very little time.   Several months afterwards,
 however,  many of thefe  mixtures  were found much
 denfer than when  he firft examined  them ; and it  was
 difcovered, that at leaft  twelve hours reft was necef-
 fary before concentrated oil of vitriol, to which even
 twice its  weight of water is added, can attain its ut-
 moft  denfity;  and ftill more  when a ■ fmaller pro-
 portion of water  is ufed.   Thus when  he made  the
 mixture of 2519.75 grains of oil of vitriol, whofe fpe-
 cific gravity was 1.819, with 180 of water, he found its
 denfity fix hours after 1.771, but after 24 hours it  was
 1.798 : and hence, according to the methods  of  cal-
 culating already laid down, the accrued denfity was at
 leaft  .064 inftead  of .045.   But by ufing oil of vitriol
 ftill more concentrated, whoSe Specific  gravity  was
 1.8846, he was enabled to make a ftill nearer approxi-
 mation ;  and found, that the accrued denfity oS oil of
 vitriol, whofe  fpecific gravity  is 1.819, amounts to
 0.104,  and confequently its mathematical fpecific gra-
 vity is  1.715.  Six grains and a half of this oil of vi-
 triol contained, as has been already obServed, 3.55 of
 mere acid, and the  remainder was water.   The weight
 of an  equal bulk of water is 3.79 grains ;  and Subtrac-
 ting  Srom this the weight oS the  water that enters
 into  the  compofition  of  the oil of vitriol,  it  will
 be found, that the weight of a bulk  of water equal to
 the acid part is 0.84 ;  and confequently the fpecific
 gravity of the mere acid part is 4.226.  Thus, by con-
 ftantly allowing the mixtures to reft at leaft 12 hours,
 until  the  oil of vitriol was diluted with four times its
 weight of water,  and then only fix hours before  the
 denfity  of the mixtures was examined, he conftructed
 another table, in which  1000 grains of liquor contain-
 ed  612.05 °f Pure  ac^>  387.95 of water,  the  ac-
 crued denfity being .07,  and the mathematical fpecific
 gravity 1.877.   Increasing the quantity  of water  till
 the acid weighed 7000 grains, and the water 6387.95,
 he found  the accrued denfity .059, and. the mathema-
 tical fpecific gravity 1.069.  By a  fimilar correction
 of his experiments on  the acid of nitre, he found its
 denfity to be  5.530; a  fimilar table was conftructed
 for it, for which we refer our readers to the 72d  vo-
 lume  of the Philofophical Tranfactions.
  Thefe experiments were made when the thermome-
 ter flood between  500 and  6o° of Fahrenheit; but, as
 it might be fuSpected that the denfity of acids is con-
 siderably altered at different degrees of temperature, he
 endeavoured to find the quantity of  this alteration in
 the following manner : To calculate what this denfity
would be  at 55°,  he took fome dephlogifticated fpirit
Of nitre, and examined its fpecific gravity at different
 degrees of heat; which was  found to be as follows,
            Degrees             Specific
            of heat.             gravity.
              30               L4653
              46               1.4587
              86               r.4302
             120               1.4123
  The total expanfion of  this Spirit oS nitre, therefore,
from  30 to.120 degrees,  that is, by  900 of heat,  was
0-.0527; for 1.4650=4.123+. 0527.   By which weSee,
 that the dilatations are nearly proportional M the de- Contents,
 grees of heat:  for beginning with  the  firft dilatation &c. of ths
 from 30 to 46 degrees, that is, by 16 degrees of heat, Sa^'
 we find that the difference between the calculated and
 obferved dilatations is only T4'^; a difference of no
 confequence in the preSent caSe, and Which might ariSe
 from the immerfion of the cold glafs-ball filled with
 mercury in  the liquor.  In the next cafe the  differ-
 ence is ftill lefs,  amounting only to TTVT?.
   With another,  and fomewhat ftronger Spirit of nitre,,
 the fpecific gravities were as follow :
            Degrees             Specific
            of heat.             gravity.
              34              I-4750
              49               1.4653
             150               I-3793
 Here alSo the expanfions were  nearly proportional t&
 the degrees of heat; for 1160 of heat,  the difference
 between 34 and 150, produce an expanfion of 0.0958  ;
 and  15°  of  heat,  the difference between  34 and 49,
 produce an  expanfion  of 0.0097 ;  and by calculation    «
 0.0123 : which laft differs from the truth  only  by
 T^oo-o-^*                                                4*4
   From this experiment we fee, that the Stronger the Strong fpf-
 fpirit of nitre is,  the more it is expanded by the fame rit °f nitrc
 degree of heat; for if the fpirit of nitre of the laft ex- more *jx"
 periment were explained in the fame proportion as in Fan e,  y
 the former, its dilatation, by  116 degrees  of heat, weak ann,
 fhould be 0.0679 ; whereas it was found to be 0.0958. why,'
   As the dilatation  of the fpirit of nitre is far great-
 er than that of water by the fame degree of heat,  and
 as it confifts only  of acid and water; it clearly follows,
 that its fuperior dilatability muft be owing to the acid
 part: and hence  the more acid that is contained in
 any quantity of fpirit of nitre, the greater is its dilata-
 bility.  We might thereSore SuppoSe,  that the dilata-
 tion of nitre was intermediate betwixt the quantity of
 water  it contains and that of the acid.   But there
 exifts another power alfo which prevents this fimple re-
 fult, viz. the attraction of the acid and water to each
 other, which makes them occupy lefs fpace than the
 fum of their joint volumes; and by this condenfation our    425
 author explains his phraSe of accrued denfity.  Taking Exact
 this into the account, we may confider  the  dilatation 4uantiry °^
 of the fpirit of nitre  as equal  to thofe of the  quan- dj.'j,m.lcnf
 tides of water and  acid it contains, minus the con- nitre-"* °
 dentation they acquire from their  mutual  attraction  ;
 and this rule holds as to all other heterogeneous com-
 pounds.                                               4a<}
   To find the quantities of acid and water in fpirit of Of the
 nitre, whoSe Specific gravity was found in degrees of quantities
 temperature different frcm thofe for which  the table of acul an*
 was conftructed, viz. 540, 55% or 560 of Fahrenheit, J"*^?1!"
 the fur eft method is to find how  much that  fpirit of f irit 0£
nitre is expanded or condenfed by a greater  or leffer de- nitre-
gree of heat; and  then, by the rnle of proportion,
find what its denfity would, be at  S5°-   But if this.
cannot be done, we fhall approach pretty near the truth
if we allow 7^iT for every 150 degrees of heat above or
below 550 of Fahrenheit, w-hen  the fpecific gravity
is between  1.409  and 1.500, and -^Vs  when the fpe-
cific gravity is  between  T.600  and i.Sco.—The di-
latations of oil and fpirit of vitriol were found to be ex-
ceedingly irregular,  probably  by reafon  of a  white
foreign matter, which is more or lefs fufpended or dif-
folyed in it, according to its greater or leffer dilution ;
                                               and 
S*
CHEMISTRY.
Theory.
Salt*.
   4»:
Dilatation
of
ri'iui or-
preet of
ke«t.
Conte-i«,  and this mrtcr our am', >r did not fcpara.c,  as he in-
*V. °f the  U"-1^CJ lo tr>" lnc ac*d in the ftate in uhich it is com-
          monly u led.   l.i  general  he found  that  150 of heat
          caufed a difference of above   ,'., in its fpecific giyvity,
          when it exceeds  i.Seu,  a;.d of TV»T, when its Specific
          gravity ft between 1.400 and 1.300—The diLt.uiouiof
   (pint  ff lpirit of fait arc very nearly proportional to the degrees
        '" of hear, as appears by th« following tide.
                      Decreet              Specific
                      of heat,              gravity.
                        33                1.1916
                        54                I.i860
                        66                1.1820
                       128                1.1631
             Ilcncc , /r5. fhould  be added or fubtradted  for every
          2t° above or below 550, in order to reduce it to 550,
          the degree for which its proportion of acid and water
          was calculated.   The dilatability of this acid is much
          greater than that of water,  and even than that of the
    , -.*    nitrous acid of the fame denfity.
Qiuntityof   Our author next proceeds to confider the quantity of
pure acid  pure acid:, taken up at the point of Saturation by the
taken upby various fubftances they unite  with.— He begins  with
J*1"'011*    the mineral alkali.  Having rendered a quantity of this
I'i') j ''.CCS.                          "            1     J
    429    cauftic in the  ufual manner, and evaporating one ounce
MIik .-.>.: al- of the cauftic  Solution to perfect drynefs, he Sound  it
kali how  to contain 20.25 grains  oS  Solid  matter.   He was af-
          fured, that the watery part alone exhaled  during eva-
          poratiem, as the quantity  of fixed air  contained iu it
          was very Small, and to dillipate  this a much gt eater
          heat would  have  been  requifite than  that which he
          ufed.  This dry alkali was diflblved in twice its weight
          of water ;  and Saturating it with dilute vitriolic  acid,
          he found it to contain  2.25 grains oS fixed air ; that be-
          in.; the weight which the faturatid Solution wanted oS
          Ik i.ig  equal to the joint weights of" water, alkali, and
    430    Spirit of \ftriol employed.
Quantity of   The quantity ot mere vitriolic acid neceffary to fa-
vitriolic   turatc ico grains of pure mineral alkali was found to
i*ad necif- ^e ,iQ or ^f grains ; the faturated folution thus form-
t*r-V°ka~ cc* being evaporated to perfect dryntSs weighed 36.5
          grains; but of this weight only 28.38  were  alkali
    4-1    and acid; the remainder, that is, 8.12 grains, there-
Qii.-iiny.-vf fore, were  water.  Heme 100  grains of Glauber's
ingredient* Sdt, perfectly dried,  contained 29.12 of mere vitriolic
in Glau-  _;c;j^ 4g ^ of mere alkali,  and 22.28 of water.   But
kcr s f-n.  Giauh.cr's fait cryftallized contains a much larger pro-
          portion of water ; for 100 grains of theSe cryftals heat-
          ed red hot loft 55 grains oS their  weight; and this loSs
          Mr Kirwan fuppofes to ariie merely  from  the evapo-
          ration of the watery p.ut,  and the remaining 45 con-
          tained alkali, water,  and  acid,  in  the fume propor-
  .        tion as the 100 grains of Glauber's fait  perfectly dried
          abovementioned.   Then thefe  45  conuir.cd  13.19
          grains of vitriolic acid, 21.87 of fixed alkali, and 9.94
          of water:  confequently  ico grains of cryftallized Glau-
          ber's ftlt contains 1 3.19 of  vitriolic  acid,  21.87 of al-
          kali,  anl  64.94 of water.
         f   On  Saturating  the  mineral alkali  with  dephlogifti-
         - cated nitrous acid, it  was found that 100 grains ofthe
prepared
for thefe
experi-
ments.
   4*?
Quar.ftty
JlllllC  ii
kali taken  aikaii took up 57 oS the pure acid in  the experiment
",',byfE"  he moft d. .ended upon; though  in fiv te others this
plllc^-iti-

lroUS aci J
quantity varied by a few grains :  he concludes, there-
fore,  th.:t the q-.'.antiry  of alkali  taken up by this acid
                    "i  that taken  up  by th«
tne fume  i.
lie.  Suppofing this quantity to be 57gvairs, then 100 Contents,
grains or cubic nitre, perfectly di) , contain 30cl acid, &c.-cf the
52.18 of alkali, and i7.°2 (I water: but cubic nine S'ba.____(
cryftallized contains Something more water; for 100
grains of theSe cryftals lofe about four by gentle dry-
ing ; thcrcSorc 100 grains of the cryftallized fait con-
tain 28.8 of acid,  50.09 of alkali, and  21.11 of wa-
ter-                                                   435
  An  hundred grains of  mineral alkali require from Uy ruariaf
63  to 66 or 67 grains of pure marine acid  to faturate «id.
it;  but Mr Kirwan fuppofes that one reafon of this
variety is,  that  it is exceeding  hard to hit  the  true
point of faturation.   Allowing  66  grains  to be  the
quantity required, then 100 grains of  prfcctly e'ry
common Salt contain nearly  35 grains of real tcid,
53  of" alkali, and  13 of water ;  but  100 grams of the
cryftallized Salt loSe five by evaporation ; lo that ico
grains of^heSe cryftals contain 33.3  of acid, 50 of al-
kali,  and 16.7 ol  water.              _
  The proportion of fixed air, alkali,  and water,  was Proportio»
thu.-, inveftigated : 200  grains of thefe  cryftals  were of fixedair,
diileftved in  240 of  water ; the folution was faturated alkali,  and
by  fuch a quantity of fpirit of nitre as contained 40 va^r>1""
of  pure nitrous  acid;  whence  it was inferred  thai 7  '^^
thefe 200 grains  of  fait of foda contained  70 of pure tyratioua"
alkaline Salt.   The faiur.tcd  folution weighed. 40
grains ltfs  than the fum  of its  original weight, and
that of the fpirit of nitre added to it ; confujiicntly it
loft 40 grains oS fixed air.   The remainder of the ori-
ginal weight oS the  cryftals therefore muft hu\c been
water,  viz. 90 grains.   Confequently  ico grains of
thefe cryftals contained 35 of alkali, 20 of  fixed mr,    4,*
and 45 of water.   This proportion differs conlidtrably Difiermco*
from that afligned by Mr Bergman and Lavoilier, \\ hich with M.
our author  imputes to their having  m^de  uSe of foda Eirgnun
recently cryftallized ; but IVr Iv irwan's had been made and Iavoi"
Sor fome months, and pre.!.;ibly  loft  much water and  lcr afc\
fixed air by evaporation, vvhieh altered the pre portion rt,r>
of the  whole.  According to the  calculations of Berg-
man and Lavoilier,  100 grains of this alkali tike up
80  of fixed air.   The fpecific gravity ofthe cryftalli-
zed mineral  alkali, weighed in ether, found to be
1.431.                                                 436
  The proportion of the  different ingredients  in vo- Propor-
latile alkalies can  only be  had from  the experiments tions ofiu-
lately made by Dr Prieftley concerning alkaline air. gredicn'«
He informs us,  that .\ of a meafure of this, and one in v°latil<
meafure of fixed  air, faturate one  another.    Then  a     '
fuppofing the meafure  to contain ico cubic inches
185 cubic  inches  of alkaline air mke up ico of fixed
air  ; but 1 ?c cubic inches of alkaline  air weigh at a
medium 42.55'grains,  and 100 cubic inches of fixed
air  weigh 57  grains;  therefore ico grains of pure
volatile alkali, free  from  water,  take up  134 of fix-
ed  air.
  On  expelling its aerial acid from a quantity of this
volatile alkali in a concrete ftate, and formed by Sub-
limation, he found, that  53  grains  of it were fxed
air: according to the preccdng calculation, 100 grain*
of it fhould contain 39.47  of real alkali, and 7.53 of
water,  the reft being fixed air.—On faturating a quan-
tity with the vitriolic, nitrons, and marine acids, 100
grains of the mere alkali were found  to take up ic6
of  mere vitriolic  acid,  115 of the nitrous, and  130 of
the marine  acid.   The fpecific gravity of the \,i'.xi'<-
                                              alkali 
Theory,
CHEMI
Content^ alkali weighed in ether (b) was 1.4076.   The propor-
&c. of the tion of water in the different ammoniacal falts could not
Salts,     be found on account of their volatility ;  but was fup-
         pofed  to be  very  fmall, as both volatile alkali  and
         fixed air cryftallize without the help of water when in
         an aerial ftate.
            In making experiments on calcareous earth, it was
         firft diffolved in  nitrous  acid;  and after allowing for
         the lofs of fixed  air and water,  100 grains of the pure
         earth was found to take  up 104 of nitrous acid; but
         only 91 or 92 of mere vitriolic acid were required to
         precipitate it from the nitrous folution.
            Of the marine acid 100 grains of the pure calcare-
ofmarine ous  earth require 112 for their folution.   The liquor
acid fatu- at firft is colourlefs,  but  acquires a greenifh colour by
rated  by  finding.
            Natural  gypfiim  varies  in its  proportion  of acid,
         water, and  earth ;  roo grains  of it  containing from
          32 to 34 ofacid and  likewife of earth, and from 26 to
          32 of water.  The  artificial  gypfum contains 32 of
         earth,  29.44  of acid, and  38.56  of water.   "When
         well dried,  it lofes about 24 of water; and therefore
         contains 42 of earth,  39  of  acid, and  19 of water, per
          hundred.
            Nitrous felenite (folution of calcareous earth in ni-
          trous acid)  carefully dried,  contains 33.28 ofacid, 32
          of earth, and 34.72 of water.
            The  fame  quantity of marine felenite (folution of
          calcareous earth in marine acid), w7ell dried, in fuch a
          manner as to lofe no part of the acid, contain of the
         latter 42 56,  of earth 38, and of water 19.44.
            Magnefia,  when perfectly dry and free from fixed
         air, cannot  be diflblved  in  any of the acids  without
         heat.   Even the ftrongeft nitrous acid did not act up-
         on it in 24 hours in the temperature of the atmofphere ;
          but  in a heat of  1800, the mineral acids,  diluted with
          four,  or even fix, times  their quantity of water, had a
          very fenfible effect upon  it; but the  quantity  of acid
          diffipated by heat  rendered it impoffible to afcertain
         how much was neceffary for Solution, except by preci-
         pitation after it  had  been diffolved.   For this purpoSe
         the  cauftic  vegetable alkali was employed ;  by which
         it appeared that 100  grains of pure magnefia take up
          125 of mere vitriolic acid, 132 of the nitrous,  and 140
         ofthe marine.   All of thefe folutions appeared to con-
         tain fomething gelatinous; but none of them reddened
         vegetable blues; and that in the marine  acid became
         greenifh on ftanding for  fome time.
            An hundred grains of  perfectly dry Epfom fait con-
         tain 45.67 of mere vitriolic acid,  36.54 of pure earth,
         and 17.8 3 of water.   Solution of common EpSom Salt,
in common however^ reddens vegetable blues,  and therefore con-
Epfomfalt; taJns an excefs  0f ac^   a like quantity of nitrons
Innltrtus  Epfom, well dried, contains 35.64 ofacid,  27 of pure
Epfom.   earth,  and  37.36 of water.  The folution of marine
   445    Epfom cannot be tolerably dried without lofing much
CaHnot be 0f jts acjd together with  the water.  The fpecific gra-
found in  yjty Qf ^jg ^^ js 2.3296.
marme Ep-   ^^ wrjters  on chemiftry have faid that earth of
   446    alum contains fcarce  any fixed air;  but  Mr  Kirwan
Earth of
alum con-
tains a
great quan-
tity of fix-
ed air.
Salts.
   437
Experi-
ments on
calcareous
earth.
   438
Quantity
this earth
   439 _
Proportion
of ingre-
dients in
natural
gypfum;
   440
In nitrous
felenite ;

   44I
In marine
felenite.
   44a
Calcined
magnefia
will not
diffolve in
acids with'
out heat.
   443.
Proportion
of the in-
gredients
447
   S   T   R    Y.                                    57
found that it contained no lefs than 26 per cent, though Contents,
it had been  previoufly kept red-hot  for half an hour. &c-
It diffolved with a moderate effervefcence in acids un-
til the  heat was raifed to  2200 ; after w hich the folu-
tion wTas found to have loft weight  in the  proportion
abovementioned.
   An hundred  grains  of  this earth, deprived of the Quantity
fixed air,  require 133  of the pure vitriolic acid to dif- °* »)grf-
folve them.   The folution was made in a very dilute J^']
fpirit of vitriol, whofe fpecific gravity was 1.093,  and
in which the proportion of acid to the water was near-
ly as 1 to 14.  It contained  a flight  excefs of acid,
turning the vegetable blues to a brownifh red ; but  it
cryftallized  when cold, and the cryftals were of the
form of alum.  Our author, therefore, is of opinion,
that this is the true proportion of acid and earth to be
ufed in the formation of that fait, though  there was    44g
not water enough to form large cryftals.   Perceiving Thisfaltal-
that the liquor contained  an excefs of acid, more ways con-
earth was added;  but  thus  it  was found  impoffibletains <|n ""
to  prevent  it  from  tinging  vegetable  blues of  ac«sofacl
red  colour  until a precipitation was formed :  and
even when  this was  the  cafe, though one part of
the fait fell  in the  form juft mentioned,  yet the  reft
would ftill redden vegetable blues as before ;  though
here our author  doubts  whether  this be  a mark
of acidity.   An hundred grains of alum, when dried,
contain 42.74  of acid, 32.14 of  earth,  and 25.02 of
water;  but cryftallized alum lofes 44 per cent, by defic-
cation : therefore  100  grains of it  contain 23.94 of    44g
acid, and 58.06 of water.  An hundred grains of this Proportion
pure earth take up, as near as can be judged, 153 of of pure
pure nitrous acid.   The folution  ftill reddened vege- carth of
table blues ; but after the above quantity of earth was alum ta.
added, an  infoluble fait  began to precipitate.  The^PJ,™^.
folution, when cold, became turbid, and could not be
rendered quite clear by 500 times its quantity of wa-    4j0
ter.  An hundred  and Seventy-three  grains of pure fjy marine
marine  acid are required  for the  diflblution of  100 acid.
grains of earth of alum, but the  liquor ftill reddened
vegetable blues.  After this an infoluble Salt was form-
ed ; but it is difficult to afcertain  the beginning of its
formation  precifely both  in  this and  the  preceding
cafes.   The fpecific gravity of pure argillaceous earth,
containing 25 per cent, of fixed air,  is 1.9901.           4-2
   In the  experiments made by our  author  on metals, Experi-
the acids employed were fo far dephlogifticated as to ments on
be colourlefs ; the metals were for the moft part redu- rnetals.
ced  to filings,  or to fine  powder in  a mortar.  They    45*
were added  by little and little to their refpective men- ,e ,mM|f
ftrua; much more being thus diffolved than if the foivine
whole had been thrown in at once, and the folution them.
was performed in glafs vials with bent tubes.             .
   An hundred  grains of bar-iron, in the temperature proportion
of 560, require for  their folution 190 grains of the real of iron ta-
acid, whofe proportion  to that of the water,  with ken up by
which it fhould be  diluted, is as 1  to 8,  10, or I2. the vitriolic:
It  would act on iron, though  its  proportion were
greater or leffer,  though  not fo vigoroufly; but by
applying a heat of 2000 towards the end,   123 grains
                          H                     of
acid.
  (b)  The fixed  and volatile  alkalies were weighed  in ether  on account  of their  great folubility in.
water. 
CHEMISTRY.
Theory.
   454
Quantity
cit uitiajn-
mjble air
product J.

V\'hy vitri'
olic air is
produced
l.y diff-!-
vin,; iron
in concen-
trated oil
of  vitriol.
   450
Solution of
         of real acid would be fufEcient.   The air produced by
         thi.-> folution is entirely  inllammablc, and generally
         amounts to 11 j cubic inches.
            By the adiil.mce of a ftrong heat, iron is alfo foluble
         in the concentrated  vitriolic acid, though in linallcr
         quantity ;  and inftead of inflammable air, a large quan-
         tity of vitriolic air is produced,  and a little fulphur is
         biblimed towards the end.   The reafon of this is, that
         the concentrated  vitriolic acid,  containing much lefs
         fpecific  fire  than the dilute kind, cannot expel the
         phlogifton in the form of inflammable air (which ab-
         f»rbs a vaft quantity of fire),  but unites with it when
         further dephlegmated by heat, and thus forms both vi-
         triolic air  and  fulphur.   An  hundred grains of iron
         didblved without  heat afford more than 400 of vitriol;
         and 100 grains of vitriol,  when cryftallized, contain
         25 of iron, 20 of real acid, and  55 of water.  When
         calcined nearly to rednefs, thefe cryftals lofe about 40
         per cent, of water.
            The calces of  iron are foluble in the  vitriolic acid
thecalcesof according to the quantity of phlogifton  they  contain ;
iron in vi- t^c m()re phlogifticated being more readily foluble, and
tnoiic acid. thofe which  arc  dephlogilticated lefs fp.   The  latter
         not only require  more real acid for their folution, but
   457    afford only a thick  liquor or magma by  evaporation,
That ofthe inftead of cryftals like the others.  Hence  alfo  folu-
dephlogif-  tions of iron, when newly made, diminifh, and conSe-
ticated cal- qllcntly phlogifticate, the Superincumbent air by their
          gradual emifhon  of  phlogifton;  at  the fame  time that
          the calx,  becoming  more and  more  dephlogifticated,
          gradually falls to the bottom, unlefs more acid be added
          to keep it in folution.
             An hundred grains of iron require for their folution
of iron dif- in nitrous acid 142  grains of real acid,  fo diluted that
folved in   jts proportion to water  fhould  be as 1 to 13 or 14 ;
          and when this laft proportion  is ufed, the  heat of a
          candle may be  employed  for a  few Seconds, and the
          accefs of common air prevented.   Thus about 18 cubic
          inches of nitrous air are produced, the reft  being ab-
          lbrbed  by  the folution, and no red vapours appear.
          But if the proportion of acid and water be  as 1 to 8
          or 10,  a  much  greater quantity of metal will be de-
          phlogifticated by the application of heat, though very
          little of it be held in folution   Thus, from 100 grains
 oTnitrous 0f iron Mr Kirwan  has obtained 83.87 cubic inches of
 air obtain- njtrous air ; and by diftilling the folution, a ftill greater
          quantity  may  be obtained  which had been  abforbed.
           The reafon  that nitrous folutions of iron or  other me-
           tals yield no inflammable air is,  becaufe  this acid has
 W! y no in- lefs affinity  to water, and more to phlogifton, than the
 nimmabl-  vitriolic, and likewife contains much leisfirethan either
 air ii here  tjut or the marine  (fee n°  278) ;  and therefore unites
           with phlogifton, inftead of barely expelling it.  Hence
           alfo the vitriolic acid, though united with 30 times its
           weight of water, will ftill vifibly act on  iron, and Se-
           parate  inflammable air  in   the temperature oS 55°;
           whereas nitrous acid, diluted with 15 times  its weight
           of water,  has no j-erccptible effect on the metal in that
           temperature.  The calces of iron, if not too much  de-
           phlogifticated, are alfo foluble in the nitrous acid.
              Two hundred and fifteen grains of reft marine mid
                  tred for the f.Union  of ico grains of iron.
 up by the  \\ hen the  proportion of water to the acid is as four to
 marine   onc, it ctferYefces rather too violently with the metal;
ces of iron
refufes to
cryftallize.


   458
Proportion
nitrous
acid.
   459
Quantity
ed from
this folu-
tion.
   460
pre J ■.iced.
   4',,
Vitriolic
acid ads
un iron in
K much
more di-
lute ftate
than ni-
trous.
   4*1
Iron taken are rcq
and heat is rather prejudicial, as it volatili/.es the acid. Content!,
No marine air hies off;  and the quantity of intlani- *<••  of '**•
mable air is exactly the fame as with diluted vitriolic /t>-^____,
acid.   The calces of iron are  alio foluble in marine    463
acid,  and may be diftinguifhed by their reddifh colour Cake* of
when precipitated by fixed alkalies, while the precipi- >ron p«ci-
tates ui the metal art greenifh.                        ''"Iwih'
   An hundred and eighty-three grains of real vitriolic *0joUrfrora
acid are required to diffolve an hundred grains of cop- t^cir f0ju.
per ;  the proportion of acid  to that of water being as  1 tion in ma-
to 1.5,  or at  leaft as 1  to 1.7;  and a ftrong heat muft rine acid.
alSo be applied. Mr Kirwan fays he never could diflblvc    464
the whole quantity  of copper;  but to  diflblvc a given Prc,Po,'tl0H
quantity of it, a ftill greater heat muft be employed in °. ,rc?pp?r
the proportion of 28 to 100 ;  but this refiduum alfo isb vitr:0jjc
foluble  by adding more acid.  Copper dephlogifticated acjd.
in this  manner is foluble by adding warm water to the
mafs.                                                   46j
   By treating 128 grains of copper in this manner, we Inflamma.
obtain 1-1 cubic inches of inflammable air and 65 ofble«.nd vi-
vitriolic acid air.  When inflammable air was obtained, tTl°h* ac,d
however, our author tells us the acid was a little more zlJr   *r\
aqueous.   The reafon why copper cannot be dcphlo- iut;on „r
gifticated by dilute  vitriolic  acid, or even by the con- copper in
centrated kind without the  affiftance of heat, is  its vitriolic a-
ftrong attraction to phlogifton,  and the great quantity cid.
it contains.                                             4°*
   An hundred grains of vitriol of copper contain  27    V 18_
of metal, 30 of acid, and 43 of water ; 28  of which not be act-
laft arc loft by evaporation or flight calcination.  An ed upon by
hundred grains of  copper,  when diflblved,  afford 373 dilute vi-
of blue vitriol.                                       triolic acid.
   An hundred grains of copper require 130 of pure    *^7
nitrous acid for  their  diflblution.  If the acid  be fo  ™VorU°B
far diluted that its proportion of water be as 1  to  14, dientsis
the alfiftance oS heat will be neceffary, but not other- blue vi-
wife.   This  Solution  affords  674. inches  of  nitrous triol.
air.—The calces of copper  are foluble in the  nitrous    468
acid.                                                Quantity
   A  like quantity of this metal requires 1190  grains j(r°iPP!f
of real  marine acid, as well as the affiftance of a mode- ],_ „itroua
rate  heat,  to diffolve  them ; the proportion of water acid.
being as 4^ to 1.  By  employing a greater heat, more    469
of the  acid will be requifite, as much more will be dif In marine
fipated :  the  concentrated acid  acts more vigoroufiy.— acid-
 Calces  of copper are likewife foluble in the  marine a-
 cid, though lefs eafily  than in the nitrous.               470
   The vitriolic acid diflblves tin but in fmall  quantity ;  Action of
 an hundred grains of the metal requiring for their fo- the vitrio-
 lution  872 of real acid, whofe  proportion to water *\c a«d-i»
 fhould  not be lefs than 1  to 0.9.  A ftrong heat is alfo tni"
 required.  When  the action  of the acid has ceafed,
 fome hot water  fhould be added to the turbid folution,
 and the whole again heated.   The metal is foluble in    471
 a more dilute acid, but not in fuch  quantity.—The Inflamrna-
 folution abovementioned affords 70 cubic inches of in- blf aiIr
 flammable air.—The calces of tin, excepting that pre- .f'nef , r'.m
         ,r        •     -j 1   /•   j   n  i-  6    ■  r   the loluti-
 cipitated from marine  acid by fixed  alkalies, are info- on>
 luble in the vitriolic acid.                                47a
    An  hundred grains  ef tin require 1200 of real  ni- Tin diffol-
 trous  acid;  whofe  proportion of water fhould be at ved in "'-
 leaft 25 to 1, and  the heat employed not  exceeding tlous ac"*'
 6c°.   The quantify of air afforded by fuch  folution  is
 only 10 cubic inches,  and it is not nitrous.   The fo-
                                               lution 
Theory.
CHEMISTRY.
59
Contents,
&c. ofthe
Salts.
   474
Lead with
vitriolic
acid.
   475
Scarce fo-
luble in
dilute vi-
triolic acid,

   476
With ni-
trous acid.
lution is not permanent;  for in a few days it depofites
a whitifh calx,  and in warm weather burits the vial.
The calces of tin are infoluble in this  acid.
  Four hundred and thirteen grains of' pure marine
acid are required to dillblve 100 grains of tin, the pro-
portion of water being as 4; to 1.   The affiftance of
a moderate heat is alfo required.  rAb°nt 90 cubic in-
ches of inflammable, and 10 of marine air, are^afford-
ed by the folution; but the calces  of  tin'are;"nearly
infoluble in this acid.
  An  hundred  grains of lead require 600  grains of
real vitriolic  acid  for  their folution, the  proportion'
being  not lefs than 1  of acid to T7T  of water V  and it
will ftill be better if the quantity of water be lefs : for
which reafon, as in copper, a greater qnlintity of me-
tal  ihould be  employed  than what  is esrpl^d TcV. be
diflblved.  A ftrong heat is alfo  requifite i^nd  not
water  fhould be added to the calcined maSs,  tnobgh in
Small quantity, as it occafions a precipitation.—This
metal is  alfo foluble, but very fparinjrly, in dilute vi-
triolic  acid.  Its calces are fomething£5|pre foluble.  An
hundred grains of vitriol of lead, formed by*precipita-
tion, contain 73 of lead, 17 of real acid, '^d 10 of wafer?'
  With fpirit of nitre,  78 grains of reai acid are re-
quired for the folution of 100 of lead, with  the  affift-
ance of heat towards the end.  The prope^hion of acid
   Mr Kirwan has never been able to diflblve Silver in Contents,
 the marine acid,  though Mr Bayen fays he effected &c. of  the
 the diflblution of three grains and a half of it by dige- Salts.
 ftion fome fome days with two ounces of ftrong fpirit of    .g0
 fait.  Newman informs us alfo,  that leaf-filver is cor-of the dif-
 roded by the concentrated marine acid.  It is diliblved, folution of
 however, by the dephlogifticated fpirit  of fait, as well filver in
 as by the phlogifticated acid when reduced to a ftate mf"ne
 of vapour.   An hundred grains of luna  cornea contain a  "
 75 of filver,  18 of acid and 7 of  water.                  .gj
   Mr Kirwan found that kind of aqua regia to fucceed Beft kind
 beft in the diflblution of gold, which was prepared by of aqua re-
 mixing together three parts of  the  real marine acid gia for dif-
 with  one of the nitrous acid.   Both of them  ought folving
 alfo to be as concentrated as poflible;  though,  when *>
 this is the  cafe, it  is almoft impoffible to prevent a
 great quantity from efcaping, as a violent efferveScence
 takes place for fome time after  the mixture.   Aqua
 regia, made with  common fait or fal  ammoniac and       *
 fpirit of nitre, is much lefs aqueous than that pro-
 ceeding  from  an  immediate  combination of  both
 jjgids ;  and hence it is the fitteft for producing cryftals
sbf gold.  Very little air is produced  by  the folution of
 this metal,  and the operation goes on  very flow.  It
 is,  however^batcr promoted by allowing it Sufficient     g
 time,  than by a^ggtyhig heat. An hundred grains of Quantity
to that of water  may be about  I to 11 ,,dr  12.   Thiswgold reqtuTe for .their Solution 246 grains of real acid, of gold ta-
fn1..»!n*> n un J.-. n n» l~.-«- atA.k» .*.--• 1^4 -^ 1 ,1 .nit an n<C rt « **  ««l.l „l-f '^Mlfl ttlTA nAi'Sn Kaiii-*. • »i f da «u«« au*. '. -. .-. „ T->_. ^—_ „_ **  .. _  I 1______1__
   477
With ma-
rine acid.
   47&.
Silver with
vitriolic
acid.
                                                      'the two aci% being in the proportion abovementioned. ken up by
                                                      Though foluble in the dephlogifticated marine acid,  it a1ua regia*
                                                      is only in very fmall quantity,  unlefs the acid be in a
                                                      ftate of vapour; for,in its liquid ftate it is too aque-     o
                                                      «us.   In vitriolic "and nitrous acids it is infoluble, tho' Calces of
                                                      the calces are fomewhat foluble in  the nitrous, more gold folu-
                                                      eafily in the marine,  but fcarcely  at all in the vitriolic bie m the
                                                      acid. .  Mr Kirwan ft?ys, that gold in its metallic ftate vitri.lic
                                                      may be^diffufed through the concentrated nitrous acid, and uitrou»-\
would be diffolved by a ftronger acid.—The calces'or^^f^;T^dij|blved in it; contrary to the opinion of other aCHls-
lead are more foluble in this acid than the metal itfelf.   chemifts', who have affirmed that a true diflblution takes Gold ctn-
An hundred grains of minium require 327 of real acid;   place.                                              not)  ac_
but white lead is much lefs  foluble.   The  fame quan-     An iimidred grains of mercury require for their fo-
tity of  plumbum  corneum, formed by precipitation,
contain  72 of lead, 18 of marine acid, and 10 of water.
  An hundred grains of filver require  530 of real vi-
triolic acid to diffolve them  ; the proportion oS acid to   c<pitate/*r fe is  ftill leSs-foluble.—An hundred grains ^ ''g.
water being: not  leSs than as 1  to r% : and when Such a   of vitriol of mercury, produced by precipitation,  con Mercur
folution produces but eight cubic inches of air,  which'
is nitrous.   The calces of the metal are foluble in this^
acid; but lefs  fo  when  much  dephlogifticated.  A&*
hundred grains of minium require 81 of real acicL i;Aii
hundred grains of nitrous fait of lead contain about 60
ofthe metal.
  Six hundred grains of the  real marine acid are re-
quired for the folution of 100 grains of lead ; the fpe-
cific gravity of the acid being  1.141,  thodghshstfyre
coram? to
   479
With ni-
trous acid.
concentrated acid is ufed, it acts nightly even in  the
temperature of 6o° ; but a  moderate heat is required
in order to procure a copious folution.  The calces of
filver formed by precipitation from  the nitrous acid
with fixed  alkalies  are foluble even in dilute vitriolic
acid without the affiftance of heat.  An hundred grains
of vitriol of filver, formed by precipitation, contain 74
grains of metal, about17 of real acid,  and 9 of water.
   An hundred grains  of the pureft filver require for
their  folution 36 of nitrous  acid,  diluted  with water
in the proportion of one  part  of real acid to fix of   already cpntainsjtriuch phtogifton.  Precipitate per fe is
of nitre.
                                                    Mercury
tain 77 o£metal, 19 of acid, and 4 of water.         withvitrio-
  In fpi^t'of nitre,  160 grains of mercury are diilbl- He acid.
ved by>fe8 of realacidy whofe proportion to the water   .486.
it confains'i£ as 1  tf^ly-.  IJV/this  acid the folution "vYit.h fPirit
takesiplaceVithout heat; ^btt-it may alfo be diflblved
in a much nvare dilute acid, -f>rovided heat be applied.
About* 12 cubk inches of  air are "produced when heat
is not-applied ;  but M/, Lavoilier found  the produce
much greater.  This,  fays Mr  Kjrwan, was evidently
caufed by his ufyfg red oryellow Spirmof nitre, which
water, applying heat only when the folution is almoft
faturated.   If  the fpirit  be much  more or much lefs
dilute, it will  not  act  without the affiftance of heat.
The  laft portions of filver thus  taken up  afford no
air.   Standard filver requires about 38 grains of real
acid to diflblve the fame proportion of it;  and the fo-
lution affords 20 cubic  inches of nitrous air; whereas
much lefs i^fil
Mr Kirwan ft
the aerial acid
iffolved' in the nitrous acid, which
Ses  to be owing to-the attraction of
                                     •                2d 486
  The marine acid, in its common-phlogifticated ftate, With ma-
does not act on mercury, at leaft in its  ufual ftate oSrine aci<i*
concentration;  though  M. Homberg,  in the Paris
Memoirs Sor the year  1700, affirms, that he diffolved
100 grains of filver revived from luna cornea .affbffd Wi>y feveral n^onths digeftion in this acid.   When de-
about 14
phlogifticated/ it certainly ads upon  it, though very
                        H 2                 weakly 
C    H    E    M    I    S    T   R    Y.
   487
Zinc with
vitriolic
aeiJ ;
With ni-
          weakly while in a liquid ftate.   Precipitate per f; is
          alfo foluble  in the  marine acid with  the  affiftance of
          heat.   An hundred grains of corrofive Sublimate con-
          t .in 77 of mercury,  16 of real acid, and fix oS water.
          The like quantity of  mercurius dulcis contains 86 of
          metal  and 14 of acid and water.
            /ftac  req lires for its folution ag equal quantity of
          real vitriolic acid, whofe proportion to  that of  water
          may be as 1 to 8, 10, or 12.  Heat  muft be applied
          towards the end, when the  faturation is  almoft com-
          pleted.   By the help of heat alfo this femimetal is fo-
          luble  in  the concentrated vitriolic acid,  but a fmall
          quantity  oS  black powder remains in all  caSes undif-
          Solved.   An hundred cubic inches of  inflammable air
          arc produced.   An  hundred grains of vitriol of zinc
          contain 20 of zinc,  22  of acid, and 58 of water.  The
          calces of zinc, if not exceedingly dephlogifticated,  are
          alSo Soluble in this acid.
            An hundred and  twenty-five grains of real nitrous
trous acid, acid,  whofe proportion to water is  that  of 1 to  12,
   489    are required for the folution of 100 grains of this femi-
Lefs metal metal, applying heat  llightly from time to time.   A
diffolved   concentrated  acid  diflblves  lefs of  the metal, as a
by concen- p-reat  qUantitity of  the menftruum efcapes during  the
trated than ha.   lr       J x,           .      , l         P   ,
ly diluted efferveScence.  No  nitrous air can be  procured,  the
          acid being  partly decompofed during  the  operation.
          The calces of zinc, if not too much   dephlogifticated,
          are likewife diflblved  by the nitrous acid.
             An hundred grains of zinc, require for their diflblu-
          tion 210 grains of real marine acid, the proportion of
          it  to the water being as 1  to 9.  If a more concentra-
          ted fpirit of fait be  made ufe of,  a confiderable part of
          it will be diflipated during the efferveScence,  and conse-
          quently more will be required for the Solmiuii.  the
          calces of zinc are alfo foluble in the marine acid.
             Only  three grains of bifmuth  were diffolved by 200
          of oil oS vitriol, whoSe  Specific  gravity  was  1.863,
 ble in vitri-though a ftrong  heat  was uSed at  the Same time.   A
 olicacid.  greater quantity was indeed (lightly dephlogifticated ;
          but when the gravity  ofthe acid was reduced to 1.200,
          only  a finale  grain of the metal wa* diflblved by  400
          of it.  The cakes  of this femimetal are much more
          foluble.   F.nr cubic  inches of  vitriolic air were  af-
          forded by the folution of three grains of bifmuth.
             In fpirit  of nitre,  100  grains of real acid are only
 dTffolvcd in required  to diflblve  100  grains of the metal.  The
 fpirit of ni- proportion of  water to the acid ought to be as 8 or 9
 trc>      to  1 ;  in which  cafe  a gentle heat   may be  applied.
          The  folution  affords  44 cubic inches of nitrous  air.
    493   The  calces of bifmuth are alfo foluble in this acid.—
 Scarce fo- Only three or four grains of  it  were diflblved by  400
 luble in
 marine a
 cids.
nitrous a-
cid.
   490
With ma-
rine acid.
   491
Bifmuth
fcarce folu-
   49*
Qiiantity
  2d 493
NLI.cI
with vitri-
ol:; acid ;
   •m
W.th ni-
trous acid.
of marine acid,  whofe fpecific gravity was 1.220.
   About four grains of nickel were diffolved  in  an
hundred of the concentrated vitriolic  acid with the
affiftance  of a ftrong  heat;  but its  calces  are  much
more foluble.—An  hundred grains of nickel  require
for their folution 112 of real nitrous acid, whofe pro-
portion to water is as 1 to 11 or 12.  The product of
nitrous air is  ->q inches.   The calces are alfo foluble.
A moderate heat is neceflary  for the diiiblntion of the
metal ; but a concentr.ned acid acts fo rapidly, that
much  of it  is diffipa'ed — Only four or  five grains of
nickel are didblved  bv 2:0 of fpirit  of fait whofe fpe-
cific gravity was  1.22c.   An acid of this  degree of
ftrcngth acts without  the affiftance  of  heat, though
                                                   Theory.
a weaker acid requires  it,  and difSolves ftill lefa of the 1 oatcnu,
metal.   The calces of nickel are alfo foluble with dif- *c« ofthe
ficulty in thfs acid.                                  ^aJt>'
   Four hundred and fifty  grains of real vitriolic acid,
whofe proportion  to water is not lefs than  1 to -,%,
are required for the diiiolution of  ico grains of co-
balt,  allifled by a  heat of 2700  at  lcift.   A  Solution
is obtained by  pouring warm water on  the  dephlo-
gifticated mafs..—The  calces of  cobalt, however, art
more foluble ; fo that even a dilute  acid  will  Serve.—
   495
With ma-
rine acid ;
   4<)6
Cobalt
with vitri-
olic acid :
of nitre ;


   49»
cid.
In Spirit of nitre,  the like quantity of cobalt requires \^-^{-,- -t
220 grains of real acid, whofe proportion  to water f
as 1 to 4 ; giving a heat of 180 towards the end.—1 he
calces of the metal are  foluble in the nitrous acid.—
An hundred grains of fpirit of fait, whofe fpecific gra- witMpirit
vity  is  1.178, diflblves, with  the  affiftance of heat, of fait;
two grains and a half of cobalt; and a greater quanti-
ty will  be diflblved  by an acid more highly concen-
trated.—The calces of cobalt are more foluble.           4yg
   An hundred grains of regulus of antimony require Regulu* of
for their  folution 725  grains of real vitriolic acid, antimony
whofe proportion  to water  is  as  1  to T%,  affifted by v!tn Vltri"
a heat of  4000.   A large quantity of regulus fhould ° lc a   '
be put into the acid ; and the refulting  fait requires
much water  to diflblve it, as  the  concentrated acid
lets fall much when water is added to it.   A lefs con-
centrated  acid will  likewife diflblve this  femimetal,
but in fmaller quantity.  The calces of antimony, even   j0C)
diaphoretic antimony, are Somewhat more foluble. Nine Withni-
hundred grains of real nitrous acid are required for the trous acid.
folution of 100 grains of regulus ;  the  proportion of
acid  to the water of the folvent being as 1  to 12, and
afhfted  by an heat of no° ;  but  the folution becomes
turbid in a few days.   The calces are much lefs feiluble   jOI
iu this acid.—Only  one  grain of the regnlus  is dif- Scarce fo-
folved by  100 of fpirit of fait, whole fpecific gravity luble in the
was  1.220, with  the  affiftance of a Sight heat ; and nanne a"
that  which is only 1.178 difiolves ftill lefs ;  but Mr ""
Kirwan is of opinion that the concentrated acid would,
ina long time, and by the affiftance of a  gent!-   heat,
diflblve much more.   The  calces diffolve more eafily
in the marine acid.
   Eighteen grains of regulus of  arfenic  are diflblved pCguTug of
in a  heat  of  2500 by  200 grains of real vitriolic acid, arlmic
whofe fpecific gravity is 1.871.   About feven of thelt with vitri-
parts cryftallize on cooling, and are foluble in a large olic acid,-
quantity of water.  The calces of arfenic  are  more
foluble  in this acid.— An hundred and forty grains of-w^n;.
real  nitrous acid are requifite for the folution of ico trous acid;
grains of regulus of arfenic ;  the  proportion of acid to
the water being as 1  to  11.   1 he folution  affords 102
cubic inches of nitrous  air,  the barometer being at
"o and the thermometer at 60.   Calces  of arftnic are
likewife foluble in this acid.                             ,0.
   An hundred  grains of fpirit of fait,  whofe fpecific With fpirit
gravity is 1.220,  diflblve a grain and an half of regu- of fait.
lus of arfenic ;  but  the marine acid, in its common
ftate, that is,  when  its gravity is  under 1.17, dots
not at all affect it. The arfenical calces are lefs foluble
in this than  in the vitriolic or nitrous acids.
  § 3. Of the Quantity of Thh.gifton containedin different
                     Subftauces.
   Having gone  through all  the various  bafes with
which acids  are ufually  combined, and afcertained the
                                            quantity
50a 
Theory.
CHEMISTRY.
61
Quantity
of Phlogi-
fton in dif-
ferent Sub-
fiances.
   5°5
Quantity
of phlo-
gifton con-
tainedinni-
trous air.
 id 505
Quantity
of phlogif-
ton in fixed
air;
quantity of different ingredients contained in the com-
pounds  refulting from  their union, we ought next to
give an account of our author's experiments on phlo-
gifton ;  but as his Sentiments on that fubject are taken
notice of  elfewhere,  we fhall content ourSelves with
briefly  mentioning  the very  ingenious methods by
which he discovers the quantities of it contained in va-
rious kinds of air and in fulphur.
  Having proved that inflammable air, in its concrete
ftate,  and phlogifton are the fame thing,  Mr Kirwan
proceeds to eftimate the quantity contained in nitrous
air in the following manner.
  " An hundred grains of filings of iron,  diflblved in
a fufficient quantity of very dilute vitriolic acid,  pro-
duced,  with  the affiftance of heat gradually  applied,
155 cubic inches  of inflammable air; the barometer
being at 29.5, and the  thermometer between 500 and
6o°.  Now, inflammable  air  and phlogifton being
the fame thing, this  quantity of inflammable air a-
niounts  to 5.42  grains  of phlogifton.—Again,  100
grains of iron diflblved in dephlogifticated nitrous acid,
in a heat  gradually applied and raifed to  the utmoft,
afford 83.87 cubic inches of nitrous air.   But as this
nitrous  air contains  nearly  the  whole  quantity of
phlogifton which iron will part with  (it  being more
completely  dephlogifticated by  this  than  any other
means), it follows, that 83,87cublcinchesofnitrousair
contain  at leaft 5.42 grains of phlogifton.   But it may
reasonably be  thought, that  the  whole  quantity of
phlogifton  which iron will part with is not expelled
by the vitriolic acid, but that nitrous acid  may expel
and take up  more  of it.  To  try  whether this was
really the caSe,  a quantity oS green  vitriol was cal-
cined until its bafis became quite infipid ;  aSter which
two  cubic inches oS nitrous air were extracted from
64 grains of this ochre ; and confequently 100 grains,
would yield 3.12 cubic inches of nitrous air.  If 83.87
cubic inches of nitrous air contain 5.42 of phlogifton  ;
then 3.12 cubic inches of this air contain 0.2 of phlo-
gifton.   The nitrous acid,  therefore, extracts from
100 grains of iron twro-tenths  of a grain  more phlo-
gifton   than  vitriolic  acid  does.   Therefore 83.87
cubic  inches  of nitrous air, containing   nearly the
whole phlogifton  ofthe iron,  have 5.62 of  this fub-
ftance.   Hence 100 cubic inches of nitrous  air contain
6.7 grains of phlogifton."
  With regard to the quantity of phlogifton  in fixed
air, after proving at length  that  it  is compofed of
dephlogifticated air united to the principle of inflam-
mability,  Mr Kirwan  afcertdns the  quantity  of the
latter in the following manner:  " Dr Prieftley, in the
fourth volume oS his Observations, p. 380, has Satis-
factorily proved,  that  nitrous air parts with as much
phlogifton to common air, as an equal bulk of inflamma-
ble does when fixed in the Same proportion  of common
air.  Now, when iuflammable air unites with common
air, its  whole  weight unites  to it, as it contains no-
thing elfe but pure phlogifton.   Since, thereSore,  ni-
trous air  phlogifticates common air  to the  Same de-
gree that  inflammable air does,  it  muft part with
a quantity of phlogifton, equal to the weight of a vo-
lume of inflammable air, fimilar to that of nitrous air.
But 100 cubic inches of inflammable air weigh three
grains and a half;  therefore 100 cubic inches of ni-
trous air  part  with 3.5 grains of phlogifton, when
they communicate their phlogifton to as much common
air as will take it up.    In this procefs, howTcver,  the Quantityof
nitrous air does not part with the whole of the phlo- Phlogifton
gifton it contains, as appears by the red colour it con- ln d'ffcrent
ftantiy aflumes when mixed with  common or dephlo- .*  anccs;
gifticated air;  which colour belongs  to  the nitrous
acid,  combined w-ith the remainder of its phlogifton,
whence the acid produced is always volatile.
   " One meafiire  oS  the  pureft dephlogifticated  air
and two oS nitrous air occupy but-^ of one meaSure,
as Dr Prieftley has obServed.  SuppoSe one meafure to
contain 100 cubic inches, then the whole, very  near-
ly, of the nitrous air will disappear (its acid uniting to
the water over which the mixture is made),  and  97
cubic inches of the dephlogifticated air, which is con-
verted into fixed  air by its union with the phlogiftoH
ofthe nitrous  air; therefore 97 cubic inches of de-
phlogifticated  air  take up  all the phlogifton which
200  cubic  inches  of nitrous air will part with; and
this  we  have  found  to be feven grains : therefore
a weight of fixed air  equal to that of 97 cubic  inch-
es of dephlogifticated  air,  and 7 of phlogifton, will
contain Seven grains of the latter.  Now, 97  cubic
inches of dephlogifticated air weigh 40.74 grains ;  to
which adding  7, we have the whole weight ofthe fix-
ed air,=47-74 grains,=83.755 cubic inches; and con-
fequently 100 cubic inches  of fixed air contain 8,357
grains of phlogifton, the remainder being dephlogifti-
cated air.   An hundred grains of fixed air. therefore,
contain 14.661 of phlogifton, and 85.339  °f  elemen-
tary or  dephlogifticated air.   Hence  alfo 100  cubic
inches of dephlogifticated air are converted into fixed
air by 7.2165 grains  of phlogifton, and will be then
reduced to the bulk of 86.34 cubic inches.               506
   To find the quantity  of phlcgifton in vitriolic acid In vitriolic
air, our author purfued  the following method.         acid air.
   1.  He found the quantity of nitrous air  afforded
by a given weight of copper, when diffolved in the
dephlogifticated nitrous  acid, and by that means how
much phlogifton it parts with.
   2. He Sound the quantity of copper which a given
quantity of the dephlogifticated vitriolic acid could dif-
Solve ;  and obServed, that it could not entirely Saturate
itfelf with copper without dephlogifticating a Surther
quantity which it does not diffolve.
   3. He found how much it dephlogifticates  what  it
thoroughly diflblves, and how much it dephlogifticates
what it barely calcines.
   4. How much inflammable air  a given  quantity of
copper affords when diflblved in the vitriolic acid  to
the greateft advantage.
   5. He deducts from the whole  quantity of phlogi-
fton expelled by the vitriolic  acid the quantity of it
contained in the inflammable air ; the remainder fliows
the quantity of it contained in the vitriolic acid air.
   The conclufion deduced from experiments, conduct-
ed after  this manner is, that 100  cubic inches of vi-
triolic air contain 6.6 grains of phlogifton, and 71.2
graius of acid  ; and 100 cubic inches oflhis air weigh-
ing 77-8 grains, 100  of it  muft contain 8.48 grains
phlogifton, and 91.52 of acid.                         507
   To find the quantity  of phlogifton in fulphur, Mr Quantityof
Kirwan propofed to eftimate that of the fixed air pro- phlogifton
duced during its  combuftion.  For this  purpofe  hemSulPhur"
firmly tied  and cemented to the open top of a glafs
bell a large bladder,  deftined to receive the  air ex-
panded by  combuftion,  which generally efcapes when
                                              this 
62
CHEMISTRY.
Quantityof this precaution  is not ufed.   Under  this  bell,  con-
Fmlojrifton uini;)(r about  3000  cubic inches of air,  a candle of
ITwi     'dplmr, weighing 547 grains, was placed ;  its wick,
 .____(,____, which  w.i*. not confumed,  weighing halt a grain.  It
   508   was fupported by a very thin concave plate  of tin, to
Proper me- prevent the fulphur from running over during the  com-
thod of   bullion ; and both were Imported by an iron Wire  fixed
 urnmg    .    flielf in a tub of water.   As foon as  the fulphur
          began to  burn witn a feeolc name, it was covered witn
          the bell,  the  air being  Squeezed out  of the bladder.
          The fifidc of the bell was foon rilled with white fumes,
          fo that the flame could  not  be feen ;  but in about an
          hour after all the fumes  were thoroughly iublided, and
          the glaSs become  cold, as  much  water entered the
          bell as was eipial to 87.2 cubic inches ; which  Space
          our author concludes to  have  been  occupied by  fixed
          air, and  which  muft have contained  7.287 grains of
          phlogifton.   The candle of fulphur being weighed was
          found  to have  loft  20.75  grains ;  therefore 20.75
          grains of fulphur contain 7.287 of phlogifton, befides
          the quantity  of phlogifton which remained in the vi-
          triolic air.  This air muft have amounted to 20.75—
          7.287=  13.463 grains,  which, as already fhown, con-
          tain t.41 grains of phlogifton.  Therefore the whole
          quantity of phlogifton iu 20.75  grains of  fulphur is
          8.428 ; of confequence 100 grains  of fulphur contain
    509   59.39  of vitriolic acid, and  40.61 of phlogifton.
 Quantity     The quantity of phlogifton contained  in marine
 of phlogif- acid air  was  found by  the  following method.—Eight
 ton in ma- grajns 0f copper diflblved in colourlefs fpirit of fait
 nne acid  a(f )r ic..i  but 4.9 inches  of inflammable  air; but  when
          the experiment was repeated over mercury, 91.28 cu-
          bic inches of air were  obtained.  Of  thefe only 4.9
          cubic inches were indammible ;  and confequently the
          remainder, 86.38 inches, were marine air, weighing
          56.49 grains.— Now "as  fpirit of fait  certainly does
          not dephlogifticate copper more than the vitriolic acid
          does,  it follows, that thefe  4.9 cubic inches of inflam-
          mable air, and 86.38 of marine  air,  do not contain
           more  phlogifton  than would be Separated from the
           fame quantity of copper  by  the  vitriolic  acid ;  and
           fince 100 grains of copper would yield  to the vitriolic
           acid 4.32  grains of phlogifton, 8.5 grains of copper
           would yield  0.367  grains of phlogifton.  This there-
           fore  is  the  whole tpiantity extracted  by  the marine
           acid,  and contained in 91.28 cubic inches of air ; and,
           deducting from this the quantity  of phlogifton con-
           tained in 4.9 cubic inches of inflammable air = o.i7i
           grains,  the remainder, viz. 0.367—c.171 =0.196,  is
           all the phlogifton  that  can be fotkd in 86.38 cubic
           inches  of marine air.  Then 100 cubic inches of  it
           contain  but 0.227 of  a grain of phlogifton, 65.173
  Why ma-  grains being acid.—Hence  we fee why i: ads fo  feebly.
  rine icid  on oils, fpirit of wine, ire. andwhyitismAdillodgedfrohi
  ■<Ss fo    any balls by uniting with phlogifton, as the vitriolic and
  weakly.   nitrous  acids are, its affinity to. it being inconfiderablc

             I 4.   Remarks on the Doctrines ofthe Quantity a--.d
                     fpecific Gravity  above delivered.    " 4 +

  M? K*i?i    To this doctrine of the fpecific gravity and qnan-
  bbjcAiom  »iry of acid contained i 1 different fubftances,, Mr Keir
  to Kir-   has made feveral objections.   1. Mr  Kirwan idppofes,
  wan's doc- tnat marine acid gas is the pure and folid marine acid
  ,r-:'^     diveftrd of  all  water and other matter.  Its apparent
           drynefs in this refpect, however, is no argument that
                                                 Theory.
it really contains no water;  for water  hfelf, reduced Remark*
to a ftate of vapour, potfclfes no  moiftcning property. on ,n« fof*
There is great rcilon to believe that water is aeonlti  m" Doc"
tuent part of'fome  gafes, and it is certain that all of tnnc*
them are capable of holding it  in Solution. As moift
materials,  there Sore,  are employed in the preparation
of marineacid air, there feems no reafon to believe,  that
in any way in which Mr Kirwan could obtain it, there
was  reafon to fuppofe it perfectly free of water  ; in
which cafe the denlity of the  acid  would be greater,
and its quantity fmaller than he fuppofes.
  2. A confiderable part of the denfity ofthe acid ab-
forbed in the experiment,  probably arofe from the  con-
denfation which always accompanies  the union  of a
concentrated acid with water.   Mr Kirwan allows this
to be the cafe with the nitrous and vitriolic acids, but
thinks it too inconfidcrable to deferve notice in the ma-
rine.  His reafoning,  however, does   not  appear fa-
tisfactory, or his experiments on the  fubject conclu-
five.   He obferves, that the  length of time taken
up in effecting an union  between the marine gas and
water,  is no argument againft their attracting one an-
other ftrongly when  once  united; and it is certain
that part of this acid  gas is  very quickly abforbed by
water.   He alfo finds fault with his  accuracy in cal-
culation ; and aflerts,  that if matters are fairly Stated,
the real denfity of the marine acid gas will be  con-
fiderably lefs than Mr Kirwan makes it.
   3. A great  obftacle even to an approximation to-
wards the real denfity  ofthe acid, arifes from the  con-
denfation which  the water,  as well as the acids,  muft
Suffer in the procefs: and in this  cafe, where a ge-
neral  condenfation takes  place,  he  aflcs, "  How
fhall we determine the part of the condenfation that
belongs to the  water, and the part that the acid fuf-
tains?"  This,  with  other confiderations,  makes Mr
Keir (t doubt of  the poffibility of Solving the queftion
concerning the actual denfity of pure  and folid acids."
The inveftigation of the queftion, indeed,  he does not
confider as a matter of great confequence, as every ufe-
ful application may be obtained, by firft investigating
the  comparative Strengths of different portions of the
fame acid rendered more or lefs dilute ;  and then by
finding out the ftrength of the vitriolic, nitrous, and
 marine acids of known denfities, fo that they may be
 compared together.  " Homberg (fays he) has the me-
 rit of making the firft  efTay  towards  this invefliga-
 tion.   Bergman and  Wenzal  have  fupplied the de-
 fect of Homberg, by taking into confideration the ga3
 united with alkaline fubftances ; and  Mr Kirwan, by
 ufing determinate quantities ofacid liquors of known
. denfities,  has  confiderably improved the  method  of
"Bergman : and whoever  Succeeds thefe able chemifts
 in this inquiry,  may avail himSelS greatly of their la-
 bours,  particularly thoSe of Mr Kirwan."   He  con-
 cludes  with ftatingthe refults ofthe inquiries made by
 the chemifts abovementioned;  on which he makes the
 following remarks.
   " The diScordancy of thefe refults is very ftriking, Great*dif-
 and gives but an humiliating representation of the pre- fcrences ia
 cifion of our prefent knowledge in chemiftry.  A great the calcu-
 part ofthe difference arifes undoubtedly from the dif hitionsof
 ferentviews in which thefe authors confidered the dry- different
 nefs or purity of the acids.   Mr Kirwan,  as we  have autho'**
 feen,  endeavoured to find their denfity and quantity in 
Theory.                           C    H    E   M

Remarks  a ftate of perfect diynefs and purity ; which he fup-
•n the for- pofed  to exift in the marine acid gas : with which he
trfnes °C"  comPared and inferred the  denfities and quantities of
■----J -   > the nitrous  and  vitriolic acids,  upon the fuppofition
         that equal quantities  of  thefe feveral acids are fatu-
         rated by a given weight of fixed alkali.   Befides the
         uncertainty of his principles, from which he deduces
         the denfity and quantity ofthe marine acid, his  appli-
         cations from thence to deduce the denfities ofthe pure
         nitrous vitriolic  acids, being founded on the  above
         fuppofition, muft partake  of its  defects.  The alkali
         which  he happened to fix on as the ftandard by  which
         he compared the ftrengths of the different acid liquors,
         in order to determine the quantity  of real acid they
         contained, and thence to determine their denfity in a
         Solid  ftate,  was  the fixed vegetable.   Having Sound
         that i oo grains of his real marine acid could faturate
         215 grains of this alkali, he infers, that the fame pro-
         portion is applicable to the other acids :  and accord-
         ingly  we find that 100 grains of each of the pure and
         real mineral acids are  Saturated  by  an equal quantity,
         viz. 215 grains of this alkali.  But if we examine the
         other columns  of his table, we fhall at once See, that,
          in other Subftances  Soluble by acids, this equality does
         not  exift ;  and that every Such Subftance has  a ratio
         peculiar to itSelf,  with refpect to the proportions of
         thefe acids neceffary for its  faturation.  It is evident,
         therefore, that if Mr  Kirwan had fixed on the mineral
         alkali,  the  volatile alkali,  lime,  or any  other  fub-
         ftance, as a ftandard, inftead of vegetable alkali,  his
         determination of the denfities of the real vitriolic and
         nitrous acids would have been  different ;  and  as no
         reafon can be afligned  why the vegetable alkali  or any
         other fubftance fhould have the prerogative over  the
         reft, it is obvious that there can be  no fuch general
         ftandard, but that  each fubftance  pofleffes folely  the
         capacity of determining the proportions of the feveral
         acids neceffary for its faturation.
            "  The other chemifts were contented to confider as
         the pure  and dry acid, that which  actually remains in
         the neutral fait, after  this has been rendered as  dry as
         poflible by expofure to a  red heat: and  having  made
         their alkalies as dry as they could,  they fuppofed thefe
         alkalies to retain the fame weight  in the dried neutral
         fait  ; and that  the augmentation of the weight  gained
         by the alkali during the formation of the neutral  fait
          fhowed the weight of  the dry acid.  The uncertainty
         which  affects this method arifes  from the different ca-
          pacities which different neutral  falts may poffefs of re-
          taining more or lefs water, either as a conftituent part
         of the dry fait, or merely by the ftrength of adhefion
         or affinity.   Neverthelefs, this method being founded
          folely on experiment, without any theoretical  induc-
          tions, feems to furnifli fome approximation, not  per-
         haps of the abfolute  quantity  of  the acids in their
         drieft poflible ftate, but of  the acids as they actually
         exift in thefe falts comparatively   with  each  other.
         Though  the difagreements between  Bergman's  and
         Wenzel's refults are  little in comparifon of the diffe-
         rence between them and  Kirwan's, yet as their expe-
         riments were made nearly in the  fame manner,  and
          upon the fame grounds,  there  feems to  be^  fufficient
          reafon to wi!h for a careful repetition of their experi-
          ments, or of others with the fame view, and lefsliable
          to objections.
I   S   T    R   Y.                                   63
   "  The  only difference in the methods employed by Rcrrark*
 thefe two  celebrated chemifts conftfted in the mode cf on the for-
 Saturation.  Bergman probably uSed the common  me- mcr Dor-
 thod, but  Wenzel employed a very peculiar one.  He t/ines'___
 added to his alkali a greater quantity of acid than was
 neceflary for the faturation ;  and after the alkali  was
 diflblved,  he added a lump of zinc, or of oyfter-fliell,  in
 order to faturate completely the fuperfiuous acid.  By
 obferving  how much of the zinc or oyfler-fhell the acid
 diflblved,  and knowing how much of thefe fubftances
 was  foluble in his acid by former experiments, he in-
 ferred  the quantity of acid left for  the faturation  of
 the alkali.  Having thus afcertained the quantity ne-
 ceflary to  faturate the alkali, he  mixed together the
 proper proportions of thefe,  and  formed his  neutral
 fait by evaporating the  mixture and drying  the  fait
 with a red heat.  Perhaps the difference in the refults-
 obtained by thefe two chemifts might arife from their
 different modes of  faturation.   The common  method
 of afcertaining the  point of  faturation by means  of
 litmus  or  other  blue vegetable juices, appears fuffi-
 ciently exact, is fimpler,  and  therefore preferable  to
 that  uSed by Wenzel.
    " The  ftandard for comparing the ftrengths of acids,
 and likewife oS alkalies with one  another,  may be ei-
 ther an acid or an alkaline Subftance ;  and if we  had
 one of each, the proportion of whofe quantities requi-
 fite for their mutual faturation  were well  afcertained,
 the  conveniency in making the experiments would be
 obvious, and the certainty greater.   Alkaline, and the
 earthy fubftances that are foluble in acids,  are feldom
 pure enough for this  purpofe.   They generally con-
 tain  quantities,  which are not eonftant,  of fixed air,
 filiceous earth, magnefia, neutral falts, and inflammable
 matter, which render any of thofe that are commonly
 met  with unfit for  the purpofe without a very fkilful
 and careful purification. The chemifts who have made
 experiments to determine the proportions of acids and
 alkalies requifite for each other's faturation, have fcarce-
 ly been explicit enough in explaining the means of pu-
 rifying the alkalies which they employed : for thofe iu
 commerce are quite uncertain  in ftrength and purity :
 and as to  the general rules for making allowances for
 any  heterogeneous fubftances they may  contain, they
 are  quite inapplicable to  delicate experiments.  No
 other method Seems proper for ascertaining  the pu-
 rity  oS alkalies but that of cryftallization : of which
 both the vegetable and mineral alkalies arefuSceptible,
 especially the latter,  which on account  of its being
 more eafily reducible into cryftals, is therefore prefer-
 able.  TheSe alkaline cryftals, however, are not fit to
 be uSed as a ftandard, becauSe  they   either are apt to
 be Sufficiently dried, or, upon expofure to air, to lofe
 a part  of  the water oS their cryftallization, and to fall
 into powder.  Even if they fhould be taken, as is pof-
 fible with due care, at the exact ftate of dry but entire
 cryftals, another uncertainty ariSes  from  a  property
 which Seems to be common to them all,  namely, that
 of retaining a greater or fmaller quantity of water, ac-
 cording to the  degree of heat in  wdiich  they were
 cryftallized ; the colder the weather the greater quan-     .«
 tity of wctcr entering into the compofition of the cry-  Mr Keir's
 ftals.   It feems poflible,  however, to make a pretty method of
 accurate ftandard of mineral alkali in the following preparing
 manner :  Let the  alkali be purified by repeated  folu- an alkaline
                                                tion ftandard- 
CHEMISTRY.
 5th 5ro
Hismcthnd
of finding
the fpecific
gravity of
different
liquji-s.
thm and cryftallization, ufing only fuch as are formed
firft, and rejecting the  remaining  liquors.  Let  the
pure cryftals be expofed to a dry air  until  they have
completely ctllorcfccd or fallen into a dry white pow-
der ;  which alteration  may be facilitated  by bruiting
the cryftals and changing the furface of the powder.
Let this powder be then expofed for a certain and  de-
terminate time to a  eonftant heat, as  that of boiling
water for 12 hours ;  letting the  furface expofed be in
fome  given proportion, fuppofe of a fquare inch to an
ounce of the powder of cr\ ftals, and let it be ftirred
every two hours.  When  thus dried, let  them be put
while hot into a bottle,  and well  flopped.  This pow-
der I  have iomid  to be an uniform and eonftant  Stand-
ard for  afcertaining the ftrength of acids ;  and alfo, by
comp.irifon by means of acids, of other alkaline fub-
ftances."
   With regard to an acid ftandard,  our  author  re-
commends oil of  vitriol; w hich, he fays, as it comes
from the hands of the Britifh manufacturers, is of the
fpecific  gravity of about  1.846,  but  foon  becomes
weaker, unlefs carefully kept from the external air ;
and in general  he rates it at 1.844.  C*nc Part  °S this
acid mixed with nine oS water, isoSa very convenient
Strength for ul'c ; and as every ten grains of the mix
ture contain one of the ftandard acid, the computations
arc thus rendered eafy : and  by  thefe  ftandards,  the
ftrength of all acids, alkalies, and fubftances foluble in
acids, may be meafured and compared together.
   To determine the  fpecific  gravity of liquors with
accuracy, our author recommends the method of weigh-
ing them in a phial fitted with a glafs-ftopper,  which
can only  enter a  certain length  into  the  neck.   In
this way, he obferves, no other inconvenience canen-
fiie than the flight one, that the glafs-ftopper, by very
frequent ufe, ie apt to wear itSclf and  the neck  of  the
phial alfo; fothat  after a great number of experiments,
it  will at  laft diminifh, in fome meafure, the capacity
of the phial itfelf. This, however, is but very trifling,
and may be corrected at any time.  Mr Keir has  be-
fides found, that after fome hundreds of experiments,
the error amounted  only to one quarter of a grain in
101 grains.
   " The methods hitherto practifed (fays  he)  for af-
certaining the quantities of acids and alkalies contain-
ed  in neutral falts, feem to be liable to feveral objec-
tions befides thofe abovementioned,  arifing from  the
different proportions of water remaining in a neutral
fait, after expofure  to  a red-heat, which heat  is alfo
very indefinite.   In  boiling the faturated  mixture  of
acid and alkali to drynefs,  and afterwards in expofing
this fait to a red-heat, it has been fuppofed that nothing
but water is expelled ; and fome chemifts, who have
given the reSults, have  alSo determined  the weight of
the alkali which enters into the neutral mixture, by
evaporating to drynefs an equal quantity of the alka-
line folution which had been employed in   the fatura-
tion, and weighing the dry folution, on the fuppofi-
tion that nothing is expelled but  water.   It  is cer-
tain, however, that in the evaporation both of alkalies
and neutral falts,  a  confiderable portion of the faline
matter is  elevated towards  the end, when  the  liquor
becomes concentrated and  acquires a degree of heat
confiderahly above that of boiling water.   The  fol-
Theory.
lowing method appears beft for determining the rela- Remarks
tive quantities of acid  and alkali, or other fubftance on the for-
exifting in neutral lalts.                             rncr 1)oC*
   " To a given number of grains, fuppofe ico of the m"c,J
ftandard vitriolic acid, or to a proportionable quantityof
any other acid, add as much of the alkali or other fo-
luble fubftance as is requifite  Sor  the Saturation, and
note the  quantity required, which fuppofe to be 150
grains.  \\ e have thus a Solution  of  the neutral fait,
which  is the object ofthe experiment; the quantities
of acid and bafis contained in which  arc known, and
the general proportion ot"  the quantity of" the acid to
its  balls  in  the neutral Salt determined, viz. as 100
to 150.  The next thing to be difcovered is the weight
of the dry neutral fait contained  in  this folution, in
order to know the proportion of the  dry neutral frit
to its  acid and bafis.  tor this purpofe,  let  a given
quantity  oS  the Same neutral fait,  either in the ftate
of cryftals or dried to any given degree, bediflolved in
water.  Let this folution be brought  to the Same den-
fity as  the former, by adding water to the  heavier of
the two:  then, by knowing the weight of each folu■•
tion, and the quantity of dry neutral  fait which was
actually diflblved in  one of them, the quantity con-
tained  in  the  other may be deduced ;  and  thence the
quantities of  ftandard acid, or of other  acid pro-
portioned to  it, and  of  the alkali  employed, or
other foluble fubftance contained in a given  quantity
of the  neutral fdt,  are determined ; alfo the quantity
of water contained in the neutral fait, that is greater or
lets than  what is contained in the quantity of acid em-
ployed, w ill be known,  over and above any water that
may have been contained in the alkali  or other bafis of
the neutral fait; the quantity of w hich water, if any,
cannot be determined.
  " By this method may  be afcertained the propor^
tion of the acid, of the bafis, and ofthe neutral fait, 10
each other ;  not indeed the quantity ofacid and of al-
kali deprived  of all water, but the quantity  of acid,
equal  in intenfity of acidity to  a  known  portion of
the ftandard acid ; and alfo the quantity of fuch alkali
or other foluble fubftance as was employed ; the rela-
tive ftrength of which is known from its ratio to the
ftandard acid."                                      6th 5J<3
  The tranflator of Wiegleb's Syftem  of  Chemiftry OhjedioH
totally  difagrees with Mr Kirwan's calculation of the toKirwan's
quantity of phlogifton contained in  fulphur; but as his calculation
objection feems to arife rather from an  inclination to of the.
the antiphlogiftic doctrine  that a real difcuffion of the 'Jfo "Son
fubject, this can have but little weight.  It is poflible f„ fulphur.
indeed  that Mr Kirwan may have over-rated the quan-
tity of phlogifton this fubftance contains, which is in-
deed larger than  that  allowed by  other chemifts.
"  Brandt (fays the tranflator), who has been moft ge-
nerally followed, reckons it only at ;7 ; and it has al-
ways appeared to me, that the  weight of phlogifton in
fulphur is almoft infinitely fmall."   His objection pro-
ceeds on a maxim which he thinks he has demonftra-
ted, viz. that fulphur is compofed,  not of the  vitriolic
acid and phlogifton, but of the bafe of vitriolic acid
and phlogifton.  No  experiments hitherto made, how-
ever, have been able to lhow this bafe diftinct from the
acid ;  nor have we any  reafon to  fuppofe that  the in-
creafe  of weight in the vitriolic acid above the fulphur
                                              from 
Theory.
CHEMISTRY.
65
 Earths,  from which it is produced,  arifes from any thing be-
    v   ' fides the accelfionof mere water,  which the air parts
         with during the combuftion.  Hence, if the fulphur is
         burnt in a very moift air, the quantity of acid obtained
         will be four or five times the weight of the fulphur.

                          Sect. IV. Earths.

            These are divided into  five claffes :  1. Abforbent,
         alkaline, or calcareous earths : 2. Argillaceous earths
         or clay : 3. The flinty :  4. The fufible earths :  and,
         5. The talks.
            1. The firft clafs comprehends all thofe that are ca-
         pable of being converted into lime.   They are  found
         of various degrees of hardnefs ; but none of them are
         capable of totally refuting  the edge of a knife, or
         ftriking fire with fteel.   They are found to confift of a
         very friable earth,  joined with a large quantity of air
         and  fome water.   They effervefce with an acid when
         poured on them ; by which they are diftinguifhed from
         all other kinds  of  earth,  except  the argillaceous.
         When calcined by  a ftrong fire,  they part with the
         water and air which they contained, and then acquire
         a  great  degree of caufticity, lofe their power of ef-
   -XI   fervefcing with acids,  and become what is called
Quicklime, quicklime.   They are foluble in acids, but not equal-
         ly fo in all.  The vitriolic and tartareous acids  form
         compounds with  them very difficultly  foluble;  thefe
         lenites, formed  by the vitriolic  acid  and  calcareous
         earth, requiring, according to Mr Beaume, an ounce
         of water to diffolve a fingle grain of it.  The folubi-
         lity of the  tartareous felenite  hath not  yet been de-
         termined.—With the other mineral acids, the calca-
         reous earths become eafily Soluble ; and by proper ma-
         nagement Sorm concretes  which appear luminous in
         the  dark, and are called phofphori.
            2. The  argillaceous earths  differ from  the calca-
         reous, in not being convertible into quicklime. When
         mixed  into a  pafte with water,  and expoSed to the
         fire, they  fhrink remarkably,  crack  in many places,
         and become exceffively hard.  By being gently dried
         in the open air before  they are  turned, they do not
         crack,  and thus may  be formed into veffels of any
         fhape.   Of this kind of earth are formed all the brown
         fort of earthen ware.   The pureftkind of argillaceous
         earth naturally  found, is that whereof tobacco-pipes
         are  made.
            All the argillaceous earths are foluble in acids. With
         the  vitriolic they diffolve into a gelatinous tough liquor
         very difficultly cry Stall izable ; but which, on the addi-
         tion  of fome fixed or volatile alkali, may be fhot into
         cryftals of the fait called  alum.  With the other.acids
         they form aftringent falts of a fimilar nature.
            The attraction between the argillaceous  earths and
         acids is very weak, yielding not only to alkaline fafts
         both fixed and volatile, but even to Some metals,  par
         ticularly iron ; but thefe earths have as yet been  but
         little the Subject of chemical examination in this  way.
         They have a  remarkable  property of abforbing the
         colouring matter of cochineal, Brafil-wood, ire as have
         alfo the calces of fome metals.
            Both the calcareous and argillaceous, and indeed all
         earths when pure, refill the utmoft violence oS fire;
         but  when mixed together will readily melt  eSpecially
         if in contact with the burning fuel.  Dr Lewis having
Earths.
   5™
Argillace
sus.
   5*3
Anomalous
earths.
Magne-fia
made covers to fome crucibles of clay and chalk mixed
together,  found that  they melted into a yellow glafs,
before the mixtures in the crucibles were fufed in the
leaft.  But though they melted thus readily when in
contact with the fuel, it was with  great  difficulty lie
could bring them to a tranfparent glafs  when put into
a crucible.
   The other fpeciesof earths, viz. the  flinty, fufible,
and  talky, being  no other way  the  fubjects of che-
miftry than as they are fubfervient to the making of
glafs,  all  that can be faid of them will  moft properly
come under that article.   For their different Species,
fee Mineralogy.
   Befides the abovementioned fpecies of earths, there
are others which may be  called anomalous, as having
fome refemblance  of the calcareous and argillaceous,
and  yet being eflentially different from them.   Thefe
are the white earth called magnefia alba,  the earth of
burnt vegetables, and that produced from burning a-
nimal fubftances.
   Magnefia alba was at firft prepared from the thick
liquor remaining after the cryftallization of nitre ;  and'
is now found to be  contained in  the liquor called bit-
tern, which is left after the Separation of common fait
from Sea-water. In the former caSe it was united with
the nitrous, in the latter  with the vitriolic, acid.   It
is alSo found naturally in  the  foft kind of ftone called
fteatites or " foap-ftone ;" and in the concrete ufed for
taking Spots  out  of cloaths, called French chalk.  It
differs Srom the calcareous earths, in not acquiring any
caufticity  when deprived of its air, of which  it con-
tains fo large  a quantity  as  to lofe two-thirds of its
weight when  calcined.   From the argillaceous  it dif-
fers in not burning hard when mixed with wrater, nor
forming a tough  ductile pafte.   It is eafily Soluble in
all the acids,  even the vitriolic ;  with which it forms
the  bitter purging  Salt  commonly called  Epfom fait,
from its being firft  discovered in the waters of EpSom.
With all the other acids  it likewiSe forms purgative
compounds, which are either very difficultly  or not
at all cryftallizable—Like  other pure earths, it can-
not be melted by itfelf;  but, on proper additions,  runs
into a beautiful green glaSs.
   The earth of burnt vegetables  is thought  by Dr
Lewis to  be the Same with magnefia alba; but on try-
ing  the common  w-ood afhes, they were  Sound  to be
very different.  This kind of earth is fufible, by rea-
fon ofthe alkaline falts contained in it.  Animal earth
is both very difficult of folution  in acids, and  impof-
fible to be melted  in the  flrongefl  fire.   It diflblves,
however, in acid liquors,  though flow ly ; but the na-
ture of the compounds formed by fuch an  union are as
yet  unknown.  The fofter parts of animals,  fuch as
blood, flefh,  ire. are faid  to yield a more foluble earth
than the  others.   Animal earth  has  lately been fup-
pofed  to be compounded of calcareous earth and phof-
phoric acid ;  but this opinion is  fhown to be erroneous
under the article Bones.   The  phofphoric acid pro-
duced from thefe, is  with reafon SuppoSed to be only
the  vitriolic acid changed.

         Sect. V.  hif.ammable Subjlancss.
                                                      516
   These comprehend all vegetable, animal, and Some  Phenome*
mineral Substances.   They are diftinguifhed  from all  "a on
                          I                  others,  burning.
   515
Vegetable
and animal
earths. 
66
C   H   E    M   I    S  ■  T   R    Y.
Inftaiu-
nnile Sub-
ftance* .
   .517
On Jiftiila
tion.
   5i*
Treated
with diffe
rent acids
   519
Singular
produc-
tions.
others, by emitting a  grofs thick  Smoke and  flame,
when a certain degree of heat is  applied.  To this,
however, Sim•;; e>f wine and all preparations from it arc
exceptions.   1 ncy ourn without the lcalt Smoke ; and
if t glafs bell  is held over  the burning fpirit, no foot
is formed, only a quantity of water is found condenfed
on its fides.   Even the grofler oils, if tlowly burnt with
a very fmall flame, will } ield no foot; and an exceeding
great quantity of water, fully equal in w tight and bulk
 to the oil employed, may be obtained from them.  \\ e
 can fcarcely, however, credit, that !o great a quantity
 of water comes from the oil;  as this w-ould be a real
 tranfmutation ; and wc know  that, befides water,  the
 oils contain alio ionic  quantity of fixea air, as well as
 earth.  It is prolublc, therefore,  that, as it is impof-
fible to fiiftai 11 flame  without a decompolition of that
 part of the air which  rufhes in  to Lpport it, part of
 the water iu  tiiL cafe comes from  the air, which al-
 ways contains moifture in abundance.
    Inrlammable matters, on being burnt, generally leave
 behind a Small quntity of earthy matter called ujhes;
 but to this, fpirit of wine,  camphor,  the more volatile
 oils, and the  mineral oil called uaptha, are exceptions.
. Vegetable  fubftances, w hen  diftilled in  clofe  velfels,
 give out a quantity of air,  fome acid, and an einpyreu-
 matic oil, le.1vi.1g behind a black fpongy mafs called
 charcoal.   To this too there area few exceptions, viz.
 fpirit of wine  and the preparations from it, camphor,
 and peril'.pi  fome of  the more volatile oils,  or naph-
 tha.   Animal fubftances  yield  only a very fetid  em-
 pyreumatic oil, and volatile  alkali.
    In general,  all inflammable matters are acted  upon
 with fome violence by the vitriolic  and nitrous acids,
 excepting only camphor and  naphtha.   With the vi-
  triolic aeid, when in a liquid itaie, they render it vola-
  tile and fulphureous;  if in a dry  ftate,  they form ac-
 tual Sulphur.  With the nitrous,  they firft impart a high
 colour and great degree of volatility to the aeid ,  then
 2  violent ilame enfnes, if the matter is  attempted  to
  be dried.  With fpirit of  wine the effects ai e consi-
  derably  different ; and  very volatile compounds are
  formed, which are called ether, on account of their ex-
  ncding great difpofitiou  to  riSe in  vapour.   Similar
  iom;-'U! ids are likcwil'e produced,  but  with more dif-
  ficuitv, from the marine acid and concentrated \ine-
  gar.   The l'al Sedativus oS borax mixes with Spirit  of
  vine, and caiifcs it burn with a green flame ; but does
  not Seem to n.oduce any other change upon  it.  Low
  ihe acid of  phofphorus and of ants act upon fpirit  of
  \\ i.ic, is not < xaetly known ; but that of tartar by di-
  ge'tion with it. is converted into the acetous acid. With
  any other inflammable matter, the phofphorine acid re-
  produce-* phofphorus.
    There are two Singularities obServed among the in-
  flammable fubftances.  One is  that bituminous matter
  calLd amber, which  yields a volatile  Salt oS an  acid
  Eature on diftillation : \\ lien combined with alkalies,
  this acid  is  found to  yield compounds fimilar to thofe
  Biade with the acetous acid and alkali.   The other  is,
  that gum called bet:zoin, which is ufed as a perfume, and
  >ields by Sublimation a kind of volatile fait in fine fhi-
  ning cryftals like fmall needles, and of a moft grateful
  *»dour.   Thefe diflblve very readily in fpirit of wine ;
  kut not at all in water, unlefs it is made very hot;  fo
  lhat ihcv feexu tv contain more oily than faline matter.
                                                  Theory.
Neither the nature of thefe flowers, however, cor that Mct»Mio«
of the lali of amber, is fully know;..                  Sbftanco.^

          Sect. VI. Metalline Sub ft antes.

   These arc  diftinguifhed from all other bodies  by
their great fpecific gravity, exceeding that of the molt
denfe and compact ftones.   1 tie hcavicft ot  the latter
do not exceed the fpecific gravity of water in a greater
proportion than that of 4 to 1 ; but tin, the lightclt of
all the metals,  exceeds  the fpeciiic gravity of u ater in
the propor tn-n of 7  to  1.   They are  alfo the moft
opaque  of all known bodies,  and reflect  the rays of
light  moft powerudiv.                                 52c
   Metallic  bodies ponds the quality of diifolving in Metals fo-
and uniting with aeid  falts, in common with  cai ths ll^lc m*r
and alkalies ; but, in general,  their union is lefs per- c
feet, and they are  more eafily Separable.   1 hey  ef-
fervelce with acids, as well as calcareous  earths and
alkalies ; but their eftcrvefcence is attended with very
different  appearances.   In  the efferveScence of acids
with alkalies, or with calcareous earths,  there is a dis-
charge of the fluid csdled fixed air, which is fo Sir from
being inflammable, that it wilt  immediately extinguifh
a  candle or other fmall flame  immerfed  in  it.  The
mixture alSo is notably  diminiihed in weight.  "W hen
a metallic Subftance  is diflblved in an acid, the weight
of the  mixture is  never very much diminiihed, and
Sometimes it is increaled.   Thus, an ounce of quick-
filver being  flowly dropped into as much aquafortis .as
was luificient  to difiolve it, and  the  folution managed
fb as to  take  up almoft a  whole day,  the whole was
Sound to have gained Seven grains. There is alSoa re-
markable difference between the  nature of the vapour
discharged  from metals and that from  alkalies ;  the
former, in mofl cafes,  taking  fire and exploding with
violence ; the  latter, as already obferved, extinguish-
ing flame.                                             5ii
   The metallic fubftances, at Itaft fuch  as we are able Their corn-
to decon pound, are all compofed of a certain kind ofpofition.
earth,  and the inflammable principle called phlogifton.
 1 he earthy part by itfelf,  in whatever way  it is pro-
cured goes by  the name of calx.   The other principle
has alieady been proved to be  the fame with charcoal.
 V> hen  thefe two principles are feparated from one an-    .a«
 other, the metal is then faid to be calcined.   The calx Calcina-
 being mixed with  any inflammable fubftance, fuch astionandre-
 powdered chatcoaf and  urged  with  a ftrong  fire vivifkation
 melts into metal again ;  and  it is then  faid to be re-
 d-e.d,  or icviviffaitd : and this takes place v hethcr
 the metal has been reduced to a calx by diilolution in an
acid or by being expofed to a violent fire.   If, how-
 ever, the calcination by fire has been very violent and
 long continued,  the  calx will  not then  fo readily
 unite with the phlogifton of the charcoal, and the re-
 dmtioi will be performed with more difficulty.  Whe-
 ther, by this means, viz a long continued and violent
 ca!nn:|ion. n.e-allic  earths might entirely fofc their
 propt ry of combining wiih phlogifton, and bf changed
 into thi fe of another kind,  dtferves well to be inquired
 into.                       ^                           si3
   When a metallic ftibftance is diflblved in any kind of Calcina-
 acid, a:d an  alkali or calcareous earth not deprived tion and i*-
 of its  fixed air  is added, the  alkali will  immediately crc»fe of
 be attracted by the  acid, at the fame tiaie that the fix- w«'8ht L?
rd
acidi. 
Theory.
CHEMISTRY.
$*!*fIUnc  ed air centred in the  alkali is difengaged, and the
t*!!r__ncc*:calx of the metal, having now no acid to keep it dif-
          folved, immediately joins with the fixed air of the al-
          kali, and falls to the bottom.  Something  fimjlar to
          this happens  when metals are calcined  by fire.   In
          this cafe there is a continual  decompofition  of  the air
          which enters the fire ; and the fixed air  contained in
          it, being,  by this  decompofition, fet loofe,  combines
          with the calx ; whence,  in both cafes, there is a confi-
          derable increafe of weight.  If the air is excluded from
          a metal, it cannot be calcined even by the moft violent
   sn    fire.
Reafon of    When a metal is precipitated by a mild alkali, or by
the increafe an uucaicineci calcareous earth, the reafon of the in-
In metab   creafe of weight is very evident;  namely,  the adhe-
line calces.  *~10n °^ t^ie ^xe^ a*r t0 tne metalline calx : but, though
          it is not fo much increafed when precipitated by cau-
          ftic alkali, or by quicklime, there is nevertheless a very
          evident increafe, which is not So eafily accounted for.
          M. Lavoilier  has mentioned  fome experiments made
          on mercury  and iron diffolved in aquafortis,  which
          deferve to be  taken notice of, as  in  a  great meafiire
          accounting for the phenomenon already mentioned of
          rhe folution of  metalline fubftances gaining an addi-
          tion of weight; and  likewife fhow the  proportion  of
          increafe of weight with the mild,  or calcined calcare-
   S2$    ous earth.
M. Lavoi-   « Exactly 12 ohnces of quickfilver (fays  he) were
fier's expe-put-into a matrafs, and  12  ounces of fpirit of nitre
piments.    poured on it.   Immediately a Spontaneous efferveS-
          cence enfued, attended with heat.  The red vapours of
          the nitrous acid arofe from the mixture, and  the liquor
          afliimed a greenifh colour.   I did  not wait till the fo-
          lution  was entirely accomplifhed before I  weighed it;
          it had  loft one drachm 18 grains.   Three hours after,
          the mercury was nearly all diflblved : but having again
          weighed the folution, I was much aftonifhed to perceive
          that it had increafed inftead of being diminimed  in
          weight; and that the loSs, which was one drachm 18
          grains at  firft, was now only 54 grains.   The next
          day the folution of the mercury was entirely finifhed,
          and the lofs of weight reduced to 18 grains ;  fo that in
          12 hours the folution, though confined in a narrow neck-
          ed matrafs, had acquired an augmentation in weight
          of one drachm.  I added fome diftilled water to my fo-
          lution, to prevent it from cryftallizing ; the total weight
          of it was then found to be 48 ounces 1 drachm and 18
          grains.
            " I weighed  fepafately,  in two veffels,   8  ounces
          15 grains of the above  folution, each of which por-
          tions,  according to the preceding  experiment,  ought
          to contain  2  ounces of nitrous acid and  2  ounces of
          quickfilver.   On the other  fide I prepared 6 drachms
          36 grains of chalk, and  4 drachms 36 grains of lime ;
          thefe proportions  having been found by former  ex-
         periments j aft neceflary to faturate two ounces of ni-
          trous acid.  I put the chalk in the one veflel, and the
          lime in the other.
            " An effervefcence attended the  precipitation by
          chalk, but without heat; the mercury precipitated in
          a light yellow powder,  at  the fame time  the  chalk
          was diflblved  in the nitrous acid.   The precipitation
          by the lime  was  effected  without effervefcence,  but
          ^'ith heat; the mercury was precipitated in a brownifh
67
 powder.  When the precipitates were well fnbfidcd, Metalline
 1 decanted off the liquors from them, aud carefully Subilancea.
 edulcorated them.  After which, I caufed them to be W"TV
 dried in a heat .nearly equal to that in which mercury
 boils.
   << The precipitate  by the chalk weighed 2 ounces 2
 drachms 45 grains;  that by the lime weighed 2 oun-
 ces j drachm 45 grains.
   " Sixteen ounces of the  nitrous  acid, the fame as
 employed iu the former experiments, were placed in
 a matrafs, and fome iron filings gradually added.  The
 effervefcence was brifk, attended with great heat,, red
 vapours, and a very  rapid difcharge of elaftic  fluid:
 the quantity of iron  neceffary to attain  the point of
 faturation was 2 ounces 4 drachms;  after which, the
 lofs  of weight was found to  be 4 drachms  19 grains.
 As  the  folution  was turbid,  I added  as much diftilled
 water as made the whole weight of  the folution to be
 exactly  6 pounds,
  t( I took two portions, each weighing  12 ounces of
 the above folution, and containing 2  ounces of nitrous
 acid,  and 3 drachms 36 grains of iron filings.   I pla-
 ced them iu two feparate  veffels.   To one were  added
 6 drachms 36  grains of chalk; and to  the other 4
 drachms 36 grains of flacked  lime, being the quantities
 neceffary to faturate the acid.
  " The precipitation was effected by the chalk with
 effervefcence and tumefaction,  that by the lime  with-
 out cither effervefcence  or heat.   Each precipitate
 was a yellow brown ruft of iron.   They were wafhed
 in feveral parcels of diftilled water, and then dried in
 an heat  fomewhat fuperior to that ufed in the laft ex-
periment.
  " The precipitate by the chalk, when  dried,  was a
 greyifh  ruft of iron, inclining even to white by veins.
 It weighed 6 drachms  35 grains. That by the lime was
 rather yellower, and weighed 4 drachms 69 grains.      „$
  " The refult of thefe  experiments  (fays M. La- Confe-
 voifier)  are, 1. That  iron  and mercury diflblved in quences
 the  nitrous acid  acquire a  remarkable  increafe of from his
 weight,  whether they be precipitated by chalk or by e*Pen_
 lime.  2. That  this increafe is greater in refpeet to ments«
iron than mercury.   3.  That one reafon for thinking
 that the elaftic fluid contributes  to this augmentation
 is,  that it is conftantly greater when an earth is em-
 ployed faturated with  elaftic  fluid, fuch as chalk, than
 when an earth is ufed which has been deprived of it,
 as lime.  4. That it is  probable that  the increafe of
 weight  which is  experienced in the precipitation of
 lime, although not fo great as that by chalk, proceeds
 in part  from a portion of the elaftic fluid which re-
 mains united to the lime, and which  could not be Sepa-
 rated by the calcination."                             „,
  But though we  are naturally enough  inclined to Not well
 think that the increafe of weight in the precipitates founded,
 formed  by lime proceeded from fome quantity of ela-
 ftic fluid or fixed air which  remained combined with
 the lime, it is by far  too great to be accounted for in
 this way,  even according to  the experiments  men-
 tioned by M. Lavoilier himfelf, and  which, from the
 manner  in which they are  told, appear to have been
 performed with the  greateft  accuracy.   He  found,
 that r ounce  5 drachms and  36 grains of flaked lime
 contained 3 drachms and 3 quarters of a grain of water,
                        I -2                    an^ 
68
CHEMISTRY.
   53°
"What me-
tali are cal-
cinable, &
with what
degrees of
heat.
   541
•Ruffing of
metal*
   541
Fufibility
of metallic
com-
pounds.
   543
Great fufi-
bility of
e ompounds
<<f tin  and
bifmuth.
   5 44
One IcliMc
by the heat
of boiling
and only 16 gr.tins and an half of elaftic fluid were Se-
parable from it.   In the experiments above related,
where only 4 drachms and  36 grains were employed,
ihc quantity of elaftic fluid could not exceed 6 or 8
grains.  Yet the calx was increafed in mercury by no
Id's than  105  grains, and  in iron by 203 grains ; a
quantity quite  unaccountable  from the elaftic fluid or
fixed  air which we can SuppoSe to be contained  in the
lime made uSc of.   It is much more probabl-, that the
increafed  weight of  metallic  precipitates, formed  by
lime, arifes from an adhefion  of part of the acid.
   Metals  arc  found  to be compounded of a kind of
earth mixed with the inflammable principle or phlo-
gifton ; and  by a  diffipation of the latter,  all metallic
bodies, gold, filver, and platina excepted,  are capable
of being reduced to a calx,  but very different degrees
of heat are required for calcining them.  Lead and  tin
begin  to calcine as foon as  they are melted, long be-
fore they are made red-hot.  The fame happens to the
femimetals bifmuth and zinc ; the latter indeed being
combuflible, cannot bear a greater  heat in  open velfels
than that  which is barely fufficient to melt  it.  Iron
and copper require a  red heat to calcine them ; though
the former may be  made partly to calcine  by being
frequently wetted in a degree of heat conliderably be-
low that which is Sufficient to make it red.
   Moft metals undergo a kind of fpontaneous calcina-
tion in the open air, which is called their ruft ing; and
which has given occafion to various conjectures. But
M. Lavoilier has fhown, that this ariSes from the fix-
able part  of the atmofphere attaching itfelf to their
earthy part, and difcharging the phlogifton.   Accord-
ing to  him, no metallic body  can  ruft  but  where
there is an abforption of air ;  and confequently metals
can be  but imperfectly rutted when  kept  under a re-
ceiver.
   If  two  metals  are mixed together, the compound
generally turns out more fufible than either of them
was before the mixture.    There  are indeed  great
differences  in  the degrees of heat requifite to melt
them.  Thus,  lead  and tin melt below that degree of
heat which is required to make quickfilver or linfeed-
oil boil.  Silver requires a full red heat,  gold a low
white heat,  copper  a full  white,  and  iron  an ex-
treme white heat, to make it melt.   The femimetal
called bifmuth melts at  about  4600 of Fahrenheit's
thermometer, and tin at about 4220.  When mixed
in  equal  quantities,  die compound  melted at 28 3°.
When the tin was double the bifmuth, it required 5540
to melt it;  with eight  times  more tin than bifmuth,
it dM not  melt  under ^92°.  If to  this compound lead
is added,  which by itfelf melts in  about 5400,  the fu-
fibility  is furprifingly increafed.   Mr Homberg pro-
pofed for an anatomical injection a  compound of lead,
tin, and bifmuth,  in  equal  parts ;  which  he tells  11s
keeps in fulion * ith a heat fo moderate  that  it will
not finn;e paper.   Sir Ifaac  Newton contrived a mix-
ture of the  abovementioned  metallic fubftances,  in
Such proportions that  it melted and  kept flnid in a heat
ftill iftmller, not much exceeding that of boiling water.
A compound of two  parts of lecd,  three parts of tin,
and five of  bilimirh,  did  but juft  ftiffen at that very
heat, and fo would have melted with very little more ;
2nd when the lead, tin, and bifmuth, were  to one ano-
tion.
346
                                                 Theory.
ther in the proportions of 1, 4, and ?, the Wtopound Metalline
melted in 2460.   We have feen,  however, a piece of Subftance*.
metal compounded of thefe three,  the proportions u:i- ~~mv--~J
known, which melted, and  even underwent a flight
degree of calcination, in boiling water, and barely ftif-
fened  in a degree of htat fo gentle that the hand could
almoft bear it.                                          riJ-
   A  flight  degree of calcination feems to give  the Solubility
acids  a  greater  power o\er metallic fubftances;  a of metals
greater makes them lei's foluble ;  and  if long and vio- "ncrcafed
lently calcined, they are  not acted upon  by acids at ,7 ™    "
all.   Of all the acids, the marine has the  greateft at-
traction for metallic calces, and volitalizes almoft every
one of them.
   Sulphur  readily unites with  moft metals,  deflroys Effects of
their malleability, and  even entirely  diflblves them, fulphur on
On  gold and platina, however, it  has no effect, till metals.
united with a fixed alkaline  fait,  when*  it forms  the
compound called  hepar J'uiphuris;  w hich is a very
powerful folvent,  and will  make  even gold and pla-
tina themfelves foluble in water,  fo  as  to pafs  the
filter.   This preparation  is thought to  be the means
by whioh Mofes diflblved and gave the Ifraelites to
drink  the golden calf which they had idolatroufly fet
up.
   When a  metal is diffolved in  an acid, it may be
precipitated, not only by means  of calcareous earth
and alkalies, but alfo by fome other metals ;  for acids
do not attract all metals with equal  ftrength ; and it
is remarkable,  that  when a metal is  precipitated by
another, the precipitate is not found in a calcined ftate,
but in a metallic one.  The reafon of this is,  that the
precipitating metal attracts the phlogifton which is  ex-
pelled from that which is diffolving, and immediately
unites with  it, fo as to appear in its proper form. The
various degrees of attraction which acids have for  the
different metals  is not as  yet fulb/-determined.  The
befl authenticated are mentioned in the Table of Affi-
nities  or elective attractions (Sect. IX.)
   Metalline fubftances are divided into metals and fe-
mimetals.   The  metals which are diftinguifhed from into metals
the  femimctallic  fubftances  by their malleability oraml femi*
ftretching under the hammer,  are in number feven ; mctals-
gold, filver, copper,  iron, lead,  tin,  and platina.   To
thefe is added quickfilver; which Mr  Brown's expe-
riments have fhown to be a real  malleable metal, as
well as others, but requiring fo little heat to keep it
in fufion, that it is always found in a liquid ftate. The
femimetals are  bifmuth or tin-glafs,  zinc,  regulus of   54$
antimony, and cobalt, nickel, and arfenic.   This laft 1>roPertl5s
fubftance is now difcovered to be compounded of an acid   arfcmc'
of a peculiar kind and phlogifton ; and as the quantity
of the latter  is great or fmall, the arfenic aflumes ei-
ther a metallic or faline form.   It  likewife unites with
fulphur,  with which it forms a  compound of  a red or
yellow colour,  according  as more or  lefs  fulphur is
ufed.   This  coinpoi..-.'  i- eafily, fufible ; though  the
arfenic, by itfelf, is So volatile as to go  all off in vapour
rather than  uitit.   In common with the falts,  it pof-
Seffesthe properties of diffolving in water, and uniting
itfelf to alkalies.   Water will diflblvc about j„ of its
weig'm of pure  arfenic ;  but if arfenic is  boiled in a
ftrmv" rlkaline lixivium,  a mudr-greater proportion
will be diffolved. Indeed ftrong alkalinelixivk will dif-
                                              fd-.e
 .  S47
Divifion 
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* 
 Theory.                           C    H    E   M
 Wafers,&c. folve a part of almoft every metalline fubftance, except
     *    ' gold,  filver,  and  platina;  but,  excepting  copper,
           which may be formed into cryftals by means of the vo-
           latile  alkali,  none  of them  will  affume a cryftalliue
           form when united  with alkalies.  Arfenic, on  the
           contrary, unites very readily with fixed alkalies,  and
           flioots with them into a neutral fait.  If it  is mixed
           with nitre, it unites itfelf to the alkaline bafis of that
           fait,  and expels the  acid in very volatile fumes, which
           are difficultly  condenfed into a blue liquor.  The rea-
           fon of this is the great  attraction between the nitrous
           acid and phlogifton,  which are always diSpoScd to unite
           when a proper degree  of heat is applied.   Was the
           phlogifton contained in  large quantity in the arfenic,
           and  the  heat  Sufficiently great,  a violent deflagration
           would enfue; but as the acid of arfenic attracts the
           alkaline part of the nitre, at  the fame time that the ni-
           trous acid attracts the phlogifton, a double decompo-
           fition enfues,  in a lefsdegree of heat than would other-
           wife be neceflary ;  and the nitrous acid arifes in a very
           volatile ftate,  as it always is when combined with phlo-
           gifton,  which is the occafion of the bluenefs in aqua-
           fortis fo produced.   The arfenic is alfo decompofed by
           being deprived of its proper quantity of phlogifton ; in
           conSequence of which its acid attaches itfelf to the fix-
           ed  alkali of the  nitre,  and forms a neutral arfenical
           fait.  For the extraction of metallic fubftances  from
           their ores, and the various methodsof refining them, fee
           Metallurgy.

                          Sect.  VII.  Waters.
            The pare element of water, like that of fire, is So
          much an agent in moft chemical operations, as to be it-
          Self very little  the object  of practical chemiflry.  Some
          late experiments, however,  have fhown that this fluid
          really confifts, in part at leaft, of phlogifton, and an in-
          vifible Subftance which Sorms the bafis oSpure air : and
          consequently water is generated in the deflagration of
          dephlogifticated  air  ; but as  the bafis of the  former
          cannot be perceived by itfelf, we can as yet fay nothing
Water|low about it.   Waters,  therefore, can only be the objects
faranobjeeft of chemiftry, in conSequence of the impurities  they
of chemi-  contain : and as  theSe impurities are moft commonly
ftry.      of the faline kind, it is impoilible that any general theo-
          ry can be given of waters, diftinct from that ofthe
          falts  contained in them ;  which  all depend on the ge-
          neral properties belonging to falts, and which we have
          already mentioned.   Any  thing that can be faid with
          regard to waters,  then, muft be poftponed to the parti-
          cular consideration of the properties of each of the fa-
          line bodies with which water  is capable of being adul-
          terated.  We fhall therefore refer entirely  to the article
          Water in the order of the alphabet, for what can be
          faid  on this fubject.

          Sect. VIII.  An'wialand Vegetable Subftances.

Chemical     The general chemical properties of thefe have been
properties, already taken notice of under  the name oS inflammable
         fubftances.   They agree in giving out a very thick fe-
         tid oil, when dtitiiied by a ftrong-fire ;  but in other
         reSpects they differ very confiderably.  Moft kinds of
         vegetables give out an acid along with the oil ;  but  all
         animal Subftances (ants, and perhaps Some other infects,
         excepted) yield only a volatile alkali.  Some kinds of
I   S   T    R   Y,                                   6c)
  vegetables,  indeed,  as muftard, afford a volatile alkali Chemical
  on diftillation, fimilar to that Srom animal Subftances ; Characters.
  but  inftances oS this kind are very rare, as well as of ,"""~v
  animals affording an acid.   Both animal and vegetable
  fubftances are fufceptible of a kind oS fermentation,
  called putrefaction, by which a volatile alkali is produ-
  ced  in great plenty : there is, however,  this remark-
  able  difference between them,  that many  vegetable
  Subftances undergo  two  kinds  of fermentation  be-
  fore they arrive at the putrefactive-ftage.  The firftis
  called the vinous, when the ardentfpiritsareproduced,
  which we have  already mentioned when fpeaking of
  inflammable fubftances.   This is Succeeded by the ace-
  tous, wherein the vegetable acid called vinegar is pro-
  duced in plenty :  ancl laftly, the putrefactive ftage fuc-
  ceeds when a volatile alkali is only produced ;  not the
  fmalleft veftige either of ardent fpirits or of vinegar re-
  maining.  On the other hand, animal fubftances feem
  SuSceptible only of the putreSactive  fermentation ;  no
  inftance having ever occurred where there was the leaft
  drop, either of ardent  Spirit or oS vinegar, produced
  from a putriiied animal Subftance.  (See Fermenta-
  tion and Putrefaction.)

  Sect. IX.  Of the Chemical Characters,  and Tables
               of Elective Attraction.

    The numerous marksor characters by which the an- invention
  cient chemifts uSed to denote many different fubftances of marks
  were invented rather from a fuperftitious and fantafti- or charac-
  cal principle than from any real neceifity ; or, pcihaps,t£rs*
  like  the enigmatical language uSed by the alchemifts,
  they  have thereby Sought to conceal  their myiteries.
  from the  vulgar.  In contriving thefe marks, they af-
  feeted a ^;reat deal  of ingenuity; intending them as
  Symbols ofthe qualities pollened by  each oS the diffe-
  rent Subftances.  A circle being SuppoSed the moft per-
  fect, figure, wastheretbreuled to repreSent the moft per-
  fect metalinnature, that is,gold.  Silverbeinglikewifea
  per Sect and indeflrucf ible metal, is placed next to gold;
  but,  on account of its inferiority, is expreffed only by a
  crefcent, as if but half gold. A circle was likewife ufed
  to denote fait of any kind, as being fomething elaborate
  and perfect.   A crofs was ufed to denote acrimony of
  any kind, and confequently employed  for the acrimo-
  nious falts of vitriol, alkali,  &c.  Hence  all  the in-
 ferior metals  have the crofs Some how or other com-
 bined with  the  marks  defigned to repreSent  them.
 Thus, the mark Sor quickfilver denotes, that it hath the
 Splendor oS filver, the weight oS gold, but its perfection
 is hindered by an acrimony represented by the  crofs at
 bottom,  &c.   Fire is represented  by   an  equilateral
 triangle,  having one of its angles uppermost.  This
 may  be confidered as a rude reprefentation of flame,
 which is always pointed at top.   Water, again, is re-
 presented by a triangle, with an angle downwards,
 mowing  the  way in which  that element  exerts its
 ftrength,  &c.   All  theSe   marks,  however, as they
 were of no real ufe at firft, fo they are now becoming
 every day more and more  neglected.  Such  of them,
 however,  as may moft readily occur in chemical books
 are reprefented and explained on Plate CXXXII.
   The French chemifts  have of late attempted to in- New che-
 troduce a kind of new chemical language ;  and by a- mical lar.-
 doptingitthemSelves, may perhaps make it at laftuni- g»age.
                                             verfal. 
CHEMISTRY.
verfal, ts it is now impoffible to underftand their wri-
tings without knowing it.  See the Table at the end
of this article.
   Tables oj affin'tti',  or ilettive attractions, are hut of
Late  invention.   They are  confequences of an impro-
ved ftate. of chemiftry, when the different  fubftances
were »>nnd to act upon one another in moft cafes ac-
cording to a fixed and fettled rule.  The moft appro-
ved  table of this  kind  for a long time was that compo-
fed by Mr Gcoftroy.   It  was,  however, found to be
very  incomplete, not only as to its extent, but  like-
wife as heat and fome other circumftances were found
to vary the attractions confiderably, and  fometimes
even to reverfc them.  Other tables have been conftruc-
ted by Mr Gellert,  &c. but none hath yet appeared fo
complete but that many additions may be made to  it.
The following is that at prefent exhibited by Dr Black
in his courfe of chemiftry.
Theory.
  i.  Vitriolic Acid.
Phlogifton
Terra ponderofa
Fixed alkali
Calcareous earth
£inc
Iron
Tin
Copper
Quickfilver
Silver
Volatile alkali
Magnefia
Earth of alum.

   2.  Nitrous Acid.
Phlogifton
Fixed alkali
Calcareous earth
Zinc
Iron
Lead
Tin
Copper
Quickfilver
Silver
Volatile alkali.

    3. Marine Acid*
Fixed alkali
Calcareous earth
Zinc
Iron
Lead
Tin
Copper
Regulus of antimony
Quickfilver
Silver
Spirit of wiit?
Volatile oils
Gold.

      4- Sulphur.
Fixed alkali
Calcareous earth
.tron
Nickel
Copper
Lead
Tin
Silver
Regulus of antimony
Quickfilver
Arfenic.

J. HEPAR SULTHURlsis
  partially decompounded
  by
Quickfilver
Solution of fixed alkali
Lime-water
Volatile alkali.

    6.  Fixed Air<
Calcareous earth
Fixed alkali
Magnefia
Volatile alkali.

  7. Alkaline Salts.
Vitriolic acid
Nitrous acid
Marine acid
Acetous acid
Volatile vitriolic acid
Sedative fait
Fixed air
Sulphur
Expreffed oils.

8. Calcareous EartA.
Vitriolic acid
Nitrous acid
Marine acid
Acid of tartar
Acetous acid
Sulphureous acid  and  Se-
  dative fait
Sulphur.

9. Metallic Subtsax-
  ces,  Lead and Regulus
  of Antimony excepted.
Marine  acid.
Vitriolic acid		mony with Metals, EUdWe
Nirtous acid		Iron Attradioa
Sulphur and acetous acid.		Copper "
		Tin
10. Lead.		Lead
Vitriolic acid		Silver
Marine acid		Gold.
Nitrous acid		M- Quicksilver.
Acetous acid		Gold
Exprefl'ed oils.		Lead and tin Copper
11. Regulus	of Anti-	Zinc, bifmuth, and regu«
mony	.	his of antimony.
Vitriolic acid		
Nitrous acid		15. Silver.
Marine acid		Lead
Acetous acid.		Copper Iron.
12. Arsenic.		
Zinc		16. Water.
Iron		Fixed alkali
Copper		Spirit of wine
Tin		Milk, alkaline falts, and
Lead		fome neutrals.
Silver		
Gold.		17. Spirit of Wine. Water
13. Regulus	of Anti-	Oils and refins.
  In confequence of heat, Sedative fait and the othe1'
folid acids  decompound vitriolated tartar, nitre, an
fea-falt.
     Double  Elective  Attractions ; which, in  fome
       cafes, may be confidered as  exceptions to the
       foregoing table.

  I. Thofe which happen in mixtures of watery fub-
ftances.
S.
Acids
Calc.earths,orme-
  tallic fubftances
Vitriolic or marine
  acids
Alkalies or easths
Lead
Nitroushiarine,or
  acetous acids
Silver
Vitriolic, nitrous,
 or acetous acids
Volatile alkali
Acids
Nitrous, marine,
  or acetous acids
Calcareous earths
Volatile alkali
Fixed air.

Mercury, filver, or lead.
Nitrous or acetous acids.
Vitriol acid
Alkalies, earths,  or
  M.S.
Marine acid
Alkaline falts,  earths, or
  M.S.
Fixed air
Fixed alkali.
Volatile alkali, magnefia^
  or earth of alum
Vitriolic acid.
  II.  Thofe which happen in diftillations or fublima-
tions, and require  heat.
                          Fixed air
                          Calcareous earths.
                          Nitrous,  marine, or ace •
                            tous acids
       Vitriol, acid       Fixed alkali.
       Vol. alkali        Acetous acid
         itrous, marine,   Fixed alkali,  or abforbeat
         or vitriolic acids     earth*.
1.
?.
J Vol. alkali
I Acids
^ Vol. alkali
V- 
Theory.
Chemical
Opera-
tions.
CHEMISTRY.
7  Reg- of antimon.
V
Sulphur
Marine acid
Quickfilver.
III. Thofe which happen in mixtures by fufion.
3-
Tin
Silver
Copper
Gold
M. S.
Gold
 Iron
 Lead.
Sulphur
Lead.
Sulphur
Reg. of ant.
  The firft of thefe tables requires very little expla-
nation.  The names printed in fmall capitals, are thofe
of the fubftances which have the affinity with or at-
tract thofe below them.   Thus,  vitriolic acid  attracts
moft powerfully the phlogifton,  or inflammable  prin-
ciple : nexL, fixed  alkali ; then,  calcareous earth; and
fo on, in the order  in which they are marked. — The
tables of double elective  attractions cannot be  made
quite  fo  diftinct; though  an  explanation of one ex-
ample will make this likewife eafy to be  underftood.
Thus in Table  I. tbe firft cafe is,  " If a combination of
acids  with calcareous earths or  metallic fubftances is
mixed with a combination of volatile alkali  and fixed
air, the acids will  unite themfelves to the volatile  al-
kali,  and the fixed air to the  calcareous earth  or me-
tallic  fubftance.

Sect.  X.  Ofthe different Operations  in  Prac-
  tical Chemiftry,  and the proper Inftruments for per-
  forming each.
554
 Operationg   The irtoft remarkable operations in chemiftry, and
 in chemi-  by which  the greateft changes are made upon thofe
 ftry-      bodies which are the objects of that fcience,  may be
          comprehended under the  following names,  i.  Solu-
          tion.  2. Filtration.   3. Precipitation, or coagulation.
          4. Evaporation.   c. Cryftallization.  6. Diftillation.
          7. Sublimation. 8. Deflagration. 9. Calcination.  10. Fu-
          fion.  n Maceration,  or  digeftion.  To  which we
    ...    may add, 12. Trituration,  or levigation.
 Chemifts    Before we proceed to a particular account of each
 how divid- of thefe  operations,  it is neceffary to take  notice, that
 «d,       there are two different things propofed by thoSe who
          enter  on the practice of chemiftry.  Some  have no-
          thing  farther  in  view than  the enlargement of their
          knowledge,  or making improvements  in  arts  which
          are to  be practifed by others for their own advantage.
          Others defign to follow chemiftry as a trade,  by which
          they hope to enrich themfelves, or to get a comfortable
          livelihood.   But the apparatus and  utenfils  neceflary
          for performing the very fame  operations are exceed-
          ingly different when experiments only are to be made,
          from what they  muft be when thefe operations are
          performed with a view to profit ;  and fo great is this
          difference, than thofe who  purfue  chemiftry  with  a
          view to advantage, will always find themfelves  very
          confiderable  lofers if they follow the plan of an appa-
          ratus or  a laboratory defigned  only for making expe-
          riments.  Along with the apparatus, therefore, which
          is commonly defcribed  in chemical books,  and  proper
          only for  experiments, we fhall alfo give that which is
          neceflary for preparing great quantities of any chemi"
   5j6    cal article in the  way of trade.
Glafs vef-    In general,  thofe who  practice chemiftry merely
fcls> wl*en  with an experimental  view, ought, as much  as pof-
chemical
veffels.
 fible, to make uSe of glafs veffels, as  not being,  liable Chemical
 to be corroded by the moft  powerful Solvents ; and, Opera-
 by  their transparency,  giving an opportunity of ob- tions.  ^ ^
 Serving what pafles within them during the operation.
 But by thofe who practiSe chemiftry with a different
 view, theSe veffels ought,  with equal  care, tobea-
 voided,  on  accouut of their  expence and brittlenefs.
 This laft quality, indeed, is poffeffed  by glaSs  in So
 eminent a degree, that  glaSs veffels will  fometimes
 fly  to  pieces,  and  that  with  confiderable  violence,
 when  ftanding by themfelves, and nothing touching
 them.   The principle objects which a  chemift ought
 to have in view, in performing his operations, ought
 to be to Save time and fuel, efpecially the former ; and
 for this purpofe,  he would find  himfelf a confiderable
 gainer, though he fhould be  at much greater expence
 in his apparatus than he  would otherewife have occa-
 fion for.      _                                       S57
   On (he fubject of chemical  veffels Dr  Black ob- Dr llack's
 ferves, that l( with regard to the material of which obferva-
 thefe are compofed,  we are very much at a lofs ;  and tI0ns on
 indeed there are no fuch materials in  nature as are ca
 pable of anfwering the  purpofes of chemifts in abfo-
 lute perfection—The qualities  are,  1. Tranfpartncy
 to allow us to fee the changes going on ; 2. The power
 of refitting  the action of  acids and corrofive fubftan-
 ces ; 3. That they bear fudden alterations of heat and
 cold withont breaking ; 4. That they be ftrong, in order
 to confine elaftic vapours ; and, 5. That they bear very
 great heat without melting.  As thefe qualities, how-
 ever, are not to be met with united in any  one  fub-
 ftance, the  chemifts are  obliged to have recourfe to
 different fubftances  which polfiefs  fome of them  dif-
 ferently.  Thefe are, glafs, metal, and earthen ware. Gcoefand
 Glafs  is poffeffed of the  two firft properties, but  has bad quali-
 the  inconvenience of being  apt to crack and  fly in ties of g13^
 pieces, on any fudden tranfition from heat to cold, or af *1Tiite"
 from cold to  heat.   The beft method of remedying "haen ° ^
 this defect,  is to have the glafs  made very  thin, and veffels.
 of a round figure, that it may be all heated as equally
 as poflible ; ^s it is the unequal application of the heat
 which caufes it break. Another requifite in the choice
 of chemical glaffes, is that they be well  annealed.   If   .._
 this is not done,  the glafs will  either immediately fly Extreme
 to pieces, or be liable to break on  the  fmalleft acci- fragility o£
 dent.   That fuch glaffes fhould be  liable to be broken gl"fs »°t
 on every flight oceafion,  is a phenomenon that has hi- we!1 ai,ne*
 therto received no  explanation.  If you touch  them   '
 with a diamond, with a  piece of flint,  gfkfs, ire or
 expofe them to the heat of the fun,, they  break imme-
 diately.   Dr  Black has   had great veffels of glafs,
 which broke immediately on his  throwing a little find
 into them to clean them.  This manifcftly depends upon
 the fame  principles as the qualities of what are called
glafs tears.                                            s6a
  Glafs when welf annealed is  univerfally to be pre- Good and
 ferred, where great and  fndden changes  of  heat, or bad quali-
 much ftrength,  are not  required.   Flint-gfafs is  theties of me"
 beft  ; but the coarfer kinds,  as bottle-elafs, are vervta'* ^ m;v"
 apt  to break.                                       cheSc^
  The  metals  have  the third  and  fourth  qualities vefleU.
 in perfection,  but are deficient in all  the reft.  The
 moft troublefome property is,  that they  are  liable
 to be corroded  by acids  and other bodies, as is the-
 cafe  with iron and   cogger ; though this is in fome-
                                           meafure
ss& 
   .<6i
Of earthen
varc.
72
Chemical  meafure remedied by tinning ; whicli, though it wants
Opcration*. (omc Qf the qualities  from its melting too Sum,  jet
          refills the action ot many acrid fubftances without be-
          ing fo readily injured by  them ;  but it is not entirely
          tree from  this  imperfection, and is liable to be fome-
          v. hat corroded  and rutted,  l.nicc operations, there-
          fore,  recourfe  is had to  filver and  e\en to gold  vef-
          fels.
             Earthen ware poffeffes only the fifth quality  in per-
          fection, viz. that of bearing a violent  heat without fu-
          lion.   The bails of thefe veffels is clay, which, when
          good, is very convenient for the formation of  veffels,
          and it has been ufed from the earlieft ages of  chemi-
          ftry for this purpofe.  The requifite  qualities  are, 1.
          A confiderable  degree  of toughnefs  when  mixed  with
          water.  2. A great degree of hardnefs when burnt in
          the fire with a violent degree of heat.  The beft kind
          of clay  thus contracts  a degree of hardnefs fcarce in-
          ferior  to flint, as is the cafe with that of which tobac-
          co-pipes are made  ; but moft other kinds, fuch as that
          of which bricks are conftructed, are  apt to melt with
          a ftrong heat into  a fpongy matter.  Clay, however,
          can feldoin be ufed alone ; for when burnt  to  ex-
          treme hardnefs, the veffels are very liable to crack.
          This is remedied by mixing land  reduced to  a parti-
          cular degree of finenefs, with  the clay of which the
          veffels are made.  For this purpofe  both the fineft
          and the coarfeft particles of  ihe fand muft be thrown
          away.
             Another fubftance Jcnown by the name of black
 a valuable lead, ufed in the making of pencils, refills the fire ex-
 material for ceedingly.   This, however, does not contain an ore
 Tome pur- of lead, but  fulphur, and  fome mineral  fubftances ;
          when mixed with clay,  however, it makes it refill the
           fire furprifingly.   But there arc fome particular cafes
          in which neither fand nor black lead can be ufed as a
          material ; for the fand is eafily corroded by acrid mat-
          ters, and the  black lead would produce other inconve-
          niences.   Clay is therefore to  be taken in its unburnt
          ftate,  reducing it  to a powder like fand ;  then burn-
          ing this powder with a  violent beat,  fo as.to convert it
          into  fand.   Mixing it then with raw clay, it  forms a
          compofition which anfwers very well  for making che-
          mical velfels, and  may be employed in thofe particular
          cafes where land  would not anfwer.  Pott of Berlin
           has written upon  the different kinds  of earthen ware
           proper to be employed in the conflruction of chemical
           velfels.   There is a French tranflation of it in four or
           five volumes.   In cafes where the utmoft compadtnefs
           of texture is required, procelain veffels are to be  cho-
C   H   E    M    I   S   T    R   Y.
Theory.
   56a
llaek lead
r
   563.
Porcelain
tv i'k Is
when to be fen ; which is compofed of the fineft clay, mixed with
ufe J.
564
a flony matter, that  has the quality  of  melting  in  a
violent heat, and  gives more compactuefs to the clay
1 ban it is naturally capable of receiving ; but thefe arc
rather too  cofllv for  moft operations.  Reaumur has
tan ' ht a way of converting glafs into porcelain.
  We fliall now proceed  to  a particular defcription
of each of the operations abovementioned.
  I.  Solution. By this is underftood the diftolving a
fem'd fubftance in a fiuid, fo as that the folid fhall totally
dii'jppear,  aid  become part  of a  tranfparent  liquor.
This operation r.ppfes j .1: ticularly to falts, earths, and
metals: as well -s to Several unctuous and inflammable
Subftmiccs.  For performing this operation  in  a Small
way, common vi 1  are in mauy calls Sufficient. Where
the folution is attended with clYcrvefence  and a dif- chemical
charge of  v-pours,  the long-necked glaties called Operations
niuti.tj/'.'.', or tK.t-heacs, (fig. 5. ), are neceflary.  Flo- £T~>'"~~~'
rencc ftaiks are indeed exceedingly well  adapted  f°r cxxxiv
this operation, «-* being of the proper lhape,  and ca-
p.ib'.e of Rearing heat fo well, that they may  be filled
with any flufti, and let on a common fire  like a me-
talline veflel.  Solution is much promoted by agitat. .:*
the velfel, and by heat.  In fome cafes, indeed, it uiil
not take  place till the mixture becomes-very hot ; and
in fuch cafes it will be proper  to make the fluid boil-
ing hot by iticlf, and then llowly to add the fubftance
to be diflolved.
   When large quantities of faline matter arc to  be
diflblved, metalline veffels muft be ufed : but before any
are made ufe of for  this purpofe, it  will be  neecll.uy
to make an experiment whether the fait receives any
impregnation from the metal of which the  \ef.el in-
tended to be  made ufe of is formed ; and  if  this  is
found to  be the cafe, it muft not be ufed.   The me-
tals  moft liable  to be  corroded by faline bodics^are
iron and copper ; and indeed, unltib it be for the fingle
purpofe of diffolving fixed alkaline falts,  iron velfels
fee 111 totally unfit for faline folutions of any kind. Cop-
per  v eil'els are alfo very liable  to be corroded, and to
communicate very mifchevous qualities to  the  liquors         7
which corrode them ;  for which reafon,   they  ought
never to be made ufe of for the purpofes of folution.
The metal leaft liable to be corroded, next to gold and
filver, is lead ; and therefore a chemift ought rather to
provide himfelf w ith leaden velfels than thofe of any         (
other metal.  But though lead is not apt to be corroded.
by many kinds of falts, there are fome which are found
to act upon it, and to form therewith a very dangerous
poifon.  The vegetable acid of  vinegar is  particularly
apt to receive a dangerous impregnation from this me-
tal ; and therefore no folution of any fait containing this
acid ought to be  made in leaden  veffels.  It appears to
be very little affected by the vitriolic or marine acids  ;
and therefore any faline fubftance containing either of
thefe acids may  be fafely enough diflblved in veflels
made of lead.
   Iu order to fave time  in  making folutions, the vef-
fels  ought  to be as large as poffible ;   though even in
this there  muft be a  certain limit: for two fmall vef-
fels  filled with water will fooner acquire the neceflary
degree of heat than one large one ; and in proportion
as the veflel is made more capacious, the fides and bot-
tom muft be thicker,  which confiderably increafes the
expence.  fifteen or  twenty Fnglifh gallons is the
utmoft capacity of which they ever will be required  ;
and is  rather above what will  on moft  occalions be
neceflary.   They  ought  to be  of a conical figure,
round at the bottom; and to  have a cover   of thick
 plate-iron  all around that part which is expofed to trie
 action of the fire, that the lead may not bend on the.ap-
plication of heat, which it would  otherwife  be  %try
apt  to do.  When the folution is to be made, the leaden
 vefTel is firft to be filled up with water fo far as 10 have
 room for the quantity of fait intended tote eiliolved t
 a fir  is then to be applied foas  to make  it boil:  and
 then the Lit is to be  added flowly, fo as Scarce ly to
 hinder the boiling ;  for if a great quantity  was thrown
 in at once, fo as to cool the liquor very  much, great
 par: of the fait would concrete on the bottom,  in fuch
                                                  a 
-». / -1rid cj Fluor
 -*■; Ar.srttic
 +d±.J}rrrt.r
 + @.S'uritr
 -t-c^ 7u7'lar
 +-§-Sorrcl
 +c Lemon
 + 3fJ3cnzoL/i
         (he mis try:
Ctjctaical Characters or Symbols.
Plate   CXXX1IL.
^(j^Aiiibet:
+@ Su par of Midi.
-*- I intent:         »
 ©Milk.
+fAnU
+0 ./to
+^ Phosphorus.
& A</ial.
■6 Colourin^mallero
  Pruiji/ntJfltie falsely
  called an Aeid.
^Phlooisticated ncri-
   olicAcid l/jc same ud
   tot SulphureoasArid.
  ^])ephlo£tsticated
   MarineAcid'.
oAlirfiJ vegetable
  AJlcali.
&/2FineratAltait.
% Fendctoias Forth.
tiPure Air
QiPlalina.
fchFaiwanese.
^SFelalltc calr.
Sjia.iO.    ^dta.Ji.
>arl;ara U laTlenire Sculp 
 
 Theory.                            C   H    E   M
 Chemical  a manner as not only to be very difficultly foluble, but
 Operations even endanger the melting oS the velfel.   It is of fome
 w"~,"—-"' conSequence alSo to avoid the hot Steam which proceeds
          from the boiling water, and which iffues with great
          force from a narrow-mouthed velfel,  fuch as we  have
          been defcribing.   That the operator may be out of the
          reach of this, and likewiSe diflblve the Salt in a regular
          and  gradual manner,  without any danger oS its concre-
          ting on the bottom, it will be proper to  have a leaden,
          or even a wooden, veflel, with a long handle ;  which
          is to be filled with the  fubftance to be diflblved,  then
          immerSed in  the  boiling liquor, and fhaken about in
          it,  till the Salt is made into a kind oS thick pap, which
          will be in no danger of  concreting.  It  will alfo  be
          proper not to faturate the water perfectly with  fait;
          for  it will in that cafe be impoffible to hinder part of
          it from fettling  on the bottom, where it Soon acquires
          Such a degree oS heat as to melt the lead.   Before any
          Saline Subftance  is put into water Sor Solution, it ought
          to be pounded and fiSted through a hair Sieve.
            Where large quantities oS metal are to be diffolved
          in acids,  eSpecially the nitrous acid, glafs veffels are in
          a  manner indiSpenSable ;  although the common Stone-
          ware bottles, efpecially thoSe made in Holland, will an-
          fwer the purpofe very well, as not being  liable to cor -
          rofion,  and not So apt to break as the glaSs veffels are.
          They may be got of Such a Size as to hold three or Sour
          gallons :  but no veflel in which metalline  Solutions are
          made ought ever to be above half full.
            In Solutions of oily and inflammable fubftances, caft
          iron veffels are perhaps the moft proper oS any ; though
          copper ones  are generally preferred.  The copper is
          exceffively foluble in oil,  eSpecially if it is left to cool
          in fuch a veflel;  but iron is not foluble in any inflam-
          mable  matter except fulphur.   Copper has, however,
          this advantage over iron, that it is fooner cooled, as the
          veffels made of  copper are thinner than  they  can  be
          made of  caft iron :  fo that if too great heat is applied
         •to a copper veflel, it may be eafily remedied by taking
          it off the-fire ; but in a caft iron veflel the heat conti-
          nues fo long as may fometimes produce dangerous con-
   56s    fequences, even after the fire is removed.
Dr Black's  Dr Black obferves, that for the purpofe of folution,
directions  if no particular nor uncommon confequence follow the
for folu-   application of the two bodies  to each other,  and if
          none of them be very volatile, any glafs  or porcelain
          veflel that can refift the action of the fubftances will an-
          fwer the purpoSe ;  but it oSten happens that they break
          out into violent ebullition, which produces fteam ; and
         here a common veflel is not fo  proper, as we would
         wifh to have the vapour confined or condenSed.  We
          therefore  chooSe a clofe veflel  that will  bear the  heat
          fuddenly produced by the mixture, or the heat that
         may be neceflary to promote the action of fuch bodies
         upon one another.   Of this kind is the phiala chemica,
         or matrafs, in which the vapours will have time to cir-
         culate and to be condenSed again, without being allowed
         to eScape.  Where the matter is in Small quantity,
         Smaller velfels Somewhat of the fame form are ufed, as
          Florentine flafks, which bear fudden changes of heat
          and cold remarkably  well, on account of their hinnefs.
          In order to promote the action of bodies, it is fometimes
         neceffary to make the fluids boil; and for  this purpofe
         we muft have a matrafs with  a  large neck, or apply
I   S   T    R   Y.                                   73
 another veflel to it that will receive thefe fteams,  and Chemical
 give them ftill more room for their condenfation,  and Operations
 direct them to fall back  again, when, condenfed, into
 the matrafs.  This is called circulation.   Macquer de-   566
 Scribes another velfel  called the pelican,  which  has Pelican.
 been made  ufe  of for this purpofe; but it is  hardly F'S-  "•
 ever employed, on account of its being fo troubleSome
 to procure and manage it; and the advantages  arifing
 from it may be obtained by a more fimple apparatus.      567
    To this head we muft refer Papin's digefter,  which Papin's di-
 is reprefented Fig. 4.  It, is generally made of cop- gefter.
 per, very thick and ftrong, open  at  the top, with pJf4VTIT
 a lid fitted  to it, which applies very exactly.   There
 are ufually  two  projections on the fide,   defigned
 to make the lid  go in a  particular manner, but they
 are unneceflary.  There are other two, to which  are
 fitted the two  fides of a crofs bar B B ;  in which crofs
 bar there is a ftrong fcrew D, by which the lid  can be
 prefled down  very ftrongly.  Its ufe is to force wa-
 ter to bear  a ftronger heat than it  can  do under the
 ordinary preffure of  the atmofphere.  It is fometimes
 furnilhed with an apparatus  for letting out  the  fteam,
 left it fhould be in danger of burfting the veffel. A pipe
 is palfied through the lid  which is fitted with a  valve,
 on which paffes a lever at a very fmall diftance from its
 centre of motion ; and this can be made to prefif.on the
 valve with different weights, according to the diftance
 of thefe weights from the centre.  In one conftructed
 by Dr Black, there was another pipe below, into which
 a thermometer could  be introduced, in order  to mea-
 fure the degree of heat to which the fteam was  raifed.
 This machine was pretty much employed  fome time
 ago, and its effects were much  admired ; but we find
 that  moft  things which can be diflblved in this way,
 can likewife be diffolved  in the ordinary way by boil-
 ing water,  provided it is  continued for a longer time,
 as animal bones, from which the gelatinous parts are
 indeed extracted very quickly by this veffel; but the
 fame change is produced by boiling them in water for a
 long time  in the ordinary degree of heat.                ^8
    II. Filtration.   This operation is generally the Filtration.
 attendant of folution : very few fubftances, of the faline
 kind efpecially,are capableof being diflblved without lea-
 ving fome impurities,from which they muft be freed; and
 the doing of this, fo as to render the folution perfectly
 transparent, is what is underftood by the word filtration.
    For  purpoSes  merely experimental,  a glaSs  funnel
 and piece of paper are generally fufficient.   The pa-
 per is formed into a conical cap, which being placed in
 the funnel with its point downwards, the funnel is then
 placed  in the mouth of  a vial ; and the  folution or
 other liquor to be filtered is poured into the paper cap,
 through which the liquor  pafles transparent, leaving its
 impurities on the paper.   For the purpofe of filtration,
 paper has come into fuch  general tuc, that a particular
 kind of it is prepared  under the name of filtering paper.
 This is of a reddifh colour ; but Dr Lewis prefers the
 whitifh grey paper which comes from Holland about
 the pill boxes, as not giving any colour to the folutions
 which pafs through it.
    This operation though apparently fo fimple and eafy,
 is nevertheless attended with very troublefome circum-
 ftances, on account of the great time it takes up.  Even
 where very fmall quantities of liquor are to be filtered,
                         K                  merely 
74
C   H   E    M    I   S   T    R   Y.
neon'
Chemical  merely for experiment's fake, the impurities frequently
?r^""» fettle o\\ the paper fo (y 0:1, and obltruct its pores to fuch
          a degree, that the operator is often quite wearied out :
          oncn,  too, the piper breaks ; and  thus the whole is
          Spoiled, and the operation muft be begun over  again.
            To avoid  theSe inconveniences,  another method oS
          filtration has  been propofed; namely,  to uSe  a num-
          ber of cotton threads, the ends of wiii-fti are to be im-
          merled  in the liquor,  and the other ends are  to hang
          over the fide  of the velfel which  contains it, and to
          Jung lower  than the  furface of the liquor.   By  this
          means they will aft as fo many capil.ary Syphons,  (See
          Syphon); the liqjor willariSe in them quite pure, and
          be discharged Sroni their lower extremities into a veffel
          placed to receive  it.  That the  liquor may flow free-
          ly into the cotton,  it will be proper to wet the threads
          bcSore they are tiled.
            1  point of  efficacy, no doubt, this method excels
          every other; and where the operator has abundance
          of time and patience,  may be proper for  experiments;
          but,  in the way of trade,  Such  a contrivance is  evi-
          dently uSeleSs.   For filtering large quantities of liquor,
          therefore, rccourfe has  been had to large  funnels ;
          earthen cullenders, or bafons full of holes in the  bot-
          tom, lined with filtering paper;  and to conical bags of
          flannel or canvas
            The inconveniences attending funnels, when ufed
          only in the way of  experiment,   are  much  greater
          when they are employed for  filtering large quantities
          of liquor ; and therefore they are generally laid afidc.
          The earthen cullenders,  too, do not anfvver any good
          purpofe ; nor indeed does filtration through paper in
          general  fucceed well.   The conical flannel or canvas
          bags are greatly preferable : but they  have  this  in-
          convenience,  that the preflurc ofthe liquor is directed
          chiefly againft one particular point, or a fmall  part of
          t\\e  bottom,  and therefore the impurities are forcibly
          driven into  that place ;  and  thus  the  operation  be-
          comes inl'ufferably tedious.
            The beft method of obviating the inconveniences
          of filtration feems to be the following.   Let a wooden
          frame of about  three feet fquare  be made,   having
          four holes, one in each corner, about three quarters of
          an inch in diameter.  This  frame  is  to be fupported
          by four feet,  the ends of which  muft  project an inch
          or two  through the holes.   Thus  the  whole  may be
          occasionally Set up and taken  down So  as to  go into
          very little compals; for if the  feet are  properly pla-
          ced,  each with a little projection outwards,  there will
          be no danger of its falling.   A  fquare piece  of can-
          vas  muft alfo  be  procured,  fomewhat  lefs than  the
          wooden frame.  On each corner of it there muft  be
          a very ftrong loop, which flips on one of the project-
          ing ends of the feet, fo that the canvas may hang a
          little flack in the middle of the frame.  The liquor to
          be filter«d is  now  poured  into the canvas,  and a vef-
          fel placed underneath to receive it.  At firft  it will
          pafs through very  foul ;  but  being returned  two  or
          three times will become perfectly  tranfparent,  and
          will continue to run with great velocity, if the filter
          ;s kept conftantly full.  A filter of the  Size juft now
          mentioned will  contain ten gallons oS liquid ; which is
         a very great advantage, as the heat of fuch a quantity
         of liquor is not foon diflipated, and every folution fil-
         ters much fafter when hot than when allowed to cool.
   "1 he advantages of a filter of this kind .ft-cve others Chemical
 arile from the preffure of the liquor being more equally Operation*
 ditmfed over a large fpace, by which the impurities are '    *
 not forced foftronglyintotheclothas to flop it up entire-
 ly.  Y et even here, where large quantities of liquor re-
 quire filtration, the cloth is apt to be flopped up So as to
 make the operation not a little tedious and difagreeable.
 It will  be proper therefore to have Several cloths,  that
 one may  be applied as foon as another is taken off.
   To promote  the operation of nitration, it  is very
 proper  to let the liquors to be  filtrated fettle for fome
 time ; that fo their grofler feculencics may fall to the
 bottom, and thus there will be the fewer to retard the
 laft  part ofthe operation.  Sometimes, however, thefe
 feculcncies rcfufe  to fettle till after a very long time ;
 and  w here this happens to be  the cafe,  a little pow-
 dered quicklime thrown into the boiling liquor remark-
 ably  promotes the feparation.   This,  however,  can
 only be ufed in certain cafes.                             ,
   In fome cafes, the difcovery of a ready way of fil- schemes
 tering a large quantity of liquor would be a matter of forfiltering
 great confequence ; as where a town is  fupplicd with large quan-
 river water,  which is generally far from being clear, titiesof
 and  often imparts  a diSagreeable  colour to   clotheswatcr-
 walhed  with it.  Some years ago, a Scheme was pro-
 poSed by  a chemift Sor filtering muddy water  in  any
 quantity.   His method was, to have a large  cafk co-
 vered over in the  bottom with  ftraw to the depth of
 Some inches, and then filled up with Sand.  This cafk
 v/as entirely open  at  one end, and had  a hole in  the
 other, which, by means of a  leaden pife> commu-
 nicated  with a large  refervoir of  the water to be fil-
 tered, and whicli  flood considerably  higher than  the
 cafk.  The water which defcended through the pipe
 into the cafk,  having a tendency to riSe up to the fame
 level with that in the rcScrvoir, would prefs violently
 againft  the fand,  and, as he thought, run over  the
 mouth of the cafk perfectly filtrated, and free from its
 impurities.  By this contrivance,  indeed, a very vio-
 lent  preffure was occafioned,  iS the height of the  re-
 fervoir was confiderable : but the confequence was,  not
 a filtration, but a greater degree of impurity in the wa-
 ter ;  for the fand was forced out of the cafk along with
 it, and, however confined, the water always arofe as
 muddy as  it went in.
  Where water is to  be filtered in large qnantity, as
 for the purpofes of a family, a particular kind of foft
 fpongy  ftones called  filtering ftones,  are employed.
 Thefe, however, though the water percolates through
 them very fine, and in fufficient quantity at firft,  are
 liable to be obftructed in the fame manner as  paper,
 and are  then rendered ufelefs.  A better method feems
 to be, to have  a wooden veffel, lined with lead,  three
 or four feet wide at top, but tapering fo as to end in a
fmall orifice at the bottom.  The under part  of  the
 veflel is to be filled with very rough  fand, or  gravel,
well  freed from earth by waffling.   Over this,  pretty
fine fand may be laid to the depth of 12 or 14  inches,
but which muft likewife be well freed  from  earthy
particles.  The veflel may then be filledup to the top with
water, pouring itgently at firft, left the fand fhould be too
much difplaced. It will foon filter thro'the fand,  and
run out at the lower orifice exceedingly tranfparent, and
likewife in very confiderable quantity.  When the upper
part of the fand begins to be flopped up, fo as not to allow 
Theory. %
CHEMISTRY.
Chemical  a free paffage to the water, it may occafionally be taken
Operations off, and the earthy matter wafhed from it, when it will
         be equally Serviceable as before.
            III. Precipitation or Coagulation. Thisope-
         ratiomis the very reverfe of folution, and is the bringing
         a body fuddenly from a fluid  to a Solid ftate.  It differs
         from cryftallization, in that  it generally requires lefs
         time ; and in cryftallization  the Subftance aflumes re-
         gular figures, whereas precipitates are always  in the
         form of powders.
            Precipitation is generally preceded by folution  and
         filtration :  it is ufed for feparating  earths  and metals
         from the acids which had kept them fufpended.  When
         a  precipitation is made of  the more valuable metals,
         glafs veffels are  to  be ufed.  When earths,  or  the
         imperfect metallic fubftances, are to be precipitated in
         large quantity, wooden ones anfwer every purpofe.
         If a metal is to be precipitated  by an alkali, this fait
         muft firft  be diflblved  in  water, then filtered,  and
         gradually added  to the metallic folution. If particular
         circtMnftances do not forbid, the fait for precipitation
         fhould be chofen  in its cauftic ftate, or  deprived of its
         fixed air,  becaufe then a very troublefome  effervef-
         cence is  avoided.  To promote  the operation alfo,
         the mixture, if contained in a glafs, is to be fhaken ;
         or if in any other veffels, to be well Stirred after every
         addition of alkali.   If an earth is employed to precipi-
         tate  a metal, the mixture  muft be in a manner con-
         ftantly ftirred or  fhaken, in order to promote the pre-
         cipitation ;  and if one metal is to be precipitated by
         another, that  which is ufed as a precipitant muft be
         beaten into thin  plates, that fo they may be frequent-
         ly cleaned from  the precipitating metal, which would
         otherwife  very foon totally  impede the operation.
            Sometimes a precipitation enfues on the addition of
         water or Spirit of wine : but in moft caSes  care muft
         be taken not to add too much of the Subftance which
         is uSed to  precipitate the  other ; becauSe,  in Such a
         caSe, the precipitate may be diflblved aSter it  has been
          thrown down.   Thus, though  volatile alkali will  Se-
         parate  copper from aquafortis, it will  as  effectually
         diffolve the precipitate, if too much of it is ufed, as the
         acid itfelf.  It is proper,  therefore, to proceed cauti-
          oufly, and  examine a fmall quantity of the liquor from
          time to time.   If an addition ofthe precipitant  throws
          down any more,   it  will be  proper to  add fome more
         to the whole folution.
            It is Seldom or never that  precipitation  can  be per-
         formed fo perfectly, but that one  or other of  the  in-
         gredients will prevail ;  and though they fhould no:, a
         new compound, confifting of the acid  united with the
         alkali,  or  other  fubftance  uSed  for precipitation, is
         contained in the liquor through which  the precipitate
         falls.  It is proper, therefore, to wafli all precipitates ;
         otherwife they can never be obtained perfectly pure,
         or free from a mixture of faline Subftances.  This is
         beft done by pouring the whole  into  a filter,  and let-
         ting the fluid part run off, as long as it will drop, with-
         out fhaking the  cloth.   Some water is then to  be Gau-
         tioufty poured all over  the  furSace oS the  precipitate,
         So as to difturbit as little as  poflible.  This water will
         pufii before it the Saline liquor which is mixed with
         the powder, and  render it  much purer than  before.
         A Second or third quantity oS  water may be uSed, in
   57i
Edulcora
tien.
                                                          /:>
order to wajh off all the Saline matter.  This is called Chemical
edulcorating the precipitate.                      _    Operation*
   IV. Evaporation. This operation confifts in diffi-    57l
pating the moift fluid or volatile parts of any fubftance Evapora-
by means of heat.  It moft  generally fucceeds folu- tion.
tion and filtration, being a preparatory for the opera-
tion of cryftallization.
   For the evaporation of faline folutions,  which  have-
been already filtered, and which it is of  confequence
to  preferVe from  even  the  leaft impurities, diftilling
veffels are unqueftionably the moft proper ;  both as,
by their means, the folution  will be kept  perfectly
free from duft, and as the quantity of liquor evaporated
can be known with certainty by meafuring that which
comes over.   This alfo is probably the moft  expediti-
ous method oS evaporating, and which requires the leaft
fuel.  (See the detached articles Evaporation and
Distillation). Withregard to veffels for evapora-          ;
tion, the fame thing muft be applicable which was men-
tioned above under Solution. No faline liquor muft be
evaporated in a veffel which would be corroded by it;
and hence .iron veffels are abfolutely improper for eva-
porations of  any  kind  of  faline liquor whatever.—
Lead is in this cafe the metal moft generally uSeful. It
muft only be  ufed, however,  where  the   evaporation
is not carried  to drynefs ; for, on accountof the great
fuftbility  of this metal,  nothing could be exiiccated in
it without great danger  of its melting.   Where a fa-
line liquor therefore is  to be perfectly exficcated, the
evaporation, if performed in lead veffels,  muft be car-
ried on fo  far only as to forma faline pellicle on the
Surface of the liquor.  It is then to be drawn off; for
which purpoSe, all  evaporating veffels fhould have a
cock near the bottom.  The liquor muft  now be put
into a number of Stone-ware baSons, Set on warm Sand,
where the exficcation may be finished.                  5j^,
   V. Crystallization.  This,  though commonly Cryflalti~
accounted one ofthe proceffes in chemiftry, is in reali- zation.
ty only a natural one, and which the chemifl can only
prepare for, leaving the operation entirely  in the hands
of nature.—By cryftallization is meant the Separation
of a fait from the water in which it has been diflblved, in
transparent maffes regularly figured, and differently for-
mfcd, according to the different nature of the falts.
   This procefs depends upon  the  conflitution of the
atmofphere more than  any other ;  and  therefore is
difficult to be  performed, nor  does  it  always Succeed
equally well; neither have there  yet been laid down
any rules whereby beautiful and regular  cryftals  can
with certainty be formed at all times.
   As the different falts  affume very  different figures
when cryftallized, they are not fubject to  the fame ge-
neral rules in cryftallization.   Nitre, Glauber's fait,
vitriol of iron, and  many others,  cryftallize  beft on
having their Solutions Set in a cold place aSter proper
. evaporation.  Sal polychreft, and common Salt, require
the Solution to be  kept as hot as the* hand can bear it
during the time of crystallizing.  Soluble tartar too,
and other deliquefcent falts, require to be  kept  warm
while this operation is going on :  and there are many
faline  fubftances,  fuch as the  combinations  of calca-
reous earths and magnefia with acids, which can fcarce-
ly be cryftallized  at all.
   Mr Beaunvi has difcovered, that when two or more
                         K  3-                  falta. 
C   H   E   M    I   S   T    R   Y.
76  .
Chrmical   Salts are diffolved in the Same quantity of w.tur, when
Q,»crjtiontonc  cryftaliize>, the cryftals of that fait will not cou-
       "" tain the leaft  quantity i.f .my of the others : neither,
          although the liquor was acid or aikaline, will the cry-
          ftals for that reafon be cither acid or alkaline, but will
          remain perfectly neutral;  and the acid or alkaline li-
          qneir which ulncrcsto the outfidc  ofthe cryftals may
          be abforbed by merely Spreading them on filtering pa-
          per.—Hence  wc are  furnilhed with  a  better method
          of mooting falts into large and well formed cryftals than
          merely by diffolving them in water ; namely, by ad-
          ding to the folutions,  when fet to cryftallize, a certain
          quantity of acid or alkaline liquor, according to the
          nature ofthe falts themfelves.  Thefe additions, how-
          ever, are not  equally proper for all falts ; and  it is not
          yet determined  what kinds of falts ought  to be cry-
          ftallized in  alkaline,  and what in  acid  liquors.—So-
          luble tartar and Seignette's fait cryftallize  beft when
          the liquor is alkaline. Sal Sedativus, Sal Glauberi, and
          Sal polychreft, require an acid if  cryftallized in  the
          cold ; but fal polychreft forms into  very fine and large
          cryftals when the folution is alkaline, and  kept as hot
          as the hand can eafily bear.
            The beft  general direction that can be given with re-
          gard to the  regular cryftallization of falts is, that they
          ought to be  fet  to cryftallize in as large a  quantity at
          once as poflible  ;  and this, as far as we  have obferved,
          without any limit ; for by this means, the  cryftals are
          formed much  larger and  better figured than they poS-
          fibly can be by  any other method hitherto known.—
          As to the form of the vcifds in which falts are  to  be
          cryftallized, little can be faid with certainty. They are
          generally flat, and wider at top than at the bottom. The
          only proper material, in  the large way, is lead.
            VI. Dis  tillation. This isakind of evaporation  ;
          only in fuch a manner,  that the part of the liquor eva-
          porated is not diflipated in the  air, but  preferved  by
          making the fteam paSs through  a  Spiral pipe, which
          goes through a large  veffel full of cold water,  or  into
          cold  glafsrcceivers.
            This is one of the moft common chemical operations  ;
          and as there are a variety of fubjects which require to
          be diftilled, there is confequently  a confiderable variety
          both in the form of the  diftilling veffels to be ufed on
          different  occ.tfions,  and likewife in  the materials of
          which they are  made, as  well as  the management of
          the fire during  the time  ofthe operation.
            The moft fimple  and  ealily  performed  diftillation
          is that by the common copper ftill, (fig. 3).   It con-
         ' Sifts of two parts ; one called the body,  and the other
          the hea.'.   The body  is a  cylindrical  veflel of cop-
          per,  which  is  fometimes tinned  over in  the infide  ;
          but where diftillation is performed without  any re-
          gard to the refiduum, the tinning is ufelefs.  The up-
          per part oS  the  body terminates in a kind  of  arch, in
          tiie middle of which is  a circular aperture, about one
          half, or fomething lefs,  in diameter, of the breadth of
          the whole body.—Into  this aperture,  a round head,
          ma !e likewife o: copper, is fitted, fo as to  be remove-
          able at pleaSure.  In the top,  or Sometimes in the fide
          ofthe head,  is inferted a pew tcr pipe,  w hich commu-
          nicates with a Spiral one  01" the fame metal, that  pafles
          through a large wooden veflel, called the refrigeratory,
          filled with cold  water;  each oS its ends projecting  a
          little above and  below.   The  ftill is  to be ST. J  two-
          thirds  full of the Subftance to be diftilled, the head put
M heoiy.
   •$■4
Diftilh-
tion.
   Plate
CXXXIV
on,  and  the junctures well clofcd  with mixture  of Chemical
lintfccd meal and water, or common flour or chalk and Opt rations
water  will anfwer  the  Same purpofe.  This  mixture
is called the luting, or lute  A  fire being kindled un-
der the ftill, the vapours will ariSc ;  and, being con-
denfed by the cold water,  through which the Spiral
pipe called the worm  paffes,  will  run in a  ftream
more or lefts ftrong as the fire  is  more or leSs  haflily
ur^ed, and  is  catched in  a  receiver  Set underneath.
   This kind of diftilling veflels is  proper for procuring
the effential oils of vegetables,  vinous Spirits from fer-
mented liquor, and for the rectification of thefe after
they are once diftilled.   Even the acetous acid may
be very conveniently diftilled in a copper  veffel, pro-
vided the  worm and all the defcending  parts  of the
pipe which communicates  with it  be of pewter, other-
wife a miSchievous impregnation of  copper would be
communicated  to the diftilled  vinegar.   The  reafon
of this is, that copper is  not diffolved by vinegar,  or
in very fmall quantity,  when that acid is  boiled in it;
but if the metal is expofed  to  the action of  the acid,    »
when  cold, or  to  its vapours,  a  confiderable dillblu-
lution takes place. For this reafon, too, the ftill muft  be
wafhed out after  the operation  while it continues hot,
and muft be very carefully  freed from the leaft remains
of acid, otherwife it will be much corroded.
   Copper-ftills ought to  be of as large a Size as pof-
fible : but Dr Lewis very juftly obferves, that, in com-
mon ones, the width of the worm is by no means pro-
portionable  to the  capacity of the ftill: hence the va-
pour which iffues from  a  large furface being  violently
forced through a fmall tube, meets with fo much re-
finance as fometimes to  blow off the Still-head.  This
inconvenience is ridiculoufly endeavoured to be pie-
vented  by ftrongly tying or otherwife Sorcing down
the head ; by  which means, if the worm fhould hap-
pen  to be  choaked up,  a  terrible  explofion  would
enSue :  for  no ligatures,  or any other obftacle what-
ever, have yet been Sound ftrong enough to refill the
elaftic force of fleam , and the greater obftacle  it has
to overcome, the  greater would the  explofion be.—
Dangers of this kind might be totally avoided by ha-
ving the worm of a proper degree of  wideneSs.           575
   Sometimes,  however,  matters  are to  be  diftilled, Mineral a-
Such as mineral acid Spirits, which would  corrode any ci.ds. now
kind of metalline veflels; and for thefe only earths,  or <hftjllod-
the clofeft kind of  ftone-ware, can be ufed.   Thefe
are more eafily condenfed  than  the fteams of aqueous
or vinous liquors, and therefore do not require to be
paffed  through a pipe of fuch  a length as  is  ufed for
condenfing the fteams from the commonftill. Intbcfe
caSes,  where a violent heat  is  not neceflary, and.the    576
diftillation is to be performed in glafs veflels,  the re- Retort.
tort  is ufed (fig. 4.)  Whena fluid is  to be put into
this velfel,  the  retort muft be laid  upon its back on
fand, or  any  other foft matter  that will Support  it
without  breaking.   A  funnel  muft  alfo  be procured
with alongftem, and a little crooked at the extremi-
ty, that the liquor may  pafs at once into the  belly  of
the retort,  without  touching any part of its  neck ;
otherwife the  quantity  which  adhered to the neck
would pafs into the receiver when the retort  was pla-
ced in  a  proper  fituation  for diftilling,  and foul the
produce.  \\ hen the veffel is properly filled,  which
ought never to be above two-thirds,  it is to  be f   in
a fand-bath : that is, in an iron  pot, of a proper thiek-
                                             nefs, 
Theory.
CHEMISTRY.
11
Chemical  nefs, and covered over in  the bottom,  to  the deph
Operations, of one or two inches, with dry fand.   When the re-
*   *   ' tort is put in, fo as to ftand on its bottom, the pot is to
         be filled up with Sand, as far as the neck of the retort.
         A glafs receiver is then to be applied, which ought to be
         as large as poflible, and likewife pretty ftrong; for which
         reafon it will be proper not to let the capacity of it be
         above what is neceflary to hold ten gallons.  In the hin-
         der part  of it fhould be drilled a Small  hole,  which
         may be occafionally flint by a Small wooden peg.   The
         mouth of the receiver ought to be fo wide as to let the
         nofe oS the retort enter to the middle oS it, or very near
         t© it; for if the vapours are difcharged very near the
         luting, they  will act upon it much more  ftrongly than
         when at a diftance.   It is likewife proper to  have the
         neck of the retort as wide as may be ; for this has a
         very great effect in the condenfation, by prefenting a
   577   larger furface to the  condenfing vapour.
Luting for   The luting  for acid Spirits  ought to be very diffe-
acid fpitits. rent from that uSed in other diftillations ; for thefe will
          penetrate the common lutes So as to make them  liquid
          and fall down into  the receiver.   Some  have uSed re-
          torts the necks oS which  were ground  to the  recei-
          vers with emery;  but thefe are very difficult  to  be
          procured, and  are  expenlive, and  consequently have
          never come into a  general uSe.  Various  kinds oS
          lutes have been propoSed, but the preference feems due
          to  a mixture of clay  and fand.   We are not  to under-
          stand, however, that every kind of clay is fit for  this
          purpofe  : it  muft only be fuch as is not at all, or very
          little, affected by acids ; and this quality is only poflef-
          ied by that kind of which tobacco-pipes is made.  Trial
          ought to be made oS this  before  the  diftillation is be-
          gun, by pouring a little  nitrous acid  on the clay in-
          tended to be made ufe of.  If a violent efferveScence
          is raiSed, we may be Sure that the clay is unfit Sor the
          purpoSe.  Finely powdered alabafter  would  anSwer
          extremely well, had it the ductility of clay.   As this
          kind  of lute remains foft for  a confiderable time, it
          ought to be farther Secured by a bit of rag Spread with
          fome  ftrong cement, fuch as  quicklime mixed with
          the white of an egg, ire.   Matters,  however, ought
          to be managed in fuch a  manner, that the luting may
          give way, rather than the veffel burft;  which, would
          not only occafion a certain loSs of the  materials,  but
          might endanger the perSons who are ftanding by.
   57?     The iron  pots commonly uSed for diftillations by the
 Balneum a- fan(j_Dath, or balneum arena:, are commonly made very
 ren*'      thick ; and  are to be Sold  at large Sounderies, under
          the name of fand-pots.  The fhape of theSe, however,
          is  by no means eligible:  for, as they are of a figure
          nearly cylindrical, if the retort is of fuch a fize as al-
          moft to fill their cavity, it cannot be  put into  them
          when full, and often pretty heavy, without great dan-
          ger of touching the fides of the pot;  and in  this cafe,
          touching and breaking are Synonymous expreflions.  It
          is much better, therefore, to have  them in  the figure
          of a punch-bowl ; and the common  caft-iron  kettles,
          which may  be had much cheaper than the Sand-pots
          ufually fold, anSwer  extremely well.   If the diftilling
          veffel is placed in a pot filled with water, the  diftilla-
          tion is faid to be performed in a water-bath,  or bal-
          neum mariee.
             When the matter  to be condenfed is very volatile,
          a number of open receivers with two necks, called a-
dopters (fig. 7.) may be ufed, with aclofe receiver at the Chemical
end.  Each of thefe adopters muft be luted with as much Opcratien»
care as when only a fingle receiver is made ufe of.  Vef-    .11
Sels of a fimilar kind were formerly much ufed by chemifts Adopters
for particular Sublimations, under the name of aludels. of aludels.
   Formerly, inftead of retorts, a veflel called 2. cucurbit,
(fig. 5, and 6.) with a head like the common ftill, called
an ale7nbic, were uSed; but the  more  fimple figure cf
the retort gives it  greatly the preSerence.  It  is  but
Seldom that veffels  of this kind are ufeful,  which  will
be taken notice of when defcribing the particular ope-
rations ;  and if at any time an alembic head fhould be
neceflary,  its ufe may  be fuperfeded by a "crooked
glafs tube, which will anfwer the purpofe equally well.
   Sometimes a very  violent fire is required in  diftil-
lations by the retrot.  Here,  where it is poflible, glafs
or earthen veffels fhould be avoided, and iron pots  Sub-
ftituted in their ftead.  The hardeft and beft caft iron,
however, will  at laft melt by a vehement heat;  and
therefore there  is  a neceflity for ufing earthen ware,
or coated glaSs.  This laft is  better  than moft  kinds
of earthen ware, as being leSs porous ; for when the
veffel is urged by a very intenSe heat,  the glaSs  melts,
and forms a kind of femivitreous compound with  the
infide of the coating, fo that its figure  is ftill  preser-
ved, and the accidental cracks in the luting are filled up.    cg0
   For coating of veflels, mixtures  oS colcothar  of vi- Coasting of
triol, fand, iron filings, blood, chopped hair, ire. have glaffes.
been recommended.   We cannot help thinking, how-
ever, that the fimple mixture oS tobacco-pipe clay and
Sand is preferable  to any other;  eSpecially if,  as Dr
Black directs, that part next the glaSs is  mixed with
charcoal drift.
   The proportions recommended by  the  Doctor  for
luting the joints of veflels, are  four parts  of fand  aud
one of clay ; but for lining the iniides of furnaces, and
we fhould think, likewife for coating  glafs veffels, he
directs 6 or 7 of fand to  1 of clay, that the contrac-
tion of  the clay in drying may thereby be the more
effectually prevented.  Befides this, he directs a mix-
ture of three parts of charcoal-duft with one of  clay
to be put next the furnace itfelf, as being  more apt to
confine  the  heat;  but  poffibly the  firft  compofition
might be Sufficient for glaffes.
   The coating of large glaffes muft be a very trouble-
Some and  tedious  operation ;  and therefore   coated
glaSs is never uSed but in experiments.  When large
diftillations are to  be performed in the way of trade,
recourSe muft be had either to iron pots, or to earthen
ware.   OS the moft proper kinds of earthen ware for
refifting violents heat,  w7e fhall take  notice under the
article  Fufton.
   In all diftillations by the retort,  a confiderable quan
tity of air,or other  incondenfible  vapour, is extrica-
ted ; and to this it is absolutely neceflary to give vent,
or the veffel would be burft, or the  receiver  thrown
off.  For this purpofe,  Dr Lewis recommends an  open
pipe to be  inferted at the luting, of fuch an height as
will not allow any ofthe vapour to  eScape ;  but this
wTe cannot approve of, as by that means  a eonftant
 communication is  formed between the external atmo-
 fphere and the matters contained in the retort  and
 receiver,  wftiich is at all times to be avoided  as much
 as poflible, and in fome caSes, as the diftillation of phof-
 phorus, would  be  very dangerous.   The having  a
                                               fmall 
                            CHEMI
fm.ill  h de el rilled in the receiver, which is to be now
and then opened, mult aufwer the purpofe much bet-
ter, although  it takes nunc attendance ; but if the ope-
rator  is  obliged to leave  the veflels for fome time, it
will be con\ client cither to leave  the  little hole open,
or to  contrive it £b that the wooden peg may be pu'.hed
out with lets  force than is Sn.'licieut to break the lute.
   VII.  St- b 1.1 mat I on.  This, properly Speaking, is
only the diftillation of a dry Subftance ; and therefore,
when volatile matters, Such as Salt oS hartihorn, arc to
be Sublimed, theopcration is performed in aglal's retort
Set in a Sand-bath; and the Salt paffes over into the  re-
ceiver,   -l'hc cucurbit and alembic were formerly much
in uSe for this purpoSe ; and a blind head, without any
Spout, was applied. A much Simpler apparatus, however,
is now made  ufe oS.  A globe made oS very thin glaSs,
or an oblong veffel oSthe fame kind, anfwers the more
common purpoSes oS  Sublimation.  For experiments,
Florence flafks are  excellent: as being  both  very
cheap, and having the neceffary fliape and thinnefs  re-
quifite for bearing the heat without   cracking.  The
matter to be Sublimed  muft not, on almoft any occafion,
take  up more  than  a third part of the  fubliming
velfel.   It is to be fet  in a fand-bath,  that the heat may
be more equally applied than  it could  otherwife  be.
The  heat muft be no greater, or very little, than is  ne-
ceffary for Sublimation, or it will be in danger of flying
out at the  mouth ofthe fubliming veffel,  or of choak-
ing it up fo as to burft.   The upper part of the veffel,
to.i, muft by  no means be kept cool, but flightly cove-
red with Sand, that the matter may Settle  in a kind of'
half melted ftate, and thus forma compact hard cake,
which  is  the appearance fublimates are expected to
have.  Hencd this operation  requires a good deal of
caution, and is  not  very eafily performed.
   VIII.Deflagration.Thisopcration is always per-
formed by means oS nitre, except in making the flow-
ers of zinc.   It requires open veflels of earth or iron ;
the latter are very apt to be corroded, and the firmer
to imbibe part of the  matter.  To perform this  pro-
cefs with fafety, and  without lofs, the nitre ought to
be mixed with whatever matter is  to be  deflagrated
with it, and thrown,  by little and little into the veflel
previoufly made red-hot.   If much is put in at  once,
a great deal  will be thrown out by the violent comnm-
tion ; and to perform this operation in clofe veffels is
in a manner  impoffible, from the prodigious quantity
of elaftic vapour generated ' y the nitre.   Care muft al-
fo be taken to remove the whole mixture  to fome   di-
ftance from the fire, and not  to bring back  any fpark
from the quantity deflagrating, with the fpoon which
puts  it in ; otherwife the whole would irremediably be
cot:fumed at  once.
   IX. Calcination-. This is the Subjecting any mat-
ter to a  heat fo violent as to didipate fome  part of it,
without melting what remains.   It  is often praetifed
on metallic fubftances, particularly lead, for obtaining
the calx of that metal called minium,  or red lead.
   This operation, as indeed all other chemical ones, is
beft performed in lar^e quantities, where a particular
firnace is conftructcei on purpofe, and  a fire  kept on
d»y and night without interruption.   The flame is made
to play over  the furface  of the metal, and it is conti-
nually ftirred fo as to expofe different puree's cf  i: to
die action of the heat.
   S   T    R   Y.                            Theory.
   X. Fusion*.  This is when a Solid body is cxpofeel Chemical
to f:cii a degree of heat as makes it pal's from a folid Operation!
to a fluid ftate; and as different  lubftanccs arc potlcf-    cgT""
fed of very different degrees of fulibility, the degrees FUUon.
of melting  heat arc very various
   KeSnhs the true fulion,  there are fome kinds of falts
which retain fo  large a proportion of water in  their
cryftals,  as  to become entirely fluid upon being expo-
fed to a very fmall  degree  of  heat.  This  is  com-
monly called the watery fufton ; but is really a folution
of the fait in that quantity of water retained  by it in
its cryflalline form :  for fuch falts  afterwards become
folid by the evaporation of the water  they contained :
and then require a ftrong  red heat to melt them tho-
roughly, or perhaps are abfolutely  infufiblc.
   Of all known fubftances,  unctuous and inflammable
ones become fluid with the leaft heat:  then come  the
more fufible metals, lead,  tin,  and antimony ;  then
fome of the more fufible falts ; and then the harder me-
tals, filver, gold, copper, and  iron ;  then the  mix-
tures for making glafs; and laft of all, the metal cnll-
ed platina,  which has hitherto been incapable of Sufion,
except by the violent action ofthe fun-beams in the fo-
cus oS a large burning glaSs.  Thie Subftance Seems to
be the moft refractory of all others,  even the hardeft
flints melting into glafs long before it. (Sec Platina.)
   Fufion of fmall quantities of matter is ufually per-
formed in pots called crucibles • which, as they are re-
quired to ftand a very violent heat, muft be  made of
the moft refractory materials poflible.                     585
   The  making of crucibles belongs  properly  to the Crucihles,
potter : but as a chemift ought to be the judge of their proper ma-
compofition, we  fhall here  give fome account  of the trials for.
different attempts to  make thefe veflels  of the  necef-
Sary ftrength.
   All earthen veflels are  compofed, at leaft partly, of
that hind which is called the argillaceous earth or clay,
becauSe theSe only have the neceffary ductility, and can
be formed into veflels ofthe proper form.  Pure clay
is, by itfelf, abfolutely unfufible ;  but is exceedingly
apt to crack when expofed  to fudden  changes of heat
and  cold.   It  is alfo very  apt to  melt  when  mixed
with other fubftances, fuch as calcareous earths,  &c.
When  mixed in  a certain  proportion  with  other
materials,  they  are  changed with violent  heat.into
a kind of half-melted  fubftance,' fuch as our  Stone-
bottles.  They cannot be melted completely,  however,
by almoft  any fire;  they are alSo  very compact, and
will contain the  moft fufible Subftances, even glafs of
lead itfelf;  but as they are very apt to crack  from fud-
den changes of  heat and cold,  they  are not fo much
ufed;  yet,  on particular occafions, they are the only
ones which can be made ufieof.
   The more denfe any kind oS veflels arc, the more apt
they are, in general, to  break by a fudden application
of heat or  cold: hence crucibles are  not, in general,
made ofthe greateft denfity poflible: which is not at
all times required.  Thofe made at Hefle, in Germai:y,
have had the  beft  reputation for a  long time.   Mr
Pott, member ofthe Academy of  Sciences at Berlin,
hath determined the compofition of thefe crucibles to
be,  one  part of good refractory clay, mixed with two
parts of find, of a middling finenefs, Srom which  the
fineft part  has b'en  Sifted.   By Sifting  the  finer par-
ticles from the ft..: J, too great annpuctnefs is avoided-. 
Theory.
CHEMISTRY.
79
   586
Platina, a
defirablc
material.
Chemical  but at the fame time this mixture renders them apt to
Operations, be corroded by vitrifying matters kept a long time in
'----*---' fufion ;  for theSe do not fail lo act upon the fand con-
         tained in the compofition ofthe crucible, and, forming
         a vitreous maSs, at laft run through it.
           This inconvenience is prevented,  by mixing, inftead
         of fand, a  good baked clay  in groSs powder.  Of a
         compofition of this kind are made the glafs-houfe pots,
         which Sometimes Suftain the  violent heat employed in
         making glaSs for feveral months.  They are, however,
         gradually confiimed  by the  glaSs, and  become con-
         ftantly more and more thin.
           As the containing veffel, however, muft always be ex-
         pofed to a more violent heat than what is contained in it,
         crucibles ought to be formed  of fuch materials as  are
         not vitrifiable by the heat of any furnace whatever.  But
         from the attempts made to melt platina, it appears, that
         of all known fubftances it would be the moft deftrable for
         a melting veffel,  Heffian crucibles, glafs-houfe pots,
         Sturbridge clay, in fhort every fubftance which could be
         thought of to refift the moft violent heat, were melted in
         fuch a manner as even to flop up the pipes of large bel-
         lows, while platina  was not  altered in the leaft ;   and
         Meffrs Macquer and Beaume  have fhown, that though
         platina cannot be  melted So as to caft veffels  of it, it
         may neverthelefs be cupelled with lead fo as to become
         Malleable, and thus veflels might otherwife be made
         from that fubftance.  The extreme fcarcity of this mi-
method of neral, however, leaves as yet little room  to hope for
making   an„ thing from jt  though Mr Achard has found a me-
crucibles of ^.' . _rr°  •_____'  :li  '&r._____i.:„ „„r„„ n.„„„ r.,i.A„„„„
   5«7
Achard's
platina.
   588
Mr Pott's
directions.
thod of forming crucibles from this refractory fubftance.
It confifts in moulding the precipitate  made  with fal
ammoniac into the form of a crucible,  and then apply-
ing a fudden and very violent heat, which fuSes this calx.
   Mr Pott has made fo many experiments upon clays
mixed with different Subftances, that he has in a manner
exhaufted the Subject.  The bafis of all his compofitions
was clay.  This he mixed in different proportions with
metallic calces, calcined bones, calcareous earths, talcs,
amianthus, afbeflus, pumice-ftones, tripoli, and many
others ; but he did not  obtain a perfect compofition
from any of them.  The beft crucibles, according to
Scheffer,  cannot eafily contain metals diffolved by ful-
phur, in the operation of parting by means of fulphur.
They  may be made  much more  durable and folid,
by fteeping them a few days in linfeed-oil, and ftrew-
ing powdered  borax upon them before  they are dried.
   The refult of Mr Pott's experiments are :  1. Cru-
cibles made of fat clays are more apt to crack when ex-
pofed to  fudden heat, than  thofe which are made of
lean or meagre clays.   Meagre clays are thoSe which
contain a confiderable  quantity of fand  along with  the
pure argillaceous  earth :  and fat clays are thoSe which
contain  but little.  2. Some crucibles become porous
by long expoSure to the fire, and imbibe part of the
contained metals.  This may be prevented, by glazing
the internal and  external furfaces ; which is done by
moiftening thefe with oil of tartar, or by ftrewing  up-
on them,  when wetted with water, powdered glafs of
borax.  TheSe glazings are not capable of containing
glafs of lead.   3.  Crucibles made of burnt clay grofs-
ly powdered,  together with unburnt clay, were much
lefs liable to crack by heat than crucibles made of the
fame materials where  the burnt clay was finely pow-
dered, or than crucibles made entirely of unburnt clay.
4. If the quantity of unburnt clay be too  great, the Chemical
crucible will be  apt  to crack in the fire.   Crucibles Operations
made of 10 ounces of unburnt clay, 10 ounces of grofs-
ly powdered burnt clay,  and three drachms of cal-
cined vitriol, are  capable of retaining melted  metals,
but  are  pervaded by glafs of lead.  The  following
compofition is better than the preceding : Seven oun-
ces of unburnt clay,  14  ounces of grofsly  powdered
burnt clay,  and one drachm of calx of vitriol.   Thefe
Crucibles may be rendered more capable of containing
glafs of lead, by lining their internal furfaces,  before
they are  baked,  with unburnt clay diluted with water.
They may be further ftrengthened  by making them
thicker than is ufually done ; or by covering their ex-
ternal furfaces with fome unburnt clay,  which is called    .g-
arming them.  5.  The compofition of crucibles moft Materials
capable of containing the  glafs of  lead, was 18 parts moll capa-
oS groSsly powdered burnt  clay, as much unburnt clay, ble ofrefift-
and one part of fufible Spar.  TheSe  crucibles  muft lDS glafs ci
not, however, be  expoSed too  fuddenly to a  violent
heat.  6. Crucibles  capable  of containing glafs  of
lead very well, were made of 24  parts of unburnt clay,
four parts of burnt clay, and one part of chalk. Thefe
require to be armed.    7.  Plume  alum powdered,  and        '
mixed with whites >of eggs and water, being applied
to the internal furface of a Heffian crucible, enabled it
to retain for a  long  time glafs of lead  in  fufion.
8. One part of clay,  and  two parts of Spanifh chalk,
made very good crucibles.  The fubftance called Spa
nifb chalk is not a calcareous earth, but appears to be a
kind of fteatites.   9.  Two parts  of Spanifh chalk, and
one part  of powdered tobacco-pipes, made good lining
for common crucibles.  10.  Eight parts  of Spanifh
chalk, as much  burnt clay, and one part of litharge,
made folid crucibles.   11.  Crucibles made of black lead
are fitter than Heffian crucibles for melting metals ; but
they are  fo porous, that fufed falts pafs entirely thro'
them.  They are  more tenacious than Heffian cruci-
bles, are  not fo  apt to burft in  pieces, and are more
durable.   12. Crucibles placed with their bottoms up-
wards, are lefs apt to be  cracked during the baking,
than  when  placed  differently.  13.  The pafte  of
which crucibles are made, ought not to be too moift ;
elfe, when dried and baked,  they will not be Suffici-
ently compact: hence they ought not to be So moift as
to be capable of being turned on  a potter's lathe ; but
they muft be formed in brafs or wooden moulds.          -9<3
   On this fubject  Dr Lewis hath alSo made feveral Dr Lewis^
observations ; the principal of which are,  1.  Pure clay obferva-
SoStened to a due confiftence for being worked, not ft°ns-
only  coheres together, but  flicks to the hands.   In
drying, it contracts 1 inch or more in  12 ; and hence
it is veiy apt to crack, unlefs it is dried exceeding flow-
ly.  In  burning,  it  is fubject  to the fame inconve-
nience, unlefs very flowly and gradually heated. When
thoroughly burnt,  if it has efcaped thofe imperfections,
it proves folid and compact ; and fo hard as to ftrike
fire with fteel.  Veffels made of it are not penetrated
by any kind of liquid ;  and refift  falts  and  glaffes
brought  into the thinneft fufion,  excepting thofe which
by degrees corrode  and  diflblve  the earth itfelf,  as
glafs of lead ; and even this penetrating glafs is refitt-
ed by it better than by almoft any other earth ;  but, in
counterbalance to thefe good  qualities, they cannot be
heated or cooled, but with  Such  precautions as can
                                             rarely 
                            C   H    E   M
rarely be complied with in the way of bufuufa, with-
out cracking,  or dying in pieces.
   2.  Clay that has been once expofed to any confider-
abic decrees of heat, and then powdered, has no longer
any tenacity.   Frefh  clay, divided by a due  propor-
tion of this powder,  proves lefs tenacious than by it-
ielf;  not flicking to the hand^ though cohering fuf-
ficicntly together.  It fhrinks  lefs in  elrying, is lefs
.;>: to crack,  aud lefs fufceptible of injury from alte-
rations of heat and cold ; but at the  fame time is lefs
Solid and compact.  Confiderable differences   are ob-
Served  in theSe refpects ;  not only according to the
quantity of dividing matter,  but according as it is in
finer  or coarSer powder.
   3.  Veflels made with a moderate proportion of fine
powder, as  half the weight of the clay, are  compact
and Solid,  but ftill  very  apt to crack,  from fudden
heat or cold :  thoSe with a larger proportion, as twice
or thrice the  quantity of the clay, are free from that
imperfection,  but So friable as to crumble between the
fin >xrs.  Nor does  there appear to be any medium be-
tween a diSpofition to crack and to crumble ; all the
compounds made of clay  and fine powders having the
one or  the   other,  or both  imperfections.   CoarSer
powders of the Size of middling fand, form,  with an
equal weight of clay,  compounds Sufficiently folid, and
much  leSs apt to crack  than the  mixtures with fine
powders.   Two parts of coarfe powder,  and one of
clay,  prove  moderately Solid,  and but little difpofed to
crack : a mixture of three parts and one, tho' heated
and cooled fuddenly,  does not crack at all, but fuffers
very  fluid Subftances  to tranfude through it ;   Solidity,
and rcfiftance to quick viciffitudes of heat and cold,
Seeming here alSo to be incompatible.
   4.  Pure  clay, mixed with pure clay that has been
burnt, is no other than one Simple earth ;  and is nei-
ther to be melted nor Softened, nor  made in  any de-
gree tranfparent with the moft intenfe fires.
   5.  Mixtures of clay with gypfeous earths burn whi-
ter than clay alone ;  in certain proportions, as two parts
of clay to three of gypfum,  they become, in a moderate
fire,  femi-tranfparent, and in a ftrong one they melt.
   6.  Calcareous earths in fmall proportion  bake to-
lerably compact and  white ;  and added to other com-
positions,  feem to improve  their compactnefs.   If the
quantity of the calcareous  earth nearly equals that of
the clay, the  mixture melts into a yellow glafs ;  if it
confiderably exceeds, the product acquires the quali-
ties of quicklime.
   7.  Veffels made  from clay  and fand, in whatever
proportion,  do not melt in  the ftrongeft fire ;  but they
Sometimes bend or foften,  fo as to yield to the tongs.
(.]:. fes in thin fufion penetrate them by diffolving the
fund.   h" gypfeous or calcareous earths e    urged in
fuch crucibles with a vehement heat,  the  veffels and
their  contents run all into one maSs.  In moderate
tires,  theSe veffels prove  tolerably  compact, and retain
moft  kinds of falts in fufion : but they  are  liable to
crack, especially when large ;  and do  not long Suftain
lilted metals, being burft  by  their weight.  Such are
the Helfian crucibles.
  8.  Mixtures of chy and black-lead, which  feems a
fpecies  of talc, :vre not liable to crack from  alterna-
tions  of heat  anJ  cold; but  are  extremely  porous.
Hence black-lead crucibles anfwer excellently for the
   S    T   R    Y.                           Theory.
melting of metals, and ftand repeated fufions ; wliilft Chemical
falts flowing  thin, tranfude  through  them almoft as Operation!
water through a Sieve : fulphureons bodies,  as .ultimo-         '
ny, corrode them.
  9. Pure clay, foftened with water, and incrufhtcd
on earthen veffels, that have been burnt, docs, not ad-
here to them, or fcales  off again upon  expofure to
the fire ;  applied to unburnt veflels, it adheres and in-
corporates. l;i\ided clay unites with them in both ftates.
Vitreous matters, melted in veflels  of pure clay, adhere
fo firmly as not to be  Separated  ;  from  veflels of di-
vided clay they may be knocked off by a hammer.
  10.  The faline fluxes which  promote the  fufion of
clay,  befides  the common ones of all earths, alkali and
borax, are chiefly arfenic fixed by nitre,  and the fufible
lalt of urine ; both which have little effect on the other
earths though  mixed  in a lager proportion.  Nitre,
which readily brings the cryflalline earths into fufion,
and fal mirabile and fandiver,  powerful  fluxes for the
calcareous earths, do not  perfectly vitrify  w ith clay.
Burnt clay does not differ in thefe refpects from fuch
as has not been  burnt ; nor in that Singular  property
of vitrifying  with gypfeous or calcareous  earths, with-
out any faline or metallic addition; the utmoft vehe-
mence of fire Seeming to deftroy only its ductility, or
that power by  which it  coheres  when its parts are
moiftened with water.
  But though  it Seems  impoffible to  make perfect
veffels from mixtures of clay in its two different ftates,
of burnt and  unburnt,  more is to  be  hoped from the
mixtures which are employed in making porcelain. Ma- Mowfper-
nuSactories of this kind of ware have been attempted fe<a veffel*
in different countries, (fee Porcelain) ;  and in fome to be hoped
places the qualities requifite for  cliemical veflels have f°r  frorn
been given to it in a very Surprifing degree.  The count Porcclain-
de Lauraguais,  a French nobleman, and member of the
academy of Sciences, has diftinguifhed  himSelS  in a
very eminent manner by attempts  of this kind.   The
tranflator of the chemical  dictionary affures us, that'he
had it from a gentleman of undoubted veracity,  that this
nobleman having heated a pieceof his porcelain red hot,
threw it into cold water, without breaking or cracking it.
  The moft ufeful attempt, however,  for the purpofe j
of chemiflry, feems to be the difcovery  by Mr Reau-
mur of converting  common green glafs  into porce- Mr Rcau-
lain.   This was  publifhed as  long ago as  the  year mur's po#-
1739 ; yet we have fcarce heard of any chemift, no not eclain.
Dr Lewis  himfelf, who  has made trial of chemical
velfels formed  of this  fort of porcelain, although the
very ufe to w hich Mr Reaumur  thought the  prepara-
tion could be  applicable was  that of bringing chemical
veflels to a degree of perfection which could not other-
wife be done.  The following is the refult of Mr Reau-
mur's experiments.
  Green glafs,  furrounded with white earthy  matters,
as white fand,  gypfum, or plafter of  Paris,  ire.  and
expofed to a confiderable heat not ftrong enough to
alter its figure, as that of a potter's furnace,  acquires
different lhades of blue,  and  by  degrees begins to
grow white.   On breaking  the  glafs, the white coat
appears to be compofed  of fine,  white,  glofly,  fatin-
like fibres, running tranfverfely, and parallel to one ano-
ther ; the g'ai's  in  the  middle being Scarcely altered.
On '•outinuing  the cementation,  the change  proceeds
funnei  and further, till at  la^th the  white fibrous
                                             parts 
Theory.                           C   H    E   M
Chemical  parts from both fides  meet in the middle, and no ap-
^perations pearance of glafs remains.   By this means, entire vef-
       "" fels of glafs may be changed into procelain.
            The fubftance into which glafs is thus converted, is
         opaque, compact,  internally of great whitenefs,  equal
         to that of the fineft china-ware ; but, externally, of a
         much duller hue.  It is confiderably harder than glafs,
         much lefs fufible in the fire, and fuftains alterations of
         neat and cold without injury.  Veffels of it,  cold, bear
         boiling liquors ; and may be placed on the fire at once,
         without danger of their cracking.  " I have put a vef-
         fel of  this porcelain (fays  the author) into a forge,
         furrounded it with coals,  and kept vehemently blowing
         for near a quarter of an  hour; I have  melted glafs in
         this  veffel, without its  having Suffered any injury in
         ks figure."   If means  could be found of giving the out-
         fide a whitenefs, equal  to the internal part, glaSs veflels
         might thus be converted info a valuable kind of porcelain
         fuperior to all that have  hitherto beenjnad'e.  Chemi-
         ftry,  fays he, may  receive from this  difcovery,  in
         its prefent ftate, fuch veffels as have been long wanted;
         veffels which,  with the compactnefs and impenetra-
         bility of glafs, are alfo free from its inconveniences.
            The common green  glafs bottles yield a procelain of
         tolerable beauty ; window-glaffes, and drinking-glaff-
         es, a much inferior one ; while the finer kinds of cry-
         flalline glaffes afforded none at all.  With regard to the
         cementing materials, he  found white fand and gypfum,
         or rather a mixture of both,  to anfwer beft.  Coloured
         earths generally make  the  external furface  of a deep-
         er or lighter brown colour ;  foot and  charcoal, of a
    . >    deep black, the internal part  being always white.
fc>r iJewis's   The account of  this  kind of porcelain given by Mr
(experi-    Reaumur, induced Dr Lewis,  who had alfo obferved
menu.    the fame  changes on the bottom  of glafs-retorts ex-
         pofed to violent heat iu  a fand-bath, to make further
         experiments on this matter; an account of which he
         has publifhed in his Philofophical Commerce of Arts.
         The refults of his  experiments were, i. Green glafs,
         cemented  with white  fand, received no change in a
         heat below ignition. 2. In a low red heat, the change
         proceeded exceeding flowly; and in a ftrong red heat,
         approaching  to  white, the thickeft pieces  of glafs
         bottles were thoroughly converted in  the  Space  oS
         three hours.   3. By continued heat, the glaSs Suffered
         the following progreffive changes:  firft, its  furface
         became blue, its transparency was diminiflied, and a
         yellowifh hue was obServable when it was held between
         the eye and the light.    ASterwards it was changed a
         little way on both  fides into a  white fubftance,  exter-
         nally ftill  bluifh ;  and, as this change  advanced ftill
         further and further within the glafs, the colour of the
         vitreous part  in the middle approached  nearer to yel-
         low :  the  white coat was of a fine fibrous texture, and
         the fibres were  diSpoSed nearly parallel to one another,
         and  tranfverfe to  the  thicknefs of the piece : by de-
         grees the glafs became  white and  fibrous  throughout,
         the external bluilhnefjs  at the fame time going oft, and
         being Succeeded by a dull whitifh or dun colour.   By
         a ftill longer continuance in the fire, the fibres were
         changed gradually  from  the external to the internal
         part, and  converted into  grains ;  and the texture was
         then not unlike that of common porcelain. The grains,
         at firft fine and fomewhat glofly, became  by degrees,
         larger and duller ;  and at laft the fubftance of the glafs
I   S   T    k   Y*                                   81
 became porous and friable, like  a ntafb of white Sand chemical
 Slightly cohering.   4. Concerning the qualities of" this Operation*
 kind oS porcelain, Lr Lewis observes,  that, while it     v
 remained in the fibrous ftate, it was harder than com-
 mon glaSs, and more able to refift the changes of heat
 and cold than  glaSs, or even porcelain ;  but,  in a mo-
 derate  white heat, was Sufible into a Subftance not ir*
 brous,  but vitreous and  Smooth,  like white enamel';
 that when its  texture had become coarfely granulated,
 it was  now much Softer and unfufihle : and laftly, that
 when Some coarSely granulated unf"ulible pieces, which,
 with the  continuance of a moderate heat, would have
 become porous and friable, were  fuddenly expofed to
 an intenfe fire, they were rendered remarkably more
 compact than  before ;  the  folidity of fome  of them
 being fuperior to that of any other ware.                 594
   It feems Surprising that this able chemift, who on Thisfub^
 other occafions had the  improvements oS the arts So jtct ftill
 much at heart, did not put  fome veflels of  this kind ,rnPcrfelft-
 of porcelain to other fevere trials, befides attempting
 to fufe it  by  itfelf with  a violent fire: for though
 pieces  of it* were  abfolutely unfufible,  we are not fure
 but they might have been corroded by alkaline  falts,
 acids, calcareous earths, or glafs of lead ; nay, it fhould
 feem very probable that  they would have been fo: in
 which  cafe they would  not be much  fuperior  to the
 veffels  made from earthy  materials.   When a firft-
 rate chemift publifiies any thing in an imperfect ftatej
 inferior ones are difcouraged from attempting to finifli
 what he has begun; and thus, hotwithftariding that thefe
 experiments have  been  fo long publifhed, nobody has
 yet attempted to investigate  the properties of  this
 kind of porcelain, by getting chemical veffels made of it,
 and  trying how they anfwer for crucibles,  or retorts;
   All that has been faid concerning the proper mate-
 rials for crucibles, muft  likewise be applicable  to the
 materials  for  retorts, which are required to ftand a
 very violent heat. Mr Reaumur's porcelain bids faireft
 for anSwering  the purpoSeoS retorts as well as crucibles.
 The great disadvantage ofthe common, earthen ones, is,
 that they fuffer a quantity of volatile and penetrating va-
 pours to paSs through them.  This is very obServable
 in the diftillation of phoSphorus ;  and though this  Sub-
 ftance has  not hitherto  been uSed for any purpofe in
 medicine, and very little in the arts, its acid only be-
 ing Sometimes  uSed as a  flux, iS veflels could  be made
 capable of confining all the fleams and  at the fame time
 bearing the heat neceffary for its diftillation,  phoSpho-
 rus,  perhaps,  might be obtained  in Such quantity, as
 to fhow that it  is a preparation not  altogether uSeleSs.   S95 [596J
   With regard to ftone-ware veffels, and all thofe  into Stone-war^
 which  the compofition of fand or flint  enters, we fliall veffels cor-
 only further obferve, that they will be corroded by fixed roded'
 alkaline falts,  efpecially of the cauftic  kind, in a very
 moderate heat. Dr Black, having evaporated fome cau-
 ftic ley in a ftone-ware bafon, and then melted the dry
 fait in  the fame veffel,  found it fo corroded, as after-
 wards to be full of fmall holes ; and he found nothing      ,
 to  refift the action oS this fait fo well as filver.  On Wedee-
 the fubject of chemical velfels, we have now, however, wood'*
 to add the improved earthen ware of Mr Wedgewood; ware.
 in which the properties of compactneSs, inSufibility and
 the powTer of  refitting  fudden  changes  of  heat  and
 cold, are Said  to be  united, So that it promiSes to be a
 very valuable addition to the chemical  apparatus.
                         L                      XL 
S2                                  CHE   M   I
chcmic*!   '  n.  Maceration, or Digesi ion.  This  is the
ijirnacCT.  m; ,ngtwobodies,  generally a folid ai.da fluid, toge-
   jy>i   ther, and then cxpofing them to a moderate degree of
Miccra-  heat tor a confiderable length of time, that fo they may
• on.     have the bcttcropportunity of acting upon one another.
         Dij/ftioi is uf.ully  performed in the  glaffes already
         mentioned, called matrafe s or bolt-heads : and is done in
         a fand-hcat.   \V hen any of the fubftances arc veryjvola-
         tilc, as fpirit of wine ; or when the matter requires to
         be heated fo confiderably that a quantity oS vapour will
         be railed, the  necks ofthe bolt-heads ought to be  pretty
          King; or a tin  pipe  may  be inferted, oS Sufficient
   59?    length to prevent the cScape of any part  ofthe  fleam.
l-*v>ga-      12. Levigation.  This is the reducing any body
Uon-      to a very fine powder, which fhall feel quite foft be-
          tween the fingers or when  pat  into the mouth.  It
         is performed  by grinding  the fubftance upon a flat
          marble ftone,  with  fome water,  or by rubbing it in a
          marble mortar.   In the large way, levigation is per-
          formed by mills drawn by horfes, or driven by water;
          fome of them are fo fmall as to be turned  by the hand.
         They conlift of two fmooth ftones, generally of black
          marble,  or fome  other ftone equally hard,  having fe-
          veral grooves  in each, but made to run in contrary di-
          rections  to one another when  the mill is  fet in  mo-
          tion.  The matter being mixed with water,  is put in
          by a funnel,  which is fixed into a hole in the upper
          ftone, and turns along with it.  The under  milftone
          has  round it a wooden ledge, whereby the levigating
          matter  is confined for fome time, and at length dif-
          charged, by an opening  made for that  purpofe, when
          it has accumulated in a certain quantity.
            Iu this operation, when the matters to be levigated
          are very hard, they wear off a part of the mortar, or
          ftones on which they are levigated ; fo that a fubftance
          perfeeftly hard, and which could not be worn by any
          attrition, is as great a defideratum tor the purpoSes of
          levigation, as one  which could  not be  melted is for
          thofe of fufion. Dr Lewis propofes the porcelain of Mr
          Reaumur  as  an  improvement  for levigating planes,
          mortars,  ire.  becaufe, while in its fibrous ftate, it is
          confiderably harder than  glafs,  and confequently much
         lefs  liable to abrafion by the harder powders.
            In many cafes levigation is  very much accelerated
          hv what  is called elutriatiou.  This is the method  by
          whl.h many of the painters colours are prepared of
          the requifite finenefs ;  and is performed by mixing any
          fubftance not  totally reduced to  the neceffary degree
         of finenefs, with a fufficient quantity  of water,  and
         ftirring  them well  te)gether.  The finer parts of the
          powder  remain  fome  time  fufpended  in the water,
          while the groffer particles  fall to the bottom.   The
          Separation is then eafily made,  by pouring off the wa-
          ter impregnated  with theSe  fine parts, and  commit-
         ting the reft to  the levigating mill, when it may a-
         gain be wafhed ;  and this may be repeated till all the
         powder is reduced to the utmoft fineneSs.   Subftances
         t«)hible irk water cannot be levigated in this manner.

                     OfCHEMiCAL Furnaces.
            The  two  general divifions we have already men-
         tioned of thofe who practice chemiftry,  namely, thofe
         who have no  other view than  mere experiment,  and
         thofe who wifh  to  profit by it,  render very  different
         kinds of furnaces neceffary.  For the *rn, thofe fur-
   S   T    R   Y.                 •         Theory.
naces are neceffary which r.re capable of acting upon Chemical
a inu.ll  quantity of matter,  yet luflicient for  all  the Fornacei.^
change* which fire can produce from fur pie digcflion
to the moft perfect vitrification.   For the others, thofe
are to be chofen which can proxlucc the Same changes
upmi very large quantities  of  mattcr, that as much
ir.jy be done at once as poffiblc.                      ^eo
  To avoid  the trouble and expence oS a number ofportahle
furnaces, a portable one hath long been a defideratum furnace.
among thofe chemifts who are fond of making experi-
riments.  One of the beft of thofe, if not the very beft,
that hath yet appeared, is that defcribed in Shaw's edi-
tion of Boerhaave's chemiftry, and reprefented fig. i. p]ate
  This furnace is made of earth ; and, as the work- CXXXIV.
manlhip of a furnace requires none of the ncatnefs or
elegance which is required in making potters veffels,
any perfon may eafily make a furnace of this kind for
himfelf, who has time and patience for So doing. With
regard to the moft proper materials, all that we have
Said concerning  crucibles and retorts muft be appli-
cable to the materials Sor conftructing a  Surnace ; only
here we need not care So much for the  porofity,  or
diSpofition to crumble,  as when crucibles or other dif-
tilling veffels are to be made.
   Plate iron  is commonly directed for the  outfide of
portable  furnaces ; but we cannot help thinking this
is a very needlefs expence,  feeing the  coating which
it neceflarily requires on  the infide  may be  fuppofed
to harden to fuch a  degree  as  foon to  Support itfelf,
without any affiftance from the plate-iron.  This will
be the  lefs neceffary,  if we confider,  that, for the
thicknefs of the walls of any  furnace where a confide-
rable heat is wanted,  two or three inches  are by no
means  fufficient.   When the  infide of a furnace  is
heated,  the  walls, if  very thin, are foon penetrated
by the heat, and great  part of it by this means diffi-
pated in the  air.  If they are of a fufficient thicknefs,
the heat cannot penetrate fo eafily ; and  thus the inner
part of the furnace preferves the  heat ofthe fuel, and
communicates it to the contained veflel.   In the con-
ftruction of a portable furnace, therefore, it  will be
convenient to have all parts of it fix inches thick at
leaft.    This will alfo  give it a fufficient  degree  of
ftrength ; and,  as  it  is formed of feveral  different
peiccs, no inconvenience can follow from the weight
of each of them taken Separately.
  In Boerhaave's chemiftry,  this furnace is reprefent-
ed as narrower at the bottom  than  at the top ; but wc
cannot fuppofe any good reafon for fuch a form, fee-
ing a cylindrical one muft anfwer every  purpoSe much
better, as allowing a larger quantity oS air to paSs through
the fuel, and likewife not being fo apt to be overturned
as it neceflarily muft be where the upper part is confi-
derably heavier than the lower.   We have, therefore.
given a representation of it as of a cylindrical form.
  The furnace  confifts of five or more  parts.   C, re-
prefents the  dome, or top of the furnace, w ith a fhort
earthen funnel E for transmitting the fmoke.   B, B, B,
are moveable cylinders of earth,  each  provided with
a door D, D, D.  In Boerhaave's chemiftry thefe doors
are reprefented as  having iron  hinges  and  latchets ;
but they may be  formed to more advantage  of  fquare
pieces of earth,  having  two  holes in  the middle, by
which they may be occafionally taken  out, by intro-
ducing an iron fork.   In like manner,  the domes and
                                        cylinder,. 
Theory.
CHEMISTRY
8
         cylinders,  in Boerhaave's chemiftry,  are  represented
         with iron handles ; but they may be almoft as eafily taken
         off by the cheaper contrivance oS having four holes in
         each, two directly oppofite to one another, into which
         two lhort forks may be introduced when the parts are
         to be Separated.
            In the lowermoft cylinder is to  be placed an iron-
         grate, a  little below the door,  for Supporting  the
         fire.   In the under part is a Small hole,   big  enough
         for introducing  the  pipe of a  pair  of  good perpe-
         tual bellows when the fire is to be violently excited,
         Dr Lewis preSers the organ-bellows to any other kind.
            When the  bellows is uSed, the whole  muft ftand
         upon a cloSe cylinder A, that the air may  be confined,
         and  made to paSs through the  fuel.   By having more
         bellows,  the  fire may  be excited to a moft  intenfe
         degree.   In this cafe, the pipe of every one of them
         muft enter the cylinder B.
            Each of the cylinders fhould have, in its upper part
         a round  hole, oppofite  to its  door,  for  carrying  off
         the fmoke, by means of a pipe inferted into  it, when
         the furnace is ufed for  diftillations by the fand-bath.
         Each cylinder ought likewife to have a femicircular
         cut in the oppofite fides, both  above and  below, that
         when the under cut of  the upper  cylinder is brought
         directly  above the upper cut of the lower one, a per-
         fect circle may be  formed.  Thefe  are for giving a
         paffage to  the necks of retorts, when diftillation  by
         the retort is to  be performed.  The holes  may be
         occafionally filled with floppies made of the fame ma-
         terials with the  body of the furnace.
            The moft convenient  fituation for  a furnace of this
         kind  would be under a chimney,  the vent  of which
         might be eafily flopped  up by  a broad plate of  iron,
         in which a hole ought to be cut for the  ireception of
         the earthen tube of the dome.   By this  means the
         ufe of a long tube,  which at  any  rate muft be  very
         troublefome,  might  be eafily  avoided, and  a  very
         ftrong blaft of air would pafs through the fuel.  If it
         is found convenient to place the furnace at fome di-
         ftance from the  chimney,  a plate-iron pipe muft be
         procured to fit  the earthen pipe  of the  dome,  and
         carry the fmoke into the chimney.   This pipe will
         alfo be of ufe, when the furnace is  ufed  for diftilla-
         tions by the fand-bath;  it muft  then be inferted into
         the hole oppofite to the door oS any of the cylinders,
         and will convey away the fmoke,  while the mouth oS
   6oI   the cylinder is totally covered  with a Sand-pot.
DrLewis's   F°r portable  furnaces, Dr  Lewis greatly  recom-
portable  mends the large  black  crucibles,  marked n°  60,  on
fcrnaces.  account of their refitting a violemyheat, and  being
         very eafily cut by a knife or faw,  fo that  doors, &c.
         may be  formed  in  them at  pleafure.   The bottom
         of one of thefe large ones being  cut out, a grate  is to
         be put into the narrow part  of it.  For  grates, the
         doctor recommends caft iron-rings, having each three
         knobs around them.  Thefe knobs go into correfpond-
         ing cavities of the outer rings, and  the knobs of the
         outermoft reft on the crucible,  which is to  be indented
         a little  to receive  them, that fo  the grate may reft
         the more firmly, and the furnace  not be  endangered
         from the  fwelling of the iron by heat.   When this
         is to be made ufe of as a melting-furnace, and a vio-
         lent heat to be excited,  ahother crucible muft be in-
         Verted on  that which contains the fuel, which ferves
inftead ofthe dome of the laft mentioned furnace :  and Chemical
as whatever is faid of it muft likewife be  applicable Furnaces.^
to the two crucibles when placed  above one another,
we need  give  no farther defcription  of  the  doctor's
portable furnace. _                                    6oa
  No doubt, the  great experience of Dr  Lewis, in objeclioa
chemical matters  muft give very  confiderable weight to their wfc
to any thing he advances ; and the warmth with which in fome
he recommends the furnaces  muft convince us, that cales'
he has found them abundantly anfwer the purpofes of
experiments.  We cannot help  thinking,  however,
that where a very great and lafting heat is to be given,
the thicknefs,  and even the form, of thefe crucibles, is
fome objection  to  their ufe.  It  is certain that Such  a
permanent, or, as the workmen call it, a folid heat,
can never be given where the walls of" a Surnace  are
thin,  as when  they are of fufficient thicknefs.  They
are alfo very apt to burft  with great  heat ; and,  for
this  reafon,   Dr  Lewis deftres his  furnace to  be
ftrengthened with copper  hoops.   This difpofition ta
burft  proceeds from  the inner parts  which are more
intenfely heated than the outer, expanding more than
theSe  do, and consequently burfting  them.   Hence
the doctor delires his  Surnace lo be ftrengthened  alSa
by putting it within another crucible of a larger fize,
and the intermediate fpace to  be filled up  with a mix-
ture of lifted  afhes and water.   For  moft chemical
proceffes, where  only a Small degree of heat is requi-
fite, theSe Surnaces anfwer beyond any thing that  has
hitherto  been attempted.   The whole is to  be fup-
ported by an iron ring  with  three  feet             2d 6oi
  Dr Black has contrived a furnace in which all thefe Dr Flack's
inconveniences are avoided.   Two thick iron plates, furnace dc>
above and below, are joined by a thinner plate, forming pi"e
the body of the furnace, which is of an oval form. (jxxXIII
The upper part is perforated with two holes ; the  one fig. 5l 8, 7,
A, pretty large, which is  the mouth  of the furnace,
and which is of a circular form: theother behind it, B,
of an oval form, and defigned  for fattening  the end of
the vent which is fcreWed down upon it.  Theunder-
moft thick plate has only the large circular  opening
G near to  the middle, but not  altogether fo,  being
nearer to one fide ofthe ellipfe than the other, where
the round hole in  the top is placed; fo that  a line paf-
fing this  circular  hole has a little obliquity forwards.
Theafh-pit C E is likewife made of a nelliptical form,
and a very fmall matter widened ;  fo that the bottom
of the furnace  is received within the ellipfe.   A little
below, there is a border D that receives the  bottom of
the furnace ; and except the holes of the damping-plate
E,  the  parts  are all  clofed  by means of foft lute,
upon which the body of the furnace is preffed down ;
by which mea?.s the joining of  the two parts, and of
all the different pieces, are made  quite tight;  for the
body, fire place, afh-pit, vent, and grate, are all fepa-
rable  from one another.  As the furnace comes from
the workman, the grate is made to apply to the out-
fide of the lower  part.  It confifts of a ring laid on its
edge, and then bars likewife laid on their edges ;  and
from  the outer ring proceed  four pieces  of iron, by
means of which it maybe fcrewed down ;  fo it is kept
out of the cavity  of  the  furnace, and preferved from
the extremity of the heat.   Thus it lafts much longer,
and  indeed hardly liable to  any decay;  for by be-
ing expofed to the cool air, it  is kept fo cool,   that  it.
                       La                       is 
CHEMISTRY.
is never hurt by ihe heat of the  fuel.   The Sides,
whicli arc   made of plate iron muft  belated within,
to confine tl.cheat, and prcScrvc them from its action.
  T<> adapt  this to  the various operations  ^f  chemi-
ftry, wc  may obfcrve,  that lor a melting furnace it is
very convenient , wc need only provide a cover for the
opening above, which  is made the door;  and which
being  immcdiitely  over the  grate,  is convenient
for introducing the fubftmces to be  acted  upon, and
U•- ali twing us to look into the velfel and  take it out.
This cover  may  be a piece of tile,  or two bricks ren-
dered flat and fipiare.   Dr  Black commonly tiles a
kind of lid with a  rim  containing a qmntity of lute;
and to augment the  heat, we  may incrcaSc the height
of  the vent.  It can be  employed in moft  operations
in the way of effaying  ; and the Situation oS the door
allows us to See the  Subftances very readily.   It does
not admit the  introduction of the muffle ; but can be
employed in all  thoSe operations where the muffle is
made uSc of; and in Cornwall in England Such a fur-
nace is made uSc of for  effayingof metals.  To pre-
fervc the fubftance  from the  contact  of the fuel, they
cut off about a third part of the length of a  brick,
and then put it on one  end on the middle of the grate.
They choofe their fuel of large pieces,  that  the air
may have free paffage through it, and  open a  little of
the door, which occafions a  ltrcam  of air to flow in ;
and this  ftrikes  upon the fubftance  and produces the
effect defired ; So that  it may be  uSed  in the calcina-
tion oS lead to convert it into litharge.   It  alSo an-
fwers very  well in  operations Sor  producing vapour.
If we defire to employ  it in diftillations which  require
an  intenfe heat, the earthen  retort is to  be fufpended
by  means of an iron ring having three  branches Stand-
ing up from it, and which hangs down about half a
foot from the  hole ; fo that  the bottom of the retort
refts upon the ring, and is immediately hung over the
fuel : and the opening between  the mouth  of the fur-
nace and retort is filled up with broken crucibles and
potfherds, which are  covered  over with  allies  that
iranfmit  the heat very flowly;  fo it anfwers for  di-
1.illations performed with the naked fire.  Dr Black
has fometimes caufed them be provided with a hole in
the fide, from which the neck of the retort may be made
to  come  out;  and in this way has diftilled the  phoS-
plmrus oS urine, which  requires a very  ftrong  heat.
For diftillations with retorts performed with the Sand-
bath, there is an iron P°t fitted for the opening of the
furnace,  which  is Set on and employed as a Sand-pot.
The vent ofthe  furnace then becomes the door ; and
it anfwers very well for  that purpofe; and is  more
eafily kept tight than if it were  in the fide, and may
be kept clofe with a lid of charcoal and  clay.  In  like
manner it anfwers  well  for the common ftill, which
may be adapted to it; part of it being made to enter the
open part of the  furnace, and  hang over the fire, as in
Plate CXXXIII. fig. 8. and 9. that the bottom part of
that ftill  may be made to enter ;  and  the vent becomes
the door, by which  frefh fuel may be added.  Indeed it is
feldom neceffary to  add frefh fuel during any operation.
In the ordinary diftillations it is  never  neceffary ; and
even in diftilling mercury, phofphorus,  &c. it generally
contains  enough  to  finith the operation; f>  effectually
is the heat  preferved  from  lofs or ditfipation, and fo
vi ry flow is  ijtc consumption ofthe fuel.
Theory.
  For luting this and other 1.  1 aces, the doctor finds
nothing perlcrable to a  Simple  mixture of Sand and
clay.   The  proportions Sor (landing  the violence  of
fire are four parts of fand to one ot clay ;  but when
defigned for the lining of furnaco,  he uks fix or feven
of land to one of clay, the more effectually to prevent
the contraction of the latter ;  for it is known from ex-
periments, that clay, when expeffed to a ftrong heat,
contracts the more in proportion to its purity. rI he land
fettles into lefs bulk when wet, and does not contract
by heat,  which it alfo refifts as well as the clay itfelf.
  Befides this outfide lining next  the  fire, Dr Black
ufes another to be laid on next the iron of the furnace ;
and this  confifts of clay mixed with a large poi tion of
of charcoal dull.  It is  more fit for  containing the
heat,  and is put  next to the iron, to the thicknefs of
an inch and a half.  That it  may be pretty dry when
firft put in, he takes three  parts  by weight  ofthe
charcoal duft, and one  of  the common clay, which
muft be mixed together when in dry powder, other-
w ife it is  very  difficult  to  mix  them  perfectly.  As
much water is added as will form the matter into balls ;
and thefe are beat very  firm and compact, by means of
a hammer upon the infide ofthe furnace.  The other
lute is  then fpread over it to the thicknefs of about-half
an inch, and this is alfo beat folid by hammering ; after
whicli it is allowed to dry flowly, that all cracks and
fifl'ures  may be avoided : and after the body ofthe fur-
nace is thus lined, the vent is fcrtwed on and lined in
the fame manner. It muft then be allowed to dry for a
long time; after which  a fire may be kindled, and the
furnace gradually heated for a day or two. The  fire  is
then to be raifed to the greateft intenfity ; and thus the
luting acquires a hardnefs  equal to that of free-ftone,
and is afterwards as lafting as any part ofthe furnace.
   When furnaces are ufed  in the large way, they are
always built of brick, and each particular operation has
a furnace allotted  for  itfelf.  The melting-furnace,
where very large  quantities of  matter are not to be
melted at once, requires  only to be built of brickinfuch
a form as we have already defcribed ; only, as it would
perhaps be troublefome to procure a dome of the proper
figure, the forepart of  it may be left entirely open for
the admiflion of melting veffels.  The opening may be
clofed up with bricks and earth during the operation.
There is no neceffity for having the infide of a circular
form ; a fquare one will anfwer the purpofe  equally
well.  According to the author of the Chemical Dictior
nary, when the internal  diameter D C of fuch a furnace
is 12 or 15 inches, the diameter of the tube G I 8 or 9
inches, and  its height  18 or 20 feet, and when the
furface  is well fupplied with fuel, and extreme heat is
produced; in lefs than an hour the furnace will be white
and dazzling like the fun ; its heat will be equal to the
ftrongeft glafs-houfe furnace ; and  in lefs than two
hours will be melted whatever is fufible in furnaces.
The hotteft part is at H F, 4 or 6 inches above the grate.
A  plate-iron tube may be advantageoufly fupplied by a
lhort chimney of bricks,  built under a pretty high vent,
fo  as the whole may eafily be flopped,  except that
paffage which tranfmits  the fmoke of the furnace.  By
this means a very ftrong current of air will be made to
pafs through the fuel.
   On  this fubject  Dr  Black  informs us,  that Mr
Pott of Berlin employs one almoft fimilar to  the above,
                                               for
   604
Luting
proper for
hia furnace.
   605
Method of
applying
the lute.
 2d 605
Meltii g
furnace.
Plate
CXXXIV.
fig. 2.
   606
Mr Pott's
melting
furnace de-
fcribed. 
Theory.
C   H   E   M   I    S    R   T   Y.
Si
Chemical
Furnaces.
   607
Reafons for
making the
fire-place
of a roun-
difh form.
   608
When bel-
lows are
neceffary.
   609
In what ca-
fes the eoli-
pile may be
made ufe
of.
for making experiments on earthen ware ; by which he
fhowed that many  fubftances formerly  rekoned infu-
fible,  might nevertbelefs be melted by fire raifed to a
very intenfe degree ;  and tharfeveral of  thefe bodies,
when mixed together, form compounds  which may  be
melted without any diffi-'ulty. From this a tube  arifes
to fome height, and there is an additional tube which
may be put on to the height of  above  10 feet.   The
fire-place is narrow below, but  widens  towards the
middle, and contracfs again at  top, for the fake of the
veffels which are put into it, and which  are wider at
top than at bottom. Thus the  veffel is  equally heat-
ed, and there is room above for containing a quantity
of fuel, which defcends as faft  as it is confumed. Dif-
ferent reaSons have been affigned for this  form :  thus
Dr Boerhaave imagines that the melting furnace fhould
be  made of a  parabolic form, and Macquer, that it
fhould be in the Sormof  an  ellipSe; and that  the cru-
cible  fhould be placed in one oS the foci,  where  they
Imagined  the  heat would  be  concentrated;  but it is
very plain, that  the  materials are  fuch as are not ca-
pable of reflecting the rays of heat in a regular man-
ner ;  and. even though  they  could do fo,  it would
be  to no purpoSe,  becauSe  the  heat  and  light  do
not come from any  fingle  point,  but from a great
number,  ftriking the furnace in  all  poflible direc-
tions, and  which  muft consequently be  reflected  in
directions as numerous.   The furnace is  made of iron
lined with clay; and as it is difficult to beat out the iron
into this roundifh form, it may as well be made cylin-
drieal; and it is eafy  to give the  infide  what form we
pleafeby means of a  luting of clay; neither need the
dome have the roundifh form,  but may be fimply made
conical.  The vein fhould be madeabout two-thirds of
the diameter  of the furnace,  or fuch as will give an
area of about one-half the grate.   A  fmall  portable
furnace of this kind is very  convenient for ordinary
crucibles ;  the largeft of which are only  about four or
five inches high ; the widefl  part of the furnace may
be  beat out about  io  inches  diameter;  and  when
made of  thin  plate iron, and lined within, are very
convenient,  and may be heated at very little expence
of fuel.  But for heating much larger veffels, it is pro-
per to conftruct them of brick, when they have pretty
much the fame form ; only it is neceffary  tomake them
fquare, and round on the infide  with a lutingof fand and
clay.   The top is generally made flat, and  covered over
with two or three bricks ;  the  vent  goes  a little back-
wards, and then is raifed to a  proper height. Where
I he veflel to be heated is very large, it is common to
leaye the frontopen for putting in the veflel; and then
to build it up with bricks, clay, and fand; which can
be eafily pulled down again when  the operation is over.
   There are fome cafes  in which it is neceffary to
have a rapidity of inflammation even beyond what this
furnace can give ; and in thefe  we have recourfe to bel-
lows of various conftructions,  by which the air can be
compreffed and made to  enter the fuel with great ve-
locity.  Thefe again are fometimes wrought by wa-
ter ;  but there is  another machine which produces a
greater effect, viz. the weiter-blaft defcribed by Lewis
in his Commerciutp Philofoph. Technician.
   The eolipile too may be employed for driving air in-
to fuel.  The effect of this has   been  confidered as a
proof that air  acts by  its elaftieity in animating  fuel,
as an elaftic fluid vapour from the eolipile produces, the Chemical
fame effect.   But when we contrive to feud fteam in- Furnace.
ftead of air, the fame effect is not  produced ; and  the '    "    '
true manner in which this inftrument increafes the in-
flammation is by  driving  air through the fuel:  the
fteam from the veflel fpreadiug and mixing with the air,
and  driving it before it, makes it ftrike upon the fuel.
   Chemifts have generally believed that a wide and
high afh-hole greatly increafes the power of a melting
furnace ; but this advantage is found to be merely ima-
ginary, as well as that of introducing the air  through
a long  tube to the afh-hole;  unlefs where the furnace ii
placed  in a clofe room, So that it is neceflary tofurnifh a
greater blaft of air than can otherwife have accefs.
   For  the form of the furnaces neceffary  in  effaying
and Smelting of ores or making glafs,  fee  Essaying
Glass, and Smelting.                              610
   When large  Stills,  Sand-pots, Sec. are  to be fixed Stills,fand-
with a view to daily  uSe, it is a matter  oS no Small Pots  &c:
conSequence to have them put up in a proper manner. ow  tolct'
The requifites here are, 1. That  the whole force  of
the fite fhould be fpent on the diftilling veffel or fand-
pot,  except what is neceflarily imbibed by the walls of
the furnace. 2, That  the veffel  fhould be fet in fuch
a manner as that  they may receive  heat even from the
furnace walls; for a ftill which contains any liquid
can never be made.fo hot as a piece of dry brick.  3. It
is abfolutely neceffary that the force of the fire be not
allowed  to collect itfelf upon  one particular  part  of
the veffel ; otherwife that part will foon be deftroyed.
3. The draught of air into-fttrnac.es of this kind ought
to be moderate ;  only So much as will prevent Smoke.
IS a ftrong blaft of air enters, not only a great part of
the heat  will be wafted by going up the chimney,  but
the outjideof the veffel will be calcined every timethefire
is kindled, and thus muft be foon rendered unfit for ufe.
   There  are few of the common workmen  that  are
capable of building - furnaces properly ;  and it is very
neceffary  for a chemift to  know when  they  are pro-
perly  done, and to make the workmen act according
to his directions.  As  the ftill, or whatever veflel is to
be fixed,  muft have a fupport from the furnace  on
which  it  is built, it  is  evident the iuhole of its furface
cannot be expofed to the fire.  For this reafon many
of thefe veffels have had only their bottom expofed to
the fire,  no more  fpace being left.for  the action of
the heat,  than  the mere circular area of the ftill bot-
tom  ;  and the fire paffing direeftly through a hole in the
back part of the building,  which communicated with
a  chimney, and  confequently had a ftrong draught,
fcarce  fpent any of  its force on the ftill, but went fu-
rioufly up the chimney.  By this means an extraordi-
nary wafteoffuel was occafioned ; and that  part of
the flill-bottom which was next the chimney receiving
the whoje force  of  the flame, was foon deftroyed.
Attempts were made to remedy this inconvenience,
by putting the fire Something forward, that itmioht
be at  greater diftance from  the  chimney, and con-
fequently might not fpend its force in the air.  This
too was found to avail very little.   A contrivance -was
then fallen upon to  make the vent pafs round the body
of the  ftill in a fpiral  form.   This was a confiderable
improvement; but  had the inconvenience of making
the fire fpend itfelf ufelefsly on the walls of the furnace
and befides wafted that part of the ftill which touched
                                               the 
86                                  CHEMI
Chemical   the under partof the vent.   A much  better method is
Furnace   robuild theback part ofthe furnace entirely clofc, and
          make the fire come out through a long narrow opening
          before ; after which it partes out  through a fine in the
          back and upper partof the furnace into  the  chimney.
            The only convenience  of  this form  is,  that  the
          vent mult  either be very wide, or  it is apt to choak
          up with foot, which laft is a very troublefome circum-
          ftame.  If the vent is made very wide, a  prodigious
          draught of  air ruflies through the fuel, and increafes
          the hear  to fuch  a degree as to calcine the metal  of
          which the ftill is made ; and, on the other hand, no-
          thing can be more difagreeable than to  have the vent
          of a furnace flopped up with foot.   Thefe inconve-
          niences, however,  arc totally avoided by making two
          fmall vents, one on  each  fide of the diftilling veffel,
          which may communicate with  a chimney by means  of
          two tubes cither  of plate-iron or formed with  clay
          or bricks, which may be occafionally  taken off if they
          happen to be choaked up.   The veffel  is  to  be Su-
          fpended by three trunnions, fo that the whole furface
          may be expofed to the fire, excepting  a ring the thick-
          nefs of a brick all round ; S>  that a very ftrong  heat
          will be communicated although the furnace draws but
          little.   The two fmall vents on each fide will draw the
          flame  equally ; and  by this  means  the moft  equable
          heat can be preServed, and may  be pufhed fo far as  to
          make the whole bottom and fides oS the veffel intense-
          ly red.  Such  a confirmation as this is more eSpecially
          ufeful for fand-pots, and thofe which are ufed for diftil-
          ling alkaline fpirits from  bones.
            In the ufe of the furnaces hitherto  defcribed, the at-
          tendance of the operator is neceffary, both for inflec-
          ting the proceffes, and for  fupplying and  animating
          the fuel.  There are  fome  operations,  of a flower
          kind,  that require a gentle  heat to be continued for
          a length of time  ; which demand little attendance in
          regard to the operations themfelves, and in which,  of
          confequence, it is extremely convenient  to have the at-
          tendance in regard to the fire as much as  poflible dif-
          penSed with.   This end has been anSwered by the Sur-
          nace called athanor ; but the uSe of it has been found
          attended with foine inconveniences, and it  is now ge-
    (n   rally laid  aiide.
 Lamp  fur-   Sundry attempts  have  been made  for keeping up a
 »»ce.     continued heat, with as little trouble as in the athanor,
          by the flame of a lamp;  but  the  common  lamp-fur-
          naces have  not anfwered So well as  could be wifhed.
          The lamps require frequent Snuffing,  and Smoke much ;
          and the Soot accumulated  on  the bottom of the veffel
          placed over them,  is  apt,  at times,  to fall down and
          put out the flame.   The largeneSs of the  wick, the
          irregular Supply of oil from the" refervoirby jets, and
          the oil being Suffered to fink confiderably in the lamp,
          fo that the upper part of the wick burns to a coal, ap-
          peared tobcthe principal caufes of thefe inconveniences ;
          \\hich accordingly were  found to be  in great meafure
          remedied by the followingconftruction.
 Tine        The lamp confifts of  a brafs pipe 10 or 12 inches
 CXXXIV. iongf  am]  aDout a quarter of an inch wide, inferted at
 8f • s'     one end into the refervoir of the oil,  and turned up  at
          the other to an elbow, like the bole of  a tobacco-pipe,
          the aperture of which is extended to  the width of near
          two inches.  On this aperture is fitted a round plate,
          kiving St 6, or 7 Small holes, at equal diftanccs, round
  S    T   R    Y.                           Theory.
its outer parr,  into which are inScrted as many pipes chemical
about an inch long : into thefe pipes arc  drawn threads Furnacci.
of cotten, all together not exceeding what in the com- '    v  "*
mon  lamps form one wick: by this eliviiion of the wick,
the flame expoScs a larger Surface to the action of  the
air, the fuliginous matter is confumed and carried  off,
and the lamp burns clear and vivid.
  The refervoir is a cylindric veffel, eight or  ten
inches  wide, compofed of three parts,  with  a  cover
on the  top.   The  middle partition  communicates,
by the  lateral pipe, with the wicks ;  and  has an  up-
right open  pipe foldered into its bottom,  whofe  top
reaches as  high as the level of the  wick ;  fo that,
when this part is charged with oil, till the oil rifes up
to the wicks in  the  other end of the  lamp, any fur-
ther  addition  of oil  will run down through  the  up-
right pipe  into the  lower divifion  of the refervoir.
The upper divifion is defigned for fupplying oil to the
middle one; and, for that  purpofe, is furnifhed with
a cock in the bottom, which is turned more or lefs,
by a key on the outfide, that the oil may drop  faft
enough to fupply the  confumption, or rather fafter, for
the overplus is of no inconvenience, being carried off
by the  upright pipe; fo that the oil is  always, by this
means, kept exactly  at  the fame height in the  lamp.
For common ufes, the middle divifion alone may be made
to fuflice ; for, on account of its width, the finking ofthe
oil will not be  confiderable in feveral hours burning. In
either cafe, however, it is expedient to renew the wicks
every two or three days ; oftener or fcldomer according
as the  oil is more or  lefs foul; for  its impure matter,
gradually left  in the  wicks, occafions the flame to be-
come more  and more dull.  For the more  convenient
renewing of them, there fhould be two of the  perfora-
ted plates ; that when one is  removed, another, with
wicks fitted to it, may be ready to fupply its place.
  One of the black-lead pots, recommended by Dr
Lewi^  for his  portable furnace, makes a proper fur-
nace for the lamp.   If  one is to be fitted  up on pur-
pofe  for this ufe, it  requires  no other aperture than
one  in the bottom for admitting air,  and one in  the
fide  for the introduction of  the elbow of the  lamp.
The refervoir  Hands on any convenient Support  with-
out the furnace.  The  ftopper of  the fide aperture
confifts of two pieces, that it may be conveniently put
in after the lamp is introduced ; and has a round hole
at its bottom fitting the pipe of the lamp.   By thefe
means, the furnace being fet  upon a  trevet  or open
foot, the air enters only underneath, and fpreads equally
all around, without coming in ftreams,whence the flame
burns fteady.  It is not advifeable to attempt raifing the
heat higher than about the /jeoth degree of Fahrenheit's
thermometer ;  a heat fomewhat more than fufficient for
keeping tin in perfect fufion. Some have propofed giving
a much greater degree of heat in lamp-furnaces, by u--
fing  a number  of large wicks ; but when the furnace is
fo heated the oil emits copious  fumes, and its whole
quantity takes fire.  The balneum or other veflel in-
cluding the fubject-matters, is fupported over the flame
by an iron  ring, as already defcribed in the fand-bath
and ftill :  a bath is here particularly neceflary, as th«
fubject would otherwife be very unequally heated, only
a fmall part of the veflel being expofed to  the flame.
Since the new  invention of Argand's lamps, which per-
fectly  confume the oil, attempts have been  made to
                                          conftntct 
Theory.
CHEMISTRY.
67
conftruct lamp-furnaces en their principles ; though,
on the whole, it is  to be  doubted whether they are
preferable to the above confirmation  or  not.
             Explanations of the Plates.
  Plate CXXXIIL fig. 1. fliows the figure of the ftill
recommended by Dr Black ; the bottom formed in fuch
a manner as to go into his furnace.  A, the body ;  B,
the head; C C, the tube conveying the fteam into the
worm ; D F, the figure ofthe worm; E,the worm-tub.
  Fig'. 2. A head taller than the common, proper for
rectifying ardent fpirits.
  Fig. 3. Another kind of ftill for a common furnace,
having a concave bottom for receiving the flame.   A,
the body ; B, the head.
  Fig. 4. Papin's digefter. See Chemistry. n° 567.
A, the body;  B B, the crofs-bars; C D, the Screw ;
E, the lid.
  Fig. e. The outer cafe of Dr Black's furnace with-
out the luting.   A, the body; B, the feet;  I G, the
opening  at top.
  Fig. 6. C, the grate of the fame, with four projec-
tions, having holes in them to fatten it by nails to the
infide of the furnace.
  Fig. 7. A crooked funnel for putting matters into a
retort without touching the fides or neck.
  Fig. 8. Dr  Black's furnace put together  in  readi-
nefs for  chemical operations.   A the mouth;  B, the
chimney; C,  the door of the afh-hole.   E,  the regi-
fters for admitting air.
  Fig. 9.  A Section of the fame,  fhowing its infide Chemical
ftructure.  F, the top-cover ;  G, the body, with part Furnaces.
of the grate ; D, the receptacle for the ailies ;  C, its '    *
door ;  E, the regifters.
  Fig. 10. An iron fupport for a crucible.
  Fig. 11. The figure of a crucible.
  Plate CXXXIV. fig.  1.   Dr Boerhaave's portable
furnace.   See Chemistry, n° 600.
  Fig. 2. Macquer's melting-furnace.  AA, the door of
the afh-pit;  B,  the fpace betwixt the top of the afli-
pit and fire-place; D C,  the bars ; G  H E F, the fire-
place ; I, the funnel.  Ibid. 2d n° 60c.
  Fig. 3.  Dr Lewis's portable furnace fitted with a
ftill, Ibid.  n° 601, 602.
  Fig. 4. Shows the figure of retorts of different kinds.
A,  the body ; B, the neck.
  Fig. 5. A matrafs and alembic head,  with a cucur-
bit and alembic head made of one piece.  A,  the body ;
B, the long neck of the matrafs; C, the alembic head.
A,  the  body of the cucurbit; B,  the  head ; C,  an
opening  in the head for putting in the matter to  be
diftilled ; D,  a  glafs flopple fitted to the opening juft
mentioned ;  E, the opening of the cucurbit mouth.
  Fig. 6. The pelican and cucurbit now in difufe. A,,
the body of the pelican ;  B,  the head; C, an opening
fitted with a flopple; D D, the arms.   A, the body of
the cucurbit; B, the head ; C, the neck ; D, the Spout.,
  Fig. 7. A row of adopters or aludels.
  Fig. 8. Dr Lewis's lamp-furnace.  Ibid. n° 611.
Part   II.      P  R   A   C  T   I   C   E.
Sect. I.  Salts.
§ I. Ofthe Vitriolic Acid, and its Combinations.
6ra
Never    rT",HE vitriolic acid is never found pure, but always
found pure. A  united with fome proportion, either of phlogifton
         or metallic and earthy fubftances.   Indeed  there Is
         fcarce any kind of earth which does not contain fome
         portion  of this acid,  and from which it may ahvays
         fome  way or other be feparable.   When pure, the vi-
         triolic acid appears in the form of a  tranfparent co-
         lourlefs liquor.  By diftilling in a glafs retort, the a-
         queous part arifes, and the liquor which is left becomes
   613   gradually more and more acid.  This operation is ge-
Re&ifica- nerally called the rectification, or dephlegmation, of the
tion.     acid.  After the diftillation has gone on for fome time,
         the water  adheres more ftrongly to what remains in
         the retort, and cannot be forced over without eleva-
         ting part of the acid along with it.  The remaining a-
         cid, being alfo exceedingly concentrated, begins to lofe
         its  fluidity, and puts on the appearance of a clear oil.
         This is  the ftate in which it is ufually fold, and then
         goes by the name of oil of vitriol.  If the diftillation is
         ftill farther continued, with a heat below 6oo° of Fah-
         renheit's thermometer, tire  acid  gradually  lofes more
         and more of its fluidity,  till at laft it congeals in the
         cold,  and becomes like ice.   In  this ftate it  is called
         the icy oil of vitriol.  Such exceedingly great  concentra-
         tion,however, is only practifted on this acid for curiofity.
         ISthe heat be Suddenly raiSed to6oo°,  the whole ofthe
         acid rifes, and generally cracks  the receiver.  Clear
                       1
oil  of vitriol is  immediately turned  black  by an
admixture oS the Smallefl portion of inflammable matter.   6 r^
  The icy oil of vitriol, and even that commonly fold, Attract
attracts the moifture oS the air with very great force, moifture
Newmann relates, that having expofedan ounce of this ir.om the
acid to the air,  from  September 1736  to September air"      <
1737, at the end of the  twelvemonth it weighed fe-
ven ounces and two drachms; and  thus  had attracted
from  the air above fix times its own weight of moi-
fture.  This  quantity, however, Seems extraordinary ;
and it is  probable,  that in So long a time Some water
had been accidentally  mixed  with  it; for Dr  Gould,
proSeffor at Oxford, who Seems to have tried this mat-
ter  fully, relates,  that three drachms of oil of vitriol
acquired, in  57 days,  an  increafe only of fix drachms
and  an half.  The  acid  was expofed  in a glafs of
three inches diameter ;  the increafe of weight the firft
day was  upwards  of  one drachm ; in the  following
days lefs and leSs, till,  on the fiSty-fixth,  it  fcarce
amounted to half a grain.   The liquor, when faturated
with  humidity,  retained  or loft part of its acquired
weight according as the atmofphere was  in a moift or
dry ftate ; and this difference was  fo fenfible as to af-
ford an accurate hygrometer.  Hoffman  having expo-
sed  an ounce  and two Scruples in an open glaSs-difh, in
gained Seven  drachms and a Scruple in 14 day's.         6r?
  This acid,  when mixed with a large quantity of Produdive
water, makes the temperature fomething colder than both of cold
before ; but if the acid bears any confiderable  propor- aD(i heat-
tion to the water, a great hea't is  produced, So as to
make the veffel infuppomble to the hand ; and there-
                                              for s 
88
C   H   E    M    I    S   T    R
1 .
Pracricc
Vitriolic
r.nd ami
it* comM
   617
r.ff(.cK on
the human
Wo*', v.
   618
I>ifnculty
ofprocu-
          fore fuh mixtures ought very  camiouly,  or  rather
          not at .il., to be made in glafs veffels, bat in the com-
          mon ftone-bottle  , or leaden veflels, which are not apt
 ^—     ■ to be corroded by this acid.  The greateft heat is pro-
   f^ft    ductd by equal parts ofacid and water.
 Quantityof   Though the \itriolic acid unites itfelf very ftron^ly
 ailali fatu- with alkalies, both  fixed and volatile, it does not ia-
 ratcd by it. turatc near fo much of the latter as of the former.  A
          pound of oil of vitriol w ill faturate two of the common
          fixed alktli, but fcarce one of volatile alkali. The fpe-
          cific gravity of  good oil  of vitriol  is to water as 17
          to 8.
            If the concentrated acid is applied flightly and fu-
          pcrlicially  to the  fkin of a living animal,  it raifes a
          violent burning  heat and  pain ;  but  a larger quantity
          preffed on, fo as to prevent the ingrefs of aerial moi-
          fture, decafions little  pain or erofion. If diluted with
          a little water, it proves corrofive in either cafe.  Large-
          ly diluted with water, this acid is employed medicinal-
          ly Sor checking putrefaction, abating  heat, and quench-
          ing-thirft;  in  debilities  of the ftomach, and heart-
          burn.  Toperfons of weak and unfound lungs, to wo-
          men who give fuck, to hydropic or emaciated perfons,
          it is injurious.  Some recommend  it as a  collyrium
          for  fore eyes; but as it coagulates the  animal juices,
          corroding and indurating  the folids,  it feems very un-
          fit for being applied to that tender organ.
            The vitriolic  acid is fo much  ufed in  different arts
          and manufactures,  that the making of it  has become a
 ring it  by trade by itfelf;  and the procuring it in plenty, and at
 ufclf.     a ciieap rate, would be a very advantageous piece of
          knowledge to any perfon who could  put it in practice.
          This, however, is very far from being eafily  done ;
          for  though it exifts in almoft every mineral  Subftance,
          the attraction  betwixt this acid and the baSes with
          which it unites, is Sound to be So ftrong, that we can
          only decompoSe Such combinations by preSenting ano-
          ther Subftance to the acid,  to which it  has  a greater
          attraction than that one wherewith it is joined.   Thus
          the firft combination  is indeed diflblved, hut we have
          another from which  it is eqally difficult to extricate
          the acid by itfelf.  Thus, if we  want to difengage the
          vitriolic acid from any metallic fubftance, fuppofe iron,
          this may be eafily done by throwing a calcareous earth
          into a Solution oS green vitriol.   We have now a com-
          pound oS vitriolic acid with the calcareous earth, which
          is known by the name of gypfum or feUnites.   IS we
          want to decompofe this we  muft apply a volatile or or
          a fixed alkali ; and the reSult of this will  conftantly be
          a new combination, which wre are as unable  to decom-
          poSe, and indeed more fo, than the firft.  There are
          two general  methods which have been in ufie Sor pro-
          curing the vitriolic acid  in  Such quantity as to fupply
          the demands of tnide. The one is from pyrites, and
          the other from fulphur.

          I. From  Pyrites, with the making of Copperas, and
               obtaining the pure Oil of Vitriol from it.

 Pyrites,      Pvrites are found in large quantity  in the coal-mines
where    of  Enghnd, where  moft  of  the  copperas  is  made. •
fcund.     They  are very  hard  and  heavy fubftances  having a
          kind of braffy appemance, as if" they contained that
         metal; and hence they are called brajfet by the work-
 men.   A very large qnatuity of thefe is collected, and Vitriolic
 fprcad out upon a bed of ftift clay to the depth of three acitl and
 feet.  After being fome time expofed  to the air, the ,ts <ombl*
 uppcrmoft onesJofe  their metallic appearance,  Split, ",t'°"1' w
 aud fall to powder.   The heaps are then turned, the
 under part  uppcrmoft,  fo as to cxpofe  frefli p> rites  to
 the air.   When they are all reduced to powder, which
 generally  requires three years,  the liemor,  which  is
 formed by the rain-water running from fuch la  large
 mafs,  becomes very  acid,  and has likewife a'ftyptic
 vitriolic tafte.  It is now conveyed into large cifterns
 lined with clay,  whence it is pumped into a very large
 flat veflel made of lead.  This Veflel, which contains
 about 15 or 20 tons of liquor, is Supported by caft-iroh
 plates about  an inch thick, between which and the
 lead a  bed of clay is intef£ofed.   The whole refts
 upon narrow arches of  brick,  under which the fire  is
 placed.  Along with the liquor, about half a ton or
 more of old iron is  put into  the  evaporating veffel.
 The liejuor,  which  is  very  far from being Saturated
 with acid,  acts upon the iron, and, by repeated filling
 up as it evaporates, diffolveR the whole quantity.  By
 the time this quantity is diffolved,  a pellicle is formed
 on the furface.   The fire is then put out;  and as fuch
 a prodigious quantity of liquor does not admit of filtra-
 tion, it is left to fettle  for a  whole day, and then  is
 let off by a cock placed a little above  the bottom of
 the evaporating veltel,  fo as to allow the impurities to
 remain behind.  It is  conveyed by wooden  fpouts to
 a large leaden cittern, five or fix feet deep, finikin the
 ground, and which is capable of containing the whole
 quantity  of  liquor.  Here  the copperas cryftallizes
 on th'e  fides,  and on  flicks put into the liquor.   The
 cryftallization ufually  takes  up  three  weeks.   The
 liquor is then pumped back into the evaporating vef-
 fel ; more  iron,  and  frefli  liquor  from the pyrites,
 are added ;  and a new folution takes place.
   Copperas is ufed, in  dyeing, for p/ocuring a black
 colour; and is an ingredient in making  common ink.
 It is alfo ufed  in medicine as a corroborant, under the
 name of fait of ft eel; but before it  is ufed  with  this
 intention, it is rediffolved in water,  and cryftallized,
 with the addition of a little pure oil oS vitriol.  Whe-
 ther it is  at all mended by this SuppoSed purification,
 either in appearance or  quality, is very doubtful.
   This procefs furniflies  us firft  with  a very impure
 vitriolic acid,  which  could not be applied to any ufeful
 purpofe ; afterwards with an imperfect neutral  fait,
 called green vitriol, which is applicable to feveral pur-
 pofes where  the pure  acid itfelf could not  be ufed ;
 but ftill the  acid by itfelf is not to be  had without a
 very troublefome  operation.                             ,
  Though this acid adheres very ftrongly to iron, it is DifUHatio*
 capable of being  expelled  from it  by  fire; yet  not «f vitrToiic
 without a very violent  and  long-continued  one.  jfacidnom
 we attempt to diftil green vitriol in a retort,  it fwells C0PPera*-
 and boils in fuch a manner by the great quantity of
water contained in its cryftals,  that the  retort will al-
 moft certainly  crack ;  and though it fhould not, the fait
would be changed into an hard ftony mafs,  which the
fire could  never  fufiiciently  penetrate fo as  to cxtri-    /
cate the acid.   It muft therefore be calcined  previous
to the diftillation.  This is beft done in flat iron-pans,
fet over a moderate fire. The fait undergoes the wa-
                                               tery 
C 11  t: m i  < try
Plate (YXXXIN
. td/ f/„/.', J« .<•, 
 
Practice.
CHEMISTRY.
89
Vitriolic
acid and
its combi-
nations.
   621
Preferva-
tives of
wood.
   622
Rectifica-
tion.
 tery  fufion,  (See Fusion); after  which it becomes
 opaque and wnite.  By a continuance of the fire, it be-
 comes brown, yellow, and at laft red.  For the pur-
.pofes of diftillation, it may be taken out as foon as it
 has recovered its folidity.
   The dry vitriol, being now reduced to powder, is to
 be put  into  an earthen retort, or  rather long neck
 (a kind of retort where the neck iflues laterally, that
 the vapours may have little way to afcend)>  which it
 may nearly fill.  This retort muft be placed in a fur-
 nace capable of giving a very ftrong heat,  fuch as the
 melting furnace we have already defcribed.  A large
 receiver is to be fitted on;  and  a Small fire made in
 the  furnace  to heat the  veffels  gradually.   White
 fumes will foon come over into the  receiver, which
 will make the upper part  warm.  The  fire is to  be
 kept of an equal degree of  ftrength,  till the fumes be-
 gin  to diSappear, and the  receiver grows cool.  It is
 then to be increaSed by degrees ;  and the acid will be-
 come gradually more and more difficult to be  raiSed,
 till at laft it  requires an extreme red, or even white,
 heat.   When nothing more  will come over,  the  fire
 muft be Suffered to go out,  the receiver be unfitted, and
 its contents  poured into a  bottle fixed with  a glaSs
 ftopper.   A Sulphureous  and Suffocating  fume  will
 come from the liquor, which muft be carefully avoided.
 In the retort, a fine red powder will remain, which is
 ufed in painting, and is called  colcothar of vitriol.  It
 is ufeful  on account of its  durability; and,  when
 mixed with tar, has been employed as a preservative
 of wood  from rotting; but  Dr Lewis prefers finely
 powdered pit-coal.  As a prefervative for  mafts of
 mips,  he recommends a mixture of tar and lampblack ;
 concerning  which he relates  the following anec-
 dote.
   "  I have been favoured  by a gentleman  on board of
 a veffel in the Eaft-Indies,  with an account of a violent
 thunder-ftorm, by which the main-maft was greatly da-
 maged, and  whofe effects  on the different parts of the
 maftwere pretty remarkable.  All the parts which
 were greafed or covered with turpentine were burft in
 pieces : thofe above, between, and  below the greafed
 parts, as alfo the yard-arms, the round-top or Scaffold-
 ing,  coated with tar  and  lamp-black, remained  un-
 hurt."
   Oil of vitriol, when diftilled in this manner, is al-
 ways  of a black colour, and muft therefore be recti-
 fied by diftillation in a glafs retort.   When  the acid
 has  attained a proper  degree of ftrength, the black-
 nefs either flies off,  or Separates and  falls to  the bot-
 tom, and the liquor becomes clear.   The diftillation
 is then to be difcontinued,  and the clear acid which is
 left  in the retort kept for ufe.
   This was the firft method  by which the vitriolic
 acid was  obtained; and from its being diftilled from
 vitriol has ever fince retained the name of oilof vitriol.
 Green vitriol is  the only  fubftance  from which it is
 practicable to draw this  acid by diftillation;  when
 combined  with  calcareous  earths,   or  even  copper
 (though to this laft it has a weaker attraction than to
 iron), it refifts the fire moft obftinately.  When diftil-
 lation from vitriol was practifed,  large furnaces were
 erected for  that  purpofe, capable  of containing  an
 hundred long necks at once : but as it has been disco-
 vered to be more eafily procurable from fulphur,  this
method has been laid  afide,  and it is now needlefs to Vitriolic
describe thefe furnaces.                              acid and
                                                   its combi-
  II.  To procure the Vitriolic  Acid from Sulphur,   nations.
  This fubftance contaifts the vitriolic acid in fuch
plenty,  that every pound of fulphur, according to Mr
Kirwan's calculation, contains more than one-half of
pure acid ;  which being in a ftate perfectly  dry,  is
confequently of a ftrength far  beyond that of the moft
highly rectified  oil  of vitriol.   Common oil of vitriol
requires to be diftilled to one-fourth of its quantity be-
fore it will coagulate when cold ; and even in this ftate
it  undoubtedly  contains Some water.  No method,
however, has  as yet  been fallen upon to condenfe all
the fteams of  burning  fulphur, at leaft in  the large
way,  nor is  any other profitable  way of decompofing
fulphur known than that by burning ;  and in this way
the moft fuccefsful operators  have never obtained more
than 14 ounces of oil from a  pound of fulphur.
  The difficulties here are,  that fulphur  cannnot  be
burnt but in an  open veffel; and the  ftream  of  air,
which is admitted to make it burn, alfo carries off the
acid which is   emitted  in the form of  fmoke.  To
avoid this, a method was contrived of burning fulphur
in large glafs  globes, capable  of containing an hogf-
head or more.   The fume of the burning fulphur was
then  allowed to circulate till it condenfed into  an acid
liquor.  A greater  difficulty,  however, occurs here;
for though the fulphur burns very Well, its fteams will
never condenfe.  It has been Said, that the condensa-
tion is promoted by keeping fome warm  water conti-
nually fmoking in the bottom  of the globe ;  and even
Dr Lewis  has  afferted this:  but the fleam of warm
water immediately  extinguifhes fulphur, as w7e have
often experienced;  neither  does the fume of burning
Sulphur Seem at all inclinable to join with  water, even
when forced into contact  with it.  As it arifes from
the fulphur,  it contains a quantity of phlogifton, whicli
in a great meafure keeps it from uniting with water ;
and the defideratum is not fomething to make the ful-
phur  burn freely, but  to deprive  the fumes of the
phlogifton they contain,  and  render them niifcible with
water.  For this purpofe  nitre has been advantage-
oufly  uSed.   This confumes a very large  quantity of
the phlogifton contained in fulphur, and  renders  the
acid eafily condenfible :  but  it  is plain that few of the
fumes, comparatively fpeaking, are thus deprived of
the inflammable principle ; for the veffel in which the
fulphur and nitre are burnt,  remains filled with a vo-
latile and moft Suffocating fume,  which  extinguifhes
flame, and iflues in  Such quantity as to render it high-
ly  dangerous  to flay near the place.  It  has been
thought that nitre contributes to the burning of the
fulphur in  clofe veflels;  but  this  too is  a miftakc.
More fulphur may be burnt  in an oil of vitriol globe
without nitre than with it, as we have often experien-
ced ;  for the acid ofthe fulphur unites with thealkaline
bafis of the nitre, and forms  therewith an  uninflam-
mable compound, which foon  extinguifhes the flanie,
and even prevents a part of the fulphur  from being
burnt either at that time or any other.
   In  the condenfation of the fumes of Sulphur by means
of  nitre, a remarkable  effervefcence happens, which
naturally leads us to think that the condenfation  is
produced by fome Struggle  between the  vitriolic and
                       M                   nitrous
   623
Quantityof
acid in tub
phur.
   624
Quantity
produced
from it.

   625.
Methods of
obviating
the difficul-
ties in this
procefs.
   626
Effervef-
cence be-
tween the.
nitrous an4
fulphure-
oV* ftiiact,
Q 
tjo
C   H   E    M    I   S   T    R   Y.
Fiadicc.
variolic   nitrous acijs.—Dr Lewis is ot  opinion,  that the acid
..nd and   the., obtained is  perfectly free from  an admixture of
\*d.°"sthc nitIuUS acid : but in this he is certainly miilaken ;
 ___Jl__. for, on  rectifying the acid  produced by fulphur  and
          nitre, the firft  fumes that come over are red, after
          which they change their colour to white.   How the ni-
          trous acid fhould exift in the liquor, indeed, does not ap-
          (< .u- ; for this acid is totally deftructible  by  deflagra-
          tion with  charcoal:  but it does not  follow,  that be-
          tnifc  the nitrous acid is deftroyed when deflagrated
          with ch 11 coal,   it muft likewife be  fo if deflagrated
          with fulphur.   Indeed  it  certainly  is  not ; for  the
          lIviIUs of nitre made with fulphur is very different from
          that made with charcoal.
             The proportions of nitre to the fulphur, ufed in the
          large oil of vitriol works, are not known, every thing
          being kept as fecret as poflible by the proprietors.  Dr
          Lewis  reckons about fix pounds of  nitre  to an hun-
          dred weight of fulphur ;  but  from fuch experiments as
          we have made, this appears by far too little.  An ounce
          and an half, or  two  ounces, may  be advantageoufly
          ufed to a  pound of fulphur.  In greater  proportions,
    ()t-   nitre feems prejudicial.
Lead vef-     A very  great improvement  in  the apparatus  for
ftU, an im- making oil of vitriol, lies  in the ufing lead veffels in-
provcincnt. ftead of glafs globes.   The globea arc fo  apt to be
          broken by accident,  or by  the action of  the acid upon
          them, that  common  prudence  would fuggeft the ufe
          of lead  to  thofe who intend to prepare any quantity
          of vitriolic acid,  as it is  known to have  fo little effect
          upon the metal.   The leaden veffels, according to the
          beft accounts we have been able to procure, are cubes
          of about three feet, having  on one  fide  a door about
          fix inches  wide.  The mixture of fulphur and nitre
          is  placed in the hollow ofthe cube,  in an earthen  Sau-
          cer, fet on a ftand made of the fame  materials.   The
          quantity which  can be confumed at once in fuch  a
          velfel is about  two ounces.  To prevent the  remains
          from flicking to the  Saucer, it  is laid on a fquare bit
          of brown  paper.  The  fulphur being  kindled,  the
          door is to be clofe ihut,  and the whole  let alone for
          two hours.  In that time the fumes will be condenfed.
          The door is then to be opened ;  and the operator muft
          immediately  retire,  to  efcape  the  fuffocating fumes
          which ilfue from the velfel.  It will be an hour before
          lie can fafely return, and introduce  another quantity
          of materials, which are to be treated precifely in the
          fame manner.
             Where oil of vitriol is made in large quantities,  the
          l;o\.nefs of the  operation  requires a  great number of
          globes,  and eonftant attendance day and night.  Kence
          the making of this acid is very expenfive : The appa-
          ratus for a hrgc work ufually cofls L.1500. fterling.

                       Vitriolic Acid combined,

             I. With Fixed  .4ik.il:.   Dilute a pound of oil of vi-
          triol with rcii times its quantity of w.ner  ; diflblve alfo
          two mmnds of fixed alkaline  fait in ten pounds of  wa-
          ter, and filter the folution.   Drop the alkali into  the
          acid a» long as  any  effervefcence arifes; managing
          in  iters fo that the acid may prevail.   The liquor will
          1w be a folution of the neutral fait,  called vitnJ.ueJ
          t.r:.:r,  which may be procured in a dry form, either
          by cxficcftcn or cr; ■lallkation.  L   cafe the.  latter
 *i8
riolated
r^r.
method is made ufe of, fome more alkali muft be added Vitriolic
w hen it is fet to evaporate, lor this fait cryftallizes bell *tul an**
in an alkaline liquor.                                »ti«,
   Other methods, befides that above defcribed,  have "a '°^ '  ■■
been recommended  for preparing  vitriolated  tartar ;
particularly that of ufing  green  vitriol  inftead of the 629 [630]
pure vitriolic acid.  In this cafe the vitriol is decom- Different
pofed by the fixed alkali: but as the alkali itftlf dif- methods of
folves the calx of iron after it is precipitated, it is next Pfcpaj-"1?
to impoffihle to procure a  pure fait  by fuch a  procefs ; vlt"ola,ed
neither is there occafion to be Solicitous about  the pre-
paration of this fait by itfelf,  as the materials for it are
left in greater enmity than will ever be demanded, af-
ter the diftillation of fpirit of nitre.                     63I
   Vitriolated  tartar  is employed  in  medicine as a   Ufe».
purgative; but is not at  all fuperior to  other falts
which are more eafily prepared in  a cryflalline form.
It is very difficultly Soluble in water, from which pro-
ceeds the  difficulty  of cryftallizing it: for if the
acid and alkali are  not very much diluted,  the fait
will be precipitated in powder,  during  the time of fa-
turation.—It is  very  difficult of fufion, requiring a
ftrong red heat ;  but,  notwithftanding its fixednefsin
a violent fire, it ariSes with  the fteam of boiling water
in Such a manner as  to be  almoft totally diflipatcd along
with it by ftrong boiling.—This Salt has been uSed in
making glaSs ; but  with  little  Succefs, as the  glafs
wherein it is an ingredient always proves very brittle
aud apt to crack of itfelf.                                gj2
   If,  inftead of the vegetable fixed alkali, the vitriolic Glauber's
acid is faturated with the  foflile  one called the fait  of fait.
Soda, a kind of neutral fait will be produced, having
very different  properties  from the  vitriolated tartar.
This compound is  called  Glauber''s fait.   It  diflblves
eafily in water, flioots into long and beautiful  cryftals,
which contain a large quantity  of water, in confe-
quence  of which  they undergo  the aqueous fufion
when expofed  to heat.  They are alfo more eafily fu-
fible than vitriolated tartar.—This kind of fait was for-
merly much recommended as a purgative,  and from its
manifold virtues was intitled by its inventor fal mira-
bile.  It is,  however,  found to pofl'efs no virtue diffe-
rent from that of other purgative falts : and its ufe is,
in many places, entirely fuperfeded by a fait prepared
from the bittern, or liquor  which remains after the cry-
ftallization of fea-falt,  which  fhall be afterwards de-
Scribed.                                                C3,
   If.  With volatile alkali.   Take any quantity oS vo- Glauber's
latile  alkaline  Spirit;  that prepared with  quicklime fecret fait
is  perSerable to the other, on  account oS its raifing ammoniac
no  efferveScence.  Drop  into  this liquor, contained
in a bottle,  diluted oil of vitriol, fhaking the bottle
after  every addition.   The faturation is known to
be complete by the  volatile Smell oS the alkali being
entirely  deftroyed.  When this happen', Some more
of  the  fpirit   muft  be added,  that the  alkali  may
predominate a  little, becauSe  the  exceSs will fly oft
during the evaporation.   The liquor,  on bein^ fil-
tered  and evaporated, will fhoot  into  fine  fibrous
plates  like  Seathers.  This  Salt, when  newly  pre-
pared, has a  Sulphureous Smell,  and  a  penetrating
punyent tafte.   It readily  diflblves  in  water,  and in-
creafes the  coldnefs ofthe liquor ;  on  ftanding for  a
little  time,  it begins to Separate from the Water, and: 
Practice.
CHEMISTRY.
91
Vitriolic
acid and
its combi-
nations.
   634
Properties
ef the Salts
  635
Gypfura.
vegetate, or arife in efnoreScences up the fides of the
glafs. It eafily melts in the fire;  penetrates the com-
mon crucibles ; and if Sublimed in glaSs veffels,  which
requires a very confiderable heat, it always becomes a-
cid, however exactly the Saturation was performed.
  This Salt has been dignified with the names of Glau-
ber'sfecretfat'ammoniac, orphilofophicfal' a?umoniac,frora.
the high opinion  which feme chemifts have entertained
of its  activity upon metals :  but from Mr  Pott's expe-
riments, it appears, that its effects have been greatly ex-
aggerated.   It diflblves or  corrodes in Some  degree all
thoSe metals which oil of  vitriol diflblves,   but has no
effect upon  thofe on  which that  acid does not act by
itfelf.
  Gold is not  touched in the leaft, either by the fait
in fufion, or by  a folution of it :  the fait added  to a
Solution of gold  in aqua-regia occafions no  precipita-
tion or change of colour.   On melting the   Salts with
inflammable matters, it forms a Sulphureous  compound,
which diflblves  gold  in fufion, in  the fame manner as
compofitions of fulphur and fixed alkaline Salt.  Melt-
ed with filver, it corrodes  it into a white clax, which
partially diflblves in water  : it likewiSe precipitates fil-
ver from its Solution in  aquafortis. It acts more pow-
erfully  on copper ;  elevates a  part of the metal in fub-
limation, fo  as  to acquire  a bluifli colour on  the Sur-
face ;  and  renders the greateft part oS the refiduum So-
luble in water.   This Solution appears  colourleSs, So
 that it  could not be Suppofed  to hold any copper; but
readily discovers that it abounds with  that  metal, by
the blue colour it acquires on  an addition  oS volatile
alkali,  and the green calx which fixed alkalies precipi-
tate.   In evaporation it becomes green without addi-
tion.  Iron is corroded by this Salt in fufion, and dif-
folved by boiling in  a  Solution of it.   Zinc diflblves
more freely and  more plentifully.   Lead unites with
it,  but  does not  become foluble in water.  Tin is cor-
roded, and  a part of  the calx is foluble in boiling wa-
ter.  Of regulus of antimony alfo a fmall portion is
made foluble.   Alkalies precipitate from the folution
a bluifli powder.   Calcined biSmuth-ore treated with
its  equal weight of the  Salt,  partly  diffolved in water
into a pale red liquor, which became green  from heat,
in  the  Same manner as tinctures made from  that ore by
aqua-regia.   The undiffolved part yielded  ftill, with
frit,  ablueglaSs.  On treating manganeSe in the Same
manner, aluminous cryftals  were obtained : the  un-
diffolved part of the manganefe gave ftill a violet colour
to glafs.
   III.  With  Calcareous  Earth.  This  combination
may  be  made by faturating diluted   oil  of vitriol
with chalk  in fine powder.   The mixture ought to
be  made in  a glafs ;  the  chalk muft be mixed with
a pretty large quantity of water,  and the   acid drop-
ped into it.  The glafs muft be  wrell fhaken  after
every addition,  and  the  mixture ought rather to be
over faturated  with  acid  ; - becaufe  the   Superfluous
quantity may afterwards be wafhed off;  the felenite, as
it is called,  or gypfum,  having very little Solubility in
water.
   This combination of vitriolic acid with chalk or cal-
careous earth, is found mturally in fuch  plenty, that it
is feldomor never made, u-cSs Sor experiment's Sake,
or by accident.   Mr Pott indeed Says,  that he found
Some flight differences between the natural and artifi- Vitriolic
cial gypSum, but that the former had all the efftntial acid and
properties oS the latter.
  The natural gypfiims are found in hard,  femitran-
fparent mafTes, commonly called alabafttr, or plafter of
Paris.   (See Alabaster, Gypsum, and Plaster.)
By expofure to a  moderate heat, they become opaque,
and  very friable.   If  they are now reduced to  fine
powder,  and mixed with water, they may be caft in-
to moulds of any fhape  : they  very foon  harden with-
out fhrinking ; and are the  materials whereof the com-
mon white  images are made.   This property belongs
li kewifeto theartificial gypSum, if moderately calcined.    ^g
  Mr Beaume has obferved, that gypSum may be  dif- reaume's
Solved in fome meafure by acids ; but is afterwards fe- cbferva-
parable by cryftallization in the Same ftate in which ittlons-
was before Solution, without retaining any partof the
acids.   This compound,  if long  expoSed to a  pretty
ftrong heat,  loSes great part oS its  acid, and is  con-
verted into  quicklime. In  glaSs veffels  it gives  over
no acid  with the moft violent fire.  It may be fufed
by Suddenly applying a very intenfe heat.  With clay
it Soon melts, as w7c have  obServed when Speaking of
the materialsfor making crucibles. Alike fufion takes
place when  pure calcareous earth is mixed with clay ;
but gypSum   bubbles and Swells much more in Sufion
with clay than  calcareous earth.
  From natural gypSum we See that  vitriolated tartar
may be made, in  a manner fimilar to its preparation
Srom green  vitriol.  IS fixed alkaline Salt is boiled with
any quantity of gypfum,  the earth  oS the latter will be
precipitated, and the acid united with the  alkali.  If
a mild volatile alkali is poured on gypSum contained in
a glaSs,  and  the  mixture Srequently fhaken, the gyp-
Sum will in  like  manner be decompoSed, and a philofo-
phic Sal ammoniac will be formed. With the cauftic vo-
latile alkali, or  that made with quicklime, no decom-
pofition enSues.                                        g„.
  IV.   With  Argillaceous  Earth.  The produce of Alum of
this combination is the  aftringent  fait  called alum, theancientB
much  ufed in   dyeing  and  other arts.  It  has its different
name from  the  Latin  word alumen  called  <nwr»|>/«
by the Greeks ;  though  by thefe  words the ancients
expreffed a  ftalactitic fubftance  containing very  little
alum, and that  entirely enveloped in a vitriolic  mat-
ter.   The alum  ufed at  prefent was firft  difcovered
in the oriental parts of the world ;  though we know
not when,  or on what  occafion.  One of the moft an-
cient alum-works  of which we have any account  wasthenameof
that of Roccho, now Edeffa, a city of Syria :  and  from rock alum
this city was derived the appellation of Roch-alum ; an is dcrived'
expreffion folittle underftood by the generality, that it
has been fuppofed to fignify rock-alum.  From this, and
.fome works in the neighbourhood of  Conftantinople,as
well as at Phocaea Nova, now Foya Nova, near Smyr-
na, the  Italians were fupplied till  the middle of the
 15th century, when they  began to  fet  up works of a .-. 639
fimilar  kind in their  own  country.  The firft Italian Alum-
alum work  was  eftablifhed about  1459  by Bartholo- works fet
 mew Perdix,or Pernix, a Genoefe merchant, who had uPia ItaI^'
difcovered  the proper  matrix,  or ore of alum,  in  the
ifland  of Ifchia.   Soon  after  the fame material was
difcovered at Tolfa by John de Caftro, who had vifit-
 ed   the  alum manufactories  at Conftantinople.   IJa-
                       M 2                   ying
from ours.
   '638
Whence 
C   H   E    M    I   S   R    T   Y.
Practice.
   640
lo >|'.iir,
1 inland,
and Swe-
den.
f:(t difcu-
v^re.fhv
Meff.liouL
«i..e and
Geoffroy.
   64a
Mr Kir
wan.
          \i.igobSc \dihc iicx aquilifolium togrowin thentigh-
          bourhood of  the Turkilh  marmfin lories, and finding
          the fame near Tolla, he  concluded that the materials
          for alum were to be found there alfo ,  and was quickly
          confirmed in  hisfiftpicions by the talte ofthe ftones in
          the neighbourhood.   Thefe alum-works prolpcrcd ex-
          rccdin;',iy. and their fuccefs was augmented by an edict
          of l\vt  I'ios  II.  prohibiting the ufe of foreign alum.
            I;. the 16th century an alum manufactory was erec-
          ted at Alamaron.in the neighbourhood of Carthagena,
          where it ftill continues.  Several others were erected in
          Germany ; and  in the reign of Queen  Elizabeth one
          was erected  in England by Thomas ChaToner.  The
          preparation of this fait was not known in Sweden till
   641    the 17th century.
ft« compn-   The component principles of this fait were longun-
ncnt parts  known ; but  at laft Meilrs  Roulduc and  Geoffroy dif-
          covered, that  it conlifted oS argillaceous earth Superf'a-
          turated  with  vitriolic acid.   This is confirmed by the
          experiments of other chemifts.   It is Sound to redden
          the tincture and paper of turnSole ;  and on takingaway
          the  Superabundant acid,  it loScs its  Solubility and  all
Miflake ofthe other properties  of alum.   Mr Morveau, indeed,
Morv-eau  will not admit of a fupcrabnndance of acid  in alum,
f"c^SJ by which  he think., would neceflarily  be  Separated  by
          cdulcoration and  cryftallization; and he is of opinion
          with Vi Kirwan, that the turning vegetable juices red
          is not any unequivocal fign  of the prefence of an acid.
          In the  pieleu cate, however,  we certainly know that
          there is a Superabundance  of  acid, and that a certain
   64,    portion ofthe vitriolic acid  adheres to the clay lefs  tc-
AUnn de-  nacioully than the remainder.  T we  put  a piece of
prived ot  iron into a Mution of alum, ft  will attract this portion
us fuper-  ,,f acjj . rnj t;lt. vitriolated'lay when deprived of the
?"""* .acid fiiperrtuous quauiity, will fall down to the bottom in an
£ water,  infolnuic powder.
            Alum 111 it  ordinary ftate  contains  a confiderable
          quantity of Water, and  cryftallizes by p  oper  manage-
          ment into ocLohe iral and perfec'ly tranlp.irent and co-
          lourlefs  cryftals. When expm'd  to  a  moderate fire,
          it melts bubbles,  and fwelli up;  being  gradually
          changed into  a light, fpongy, white mafs, called burnt
          alum.   This,  with the addition or fome vitriolic  acid,
          mav be cryftallized as before.   The principles it con-
   644    tains, therefore,  are water, vitriolic acid, and argilk-
Eergman's  ceous  earth.   The proportions may be  afcertained in
method of  the following  manner.   1.  The wTater and fuperfluous
nnding the vitriolic acid mav be diffipated  bv evaporation, or ra-
ISffri,^l* ther diftillation;  and the lofe of weight  fuftained  by
tu-opor-    tnc '"alt, as well as the quantity of liquid which comes
ne-us.      over into the  reccivt r, fhows the qwantity of aqueous
          phlegm  and unfaturated acid.   2.  By combining this
          w ith as much cauftic fixed  alkali as is fufficient to fa-
          turate the acid which cemies over, wcknow its propor-
          tion  to  the water ; and by rediftilliug this new com-
          pound, we have the water by itfelf.  5. The earth may
          be obtained bv precipitation with an alkali in its cau-
          ftic ftate, either fixed or volatile : but this part ofthe
          procefs is attended with confiderable diffic my ; Sor the
          alkalies  firft abSorb the Superfluous acid, at- r which
          the earth combined  to faturation with the acid falls to
          the bottom, and  the  digeftion with  the alkaline  fait
          muft be continued  for a  very confiderable time before
         die acid is  totally f'eparated.   By analyfing alum in
         phi:- m-nttcr, Mr Bergman dcicrmmic thepvn.cipki of
   645
n (Faulty
in obta'un-
nij: the
pure c-rth
•f alum.
alum to be 38 pans of vitriolic acid,  18 of clay,  and a itriolic
44 of water, to luoot the crvftaliizcd fait.            aciJ tn^
   1: has been a queftion among chemifts, whether the i*»combi-
earih of alum is to be confidered as a pure clay or  not. n^t'°°*' _.
The fait was  extracted from common clay  by Mcll'rs   646
Hellot and Geoff roy.  The  experiment was repeated Propor-
with fuccefs by Mr Pott ; but he leaned to  confider it tions of in-
rather as the production of a new  Subftance dm ing the Prcdicnt8
operation,  than a combination of any principle already ^^T'n^
exifting with the \ itriolic acid.  Margraaf,  however, mar#
from fome  very accurate experiments, demonftratcd,    647
that all kinds of clay confift of two principles media- Whether
nically mixed:  one of- which conftantly is the pure thecarthof
earth of alum.   This opinion is efpoufed by Bergman ; alum ^c a
who concludes, that lince an equal quantity of it may Pureiay
be extracted from clay by all the acids,  it can only be    g.jj
mixed with thefe clays ;  for if it was generated by the Compo-
menftrua during the operation, it  muft  be procured in nent parts
different quantities, if not of different qualities alfo, ac- of au kinds-
cording to the difference of the Solvents made ufe of. °fclayinve-
Notwithitandinp- this, the matter feems to be rendered ,iKa   V
fomewhat  obfeure  by an  experiment of Dr Lewis.    640
" Powderedtobacco-pipe clay (fays he) being boiled in Lewis's
a confiderable quantity of oil of vitriol, and the boiling experi-
contilined to drynefs,  the matter when cold difcovers nunt, ten-
very little tafte, or only a flight acidulous one.    Ex. *J*nK to
pofed  to the  air for a few  days, the greateft part of j  w l^at
it was changed into  lanuginous  efllorefcenccs tafting goIsUf0inT
exactly like alum.   The remainder, treated with frefh change in
oil of vitriol, in  the fame  manner  exhibits the fame being con-
phenomena till nearly the whole of the clay is convert- verted into
ed into an aftringent fait."  Hence  he concludes,  that ctirth of
the clay is in fome degree changed before the alumi- alun1,
nous fait  is produced.  Without  this fuppofition, in-
deed, it is difficult to fee why the Salt fhould not be pro-
duced  immediately  by the  combination  of  the   two    g.0
principles.  An hundred parts of cryftallized alum re- Solubility
q fires, according to  Mr  Bergman,  in  a mean heat of alum in
1412 parts of  diftilled water,  but  in  a  boiling heat warm and
only 75 of the fame parts for its folution.   The  fpeci-in coltl  v,u"
fie gravity of alum,  when computed  from the  increafeter"
of bulk in its  folution, is 2.071 when the air-bubbles
are abftradted  ; but if they are fuffered to remain, it is
no more than  1.757.  Thefe bubbles confift of  aerial
acid, but cannot be removed by the  air-pump, though
they fly off on the application  of heat.                   g?I
   The ores from which alumis prepared for fale, accord- Tcruman's
ing toMr Bergman, are of two kinds : one containing the account of
alum already formed, the other its principles unitedby theSwcdifli
roafting.   What he calls the aluminous Schift, is no- ores of
thing but an argillaceous fchift impregnated v. ith a dried   T"
petroleum,  from whence the oil is eafily  extracted by Conipo-
diftillation; but by applying proper menftrua it  di.'co- nent parts
vers Several other ingredients, particularly an argilla- of the alu-
ceous martial Subftance, frequently amounting to -< of rninous
the whole ; a Siliceous matter amounting to j; and com- fchlft*
monly  alfo a Small proportion of calcareous  earth and
maamefiii ;  the reft being; all  pyritems.    By roaftirp- x3  ' s%
 ,.      !   ,.        6   .*].  _     . J  , ,   "SHowchan-
this ore the m luminous part is deftroyed and the  py- „ed Dy
rites decompofed ; on which part ofthe vitriolic acidroafliir'.
adheres to  the iron of  the pyrites,  and the reft to the
pure clay of the fchift, forming green vitriol with  the
former, and alum with the  latter.   If any calcareous
earth or magnefia are tveftnt,  ^ypfom and KpSmi  ftlt
v, :il be  prudu-.cd at the £m.c tine, fso Salt it. obtained
                                                bv 
Practice.
CHEMISTRY.
93
   654
The pre
fence of
   655
Ores con-
taining
with in
volcanic
countries.
          by lixiviating this fchift before calcination, thought Mr
          Bergman thinks nothing more is neceffary for the pro-
          duction ofthe fait but the prefence of a pyrites.  This,
          he tells us, is generally difperSed through the mafs in
          form of very  minute particles, though it fometimes ap-
          pears in fmall nuclei.   The goodnefs of the ore, there-
          fore, depends on the proper proportion ofthe pyrites to
 pyrites on- ,-h.g cjay^ anc| -ns e<^aa\ diftribution through the whole.
 /"eLe irf The moft denSe and ponderous is moft efteemed, while
 lor the pro-  ,     ...       .   r         '  _             .,-,,.
 duction of t'iat wnich contains So much pyrites as to be  vifible is
 alum.     rejected as having too much iron.   The ore which pro-
          duces leSs than Sour pounds of  alum from  100 of  the
          ore does not pay the expence of manufacturing in Swe-
          den.   Sometimes this kind of ore produces Salts with-
          out the application oSfire ; but this muft be attributed
          to a kind of fpontaneous calcination.
             That fpecies of  ore  which contains the principles
          already united into alum, according to  Mr Bergman, is
 alum ready to be met with only in  volcanic countries ; and of this
 formed,on- kind are the principal  Italian ores of  alum, partial-
 is' ;nmet *arty r^at: emPl°yed at Tolfa near Cincelles, for boiling
          the Roman alum.  Mr Monnet, however, is of opinion,
          that even this ore does not contain  alum  perfectly
          formed, but a combination  of nearly  equal  parts  of
          clay and fulphur,  which  by expofure to air during
          calcination, is converted into alum.  He found a little
          martial earth  alfo contained in it, to which he afcribes
 Aluminous the reddifh colour of that  alum.   The aluminous  ore
 ore at Sol- at Solfatara in Italy confifts of old lava whitened  by
          the phlogifticated vitriolic acid.   The  clay  thus be-
          comes a component part of the aluminous fait, and  the
          mafs efflorefces in the fame manner, and for the fame
          reafon,  as the mafs left after boiling tobacco-pipe clay
          in oil of vitriol mentioned  by Dr  Lewis.  Mr  Berg-
          man,  who examined this ore,  found,  that 100 pounds
          of it contained eight of pure alum, befides four of pure
          clay ;  and that the remainder was filiceous.   This pro-
          portion, however, muft be very variable, according
          to the quantity of rain which falls upon the ore.
            A variety of aluminous  ores are to  be met with in
          different parts of the world.  In Haflia  and Bohemia
 Haffia, Bo- this fait is obtained from wood impregnated with bitu-
 hemia, and men.  At Helfingborg in Scania, a turf is found con-
          fifting of the roots of vegetables mixed with nuts, ftraw,
          and leaves, often covered with a thin pyritous cuticle,
          which, when elixated, yields alum : Even the fulphu-
          reous pyrites is generally mixed  with an argillaceous
Alum,'ful- matter, which  may  be feparated by  menftrua.   In
 phur, and Some places,  Sulphur, vitriol, and alum are extracted
vitriol ex- from tne fame material. The Sulphur riSesby diftilla-
tracted   tjon . ^ replciLlam js expoSed to  the air till  it efflo-
fame ore.  ref-'es>  afrer which a green Vitriol is obtained by lixi-
   660   viation,  and alum from the Same liquor, after no more
Alum flate vitriol will cryftallize.   The alum flate, from which
found at  Sail is made near York  in England, contains a confi-
         derable quantity^ oS  Sulphur;  and  therefore  produ-
         ces alum on the principles already mentioned.
            Mr Bergman has given very  particular directions
         for the preparation of this fait from its ores,  and  mi-
         nutely defcribes  the  feveral  operations which  they
656
fatara in
Italy.


   657
Analyzed
by Mr
Uergman
   658
Aluminous
Scania.
659
York in
England.
   661
l«ergman's
directions
for the pre
paration of muft undergo.   TheSe are.
alum.
   66z
tTfeof
noafting
&j»e ore.
  1. R.o ast 1 n g .  This is absolutely neceffary in order
to deftroy the pyrites ;  for on this the formation of the
alum entirely depends ;  as.the  fulphur of the pyrites
will, not part  with its  phlogifton without a burning
repeated.
 heat in the open air.  By long expofure to the air, in- Vitriolic
 deed, the fame effect will follow; but unlefs the ore be acid and
 of-^a particular kind, andloofein texture, fo that the air lts foml>1"
 can freely pervade it, the procefs  we fpeak of cannot ^a ' ^ ' a
 take place.  The  hard  ores,  therefore,  cannot  be    663
 treated in this manner ; and  the earthy  ores  are  not Expofuret».
 only unfit for fpontaneous calcination, but for roafting Jrc Z1T. has
 alfo, as they will not allow the air to pervade them and j°metinies
 extinguifh the fire.   Such as are capable of fpontane- effe<a#
 ous calcination, Iliould be fupplied with fome quantity    664
 of water, and laid on a hard  clay bottom, as directed Earthy ores
 for making green vitriol.  The roafting is performed unfit for
 in Sweden in the following manner.  Small pieces  of ".ot^ °Pera"
 the ore are ftrewed upon a layer of burning  flicks  to tloni6c
 the thicknefs  of half a foot.  When  the  flicks are Method of
 confumed,  thefe are covered,  nearly  to the fame roaftingthe
 thicknefs, with pieces burned before and four times ore in Swe~
 lixiviated : Thus Strata are  alternately laid  of fuch a den.
 thicknefs, and at fuch intervals of time, that the fire
 may  continue,  and  the  whole mafs grow  hot and
 fmoke, but not break out into  flame.  The upper ftra- -
 ta  may fometimes be increafed to  a double thicknefs
 on account of the long continuance of the fire.  When
 eight ftrata are laid, another row is placed contiguous
 to the former ; when this is finifhed, a third ;  and fo
 on until the heap be of a proper fize, which rarely re-
 quires more than three rows.  When the ore  is once
 roafted, it ftill contains fo much phlogifton that water   666
 acts but little upon it; but after the operation  is two How often
 or three times repeated, the  ore yields  its principles *c opera-
 more freely :  the roafting may even be  repeated to ad-tloms t0 be
 vantage till the whole be reduced to powder.   The bi- '"
 tumen keeps up the fire; for which reafon alternate
 layers of the crude ore are ufed ; and in rainy weather
 thefe layers of unburnt ore fhould be thicker.  An heap,.
 20 feet broad at the bafe,  two feet at the top, and con-
 fining of 26 rows, is finifhed  in three weeks, but re-
 quires two  or three months  to  be w7ell burned, and
 three weeks to cool.  The greater pyritous nuclei ex-
 plode like bombs.  In this procefs  the fulphur of the
 pyrites is flowly confumed, and the phlogifticated acid
 penetrating the mafs, is fixed;  after which  the re-
 maining phlogifton is gradually diffipated.  The chief Danger of
 art confifts in moderating  the heat in fuch a manner as raifing »h&.
 to avoid with fafety  the two extremes ;  for too fmall heat t0°
 a fire would not be capable of  forming the fait,  vftiile much-
 a heat too ftrong would deftroy it by melting the ore.
 The fcoriaare infoluble in  water, and therefore thrown
 away as ufelefs.   They are produced by  violent winds,,
 or by a ftrong heat too much  clofed up  ; for it  is ne-
 ceffary to  make holes in the  red ftrata,  that the fire
 may reach the back  Stratum whicli  is to  be  laid on.
 Another method of burning was  invented by the cele-
 brated Rinman, and is practifed  at a place called Gar-
phyttan in Sweden.  There the ore itfelf is fet on fire ; method of
 and afterburning is boiled, and yields alum in the fame burningthe
 manner as the former.   The heaps are  formed in the °fe at Gar~"
 following manner :  Firft the fchift,  burning from the **iy
 furnace, is laid to the depth of four feet ; if the fire be
 flow,  then wood is added ; after that a thin ftratum of
elixated fchift ; the third confifts of fchift not burned ;
 and the fourth of elixated fchift a foot and a half thick ;
 after that the burning fchift, and  fb on.   This method,
 however,  is attended with fome inconveniences.  The
 vitriolic acid is partly diflipated  by the fire, and thus;
                                                the'
667-
   668
Rinman's 
CHEMISTRY.
Practice.
Method of limcitone, until they
b rnin^the , ftorc(CCi   pjlc  ^re
uird ores
at Tulfa in
«:.dy.
          the quantity of alum  is dimimft.ed : fo much fchift alfo
          i* reip.iiitc in tiiis method that it cannot all  be elixa-
          ted ;  and thus the heap muft be perpetually incrcaiing.
          The hard ores containing bitumen, fuch as thofe  of
          Tolfu,  are bunted  .y<on wood  for  fome  hours  like
                               become  pervious to water, and
                              is  extm^uifhed as foon as  the
          name becomes  white,  and the  fmell  of  Sulphure-
          ous acid  begins  to  be  perceived.   When  the  ore
          cools, thofe particles which  were neareft  to the fire
          are placed ontcrmoit, and thoSe which had been outer-
          molt  within, the  fire being again lighted.  The ore is
          Sufficiently  burned when it can be  broken with the
          hands.  It  is then hejped  up near  certain trenches,
          and watered five times a-d.iv,  particularly when the
          Sun fhines clear; the operation being deftroyed by  a
          continued  rain and cloudy fky.  In fomc  places the
          ore is firft burned and afterwards  elixated ;  neither is
          there any way of knowing the proper methods  of ma-
    670    nagingit but by experiment.
 Mithod of   2.  Elixation.   This is performed in fome places
  '"ting   with hot, and at others with cold, water. AtGarphyttan
          in Sweden, where the latter method ischofen,  the re-
          ceptacles, in the year 1 772, were of hewn ftone, having
          their joints united by Some cement capable of refilling
          the liqlGr.   Every Set  confifted of four fquare  recep-
          tacles difpofed round a  fifth,  which was deeper than
          the reft.  The firft  receptacle is  filled  with roafted
          fchift, and the ore lies in water for 24 hours ; the wa-
          ter is then  drawn off by a pipe into the fifth; from
          thence into the Second, containing fchift not yet wafhed;
          from that in like  manner, after 24 hours, through the
          fifth  into the third, and fo into the fourth  The lixi-
          vium  is then conveyed  to the fifth, and allowed  to
   671    ftand in it; and laftly is drawn off into a veffel  appro-
Other mc-  priated for its reception.—In  other places the  water
the burned
urc at Gar.
phyttan
with cold
*.itcr.
thods

Singular
circum-
ftance by
which the
alum piay
          paffes over the fchift that has been wafhed three  times
          for fix hours ;  then that which has been twice wafhed,
          next what has been once  w allied, and laftly, the ore
          which has been newly roafted. Thofe who fuperintend
          the  alum manufactories are of opinion that the  alum
          is deftroyed by pafling the water  firft over the newly
be deftroy- burnt ore, and then over that which has been previouS-
eef.       ly elixated.
   673       The lixivium, before boiling, ought to be as richly
    K P °" impregnated with alum  as poflible,  in order to fave
ftrength of fuel, though  this  is Srequently  neglected.  In fome
the luivi-  places the tafte is ufed as  the only  criterion;  but  in
um before  others the weight oS water which fills a  Small glafs
boiling.    bottle is dhidedinto 64 equal parts,  each of which  is-
          called in Sweden  a  panning;  and the quantity  by
          which the fame bottle, full of lixivium, exceeds it when
          filled with water, is fuppofed to indicate the  quantity
          of fait diffolved.—This  method   may undoubtedly be
          reckoned fufficient ly accurate for work  conducted on
          a large fcale : and though M;- Bergman gives formulae
          bv which the matter may be determined to a fcrupu-
          Lms exactnefs, it does not appear that fuch  accuracy
          is either neceflary or indeed practicable in works con-
          ducted in a great way.
           Thofe who manage  the alum   manufactories  afferr,
          that the cold lixivium ought to be made no richer than
          v. hen the weight of the  bottle filled with  lixivium
         wee'eds  ft when  filled  with water by 4; pjunings,
which fliows the  water to  be loaded  with ,'.  of its
weight of alum.  If the overplus amounts to fix pan-
nin^s, which indicates its containing  'M  oflalt, cry-
ftals arc  then depofited. — Congelation is  of  no i.fc
to concentrate  the aluminous  lixivium ;  for  water
faturatcd with alum freezes almoft as  readily as pure
water.
   3. Boiling the ley ior chrystallization.
The ley being firft brought from  the pits through ca-
nals made for the purpofe, is put into a  leaden boiler, at
the back of which is a refervoir, out of w hich the lofs
fuftained by evaporation is  conftantly fupplied, fo that
the furfaceof that in the boiler continues always nearly
at the fame height.  Various Signs are ufed by different
manufacturers to know when the ley is properly evapo-
rated:  fome determining the matter by  the floating of a
new laid egg; others by dropping a fmall quantity on a
plate, and obfervingwhetherit cry ftallizes on cooling;
and laftly, others weigh  the lixivium in the bottle
abovementioned.   The boiling  is  fuppofed  to  be  fi-
nifhed  if the increafe of weight  be  equal to  10 pan-
nings; that is, if the  water  be loaded with T.j7 of
its own weight.   It might, however,  take up above '7
of its weight, or  nearly 27 pannings ;  but as it has to
be depurated by ftanding quiet before the cryftals are
formed, the liquor muft not be  fully  Saturated  with
fait.
  The lixivium,  when  Sufficiently concentrated  by
evaporation,flow s  through proper channels into coolers,
where it is allowed to reft  Sor about an hour to free it
from the grofler Sediment ; aSter which it is put into
wooden or ftone receptacles to  cryftallize.   In eight
or ten days the remaining  liquor,  commonly  called
mother ley, or 7/iagiftral water, is let off into another vcS-
Sel.  A great number of cryftals, generally fmall and
impure, adhere to the bottom and  fides of  the veffel,
which are afterwards  collected and wafhed in cold
water.
  When a Sufficient quantity of the fmall cryftals are
collected,  thy muft then  be put into the boiler for de-
puration.  They are now diflblved in as fmall a quan-
tity of water as poflible ;  after which  the lixivium is
poured into  a great tub  containing as much as the
boiler itfelf.   In 61 or  81 days  the hoops of the tub
are loofed, and the  aluminous mafs  bound  with an
iron ring; and in 28  days more  the refiduum of the
folution is let out  through a hole,  and  collected in  a
trench; after which the  faline  mafs,  which  at  Gar-
phyttan in Sweden amounts to 26 tons, is dried and fold
as depurated alum.  The boiler emptied  for the firft
cryftallization is next filled two-thirds full with the
magiftral lixivium ; and as foon as the liquor arrives
at the boiling point, the otherthird is filled with crude
lixivium,  with which the evaporation is alfo conftantly
fupplied.  A certain quantity of  the  aluminous  im-
purities left by warning the falts  of the  firft cryftalliza-
tion in water is then added, and the abovo  defcribed
procefs repeated.   Only the firft boiling in  the fpring
is performed w ith the crude lixivium alone, the reft
are all done as juft now  related.— Mr Bergman re-
marks, that the time required for cryftallization may
undoubtedly  be lhortened.   The  refervoirs ufed in
Sweden for  this purpofe (he fays), are deep and nar-
row at the top ;  on which account they  are not only
                                              long
   674
C'onft ruc-
tion of the
evapora-
ting veffel.
   675
Proper
ftrength of
the evapo-
rated li-
quor.
   676
Ofthe firft
cryftalliza-
tion.
   677
Depuratiofi
of the cry-
ftals.
   678
Bergman's
remarks on
the proper
form ofthe
coolers. 
Practice.
CHEMISTRY.
   679
Alum can
not be
          long in cooling, but the  evaporation, which is abso-
          lutely neceflary for the cryftallization,  goes on very
          flowly, excepting in extremely warm weather, at the
          fame time that- the doors and windows are difpofed in
          fuch a manner as  to direct a current of air along the
          furface.  In Italy he tells us that conical refervoirs are
          ufed with the wide part uppermoft.
            It is remarkable,  that pure alum cannot be obtained
          in very confiderable quantity by merely evaporating
formed by aru| COoling the ley.   The reaSon of this  is, that the
merelyeva- j}xjv}um fometimes acquires fuch a confiftence,  that it
a„"Co°j;   both cryftallizes  with difficulty, and  produces im-
the ley, on Pure cryftals.   The caufe was unknown till the time
account of of  Mr Bergman,  who  has  fhown  that  it  proceeds
the excefs  from an excefs of vitriolic acid.  Hence alfo we may
ef acid.    fee  rhe reafon  why alkaline falts, volatile alkali in its
          pure ftate,  or  even putrefied urine, when added to this
    680   thick folution, produce good cryftals  of alum  when
This excefs they cannot be obtained otherwife.   It is remarkable
cannot be  that this  impediment  to  cryftallization  is  not  re-
removedby moved by mineral alkali, though it is  fo  by the  ve-
kahth1 ehSeta^e anc* volatile alkalies, which is a phenomenon
itmaybeby hitherto unexplained.  According to our author, how-
vegetable  ever,  an addition of  pure clay, to abforb the fuper-
and volatile abundant acid, is preferable to any other ;  and indeed
alkalies,   it  is reafonable to think fo, as the union of vitriolic
a"('11)eft °* acid and pure clay forms the fait defired, which is not
a   ypure ^ care ^[^ any 0f thc alkalies.   To afcertain this,
   ^gj   he made the following experiments.
Experi-     i. He diffolved 215 grains of pure alum in diftilled
mentfhow-water, in  a fmall cucurbit,  and evaporated it over the
ing that an fire till the furface of the liquor flood at two marks,
excefsof yi- which  indicated,  in a former evaporation, that it was
im  ed""1 ^l ^or cry^^iZiL^on-   2- Having poured out this into
thecrvftal-a ProPer glafs veflel,  he diffolved  other  215 grains,
lization of and added to the folution 241 grains of concentrated
alum.     vitriolic acid.   3.  This folution being likewife poured
          out, the experiment was repeated a third  time, with
          the addition  of 55 grains of vitriolic acid; and  the
          glaffes  being at laft Set in a proper place for cryftal-
          lization, the firft yielded 1 cc|, the Second 130, and the
          third 100:.  grains oS alum.
            This fhows  that an exceSs of vitriolic acid impedes
ment to de- the cryftallization of the alum ;  but to determine how
•ermmethe par  tp,is could be remedied by the addition of clay, far-
UfC da     t^ier exPerimeilts were neceffary.   Having therefore
clayto'the employed  a magiftral refiduum, in which  the  excefs
          of acid was  nearly in the proportion already related,
          he added two  drachms  of clay in  fine powder to a
          kanne, or Swedilh cantharus, of the liquor : he boil-
          ed the mixture for ten minutes;  and  on feparating
          the  clay that remained, he found that  25; grains were
          diflblved, which indicates an increafe of 141 grains of
          alum.   On gently boiling the liquor for half an hour,
          75 grains of the clay were diffolved,  which indicated
          an increaSe of  416 grains of alum.
            The addition of clay muft therefore be much pre-
ges of ufing ferahle to that of alkaline falts, not only as the former
clay rather produces a  confiderable increafe oS alum, but alSo  as
than alia-  there is no danger of adding too much; for we have
          already fhown, that when the  liquor is entirely  de-
          prived of its fuperabundant acid, the neutrallized clay
          is infoluble in water.   The earth itfelf, however, dif-
          folves fo flowly-, that there is not. the Leaft danger of
   68a
Experi-
ky.
   683
Advanta
Be
the acid being overfaturated  by fimply  boiling them
together.
   Alum, as commonly made, though depurated by a
Second cryftallization, yet is almoft always found con-
taminated by dephlogifticated vitriol;  whence it grow7s
yellow, and depofits an ochre in folution when old.
This is equally ufeful in fome arts with the pureft kind,
and is even fo in dyeing where  dark colours are re-
quired ; but where the more lively colours are wanted,
every thing vitriolic muft be  avoided.   This is  done
by the addition of pure clay, which precipitates the
iron,  and produces an alum entirely  void of any  nox-
ious or heterogeneous matter.   Nor is this contrary
to the laws of chemical attraction ; for though iron is
diffolved by a  folution of alum, and the earthy bafe oS
alum  precipitated, and though in a Solution of vitriol
and alum the white earth  falls firft on an addition oS
alkali, and then the ochre; this happens only in conSe-
quence of employing phlogifticated or metallic iron, or
fuch as is but very little dephlogifticated ; for if the
inflammable principle be any  further diminiflied, the
attraction is  thereby fo  much weakened,   that  the
clay has  a greater attraction for the vitriolic acid  than
the iron.  The truth of this may be proved  in many
different ways.  Thus, let a  portion of alum be dif-
folved in a folution of highly  dephlogifticated vitriol,
and an alkali then added, the ochre of the vitriol will
be firft depofited  and then the  clay :   and  provided
there be a fufficient  quantity of the latter,  the  iron
will all be precipitated ; and hence wTe fee that an alu-
minous folution mixed only with  one of dephlogiftica-
cated  vitriol may readily be freed from it
   But a folution  of alum   containing  perfect  vi-
triol cannot be  freed from  it  effectually either by
clay or  alkali;  for  the former  effects  no decompo-
fition,  and the latter, although it can deftroy the vi-
triol,  will  undoubtedly decompoSe the  alum in  the
firft place.   As long, therefore, as the folution is rich
in alum, in may be employed in the common  manner ;
but when the vitriolic  fait  begins to predominate, it
muft either be cryftallized in its proper form,  or be
deftroyed in fuch a manner as  to produce alum, which
may be accomplifhed in the following manner.  Let
the lixivium be reduced to a tenacious maSs with clay,
and formed into cakes, which muft  be expofed in an
houfie to  the open  air.  Thus the phlogifton, which
is powerSully attracted by the dephlogifticated part of
the atmofphere,  by degrees Separates  from  the iron,
while the clay is taken up by its fuperior  attraeftion
for the acid.   The calcination is accelerated by fire ;
but it muft  be  cantioufly employed, left the acid fhould
be expelled..
   In the alum manufactories  Tn  Sweden, a confide-
rable quantity  of vitriolated  magnefia, or Epfom  fait,
is mixed with the alum.   Mr  Bergman directs this to
be Separated  by means of  an uncalcined calcareous
earth,  which  entirely deftroys both the alum and vi-
triol ; falling  down  to  the  bottom with the acid in
form of a Selenitic matter.   This  muft be added to the
boiling liquor  gradually, left the effervefcence fhould
caufe the mafs to fwell and- run  over the top of the
veffel.   A  juft proportion  deftroys  both the alumi-
nous and vitriolic fait, on being properly agitated and
heated; neither is there  any danger of the Epfom
                                                fair
      95
Vitriolic
acid and
its combi-
nations.
*   v/ ■■■*
   684
Alum ge-
nerally
contamina-
ted by de-
phlogifti-
cated vitri-
ol.

   685
This defetft.
remedied
hy the ad-
dition of
pure
clay,
   686'
Perfect vi-
triol cannoir:
be deftroy-
ed by clay..
   687
How the
phlogifton
may be ab-
ftraded
from the
vitriol.
   68&
Epfom falfc
may be
produced
from the-
mother hV
quor. 
9'>
V.triol;*
•cid and
iti combi-
nations.


Superflu-
ous acid
might be
■dvantjge-
oufly dif-
xilled.
CHEMISTRY.
Pra(fticct
   *90
Ipfona fait
fait bang decemrpofcd in this procefs, the uncalcined
earth being unable to Separate the magnefia from  the
acid.   Were this method followed in the Swedifhma-
nur.mtorics, he  is of opinion,  that as  much Epfom
Salt might be produced from them as would Supply the
conSumpt of that kingdom.
   With  regard  to the  quantity  of  fupcrfluous  acid
found in the magiftral lixivium, Mr Bergman informs
us, that  it  amounted to five ounces  in one kanne ; fo
that in a fingle boiler there is nearly 250 lb.  But vi-
triol, when well  dephlogifticated, retains its acid fo
loofely that it may eafily be Separated by fire.  He has
no doubt, thereSore,  that if the furface of fuch a lixi-
vium were firft increafed in order to let the phlogifton
evaporate,  the liquor might afterwards  be  advanta-
geoufly committed to diftillation  for the  fake of  its
•acid.
   Krom  what has been above  delivered  the neceflity
will  be  fufficicntly  apparent of  not  continuing the
coction even with pure clay to  perfect faturation of
the  liquor: and  this is  further confirmed by  M.
Beaume, who relates,  that  having  boiled four ounces
of earth of alum with two ounces of the fait, in a fuf-
ficient quantity  of water, the acid became faturatcd to
fuch a degree with earth,  that the  liquor loft its alu-
minous tafte entirely, and  affumed that of hard fpring
water.   After filtration and evaporation, only a few
micaceous  cryftals, very  difficult  of folution, were
formed by letting the liquor ftand for fome months.-—
Dr Sieffert  informs us,  that by boiling half an ounce
of  alum with half a drachm of flaked  lime,  cubical
cryftals of aldm may be obtained.
   V. With Magnefia. The earthy fubftance called mag-
nefia alba is never found by Itfelf, and confequently this
combination cannot originally take place by art.   The
vitriolic  acid, however, is found combined with magne-
fia in great plenty in the bitter liquor which remains af-
ter the cryftallization of common fait; from whence the
magnefia is procured by precipitating with a fixed alkalh
If this liquor, which, when rhe common fait is extrac-
ted, appears like clean oil of vitriol,  is fet by for fome
time in a leaden veffel,  a large quantity of fait fhoots;
very much  refembling  Glauber's  fal mirabile.  This
fait is in many places fold inftead of the true Glauber's
fait  ; and is preferred to it, becaufe the true fal  mi-
rabile calcines in dry air, which the  fpurious kind does
not.   If after the firft cryftallization of the bittern,
the  remainder is gently evaporated farther,  a frefli
quantity of Glauber's fait will fhoot; and if the liquor
is then haftily evaporated, a fait will ftill be cryftal-
lized ; but  inftead of  large regular cryftals, it will
concrete into very  fmall  ones, having  fomething of
the appearance of fnow when taken out of the liquid.
Thefe Salts are  eflentially  the  Same, and are all ufed
in  medicine as  purgatives.  The  Salt lhot into Small
cryftals  is  termed £/for: fait, from  its being firft pro-
duced Srom the  purging waters at EpSom in England.
The bittern affording  this kind of fait in fuch great
plenty,  thefe waters were foon neglected, as they
yielded  it  but very Sparingly, and  the  quantity pre-
pared from them was inefficient  for  the demand.
Neumann  Says, that having inSpiffated 100  quarts of
fepScm water, he fcarce obtained  half an ounce of fa-
line matter.—According to Mr Scheelt's experiments,
if a folution of Epfom and common fait  be  mixed to-
gether, a double decompolition enfues,  and  the mix-
ture contains Glauber's fait and a combination of mag-
nefia with marine acid.   From this lixivium the Glau-
ber's  fait may be cryftallized in winter, but  not  in
fummer;  a great  degree of cold being neceflary for
this purpofe.   From twelve pounds of Epfom fait and
fix of common fait, Mr Scheele obtained, in a tempera-
ture three degrees below the freezing point,  fix pounds
of Glauber fait;  but in a degree  of cold confiderably
greater,  the  produce  was  feven pounds   and three
quarters.
   VI. With Silver.   Oil of vitriol boiled on half its
weight of filver-filings, corrodes them into a faline mafs.
This  fubftance is not ufed in medicine nor in the arts.
The only remarkable property of it is, that it  has a very
ftrong attraction for mercury; coagulating  and hard-
ening as much quickfilver as the acid weighed at firft.
If the hard concrete be  diluted  with  frefli acid, it
melts eafily in the  fire, and does not  part  with  the
mercury in the greateft heat that glafs veflels can fuf-
tain.   The  vitriolic acid, by itfelf,  ftrongly  retains
mercury,  but not  near fo  much as when  combined
with filver.
   Silver thus corroded by the vitriolic acid,  or preci-
pitated by it from the  nitrous,  may in great part  be
diflblved,  by cautioufly  applying  a very little water at
a lime; and more effectually by boiling in frefli oil of
vitriol.
   VII. With Copper. With this metal the vitriolic acid'
cannot be combined, unlcSs in its concentrated ftate,
and ftrongly heated.  If pure oil of vitriol is boiled on
copper filings, or fmall  pieces of the metal, it diflblves
it into a liquor  of a deep blue  colour, which eafily
cryftallizes.   The cryftals ate of a beautiful blue co-
lour,  and are fold under the name of blue vitriol, or Ro-
man vitriol.
   Where fulphur is found in great plenty,  however,
Roman vitriol  is made by ftratifying thin plates of cop-
per with fulphur; and upon flowly burning the fulphur,
its acid corrodes  the copper.  The metal is then to be
boiled in water, that the faline part may be diflblved.
The operation is to be repeated till all the copper is
confumed; and all  the  faline liquors are to  be evapo-
rated   together to  the cryftallizing  point.  By this
method, however, a great part of the acid is loft; and
in Britain, where the  fulphur muft be imported, we
fhould think the pure  acid preferable  for  thofe who
prepare blue vitriol.
   This fait, on  being expofed to the fire,  firft turns
white, then of a yellowifh red colour.   On urging it
with a ftrOng fire,  the  acid flowly exhales,  and a dark
red calx of copper remains.  The whole of  the vi-
triolic acid cannot be expelled from copper by heat:
as much of it ftill remains as to render a part of the
metal foluble in water.  After  this foluble part  has
been extracted, a little  acid is ftill retained amounting
to about r'- of the calx.
   Vitriol of copper is  employed in medicine as a cau-
ftic, in which refpect it is very ufeful;  but when ufed
internally, is dangerous, as indeed all the preparations
of copper are found fo  be.   It has, neverthelefs, ac-
                                           cording
   691
With fa.1-
   69%
Coppef*
   ^93
Blue vitri
ol, how
made.
   094
Phenome-
na on dif-
tillation.
60.>
Lfr;, 
Practice.
CHEMISTRY
97
Vitriolic
acidand
its combi-
nations.
696
Jron.
697
   698
Precipita
vitriolic
acid.
          cording fo Neumann, been  recommended  in all  kinds
          of intcrmittents, and  the  lepra.   The fmalleft por-
          tion, he fays,  occafions a ficknefs and naufea;  a  fome-
          what larger,  reaching and  violent vomitings, accom-
          panied  often with convulfions.  If the  quantity taken
          has been  confiderable, and  is not Soon discharged  by
          vomiting,  the Stomach  and  inteftines are corroded, in-
          tenSe pains, inflammations, and death, Succeed.
            VIII. With  Iron. The vitriolic acid  does not act up-
          on this metal till confiderably diluted. Common oil of
          vitriol requires to be mixed wish ten or twelve times its
          quantity of water before it will act brifkly on  the me-
          tal.   In this ftate it effervefces violently with  iron  fi-
          lings, or fmall bits of  the metal, and a  great quantity
          of inflammable vapour  is difcharged (fee Air).   The
          liquor affumes a fine green colour;  and by evaporation
          and flow  coolings, very beautiful  rhomboidal cryftals
Salt of Steel are  formed.  Thefe are named fait of fteel,  and are
          ufed in medicine; but  for  the fait made  of the  pure
          acid  and  iron, the common copperas,  made  with the
          impure acid extracted from pyrftes, is commonly fub-
          ftituted. This is generally efteemed a venial fraud,
          and no doubt  is fo  in medicinal refpects; but when
          it is  confidered,  that,  by  this fubftitution,  common
          copperas  is  impoSed  on the ignorant,  at  the price
          of 2 s per pound,  the affair appears in a different light.
            Pure vitriol of iron is originally of a  much more
iion of ii on beautiful appearance  than  common copperas,  and re-
from  the   tains its  colour  much better;  the  reafon of which
          is, that the  fait  thus  prepared has more phlogifton
          than the copperas.  If either of  the kinchi, however,
          are expofed to the air for  a  fufficient length of  time,
          part ef the  acid is diffipated, and the vitriol  becomes
          yellowifh or brownifh.  If  the fait is now diffolved  in
          water,  a brown precipitate  falls,  which is part ofthe
          iron  in a  calcined ftate.   If the liquor  is feparated
          from this  precipitate by filtration,  a limilar one forms
          in a  fhorr time,  and  by long  ftanding  a  confiderable
          quantity fubfides. According  to  Dr Lewis,  the  pre-
          cipitation  is  greatly  expedited by a boiling heat; by
          which more of the metal feparates in a few minutes
          than by ftanding without heat for a twelvemonth.  This
          change takes place in no other metallic folutions.
            The  calx of iron, precipitated by  quicklime  from
          green vitriol, appears,  when  dry of a yellow  colour ;
          and it is recommended in the Swedifh tranfadtions,  in-
          ftead of yellow ochre> as a colour for houfe-painting.
          Solutions of green vitriol  are alfo recommended for
          preferving  wood,  particularly  the wheels of carriages,
          from  decay.   When  all the  pieces are fit for being
         joined together,  they are directed to be  boiled in a
         folution of vitriol for three or four hours; and then
         kept in a warm  place  for fome days to dry.  By this
         preparation, it is faid, wood  becomes  fo hard,  that
         moifture cannot  penetrate  it; and  that iron nails are
         not fo apt to  ruft in this vitriolated wood  as might be
         expected, but laft as long as  the wood itfelf.
            IX. With Tin.  This metal cannot be diflblved in the
         vitriolic acid, but in the fame manner as filver; namely,
         by  boiling concentrated oil of vitriol  to drynefs upon
         filings of the  metal.   The faline mafs may then be
         diflblved in  water, and the folution will  cryftallize.
         The  fait, however, formed by  this union, is  not ap-
         plied  to any ufeful  purpofe.   A  fait  of tin,  indeed,
   699
Yellow for
houfe
painting .

   700
Preferva-
tive for
tvood.
701.
Tin.
 formed by  the union  of vitriolic acid with this metal, Vitriolie
 has been recommended for fome medical purpofes, and acid ami ^
 proceffes  are given  for it in the  difptnfatories; but,ts J-'01"01*
 they have never come much into practice.              "a 10"s'  ifl
   X. With Lead.  While lead  is in its metallic flate,    70s
 the vitriolic acid acts very little upon it, either  in a di- lead.
 luted  or concentrated ftate *  but if  the metal is  dif-
 Solved  in  any other acid, and oil of vitriol  added,  a
 precipitation immediately enfues, which is occafioned
 by the  combination of vitriolic acid  with   the lead.
 This precipitate will  be more or  lefs white  as  the
 metal is more  or  lefs deprived of its phlogifton by    „0*
 calcination before folution.  If  a little ftrong fpirit ofAbeautiftd
 nitre is poured upon litharge,  which is lead calcined to white co-
 the  greateft  degree poflible  without vitrification,  the l°ur«
 acid  unites itfelf to the metal with confiderable ef-
 fervefcence and heat.   Some  water being now poured
 on,  and the  phial containing the mixture  fhaken,  a
 turbid folutioH of the  litharge is made.  If  a little oil
 of vitriol is then  added, it  throws down^a beautifully
 white precipitate ;  and the acid of nitre, Toeing left at
 liberty to ait  upon  the remaining part of the litharge,
 begins anew to diffolve it with  effervefcence.   When
 it is again  faturated, more oil of vitriol is  to  be drop-
 ed in,  and a white precipitate  is again thrown  down.
 If any of  the litharge is ftill undiflblved, the nitrous
 acid, being fet at liberty  a  fecond  time, attacks it as
 at firft;  and by  continuing  to add oil of  vitriol,  the
 whole of  the litharge may be  converted  into a moft
 beautiful and  durable  white.   Unfortunately this  co-
 lour cannot  be  ufed in oil, though in water it feems
 fuperior to any.   If  the procefs   is  well managed,
 an ounce of fpirit of nitre  may be made to convert
 feveral pounds of litharge into a white of this kind.
   XI. With Quickfilver. The diffohuion of quickfilver QU;!-kfil-
 in vitriolic acid cannot be performed but by a concen- ver."
 trated oil  and ftrong boiling heat.   The metal  is firft
 corroded  into a white calx, which  may afterwards be
 eafily  diffolved  by  an addition  of frefli acid.   Every
 time it  is  diflblved, the  mercury becomes more and
 more fixed and  more difficult  to dry.  If the exficca-
 tion  and  diflblution has  been repeated Several  times,
 the matter becomes  at laft So  fixed as to bear a degree
 of red heat.  This combination  is the bafis of a medi-
 cine formerly of fome repute,  under the name of tur-
 bith mineral.  The procefs for making turbith mineral
 is  given  by the author of the Chemical Dictionary as
 follows.
   "Some  mercury is  poured into a glafs  retort,  and Turbith
 upon it an equal quantity of concentrated oil of vitriol, mineral.
 or more, according to the ftrength of the acid.   Thefe
 matters are to be  diftilled together,  in  the heat of a
 fand-bath,  till nothing remains in the retort  but a dry
 faline mafs, which is a combination oS the vitriolic acid
 and mercury.  The acid which  paffes into the re-
 ceiver is very fuffocating and Sulphureous ;  which qua-
 lities it  receives  Srom  the phlogifton of the mercury.
 The white  Saline  maSs which is left at  the bottom of
 the retort is  to  be put into a large  veffel; and upon
 it  are to be  poured large quantities oS hot  water at
Several different times.   The water  weakens the acid,
and  takes  it Srom  the  mercury; which is then pre-
cipitated towards  the  bottom  of the  veffel,  in form
of a very fhining yellow powder.   The water  with
                         N                  whic* 
98
CHEMISTRY.
Practice.
Vitriolic
acid aid
iu combi
   706
Dr Lewis's
 707
Zinc.
         which  it is washed contains the acid that was united
         with the mercury,  and likewife a little mercury  ren-
         dered Soluble  by means of the very large  q untity of
         acid
           Moft chemifts have  tei cvrd, that a portion of vi-
         triolic acid  remains  united  with  the tnrbith mineral,
         only too little  to render it foluble  iu  water.  But Mr
         II..-. uue, having examined  this mattcr, affirms, that
         turbith mineral  contains no  acid, when it has  been-
         Sufficiently  wafhed ,  and  that, by frequently boiling
         this prepjratim in a large quantity of diftilled water,
         not a veitige of acid will adhere to it."
           Dr Lewis, who is of opinion that the whole of this
         mercurial  calx is  foluble in a very  large  quantity of
         water, deiires the water with which it is  wafhed  to
         be impregnated with fomc alkaline fait;  which makes
         the  yield of  turbith greater than  when  pure water is
         ufed.   The author of the  Chemical Dictionary alfo
         obferves, that the precipitate remains white  till well
         freed  from  the acid ; and  the  more perfectly  it is
         wafhed, the deeper yellow colour  it acquires.
           XII.  IV.th Zinc.  This femimetal is not acted  upon
         by the vitriolic acid in its concentrated ftate; but, when
         diluted, is  did dved  by it  with effervefctnee, and  with
         the .xirication of  an  inflammable vapour in the  fame
         Marnier as iron.   Neumann  obferves, that,  during the
         diflblution,  a grey and  olackilh Spongy matter fell to
         the bottom , but, on ftanding for  fome days,  was ta-
         ken up, and diffolved in the  bqnor, nothing being left
         b.n a little ycllowifh dull  fcarcely worth mentioning.
         Six pans of oil of vitriol, diluted  with an equal  quan-
         tity of waier,  diflblves  one part of zinc.
           The  product  of this combination  is  -white vitriol;
         whicit is ufed in  medicine  as an  ophthalmic, and in
         painting for making oil-colours dry  quickly :  what is
         ufed for this  purpofe, however, is not made in  Bri-
         tain, but comes from Germany.   It is made at Goflar
         by  the  following procefs.   An  ore containing  lead
         and filver,  having been previoufly roafted  for the ob-
         taining of fuphur (fee  aIetallurgy),  is  lixivia-
         ted with water, and  afterwards evaporated in leaden
         boilers, as for the preparation  of green vitriol : but
         here a regular cryftallization is prevented; for  when
         the Silt hasaffumed any kind of cryflalline form,  thefe
         cryftals are made to undergo the watery fufion  in
         copper  cal lions.  It is then kept conftantly Stirring
         till  a confiderable  part of the moifture  is  evaporated,
         and the matter has acquired the confiftence of fine fu-
         gar.  White  vitriol  generally  contains Some ferrugi-
         nous  matter,  from which  it may be entirely  freed by
         foine frefh  zinc;  for  this  femimetal precipitates from
         the vitriolic acid all other metallic fubftances; but not-
         withftanding  this ftrong attraction, the vitriolic acid  is
         more eafily expelled by  diftillation  from   white than
         green or  blue vitriol.   Towards the end  of the  di-
         ftillation of white vitriol, the acid arifes exceedingly
         concentrated, though  fnlpimreous :  So that, iS mixed
         with  common oil of vitriol, it will heat it  almoft as
   lftti   much as oil of vitriol heats water.
Rtgulu* of  XIII. With Regulus of Ai.tin::r.y. Tocombine vitriolic
aatimony. acid with regulus of antimony, the fame method muft be
\        afcd  as directed  for uniting it with quickfilver,  for
     -—  ■lilting turbith mineral, vh. to employ a very con-
         centrated acid, and todiftil in clofc veffels.  The face
   708
White vi-
 t^ioL.
phenomena  alfo  occur  iu  this cafe  as in making tnr- Vitriolic
bith mineral; a very fuffeicating fulphurcous acid arifes; .ac,d *"Jy
and as Mr Geoffroy obferves, a true fulphur Sublimes |U 5om
     1      iri          ',./.,?          .,  nations.
into the neck of the retort; a white, faline, mmrrtrH, ..
mafs  remains in  the veffel;  and when the veflels are
unluted, a white fume iffies, as in  the Smoking Spirit
of libavius. See Combinations of marine acid with tin,
infra.                                                  710
   XIV. With Regulus of Cobalt. From acombination of Regulus of
the vitriolic acid with cobalt, a red fait may be obtained, cobalt.
To procure it,  one part of  cobalt,  reduced to a very
fine powder,  may be mixed with two or three of con-
centrated  acid,  diluting the  liquor after it has been
digefted for 24 hours, and  then  filtering and evapora-
ting it.                                                 711
   XV.  With arfenic. Neumann relates, that powdered Arfenic.
white arfenic being diftilled in a retort with oil of vitriol,
a tranfparent  Sublimate like glaSsaroSe, which in a tew
days loft its transparency, and became opaque like the
arfenic itSelf.  The  arfenic remaining in the retort
fuftained an open fire  without any fenfible alteration.
The authjor of the Chemical Dictionary fays, that if a
concentrated vitriolic  acid is diftilled from arfenic, the
acid which comes over fmells exactly like marine acid.
When the folution is diftilled till no more acid arifes,
the retort is then almoft red-hot,  and no arfenic is fub-
limed ;  but remains futed  at  the bottom of  the re-
tort;  and, when cold, is found to be an heavy,  com-
pact mafs, brittle and tranfparent  as cryftal-glafs.  This
kind  of arfenical glafs, expofed to the air, Soon loSes
its transparency  Srom the  moifture it attracts, which
diflblves and partly deliquiates it.  This  deliquium  is
extremely acid—By digesting one part of arfenic with
two of concentrated oil of  vitriol, diluting the folution
with water, and then filtering and evaporating, we ob-
tain a yellowifh  fait which  flioots  into pyramidal, tran-
fparent, and fhining cryftals.  None of the  three laft
mentioned combinations have  been found  applicable  to
any ufeful purpofe.
   XVI. With Oil. The product of this combination is a
thick black fubftance, very much refembling balfam  of
fulphur in colour and  confiftence ; to which it is fome-
times fubftituted.   If this fubftance is  diftilled with a
gentle heat, great part  of the acid  becomes  volatile,
and evaporates in white fumes, having a pungent finell
refembling that of burning fulphur.   This goes by the    713
name of volatile or fu phureous vitriolic acid; and a fait Volatile
was formerly prepared  from it by faturation with fixtd fulphure-
alkali, which was thought to poffefs great virtues.  From ous acu*'
its inventor it was called the fulphureous fait of Stahl.
The  moft lingular  property  of  this  volatile  acid is,
that though the vitriol c in its fixed ftate is capable  of
expelling any other  acid from  its  bafis,  the  volatile
one is expelled  by every acid, even that of vinegar.
It is very difficultly  condenfible, as we  have already
taken notice ;  and, when mixed wiib water, fcems
fcarcely at all acid, but rather to have a bitterifh tafte.
   Several methods have  been  propofed for procuring
 this acid  Srom  burning Sulphur, w hich yields it in  its
 greatett degree  ©t volatility, as w til as concentration ;
 but the produce is fo exceedingly Small,   that  none of    714
 them arc worth mentioning.  Dr  Prieftby has given  How Pr°-
very  good directions for obtaining the volatile vitriolic cured by
acid in  the form of air.  His method was,  to  pour,  on  £P i>mft'
                                                Some
 7i»
Oil. 
Pradice.
CHEMISTRY.
99
   715
Charcoal.
   716
Sulphur
prepared
from vitrio-
lated tartar
   717
Spirit of
wine.
Ether.
fome oil of vitriol  contained in a phial, a very fmall
quantity of oil olive ; as much as was fufficient to co-
ver it. He then applied the proper apparatus for the re-
ception of  air in  quickfilver (fee Air); and, holding
a candle to the phial, the volatile vitriolic acid ruflied
out in great quantity.   Had he received this air in vva*
ter, inftead of quickfilver, the confequence would have
been, that  fome part of it, at leaft, would have been
abforbed by  the  water, and a fulphureous acid liquor
produced.  This  feems indeed almoft the only method
of procuring  the  fulphureous vitriolic acid  of any to-
lerable ftrength ;  but it is  never required in the form
of a liquor,  except for experimental purpofes.  The
only ufeful property hitherto difcovered about  this kind
of acid is,  that it is remarkably deltructive of colours
of all kinds ; and hence  the fumes  of fulphur are em-
ployed to whiten wool, &c.
   XVII. With Phlogifton of charcoal.  If charcoal is
mixed with concentrated  vitriolic acid, and the mixture
diftilled, thefame kind ofacid isat firft obtained, which
comes over when oil is ufed ;  and towards  the end,
when the matter begins to grow dry, a true fulphur fub-
limes.  The beft way, however, of producing fulphur
from the vitriolic acid is by combining it, when in a
perfectly dry ftate, with the phlogifton.  By this means
fulphur may very readily be made at any  time.  The
procefs is  generally directed to be performed in the
following manner.
   Reduce  to fine powder any  quantity of vitriolated
tartar.   Mingle  it  carefully with a 16th part of its
weight of charcoal-duft.   Put the whole into  a covered
crucible fet in a melting  furnace.   Give a heat fuffi-
cient to melt the fait ; and when thoroughly melted,
pour it out on  a  flat ftone.  The vitriolated tartar and
charcoal will  now  be converted  into a fulphureous
mafs, fimilar to a combination  of  alkaline   falts with
fulphur.  See Alkaline Salts, below.
   XVIII.  With Spirit of wine.  The refult of this com-
bination is  one of the moft extraordinary phenomena in
chemiftry; being that fluid, which, for its extreme de-
gree of volatility, was firft diftinguilhed  by the name of
ether :  and now,  fince a  liquor of the like kind is dif-
covered to be preparable from fpirit of  wine  by means
of other acids, this fpecies is diftinguifhed by  the name
of vitriolic ether.  The method  of preparing this fubtle
liquor recommended by  M» Beaume, fcems  to be the
beft of any hitherto difcovered.
   Mix together equal parts by weight, of highly rec-
tified  fpirit of  wine and concentrated oil of  vitriol, or
fomewhat more than two meafures of fpirit of wine with
one of  the acid4   The mixture is to be made in a flint
glafs retort,  the  bottom and fides of which are very
thin, that  it  may not  break  from  the  heat  which  is
fuddenly generated by the  union of thefe two fubftan-
ces.  The fpirit of  wine is firft put into the retort,
and then the acid is poured in by a glafs-funnel, fo that
the  flream may be directed againft the fide of  the glafs ;
in which  cafe it will not exert much of its force on
the  fpirit,  but will lie quietly  below  at the  bottom.
The retort is  now to be very gently fhaken, that the
acid may mingle with it by  little  and  little.  When
the  mixture  is completed) very little more heat will be
neceffary to make the liquor boil.
   This mixture  is  to be  diftilled with  as  brifk and
•[Hick a heat  as poflible;  for which reafon, immediately
after the acid and  fpirit  are mixed,  the  retort fhould Vitriolic
be put into a fand furnace h«ated as much  as the mix- acidand if
ture is.   The  diftillation fhould  be continued only till ""J**11*'
about one-third  of the liquor is come over ; if it is .....*v---.
continued farther,  part of the vitriolic acid rifes in a
fulphureous ftate.  In the retort a thick, black,  acid
matter remains,  which  is Similar to a combination  of
oil of vitriol with  any inflammable matter, and from
which  a little fulphur  may  be obtained.   Along with
the fulphureous acid, a greenifh-oil, called oleum vitri-
eli dulcis, arifes, which has a fmell compounded  of
that ef the ether and fulphureous acid  : and Mr Beaume
has fhown that it is compounded of  thefe two ;  for if
it  is  rectified with  an  alkali,  to attract the acid, it  is
changed into ether.  If, after  the diftillation of the
ether, fome water be poured into the  retort, the liquor
by diftillation  may  be brought back  to the ftate of a
pure vitriolic acid.
   As the fteams of  the ethereal liquor are exceedingly
volatile, and at the fame time a quick fire is neceffary
to the fuccefs  ofthe operation, the receiver  muft be
carefully  kept  cool  with very  cold water  or with
fnow.   Care  muft  alfo be  taken to prevent any  of
the fulphureous acid fleams from coming over; but  as
it is impoffible  to prevent this totally,  the liquor  re-
quires  rectification.  This is the  more neceffary,  as a
part  of the  fpirit  of wine  always  rifes  unchanged.
From this acid the liquor is eafily fet free, by adding
a fmall quantity of alkaline fait,  and re-diftilling with
a very gentle  heat ; but as fpirit  of wine is  likewife
very volatile,  the diftillation muft be performed  in a
very tall glafs.  Dr Black  recommends a matrafs,  or
bolt-head,  with a  tin-pipe adapted to the head, fo as
to convey the fteams at a right angle, to  be conden-
fed in  the receiver.  When this fluid is  to be prepa-
red in great quantities, the ethefc, by proper manage-
ment,  may be made to equal  half the weight of the
fpirit of wine employed.   Mr Dollfufs has made many
important experiments on this fubject ; of which the
following is an abftract i  1. Two pounds  of vitriolic
acid  were mixed with  as much of fpirit of wine, and
the mixture diftilled with a very, gentle fire.  The firft
ten ounces  that came over confuted of a  liquor ftrong-
ly impregnated with ether,  and of an agreeable odour:
This was put by itfelf and marked A.  It was followed
by a ftronger ethereal liquor, of which a  fmall quantity
only would mix with  water.    Of this  there  were
12 ounces, which  were alfo  put  by themfelves, and
marked  B.  By continuing the  procefs  two  ounces
more were obtained, which fmelled of fulphur, and
Were marked  C.  The diftillation was now continued
with a view  to concentrate the  vitriolic  acid,  when
three  drachms of a  thicker kind of  ether were found
Swimming on a weak Sulphureous acid.    This thick
liquid was not in the leaft volatile, and in confiftence
reSembled  an  expreffed  oil.   2. Twenty-four ounces
of Spirit of wine were now added  to the refiduum of the
former diftillation, and the procefs recommenced.  The
firft feven ounces  that came over were  poured to  the
dulcified fpirit marked A.  Next paffed over  ten  oun-
ces of a tolerably pure ether, which was mixed with the
contents of B ;  befides two ounces that had  a fulphu*
reous fmell, which were mixed with  C.   By  a repeat-
 ed dephlegmation of what remained  in the retort were
Obtained five ounces of a weak fulphureous acid j and 
100
C    H   E    MIST    R    Y.
Pradicc.
the  remainder being again  mixed with 20 ounces of
fpirit of wine, yielded  firft  fix ounces of the  liquor
marked A ; then  four  ounces of pure ether pit  into
that marked B ; and after that another ounce marked
C.   By continuing the di If illation four ounces of weak
fid,diurcous acid were  obtained, on  which  floated  a
little oil of wine.   ?. The remainder, which was very
thick,  and covered with a flight pellicle, was mixed
with 20 ounces of fpirit  of wine, and yielded  five oun-
ces of dulcified fpirit marked A ;  eight ounces of pure
ether marked B ;  and at laft one ounce  of the  fame,
which had rather  a fulphureous fmell.   This was fol-
lowed by  a few drops of acid ; but the remainder fro-
thed up with fuch  violence,  that an end was put to the
operation, in order to prevent its paffir.g over into the
receiver.
   By thefe four diftillations  there were obtained from
fix pounds of  fpirit of wine  and two  of  oil of vitriol,
28 ounces of dulcified fpirit of vitriol and 38 of ether ;
which laft, when  rectified by diftillation over manga-
nefe, yielded 28 ounces  ofthe beft ether.   At the end
of  this  diftillation were produced  13  ounces of weak
acetous acid ; and the liquor of the lalt running marked
C, afforded, by rectification, four ounces of good  ether.
The f.dpbureous  acid  liquor yielded Sour ounces of
weak acetous  acid,  and three drachms  of naphtha
refembling a diftilled oil in confiftence.
   By thefe proceffes the vitriolic acid was  rendered
quite thick and black ;  its weight being  reduced to 24
ounces.    The blacknefs was  found to be owing to  a
powder which floate-i in the  liquid, and  could neither
1 c feparated by fubfiding to  the bottom  nor riling to
the  top.   The liquor was ihereSore diluted with eight
ounces of water, and filtered  through  powdered glafs ;
by which means  the black  fubftance was collected,
partly in  powder,  and  partly in  grains of  different
fu.es.  It felt very  foft  between the fingers, and left a
ftain upon paper  like Indian ink ;  but though wafhed
with 24 ounces of   water, ftill  tailed  acid.  Half an
ounce of it diftilled in a retort yielded a drachm  and
an half of weak acetous  mixed with a  little fulphureous
acid ; the refiduum was a black coal, which by  calci-
nation in an open  fire for a quarter of an hour, yielded
25 grains of white allies, confifting of  felenite, calcare-
ous  earth, and  magnefia.   A  drachm  of it digefted
with nitrons acid,  which was afterwards diftilled from
it,  and then  diluted with diftilled water and filtered,
yielded  a few  cryftals,   which appeared  to be genuine
fait of tartar,  an infoluble felenite being left behind.
On  rectifying  the vitriolic acid freed from the  black
matter and diluted with eight ounces of water,  nine
ounces of fulphureous acid  were  firft obtained, after
which followed an  ounce ofacid rather high-coloured,
and then the  vitriolic acid quite colourlefs.   It now
weighed only   19^ ounces, and its fpecific gravity was
but  1.72?, while tha< of the acid  originally employed
had  been 1.989.
   On repeating the procefs with  fix pounds of  fpirit
of  wine to two of oil of vitriol, the firft 12 ounces
that came over were  fpirit of wine almoft totally  un-
changed  ;  then two ounces fmelling a little of ether ;
and  afterwards two pounds, of which about one-third
were ether.  When about five pounds had been drawn
eft,  the  diftilling liquor  began to  fmell  fulphureous ;
and after nine  ounces more had been drawn off,  the
frothing up ©f the matter in the retort obliged him  to Vitriolic
put an  end  to the operation.    The acid  was then a*ul*fd'"
filtered  through pounded glafs  as before, and after- c.omb*"t*
wards  committed  to  diftillation.    The  three  firft >'°
ounces were a weak fulphureous acid  ; then  followed
in ounce  more concentrated, and  of a  red  c<>K ur ;
then  another of a  yellowifh caft ; after which the reft
of the  acid came over quite colourlefs.   The whole
weighed 27 ounces, and the fpecific gravity of it com-
pared uith diftilled water was as 1.667 to  i.eoo.          719
  Ether is  the lighted  of all  know;-; fluids,  except Properties
air ; and is fo volatile, that  in vacuo its boiling point is°f ether.
20° below o° of Fahrenheit's thermometer.  If a fmall
quantity is poured out on the ground, it inftantly eva-
porates, diffufing its fragrance  all through the room,
and  fcarce perceptibly moiflening the place on which
it fell.  It difficultly  mixes with water,  as  being  of
an oily nature : ten parts of water, however,  will take
up one part of ether.   Its  great  volatility renders  it
ferviceable in nervous difeaSes,  and  removing pains,
when rubbed on with the hand,  and kept Sroni evapo-
rating immediately.  By  Spontaneous evaporation, it
produces a great degree of cold.   (See Evaporation
and Congelation).   The moft extraordinary  pro-
perty, however, is, that iS gold is diffolved  in aqua-
regia) fee Metallic Subftances, below), and ether add-
ed to the Solution, the gold  will leave the acid  and
permanently  unite with the  ether.   The exceeding
great  volatility  of ether renders it very eafily inflam-
mable even  on the approach oS flame ; and therefore
it ought never to  be diftilled,  or even poured from
one veflel  to another,  by  candle-light.   If a lefs quan-
tity of the vitriolic acid  is added to the fpirit of wine
than what is fufficient to  produce ether, the product
is called fpiritus vitrioli dulcis.  The following experi-
ment made by  Wallerius,  induced him and others  to
think, that the vitriolic acid  was convertible into the
nitrous.                                                720
  "  Some fait of  tartar (fays he) being  mixed with Experiment
the  dulcified fpirit of vitriol,  or perhaps  with the in favour of
ether  (for the author expreffes  himfelf a  little ambi- the tranf-
guoufly),  the full bottle ftopt with a  cork,  tied over mutation af
with bladder, and laid on its fide  ; on ftanding for four vltn.ollc ,n~
months, the  greateft  part  of the fpirit was found  to a°jj' r°*
have  efcaped, and the fait was  fhot  into hexangnlar
prifmatic cryftals refembling nitre.  It tailed ftrongly
of the fpirit,  but had no other  particular tafte.  Laid
on a burning coal, it crackled, exploded with  a bright
flalh,  and flew into  the  air.  He afterwards found,
that by adding to the fpirit  a drop or two of any acid,
the fait  cryftallizes the fooner ;  that in this cafe it has
a fourifh tafte, but in  other refpects is the fame with
that made without  acid.  This Salt-petre (Says the au-
thor)  promiSes, from  the violence of  its explofion,  to
make the  ftrongeft gun-powder  in the world, but a
very dear one.   Though the experiment fhould not
be applicable to any ufe in  this way,  it will  probably
contribute to illuftratc the  generation  of  nitre : as it
palpably fhows nitre, that is, the acid or characterise
part of  nitre, produced  from  the  vitriolic acid and
phlogifton.                                             -2r
  Wecannot here help again regretting that  chemifts Notconclu-
of fuperior abilities fhould fometimes leave very import- fiv««
ant  difcoveries only  half finifhed, fo  that chemifts  of
an inferior rank know not what  to make of tl.tm.  Had
                                         Wallerius, 
Practice,
CHEMISTRY.
   74Z
Violent ex-
plofions
from the
application
of heat.
  ad 714
Cavallo's
method of
purifying
ether.
Wallerius, who fcems more than once to have been in
poffeflion of this fait,  only poured on it a few drops of
oil of vitriol,  the peculiar colour and fmell of its fumes
muft have been a much  more convincing proof of the
reality of the tranfmutation than that of mere defla-
gration ; becaufe the latter can be otherwife accounted
for.
  It is certain, that  many fuftances, water itfelf not
excepted, will explode with great violence if fuddenly
heated beyond what they are able to bear.   If fpirit
of wine is confined in  a clofe  veflel, it  will alfo  by
means of heat burft it as effectually as water;  and as
the vapours of this fubftance are inflammable, the ex-
plofion will  be  attended with a flafh if any flame is
near.  In like  manner ether, on the  approach  of a
candle, takes fire, and goes offin a flafh like lightning;
but this happens, not  from any thing nitrous, but from
its great volatility and inflammability.  If therefore the
vapours of the ethereal  liquors are confined,  and heat
is applied fuddenly to the containing veflel, their great
volatility will caufe them make  an inftantaneous effort
againft the fides of it, which increafing with a fwift-
nefs far beyond  that of  aqueous or fpirituous vapours,
will make a much quicker as well as  a much ftronger
explofion than either  of them ;  and if  a flaming fub-
ftance  is near, the explofion will be attended  with a
bright flafh like  that of the ether itfelf.
  In  the experiment now  before  us,  the fait tailed
ftrongly of the fpirit,  or ether, from  which it was
made.   The fpirit was therefore confined in the  cry-
ftals of fait; and this volatile liquor, which, even under
the preflare of the atmofphere, boils with the heat of
ioo° of Fahrenheit, was,  in a confined ftate, fubjected
to the  heat of  a burning coal  ;  that is,  to more  than
tefti times the degree of heat  neceflary  to convert it
into vapour.  The confequence of  this could be  no
other,  than that the  particles of fait, or perhaps the
air itfelf, not being capable of giving way foon enough
to the  forcible expanfion of the ether,  a violent ex-
plofion would happpen,  and the fait be thrown about;
which accordingly came to pafs, and might very reafon-
ably be expected,  without any thing nitrous  contained
in the  fair.
  Mr Cavallo defcribes  an eafy and expeditious method
of purifying  ether, though a very expenfive one ; as
out of a pound  of the common kind fcarce three or
four ounces will remain of that which is  purified.  The
method of purifying it, he fays,  was  communicated
to him by Mr Winch  chemift in London,  and is to be
performed in the  following manner.  " Fill abont a
quarter of a ftrong bottle with common ether,  and
pour upon it twice as much  water ;  then flop the
bottle and  give it a fhake,  fo  as to mix the ether for
fome  time with the  water.   This  done,  keep  the
bottle  for fomc time without motion, and rhe mouth
of it downwards,  till the ether be Separated from the
water, and fwims  above it; which it will do in three
ot four minutes.   Then opening the bottle with  the
mouth ftill inverted, let the greateft part of the warer
run out  very gently ; after this, turn the bottle  with
the mouth upwards; pour more water upon  the ether,
fliaking  and  feparating the water as before.   Repeat
this operation three or  four times ; after which the
ether will be exceedingly pure,  and capable of diiTol-
ving elaftic gum; though it could not do So before."
lichot is prepared in the Eaft Indies, no perfon on the
it having taken particular notice oS the manufacture.
   As great  part  of  the ether undoubtedly  remains Nitrous
mixed with the water  after this  procefs, our author *cld an'1.
remarks,  that it might  be worth while to put  the wa-lts ^ombl"
ter into a retort and  diftil the ether from it, which -a ' ^ '  -
will come fufficiently  pure  for  common ufe.   He  ob-
ferves alfo, that " it is commonly believad that  water
combines with the pureft part of the  ether when  the
two fluids are kept  together ; though  the  contrary
feems to be  eftablifhed  by this  procefs.  According
to Mr Waftrumb, we may obtain  from  the refiduum
of vitriolic ether a refin containing vitriolic acid,  vine-
gar, Glauber's fait, felenite,  calcareous  earth,  filex,
iron,  and phofphoric acid.

    §  2. Ofthe Nitrous Acid and its Combinations.

   This acid is far from being fo plentiful as the viiri-
6lic.  It has been  thought to exift in the  air;  and the
experiments of Mr Cavendilh have fhown,  that it may
be artificially compofed,  by taking the electric  fpark
in a mixture of dephlogifticated and phlogifticated air.
See Aerology,  n° 77.                                714
   With regard to the preparation of nitre, Dr Black ob- Of the pre-
ferves, thatit is made in great plenty in the more South- Paratlon of
ern parts of Europe;  likewife  in the fouthern  parts of mtre"
Perfia, in China, the Eaft Indies, and in North Ame-
rica.  We have  had no accounts of the manner in
whi
fpot
The general account is, that it is obtained  from the foil
of certain diftricts which are called faltpetre grounds ;
where the foil is very  cold, barren, and unhealthy.
The  fait  is  there ready formed  by  nature.   It  is
only neceffary to gather large quantities of the earth,
and to  put it  into  a cavity through which  a  great
quantity of water is poured, which diflblves the nitre ;
and the lixivium runs  into an  adjacent pit, out of
which it is lifted in order to be evaporated and obtain-
ed in the form of cryftals.  This account, however,
has been thought unfatisfactory; becaufe there is hard-
ly  any  part  of Europe  in which it  is found in this    7*5
manner.   It  is difcovered indeed  in fome very  large Difcovered
diftricts in Poland, particularly in Podolia, where  the in foir,f
country is flat and fertile,  and  had been once  very no- £ ,e?.m.
   1    1   •       •              r    1  r    i,r.  Podolia in
pulous, but is now in a great meafure deferred.   Ir is p0iand-
there obtained from  tumuli or hillocks, which are the
remains of former habitations; but thefe  are  the only
places in which  it is found in any confiderable quan-    726
tity.  In  Spain,  it  is faid that  the  inhabitants  ex- In Spain
tract ir from  rhe foil after a crop of corn.   It has been aRd Amc-
found in America  in lime-ftone grounds,  in the floors
of pigeon-houfes, tobacco-houfes, or  the ruins of old
ftables, where a number of putrefying vegetables were
once  collected.   In general, however, it is extracted
from artificial compounds or accidental mixtures, where
animal  and vegetable fubftances have been fully  putre-
fied by being expofed to the air with any fpongy or
loofe  earth, efpecially ofthe calcareous kind, and open
to the north or norrh-eaft wind, and  more or  lefs co-    727
vered ■"mm the  heat or rains.  This  laft  particular  is Requifite*
;'b:o!utely  neceffary  to its formation in any quantity ; f°r lli f°r-
for the  heat, by  evaporating  the  moifture too much, mati0n-
prevents it from b< ing produced,  and the rains wafti it c     .
away after it  is already made.  Cramer, an author of artificial*5
the greateft credit, informs us  in his Docimaftics, that compoft
he made a little hut expofed  to the frefh air of  the for making
                                            country; uitre» 
IOZ
CHEMISTRY.
Practice.
   :»9
II >w pre-
pared in
Hanover.
In other
parts of
Germany.
   7.U
In France.
   7.U
Dr it lack's
condufions
concerning
the nature
•f falt-
pctre.
   ^3.1 ,
ruppcfculo
be the laft
erTcciof pu-
♦rcf^Ctiuii.
country, with windows  to admit the winds.  In this
he pjt a mixture of garden nuU, the rubbiih. of lime,
and putrid animal  -nd vegetable Subftances.  This  he
frequently moiftened  with urine ;  and in  a month or
two found his compofition very rich in nitre, yielding
at leaft one-eight part of its weight.
  It is nun.iiactured  in  Europe  by making artificial
compound with  lefs   trouble.   In Hanover it is got
by collecting  the rakiugs of the Streets; which arc built
up iato mud-walls that are allowed to remain a certain
time, when the furface is found covered with a white
faline efHorefccnce.  A perfsn is employed to fcrapc
this off;  and  putting  it into a veflel,  it is wafhed  with
water to diffolve the nitre, and the remaining  earthy
matter is again plaftered on the mud-walls, and  frefh
matter brought from the ftreets to renew  them occa-
sionally :  and by  this fimple method a  confiderable
quantity  is obtained.   In Germany the  pcaSants arc
directed by law to build  mud-walls of this  kind  with
the dung and urine of animals, and fome ftraw.   After
they have flood for fome time, and the vegetable and
animal fubftances are rotten,  they afford a confiderable
quantity of nitre.   In  France it is obtained  from ac-
cidental collections of this kind ; as where loofe earth
has been long expofed to the  contact of animal fub-
ftances, as the ruins of old flables,  pigcon-houfes, &c.
Sometimes from the  mould upon  the grounckjvherc
dunghills have been lying.   A particular fet of^>eople
go about in fearch  of  thefe materials; and when,  by
nuking a fmall  effay,  they find that  they will  turn to
account,  they put the materials into a  large  tub  with
a perforated bottom, and another which is water-proof
put below it.   Some  ftraw  is  intcrpofed betwixt the
two ; and on pouring water upon  the  materials, it
foaks thre.ugh them, undergoes a kind of filtration in
pafling through the ftraw, and is then drawn off  by a
cock placed in the the under^tub, and boiled to a proper
confiftence for cryftallization.   The cryftals are at firft
brown and  very impure, but  by repeated diflblution
and cryftallization become pure and white.
  From thefe particulars relating to the hiftory of fait-
petre, Dr Black  concludes,  that it is not properly a
foffil, being  produced at the furface  of the ground.
Margraaf difcovered a fmall quantity of it in the  ana-
lylis of  fomc of the waters about Berlin, and others have
found it in the wells about fome great cities :  but  no
true nitre has ever been found in Springs ; fo that this
nitrous fait may be fuppofed  to have derived its origin
from the quantity of putrid matters  with which  all
cities abound.  All rich  and  fertile foils arc found to
contain it ; and in the hot  countries, where the pro-
ducts of nature are numerous, and putrefaction carried
on very faft,  they arc  often very rich  in nitre.   This
may happen in fome  places  from the conflux  of wa-
ters; which  remaining for fome  time  on the furface,
and  afterwards exhaling, left the Saline  panicles be-
hind.
  On the whole,  Dr Black concludes, that neither
nitre nor its acid  does  exift in the air,  becaufe  it
might eafilv  be detected there ; though  many  have
embraced :; is opinion Srom  its being  uSually Sound at
the Surface  of the ground.   He is of  opinion,  that it
is tie effect of the Lift ftage of putrefaction of  animal
and vegetable fubftar.ces; and it is never to be  fout.d
except where thefe or  their effluvia arc prefent, and
never till the putrefaction  is complete.  It his been a Nitrous
matter of dilute,  whether  it cxiftcd in thofe matters acid a,lJ
before the procefs of putrefaction,  or was produced by ,u ™mb**
it.  But  it  is pretty  certain,  fays  the Doctor,  that natl0^'-  .
it originated in them ;  for the fun-flower, tobacco, and
other plants, are found to contain it  before putrefac-
tion :  and fomc have even aliened,  that plants placed
in the earth, deprived of  all its faline fubftances, will
yield it.  The  compofitions recommended by  Cramer
are the fitteft for producing a  complete  degree of pu-
trefaction, provided  they  contain a moderate  degree
of humidity, and that the quantity expofed to the  air
be defended from  too great a heat by the fun, which
would dry up its moifture ; and likewife from too great
a degree of cold, which likewife checks fermentation.
The importance of the calcareous earth in fuch a com-
pofition would likewife favour the  conclufions juft now
drawn ; for  the moft remarkable effect of this earth is
to promote and perfect  the  putrefaction of thefe fub-
ftances.  It  would  feem, therefore,  that the  true  fe-
cret of the production of nitre is to mix properly  to-
gether animal  and  vegetable fubftances with earth,
particularly of the calcareous  kind ;  expoling them to
the air with a moderate degree of humidity,  fufficient
to promote  their  putrefaction  in  the moft effectual
manner ;  and when the putrefaction is  carried to the
utmoft height, we may then expect that nitre will be
produced.                                              734
   The diftinguilhing characteriftic of the nitrous acid Diftin-
is its great  difpofition to unite with the phlogifton ; guiding
and, when  fo united,  firft to become exceedingly vo- ?*iara<i*cf''
larile, and ar laft to be diflipatcd  in a very white bright ),itrousa-'
flame : this  is called its detonation or deflagration.   In ^x
the ftrongeft ftate  in which this acid is procurable in a
liquid form,  it is of a reddifh yellow colour, and  con-
tinually exhales in denfe, red, and very noxious fumes j
and in this ftate is called fmoking, or, from its inventor,
Glauber's, fpirit of nitre.
I.  To extract the Nitrons Acid by means of the
                  Vitriolic.
735
  Into a  glafs retort  put two  pounds of good fait- Spirit of
petre, and pour upon it  18 ounces of concentrated oilnitre-
of vitriol; fet the  retort in a fand*heat,  and lute on
a large receiver  with the compofition already recom-
mended, for refitting aeid fumes; the mixture will grow
very warm, and the retort and receiver will be filled
with red vapours.   A fmall fire is then to be kindled,
and cautioufly raifed till no more drops will fall from
the nofe of the retort.   What comes over will be a
very ftrong and fmoking fpirit of nitre.                   -.$
  In this  procefs,  the  nitrous acid is  generally mixed Redtifiot*
with part  of the vitriolic which comes over along with tion.^
ir, and  from which it  muft be freed if  defigned for
nice purpofes.  This is moft  effectually done by  dif-
folving in it a Small quantity of nitre, and rediflilling
the mixture.  The vitriolic  acid which came over in
the firft diftillation  is kept bsck by the nitre in the Se-
cond, combining with its alkaline bafis, and expelling
a proportionable quantity ofthe nitrous acid.              ...
  We have here directed the pure  vitriolic acid to be Different
ufed, in order to expel the nitrous one ;  but  for  this methods of
purpofe any  combination of  the vitriolic acid  with adlfti^ixi6'
metallic or earthy bafis may be ufed,  though not with
equal advantage,   if calcined vitriol is made  ufe of,
                                                 as 
Pra&ice.
CHEMISTRY.
103
 Nitrous   as much phlogifton  is communicated  by the calx of
 acid and   jron  contained  in  that fait as makes the nitrous acid
its combi-  exceedingly volatile,  fo  that great  part of  it is loft.
nations.    j^ ca]cmcj z\nm> or felenite, is made ufe of, the virio-
          lic acid  in  thefe  fubftances  immediately leaves  the
          earth with  which ir was  combined, in order to unite
          with  the alkaline  bafis  of the  nitre, and expels  its
          acid : but the moment the nitrous acid is expelled from
          the alkali, it combines with the earth which the vitrio-
          lic acid had left; from  which it cannot be  driven
          without a  violent fire ;   and part  of  it remains obfti-
          nately  fixed, fo as not  to be expelled by any  degree
          of heat.  Hence the produce  of  fpirit, when nitre is
          diftilled with fuch  fubftances, always turns out confi-
          derably leSs than when the pure  vitriolic acid  is uSed.
          Alum is  preferable  to  felenite, for  the purpofes  of
          diftilling fpirit of nirrc ;  becaufe the acid doesnotad-
          here  fo ftrongly to  argillaceous as to calcareous earth*
            According ro Weigleb, the nitrous acid may be ex-
          pelled not only  by clay, gypfum, and other fubftances
          containing the vitriolic acid,  but  even by various kinds
          •f vitrifiable earth. Clean pebbles, quarrz in the form of
          fand, pieces of broken china and ftone ware, powdered
          glafs, ir c mixed with nitrein the  proportion of fix to
          one,  always expel the acid, though  imperfectly.   In
          France the  acid is always extracted by means of clay.
            The reafon of thefe decompofitions is,  that the  al-
          kaline  bafis of the nitre attracts  the filiceous earth,
          whofe  fixednefs in a vehement  fire gives it an  advan-
          tage over the volatile nitrous acid,  in the Same manner
          that the weak  acid of phofphorus  or arfenic will  alfo
          expel it by  reaSon of their fixednefs in the fire.
            Even fpirit of fait, according  to Margraaff's experi-
          ments, may be  ufed for diftilling  the fpirit of nitre.
          That celebrated chemift informs  us, that on diftilling
          nitre with  eight or nine times  its quantity of  ftrong
          marine acid, a  fpirit comes over which confifts  chiefly
          of the nitrous acid, but  has alfo fome portion  of that
          of fea fait.   The reafon  of this is fhown in Mr  Kir-
 * See     want's experiments on chemical attractions*.  In the
n°aoa.    prefent cafe, however, the decompofition may  be faci-
          litated by the ftrong attraction of the nitrous  acid  for
          phlogifton ;  for  it  is  well known, that  on mixing the
          nitrous and marine acids together, the larter is always
          dephlogifticated.  It  feems therefore that in this  cafe
          a  double decompofition takes place,  the nitrous  acid
          uniting itfelf to  the phlogifton of  the marine, and the
          latter attaching  itfelf to the alkali of the nitre.
   738       Spiritof nitre is very ufeful in the  arts of dyeing and
  Ufes.    refining, where it is known  by the name of aquafor-
          tis ;   and therefore  an eafy and cheap method of pro-
          curing  it is a  valuable  piece of knowledge.  Many
          difficulties,  however,  occur in this  procefs, as well  as
          that for rhe  vitriolic acid.  Oil of  vitriol, indeed, al-
          ways expels the nitrous acid with  certainty ; and on
          diftilling the mixture, a fpirit of nitre arifes ;  but  if a
          glafs  retort  is ufed for  the purpofe of diftilling  this a-
          eid,  the quantity of refiduum left  in diftillation is fo
          great,  and  fo infoluble in water, being no other than
          vitriolated tartar, that the retort muft always be broken
          in order to  get   it oot ; and  the  produce of fpirit will
          fcarce  afford the breaking a retort.  If earthen  re-
          torts are made  ufe of,  they muft certainly be of that
          kind called  ftone-ware, and  the  price of them will be
very little if at all inferior to that of glafs.   Iron  pots Nitrous
are faid to be made ufe of in the diftillation of common *c'd and
aquafortis in large quantities ;  but they have the grearlts pombl"
inconvenience of making a quantityof  the acid  fo vo- .        .
latile, that it not only will not condenfe, but fpreads its
fuffbeating vapours all  round in fuch a manner as to
prove very dangerous to  thofe who  are near it.  If an
iron veffel,  therefore,  is thought of for the  purpofe of
diftilling aquafortis, it will be  proper at leaft  to at-
tempt luting over the  infide with   a mixture of gyp-
feous  earth  and  fand, to prevent  as much as poflible
the acid from attracting the metal.
  Dephlogifticated fpirit of nitre is obtained by  diftil-
ling the fmoking kind  with  a  gentle hear, until what
remains is as colourlefs as water.   It is diftinguifhed
by  emitting  white  and not red fumes like the  other
kind, when  fet in a  warm place.  It muft be kept
conftantly in the dark, otherwife it will again become
phlogifticated,  and emit red vapours by the action of
the light; the fame  thing will alfo take place if it be
heated with  too violent a fire.

  II.To procure the Nitrous Acid by means of Arfenic.
                                                       729
  Pulverife  equal quantities of dried nitre  and  white TJueaqu*-
cryflalline arfenic; mix them  well together, and diftil fortis*
in a ghfs-retort with a fire very  cautioufly applied ;
for the arfenic acts on  the  nitre with fuch a violence,
and the fumes are here fo volatile, that unlefs  great
care is taken, a moft dangerous explofion  will almoft
certainly happen.  As, in this cafe, the nirrous  fumes
arife in  a perfectly dry ftate,  fome water muft be put
into the receiver, with which  they may unite and con-
denfe.   The aquafortis  fo produced will have  a bine
colour, owing  to  the  inflammable principle feparated
from the arfenic, by which its extreme  volatility is
likewife  occafioned.   If this  blue  aquafortis is  expo-
fed to the air,  its colour foon flies off.   If inftead of
the white arfenic we employ the pure arfenic acid,  the
diftilled liquor will have no blue colour.

              Nitrons Acid combined,

  I. With Vegetable fixed Alkali. This fait,  combined SalJpcwe.
with the nitrous acid to the point of faturation, regene-
rates nitre.   It  is obfervable,  however,  according to
Neumann, that  there  is always fome diflimilarity be-
tween the original and regenerated  nitre, unlefs quick-
lime is added.  The regenerated fait, he fays, always
corrodes tin, which the original nitre does not;  owing
probably to a quantity of phlogifticated acid  remaining
inir. Boiling with quicklime deprives it of this quality,
and makes it exactly the fame  with  original nitre.
  II.  With Fofiile alkali. The neutral fait arifing from Cubic-1
a combination  of the  nitrous  acid  and foffile alkali is nitre.
fomewhat different from common   nitre; being more
difficult to cryftallize,  inclining todeliquate in rhe air,
and  fhooting  into cryftals of  a cubical form, whence
it gets the name of cubic nitre.   Its qualities are found
fomewhat inferior to rhe common nitre; and therfore
it  is never  made, unlefs by  accident,  or for experi-
ments.                                                 n%
  Nirre is one of  the moft fufible falts.   It  is liquefied Fufibility.
in a heat much lefs than what is neceffary to make it
red ;  and thus remain  in tranquil fufion,  without fwel-
ling.   If nitre thus  melted  be left to cool and fix,
                                              \vh«- 
104
C   H   E    M    I   S   T    R   Y.
Pra&ice.
comb
•ions
Nurr.iu    whctl.fr ii h.u been nude red-hot or not in the fufion,
•cidanditi jt Coa,; dates into a white, femi-tranfparcnt, Solid innf,
          called mineral cryftal, having all the properties of nitre
           rfelf.  By  this  fufion, Mr Beaume obferves that nitre
          leifes very little, if any,  of  the water contained in  its
          cryltils, fmcc the weight of mineral cr\ ftal is nearly
          li.c fame with that of the nitre employed.
            When uitre is kept in  fufion with  a moderate hear,
          and at rhe fame time docs not touch  any inflammable
          mattcr, nor even flame,  it remains in that ftate with-
          out fnffering any very fenfible alteration ; but if it is
          long kept in fufion with a ftrong fire, part of the acid
          is deftroyed by the phlogifton which penetrates the cru-
          cible; and  hence the nitre becomes more and more
    -k\   alkaline.
   ^fcfc      Nitre is of very extenfive ufe in  different arts ; being
           the principal ingredienr  in  gun-powder; and  Serving
           as an excellent flux to other matters; whence its nfe in
           glafs making.   (Sec Glass.)  It  is  alfo poffeffed of a
           confiderable antifeptic power; whence its ufe in preferr-
           ing meat,  to which it communicates a red colour.  In
           medicine,  nitre  is ufed as a  diuretic,  Sedative, and
           cooler; but very often fits uncafy on the ftomach. The
           rcfemblancc of the cryftals of nitre to thofe of Glau-
           ber's fait has fometimes  been the occafion of dangerous
           miftakes.   Dr Alexander mentions a Swellingfter the
           whole body of a woman,  occafioned by her takirTg a fo-
           lution of nitre inftead of  Glauber's fait.   Two miftakes
           •f the fame kind  we have alfo known.   In  one an
           •uncc, and in the other  upwards of two ounces, of ni-
           tre were Swallowed.   The  fymptoms occafioned were
           univcrfal ccddneSs and fhivering,  extreme debility aud
           ficknefs at ftomach, cold fweats and faintings.  Nei-
           ther of the cafes proved  mortal.  The cure was effect-
           ed by cordials and corroborants.
             A procefs has obtained a place in  the  difpenfatories
           for a fuppofed purification of nitre by means of flower
           of brimftone.   A pound of falt-petre is  to be  melted
           in a  crucible,  or fmall  iron veffel; and an ounce oS
           flowers of fulphur thrown upon it, by  fmall quantities
           at a time: a  violent deflagration enfues on each addi-
           tion ; and after the whole  is put in, the fait is poured
           out in moulds,  and then  called  fal prunella.   It has
           been difpured  whether the nitre   was at all  depu-
           rated by this procefs ; Dr Lewis thinks it is not.  From
           our own  experience, however, we can affirm, that by
           this means a fediment falls to the bottom, which car-
           ries with it  any impurities that may have been in the
           nitre, and leaves the fluid  fait clear  and tranfparent as
            water.  This precipitate is probably no other than a
           vitriolated tartar formed by the  union  of the fulphu-
           reous acid and alkali of  the nitre, which being lefs fu-
           fible than the nitre,  fubfides in a folid  form and clari-
     -4>-    fies it.
  Nitrous      III. With Volatile Alkali. The nitrons acid Seems pecu-
  ttnmoniac. liarly adapted to an  union  with volatile alkali; Satura-
            ting as much, or rather  more of it than the ftrongeft vi-
            triolic acid is capable of  doing.  The product is a very
           beautiful fait,  called volatile nitre, or nitrous fal ammo-
           niac.  It  very readily diflblves, not  only in water, but
           in fpirit of wine, which diftinguifhes it from the vitrio-
           lic and common kind of fal ammoniac.   It alfo requires
           lefs heat for its fublimation :  indeed  care muft be taken
           *«rt  te  apply  too  great a heat  for this  purpofe, as
   ;44
 •A prunel-
la
the nitrous fal ammoniac  has the property of  dcfli- Nitrous
grating by itfelf wirhout  any addition of inflammable acidanditi
matter; and  this  it docs more or lefs readily,  as the c.0,n ,na"
volatile alkali with which  it was made was more  or ■"  '_  -^
lefs impure and oily.                                    746
   The medical virtues of  this kind of nitre have  not Dr  Ward's
been inquired into.  It feems to have made the prin- w,,ltc JroP-
cipal ingredient in the famous Dr Ward's white drop,
which  was celebrated as  an antifcorburic;  with what
juftice  thofe who have tried  it muft determine.            747
   IV.  With Calcareous Earths.  Thefe the  nitrous acid Calcareous
diflblves into a tranfparent colourlefs liquor; but for this nitre.
purpofe it  muft be  very much diluted, or rhe folution w ill
have a gelatinous confiftence. This compound is not  ap-
plicable to any  ufeful purpofe.   It  has  a   very acrid
tafte ;  and, if infpiffated, attracts moifture from the air.
If it is totally dried, it then refembles an  earthy mat-
ter, which deflagrates very weakly.  By diftillation
in a retort, almoft all the  acid  may  be expelled,  and
what little remains flies off in an open fire.               74jJ
   Mr  Pott, who  has particularly examined the com- Nitrous
bination of nitrous  acid with quicklime,  fays rhar  the acid de-
acid fuffered remarkable alterations by diftillation from compofed;
quicklime,  and  repeated cohobations upon   it.   By
thefe  experiment he obtained a fait more  fenfibly  fiif-
ceprible of cryftallization and detonarion,  than what
can be obtained by a fingle combination.  From his  ex-
periment it would feem,  that  nitrous  acid,  by   this
treatment with quicklime, was capable of being entire-
ly decompofed.
   If a folution of chalk in  the  nirrous acid be evap<>-
 rared  to drynefs, and then  gently calcined, it acquires
 the property of fhining  in the  dark, after  having been
 expofed to the fun's rays,  or  even  to the light of  a
 candle.   This fubftance, from  its viventor, is called   -i4)
 Baldwin's phofphorus; or,  from its being   neceflary lo Phofph»-
 keep  it in a glafs hermetically fealed, phofphorus her- *us«
 meticus.   (Sec Earths).
    V.  With Argillaceous Earths and Magnefia. All that
 is known concerning the combinations of  nitrous  acid
 with  thefe earths is, that the  firft produce aflringenr,
 and the  Second  purgative  compounds, fimilar to alum
 and  Epfom fait,  and which are not fufceptible of cryf-
 tallization.
    VI. With Gold.—Till very lately it has been the o-
 pinion of chemifts, that the  nitrous acid by itfelf was in-
 capable of acting  upon this metal.—Dr Brandt, how-
 ever, produced before the Swedifh academy of Scien-
 ces,  a folution of gold  in the nitrous acid, obtained
 in parting, by that  acid,  a  mixture of gold and filver.
 —The mixed  metal  was  boiled  with  aquafortis in a
 glafs  body fitted with a head and receiver, the liquor
 poured  off, and the coction repeated with frefh parcels
 of ftronger and  ftronger nitrons fpirit, till all the fil-
 ver  was judged  to be extracted.   The laft parcel was
 boiled down till the mattcr  at  the botrom  looked  like
 a dry fait; on boiling this in frefh aquafortis in clofc
 veffels, as before, a part  of  the gold  was  diifolved,
 and  the  liquor  tinged yellow.   But though gold is by
 this  means truly foluble in the nitrous acid, the union
 is extremely flight; the  gold  being not  only  precipi-
 tated on  the  addition of filver, but likewife fpontanc-
 onfly on expofure to the  air.—Dr Lewis very jaflly
 obferves, that this folution may have been often made
                                            unknown
 75«
Gold. 
Practice.
CHEMISTRY.
751
Silver.
152
          unknown to the cheiuiil  who did  fb ;  ant*, probably
          occafioned  the miftakes which Some have fallen into,
          who thought that they  were  in poffeflion of aquafor-
         tis capable of tranfmuting filver into gold.   Notwith-
          ftanding theSe  authorities,  Mr Kirwan  is of opinion
          that the nitrous  acid is  in no cafe able to diffolve
          gold ; the metal  being only intimately  mixed or dif-
          fufed through it.
            II. With Silver.—Pure fpirit of nitre will diffolve its
          own weight of filver;  and flioots with it into fine white
          cryftals of a triangular  form, confifting of very thin
          plates joined clofely one upon another.  Thefe cryftals
          are fomewhat deliquefcent; of an  extremely bitter,
          pungent, and naufeous tafte ;  and, if taken internally,
          are highly  corrofive  and poifonous.  They  melt in a
          fmall heat, and form,  on cooling, a dark-coloured mafs
Lunar cau- ftill more corrofive,  called lunar cauftic, or lapis infer-
ftic>       nalis.  They  readily  diffolve  in water; and, by the
          affiftance of warmth,  in fpirit of wine.   In  the Acta
          Natura Curioforum, torn. vi. there is a remarkable hi-
          ftory of filver being volatilized by its combination with
          the nitrous  acid.  Four ounces of  filver being  dif-
          folved  in aquafortis,  and  the folution fet to diftil in
          an earthen  retort,  a  white  tranfparent butter rofe in-
          to  the  neck, and nothing remaining behind ;  by de-
          grees the butter  liquefied,  and paffed down into the
         . phlegm in the receiver.   The  whole being novfpour-
          cd back into the  retort, the  filver  arofe  again  along
          with the acid.   The  volatilization  being attributed to
          the liquor having flood in  a laboratory where charcoal
          was  bringing  in, the experiment was repeated with a
          frefh folution of filver,  and a little powdered  charcoal,
          with the fame event.
            Solution  of  filver in  the  nitrous acid ftains hair,
          bones,  and other folid  parts of animals, and  different
by folution kinds of  wood, of all the intermediate fliades from a
of filver.   light brown to a deep and lading black.   The liquors
          commonly fold  for ftaining hair brown  or black, are
          no other than folutions of filver in  aquafortis, fo far
          diluted  in water  as not fenfibly to corrode the hair.
            It  gives a permanent ftain likewife to fundry ftones ;
          not only to thofe  of the fofter kind,  as marble, but to
          fome of confiderable hardnefs, as agates and jafpers.
          The  Solution Sor  this  purpoSe fhould  be fully  faturated
          with  the metal;  and  the  ftone, after  the liquor has
          been applied,  expofed for fomc time to  the fun.   M.
          du  Fay  obferves  (in  a paper  on this fubject in  the
          French memoirs  for  1728), that  if the folution  be
          repeatedly applied, it  will penerrare into the whitifh
          agate, or chalcedony,  about  one-twelfth of an inch:
          that the tincture  does not prove uniform, on account
          ofthe veins in  the ftone:  that  the colours, thus com-
          municated by art,  are readily  difliinguifhed from the
          natural, by  disappearing on  laying the   ftone for a
         night in aquafortis :  rhat, on expofing it to the  fun
         afterwards  for fome days, the colour  returns:  that
         the  folution  gave fomewhat different tinctures  to dif-
         ferent ftones ;  to  oriental agate, a deeper black than
         to the common  chalcedony;  to an agate  Spotted with
         yellow, a purple ;  to rhe jade ftone,  a pale brownifh ;
         to the common emerald,  an opaque black  ; to common
         granite, a violet unequally deep ; to Serpentine  ftone,
         an olive ; to marble,  a  reddifh,  which changed to pur-
         ple, and fixed in a brown;  that on   Slates, tiles, and
         amianthus, it had no efflct.
   753
Colours
produced
                                                         *°5
   If a Solution of filver  be diluted with pure water, a Nitron*.
 confiderable quantity of pure  mercury added, and the acid and
 whole fet by in a cold place; there will form  by de- its  fornDi-
 grees a precipitation  and cryftallization refembling a "atl0^6, .,
 little tree,  with its root,  trunk and branches, called    754
 arbor Diante,or rhe philosophic filver tree. Another kind Arhor Bia-
 of artificial  vegetation may be produced  by fpreading na5-
 a few  drops of folution  of filver upon a glafs plate,
 and placing in the middle a Small bit  of any  of the
 metals  that precipitate Silver,  particularly iron.   The
 filver quickly concretes into curious ramifications all
 over the plate.                                          y^-
   Like other  metallic Solutions,  this  combination  oS Solution cf
 the nitrous acid wirh Silver is decompoSed by fixed and Clver de-
 volarile alkalies, calcareous earths, and feveral metals, compofed.
 (fee the Table  of Affinities);  but  with feveral pecu-
 liar circumftances  attending the prccipitarion.  With
 metals, the filver is readily and copioufly thrown down
 at firft, but flowly and  difficultly towards the  end.
 The menftruum generally retains fome portion  of the
 filver, as the filver almoft always  does  of the metal
 which precipitated  it.   For recovering the filver from
 aquafortis after parting, the refiners  employ copper.
 The  folution, diluted  with water, is put  into a  cop-
 per veffel, or inro  a glafs one with thin plates of  cop-
 per, and fet into a gentle warmth.   The filver  begins
 immediately to Separate Srom the liquor in form oS fine
 grey  fcales,  or  powder;  a part  of the copper being
 diflblved in  its place, fo as  to tinge the  fluid  more or
 lefs of a bluifli green colour.  The plates are now and
 then  fhaken,  that fuch part of  the filver as is depo-
 fited upon them may fall off, and fettle to the bottom.
 The  digeftion is continued  till a  frefh bright plate,
 kept for fome time  in  the warm  liquor,  is  no longer
 obferved  to  contract   any  powdery matter on the fur-
 face; when the liquor is  poured  off, and the preci-
 pirate waflied wirh frefh  parcels of boiling warer.  It
 is obfervable,  that though the acid in this procefs fa-
 turates itfelf with  the copper, in proportion as it lets
 go the filver, yet the quantiry of copper which ir takes
 up is not near fo great as  that of filver which  it de-
 pofits.  One drachm  of  copper will precipitate three
 of filver,  and faturate  all  the acid  that held the three
 drachms diffolved.                                      - g
   Calcareous earths,  as chalk  or quicklime,  throw Characters
 down a part of the filver, but leave  a very confide- curiotifly
 rable part fufpended in the  liquor.  If the earth be marked  on
 moiftened with the folution into the confiftence oS a the inn(Je
 pafte, and  expoSed to the Sun, it changes its white f   g
 colour to  a  dark  purplifh black;  diftinct  characters ofthefun^s
 may  be exhibited  on  the  matrer, by  intercepting alight.
 part ofthe fun's light by threads, flit paper, ire. placed
 on the outfide of the glafs.   Culinary fire does not af-
 fect its colour:  after the  mafs has been exficcated by
 this,  it changes as beSore, on expoSure to  the Sun.
   Mild  volatile alkaline Spirits, added  to a  Solution of
 filver, precipitate but little, and  cauftic volatile alka-
 lies none.  Pure fixed  alkalies, and alkalies rendered
cauftic by quicklime, throw down the whole. Fixed al-
kalies impregnated with inflammable matter by calci-
 nation with  animal coals,  occafion at  firft a  confide-
rable precipitation ; but if acided ro a larger quantiry,
take up  a great  part   of the metal again.   Mr Mar-
graaf relates, that  edulcorated calces of filver totally
diffolve,  both in a lixivium of thefe alkalies and in vo-
                         O                   Utile 
IOfj
CHEMISTRY.
Pra&ice.
Nitroi^
. id a ;
its coml
r. tions.
  75 7
tejpcr.
 758
:rJitcr.
 759
Iron.
 -n0
Tin.
 r6i
Lead.
   76-
Quickfilver
fuppofed to
fce extraft-
«  ': from
lead.
Utile fpirits; and that the marine acid precipitates the
filver fum  the volatile,  but not from the fixed, alka-
line folution.   Kunckel reports  that the calx precipi-
tated  by  volatile Spirits made with  quicklime,  fulmi-
nates or explodes in the fire ;  and that  by infpiffating
a  Solution of  pure  Silver,  niching the dry  refiduum,
p mring it on Spirit  of urine SuperSaturated with Salt,
and Setting the mixture in a  gentle warmth,  a  blood-
red  maSs is   produced,  So tough,as to admit  of  being
wound about the fingers.
   III.  With Copper. The nitrous acid very readily dif-
Solves this metal into a green-coloured and very cauftic
liquor.  The Solution, if properly evaporated, will cry-
ftallize ;  but  the cryftals are deliqueScent, and there-
fore difficult  to be preServed.   The only uSe of this
combination is for the preparation  of the pigment cal-
led verditer.  Of this there arc two kinds, the blue and
green.   The blue is  by  far  the brighteft colour, and
confequently  the moft valuable.  It has been  faid that
this is  obtained  by precipitating a folution of copper
by any  calcareous  earth;  and therefore  is fold by the
refiners who  have large  quantities of folution of cop-
per accidentally made.  The folution is  faid to be pre-
cipitated by chalk, or whiting ;  and that the precipitate
is the  beautiful blue  colour called verditer.  By this
method, however,  only the green kind  can be obtain-
ed.   The blue we have found to be of a quire different
nature, and formed by precipitation with a gentle heat
from a folution of copper iu volatile alkali.  See the
article  Colour-making.
   IV.  With Iron.  On this metal the concentrated ni-
trous acid acts very violently, and plentifully corrodes,
 bat does not diffolve it ; the calx falling almoft  as fait
 as diffolved ; and when it  is once let fall, frefli acid will
 not take it up again.   If the acid was diluted at firft,
 it takes  up  a confiderable  porportion,  provided the
 metal  be lcifurely added.   If  the  folurion is perform-
 ed  with extreme  flownefs, the colour will  be green ;
 but if  otherwife, of a  dark red.  It does not cryftal-
 lize ;  and, if infpiffatcd to drynefs, deliquates in the
 air.
    v\  With Tin.  Concentrated nitrous  acid acts upon
 tin with  great force,  but only corrodes the  metal into
 a white indiffbluble mafs.  In order to obtain a perfect
 folution of tin in the nitrous acid, the metal muft be put
 in by  very  little at a rime, and a dilured  aqnaforris
 made ufe of.   This folurion has been confiderably ufed
 in dyeing,  and is remarkable for heighrening red co-
 lours of all kinds; but the folution  made wirh agua-
 ref-.< is preferable.
   VI.  With Lead. Proof aquafortis, lowered wirh an e-
 qual quantity of water, diflblves about half its weight of
 lead.  On diluting the folution with a  large qnanriry
 of w^rcr it  rurns milky, and  depofites grear  part of
 the metal.   The  folution flioots, upon exhaling  part of
 the menftruum, into fmall pyramidal cryftals with Square
 bafes,  of an auftere Sweet tafte.
   In the memoirs of  the French  academy for 1733,
 there is a particular account of an experiment, in which
 merc.:ry is faid to have  been  extracted from lead by
 diffolving in it  the nitrous acid.   During the diflblu-
 tion, ttc;e  Sell a  precipitate which is plainly  proved
 to be  mercury, and  was looked upon to be one of the
 condiment parts of  the  lead feparated  by  this fimple
 procefs:  it fcems probable, however, that the mercury
in this c.ifr had been contained in the aquafortis ;  for Njtrou.
pure lead diffolved in pure aquafortis eives no fuch pre- acid an'1.
c.pir.te.                                             '"lo", *
   The  cryftals of lead in  the  nitrous acid,  when "a       .
thrown  inro  rhe fire,  do not deflagrate as other com-
binations  of  this acid   wirh  metallic  or faline  bafes;
but crackle  violently,  and fly round, with great dan-
ger to the by flanders.   If they  arc rubbed into very
fine  powder, they may then be  melted  without any
danger.   By repeated  diffohuions in frefli aquafortis,
they at laft forma thick  fluid like oil, which cannot
be dried withoutgreat difficulty. This compofition is not
adapted to any  particular ufe, and is a violent poifon.      .6
   VII.  With Quukftlver.  Aquafortis  of fuch a degree Quickhl-
of ftrength as to take up half its weight of filver, dif- ver.
folves with cafe above equal its weight of  mercury in-
to a limpid liquor,  intenfely  corrofive and poifonous,
which fponraneoufly lhoors inro whire  cryftals.  TheSe
cryftals, or  rhe Solution exficcated,  and  moderately
calcined, affume a Sparkling red  colour; and are uSed      .
in medicine  as  an efcharotic,  under rhe name  oS >'*•</Red*ci-
precipitate.   The precipitate has  Sometimes  been gi- pitatc.
ven  internally, it is Said, in  very large  quantities ;
even a  whole drachm  at  one dote.  But this  would
Seem  incredible;  and  the  peSenr practice  does not
countenance  the taking of  red precipitate inwardly.
This Solution feems to have been what gave the efficacy
to Ward's white drop.
   When  red precipitate is prepared in quantity, it is
proper  to  diftil the  mercurial  Solution; becauSe moft
ofthe aquafortis may rhen be faved.  It is exceeding-
ly pure, if by purity we mean its being free of any ad-
mixrurc of vitriolic or marine acid ; but is confiderably
tainted  with  the inflammable principle of the mercury
exrricated during the diflblution.  In  confequence of
this,  it is very volatile  and fmoking ; which has gene-
rally,  though  improperly,  been  taken as  a  fign of
ftrength in the nitrous acid.                              y(,s
   V11I. With Bifmuth. This femimetal is  very readily Bifmuth.
acted upon by the nitrous acid. Proof aquafortis diflblves
about half its weight of bifmuth.   If the metal was ha-
ftily  added,  the folurion  proves of a greenifh colour;
if otherwife, it is colourlefs and tranfparent.   Unlefs
the  acid  was  diluted  with  about an equal qnanriry of
warer,  a part of rhe  bifmuth cryftallizes almoft as faft
as it  diflblves.   The  metal is totally precipirared  both
by fixed  and  volatile  alkalies.  The  laft, added in
grearer quantities  than are  fufficient for precipitation,
take  it   up  again.  The  liquor  generally  appears
greenifh;  by alternate additions of  the alkaline fpirit
and folurion, ir becomes bluifli or purple.   Fixed alka-
lies calcined wirh inflammable matrer likewife diflblve
the bifmuth  aSter they have precij.ftated ir.                766
   The only ufe of this compound is for the precipi- Magiftery
tate, which  is  ufed as a cofmetic, under  the name ofoibifmuth.
magiftery of bifmuth.   The  common way  of preparing
this is by dilming the folution very largely  with  water,
upon which  it turns milky, and a fine  white  precipi-
tate falls, which is to be well edulcorated with water
and is then  employed as a cofmetic both in wafhes and
pomatums.
   Concerning  the preparation of  this cofmetic, Neu-
 mann  obferves,  that  there arc fundry variations.__
 " Some (fays he) takes aqua-regia for the  menftruum;
 and  far the precipitant a folution of fea-falt, alkalies,.
                                                fpirit 
Practice.
CHEMISTRY*
107
         fpirit of wine, &c.   Some mix  with the  folution  of
         bifmuth a folution of benzoin  in fpirit  of wine, and
         thus  obtain a magiftery compounded of bifmuth and
         benzoin.   Others add  a folution of  chalk to the me-
         talline  folution, and  precipitate  both together by al-
         kalies.   I have made trial with a good number of dif-
         ferent  precipitants ;  and found,  that with  common
         fixed alkali and cauftic alkali,  with watery and vinous
         alkaline fpirits, the magiftery  was white, and in con-
         fiderable  quantity ;  the liquor,  after the precipitation
         with volatile fpirits, appearing blue.  That oil of vi-
         triol  threw down a white  precipitate very copioufly :
         but  that  with fpirit of fait, or fpirit of vitriol, the
         precipitate was in very fmall quantity,  in colour like
         the  foregoing ; diftilled vinegar making no precipita-
         tion at all.  Common rectified  fpirit  of wine, and tar-
         tarized fpirit,  common water,  and lime-water,  gave
         white precipitates. Solutions of nitre, vitriolated tartar,
         fal mirabile, alum, borax,  common fait, fal ammoniac,
         the combination of marine acid with calcareous earth,
         and terra foliata tartari, all precipitated  the bifmuth
         white.   With a folution of gold in  aqua-regia  the ma-
         giftery  proved grey ;  with a folution of the fame metal
         in aqua-regia made with fpirit of fait,  the precipitate
         was likewife grey, and in  fmall quantity ; with  folu-
         tion of copper in  aquafortis, white^. and in very fmall
         quantity, the liquor continuing blue ; with folution  of
         Vitriol of copper, white ; with  folution of mercury fub-
         limate, white and plentiful ;  with folution of iron in
         aepiaforris, yellowifli;  With folution of lead in aqua-
         fortis,  and of fugar  of lead, white ; with  folution of
         zinc in aquafortis there was little precipitate; and with
         folutions  of filver, tin,  regulus  of antimony, and  of
         mercury, in the fame acid, none at  all."
            IX. With Zinc. Upon this femimetal the nitrous acid
         acts with greater violence than any other, and will for-
         fake any other metallic fubftance for it.   The whole is
         very foon diffolved into a  tranfparent colourlefs liquor.
         The calces of flowers of zinc are likewife foluble in the
         nitrous acid ;  but neither the  folution of  the  flowers,
         nor of the metal itfelf, have been yet fonnd applicable to
         any  ufeful  purpofe.  Neumann remarks, that on ex-
         tracting with nitrous  acid the foluble parts of calamine,
         which is an ore  of  zinc, the folution,  infpiffated to
         drynefs, left a reddilh brown mafs, which on digeftion
         with fpirit of wine exploded and burft the veffel.
K   ,   e   X. With Regulus of Antimony. The nitrous acid ra-
.„.!" "*v  ther corrodes than diflblves this femimetal.  The cor-
          roded  powder forms a medicine  formerly ufed under
          the name of bezoar mineral, but now disregarded.
            XI.  With Regulus of Cobalt.  This femimetal  diflblves
          readily in the nitrous  acid, both  in its metallic form
 .        and when reduced to  a calx.  The Solution is of a red
Regulus of colour.   Hence the nitrous acid  furnifhes means of
cobalt,how difcovering  this  femimetal in ores after Strong calci-
difcovered  nation  ; very few other cakes being foluble in the ni«
in ores.    trous  acid^  and  thofe that  are  not influencing the
          colour.
            XII. With Nickel. This femimetal is eafily diffolved
          by the  nitrous acid into a deep green liquor; but neither
          this folution, nor indeed the femimetal of  which it is
          made, has hitherto been found  of any ufe.
            XIII.  With Arfenic. This fubftance is readily diflbl-
          ved by the nitrous acid ; which abftracts the phlogifton.
See below Nitrious
          acid and
 767
Zinc.
768
antimony.

   769
Regulus of
cobalt.
 and leaves the pure  arfenical acid behind.
 Acid of Arfenic.
   XIV. With Expreffed O'ils. Thefe, as well as all other |£t£™bl"' ■
 fatty or unctuous fubftances, are confiderably thickened v----Jl—,
 and  hardened by their union with  the  nitrous acid.    771
 There is only one preparation where this combination   0u*s-
 is applied to any ufe.   It is the unguentum citrinum of    77s
 the fhops«  This is  made  by adding to fome quantity tunf "nri-
 of melted hog's-lard a folution of quickfilver  in  the num#
 nitrous acid.   The  acid, though in a diluted ftate, and
 combined  with mercury,  neverthelefs acts with  fuch
 force on the lard, as to render the ointment almoft of
 the confiftence of tallow.                                 773
   XV. With Vinous Spirits. If highly rectified fpirit of Spirit of
 wine and ftrong fpirit of nitre are fuddenly mixed to-wine.
 gether, the  acid inftantly becomes volatile, and is dif-
 fipated with great  heat and effervefcence  in  highly
 noxious  red fumes.   If  the acid is cautionfly  poured
 into the fpirit, in the proportion of five, fix, or even
 ten parts of fpirit to one of  acid, and the  mixture di-
 ftilled in a glafs retort fet  in a water-bath, an exceed-
 ingly fragrant and  volatile  fpirit comes over, ufed in
 medicine as a diuretic and cooler, under the name of   ~
fpiritus nitri dulcis.   This liquor is not acid ; nor has Spiritus ni-
 what remains in the retort any more the characteriftics tri dulcis.
 of nitrous acid, which feems to be entirely decompofed
 in this procefs.   (See the following article.)             77j
   With the nitrous  acid and fpirit of  wine,  may  alfo Nitrous 6>
 be made an exceedingly volatile liquor, called  nitrous ther.
 ether, to diftinguifli it from the vitriolic abovemen-
 tioned.  The  proportions of nitrous acid and fpirit of
 wine to each other for nirrous ether, are two of the acid
 by weight to three  of  the fpirit.   Dr Black's  procefs
 for making it is as  follows.  Take  four  ounces of
 ftrong phlogifticated nitrous acid ; and having cooled
 it  by putting it into a  mixrure of  fait and  fnow, or
 into water cooled very  near  the freezing point,  by  put-
 ting pieces of ice  into it,  he  puts  it into a phial,
 and pours upon  it an equal quantity of water, likewife
 cooled very low, in fuch a manner that the water may
 float as much as poflible on the furface of  the fpirir.
 Six ounces of  ftrong fpirit of wine are then put in, fo
 as to float in like manner on the furface of the  warer ;
 the  phial is placed in a veffel containing  cold  water  :
 and fo great is the power of  cold in reftraining the ac-
 tion of  bodies, that if the  mixture was  too cold, no
 ether would  be produced ;  but at  the  temperature
 juft mentioned, the  ether  begins to be formed in a few
 hours, with fome little effervefcence, and  an expulfion
 of a fmall quantity of nitrous air.  We muft provide
 for the  efcape of this elaftic fluid,  by having an hole
sin the cork, or the  veflel  woald  be broken.  The
 whole of the ether will be formed ilia few days,  and
 may  be  feparated  from  the  reft of the liquor by
 means  of a  funnel,  fhaped  as in  PI.  CXXXIV.
 fig-  9-                      ,                          776
    To procure  the  nitrons ether in large quantities, Woulfe's
 Mr  Woulfe recommends the following procefs.   Put procefs for
 into a retort four pounds  of nitre,  then  mix together procuring
 four pounds of vitriolic  acid, and  three  pounds  five lt m lar.Sc
 ounces of fpirit of  wine.   Thefe are poured  on  the 1u*nUtlt8>
 nitre by adding only two ounces  at a time :  the vi-
 triolic acid acting  on the nitre, produces a fufficient
 degree of heat j  and the  acid of the nitre uniting  with
                          O  i                 '   the 
ioS
C    H   E    M    I    S   T    R   Y.
Pra&iec.
   7"'
Inquiry ui
to the na-
t ;rt uf e-
ther.
   77*
Oils fired
         the f/ri:,  for n* a nitro ;s  ener, which flics off from
         rhe mixture, and is condenfed  in a number of veffels
         placed in coid  water.—To obtain good nitrous ether
         readily, and at  one diftillatim,  Mr Dollfufs adviSes  to
         di:lil four p.irts of  nitre of  manganefe, four of vitriolic
         acid, and ei„ht  parts of Spirit of wine.
            Macquer f pp.fes th.n ether is  the moft  oily part
         or quintcflence  of Spirit of wine.   But it  cannot  be
         proved  that ether contains  any oil.  And, btfides, if
         this were the cafe, thofe adds which  have  the ftrongeft
         attraction  for water would  produce the greateft quan-
         tity of ether ; which is found not ro be rhe  cafe : and it
         ii moft probable that ether is produced by a combina-
         tion of fome part  of the acid  with a portion, particu-
         larly thr inflammable parr,  ofthe fpirit of wine ;  and
         it has been mown by chemical experiments, that every
         kind  of ether contains a  part of the acid employed.
         Dr Black  himfelf has formed erher  without  any fpirit
         at all, by expofing nitrous  acid highly phlogifticated
         for fomc months to rhe light  of the fun.  This was
         owing to rhe attraction of  rhe principle of inflamma-
         bility ; which it is well known that light has the power
         of affording to bodies that attract it with force.
                     Nitrous Acid  decomposed,

            I. By Effential Oils.  If equal quantities of ftrong
by fpirit of nirroas acid and oil of  cloves are poured into the fame
nitre.     veffel, the mixture inftantly takes fire ; both acid and
         oil burning with great  fury  till only a light fpongy coal
         remains.   Dr  Lewis obferves, that this  experiment
         does  not  always  fucceed,   and that there are but few
         oils which  can  be fired with certainty, without attend-
         ing to a particular circumftance firft difcovered by  M.
         Rouclle, and  communicated  in  the French Memoirs
         for the year 1747.   " On  letting fall into the oil equal
         its quantity of  acid, the mixture effervefces, fvvells,
         and a light fungous coal arifes: a little more of the acid
         poured upon this coal Sets it inftantly on fire.   By this
         method almoft all the  diftilled  oils may be fired by Spi-
         rit of  nitre of  moderate ftrength.   Expreffed oils  alfo
         maybe fet on fire by a mixture of the nitrous  acid and
         oil of vitriol ;  the ufe of  which laft feems to be to  ab-
         forb the aqueous humidity  of the fpirit of  nitre.
            II.  By  Charcoal.  By this fubftance the nitrous acid
         cannot be  conveniently decompofed, unlefs it is combi-
         ned with an alkaline or metallic bafe.  For the purpofe
         of decompofing the  acid, common faltpetre is moft
         convenient.    The proportions recommended by  Dr
         Lewis for alkalifating nitre, are four ounces of the  fait
         to five drachms of powdered  charcoal.  If thefe  are
         carefully mixed, and  injected  by little  and little into a
         tubulated  retort made red hot, and  fitted with a large
         receiver and a number of  adopters, a violent deflagra-
         tion will enfue on every addition, attended with a great
          quantity of air, and fome  vapours which will circulate
          for fomc time, and then condenfe in the veffels.  This
 flyfruTof  liquor is called clyjfus of nitre.  If fulphur is ufed inftead
 i.crc.      of nitre, the clyffus is of a different kind, confuting of
          a mixture of the nitrous and  vitriolic acids.   The re-
          fiduum, when charcoal is ufed, is a very ftrong and pure
          alkali ;  with fulphur  it  is vitriolated  tartar.   To pre-
          vent  the  lofs occafioned by  the  violent  deflagration,
          when this operation is performed  in open veffels, Dr
          fclack recommends to have  the materials fomewhat moift.
            III.  By Vr.c-.ii Spirits.   In the procefs already men-
   779
Nitre alka
lized.
lioncd for mikiu^fpirUus n'rtri dul.'u, a total decompo- Marine
fit ion ofthe acid Items to take place : fer neither  the ?CI<1 a"^
dulcified  fpirit itfelf, nor  the acid matter left in the re- lt!
tort, (how any Signs of deflagration with  inflammable
matters, which is the peculiar charactcriftic of nitrous
acid.,                                                 :8i
  Mr Pott has given an  analyfis of the  oleaginous re- Refiduum
fiduum oS the  diftillation.  Diftilled by a ftronger fire, of ^J".
it gave  over  a yellow,  acid,  llightly  cmpyiuimatic "^lizedh/
Spirit ; which being Saturated  with  fixed alkali, the Mr 1>ott
liquor  evaporated,  and  the  dry  neutral Salt laid on
burning coals, did not deflagrate.  ASter  this Spirit a-
roSc a red  empyreumatic oil ;  and in the  bottom of
the retort was leSta Shining black maSslike. Soot; which,
burnt in  a crucible,  left  a white lixed earth, convert-
ible by a vehement fire into glafs.   Another  p.irccl
of  the above  refiduum was evaporated to the confift-
ence oS  pitch.  In this ftate  ir gave a yellow tincture
to Spirit of wine, flamed vividly and quietly on burn-
ing  coals, and at laft fwelled up like bitumen.  Ano-
ther portion was  Saturated with  alkaline  ley, wirh
which it  immediately efferveSced, and then evapora-
ted as the former.   It gave,  as before, a yellow  colour
to rectified fpirit of wine, and a much deeper yellow to
dulcified fpirit of nitre ; and in the fire difcovered no
footftep of detonarion.  M. Macquer fuppofes this acid
to have been  not the nitrous, but the acetous, which
enters into the compofition of the Spirit of wine ;  and
his conjecture is now confirmed by late experiments.
?8o
§3.   Of the Marjke Acid and its Combinations.
782
  This acid is never, at leaft very rarely, found  but Marine *-
in a ftate  of  farurarion wirh the  mineral alkali; inc"*'
which cafe it forms the common fait ufed in food.   Al-
moft the only exception to this is human urine, and
perhaps that of fome other animals ; for there  the ma-
rine acid is found faturated, not with  the  mineral, but
the common vegetable, fixed alkali. From being found
in fuch plenty in the waters  of the ocean, it  has  the
name of marine acid.                                   ^gj
  It is commonly thought  that this acid  is  no other Marine a-
than the vitriolic, fomehow or other  difguifed by the cid thought
inflammable principle ; to which fome have added ano-t0 be th.c.
ther, called by them a mercurial earth.               thTvi7rio-
  Thc  reafons  given  for  this fuppofition, however, uc
are but  very  flight,  confifting chiefly in the refem-
blance between  the volatile vitriolic acid  and the  ma-
rine,  both in the white  colour of their  vapours,  and
likewife  the great volatility of both.   As to the exift-
ence of that principle called a mercurial earth, it hath
never been proved ; and,  till that time, can never be
allowed to be an ingredient in the compofition  of  any
fubftance whatever.  As  we do not remember to have
read of  any experiments where the  marine  acid was
directly produced from that  of  vitriol, we fhall con-
tent ourfelves with relating one very remarkable  fact
which happened  to fall under our  own obfervation.       784
   As vitriolated tartar, or  Glauber's  fair, when fufed A tranfnw.
with  charcoal duft, is converted  into an hepar  ful- nation.
phuris, attempts  have been made  on this  principle
to Separate  the pure alkali  from the refiduum of Glau-
ber's fpirit of nitre and  fpirit of  fait.  In an attempt
of  this  kind,  which, by the bye,  proved  unfaccefcful,
as  all  others of the  fame  kind  muft do, 30  or 40
                                             pounds 
Pra&ice.
CHEMISTRY.
09
   785
©r Prieft-
ley's obfer
vation* on
marine a-
•id.
pounds ofthe mafs for Glauber's fait  were fufed in a
ftrong iron pot, with  a fufficient quantity of common
coal  powdered  and fifred.  As the quantity of pow-
dered coal  was pretty large,  the  mafs was  thereby
hindered from flowing into thin fnfion ;  and, that  the
whole might be perfectly  alkalifated,  it wasTrequent-
ly ftirred up with an iron ladle,  and kept very intenfe-
ly heated for fome hours.  The mafs was now  taken
out by means of an iron ladle, and laid on a flat ftone ;
and,  as it was but half fluid, every ladleful  concreted
into  a black irregular faline mafs,  which had the  ap-
pearance of a  cinder  : bat which, however, outfitted
of an hepar fulphuris mixed with fome coal-duft.  As
there was a confiderable quantityof this matter, and
the ladlefuls were thrown at random above one ano-
ther, it fo happened,  that between two or three of  the
pieces, a kind of chimney was  formed,  fo that there
being a  fmall draught of  air through the interfaces,
and  the  maffes containing a quanrity of coal-duft,  the
internal parts were in a ftate of ignition, while the  ex-
ternal were quite cold.   From thefe ignited places a
white fume arofe ; which  being collected on the colder
maffes, afnuned the form of white flowers. Thefe were
found to be genuine fal ammoniac, compofed of a vola-
tile  alkali and marine acid ; both  of  which we have
the greateft reafon to think were produced at that very
time, and  that  a double tranfmutation took  place;
namely,  ofthe vitriolic acid into the marine,  and of
the fixed alkali into rhe volatile.  Our reafons Sor  be-
ing of this opinion are, 1. That the matter had been
Subjected to fuch an exrreme and long conrinued hear,
that, had any fal ammoniac been  pre exiftent  in  the
mixture, it muft have certainly been diflipated,  as this
fait always fublimes with  a degree of heat below  ig-
nition.   2. Though the matter was taken out of the pot
of a  very intenfe red heat? fo that  the faline part was
evidently melted, yet no arhmoniacal fume iffued from it
at that time,  nor till the maffes  had  been for fome time
expofed to the air,  and were become cool, excepting
©nly thofe  interfaces  where the air kept up a burning
heat, by a fmall draught being formed from the fitua-
tion  of the faline maffes.   3.  In thofe ignited  places,
when cool, the  fixed fait  was entirely decompofed,
neither alkaline fait,  Glauber's fair,  fixed alkali,  nor
fulphur remaining ; but the  whole was  confumed to a
kind of ferruginous afhes.  We are therefore of opi-
nion, that  the marine  acid and volatile alkali are, in
fome cafes,  mere creatures of the fire, and moft com-
monly produced at the fame time,  from the flow com-
buftion  of  mineral  fubftances.   Hence,  where heaps
of hot cinders are thrown out,  fmall quantities  of  the
true  fal ammoniac are always formed^ when the ignited
ones  happen to fall in fuch a manner  as  to occafion  a
fmall draught of air through them.
  The marine acid, or fpirit of fait, is  weaker than
either the  vitriolic or nitrous  ; though  Dr  Prieftley
hath obferved, that, when concentrated to  the utmoft
degree,  in which ftate it was  perfectly  invifible and
elaftic as air, it was  then able to feparate the  nitrous
acid  from an alkali.   In fome other cafes,  too,  it  ap-
pears not only ftronger than the nitrous, but even than
the vitriolic; of  which we fliall take  notice in courfe.
—Mr Berthollet fays, that  he  has been able  alfo to
procure  the marine acid in a folid ftate,  by diftilling it
in Mr Woulfe's apparatus, kept perfectly cool with  ice.
  The yellow colour of the marine  acid is Sometimes Marine
owing to iron, which may  be precipitated  Srom it  by fcid  2,1<*
means of an alkali.  In certain cafes, however,  it is lts "'™ l-
obferved to have a much darker and nearly a brown .____^..'....
colour, without containing  the fmalleft particle of this
metal.—Mr Dollfufs is of opinion, that the yellow co-
lour of the marine acid is  owing  to a porrion of de-
phlogifticated air which it generally contains. A pretty
ftrong proof that it emits  this kind  of air indeed  is,
that a candle will burn longer in  a  bottle containing
fome marine acid,  than it will in an equal quantiry of
common air.

I. To procure the  Marine Acid by means  of  the  Vi-
                       triolic.
  Put any quantity of fea-falt into a tubulated  glafs-
retort, to which a large receiver is  firmly luted,  ha-
ving a quantity of water in it,  more or lefs as  you
Want  your fpirit of  fait  to be  more or lefs ftrong.
Having placed your retort in a fand-bath, take of con-
centrated oil  of vitriol half as much  as you  put  fait
inro the retort.  Through  the  aperture in the  upper
part of the retort, pour a fmall quantity of the vitrio-
lic acid ; a violent effervefcence  will immediately a-
rife, and white vapours will afcend, and come over into
the receiver.   Thefe  vapours are the marine  acid in
its moft  concentrated  ftate  ; and, as they are very
greedy of moifture, they  will unite with the warer in
a very fhort time,  unlefs too much oil of vitriol is  put
in at once ; in which cafe, part of them will be difli-
pated  through  the fmall hole in the receiver.  When
you perceive the firft fumes condenfed, add a little more
oil of vitriol, taking  care to flop the aperture of  the
retort as foon as yon  drop in the vitriolic acid, that
the marine acid  may  not  efcape.  Continue  this by
intervals,  till your acid is all put  in ;  and then  make
a very gentle fire, that the  retort may be no warmer
than the hand  can  bear.  This degree of heat muft
be continued a long rime, otherwife very much of  the
acid will be loft.  To perform this operation perfectly,
no more acid  fhould be forced over, than what  the wa-
ter in the receiver can take up ; and by this means
the operator's patience will be rewarded with a vaftly
larger produce of acid than  can be procured by  hafty
diftillation.  When the vapours become a little  more
fixed, a greater heat  is neceffary, but nothing  equal
to what the nitrous acid  requires.  For diftilling  fpi-
rit of  fait, Mr Wiegleb recommends four pounds of
oil of vitriol to fix of common fait.—It may alfo be
obtained  from  the bittern  remaining after  the cry-
ftallization of common fait,  by adding  one pound of
oil of vitriol  to five of bittern.  It may even be  ob-
tained from  this liquid  by fimple diftillation  without
any additional acid ; but a violent fire will then be ne-
ceffary, and it is almoft impoffible to prevent the li-
quor from fwelling  and running over the neck of  the
retort in the beginning of the procefs.
  The marine  acid cannot be procured by means of
combinations of  the  vitriolic acid with metallic  and
earthy bafes,  as the nitrous  is ; for though, by means
of calcined vitriol, for inftance,  the marine acid is ef-
fectually  expelled from its alkaline bafis,  yet  it imme-
diately combines with  the calx of iron left by the vi-
triolic acid,  and not only adheres obftinately,  but even
fabliraes the metal •, fo that what little Spirit can be
                                                ob-
   786
Spirit of
fea-falt.
   787
Why diftik
lation of
fea-falt
with cop-
peras does
not Sue*
ceed, 
1 10

M ,-ir.e
a..J and
its Ctimli-
natiorts.
C    II   E    M    I    S   T   R   Y.
Pra&ice.
-regis
Spirit of
tlV.p.-rfi.
   790
Marine «-
cid de-
phlogifti-
cated by
•hat of
obtained,  is never  pure.   This inconvenience  is not
l'i great when uncalcined c pperas is made ufe  oS:
for the marine acid has a  very  ftrong attraction to
water ;  which  partly difSolves its union with the  me-
t.illine  calx.   If gypfum is  ufed, inftead of calcined
vitriol,  not a drop  of fpirit will be obtained.   Alum
and fal  catharticus amarus amfwer better.

   II. To procure the Marine Acid by  means of the
                      Nitrous.

   Take equal  quantities of fea-falt and Glauber's fpi-
rit of nitre;  put the  fait into a retort,  and pour on it
the nitrous acid; let  them ftand for 10 or la  hours ;
then diftil with a gentle heat; an acid  liquor  will come
over, which is a compound of the nitrous  and marine
acids,  called aqua-regis.   When  the  diftillation is fi-
nifhed, and the veflels cooled, pour back the diftilled
liquor on  the  maSs which is lcSt on  the  retort,  and
diftil again: the Second produce  will  be more  of the
nature of fpirit of  fea-Salt than the former.   Continue
to do  this, pouring  the  diftilled  liquor cither on  the
mafs left in the retort, or upon frefh  fea-falt,  till you
obfcrve that no nitrons acid arifes.   No experiments
have been made on this fpirit of fait, by which we can
jud^e whether it is different  from that procured by the
vitriolic acid or not.

  III. To procure the Marine Acid, by diftilling Sale
                      per fe.
   Pur into a retort any quantity of common fait  which
has not been  dried, and diftil  in a fand-heat  till  no-
 thing more will come over.  In the receiver you will
have a liquor  confiderably more acid  than vinegar, in
weight about  the fourth  part  of the fait  employed.
 On the dry fait left in  the  retort,  pour fome  water,
 fomewhat lefs in quantity than  the liquor which came
 over.   Let it  ftand  till  the fait has thoroughly imbi-
 bed the moifture, and then diftil again. You will again
 have an acid,  but  weaker than  the former.  Repeat
 this fix or feven times ;  aSter which  you will obtain
 no more marine acid in this way.   It has been  thought
 that  Sea-Salt   was  capable of total decompofition by
 means  of moifture alone  ; but that is found  to  be  a
 miftake.   The reafon of  any acid being procurable in
 this way, is the impurity of the common fait, which is
 always mixed  with a quantiry of fal carharticus ama-
 rus,  and of marine acid  combined with magnefia,  from
 which  laft it is feparable by moifture. If a pure fait
 be formed by  combining marine acid with fait of  foda,
 no fpirit  will be obtained.
        IV. To dcphlogifticate the Marine Acid.
   The marine acid, when  mixed either with that of
 nitre or  wirh  manganefe, lofes rhar peculiar fmell by
 which  it is ufually diftinguifhed, and acquires one much
 more volatile  and  fuffocaring.   When mixed with the
  former, the compound is called  aqua-regia;  when fub-
"lancanefe. jected to the action of manganefe, the product is called
P' jai    dephlogifticated fpirit of fait.  The method of procuring
Check's   this acid recommended by Mr Scheelc is as  follows:
method of  j\ijx common muriatic acid in any quantity with levi-
dephlogif-  gated  manganefe in a glafs retort ; ro which lure on
tu-ating n  wjtj1 blotting  paper  a receiver capable of containing
    unjra-  ajJQUt I2 ou:iccs 0f water.  Put about  two drachms of
          liquid into it; and in abour a quarrer  of an  hour,  or
          fbmew'u: :r.x e, a quantity of ciaftic fluid, which is the
true dephlogifticated fpirit of fait,  will pafs over, and Marine
communicate a yellow colour to the air in the receiver; ac»d and.
after which  the latter is  to  be  fcparated from the re- «t»«>mD'-
tort.   If the paper has been  clofcly applied, a quantity nat10"*'  ,
of the air will now rufli out with fome violence; a cork
muft therefore inftantly be put into it, and another re-
ceiver applied, having in like manner two drachms of
water in it, which will alfo be filled in  a lhort time ;
and thus may feveral phials full of this  aerial acid  be
procured in a fhort time.   Care fhould be taken, that
the retort be placed in fuch a manner as  that any drops
of liquid which chance to arife may fall down again in-
to it.  The warer put into the receivers  feems to con-
denfe the vapours of  the marine  acid ;  and it is moft
proper to ufe fmall receivers, 9k account  of the great
quantity of vapour which is loft at every  operation.        7jj
   The  effects  of this  dephlogifticated marine acid, Properties
which can fcarcely be condenfed into a  liquid,  arc, 1. of dephlo-
The lute is corroded in  diftillation,  and the corks be- j?1*1."*?1
come yellow, as from aquafortis.   2. Paper coloured f\nt °
with lacmus becomes nearly white, as well as all vege-
table  red,  blue, and yellow flowers;  and the fame
change  is likewife produced upon the green colour  of
vegetables ; nor can any of thefe colours be recovered
cither by alkalies or acids.  3.  Expreffed  oils and ani-
mal  fats, expofed to the vapour,  become as tenacious
as turpentine.  4.  Cinnabar grew white on  the fur-
face ; and when it was wafhed, a pure folution of corro-
five  fublimate  was  obtained ;  but  fulphur was  not
changed,  c.  Green vitriol became red and deliquef-
cent; but white and blue vitriol remained unchanged,
6. Iron filings were diffolved ;  and on evaporaring the
Solution to dryneSs, common muriatic acid was  obtain-
ed by diftillation with marine  acid.   7. In like man-
ner all  the metals, even gold itSelS, were diffolved ; and
by precipitation with volatile  alkali, rhe Solution of
gold yielded aurum fulminans.  8. The cauftic volatile
alkali produced a white cloud,  and em-itted  a number
of air-bubbles, which on bursting discharged an elaftic
vapour.  9. Fixed alkali was  changed into common
Salt, which decrepitated in the fire.  10. ArSenic be-
came deliqueScent,  inSects died, and fire was inftanta-
neoufly  extinguifhed in the vapour.                      703
   TheSe phenomena proceed Srom the ftrong attrac- Miftakc of
tion  of  dephlogifiicared  marine acid  for  the phlogifton Stahl ac-
it has loft ; and which is one of the effenrial parrs of it,countC(*
without which it can  fcarce  at all be  condenSed into a
liquor.   " Perhaps (fays Mr Scheele)  Stahl obtained
fuch a dephlogifticated muriatic acid by means of iron;
and from the yellow colour of the cork was led  to fup-
pofe that the muriatic acid had been changed into the
nitrous. If you make a mixture of manganefe, muria-
tic acid, or diluted vitriolic acid, and alcohol;  and  af-
ter fome days digeftion diftil it by a  gentle fire, no  ef-
fervefcence enfues :  but  the fpirit of wine goes over ;
and,  what is  very remarkable,  has a ftrong fmell of
nitrous  ether.                                         ad ?
   A new fait has been produced by Mr Berthollet from New fait
the union  of dephlogifticated fpirit of fait with vege- refembling
table alkali.  This appears to be of the  nitrous kind, nitrc b7
as having  a  cool tafte and detonating ftrongly in  the ^'iP""
      The compound was in very fmall quantity,  and* °
fire.
tufc.
Seemed to require more pure air for its compofition than
an equal bulk of acid.   The greateft part  of the fait
produced was the common fait of Sylvirs, or digcflive
fin, formed by a combination ofthe phi gifticated ma- 
Practice.
CHEMISTRY.
          rine acid with alkali.  Six parts of the dephlogifticated
          acid are  required to give their air ro one of  the  fait.
          When the fixed alkali is employed, fome of the dephlo-
          gifticated acid efcapes with the pure air;  and in gene-
          ral, when not expofed to a bright heat, the fair we Speak
          oS is formed.   Some of  the dephlogifticated  acid  re-
          mains in its proper form after  the  fait is made, and
          may be feparared by rhe volatile alkali.   It is  to be ob-
          ferved,  that if  the cauftic alkali be employed, and the
          folution  much concentrared, even rhough not under the
          influence  of  a bright light  (for it is the light which
* SteA'er*- produces the extrication of the dephlogifticated air*),
Ugy, n* 36, a  great effervefcence will enfue, and a quantity of de-
'tf'f-
   794
Sal digefli-
vus fylvii.
 phlogifticated air efcape ; whence of confequence, little
 fait can be obtained.
   This fait is foluble in greater quantity in hot than in
 cold water; and not only detonates like nitre,but with
 much greater violence.  The reafon is,  that, like  ni-
 tre,  it not only contains dephlogifticated air, but has
 it in greater quantity ; an hundred grains of fait giving
 75 of air.   Attempts have been made to procure  gun-
 powder by means of this fait, but as yet they have been
 attended with little fuccefs.
   The other  properties  of this fait as yet difcovered
 are, that it flioots into rhomboidal cryftals ; it does not
 precipitate mercury,  filver, or  lead,  from their folu-
 tions in nitrous acid ;  and  it gives out irs air again in
 fuch a pure flare as fcarcely to be  paralleled in any other
 fubftance.
   With the mineral  alkali the dephlogifticated acid
 forms a deliquefcent fait, foluble in fpirit of wine ;  and
 Which,  even  in  a  fluid ftate, detonates with burning
 charcoal.  With lime, when  fo far quenched thai the
 air in  its  interftices is feparared,  rhe dephlogifticared
 acid unites  but  weakly.  It may  be recovered  from
 the lime, however,  provided the light be obfeure, with
 very little lofs, and almoft unchanged.
              Marine Acid combined,

   I. With Vegetable Fixed Alkali.  This combination is
 accidentally  formed  after the  diftillation of volatile
 falts, by means of fait of tartar (fee Alkaline Salts). It
 was  formerly known  by the name of fal digeftivus Syl-
 vii;  and a procefs for making   it  was inferred in  the
 difpenfatories, under the name of fpiritus falis mari-
 ni coagulatus ; but as it has been  found to poffefsno vir-
 tues  fuperior, or even equal, to common fait, it  is
 fallen into difufe.
   The cryftals of this kind of fait are not cubical, like
 thofe of common fair,  bur parallelopipeds, and if thrown
 into the fire crack and leap about with violence. They
 are foluble in greater  quantity  by hot water than cold ;
 and  rherefore are cryftallized by evaporaring the folu-
 tion  to  a pellicle,  and then letting it cool.—It is very
remarkable, that though by a  direct combination of
vitriolic acid with vegerable fixed alkali, the fait called
vitriolated tartar is  formed ; yet if  this alkali is  once
faturated with fpirit of fait,  foas to  form a fal digefti-
vus,  upon the decompofition of  this fait  by means of
oil of vitriol, the refiduum of the diftillation  will  not
be a vitriolated tartar, but a fair-eafily foluble in water,
and which  bears a ftrong  refemblance  to Glauber's
fait.  Whether, by  means of  fpirit of  fea-falt,  the
vegetable alkali could  be converted into the mineral,
•r fait of foda, is a queftion well worthy of being folved.
                                               1
                                                         rrr
   II. With Minenal Alkali.  This  combination is  the Marine
 common alimentary fair,  and is never made but for ex- acid and
 periment's fake ;  as the marine acid cannot be had butItsC0
 from fea-falt.  For the extraction of  this fait from fea-    ^'. *
 water, fee the article Salt.                            795
   III. With  Volatile Alkali.  The produce of this com- Salammo-
 bination is the common fal  ammoniac,  which is  ufed nmc-
 in different arts, and which has the property of making
 tin unite very readily with iron and copper, fo is much
 ufed by copperfmiths and in the manufactory of tinned
 iron.
   Sal  ammoniac is ufually fold in large femi-tranfparent
 cakes, which are  again capable of  being fublimed into
 maffes of the like kind.   If they are diffolved in water,
 the fait very eafily flioots  into fmall cryftals like  fea-
 thers.  Expofed to a moift air,  it deliquates.   It is one
 of the fairs  which produces the moft cold by irs folu-
 tion; fo as to fink the thermometer 18 or 20 degrees,
 or more, according  to  the temperarure of the atmo-
 fphere.  According to  Mr Gellerr, a folurion of  fal
 ammoniac  has the properry of diffolving refins.   Ac-
 cording to Neumann, the volatility of fal ammoniac is
 fo much diminiflied by  reppated  fublimations,  that  at
 laftit remains half fluid in the  bottom of the fublime-
 ing veflel.   In its natural ftate, it fublimes with a de-
 gree of heat  neceffary to melr lead.    Pott fays, thar a
 fmall quanriry of  fal ammoniac may be produced  by
 diftilling fea-falt with charcoal, or with  alum, or  by
 diftilling marine acid with Armenian bole.  The fame
 author affirms,  that the inflammability of fulphur is de-
 ftroyed by fubliming it  with  twice its quantity of  fal    •
 ammoniac.                                              g
   The method of making this fait was long unknown ; Howmade.,
 and  it was  imported from Egypr,  where ir was  faid
 to be  prepared  by fublimation from  foot alone, or
 from a mixture of fea-fiffr, urine,  and foot.    That it
 fhould be  produced  from  foot alone is  very  impro-
 bable; and  the other method, from  the known prin-
 ciples  of chemiftry,  is abfolutely  impoffible.   The
 compofition of this Salt, however,  being once known,
 there  remained no other defideratum than a method
 of procuring thofe competent  parrs  of  fal ammoniac
 fufficienrly cheap,  fo as to afford fal ammoniac made
 in Britain at a price equally  low  with  what  was im-
 ported.  The volatile alkali is to be procured  in plenty
 from animal fubftances or from foot ;  and  the low
 price of the  vitriolic acid  made  from fulphur  affords
 an eafy method of decompofing Sea-Salt, and cbtaining-
 its acid at a low rate.   A Sal  ammoniac work has, ac-
 cordingly, been eftablifhed for feveral years paft in Edin-
 burgh ; the principal material made choice of for pro-
 curing the volatile alkali is foot; and though no per-
 fons  are admitted to fee  the work, the large quantities
 of oil of  vitriol broughr into it, and  the quantities of
 genuine fal mirabile which are there made, evidently
 fhow  that the  procefs  for making fal ammoniac alfo
 produces Glauber's fait,  by the decompofition of com-
 mon fait by means of vitriolic  acid.  The method of
 conducting the procefs is unknown; but it  is plain
 that  there can be no other difficulty than what arifes;
 from the volatility of the vapours of the alkali and of
the marine acid. In the common way of diftilling thofe
fubftances,  a great part of both is loft ;  and if it is at-
 tempted  to  make  fal ammoniac  by combining thefe
 two when diftilled by the common apparatus, the pro-
                                              duce 
I 1 z
C   II.   E    MIST    R   Y.
Practice.
Muine
* if and
its >-ombi
        ducc  will  not  pay the Colt;  a little ingenuity, how-
        ever, will eafily  fuggeft different  forms and  mate-
        rials for dillilling-veffels, by  which  the  marine  acid
        and volatile alkali may be united without lofing a  par-
        ticle ot either.
           If a folution  of  vitriolic or Glauber's fecret fal  am-
        moniac is mixed with fea-falt,  the vitriolic acid Seizes
        the alkaline bafis of the fea-falt, and expels the marine
        acid; which immediately unites with the volatile alkali
        left  by the vitriolic acid,  and forms a true fal ammo-
        niac.   It this folution  is now evaporated to drynefs, and
        the faline mafs fublimed, the  fal ammoniac rifes, and
        leaves a combination of vitriolic  acid and  mineral al-
        kali at the bottom.  This fixed  mafs being diffolved,
        filtered, and evaporated, affords Glauber's falts.   This
         has fometimes been  thought  a preferable method of
         making  fal ammoniac, as the trouble of diftilling the
        marine  acid  was  thereby prevented ;  but it is found
         vaftly inconvenient on anotlier  accounr, namely, that
         when fal ammoniac is mixed with any fixed fair, it is al-
         ways more difficult  of fublimation, and a part  of  it
         even remains  entirely fixed, or is deftroyed. The mafs
         of Glauber's  fait  alio, by reafon of the inflammable
         and oily matter contained  in impure  volatile alkalies,
         is partly changed  into a fulphureous mafs,  fo that the
         folution refufes  to cryftallize ; at leaft the operation  is
         attended with intolerable trouble
           IV. With Earths.   The  combinations of this acid
ammoniac, with earths of any kind have never  been found applica-
         ble to any purpofe, and therefore they are Seldom  made
         or inquired into.  The combination  with calcareous
         earth is indeed prerty frequently made accidentally,  in
         the  diftillation of volatile alkali from  fal ammoniac
         by  means  of  chalk or quicklime.   When melted  in
         a crucible  and  cooled,  it  appears  luminous   when
         ftruck, and has been called phofphorus fciutillans.   See
         Earths.
            V.  With Gold. The  marine  acid has no action  on
gold in fpi-gold in its metallic ftate,  in whatever manner the acid
         be applied ; but if the metal is previoufly  attenuated,
         or reduced to a calx,  either by precipitation from aqua-
         regis or by calcination in mixture  with calcinablc me-
         tals, this acid will then perfectly diffolve, and keep it
         permanently  fufpended.  Gold, precipitated from aqua-
         regis  by fixed  alkalies,  and edulcorated by  repeated
         ablutions, may be diffolved  even in a very weak  fpirit
          of fait by moderate  digeftion.   This folution appears
          of the  fame yellow colour as that made in aqua-regis;
          gives the purple ftain  to  the fkin,  feathers,  bones,
          and  orher folid parts of animals;  the fame violcr ftain
          to marble ; and  llrikes the fame  red colour with tin.
          Even when common aqua-regia is made ufe of for  the
          menftruum,  it feems to  be  chiefly by the marine acid
          in that  compound liquor that the gold is held in folu-
          tion.   In diftillation  the nitrous  acid  arifes, and  the
          marine  acid remains combined wirh rhe gold in a  blood-
          red mafs, fobible, like moft of the combinations of me-
          tallic bodies  with this acid, in fpirit of  wine.   If,  to-
          wards the end of  the diftillation,  the  fire is  haftily
          raifed, part ofthe gold diftils in a high Saffron-coloured
          liquor;  and  part fublimes into the neck of the  retort
          in clnftersof long Slender cryftals of a deep red colour,
          (e.jiW.e in a fmall heat, dtliquating in the air, and eafily
          1 d  i>!e in water.  By repetitions  of this  procefs  the
          whole ojf the gold  may be  elevated, except a fmall
   W
Fixed fal
   798
Phofpho
rus.
   799
Solution of
rit of fait.
quantityof white pewder whofe nature is not  known. Marine
—This red fublimate of gold is i'ftd to be  eafily fufible acid and
with the heat of one's hand,  and to be fhown by ti,c n» coutb»-
Pajifts  for the blood  of  St Januarius; the fublimate .a ' v
contained in a phial, being warmed  by the hands of    800
the priefts who hold it, constitutes the  miracle of that Wood of St
faint's blood melting on Ins birth-day.                  Januarius.
  VI.  With Siher.  Strong Spirit of fait corrodes leaf-   J!01
Silver into a white powder, but has no effect on filings
or larger maffes of the metal.   If applied in  the  form
of vapour to maffes of  filver, and ftrongly heated at
the fame time, it readily corrodes them. Thus, if filc-
ings, grains, or plates, of filver are mixed with  about
twice their weight of mercury fublimate, and expofed
to a moderate fire, in a retort, or other diftilling veffel,
a part of the marine acid in the fublimate will  be  fepa-
rared and unire wirh  the  filver,  leaving  the  mercury
to arife in the  form of mercurius dulcis.  Marine acid
is commonly fuppofed  to  be incapable of diffolving fil-
ver into a liquid ftate; but Henckel relates, that if red
filver  ore, which confifts  of  filver  intimately mixed
with red arfenic, be digefted in fpirit of fait, the fil-
ver will be extracted and kept permanently diffolved.     goz
   The combination  of marine acid with filver is called j una cor*
tuna cornea.  The moft ready way of preparing it is by nea.
diffolving filver in the nitrous  acid, and then adding
fpirit of lalt, or a folution of fea-falt, when a precipitat on
iuftantly enfues; the  marine acid  expels< the nitrous,
and uniting  with the filver,  falls  to the bottom in
form of a whire  powder.  The fame  precipitation
would take place, if a folution of filver was made in the
vitriolic acid.                                           g03
    Luna cornea weighs one-fourth more than the  filver Its proper*
 employed ;  yet, when perfectly waflied,  it is quite in- ties.
 fipid to the tafte.  It does not  diffolve in water, fpi-
 rit of wine, aqua-fortis,  or aqua-regis; but  is in fome
 fmall  degree acted upon  by the  vitriolic  acid.  It
 melts  in the fire as foon as it  grows  red-hot;  and, on
 cooling,  forms  a  ponderous brownifh mafs, which be-
 ing caft into thin plates, becomes femitranfparent, and
 fomewhat flexible, like horn; whence irs name  luna
 cornea.   A ftronger fire does not expel  the  acid from
 the metal, the whole concrete either fubliming entire,
 or paffing through the crucible.  It  totally diflblves in
 volatile alkaline fpirits without  any Separation of the
 metal.  Expofed  to  the  fire  in  a  clofe  copper  veffel,
 it  penetrates the copper,  and  tinges  it  throughout of
 a filver colour.  Knnckel obferves, that when carefully
 prepared, melted  in a  glafs veffel,  and  fuffered  to
 cool flowly, to prevent  its cracking, it proves  clear
 and tranfparent; and may be turned into a lathe and
 formed into elegant  figures.   He  fuppofes this  to be
 the preparation which gave  rife to the notion of mal-
 leable glafs.                                            ofi(
    VII. With Copper.  In the marine acid, copper dif-  Copper
 Solves but flowly.  The folution, if made without heat,
 appears at firft brown ; but, on ftanding for fome time,
 depofits  a white  fediment, and becomes green.  On
 adding frefh copper, it becomes brown again, and now
 recovers its greennefs more  flowly than before.   The
 w line fediment, on being barely  inched, proves pure
 and perfect copper of the fame colour as at firft.   Cop-
 per calcined by fire communicates a  rcddilh colour  to
 this acid.
    VIII, With Iron.  The  marine acid acts upon iron
                                                 lefs
Zcs
Iron. 
Pra<ft ice.
CHEMISTkY.
*3
   806
Iron volati-
lized.
   807
Tinctura
martis.
   808
Floresmar-
kales.
  ad 808
Beftuchef's
tiu&ure.
  3d 80S
Miftakes
concerning
it.
 4th 808
True me-
thod ofpre-
paring it.
lefs vehemently than the nitrous, and does not diflblve
fo much » nevertheless, it attacks the metal brifkly, fo
as to raife confiderable heat and effervefcence, and dif-
folve it  into a yellow liquor.  During the folution, an
inflammable vapour arifes as in the folution of this me-
tal  by  vitriolic acid.   This folution of iron does not
cryftallize.   If it is  evaporated, it leaves a  greenilh
faline mafs,  which is foluble in fpirit of wine,  and runs
in the  air  into a aftringent  yellow  liquor.   On di-
ftillation,  fome of the acid Separates,  and towards the
end of the operation the fpirit becomes yellow.   This
is followed by  a yellowifh, or deep reddifh fublimate,
which gliftens  like  the fcales of fifties; leaving be-
hind a fubftance which confifts of thin,  glofly plates,
like talc.
  The folution of iron in fpirit of fait, with the addi-
tion of fome fpirit of -wine,  is ufed in  medicine as a
corroborant,  underthe name of tinflura martis.   The
fublimate of  iron is alfo ufed for  the fame  purpofe,
and called ens veneris, or flores marttales.  It is com-
monly directed to ^e prepared by  fubliming iron fi-
lings and fal ammoniac together.  In the procefs, the
fal  ammoniac is partly decompofed,  and a cauftic al-
kaline liquor diftils.   TheH the undecompofed fal am-
moniac,  and the martial fublimate  abovementioned,
arife together.   The  fublimate has a deeper or lighter
yellow colour, according as it contains more or lefs iron.
The name ens veneris is improper.  It was given by Mr
Boyle, whodifcovered this medicine.  He imagined it to
be a preparation of copper,  having made ule of a colco-
thar of  vitriol containing both iron and copper.  A me-
dicine of this kind was lately fold with great reputation
on the Continent, under the name of Beftuchef's nervous
tiaiture. \t was introduced by M. Beftuchef Field Mar-
shal in the Ruffian Service : but not long after it came
into vogue in  Pruffia and other northern kingdoms of
Europe  ; it made its appearance alfo in France,  under
the name of General de la Motte'sgolden drops.   This
happened through the infidelity of Beftuchef's opera-
tor, who, for  a fum of money, violated the oath  of
fecrecy  he had taken to Beftuchef, and difcovered the
fecret to de la Motte.  To the latter  it proved a  very
valuable acquifition ; for he  not only procured a pa-
tent for it from the king of France in 1 730,  with the
exclufive  privilege of felling it, but had a handfome
penfion  fettled  upon him ; felling his medicine befides
a half a Louis d'or per phial.
  The attention of the public was particularly drawn
to thefe drops, by fheir remarkable property  of lofing
their yellow colour  in the fun,  and regaining it  in
the ihade, which induced many to believe that  they
contained gold ; and in which opinion they were en-
couraged by de la  Motte.  Even chemifts of no little
reputation were deceived by this appearance ; and M.
Beaume, imagining he had difcovered the fecret,  pub-
lifhed a preparation to the world as the true arcanum
of la  Motte's  drops.   It confifted of a calx of gold
precipitated  from aqua-regia by means of  fixed al-
kali, and rediffolved in nitrous acid,  to which was ad-
ded a large quantity of fpirit of wine.   Others, how-
ever,  who could find nothing but  iron by an analyfis
ofthe drops,  refufed  their affent; and  at length,  in
1780, M. Beaume's miftake was made evident by the
publication ofthe procefs at the defire ofthe  emprefs
of Ruffia, who  gave 3000 rubles for the receipt,   The
original recipe  is perplexed,  tedious,, and expenfwe ;
bat when deprived of its fuperffuous parts, is  nearly Marine
as follows.  Six pounds of common pyrites ar.d  twelve acid and
of corrofive fublimate are  to  be triturated together,its coml>i-
and then fublimed fix or eight times till  all the mer- natlon-  ,
cury is expelled.  The refiduum  is to be  boiled three
times with thrice its quantity of water, and as often
filtered,  and laftly,  diftilled to drynefs.  By  increa-
fing the  fire,  a martial fait is  at laft fublimed into the
neck ofthe retort;  to three drachms of which are to
be added 12 ounces of highly  rectified  fpirit of wine,
and the whole  expofed to the rays of the lun.  This is
the yellow tincture ; but there was  alfo a white one,
which,  however, feems to be  but of little value.  It is
made by  pouring  on the  refiduum of the laft Sublima-
tion twelve pounds of highly rectified  fpirit of wine,
and drawing it off by a gentle diftillation after a few  .tj, g0g
days digeftion.—Mr Klaproth  imagines, from the fol- Suppofedte
lowing  experiment, that Beftnchcf's tincture  abforbs abforb
phlogifton from  the rays of  the fun.   He poured a phlogiftoa
few drops of a folution  of tartar into  two ounces of from the
diftilled water, and divided  this into two parts.  lntofun sray5*
one glafs having  poured a few drops of the tincture
that had not been expofed  to the fun,  the iron wras
precipitated in the ufual  foim  of a yellow ochre ;  but
on treating in the fame manner a portion of the tinc-
ture that had  been  expofed to  the Solar  rays, the pre-
cipitate fell of a bluifli green colour.                     809
  IX. With Tin.  Though the concentrated marine acid Solution •£
has a greater attraction for tin  than any  other acid, ittin<
does not readily diflblve this metal while the acid is in its
liquid ftate;   but may be made to diffolve it perfectly
by the addition of a Small quantity of  fpirit of nitre.
Neumann obferves, that an ounce of fpirit of fait, with
only a fcruple  of fpirit of nitre, diffolved tin perfectly:
but on inverting the proportions,  and taking a fcruple
of marine acid to an ounce  of the nitrous, four fcru-
ples,  or four and an halS, of tin,  were diflblved into a-
thick pap; fome more of the marine acid being gra-
dually added,  the whole was diffolved into a clear li-
quor.  In making theSe Solutions, a  Small quantity of
black matter ufually fubfides.
  The folution of tin is  fometimes colourlefs ;  fome-
times of  a bluifli, or yellow colour,  according  to dif-
ferent circumftances of the  procefs.   It is  of  the
greateft confequence i-n dyeing, by not only heighten-
ing the colours,  but making them more durable (See
Dyeing).  It flioots into fmall cryftals ; and,  if  in-
fpi(fated,  deliquates in the air.                         gia
  Marine acid in its concentrated ftate volatilizes tin, Smoking.
and forms with it a thick liquor, which,  from  its in- liquor of
ventor,  is called fwoking liquor of Libavius.  To pre- Libavis*..
pare this  Smoking liquor, an  amalgam  muft be made
of four parts of tin  and  five of mercury.  This amal-
gam is to  be  mixed with  an  equal  weight of  corro-
five  mercury, by  triturating  the whole  together in
a glafs mortar.  The mixture is then to be put into a
glafs retort, and the diftillation performed with a  fire
gradually increafed.  A  very  Smoking liquor  pafles
into the  receiver; and towards the end of the diftil-
lation, a  thick, and  even concrete matter.   When
the operation  is 'finifhed, the  liquor is to be  poured
quickly into a  cry ftal glafs-bottle, with aglaSs Stopper.
When this bottle is  opened, a white, copious,  thick,.
the poignant fume iflues, which remains long is the
air without difappearing.
  The acid in this  liquor is far from being faturated^
                        P                       aadi 
»>4
C   H   E    M    I   S   T    R   Y.
Practice
l.C-iJ.
        and is cip.ible of  ftiii diffolving much tin in the ordi-
        nary way.   K;-.>:.i  this impirfVu faturation, together
        v.uh its concentration, proceeds  partly its property of
        finoking  fo  considerably: ntvc: ;hcleh>,  fome  other
        caufe probably concurs to ^ivc it this property ; for
        th<>.igh it fnokes  infinitely more than the  moft con-
        centrated fpirit  of I'll:, its vapours are, notwithftand-
        ing, much  lefs  elaftic.  It has all the other properties
        of concentr.tied marine acid when imperfectly faturated
        with tin.   If it is diluted with  much water, molt of
        the metal Separates in light white flocks.   In dyeing,
        it produces the Same effects as Solution of tin made in
         the common way.  If the diftillation is continued af-
         ter the Smoking liquor of Libavius has come over, the
         mercury oS the  corrofive fublimate w ill then arife in its
         proper form.
           X. With Lead.   Marine acid, whether in  its concen-
         trated or diluted ftate, has little effect upon lead,  unlefs
         a'.lifted by heat.   IS Spirit oS Salt is poured on filings of
         lead,  and the  heat is increaSed So as  to make  the li-
         quor boil and diftil, a part ol the acid will be retained
         by  the metal,  which will be  corroded into a Saline
         maSs;  and  this, by a repetition of the procefs, maybe
         diffolved into a limpid liquor.   If lead is diffolved in
         aq i.ttortis,  and Spirit of Sea-Salt,  or Sea-Salt itfelS, ad-
         ded, a precipitation  oS the metal enSues ; but  iSSome
         uqua-regia  is added,  the  precipitate is redilfolved.
            The combination of lead  with marine  acid,  has,
         when melted, fomc degree oS transparency and flexi-
         bility like horn ;  whence, and from its refcmblance to
         luna cornea, it  is called plumbum comeum.   This fub-
         ftance is ufed in preparing  phoSphorus, according to
         Mr Margraaf s method.
            XI. With Qjickftlver.  Marine acid in  its  limpid
         State,  whether concentrated or  diluted, has no effect
         upon quickfilver,  even when affifted by a boiling heat;
         but if mercury is diffolved in the vitriolic or nitrous
         acids,  and  fea-falt, or its fpirit, is added to the folu-
         tion, it immediately precipitates the quickfilver in the
         fame manner as  it does filver or lead.  IS concentra-
         ted marine acid, in the form of vapour, and ftrongly
         heated, meets with mercury in  the Same ftate,  a very
         intimate union  takes place ;  and the produce  is a moft
         violent corrofive and poifonous fait, called  carry ve
        fublimate mercury.   This fait is  foluble, though  ipa-
         iin^lv, in  water ; but is far from being perfectly Satu-
         rated with  mercury ;  for it will  readily unite with al-
         m vt  its own weight of frefh quickfilver, and fublime
         with it into a folid white mafs (which, when leviga-
         red, aifumes a vellowilh colour) called mercurius dulcis,
   815   aquiia cue a, or calomel.
D.r rent     There have  been many different ways of preparing
methods of corrofive mercury, recommended by different chemifts.
making.   »<cuinaun. mentions no fewer than ten.  1.  Frommer-
         c/.rv,  common fait, nitre, and vitriol.  2.  From mer-
         cury, common  f.dt. and vitriol.   ?.  Mercury, common
         !.:!:, and Spirit of-nitre.  4.  Solution of mercury  in
         a  aafortis,  and fait.   5. Solution of mercury in  a-
         ouafo;ti-s -nd  fpirit  of Salt, or  the white precipitate.
         6.  Mercury, conmon fait,  nitre, and oil of vitriol.
         7.  Eekilcorated turbith mineral,  and common fait.   8.
         Red precipitate, common fait, aud oil of" vitriol.  9. E-
         d-ilcorated pirbith mi tend, and Spirit of fait. 10. Mer-
         cury,  fal ammoniac,  and oil of vitriol.
            From a view of t-efe  - ycrent methods, it  is  evi-
         dent, that  the inteiuio:; of them all  is to combine the
   812
Plumbum
corncuin.
   81.I
QuickC!
Vcr.
   814
Corrofive
fublimate
nuruieacid with quickiftvcr ;  and as this combination Marine
can be effefted witnout making ufe of the nitrous acid, acid and
the great tit  chemifts have imagined that this acid,lUcom ,l"
  1 •  1 ■ ,   ,-   1     n           1-11       -ii  ration*.
which is b) tar the molt expentn cot the three, might be -,.  y
thrown out of the procefs altogether, and the Sublimate
be more conveniently made by directly combining ma-
rine acid and mercury in a  procefs Similar to the  di-
ftillation  of fpirit of fait.  This method was formerly
recommended by Kunckcl;  then  publilhcd in the me-
moirs of  the  Academy of Sciences for 17^0 ; and has
been adopted  and recommended byDr  Lewis.
  The procefs confifts in diflblving mercury in the vi-
triolic acid,  as directed for making  turbith mineral.
The white mafs remaining  on the  exficcation of this
folution is to be  triturated  with an  equal  weight of
dried fait, and the mixture is then to be fublimed in
afand-heat;  gradually increafing the  fire till nothing
more  arifes.                                           g,g
  Neumann  obferves, that there  is a confiderable dif- Differences
ference in the  quality of fublimates made  by the dif-of quality.
ferent methods he  mentions; particularly  in  thofe
made  with  or without nitre.  This  we  have  alfo
found to  be the cafe  ; and that fublimate made with-
out the nitrous acid is never fo corrofive, or foluble in
water, as that which is made  with it: nor will it af-
terwards take up fo large a quantity of crude mercury
as it otherwife  would,  when  it  is to  be formed into
calomel.   The above procefs, therefore, tho' very con-
venient and  eafy, is to be  rejected;  and  fome other
in which the nitrous acid  is ufed, Subftituted  in  its
Stead.  The reaSon  of theSe differences is, that the Spi-
rit of'  Salt, muft  by Some means or other be dephlogi-
fticated before it can unite  in fufficient quantity with
the metal, into the compound defined,  w hich is accom-
pliihed by the addition oS nitrous  acid.
  From  Tacheni is,   Neumann gives us the following
procefs,  which he Says was  the method  of making
fublimate at London,  Venice,  and Amfterdam.   Two
hundred and  eighty pounds oS quickfilver, 400 pounds
of calcined  vitriol,  200 pounds  of nitre,  the  fame
quantity  of common fait, and  50 pounds of the caput
mortuum  remaining  after  a  former  Sublimation,  or
(in want oSit) of the  caput  mortuum  of aquafortis,
making,  in all, 1130 pounds, are well ground, and
mixed together;  then fet to fublime in proper glaffes
placed in warm aflies, the fire is  increafed by degrees,
and continued for five days and nights.   In the making
fuch large quantities, he fays, fome  precautions  are
neceffary, and which thofe conftantly employed here-
in  are beft  acquainted  with.   The principal are,
the due  mixture of the ingredients,  which in fome
places is  performed  in the fame manner as that of
the  ingredients for  gun-powder: that a  head and
receiver be  adapted  to the fubliming  glafs, to fave
fome fpirit of  nitre  which will  come  over.  (Here
a bent tube of glafs will  anfwer the purpoSe,  as  al-
ready mentioned).   The  fire muft not be  raiSed too
haftily.  When  the  Sublimate begins  to  form,  the
aflies  muft be  removed a little  from the fides,oS the
glaSs,  or the glafs cautioufty  raiSed  up a lfttle from
the aflies.  (Thislaft, wethiuk, is highlyimprudent.)
Laftly, the laboratory muft  have  a good chimney, ca-
pable of carrying off the noxious  fumes.   The above-
mentioned quantities  commonly  yield 360 pounds  of
fublimate; the 2-0 pounds of quickfilver  :;ai:ftncr 80
from the  ;co pounds of fea-falt.  The makers of fub
                                             liinate 
Practice.
CHEMISTRY.
   si?
Obfcrva-
tionson the
different
methods.
Suppofed
adultera-
tion with
arfenic.
   819
Mercurius
dulcis.
   800
Zinc vola-
tilized.
limate in France, he fays, employ,  in one operation,
only 20  pounds of mercury.   This they diflblve in
aquafortis, evaporate the folution to drynefs, mix the
dry  matter with 20  pounds of  decrepitated fea-falt
and 60 of calcined vitriol,  and then proceed to Subli-
mation.
  The above  proceffes, particularly the  laft, are un-
exceptionable  as  to the production of a fublimate  per-
fectly corrofive; but the operation, it is evident,  muft
be attended with confiderable difficulty,  by reaSon of
the large quantity of matter put into  the glafs at once.
Wc  muft remember, that always on  mixing "a volatile
Salt with a quantity of  fixed matter,  the Sublimation
of it becomes  more  difficult than it, would have  been
had  no  Such  matter been mixed  with it.   It  is of
confiderable confequence,  therefore,   in all Sublima-
tions, to make  the quantity of  matter put  into the
glaSs as  little  as poflible.   It would   Seem more  pro-
per, inftead of  the  calcined vitriol  uSed in  the  pro-
ceffes laft mentioned,  to  diflblve  the  mercury in
the  vitriolic  acid, as  directed  in  turbith  mineral,
and  fublime the dry maSs  mixed with nitre  and fea-
falt.
  It has been faid, that corrofive fublimate  mercury
was  frequently adulterated with  arSenic ;  and means
have even been pointed out Sor detecting this Suppo-
fed adulteration.   TheSe means are,  to diffolve a  little
of the SuSpecxed Salt in water,  and add an alkaline
lixivium to precipitate the mercury.   If the precipitate
was  of a black colour, it was Said to be a certain Sign
of arfenic.  This, however, fliows nothing at all, but
that either the alkali contains Some  inflammable  mat-
ter,  which, joining with the precipitate, makes it ap-
pear black ; or that the Sublimate is  not perfectly cor-
rofive ;  for  if a volatile alkali is poured on levigated
mercurius dulcis, the place it touches is inftantly turned
black.
  Mercurius dulcis, or calomel, is prepared by mixing
equal parts, or at leaft three of quickfilver with  four
of fublimate ;  after being thoroughly ground together
in a glafs or ftone mortar, they are to  be  poured
through a long funnel into a bolt-head, and then fub-
limed.  The  medicine has been thought to be im-
proved by repeated fublimations, but this is found to
be a miftake.   Mr  Beaume has found  that mercu-
rius dulcis cannot be united with corrofive fublimate
in the way of fublimation; the former,  by reafon  of
its fuperior volatility,  always rifes to the top of the
veffel.
  XII.  With Zinc.  This femimetal diflblves readily
in the marine  acid into a tranfparent colourlefs liquor.
It is volatilized, as well as moft other metallic Subftan-
ces by this combination, as appears  from the follow-
ing proceSs delivered by Neumann.
  il Equal parts of filings of zinc and powdered fal
ammoniac being mixed together, and urged with  a
gradual fire in a retort; at firft aroSe, in a very gentle
heat, an exceffively penetrating volatile Spirit, So ftrong
as to ftrike a man down who fhould  inadvertently re-
ceive its vapour freely into  the nofe.   This came  over
in fubtile vapours, and was followed by a fpirit of fait
in denfe white fumes.  In an open fire, white flowers
fucceeded; and at length a reddilh and a black butter.
In the bottom  of the retort was found a portion of the
                                                        "5
zinc in its metallic form, with a little ponderous and Marine
fixed butyraceous  matter which liquefied in the air. acid and
The lump was far more brittle than zinc ordinarily is;lts ^omt)1"
of a  reddifh colour on theoutiide, and blackifli within.         >
The bottom of the retort was variegated with yellow
and red colours, and looked extremely beautiful.  The
remaining zinc was mixed aSreili with equal its weight
oS fal ammoniac, and  the proceSs repeated.  A vola-
tile alkaline Spirit  and marine acid were obtained  as
at firft ; and in the retort was found only a little  black
matter. When the zinc was taken at firft in twice the
quantity of  the fal ammoniac, the part that preServed
its metallic form proved leSs brittle than in the forego-
ing experiment, and the retort appeared variegated  in
the  fame  manner.  On endeavouring  to rectify the
buttter, the retort parted in two by the time that one
half had diftilled." The nature of this combination is
unknown.                                             g2I
  XIII. With Regulus of Antimony. This femimetal can- Butter of
not be united with the marine acid  unlefs the latter is antimony.
in its moft concentrated ftate.   The produce  is an
exceffively cauftic thick liquid, called butter of antimo-
ny.  The procefs for obtainining this butter is fimilar
to that for diftilling the fmoking  fpirit  of  Liba-
vius.  Either  crude antimony,  or its  regulus, may
be ufed: for the fpirit of fait will attack the reguline
part of this  mineral without touching  the fulphureous.
Three parts of corrofive fublimate are to be mixed
with one of crude antimony  ; the  mixture  to be di-
gefted in a  retort fet in a fand-heat;  the marine acid
in the fublimate will unite with  the  reguline part  of
the antimony.   Upon  increafing  the fire, the regulus
arifes, diffolved in  the concentrated  acid,  not into a li-
quid form, but that of a thick unctuous fubftance like
butter, from  whence it takes its  name.   This fub-
ftance liquefies by  heat,  and  requires the cautious ap-
plication of a  live  coal to melt it down from the neck
of the retort.  By rectification, or  expofure to the
air,  it becomes fluid like oil but ftill retains the  name
of butter.   If water is added to  butter of antimony,
either when in a  butyraceous form, or when become
fluid by rectification,  the antimony  is  precipitated in a
white powder  called powder of algaroth, and improperly
mercurius vita.  This powder is a violent and very un-
fafe  emetic.   The butter itfelf was formerly ufed as a
cauftic; but it was totally neglected in  the  prefent
practice, until lately that it has been  recommended as
the moft proper material for  preparing emetic tartar.
(See below.)   Mr Dollfufs recommends the following
method as  the beft  for making butter  of antimony ;
viz.  two ounces and a quarter of the grey calx of an-
timony, eight ounces of  common fait, and fix of acid
of vitriol.   By diftilling this mixture,  ten  ounces  of
the  antimonial cauftic were obtained; and in order to  .
determine the quantity of metal contained in if,  he
mixed two  ounces of the. cauftic with four ounces  of
water j hut  thus fuch a ftrong coagulum was formed,
that he was not able to pour off any of the water even
after ftanding 24 hours.   The precipitate, when care-
fully dried,  weighed 50 grains.  , The reSult was much
the  Same when glaSs of  antimony was uSed, only that
the precipitate was much more  confiderable , half  an
ounce  of the cauftic then yielding 60 grains, though ac
another time only 50 grains were obtained.  In the re •
                      P 2                   fiduum 
n6
CHEMISTRY.
Practice.
 Mamie    "* lu im of the fbmer experiment he Sound  30 grains of
 •cid and   a.JCirlhv fubftance, chicrly a combination, of olcarc-
 itt com..- ou, rirlh wi[h ,nuriatic   jj

 ----^™—>   \> lien the mercurius vitje precipitates, the union be-
          tween the marine acid and regulus is totally difl'ol.ed ;
          fo thit the powder, by frequent Wafhings, becomes per-
          fectly free from every particle of 1 id, which unites
          with the water made ufe of,  and is then called very
    8it   improperly, phthfophh  I'pirit of vitriol.
 Sympuhc-   \1Y\ With Regulm of Cobalt.  Pure fpirit of fait dif-
 nc ink.   folves this femimetal into a reddifh yellow liquor, which
          immediately becomes green from a very gentle warmth.
          On Saturating  the  folution  with urinous  fpirits,  the
          precipitate appears at firft white, but aftenvards  be-
          comes blue, aud at length yellow.  If the nitrous arid
          is added to folutions of  regulus of cobalt,  they affume
          9 deep emerald green when moderately heated, and on
          cooling become red as at firft.  Duly evaporated, they
          yield rofe-coloured cryftals,  which change their colour
          by heat  in the fame manner.  This  folution makes a
          curious  fympathetic ink, the  invention of which is
          commonly afcribed to  M.  Hellot, though he himfelf
          acknowledges that he received the firft hint of it from
          a German chemift  in  1736.   Any thing wrote with
          this folution is invifible when dry and cold ; but af-
          fumes a  fine green colour when warm, and  will again
          difappear on being  cooled ;  but if the  heat has been
          too violent, the writing ftill appears.   M.  Hellot ob-
          ferves,  that if nitre or borax be added  to the nitrous
          folution,  the  characters wrote  with it become rofe-
          colourcd when heated ,  and if fea-falt  is afterwards
          paffed over  them, they become blue; that with alkali
          fufficient to faturate the acid,  they change purple  and
          red with heat.—A blue fympathetic ink may be made
          from cobalt  in the following manner.   Take of an
          earthy ore of cobalt, as free from iron as poflible*  one
          ounce.  Bruife it, but not to too fine a powder.  Then
          put it into a cylindrical glafs,  with 16 ounces of diftil-
          led vinegar,  and  fet the mixture in hot fand for  the
          fpace of fix days,  ftirring it frequently ; or  elfc boil it
          directly  till there remain but four ounces.   Filter  and
          evaporate it to one  half.  If your folntion be of a rofe
          colour, you may  be certain that your cobalt is of the
          right fort.  A red brown colour  is a fign of the folu-
         ' tion containing iron; in which cafe the proceSs Sails.
          To two  ounces of the folution thus reduced, add  two
          drachms of common falt.-^Set the whole in a warm
    823   place to  diffolve,  and the ink is made.
 Oilofarfe-   XV.  With  Regulus of Arfenic.  This  fubftance is
 fclk:       foluble in all acids  ; but the nature of the compounds
          formed by fuch an union is little known.  If half a
          pound of regulus  is diftilled with one pound of corro-
          five fublimate, a thin fmoking liquor and  a butyrace-
          ous fubftance wnll be obtained,  as in making the fmo*
          king liquor of Libavius.  By repeated rectifications,
          this butter may be almoft all converted into  fpirit.   If
          equal parts of the arfenic and fublimate are ufed, a pon-
          derous black oil comes over along with the fpirit, which
          cannot be mixed  with it.  By rectification in a clean
          retort they will become clealr,  but ftill will  not incor-
          porate.   If they  are now returned upon the red mafs
          remaining in  the firft  retort, and again diftilled,  a
          much more ponderous oil than the former will  be  ob-
    8i4   tained.
 Maria.      X\'l.  W:th  Infiammabl:Subfta>:.;s.  The acid of fca-
itbfr.
fait is very little difpofed to «ontrjct  any union with Marine
the phlo^iiion,  while in a liquid ftate; and much \cf> ac,d anJ.
fo,  even in fts moft concentrated ftate, than cither the ,ts combl"
vitriolic or nitrous.  Mr Beaume, however, has found, "       .
that a fmall quantity of ether, fimilar to that prepared
with  the vitriolic and nitrous acids, may be obtained
by caufing the  fumes  pS the marine  acid  unite with
thofe of fpirit of wine.  Others, and particularly fome
German Chemifts, attempted to make this liquor, by
employing a marine acid previoufly combined with me-
tallic  fubftances, fuch- as butter of antimony.   The
fmoking liquor ot Libavius fucceeds beft.  If  equal
parts  of this liquor and  highly rectified fpirit of
wine are diftilled together, a confiderable quantity of
true ether is produced ;  but which,  like the vitrio-
lic and nitrous ether, muft be  rectified in order to its
greater purity.   The tin contained in the fmoking li-
quor is Separated and precipitated in white powder.  In
this procefs, the acid is probably more difpofed to
unite  with the  fpirit of wine,  by  having already be-
gun to combine w ith the inflammable  principle  of the
metal.—For marine ether, Mr Dollfufs recommends to
put into a retort four ounces of digeftive fait previouf-
ly well dried and powdered, and two ounces of  man-
ganefe ;  pouring upon this a mixture of five ounces of
fpirit  of  wine and two of oil of vitriol; the firft five
ounces and a half of the diftilled liquor being poured
back on the refiduum, and the whole afterwards drawn
off by a gentle heat.   The fpirit of fait thus obtained
had a very penetrating agreeable odour, fomewhat like
that of nitrous ether ; and at firft Swam upon the top
of water; but at length mixed with it on being agi-
tated for a long  time.  Towards the end of the diftil-
lation a little oil was obtained, which did not  mix
with  the water ; and  by the addition of four ounces
more  of fpirit of wine, more of the dulcified acid was
obtained.  With regard to this kind of ether, however,
Mr Weftrumb denies that it can be made by any me-
thod hitherto known ; and infills,  that all  the liquids
as yet produced under the name of marine ether are
in reality dulcified fpirit of fait, and  not true  ether,
which will Swim on the top of water.                   ga-
  Dr Prieftley has obferved, that the pure marine acid, Attraction
when reduced to an invifible aerial ftate, has a ftrong for phlogif«
affinity with  phlogifton; fo that it decompofes many ton«
fubftances that contain it, and forms with them  an air
permanently inflammable.  By giving it more time, it
will extract phlogifton from dry wood, crufts of bread
not burnt,  dry flefh; and, what is ftill more extraordi-
nary, from flints.  From what has been above related,
it appears that the dephlogifticated fpirit of fait has a
very ftrong attraction for phlogifton.
   Effential oil  of mint abforbed the  marine  acid  air
pretty faft, and prefently became of a deep brown co-
lour.  When taken out of this  air, it was of the con-
fiftence of treacle, and funk in water, fmelling different-
ly from what it  did before ; but ftill the fmell of the
mint was predominant.   Oil of turpentine was  alfo
much  thickened ; and became of a  deep brown colour^
by being faturated with acid air.   Ether abforbed the
air very faft ; and became firft of a turbid white, and
then of a  yellow and brown colour.  In one night a
confiderable quantity of ftrongly* inflammable air was
produced.
  Having once  faturattd a quantity of ether with acid
                                               •irj 
Practice.
CHEMISTRY.
17
 air, he admitted bubbles of common air to it, through
 the quickfilver  by which it  was confined,  and ob-
 ferved that white fumes were made in it, at the  en-
 trance of every  bubble, for a confiderable time.  Ha-
 ving at  another time,  faturated a fmall quantity of
 ether with this kindof air, and the phial which contain-
 ed it happenning to be overturned,  the whole room
 was inftantly filled with  a white cloud,  which had
 very much the fmell of ether, but peculiarly offenfive.
 Opening the door and window oS the  room,  this light
 cloud filled a long paflage and another room.   The
 ether, in  the mean time,  was  Seemingly all  vanifh-
 ed : but, Sometime after, the furface of the quickfil-
 ver in which the experiment had been made was  co-
 vered with a very acid  liquor,  arifing probably from
 the moifture in the atmofphere, attracted from the acid
 vapour with which the ether had been impregnated.
 This feems to  fhow,  that however  much difpofed
 the marine acid may be to unite with phlogiftic mat-
 ters when in its aerial ftate,  the attraction it has  for
 them is but very flight, and ftill Inferior to what it has
 for water.
   Camphor was prefently reduced into a fluid ftate by
 imbibing this acid air;  but there Seemed to  be fome-
 thing of a whitifh  fedimem  in  it.   After continuing
 two days in this fituation, water  was admitted  to it,
 upon which  the camphor immediately refiimed its for-
 mer folid ftate ;  and to appearance was the  fame Sub-
 ftance that it had been before.
   Strong concentrated oil of  vitriol, being put to ma-
 rine acid air, was not at all affected by it in a day and
 a night.   In order to try  whether it would not have
 more power in  a condenfed  ftate, it  was compreffed
 with an additional atmofphere ;  but, on taking off rhis,
 the air expanded again, and  was not in the leaft di-
 miniflied.  A quantity of ftrong fpirit of nitre was alfo
 put to it without any fenfible effect.   From  theSe laft
 experiments it appears, that the marine aeid is not able
 to difloge the other acids from their  union with water.
   Befides the acids already mentioned,  Mr  Homberg
 defcribes an  artificial  one generated by mixing two
 ounces and a half oS luna cornea, with  an ounce and
 a half of tin calcined alone and  without addition, by
 means of fire.   The mixture  is to be  expofed to a
 naked fire in a coated retort, of which two-thirds ought
 to  be left empty ; when a brownifh matter,  an ounce
 and a half in weight, will adhere to the neck  of the
 retort.    This matter is tin combined with the  marine
 acid, and the refiduum is filver deprived of the fame
 acid, which  may therefore now be melted together
 without any lofs.  The fublimate, well  powdered and
 dried, is to  be  equally divided  into  two phials, and
 fublimed; by repeating which operation two or three
 times, a volatile  fait, of an acid nature, very white and
tranfparent, is obtained.  The refiduum of thefe fubli-
mations  is alwavs calx of tin.
                       § 4. Ofthe Fluor Acid.
   8*6
Firft difeo-   T h i s acid was difcovered fome time ago by Mr Mar*.
veredby  graaf, and more fully  inveftigated  by  Mr Scheele.
         The experiments by which it was originally produced-,
         and its properties afcertained,  are as follows:
            I. Two ounces of concentrated vitriolic  acid were
         poured upon an equal quantity of fluor, which had been
  ad 825
!Hew acid
difcovered
by Mr
Homberg.
Mr Mar-
graaf.
   827
How pre-
pared.
8*8
earth.
 previoufly pounded in a glafs mortar,  and then put in- Fluor acit
 to a retort,  to which a receiver was adapted, and  the and '*
 juncture clofed with  grey blotting paper.   On  the
 application of heat, the mafs began to effervefce and
 fwell, invifible vapours penetrated every where through
 the joining  of the veffels, and towards the  end of the
 procefs white vapours arofe, which covered all the in-
 ternal parts of?the  receiver with a white  powder.—
 The mafs remaining in  the  retort  was as  hard as a
 ftone,  and  could not be taken out  without break-
 ing  the veflel.    The  lute  wras quite corroded and
 friable.
   II. The procefs was  repeated exactly  in the fame
 manner, excepting only that a quantity of diftilled wa-
 ter was put into the receiver.   A white fpot foon be- Forms a
 gan to form on the furface 0/ the water, juft in the white ear-
 centre, and  immediately under the mouth  of the  re- th7,c
 tort.  This fpot continually increafed, till at laft it co-WIth water
 vered the whole furface of the water,  forming a pretty
 thick cruft, which prevented the communication ofthe
 water with new vapours that came over. On gently agi-
 tating the receiver, the cruft broke, and fell to the bot-
 tom ; foon after which a new  cruft like the former was
 produced.   At laft the receiver, and foon after the re-
 tort alfo,  became white in the infide.  The veffels,-
 when cooled, were found much corroded internally. In
 the receiver was an acid liquor mixed with much white
 matter, feparable by filtration.                         gif
   III. This white matter when edulcorated  and dried, Which ha»
 fhowed  itfelf to be liliceous  earth  by the  following the proper-
 properties.   1. It was rare, friable, and white.. 2. Ittics of u!i"
 was not fenfibly foluble in a^ids.  3. It did not make ceo .,*
 a tough pafte with water, but  was loofe  and incohe-
 rent after being dried.   4.  It diffolved by  boiling in
 lixivium tartari, and  the folution  in  cooling aflumed
 a gelatinous  confiftence.   5. In its pure ftate it fuffered
 no change in the ftrongeft  heat;  but  when mixed
 with alkali, it boiled, frothed up,  and formed a glafs
 in a melting heat.   6.  It diffolved  in borax  without
 fwelling.
   IV. To determine whether this earth wTas formed Scheele'*
 during the procefs, he poured vitriolic acid upon pow- experiment
 dered fluor contained in a cylinder of brafs w hich was to deter-
 clofed exactly with a cover, after  having fufpended m\ne. the(
 over the mixture an iron nail  and a  bit of charcoal. ^"Vtfc
 On opening the veffel two hours.afterwards, he found
 the nail and charcoal unchanged ;  but on moiftening
 them, he found both covered  with awhite powder in a
 fhort time.  This powder had all the properties of lili-
 ceous earth;  and as in the experiment he had made no
 ufe of glafs  veflels, he  concluded that it did  not pro-
 ceed from the glafs veffels as might have been fufpect-
 ed from their being fo  much corroded, but was gene-
 rated in fome other way.                               g-t
   V. Having recompofed fluor by faturating the a- Artificial
 cid with calcareous earth, he treated the  compound in fluor yield*
 the fame manner as the  natural fluor,  with a  fimilar a fimilar
 refult;  and repeating the experiment  five times over, rtfv.lt.
 he Conftantly found the  filiceous earth and acid dimi-
 nifh confiderably, fo that at  laft fcarce any mark of
 aridity was left.   Thence he concluded, that all the
 fluor acid united  itfelf by  degrees with the  vapours of
the water, and thus formed the filiceous earth. %t 11 may
be objected (fays Mr Scheele),  that the fluor acid is per-
haps already united by nature with a finefiliceous pow-
                                              der,
83* 
C   H   E    M    I   S   R    T   Y.
Pracucc.
    8j;
 Mr
S;h-'!e's
 conclufion
 that the
 earth pro-
 ceeds from
 an union of
 the acid
 with-.vatcr.
Conceited
by Meffrs
Boullaager
Monnet,
&c.
   *34 .
Their opi-
nions
fhown to be
erroneous
by Mr
Scheele.

Fluor acid
proved to
b- different
from that
#1  fea-falt,
der, which it vol.n;U/.c>, ~nd carries over indiftiilation,
but leaves i: a>> fi»oii as 1:  liuils water to unite with,
j  ill as muriatic aeid parts with the regulus  ot antimo-
ny, when butter of antimony is dropped  into water.
But if this was  the r..:r, the fluor acid  would leave
the whole ipuntity of filiceous earth thus  combined
with  i: in the firft diftillation,  and thcruorr fhow no
mark  '1 its prcScncc in the following procelie^.  \\ hen
1 put  fpirit  of wine  into the receiver inftead of water
no filiceous  earth was produced ; but  the alcohol be-
came four.   When  1 put an umnious oil into the re-
ceiver, ail the fluor acid penetrated through the crevi-
ces of the lute, and neither united with the oil, nor
produced a liiice >.:->  earth.  This happened alSo when
acid of vitriol was put into the receiver.  If therefore
the filiceous earth was n n. a product of each diftillation,
but, being previoufly contained in theacid, was only de-
pofited  Srom it in conSequer.ee oS the union of the acid
with  a third Subftai.ee, I think thefiliceous earthought
equally to appear when alcohol was put into the recei-
ver, with which it  unites,  as well as with water; but
as this  does not happen, I  conclude that not  all the fi-
liceous  earth, which is depofited  upon the Surface of
water during the diftillation ofthe fluor acid, was pre-
vioufly diffoved in this acid."
  This opinion of Mr  Scheele did  not meet with ge-
neral  approbation.   M.  Boullangcr  endeavoured to
fhow,  that  the fluor acid is no other than the muria-
tic intimately combined  with fome earthy fubftance;
aud Mr Monnet maintained that it is  the  fame with
that of vitriol volatilized by fome extraordinary con-
nection with  the  fluor;»which   opinion   was  alfo
maintained by Doctor  I'rieftky.  Mr Scheele contefted
thefe  opinions, but  found  much greater difficulty  in
Supporting his own opinions  than in overthrowing
thoSeofhis adverfaries.  Boullanger infilled  that fluor
acid precipitates the Solutions oS Silver  and quickfilver,
producing luna  cornea with  the  former,  and mer-
curius  dulcis with  the latter.   Mr  Scheele  owns
that  fluor  acid precipitates  both theSe metals,  but
the precipitate obtained is in very  Small   quantity,
and the little that is produced  ariSes only from a Small
quantity of Sea-Salt with which the fluor, as well as all
other calcareous Subftances, is generally mixed.  The
greateft part of theacid, therefore, will not precipitate
the Solutions of thefe metals, which it ought to do up-
on Mr  Boulanger's hypothefis.    Mr Scheele  then
proceeds to  fhow a method  of Separating this fmall
quantity of marine  acid from that of fluor. A folu-
tion of filver made  with nitrous acid is to be precipi-
tated  with alkali of  tartar,  and as  much acid of fluor
peured  upon the edulcorated powder as is Sufficient to
give an excefs of acid;  after which the  folution is to
be filtered.   This Solution of filver  in fluor acid is then
to be  dropped into that acid we defire to purify,  till no
more  precipitation enSues; aSter which the acid is  filter-
ed through  grey  paper, and diftilled to  dryneSs in a
glafs retort.   The aqueous part comes over firft, but is
foon followed by fluor acid, which covers the infide of
both the veffels, togetherwith the furface ofthe water
1,1 the receiver, with a thick filiceous cruft.   The acid
thus rectified, does not precipitate  folution oS filver in
the leaft,  or otherwife ftiow the Smalleft Sign of muri-
atic acid.
  That the ft..or acid is dine:en: from  that  of  vitriol
  Mr Scheele proved by the:following experiment.   Up- Fluor acid
  on one ounce of pure levigated fluor with  alkohol, he and '*»
  poured three ounces of concentrated oil of vitriol,  and ".nil,u,a"
  uiltilhd the mixture in a fand-bath, having prcvioufy .
  put 12 ounces of diftilled water into the receiver.   He    836
. then took other three emnccs of the fame acid  diluted And from
  with 24 >unces of water,  to which he  afterwards ad- that of vi-
  ded lixivium tartari  previoufly weighed,  till  he at-a
  tained the exact point  of faturation.  Alter the diftil-
  lation he v. eighed the remaining lixivium ; having kept
  t:p Such a degree oS heat  for eight hours  as was not
  Sudicient to raife the vitriolic acid.  On breaking  the
  retort, and  reducing the maSs to powder he boiled  it
  in a glafs veflel with 24 ounces of water for fome mi-
  nutes; after which he added  jult as  much lixivium
  tartari as he had found before  to be requifite for  the
  fatur; tion of three  ounces of the vitriolic  acid,  and
  continued the boiling for a few minutes longer.   On
  examining the folution, it was  found  to contain a vi-
  triolated tartar perfectly neutralized,  neither acid nor
  alkali prevailingin any degree ; which fhowed that no
  vitriolic  had palled into  the receiver.   The faline
  matter  being then extracted with hot  water, the re-
  maining earth was found to weigh 9^ drachms.   Two
  drachms of this diflblved in muriatic  acid,  excepting
  only a fmall  quantity  of matter which  feemed to be
  fluor undecompofed, and which  on being dried weigh-
  ed only nine grains.  Into  one  part oSthis Solution he
  poured Some acid oS Sugar, ancl into another vitriolic
  acid.   The  former produced faccharated lime, and the
 latter gypfum.   A  third part was  evaporated to  dry-
  nefs, and left a dcliqucfcent fait;  and  the  remaining
 part of the earth burned in a crucible, produced a real
 quicklime.                                            g
   Thus it appeared that the real bafis of fluor is  quick- Quicklime
 lime,  and likewife that the fluor acid is different from the bafis of
  that of vitriol, as appears  farther from the following fluor.
 coniiderations : 1.  Pure fluor acid does not precipitate
 terra ponderofa, nor folution of lead in nitrous acid.
 2. The fame acid,  when faturated with  alkali of tar-
 tar, evaporated to drynefs, and afterwards melted with
 powdered charcoal,  does not produce  any  hepar ful-
 phuris.                                                g3g
   Mr Monnet,  in order to fupport his hypothefis,  de- Miftake of
 mies that fluor contains any  calcareous earth.  In proof Mr Mon-
 of which he adduces the  following experiment: E- ne.t on this
 qual quantities of alkali and fluor  were  melted toge- Subject.
 ther, with little or no change on the mineral; for, af-
 ter having taken away by lixiviation   the  alkali  em-
 ployed, he diffolved  the fluor remaining on the filter
 in nitrous acid,  adding vitriolic acid to the folution ;
 and becaufe he obtained no precipitate, concluded at
 once,  that fluor contains  no calcareous earth.    Mr
 Scheele on  the contrary affirms, that all folutions of
 fluor yield a precipitate of gypfum whenever vitriolic
 acid is added to them.  He explains  Mr Monnet's
 failure,  by Suppofing that  he had  diluted his Solution
 with too great a quantity of water.                      j>
   Mr  Wiegleb,  diffatisfied  with  the  hypothefis  ofwieglcVs
 Scheele,  as  well as others, concerning the fluor acid, experi-
 began a new Set of experiments on the mineral.  Ha- rnents on
 ving firft accurately  repeated  thofe   made by  Mr the °"g«
 Scheele,  he proceeded to inquire into the origin 0foftnefib-
 the filiceous earth, in the following manner: HavingCC0U8canfe
 firft weighed the retort deftined for the experiment in
                                                 an 
Pra6li.ee.
C   H    E   M   I    S   T    R   Y.
Fluor acid an accurate manner, and  found that its weight was
and its   two ounces and five drachms, he put into it two oun-
         ces of calcined fluor  in powder, adding, by means of
         a glafs tube,  27 ounces of  oil of vitriol.  The retort
         was then placed on the  furnace ; and a receiver, which
         when empty weighed two  ounces,  two drachms, and
         30 grains,  and now contained two ounces of  diftilled
         water, was luted to it. The diftillation was conduct-
         ed with all poflible care, and at laft puflied till the re-
         tort grew red hot ; but it was found impoffible to pre-
         vent a few vapours from penetrating through the lute.
         Next day the retort, Separated from the receiver, was
         found to weigh, together with its  contents, five oun-
         ces, five drachms, and 30 grains ; and confequently had
         loftin weightone ounce, three drachms, and 30 grains,
         The receiver, which,  with the water, had originally
         Weighed four ounces,  two drachms,  and  30 grains,
         now weighed five ounces and three drachms,  and had
         therefore gained one ounce  and 30 grains.  This gain,
         compared with  the lofs of  the retort,  fhows that  the
         retort loft more by three drachms  than the  receiver
         gained ; fo that thefe  muft have  undoubtedly paffed
         through the luting in form of vapour.
           To determine the point  in queftion, the empty vef-
         fels, with what had been put into them, were accurate-
         ly weighed ; when the weights and lofs upon the whole
         were found to be as  follows.
.  dr. gr.
250
200
240
7  1    o
5  5   do

I___3   So
2  2   30
 200

4  2   50
 5  3    o
The empty retort
Calcined fluor
Oil of vitriol

    Total weight before diftillation
                 After it

    Lofs of  retort

   The  empty receiver weighed
   The  water put into it

    Total weight before diftillation
    Total weight after diftillation
          Gain of receiver       -         1  o   30
Deducting this grain of weight in the receiver from
the lofs of weight in the retort, we find,  that three
drachms were wanting on the whole, which muft un-
doubtedly, as already obferved, have  been  diffipated
in vapour.   The retort  being now broken,  and  the
dry earth both  in its neck and arch Separated as accu-
rately as poflible, it was found to weigh three drachms ;
the refiduum in the retort weighed three ounces, two
drachms, and 40 grains.  Now, as the mafs in the re-
tort  had  originally  weighed  four  ounces and four
drachms, it appeared, by deducting the refiduum, to
have fuffered,  on the whole, a loSs of one ounce, one
drachm, and 20 grains.   To determine thcloSs more
accurately, the following calculations were made :
                                       oz. dr. gr.
The white earth feparated from the neck
  and arch oS the retort          -          030
Gain of the receiver  .     -     -          1   o   30
Loft in vapour       -     -    -      -     030

                                Total     163
  Here Mr Wiegleb  was furprifed  to  find,  that  the
matterwhich came  from the retort amounted to  more
by five drachms ten grains than the maSs in the retort
had  loft oSits original weight ;  to illnftrate which it
was  neceflary to weigh the retort  and receiver  by
themSelves.  The pieces oSthe retort now weighed on-
ly one ounce Seven drachms and 50 grains ;  whereas,
before the  procefs,  the  weight of the retort  was two
ounces  five drachms.  It appeared, thereSore,  that  it
had  loft five drachms ten grains,  the  very   quantity
which had  been gained by the receiver. This laft had
loft  nothing oS its original weight.
  The fluid in the receiver was next diluted with four
ounces of diftilled  water, and the whole poured out
on a filter, in order to Separate  the  earthy matter
with which it was mixed, and frefh  water poured up-
on it to take out all the acid : after  which the earth
was  dried,  and found to  weigh 57 grains.  The  clear
liquor was  then diluted with more diftilled water, and
afterwards  precipitated with fpirit of fal ammoniac pre-
pared with fixed  alkali. A   brifk effervefcence  took
place before any precipitate  began to  fall, but ceafed
foon after the precipitation took place. The whole mix-
ture  become gelatinous ;  and the precipitate, when dry,
weighed two drachms.  The whole quantity of earth,
therefore,  obtained in  this procefs amounted to five
drachms 47 grains, which is forty-Seven grains more
than the retort had  loft in weight.   This exceSs is, by
our author, attributed to part of the acid ftill  adhering
to it, and to the  acceffion of fome moifture from the
air;  to determine which he heated each ofthe parcels
of earth red hot Separately,  and thus reduced  them to
Sour drachms 52  grains, which is lefs by 18 grains
than the loSs  of the retort,  and which, he  is of opi-
nion, muft  have efcaped in the three drachms of va-
pour.
  From this experiment Mr  Wiegleb concludes,  that
the  earth produced  in the diftillation of fluor proceeds
neither from the fpar nor from a combination of the
acid  with water,  but from the folution  of the  glafs  by
the  fparry  acid. To his opinion alfo  Dr  Crell ac-
cedes.  " In diftilling fluor (fays he) with oil of vi-
triol, I  have found  the  retort as well  as the receiver
very much  corroded.  I poured the acid obtained  by
the procefs into a phial furnifhed with a glafs ftopper,
and  obferved after  fome time confiderable depofition.
I then poured  the liquor into another  phial  like the
former;  and that it might neither on  the one hand
attack the  glafs, nor on the other compofe  filiceous
earth with the particles  of water,  according   to  Mr
Scheele's hypothefis, I added highly rectified fpirit of
wine. I faw, however, after fome time, another confi-
derable depofition.  This Seemed alfo to proceed from
the glafs that had been before diffolved, which the acid
let fall in confequence of the gradual combination with
the fpirit of wine ; otherwife we muft  fuppofe, what
to me appears incredible, that the acid decompofes the
fpirit, attracts the water, and forms the earth."
  This fingularacid has been ftill further examined by
Mr Meyer. He informs us, that, among Mr Scheele's
experiments, he  was  particularly ftruck by one  in
which no earthy  cruft was obtained, after putting fpi-
rit of wine into the  receiver.  IVfr Meyer repeated this
experiment, hoping, that when but little fpirit was put
into  the  receiver, he  might be able fo  procure a new
kind of ether. Anounce of finely powdered fluor, which
had been previoufly heated  red hot, was put into a
                                             glafs
   840
The earthy
cruft pro-
ceeds from.
the folution
of the glafs
diftilling
veffels.
Mr May-
er's exami-
nation of
the fluor
acid. 
I 10
CHEMISTRY.
Practice.
Cuiiihuia-
FlM.iracid  glafs retort, to whicli  was fitted  a receiver contain-
- ul '^    i i;*  three ounces of higldy rectified  French  brandy.
          The diftillation was continued for three hours  with
          a gentle  heat : when the acid, having made its way
          through the bottom, put and end to the procefs.   No
          eruft could  be pence a ed   on the   furface of  the  Spi-
          rit : but  in  the  place  where it  had  been in con-
          tut with  the receiver there was a thinringof tranfpa-
          rent jelly.  The fame mixture of oil of vitriol and fluor
          was therefore again put into a retort  of  very ftrong
          glafs,  and the fame fpirit  put into the  receiver.   The
          diftillation was conducted two hours with a gentle and
          afterwards  with a ftronger, heat.   When it was half
          over, the fpirit began to change into a thin jelly ;  and
          at the end of the procefs fome firmer pieces were  found
          at the  bottom.   Thefe  were  wafhed  with  fpirit of
          wine;  and  in order to obtain the fpirit together  with
          the  acid in a pure ftate, it was put into a large retort,
          and again Subjected to diftillation.   As the retort grew
          t.arm, the opal-coloured fpirit became clear and Swell-
          ed,  what remained becoming again gelatinous ; a good
          deal of earth remained behind, but did not adhere firmly
          to the retort, which was fmooth in the infide, though full
          of (hallow excoriations.   It was alfo evident, that the
          glafs was actually  corroded,  and that the earthy mat-
          ter is not a mere cruft adhering to  the infide.   The
          jelly being thoroughly edulcorated, as well as the earth
          that remained  in the retort after the rectification, and
          that which  was diflblved  in the water precipitated by
          fpirit  of  fal ammoniac, the  whole quantity amounted
          to two drachms. That which had Separated fpontane-
          oufly was femitranfparent.   " As  this earth (fays he)
          fhowed the properties of filiceous earth, and the glafs,
          which  was fo much corroded, confifts in great  meafure
          of it, the greateft part of it might come from the glafs,
          and the reft of it perhaps beaconftituent part of the fluor
          itfelf.   In order to afcertain this it was neceffary to ob-
procure th- tain the fluoracid quite free from filiceous earth. I there-
acid free   fQrc expofed the ley, w hich I had procured by the pre-
from fihee- cipitatlon 0f  the earth with fal ammoniac, to a gentle
 *w» ear:  ,  cV;,p0ratjola jn a flightly covered glafs veffel.   The pro-
          duct was one drachm 56 grains of an ammoniacal fait ;
          the  glafs did not appear to have been attacked.   Half
          i  drachm of this fait was fublimed in a  fmall retort,
          which, towards the end of the operation, was laid on
          the  bare fire.   No cruft appeared on the furface of the
          water in  the  receiver.   At  the bottom of the retort
          lay a little flocculent earth of a light grey colour, above
          which the internal furface  was covered with a white
          pellicle that reflected various  colours; and in the neck
          there w^s a fublimate*  The thin pellicle eafily fepa-
          rated  in  many places  from the   glafs,  which  was
          tnooth beneath, though not without  fome fmall fur-
          rows.   I  poured water both apon the  ammoniacal fait
          and cruft  ; in confequence of whkh it acquired a very
          fon tafte, and  coloured the tincture of turnfole  red.'
          The white cruft that was left behind undiffolved weigh-
          ed five grains,  and  melted into a green glafs without
          iddition.  This was nothing but the  glafs  that had
          been corroded by the fluor acid ; but as this acid can
          fee fet loofe only by ftrong heaf, it had done no  more
          ihan corrode the glafs, without paffing over along with
          it in the form of vapour,  and then  depofing  it  again
          on the water.   For, upon pouring two drachms of oil
          of , liriol  upon half a drachm of this ammoniacal fait
   t/\2
liow to
   843
Experi-
mentamade
a little moiftcned, and  placed in a glafs retort, a great Fluor aeid
foam arole, and the thick vapours that afcended cover- »ml u»
ed the water in the receiver w ith a white cruft. A ficru con,bina-
plc of the fait on  folution, left behind a grain of earth, V""8"
which, as 1 conjecture, it had taken up during the eva-
poration in the glafs veflel."
   To prevent this,  our author  diftilled half  an ounce
of fluor with an ounce of oil of vitriol for five hours.
The crults w ere feparated from th w atcr ; they weigh-
ed, after being well walked and dried, eleven grains;
they were white and very flocculent; thirty-two grains
of Siliceous earth  were precipitated  fiom the filuitd
water :  the ley was then evaporated in a leaden \ei,cl
 and yielded 80 grains of fait.  As glafs veflels were no
longer to be trufted, a piece of a gun-barrel furiiilhcd ^^"n
with a cover, and terminated by a bent tube, intended to jron diftil-
ferve inftead of the neck of a retort, was  afterwards UngvcfW.
ufed;  and with  this  apparatus the following experi-
ments were made :
   1. Haifa drachm of the  newly prepared fal-ammo-
niac was diftilled for two hours with two drachms of
oil of vitriol,  into a glafs receiver containing an ounce
of water.  No veftige of a cruft could be perceived on
the water, but fome earth was perceived in thereceiver,
where the vapours having afcended through the tube,
came into  contact with the wet glafs ;  and here  the
furface was become fenfibly rough.  On the  addition
of volatile alkali, a few flocculi of  filiceous  earth, a
mounting only to one-fourth of a grain,  were thrown
down out of the water.
   3. A drachm of  vitriol was added  to a drachm
and  an half of the fait; but a leaden receiver was now
ufed, containing  an  ounce of water as before.  The
water  acquired an unpleafant fmell, but fhowed  no
figns of a cruft.   On the addition of fpirit of fal am-
moniac, a little grey carrh weighing half a grain fell to
the bottom.                                            «
   3. A fcruple of this fair, mixed with an equal quan- No cruft
tity  of white  fand in fine powder, and diftilled with a formed by
drachm and an half of oil of vitriol, into an ounce of mixing
wrater in the leaden  receiver, fhowed no fign of a cruft. frnd.witha
The water had a putrid fmell, and  left on the filter iz. .cou"
two grains and an half of grey earth, which ran under fl"^"^.
the blow-pipe into  a grain  of lead.  Volatile  alkali
precipitated five grains of grey earth, which melted on
the addition of a little fait of tartar into a black glo-
bule, though the blow-pipe alone made  no  change
in it.                                                 -
   4. To 13 grains ofthe fame ammoniacal fait a drachm ytUt  *lTeit.
of oil of vitriol and two Scruples of green glafs, broken one by
into fmall pieces, were added.   The  iron tube had ufing pow-
fcarce become warm, when a great cruft  of  filiceous deredglafu,
earth was perceived on the furface of the  water, aud
the fame appearance on the moift  fides of  the  veflel.
It did not, however,  feem  to increaSe during the re-
mainder oS the diftillation.  A grain and  a quarter of
earthy matter remained on the filter, confiding  partly
of white films, which  ran under the blow-pipe into a
greenifh glaSs.
   5. To  afcertain  this matter  ftill more clearly, a
different fpecies of mineral fluor was ufed,  which  be-
ing diftilled with  a  double  quantiry of  oil  of vitriol,
and with a drachm of water in the receiver, yielded 2
thin pellicle of the appearance of lead, but no  filiceous
cruft.  Volatile alkali threw down a^ grains  of grey
                                             taiit^ 
Pracli.ce*
CHEMISTRY,
Fluor acid earth.—A drachm mixed with  the  fame quantity of
         pulverized fand afforded a pellicle of lead  interfperSed
         with a few  particles of  white cruft, which ran into
         glafs under the blow-pipe.  Volatile alkali precipitated
         eight grains.—A drachm,  mixed with an equal quan-
         tity of green glafs reduced to powder, Swelled  a good
         deal, and  yielded a thick filiceous cruft.
            6.  To a drachm of green fluor that had  been heat-
         ed and powdered were  added two  drachms of  oil of
         Vitriol, ftill employing the iron  tube.  A piece of wet
         charcoal was alfo fufpended in the Infide, a cover fixed
         on the tube, and the  latter was heated  for  about 15
         minutes   in a fand-bath.   Obferving  now  that  the
         charcoal  was dry, and  had no earth upon, it, a fcruple
         of fand in fine powder was added,  the charcoal was
         wetted  and replaced,   but  nothing appeared.  Some
         bits of green glafs were then thrown into the mixture
         which inftantly foamed up and  ran over.   The char-
         coal  was not replaced in the  tube,  nor was it  any
         longer neceffary, as  it gained  a covering of  white
         powder by  being held  a  very few moments over the
         orifice.
An experi-   Mr Scheele, in one  of  his experiments, obferves,
hientofMr t}iat; j^ obferved the white powder on a piece of char-
         coal  that had been moiftened and fufpended over fluor
         to which vitriolic acid was added.  As this experi-
         ment was made in metallic veffels,  Mr Meyer conjec-
         tures, that  the mortar ufed for  reducing  the fluor to
         powder was of foft  glafs, and  that  the phenomenon
         was  occafioned by the abrafion of fome  particles of
         glafs.
            7. To  determine  whether the  acid can carry up
quantity of much more of the  filiceous earth  than  is  fufficient
filiceous  to faturate it, an ounce and an half of pure oiFof vi-
         triol was  added in a retort of glafs,  and three ounces
         of water put into the. receiver.  The retort was cor-
         roded through in an hour's time, and the cruft on the
         water weighed ten grains   The  liquid being then
         filtered and divided into two equal parts, one was pre-
         cipitated  with cauftic volatile, and the other with mild
         fixed vegetable  alkali.  The former  yielded 2J  grains
         of filiceous earth, and the latter 68 grains of a  preci-
         pitate, which flowed under the blow-pipe,  ran into
         the  pores of charcoal, and gave  out  ftrong vapours of
         fluor acid.   The reafon oS this  difference fhaTl be  ex-
         plained when we  come  to  treat of Siliceous earth.
            8. To  a mixture  of half an  ounce of fluor and the
         fame quantity of glafs,  in powder,  12 drachms  of  oil
         of vitriol were put in a  fmall retort, half filled with the
         mixture.   The ingredients acted upon each  other fo
         violently that they rofe up into the neck of the retort;
         and the operation being intermitted on account  of the
         noxious vapour they emitted, the retort was found next
         day  covered with fafciculated cryftals like hoarfroft.—
         The experiment being  repeated in a more  capacious
         retort, and the mixture thoroughly  blended by agita-
         tion, it became a thick maSs, and Swelled like  dough
         in fermentation :  the bottom  of the retort grew very
         hot, and the filiceous cruft appeared on three ounces of
         water in  the receiver.  The diftillation being continu-
         ed for three hours, 16 grains of filiceous earth were
         found on  the furface, and  the  precipitate  by  volatile
         alkali weighed c6 grains; the retort was much lefs cor-
         toded than ufual.
            9. Thirty grains of this precipitate,  diftilled in a
846
Scheele's
explained.
   847
Of the
earth car-
ried along
With fluor
acid.
Violent ac-
tion of
ffuor acid
upon glafs.
                                                       121
glafs retort with a drachm and an Laif of oil of vitriol, Fluor acid
produced no filiceous earth on the water in  the  re-andlt.s
ceiver, or  that with which the earth was edulcorated. c.omia"
The ley of ffuorated volatile alkali was mixed with a >lons'v
folution of chalk in nitrous acid till no more precipi-
tation  took place.  The mixture was  paffed  through
nitrous acid, and the precipitate edulcorated. It weigh-
ed, when dry, two drachms and 36 grains.
   10. Two drachms of oil of  vitriol being added to 2
drachm of this precipitate contained in a glafs retort,
the precipitate Was attacked in the cold,  but no cruft
appeared ; the heat, however, was fcarce applied, wThen
the whole furface of the water was  covered, and  the
fame phenomena exhibited which are  produced by  the
natural fluor.                                          g^a
   11.  Mr Scheele having obferved that a mixture of Farther
fluor  as tranfparent as  mountain cry ftal, and  oil of proofs that
vitriol in a metallic cylinder, produced no appearance ofthe eartby
filiceous earth, on a wet fponffe fufpended on the infide, cru^sPro"
   n«  -.«    ,'       n  i   °  1 r             .     ceeds fronl
at Mr Meyer s  requeft  he  made a new  experiment tlae  lafs
by adding  oil  of vitriol to portions of fluor of this veflels^
tranfparent kind  placed in  two tin cylinders ;  fome
filiceous  earth  was  put into one, and a w7et  fponge
fufpended in  both.  The  next morning the  fponge
that was  fufpended over the cylinder which held  the
filiceous earth, was covered with the white powder, but
no appearance of it was feen on the other.  The expe-
riment was repeated by Mr  Meyer with the  fame re-
fult, but  the white cruft did not  appear till after 2
night's ftanding.
   12.  A drachm of fluor, mixed with two of oil of vi-
triol, afforded, after a diftillation of two  hours, a thin
film of lead on the furface of the water in the receiver,
but no filiceous earth.  The fame mixture was after-
wards diftilled with the ufe only of a glafs receiver in-
ftead  of a lead one. In the beginning of the diftilla-
tion a  fmall fpot appeared under the neck of the  re*
tort,  and the neck itfelf was  covered with white pow-
der, but it foon difappeared ;  and  though the  empty
partof the receiver  was corroded,  yet no more than
half a grain of earth was procured.
   Thefe experiments  fo clearly point out the origin
of the filiceous Cruft  on the  furface of the fluor acid,
that its exiftence  as a diftinct  acid is  now univerfally
allowed, even by thofe who formerly contended for its
being only the vitriolic or fome other acid difguifed.—   gfd
Experiments of a fimilar kind were made by Mr Wen- Mr  Wens-
zel,  who  performed his  diftillation in a leaden retort, zel's cxpc»
furnillied with a glafs receiver. The water was covered riir*ents in
with a variegated cruft, and yielded a gelatinouspreci- aleaJen
pitate with fixed alkali.  On examining- the receiver,retorti
he found  its internal furface  corroded, fo that  it  ap-
peared as if it had been rubbed with coarfe fand.   By
fubftituting a leaden receiver,however, inftead of a glafs
one, he obtained the acid entirely free  from filiceous
matter, and containing only  a fmall quantity of iron
and aluminous  earth.                                  2(j g-0
   The fluor acid may alfo be procured by the nitrous, Fluor acid
muriatic,  and  phofphoric acids.—MrScheele-diftilled procurable
one  partof the mineral with two of concentrated ni- by nitrous*
trous acid.  One part went over  into the receiver munatic>
along with the fluor acid, and a thick cruft was  form- a£d ?
ed on the water of  the receiver. The  maSs remaining acid.^
in the retort was calcareous  earth  faturated  with ni-
trous acid.
                          &                  Wirh 
1 12

llinr a> il
.ml hi
CHEMISTRY.
Pra& ice.
 3d 850
Appear-
ance and
properties
of fluur a-
cid.
 4th 850
Combined
with fixed
alkali.
   8jr'
With vola^
tile alkali.
   '5-
VTith
*.:th*.


With me-
•al.
  With an eqnlq•:  -ity of marine acid, that of fluor
palled o\cr into  t.u-receiver with a large quantity of
the muriatic ;  the internal fun.ice  ofthe receiver, as
well as  of the water  contained  in it,  being covered
with a white cruft.   The refiduum was fixed Sal  am-
moniac.
  Phofphoric acid digeftcd with  powdered  fluor, dif-
folved a good deal of it; and  on diftilling  this folu-
tion, the fluor acid went over together  with the  watery
particles of the mixture ; the remaining mafs in the re-
tort had the properties of the afhes of bones.
  The fluor acid procured in any of thefe ways is not
diftinguiihable by the fmell from that of fea-falt:  in
fome cafes it acts as muriatic acid, in others like that
of tartar •, but in moft cafes it  fliows properties peculi-
ar to  itfelf.
   With fixed alkali the fluor acid forms a  gelatinous
and almoft infipid matter, which refufes to cryftallize.
By evaporation a Saline maSswas obtained, which was
in weight only the  Sixth part of the fixed alkali dif.
Solved ; did not change the colour of fyrup  of  violets,
but precipitated lime water, and likewife the Solutions
of gypSum  and EpSom  Salt.   With   mineral alkali
the Same phenomena were produced as with  the  ve-
getable.
   Volatile alkali with fluor acid formed  likewife a
jelly, which when Separated Srom the liquor appeared
to be filiceous earth.  The clear liquid tailed like vi-
triolic ammoniac,  and  fliot into  very Small cryftals,
which by Sublimation yielded firft a volatile alkali, and
then a kind oS acid Sal ammoniac. By diftillation with
chalk and water,  all the volatile alkali quickly came
over. Lime water inftantly threw down a regenerated
fluor, which was  the cafe alSo with Solutions of lime
in the  nitrous and  muriatic acids.—Solution of filver
let  fall a powder,  which, before  the blow-pipe, re-
Snmed its  metallic form, the acid being diflipated, and
forming a white  fpot on the  charcoal round  the re-
duced filver.  Solution of quickfilver  in nitrous acid
was precipitated, and the powder was entirely volatile
in the fire ; but a folution of corrofive  fublimate re-
m.:incd   unchanged.   Lead w~as  totally precipitated
from nitrous acid; and a folution of  Epfom  fait was
rendered turbid.   Oil of vitriol produced a  fluor acid
by diftillation, which formed at the fame time  a thick
cruft on the water of the receiver. The  regenerated
fluor procured either by means of lime water or folu-
tions of the earth in acids, was decompofed by fixed,
but not by volatile alkali.
  Willi lime, magnefia, and  earth  of alum, this acid
became  gelatinous.  Part  of the  two laft  were  dif-
folved.
  Gold  was not touched by the fluor acid either alone
or mixed  with  that of nitre.  Silver, in its metallic
fine, underwent  no change.  Its  calx, precipitated by
an  u'k-.l',  was  partly  diilMvcd ;  but  the  remainder
formed an infoluble mafs at  the   bottom    Vitriolic
acid expelled the Huor acid in its ufual form.   Ojdcy-
filvcrwas  :>n diflblved, but its  calx precipitated from
the nitrous folution was p.rtially S>.  The remaining
infoluble p;.rt of the  calx  united  with the acid,  and
I   med a white powder, from  which the fluor acid was
entiled by  the vitriolic.   The fame  powder formed,
i   mens of  the blow -p: e, a yellowifh glafs; which,
fcowv-r, evaporated by  !,^.ees, leaving a fmall glo-
bule of fixed  glafs behind.   Lead  was net diffolved, Huor acid
but the acid formed  a Sweet  fedution with its calx ; »c»daml
ti0111 whence the  latter could  be  precipitated bv  the lts fombl"
acids of vitriol, and fea-falt, as alfo b,  h,l  ammoniac. 'ilill^L.
On digefting  a  quantity  of acid  with calx of lead,
which had  been previoufly  digefted  in the  fame, a
fpontaneous precipitation  took  place.  The  precipi-
tate melted eafily before the blow-pipe, and ran into
metal ; but part ofthe glafs remained fixed in  the fire.
Copper was partially  diffolved, as  appeared   by  the
blue colour affumed by  the liquid  on the addition  of
volatile alkali. The calx of copper was eafily  foluble ;
and the liquor, though gelatinous, yielded blue cryftals,
partly of a cubic and partly of  an oblong  form, from
which the acid could not be  feparated but by heat.
Iron was violently attacked, and gave out inflammable
vapours during the folution.   The  liquor  refufed  to
cryftallize ; but, by  evaporation, congealed  into  an
hard mafs after the moifture was diflipated ; and from
this mafs the  fluor acid might be expelled as ufual  by
oil  of vitriol.  The fame effect was alfo produced  by
heat alone ; the acid rifing in vapours,  and leaving a
red ochre behind.  Calx of iron was alfo diffolved, and
the folution tailed like alum ; but it could not  be re-
duced to  cryftals.  Tin, bifmuth,  and regulus  of co-
balt, were not attacked in their metallic ftate ; but the
calces  of all of them were foluble.   Regulus of anti-
mony and powdered antimony were not  fenfibly acted
upon.  Zinc produced  the fame effects as iron,  ex-
cepting that the folution Seemed more inclined to cry-
ftallize.
«54
  The moft remarkable property of this acid, however, Glafs cor-
is its readily diffolving glafs and carrying it off in the roded by
form of vapour.   This Angular property belongs  notthis acid>a»
only to  the pure  aeid, but alfo to the ammoniacal fait J"?11/"11^
formed by  combining it with the volatile alkali.   Mr \  [™com*
Wiegleb informs  us, that on evaporating to drynefs, in bfnation
acupofMifnia porcelain,  a folution of this kind ofwithvola-
ammoniac, which by its  fmell fhowed  an excefs of vo- tile alkali.
latile alkali, the glazing of the infide was entirely cor-
roded, and the bottom left as rough as a file.  During
the evaporation the cup was covered with white paper,
which when dry appeared full of fmall cryftals  of an
acid  tafte,  eafily  diftinguiihable by  the  naked  eye.
TheSe, as  well as the ammoniacal Salt, powerfully at-
tracted the moifture of the air.                          8
  This property ofthe floor acid renders it extremely It ;,,**
difficult  to be kept.   Mr  Meyer  informs us,  that difficult to
having kept fome  upwards of a year in a glafs phial, be k«pt.
it corroded  the glafs in many points furrounded with
concentric circles, depofiting a powder which adhered   856
to the bottom.  He is of opinion that golden  veffels Golden vcf-
would be moft proper for keeping  this acid, as alfo for fels moft
making experiments on the fluor itfelf.'  A phial  co- ProPer for
vered in  the infide with wax and oil has been recom-this pur"
mended for the fame purpofe.                        *'° ^
  This acid, as well as thofe of vitriol, nitre, and fea- Dr Prieft-
falt, has been exhibited by Dr  Prieftley iu an aerial l*y'» expe-
form.  Having put fome  pounded  fpar into a  phial, rimenu on
and poured oil of  vitriol upon it, adopting at the fame co|lvcrting
time the ufual apparatus  for obtaining air, he obferved thisacu^iu"
that a  permanent cloud  was formeel  by  the vapour*°
iffuing out from the mo ith  of the tube, which he at-
tributed  t-i  the attachment ofthe ;• id to the aqucus
moifture of the «.i:n Sphere. - The moment that water
                                              came 
Practice.
CHEMISTRY.
123
 Sal fedati-  came tn contact witfh this air, its furface became opaque
 v«8 and its  and white by a ftony film, which retarded the afccnt of
          the water, till the air infinuating  itfelf through the
          pores and cracks  of  the cruft,  the water neceflarily
          rofe as the air diminiflied ;  and breaking the cruft, pre-
          sented a new furface to the air,  which was immediate-
          ly covered  with another cruft.  Thus one ftony in-
          cruftation was formed after another till every particle
          of the air was united to the water ; and the different
          films being collected and dried, formed a white pow-
          dery fubftance,  generally a little acid to the tafte ; but
          when waflied in much  pure water, perfectly inlipid.
          The property of corroding glafs he found to belong to
          the fluor  acid air only  when hot.  From fome other
          experiments he concluded, that the fluor acid air was
          the fame with what he had formerly obtained from vi-
          triolic acid: but the experiments made fince that time
          by various chemifts,  have now convinced him that it is
  ad 857   an acid of a nature entirely different from all others.
 Method of    By means of the fluor acid, a new art has been dif-
 cngraving  covered,  viz. that of engraving upon glaSs.  For this
*n gbfs.   purpofe  a looking-glafs  plate  is to be covered  with
          melted wax or maftic ; and when the coating becomes
          hard, it is to be engraved upon by a very fliarp -pointed
          needle or other instrument of that kind.   A mixture
          of oil of vitriol and fluor acid are then to be put  upon
          the plate,  and the whole  covered with  an inverted
          China veffel, to  prevent the evaporation  of the  fluor
          acid.  In two days the glafs plate may be cleared oSits
          coating, when all the traces of the needle will be Sound
          upon it.

              § 5. Ofthe Sal Sedativvs,  or Acid of Borax,

 Found in a   This is a Saline Subftance of a very  fingular nature,
 mineral in  and till lately found no where but in borax itfelS.  Its
 Germany,  origin in different parts of the world is related under
          the article Borax :  but  fince that article was printed,
          we have accounts of its being difcovered in a mineral
          of a peculiar kind found  at Lunenburg near Hartz.
          This is frequently  tranfparent, but fometimes alfo a
          little opaque, and ftrikes  fire Slightly with fteel.  It
          has hitherto been found only  in Small cryftals inve-
          loped in a  gypfeous  matter.  TheSe generally  affect
          the cubical form,  though they are fometimes irregular,
          and from the truncatures frequently appear to be of dif-
          ferent kinds.  One of them had  fourteen faces, fix
          fmall fquare planes, and eight hexahedral; though all
          thefe are modifications of cubes.  Mr Weftrumb ana-
          lized it with fome difficulty ; but  at  laft  found  that
          100 parts of the mineral contained 60  of Sedative fait,
          ten of magnefia, and  ten of calcareous  earth ; of clay
          and flint five parts, fometimes ten of iron,  though fre-
          quently but  five.  The  fame acid  has  alfo been dis-
          covered in Peru,  and a little in Hungary from an ana-
          lyfis of petroleum.  This bitumen  ariSes from  a rock
          between Pecklemcza and Mofcowina.   It feems at firft
          to be white, bur foon grows black by expofiire to the
          air.   It was analySed by profeflbr Winterl, who found
          it to contain a tranfparent  oil in a butyraceous form,
          and a true fedative fait, united with "the oil by means
          of an excefs of phlogifton.  The  fedative fait was firft
          difcovered by Bechr,  and afterwards more accurately
          defcribed by Homberg; but its nature was at firft very
          much mifunderftood,  being named  the narcotic fait of
&c.
 vitriol, on account of the vitriolic acid ufed infepara-Salfedati-
 ting it from the  borax.   From this it  is Separable v"« and lt*
 either by fublimation or cryftallization.  The method combina-
 by fublimation is  that recommended  by Homberg. *lon8,    f
 His procefs confifts in mixing green vitriol with borax,  2d 858
 diflblving  them in water, filtering the folution,  and How pre-
 evaporating till a pellicle  appears :  the liquor is  then Pared from
 to be put into a Small glaSs alembic, and the Sublima-00rax'
 tion promoted till only a dry matter remains  in  the
 cucurbit.  During this operation,  the liquor paffes
 into the receiver;  but the internal Surface ofthe capi-
 tal is covered with a faline matter forming very Small,
 thin,  laminated cryftals, very fhining, and very light.
 This is the Sedative Salt.   The capital is  then to be
 unluted, and the adhering Salt Swept off with, a feather;
 the part of the liquor  which  paffed laft into  the re-
 ceiver, is to be poured  on the dry  matter in  the  cu-
 curbit  ; and  a new fublimation  is to be promoted as
 before, by diftilling till the matter in the  cucurbit is
 dry.   Thefe operations are to be frequently repeated
 in the fame manner, till  no more Sedative Salt can be
 obtained.
   To obtain the Sedative Salt by  cryftallization, borax
 is to be diflblved in hot water ; and  to this folution any
 one of the three mineral acids is  to be gradually added,
 by a little at a time, till the  liquor be faturated, and
 even have an excefs oSacid, according to Mr Beaume's
 proceSs.   The liquor is then to be left in a cold place ;
 and a great'number of  fmall,  fhining, laminated cry-
 ftals will be formed;  thefe muft be wafhed  with a
 little very cold water, and drained upon brown paper.
 The fedative fait  obtained by this procefs is fomewhat
 denfer than that  obtained by  fublimation; the latter
 being  fo light  that 72 grains  are fufficient to fill a
 large phial.                                        .   g5?
   Sedative  fait, though  thus capable  of being  once Fixed in
 fublimed, is not, however, volatile; for it arifes only the fire-.
 by means of the water of its cryftallization ; and when
 it has once loft its water by drying, it cannot be rai-
 fed into vapours by the moft violent fire, but remains
 fixed,  and melts into a vitreous  matter like borax it-
 felf.   This glafs is foluble in water; and then becomes
 fedative fait again.   A great  quantity of water is  re-
 quired to diffolve the fedative fait, and  much more of
 cold than of boiling water ; whence it is cryftallizable
 by cold,  as it alfo is by evaporation; a fingular  proper-
 ty, which fcarce belongs to any  other known fait.        gg0
   This fubftance  has  not an  acid, but a fomewhat its proper-
 bitterifh, tafte, accompanied with a flight impreflion of ties.
 coolnefs.   It neverthelefs unites with alkaline falts as
 acids do, and forms with them neutral falts.  It is fo-
 luble in fpirit of wine, to which it communicates the
property of burning with a green flame.  It makes no
 change on the blue colour of vegetables, as other acids
 do.  It expels the other acids  from  their bafes, when
 diftilled  with a ftrong heat;  though thefe are^all  ca-
 pable of expelling  it in the cold, the acid  of vinegar
 not excepted.
  The compofition of fedative fait  is very much un- Mr liour-
known, as no means fufficient  for its  decompofition delin's ex-
have hitherto been found out.  Mr Bourdelin, who perimenta.
made many experiments on this fait, found that it was
unalterable by  treatment  with  inflammable matters,
with fulphur, with mineral acids difengaged, or united
with metallic fubftances, and with Spirit of wine.   He
                        0,2                  could 
                            CHEMI

could c;dy perceive fo.r.c marks of an inflammable nut-
ter,  andi little marine  acid.   l:e former uifcovered
itfelf by its communicating a fulphurto o Smell to the
vitriolic acid employed, and the  latter  by  a white
precipitate formed in a Solution of mercury in the  ni-
trous acid, by the liquor which came oven on diftilling
tiw. fait with powdered  charcoal.
   Mr  Cadet,  in  the  Memoirs ot the  Royal Academy
of  Sciences lor  176^,  has given  an account of fome
experiments made hy him on botux and its acid : from
which he infers (i\ That theacid contained in borax
itfclfis the marine, and not Sedative, Salt.   (2.)  That
it b the marine,  he proves by ha\ ing made a corrofive
Sublimate with this acid aud mercurius precipnatus per
fe.  That Sedative Salt docs not enter the compofition
of borax itfelf, he proves,  by theimpoflibility of recom-
piling borax from uniting the fedative fait with foffile
alkali.   The fall fo produced, he owns, is very likebo-
rax, but unfit for the purpofes of foldering  metals as
borax  is.   He therefore thinks, that,  in the deeou:vo-
fition of borax, the principles of the fait are fome \ hat
changed, by the  addition of that acid which extricates
the fedative fait;  and that this fait is compofed ofthe
marine acid originally exiftingin the borax, of the vi-
triolic acid employed in the operation, aud of a vitref-
ciblc earth.   (If this is true, then fedative Salt cither
cannot be procured by any other acid than the vitrio-
lic, or it mult have different properties according to the
acid which procures it.) The vitreScibleearth, he Says,
is that which Separates Srom borax during its Solution
in water, and which abounds more in the unrefined than
refined borax,  and which he thinks confifts of a calxof
copper, having obtained a regulus  of copper from if.
As he has never been able, however,  to compofe borax
by the union of thefe ingredients,  his experiments are
by no means  decifive.   Mr Beaume  has allerted that
it is always produced by  rancid oils ; but  Dr Black
 thinks his proofs by no means  fatisfactory.

              Sedative Salt combi ked,

   I. With  Vegetable Alkali.   This fait forms a  com-
pound very much refembling  borax itfelf in quality;
but in what refpects it differs from, or how far it is ap-
plicable to, the  purpofes of borax, hath not yet  been
determined.
   II.  With Mineral A/kali. Tin fait hasgenerally been
 thought to  recompofe borax :  and though  Mr Cadet
 has denied this, yet ashis experiments are hitherto im-
perfect and unsupported, we fhall here give the hiftory
 of that fait, as far as it is yet known.
   This Salt is prepared in the  Eaft Indies.   It is Said,
that from certain hills  in  thefe countries there runs a
green Saline liquor, which  is  received  in pits  lined
with  clay, and Suffered to evaporate with  the  Sun's
heat;  that a bluifh mud which the liquor brings along
with it is frequently flirred up, and a bituminous mat-
ter, which floats upon  the furface, taken off ;  that
when  the  whole  is reduced  to a thick  confiftence,
fome melted fat  is mixed, the matter covered  with
vegetable fubftances  and a thin coat oS clay ;  and that
v. hen the Salt has cryftallized,  it is Separated from the
earth  by a fieve.   In  the  fame countries is  found na-
tive the mineral alkali in confiderable quantity ;  Some-
times  tokubly pie, at other times blended  with he.
  S    T   R    Y.                            Fradice.

tero^cneotis matters of various kinds.   This alkali ap- Sal frdati-
pears to exift in borax, as aGlaubcr's Salt may be Sonu- v"» andit*
ed from a combination of borax  with  vitriolic  aeid. coni'),n*"
For a further account Sec Borax.                    """^
  Borax, when imported from the baft Indies,  con-    864
lifts of fmall, yellow,  and glutinouscryllals.  It is re-  Refined.
lined,  fome fay, by diiiolving it in lime-water; others,
in alkaline lixivia, or in a lixivium of cauftic alkali;
and by others, ir. a'.um-w ater.  Refined borax confifts
of large tight-lidcd cryftals,  each of  which is compo-
fed of fmall,  foft,  and  bittcrifli Scales.  It has  beta
faid that cryftals of this  Size can by no means  be ob-
tained by diffolving unrefined borax in common water;
that tiie cryftals obtained in this way  are extremely
fmall,  and differ confiderably from the refined borax
of  the flu ps;  infomuch  that Cramer calls  the  large
cryftals, not a  purified,  but an  adulterated borax-.
When diffolved  in lime-water, the borax  flioots into
larger cryftals;  and largeft of all,  when  the veflel is
covered, and a gentle  warmth continued during the
cryftallization.  All this, however,  is denied by Dr
Black ; who fays, that in order to accompli lb the pu-
rification, we have only  to diffolve the  impure borax
in hot water ;  to Separate the impurities by filtration,
after which the fait  ihoots  into the cryftals we com-
monly See.   During the diflblution, borax appears glu-
tinous,  aud adheres in part to  the bottom of the  veS-
Sel.   From  this  glutinous  quality, peculiar to borax
among the Salts, it is tiled by dyers Sor giving a  gloSs
to filks.                                               865
   All acids diflblve borax  flowly, and without  effer- Itsprepc-r-
veScence.   It precipitates from them moil, but not all, ties.
metallic fubftances ; along with which a confiderable
part of the  borax is  generally depofited.   It does not
abSorb the marine  acid of luna cornea, or of mercury
f iblimate.   It  melts  upon the  SurSace oS the former
without uniting, andfufters the latter to rife unchanged:
the borax in both cafes becomes coloured ;  in the  firft,
milky with red  ftreaks; in the  latter,  amethyft or
purple.  Mixed with  fal ammoniac,  it extricates the
volatile alkali,  and retains the acid ; but mixed  with
a combination oSthe marine acid with calcareous earths,
it unites with the  earth,  and extricates the acid.  It
extricates  the acid of nitre without  Seeming to  unite
with the alkaline bafis oS that Salt; nor does it mingle
in fufion with  the common fixed alkaline falts, the
borax flowing diftinct upon their furface.   A mixture
of borax with twice its  weight of tartar,  diflblves in
one Sixth oS the quantity of water that would be ne-
ceffary to diffolve  them Separately : the liquor yields,
on  iiifpiflation,  a vifcous, tenacious mafs  like glue ;
whicli refutes to cryftallize, and which deliquates in
the air.   Borax affords likewife a glutinous compound
with the other acids, except  the vitriolic;  whence
this laft is  generally preSerred for making the  feda-
tive Salt.  It proves moft glutinous with the vegetable,
and leaft with  the marine.   W ith oils, both expref-
fed and  diftilled,  it forms a  milky, feini-faponaceous
compound.  It  partially  diflblves in fpirit of wine.
In conjunction with  any acid, it tinges the flame of
burning matters green ;  the  precipitate thrown down
by it from  metallic folutions has  this  effect.  It does
not  deflagrate with  nitre.   Fufed with inflammable
matters, it yields nothing fulphureous, as thofe falts do
                                             which. 
Practice.
CHEMISTRY.
Acet«us   which contain vitriolic acid.  By repeatedly moiften-
acid and   ing  it when confiderably heated, it may be entirely
itscombi- fublimed.
nations.  ^   Borax retains a good quantity of water in its cryftals ;
         by which it melts and fwells up in a heat infuificient
         to vitrify it.   It  is then fpongy and light,  like calci-
         ned  alum;  but,  on increafing  the fire,  it flows like
         water.
   867
How pro-
cured.
   868
Sal diureti-
             § 6. Ofthe Acetous Acid and its Combinations.

            This acid is plentifully obtained from all vinous li-
          quors,  by a fermentation of a  particular  kind,  (fee
          Fermentation, and Vinegar.) It appears firft in
          the form of an  acid  liquor,  more or  lefs  deeply co-
          loured, as the vinegar is more  or lefs pure.  By di-
          ftillation in a common copper-ftill, with a pewter head
          and worm, this  acid  may be Separated from many of
          its oily and impure parts.  Diftilled vinegar is a purer
          but not a ftronger acid than the vinegar  itfelf; for
          the acid is originally lefs volatile than water, though,
          by certain operations, it becomes more fo.   After vi-
          negar has been diftilled to about T'- of its original bulk,
          it is ftill very acid, but thick and black.  This matter
          continues to yield, by diftillation,  a ftrong acid fpirit,
          but tainted with an  empyreumatic oil.  If the  diftil-
          lation is continued, a thick black oil continues to come
          over; and  at laft fome volatile alkali, as in the diftil-
          lation of animal  fubftances.  The caput mortuum left
          in the diftilling veffel, being calcined in an open  fire,
          and afterwards lixiviated,  yields fome fixed alkaline
          fait.
                       Acetous Acid combined,

             I.  With Vegetable Alkali. The produce of this combi-
          nation is the terra foliata  tartari, or fal  diureticus of
          the Shops ;  but to prepare this fait of a fine white flaky
          appearance, which is neceffary for fait, is a matter of
          fome difficulty.  The beft method of performing this
          operation is, after having faturated the alkali with the
          vinegar,  which  requires about 15 parts of common di-
          ftilled vinegar to one of alkali, to evaporate the liquor to
          drynefs ; then melt the faline mafs which remains with
          a gentle heat; after  which it is to be diffolved in wa-
          ter, then filtered,  and again evaporated to drynefs.  If
          it is now diffolved in fpirit of wine, and the liquid ab-
          stracted by diftillation, the remaining mafs being melted
          a fecond time, will, on cooling, have the flaky appear-
          ance defired.
            A good deal of caution is neceffary in the firft melt-
          ing ; for the acetous acid is eafily diffipable, even when
          combined  with  fixed  alkali, by fire.  It is proper,
          therefore, that,  when the fait is melted, a little fhould
          be occafionally  taken out, and  put into water;  and
          when it readily  parts with its blacknefs to the water,
          muft then be removed from the fire.  The fait, when
          made, has a very ftrong attraction for water, infomuch
          that it is not eafily preferved, even when put into glafs
          bottles.   To  keep it from deliquating,  Dr Black,
          therefore, recommends the corks to be covered with
          fome bituminous matter; otherwife they would tranfmit
          moifture enough  to make the fait deliquate.
            II. With Foftile Alkali.   This alkali, combined with
          the acetous acid, forms a fait whofe properties are not
foffile alka- well known. Dr Lewis affirms, that it is nearly fimilar
li.
   869
Acetous a
cid with
to the terra foliata tartari. The author of the Chemical
Dictionary,  again,  maintains  it to be quite different:
particularly that it cryftallizes well, and is not d-.lique-
fcent  in the air ; whereas the former cannot be cry-
ftallized ;  and even when obtained in a dry  form,  un-
lefs great care is taken to exclude the air, will present-
ly deliquate.
  III. With Volatile Alkali. This combination produces
a fait So exceedingly deliqueSceut, that it cannot be pro-
cured in a dry form without the greateft difficulty.  In
a liquid ftate, it is well known in medicine, as a Sudo-
rific,  by the name of'fpiritus mindereri.  It may, how-
ever,  be procured in a dry form, by mixing equal parts
of vitriolic fal ammoniac and terra foliata tartari,  and
Subliming the mixture with a very gentle heat. When
the Salt is once  procured, the utmoft care is requifite to
preferve it from the air.
  IV. With  Earths. Combinations of this kind are but
little known.   With  the calcareous and argillaceous
earths compounds of an aftringent nature are formed.
According to the author ofthe  Chemical Dictionary,
the Salt  refulting from a combination of vinegar with
calcareous earth eafily cryftallizes, and does not deli-
quate.  With magnefia the acetous acid does not cry-
ftallize ;  but, when inSpiffated, forms a tough mafs, of
which two drachms, or two and a half, are a brifk pur-
gative.
   V.  With Copper. Upon this metal the acid of vine-
gar does not act brifkly,  until it is partly at leaft calci-
ned.  If the copper is previoufly diflblved in a mineral
acid^ and then precipitated, the calx will be readily dif-
folved by the acetous acid.   The folution is of a green
colour, and beautiful green cryftals may be obtained
from  it.   The  folution, however, is much more eafily
effected,  by employing verdegris,  which is copper al-
ready united with a kind of acetous or tartareous acid,
and very  readily diflblves in vinegar.   The  cryftals
obtained by this procefs are ufed in painting, under the
name oS diftilled verdegris.
   The moft ready,  and in all  probability the cheapeft,
method oS preparing the cryftals of verdegris is that
propofed by Mr Wenzel, by mixing together the fo-
lutions of Sugar of lead  and blue vitriol,  when an ex-
change of bafes takes place;  the lead  being inftantly
precipitated by the  vitriolic acid, and the acetous acid
uniting with the copper.   From  15 ounces and  two
drachms of  fugar of lead with twelve ounces of blue
vitriol, five ounces  of the cryftals were obtained.  The
precipitate of lead, though wafhed feveral times  with
water, never loft its  green colour.  It may either be
uSed,  he Says,  in this ftate, as a green pigment,  or it
may be made perfectly white by digeftion in dilute ni-
trous acid.
   VI. With Iron. Vinegar acts very readily upon iron,
and diflblves it into a very brown and almoft black li-
quor,  which does not eafily cryftallize,  but, if inSpiS-
Sated, runs per deliquium.   This liquor is employed
in the printing of linens, calicoes, &c. being  found
to ftrike a finer black  with  madder,   and te injure
the cloth lefs, than  folutions of iron in the other acids.
   VII.  With Lead. The acetous acid diflblves lead in
its metallic  ftate very fparingly ; but if the metal is
calcined, it acts upon it very ftrongly.  Even after lead
is melted  into  glafs,  the acetous acid will receive a
ftrong impregnation from it; and hence it is dangerous
   870
Vegetable
ammoniac.
   871
Anomalous
falts.
   87a
Diftilled
verdegris*
   S73
Iron licjuot
for print-
ing cloth.
Lead. 
C    H   E    M    I   S   R    T   Y.
Practice.
to f  :  vinegar into fuch earthen veffels as arc glazed
with lead.  In thej metallic ftate, only a draci;:  of
lead can be diflblved in eight ounces ot diftilled vine-
gar.
   It lead is expofed to the vapours of warm vinegar,
it is  corroded into a k::d of calx, which  is  ufed in
great quantities in p fining, and is known by the name
ot cerufs or white ttad.   The  preparation ot" this pig-
ment has become a diftinct trade, and is practised in
I  >mc places in Britain where lead  is procurable at
the  loweft  price.   The  procefs for making cerufs
is thus given  by the author of the Chemical  Dictio-
nary.
   " To make cerufs, Jcnicn  plates rolled fpirally, fo
that the fpace of an inch fhall be left  between each
circumvolution, muft be  placed  vertically in earthen
pots of a proper  Size, containing fome good vinegar.
Thefe leaden rolls ought  to be fo fupported in the pots
that they do not touch  the vinegar,  but that the acid
v.ipo.irhnay circulate freely betwixt the circumvolu-
tions.   The pots are to be covered,  and placed  in a
bed of ehm£, or in a fand-bath, by which a gentle heat
may be applied.  The acid of vinegar being thus redu-
ced into vapour,  eafily  attaches itfelf to the furface of
thefe plates, penetrates them,  and is impregnated with
the'metal, which it reduces to a beautiful white pow-
der, called  cerufs.   When a fufficient quantity of it
is collected on the plates, the rolls are taken out of the
pais, and unfolded  ; the cerufs is then taken off",  and
they arc  again rolled up, that the operation  may be
repeated.
   " In this operation, the acid being overcharged with
lead,  this metal  is  not  properly in a  faline ftate;
hence  cerufs is not in cryftals, nor is foluble in water:
but a faline property would render it unfit for painting,
in which it is chiefly employed."
   Though  this procefs may  in general be juft, yet
there are certainly Some particulars neceffary to make
cerufs of a proper colour,  which this author has omit-
ted ; for though we have  carefully treated thin plates
of lead in the manner he directs, yet the calx always
turned  out  of a  dirty  grey colour.   It is probable,
therefore,  that after  the lead has been corroded  by
the  fleam  of vinegar,  it may  be waflied with water
lightly  impregnated with the  vitriolic and  nitrous
acids.
   This preparation is the only white hitherto found fit
for painting in oil :  but the difcovery of another would
be very defirable, not only from the faults of cerufs as
a paint, but alfo from its injuring the health of perfons
employed in its manufacture,  by affecting them with a
Severe colic ; which lead, and all its preparations, fre-
quently occafion.
   If diftilled vinegar is poured on white lead, it will
diflblve it in much greater quantity than either the lead
in its metallic  form, or any of its calces. This folution
filtered and evaporated, flioots into fmall cryftals of an
auftere fweetifli tafte called*fugar of lead.   Thefe are
ufed in dyeing, and extern; 'ly  in medicines.   They
have been even given internally for  Spitting of blood.
This they will very certainly  cure;  but at the  fame
time they as certainly kill the patient by bringing on
other difeafes.  If thefe cryftals  are repeatedly diflblved
in. frelh  acids, and  the folutions evaporated, an oily
kind of fubftance will at laft be obtained,  which  canAcetou*
fcarcely be dried.                                   acid a,,d
  From all  the metallic combinations of the acetous ,,s COITlb,~
acid,  it may  be recovered  in an exceedingly concen- "  '°"$'  .
irated  form,  by fimple diftil III ion,  Sugar of lead only   878
excepted.   If this fubftance is diftilled in a retort with Inflamnia-
a ftrong heat,  it hath been faid  that an inflammable blc fPJm
fpirit,  and not  an  *eid conies over ;  but this is  denied f01" jgar
1   -r»   in  1,                                        of lead-
by Dr Black.                                          j...
  \ 111. With Tin.  The combination of acetous acid   Tin.
with tin isfolittle known, thatmany  have doubted whe-
ther diftilled  vinegar is capable of diliolvingtinornot.   gj0
Dr  Lewis oi.icrvcs,  " 1 hat plates of pure tin put intopr Lewis'*
common vinegar begun in a few hours to he corroded, experi-
without the  application  of heat.  By degrees a por- menu con-
tion of the metal was taken up  by  the acid, but  did "rn'"K,,,c
not  feem to be perfectly diffolved, the liquor appear- j".   1,y
ing quite opaque and  turbid, and dcpoliting great part
of the corroded tin to the bottom, in a whitifh powder.
A part of the tin,  if not truly diffolved, is  exquifitely
divided in the liquor; for,  after ftanding  many days
and after  pafling through a filter,  fo much remained
fufpended as  to  give a whitifhnefs and opacity  to  the
fluid.  Acid juices of fruits,  fubftituted to the vinegar,
exhibited  the fame phenomena.  Thefe experiments.
are  not fully concluftve for the real  fallibility of tin in
thefe  acids, with  regard  to the  purpofes  for  which
chemifts have wanted fuch a folution:  but they prove
what  is more important; that  tin,  or tinned veffels,
however pure the tin be, will give a metallic impreg-
nation to light vegetable acids Suffered to ftand in them
for a few hours."
  With regard toother metallic fubftances, neither the
degree of attraction which  the  acetous acid has  for
them, nor the nature of the compounds formed  by  the
union of it with Such Subftances, are  known; only, that
as much oS the reguline part of antimony is diflblved
in this acid as to give it a violent emetic quality.   See
Regulus oj Aatimony.

         Concentration of the Acetous Acid.
                                                      881
  Common vinegar, as any other weak acid, may be Conccntra-
advantagcoufly concentrated by froft ; as alfo may its ted vim-
Spirit  or the  diftilled vinegar ofthe fhops : but as  the gar.
cold,  in this  country,  is Seldom or never So intenSe as
to Sreeze vinegar, this method of concentration  cannot
be made ufe of  here.   If diftilled vinegar  be fet in a
water-bath, the moft aqueous part will ariSe, and leave
the more concentrated acid behind.  This method,
however, is tedious, and no great degree of concentra-
tion can be produced, even when the operation  is car-
ried to its utmoft  length.   A much more  concentra*
ted  acid may  be obtained by diftilling in a retort  the
cryftals oS  copper,  mentioned (n°  872)  under  the
name  of diftilled verdegris.  A very ftrong acid may
thus be obtained,  which has a  very pungent  fmell,
almoft as  fuffocating as volatile  fulphureous acid.
The Count  de  Lauraguais  difcovered that this  fpi-
rit, if heated  in a  wide-mouthed  pan, would take
fire on the contact of flaming fubftances, and burn  en-
tirely away, like fpirit oS w ine, without any refiduum.   «<>
The Same  nobleman  alSo  obServed, that this  Spirit, Saltofvi-
v hen well concentrated, eafily cryftallizes without  ad- negar.
didon.
                                              This 
P raclice.
CHEMISTRY.
127
   883
Dr Prieft-
ley's expe-
riments.
            This may feem to be the moft proper method of ob-
          taining the acetous acid in its greateft degree of ftrength
          and purity : but as  the  procefs requires a very ftrong
          heat to be ufed towards the end of the operation, it is
          probable that part of the acetous acid may  be by that
          means entirely decompofed.  It would feem preferable,
          therefore,  to decompofe pure terra foliata tartari by
          means of the vitriolic acid,  in the fame manner as nitre
          or fea-falt are decompofed  for obtaining  their  acids.
          In this cafe, indeed, the acetous acid might be a little
          mixed with the vitriolic ;  bur that could eafily be fe-
          parated by a fecond diftillation.   A  ftill  better me-
          thod  of  preparing the  acid feems to be  by  diftilling
          Sugar of lead with oil of vitriol.   The proportion ufed
          by M. Lorenzen of Copenhagen,  is three ounces of
          vitriolic acid to eight of the  fiigar of lead.  Mr Doll-
          fufs recommends two parts of Sugar of lead to one  of
          vitriolic acid.
            Dr Prieftley, who gives us feveral  experiments on
          the vegetable acid when reduced to the form of air,
          mentions his being eafily able to expel it from fome
          exceedingly ftrong concentrated vinegar, by  means of
          heat  alone.   This feems fomev/hat  contrary to  the
          count de Lauraguais's obfervation of the diSpofition of
          the fpirit  of verdegris,  as it is commonly called, to
          cryftallize : but a ftill greater difference is,  that  the
          vegetable acid air extinguifhed a candle, when accord-
          ing to the Count's observation, it  ought to have been
          inflammable.   The moft curious property obServed by
          Dr Prieftley is, that the vegetable acid air being im-
          bibed by oil olive, the oil was rendered leSs viScid, and
          clearer, almoft like an ejfential oil.   This is  an  uSeful
          hint; and,  if purfued,  might lead to important disco-
          veries.

   -g      Acetous acid combined with Inflammable Matter.
Vegetable    The only method yet known, of combining acetous
          acid with the principle of inflammability, is  by mix-
          ing together equar parts of the  ftrongly  concentra-
          ted acid called fpirit of verdegris, and fpirit of wine.
          The refult is, a new kind of ether, fimilar to the vitri-
          olic, nitrous, and marine.   This ether, however,  re-
          tains fome oSthe acidity and peculiar Smell of the
          vinegar.  By rectification with fixed alkali, it may
          be freed from this acidity,  and then Smells more like
          true ether,  but ftill retaining Something of the fmell,
          not of the acid, but the inflammable part of the vine-
          sar-
           In this procefs a greater quantity of ether is obtain-
          ed than by employing- the vitriolic  acid : which fliows
          that the vegetable acitfis efl'entially  fitter to produce
          ether than the vitriolic.   For making the acetous ether
          readily, Mr Dollfufs recommends eight ounces of fugar
          of lead dried by a very  gentle heat,  until it  lofes the
         water of cryftallization, when it will weigh five ounces
         and fix drachms.   It is  then to be put into  a  glafs re-
         tort and  a mixture of five ounces of vitriolic  acid,
         with eight of fpirit of wine, poured upon it, and the
         whole diftilled with a very gentle fire.  The firft ounce
         that paffes over will be dulcified acetous acid,  the next
         almejft  all ether,  and the third ether in its  pureft
         ftate.
           An  ether  may  alfo  be obtained  from  vinegar  of
         wood. • To make it, the moft concentrated acid of this
         kind is to be made ufe  of.   For this purpofe an cat-
                                                   1
ether.
its combi-
nations
pyreumatic acid muft firft be diftilledfrom beech-wood, Acid t>f
and then rectified by a fecond  diftillation.   Three *artar ^
pounds of this require for their faturation  five ounces
of purified alkali,  which by evaporation and fufion af- ^
fords three ounces and a quarter of terra foliata tartari.
From  this, one ounce fix drachms of concentrated a-
cid are obtained;  and this,  on being mixed with an
equal  quantity  of alcohol,  yields   two  ounces one
drachm and a half of genuine ether.

            § 7.  Of the Acid of Tartar.
                                                      I88j
   Tartar is a fubftance thrown off from wine,  after tartar.
it is put into cafks to depurate.  The more tartar that
is Separated, the more fmooth  and palatable the  wine
is.   This fubftance forms a thick hard cruft on the
fides of the cafks : and, a3 part of the fine  dregs of
the wine adhere to it, the tartar of  the white wines
is of a greyifh white colour, called white tartar ;  and
that of red  wine  has a red colour, and is called red
tartar.                                               886
  When Separated from the cafks on which it is form- Cream of
ed, tartar is mixed with much heterogeneous  matter; tartar.
from which, for the  purpofes  of medicine and  che-
miftry, it requires to be purified.   This purification
is performed at Montpelier ; and confifts firft in boiling
the tartar in water, filtrating the folution,  and allow-
ing the fait to cryftallize, which it very foon does ; as
tartar requires nearly twrenty times its weight of water
to diffolve it.
  The cryftals of tartar obtained by  this operation
are far from being perfectly pure ;  and therefore  they
are again  boiled in  water,  with an addition of clay,
which abforbs  the colouring matter; and  thus,  on a
fecond cryftallization, a very pure  and white fait is ob-
tained.  Thefe cryftals are called cream,  or cryftals
of  tartar;   and  are  commonly fold  under thefe
names.
  Dr Black obferves, that in the purification of tartar,
it is neceflary to add fome earthy fubftances, in order to
abforb or carry down the colour.   Macquer thinks  that
thefe fubftances unite in part with the tartar,  and render
it more foluble, but they have little difpofition to units
with acids ;  they are the purer kinds of" clay,  and  pro-
mote  the complete depofition  of its impurities ;  fo
that in the management of wines it is neceffary to add
certain powrdery fubftances which  have fome weight,
anff fall to the bottom readily ; and which, in 'falling,
carry down a  number of particles  that  would  other-
wife float in the liquor for a long time, being fo light-
that they  could  hardly be made to  fubiide; but  the
particles of clay adhering toihem increafe their gravi-
ty; and  probably  it anfwers the fame purpofe in the
refinement of tartar.
To obtain the pure Acid of Tartar.
887
              .                                        00/
  For a longtime  the  cream or cryftals  of tartar Scheele's
were confidered  as the pureft acid which could be analyfis 06"
obtained from this fubftance ; but, in the year 1770, cream °*
an analyfis of tartar  was publifhed in  the Swedifhtartar-
transactions,  by  Mr  Scheele.   His method  of de-
compofing  the fait  was, to diffolve  it  in a fufficient
quantity of boiling water, then  to add chalk in fine
powder till the effervefcence ceafed.  A copious  pre-
cipitation enfued ; and the remaining liquor being eva-
                                           porated;; 
C   II   E    M   I    S   T    R   Y.
Pradticc.
   S88
Effential
fals of le-
mon.
         prated, afforded a Soluble tartar.   This  proved that
         cream of tartar is not, as was com mo; .ly  luppofed,  an
         acid of a peculiar kind, joined with  a great deal  of
         earthy impurities ; but really  a  compound lilt, con-
         taining  an alkali joined  with an acid ; and that the
         alkali produced from burnt tartar is  not  generated  in
         the fire, but prc-cxiftcnt in the Salt.
            The whole Sediment contained in  this experiment, is
         th.: calcareous earth combined with the acid of" tartar,
         which may j uft ly be called fe Unites tattareus.  If Some
         diluted vitriolic acid is poured upon ihis  felenitcs tar-
         tarcus, the vitriolic acid expels the acid of tartar, form-
         ing a  true felenite  with the earth, while the liquor
         contains the pure acid of tartar.   By  inlpillation this
         acid may be made ftronger, and even formed into  fmall
         white  cryftals, which do not deliquate in the air.   A-
         partienhr fpecies of tartar extracted from forrel hath
         been fold for  taking fpots out of clothes, underthe name
         of effential fait of lemons, and which is now difcovered
         to be the fame with the acid of fugar.
            This experiment was foon  after  confirmed by Dr
         Black ; who farther obServed, that if quicklime was ufed
         inftead of chalk,  the whole acid would be  abforbed  by
         the lime, and the remaining liquor, inftead of being a
         folution of foluble tartar, would be a cauftic lixivium.
         The moft ready method, how c\ er, of procuring the pure
         acid of tartar feems to be that recommended  by Mr
         Schiller in the Chemical Annals for 1787.  One pound
   '      of cream of tartar is to be boiled in five or fix pounds
         of water, and a quartar of a pound  of  oil of vitriol
         added by little and little, by  which means a perfect
         folution will  be obtained.  By continuing  the boiling,
         all the vitriolated tartar is precipitated.   When the  li-
         quor is evaporated to one half, it muft be filtered  ; and
         if, on the renewal of the boiling, any thing farther is
         precipitated,  the  filtration is to  be repeated.   The
         clear liquor  is then to be reduced  to  the confiftence
         of a fyrup, and fet  in a temperate, or rather a warm
         place, when very fine cryftals will be formed, and as
         much  acid obtained as is equal in weight to half the
         cream of tartar employed,   ft  too  fmall a quantity of
         vitriolic acid has been employed,  the  undecompofed
         cream of tartar falls along with the vitriolated tartar.
                      Acid of Tartar combined,
   60.
Solublctar-   I-  With Vegtable Alkali.  If the pure acid of  tartar
tw.      be combined  with this alkali to the point of faturation,
         a neutral fait is produced, which deliquates in the air,
         and  is not eafily cryftallized,  unlefs die liquor be kept
         warm, and likewife be fomewhat alkaline.  This fait,
         called foluble tartar, is ufed in medkine as a purgative;
         but as its deliquefence  does  not  admit ot its  being
         kept in acryftalline form, it is always fold in powder.
         Hence thofe who prepare foluble tartar, take no fur-
         ther trouble  than merely to rub one partof fixed  alka-
         line fait with three of cream  of tartar, which  renders
         the compound fhriiciently neutral,  and anfwers all the
         purpofes of mediednc.  Dr Black informs us,  that in
         medical prefcriptfms, where foluble tartar is ordered
         as a p.irgative  along with a  decoction  oS tamarinds,
         the acid ofthe latter will decompofe the Soluble tartar,
         and  thus the  prefcription may perhaps be rendered  in-
         effectual.  The Saline mixture uSed in fevers is nothing
         but a tartarr.s folubilis in folution.
            According to Mr Scheele,  cream of tartar may be
rccompoScd from the pure acid and alkali in the  fid- Acid of
lowing manner :  " Lpn fixed  vegetable  alkali pour tartar and
a Solution of the acid of tartar,   Continue this till the ,t9fl   '"
tircrvclccncc is over; the fluid will then be tranSpa- -
rent; but if more of the acid is added,  it will become   _
turbid and  white, and fmall cryftals like white Sand R  ncra.
will be formed in it.  ThcSe cryftals arc a perfect cream tcd cream
of tartar.                                          of tartar.
   Upon  thefe principles, another method of decompo-
fing cream of tartar might  be tried;  namely, adding
to it as much oil of vitriol as  would faturate the alkali,
then diflblving and cryftallizing the fait :  bur, by this
method,  there would be danger of the acid being adul-
terated with vitriolic tartar.                            g9I
   II.  With  Foffile Alkali.  The fait produced from an Siegnette'a
union of cream of tartar with foffile alkali, has  been or Rochelle
long known under the names of Siegnette's fait, fal Ru- ^h-
pellenfts, or Rochelle fait; but as the cream of tartar is
now difcovered to be not  a pure acid,  but adulterated
with a portion of foluble tartar, poflibly Some differen-
ces might be obServed iS the pure acid was uSed.
   This falf was firft invented and brought into vogue
by one Seigneitc, an apothecary at Rochelle, who kept
the compofition a Secret as  long as he  could.  Meffrs
Boylduc and Geoffroy  afterwards discovered and pub-
lifhed its compofitioni
   To prepare this Salt, cryftals of mineral alkali  arc
to be diflblved in hot water,  and  powdered cream of
tartar thrown in as long as  any efferveScence arifes;
For the  better cryftallization of the Salt, the  alkali
ought to prevail.  The liquor  muft then  be filtered
and evaporated, and very fine large cryftals may  be
obtained by cold, each oS which is the half'of a poly-
gonous  prifm  cut in the direction of its axis.   This
Section,  which forms a face much larger than the reft,
is, like them, a regular rectangle, diftinguifhable from
the others,  not only by  its breadth, but alfo  by two
diftinct diagonal lines which interfect each other in the
middle.   The  following  method oS preparing  Sieg^
nettc's Salt, recommended by Mr  Scheele, Seems pre-
ferable to any other on account  of its eafe and cheap-
nefs.   Thirty fix ounces of cryftals of tartar are to be
faturated with  potafli, and  eleven ounces of common
fait diffolved in the ley.  VY hen it is grown cold,  and
the vitriolated  tartar has fubfided to  the bottom, it is
filtered and evaporated till a pellicle appears ; the two
firft cryftallizations yield a fine Seignctte's fait  ;  the
third  contains fome  digeftive fait ; and  the fourth is
entirely compofed of it.  The reafon of this formation
ot Seignette's  fait is, that the  vegetable alkali has  a
greater attraction for acids than the mineral, and there-
fore decompofes the fea-fitlt, whofe bafis is then atli^
berry to combine with the acid of tartar ; while the
ftronger marine acid takes the  vegetable  alkali.-—A
fait of the fame kind will be produced by adding Glau-
ber's  fait inftead of common fea-falt.
   III. With Volatile Alkali.   V> ith regard to this com- c
bination, all we know as yet is,  that if  the alkali is
over-faturated  w ith acid,  a  cream  of tartar, almoft as
difficult of  folution as  that of fixed alkali, will be ob-
tained.   When the faturation has been pretty exact, a
beautiful fait,  compofed of four  fided  pyramids,  and
which does not deliquate in  the air, is produced.  It
is inftantly decompounded, and emits  a pungent vola-
tile Smell on being mixed with fixed alkali.
                                                IV,
     %
 ream of
tartar. 
Practice.
CHEMISTRY.
129
   893
Selenitcs
tartareous
   894
A fine
green
•ole>ur.
Acid of      IV. With Earths.  All  that is  as  yet  known con-
tartar and  cerning thefe combinations, is, that with the calcareous
its combi-  earth a compound not eafily foluble in water is form-
nations.    c(jj   The other properties of this fubftance, and  the
          nature of combinations of tartareous  acid with  other
          earths, are entirely unknown.
            V. With Copper.  In its metallic ftate, cream of tar-
          tar acts  but weakly on  the metal, but diflblves ver-
          degris much  more prfectly than  diftilled vinegar can.
          The  folution of cream  of tartar, being  evaporated,
          does not cryftallize, but runs into a gummy kind of
          matter ;  which, however,  does not attradt the moifture
          of  the air.  It readily diflblves in water,  and makes
          a beautiful bluifh  green on paper, which ha&the pro-
          perty of  always fhining,  as  if covered with varnifh.
          The effects of the pure acid on this metal have not  yet
   o      been tried.
Chalybeat-   VI. With  Iron.  The  effects  of  a combination of
sd tartar,  iron  with the pure acid have not hitherto been  fried.
          Cream of tartar diflblves this metal into a green liquor,
          which being evaporated runs per deliquium.  It has been
          attempted to  fubftitute  a folution of this kind to  the
          liquor ufed in printing calicoes formed of iron and four
          beer; but this gave a very dull brownifh colour with
          madder.  Poffibly,  if the  pure acid  was ufed, the  co-
          lour might be improved.   In medicine,  a combination
          of cream of tartar with iron is ufed, and probably may
          be an ufeful chalybeate.
            VH. With Regulus of Antimony.   See Sect.  III.
896
§ 8. Ofthe Acid of Sugar.
Saccharine    Th at Sugar contains an acid,  which  on diftillation
acid.     by a ftrong fire arifes in a liquid form, in common with
         that of moft other vegetable  fubftances,  has been ge-
         nerally known ; but  how to obtain  this acid in a con-
         crete form,  and to  appearance  as  pure and  cryftal-
         lizable as the acid of tartar, we were entirely ignorant,
         till the appearance of atreatife intitled, Difertatio Che-
         mica, de acido Sacchari, auttore Johanne Afzelio Arvidf-
         Son, 4to, Upfalia.
            OS the method of  procuring, and  the properties of,
         this new acid,  we iiavc the  following account  in the
         Edinburgh Medical Commentaries, vol. iv.
            "  1.  To an ounce of  the fineft white fugar in pow-
         der, in  a tubulated retort,  add three ounces of ftrong
         fpirit of nitre.
            " 2.  The folution being finifhed,  and the phlogifton
         of the fpirit of nitre moftly exhaled, let a receiver  be
         properly  fitted to the retort and luted,  and  the liquor
         then made to boil gently.
            "  3.  When the folution has obtained  a brownifh co-
         lour, add three  ounces more of  fpirit of nitre,  and  let
         the ebullition  be continued  till  the fumes of the acid
   g97   are almoft gone.
Chryftals     "  4-  The liquor being at length  emptied in a lar-
of faccha- ger veffel, and expofed to a proper degree of cold, qua-
rine acid, drangular prifmatic  cryftals  are obferved  to form;
         which  being collected,  and  dried  on foft paper, are
         found to weigh about 109 grains.
            "  5.  The remaining liquor being again boiled in. the
         fame retort,  with two  ounres of frefli  fpirit of nitre,-
         till the red vapours begin to difappear, and being then
         in the  fame manner expofed to  cryftallize,  about  43
         grains of  faline fpiculas  arc obtained.
   " 6. To the  liquid that ftill remains, about two Acid of fu-
ounces  more of  Spirit of nitre being added, and afrer-£ar a"" ,t5
wards the whole being, both by  boiling and evaporation,c.om m*~
reduced to  a  dry  mafs,  a  brown,  Saline,  gelatinous  .
kind oS Subftance is produced, which, when thorough-
ly dry,  is Sound to weigh about half a drachm.
   " In the Same manner,  a Similar acid, we are told,
maybe obtained Srom different fitccharine fubflances,
as gum-arabic, honey, ire.; but from none in fuch quan-
tities, or So  pure, as Srom fine Sugar."                   898
   This Salt  poffeffes fome  very  fingular properties,  ofPrefump-
which  what appears to us  the moft  remarkable, andtionofits
which  we  cannot  help reading- with Some  deoree of e,xPe. "5
 ...    ,     t     j          re   r         1 •   thevitno-
doubt, is,  tnat  it  produces an effervefcence  on being,.    •.
added to Such  alkaline, earthy,  or metallic fubftances, as
contain the  vitriolic acid.  From  this we  iliould be apt
to think, that  this acid was capable of diflodging  even
the vitriolic acid from its bafis.
   Acid of fugar,  being diftilled in a  retort, gives over
about -,'„ of  its weight of water.   By an  intenfe heat
it melts, and  is  partly fublimed ;  leaving in  the retort
a dark grey mafs, of about the fifth part of the weight
of the cryftals made ufe of.   The fublimed fait eafily
recovers the cryflalline form, and feems to have under-
gone no fnrther change by fublimation than being ren-
dered more  pure.   During the diftillation  a great quan-
tity of  elaftic vapour ruflies out (about 100  cubic in-
ches from half an ounce ofthe  cryftals), which,  from
■ the diftilled liquor's precipitating lime-water, we may
judge  to be fixed air.   In a fecond fublimation, white
fumes are fent over, which, when cold, appear to  be
an  acid, glaffy-coloured liquor,  but cannot  be again
cryftallized.  "  Such  parts of  the  falts as adhere  to
the fides and  necks of the veffels do not appear to  be
in the  leaft changed in the procefs."  On a third Sub-
limation, theSe  parts  produced Such elaftic vapours as
burft the receiver.                                      g9(J
   This  fingular Salt  has  a confiderable acid power; Great acid
twenty grains oS it giving  a very confiderable degree power.
oS acidity to a large tankard oS water.  Ir diflblves in
an equal weight oS  diftilled water, but  concretes  on
the liquor's growing cool.   It  is  alio Soluble in  Spirit
oSwine ; 100 parts of boiling fpirit of wine diffolving
56 of the Saccharine  cryftals,  but  no  more  than  40
when cold.   The  folution in fpirit  of  wine  foon be-
comes  turbid; and depofues  a  mucous  fediment,  in
quantity about Jv of the acid made ufe of.  When cold,
irregular fcaly cryftals are formed,  which-when dry
are perfectly  white.
   With vegetable alkali,  the acid of fugar can fcarcely
be formed into cryftals, unlefs either the alkali or acid
predominate.  With  mineral  alkali, a fait very diffi-
cult of folution  is  formed.   The quantity of volatile
alkali faturated by this acid is  incredible. " Six parts incredible
ofapure volatile alkali may be faturated with one of quantity of
the acid of  fugar.  The produce  is a  qnadrangularvolatile al-
prifmatic fait. With lime  this acid unites So ftrongly, kalifatura-
as to  be Separable by no other means than a ftrongtecl b>' lt'
 heat.   What kind of  a fait refults from this  combina-
 tion we are not told ;  but the author is of  opinion, that
 this fhows  the ufe of lime in the purification of fugar
 in order to abforb the fuperfluous acid.  Being fatu-
 rated with fome of the terra ponderofa, the acid of fu-
 gar immediately depofits a quantity of pellucid  angu-
 lar cryftals,  fcarcely  foluble in  water.   With rnagne-
                           R                      fta 
CHEMIST
R
Y.
Practice.
   9'i
Its effects
«n metals.
   901
Saccharine
ether.
   9°5
Whether
this acid it
produced
from the
nitrous.
 id 9°3
Th. fame
with t!ie
acid oi l'c:
li.t tlie Silt appears in form of a white powder, foluble
neither in  water nor  Spirit  of wine,  unlefs the acid
prevails.  It has .1  ftronger affinity with magnefia than
any of the  alkaline falts.   With earth of  alum,  no
cryftals are obtained ; but  a yellow pellucid mafs, of
a fvectith  and iomtwhat  aftringent  tafte; which, in
a  moift  air, li(picfie>, and  increafes two-thirds  in
wci [l:i.
   This acid acts  upon all metals,  gold, filver,  platina,
and ijuickfilvcr, not excepted, it  they have been pre-
viously  diffolved   in an acid, and  then precipitated.
Iron  in its metallic  ftate is diflblved in very large
quantity by the Saccharine acid ;  45  parts of iron  be-
ing Soluble in 55  oSacid.  By evaporation, the liquor
flioots into yellow priSmaiic cryftals,  which are eafily
foluble in  water.   With cobalt,  a quantity of  ycllow-
colourt 1  cryftals are obtained,  which being diffolved
in  water,   and fea-falt added to  the  folution,   form  a
fympathetic  ink.   The  elective attractions  of this
lingular acid Lire, firft, lime, than  the  terra poi.de-
rofa,  magnelia,  vegetable alkali mineral alkali,  and
laftly clays.  With fpirit of wine  an ether was  ob-
 tained  which cannot  ealiiy be  fet on fire unlefs pre-
 vioufly heated, and burns with a blue inftead of a white
 flame.
   Towards  the  conclufion of his differtation   the au-
 thor obferves, that fome may imagine that the acid of
 nitre  made ufe of in thefe experiments,  may  have  a
 confiderable  (hare in the  production oS what he  has
 termed  acid of fugar.   But though he acknowledges
 that this  acid cannot in any way  be obtained  but  by
 the affiftance of fpirit of nitre, he is thoroughly convin-
 ced that  it docs not, in any degree,  enter into its com-
 pofition.
   What occurs to us on this Subject is, that if the acid
 really pre-exifts in the fugar, it muft give fome tokens
 of its exiftence by mixing the fugar with other fubftan-
 ces befides fpirit of nitre.   The author himfelf thinks
 that lime  acts upon the acid part of the  fugar: from
 whence  we are  apt to conclude,  that by mixing lime,
 in a certain proportion, with  fugar, a compound fhould
 be obtained fomewhat  Similar to  what was  formed by
 a direct  combination of lime with the pure acid.   In
 this cafe,  we might conclude that the nitrous acid pro-
 duces this fdt, by combining with the inflammable part
 ef the fugar, becoming thereby volatile, and flying en-
 tirely off, fo as to leave the acid  of the fugar pure.   In
 the diftillation of du'eified fpirit of nitre,  however, we
 haw an inftance  of the nitrous  acid itSelS  being very
 in'.:ch altered.   This  muft therefore Suggeft   a doubt
 that theacid Salt obrained in the preSent caSe is only
 the nitrous  acid deprive 1 oS  its phlogifton,  and united
 with Srmc earthy particles.
    In a trc«:ife  lately  pablifhed  by  Mr Righy, how-
 ever, we are informed that fugar itfelf may be recom-
 piled  by  uniting the  acid of"  Sugar with phlogifton;
 which affertion," if well founded, undoubtedly decides
 the difpute in favour of the Saccharine acid being ori-
 ginally contained  in  the  Sugar.   Late experiments
 have determined it to be the Same with  that of forrcl;
" for which, as well as many other val lable acqnifitions,
 the  fcL-nce  of  chemiflry  is indebted to Mr Sci.etlc.
 H.i\ini diflblved as much acid of fuL'ar in  cold water
 as the "liqr.or could take up, he  cdd.d to this .'jlution
fome 1  \i\aim of tart tr drop bv  drop, waiting a  little -\ci<l of
after each drop,  and  fo.nid ilie  mixture,  during the ^t ,oru>
eifei vefcence, fill of Small cryftals, which were genuine ^lllbinatj.
Silt of  wood-Sorrel.  M. Kliprodi having  precipitated ons
a nitrous Solution  of ep.iicklilver wi'h  Salt  of wood- v----„----■>
forrel,  perfectly neutralized by vegetable alkali, obtain-   ;,d 90.1
ed a white precipitate ;  whicli, when  edulcorated and l-ulnuna-
drird,  and gently heated  in  a ua-fpoon, fulminated L'J1^   ~
with  a noife not  inferior to that of  fulminating  gold.
Acid of fugar perfectly neutralized  with vegetable al-
kali, afforded the  fame  precipitate, and fulminated in
ihc fame manner.

          § 9. Of the Acid of Phosphorus.
                                                        904
   This  acid was firft difcovered   by Homberg in phofpho-
urine;  afterwards by Margraaf  in muftard and cruci- ric acid.
ferous plants: IM. B-tchante  difcovered it in wheat;
and laftly, M. Haffcnfratz has  traced it in  the  mineral
kingdom with great attention.—He has found that
 phofphorared iron is contained in all the Pruflian  blues,
when  not purified ; but that  this acid is produced by
the coals employed  in the procefs, and  is no conftitu-
ent part of the tinging  matter.   According  to him  it
occurs almoft univerfally in the minerals of iron which
are found in the flimy ftrata of the  earth, as  well  as
thofe which are undenibtedly  modern, whether primary
or Secondary; unlefs the iron  be fo  far of a  metallic
 nature as to be attracted by the  magnet, or very near
 that ftate.  It is afforded by the ochry  ftrata, and
 thofe  which contain haematites  as well as  the  flimy
kind.   Into thefe it is fuppofed  to have come by the
 decompofition of  vegetables;  and to inveftigate this
 matter he examined  the hibifcus paluftris, Solidago,
 virga  aurea,  antirrhinum,  lunaria,  folanum  nigrum,
 vulgatum,  flachys  paluftris,  artemifia   Zeylandica,
 ruta graveolcns,  lycmpus  Europeus,  carex acuta; vinca
 major,  nepeta  Pannonica,  and noa  Abyflina.  All
 theSe  plants afforded the acid of wood-forrel and the
 phoSphoric acid.   The  quantity oS the  former varied
 from two ounces to two drachms 18 grains of  acid Salt
 containing Some  calcareous  earth,  to two drachms 24
 grains in a pound of each plant; the quantity of cal-
 careous  phofphoric  fait  being   from  one  ounce fix
 drachms 48 grains  to  one  drachm   12 grains.—M.
 Haffenfratz alfo obferves, that the  phofphoric acid  is
 procurable from  all forts of iron ;  though in fome  it
 feems to proceed  from  that contained in the earth, and
 in others from the coals employed in the reduction.
    The  phofphoric acid is alfo  fouud by Dr Marquart
 to be contained  in the  gaftric  juice of animals.   One
 pound four ounces of the  gaftric juice oS oxen  gave 10
 grains of a lymphatic matter, exactly  like the blood
 in its qualities;  i6grainsand  fix-fevenths of phofpho-
 ric acid, which with a blow-pipe was changed  into a
 very  pure  and  deliquefcent glafs of phofphorus; five
 grains oS phoSphorated lime, two grains  oS refin,  14
 grains of fid ammoniac, 29 grains of common  fair,  a
 very  fmall  quantity of an extract  whofe nature was
 difficult  to  afcertain;  one  pound   three  ounces fix
 drachms and 67;  grains of water; fo that the folid
 contents were only  166th  part of the bulk.
    In  ff.eep, the quantity of  gaftric juice  was  about
 eight ounces in  quantity, of a deeper and  brighter
                                               green 
Practice.
CHEMI
   905
Microcof-
mic fait,
Acid of    green  than that of oxen or calves; but affording the
phofphorus fame ingredients,  though  in  a different proportion ;
          though no other acid  than that  of phofphorus could
          be difcovered.  It  was alfo more difpofed  to  putrefac-
          tion.   Calves  furnifhed from  four  to  fix  ounces of
          gaftric  juice, wdiich contained  very little lymph, but
          afforded  fome quantity of dry  jelly, though the whole
          was  not equal to   the proper proportion  of lymph.
          The phofphorated lime was in the uSual quantity, but
          the difengaged phoSphoric  acid in a very Small propor-
          tion.   The lacteal acid was Sound in great  quantity ;
          to which,  along with  that oS phofpherus, our  author
          fuppofes  the property  of curdling the milk in the ani-
          mal's ftomach to be owing.
            The phofphoric  acid has alfo  been Sound in  very
          large quantity  in  the  calcareous  ftones oS Andalufia;
          and Mr  Klaproth  has  Sound the  Same combined  with
          calcareous earth in a kind oS beryl, cryftallized in hexa-
          hedral  prifms, called by M. Verner apatit.—Formerly
          the belt method of obtaining it  was from urine, where
          it is contained in very confiderable quantity in  combi-
          nation  with the volatile alkali,  and forming a fait call-
          ed the  microcof nic, or eftential fait  of urine.
            To procure this, a large quantity of  urine is to  be
          evaporated to the confiftence of a thin fyrup ;  which,
howprocu- being  fet jn a cold  place, will yield,  in three or four
          weeks, foul brown-coloured cryftals, which are  the
          microcofmic  Salt,  mixed with  the marine, and other
          Salts oS urine.  TheSe cryftals are  to be diffolved in
          hot water ;  the folution filtered whilft it continues hot,
          and fet to  cryftallize  again;  and  the Solution, filtra-
          tion, and cryftallization, repeated till  the Salt becomes
          pure and white.  In all the cryftallizations the  micro-
          cofmic  fait flioots firft, and is eafily diftinguifhed and
          feparated from the others.   If the urine which re-
          mains  after the  firft cryftallization be further  evapo-
          rated,  and again fet in  the  cold,  it will yield more
          cryftals ; but browner and more impure than the form-
          er; and therefore requiring to be purified by themfelves.
          From 20 gallons of urine may be  obtained four  ounces
          of pure fait ; a confiderable part  being ftill left in the
          refiduum.
            In  thefe operations the heat  ought to be gentle,
          and the veffels either  of glafs or compact ftone-ware.
          Urine  being evaporated in a copper veflel, afforded on-
          ly a green folution  of that metal.
            Concerning  the  nature of the  microcofmic fait ob-
graafsex- tained  by the  above procefs, Mr Margraaf gives the
periments. f0nowing account in the Berlin memoirs for 1746.
            " Sixteen ounces ofthe fait, diftilled in a  glafs re-
          tort, in a heat gradually raifed, gave over eight oun-
          ces of  a volatile urinous fpirit, refembling that made
          from fal ammoniac by quicklime.  The refiduum was
          a porous brittle  mafs,  weighing eight ounces.  This,
          urged  with a ftronger fire in a crucible, bubbled and
          frothed much,  and at length funk down into the ap-
          pearance of glafs,  without feeming to  fuffer any fur-
          ther diminution of its weight in  the moft vehement
          heat.
            The vitreous matter diflblved in twice or  thrice its
          quantity  of  water,  into a clear,  tranfparent, acid li-
          quor, fomewhat thick,  not ill refembling in confiftence
          concentrated oil of vitriol.   This liquor totally  cor-
          roded zinc  into a white powder,  which, being  diluted
   906
Mr Mar-
   S   T   R    Y.                                  131
with water, appeared in great part  to diffolve, fixed Acid of
alkalies occafioning a plentiful precipitation.  It acted pbofphorui
powerfully upon iron, with  fome effervefcence ; and
changed the metal into a kind of muddy  fubfiance in-
clining to  bluilh, in part  foluble in water like the pre-
ceding.  It diflblved likewife a portion of regulus  of
antimony, and extracted  a red tincture  from cobalt. On
lead and  tin it had  very little action.   Copper it cor-
roded  but flightly.   On  bifmuth,  filver,  and gold, it
had  no effect at all, either by ftrong  digeftion, or  a
boiling heat.   Nor did the adding of a  confiderable
portion of nitrous acid enable  it to act upon gold.
  " The vitreous fait in  its dry form, melted with me-
tallic bodies with a ftrong  fire, acts  upon them more
powerfully.  In each of the following  experiments,
two drachms ofthe fait  were taken to two Scruples  of
the metal  reduced  to fmall parts.    (1.)  Gold com-
municated  a  purple  colour to the vitreous  fait ;  on
weighing  the metal,  however, its diminution was not
confiderable.  (2.) Silver loft four grains, or T'T ; and
rendered  the  fait  yellowifli,  and moderately opaque.
(3.) Copper loft only two grains,  or  ^, though the
fait was tinged of a deep  green colour.  It feemed as if
a portion of the fait  had been retained by the  metal,
which, after the fufion,  was found to  be whiter and
more brittle than before.   (4.) During the fufion with
iron, flafhes like lightning were continually thrown out;
a phofphorus being generated from the combination  of
the acid with the  inflammable principle  of  the iron.
Great  part of the  mixture rifes  up in  froth ; which,
when cold, appears a vitreous fcoria,  covered on the
furface with a  kind of metallic fkin,  which,  on  being
rubbed, changes its green colour to a yellowifli.  The
reft  of the iron remains at the bottom  of the crucible,
half melted, half vitrified,  and fpongy.  (5.) Tin loft
18 grains, or nearly one-half its weight, and rendered
the fait whitifh ; the remaining metal being at tfie fame
time remarkably changed.   It was all over leafy and
brilliant, very brittle, internally  like  zinc.   Laid on
burning coals, it firft began  to melt, then burnt like
zinc, or  phofphorus.   (6.) Lead loft  16  grains, and
gave the  fame whitifh colour to  the  fcorias  that  tin
does. The remaining lead  was in like manner inflam-
mable, but  burnt  lefs vehemently than the tin ; from
which  it  differed  alfo in  retaining  its malleability.
(7.) Mercury  precipitated  from aquafortis,  and  well
edulcorated,  being treated with the fait in a glafs re-
tort, with a fire raifed to the  utmoft, only  12 grains  of
mercury fublimed ; 28 remaining united with the acid,
in a whitifh,  femi-opaque  mafs.   A  folution of this
mixed in  diftilled  water, depofited a qiiantity of a yel-
lowifli  powder ; which, by diftillation in a glafs retort,
was in great part revived into a running mercury.  A
part alfo remained  diffolved in the  clear liquor;  for  a
drop let fall on poliflied  copper inftantly  whitened  it.
(8.) Regulus  of antimony melted with  the vitreous
fair, loft eight or nine grains, (about 1); the regulus
aflhmed a fine, brilliant,  ftriated appearance ;  the fco-
rias were  fomewhat  opaque.   (9.) Bifminh loft eight
grains ; the fcoriae were like the preceding,  but  the
bifmuth itfelS Suffered little change.  (10.) Zinc, mix-
ed with the Salt, and diftilled in a glafs retort, yielded
a true phofphorus, which  aroSe in a very moderate heat.
The refiduum was of a grey colour,  a little mehed  at
                         R  2                   th- 
i  ;2
C   H   E    M    I    S   T   R    Y.
Practice.
A u! v.t'    th-bv:.->:^, in w:liln not e>.Te ling two drachms;  fo
pSofphorut ,hat two fcnples had fublimed.   i his rcfidiium, nyed
*n  ''.'     furthering Imal! Hcfliin crucible to perfect fulion, cum-
tjori,      ie i an intmny of phofphorine flames, witn a kind of de-
>----v----' tonation. T;,e matter, grown cold, looked like the fo-
          ri v  of  m'.tcd glafs.    (ti.)  White arfeme, mixed
          witii this  l.dr,  Separated in  the fire, greatcSt part i-f it
          I i.Aiming, and only as much remaining behind as in-
          crcifVd  the weight of  the  Salt cigbt or nine grains.
          This compound appeared  at firft tranl'p..rent;  but, on
          being expofed to  the air,  became moilt, and of  an o-
          piq ic whitenefs,  much refembling cryflalline arfenic.
          (12.) Cinnabar totally fublimed ; Suffering; no change
          i'leit, and occfioning none in the  Salt.  Sulphur  did
          the Same.   (1 *•)  One  part oS the Salt, mixed with ten
          of manganefe, and melted in a clofe veffel, gave a femi-
          tranSpirent  mafs,  Some parts  of  which  were  bluifh.
          The cruciule was  lined with a fine purple glazing, and
          the edges of the  mafs  itfelf appeared of  the fame co-
          lour.
             " The vitreous fait  diffolved alfo, in fufion, metal-
          lic calces and earths.  Chalk, with one-third its weight
          of  the Salt,  formed a femitranfparent vitreous mafs :
          calcined marble,  with  the  fame proportion, flowed fo
          thin as  to run all  through the crucible ;  gyplum, like-
          wile, ran moflly  through  the crucible ;  what remain-
          ed was SemitranSparent.   Lapis fpecularis  ran entire-
          ly through the vcflll.   Spaml'ii chalk gave a Semitran-
          Sparent  maSs, which Sparkled  on  breaking ;  and fine
          white clay,  a Similar one.   Saxon topaz and flint were
          changed into beautiful opal-coloured  inaiies ; the earth
          of  alum  into a  femitranfparent  mafs, and quicklime
           into  an opaque white one.  The mafs with flints  im-
           bibed moifture from the air ;  the others not.
             '< Oil  of  vitriol,  poured  upon one fourth its weight
           of this fait in a retort, raifed an effervefcence, acquired
           a brownifh  colour, and afterwards became turbid  and
           white.   On railing  the fire, the oil oS vitriol diftilled,
           and  the matter  in  the bottom of  the  retort melted.
           In the  neck was found a  little S.iblimate,  which grew
           moift in the air; as did likewife the remaining  fait,
           which  was opaque  and whitifh.   Concentrated  fpirit
           of nitre, diftilled  with  this  fait in the above proportion,
           came over unchanged ;  no  fublimate appeared ; the re-
           fiduum looked like  glafs of borax.  The diftilled Spirit
           did not  act  in the leaft upon gold, even  by  coction.
           Strong fpirit of fea-falt being diftilled in the fame man-
           ner, no fenfible change was made either in the fpirit or
           the fait.
              " Equal  parts of the vitrified  microcofmic fait and
           fait of  tartar being urged with the ftrongeft  fire  that
           a  glafs retort could bear, nothing fenfible came over,
           nor did  the mixture appear in thin fufion.  Diffolved
           in water, filtered, and duly evaporated, it afforded, very
           difficultly,   oblong  cryftals,  fomewhat  alkaline ;  the
           quantity of alkali having been more than enough to fa-
           turate  the  acid.   A  whitiih  matter remained  on the
           fiber, amounting 10 feven or  eight  grains, from two
           drachms of the  mixture ;  this, after being wafhed and
           dried,  melted before a blow-pipe, as did likewife the
           cryftals.
              " This  fait feems to extricate,  in part, the acids of
           vitriolated  tartar,  nitre, and Sea-Salt,   (i.) On diftil-
           linjr a mixture of it with  an equal quantity of vitrio-
           lated urur, '.'-ere came over fome ponderous acid drops,
   9=7
V \ j. 's the
«;. ■« of *i-
inflated
lortar, ni-
u-e, and
leu-i*.:.
which, Saturated with fixed alkali, formed a neutral fait Acid of
^really  refembling the vitriolated tartar.  The relidu-jlh'j,rh,,r"»
uui readily diflblved  in water, and difficultly cnftalli- ™nib"1B.
zed.  (2.) Nitre, treated with the fame proportion ot ti( ni
i!ie fait, began to emit  red  vapours.   The  refiduum w—v----'
was of a pcich-bloffom cob) n, appeared to In ve inelicd
leSs  perfectly than the preceding, and diliofved nunc
difficuhly in water. The Solution depofited a little earthy
matter;  and, on b< ing flowly  evaporated, fliot into
cryftals, which did not deflagrate in the Srr.  (;.)  Sea-
led t, diftilled in the Same manner, manifestly parted with
its acid ;  the  refiduum was whitifh, readily diliolvcd in
water, and afforded fome cubical cryftals.  (4.) Sal am-
moniac Suffered  no change.   (5.) Borax, with an equal
quantity of vitreous Salt, run  all through the  crucibles.
   " Solutions oS this Salt precipitated  the earthy part
of lime-water, of folution of alum, of flint diflblved in
fixed alkali, and the combination of marine  acid  with
chalk or quicklime.    The  precipitate  from  this laft
liquor is tenacious like glue, and  eleus not  diffolve
even in  boiling  water ; expofed  to  a ftrong fire,  it
froths prodigioufly, and at laft melts into a thick fcoria.
   " Solutions of this fait precipitate alfo Sundry me-
tallic  Solutions;  as  butter  of antimony, Solutions of
filver,  copper,  lead, iron,  mercury,  and bifmuth,  in
 the. nitrous acid ; and of tin in aqua-regis.   The pre-
cipitate of iron from fpirit of fait is a tenacious  mafs ;
 that of filver from aquafortis, fometimes a white pow-
 der, fometimes tenacious.   Copper from aquafortis  is
 fometimes thrown down in  foim of  a white  powder,
 and fometimes  in that of a green oil, according to the
 proportions and dibiienefs  of the liquor.  Silver is not
 precipitated  at all by this acid from its folution in vine-
 gar, nor gold from aqua-regis.
   " An ounce of the vitreous fait,  well mixed with
 half an ounce of foot,  and committed to diftillation,
 yielded a drachm of fine phofphorus.   The black refi-
 duum, being  elixated with  boiling water, at d the li-
 quor paffed through a  filter, there remained upon the
 filter tight fcruples of a black matter ;  and, on evapo-
 rating and cryftallizing the liquor, about feven drachms
 were obtained  of oblong cryftals, which did  not deli-
 quate in  a moift air, but became powdery  in a warm
 one.  Thefe cryftals, treated  afrefh  with inflammable
 matter, yielded no  phofphorus.   Before a blow-pipe
 they melted into a tranfparent globular mafs,  which on
 cooling,  became turbid and  opaque.  Diffolved in wa-
 ter, they precipitated folutions of filver,  mercury, cop-
 per, and of chalk ;  though they did  not  act upon
 the latter fo  powerfully, nor  produce with it  a gluey
 mafs, as  before they had been deprived  of their phof-
 phorine acid."
    Mr  Wiegleb informs us, that  the phofphoric  acid
 exhibits lefs  affinity with calcareous earth, in the moift
 way, than the vitriolic ;  though  it cannot  be Separa-
 ted from the ultimate  refiduum of the calcareous earth
 by that acid.   It expels, however, all the liquid acids
 from their bafis in the dry way.   It  precipitates  iron
 from a folution in   vitriolic acid, of a perfectly white
 colour.  For the ufes of this acid as a flux, fee the arti-
 cle BLOjy-pipe.


              S  10. Ofthe  Acid of Asts.
              y       J            J                     adoo?
    The  acid may be obtained from thefe infects either  Ht.v. pro-
                                                   by  cured. 
Practice.
CHEMISTRY.
combina
tions.
Acid of    by diftillation,  or fimple infufion  in water.   From
phofphorus twenty-Sour ounces of ants, Neumann obtained eleven
    lts     ounces and a  half of acid as ftrong as  good vinegar,
          by diftillation in balneo mariae.  Oi this acid, Mr Mar-
          graaf gives  the following account in the Berlin Me-
   9°8    moirs for  i 749.
Its proper-    «  Tile ac,j 0f ants effVrvefces with  alkaline Salts,
**es'      both  fixed and volatile.   With volatile alkalies it Sorms
          a  neutral liquor, which, like  that compofed ofthe fame
          alkalies and vinegar, yields no concrete Silt on distilla-
          tion.   With  fixed alkalies it concretes,  upon proper
          exhalation, into oblong  cryftals,  which  deliquate in
          the air.   The cryftals,  or  the  Saturated neutral  li-
          quor  uncryftallized,  on  being  diftilled  with a fire
          increafed  till   the  retort began  to melt,  yielded, a
          liquor  fcarce  fenfibly acid,  and afterwards a Small
          quantity of an  urinous and  partly ammoniacal liquor.
          The  remaining black matter,  diffolved  in  diftilled
          water, filtered and  evaporated, fhot into large cryftals
          which did not deliquate in the air,  though they were
          in tafte  ftrongly alkaline, effcrvefced with  acids,  and
          had  all the other properties by which fixed alkaliesare
          diftinguifhed.
             "  This acid diflblves, with  great effervefcence, coral,
          chalk and quicklime; and concretes with them all into
          cryftals which do not deliquate in  the air.
             " It does not precipitate filver,  lead,  or mercury,
          from-the nitrous acid ;  nor  quicklime  from  the ma-
          rine.  Hence it appears to have  no analogy to the ma-
          rine  or  vitriolic acids;  the  firft of which conftantly
          precipitates the metallic folutions, and  the other the
          earthy.
             " It does not  act  upon filings of filver; but (like
          vegetable acids), it totally diflblves, by the affiftance of
          heat, the calx of filver precipitated from aquafortis by
          fait of tartar.
             *' It does not diffolve  calces of mercury,  (as vege-
          table acids do)  ; but revives them into running quick-
          filver.
             "  It acts  very weakly upon filings of copper; but
          perfectly diflblves copper that has been calcined.  The
          folution yields beautiful compact green cryftals.
             "  It diflblves iron-filings  with violence ; the folu-
          tion dnly evaporated,  fhoots  into cryftals more readily
          than that made in diftilled vinegar.  It Scarcely acts at
          all upon filings of tin.
             "  It does not, according to Mr Margraaf, corrode
          filings of lead; but diflblves, by the affiftance of heat
          the red calx of lead.  The folution  cryftallizes into a
          faccharum faturni.   In Mr Ray's philofophical letters,
          it is faid,  that lead put into the acid fpirit, or  fair wa-
          ter,  together with  the animals themfelves,  makes a
          good faccharum faturni; and  that this faccharum, on be-
          ing diftilled  will  afford  the fame  acid  fpirit again,
          which the faccharum faturni made with vinegar will
          not do, but returns an inflammable oil  with water,
          but nothing that is acid;  and faccharum faturni made
          with  fpirit of verdegris  doth the fame in this refpect
          with the fpirit of pifmires.
            "  It diflblves zinc with vehemence, and flioots, up-
          •n due evaporation, into inelegant cryftals,  not  at  all
          like  thofe  produced with diftilled vinegar.  On bif-
          muth,  or regulus of antimony, it  has little  effect, ei.
          ther  when calcined or in their metalline ftate.
§ n. Of the Acid of Amber.
     l33
Acid of
amber and
its combi-
nations.
  The nature of  this acid is as yet but little known,
and  Mr Pott is the only chemift  who  fcems to have
examined it with accuracy.   We fliall  therefore give
an abstract of the principal observations  and  experi-
ments he has made on this fait.                          909
  "  Salt of amber requires a  large quantity of water Mr Pott'
for  its  folution.   In the  firft  cryftallization  (being cxPen"
much impregnated with the oil  which rifes from the ments-
amber along with  it), it fhoots into Spongy flakes,  in
colour  refembling  brown  fugar-candy;  the cryftals
whicli fucceed prove darker and darker  coloured.  On
repeating  the depuration,  the cryftals  appear at  top
of a clear  yellow or whitifh colour,  in form  of  long
needles or  feathers;  at bottom, darker, and more ir-
regular, as are likewife the cryftals which fhoot aSter-
wards.  The  cryftals neither liquefy nor become pow-
dry in the air:  rubbed, they emit  a pungent fmell like
that of radifhes, efpecially  if warmed  a little;  their
tafte is acid, not in the leaft corrofive, but with a kind
of oily  pungency.
  "  This fait, kept in the heat of boiling water, lofes
nothing of its  weight, and  Suffers no  alteration.   In a
great heat  it  melts  like oil ;  after which a little oily
acid arifes,  then oily ftrise  appear in the lower part of
the retort,  and the fait fublinies into the neck,  partly
in the form of a dark yellow butter,  and partly  in
that of feathers, a  black  coaly matter  remaining  at
bottom ;  fo  that, by this procefs,  a part of  the fait is
deftroyed.
  "  Oil of turpentine has  no action  on  this  fait.
Highly rectified fpirit  of  wine gains from it a yellow
colour in the cold; and,  on the application of  heat,
diflblves  a  confiderable quantity, but depofites  great
part of it on cooling.  The fait thus depofited is fome-
what  whiter  than before, but  ftill continues fenfibly
yellow.  The dulcified fpirit of fal ammoniac diflblves
it readily, without  effervefcence, into a yellow liqour;
if the fait was foul,  the folution proves of a red co-
lour; on burning of the vinous fpirit, a neutral liquor
remains.
  "  A  folution of fait of amber in water, faturated
with a pure alkaline lixivium, yielded,  on infpiffation,
a  Saline matter,  which would not  cryftallize,  anel
which  when exficcated by heat, deliquated in the air,
leaving a confiderable  proportion oS an earthy, unc-
tuous matter.   Being again gently  inSpiffated,  it left
a brownifh  fait very foluble, weighing one half more
than the fait of amber employed.   This fait effervef-
ced with the  vitriolic  and nitrous acids : the vapour,
which exhaled,  was not acid, but oily and fulphureous.
On repeating the experiment, and fully  faturating the
alkali with the fait of amber,  the neutral fait made no
effervefcence with thefe acids.   This fait did  not per-
fectly  melt before a blow-pipe; continued  in  the fire
for fome time, it  effervefced with aquafortis.   In dif-
tillation it  yielded a bitter,  oily, alkalefcent  fpirit,
much refembling the fpirit of tartar ; and towards the
end, an  empyreumatic oil.   The refiduum elixated,
yielded the  alkaline fait again of a brown colour.
  tl  Salt of amber  effervefces  ftrongly with  volatile
alkalies; and, on Saturation,  forms with them an oily
                                                am- 
C    H   E    M   I    S    T   R   Y.
Practice,
   9ii
Purified by
the marine
acid.
   911
F.ffcds of
fpirit of
i.itre on it.
   9»3
Of oil of
vitriol.
   9'4
Of qnic!<
Clver.
■ mmv.'.:.;c.:l liquor, w'««ch, in diftillation, totally arifes
in a :in i  tsim, except that a fmall  portion of a pt-
ncii.it:ug, oily, Saline matter, concretes towards  the
end.
   " On  diftilling fait of amber with an equal q lanti-
ty  ot  common  fal  ammoniac, a  marine acid fpirit
tame over, of a ftrong fmci,  and a  brown  colour:
afterwards, a  little white fal ammoniac fublimed; at
length  arofc  fuddenly a large quantity of a  fuliginous
or bituminous matter, leaving behind a fmall  portion
ota like  ihining black fublLucc.   The cojly  matter
was confiderably more in quantity than the  fait rf am-
ber  employed.   On Heating it with  nitre,  red va-
pours  arofe,  and  the  mixture  detonated  with vio-
lence.   A mixture of it with borax, frothed and fuell-
ed up much more than borax by  itfelf; and,  on rai-
ling the fire, yielded only fome  oily drops ;  the acid
being  deftroyed by  this fait, as  by fixed alkalies and
qiicklime.
   " Spirit  of  fea-falt, poured  npon  one-fourth  its
weight of fait of  amber,  made  fcarce any folution  in
the cold :  on the application of heat, nearly the whole
coagulated into the confiftence oS  a jelly.   In  diftilla-
tion, the  Spirit of fait arofe  firft ; then almoft the whole
ofthe  fait of amber,  partly  like firm butter, partly like
long filiated plumous alum,  very pure, and of a fine
white  colour,  its oily  matter being  changed  into  a
coal at the  bottom.   The fait, thus purified, makes
no precipitation in  the folution  of Silver,  and conse-
quently retains nothing of the marine acid ; nor does
it precipitate Solution oS quicklime made  in Spirit oS
fait, and  confequently  contains nothing vitriolic.  If
any ot  the mineral acids was  contained  in  this fait,  it
could not  here tfcape difcovery ;  ihe oil, which in the
rough  fait is fuppofed to conceal the acid, being in this
procefs Separated.
   "  Aquafortis being  poured  upon one-founh  its
weight of fill  of amber,  extracted a yellowifli colour
from it in the  cold,  but diffolved  little : on the appli-
cation of  heat,  the whole diflblves  into a clear  liquor,
without any coagulation : if the  fait is very oily,  the
folution proves red.   In diftillation, the greateft part a-
rifes in a  liquid  form, with only a  very  fmall quantity
of  concrete  Silt.   The Spirit does not act upon gold,
butditfdves filver, and quickfilver, as at lirft ;  a proof
that it has received no marine  acid from the  fait of
amber.
   " Oil of vitriol being added to twice its weight of
fait of amber diluted with  a  little  water, a moderate
fire elevated  an acidulous,  liquor, which  appeared to
proceed   from  the fait of  amber; fen-  its making no
change in  folution of  fixed fal  ammoniac, fhowed  it
not to  be  vitriolic.  On continuing the diftillation  by
a ftronger fire, greateft part of  the  fait  arifes undc-
ftroyed^ and the oil  of vitriol along with it;  a black,
light,  porous earth remaining.
   <• Kq:ial  parts of quicklime and  fait of  amber gave
over in diftillation  only an acidulous phlegm ; the refi-
duum,  e  ixned  with water,  yielded  a folution of the
liiv.t in the acid of amber,  refembling a folution  ofthe
fame earth in vegetable acids, precipitable by  alkaline
falts, and by the viniolic arid.  Lime, added to a wa-
tery Sol it ion of  Salt oS  amber,  diflblves with fome ef-
luvcf-cncei after which, the whole coagulates into
the confiftence of a jelly:  this, diluted  with water, Acid <>f ar-
proves fimilar to the  foregoing folution.               feme and
  "  Solution  of  fait  of amber makes no precipitation |U c°™°1'
in folution of Silver or  quickfilver.  It diflblves  /.incT .   J'   .
as all acids do : fixed alkalies precipitate the zinc:  the    915
volatile do not; and  when a Sufficient quantityof  the 1-fficK of
volatile has been added, the  fixed make  no prccipita-*"a,t of ;"''"
tion.   It  acts exceedingly flowly and difficultly upon  """
copper; but corrodes calcined copper in a lhorter  time.
It foon corrodes iron, by coction,  into a  crocus, and
diflblves  a part into a  liquid  form :  the  folution  has
little  colour;  but alkair.e falts readily difcover that
it holds iron,  by  rendering it turbid and  whitifh, and
throwing down a confiderable quantity of a greenifh
calx."
§ 12. OftheacidofARSESic.
916
  Mr Scheele firft perceived, from  fome experiments How firft
on manganefe, that arfenic contained phlogifton :  from difcovered.
whence he  was  led  to an analyfis  of this fubftance,
which produced an acid of a very  fingular kind;  by
uniting  of which with  phlogifton  in certain propor-
tions, either white arfenic or its regulus may  be  com-
pofed at pleafure.                                       917
  White arfenic  may  be decompounded in two ways.Two ways
1. Put two ounces of it  reduced to a fine powder in a °f decom-
glafs mortar into a retort of the fame materials;  pour P°«ndinS
upon it feven ounces of pure muriatic acid,  whofe fpe- ar cmc'
cific gravity is to that of water as 10 to 8 ; and lute on
a receiver.   The arfenic is quickly diffolved in a  boil-
ing heat, which mult be  brought on as quickly as pof-     rg
fible.  After the  folution is accomplifhcd, while the \\y mean«
liquor is ftill warm, three ounces and a half of nitrous of nitrou*
acid,  of  the fame fpecific gravity  with the  muriatic acid,
above-mentioned, is to be added, and the  liquid which
had already gone over into the receiver  poured back.
The receiver is then to be put on again, but not luted ;
the mixture foon begins  to effervefce, and red vapours
g« over into the receiver.  The diftillation is to be con-
tinued  till  thefe  vapours ceafe;  when an  ounce of
finely powdered arfenic is again to  be added, the re-
ceiver  applied  as before, and a gentle ebullition con-
tinued till the fecond quantity of arfenic be diffolved.
An ounce and an half of nitrous acid is then  to be
added, and the mixture diftilled to drynefs, increafing
the fire  towards the end,  fo as to make the retort reel
hot. Theacid which comes over into the receiver may
Serve again Several times.  The white maSs which re-
mains in the retort is the dry acid of arfenic.   It may
be  reduced to  a  liquid  form  by pouring  upon  it, in
coarfe powder, twice its  weight  of  diftilled  water, and
boiling  for a few minutes, pouring  back the liquor
which comes over,  and  afterwards  filtering  the folu-
tion through blotting paper, which has  been previoufly
wafhed in hot water.
  In this procefs the nitrous  acid  attacks the  phlo-
gifton  of the  arfenic, is volatilized in confequence of
its  union with it, and leaves the more f:xed but lefs
powerful acid of  arfenic behind.   The  nitrous acid
would alone  be Siflicient Sor this ptirpoSe, could  it ac-
curately  come into contact with the particles oS arSe-
nic; but this cannot be  done  witthout  Solution, and
the nitrous acid is capable ©f diffolving arScnic only  in
                                               pro- 
Practice.
CHEMISTRY.
l3S
   919
I>y dephlo-
gifticated
fpirit of
fait.
   920
Acid of ar-
fenic equal-
ly poifon-
ous with
the white
arfenic it-
felf.
proportion to the water it contains.   Too great a quan-
tity would  therefore be required were this  acid to be
ufed by itfelf";  but  by  the ufe of muriatic acid for  the
folution, a fmaller  quantity of  fpirit of nitre is admit-
ted to intimate contact with all  the arfenical particles,
and has an opportunity of depriving them of  their phlo-
gifton.  Aqua-regia might be poured upon the arfenic
at  once; but the greateft effervefcence it excites would
throw  the  mineral up to the top in fuch a manner  that
the menftruum could not act upon it.   By  the  opera-
tion of dephlogiflication,  arfenic  loSes  a  fifth part,
which is fuppofed to be pure phlogifton.
   The other  method  of  decompoling arfenic  is, by
means of the dephlogifticated fpirit  of  fait.  For this
purpofe, take one  part of  powdered manganefe, and
mix it with three of the muriatic acid above-mention-
ed.  Put  it  into'a  retort,  of  which it may fill one-
fourth ; a  receiver containing one-fourth of powdered
arfenic, with one-eighth of diftilled water, is to be luted
on, and the  retort put into a fand-bath.  The dephlo-
gifticated muriatic  acid,  going over into the receiver,
is  inftantly abforbed by the arfenic ;  which  fome hours
afterwards will be diffolved, and two  different  liquid
ftrata, which cannot be mixed together,  will be per-
ceived in  the receiver.   This folution is now to be  put
into a clean  glafs  retort,  and diftilled to drynefs ;  in-
creaiing the  fire at laft to fuch a degree as  to make
the whole  red hot : and in  this procefs  alfo two dif-
ferent liquids pafs over into the receiver which  do  not
unite together.
   Here the manganefe  attracts the phlogifton  of  the
muriatic acid ; and as this dephlogifticated acid has a
very  ftrong  attraction for phlogifton, it  deprives  the
arfenic of  its phlogifton, and thus recompoSes the  or-
dinary  phlogifticated muriatic  acid.  This  portion  of
recompofed acid diflblves part of the arfenic, forming
with it what is called butter of arfenic.  The other part
of the arfenic which has been decompofed,  diflblves in
the water, and forms a liquid  fpecifically lighter than
the butter, and therefore  Swims above it.  On recti-
fying  the  two liquids,  the undecompoSed  portion  of
the arfenic arifes along with  the muriatic acid, and
goes over  into the  receiver in  form of an  heavy  oil,
while the acid  of arfenic remains behind in  the  retort.
The acid obtained  in this  way is precifely the fame
with the former, and one would hardly believe  that it
is  an acid,  becaufe it has no acid tafte ;  but  after fome
days it grows moift in the air,  aud at  laft  deliqnates,
alfuming the appearance of oil of vitriol.  As the  de.
liquefcence,  however, is very  flow, it is proper  to dif-
folve it in  a  certain quantity of water, when a fmall
quantity of white  powder  remains undiffolved, after
preparing it by the firft procefs, which is filiceous earth
derived from the retort.   This  ought to  be carefully
feparated from the acid by  filtration ; and in order  to
prevent the  glue  of the  blotting-paper from mixing
with the acid, it  was directed  to walh  the  filter wkh
hot water previous to the operation.
   The firft experiment  M. Sc'recle  tried  on this acid
after he had obtained it, was to difcover  if it was  as
noxious to animals as when combined with  phlogifton.
Having mixed  a little with honey, the flies  that eat of
it  died in an hour ; and eight grains reduced a cat to
the point  of death in two  hours.   Some milk, how-
ever,  being then given to the animal, it vomited vie-Acid of
lently, and  ran  away.                               arfenic and
  2. An ounce of dry acid of arfenic,  heated in a fmallIts c_orn"lm
phial  to near  the point of ignition,  melts into a clear t  nJ'   ,
liquid, which congeals when cold ; but if the heat be   921
increafed till the veffel begins to melt, the acid begins Eafily re-
to boil,  refumes its phlogifton,  and arfenic fublimes infumes'ts
greater quantity as  the heat is longer continued.  Af-Pblogilton.
ter Subjecting the acid to this violent  heat in a retort
for an hour, the veffel melted, and the  acid had rifen
up as high as the neck.
   3.  In a  crucible  the arfenic attracts  phlogifton in
greater quantity, and is entirely diflipated in arfenical
vapours ; a little clear and difficultly fufible glafs, con-
fifting of clay and the acid of arfenic, remaining in the
crucible.                                               ^22
   3.  With  powder of charcoal the arfenical acid un-Takesfire
dergoes no change ; but if the mixture  be  put into a and fub-
retort, the moifture all driven off, a receiver then luted limes cn:n>
on, and the heat increafed till the bottom ofthe retort0
becomes red hot, the whole  mafs  takes fire  with  vio-
lence ; all the acid is reduced,  and fublimed into the
neck of the retort; a fhining regulus is obtained, mixed
with  a little arfenic and charcoal duft.   A  few drops
of water are found in the receiver, but they do not
contain a particle of acid.                                0I»
   4.  The arfenical acid, after  fome days digeftion Appc*r-
with oil of turpentine, unctuous oil, and fugar, becomes ance wifb
black and thick.   If fome muriatic  acid  be diftilled oll°? tur"
from  this, a little nitrous  acid added, and the  diftilla- P^ntine>
tion repeated,  fome acid of arfenic is left behind. Spi-
rit of wine undergoes no change either by digeftion or
diftillation with arfenical acid.                           024
   5.  Six parts  of  acid digefted  with one  of Sulphur With ful-
fnffer no change ; but when  the mixture is evaporated phur.
to drynefs, and  then Subjected  to diftillation in a glafs
retort, the two unite  with great  violence at  that de-
gree of  heat in which fulphur  melts; and  the whole
mafs rifes almoft in the fame inftant,  in  form of a red
fublimate ; a little  fulphureous acid  in  the mean time
going over into  the receiver.                            a2s
  6.  Acid of  arfenic, faturated with  vegetable fixed Combined
alkali, forms  a  deliquefcent  fait which  does not cry- whh  vege-
ftallize, but turns fyrup of a violet  green,  though  jt table fixed
produces no change  on  the tincture of lacmus.  On      '
the addition of a little more acid, however, when  it
reddens lacmus, but makes no alteration on  the fyrup
of violets, the liquor will afford fine  cryftals like Mr
Macquer's neutral fait of arfenic.  On keeping this fait
for an hour in  fufion in a crucible covered with another
luted  upon it,  the infide  of  the veflel was found co-
vered with a white glazing, and a fait remained, which
was ftill the  fame arfenicated Salt with exceSs of acid.      020*
   7.  On diftilling this fait in a  retort with an  eighth- This fait
partof charcoal-duft, it  began to boil  very violently decompo-
as foon as the  retort became  red-hot,  and a  very  fine^^y
regulus  of arfenic  fublimed.   The black  refiduum charccaL
contained the alkali entirely Separated Srom the arfeni-
cal acid.                                                92?
  8.  With  mineral alkali the acid  of  arfenic forms Combined
cryftals  when  perfectly neutralized, but not if added with mire-
to excefs.   In  that cafe,  the mafs becomes deliquef-ral alkali-
cent  like the former when neutral.                         g
  9.  With  volatile alkali  a  fait much refembling the With vol?.-
                                                tWO Ida alkali. 
~f\
C    H   E    M    I    S    T   R   Y.
Practice.
   9*9.
Expels the
■cid of vi-
t  ioliited
t >rtar by
dry diftilla-
t.ull.
   9.i ^
Acid of
i.itre ;

   931
Of com-
mon fait.
   93*
Phenome-
na with fal
ammoniac.

   633
Decompo-
1. - r,u-
thum pon-
derofum
and gyp-
fa ni.
   634
Cannot ex-
y 1 the
r'.'i r acid.
   635
Precipi-
tates lime
water
   636
Phenome-
na with
   93"
Wi:h mag'
ucfia.  •
 two former is  produced.   It  docs  not change  l.i.-mus,
 bin turns the fyrup of violets  green.  A  gentle  heat
 drives off part of its volatile alkali, and leaves the re-
 mainder  Sine:faturated with  acid ;   in  which cafe it
 fhoots iHto  long radiated and deliquefcent  cryftals.
 Thefe, urged  by a ftronger he;:, part with the whole
 of their  alkali,  which is partly  decompofed ;  fome
 arfenic is formed by  the union of the phlogifton  of
 the alkali with part of the arfenical acid ;  the remain-
 der of which affumes a milky colour, and lies in the
 bottom of the* re tort.
   10. Acid of arfenic  diftilled  with  viiriolated tartar
 expels the vitriolic acid in a violent heat, which comes
 over in a concentrated but fulphureous  ftate,  leaving
 the arfenical fait formed of the acid and  alkali united.
 With Glauber's fait the vitriolic acid alfo riSes, and with
 leSs beat  than  when vitriolated tartar  is made uSe of.
   11. One part of nitre diftilled with three of acid  of
 arfenic,  yielded a  fpirit  of  nitre, together with the
 neutral arfenical fait already mentioned.
   12. One part of common fait with  three of arfeni-
 cal acid,  yielded fome fmoking part of fait.   The re-
 fiduum diffolved  in water gave cryftals of  common
 filt,  and  a thick magnum, which would  not  cryftal-
 lize till the fuperfluous arfenical acid  was  taken away
 by adding powdered chalk, when  it  yielded  cryftals
 fimilar to thofe produced by the acid and  pure alkali.
   13. With fal ammoniac the product was  firft fuming
 muriatic acid,  then volatile alkali in a liquid  ftate, af-
 ter that arfenic,  and  laftly part of the arfenical  acid
 remained in the retort.
   14. Sjuthum  pondcrofum,  and  gypSum, both part-
 el with their acids, which were become Sulphureous.
 The  former did not yield its  acid till the retort be-
 gan to melt.
   15. One part  of fluor mineral was  mixed with  four
 of acid of arfenic. and diftilled into a receiver having
 a  little v  ucr in it.  When the retort grew  red-hot,
 firt a y. bow and then a red Subftance  fublimed.  Some
 fn'phiirco.is acid,  bur none of the  acid of  fluor, went
 over.  A grey-coloured refiduum was left in the retort;
 which being divided  into, two parts,  one  was  mixed
 wi'h charcoal-powder and diftilled with  a  ftrong  fire,
 without  the production of cither arfenic or regulus ;
 the other was  mixed with four parts  of acid of arfe-
 nic,  and  fubjeeted to a fecond diftillation.  When the
 mafs grew dry, a little yellow fal ammoniac  was  fub-
 limed, and the water was covered with a cruft of  Sili-
 ceous earth, as in the ufual diftillations of that  mineral.
   16. Arfenical acid  precipitates lime-water, by  uni-
 ting  with the calcareous earth diffolved in  it.   By the
 addition of more acid,  the precipitate is diffolved,  and
 the  liquor yields Small cryftals, which let fall a Sele-
tiiteon the addition of vitriolic acid.
   17. On the addition of powdered  chalk to  arfenical
 acid diluted with water, the  earth is  at firft diifidvtd,
 but by adding  more chalk the whole  is coagulated in-
 to fmall cryftals.
   iS. Magnefia  dilfolves in the arfenical  acid, and the
 folution coagulates when  it comes to tie point of Satu-
 ration.   On diflblving  the coag'.dum in a larger quan-
 tity of warer,  it  becomes gelatinous  by evaporation ;
 and if the jelly be lixiviated with water, filtered,  and
 cv-pirarcd,  a  >;;..d mafs rcina:ns,  whiea refuScs  to
 crv ft-! i.zc.
   19.  Earth of alum precipitated by alkali of tartar, Acid of ar-
is eafily foluble  in arfenical acid,  and coagulates as {emc Wld
foon as it arrives at the point of faturation.  Evapo-,tH conil>1"
rated to drynefs, mixed with  fome charcoal powder, ,__'ZJl__,
and then fubjeeted  10 ftrong diftillation,  a little yellow   ,,\t
fublimate arifes into the neck ofthe  retort,  as likewife With earth
Some (hilling regulus, while a volatile Sulphureous acid of a,um-
pules over into the receiver.   The  refiduum diflblves
with diificulty in the vitriolic acid,  though  Some cry-
ftals of alum will form in the (pace of two months.       „,,,
   20.  four  parts  of  arfenical acid mixed with  one Withwhite
of powdered white clay,  did not diflblvc any part  by clay.
rbgeftion for a fortnight.   By  diftillation  in a  retort
till the veffel began to melt,  it was converted into a
thick flux, and  a little arfenic Sublimed.  By mixing
the refiduum \\ iih a little powdered charcoal, a fhining
regulus was fublimed.                                   040
   21.  Terra pondeiofa diffolves readily  in theacid of with terra
arfenic,  but precipitates again as foon as  it has attained ponderofa.
the  point  of  Saturation.   The  Solution   is  precipi-
tated by acid of vitriol, and forms  regenerated  pon-
derous fpar.                                            04i
   22.  Gold is not adted upon by acid of arfenic, either With gold.
by digeftion  or otherwife ; nor is its folution  precipi-
tated,  though the retorts ufed in the operation were
(tained with red and yellow Spots, which could  not  be
taken off;  nor is its action increafed by  mixture  with
muriatic or with nitrous acid.                            g.t
   2?.  Pure platina is  not acted upon.  Its folution Platina.
is not precipitated  by the pure arfenical  acid,  but rea-
dily by the arfenical falts.   The precipitate is yellow,
and diffolves in a large quantity of water, hut contains
no mark of arfenical acid.  Addition of muriatic or of
nitrous acid makes  no change in its effects.               043
   24.  Pure filver is  not  acted  upon by the arfenical Silver.
acid  in  digeftion.   On augmenting the fire till the
acid melted,  and keeping up  this degree of hen for
half an hour,  the metal diffolved, and on breaking the
retort,  a colourlefs glaffy mafs, nearly tranfparent, was
found  in it ; the retort being covered  with a flame-
coloured glazing, which could not be Separated Srom
it.  By a great degree oS heat  the Silver was reduced
without addition.   Solution of^filver is precipitated by
pure acid  of arfenic,  but  more  effectually  by  the
neutral arfenical  falts : the precipitate is of" a brown
colour,  and by digeftion in  muriatic acid is changed
into lunea cornea ;  it is alfo foluble in  fpirit of fal am-
moniac prepared with  quicklime.   The  action  of the
arfenical acid  upon filver  is confiderably increafed  by
mixing it with fpirit of fea-falt ; the former attacking
the phlogifton of the metal,  while  the  latter attacks
its earthy bafis.                                         044
   25.  Quickfilver is not acted upon by  digeftion with Quick-
arSenical acid.  On putting the mixture into a retort, fib'tr.
diftilling to drynefs, and then increafing the fire, the '
mafs becomes yellow, quickfilver rifes  into the neck of
the retort,  with  a little  arfenic.  and fome yellow fubli-
mate ; but though  the fire was augmented  till the re-
tort began to melt,  the n afs could not be fifed.  Three
drachms and an  half  ',,f quickfilver  were obtained out
of fix employed in the experiment;  the  arfenical acid,
thcreSore,  contained two and an half.    The mafs was
fomewhat yellow :  it diffolved  veiy readily  in muriatic
acid, but Scarcely at all in the nitrous or vitriolic ;  on
evaporation to drynefs and  diftillation, Some corrcfivc
                                           fublimate 
Practice.
CHEMISTRY.
l37
   945
With cor-
rofive fub-
limate.
   946
Dutter of
arfenic is
not obtain-
ed by this
procefs.
   947
With cop-
per.
   948
With iron.
   949  ,
With lead,
fublimate rofe into the neck of  the  retort ;  the refi-
duum, melted in a very ftrong fire,  proved to  be acid
arfenic.  Another portion of  the mafs,  diftilled with
two  parts  of  common fair,  yielded  corrofive fubli-
mate.
  26.  Acid of arfenic diftilled with  corrofive fubli-
mate  undergoes no  change;  but  by fublimation wirh
mercurius dulcis, a   corrofive fuhlimate is  obtained.
Some have  afferted, that by fubliming arfenic with cor-
rofive fublimate,' a butter  of  arfenic is obtained ;  but
Mr Scheele informs us that this is a miftake; and that
by diftilling this mixture,  he conftantly  obtained cor-
rofive Sublimate at firft, and arSenic afterwards.   With
regulus  of arfenic,  however,  a fmoking  butter of
arfenic,  mercurius  dulcis, anel  finnc quickfilver,  are
obtained.  The Same  thing happens with a mixture of
orpiment and corrofive Sublimate.
  27.  ArSenical acid  diflblves copper by  a  digesting
heat.   The Solution is of a green colour : a quantity of
light blue powder  is  depofited, and  attaches itfelf to
the copper.   This powder confifts oS  the acid  oS arSe-
nic and calcined copper.   On  mixing two parts of  dry
acid of arfenic, in fine powder, with one of  filings
of copper,  and diftilling the mixture,  fome  arfenic
*ofe  into the neck,  and  the  mafs melted and turned
blue.   On  boiling it  with water, the folution was fi-
milar to one  made directly from acid  of arfenic  and
copper.  A little  copper  remained in  the  bottom of
the retort,  which  was tinged with  brown, red,  and
yellow fpots, infoluble in  any  menftruum.  The folu-
tions  of  this  metal  are not  precipitated by arfenical
acid,   but  the acetous folution is.   Neutral arfenical
falts throw down a blue precipitate, which  by expo-
fure to a  ftrong fire, turns brown and covers  the infide
of the containing veffel with  a yellow  enamel.  On
mixing the fcoria in  a fine powder with a little lamp-
black, fome fine regulus of arfenic fublimed, and  the
copper in the refiduum was reduced.
  28.  With iron the  acid of arfenic  forms a gelati-
nous folution,  which by expofure to  the air grows fo
thick that in two hours time it  will not  flow out  at the
month of a .phial.   With alkali  of tartar  a  whitifh
green powder is  thrown  down; which  being  edulco-
rated and diftilled in a glafs retort, yields fome arfenic,
and leaves  a  red ochre  behind.   On  diftilling four
parts  of arfenical acid with one oS iron  filings, the maSs
efferveSced ftrongly towards the end;  and when it be-
came dry,  took fire in the retort upon increafing the
heat, when both  arSenic  and  regulus of arfenic were
fublimed.  The refiduum was black, friable, and con-
tained but little acid of  arfenic ;  the retort was co-
vered  with yellowifli brown  fpots.   Solutions of iron
in mineral acids are not precipitated  by  acid of arfe-
nic,  but  the acetous  folution  lets fall a  dark   brown
powder.    All  the  folutions  are .precipitated  by  the
arfenical neutral falts, the precipitates by a  ftrong
fire, converted into  black fcoria^; which mixed with
powdered charcoal,   and  calcined,  yield  copious va-
pours of  arfenic, and  are  afterwards attracted  by the
magnet.
  29.  Lead digefted  with arfenical acid  turns black
at firft, but in a few days  is furrrounded  with  a light
greyifh  powder,  containing fome arftnic  which may
be Separated by fublimation.  O \  diftilling one  part
of fhavings of lead with two  of dry acid of  arfcnicf
95«
the lead  was diflblved,  the  mafs flowed clear,  and a Acid of
little  arfenic  rofe into the ntck of the  retort.  A arfenic and
milky glafs was found  in  the  bottom, which by boil-
ing in diftilled water, let fall a quantity of white pow-
der, the fnperfluous acid being diffolved in  the water?
the edulcorared powder yielded regulus of arfenic  by
diftillation  with charcoal.   Solutions of  lead in  ni-
trous and  muriatic acids are  precipitated by arfenical
acid.
   30. Tin digefted  with acid of arfenic becomes firft With tin.
black,  then is covered with  a white powder, and af-
terwards becomes gelatinous.  One part  of tin filings
diftilled with  two of acid of arfenic, took fire as foon
as the retort  became red-hot,  and immediately after
both arfenic and a little regulus were fublimed.   The
tin was diflblved into a limpid  liquor, which became
milky  when  cold.—By wafhing in water, a quantity
of white powder was fcparated, infoluble in  any acid,
and containing very little of that of arfenic.             tsr
   31. Arfenical acid diflblves zinc with  efferveScence. with zinc.
The metal grows black, and the transparency oS the
acid is deftroyed by a quantity of black powder.  This s
powder edulcorated,  dried,  and  put on  an iron  plate
heated nearly  red-hot, emits a blue  flame  and  white
arfenical Smoke in the  dark, leaving behjnd  a  white
powder; thus  manifefting itfelf to be moftly regulus
of arfenic.  One part of filings of zinc diftilled with
two of  acid of arfenic, took fire in the retort with a
very bright flame,  and burft the veffel with an explo-
fion.  Some regulus of arfenic and flowers of zinc were
found in the neck.
   32. Bifmuth digefted with acid of arfenic  is cover-v'ithb<f-
ed with a white powder;  water precipitates  the  folu-muth.
tion, and  the  precipitate confifts of calcined bifmuth
and acid of arfenic.   On diftilling  one part of the bif-
muth with three of arfenical  acid,  the mafs melted, the
metal was calcined, but remained undiflblved in the bot-
tom of the veffel;  a  little arfenic rofe into the neck ;
and  after the retort became cool,  water  was poured
on the refiduum, which diflblved the acid,  but the calx
of bifmuth remained  unchanged. Solution of this femi-
metal in the acid of nitre was precipitated by arfenical
acid.   This precipitate, as  well as the calx,  are very
difficult of fufion, but on adding a little powdered char-
coal, the  mixture inftantly  melts, the arfenic goes off
in vapours, and the bifmuth is reduced.                  -.«
   33. With regulus of antimony a quantity  of  white Regulus of
powder is  produced by digeftion, and the clear folu- antimony*
tion is likewife precipitated  by  dropping it into  pure
water.  This powder is foluble only by muriatic acid,
and may  be   precipitated again by the addition of wa-
ter.  One part of regulus of  antimony diftilled with
three parts of  arfenical acid,  took fire as  foon as the
mafs melted,  and regulus of arfenic with a red mattet
were fublimed;  a  little volatile fulphureous acid came
over into the receiver.  On  boiling the refiduum in
water, the acid was diflblved,  a  white fhining pow-
der remained behind, which,on being mixed with char-
coal powder   and  diftilled,  an  ebullition  took  place,
fome regulus of arfenic rofe  into the neck of the retort,
and the  antimony was reduced.   Butter of  antimony
was not precipitated by  the  pure acid, but very rea-
dily by  the  arfenical  falts.  Acetous  a*d tartareoui
folutions of glafs of antimony are preciptated  by arfeni-
cal acid
                         S              34. Cobalt 
«3«
C    II   E    M    1   S   T    R   Y.
   955
With nic-
kel.
Acid of      ;4. Cobalt is partially  diflblved,  and the folution
arfenic and affumesa role-colour;  on putting the  whole  mafs in-
          to  a retort,  diftilling off the liquid, and  then  aug-
          menting the fire, the inafs melted, and  a little arfenic
          was  Sublimed.  The refiduum when  cold had a femi-
          tranfparent violet colour.  On pouring water upon  it,
          and putting it  on  hot fand,  the  acid  was diiiblved,
          the violet  colour  disappeared,  and  the  folution af-
          fumed  a dark-red colour.  The  bottom oS the  retort
          had a blue tinge,  which could not be taken  off.   So-
          lutions of cobalt in  mineral  acids are readily precipi-
          latcd by the arfenical  neutral falts.  The precipitate is
          of a rofc-colour,  but  melts  with difficulty  into a dark
          blue Scoria.
             35.  Nickel,  with  acid of arfenic,  alfumes  a dark
          green colour, and lets fall a green powder containing
          arfenic in fubftance, which  may be  Separated Srom  it
          l>y  a gentle heat.   One part oS nickel diftilled  with
          two of dry  arfenical acid,  melted  with fome appear-
          ance  of  inflammation,  yielding fome  arfenic at the
          fame time.  The mafs  was  yellow,  with a number of
          grey elevated ftreaks upon it,  which  appeared like ve-
          getation, and were  formed during the. diftillation.  On
          boiling the yellow mafs in water, the  acid was diffolved,
          leaving a yellow powder behind  ; which, when treated
          -with charcoal-powder,  yielded regulus of arfenic, but
          Mas not reduced  itfelf.  The  folutions of  nickel in
          acids are not  preciptated by arfenical acid,  not  even
          that in vinegar, but the neutral arfenical  falts  throw
          down a whitifh green powder.
             36. Manganefe in  its natural  ftate is diflblved only
          in fmall-part;  but when phlogifticated it diflblves rea-
          dily and totally ;  though, whenever the acid  arrives
          at  the  point of faturation, the folution coagulates into
          fmall cryftals.
             Vi.  Regulus of arfenic digefted with its own acid
              Practice.
then treated this Atid of
   95fi
With man-
ganefe.
   957
With rcgu
  sd 957
.Strange
 1 henome-
 n on of arfe-
 nic with
 Icrr-i foliata
 tartari.
L.s of arfe-foon becomes covered with  a  white powder, which is
          arfenic in fubftance.  On diftilling one part of  the re-
          gulus with two  of  the  acid,  the former fublimed and
          the latter melted.   If fmall pieces of regulus of arfenic
          be gradually added to  the  acid of arfenic in fufion, an
          inflammation takes place, and arfenic is fublimed.
            On diftilling a mixture  of  equal parts of terra folia-
          ta tartari and arfenic,  a limpid liquor like  water  firft
          came over, Smelling ftrongly of  garlic ;  on changing
          the receiver, a liquor of a  brownifh red colour was col-
          lected, which filled the receiver  with  a  thick  cloud,
          emitting an intolerable  fmell  of arfenic.   On pouring
          this upon a filter, hardly a few drops  had paffed whea
          a  very thick ftinking fmoke fuddenly arofe as high as
          the cielingof the room ; an ebullition enfucd towards
          the edge of the filtering-paper, and a fine  rofe-colour-
          ed rhinc broke out, that lafted for fome moments.

                   § 13. Of the Acid of M0LYBDS.KA.

How'to      We owe this, as well  as  the  Succeeding a-ids  to
reduce mo-the induftry of  the  late Mr Scheele. "The fubftance
lybdxna to fro:n  which he extracted it is  named  by Cronftedt mo-
powder.    l^ldana t:iev.rrunacea  nittns___As this fubftance is of
          a flaky nature,  and incapable of  pnlvcrization  by it-
          ftlf, our  author mixed fomc pieces of vitriolated  tar-
          tar along  with  i: in a  glafs mortar; by  the attrition
          yif which it  was at laft reduced to a fine powder,  and
          which was afterwards  freed from  the yitriolated tar-
                                                      2
tar  by wafliin^ with hot water.   I]
powder  with all  the known acids, but found none of molyfedxni
them to  have any  effect upon it excepting thofe of arfc- '. ,,.*ct,m"
nic  and  nitre.   No fenfible effect  was  perceived from .---v
the acid of arfenic  until  the water was evaporated ;    959
after which, by increaling the fire, a little yellow orpi- r.ffeds of
ment was fublimed in the neck of tin retort, and fomc tVx *"d of
fulphureous  acid  paffed over into the receiver.   On °* Cjj1C U^"
pouring  two parts of concentrated  nitrous acid upon one     '00
part of powdered  molybdaena,  the mixture  was fcarce violent ac-
warni in the  retorr,  when it  paffed  altogether into tion of con-
the recipient with great heat, and in the form of dark centrattd^
red vapours.  Had  the quantity  been  larger, he  had nitrous acid
no doubt that it would have take n fire ; for  which rca- UF°°* ,l8
fon the  experiment was repeated  with  diluted nitrous"1  ancc"
acid.  Six  ounces of diluted nitrous acid being poured
on  an ounce and a half of powdered molybdaena, no
effect was perceptible till the liquor began to boil;  after
which a great number of red elaftic vapours  began to
appear,  and the  mixture  fwelled confiderably.   The
diftillation  being continued to drynefs,  the refiduum
appeared of a grey colour;  the  fame quantity of ni-
trous  acid was  poured on, and the procefs repeated,
when the refiduum was whiter ;  and  on ftill repeating
the operation a fourth and  fifth  time,  the remaining
powder became at laft as white  as chalk.  This re-
fiduum, after being edulcorated  with hot  water,  was
quite  taftelefs and infipid  when  dry.   The limpid li-
quor which ran from it being evaporated  to  half an
ounce,  firft aflumed a fine  blue colour,  and  then
grew thick.  On being  examined, it was  found to
contain fome iron,  and was otherwife chiefly acid of
vitriol.   The colour difappeared  on diluting the acid
with water.                                           _gr
  The  white powder juft  mentioned is the true acid Acid of
of molybdaena,  and may be obtained by the help of molybd.tra
fire alone.   A fmall piece of molybdaena expofed on a obtained by
filver plate to the blow-pipe, makes a  beautiful appear- fir*»k>«e.
ancc, when the white vapours attach themfelves to the
plate  in the form  of fmall  fliining fcales,  in the direc-
tion of the  flame.   This white fublimate becomes blue
whenever  it is in  contact  with  the blue flame; but
changes to white whenever  the point of  the flame is  .
directed againft  it.   An  ounce  of powdered molyb-
daena was  mixed with  four ounces of purified nitre,
and detonated in  a crucible heated thoroughly red hot.
The  mafs  thus obtained  was of a reddifh colour.   On
diffolving it in water, the folution was clear  and co-
lourlefs.  A fmall quantity of red powder  fell to the
bottom of the veffel; which,  when dry, weighed 11
grains,  and fhowed itfelf to be  an  iron  ochre.  By
evaporation vitriolated tartar and nitre were obtained ;
but a  good  deal of lixivium remained,  which refufed to
cryftallize,  though no  mark of fupcrfluous alkali re-
mained. It was then mixed with fome water, to which
diluted  acid of  vitriol  was added, until no more pre-
cipitate  fell.   The  white powder  which  precipitated
weighed three  drachms ;  but if too  much  acid be
added,  the  precipitate will be rediffolvcd, and the wa-
ter itfelf retains  a  part of it in  folution.   A precipi-
tarc is likewife obtained by  means of nitrous or muri-
atic acid.                                              9ga
  The  precipitate thus obtained,  like  ihofe which re- kscheml-
f It from the two former proceilcs, is the  true acid ef cal f,r<,p«-
molyb-xna, and has the following chemical properties, tics.
                                            1.  The 
Practice.
C    H    E   M
Acid of
molybdae-
na and its
combina-
tions.
  i. The  folution  reddens lacmus, coagulates a folution
  of foap, and  precipitates  hepar fulphuris.  2. If this
  folution  be boiled with  the filings of any of the  im-
  perfect metals, it affumes a bluifh colour.   5. By the
t addition of a little alkali of  tartar, the  earth becomes
  folub'e in greater quantity in  water ;  and after evapo-
  ration fhoots  into fmall confufed  cryftals.  4.   Under
  the blow-pipe this earth is foon abforbed by  charcoal ;
 but when placed on  a filver plate it melts, and evapo-
  rates with  the Same phenomena as  molybdaena  itfelf.
  5. By the addition of alkali,  the earth  is deprived of
  its property of being volatilized in the fire. 6. The fo-
 lution, whilfl hot, fhows its acid power more evidently
  than when cold, and tinges lacmus of a deeper colour.
 It effervefces with  chalk,  with magnefia,  and  with
 earth of alum ;  with all of which it forms falts  very
  difficult of folution in water.  7. It precipitates, from
  the nitrous acid, filver,  quickfilver,' and lead, as alSo
  lead  diffolved  in marine  acid.   TheSe precipitates are
 reduced  on burning charcoal, and the  melted  metal
 runs into the pores.   Corrofive  Sublimate is not  pre-
 cipitated ; neither are the Solutions of the other me-
 tals.   8. Terra ponderofa is alfo precipitated from  the
 nitrous and marine acids ; and the precipitate is fiftuble
 in a  large quantity of  cold  water.  None of the folu-
 tions of the other earths are  precipitated.  9.  Fixed
 air is alfo expelled by this acid from the  fixed and vo-
 latile alkalies, and forms with  them neutral falts which
 precipitate all other metallic  folutions.   Gold,  corro-
 five fublimate,  zinc, and manganefe, are  precipitated
 in form of a white powder ;  iron and tin, from their
 folution in marine acid, of  a brown colour ;  cobalt of
 a rofe colour ; copper of a blue ;  the folutions of alum
 and quicklime, white; and if the ammoniacal fait form-
 ed by the earth of molybdasna and  volatile  alkali be
 diftilled, the earth parts with its alkali in a gentle heat,
 and remains in the retort in form of a  grey powder.
 10.  Concentrated vitriolic acid diffolves a great  quan-
 tity of this earth by means of heat.   The folution ac-
 quires a fine blue colour ;  which, however, difappears
 on being heated, or by  diluting the acid with water.
 In a  ftronger heat the acid flies off,  leaving  the earth
 unaltered  behind.   This  folution  becomes  thick on
 cooling,   n. The  nitrous acid has no effect  upon the
 earth  of molybdaena.   12. Boiled  with the muriatic
 acid it diffolves in confiderable quantity ; and,  on di-
 ftilling the mixture  to drynefs, a dark-blue refiduum
 remains.   On increafing the heat, white flowers arife,
 with  a little  blue  fublimate, and a  fmoking  muriatic
 acid is found  in the  receiver.   The refiduum is  of a
 grey colour.   Thefe  flowers are only the earth of mo-
 lybdaena  volatilized  by means of the muriatic  acid,
 and  therefore  manifefts  the fame properties.  13. If
 one part of this earth be  diftilled with  two parts of
 vitriolated tartar, a  little vitriolic acid paffes over, at
 leaft when the heat is very  ftrong ; and the remaining
 earth is more foluble  in water  than before.  14. With
 two parts of nitre it expels, by means of diftillation,
 a ftrong nitrous acid ; the refiduum diffolved in water
 is a neutral fait which precipitates all metallic  folutions,
 and is fimilar  to that formed by a direct union of the
 acid and fixed alkali,   if. Diftilled with two parts of
 pure common fait,  the acid is  expelled in a  fmoking
 ftate, and white, yellow, and  violet-coloured flowers
 arife, which become moift in the air, and when fprinkled
 on metals giye thim a blue colour.  Thefe flowers,
I   S   T    R    Y.                                    139
  as has been already remarked,  are only the acid ®f Acid of
molybdaena volatilized by that of fea-falt.
                                                    na and it*
                                                     molybdae-
    The blue colour acquired by  this earth on the con-
   r>   c  n       \c  ■    1       n.      •   r       r   combina-
 tact  of  flame-,  alfo in the moift way in fome  cafes, tions<
 fliows that it is capable of contracting an union with <•---^----
 the  phlogifton.    To  reduce  this to certainty, Mr    963
 Scheele diffolved fome of the earth  of  molybdaena in Is capable
 boiling water, with the addition of a little alkali.  In- of uniting
 to this Solution  he poured Some drops of  muriatic acid, V'7*P°"
 and divided it  into feveral parts, into  each of  whicli ot
 he  put  filings  of feveral metals.   The folutions foon
 acquired a bluifli colour,  which grew deeper and deep-
 er ; and  in an hour's  time,  during which the bottle
 wras now and then  fhaken, the liquor  affumed a  fine
 dark blue.  That this colour  depends on  phlogifton,
 he inSers Srom the following circur fiances :  1. If, in-
 ftead of  the metals  themfelves, you take their  calces,
 no blue colour  is produced.   2. If  there be dropped
 into the blue folution a few drops of acid of nitre, and
 the folution  be then put  into a warm place,  the colour
 difappears.  It is therefore no matter of furprife, that
 both filver and  quickfilver fhould be attacked, Since a
 double  elective  attraction  takes place ;  the  muriatic
 acid uniting with the  metallic calx, and the earth  of
 molybdaena  with the  phlogifton of the metals.  Gold,
 however,  is not  attacked in this way.   3.  Too  great
 a  quantity of muriatic acid produces not a blue but  a
 yellowifli colour, which at laft turns brown if the mix-
 ture be digefted  ; but on adding this folution to  a fo-
 lution ofthe earth of  molybdasna, a  blue colour as  u-
 fual is produced.   4. Lixivium Sanguinis, in  which
 the acid  prevails, throws down the earth oS a  brown
 colour, and the infufion of galls of a dark brown.
   The acid of molybdaena, treated with various fluxes, she
 and with  charcoal,  fhows no figns  of containing any fign of con-
 metallic matter.   Moiftened with oil-olive,  and com- tabling anjr
 mitted to diftillation  in  a ftrong fire,  it did not  fub-lncta^
 lime, but remained in  the retort in the form of a black
 powder ;  which, on  being calcined in a crucible, fub-
 limed in white flowers as  ufual.   On inverting another
 crucible into the  former,  and  luting  the juncture, the
 earth remained unchanged and of a black colour, with-
 out any  fign of  fufion.   This  black powder did not
 diflblve in  boiling water,  nor  even with alkali, which
 on other  occafions fo  readily  diflblves it ; but when
 mixed  with a triple  quantity of fait of tartar, a great
 effervefcence enfued ;  the produce was  a neutral Salt
reSembling that Sormed by the direct union of the acid
 and alkali.                                             _g.
   The earth of molybdasna,  procured  by nitre, re- Properties.
 quires  much lefs water  for its folution ; it does not ofthe acid
 expel the  acid from  vitriolated tartar;  is  more eafily obtained by
 fufed, and  does not fublime in an open crucible. When1"*"'
 fufed  with charcoal-powder, it affords a folution with
 water, containing a neutral fait, which precipitates all
others.   The reafon  of  thefe differences  is,  that  it
contains a  portion of alkali, though it  be ever fo  fre-
quently purified  by folution and  cryftallization.  That
this is the cafe we know from the  following experi-
ments : 1. If to  a folution of the nitrous earth of mo-
lybdaena  we  add  fome nitrous acid, the  latter  attacks
 the alkali, and the greateft part ofthe diflblved earth
is  precipitated.   This, however, dues pot happen, ex-
cept by long boiling.   2. The  neutral  fait obtained
by  fufion' proves the fame.  This  neutral fait is pro-
duced in the following  manner.  The  earth which  con-
                         S 2                   tains
  964
lows u* 
140
   966
Molybdx-
■a recom-
pofe-d by
uniting iti
aeid with
lulphur.
                             CUE   M
tai:.« only a  fmall quantity of alkali operates as an acid,
as appears from its ch*  .'.ing  the colour of lacmus to
red ; cm the alkali prevents as much earth  from enter-
ing into it  as  is neceffary to its faturation  with phlo-
gifton ; for the acid  of molybdasna has a greater  at-
traction for alkali than for phlogifton.  The  charcoal
which remains after lixiviating the compound of aciJ
of molybdaena and  charcoal, yields vapours in an open
crucible,  and gives a  fublimate containing the  phlo-
gifticated earth of manganefe.  This  alkali  fixes  the
earth in the open air ; and hence we  fee alfo the rea-
fon why this earth does not expel the  acid from  vitri-
olated tartar ;  for its attraction for the alkali muft di-
minifh  in  proportion as it comes  nearer the point of
faturation ;  and  as the pure earth  contains  no alkali,
it attracts a little from the vitriolated tartar ;  and con-
fequently there can appear but  a  flight veftige of vi-
triolic acid.  This fmall quantity of acid  likewife oc-
casions its more eafy Solubility  in water.
   The pure acid of molybdasna  recompofes that fub-
ftance by being combined with  fulphur.   Mr Seheele
having mixed fome very fine  powder of this earth with
three  parts of fulphur, and committed the mixture to
diftillation  in a glafs retort, the receiver was filled with
the Superfluous fulphureous vapours,  which had  alfo
the fetid fmell of volatile fpirit  of fulphur.   In  the
retort a black powder remained,  which on every che-
mical  trial  was found to be a  true molybdasna ; fo that
there is now no doubt of this fubftance  being  compofed
•f a particular kind of acid united to fulphur.
§14.   Ofthe Acid of Lapis Pokderosus,Tvxcstes,
                   or Wolvram.
   967
This fub-
ftance  con-
fidered as a
metallic
earth by
*1 r Berg-
man.

•heele*
method of
»iMi\fing
it.
  This fubftance has been analyfed both by Mr Scheele
and Mr Bergman, though the former has  the merit of
difcovering the acid contained in it; which the latter
confiders, as  well as the  eanh of molybdaena,  not as
truly  acid, but as metallic earths.   Mr Scheele's ex-
periments for analysing this Subftance were as  Sollow :
1. On one part of finely powdered tungften were pour-
ed  two parts  of concentrated acid of vitriol.  By di-
ftillation the acid paffed  over unchanged ; the refidu-
um, which was of a bluifli colour, after being  boiled
for  a short  time,  and the  liquor  filtered off, depofited
fome  vitriolated   lime or gypfum  by Handing.  2.
Twelve  fcruples of  common nitrous  acid,  or pure
aquafortis, being  poured  on  two  of finely  powdered
innrften,  no  effervefcence  enfued  ; but  on  expo-
Sing0 the mixture  to  a ftrong  digefting heat, it af-
fumed  a citron yellow colour.   The acid  was then
paired off into another phial, and the  yellow powder
edulcorated with water.   3. On this yellow powder
chTlu fcruples  of cauftic volatile  alkali were  poured,
and  the  phial Ovofed to heat  ;  on which  the yel-
knv  colour  inftantly vanifhed,  and   the  powder  be-
came white.   This  folution was  in like  manner
put  into  a Separate  phial,  and  the powder edulco-
rated ;  and as the  matter was fenfibly  diminiihed  by
inefe operations,  they  were  alternately repeated, till
it length  the whole  wat, didblved, excepting three
T'.-Am,  which feemeJ  to be filiceous  earth.  Thefamc
ctfects  enfued en ireating  this fubftance with  muriatic
a -. '., o;.lv the  folution was of a  deeper yellow colour.
4. The  Solutions made  in  the foregoing manner with
aitrous  acid bci;  <:  all  mixed  together, fomc drops of
I   S   T    R   Y.                           Practice.
 phlogifticated  alkali  were  added;  by  which  about Acid of
 three grains of Pruflian blue were precipitated. 5. lie ^l,J on*.
 mixture  was  then  Saturated  with  cauftic  volatile dfro'D»ar*
 alkali;  but  as no precipitate  appeared,  a  Solution  °fna,ion,. "
 fixed alkali  was added,  which threw  down two ^—s^—>
 Scruples and  five grains  of white  eartli  of  a  mild
 calcareous kind.  On adding fome nitrous  acid  to the
 extracts made by volatile alkali, a white powder was
 precipitated, which, on cdulcoration, proved to be the
 true  acid of tungften.                                    9^_
    On treating tungften with a ftrong heat in the dry Effcclaof
 way, the following appearances took place :  1. One heat upon
 part of  tungften mixed with four of alkali of tartar ft-
 was  melted in an iron crucible, and then  poured out
 on an iron plate.  Twelve times its weight  of boiling
 water being then poured upon it, a white powder fub-
 fided to the bottom, which diffolved in a great meafure
 in nitrous  acid.   2. The  undiffolvcd part of the pow-
 der was tried ; and being again mixed with four parts
 of alkali, was melted  as  before:  and the mafs being
 alfo  diflblved  in water, and nitrous acid  poured  on
 the  refiduum, only a very fmall portion  of grey pow-
 der  was left undiffolved.   3.  The ley being faturated
 with nitrous acid, grew thick by the precipitation of a
 white powder;  which was afterwards waflied with cold
 water and  dried, and then proved to be  the  fame acid
 of tungften with that already defcribed.   The folu-
 tion in nitrons acid precipitated with fixed  alkali gave
 a white  precipitate, which was found to be calcareous
 earth.
    The properties of  the  acid of tungften are, 1. Un- its chemi-
 der  the blow-pipe it  became firft of a reddifh  yellow cal proper-
 colour,  then  brown,  and at laft black.   It neither ties.
 fmoked  nor gave any figns of  fufion.   2. With borax
 it produced a blue, and with microcofmic fait,  a fea-
 green  glafs.  3. Boiled  with  a fmall portion  of  the
 nitrous or marine acids, the powder becomes yellow,
 and with  the acid of vitriol bluifh.   4.  On faturating
 a folution of the  acid with fixed alkali, a  neutral  fait in
 very fmall cryftals is obtained.   5. With volatile alkali
 this acid forms an ammoniacal  fait, fhaped like  the
 points of fmall  pins.   On diftillation the  alkali fepa-
 ratcs in a cauftic ftate,  the acid  remaining behind  in
 the  retort in  form of  a dry yellow powder.   On mix-
 ture with a folution of lime in fpirit of nitre,  a  double
 elective attraction  takes  place,  the acid  of tungften
 uniting itfelf  with the lime, and that of  nitre with the
 volatile alkali.   6. With magnefia  the  acid  of tung-
 ften forms  a fait very difficult of folution.   7.  It pro-
 duces no change on foluiions of alum or lime, but  de-
 com pofes a folution of  terra ponderofa in acetous acid,
 and the compound is totally infoluble in water.   8. It
 precipitates of  a white colour folutions  of iron, zinc,
 and copper, in  the vitriolic  aeid ; filver,  quickfilver,
  and lead, in that of nitre  ; and lead in the acid  of  fea-
 falt.  Tin combined  with the  fame acid is  thrown
  down of a blue colour ;  but  corrofive  fublimate  and
  folutions of gold undergo no change.    9.  On cal-
 cining  the acid  of tungften in a crucible,  it lofes its
  Solubility in water.   10.  It  turns black  by calcination
 with inflammable  matters and with fulphur,  but in
  other  refpects  continues unaltered,  n.  Solution of
  hepar fulphuris is precipitated of a green colour  by  this
  ackl, and  the  phlogifticated  alkali white  ;  the latter
  precipitate being folub'e  in water.   On the addition
  of a few drops  of muriatic acid to a folution  of the
                                                 acid 
Pra&ice.
CHEMISTRY.
141
Acid of   acid of  tungften in water,  and fpreading the liquor on
lapis pon>-  polifhed iron, zinc, or even tin, it acquires a  beanti-
derofusand fa biue colour; and  the fame  thing happens  when
nations '"  thefe nietals are put into the acid.   12.  It differs from
v----J.—/ the acid of molybdaena in not being volatile in the fire 3
   97i    in having  little attraction for phlogifton or fulphur; in
Differences turninp; jj,ne yellow,  and  forming an  infoluble com-
betwixtthe     j   • u •.       n      -.v.    j         .u    t. u
acid of     pound with it as well  as with ponderous earth.   It has
tungften   a^° a ftronger attraction for lime than the acid of mo-
and molyb- lybdaena;  for if a combination of lime and acid of mo-
dasna.     lybdaena be digefted in a folution of  the ammoniacal
          fait formed by  uniting the acid of tungften with vola-
          tile alkali,  the latter  expels  the former, and produces
          regenerated  tungften.   13. By  uniting the acid of
          tungften to a calcareous earth,  a regenerated tungften
   072,    is conftantly procured.
Bergman's   Mr Bergman obferves,  that the  acid  earth of tung-
opinion    ften is  nearly allied to that of molybdaena; and both are
concerning jn a ftate mach refembling that of white arfenic.  " It
the aads of js wcll  known (fays he) that arfenic,  in its femimetal-
andSmolyb- ^c ^ate> 1S  nothing but a peculiar  acid  Saturated with
dsena.     phlogifton;  and that the white calx is an intermediate
          ftate between acid and metal, containing juft phlogifton
          enough to coagulate the acid, but  remaining ftill folu-
          ble in water, and fhowing figns of acidity.   If  a con-
          clufion from analogy be admilfible, all the other metals
          fhould confift in a combination  of  the fame  nature of
          the different radical acids, which with a certain quan-
          tity  of phlogifton are coagulated  to  a  dry earthy fub-
          ftance ; and on full faturation are reduced to the ftate
    973   of complete metals."
Why he     The reafons  which  induced Mr Bergman to fuppofe
fuppofed   t]iat  tne aci(]s jn queftion are metallic  earths,  are as
b^me'tlf0 follow: J- Thev both ftlow a ftriking refemblance to
earths,   ' white arfenic in form, in producing effects like acids,
          and in their difficult folubility in water.   2. Their fpe-
          cific gravity ; that of  arfenic being 3750, the earth of
          molybdasna 3460,  and  the acid of tungften  3000.
          3. Their  precipitation with phlogifticated  alkali;  a
          property hitherto deemed  peculiar  to metallic calces.
          Arfenic alfo,  properly diffolved in muriatic acid,  gives,
          with the phlogifticated alkali, a precipitate foluble in
          warer,  in  the  fame  manner as the acid of tungften.
          4. From their  property of tinging vitreous  matters;
          which,  as well as that of  precipitating with the phlo-
          gifticated  alkali, is  reckoned   to be a peculiar pro-
          perty of metals.  The acid of tungften produces by" it-
          felf feme effervefcence with mineral alkali.   With mi-
          crocofmic fait it produces a globule at firft of a light blue;
          more ofthe acid makes it a dark blue;  but ftill  it re-
          mains free from rednefs by refraction.   A further ad-
          dition makes it brown.   Borax  requires  a flight tinge
         of blue, and  with more ofthe acid becomes ef  a yel-
         lowifli brown colour; but remains tranfparent, provided
         no further  addition be made.  This  ultimate  brown
         colour cannot be driven off either by nitre or the point
         of the  flame  urged by a blow-pipe.   Acid of molyb-
         daena is no lefs powerful; for with microcofmic  fait it
         produces a  beautiful green colour:  borax Well fatura-
         ted with it appears grey when viewed  by the reflected
         rays,  but of a dark violet by the refracted.

                     § 15. Of the Acid of Milk.

            Ir  is univerfally known, that in the Summer-time
 milk grows Sour and thick in a few days,  and that this Acid of
 fourneSs  continues for  fome time  to  increafe.  It is mi^ an<|
 ftrongeft after a fortnight has elapfed ; after  which, JJt"™
 if the whey be filtered  and evaporated  to one-half the         .
 quantity, a  few curds  will ftill fettle  to  the bottom.    974
 By Saturating the  whey with  volatile  alkali, a fmall Milk moft
 quantity of animal  earth  precipitates;  and  the  fame fcpngJY
 thing takes place on the addition  of lime-water.   On ZnCi  f. ter„
  ■•  ° 1  1. •    r   r   11      •    /••!/•         1   ltandinga
 the addition of a fmall  quantity ofacid of tartar, the fortnight.
 latter foon becomes partially faturated with  vegetable    075
 alkali,  and is converted into tartar.  Thus the acid of Component
 milk befides its proper acid   part, contains  animal principles
 earth and  vegetable alkali in a loofe ftate, and which of,four
 is  attracted  by the acid of tartar; befides all thefe it w e*'
 has alfo a fmall quantity of  the fame alkali  faturated
 with muriatic acid.   It  is  no  eafy  matter to feparate
 thefe fubftances from one  another; becaufe the acid
 is not fufficiently volatile to rife  in diftillation by a gen-
 tle heat,  nor are its principles fufficiently fixed  to bear
 the action of a ftrong fire.   With the one therefore  it
 remains almoft entirely in the retort, and  with the
 other it is deftroyed.  Mr  Scheele  therefore ufed  the
 following procefs.                                      ^6
   He evaporated four whey till only one-eighth part Scheele's
 remained; when the cheefy part being totally fepa- method of
 rated,  he ftrained the acid ;  and in order to obtain  the procuring
 animal  earth,  faturated the liquor with lime, diluting thf/u5e
 the folution  with a  triple quantity of water.  In or- ^^
 der to feparate the lime, he employed  the acid of fu-
 gar,  which has a ftronger attraction than any other for
 lime.   This earth therefore being fep.irated,  the mat-
 ter was evaporated to  the confiftence  of  honey, and
 highly  rectified fpirit of wine poured upon it  to diffolve
 the acid part; which being accomplifhed,  the  other
 faline fubftances were left  by themfelves:  and, laftly,
 the acid folution being  diluted  with pure  water, and
 the  fpirit feparaied by  diftillation, the pure acid  re-
 mained in the retort.
   The  properties  ofthe acid of milk are, 1. Evapo- Properties
 rated to the confiftence of a fyrup, it yields no cryftals; of thisactdv
 and when evaporated to  drynefs, it deliquefces.  2. By
 diftillation it  yields firft water,  then a weak  acid like
 fpirit of tartar; afterwards fome empyreumatic oil,
 with more of the fame acid, fixed  air, and inflammable
 air;  in the  retort was left  a fixed  coal.   3. By fatu-
 ration with  fixed vegetable alkali it yields a  deliquef-
 cent fait,  foluble in fpirit of wine.  4. A  fait of a Si-
 milar kind is obtained by  combining it with mineral
 alkali.  5. With volatile alkali  a deliquefcent  fait  is
 produced, which by diftillation  yields a great deal of
 its alkali before the acid is  deftroyed by heat.   6.  It
 forms deliquefcent falts with terra  ponderofa,  lime, and
 clay; but with magnefia  it  forms fmall cryftals, which,.
 however,  are again  deliquefcent.   7. It has no effect
 either by  digeftion or boiling on  bifmuth, cobalt, re-
 gulus of antimony,  tin, quickfilver, or gold.  How-
 ever,  aSter digeftion with tin, it precipitated gold from
 its Solution in aqua-regia, in the form oS a black pow-
 der.  8. It diffolves iron and zinc,  producing inflam-
 mable air  during  the Solution.   The liquor produced
 by  the diflblution of iron was brown, and  yielded  no
 cryftals; but the folution of zinc cryftallizes.   9.  Cop-
 per diflblved in this acid communicates to the liquor
 firft a blue, then a green, and then a dark blue colour,
Without  cryftallizing.   10. Lead  was  diflblved  after
                                               fome 
1
A .-id of
m.iH anl
   9?8
It fcenit to
Ne of the
acetous
kind.
   97)
Milk ca-
pable of
complete
fermenta-
tion.
CHEMISTRY.
PraAice.
  vi 9*9
Converted
int > vine-
gar.
   980
Acid of
fugar of
mrlk how
procured.
fi"ir days digeftion; the Solution  had ■•. fveet aftrin-
gent taite, and w.i ild not cryitallize.   A  Small quan-
ti:y uf white matter fell to ihc boitom,  which on  exa-
mination was fo.inJ to be vr.r.ol 01  lea;!.
   " From thel'c experiments  (fr, s Mr .Scheele) it ap-
peals, that rhe acid ot milk is of a peenbar kind ;  and
though it expels the  vim gar from  the a:etatcd vegeta-
ble alkali, yet it feems dell:ned, ii !  may So fpeak, to
be vinegar; but fro. 11  ilie warn of Inch fubftances as,
during fermentation, produce ionic fpirituous matter,  it
fcems not n. be volatilized, though a  y rtion of it in-
deed arrives at this point, and  really becomes vinegar :
for without  a previous fpiritous ferment, tion, or with-
out brandy, there never arifes any vinegar.  But  that
the  milk enters into a  complete  fcrmcrtation  though
there be no fig 11 of  brandy prefent,  a>peirs from the
following experiment :  If a bonlc full of frefh milk be
inverted into a veflel containing So much  of the  fame
liquor that the mouth  of  the  bonlc reaches below the
furface of the latter, and if you cxpofe this bottle  to
a degree of heat a little greater th -u our fummer, you
will find, in the fpace of 24 hours, that the milk is not
only coagulated, but in part expelled out of the bottle ;
and that in a couple of days afterwards, the aerial acid
extricated from the milk will have expelled the greater
part of it.  It was  Slid above,  that the acid of milk
cannot be converted into vinegar, from the want of fuch
 fubftances as during  fermentation  produce brandy ;
 which appears to be evident from  this : If to a kanne
of milk you add five fpoonfuls of goe)d brandy, and ex-
 pofe the veffel, well corked, in fuch a manner, howe-
 ver,  that you now and then give vent to  the air deve-
loped during fermentation,  you will find  in a month,
 Sooner or latter, that the whey  will  be changed into
 good vinegar, which, ftrained  through a cloth,  may
 be kept  in bottles."
   The acid of fugar of milk  is confiderably different
 from that  juft now  defcribed.  To procure it, Mr
 S: heele poured  12  ounces of diluted nitrous  acid  on
 four  ounces  of  finely powdered fugar of milk  con-
 tained in  a  glafs retort,  to which  a receiver was
 adapted.  The retort was placed in  a fand-bath, and
 as foon as the mixture  acquired  a certain  degree  of
 heat, it began to effervefce violently ; for  which rea-
 fon, the retort and receiver were taken  away  from
 the fire. The mixture,  however, continued to  grow
 hotter and  hotter, with  a  great  emiffion of dark red
 vapours continually increafing, for  half an hour.  A
 confiderable  quantity  of nitrous air  and  aerial acid
 were extricated during that  time.  Care  muft be  ta-
 ken,  therefore, to have  ihe retort and receiver both of
 a fufficient  Size, and not to make the luting too tight.
 When the  efferveScence had Subfided, the retort was
 a Tain placed  in the Sand-bath, and the nitrous acid thus
 diftilled off till the maSs acquired a  yellowifli colour ;
 on which the retort was immediately taken away from
 the  fire.   In  two days time the folution  fcemed to
 have undergone no remarkable change, nor was  there
 any appearance of  cryftals.   Eight ounces  more of
 the fame nitrous  acid  were  therefore added, and the
 whole expofed to the fame degree of heat  as before.
 W'm  the  mafs grew  warm, another effervefcence,
 though  weaker than the former, enfued ;  the yellow
 colour disappeared,  and the nitrons acid was again ab-
 firicled, till the  folution,  which had been  rendered
opaque by  the appearance of a white  powder in  it, Aeid of
affumed a yellowifli colour,  on which the retort was -- n"lk '
gain removed from  the fand.  After  it was grown  '
c ol, the mafs in the retort was found to  be infpiliated ;  «
it was rediffolved in cightounces of watt r, and  filtered.
S :ven and a half  drachms of  white powder remained
0.1 the filter; the folution which  paffed through  the
li ter was very acid.   It was evaporated to  the con-
1 fence of  a Syrup,  Sour  ounces  more nitrous  acid
poured upon it, and the evaporation repeated in a Sand-
lie u.   After the whole was cool,  fome fmall long 3-
cid cryftals were found, together  w ith a fmall quanti-
ty of  white powder  which was Separated Srom it,  and
Some more >.:trous acid poured on the remaining  mafs,
and on evaporation,  more fuch  cryftals made their ap-
pearance.   The  fame procefs was  repeated fevcal
times ;  by which  means the  whole  mafs was at  laft
changed into fuch  cryft'ls, and  weighed  about  five
drachms, (bowing in every retpect the fame phenome-
na produced by acid  of fugar.  The white  powder,
weighing feven and  a half drachms,  was the true acid
of fugar of milk ; and its properties are,                  08r
   1.  It  burns in  a  red hot-crucible like oil, without  Pi<.;>trtiei
leaving behind it  any mark  or afhes.   2.  It  diffolves  otthi» aeiJ.
 in  boiling water  in  the proportion  of one of fait to
 60 of the liquid.    3. One fourth part of  the diffol-
 ved powder feparates from  the liquid  on cooling, in
 form  of very fmall cryftals.  4. Half an ounce of the
 fait was  diifolvcd in  a glafs velfel in 30  ounces of boil-
 ing water, and the folution filtered when cold.  It had
 a fourifli. tafte, reddened the tincture of lacmus,  and
 effervefced  with chalk.  5.  Two drachms of the fait
 expofed  to an open fire in a glafs retort,  melted, grew
 black, and frothed very much ; a brown fait was found
 fublimed into the  neck of the retort,  which fmellcd
 like a mixture  of fait of benzoin and  fait  of amber,
 eleven grains of coal  remaining in  the retort.   The
 receiver contained  a  brown liquid without  any mark
 of oil, fmelling like the fublimed fait.  It contained
 alfo fome  of the  fait diffolved, which was Separated
 Srom it by  a gentle evaporation.  The Sublimed fait
 weighed 35 grains, had a  Sour tafte, and  was eafily
 Soluble in Spirit of wine, but with  more difficulty in
 water, and burned in the fire with a flame.  6.  Con-
 centrated vitriolic acid,  diftilled with this fait, became
 very black, frothed much, and decompofed the  fait
 entirely.  7. Acid of fugar of milk, gradually added
 to a hot folution of alkali,  occafioned an effervefcence
 and coagulation in confequence of the  formation  of a
 vaft number of cryftals, which require eight times their
 weight  of water  to diffolve  them, and Separate again
 in a  great meafure from the  liquid on  cooling.   The
 fame phenomena took place with the  mineral  alkali,
 only the  fait was  fomewhat  more  foluble,  requiring
 only five times its  weight of water for folution.  if
 to a  folution of it a Solution of alkali of  tartar be
 added,  a number of fmall cryftals will  foon  be formed
 at the  bottom of  the  veffel, on account of the greater
 attraction of this  acid  with  the  vegetable alkali.
 8. With volatile alkali it forms a kind of  fal ammoni-
 ac, which, after being gently dried, has a fourifh tafte.
 By diftillation, the  volatile alkali is firft Separated^ the
 lime-water  precipitates, and the refiduum  yields the
 Same products by  diftillation as the pure acid.  9. With
  all the  earths, acid of fugar of milk  forms infoluble
                                                Saks. 
Pra&ice.
CHEMISTRY.
   98a
Calculi all
of the fame
nature.
   953.
Properties
of the acid
of calculus.
falts.   If a folution of ponderous earth in muriatic or
nitrous  acid  be dropped  into a folution of acid of fu-
gar of milk, the former is inftantly decompofed,  and
the earth falls to the bottom  in combination with the
acid of faccharum lactis.  The  fame phenomena take
place  with folutions of lime in the nitrous and marine
acids; but  folution  of  gypfum  is  not  decompofed.
The  fame alfo  takes  place  with folutions of magne-
fia in  vegetable or mineral acids, and with earth  of a-
lum ;  all of which are decompofed by the neutral falts
abovementioned.   10. The  folution of this acid,  by
reafon of the  fmall  quantity  diffolvable in water, has
no fenfible effects on metals in their perfect  ftate; but
when they are reduced  to calces, it then  acts  upon
them, and forms falts, very little or not  at all foluble
in water.  Silver, mercury,  and lead are  precipitated
in form  of  a white  powder  ; blue, green,  and white
vitriol,  as well  as  manganefe combined with acid of
vitriol, are not precipitated ;  but  all  metallic folutions
are precipitated by the neutral falts.

§  16. Of the  Lithisiac  Acid, or Acid of the human
                      Calculus.

   The calculi examined by  Mr  Scheele,  with a  view
to difcover their conftituent parts, were, as he informs
us, all of the  fame nature, whether  flat and polifhed,
or rough  and  angular.  A fmall quantity of calculus
in powder was put into a retort,  and  fome diluted vi-
triolic acid, poured  upon it.    The  powder was not
affected by a digefting heat;  however, it was diflblved
when the humidity  was abftracted by diftillation.  Af-
ter the diflipation of the acid, a black coal was left in
the retort, and  the  vitriolic acid which bad  paffed in-
to the receiver was become fulphureous.   The marine
acid,  whether diluted  or concentrated, had no effect
upon  the calculus, not even when  boiled with it.  The
nitrous acid diluted, or aquafortis, had fome effect on
the calculus,  even when cold.  On the applanation of
heat,  an effervefcence enfued  with red vapours, and the
calculus  was diffolved.   Repeating the experiment in
a retort with  lime-water,  the latter  was  precipitated.
The  folution  of calculus is  acid, though  the  men-
ftruum  be boiled with  a Superabundant quantity of
powder,  fo  that  there may remain a  portion of it un-
diflblved.  It  produces deep  red fpots on the fkin in
half an hour  after it is applied ;  and  if the  faturated
folution be a little more evaporated,  it  afl'umes of it-
felf a  blood-red colour, which however, difappears on
dropping in  a fingle  drop of nitrous acid.  Terra pon-
derofa is not precipitated by it from the muriatic acid ;
nor are metallic folutions fenfibly changed.  With al-
kalies it becomes fomewhat more yellow when the al-
kali is fuperabundant.   The  mixture,  in  a  ftrong di-
gefting heat affumes  a rofe  colour, and  ftains  the fkin
in the fame manner,  without any fenfation of burning.
The  mixture likewife precipitates metals of different
colours;  vitriol of iron, black; of copper, green ; fo-
lution of filver,  grey;  corrofive  fublimate,  zinc,  and
lead,  of a white colour.  Lime water precipitates  a
white powder foluble in  muriatic and nitrous  acids
without effervefcence ; and though there be  an excefs
of precipitated  powder,  the folution will   be  acid.
This  white powder, therefore,  is the acid of the cal-
culus  itfelf, the exiftence of  which is alfo  confirmed
                                                        143
by Mr Bergman's experiments.  The further analy fis Flowers of
of this is related under the article Calculus, below. benzoin»
&.C.
§ 17. Of the Flowers of Bexzoix, Acid of Leh:oks,
  with other anamolous vegetable acids, and the refai:-
  blance -which the vegetable acids in general bear to one
  another.
9U
   It has long been known, that the refinous Subftance, Flowers of
improperly  called gum benzoin, yields by Sublimation benzoinob-
with a gentle  heat a quantity oS fine  Saline matter of *ai"?d liv
a moft agreeable odour, and Slightly  acid  tafte,  called o^  ima x"
flowers of  benzoin.   Another   method  of obtaining  ' „g^
this fubftance is  by lixiviating  the gum  with  water, r?y  lixivia-
and cryftallizing the fait.   Mr  Scheele, determined lotion.
try what quantity of the  flowers could  be  obtained    986
from the refin, found  that,  by fublimation, he was able Q"antlties
    1   •   r             1  r  1     -i              obtained
to obtain from one  pound of  benzoin between nine,   ,  .
and  twelve drachms of flowers.   By lixivation the meth0ds.
quantity obtained  was  confiderably lefs than the for-
mer, owing to the faline particles being fo much cover-
ed by  the refin,  that the water could not have fuffi-    987
cient accefs  to diffolve them all.   It was next  attempt- Attempts
ed  to  procure all the flowers which  the benzoin was *° procure
capable of yielding.  This was firft  done by boiling Jy     ,
pounded chalk and benzoin in  water,  and then  filter- rtfin is ca_
ing the decoction ; but no cryftals appeared.  On pour- pahle of
ing fome drops of vitriolic acid  into the liquor, the fait yielding.
of benzoin  foon afterwards  precipitated  (for this fait,    988
which  is  an acid, was  united  to the  chalk);  but the L'0llmg
quantity  of  fait was no  greater  than  that obtained by ^'k c-
!•'•••      ah  i-   1              -j     j   1  r   lnfufhcient:
lixiviation.  Alkaline ley was next tried,  and the fo-     g
lution  faturated  with an acid.  Thus the fait of ben-And with
zoin was obtained  by  precipitation;  but  here this in-  alkaline
convenience was met with,  that the powder of benzoin ley.
ran together during  the boiling,  and floated on  the    g^,
furface like a tenacious refin. One only method, there- Boiling
fore,  remained to be tried, and that was to boil the with lima
benzoin with quick-lime; and as the particles of  lime,  the  beft
by interfperling themfelves betwixt thofe  of the  ben- luctnod.
zoin would prevent their running together, and  lime
has likewife the  property of acting upon the refinous
particles, this feems  to  be the  beft  method  of  pro-
curing the flowers of  benzoin in the greateft quantity,
and alfo of the beft quality ; and thus we may obtain
from 12 to 14 drachms  of flowers from  a pound  of    99l
benzoin. Mr Scheele's receipt for preparing them after Mr
this new method,  is as  follows: " Pour  12 ounces of Scheele's
water upon four of unflaked lime, and after the  tbul- receipt for
lition is over, add eight pounds (of  12  ounces  each)  Preparing
of water; put  then a pound of  finely powdered refin* e  ?™~
of benzoin  into a tinned pan,  povir upon it firft  about zojn ^
fix ounces  of the lime-water  abovementioned; mix thism«-
them well together, and thus add  all the  reft of the thod.
lime-water  in fucceflion.  The reafon of  adding the
lime water thus by portions, is, that if it be poured  in
all at once,  it  will not mix with the benzoin,  which
will likewife coagulate and  run  together  into a  mafs.
This mixture muft be boiled over a gentle fire for half
an hour,  agitating it conftantly;  then taking it from
the fire,  let it ftand quiet for fome time to fettle,  after
which  the clear liquor is to be  poured off into a glafs
veflel.   Pour  then eight pounds of  water  more upon
the lime in the veffel, and ufe this lime-water as before,
repeating this procefs  twice more,  making four times
                                                 it 
14*
U jwcrt of
frnsuiu,
C    H   E    M   I    S    T   R    Y.
Practice.
   9)i
Flavour of
the flowers
may be ta-
ken away
and produ-
ced at plea-
fare.
   993
AlU'Ru!'!'.!!
Vegetable
Uwub  how
divided.
   994
Of the ef-
liutial
acids.
F.m;.
naaue
■ ^41
9J5
in all ; and lailljr, putting all  the  rcliduum  together
on i filter, pour  hot  water upon thtm.  Duritg this
procefs,  the calcareous earth of the lime-water com-
bines with  the acid of benzoin, and feparaiesit from
the  refinous  pirticlcs of thit fubftance;  but  a fmall
quantity of refin is diffolved by the lime-water, aud
gives it a yellow colour.
   '' All thefe liquors being mixt d together and boiled
down  to  two pounds,  are then to be ftrair.cd into ano-
ther gUfs velfel.  They are infpiffated fo tar,  becauSe
the fiijviHiio.is  water would  hold a great quantity of the
Salt in Solution ; and a little of" the  refin being  Soluble
in a large quantity of lime-water, but not in a fmall,
fills  to  the  bottom on  the liquor being   infpiffated.
When the liqour has become cold,  after being ftrained
the laft time,  add  muriatic acid till  the flowers be to-
tally precipitated, which happens by  reafon  of  the
ftronger attraction of the marine acid for the calcare-
ous  earth.  The precipitated coagulum is then to be
put upon  a filter ; and,  after being  well drieel, to be
edulcorated  fufficiently, by repeatedly pouring  cold
water upon  it,  when it  muft  be  dried with a gentle
heat.  As the water made ufe of for this purpofe, how-
ever, is capable of diffolving a little of the  fait  of ben-
zoin, it ought to be evaporated, and afterwards fet to
cryftallize.  In order to  give this fait a fhining appear-
ance,  let it  be  diflolved in a fufficient quantity,  fix,
ounces, for inftance, of waier by gentle boiling ; then
ftrain it immediately, while yet warm, through a cloth,
into a glafs veflel which has been  heated before ; and
thus a number of fine cryftals will  flioot as foon as the
folution  is  grown cold.   The water is  then to be
ftrained from the cryftals, and  the reft of the fait  fuf-
pended in the water may be obtained by repeated  eva-
poration and cryftallization.   Iu this method, however,
a great quantity of the flowers arc loft by reafon of
their volatility ;  it will therefore be more  convenient
to keep them in the form of their original precipitate,
which  is  always in  fine powder.   Cloth anfwers belt
for  the filtration of the hot folution: when  blotting
paper is ufed,  the Salt Sometimes cryftallizes in  the fil-
ter, and obltructs it.   The  Alteration hfelf might be
omitted,  were  it not that about two grains of refin of
benzoin remain united to  the liquor, from whence it
cannot be Separated but by the operation juft mention-
ed."-----The  properties of this fait  as an acid  are but
little known.   It has a moft agreeable flavour;  which,
however, ceafes as foon as  it  unites with calcareous
earth, but is recovered again on being feparatcd by
any other acid.
   With regard to the  other vegetable acids, they may
be divided into  the effential, the fermented,  and era-
pyreumatic.   The effential  acids  are pure, as  exem-
plified in thofe of lemons, forrel, and  forrel-dock; or
but  little altered by  the admixture of other matters,
as thofe of cherries, barberries,  tamarinds, &c.  In
fwect fruits they are generally fo  much covered when
ripe as  Scarce to be diftinguifhed:  however,  thefe la-
tent acids become more evident, partly in fermentation,
and partly by dry diftillation.   By the former method,
all flowers, excepting a few which bear cruciform flow-
ers, are made to yield vinegar;  and by dry diftillation
only a very few yield a volatile alkali.
   The acid  which paffes  over in  dry diftillation is
("•arce perceptible while th* Subjed retains its  natural
                                              I
form ; but when once produced,  has  the fame tlft ntial Flower*of
qualities  with the other ; whence it was naturally fiip-biiuom,
pofed that all vegetable acids arc at bottom the lame. . ''  ^____,
Chemifts, iiowevcr, hive beendivided in their opinions    996
on this fubject , fome iuppotlng that the acid of fugar 01 Whether
of tartar is the bafis, and others that vinegar is  the ta- the acid ot
fis of them all.   In prcol oS  this latter  hypoilulis, it fuSar?r°f
1     1         111      1   r 1             1       taitaris the
has  been urged, that the acid ot lemons may  be cry- ba|lS,6f ve-
Itallized ; of" winch  we have ihe following account m gtt'abic of
Scheele's E flays.   "  The juice will not  flioot into acids.
cryftals by  mere  cv;j oration,  even  when thickened    997
to the  confidence of a  fyrup.   This our au*ln>r fuppo- l> I'rll'i
fed to proceed from the great quant:7 of mucilaginous ",t'ho«lof
matter with which the  juice abounds;  for  which rea" ^n£ the'a-
fon he mixed the infpiilatcd juice with ftrong fpirit of dd*f je.
wine which coagulated  the  whole: but  even thus  he mon5.
could obtain  no cryftals by  evaporation.  He there-
fore  employed  the  method ufed for procuring the pure
acid  of tartar, and which is formerly  defcribed.  The
lemon juice,  while boiling,  was faturatcd  with pulvc-
rifed chalk, and the compound  immediately fell to the
bottom in a  form nearly refembling  tartarifed lime.
To feparate the  acid, a quantity of oil of vitriol, equal
in weight to the chalk employed, but diluted with ten
times it weight of water was neceffary.  This mixture
muft be boiled in a glafs veffel for a few minutes ; and
when grown cold, the  acid is to be feparattd from the
gypfum by filtration. In order to cryftallize it, we muft
evaporate the whole to the confiftence of a  thin fyrup;
but great care is to be taken,  left any of the calcareous
earth remain in the evaporated  liquour : to determine
which,  a little of it  is to tried with frefh  oil of vi-
triol, which will throw drown  the remainder: and in
this cafe fome more mult be added to the  whole quan-    «0$
tity; for  the leaft particle of lime re mail, ing prevents The cryf-
the  cryftallization, while  the  fnperrfiictffs"" quantity of tallization
oil of vitriol,  if too much happens  to  be added, re- prevented
mains  in the liquor.   The cryftals  flioot equally well j?yt!,eft
in a hot as in  a  cold temperature, which is very un- ™atei   *
ufual."                                             Le
   It is very  remarkable that  this cryftallized fait of    999
lemons cannot  be  convened  into acid of fugar  by Salt of le-
means of that of nitre, though the extract of the juice mons caDr
itfelf may.   Sour cherries afford  acid of fugar, andnotb'"n"
another fait fuppofed to*be  tartar; and a  kind of fu- ac^jC0f fu.
gar may   be  obtained  not  only from roots of  various gar#
kinds, but from fine raifins, and, as Dr Crell  thinks,
from expreffed muft ; but whether the faccharinc acid
can be procured from this kind of fugar in equal quan-
tity  as from  the common, or  even whether it yields
the fame products with common fugar by  dry diftilla-
tion, is ftill a matter of doLibr.                          JCC0
   Pure acid of  tartar  yields on diftillation per fe  an Productof
empyreumatic acid,  and a  coal confifting  of oily par-acid of tar-
ticles and calcareous earth.  Dr Crell therefore  afks, tar by dry-
May not  the acetous acid be mere acid of tartar, which diftillatioa.
did not meet  with alkaline fait and earth enough with
which it  might  combine and  become more fixed ; but,
on the contrary, attracted  more Subtile  oily ptntides,   1001
and thas  become more volatile? In diftilling terra fo- Acetous
liata tartari in the  dry  way, the acid of vinegar wjiich acid almoft
enters its compofition  is  almoft  entirely  deftroyed, jntn'rcl3r.
only 7;Tth of pure acid being obtained, the refiduum ^1^
in the retort, as well  as the reft of  that which comes
oyer into  the receiver, being entirely alkakinc ; and the
                                              fa«ne 
Practice.
CHEMISTRY.
&c.
  IOOZ
Requifites
for bring:-
tar.
   1003
Mr Wef-
trumb's
Identity of fame thing happens to the acid of tartar, the eropy-
the vegeta- reumatic  acid abovementioned being extremely weak.
ble acids,  jyjr Beaume likewife informs us,  that if any calcareous
          earth, egg-(hells, for inftance, be diflblved in vinegar,
          and the cryftallized fait be diftilled, we obtain i\  of  a
          red and very fiery inflammable fluid, fmelling like em-
          pyreumatic  acetous ether, which reddens  tincture of
          Mrnfole.  Muft,  diftilled  before fermentation, yields
          only an empyreumatic acid refembling Spirit oS tartar.
          The conjecture thereSore Seems reaSonable, that vine-
          gar and tartar have Sor their  bafis  the Same Species of
          acid,  which  in the cafe of vinegar is combined with a*
          greater proportion  of oil,  and  in  tartar with  more
          earth.  To bring vinegar therefore nearer the ftate of
          tartar, we muft deprive it of its  fine volatilizing phlo-
ing vinegar gifton,  combine it  with  more fixed matter,  and  re-
npar^r trip
ftate ft r- ^ore  ns gro^er °''«  ^ l^is> however,  is  extremely
          difficult to be effected.  Mr  Weftrumb,  who  attempt-
          ed it,  added nitrous  acid  in  various proportions,  but
          could only produce a phlogiflication of the latter, and
          dephlogiflication  of  the  vinegar;  but as he could  not
unfuccefsful ti1in|i 0f ariy method of feparating the two acids from
attempt.   Qne  anotKer  jle  was  unaD]e  to inveftip-ate  the  pro-
Dr Crell's  perties  of  vinegar  thus dephlogifticated.  Dr  Crell
opinion of  is  of opinion,  that  this  might have been done by ve-
the poffibi- getable alkali, lime,  and terra  ponderofa.   The ni-
lityoftranf- trous  acid, with vegetable alkali, would  have fliot in-
clination.  t0  the ordinary hexangular cryftals of nitre:  the ace-
          tous acid  would have  formed a  compound  not eafily
          cryftallized, provided it had remained unchanged ; and,
          though  it had  approached the  nature of  Saccharine
          acid,  would  ftill  have  formed  a compound difficultly
          cryftallizable.  The effects of thefe acids, indeed, on
          lime,  are  directly oppofite to  what they  are on  terra
          ponderofa.   With the former,  nitrous acid  forms a
          liquor which  can fcarce be cryftallized ;  with the lat-
          ter it produces falts  difficult to be  diffolved : while
          the acetous acid, with  terra ponderofa, forms deliquef-
          cent falts;  with lime, fuch as efilorefce in the air.  But
          if the vinegar, by means of the operation already men-
          tioned, had been  made to approach towards  the na-
          ture of acid of fugar,  tranfparent  cryftals would im-
          mediately  have fallen by reafon  of the ftrong attrac-
          tion of this acid for lime.  Dr Crell therefore recom-
          mends the following method.   Let  nitrous acid be fe-
          veral  times diftilled off from  vinegar; and  when the
§d by him  former, upon being newly added, produces no more
          red  vapours,  faturate  the  liquor with lime or terra
          ponderofa, feparating the ley, which  will  not fhoot,
          from  the  cryftals.   The nature of the  fait which
          does   not  contain nitrous acid, may  be determined
          from the figure of its cryftals, or from the effects of
          other  falts  in confequence of a  double  elective  at-
          traction.   We might likewife add  frefli  nitrous acid
          to the feparated fait,  or to the whole mixture,  with-
          out any feparation of the nitrous  fait,  till the  earthy
          fait, which does not contain any nitrous acid,  be fatu-
          rated.  The vinegar,  if unaltered  by the operation,
          would rife  on diftilling the liquor; and  if  converted
          into faccharine acid,  would not be diflodged from lime
          by fpirit of nitre.   In  like manner, diftilled  vinegar
          Iliould be  faturated  with  chalk,  the compound  redu-
          ced to cryftals, and then expofed  to as  ftrong a fire as
          it  can  bear without expelling the acid, in order to dif-
   1005
Method re
commend-
for at-
tempting
the experi-
ment.
                                                          H5
 fipate fome phlogiftic particles.  Let it then be  dif-Identity of
 folved,  filtered, and cryftallized again;  after which  it the vegeta-
 may be treated  with nitrous acid as above  directed, bleaaas,
 " Perhaps (fays Dr Crell), the  acetous acid may by .
 this combination acquire more  fixity; fo that the ni-
 trous acid fhall be  able  to produce a greater change.
 Should  it pafs over  again in the  form of acetous acid
 unchanged, let  it be combined  once more with calca-
 reous earth ;  and let the foregoing experiment be  re-
 peated,  in order  to  try  whether Ionic fenfible change.
 will not enfue.  Should  this method fail, try the  op-
 pofite ;  that is,  endeavour to add  more  grols  phlogi-
 ftic  matter to the vinegar.  Try to combine ftrong vi-
 negar,  and that which has been diftilled, with unctu-
 ous  oils.  Thus we might perhaps bring it nearer to
 tartar ; and again, by means oS  nitrous acid, convert it
 into acid of fugar.                                      ico5
   In another  dilfertation on this  fubject,  Dr Grell His at-
 undertakes to fhow, that all the vegetable acids  may tempts to
 be  converted  into  one,  and that  this is contained in Prove that
 the  pureft fpirit of wine.  The  following are adduced    ^f ve"
 as proofs.                                           getable a-
   1. If the refiduum of dulcified fpirit of nitre  be be reduced
 boiled with a large quantity of nitrous acid, care being to one.
 taken at  the  fame  time to  condenfe the vapours by   1007
 a proper apparatus;  and  if the liquid which has paf-From the
 fed  over be faturated  with vegetable alkali,  nitre  and ^d"um°f
 terra foliata tartari will be obtained ; and on feparating fp^i  f •
 the  latter by means of Spirit  oS wine,  the vinegar may tre/
 be had in the ordinary way oS decomposing the fait.
   2. On boiling the refiduum over again with nitrous
 acid, the  fame products are obtained;  and the more
 frequently this proceSs is repeated, the leSs acid of  fu-
 gar  is procured, until  at  length  no veftige of it is to
 be met  with.                                           Ioo8
   3. Pure acid of fugar,  boiled with 12 or 14 times  its From the
 quantity  of  nitrous acid,  is  entirely decompofed, and decompofi-
 the  receiver is found to contain  phlogifticated nitrous tionofacid
 acid, vinegar,  fixedair,  and phlogifticated air, whileoffu£ar'
 a little calcareous earth remains in the retort.
   4. Acid of fugar  is likewife decompofed by boiling From°he
 with fix  times its quantity of vitriolic  acid.   In the production
 receiver we  find  vinegar phlogifticated  with vitriolic of acidof
 acid, aerial acid ; while pure vitriolic acid remains in tartar from
 the retort.                                          the refi-
  5. Byfaturating the refiduum of  dulcified  fpirit of duldfied
 nitre with chalk, there  is  formed an  infoluble  fait, MT\t of
 which by  treatment with vitriolic acid yields a real nitre.
 acid  of tartar, conftituting a cream  of tartar  with vc-   1010
getable alkali.                                       From the
  6. On  evaporating  the liquor from which  the tar- P™du<ai°n
tareous felenite was obtained, a dark-coloured matter    mp?"
remains, yielding on diftillation an empyreumatic  acid "i^of'tar-
of tartar,  and a  Spongy  coal.  Hence it  would fecm,tarfrom
that  fpirit of wine confifts of acid of tartar, of water, the liquor
and  phlogifton; fo that it is  a native  dulcified acid :in which
and nitrous acid,  on being mixed with it  in  moderate tartafou»
quantity,  diflodges the acid of tartar.  On the addi- ^n-|V
tion  of  more nitrous acid, the acid of tartar is refol-"  °lj7*
ved into acid of fugar  and phlogifton ; and by  a  ftill From the
greater  addition, the facchaiine acid is changed  into folution of
vinegar.                                             manganefe
  7. On boiling one part of the acid of fugar with one H nitrous
 and  an half of manganefe  and a fufficient quantity of a^d Jnfd a~
nitrous
gai. 
'4*
C    H    E   M
A.idof f,:. nitrous acid, the man»»n< fc will be almoft entirely dif-
        -folved, and phlogifticated nitrous acid along wnil vine-
          gar will paK over into the receiver.
            ?. On boiling  together  acid  of tartar,  manganefe,
          and  nitrous acid,  wc obtain a  filiation of the mauga-
          ncle, w;th phlogifticated  nitrous  acid and vinegar  as
   tttj   before.
From the    9. If acid of  tartar be  boiled  along  with vitriolic
folution of acid and manganefe,  the latter  will be diflblved, and
  c.inic.  vinegar with  vitriolic acid will pafs over into the re-
withvitri-      °                        r
olicacid   CC1Vcr'     ,    „
and that of  10- On digcfting  acid  oS tartar and  fpirit of wine-
t trtir.     Sor Several months, the whole  is converted into vinc-
   1013   gar, the  air in the veffel being partly converted into
From the  cretaceous acid,  and partly into phlogifticated air.
digcftionof   TT A„ k_:i:_„ /v.-:. „t•„.:_____:.u ..:._:..i:_ „_:
acid of tar-
tar with
fpirit of
wine.
   icr4
From the
folution of
            11. On boiling Spirit of wine with vitriolic acid and
          manganefe, it will be converted into vinegar and phlo-
          gifticated air.
            12. 3y diftilling  fpirit of  wine upwards of 20 times
          from cauftic alkili,  it was changed into vinegar, and a
          confiderable quantity of water was obtained.
            Hence it  appears,  fays Dr Crell, that tho  acids of
withvitri-  tar,ar>  f"llgar>  afid  vinegar, are modifications  of the
          fame acid, as it contains more or lefs phlogifton.  The
          acid  of  tartar has  the greateft quantity, the  acid of
          fugar fomewhat  lefs, and vinegr the leaft of all.  In
          thefe experiments,  however, care muft be taken  that
          neither the nitrous acid nor fixed alkali employed con-
 f'fpirk^f  tain any marine acid, otherwife the refults will be un-
wiue with  certain. r
olic acid
and fpirit
of wine.
   IOIJ
Fr.in: the
diftillation
cauflic al-
kali.

 ad ion
How pro-
cured.
 "d IOX5
Its effect*
                       § 18.  Of the Acid of Fat.

            This  may be  obtained  from fuet by means of
          many repeated diftillations.   A fmall quantity is fepa-
          rated at each diftillation ;  but  by diftilling  the empy-
          reumatic oil into which the fuet is  thus converted  over
          and over, a  frefh quantity is always obtained.   The
          acid of fat in fome refpects has a refemblance to that
          of  fea-falt; but in others is much more like the vege-
          table kind,  as being deftrucftible in a ftrong fire,  form-
          ing compounds which do not deliquefce with  calcare-
          ous earth, and uniting intimately with oily fubftances.
          With alkalies it forms falts entirely different from thofe
on alkalies,yielded  by  the  other acids;  with the volatile alkali,
&c.       particularly, it produces  a concrete volatile fait.  When
          faturated  with calcareous earth,  it yields  brown cry-
          ftals;  and a  fait ofthe fame kind was obtained by Dr
          Crell from a mixture of  quicklime and fuet diftilled to
          drynefs, and boiling up  the refiduum with water.  The
          cryftals were hexagonal,  and terminated by  a  plane
          furface ; their tafte was acrid and  faltifh; they  did
          vol deliquefce in the air, and were eafily and copioufly
          diffolved in water.  With magnefia  and earth of alum
          a gummy mafs is obtained, which refufes to  cryftal-
          lize.
           With regard to the  metals,  Dr Crell  informs us,
          that the acid of fat copioufly  diffolves manganefe into
          a clear and limpid liquor.  It diffolves the precipitate
          of  cobalt,  but not  the regulus.   White arfenic is act-
          ed  upon  but Sparingly, and  nickel  not at all, though
          it forms a green folution with the precipitate from  ni-
          irous  acid.   Regulus  of antimony,  by  the affiftance
          of  heat is diffolved into a clear liquor,  which became
          milky  in  the cold:  it  cryftallized   on  evaporation,
 4th  1015
On metal*
combina-
tion'.
I   S   T    R   Y.                            Practice.
 and did not deliquate in  the air.   Zinc readily dif- Fixed alka-
 lolvcci,  and imparted a peculiar metallic tafte, tailing lint" falts
 to the bottom  in the  form of a  white powder on the *"_*:"'
 addition of  an alkali.  Bifmuth in  the  metallic  ftate
 was  not diffolved ; but the precipitate was.  It  acted
 upon  mercury after being  twice  diftilled from n, and
 poured  afreih upon the   metal.  The mercury  could
 not be  entirely  precipitated by common  fait.  It acted
 more vigoroufly  upon a precipitate from corrofive fub-
 limate; from  the folution  of whicli a  white fublimate
 was  obtained  after the liquor had  been drawn off  by
 diftillation.    A gold-coloured folution  was obtained
 from  platina by  diftilling  the acid from  it to drynefs,
 and  then pouring it back again;  the  precipitate  of
 this  metal from aqua-regia by  fpirit  of wine was dif-
 folved in great abundance.   Iron was very eafily dif-
 folved in it,  and  exhibited a liquor  of an  aftringent
 tafte, which fliot into needle-like cryftals that did not
 deliquefce in  the  air.  Lead  was  corroded and  ren-
 dered the acid turbid.  Minium  was converted into a
 white powder, and then  diffolved with greater  cafe.
 The folution has a fweet tafte, and cannot be precipi-
 tated by fea-falt.  Tin was corroded into a yellow calx,
 and  diffolved  but in very fmall quantity.  Copper was
 diffolved, even  in the cold,  into a green  liquor; but
 the folution was greatly promoted  by heat.   On eva-
 poration it  fhowed fome  difpofition to cryftallize, but
 again attracted moifture from  the air.  Silver-leaf was
 attacked only  in a very fmall degree; however,  fome
 was  precipitated by  means of copper, aud the marine
 acid rendered the  liquor turbid.   The calx precipitated
 from  aquafortis was  diffolved more copioufly.  Silver
 WuS  precipitated of a white colour from aquafortis by
 the pure acid itfelf, as well as by its ammoniacal faltr.
 Half an ounce of  the acid diftilled four times almoft
 to drynefs from  fome gold-leaves,  and at length pour-
 ed back upon them,  the precipitate  of a  dilute  folu-
 tion  of tin obtained by it, gained  only a faint colour,
 rather inclining to red ; but a mixture of two parts of-
 acid with one of aquafortis, diffolved gold  very rea-
 dily.

           $  19.  Of Fixed Alkaline Salts.
  Of thefe there are  two kinds;  the vegetable and How pro-
mineral.  The  former is never  found by itfelf, and cured.
but rarely in combination with any acid ; but is always
prepared from  the  aflies  of  burnt vegetables.   It  is
got in the greateft  quantity from crude tartar;  from
which,  if burned  with proper care and attention, we
may  obtain one pound of alkali out of  2^.  of  the tar-
tar.   The latter is found  native  in  fome parts of the
earth.  Ir is likewife  found in  very large quantities
combined with the marine acid,  in the waters of tfie
ocean, and in the bowels  of the earth ; thus  forming
the common alimentary fait.   It  is alfo produced from
the aflies of certain fea-plants,  and of the  plant called
kali; from whence both the mineral and vegetable al-
kalies have taken their name.                            x
  The vegetable alkali difficultly affumes a cryflalline Vegetable
form; neverthelefs, it may be partially  united with alkali cry-
fome  acids in fuch a manner as to cryftallize, and lofe ftallized.
its property of deliquating in  the air, without at the
fame  time ceafing to be an alkali.  Of this we  have
an example in the acid of  ants abovementioned.  Some-
                                              thing 
Practice.
CHEMISTRY.
H7
table alkali.
   1019
Difference
between
vegetable
and mine-
ral alkalies
 Fixed alka-thing of the  fame kind  we have obServed  in treating
 line falts   vegetable  fixed alkali with fpirit of  wine.   A  gallon
           of pretty ftrong fpirit of wine being drawn over from
           a pound of fait of tartar, a black  unctuous liquor  was
           eft, which fhot into cryftals very much refembling vi-
           triolated tartar, and  which did  not deliquate  in  the
           air, but were neverthelefs ftrongly alkaline.  Dr Black,
           however, informs us, lhat the vegetable alkali may be
           fhot into fine  cryftals ; but which  cannot be  preferved,
           on account of their great  attraction for moifture,  un-
           lefs clofely fhut  up from the air.   They have not fuch
           a quantity of water as to undergo  the aqueous fufion.
            The mineral alkali in its natural ftate always affumes
           a cryflalline  form, fomewhat reSembling that  of  Sal
           mirabile.   It does not deliquate in  the air, nor does  it
           feem to have  So  ftrong  an attraction  Sor  water, even
           when iu its moft cauftic ftate, as the vegetable alkali :
           hence mineral alkali is preferable to it in making foap,
   IQIg    whicli  is always of a firmer confiftence with  mineral
 Change  on  than with vegetable alkali.  If vegetable alkali iscom-
 the vege-   bined with  fpirit  of Salt,  Some  change  Seems to  be
           thereby induced  upon it ; as the Salt  produced by  ex-
           pelling the marine acid by means  of the vitriolic, and
           then cryftallizing the mafs, cryftallizes differently from
          vitriolated tartar. Whether the vegetable  alkali might
          by this  means be entirely converted into the mineral,
           deferves a further  inquiry.
            Both  mineral  and  vegetable alkalies, when applied
           to the  tongue, have  a  very fharp,  pungent, and uri-
           nous tafte; but the vegetable confiderably  more fo than
           the mineral.   They both unite with  acids, and form
          different neutral falts with them :  but  the  vegetable al-
          kali feems to  have rather a greater  attraction for acids
          than the other; although this difference is not fo great
          as that a neutral  fait, formed  by  the union of mineral
          alkali with any acid, can be perfectly decompofed by
          an addition of the vegetable alkali,  unlefs in confider-
          able excefs.
            Both  vegetable and  mineral  alkali  appear to be
of a cauftic compofed of an exceedingly cauftic fait united with  a
fait aud fix- certain quantity of fixed air. This may be increafed fo
          far, as to make the vegetable alkali affume a cryflalline
          form, and lofe great part of its alkaline properties :  but
          as the adhefion of great part of this air is very flight, it
          eafily feparates by a gentle heat.  Some part, however,
         is obftinately  retained ;  and the  alkali cannot be de-
         prived of it by the moft violent calcination per fe. The
         only method of depriving it entirely of its  fixed air  is,
         by mixing an  alkaline folution with quicklime.

                     Fixed Alkalies combined,

            I. With Sulphur.  The produce  of this is the red
         fetid compound called hepar fuJphuris, or  liver of fill-
         phur.  It may be  made by melting  fnlphur  with a
         gentle heat, and  ftirring into it,  while melted, four
         times its weight of  dry alkaline fait.    The whole
         readily  melts  and  forms a red mafs  of a very  fetid
         fmell, and which deliquates in  the air.  If fulphur is
         boiled in a folution  of  fixed  alkaline fait,  a like ccun-
         bination will take place.
           In this  procefs, when the hepar is made either  in
         the dry or the moift way, the fixed air of the alkali is.
         difcharged, according to Dr Prieftley's  obfervation.
         Neither does a fixed alkali, when combined with fixed
         air, feem capable of uniting with fulphur ;  nor will
   IOZO
C«wnpofed
ed air.
   IOZI
Hepar ful
p bur is.
  the union be accompliflied without heat, unlefs the al-  Fixed alka-
  kali is already in a cauftic ftate.  Hence a cold Solution  1,nc fa^f
  oS hepar fulphuris may  be decompounded,  partly  at     *. '*
  leaft, by fixed air.   On  adding an acid, however, the tiong>
  decompofition takes place much more rapidly ;  and the  <•----v----»
  fulphur is precipitated  to the  bottom,  in  form of a    *°2a
  white powder.                                       Decompo-
   During the precipitation of the fulphur from an al-  c  '
  kali, by means of  acids,  a thick white fmoke arifes,  of
  a moft fetid  fmell and  fuffocating nature.  It  burns
  quietly, without  explofion, on a candle's being  held'in
  it.  Calces of filver, lead, iron, or  bifmuth, are ren-    IOi3
  dered black by it.   Hence, if any thing is wrote  with fnflamma-
  a folution of lead,  and a folution of hepar fulphuris is We vapour
  paffed over it when dry, the writing, formerly invifible, in the -
  will  immediately  appear of a  blackifh brown  colour. comP0»-
 Silver, in its metallic  ftate, is prodigioufly  blackened tlon ° lt-
 either by the contact of  this vapour,  or  by  being im-
 merfed in a folution of the hepar fulphuris itfelf.   Li-
 tharge is inftantly reftored  to  its metallic  ftate, on
 being immerSed even in  a cold Solution of hepar  ful-
 phuris. _                                              I024
   By being united  with  an alkali, the acid of fulphur Phlogifloa
 feems very much difpofed to quit the phlogifton.   If  a of fulphur
 folution  of hepar  fulphuris is expofed  to the  air  for difpofed to
 fome time, it is  fpontaneoufly  decompofed;  the phlo-1U.^ thc
 gifton of the fulphur flying off, and the acid remaining"
 united with the alkali into a vitriolated  tartar.  This
 decompofition takes place fo remarkably, when liver
 of fulphur is diffolved in water, that,  by a fingle  eva-
 poration to drynefs, it will be almoft  totally  changed
 into vitriolated tartar.  If this fubftance, in a dry ftate,
 be expofed to a moderate degree of heat, and the mafs
 kept  conftantly  ftirring, a like decompofition will Sol-
 low ; the phlogifton oS the Sulphur will fly off, and the
 acid unite with the  alkali.
   Liver oS Sulphur is a great Solvent of metallic mat- Metals and
 ters ;  all of which, except zinc, it attacks, particular- charcoal
 ly in fufion.   It feems to diffolve gold more  effectu- diffolved
 ally  than other metals.   This compound alfo diflblves b* lt'
 vegetable coals, even  by  the humid  way ; and thefe
 folutions, if fuffered  to ftand in the open air, always
 precipitate a black  powder, no other than  the  coal
 they had  diffolved,  in  proportion  to the quantity of
 hepar fulphuris decompofed.   When  vegetable coal is
 thus diffolved by liver of fulphur in fufion, it is of a
 much deeper red  than in  its natural ftate.  The folu-
 tion in water is of a green colour.
  II.  With Expreffed Oils.  The refult of this combi-
 nation is foap ; for the preparation of whicli in large
 quantities  in the way of   trade, fee Soap.   The foap
 which is  ufed in  medicine is  prepared without heat,
 in the following  manner, according  to the author of
 the Chemical Dictionary.
  " One  part of quicklime,  and two parts of good
Spanifh foda (the  fait prepared from the afhes  of  the
herb kali), are boiled together during a fhort time in
an iron caldron.   This lixivium is to  be filtered,  and
evaporated by heat, till a phial, capable of containing
an ounce of water, fhall  contain an  ounce  and  216
grains  of  this lixivium.   One part of this lixivium is
to be mixed with two parts of oil of olives, or of fweet
almonds, in a glafs or flone-ware veffel.  The mixture
foon becomes thick  and  white ; and  muft  be ftirred
from time  to time with an iron fpatula.   The combi-
                       T 2                  nation
1036
Soap. 
r ixed alka-
line falti
and their
combina-
CHEMISTRY.
Practice.
   is-. 7
Starkey'i
l^ap.
  roi8
Phlogifti-
nation  is gradually completed, and  in  feven or eight
days a ver» white and firm foap is obtained."
  In attempting combinations of  this kind, it is abfo-
lutely neceffary that the alkali be deprived of  its fixed
air as much  as  poflible ;  otherwife  the foap  will  be
qaite unctuous and foft:  for fixed alkalies have a great-
er attraction for fixed air  than for oil, and hence foap
is  decompounded by blowing fixedair  into a folution
of it in water.   It may be  made either  with tallow,
wax, fpemiceii, butter of cocoa, the coarfer refinous
fubftance^, or animal oils.
   III. With EJfential Otis.  The  volatility of thefe oils
in a great meafure hinders them from being acted upon
by alkalies :  neverthelcfs, combinations of this  kind
have been attempted ; and the compounds fo produced
have  been called Star key's foap,  from  one Starkey a
chemift, who endeavoured to volatilize fait of  tartar by
combining it  with oil of turpentine.  His method was
to put dry  fait of tartar into a matrafs,  and  pour upon
it effential oil of turpentine to the height of two or
three fingers  breadth.  In five or fix months, a  part
of the alkali  and oil were combined into a white  fa-
poniceous compound.  This muft  be  feparated  from
the mixture, and more  of it  will afterwards be formed
by the fame method.
   Chemifts, imagining this  foap to be poffeffed of con-
siderable medical virtues, have endeavoured by various
methods to fhorten this tedious procefs.  Of thefe one
of the moft  expeditious  is  that  recommended by  Mr
 Beaume' ; which confifts in triturating,  for a long time,
 alkaline fait upon  a porphyry, and  adding oil of tur-
 pentine during the trituration.   According to him, the
 thick refinous part of  the oil only  can combine with
 the fait ; and, during  the time this combination is ef-
 fected, the more fubtile and attenuated parts will fly
 off.   Hence he finds  that  the  opeartion  is confide-
 rably abridged by  the addition of a  little turpentine or
 common  foap.   The  moft expeditious of  all, how-
 ever, is that  mentioned by  Dr Lewis ; which confifts
 in heating the alkali  red hot,  and then throwing it
 into oil  of turpentine, ftirring  them  well  together ;
 on which they  immediately unite  into a Saponaceous
 mafs.
   This kind  of foap  is Subject to great alterations from
 keeping;  particularly  the lofs of its colour, and a kind
 of decompofition occafioned by the extraction oS  an
 acid from the oil of  turpentine, which  unites with the
 alkali, and cryftallizes not  only all over the furface,
 but in the very  fubftance of the foap.   The nature of
 this fait is unknown, but certainly  deferves confidcra-
 tion.
    IV. V/ith Phlogifton.   This combination is effected
purity, by repeated calcinations in a  ftrong fire, and Fixed alka.
deliquations in the air, all of them, the marine  alkali lm« f"lt*
excepted, appear to be  the very fame.                and their
  On  this lubjecl  Mr Gmelin  has given a great nnm- tiol)i
ber of experiments in  the  fifth volume of the fow-
led alka-by calcining them with the charcoal either  of vege-
lic.       table  or animal matters.  The confequence is,  that
          they are greatly altered in their properties ; fometimes
          fo much as to be enabled to precipitate calcareous earths
          from  their folutions in acids.  Metallic folutions pre-
          cipitated by them in this ftate, affume different colours.
          Differences  obferved  between Fixed Alkalies obtain-
                       ed from different Vegetables.
            Thefe differences we muft conceive to arife  from
          Some  proportion of the  oily and  phlogiftic  matter of
          the vegetable remaining in the afhes from whence the
          falts arc extracted ; for  when reduced  to their utmoft
mentarui Pttropolitana ;  and found  very  confiderable   io19
differences,  not  only  between  the  alkaline falts, bin Mr Gmc*
likewife the pure vegetable  earths obtained  from  dif-   s c,xpc"
ferent vegetables by burning.   The falts of the feveral
plants examined were prepared  with great care, and all
of them exactly in the fame manner; each vegetable be-
ing burnt in a feparate crucible, with the  fame degree
of fire, till no remains of coaly matter could any longer
be  perceived ; and the aflies elixated in  glafs veflels
with cold diftilled water.  The falts,  thus obtained,
were  found to  produce  different  colours on  mixture
with certain  liquors,  and to effervefce in  very diffe-
rent degrees  with acids :  certain  metallic folutions
were  by fomc  precipitated,  by others only rendered
thicker,  by  others  both precipitated and   rendered
thick ;  whillt fome occafioned  neither the one nor the
other of thefe changes, but left  the  fluid  clear  and
tranfparent.   Thus,  with the vitriolic acid, the  falts
of  fouthernwood and fage ftruck a pale brown colour ;
thofe  of pine-tops and rue,  a yellow ;  that  of fern, a
reddifh yellow;  and that of fanicle, a dark leek-green:
that of dill yielded a  leek-green precipitate, with ele-
gant green flakes floating  in  the  liquor.  This laft
fait alfo  gave a  greenifh  precipitate with the  marine
acid,  and  a red  one with  the  nitrous.   Solution  of
corrofive  fublimate  was changed  yellow  by fait  of
fouthernwood ;  of a brownifh colour, by that of coh's-
foot ;  of a deep red,  by that of wormwood  ;  and of a
pitch-colour, by that of dill.  That of fern threw down
an  opal-colour ; of fage, a fulphur-yellow ;  of elder
flowers, a citron yellow ; of fanicle, a Saffron colour ;
and of milfoil, a deep-red precipitate.   From Solution
of  filver, fait of carduusbenedictui threw down a white;
of  camomile, a grey ; of hyffop,  a brownifh ;  of dill, a
blackifti brown ; of  fcabious, a yellowifli ; and that  of
pine-tree tops,  a fulphur yellow  precipitate.  Solution
of  vitriol of copper was  changed  by fait of fouthern-
wood to a bright fea-green ; by  that of dill, to an un-
fightly green ; of agrimony, to a  greenifh blue ; and  by
 that of milfoil,  to a bright fky-blue :  the fait of  pen-
 ny-royal  made the  liquor thick as  well as blue, and
 that of feverfew made it thick and green :  the  fait  of
 byffop threw down a green precipitate, that of fcurvy-
 grafs a blue  one, and that of fumitory  a greenifh blue :
 whilft the fait of  fern made fcarcely any change either
 in  the colour or confiftency of the liquor.

             §  19. Of Volatile Alkali.
                                                       1030
    This is a kind  of  fait  obtained from  all animal, whence
 fome  vegetable, fubftances, from  foot  by diftillation obtained.
 with  a  ftrong  heat,  and from all  vegetable  fubftan-
 ces by  putrefaction.   Though a  volatile  alkali   is
 procurable  from all  putrid animal fubftances by  di-
 ftillation, yet  the putrefactive procefs does  not  feem
 to prepare volatile alkali in all oS theSe.  Putrid urine,
 indeed, contains a great quantity of alkali ready form-
 ed,  whence its uSe  in  Scouring, ire. but  the caSe is
 not So with putrid blood or flefli.   Thefe afford no  al-
 kali till after the phlegm  has arifen ;  and  ihis they
                                               would 
Practice.
CHEMISTRY.
1031
 would do, though they  had not been putrefied.   Ac-
 cording  to Mr  Wiegleb,  volatile  alkali is  found in
 limeitone, lapis  fuillus,  chalk,  marble, coals,  turf,
 loam, clay, and  many other kinds of earth.   Its exift-
 ence  in thefe fubftances may be difcovered merely  by
 diftilling them with  a brifk fire, but ftill better by the
 addition  of fome quantity of fixed alkali  or quicklime
 before the diftillation.—It has even been found in all
 mineral  falts and their acids, as vitriol, nitre,  com-
 mon fait, and the acid liquors drawn  from thefe  fub-
 ftances, alfo in  gypfum and fulphur :  from  all which
 it may be Separated by means of quicklime.—-In the
 vegetable kingdom it is  produced  by  dry diftillation
 from  muftard-feed, elder flowers and leaves; the leaves
 of  the wild  cherry-tree,  white  water-lilies, tobacco,
 and fage;  as  well as  from many other  plants.   Ac-
 cording  to our  author, the plaineft  proof of its exift-
 ing almoft univerfally  in the vegetable kingdom, is,
 that the  foot of  our  chimneys affords a volatile  alkali
 by  diftillation, either with or without quicklime.
  Volatile alkali, when  pure,  appears  of  a fnowy
 whitenefs; has  a very pungent fmell, without any dif-
 agreeable empyreuma; is very eafily evaporable, with-
 out leaving any refiduum ;  effervefces with acids much
 more ftrongly than  fixed alkali ;  and forms with them
 neutral compounds called  ammoniacal falts, which we
 have  already  defcribed, and  which  are different ac-
 cording to the nature of the acid made ufe of; for all
 volatile alkalies, when perfectly purified, appear  to be
 the very fame, without the fmalleft difference.
  Like fixed alkalies,  thefe falts contain a great quan-
 tity of fixed  air, on  which  their folidity  depends;
 and which may  be fo increafed  as  perfectly  to  neu-
 tralize, and  deprive them of their peculiar  tafte  and
 fmell.  When neutralized  by fixed air,  they have a
 very  agreeable  pungent tafte,  fomewhat refembling
 that of weak  fermenting liquors.  When totally de-
prived of fixedair, by means of lime, they cannot be re-
duced to  a folid form ;  but are diflipated in an invifible
and exceedingly pungent vapour, called by Dr Prieftley
alkaline air.  When volatile alkaline fait is  diflblved
in water, the folution  is called volatile alkaline fpirit.
  Diftillation and Purification of  Volatile Alkalies.
                             149

fixable  air, and Some oil. Volatile
 the  water, and1 likewife alkali and
Diftilling    The materials moft commonly ufed for preparing vo-
veffel,and  iatj)e alkalies are the folid parts of animals, as  bones,
method of  nornSj ^  Thefe are to be  put into an iron pot of the
the opera"S ^iaPe recommended for folution ; to this muft be fined a
tion.      Aat head, having a  hole in the middle about two inches
          diameter. From this a tube of plate-iron muft iffue, which
          is to be bent in fuch a manner that the  extremity of it
          may enter an oily jar, through an hole  made in its up-
          per part,  and dip about half an inch under fome water
          placed in the lower part.   The mouth of the jar is to be
          fitted with a cover,  luted on very  exactly; and having
          a fmall  hole,  which may  be occafionally  flopped with
          a wooden peg.  The junctures  are to be all  luted  as
          clofe as poflible, with  a  mixture of clay, fand,  and
          Some oil ; and thoSe which are not expoSed to a burn-
          ing heat,  may be  further fecured  by  quicklime  and
          the white of an egg, or by means of glue.  A fire  be-
          ing  now kindled,  the  air contained in the diftilling
          veffel is firft expelled, which is known by the bubbling
          ofthe water; and  to this vent  muft be given by pull-
          ing  out  the wooden  peg.   A confiderable quantity of
          phlegm will then come over, along with  fome volatile
 alkali,  a great  quantity of
 The alkali  will unite  with _
 fome part of the fixed air, the oil Swimming  above. ,ts ^01tlbl"
      r           •      -i 1            »           -n nations,
 A  great many  incoercible  vapours,  however, will .____^___
 come over, to which vent muft be given from time to
 time, by pulling out •the  peg.   The diftillation is to
 be  continued till all is come  over;  which may  be
 known  by the ceffation, or very flow bubbling  of  the
 water.   The iron pipe muft then be  fcparated from
 the cover of the diftilling veffel,  left the liquid in the
 jar fhould return into  it,  on the  air being condenfed
 by  its cooling.  In the jar  will  be  a  volatile fpirit,
 more or lefs ftrong according as there was lefs or more
 water put in,  with an exceedingly feiid  black oil float-
 ing upon it.                                           1032
  The  rectification of  the volatile alkali  is moft com- Rec^lifica*
 modioufly performed at once by combining it with an tion.
 acid ; and, as fpirit of  fait has the leaft  affinity with
 inflammable matter, it  is to be chofen for  this pur-
 pofe, in  preference to the  vitriolic or  nitrous.   As
 the  fpirit is  exceffively  oily,   though  already much
 weakened by the admixture of the water in the jar,
 if a very large quantity  was not originally put in,  an
 equal quantity of water  may ftill be added, on  draw-
 ing off the Spirit.  That as little may be loft  as pof-
 fible, the Spirit  flionld  be received in a ftone bottle ;
 and the marine acid, likewiSe in a diftilled  ftate, add-
 ed by little and little, till the efferveScence ceaSes. The
 liquor,  which is now an impure Solution of  fal ammo-
 niac,  is  to be left for fome time, that the oil may  fe-
 parate itfelf; it  is then  to be-filtered, evaporated, and
 cryftallized in a  leaden  veffel.  If the cryftals are not
 fufficiently pure  at the firft, they will  eafily become
 fo on  a fecond diflblution.                               1033
  From  fal  ammoniac thus obtained pure, the volatile Volatile fal
 alkali may be extricated by diftillation with  chalk,  al- ammoniac.
 kaline falts,  or  quicklime.   Alkaline  falts  act more
 brifkly than chalk, and  give  a  much ftronger volatile
 alkali.  The  ftrength  of  this,  however,  we  know
 may be  altered at pleafare, by adding to, or depriving
 it of,  its natural quantity  of fixed  air.   Hence, per-
 haps, the beft  method  would  be,  to prepare volatile
 alkalies altogether in a fluid  ftate,  by means of quick-
lime; and then add fixed air to them, by  means of
an  apparatus  fimilar to that  directed by Dr Prieftley
for  impregnating  water with fixed air.   To prevent
lime  from adhering to the diftilling veffels in which it
is put, the tranflator of Wiegleb's chemiftry recom-
mends the putting in three or four ounces of common
fait along with the other ingredients.
Volatile alkalies combined,
1034
  I. With Metals.  There are only three metals, viz. Cuprum
copper, iron, and lead, upon  which,  while in their ammonia-
metallic form,  volatile alkalies arc capable  of acting. ca^e-
Copper-filings are diffolved by  volatile  alkali, efpecial-
ly in its cauftic ftate,  into a liquor  of a moft admi-
rable  blue  colour.  It is remarkable,  that this colour
depends  entirely upon the air having accefs to the fo-
lution : for  if  the  bottle containing it is clofe  ftopt,
the  liquor becomes colonrlefs;  but, however, refumes
its blue colour on being expofed to the air.  On evapo-
poration, a blue faline mafs is obtained, which, mix-
ed  with  fats, or other inflammable matters,  tinges
their  flame green, leaving a  red calx of copper, fo-
luble again in volatile  fpirits as at firft.  This faline fub-
                                              ftance 
!5°
Volatile
alkali .md
it* cotnbi-
n it ions.


Copper,
fulmii.j-
Mg.
   1036
ftal volatile
•k..'l..::i.
                             CHEMI

ftincc \.i% bred received  into the laft edition of the KJ-
dinburgh Difpenfatory, under the name of cuprum an-
moniacale, a? an anticpilepiic.
  The blue mix; ire of folution of copper in aquafortis
with volatile Spirits,  yields Sapphire-coloured cryltaL,
which diflblve  in  fpirit of wine, and impart their co-
lour to  it.   lt, inftead  of cryftallization,  ihe  liquor
be  totally  evaporated, the remaining dry  mattcr ex-
plodes,  in  a moderate  heat, like aurum  fulminans.
This is given as a fact by Dr Lewis; but hath not Suc-
ceeded upon trial  by Dr Black.  Various phenomena,
fays Mr Wiegleb,  occur in the diffobuion of copper
bv  the volatile  alkali.—On  Saturating dilute fpirit  of
fal  ammoniac  with copper-filings, cryftals  arc formed
of a dark-blue colour, but which, by  expofure  to the
air, fall to  pieces and  become green.   Vinous fpirit
of fal ammoniac impregnated  with copper,  lofes in  an
inftant  its  blue colour,  on  the affufion  of an  equal
quantity of faturated folution  of  fixed  alkaline  fait.
The copper is then  taken up  by  the fixed alkaline
folution, which of confequence acquires  a blue colour,
while the fpirit of wine, deprived of the  metal, floats
clear on the top.  When filings of  copper are put into
a bottle, and that bottle quite filled with cauftic vola-
tile alkali,  and is immediately  flopped up, no folution
takes place:  but when  the bottle is left  open,  only
for a fhort time, or an empty fpace is left  in it, a
colourlefs  Solution  is obtained, which in  the air ob-
tains a blue colour, but which may be; deprived  of
this  colour as often as we pleafe, by fliutting it up ex-
actly from  the air,  and letting it  ftand, in this Situa-
 tion, on frefh filings of copper—From theSe  pheno-
 mena Mr  Wiegleb concludes,  that  copper does not
 diflblve in volatile  alkali until it has loft part  of  its
 phlogifton, to which the air,  by  the attraction it ex-
 erts upon  it, contributes its  fhare.  If  this has taken
 place only in a  fmall proportion,  and  the farther  ac-
 cefs of air be prevented, the remainder will  be dif-
 folved  without any  colour; which, however, appears
 in  the  inftant that, by a  frefli acceflion of air,  the
 phlogifton ftill remaining finds means to efcape. The
 diffolved  copper is always  precipitated  when  the  fo-
 lution  meets with phlogifticated copper.   The colour-
 lefs folution is precipitated by zinc and vitriolic acid,
 bit not by iron.  It taftes rather fweet, and does  not
 fmell very ftrong of volatile alkali  ; while, on the con-
  trary,  the blue folution has a pungent fmell,  and is
 precipitated by diftilled water.
    On  the other two metals  the action of volatile alkali
  is by no means fo evident;  it difSolves iron very flowly
  into a  liquor,  the nature of which is not known;  and
  lead is corroded by it into a mucilaginous fubftance.
    II.  With Inflammable Subftances.  With expreffed
  oils, the cauftic  volatile alkali unites into a foft unc-
  tuous  mafs, of a very  white colour, imperfectly fo-
  luble in water,  and which  is foon decompofed  fpon-
  taneoufly.  Compofitions of this kind are frequently
  ufed for removing pains, and fometimes with fuccefs.
  With  effential oils, volatile alkalies may be united,
  either in  their dry or liquid form,  by means of diftilla-
  t'u n.   The produce is  called fal volatile oleofum ;  it is
  much more frequently  ufed in a  liquid  than in  a  dry
  form.   The  general  method of preparation is  by  di-
  ftl.hng volatile alkali along with effential oils  and  fpi-
  rit of  wine, or  the aromatic  fubftance from  whence
S    T   R    Y.
Praclicc.
the effential oils are  drawn.  Thefe competitions arc Volatile
variable at pleafure ;  but certain forms are laid  down ->^»b ^ »
in the difpeulatories, with which it is expected that all ^*"8 '"
the chemifts lhould comply  in the preparation of  thefc J__^l_^
medicines.                                            I( \<T
   III.  Eau de Luce.   This  is  the name given  to an Spiritut
exceedingly volatile  fpirit, which fome years  ago was *oIajt^*Mg
pretty  much in vogue;  and indeed fcems very well
calculated to anfwer  all the purpofes for which volatile
alkalies can be ufed.   It was of  a thick white colour,
and fmelled fomewhat of oil of amber.   A receipt ap-
peared in Lewis's Difpenfatory for  the preparation of
this fluid, under the name of fpirit us volatilis fuccinatus.
The method there directed, however, did not fucceed ;
becaufe, though the alkaline fpirit is capable of keeping
a fmall quantity of oil of amber fufpended, the colour
is greatly more dilute than that of genuine eaude luce.
In the Chemical Dictionary we have the following re-
ceipt:  " Take four  ounces of  rectified fpirit of wine,
and in it diffolve  10  or 12 grains of  white foap ;  filter
this folution; then diffolve in it a  drachm of rectified oil
of amber,  and filter again.   Mix as much of this folu-
tion with the ftrongeft volatile fpirit of fal ammoniac,
as will be  fufficient,  when thoroughly ihaken togive it
a  beautiful milky appearance.   If upon  its furface be
formed a cream,  fome  more  of  the oily fpirit muft be
added."
   This receipt likewife feems infufficicnt.  For the oil
of amber does not diffolve  in fpirit of wine : neither
is it probable that the fmall quantityof foap  made ufe
of could be of any Service ;  for the foap would diffolve
perfectly in  the  alkaline fpirit,  without  fuffcring any
decompofition.  The  only  method which  wc   have
found to anSwer is the Sollowing.   Take an  ounce,  or
any quantity at pleafiire, of balSamum CanadenSe ; place
it in a Small china baSon, in a pan oS boiling water,, and
keep it there till a drop of it  taken out  appears of  a
 refinous confiftence  when  cold.  Extract a tincture
 from this refin with good fpirit of wine; and having
 impregnated your volatile  fpirit  wiih oil of  amber, la-
 vender or any other effential oil,  drop 'in as much of
 the fpiritous tincture as will give it the defiled colour.
 If the volatile fpirit  is very  ftrong, the eau de luce will
 be thick and white,  like the cream of new milk ; nor is
 it fubject  to turn brown with keeping                   Ic.$
    IV. With Volatile Tincture  of Sulphur. This is a Volatile
 combination  of the  cauftic volatile alkali, or  Spirit alkali com-
 oS Sal ammoniac,  with  fulphur.  It  is ufually di- bined with
 reeled to be  made  by grinding lime with the ful- fuhA*>
 phur and  afterwards with  the fal ammoniac, and  di-
 ftilling the whole in  a retort,  but the produce  is by
 this method very fmall, and  even the  fuccefs  uncer-
 tain.   A  preferable method feems to be, to impreg-
 nate  the ftrongeft  cauftic  volatile fpirit with the va-
  pour  which arifes in the decompofitions  of  hepar ful-
  phuris by means of an acid, in the  fame  manner ai
  directed for impregnating water with  fixedair.         1039
    This  preparation has a moft naufeous fetid  fmell, Sympathe*
  which fpreads to a confiderable diftance ; and   the ef- t«c "*k.
  fluvia will  blacken filver or copper, if barely placed in
  the  neighbourhood of the  unftopped  bottle.   This
  property  renders it capable of forming a curious kind
  of fympathetic  ink; for  if  paper is wrate cpon  with
  a folution of faccharum  faturni, the writing,  which
  difappears when dry,  will appear legible  and oS a
                                            brownifh 
Practice.
CHEMISTRY.
i ci
Phenome-  brownifh black,  by barely holding it near the month
nafrom    0f the bottle containing volatile tincture of  fulphur.
mixture$of The vapours  of this tincture  are  fo exceedingly  pe-
          netrating,  that it is faid they will even  penetrate
acid,
falts.
&c.
   1040
Of mixing
the acid fpi-
rits with
one ano-
ther.
   1041
Diffolving
vitriolic
falts in  ni-
trous or
marine  a-
cids.
   I04Z
Decompo-
fition of vi-
triolic falts
by folutions
of earth,
&c. in ni-
trous or
marine  a-
eid*.
   1043
ByTime-
water.
   1044
Of green
vitriol by
faccharum
faturni.
through  a wall, fo  as to make  a writing wfth faccha-
rum faturni appear legible on the other fide ; but this
is much  to be doubted.   It  is even Said that it cannot
penetrate througn the Subftance of paper,  but only in-
sinuates  itSelf  betwixt the  leaves ;  aqd hence if  the
edges of the leaves are glued together no black colour
will appear.

§ 20. Of the Phenomena refulting from different mix-
   tures of the Acid,  Neutral, and  Alkaline Salts, al-
   ready  treated of

   1. If concentrated oil of vitriol is mixed with ftrong
fpirit of  nitre,  or fpirit of fait, the weaker acid will
become  exceedingly volatile,  and emit  very elaftic
fumes  ;  fo that if a mixture of this kind is  put into a
clofe flopt bottle, it will almoft certainly burft it.  The
fame effect follows upon  mixing  fpirit of fait and fpi-
rit of nitre together.   In this cafe, both acids become
furprifingly volatile ; and  much of the liquor will be
diflipated in  fumes, if the  mixture, is fuffered to ftand
for any  confiderable time.   Such  mixtures  ought
therefore to be made only at the time they are to  be
ufed.
   2. If vitriolated tartar is diffolved in an equal quan-
tity of ftrong fpirit of nitre, by heating them together
in a matrafs, the ftronger vitriolic acid will be difpla-
ced  by the weaker nitrous one, and  the liquor,  on
cooling,  will fhoot  into cryftals of nitre.  The fame
thing happens alfo  upon diffolving vitriolated tartar,
or  Glauber's fait,  in fpirit of fait.  This obfervation
wc owe  to Monf. Beaume, and the reafon  of it has
been already explained.   See n° 285.
   3. If vitriolated tartar, or Glauber's fait, is diffolved
in water, and this  folution mixed  with another con-
Sifting  of calcareous earth,  filver,  mercury, lead,  or
tin, diffolved in the nitrous  or marine acids, the vitrio-
lic acid will  leave the fixed alkali  with which  it was
combined,  and, uniting  with the calcareous earth  or
metal,  fall with it to the bottom of the veffel.   This
decompofition takes place only when the vitriolic acid
meets  with fuch bodies  as  it cannot  eafily diffolve in-
to a liquid,  fuch  as thofe  we have jufl  now  men-
tioned  ;  for  though vitriolated tartar is mixed with a
folution of iron, copper,  ,&c. in the nitrous or marine
acids, no decompofition  takes place.  The cafe is not
altered,  whatever acid is made ufe of ;  for the marine
acid will effectually  feparate filver,  mercury, or lead,
from the vitriolic or  nitrous acids.
   4. According to Dr Lewis, if a folution of vitriola-
ted tartar is dropt into lime-water, the  acid will  unite
with the lime, and precipitate with it in an indiffoluble
felenite,  the alkali  remaining in the water  in a pure
and cauftic ftate.
   5. If green vitriol is mixed  with any folution con-
taining fubftances which cannet be diflblved into a  li-
quid by  the vitriolic acid, the vitriol will be immedi-
ately  decompofed, and the  liquor will become a folu-
tion of iron only.  Thus, if green vitriol is mixed with
a  folution of faccharum  faturni, the vitriolic acid im-
mediately  quits the  iron for the lead, and falls  to the
ottom with the latter,  leaving  the vegetable  acid  ofPSenome-
!ie faccharum faturni to combine"with the iron.       nafrom
mixtures of
   6. If folution of tin in aqua-regia is mixed with fo-
 lution of faccharum faturni, the marine acid quits the falts] '
 tin for  the lead  contained  in  the  faccharum ; at the *----w---->
 fame time, the acetous acid, which was combined with   io45
 the lead, is unable to diffolve  the tin which was be- ^/J"^'0"
 fore  kept fufpend  by the marine acid.   Hence, both fac"^anfirj
 the fiiccharum Saturni,  and Solution of tin, arc very e^- faturuj#
 fectually decompofed, and  the mixture becomes en-
 tirely ufelefs.  Dyers and calfico-printers ought  to at-*
 tend to this, who are very apt  to mix thefe two folu-
 tions together ; and  no doubt many of  the  faults of
 colours dyed  or printed in particular places, arife from
 injudicious mixtures of a fimilar kind.   See Dyeing.   1046
   7. If mild volatile alkali, that is, fuch  as remains in Of calcare-
 a concrete form,  by being united  with  a large quan-ous f°lu-
 tity  of  fixed  air, is poured into  a folution  of chalk in tl0"s D7
 the  nitrous or  marine acids,  the earth will be  preci- ]Tnearkar
 pitated, and  a  true  Sal  ammoniac  Sormed.   IS the
 whole  is  evaporated  to dryneSs, and a confiderable
 heat  applied,  the acid will again part with the alkali,
 and  combine  with ihe chalk.   Thus, in the purifica-
 tion oS volatile  alkalies by means oS Spirit of fait, the
 fame quantity of acid may be made  to Serve a number
 of times.  This.will not hold  in volatile fpirits prepa-
 red with quicklime.                                    1047
   8. If equal parts of  fal ammoniac and corrofive fub- Salalem-
 limatc mercury  are mixed together and fublimed, they broth.
 unite in fuch a manner as never to  be feparable  from
 one  another without decompofition.   The compound is
 a\\ed fal alembroth;  which is  faid to be a very power-
 ful folvent of metallic fubftances,  gold  itfelf not ex-
 cepted.   Its powers in this, or any other refpect, are
 at prefent but  little  known.   By  repeated fublima-
 tions, it is faid this fait becomes entirely fluid, and re-
 fufes to arife in  the ftrongeft heat.                       I0.g
   9. If vitriolic acid  is poured upon any fait  difficult Solution of
 of folution in water, it becomes then  very eafily  folu- falts  pro-
 ble.   By this  means, vitriolated   tartar,  or  creammoted by
 of tartar,  may be  diffolved in  a very fmall quantity of v.'V"lollc *"
 water.                                               Cld"

                 Sect.  II.  Earths.

   The  general divifions and  characters of thefe fub-
 ftances we have  already given ;  and moft of  their
 combinations  with faline  fubftances have been  men-
 tioned,  excepting  only thoSe oS the terra ponderoSa ;
 a Subftance whoSe properties have  been but lately in-
 quired  into, and are  not yet fufficiently inveftigated.v
 In this Section,  therefore we have  to take notice  only
 of their .various combinations  with one  another,  with
 inflammable,  or metallic fubftances,  &c.   As  they do
 not, however, act upon one another till fubjeeted to a
 vitrifying heat, the changes then induced upon them
 come more properly to be treated of under the  article
 Glass.  Upon  metallic and  inflammable  fubftances
 (fulphur alone excepted), they have very little effect -,
 and  therefore what relates to thefe combinations fliall
 be  taken  notice  of in  the following  Sections.  We
 fhall  here confine ourfelves to  fome remarkable altera-
 tions in the nature of particular earths by  combination
with  certain fubftances, and to the phofphoric  quality
of others.
                                                §  1. 
                             CHEMISTRY.
            i t. T'-e Terr 4 Poxde*',<4.
  This earth is ofthe true calcareous kind, and capable
of being  converted ir to a very acrid lime ;  but in other
Practice.
   i°<9
Cf.ally
found unit-
ed with the
vitriolic
   loco
Dr Withe-
ring ex-
periment.
   1051
Combina-
tion of ter-
ra ponde-
rofa with
aerial acid
defcribed.
   105 a
Effcds of
fire upon it
  1053
Treated
with ma-
rine acid.
   I<y54
Precipitat-
ed by mild
and cauftic
fixed alka-
lies.
Converti-
ble into
lime capa-
ble of de-
ronapofing
▼ triolk
f«Jt*.
refpects  L vrry dillercnt.  It  is  moft commonly met
with in the veins of rocks, mftted with the vitriolic acid
in a mafs fomewhat refembling gypfum, but much hea-
vier and  more opaque;  and Irom the great weight of
this fubllaucc the  earth  iifciS has its  name, though
when  freed from the acid ii is by no means remarkable
for this prcpeity.  Its properties were tint taken notice
of by the foreign chemifls; but they have  been more
accurately  invefligated  by Dr Withering,   who  has
publifhed his observations in the 741I1 volume of the Phi-
lofophical Tranfaclions.   lbs experiments were  not
made on the gypfeous fubftance abovementioned ; but on
a combination of the earth  with  fixed air,  which is
much  more uncommon, and like the other pi-fie lies a ve-
ry confiderable degree of fpecific  gravity.  Both thefe
combinations have the general name of fpathumpen-
derojum, or  ponderous fpar;   the former being  alfo
called barofclenite,  &c.
   The fpar ufed by Dr Withering was got out of a lead
■ mine  at Alflon moor in  Cumberland.   Its appearance
 was not unlike that of a lump of  alum ; but on clofer
 inflection it appeared to be compofed of  flender fpiculae
 in  clofe  contact,  more or lefs diverging, and fo foft
 that  it might be cut by a knife; its fpecific gravity
 from  4.300 to 4.338.  It effcrvefced  with acids,  and
 melted,  though not very readily,  under the blow-pipe.
 In  a common fire it loft its tranfparency ; and on being
■ urged with  a ftronger  heat in a melting  furnace, it
 adhered  to  the crucible, and  fhowed figns of  fufion;
 but did not appear to have loft any  of its fixed air, either
 by diminution in  weight, becoming cauftic,  or lofing
 its power of effervefcing with acids.
    Five hundred grains of this  fpar, by folution  in mu-
 riatic  acid, loft 104 grains in weight,  and left an info-
 luble  refiduum of  three grains.   In another  experi-
 ment, 100 grains of fpar loft 21;  and there  remained
 only 0.6  of a grain of infoluble mattcr.
   On diffolving another hundred grains in dilute mu-
 riatic  acid, 25 ounce-meafures of air  were obtained,
 which by proper trials appeared to be  pure aerial acid ;
 and,  on  precipitating  the folution with mineral, alki,
 100 grains of earth were again obtained; but on  dif-
 folving the precipitate  in frefh muriatic acid, only 20
 ounce-meafures of  air were produced.
    Mild  vegetable  alkali precipitated  a faturated  folu-
 tion of this fpar in marine acid,  with the  efcape of a
 quantity  of fixed  air;  and the fame  effect took place
 on the addition of foflil alkali; but with cauftic alkalies
 there  was  no appearance of effervefcence,  though a
precipitate likewife fell.
   Fifty  parts  of fpar,  diflblved  in marine  acid, loft
 101;  and with cauftic vegetable alkali, a precipitate
 weighing 45;  was obtained.   Phlogifticated  alkali
 preeipitated the whole  of  the  earth,  as appeared by
 the addition of mild fixed alkali afterwards, which oc-
cafioned  no farther precipitation.
   Fart of the precipitate  thrown down by the  mild
 alkali was expofed to a ftrong heat in a crucible,  and
 then  put  into water.   The liquid was inftantly con-
 verted into a very acrid lime-water, which had the fol-
 lowing  remarkable  properties: The fmalleft  portion
 of  vitriolic acid, added  to  this water,  occafioned an
immediate and copious  precipitation, which appeared  Terra pon-
even  after the liquid was diluted with 2CO times its  dcrofa and
bulk of pure  water.  2.  A finale drop let fall into a  lU .°")
        *                    01               nations.
folution of Glauber's fait, vitriolated  tartar, alum,  vi-  *
triolic  ammoniac,  Epfom Salt, or felenite, occafioned
an immediate  and copious precipitate in all  of them :
the reafon of which  was the fuperior  attraction of the
ponderous earth  for  the acid of thefe falts, which
forming with  it an  indilfolubic concrete, inftantly Sell
to the bottom.                                          1056
   The precipitate thrown down by the cauftic  vege-  Infoluble
table alkali was put  into water,  but exhibited  no Such  precipitate
appearances as the other : even the mixture was boiled;  tnrow"
nor had  it  any acrimonious  tafie.   Cn adding the   0*J.1 \
three  mineral acids to Separate  portions ofthe preci-  j^
pitate itfelf, neither effervefcence, nor any fign of  fo-
lution, appeared.   After ftanding an hour, water was
added, and  the acids were fuffered to remain another
hour on  the powder ; but on decanting them after-
wards, and adding  foffile alkali to the point of fatura-
tion, no precipitate appeared.
   The precipitate  thrown down  by the phlogifticated
alkali, mixed  with  nitre  and borax, and melted with a
blow-pipe on charcoal, formed a black glafs ;  on flint-
glafs, a white  one ; and  on a  tobacco-pipe,  a  yellow-
ifli white one.  Another portion, melted with  foap and
borax in  a crucible, formed a black glafs.
   The fmall  quantity of infoluble refiduum  formerly
mentioned,  appeared to be the combination  of ponde-
rous earth with  vitriolic acid, called heavy  gypfum,
marmor  metallicum, barofclenite, ire.                   I0„
   From  thefe experiments the Doctor concludes, that Analyfis
100 parts of this  fpar contain  78.6 of pure  ponderous and proper-
earth, T6T of a grain of marmor   metallicum, and 20.8  *»« °f
grains of fixed air.   2.  The  quantity of mild  alkali  aerated
neceffary to faturate any given  portion of acid, con-  Ponderoiw
tains  a greater quantity  of  fixed air  than can be ab-  par
forbed by that quantity of terra  ponderofa which  the
acid is able to diffolve.   3. The  terra ponderofa, when
precipitated by means of a mild  alkali,  readily burns
to lime;  and  this lime-water proves a very nice teft of
the prefence oS vitriolic acid.    4. In its native ftate
the terra ponderoSa will not burn to  lime;  when  ur-
ged with a ftrong  fire,  it melts and unites with  the
crucible,  without  becoming  cauftic ;  nor  can it be
made  to part  with its fixed  air  by  any addition of
phlogifton.   He conjectures, thereSore, that as cauftic
lime  cannot unite  to fixed  air without moifture, and
as  this Spar Seems  to contain  no water in its compo-
sition, it is the  want  of water which prevents  the
fixed  air affuming its elaftic aerial ftate.  " This fup-
pofition (fays  he) becomes-ftill  more  probable, if we
obferve,  that when the  folution  of the fpar in an  acid
is precipitated by a mild alkali,  fome water enters  in-
to the compofition of the precipitate ; Sor  it has the
Same  weight as before it was diffolved, and yet pro-
duces only 20 ounce-meafures of fixed air, while  the
native fpar  contains 25-of the fame meafures  : fo that
there is  an addition of weight  equal  to five ounce-
meafures of air, or three one-half grains, to be  account-
ed for ;  and  this  can  only arife  from  the water.
5. The precipitate  formed by  the cauftic alkali, taking
fome  of the  latter down with it, forms a  fubftance
neither foluble in  acids nor  water.   This infoluble
compound  is  alfo formed by adding  the lime-water al-
                                              ready 
Pra (ftice.
C   H   E    M    I   S   T   R   Y.
* S3
   1058
Terra pon-
derofa at eft
of the pre-
fence of vi-
triolic aeid.


  1059
White mat-
ter contain-
ed in vitri-
olic acid
found to be
gypfum.
  1060
Experi-
ments on
the mar-
mor metal-
licum.
   1061
Defcription
of a kind
found near
Edinburgh.
ready mentioned, to a folution of cauftic vegetable, or
foffile fixed alkali, but not with volatile alkali. 6. Fix-
ed vegetable as well as mineral alkali, and even vola-
tile alkalies, whether mild or cauftic,  are capable of
feparating  terra  ponderofa from  any  other acid ex-
cepting the  vitriolic ; but from it neither mild nor
cauftic alkalies are  capable of feparating  this earth,
excepting the  vegetable fixed alkali, which will partly
do it  by an intenfe heat  in  the dry way.   7.  This
earth affords an excellent method of purifying the  ni-
trous and marine acids from any portion of the  vitri-
olic;  for the attraction between terra ponderofa and
this acid is fo ftrong, that the  leaft portion of the lat-
ter will be inftantly detected by the lime-water above
mentioned.   The vitriolic acid,  Dr Withering  ob-
ferves, is commonly adulterated with a white powder,
which difcovers itfelf by turning the liquor milky when
the acid is  diluted with  water ;  and this  powder he
finds to be gypfum, from the  following  properties:
   1.  By repeated boiling  in water, fix grains  and  a
half were reduced to two.  2. By gentle evaporation
this folution afforded five grains of cryftals as hard and
taftelefs as felenite.   3.  A precipitate was formed by
mild foffile alka   on adding it to a folution of thefe
cryftals in water.   4. On expofing this powder to  a
pretty ftrong heat,  and then putting it into water, the
latter became  acrid, and acquired  the  tafte of lime-
water.   5.  The  infoluble  part fuffered no  change by
boiling in nitrous acid :  one half of it mixed with bo-
rax,  and expofed to the  blow-pipe upon charcoal,
melted into glafs ;  the other halt, mixed with  borax,
and expofed to the blow-pipe  upon charcoal,  did  the
fame; whence it appears,  fays our author,  that  the
greateft part of this fubftance  was calx  vitriolate or
felenite ;  the  remainder  a  vitrifiable earth.  He had
before found, that the heavy gypfum, or marmor me-
tallicum, would diffolve in concentrated vitriolic acid,
but always Separated upon the  addition of water ; and
from his experiments it now appears that felenite does
the fame.
   Dr Withering next proceeds to  give a fet of  expe-
riments on the heavy gypfum, marmor metallicum of
Cronftadt, or the Barofelenite  of others, already men-
tioned.  The fpecimens he obtained Were from Kil-
patrick hills near Glafgow, and a fort with Smaller
cryftals found among the iron ore about  Ketley in
Shroplhire, and  in the lead-mines at Alfton-Moor.
He defcribesit as white,  nearly tranfparent, but with-
out the  property of  double refraction ; compofed of
laminae of rhomboidal cryftals, and decrepitating in
the fire;  the fpecific gravity from 4.402 to 4.440.
The fpecimens we  have feen differ confiderably from
this  defcription, being  compofed, to  appearance, of
thin laminse ; which all together form a very opaque
white mafs, whicli has not the leaft transparency un-
lefs fplit exceffively thin. They are found about three
miles to the fouthweft of Edinburgh, near Pentland
hills, and likewife  betwixt Edinburgh and Leith. In
the former place they lie  in fmall veins of a rock con-
fifting of a kind of iron ftone, and fo clofely adhering
to it, that it would Seem either that the ftone is con-
verted  into the Spathum  ponderoSum, or the latter in-
to the ftone.  It is therefore often  intermixed with
the rock fo intimately, thatit is impoffible to feparate
them perfectly from each other.
the Terra pon-
    derofa and
  Dr Withering having expoSed  ice grains ef
marmor metallicum to a red heat  for  an hour, in  a .
black crucible,  Sound that it had loft five grains oS its lts ccm u*
weight;  but as a Sulphureous Smell was perceptible, he v—l^J—/
SuSpected that a  decompofition  had  taken place, and    r°6z
therefore expofed anotlier portion to a fimilar heat in Effects of
a tobacco-pipe,  which had no  fmell of  fulphur, nor heat UP0H
was it diminiihed in weight.  It melted  with  borax
into a white opaque glafs, but w as barely fufible by    10^3
itfelf under the blow pipe.  It did not feem to  diffolve May be
in water, nor in any of the acids, except  the vitriolic, diffolved in
when by long boiling it had become very  concentrated vei7  con"
and almoft red  hot.  It then appeared perfectly  dif- c^nt.rat;ed
folved ; but feparated again unchanged on the addi- aci(j
tion of water.   On  expofing  the  vitriolic Solution to
the atnioSphere for fome days, beautiful radiated cry-
ftals were formed in it.                                 1064
  Onadding a Solution of mild vegetable alkali to this Precipi-
vitriolic folution, a precipitate appeared; but it con- tatedfrom
fitted of marmor metallicum unchanged. An  ounce K "n^han"
of it in fine powder was then fufed with two of fait of ge^ , .y yf~
         •1 •      1 •     1    ,•   1   1     r    r 1   getable nx-
tartar until it ran thin, when fix drachms of arelidu- £d aii^n.
urn infoluble in water were left.   On the addition of   1Q(,S
nitrous acid, only 52 grains were left, which appeared Maybe dc-
to be marmor metallicum unchanged.  On Saturating compofed
the alkaline Solution with diftilled vinegar, and wafhing in th^ dr|
the precipitate,  the liquor was Sound to  contain  ter- waJby falt
  r t   *       ,     1  ,    ,     .     r -i          of tartar.
ra foliata tartar, formed  by the union of the acetous
acid with part of the alkali  ;  and of vitriolated  tar-
tar, formed by that of the alkali with  the native acid
ofthe marmor metallicum.                              io^
  The fait formed by the nitrous acid fhot readily  in- Nitrous fo-
to beautiful permanent cryftals of a rough bitterifh tafte. lution
Some of the fait deflagrated with- nitre and  charcoal, A100^ »"*•
left by wafhing the  terra ponderofa very white, capa- ^fc CT"
ble of being burnt into lime,  and again forming an  in-
foluble compound with  vitriolic acid.   An hundred
grains of aerated terra ponderofa,  diffolved in marine
acid, and precipitated by the vitriolic, were augment-
ed 17 grains in weight.  Hence it appears,              Io()j
  1. That the marmor metallicum  is compofed of  vi- Analyfis
triolic acid and  terra ponderofa.   2. That this  com- andpmper-
pound has  very little folubility in water.  3. That ittics °f the
can only be diflblved in highly concentrated oil of vi-
triol, from which it Separates unchanged  on the addi-
tion of water.   4. That it cannot  be decompofed in
the moift way, by mild fixed alkali, though it  may be
fo in the dry.   5. That it may  be decompofed by the
union of inflammable matter to its acid, by which ful-
phur is formed,  though the acid cannot  be  diflipatcd
by mere heat.   6. An hundred parts of this  fubftance
contain 32.8 of pure vitriolic acid, and  57.2  of terra
ponderofa.   The marmor metallicum, our author  re-
marks, may poffibly be ufeful  in fome cafes where  a
powerful flux is wanted ;  for having mixed fome of it
with the black flux,  and given the mixture a  ftrong
heat in a  crucible, it ran entirely through the pores
ofthe veffel.                                          Io6g
  Dr Withering defcribes two  other  kinds   of this Gauk, a
fubftance, known by the name of cauk,  and found in fubftance of
the mines of Derbyftiire,  and other places.   T hefe this killd>
differ from the other only in containing a fmall propor- foui,d in.
tion of iron.   On the whole, he  concludes, that"  the P^^'j
tetra ponderofa feems to lay claim to a middle  place"1 n^ an
betwixt the earths and metallic calces.   Like the for-
                         U                   mer-
marmor
metalli-
cum. 
CHEMISTRY.
Practice.
  Tct'19
Solution of
flint.
mer it cannot be reduced to  a metallic  finm,  though
like the latter it  may  be precipitated by phlogiftica-
ted alkali.   In many of  its pre>perties it much refem-
blcs the clax of lead,  and in others the common cal-
careous earth,   lis moft remarkable properties arc its
decompoling the \ itriolic neutral Salts,  and  forming,
with the nitrous and nurinc acids,  cryftals  which do
not deliquefce.

\  2.  Tranfmutation of Flists into an Earth foluble i;.
                        Acids.
   This  is effected by mixing powdered flints  with
alkaline fait, and  melting ihe mixture by a ftrong
fire.   The melted mafs deliquates in  the air,   like
alkaline falts; and if the  flint is then precipitated,
it becomes foluble in acids, which  it entirely refitted
            In this proceSs the alkali, by its union with the flint,
          is deprived of  its fixed air, and becomes cauftic.   To
          this caufticity its folvent power is owing ; and  there-
          fore the flint may be precipitated  from the alkali,  not
          only by acids, but by any fubftance capable of furnifh-
          ing  fixed air ;  fuch  as magnefia alba or volatile  alkali.
          The precipitate in both cafes proves the fame ;  but  the
          nature  of it hath not hitherto been determined.  Some
          have conjectured  that the vitriolic acid exifted in  the
          flint;   in which cafe,  the alkali  made ufe  of  iu  this
          procefs  ought to be partly  converted into vitriolated
          tartar.
            The above procefs  is delivered on the authority of
ofthisearth former chemifts; but Mr Bergman, who has publiflied
denied by  a differtation on this fubject, afferts  that it cannot be
          diilblved except by the fluor acid.   The vitriolic,  ni-
          trous,  or marine acids, have no  effect upon it, even
          w hen  newly  precipitated Srom the liquor  oS  flints
          w allied and ftill w ei, and though a thoufand parts  of
          acid be added to one of the earth, and boiled upon it for
          an  hour : but  when three parts of  alkaline fait  are
the miftakc melted  jn a crucible  with one of quartz,  the fait dif-
"h •^n"^  f°lves  at the Same time about Seven hundreth parts of
          its own weight of ihe clay which compofes the  crucible ;
          and the folubility of this has given occafionto the mif-
          take abovementioned.  If the fufion be performed  in
          an iron veffel, no Soluble part will  be  obtained, except-
          ing  the very Small portion of  clay which the  quartz
          contains ;  and when this is once exhaufted by an acid,
          no more can be procured  by any number  of  fufions
          with alkaH.
            The  fluor acid,  he obferves, is   never obtained en-
          tirely free from filiceous earth, and consequently  its
          power as a menftruum muft be weakened  in propor-
          tion to  the quantity it contains.  In order to obServe
          its Solvent  power, however, our author, in  the year
          1772, put fome quart/., very finely pow7dered,  into a
          bottle   containing  ; oS a kanne oS  fluor acid.  The
          b.ntle was then nightly corked, and Set by in the cor-
         ner oS a room.  Two years aSterwards it  was exa-
          mined  ; and on  pouring out the liquor there were Sound
          concreted at the bottom oS the vedel, befides innume-
          rable Small priSmatic Spiculae, 13 cryftals of the  Size of
          Small peas, but moftly of an irregular form.  Some  of
          thefe rcfembled cubes, whofe angles were all truncated,
         fich as are often found  in the cavities of flints.  1 hefe
         were perfect  filiceous cr\ ftals, and very hard, but  not
         comparable with quartz, though  they agreed  with it
  1070
Folubility
Mr Uerg
man
  1071
Reafon of
Cn ftals of
flint artifi-
cially
formed by
Mr Berg-
man.
in effential properties.   " Poflibly (fays he) the length
of a century may be neceffary lor them to acquire, by
exficcation,  a luflicient  degree of  hardntis.    1 he
bottom  iifelf, as Saras the liquor  had  reached,  was
found covered with a very thin filiceous pellicle, which
was fcarcely  vilible, but Separated on  breaking the
bottle.  It was extremely pellucid, flexible, and Ihow-
ed  priSmatic colours.   Thefe phenomena (how  that
much filiceous matter is diffolved and fufpended." (in
the fluor acid).   " Whether any  ofthe  quartz was
taken up  in  this experiment is uncertain; but it ap-
pears probable that little or none was diflblved ; fince,
by  the  help of heat  during the  diftillation, the  acid
had  previoufly taken up fo  much filiceous earth,  that
upon  flow  evaporation  it was  unable  to retain it.
Hence appears the origin of the cryftals and the  pel-
licle ; and hence appears the caufe which impedes the
action of fluor acid upon flint; namely, that the  acid
obtained in the ordinary way is already faturatcd with
it.
   The  volatile alkali precipitates filiceous earth moft
completely from fluor acid :  and thus we find, that one
part of it is contained in 600- of the acid, diluted to
fuch a  degree, that its  fpecific gravity is only  1.064.
'J his precipitate  has all the properties of  pure flint  ;
but that precipfated either  by vegetable  or  mineral
fixed alkali does not afford a pure filiceous earth, but
a peculiar kind  of triple  fait, formed of the  earih,
fluor acid,  and fixed  alkali,  which  diffolves,   though
with difficulty, in warm water, efpecially the earth
procured by vegetable alkali,  but is  eafily  decompofed
by lime-water and lets  fall the mineral fluor regene-
rated.
  Fixed alkaline falts attack this  earth by boiling, but
not unlefs it be reduced to very fine powder, and new-
ly precipitated from the liquor.  Oil of tartar per de-
liquium takes up about one-fixth of its  weight, and the
liquor becomes gelatinous  on cooling,  though at  firft
diluted with 16 times its weight of water.  This fo-
lution is effected  only by  the cauftic  part; for when
fully faturated with fixed air, it cannot enter into  any
union with it.   Volatile alkali, even though cauftic,
has no effect.
  The attraction  betwixt filiceous earth  and fixed al-
kali is much more  remarkable in the  dry way ; for
thus it melts with one half its weight of alkali into an
hard, firm, and tranfparent glafs, the aerial acid  and
water going off in  a violent effervefcence.  In pro-
portion  as the alkali is increafed, the glafs becomes
more foft and lax, until at  laft it diflblves totally in
water, as  has been already mentioned.  The filiceous
matter thus precipitated is of a very rare and  fpongy
texture, and fo much Swelled by water, and its bulk
when wet is at leaft  twelve times greater  than  when
dry ; nor does it  contract more though Suffered to re-
main a  long time in the water.    Hence it is eaSy to
reduce the liquor oS flints  to a jelly, by diluting it
w ith Sour or eight times its weight  oS water,  and ad-
ding a Sufficient quantity oS precipitate ; but if an over-
proportion of water be uSed,  for inftance, 24  times
the weight, the liquor will then remain limpid though
we add  as much acid as is fufficient for Saturating the
alkali.  The rcaSon of this  Mr Bergman fuppofes to
be, that the filiceous particles are removed to  fuch  a
diftance from one another, that they  cannot overcome
                                                the
   107J
Why the
fluor acid
will not
diffolve
flint di-
rectly.
 . .I074
Siliceous
earth moft
completely
precipitat-
ed by vola-
tile alkali.
  1075
A triple
fait formed
by precipi-
tin with
fixed alkali.
   1076
Siliceous
earth dif-
folved by
boiling in
folution of
alkali.
   1077
Has a re-
markable
attraction
for it in the
dry way.
  1078
Is very rare
and fpongy
when pre-
cipitated.
   1079
Whyit can-
not fome-
times be
precipita-
ted by an
acid with
out beat. 
Pradtice.
CHEMISTRY.
*SS
Phofphoric
earths.
   1080
Liquor of
flints de-
compofed
by too great
a quantity
of water,
and by flu-
or acid
the fri&ion they muft  neceflarily  meet with in their
paffage downwards  through the fluid ; but if the li-
quor be boiled, which at once diminifhes its quantity
and tenacity,  the filiceous  matter is inftantly Separa-
ted.
  Liquor of flints is alfo decompofed  by too great a
quantity of water ;  for by this the efficacy ofthe  men-
ftruum is weakened, and it is alfo partly faturated by
the aerial acid contained in the water.   A precipitate
alfo falls when the fluor acid is made ufe of ; the rea-
fon of which is the fame as the precipitation by  other
acids : in this cafe, however, the alkali makes part of
the precipitate, as has been already obferved; and there-
fore the matter which falls is fufible before the blow-
pipe,  and foluble in a Sufficient quantity oS water.

            § 3. Of Phosphoric Earths.
1081
Bolognian    These are So called from their property of fhining
ftone.     in the dark.  The moft celebrated and anciently known
         of this kind  is that called  the  Bolognian ftone, from
         Bologna,  a city in Italy, near which it is found.  The
         difcovery, according to Lemery, was accidentally made
         by a {hoe-maker called Vincenzo Cafciarolo, who ufed
         to make  chemical experiments.   This man, having
         been induced to think, from the great weight and luftre
         of thefe ftones,  that  they  contained filver, gathered
         fomc,  and calcined them;  when carrying them into a
         dark  place,  probably  by accident, he obferved them
         fhining like hot coals.
            Mr Margraaf defcribes the Bolognian  ftone to be
         an heavy, foft, friable, and cryftallized fubftance, in-
         capable of effervefcence with acids before  calcination
         in contact with burning fuel.  Thefe properties feem
         to indicate this ftone to be  of a Selenitic or gypfeous
   loga   nature.
How ren-    When  thefe  ftones are  to be rendered phofphoric,
dered lu-  fuch of them ought  to be chofen as are  the cleaneft,
minous,   beft cryftallized, moft friable and heavy ;  which ex-
         foliate when broken,  and which contain  no heteroge-
         neous parts.   They  are to be made red  hot in a cru-
         cible ; and reduced to a very fine powder in a glafs-
         mortar, or upon a porphyry.  Being thus reduced to
         powder, they are to be formed into a pafte with mu-
         cilage of gum tragacanth, and divided into thin cakes.
         Thefe are to be dried with a heat, which at laft is to
         be made pretty  confiderable.   An  ordinary reverbe-
         rating  furnace  is to be filled to  three quarters of its
         height with  charcoal, and the fire is to be kindled.
         Upon this charcoal the flat furfaces of the cakes are
         to reft, and  more charcoal to be placed  above them,
         fo as  to fill  the furnace.   The furnace is then to be
         covered with its dome,  the tube of which is to remain
         open ; all the coal is to be confumed, and the furnace
         is to be left to cool;  the cakes are then to be cleanfed
         from  the alhes  by blowing with bellows upon them.
         When  they  have been expofed during Some minutes
         to light, and afterwards carried to a dark place, they
         will feem to fliine like hot coals; particularly if the
         perfon obferving them has been fome time in the dark,
         or have fhuthis eyes,  that the pupils may be Sufficient-
         ly expanded.  ASter this calcination through the coals,
         if the ftones  be expofed to a  ftronger calcination, du-
         ring a full half hour, under a muffle, their phofphoric
         quality will be rendered ftronger.
  From attending to  the  qualities  of this ftone, and Phofphoric
the requifites for making this phofphorus,  we are na- earths.
rurally led to think,  that the Bolognian phofphorus is    \~CT\
no other than a compofition of fulphur and quicklime. Am\yiLi'(
The ftone itfelf, in its natural ftate,  evidently contains the phof-
vitriolic acid, from its not effervefcing with acids of pboru*.
any kind.  This acid cannot be expelled from eaithy
fubftances by almoft any degree of fire, unlefs inflam-
mable matter is admitted to it.   In this cafe, part ot
the acid becomes fulphureous, and flies off;  while part
is converted into fulphur, and combines with the earth.
In the abovementioned procefs,  the inflammable mat-
ter is furnifhed by the coals in contact with which the
cakes are calcined, and by  the mucilage of gum tra-
gacanth with which the cakes are made up.   A true
fulphur muft therefore be formed by the union of this
inflammable matter with the  vitriolic  acid contained
in the ftone ; and part of this  fulphur muft  remain
united   to the  earth leSt in a calcareous  ftate,  by
the  diffipation,  or cdnverfion   into  fulphur,  of its
acid.
1084
  In the year 1730,  a  memoir  was publiflied by Mr All caka-
du Fay ;  wherein he afferts, that all calcareous ftones, reousftones
whether  they contain vitriolic acid or not,  are capa- pbofpho-
ble  of becoming luminous by calcination:  with this "c' acc^T
difference only,  that the pure calcareous ftones require jin|t0   r
a ftronger,  or more frequently repeated, calcination to
convert them into phofphorus;  whereas thofe which
contain an acid,  as  Selenites, gypSum,  Spars, ire. be-
come  phofphoric by a  Slighter  calcination.   On the
contrary, Mr  Margraaf afferts, that no other ftones
can be rendered  phofphoric  but  thofe which are fatu-
rated with an acid;  that purely calcareous ftones, fuch
as marble, chalk, limeftone, ftalactites, ire.  cannot be
rendered luminous, till Saturated with an acid previ-
oufly to.their calcination.
  We have already taken notice, that the compounds
formed by uniting calcareous earths with the nitrous
and marine acids  become a kind of phofphori; the
former of which emits  light  in the dark,  after ha-
ving been expofed  to the fun  through  the day;  and   I0g,
the latter becomes luminous by being ftruck.  Signior Signior
Beccaria  found,  that this phofphoric quality was ca- Beccaria's
pable  of  being  given to almoft  all fubftances in na- °bferva-
ture,  metals perhaps excepted.  He found that ittlon'
was widely diffufed  among animals, and that even his
own hand and arm  poffeffed it in a very confiderable     „,
degree.  In the  year  1775,  a treatife on this kind of MrWil-
phofphori was publiflied by B.  WilSon, F. R. S. and fon'sexpe-
member ofthe Royal Academy at Upfal.  In thistrea- riments.
tife he fliows, that oyfter-fhells,  by calcination, ac-
quire  the phofphoric  quality  in a very great degree,
either  when  combined  with the nitrous acid or with-
out  it.
  The firft experiment made by our author was the
pouring fome aquafortis, previoufly impregnated with
copper, on a quantity of calcined  oyfter-fhells,  fo as
to form them into  a kind of pafte; he  put this  pafte
into a crucible, which was kept in  a pretty hot fire for
about  40 minutes.   Having  taken out the  mafs, and
waited till it was cool,  he prefented it to the external
light.  On bringing it back  fitejdenly into the dark, he
was furprifed with  the  appearance of a  variety of co-
lours like thofe ofthe rainbow,  but much more vivid.
In confequence  of  this appearance  of the  priSmatic
                        U  2               colours, 
i56
H    E   M    I    S    T   R    Y.
Pracflicc.
Vegetable  colours, be repeated the experiment in various ways,
earth.      combining the calcined oyfter-fhells with different mc-
'---v----' tals and metallic Solutions, with the different acids, al-
          kaline  and  neutral Salts, as well as with Sulphur, char-
          coal, and other inflammable Subftances ; and by all ot
          thefe he produced  phoiphori, which emitted varumuy
   i-S-   coloured tight.
 Surprifmg    Whit is more  remarkable,  he  found  that oylter-
 phofphoric (hells poil'effed the phofphoric quality in a furpnling de-
 quality of „rfc .  a.,j for this purpofe nothing  more was requifite
 ly(!.cr"    than pulling them into a good lea-coal fire,  and kcep-
 Blcl      in.r ibcm there for Some time.   On Scaling off the in-
          ternal  yellowilh Surface of each fhell, they become ex-
          cellent phofphori,  and exhibit the moft vivid and beau-
          tiful colours.   As we know that neither the  vitriolic
          nor any other acid is contained in oyfter-fhells,  we can-
          not as  yet fay any  thing fatisfaftory concerning the na-
          ture of this phofphorus.
§ 4. Ofthe Vegetable Earth.
   1088
DrLewi
opinion.
           Th is is produced from vegetables by burning, and,
         when perfectly  pure, by lixiviating the alhes with wa-
         ter,  to extract the fait;  and then repeatedly calcining
         them, to burn out all  the inflammable matter;  and is
         perhaps the  fame  from  whatever fubftance  it is ob-
         tained:  iu this ftate, according to Dr Lewis, it is  of
         the fame nature with magnefia.   In the  ftate, how-
         ever, in which this earth is procurable by limply burn-
         ino- the  plant, and lixiviating the aflies,  it is conlide-
  lo8o   rably different, according to  the different plants from
Mr Gmc- which it is obtained.   The  aflies of mugwort, fmall
lin'sexpe- centaury, chervil, and dill,  are  of a brownifh grey ;
riments.      at»s fand and lungwort afford white aflies;  thofe of
         fanicle  are whitifh > thofe  of Roman wormwood  of a
         preenifh  grey ; thofe of  rue,  agrimony,  faxifrage
         brown; thofe  of  tanfev, of a dulky green; thofe of
         dodder, of a fine green;  eyebright   fouthem-wood,
         common wormwood,  and fcabious,  afford them grey ;
         fcurvy-grafs,  of a whitifh grey ;  by flop,  yarrow,  and
         fowbane, of a dufky  grey;  melilot, and  oak-leaves,
         as alfo plantain,  colts-foot,  pine-tops, and fumitory,
         »f a dulky  brown ;  penny-royal,  of  a  pale brown,
         with fome  fpots  of white ; elder-flowers  fage  and
         mother of thyme, afford yellow afhes;  thofe of Araw-
         berry-leaves are of a  pale brimflone colour; thofe of
          cat-mint, of a dufky red;  of prunella,  brick-coloured;
          of honey-fuckle, blue;  of fern, blackifh ; and thofe of
          St lohn's wort,  feverfew, origanum,  and pimpernel,
          all  of  a deep black.   The only ufe to which  this
          kind of earth has yet been put, is that of glafs-making
          and manure.

                   Sect. HI.   Of Metallic Subftances.

                              §  1.   Cold.
  This metal  is  reckoned of all  others  the  moft
perfect and indeftructible.  When in its greateft  pun-
fv,  it has very little elaftieity, is not fonorous its co-
lour is vellow,  it is exceedingly foft  and flexible, and
is more ductile  than any other metal whatever   (See
GoivLcaf, and Wire-Drawing.)  Of all bodies it
i< the moft ponderous, except platina; us gravity be-
iiio- to that of water, according to Dr Lewis, asio,28o,
or 19,290,  to o.:c.  For its fufion it requires a low de-
gree of white  heat, fomewhat greater than that in
which filver melts.  \\ hillt fluid, it appears of a bluifli
green colour;  when  cold, its  furface looks Imooth,
bright,  and confiderably concave :  it feems to expand
more in the act of fufion, and to (brink more in its re-
turn to folidity, than any of the other metals ; w In mr
the greater concavity of its furface.   Before fufion it
expands the leaft of all metals, except iron. By fud-
den cooling it becomes, as well as other metals, brutle ;
which effect has been erroneoully attributed to the con-
tact of fuel during fulion.
   Gold amalgamates very  readily with mercury,  and
mingles in  fulion with all the metals.  It is remark-
ably difpofed to unite with iron ;  of which it diilolves
many times its own weight, in a heat not much greater
than that in w hich gold itfelf melts ; the mixture is of
a filver colour, very brittle and hard.   All the metals,
except copper, debate the colour of gold ; and, if their
quantity is  nearly equal to that ofthe gold, almoft en-
 tirely conceal it.
   The malleability of gold is  impaired by all the me-
 tals, but lefs  by copper and  Silver than any  others.
 Tin has had  a remarkably bad character 111 this re-
 fprct;  and it has been a  received opr ion among me
 tall■trgiits, that  the fmalleft quantity ot this metal en-
 tirely^deftmys the ductility  of gold; and  pr  Lewis
 tells us, that  "  the moft minute portion of tin or lead,
 and even the vapours which rife from them  in the fire,
 though not fufficient  to  add  to  the gold  any  weight
 fenfible on the  tciidereft  balance, make it fo  brittle,
 that it flies to pieces  under t»>c hammer."   On fo re-
  fpectable  an  authority, this continued to be believed
  as an  undoubted ui.t, urJl,  in the year 1784, a pa-
  per appeared in  the Philofophical Transactions by Mr
  Alchorne of the mint: in which f was clearly diSpro-
  ved by the following experiments :
    1. Sixty Troy grains of pure tin  were  put  into 12
  ounces of  pure  gold in fufion ; after which the mix-
  ture was caft into a  mould  u' find, producing a flat
  bar an inch  wide, and  an  eight of an  inch  thick.
  The  bar  appeared  found and good, fuffered  flatting
  under the  hammer,  drawing  feveral times between a
  pair of fteel-rollers,  and cutting into circular pieces of
  near an inch diameter, whifti bore  ltamping in the
  money-prefs by the ufual Stroke,  without {bowing the
  leaft brittleneSs, or rather with much the  Same ducti-
  lity as pure gold.
    2. With 90 grains of tin the bar was Scarce diftin-
  guiihable Srom the Sormer.
  3  3. With 120 grains it was rather paler  and harder ;
  and on drawing between the rollers the edges were a
  little diSpoSed to crack.
     4. With 140 grains, thcpaleneSs, hardneSs, anddiS-
  pofttion to crack, were evidently increaSed ; neverthe-
  less it bore every other operation,  even ftamping under
  the preSs, without any apparent injury.
     c.  With  an  ounce of tin the bar was lead-coloured
  and'brittle,  Splitting into Several pieces  on  the firft
  paffing between the rollers.
     6   A fmall crucible filled with ftandard gold 4 ; fine,
   was placed in a larger one, having in it  an ounce of
   melted tin.   The whole was covered with a large cru-
   cible  inverted, in order to direft the fumes ofthe tin
   downward upon the gold.  The  metals  were kept in
                                               fufion
t.o'.d.
   louc
Unites rea-
dily with
all the me-
tals.
   1091
Said to lofe
its mallea-
bility re-
markably
with tin.
   1092
Mr Al-
chorne's
experi-
ments in
oppofition.
   l°5>3
Gold not
rendered
brittle by
the fumct
ef tin. 
Pradlicc.
C   H   E   M
Gold.
          fufion for half an hour, during which time a full quar-
 *"—*~~~* ter of the  tin was calcined ;  yet the gold remained al-
          together unchanged.
             7. The mixture of gold and tin produced in exp. 1.
          was melted a fecond time in a ftronger fire than at firft,
          and kept in fufion for half  an hour ; during  which
          time fix grains of weight were loft, but the gold  re-
   1094   mained equally perfect as before.
 Nor by the    8. and 9. The mixtures of exp.  2.  and 4.  viz. 90
 addition of an<]  j^0 graias to 12 ounces of gold, were re-melted
 cwpper.    Separately, and an ounce of  copper added  to each.
          On being  caft as ufual, they bore all the operations of
          maufacturing as before, though fenfibly harder.  The
          laft cracked at the edges as it had done without  the
          copper,  but bore cutting rather better than in its for-
          mer  ftate.
             10. and 11. A quarter of an ounce oS the laft mix-
          ture, being tin 140 grains, and copper an ounce,  and
          gold 12 ounces,  with as much of the bar from expe-
          riment 3.  confifting of T40 grains oS tin to 12 ounces
          of gold, were  each melted by a jeweller in a common
          fea-coal fire, into  fmall buttons,  without any lofs  of
          weight.  Thefe buttons were afterwards forged into
          fmall bars,  nealing them often with the flame of a
          lamp, and afterwards drawn each about twenty times
          through the apertures of a Steel plate,  into fine wire,
          with as  much  eafe as coarfe gold commonly pafles  the
          like  operation.
             12. Sixty grains  of tin were added to 12 ounces of
          ftandard gold 44 fine ;  and the compound paffed every
          one of the operations already deScribed, without fhow-
          ing the leaft alteration from the tin.
             Several  other trials were made with different mix-
          tures of copper, tin, and  filver, with gold,  even as
          Jow as two ounces and a half of copper, with half an
          ounce of tin, to twelve ounces of gold; all  of which
          bore hammering and flatting by rollers to the thinnefs
          oS Stiff paper, and  afterwards working into  watch-
          cafes, cane-heads, &c. with great eafe.  They grew
          more hard and harfh indeed in proportion to the quan-
   IO0j   tity of alloy ;  but  not  one  of them  had the appear-
 Malleabili- ance of what workmen call brittle gold.   Mr Alchorne
 ty of gold  therefore is of opinion, that when brittlenefs has been
 deftroyed  occafioned by the addition of tin to  gold, the  former
 hr r<lgu. s  has been adulterated with arfenic;  as  he has found,
 e at emc.  ^^ ^ a^mg I2 grains of regulus of arfenic to as
          many ounces of fine gold, the compound has been ren-
          dered altogether unmalleable,
            When gold is  ftruck during a certain time by a
          hammer, or when violently compreffed, as by the wire-
          drawers, it becomes more hard, elaftic, and lefs duc-
          tile ; fo  that it is apt to be cracked and torn.   Its duc-
          tility is, however, reftored by the  fame means ufed
          with other metals, namely, heating it red hot, and let-
          ting it cool flowly.  This is called annealing metals ;
  1096   and gold feems to be more  affected  by this operation
Surprising than  any other metal.  The tenacity of the  parts of
tenacity of gold  is alfo very furprifing; for a wire of T's-  of  an
its parts,  inch jn diameter will Support a weight of 500 pounds.
            Gold is unalterable by air or water.  It  never con-
         tracts ruft  like other metals.  The  action of the fier-
         ceft furnace-fires occafions no alteration in it.  Kunc-
         kel kept gold in a  glafs-houfe furnace for a month,
         and Boyle  kept fome  expofed to a  great heat for a
         ftill longer time,  without the lofs of a fingle grain.
   1097
Not liable
to ruft.
I   S   T    R   Y.                                  157
  It is faid, however,  to be diffipable in the  focus of a   Gold.
  large burning mirror.                               '    ^~o~"
    Mr Boyle relates a very curious and extraordinary m/bovIc's
  experiment, which he thought was fufficient to prove experi-
  the total deftructibility of gold.   About an eighth part ments for
  of a  grain  of powder, communicated  by a ftranger, thedeflruc-
  was projected upon two drachms of fine gold in fu- tibility of
  fion,  and the  matter kept  melted for a  quarter of§old'
  an  hour.   During the fufion, it  looked  like ordi-
  nary gold; except  only  once, that his  affiftant ob-
  ferved it  to look exactly of the colour of opal.  When
  cold, it was of a dirty colour, and, as it were, over-
  caft with  a thin coat, almoft like half-vitrified litharge:
  the  bottom of the  crucible was overlaid with a vitri-
  fied fubftance, partly yellow, and partly reddifh brown ;
  with a few fmall globules,  more like impure filver than
  gold.  The metal w7as brittle,  internally like brafs or
  bell-metal; on the  touchftone  more  like filver than
  gold : its fpecific gravity was to that of water  only
  as 15* to  1.  There  was no abfolute lofs of weight.
  By cupellation, 6ograins of this mafs yielded 53 grains
  of pure gold, with Seven grains of a ponderous, fixed,
  dark-coloured fubftance.
    We have already  mentioned, that in  certain cir- Solution in
  cumftances  gold  is foluble in the nitrous and marine aema-rc-gia.
  acids Separately.  It is, however,  always  foluble by
  the two united,  but  diflblves flowly even  then.   The
  moft  commodious method of obtaining this folution
  is, by putting the gold, either in leaves, or granulated,
  or cut into  fmall thin pieces, into a proper quantity
  of aquafortis ; then adding, by degrees, fome powder-
  ed fal ammoniac, till the  whole  of the gold is diflbl-
  ved.  By this means  a much Smaller quantity of  the
  menftruum proves Sufficient,  than if the fal  ammoniac
  was previoufly diffolved in the aquafortis ; the conflict,
  which each addition of the fait raiSes with the acid,
  greatly promoting the  diflblution.   AquaforBS oS mo-
  derate Strength will, in this way, take up about one-
  third oS its weight of gold ; whereas an aqua-regis,
  ready prepared from the fame aquafortis, will not take
  up above one-fifth its weight.  Common fait  anfwers
  better for the preparation of the aqua-regis than fal
  ammoniac.
   This folution, like all other metallic ones, is corro- properties
  five.  It gives a violet colour to the fingers,  or to any of the folu-
  animal  matters.   If  the  folution  is evaporated and tion.
  cooled,  yellow tranfparent  cryftals will be formed:
  but,  if  the  evaporation is  carried  too  far,  the acids
  with which the gold is combined may be driven from
  it  by heat  alone; and the  gold will  be left in the
  ftate of a yellow powder,  called calx of geld.            1I0^
   Gold may be precipitated from its folution by thofe Gold pre-
  fubftances which commonly precipitate metals, fuch cipitated
  as alkaline  falts and calcareous earths.  It  may alfo from it.
  be precipitated in a fine purple powder, by tin or its
  folution.
   When  fixed alkalies are made ufe of,  the precipi-
  tate weighs about one-fourth more  than the gold  em-
 ployed.   With volatile alkalies alfo, if they are added
 in no greater proportion than  is Sufficient to faturate
  the acid,  the quantity of precipitate proves nearly the
  fame: but if volatile fpirit  is  added in an over-pro-
  portion, it rediffblves  part of the gold wftiich it had
  before precipitated, and the liquor becomes again con-
  fiderably yellow.   The whole of the precipitate, how-
                                               ever. 
•s«
CHEMISTRY.                           Practice.
   IIOI
Separated
vitriol of
iron.
   1103
Aurum ful
minans.
   1104
Known in
the 15th
century.
   1105
Bafil Va-
  Gold.   ever, rnld mn be rcdilf.lved, either by the mild  or
    -   ' cauftic alkali ;  nor did  cither of thefe fpirits fenfibly
         dimdve or cxmet .iny  tinge from precipitates of gold
         which had ucn thoroughly edulcorated with boiling
         water.
            All  he met ftlic bodies which diffolve in aqua-regia,
         pte\M.t.ne gold from it.  Mercury and copper throw
         down  the gold in  its  bright  metalline form;  the
         others, in  that of a calx or powder, which has no me-
         tallic afpect.   Vitriol of iron,  though it precipitates
from other gold,  yet has no effect  upon any other metal ; hence
 ictabby  jc aff0rds an eafy me*.hod of feparating  gold  from all
         other  metals.   The precipitation with  tin  fucceeds
         certainly only when the metal in fubftance  is ufed,
         and the Solution oS gold largely  diluted with water.
         It is obServable, that though the  gold is precipitated
         Srom the diluted Solution by tin, yet,  if the whole is
         fuffered  to ftand till the water has in a great meafure
         exhaled, the gold is taken up afrefli,  and only a white
         calx of tin remains.
            Gold  precipitated  from  its folution  in aqua-regia
         explodes by heat with much greater violence than any
         other fubftance in nature.   This property was known
         in  the  icth  century ; but whether the ancient alche-
         mifts knew any thing of it  or not, is a mattcr of  un-
         certainty.   Balil Valentine  firft gave any diftinct ac-
         count oS it.   He directs the gold to be diffolved in
Icutine'sdi-aqua-regia made with Sal ammoniac, and then preci-
rc<a'onsfor pitated  by vegetable fixed  alkali,  to  be twelve times
its prcpara- wa(jlej wit]a waler> ailj laftly dried  in  the open air,
         where the Sun's rays cannot reach it.   He forbids it
         to  be dried over a fire, as  it explodes with a gentle
         heat, and flies off with inconceivable violence.
            Succeeding  chemifts have performed  this operation
         with fome little differences ; but  the neceflity of em-
         ploying volatile alkali  was but little regarded till the
             iin.ingof the prefent century.
             The  calx of gold  is  always  fomewhat increafed in
1 <tile alkali weight by being converted into  aurum fulminans ; but
but lately authors  arc not agreed  about the quantity of augmen-
known.   tation.   Becher makes it heavier by one-fifth part  ;
.  I10J  e Lemery by one-fourth ;  and Tuncker by one-fourth.
Increafe of  ...   }  },          ,  •   J  ,  1     • 1    • 1
the weight A^ agree> however, that it explodes with  a  violence
ofgold°by almoft inconceivable.   Crollius  relates, that 20 grains
beingchan-of this powder explodes with more force than half a
gcd into   pound of gun powder, and exerts its force downwards,
aurum ful- though  ]\j, Teykmeyer frequently fhowed  in his lec-
imuans.   lure:,  ^^ ^ ^jj throw  a  florin upwards above  fix
Prodigious clls-   A Srcat uumDer  °f experiments were made he-
force with fore the Royal Society at London,  in order to deter-
which it   mine the  comparative  forces of  thefe  two powders.
         Equal parts of gunpowder and aurum fulminans were
         included in iron globes placed among burning coals  ;
         thofe which contained the former  burft with great vio-
         lence, but the  globes containing the aurum fulminans
         remained perfectly fftent.   But though no explofion
         takes  place in clofe veffels, the uimoft caution is ne-
         ceflVv  in managing this fubftance in the open air ; e-
         fpi ially when it is fubjeeted  to friction,- or to a flight
         de?rce of heat  ;  for fuch is the nature of the calx  we
         Speak 01, that  it is  not neceffary, in order  to caufe it
         explode, to touch  it with an ignited  fubfiance, or to
         make it  red-hot.  The heat requifite for this purpofe
  ito6
Ufe of vo-
cjtplodc
   no;
1>ojs not
ixploio ■
dofj vef-
I.-Is.
th- >.
floa.
ite for i.s  iccording to Dr Lewis, intermediate between that
^  : '-• of boiliii" water and  the  heat which makes metals of
an obfcurc red. With frictietfi, however, it feems ftill
more dangerous ; for in this cafe it explodes with what
we lhould think fcarce Sufficient to  communicate any
degree of heat whatever.   Orfehal  relates,  that this
powder ground in  a j .if per mortar, exploded with Such
violence  as  to burft the velfel in a  thouSand pieces ;
Dr Lewis gives aninftance of a fimilar kind in England ;
and Dr Birch tells us of  doors  and  widows torn to
pieces  by the violence of this explofive  matter.  Mr
Macquer relates  the  following accident  to which he
was witnefs. " A young man, who worked in a  la-
boratory, had put a drachm of fulminating gold  into
a bottle,  and had neglected  to wipe the  inner furface
of the  neck  of the  bottle, to which fome of  the pow-
der adhered.  When he endeavouredto clofe the bee-
tle, by turning round the glafs  ftoppcr, the friction
occafioned an  explofion of part of the powder.   By
this the young man was thrown fome Steps backward,
his face and hands wounded by the fragments oS the
bottle, and  his eyes  put  out ;  yet, notwithstanding
this violent explofion,  the whole  drachm of fulmina-
ting gold certainly  did not take  fire  as much of it
was  afterwards  found Scattered about  the  labora-
tory."
   lt has already been mentioned, that fome imagine the
force of this explofion to be directed  downwards ; but
Dr Lewis is of opinion that it is equally directed every
way.   Certain it is, that  the quantity of from  10  to
12 grains of aurum fulminans, exploded on a metalline
plate, lacerates it ; a Smaller quantity  forms a cavity,
and a ftill Smaller  only Scratches the Surface ;  effects
which are never produced by gunpowder in  ever  fo
large  a quantity.   A weight laid upon  the powder  is
thrown upwards in the moment  of  explofion.  If it
be ot  Silver  or copper, this weight  is  marked with  a
yellowifli Spot, as  the  Supports will alSo be, if made
of either of theSe  metals.   A large grain,  Says Mr
Bergman, brought  near to the fide  of the flame of  a
candle, blows it out with great noife  ;  and a  few oun-
ces exploding together by incautious  drying,  has been
known to fhatter the doors  and windows  of the apart-
ment  : hence it  is evident, that aurum fulminans ex-
erts its force  in all directions ;  yet  it cannot be de-
nied,  that it ftrikes bodies  with which it is in contact
more  violently  than thofe which are at a  fmall dif-
tance, though in its vicinity: thus,  if a fmall portion
of it explodes in a paper box, it lacerates only the bot-
tom, unlefs  the top be preffed down clofe,  in  which
cafe it perforates  both  the top  and bottom.  When
carefully and  gradually exploded in  a glafs phial or a
paper be>x, it leaves a purple foot, in which are found
many  particles of fliining  gold ; and  if the  quantity
exploded be large,  Several  grains remain totally un-
changed,  as it is only the  lowermoft ftratum that  is
inflamed.
   Aurum fulminans,  when moift, does not explode at
all: but as it dries, the grains go off in fucceflion like
the decrepitation  of common fait.—In  glafs  veflels
clofed, or with  their  mouths immerfed in water,  it
explodes, but with  a very weak report.  An elaftic
vapour,  in  the quantity of feven inches, from  half a
drachm ofthe  powder, broke forth  in the moment of
explofion, which, by our author's account,  feems  to
be phlogifticated air.   In  metallic veffels  fufficiently
Strong, the gold is filently  reduced when they are per-
                                             fectly
  Co) A.

   IIII

re uii y hj
friction.
   11 ia
Inftances of
it. milVhir-
vou» *'. ■
leer..
  1113
Force of
the explo-
fion is not
diredted
entirely
down-
wards.
F.xplofion
of moift
aurum ful-
mn.ans. 
Practice.
CHEMISTRY.
Gold
   ni5
Caufe of
this explo-
fion attri-
buted to a
faline prin-
ciple.

   1116
This opi-
nion fhown
to be erro-
neous by
Mr Berg-
man.
          fectly found ; but if they have any very fmall chinks in
          them, the vapour  makes its way through them with
          a hilling noife.
            The caufe of this extraordinary explofive force of
          gold has been attributed chiefly to  a faline principle,
          viz. The combination of nitrous acid with volatile al-
          kali ;  and this  opinion  has  been  fupported by an af-
          fcrtion,  that the fulminating  property is deftroyed by
          treating the calx with vitriolic  acid or with fixed al-
          kali ;  the former expelling the nitrons acid, and the
          latter  difl'engaging the volatile alkali.  Mr Bergman
          allows that fixed alkali deftroys the fulminating pro-
          perty  ; but affirms, that it acts  only by feparating the
          particles when  the vwo are triturated together;  and
          this might be done by many other  fubftances as well
          as fixed alkali:  But when the alkali,  inftead of being
          triturated in the dry way with the  calx, was boiled in
          water  along with  it,   the explofion  not only took
          place, but  was  much more violent than ufual.   It
          muft be obferved, however,  that  heat alone deftroys
          the  fulminating property of this calx ;  and therefore,
          if the alkaline folution be made too ftrong, the addi-
          tional heat which  it then becomes capable of fuftain-
          ing, is fufficient to deprive the calx of its fulminating
          property.   The cafe  is the  fame with  the vitriolic
          acid ;  for this has no  effect upon the calx,  either by
          digeftion in its  concentrated ftate, or by boiling in its
          diluted ftate.  If it be boiled in its concentrated ftate
          indeed with the fulminating calx, the  heat conceived
          by*  the acid is  fufficient to  deftroy the fulminating
          property of the former; and  in like  manner,  unlefs
          the  calx be in fome meafiire deftroyed, or reduced  to
          its metallic ftate, it can never be  deprived of its ful*-
          minating property.
            It  was further  proved, that the fulminating pro-
minans can perty did not depend on the preSence either of nitrous
          or marine acids, for it can be made without them.  A
          calx of gold, not  fulminating, diflblved in vitriolic
          acid, and precipitated by cauftic  volatile  alkali, had
          acquired this property.  A folution of  the. fame calx
          in nitrous acid, let fall  a precipitate by the addition
          of pure water ;  and this precipitate edulcorated, and
          digefted with volatile alkali, fulminated  as if it had
          been originally precipitated with that alkali.  The ex-
          periment was repeated on th e other non- fulminating pre-
          cipitates with the fame fuccefs.   Left any fufpicion,
          however, fhould remain, that a fmall quantity of aqua-
          regia might ftill be  left, which, by combining with
          the volatile alkali,  would make a proportionable  quan-
          tity of nitrum flammans, the precipitate was digefted
          24 hours in vitriolic acid, then  waflied  in pure water,
          and immerfed in aqueous and fpirituous folutions  of al-
          kali, both  mild and cauftic; but  the event was the
          fame.   Laftly,  an inert calx  of gold may always  be
         made to fulminate by digefting  it with volatile  alka-
         li ; nor can  this property be  communicated  to it  by
         any means  without the ufe of this alkali.
            It  has been fuppofed by fome very eminent chemifts,
         among whom we may number Dr Black, that  fixed
         air is the caufe  of the  fulminaiion of gold :  but it  is
         evident that this caunot be the cafe: becaufe, 1. Gold
         fulminates as well when precipitated by  the cauftic
         volatile alkali,  as by that which contains  fixed air,
         2.  This metal does not combine, during precipitation,
         with fixed air.   3. Gold, when precipitated by mild
  1117
Aurum ful-
be made
without
nitrous or
marine
acids.
   ITlS
Fxed air
not the
caufe ofthe
explofion.
 fixed alkali,  does not fulminate, unlefs the menftruum
 contain volatile alkali.
   The fulminating calx of  gold may be prepared ei-
 ther with the compound aqua-regia of pure nitrous and
 marine acids  ; of pure nitrous acid and fal  ammoniac;
 or of a compound of alum,  nitre, and fea-falt.   When Menftr^_
 this  kind of liquor is made ufe of, the acid of the um fine
 alum expels the  other two, and  thus forms an  aqua- ftrepitu.
 regia.  This was formerly called menftruum fine ftrepi-
 tu.   By whatever  method the gold  is diffolved, it al-
 ways affords  a yellow calx with alkalies,  but the vo-
 latile alkali moft readily throws down the metal.  De-
 phlogifticated fpirit of fait very  readily diflblves gold,
 and produces  a fulminating precipitate as well as aqua-
 regia.                                                 1120
   We fhall conclude this account of  aurum fulminans Mr r«erg-
 withan abftract of Mr Bergman's theory of the ex- man's the-
 plofion.—He  obferves,  that volatile alkali  contains 017 of the
 phlogifton ;  an undoubted proof of which is given by '?ueo, ~m
 Dr  Prieftley, by  coverting  alkaline into phlogifti- 0Ui
 cated air.   This phlogifton, fays he, may be fepara-
 ted by means of a fuperh>r attraction ; fo that the vo-
 latile alkali is  decompofed,  and  the  refiduum diflipa-
 ted  in form of an  elaftic fluid,  altogether  fimilar to
 that  which is extricated during the fulmination : the
 Source then from whence  the elaftic fluid  is  derived
 muft be obvious ; and it only remains to examine the
 medium by which the volatile alkali  is  dephlogiftica-
 ted.
   ' In thoSe metals whicli are called perfect,  fo great
 is the firmnefs  of  texture, and  fo cloSe the  connec-
 tion ofthe earthy principle with the phlogifton, that
 by means oSfire  alone theSe principles cannot  be dis-
 united:  but  when  diflblved by  acid  menftrua,  they
 muft neceflarily lofe a portion of their phlogifton; and
 therefore,  when afterwards  precipitated  by alkalies
 which eannot  fupply the lofs,  they fall down in a cal-
 cined ftate, though they attract phlogifton fo ftrong-
 ly,  that they  can be reduced  to  a metallic  ftate,
 merely by an  intenSe heat penetrating the veffels.  It
 may  therefore be laid down as a  fundamental pofition,
 that gold is calcined by folution.                       IIaI
   "  Let us now confider the  confequence of  expo- Volatile al-
 fing the powder confuting of calx of gold and  volatile tali the
 alkali intimately  united, to an heat gradually increa- caufe ofthe
 fed.  The calx which is united  with the volatile al- exPloS1£>n-
 kali,  by the affiftance of a gentle heat, Seizes its phlo-
 gifton ;  and when this is taken  away,  the refiduum
 of the fait  is inftantaneoufly  expanded into the form
 of an elaftic fluid,  which is performed with fo much
 violence, that the air muft yield a very acute found."     II2a
   Our author  proceeds to  explain this phenomenon Volatile al-
 upon  the principles affumed by him and Mr Scheele, k»b exhi-
 of heat being  a  compofition  of light, and the phlo- bits
 gifton or'principle of inflammability; but  as this hy- a ?afil
 pothefis is by no means fatisfactory,  we  fhall omit ^r^n  •
 his reafoning founded upon it: That the volatile alkali, t0 a hot
 however, is really capable of producing a flafh  is eafily crucible.
 proved, becaufe it exhibits one  when thrown into a
 hot crucible.   A  fingle cubic inch of gun-powder ge- r  II23
 nerates about 244 of elaftic fluid; but the fame quan- quantit   f
 tity of aurum  fulminans yields at leaft  four times  as elaftic fluid
 much; and  hence we may eafily understand  the dif- produced
ference in their explofive force.                      by aurum
  "  That careful calcinations fhould  deftroy the ful. fuIminan&;
                                               mi- 
i6o
C    H   E    M   I    S    T   R    Y.
Practice.
  ColJ.

   t;:i
Why flight
rsK'ination
dcltroys
the fulmi-
■ itin^ pro-
perty.
Why itwill
not explode
in clofe
veiTcls.
   1126
Mr Berg-
man's opi-
nionsofthe
fublimati-
•n ofother
calces.
Solution of
jjold b\ he-
pjr fuiphu-
ris.
miruting property, is  not to be wondered at,  as the
volatile alkali is the indifpenfible matcri.d canft , but, the
peculiar alacrity which it acquires  before the explofive
force is totally extinguifhed, depends upon the nature of
the materials, and  of  the operation.   Thus the heat,
when inferior to  that neccliary  for  fulmination,  acts
upon  both  the principles of the aurum fulminans, it
prepares the metallic calx for a more violent  attrac-
tion for phlogifton; it alfo  acts upon the  phlogifton
of the volatile alkali, and leffens its connection; which
two circumftances mult  tend to the  union  producing
the explofion.  But this effect has  a maximum ; and at
this period the flightcft friction fupplies the defect of
neceflary heat, and produces  the  fulmination.   The
calcined  gold alfo  fcems to collect  and fix the  matter
of heat,  though ftill infufficient by means of its phlo-
gifton, in a certain degree ; fo that by means of fric-
tion,  though  but  very flight, it  becomes  capable of
exerting its force  ; but when the heating is of en repea-
ted without procuring  its effect, the  volatile alkali is
by degrees diflipatcd, and at length fo much diminifh-
cd that the calx becomes inert.
   " But if aurum fulminans is capable of  producing
Such a prodigious quantity  of elaftic  fluid,  how  does
it happen that it remains mute and inert when reduced
in clofe veflels ? Of this the reafon may be,  that every
elaftic fluid, in the act of breaking forth,  requires a
fpace to  expand in ; and if this be  wanting,  it remains
fixed.   Taking this for granted,  a calx of gold can-
not be reduced in clofe  vefftls  either by  he;1! or  by
the phlogifton of volatile alkali;  for in cither  cafe it
muft evolve  its elaftic fluid, which by fuppofition it
cannot do.   Nothing remains to  folve this difficulty
bin the ignition of the furrounding metal;  by means
of which the calx,  in virtue of its Superior  attraction,
Seizes  the  phlogifton  of the metal,  which that fub-
ftance here, as well as in other inftances,  is capable
of lofing without the  eruption or abforption  of  any
fluid whatever."
   Several  chemifts have aflerted, that the calces of
copper or filver may be made to fulminate like that of
gold.  But  Mr Bergman informs us, that thefe experi-
ments never fucccedcd with him ;  " fo (Says he) they
have  either been Silent  upon Some circumftances  ne-
ced'iry in the operation, or perhaps have been deceived
by the detonation of nitrum flammans, or fome other
accidental  occurrence.  It is not  Sufficient for  the vo-
latile alkali to adhere  to the  precipitate; for  platina
thrown down by this alkali  retains a portion of it very
obltinately,  but yet does  not  fulminate 011 the  ex-
pofure of fire —Befides the pretence of volatile  alkali,
it feems  to  be  neceflary that the  metallic calx fhould
be reducible by a gentle heat, in  order to  decompofe
it ; but every explofion is not to be derived from the
fame  caufes;  nay, in  this refped, aurum  fulminans,
gun-powder, and  pelvis fulminans, differ very much,
though they agree in feveral particulars."   Of late,
however, it has been found  that the calx of  filver may
be made to fulminate in a manner ftill more  extraordi-
nary than that of gold.  See the next article.
   If gold is melted with an hepar  fulphuris, compoSed
of equal  parts of  Sulphur and fixed alkaline Sdt,  the
metal  read;'. unites with it into an uniform mafs, ca-
pable vf  ditlolution in  w iter without -any feparation of
                                           2
   1129
Etheral fo-
ils parts.   The Solution, befides a nauSeous tafte from   Gold
the Su phur,  has a peculiar penetrating bitterne'.s, vol y----*---
diScoverable in any  other metalline Solution made  by
the Same means.
  Though the compofitions of fulphur and alkali feeni
to unite more  intimately with gold than any other me-
tal, their affinity with it is but flight; copper,  or iron,
added to the matter in fufion, difunite, and precipitate
the  gold.   The metal thus recovered, and purified by
the  common proceffes, proves remarkably paler-colour-
ed than at firft.   In an  experiment related by Dr
Brandt, in the  Swedifh Memoirs, the  purified gold
turned out nearly as pale as Silver, w ithout any dimi-
nution of weight.                                      xug
  Gold has been thought to  be poffeffed of many ex-Medicinal
traordinary virtues  as a medicine; which, however, virtues of
are  long ago determined to be only imaginary.   It is 6°^-
not  indeed very eaSy to  prepare  this  metal in Such a
manner that it can be Safely taken into the human bo-
dy.   The Solution in aqua-regia is poiSonous  ; but if
any effential oil is poured  on this folution, the gold
will be Separated Srom the acid,  and united to the ef-
fential oil; with which, however, it contracts no laft-
ing union, but  in  a few hours  Separates in bright
yellow film to the fides of the glafs.   Vitriolic ether
diffolves the gold more readily aud perfectly than the ^r"er
common ellential oils ; and keeps it  permanently fuf-
pended, the acid liquor  underneath appearing colour-
lefs.  The yellow  ethereal  folution poured  off, and
kept for fome time in a glafs ftopt with a cork, fo that
the  fpirit may flowly exhale,  yields long,  tranfparent,
prifmatic cryftals, in fliape like thofe of nitre, and yel-
low like topaz.  What  the nature of thefe  cryftals is,
either as to medicinal effects, or other purpofes, is as
yet  unknown.
  Rectified fpirit of wine mingles uniformly with the
folution of gold made  in acids  : if the mixture is fuffer-
ed to ftand for fome days in  a glafs Slightly covered,
the  gold is by degrees  revived,  and arifes in bright
pellicles to the furface.   Grofler inflammable matters,
wine,  vinegar,  folutions of  tartar,  throw  down the
gold,  in its metallic  form, to  the bottom.   Gold is
the  only metal whicli is thus Separable from its fo-
lution  in  acids  by  thefe fubftances;  and hence gold
may be purified  by  thefe means from all  admixtures,
and  fmall  proportions of it  in liquors readily difco-
vered.
  When the colour of g$d is by any means rendered Colour'of
pale,  it may be  recovered again by melting  it with gold  refto
copper, and afterwards  feparating the copper ;  or by red.
a mixture  of  verdigris  and  fal  ammoniac with  vi-
triol or nitre.  The colour  is alfo  improved by fu-
fion with nitre,  injecting Sal  ammoniac upon it in the
fufion, quenching it in urine, or boiling  it in a  folu-.
tion of alum.   When borax is  ufed as a flux,  it is
cuftomary to  add a little  nitre or fal ammoniac,  to
prevent its being made pale  by the borax. Juncker
reports,  that  by melting  gold   with four times its
weight of copper,  feparating the copper by aquafortis
unpurified. then melting the  gold with the fame quan-
tity of frefh copper,  and repeating this procefs e jght
or nine times,  the gold becomes at length of a  deep
red  colour, which fuftains the action of lead,  antimo-
ny, and aquafortis.
IT30 
Practice.
CHEMISTRY.
161
Silver.
   H3I
Ductility
»»f filver.
2.   S I L V
e r.
   113*
Effects of
fulphur on
it.
  "33
Purifica-
on.
   H34
Luna cor-
nea redu-
ced.
  "35
Mr Mar-
graaf*
method.
  This,  next to gold, is the moft perfect, fixed, and
ductile of all  the  metals.   Its fpecific gravity is  to
that of water nearly as 11 to 1.   A  fingle grain has
been drawn into a wire three yards long, and flat-
ted into a plate an  inch broad.  In common fire it Suf-
fers no diminution of its weight; and, kept in the vehe-
ment heat of a glafs-houfe for a month, it lofes no
more than one fixty-fourth.  In the focus of a large
burning-glaSs,  it Smokes for a long while, then con-
tracts a greyifli afh on the furface, and at length is to-
tally diflipated.
  Silver is fomewhat harder and more fonorous than
gold, and is fufible with a lefs degree of heat.  The
tenacity of its parts alfo is nearly one half lefs than
that of gold;  a filver wire of T*T of an inch diameter
being unable to bear more than 2 70 pounds.
  Mercury  unites  very readily with filver-leaf, or
with the  calx  of  filver precipitated  by  copper; but
does not touch the  calces  precipitated  by alkaline
falts.  The vapours of fulphureous folutions ftain fil-
ver yellow  or  black.   Sulphur,  melted with  filver,
debafes its colour to a leaden hue, renders it more
eafily fufible than before, and makes it flow fo thin as
ro be apt in a  little time to penetrate the  crucible :
in a heat juft below fufion, a part of the filver fhoots
up, all over the furface, into capillary efflorefcence.
Aquafortis does not act upon  filver in  this com-
pound ; but fixed  alkaline  falts will abforb the  ful-
phur, and from a hepar fulphuris, which, however, is
capable of again  diffolving  the  metal.   If the  ful-
phurated filver is mixed with mercury fublimate,  and
expofed to the fire, the mercury of the fublimate  will
unite with the fulphur, and carry it up in the form of
cinnabar, whilft the marine acid of  the  fublimate u-
nites with the  filver into a luna cornea,  which  re-
mains  at the bottom of the glafs.  Fire alone is fuf-
ficient, if continued for fome time, to expel the fulphur
from filver.
  From the bafer  metals, filver is purified by cupel-
lation with lead.   (See Refining.)   It  always re-
tains,  however, after that operation, fome fmall por-
tion of copper, fufficient to give  a blue  colour to vo-
latile fpirits, which has been erroneoufty  thought to
proceed from the filver itfelf. It is purified from this
admixture by melting it twice  or thrice  with nitre
and borax.  The  fcoria, on the  firft fufion, is com-
monly blue ;  on the fecond, green ;  and on the third,
white, which is a  mark of the purification being com-
pleted.
  The  moft effectual  means,  however,  of purify-
ing filver, is by  reviving  it from luna  cornea; be-
caufe fpirit  of fait will not precipitate  copper as it
does filver.   The filver may be  recovered from lu-
na  cornea, by  fufion with  alkaline  and inflammable
fluxes ; but, in thefe operations,  fome lofs is always
occafioned by the  diffipation of  part of the volatile
calx, before the alkali  or  metal can abforb its acid.
Mr Margraaf has  difcovered a method of  recovering
the filver with little or no lofs ; mercury affifted by
volatile Salts,  imbibing it by trituration without heat.
One part of luna cornea, and two of volatile fait, are
to be ground together in a glafs-mortar,  with fo much
water as will reduce them to the confiftence of a thin   silver,
pafte, for a quarter of an hour, or more;  five parts of   '  -
pure quickfilver are then to be added, with a little
more water,  and the triture to be continued for fome
hours.   A fine amalgam will thus be obtained ;  which
is to be wafhed with frefh parcels of water, as long as-
any white powder Separates.   Nearly the whole of the
filver is contained in the amalgam, and may be obtain-
ed perfectly pure by diftilling off the mercury.  The
white powder  holds a fmall proportion Separable by
gentle fublimation;  the matter which Sublimes is near-
ly fimilar to mercurius dulcis.
   The colour of filver  is debafed by all  the metals,
and its malleability  greatly injured by all but gold and
copper. The Engliih ftandard filver contains one part
of copper  to twelve and  one-third  of pure  filver.   ir.$
This metal difcovers in fome circumftances a great at- Attraction;
traction for lead ; though it does not retain any of that for lead*
metal in cupellation.  If a mixture of filver and cop-
per be  melted with lead in certain proportions, and
the compound afterwards expofed to a moderate fire,
the lead and filver will melt out together, bringing ve-
ry little of the copper with them ; by this means fil-
ver is often  Separated from copper in  large works.
The effect does not wholly depend upon the different
fufibility of the metals ;  for if tin,  which is ftill more
fufible than lead, be treated in the fame manner with a
mixture of filver and copper, the three ingredients are
found to attract one another fo ftrongly as to come all
into fufion  together.  Again,  if iilver be melted with
iron, and lead added to the mixture, the filver will for-
fake the iron to unite with the lead, and the iron will
float by itfelf on the furface.                           IT *
   Silver is purified and whitened externally by boiling Whitened
in a folution of tartar and common fait.   This is no externally.
other than  an extraction ofthe cupreous particles from
the furface of the filver,  by the acid of the tartar acu-
ated by the common fait.                                 .
   M. Berthollet has lately difcovered a  method  of Fulmina-
imparting to the calx of filver a fulminating property, ting  filver.
and that much more terrible than fulminating gold it-   n39
Self.  His  receipt for making it is, " Take cupelled How pre-
filver,  and diflblve it in the  nitrous acid ;  precipitate pared.
the filver from the folution by lime-water,  decant the
clear liquor,  and expofe the precipitate three days to
the  open  air.  Mix this dried  precipitate with the
cauftic volatile alkali, it will turn black;  and when
dried in the air, after decanting the clear liquor, is the
fulminating powder required."
   The properties of  this powder are faid to be fo ex-
traordinary,  that it is impoffible to imagine how any
part of it can ever be Separated from the reft after it   n40
is  once  prepared.   To make this fulminate, it feems Fulminate*
no fenfible degree of heat is neceffary,  the contact of by the
a cold body anfwering that purpofe as well as any other.toucl1 of
After it is once made, therefore, it muft not be  touch- „ny fub",
ed, but remain in the veflel in which it is dried ; and thcr ™\&~
fo violent is  the explofion,  that it is dangerous to at- 0r hot.
tempt it in larger quantities than a grain at a time.   1141
For  the Same reaSon it  undoubtedly follows, that no Dangerous
more than a  grain  ought to be made at a time, or at wlieu morc
leaft in  one veffel,  becauSe no part oSit could ever aS- '•  a.
terwards be  Separated from the reft.   We are told, fulminated
that, " the wind having turned over a paper contain- at a  time.
ing  fome atoms of this powder," (we  ought to have
                        X                   been 
CHEMISTRY
  14:
Fulmir. 1-
M-.g cry-
ftals.
   "43
Cautions
tn be ufed
in prepa-
ring it.
  II-ll
A'.mir.l
theory of
the anti-
phlogif-
tOIlk.
• Dcphlo-
gitl-A-ned
air.
t Inflam-
mable air.
t I'Mogift
1 i:> ,1 air.

Remarks
tin this a:u
«ii-  r theo
ries.
The phe-
nomenon
probably
rwing to
tl.^.iy,
 been inf< rmed how the moms came there, confidering
 what wc have juil now related,)  " the portion touch-
 ed by the hand fulminated, and of courfe that which fell
 upon the ground.   A drop of water which fell upon this
 powder cauled it to tulminate.  A Single grain ot" Sul-
 inin.iting filver, which was in a gifts cup, reduced the
 gluh to powder, and pierced Several doubles of paper.
   '* ll  the  vol.uile alkali, which has been employed
 with the ai).\c powder, .be put into a thin glafs 111a-
 trals aud boiled, then, on ftanding in  the cold, Small
 cryftals will be Sound fublimed on  the interior fides of
 the  veifel, and covering the liquor.  On touching one
 of thefe cryftals  the matrafs will  be burft with confi-
 derable explofion.
   " The dangerous properties of this  powder fuggeft
 the  nccellity of not preparing  it but  when the face is
 covered with a mafk with glafs eyes ; and to avoid the
 rupture of the glafs cups, it is prudent to dry  the ful-
 minating filver iu fmall metalline veffels."  To this
 we  may add, that as the powder does not fulminate
 when wet, it may  in that ftate be put up in very fmall
 quantities on paper,  to  be fulminated afterwards  as
 occalion offers.   This will perhaps account Sor the ap-
 pearance  of the  Sew  atoms  abovementioned  on the
 paper which the wind overturned.
   \Vrith regard to the caufe of this extraordinary ful-
 mination wc can fay nothing Satisfactory ; the follow-
 ing curious  reafon is afligned by  the antiphlogiftons ;
 which at once fliows the  futility  of  their theory, and
 fets in  a very  ridiculous light the  hard  words  with
 whicli  they would obfeure the Science oS chemiftry.
 " The oxygenous principle*  (Say they) unites  with
 the hydrogenous principle f oS the volatile alkali, and
 form water  in a vaporous ftate.  This  water (in  a va-
 porous ftate) being inltantaneoufty thrown into a ftate
 of valour,  po.idling elaftieity and expanfive force, is
 the princijvd caufe of this phenomenon,  in which the
. a~)tic% air  which is difengaged from  the volatile al-
 kali, with its whole expanffie power, hasagreatfhare."
   On this,  as well as other theories,  in which elaftic
, finds are alleged  to be the  cauSe  of explofions,  it is
 obvious to remark, that fhould we allow this to be the
 caSe,  wc are utterly at a lofs  to find a Source  of heat
 fufficient to  rarefy the vapour  to fuch  a degree  as is
 neceflary for producing the effect afcribed to it.   In
 the prefent  die, we can fcarce fuppofe a grain weight
 of metalline calx,  already dry, to contain as much ei-
 ther of fire or water as is neceflary to  produce  the ef-
 fect ; nor can we explain why the touch of any cold
 k^dy,  and which may be fuppofed to contain lefs fire
 than the calx uSelf, fhould produce Such  an effect. As to
 1',.  oxygenous aud hydrogenous principles, they were
 there before the  touch,  and  ought  to have produced
 their effects, not to mention that the  water produced
 by  them could not have amounted to  the  thouSandth
 par; of a i;riin.   It is much more  probable, thereSore,'
 that the whole is  10 be confidered as an effect  of  elec-
 tricity, though we cannot tell how the fluid conies
 here to lit excited in fuch a violent  manner.
S  3-
O P P  E R.
   This is one of thofe metals which, from their de-
ftnntibilitv  by fire, and contracting ruft in the air,
arc called imptrf-. I}. Of thefe, how ever, it is the m>!t
perfect  and indcftrnctihle.   It is  of a reddifh colour
v.hcnpeirtj eafily  t-rniihea  in a moift  air, and  con«
tracts a green ruft.   It is the moft fonorous of all the
metals, and the hardeft and molt el aft c of all  but iron.
In fome of its fta;e>,  copper is as difficultly cxteiuhd
under  the hammer as iron, but always proves fofter to
the file ;  and is never found hard  enough to Strike .1
fp.nk  with flint or other ftones ; whence its ufe lor
ehilicls, hammers, hoops, trc. in the gunpowder works.
"W hen broke by often bending backw.u\!s and forwards,
it appears internally of a dull red colour without any
bri^luntfs, and  of a  fine  granulated  texture refem-
bling fome kinds of earthen ware.   Ii is  confiderably
ductile, though lefs fo than either gold or filver ;  and
may be drawn into wire as  fine as hair, or beaten into
leaves almoft as thin as thofe of li.vcr.  The tcnaeiiy
of its parts is very confiderable ; Sor a copper wire of
T'T oS an inch diameter will Support a weight of 299\
pounds without breaking.   The Specific gravity oS ibis
metal, according 10 Dr  Lewis, is to that o\  water as
8.830  to 1.
   Copper continues  malleable  when  heated  red ; in
which relpectit agrees with iron ; but is not, like iron,
capable ot" being welded,  or having two pieces joined
into one.  It  requires for  its  fiifion  a ftronger  heat
than either gold or Silver, though leSs  than that requi-
fite to  melt iron.  When in fufion,  it is  remarkably
impatient of moifture  ; the contact of a  little  water
occalioning  the  melted  copper to  be thrown about
with violence, to the great danger oS the  by-ftanders.
It is,  nevertheless,  Said to  be granulated in the brafs-
works at Briftol,  without explofion or danger, by let-
ting it Sail in little drops, into a large  cittern of  cold
water  covered with a braSs-plate.   In the middle of
the plate is an aperture, in which is Secured with Stur-
bridge clay a Small veflel, whoSe capacity  is not above
a Spoonful, perforated with a number of minute holes,
through  which the melted copper paffes.  A Stream
oS cold water paffes through the cittern.   If Suffered
to grow  hot, the copper falls liquid  to  the bottom,
and runs into plates.
   Copper, in fufion,  appears of a bluiffi green colour,
nearly like that of melted gold.  Kept in fufion for a
long time, it becomes gradually more and more brittle ;
but does not fcorify confiderably, nor lofe much oS its
weight.   It is much  leSs destructible than any oS the
imperfect metals, being very difficultly Subdued even
by lead or bifmuth.   IS  kept  in a heat below fufion,
it contracts on the furface thin powdery fcales; which,
being  rubbed off", are fucceeded by  others, till  the
whole quantity of the metal is thus  changed into  a
Scoria  or calx, of a dark reddifh colour.   This  calx
does not melt in the ftrongeft furnace fires; but, in the
focus of a large burning mirror, runs eafily into a deep
red, and almoft opaque,  glafs.  A  flaming fire,  and
ftrong draught of air over the furface of the metal,
greatly promote  its  calcination.   The  flame  being
tinged of a green, bluiffi, or rainbow colour, is a mark
that the copper burns.
   This metal is very readily foluble by almoft all fa-
line fubftances ;  even common y are r, fuffered to ftand
long in copper-velfels, extracts fo much as to gain a
coppery tafte.  It is obfervable, that water  is much
more impregnated with this  laytc, on being Suffered
to ftand in the cold, than if boiled for  a longer time in
the veffel.   The fame thing happens in regard to the
mild vegetable acids.  The confectioners prepare the
;.■■'j.i acid fyrup.s, even thofe of lemons and  oranges,
                                                by
V.iCtice.
   lopi-cr.
   1148
How gra-
nulated.
  1140
Calcined.
   1150
Solubility. 
Practice.
CHEMISTRY.
Copper.
   H5i
Altered by
combina-
tion with
vegetable
acids.
   115a1
Amalga-
mation
with mer-
cury.
  H53.
Dr Lewis's
method.
   "54
Erafs, how
prepared.
 by boiling in clean copper-veffels,  without the prepa-
 rations receiving any ill tafte from the metal;  whereas,
 either the juices themfelves, or the fyrups made from
 them, if kept cold in copper veflels, foon become  im-
 pregnated with a difagreeable tafte, and with the per-
 nicious qualities ofthe copper.
   By combination with  vegetable acids, copper  be-
 comes  in fome refpects remarkably altered.  Verdi-
 gris, which is  a combination of copper with a kind
 of acetous  or tartareous acid, is partially foluble  in
 diftilled vinegar ; the refiduum,  on being melted with
 borax and  linfeed oil, yields a  brittle metallic fub-
 ftance,- of a whitifh colour, not unlike bell-metal. The
 copper alfo, when revived from the diftilled verdigris,
 was found by Dr Lewis to be different.Srom the  metal
 before diffolution ;  but neither of theSe changes have
 yet been Sufficiently examined.
   Copper, in its metallic ftate,  is very difficultly  amal-
 gamated with mercury; but unites  with it more  eafily
 if divided by certain admixtures.  If mercury and
 verdigris be  triturated together with common fait,
 vinegar,  and water, the copper in  the verdigris will
 be imbibed by the mercury, and form with it,  as Boyle
 obServes, a  curious amalgam, at  firft So SoSt  as to  re-
 ceive any impreffion, and which, on ftanding, becomes
 hard like brittle metals.   BraSs leaf likewife  gives out
 its copper to  mercury, the  other  ingredient of the
 brafs feparating in the form of powder.
   Eafier methods of amalgamating copper are publifh-
 ed by Dr Lewis in his notes on Wilfon's Chemiftry,
 p. 432.   His receipts are,—" Diflblve fome fine cop-
 per in aquafortis :  when the menftruum will take up
 no more of the  metal, pour it into an iron mortar,
 and add  fix times the  weight  of the copper, of mer-
 cury, and a little common fait: grind  the whole well
 together with an iron peftle; and, in a little  time,
 the copper will  be imbibed  by the  mercury, and  an
 amalgam  formed, which may be rendered bright  by
 wafhing it well with repeated affufions  of water.
   " Another method.  Take the, muddy fubftance which
 is procured in the polifhing of copper plates with  a pu-
 mice  ftone, and  grind it well  with a fuitable portion
 of mercury, a little common fait,  and fome  vinegar,
 in an iron mortar, (a marble one will do, if you make
 ufe of an  iron peftle), till  you perceive the  mercury
 has taken up  the copper."   The  copper recovered
 from thefe amalgams retains its original colonr, with-
 out any  tendency  to  yellow.  Even  when  brafs  is
 made ufe  of for making the  amalgam, the recovered
 metal is  perfect red  copper; the  ingredient  from
 which the brafs received its  yellownefs  being,  as a-
 bove obferved, Separated in the amalgamation.
   Copper is the  bafis oS Several metals for mechanic
 ufes; asbraSs, prince's metal,  bell-metal, bath-metal,
white copper, ire.  BraSs is  prepared from copper
and calamine, with  the addition  oS powdered char-
coal, cemented together, and at laft brought into fu-
fion.  The calamine is to be previoufly prepared  by
cleanfingit from adhering earth, ftone, or other  mat-
ters ;  by roafting, or calcining it; and by grinding it
into a fine powder.  The length of time, and degree of
heat,  requifite  Sor  the calcination  oS  the calamine,
are different according  to the qualities of that  mineral.
The calamine, thus calcined, cleanSed,  and ground,  is
to be mixed with about a third or fourth part of char-
 coal duff,  or  powdered pit-coal,  as  is done  in Some
 parts of England.  The malleability ofthe bafis is di-
 miniflied by the uSe of pit-coal,  which is therefore
 only employed for the  preparation oS the  coarSer
 kinds.   To  this compofition of  calamine  and coal,
 fome manufacturers add common  fait, by which  the
 procefs  of making brafs is faid  to be  haftened.  In
 Goflar, where the cadmia  adhering to the infides of
 the  furnaces is ufed inftead of the native calamine,  a
 fmall quantity  of alum is added,  by whicli they pre-
 tend the colour of the brafs is heightened.  With this
 compofition,  and with thin plates or grains of copper,
 the crucibles are to be nearly filled.   The proportion
 of the calamine to  the copper varies according to the
 richneSs of the former, but is generally as three to two.
 The copper muft be difperfed through the compofition of
 calamine and coal;  and the whole muft be covered with
 more coal, till  the crucibles  are  full.   The crucibles,
 thus filled, are to be placed in a furnace funk in the
 ground, the form of which is that of the fruftum of a
 hollow cone.   At the bottom ofthe furnace,  er great-
 er bafis of the fruftum, is  a  circular grate, or iron-
 plate.   This plate is  covered with a coat oS clay and
 horfe-dung, to deSend it from the  action ofthe fire;
 and pierced with holes, through which the  air main-
 taining the fire pafles.   The crucibles ftand upon the
 circular plate, forming a  circular  row, with  one  in
 the middle.   The fuel is placed betwixt the crucibles,
 and is thrown into the furnace at the upper part of it,
 or the leffer bafis oS the fruftum.   To this upper part
 or mouth of the furnace is fitted a  cover  made  of
 bricks or clay, kept together  with bars of iron, and
 pierced  with holes.  This cover ferves as a regifter.
 When the heat is to be increaSed, the cover muft be
 partly  or entirely  taken  off, and a free draught is
 permitted to  the external air, which  pafles along a
 vault under-ground to the afh-hole, through  the holes
 in the circular grate  or plate, betwixt the crucibles,
 and through the upper mouth, along with the fmoke
 and flame, into an area where the workmen ftand,
which is covered with  a large  dome or  chimney,
 through which  the fmeke and air aScend.  When the
heat is  to be diminiflied, the mouth oS the  furnace
 is cloSed with the lid;  through the holes of which the
 air, fmoke, and flame pafs.   The  crucibles are to  be
kept red-hot  during eight or ten hours; and in fome
places much longer, even feveral  days, according to
the nature of the calamine.  During this time, the
 zinc rifes in  vapour from the calamine, .unites  with
 the copper, and renders that metal confiderably more
fufible than it is by itSelS.   To render the metal \ery
fluid,  that  it may flow into  one uniform mafs at the
bottom, the fire is to be increafed a little before the
 crucibles are  taken out, for pouring off the fluid me-
 tal into  moulds.   From  60 pounds of good calamine,
 and 40 of copper, 60 pounds of brafs may be obtain-
 ed,  notwithftanding a confiderable  quantity ofthe zinc
 is  diflipated in  the operation.  The quantity of brafs
 obtained has  been confiderably augmented fince the
 introduction of the method now commonly practifed,
 of granulating  the copper; by which means a larger
 furface of this metal is expofed to the vapour of zinc,
 and  consequently leSs  of that vapour  efcapes.   To
 make the finer and more malleable  kinds of brafs, be-
 fides the choice of pure calamine and  pure copper,
                       X 2                  fome 
164                                 CHEMI
 C i-per.  f)nie  miuufaclurers cement the brafs a Second time
    «r—' with calamine and charcoal; and Sometimes add to it
         •)ld braIV, by which the new is Said to  be meliorated.
            BraSs is brittle when hot; but fo ductile when cold,
         that it may be drawn into very fine wire, and  beat
         into very thin leaves.   It,  beautiful colour, malleabi-
         lity,  and its fulibility, by  which it may be eafily caft
         huo moulds, together  with its being lefs liable to ruft
         than  copper, render it fit  for the  fabrication of many
         utenlils.
            Although zinc be fixed to a certain degree in braSs,
         by the adhefion which  it  contracts with the copper;
         ) e t when brai's is melted, and expoSed to a violent fire,
         during a certain  time, tlie zinc diffipates in vapours,
         and even flames  away, iS  the heat be  ftrong enough ;
         and if the fire is long enough continued,  all the zinc
         will be evaporated and deftroyed, fo that what remains
 id 1154 is copper.
Trince*      Prince's metal is made by melting zinc in fubftance
metal.    with  copper; and  all  the yellow compound  metals
         prepared in imitation of gold  are no other than mix-
         tures of copper with different proportions of that fe-
         mimetal, taken either  in  its pure ftate, or in  its  na-
         tural ore  calamine,  with  an addition  fometimes  of
         iion-filings, cc.   Zinc itfelf unites  moft eafily with
         the copper ; but  calamine makes the moft ductile com-
         pound, and gives the moft yellow colour. Dr Lewis ob-
         ferves, that a little of the calamine renders the cop-
         per pale ; that  when it  has imbibed about  y%  its own
         weight,  the colour inclines to yellow ; that the yel-
         lownefs increafes more  and more,  till  the proportion
         conies to almoft one half;  that on  further augmenting
         the calamine, the compound becomes paler and paler,
         and at laft white.   The crucibles,  in which the fufion
         is performed in large works,  are commonly tinged by
   ,Tj5  the matter of a deep blue colour.
Bell-metal.   Bell-metal is a mixture of copper and  tin ; and tho'
         both  thefe metals fingly are malleable, the compound
         proves  extremely brittle.  Copper is diffolved  by
         melted tin  eafily and intimately,  far more fo than by
         lead.  A fmall portion of  tin renders this metal dull-
         coloured, hard, and brittle.  Bell-metal is compofed of
         shout  ten parts of copper to one of tin,  with the  ad-
         dition commonly of a little brafs or zinc.   A fmall pro-
         portion  of  copper, on the other  hand, improves the
         colour and conliftency of  tin,  without much injuring
         its ductility.  Pewter  is  fometimes made from  one
   ,r-6   part of copper and twenty or more of tin.
Dr Lewis's   It has long been obferved, that  though tin is fpeci-
i.'.:-rvat'- fically  much lighter than copper, yet the gravity of
ou»ont!n  [nc compound, bell-m«tal, is greater  than that of the
fpecific   COppcr itfelf.  The Same augmentation of gravity al-
jcravity o  ^ la^cs  piacc where the lighter metal is in  the greateft
         proportion ; a mixture  even  of one part of tin with
         two of copper, tuning out Specifically heavier than
          pare copper.   Moft metallic mixtures anfwer to the
          1  can gravity ofthe ingredients, or fuch as would re-
          lult from a  bare appolition oS parts.  OS thoSe tried by
          Dr Lewis,  Some exceeded the mean,  but  the  greater
         number fell  ff.ort of it ;  tin and copper were the only
         ones th u formed a compound heavier than the heavicft
      .  of the metals Separately.
White c^-   White copper  is prepared by mixing together equal
r«r.    '  prts of arfenic and nitre, injecting the mixture into
         4 red-hot crucible, which  is to be kept in a moderate
   S   T    R   Y.                           Practice.
fire till they  fubfide, and  flow like  wax.   One  part    iron.
of this mixture is injected upon four parts of melted     v
copper,  aud the metal,  as foon  as  they appear  tho-
roughly united together, immediately poured out. The
copper,  thus whitened,  is commonly melted  with a
confiderable proportion  of filver, by which its colour
is  both iir.provtd and rendered more permanent.  The
white copper of China  ai.d  Japan  appears to be no
other than a mixture of  copper and arfenic.  Geoffroy
relates,  that, on repeated fufions, it exhaled arfenical
fumes, and became  red  copper,  lofing with its white-
nefs, one Seventh of its  weight.

                  \  4.  I R 0  A.

   Iron is a metal of a greyifh colour ;  Soon tarnifhing
in  the air  into a dufky blackifh hue ;  and in a Short
time  contracting a  yellowifli, or reddifh ruft.   It is
the hardeft of all metals: the moft elaftic  ; and, except-    TI j
ing platina,  the moft difficult to be fufed.  Next to Tenacity of
gold, iron has the greateft tenacity of parts;  an iron its parts.
wire, the diameter  of which is the  tenth part of an
inch, being capable of fuftaining 450 pounds.  Next
to tin, it is the lighteft of all the metals, lofing between
a Seventh and eighth part oS its weight when immerSed
in water.  When very pure, it may be drawn into wire
as fine as horSe-hair ; but is much leSs capable of being
beaten into thin leaves than the other metals, except-
ing only lead,
   Iron  grows  red-hot  much  fooner  than any other
metal; and  this, not only from the application of ac-
tual fire, but likewife  from ftrong hammering, fric-
tion, or other mechanic violence.   It neverthelefs melts
the moft difficultly of all metals except manganefe and
platina;  requiring,  in its moft fufible flate,  an  in-
tenfe, bright, white heat.  When perfectly malleable,
it  is not Suiiblc at all by the heat of furnaces, without
the addition  or the immediate contact of burning fuel;
and, when melted, lofes its malleability : all the com-
mon operations which communicate one of theSe qua-
lities deprive it at the  Same time oS the other; as if
fulibility and malleability were in this metaLincompa-
tible.  When expoSed to the Socus of a  large burning
mirror,  however, it quickly  fufed, boiled, and emit-
ted an ardent fume, the  lower part of which  was a
true flame.   At length it was changed into a blackifh
vitrified fcoria.
   From  the great wafte occafioned by  expofing iron ironacom-
to a red but  eSpecially to a white heat, this metal ap- buftible
pears to be a combuftible fubftance.   This combuftion fubftance.
is  maintained,  like that of all other combuftible  fub-
ftances, by contact of air.   Dr Hook, having heated
a bar of iron to  that degree called white heat,  he pla-
ced it upon an anvil, and blowed air upon it by means
of bellows,  by which it  burnt brighter and  hotter.
Expofed  to  a white heat,  it  contracts a femivitreous
coat, which  burfts  at times, and flies off in fparkles.
No  other metallic  body  exhibits  any  fuch appear-
ance.  On  continuing  the  fire, it changes  by  de-
grees into a dark red calx, which does not melt  in
the moft vehement heat  procurable  by furnaces, and,
if brought into fufion by  additions, yields an opaque
black glafs.  When ftrongly  heated,  it appears  co-
vered on the furface with a  foft vitreous matter like
varnifh.  In this ftate, pieees of it cohere ; and, on
                                             being 
Practice.                           C   H   E    M
   Iron,   being hammered together, weld or unite, without diSco-
^   *--- vering a juncture. As iron is the only metal which ex-
The only habits this appearance in the fire, So it is the only one
metalcaua- capable of being welded.  Thofe  operations  which
bleof being prevent the Superficial  Scorification,  deprive it likewiSe
welded.   of this valuableproperty : which rhaybe reftored again,
         by Suffering the iron  to  refiime its vitreous  aSpect;
         and, in Some meafure, by the interpofition of foreign
         vitrefcible matters ; whilft none of the other metals will
   jjgt   unite in the fmalleft degree, even with its own  Scoria.
Contracts    Iron expands the leaft of all metals by heat.  In the
in fufion.  act of fufion, inftead of continuing to expand, like the
         other metals, it fhrinks;  and thus becomes fo much
         more denfe,  as to throw up fuch part as is unmelted to
         the furface ;  whilft pieces of gold, filver, copper, lead,
         or tin,  put into the refpective  metals in fufion, link
         freely to the bottom.  In its return  to a  confiftent
         ftate, inftead of fhrinking like  the other  metals, it
         expands ; fenfibly riling  in the veflel,  and affirming a
         convex furface, while the others become concave. This
         property, firft obServed  by Raumur, excellently fits it
         for  receiving impreffions from  moulds.   By  the in-
         creafe of bulk which the metal receives in congelation,
         it is forced into the minuteft cavities, fo  as  to take
         the impreffion far more exactly than the  other  metals
  n6s   which flirink.
Diffolved    lr°n is diffolved by all the  metals made  fluid, ex-
by all me- cept lead ; though none of them act fo powerfully up-
tals except on it as  gold :  but, as Cramer obferves, if the iron
lead and  contains any portion  of fulphur, it can fcarcely be made
mercury. tQ unjte at ali with g0\d.
            Among the femimetallic  bodies,  it  is averfe to an
         union with mercury  ; no method of amalgamating thefe
         two having yet been difcovered ; though quickfilver,
         in certain circumftances, feems in fome fmall  degree
         to act upon it.   A plate of tough iron, kept immerfed
         in mercury for fome days, becomes brittle  ; and mer-
         cury will often  adhere to and coat the  ends  of iron
         peftles ufed in triturating certain amalgams with faline
         liquors.   Mr Jones has alfo difcovered,  that by plun-
         ging iron, while heated to an intenfe white heat, into
         mercury, the latter will adhere to  the furface  of the
         iron, and completely filver it over.
            Next to mercury,  zinc is the moft difficultly  com-
         bined with iron ; not from any natural indifpofition to
         unite, but from  the zinc being difficultly made to fu-
         ftain the  heat requifite.   The mixture is hard, fome-
         what malleable, of a white colour approaching to that
         of filver.  Regulus  of antimony, as foon as it melts,
         begins to act on iron, and diffolves a confiderable quan-
         tity.   If the  regulus  be ftirred with a iron  rod, it
         will melt off a part of it.   Arfenic likewife eafily
         mingles with iron, and has a ftrong attraction  for it;
         forfaking all the other metals to unite with  this.   It
  ufij   renders the iron white, very hard,  and brittle.
Pruffian      This metal is the bafis ofthe  fine blue pigment, cal-
blue.     led, from the place where it was firft difcovered, Ber-
         lin or Pruftianblae.    This colour was accidentally dif-
         cevered about the beginning ofthe prefent century, by
         a chemift of Berlin, who, having fucceffively thrown
         upon the ground feveral liquors from  his laboratory,
         was  much furprifed to See it  Suddently ftained with a
         beautiful blue colour.   Recollecting what  liquors he
         had thrown out,  and obferving  the Same effects from
         a fimilar  mixture, ke  prepared  the blue  for the ufe of
I   S   T   R   Y.                                  165
 painters-,  who found that it might be fubftituted toul-    Iron.
 tramarine, and accordingly have ufed it ever fince.        ^7  "
   Several  chemifts immediately  endeavoured to  dif- pr wooj.
 cover the compofition of this pigment;  and in the year ward's re-
 1724 Dr Woodward publifhed  the following procefs, cept for.
 in the PhiloSophical Transactions, for making it. "  Al-
 kalize together four ounces  of  nitre, and as much tar-
 tar as is  directed for charcoal (11 ° 779). Mix this alkali
 well with  four ounces of dried bullocks blood ; and put
 the whole  in a crucible covered with a  lid, in which
 there is a fmall hole.  Calcine with a moderate  heat, till
 the blood be reduced to a perfect coal; that is, till it e-
 mits no  more Smoke or flame capable of blackening any
 white bodies that are expoSed to  it.   IncrcaSe  the
 fire towards the  end, So that the  whole matter  con-
 tained in the crucible fliall  be moderately,  but fen-
 fibly, red.
   " Throw into two pints of water the matter  con-
 tained in the crucible, while yet red, and  gave it half
 an hour's  boiling : decant this firft water ; and pour
 more upon the black charry coal, till it becomes almoft
 infipid.   Mix  together all thefe waters ; and reduce
 them, by boiling, to about two pints.
   " Diffolve alSo two ounces of  martial  vitriol, and
 eight ounces of alum,  in two pints of boiling water.
 Mix this folution when hot with  the preceding  lixivium
 alfo hot.  A great effervefcence will then be made :
 the liquors will be rendered turbid  ; and  will become
 of a green colour, more  or lefs blue ; and a precipi-
 tate will be formed of the Same  colour.   Filtrate,  in
 order to Separate this precipitate ; upon which pour
 Spirit of fait, and mix them well together ; by which
 means the  precipitate will become of a fine blue colour.
 It is neceflary  to add rather  too much of the  fait than
 too little,  and  till it no longer increafes  the beauty of
 the  precipitate.  The next day  wafh this blue, till  the
 water comes off from it infipid; and then gently dry it."    Il6
   Mr Geoffroy was the firft who gave any  plaufible Mr Geof-
 theory of  this procefs,  or any rational means of im- froy'stheo-
 proving it.   He obferves, that the Pruffian blue is  no ry.
 other than the iron of the vitriol revived  by the  in-
 flammable matter of the alkaline lixivium, and  per-
 haps a little brightened by the earth of alum,;  that  the
 green colour proceeds from a part  of the yellow fer-
 ruginous clax, or ochre, unrevived, mixing  with  the
 blue; and  that the fpirit oS Salt diffolves this  ochre
 more readily than the blue part;  though  it will dif-
 folve that alfo  by long Handing, or if uSed in  too large
 quantity.   From  theie principles,  he was led to  in-
 creaSe the  quantity oS inflammable matter ; that  there
 might be enough to revive the whole of the  ferrugi-
 nous ochre, and  produce a blue colour at once, with-
 out the uSe ofthe acid  fpirit.  In this he perfectly fuc-
 ceeded ; and found,  at the fame time,  that the colour-
 might be rendered of any degree of'deepnefs,  or light-
 nefs, at pleafure.  .If the alkali is calcined with twice
 its weight of dried  blood, and  the lixivium  obtained
 from it poured into a folution of one part of vitriol to
 fix of alum, the  liquor  acquires  a very pale blue  co-
 lour, and  depofits as  pale a precipitate.  On adding
 more and  more of a frefli folution of vitriol, the  co-
 lour  becomes deeper and deeper,  almoft to blacknefs.
 He imagines, with great probability, that the blue pig-
 ment, thus prepared, will prove more  durable in  the
 air,  mingle more perfectly with other colours, and be
                                                 lefs, 
166
Iron
   1166
.A muting
p icnome-
nonin the
y cpara-
tlon.
   lif-i
Mr Mac-
rjicr's the-
•ry.
   1168
Phlogifti-
cated alka-
li lofes its
alkaline
properties.
  T169
Earths do
not attract
the colour-
ing mattcr.
                            CHE   M
lefs apt to inj;;r the l ,ftrc officii as are rixed with
or applied in its neighoourhood, than that made in ihe
common manner ;  the tarnilh to which common Pruf-
fian blue  is fubject,  feeuiingto proceed fromthe  acid,
which cannot  be Separated by any ablution.
   He take s  notice of" an amuling  phenomenon which
happens upon mixture.   When t lie  liquors are  well
ftirred together; and  the circular motion, as Soon as
pxiiffc,  ltopped ;  Some drops  oS Solution oS vitriol,
(depurated, by longlettling), let fall on different parts
of tlie lurfi■-c, divide, fprcad, and form curious repre-
fe ntations of flowers, trees, lhrubs, flying infects, &c.
in great regularity  and  perfection.   Thefe continue
10 or 12  minutes :  and  on ftirring the  liquor again,
and dropping in fome  more of  the folution of vitriol,
arc fucceededby a new picture.
   Tiiis theory is confirmed by Mr Macquer, in a Me-
moir  printed  in the  year 1752.  He obferves,  that
the qua tity of  phlogifton communicated to the iron
in this  procefs is fo great, as not only to caufe the me-
tal refift in a  great  nieaSure the action  of acids, and
become totally unaffected  by the  magnet  ; but by a
flight calcination it  becomes entirely fimilar to other
iron, and  is at once  deprived of its blue colour.  Pie
further obferves, that  fire is  not the only means by
which Pruffian blue may be deprived of all the proper-
ties which diftinguifli.it  from ordinary iron.  A  very
pure alkali  produces the fame effect.   He has alfo dis-
covered, that the alkali which has thus  deprived the
Pruffian blue of all the properties which  diftinguilh
it  from ordinary  iron,  becomes,  by that operation,
entirely fimilar  to  the phlogifticated alkali ufed for
the preparation  of Pruffian blue.
   By a more  particular examination^ he  found,  that
the alkali might become perfectly faturated with the
colouring matter ;  fo  that, when boiled on  Pruffian
blue, it extracted none of its colour.   When the fait
was thus  perfectly  faturated, it feemed no longer to
poflefs any alkaline qualities.  If poured into a folution
of iron  in any acid, a fingle, homogeneous, and perfect
precipitate, was formed ;  not green, as in  Dr Wood-
ward's  procefs, but a perfect  Pruflian  blue ; which
needed  no acid  to brighten its  colour.  A pure acid
added to  the  alkali  was not in  the leaft neutralized,
nor in   the leaft  precipitated  the colouring matter.
From hence Mr Macquer concludes, that,in the making
of Pruffian blue, vitriol is decompofed ; becaufe the iron
has a  ftrong  attraction  for the  colouring  matter, as
well as the acid for the  alkali ;  and the fum of the at-
traction of the acid  to the alkali, joined to that of the
iron for the colouring matter, is greater than the fingle
attraction of the acid to  the  metal.
   Another very important phenomenon is,  that earths
have not ihe fame attraction for  this colouring matter
that metallic fubftances  have.   Hence, if an alkali Sa-
turated with this colouring matter be poured into a So-
lution of  alum,  no decompofition is effected, nor any
precipitate  formed.   The alum continues alum,  and
the alkali remains unchanged.   From  this experiment
Mr Macquer concludes that alum does not directly con-
tribute  to the formation of  the Pruflian blue.   The
purpofe he thinks it  anfwers  is  as follows.   Fixed al-
kaline falts can never be  perfey.';. faturated  with phlo-
giftic matter by calcination ; alkalies, therefore, though
calcined with inflammable fubftances,  fo as to make  a
I   S   T    R   Y
Practice.
proper lixivium  f.-r Pruflian blue, remain  ftill alka-
line.   Hence,  when mixed with  a  folution of  green
vitriol, they lorm, by their purely alkaline part, a yel-
low precipitate, fo much more copious, as  the alkali
is'lcls Saturated with phlogifton.   But nothing is more
capable of  Spoiling the fine colour of the Pruflian blue,
than an  admixture of this yellow precipitate:  it  is
therefore neceflary to add a  quantity of alum,   which
will take up the  greateft part  of the  purely  alkaline
fait,  and of  confequence the quantity  of yellow fer-
ruginous  precipitate is  much diminiflied.  But the
earth of  alum,  being of  a fine fhining white, does not
in the  leaft alter  the purity of the blue colour, but is
rather neceffary to dilute it.   From all this  it  follows,
that  it is a matter  of indifference whether  the green
precipitate is to be  again diffolved by an acid,  or  the
alkaline  part of  the lixivium faturated with alum
or with  an  acid, before  the precipitate  is  formed.
The latter indeed feems to  be the moft eligible me-
thod.
   Moft alkalies obtained from the aflies of vegetables,
being  combined, by their combuftion, with a portion
of inflammable  matter,  are capable of furniihing a
quantity  of Pruffian blue, proportionable to  the  quan-
tity of colouring matter they  contain,  even  without
the neceffity of mixing them with a folution of iron;
becaufe they always contain  a  little of this  metal  dif-
folved, fome of which may be found in  almoft all  ve-
getables  ;  therefore it is fufficient to faturate them
with an  acid.   Henckel obferved the production of
this blue in the faturation of the foffile  alkali, and re-
commended to  chemifts  to inquire into its nature.
   The theories of Geoffroy, Macquer, &c. however,
withrefpect to Pruffian blue, have now given place to
that oS Mr Scheele ; who has  examined the Subftance
with the utmoft care, and found  the colouring matter
to confift of an extremely volatile fubftance,  capable of
uniting with and neutralizing alkalies,  but  eafily  ex-
pelled  from them  by any other acid, even  by that of
rixed air.   He  begins his diflertation  on this fubject
by obferving, that the folution  of alkali calcined with
dried blood, which he calls lixivium fanguinis, by ex-
pofure  to the air, lofes  its property of precipitating
the iron of a blue colour ; and that the precipitate thus
obtained  is entirely foluble in the acid.  In order to
determine  whether the air had thus  undergone any
change, he put  fome newly prepared lixivium  into a
glafs veflel  well Sealed with rofin ; but after  fome time
finding no  change on the lixivium, or on the  air con-
tained  in the veffel, he began to think that this  might
be occafioned by theabfence oS fixed air, which always
abounds in  the open atmoSphere, though not in any
confined portion oS it,  at leaft in  an equal proportion.
Having therefore filled a glaSs veflel with fixed air, he
poured into it a little lixivium Sanguinis ; and next  day
found,  that it threw down from green vitriol  a  preci-
pitate  entirely  Soluble in acids.   With, other acids he
obtained no precipitate.
   On  inverting the  experiment, and mixing fome
green vitriolwith lixivium Sanguinis, the mixture grew
yellow ;  and he found   this addition capable oS fixing
the colouring matter So that neither the acid oS fixed
air nor any other could expel it Srom the alkali.  For
having poured the mixture abovementioned  into a So-
lution of green  vitriol,  and afterwards fuperfaturatcd
                                                the
Iron.
  1170
lftue pro-
ducible
fi om other
alkalies.
   T171
MrScheele
difcovers
the colour-
ing matter
of Pruflian
blue.
  1171
Lixivium
fanguinis
lofes its co-
louring
propertyby
expofure to
the air.
   H73
Suppofed
to arife
fromthe
fixed air
abforbed
from the at-
mofphere.
   1174
The matter
fi.M-d by the
addition of
fe;me green
vitriol to
the lixivi- 
Practice.
CHEMISTRY.
167
Iron.
  "75
Calx of i-
ron foluble
in lixivium
fanguinis;
   1176
But not
when high-
ly dephlo-
gifticated.
  "77
The colour
cids.
          thelixivium with acid,  he obtained aconfiderable quan-
          tity of blue. To the fame lixivium fanguinis, in which
          a fmall quantityof green vitriol was diliolved, he after-
          wards added of the other  acids  fomewhat more than
          was neceffary for its  faturation ;  and though  this was
          done, a confiderable  quantity of Pruffian  blue was af-
          terwards obtained.   Again, having  precipitated a fo-
          lution of green vitriol with alkali, and boiled the pre-
          cipitate for fome minutes  in lixivium fanguinis, part
          of it was diffolved : the filtered lixivium underwent no
          change  when expofed to the upen air or to the aerial
          acid, and precipitated  the folu)ion ot vitriol of a blue ;
          and though the lixivium was fuperfaturated with acid,
          and Some green vitriol  added, a very  beautiful Pruffian
          blue was obtained.  This, however, will not hold when
          a perfectly dephlogifticated calx oS iron is employed,
          of which none can be diffolved by the lixivium Sangui-
          nis  ; nor will any Pruffian blue  be obtained by preci-
          pitating with lixivium Sanguinis a perfectly dephlogi-
          fticated Solution of iron in  nitrous acid.
            To  determine what had become  of the colouring
 ing matter matter  ill thofe experiments where it feemed to have
 taken up   been diflipated,  fome lixivium fanguinis was poured in-
 by the air  tQ a veipci £r|ec| ^fa  aerial acid.  It was kept well
 after it has    1  1  1  •    1     •  1     1        1         r -•
 been expel- col"ked  during the night, and  next day a piece ot pa-
 led by a-   Per dipped in a folution of green vitriol was fixed to
          the cork,  pencilling it over with two drops of a folu-
          tion of alkali in water.   The paper was thus foon  co-
          vered with precipitated iron ;  and on being taken out
          two hours afterwards,  and dipped in muriatic acid,  be-
          came covered with moft beautiful Pruffian blue.  The
          fame thing happened when lixivium  fanguinis fuperfa-
          turated  with vitriolic acid  was employed ; for  in this
          cafe alfo the air was filled with  the  colouring  matter
          capable of being in like manner  abforbed by  the calx
          of iron.   But though from thefe experiments it is plain
          that acids  expel this colouring fubftance from  the
          lixivium,  a given quantity of air is  only capable of
          receiving a certain quantity of it; for the  fame mix-
          ture removed into another veffel imparts the colouring
          property to  the air  it  contains according to its quan-
          fity.  On  putting perfectly dephlogifticated calx  of
          iron upon the papers,  no Pruffian blue was  formed;
          but  the  muriatic acid diffolved  the calx entirely.
            Our author having  now  affured himSelS that acids
          really attract the alkali more than the colouring mat-
          ter,  proceeded  to try the effects  of diftillation.  Ha-
          ving therefore fuperfaturated fome lixivium fanguinis
          with vitriolic aciel, he  diftilled the mixture in a glafs
          retort with a gentle fire.   When about one-third had
          paffed over,  he changed  the receiver, and continued
          the  operation till one  half was diftilled.   The firft pro-
          duct had a peculiar tafte and Smell ; the air in the  re-
          ceiver was filled with colouring matter, and the aque-
          ous fluid was alSo ftrongly impregnated with it,  as ap-
          peared by its forming a fine Pruflian blue with phlogi-
          fticated calx of iron.   Part of it  being expofed  to the
          open air for fome hours, entirely loft its power, and the
          product of  the fecond operation was no other than wa-
          ter mixed with a little  vitriolic acid.  -
            The next ftep was to procure, if  poflible, the co-
to procure  ]ol,rjng  matter  by itfelf;  and  this he attempted  to
    matter 0Dtain from  the Pruffian blue,  rather than the lixi-
          vium fanguinis, as he would thus not only avoid the
          troublefome calcination of  the alkali and  blood, but
Iron.
   X178
The co-
louring
matter ex-
pelled by
diftillation
with vitri-
olic acid.
  "79
Attemps
ing
by itfelf.
118a
neral wa-
ters.
1181
with oil o£
vitriol.
obtain the colouring  matter im much larger  quantity
than could be done from the lixivium.   On examining
feveral kinds of this pigment,  he found in them  evi-
dent marks of fulphur, volatile alkali, vitriolje acid, and
volatile fulphureous acid ; all of which fubftances are to
be found in the lixivium Sanguinis as well  as in that of
foot,  and adhere to the precipitate  in the  preparation
of Pruffian blue.   Finding, however, tharhe could not
obtain his purpofe by any  kind of analyfis of theSe by
fire alone, he had recourSe to a neutral  Salt ufed by
chemifts for  discovering iron in mineral waters. This Neutral
is formed by digefting cauftic  fixed alkali on Pruflian fait for dif-
blne,  which  effectually extracts the colour from it even covering ^
in thecold, in a very fliort time, and being neutralized, ir
may eafily be reduced into a dry form.  But  it is not
entirely  to be depended upon for this  purpofe; for it
always contains Some iron which indeed is  the medium
of. its connection with the  alkali.  The lixivium  fan-
guinis is preferable,  though  even this contains fome
iron,  as well as the lixivium of Soot; our author's ex-
periments, however, were made with the neutral  Salt,
for thereaSon already mentioned.
   r  An ounce oS the Salt was diflblved in a glafs re- Effects of
tort in four ounces of water,  afterwards adding three diftilling
drachms oS concentrated vitriolic acid ; and  the mix- this fait
ture was diftilled with a gentle fire.  The maSs grew
thick as  foon as it began to boil; from a great quan-
tity  of Pruffian blue, a quantity of the colouring mat-
ter) appeared by the  fmell to penetrate the lute:  and
partof it was abforbed by the air in the receiver, as in
former experiments.   "The diftillation was continued.
till about an ounce had paffed into the receiver.  The
blue maSs remaining in the retort was put into  a ftrain-
er, and a piece Of green  vitriol put  into the  liquid
which paffed through ;  but by  this laft  no  Pruffian
blue was produced.   The bine which remained in the
filter  was again treated with lixivium  tartari:  the So-
lution freed from its ochre by filtration, and the clear
liquor committed a fecond  time to diftillation with vi-
triolic acid. Pruflian blue was again feparated, though in
Smaller quantity than before, and the colouring matter
came  over into the receiver.   After one third  ofthe
matter had paffed over, that which had been obtained
by the firft diftillation was added to it, the  Pruffian
blue was  feparated from the  lixivium in  the  retort,
and extracted a third  time.  Some Pruffian blue  was
formed again, though in much fmaller quantity ; whence
it is apparent that Pruffian  blue may at  laft be totally
decompofed by means of alkali. Lime, or terra pon-
derofa, likewife extract the blue colour, and fhow the
fame phenomena as alkali.
  With volatile  alkali a compound, confifting  of the Colouring
alkali, iron, and  colouring matter,  is formed, which matter u-
fliows  the  Same phenomena with  that formed with "bes with
fixed  alkali.   By diftillation  per fe after  it has been vo^tile a^-
diflblved in water, the liquor  grows thick in confe
qnence of a Separation of Pruffian blue,  and volatile al-
kali paffes over into the receiver.  This volatile  fpi-
rit  is  impregnated with ihe colouring matter; it  is
not precipitated  by lime water;  but green vitriol  is
precipitated by it ; and  on adding  an acid,  Pruflian
bine is formed.  If a piece of paper, dipped in a fo-
lution of green vitriol, be  expofed to  the vapour  of
this alkali, it is foon  decompofed ; and  if the fame  be-
pencilled over with muriatic acid, it inftantly becomes
                                              blue.
ii8&
kali. 
i68
CHEMISTRY.
Practice.
  Iron.

  1183
How t>-
frec the
colouring
matter per-
fectly from
it« vitriolic
taint.
   11S4
How to
prcvcntthe
rlcupe of
the colour-
ing mattcr
thro' the
lute.
   "85
This mat-
ter neither
acid nor al-
kaline.
   1186
Forms a
kind of am
moniacal
fait with
volatile al
kali.
   1187
Diffolves
magnefia
alba.
   1188
Very little
terra pon-
derofa.

   1189
Diffolves
lime, but
■to clay.
blue.  On expofing the liquor to the open air, it all
evaporates, leaving pure water behind.
   .*\s in a 1 the operations with  vitriolic acid hitherto
rekted, ley_u-  fmall quantity of  it pafles  into the re-
ceiver, our author fhows how to  deprive the colouring
matter, of that vitriolic taint.   For this purpofe no-
thing more is neceflary than to put a little  chalk into
the matter, and rcdiftil it with a  very gentle heat; the
jrd unites with  the chalk,  and  the  colouring  matter
goes over in its  greateft purity.   In order to hinder,
as much as poflible, the  efcape oS the volatile'colour-
ing  mattcr through the lute,  he  makes ufe of a fmall
receiver,  putting  into  it a little diftilled water, and
placing it fo  that the  greater part fhall  be immerfed
in cold water during  the  operation.  The water im-
pregnated with  this colouring matter has a peculiar
but not diSagreeable fmell,  a talte fomewhat approach-
ing to fweet, and warm in the  mouth,  at  the fame
time exciting cough.   When rectified as above direct-
ed,  it appears to be neither aeid nor alkaline; for it
neither reddens paper dyed with  lacmus, nor does it re-
ftore the  colour of fuch paper after it has been made
 red  ;  but  it renders  turbid the  folutions of foap and
 hepar fulphuris.   The  fame liquor mixed with  fixed
 alkali, though it contains a fuperabundance of colour-
 ing matter,  reftores the blue colour of paper reddened
 by an  acid.   By  diftillation to drynefs, there goes
 over a part ofthe  colouring matter which difengages
 itfelf from the alkali; the refiduum is foluble in water,
 and has all the properties of the beft lixivium  fangui-
 nis; but, like the  true lixivium, it is decompofed  by
 all the acids, even by that of fixed air.   With cauftic
 volatile alkali it forms a kind of  ammoniacal fait;
 which, however, always fmells volatile, though the co-
 louring matter  be in ever fo great  proportion.  By
. diftillation the whole inftantly rifes,  and nothing but
 pure water is left in the retort.
   Magnefia  precipitated from Epfom fait  by canftic
 veffatile alkali, was diffolved in the colouring matter by
 allowing them to  ftand together for feveral days in a
 warm clofe bottle.  On expofure to the open air, the
 magnefia  feparated from  it by  its fuperior attraction
 for  aerial  acid,  and  formed on the furface  of the
 water  a  pellicle like that  of cream of tartar.   This
 folution was likewife  decompofed by alkalies  and lime-
 water.
   The colouring  mattcr  diffolves but  a  very  fmall
 quantity  of  terra  ponderofa, which may be  after-
 wards precipitated by  vitriolic and even  by aerial
 acid.
   Pure clay, or the bafis  of alum, is not attacked by
 it.   Lime is diffolved in a certain quantity.  The fu-
 perabundant portion fhould be feparated by  filtration ;
 and as the liquor contains, befides the  combined lime,
 the portion which  water itfelf is  able  to take  up,  in
 order to free it from  this,  precifely the fame quantity
 of water impregnated with aerial acid is to be added
 as is requifite for precipitating  an equal quantity  of
 lime-water.   The colouring matter,  thus faturated
 with lime, is to be filtered again, and then to be pre-
 ferved in a well  clofed  bottle to  prevent  the accefs  of
 fixed air.    This folution is decompofed by  all the
 aciis, and by the pure or cauftic  alkalies.  ^ By  diftilla-
 tion the colouring matter  rifes,  and nothing but pure
 ii.nc L> left in the  retort.—This folution of lime ap-
                                          1
pears to our author to be fo perfectly Cuurated,  that he
employed it i;i  preference to any other in the  experi-
ments he made on metals,  and which wc are now about
to relate.
  from the trials made  by Mr Scheele, it  appears
that the colouring matter  has no effect upon  any  me-
tal or  niculiic folution, excepting thofe of filver and
quickfilver in nitrous acid, and  that of iron in fixed
air.   The firft is precipitated in a white powder : the
fecond in  a black  one ;  and the third affumes a fea-
green colour, which afterwards turns to blue.   \\ ith
metallic calces it produces the following  phenomena.
1. Gold precipitated by aerated alkali becomes white.
2. The fixed air  is difengaged from a precipitate of
filver with a flight effervelcence.   3. Calx of mercury
is diffolved,  and yields cryftals by gentle  evaporation.
4. The calx of copper precipitated  by aerated alkali
effervefces, and aftumes a faint citron colour.  5. Calx of
iron precipitated from its  folution in the vitriolic acid
by the fame alkali, effervefces, and affumes a dark blue
colour.  6.  Precipitated   cobalt fhows fome  figns of
effervefcence, and changes into a yellowifli brown co-
lour.  The other calces are not acted upon.
  The precipitating  liquor  abovementioned,  poured
into metallic folutions, produces the following  appear-
ances by means of double  elective attraction.   1. Gold
is precipitated of a white colour, but by adding a fu-
perabundant quantity  of  the precipitating liquor the
calx is rediffolved.  The  fecond folution is colourlefs
as water.   2. Silver is precipitated in form of  a white
fubftance  of the confiftence of chetfe ; by  adding more
of the  liquor the precipitate  is rediffolved, and the fo-
lution  is not decompofed either by  fal ammoniac or
marine acid.  3. Corrofive  Sublimate apparently un-
dergoes no change,  though it  is  in reality  decom-
pounded ; the calx being diffolved  in the colouring
matter.   Mercury diffolved in the nitrous acid  without
heat, is precipitated in Sorm oS a black  powder.  4.
The Solutions of tin and bifmuth  are precipitated, but
the calx is not acted  upon by the colouring  matter.
5. The Same effects are produced  on the folution of
butter of  antimony, as  well as on  that  of well de-
phlogifticated calx of iron.   6.   Blue vitriol is preci-
pitated of a yellow citron  colour : if more of the pre-
cipitating liquor be added,   the precipitate is redif-
folved into a colourlefs liquor and a colourlefs folu-
tion of the fame calx is likewife obtained by  volatile
alkali.   On adding more of the folution of  blue vi-
triol,  the folution likewife difappears, and the liquor
affumes a green colour.   Acids  diffolve  a portion of
this precipitate, and  the  remainder is white.  The
muriatic acid diflblves the precipitate completely, but
lets it  fall again on the addition of water.   7.  The fo-
lution  of white vitriol yields a white precipitate, which
is not  rediffolved  by addition  ofthe  precipitating li-
quor,  but is foluble in acids.  Thefe folutions fmell
like the colouring  matter, which   may be  feparated
from them by diftillation.   8. Green vitriol is preci-
pitated firft of a yellowifli brown colour,  which foon
changes to green, and then  becomes blue  on the  fur-
face.  Some hours afterwards the precipitate  fubfides
to the bottom of the veffels,  and  then the whole mix-
ture turns blue ; but on  addiny any acid the preci-
pitate  becomes inftantly blue.   If a very fmall quanti-
ty of green vitriol be put  into the precipitating liquor,
                                                the
Iron.
   1190
The lo ani-
on of lime
tin- moft
proper for
experi-
ments on
metals.
   1191
Silver,
quickfilver,
and iron
precipita-
ted by the
colouring
matter.
   119a
Its effe&t
on metal-
lic calcee;
  "93
On metal-
lic folu-
tions. 
Practice.
C   H   E    M
Iron.
   1194
Investiga-
tion of the
conftituent
part of the
colouring
matter.

   "95
Inflamma-
bility ofthe
colouring
matter.
   1196
Aerial acid
and phlo-
gifton fup-
pofed to
exift in it.
   1197
Pruffian
blue yields
volatile al-
kali by di-
ftillation.
   1198
Appearan-
ces on di-
ftilling o-
ther preci-
pitates
thrown
down by
Pruflian
alkali.
the precipitate is entirely diffolved,  and the whole af-
fumes a  yellow  colour.   7. Solution  of cobalt lets
fall a brownifh  yellow precipitate, which is  not dif-
folved  by  adding more of the precipitating liquor,
neither is  it foluble in acids.  By diftillation the co-
louring matter goes over into the receiver.
   Laftly, our author undertook an investigation of the
conftituent parts oS the colouring matter  itfelf; and
in this he  fucceeded  in fuch a manner as muft do ho-
nour to his memory, at the fame time that it promifes to
be a real  and lafting improvement  to Science, by fhow-
ing a method oS preparing this valuable pigment with-
out that nauSeous and horrid ingredient, blood, which
is now uSed in great quantities  Sor that purpofe.—His
firft hint concerning  this matter Seems to  have  been
taken Srom an observation oS the  air in  his receiver
accidentally taking fire Srom the  neighbourhood of a
candle.    It  burned without any  explofion,  and he
was able to inflame it feveral times fucceffively.  Wifh-
ing to know whether  any fixed air was contained in
the colouring matter,  he filled  a retort half full of
the liquor containing the colouring matter,  and ap-
plying a receiver immediately after, gave the retort
a brifk heat.  As foon as the receiver was filled  with
thick vapours ofthe colouring  matter, he disjoined it,
and, inflaming  the vapour by a little burning fulphur
introduced into the cavity, found that the  air which
remained threw down a precipitate from lime-water.
" Hence (fays he) it may be concluded, that the aerial
acid (a) and phlogifton exift in this colouring matter."
   It has been afferted by feveral chemifts,  that Pruf-
fian blue by diftillation always yields volatile alkali.—
To determine this, Mr Scheele prepared fome exceed-
ingly pure from the precipitating liquor  abovemen-
tioned and green vitriol; diftilling it afterwards in a
glafs  retort, to which he adapted a receiver contain-
ing a little diftilled water.  The operation was  con-
tinued till the retort became red-hot.    In the re-
ceiver was found  the colouring  matter  and volatile
alkali,  but no  oil; the air  in the receiver was im-
pregnated  with  aerial acid, and the fame colouring
matter;  the refiduum  was very black, and obeyed the
magnet.   On fubftituting, inftead  of the Pruffian  blue,
the precipitates of  other metallic  fubftances preci-
pitated   by the  Pruflian  alkali,   the  refults were:
1. The  yellowifli brown precipitate of cobalt yield-
ed the very fame  products  with  Pruflian blue it-
felf ; the  refiduum  in the retort was black.  2.  The
yellow  precipitate of  copper took fire, and emitted,
from time  to time, fparks during the diftillation.   It
produced little  colouring matter, but a greater quan-
tity of aerial acid and volatile alkali than  had been ob-
tained by  the former  precipitates.  A fublimate  arofe
in the neck of  the retort, but  in  too fmall a quantity
-to make any experiment ;  the refiduum  was reduced
copper.  3.  The precipitate of zinc yielded the fame
with  ^ruffian blue.   4. That  of filver yielded  -like-
wise volatile alkali and fixed  air, but  chiefly colour-
ing  matter; a  ffibb nite containing fome filver  aroSe
into the neck of tire retort;  the refiduum was reduced
"99
I   S   T    R   Y.
 filver.  5. Calx of mercury cryftallized by means of
 the colouring matter, yielded fome of that matter,
 but fcarce any mark of" volatile alkali.  Some mercury,
 with a portion of the original compound,  arofe in the
 neck of the retort.
   From thefe experiments Mr Scheele concluded, that Ingredient*
 the colouring matter  of  Pruffian  blue  was compofed contained
 of volatile alkali  and an oily matter.   He  was con- m rl]e co"
 firmed in his  conjecture, by obtaining Pruflian blue   nng
 from  green vitriol and Spirit of hartfhorn recently di-
 ftilled on the addition oS muriatic  acid.  The fame
 product was  obtained  by means of  the volatile fpirit
 drawn from ox's blood ;  fo  that nothing now remain-
 ed, but to imitate thefe natural proceffes by artificial-   Iaoo
 ly combining  the two   ingredients together.    For Unfucceft-
 this  purpofe  he  diftilled a  mixture  of volatile  Salt ful at-
 and unctuous oil ;  a  mixture of the  fame alkali with tempts to
 animal fat, and with oil of  turpentine; a  mixture ofPrePar!e,t
 quick-lime, fal  ammoniac,  and auxunge, with others drU  cia  7
 of a fimilar kind ;  but in vain.   He began therefore to
 conclude, that as  long as the volatile alkali contained
 any water, it  could not enter into  an union fi'.fficiently
 intimate with the other principles to form the colour-
 ing matter ;  and  finding alfo  that the coal  of blood,
 mixed with fait of tartar, yielded very good lixivium
 fanguinis, he concluded  that no oily mattcr was  ne-
 ceflary for the fuccefs of the experiment.                I20I
    Thus  was  our  author  led  to make the follow- True me-
 ing decifive  trials, which  at once  accompliflied  his thod of
 purpofe, and Showed the truth ofthe principles he  had forming in
 affirmed.  Three  table-fponfuls  of charcoal powder
 were mixed  with an  equal  quantity of alkali of  tar-
 tar,  and the  mixture  put into a crucible.   A  fimilar
 mixture was  put into  another crucible, and  both  put
 into a fire, and  kept red-hot for about  a quarter of an
 hour.   One  of them was  then  taken out, and  the
 contents thrown,  while  perfectly red-hot, into eight
 ounces  of water.   At the fame time he put  into the
 other quV^ty  an ounce of fal  ammoniac  in  fmall
 pieces,f^zgitating  the whole  brifkly  together,   and
 taking care  at the fame  time to pufh the  fal  ammo-
 niac down towards the bottom of  the crucible, which
 he replaced in the fire.  Obferving  in two minutes af-
 ter,   that no  ammoniacal vapours  arofe,  the whole
 mafs  was thrown, when red-hot, into  eight ounces
 of water.  The former  lixivium,  into which no fal
 ammoniac had been put,  yielded no Pruflian blue ;  but
 the  latter fhowed the fame phenomena with the  beft
 lixivium fanguinis, and  produced a  great  quantity of
 blue.   By mixing plumbago with  the alkali inftead
 of charcoal,  a tolerable lixivium was obtained.          x
    "  From thefe experiments (fays Mr Scheele),  it Volatile al-
 appears,  that the  volatile alkali is  capable of uniting kali  cspa-
 with the carbonaceous matter,  after it has been  fub-tie of uni-
 tilized by a ftrong heat ; that it thus  acquires the re- tinS Ynh
 markable property of  combining So  firmly with Salt Df Ph*°j:,ft°a
 tartar as  to be able to fuftain the moft violent degree afi  y*r  .
   ri        11    ......    .,.„.,   . .    >=>    alkali,loal
 of heat;  and  when this lixivium is diffolved in water, t0 fufl.ain a
 there is obtained  lixivium fanguinis, as it is called.-— great de-
 It is  now eafy to  explain what happens in the diftil- gree of
                           Y                  lation heat«
   (a)  This reafoning Seems not to be Sufficiently conclufive ; for late experiments have fhown that inflamma-
tion is generally attended with the production of fixed air, which could not be proved to have an exiftence ei-
ther in the materials or common atmofphere before* 
i7o
  Iron:
CHEMISTRY
Practice.
 lation of lVflun blue, as well  as that  of  the  other
 abovcuicn;!.>i;rd  metallic precipitates.—In the diftil-
 lation of I'rulfian blue, for  inftance,  the calx of iron
 attracts a portion  of  phlogifton  from .the  colouring
 nutter.  The aerial acid being thus difengaged, muft
 goover iitothe receiver with the volatile alkaii, which
 i> let  free at the fame  inftant;  but as the calx of iron
 in  the heat of this  diftillation cannot unite with more
 phlogifton,  a  portion  of the colouring mattcr,  not
 decompofed, mull likewife ariSc.   If the calx of  iron
 could  combine with the whole of the phlogifton,  there
 would  come nothing over into the rcciever  but aerial
 acid  and volatile alkali.  In order to  prove this,  I
 diftilled a mixture of fix parts of manganefe finely
 powdered, and one part of pulverized Pruffian blue,
 and obtained nothing but aerated volatile alkali, with-
 out the leaft mark of colouring matter."
   Mr  Scheele  further remarks,  that  this  colouring
 mattcr m ly prob.ibly be obtained  in an aerial form,
 though  he  had not been able  to  do  fo.   It is alfo
 worth  notice,  that, excepting the  folutions of filver
 and mercury in nitrous acid, the colouring  matter of
 Pruffian blue is  not able to decompofe any other by  a
 fingle  elective  attraction.   Now, as  we know  that
 Pruflian blue is  not foluble  in acids, it  naturally fol-
 lows,  that the colouring matter has a greater affinity
 with iron than  acids have, notwith(landing there is
 no  precipitation  perceived when this matter is mixed
 with the foluiion of vitriol of iron.  " It may not be
 eafy (fays Mr Scheele) to give a fatisfactory explana-
 tion of this phenomenon."
   Iron deflagrates with nitre, and  renders the fait al-
 kaline and cauftic.   A  part ofthe iron is thus  render-
 ed foluble, along with  the alkalized fait.  A mixture
 of equal parts of iron filings and nitre,  injected into a
 ftrongly heated  crucible, and,  after the detonation,
 thrown  into water, tinges  the liquor of a  violet or
 pirplifh blue colour.  This Solution, however, is not
 permanent.  Though the liquor at firft pjfl'es through
 a filter,  without any Separation oS the  iron; yet,  on
 ftanding for  a Sew  hours,  the  metal falls to the bot-
 tom,  in form of a  brick-coloured powder.   Volatile
 alkalies inftantly precipitate  the iron from this fixed
 alkaline folution.
  Iron  readily unites with  fulphur; and when com-
 bined with it, proves  much eafier  of fufion than  by
 itfelf.   A mixture of iron filings and fulphur, moiften-
 ed with water, and preffed down clofe, in a few hours
 fwclls  and grows hot;  and, if  the quantity is large,
 binds into flame.
  By cementation with inflammable maters, iron im-
bibes a larger quantity of  phlogifton ;  and becomes
much harder, lefs malleable, and more fufible.  It is
then called fteel.  See Metallurgy, and Steel.

                   § 5. Lead.
            Lead is a pale or livid-white metal, foon lofing its
          brightness  in  the  air, and contracting  a blackifh or
          grcyifh ath-colour.   It is the SoSteSt and moft flexible
          oS all metallic bodies ; but not ductile to  ..iy great de-
   iacS    £*""> cither in the  form oS wire or leaS; coming far
r.aJ very   fhorr,  in this refpect, of all other metals.   It has alfo
little tena-  the leaft tenacity of  all metallic bodies ; jn leaden wire
uty.
I.rati.
   IZ04
Colouring
mattcr
kept lroro
riling by
manganefe
   1105
Tiu- co-
louring
matter can
feparate
<>:ily mer-
cury and
filver from
their folu-
tion in ni-
trous acid.
  iao6
Nitre alka^
lized by
iran.
   zzc?
Iron filings
and ful-
phur take
tire f\ ouia-
neoufly.
1109
 of ,■„  of an inch diameter being capable of Supporting
 only 29' pouiui>.   Lead has, however, a conliderablc
 Specific  gravity ; lofing, when immcrfed in water, be-
 tween .,.*,. and y"T of its weight.  It is of all metals the
 moft  fufible, excepting only tin and  bifmuth.   The Shccfr-lcad.
 plumbers caft thin lhccts of lead  upon a table or mould,
 covered with a woollen, and above this with a linen,
 cloth, without burning or Scorching the cloths.   The
 melted  lead is received in  a wooden  caSc without  a
 bottom ; which being drawn down  the (loping  table
 by a man on each  fide, leaves a fhect  oS its own width,
 and more or lcls thin according  to the greater or lefs
 celerity of  its deScent.  For thick plates, the table is
 covered over with moiftcned Sand, and the liquid me-
 tal conducted  evenly  over  it,  by a  wooden  ftrikc,
 which bears on a  ledge at each fide.                     , 2t«
   Some have preferred, for  mechanic ufes, the milled Advanta-
 lead, or flatted lheets, to the call; as being more equal, gesof mil-
 fniooth, and  folid.   But whatever advantage of this lcd lcad
 kind the milled fort may appear  to have at firft,  they Precanol,s*
 are not  found to  be  very durable.  \\ hen  the  lead
 is ftretched between the rollers, its  cavities  muft ne-
 ceflarily  be enlarged.  The particles  of metal  that
 may be  Squeezed  into them can  have no union or ad-
 helion with the contiguous particles ; and of confe-
 quence, muft  be  liable, Srom bending, blows, jarrs,
 &c. to Start out again, and  leave the maSs Spongy and
 porous.                                                I2ir
   Lead  yields the dulleft and weakeft Sound oSall me- Rendered
 tallic bodies.  Rcaumer obServes,  that it is rendered So- fonoiou*.
 norous by catling a fmall quantity into  a  Spherical or
 elliptical fegment, as in the  bottom of an iron-laddle ;
 from  hence he conjectures,  that the found of the fo-
 norous metals might be improved for the  bells of
 clocks, &c.  by giving them a  fimilar form.
   Though this metal Tery foon lofes its luftre, and tar-
 niflies in the air,  it  refifts much longer  than iron or
 copper the  combined  action of air and water, before
 it is decompoSed or deftroyed ;  and hence it is exceed-
 ingly uSeSul  for many purpoSes to which theSe metals   iaia
 can by no means be applied.  When juft become fluid, Calcined.
 lead looks bright like quickfilver ;  but immediately
 contracts a varioufly coloured pellicle on the furface.
 If this is taken off, and the fire continued, a frefli pel-
 licle will always be formed, till the metal is by degrees
 changed into a dufky  powder or  calx.   The injection
 of a little fat, charcoal-powder,  or other inflammable
 matter, prevents this change,  and readily revives the  '
 calx into lead again.   It is faid,  that lead, recovered
 from  its calces, proves fomewhat  harder and whiter
 than  at firft,  as well as lefs  fubject to tarnifh in the
 air'        •                                         I*T3
   The blackifh calx or afhes  of lead become of a very Minium.
 different appearance if the  calcination is continued
 with a fire fo  moderate as not to  melt them, and  par-*
 ticularly if  expofed to flame.  By  this treatment  it is
 faid that  they become firft yellow ;  then they are call-
 ed maflicot or yellow lead.  This  colour becomes  gra-
 dually  more and more intenfe, till at laft the calx is of
 a deep red;  and then is called minium or red lead;
 but it is certain, that by proper management this  calx
 never becomes yellow,  affuming a reddifh colour from
 the beginning.  Too great a heat makes it irrecover-
ably yellow.   It can  be more eafily prepared without
                                           expofure 
Practice.
CHEMISTRY.
lll
   1214
Litharge
   1215
Phenome-
ea with o-
ther me-
tals.
Lead,   expofure to the flame.   The degree of heat neceflary
  vr~~-' for converting it into minium is between 600 and  700
       of Fahrenheit.                        /
          If inftead of keeping this  calx in a continued mo-
       derate heat, it be fuddenly fufed, the matter then puts
       on  a  foliated  appearance, changing to a dull kind
       of brick-colour when powdered, and is then called li-
       tharge.   Moft of this fubftance is produced by refining
       filver with lead (fee Refining) : and is of two kinds,
       white and red.  Thefe two are diftiuguiihed by  the
       names of litharge  of gold, and litharge of filver.  The
       moft perfect is that called litharge of gold : the pale
       fort contains a confiderable proportion of lead in its
       metallic ftate; and  even the higheft coloured litharge
       is Seldom free  from a little metallic lead, discoverable
       and Separable by melting the maSs in a crucible; when
       the lead Subfides to the bottom.
         Lead mingles in fufion with all the metals except
       iron,  with wrhich  it refuSes any degree of union as
       long as the lead preferves its metallic form.  On con-
       tinuing the fire,  the lead, Scorifying or calcining, ab-
       forbs the phlogiftic principle of  the iron, and  confe-
       quently promotes  the  calcination of that metal; both
       being at length reduced to  calces.   The fufible calx of
       lead eafily unites with the calx of iron,  and both melt
       together into an opaque brown or blackifh glaSs.  Cop-
       per does not unite with melted lead till the fire is rai-
       Sed So high as  to make the lead  Smoke  and  boil, and
       of a bright red heat.  Pieces of copper,  now thrown
       in,  foon diffolve and difappear in the  lead :  the mix-
       ture,  when cold,  is brittle, and of a granulated tex-
       ture.   The union of theSe two metals is remarkably
       flight.   If a mixture  of copper and lead is expoSed
       to a fire  no greater than that in  which  lead  melts,
       the lead  almoft entirely  runs off by itfelf; a  Sepa-
       ration of which no other example is known.   What
       little lead is retained in the pores of the copper, may
       be fcorified,  and melted out, by a fire confiderably lets
       than is fufficient to fuSe copper.  If any of the copper
       is carried off by the lead,  it fwims unmelted  on the
       furface.
         Gold and filver are both diflblved by lead in a flight
       red heat.  They are both rendered extremely brittle
       by the minuteft quantity of this metal; though lead is
       rendered more ductile by a fmall quantity of either of
       them.  In cupellation,  a portion oS lead is retained by
       gold, but Silver parts with it all.  On the other hand,
       in  its eliquation from  copper,  if the copper contains
       any of the precious metals, the filver will totally melt
       out with the lead, but the gold will not.  The attrac-
       tion of lead to copper,  however flight, is greater-than
       that of copper  to iron :  a mixture of copper and iron
       being  boiled in melted lead, the copper is imbibed by
       the lead,  and the  iron thrown up to the top.   Silver
    *" is in like manner  imbibed from iron by lead ; whilft
       tin, on the  contrary, is imbibed from lead by iron.
       If two mixtures, one of lead and tin,  and another of
       iron and filver, be melted together, the refult will be
       two new combinations, one of the tin with the iron at
       the top, the  other with the lead and filver at the bot-
       tom : how carefully foever the  matter be ftirred and
       mixed  in  fufion,  the  two compounds,  when  grown
       coild, are found diftinct, fo  as to be parted with a blow.
         This metal is foluble in alkaline lixivia and expref-
 fed oils.   Plates of lead boiled in alkaline lixivia, have   Tin.
 a Small part diflblved, and a confiderable quantity cor- '---- 7—'
 roded : the folution  ftains hair  black.   Lead, fufed c  ^l} -.
   • 1      1  -ii  i-    1^    •   ■             11.       soluble in
 with fixed alkaline  falts, is  in part corroaed into  a alkaliesand
 dark-coloured fcoria, which partially diflblves iu wa- in oils.
 ter.   Expreffed oils diflblve the calces of lead,  by boil-
 ing,  in fuch large quantities as to become thick and
 contingent: hence platters, cements for water-works,
 paint for preferving nets, &c.  Acids have a greater
 affinity with leads  than oils have.   If the common pla-
 tter, compofed of oil and litharge, be boiled in diftil-
 led vinegar, the litharge will be diflblved, and the oil
 thrown up to the top.  The oil thus recovered, proves
 Soluble like effential oils in Spirit of wine ; a  pheno-
 menon firft taken notice of by Mr Geoffroy.

                   § 6.  T 1 n.

   The colour of this metal  refembles  filver,  but is
 fomewhat  darker.  It is  Softer, lefs elaftic,  and fo-
 norous, than any other metal  except lead.   When
 bent backwards and forwards, it occalions a crackling
 Sound, as if torn afunder. . It is the lighteft of all the
 malleable metals, being little more than feven times
 Specifically heavier than water.  The tenacity  of its
 parts alfo is not very  confiderable ; a tin wire  of T'T
 of an  inch diameter being able to fupport only 404
 pounds.                                                T2i7
   Tin is commonly reckoned the leaft ductile  of all Capable of
 metals except lead ; and certainly is So,  in  regard to being beat
 ductility into wire, but  not in regard  to  extensibility into thin
 into leaves.   TheSe two  properties Seem not to be So leaves-
 much connected with one another as is generally ima-
 gined.  Iron and fteel may be drawn into very fine
 wire,  but cannot be beat into leaves.   Tin,  on the
 other hand,  may be beat into very thin leaves, but
 cannot be  drawn into  wire : gold and  filver poffeSs
 both  properties in a very eminent  degree ;  whilft
 lead, notwithftanding its  flexibility and Softnefs, can-
 not be drawn into fine wftre, or beat into thin leaves. It
 melts  the  moft eafily  of all the metals ;  about  the
 430th degree of Fahrenheit's  thermometer.   Heated
 till almoft  ready  to melt, it  becomes fo brittle that
 large blocks may be eafily beat to  pieces by a  blow.
 The purer fort, from its facility of breaking into long
 fhining pieces, is called grain-tin.   Melted, and nim-
 bly agitated at the inftant of its beginning to congeal,
 it is reduced into fmall grains  or powder.               I2Ig
  With the heat neceffary for fufion,  it may alfo be Calcined.
 calcined ;  or at leaft fo far deprived of its phlogifton
as to appear in the  form of a  grey calx, which may
be entirely reduced to tin by  the  addition of  inflam-
mable  matter.   The  calcination of tin, like  that of
lead,  begins by the melted metal lofing its brightnefs,
and contracting a pellicle on its furface.   If the fire is
 raifed  to a  cherry-red,  the pellicle fwells and burfts,
 difcharging a fmall bright flame of an arScnical Smell.
 By longer  continuance in the fire, the metal is con-
verted firft into  a greyifli, and then into a perfectly
white calx, called putty,  which is uSed Sor polilhing
glaSs and other hard bodies.
  The calx of tin is the moft  refractory of all others.
 Even in the focus of  a  large burning mirror,  it only
foftens a little, and forms cryftalline filaments.   With
                         Y  2                  glaSs 
/
 Tin.
C   II    K    M   I   S   T    R   Y
   1119
^ '"'inity
nn with
arfenic.
of
   TZ20
Arfenic
parable
from tin
fe-
gl.ils of bifmuth, and the fimple and arSenicated glaffes
 >i  lead,  it forma opaque milky compound,.,.  15,  this
prope: ty it is  fitted for making the bafis of the im-
perfect glaffes called enamels ; (fee Glass and Lna-
 vn).   The author of the Chemical Dictionary re-
buts, "  that having expofed very pure tin,  Singly, to a
 fire as ftrong as that of a glaSs-houSe Surnace,  during
 two hour ,  under a muffle,  in an uncovered  telt, and
 having then examined it, ihe metal \va. found covered
 with an exceedingly while calx, which appeared to
 have formed a vegetation ;  under this  matter was a
 reddilh calx, and an hyacinthine glafs ;  and  laftly, at
 the bottom  was a piece of tin  unaltered.    The  expe-
 riment was Several times repeated with the fame fuc-
 cefs."
   Nitre deflagrates with tin,  and haftens the calcina-
 tion of this as well as of other imperfect  metals.  The
 vapours which  rife from tin,  by whatever method it
 is calcined, have generally an  arfenical Smell.  Tin
 melted with arSenic Sails in great part into  a whitifh
 calx : the part which  remains uncalcined proves very
 brittle, appears of a  white colour, and a fparkling
 plated texture,  greatly refembling zinc.  The  arfenic
 is Strongly retained by the tin, So aslcarcely to be Sepa-
 rable by any degree of fire ; the  tin always  difcover-
 ing, by its augmentation in weight, that it holds a por-
 tion of  arfenic, though  a very  intenfe  fire has been
 uft'd.  Hence, as the  tin ores abound in arfenic, the
 common  tin is found  alfo to participate of  that mi-
 neral.
   Henckel difcovered a method  of feparating  actual
 arfenic from tin ;  namely, by (lowly diffolving the tin
 in eight times  its quantity of an aqua-regia made with
 fal ammoniac,  and Setting the Solution to evaporate in
 a  gentle warmth :  the  arSenic  begins to concrete whilft
 the liquor  continues hot,  and  more plentiSully on  its
 growing cold,  into white cryftals.  M.  Margraaf,  in
 the Berlin  Memoirs for 1746, has given a more par-
 ticular account of this procefs.   He obferves, that the
 white fediment which at firft feparates during the dif-
 S Union, is chiefly arfenical;  that Malacca tin, which
 is accounted one of the pureft forts,  yielded  no lefs
 than ;th its weight of arfenical cryftals ; that fome forts
 yielded more ;  but that tin extracted from  a particular
 kind of ore, which contained no arSenic, afforded none.
 That the cryftals were truly arienical, and appeared from
 their being totally volatile;  Srom  their fubliming (a
 little  fixed alkaline fait  being  added to  abforb the
 acid)  into a  colourleSs pellucid concrete;  Srom the
 Sublimate, laid on a heated copper-plate,  exhaling in
 fumes of a  garlic fmell; from its ftaining  the  copper
white :  and from its fe
with fulphur,  a com-
Dr Lev,.
t  Terva-
»'<>n,
  poind Similar to  the  yellow or fulphurated arfenic.
  He found that the arfenic was Separable alfo by means
  ofmercuiv ; an amalgam of tin being long triturated
  wiJi water,  and the powder which was  wafhed  off
  committed to diftillation, a little  mercury  came ewer,
  and bri nit arfenical flowers aroSe in  the  neck ofthe
s  retort.   Dr Lewis obferves, that the crackling noife
  of tin in bending r.i:>>  poffibly arife  from  its arfenic ;
  as thofe operations which are faid to fVpsrate arSenic
  liom the metal, like wile deprive i: of this property.
    Tin may be?'layed, in any proportion, with all me-
  ikls bv -Lifion :  1  .it nbicdutcly  deftroys their ductili.y,
                                                 Pradticc.
and renders them brittle, as in hell-metal ; whence this  M<u»ny
metal has obtained the name  oS Jtubolns metalici :,<:.  °r »pi»ck-
  Iron is diflblved by tin in a heat far lets than that in   vtr'r  ..
w Inch iron itfelf melts ; the  compound is  white and    nzi
britile.   Iron added  to a mixture of lead and tin, takes InjuriouMo
up the tin, leaving the lead at the bottom ;  and in like other mc-
manncr, if lead, tin, and Silver, arc melted together, uls-
the addition of iron will abforb all the tin,  and the tin
only.  Hence an eaiy method of purifying filver from
tin.                                                   1213
  Tin notwithftanding it is,  like lead, foon  deprived Not liable
of its luftre by  expofure  to the air,  is ncvcnhelefs t0 ruft-
much lets liable to  ruft than  either  iron,  copper,  or
lead ; and hence is  advantageouily ufed  for covering
over the infides ot other metalline veffels.   The amal-
gam of" mercury and tin is  employed to cover one  of
the furfaces of looking-glaffes ; by which they arc ren-
dered capable of reflecting  the  rays of light.  The    1224
amalgam alfo,  mixed with fulphur and fal  ammoniac, Aurum
and fet to fublime,   yields a  fparkling gold - coloured mofaicuin.
fubftance called aurum viofaicum ; whicli is fometimes
ufed as  a pigment.   This preparation is commonly
made Srom quickfilver and  tin, of each  two parts,
amalgamated together ; and  then thoroughly  mixed
with fulphur and fal ammoniac, of each one part and
a half.  The mercury and fulphur unite into a cinna-
bar, which fubliines along  with the  fal  ammoniac;
and, after fublimation,  the aurum mofaicum remains
at the bottom.
  Sulphur may be united with tin by fufion  ; and forms
with it a brittle mafs, more difliculily fufible than pure
tin.  Sulphur has, in this reSpect, the Same effect  up-
on tin as upon lead.   The allay of tin leffens the fufi-
bilily oS theSe very fufible  metals, while it  increafes
the fulibility of other difficultly fufible  metals, as iron
and copper.

          § ".  Mercury or Quicksilver.

  Mercury is a fluid metallic fubftance,  oS a  bright
filver colour, refembling lead or tin when melted ;  en-
tirely void oS tafte and Smell;  extremely divifible; and
congealable only in a degree  oS cold  very difficultly
produced,  in this country, by art (See Cold and Con-    122^
gelation),   ltis  the moft ponderous oS all  fluids, Heavier in
and of all known bodies,  gold  and  platina excepted ; wintcrthan
its  Specific gravity being to that of water nearly as  14 'n fummer.
to 1.  It is found to be Specifically heavier in winter
than in fummer by 25 grains  in 11 ounces
  Neither air nor water, nor the united action of thefe
two, feem to make any  impreflion upon mercury : nor
is it more fufceptible of ruft than the perfect metals.
Its  furface, neverthelefs,  is more   quickly tarnifhed
than gold or filver ;  becaufe  the  dull which  floats  in
the air,  quickly feizes on its furface.  The watery  va-
pours alfo, which float  in the air, feem to be attrac-
ted by mercury.                                        J%%()
  From  thefe extraneous matters, which only flightly Purifica-
adhere to it, mercury may be eafilv cleanfcd by p4J- tion.
ling it through  a clean new cloth,  and  aSterwards
heating it: but if mixed with any other metal, no  Se-
paration  can be  effected without  uiltillation.   In this
prncef,,  a Small portiem oS Some  ofthe metals  gene-
rally miles along with the mercury.   Thus,  quickfil-
                                               ver 
Practice.
CHEMISTRY.
H3
Mercury
or quick-
filver.
Curious
mercuries
by Boyle.
   12*8
Mercurius
precipita-
tus per fe.
   1229
Mercury
unalterable
by a gentle
heat;
   1230
Or by di-
ftillation;
   1231
Explofion
by the va-
pours of
mercury.
 ver  diftilled from lead,  bifmuth,  or tin,  appears  lefs
 bright than before ; Stains paper black ;  Sometimes ex-
 hibits a fkinupoa theSurSace ;  and does not run freely,
 or into round globules.   Mr Boyle relates,  that he has
 obServed  the weight of mercury fenfibly increafed
 by diftillation from lead, and this when  even a very
 moderate fire was made ufe  of.   By  amalgamation
 with ftellated regulus of antimony,  and then  being
 diftilled after a few hours digeftion, mercury is faid to
 become, by a few repetitions of  the  procefs, more
 ponderous,  and  more active.   The animated, or phi-
 lofophic mercuries of fome of the alchemifts, are fup-
 poSed to have been mercury thus  prepared.  By the
 Same, or fimildr proceffes,  feem to have been obtained
 the curious mercuries which  Boyle  declared he was
 poffeffed of, and made himSelS; which were u  confi-
 derably heavier in Specie than common quickfilver,—
 diflblved gold more readily,—grew hot with gold, So
 as to be offenfive to  the hand, and elevated gold  in
 diftillation."  When quickfilver is to be diftilled, it is
 proper to  mingle  it  with a quantity oS iron-filings;
 which have the property of making it much brighter
 than it can be otherwiSe obtained, probably by furnifh-
 ing phlogifton.
   By digeftion in  a ftrong  heat  Sor  Several months,
 mercury undergoes aconfiderable alteration, changing
 into  a powder,  at  firft afti-coloured, afterwards yel-
 low, at  length  of a bright red colour, and  an acrid
 tafte ; and is then called mercurius precipitatus per fe.
 In this laft ftate  it  proves fimilar  to the red precipi-
 tate, prepared from a folution of mercury in nitrous
 acid.  This calx proves  leSs volatile  in the fire than
 the mercury in  its fluid ftate.  It Supports for  fome
 time even a degree  of  red heat.  In the focus of
 a burning  mirror,  it is  Said  to melt into glaSs when
 laid  upon  a piece oS charcoal,  and to  revive into
 running mercury beSore it exhales.  Evaporated by
 common fire, it leaves a Small portion of a light brown
 powder; which, Boerhaave relates, boreablaft-heat;
 fwelled into a fpongy mafs ; formed with borax a vi-
 treous friable Subftance; but  vanifhed in  cupellation.
 By a long continued digeftion in a gentle heat, mercury
 Suffers little change.  Boerhaave   digefted  it in low
 degrees of  heat, both in open and cloSe  veflels,  Sor
 15 years together,  without  obtaining  any other re-
 ward for his labour than a fmall quantity of black pow-
 der ;  which, by trituration, was quickly revived into
 running mercury.   Conftant triture, or agitation, pro-
 duce  a change  fimilar to this in a fhort  time.   Both
 the black and red powders, by bare expoSure to a fire
 Sufficient to  elevate them,  return into  fluid mercury.
 The red powder has been revived  by Simply grinding
 It in a glaSs  mortar.
  In  like manner, quickfilver remains unchanged by
 diftillation.   Boerhaave had the patience  to diftil  18
 ounces of mercury upwards  oS foo times over,  with-
out obServing any other  change than that its fluidity
and Specific gravity were a little increaSed, and that
Some grains of a fixed matter remained.  The vapours
oS mercury, like  thoSe  oS all  other volatile bodies,
cauSe violent explofions if confined.   Mr Hellot gives
an account oS his being  preSent at  an  experiment of
this  kind :  a perfon pretending to  fix mercury,  had
inclofed it in an  iron box cloSely welded.  When the
 mercury was heated, it burft the box,  and diflipated Mercury
 in invifible vapours.                                 or «luick_
   Mercury diflblves or unites witkyall metallic bodies, . ver^
 except three, viz.  iron, arSenic, and nickel: in fome   123a
 caSes it will abforb metals,  particularly gold and filver, Amalga-
 from their folutions in acids or alkalies ;  but  does not matcdwith
 act upon any metal when combined with fulphur, nor different
 on precipitates  made by alkalies, nor on calces  by lubitances'
 fire.   Whatever metal it is united with,  it conftantly
 preferves its own white colour.  It unites with  any
 proportion of thofe metallic fubftances with which it
 is capable of being combined ;  forming, with different
 quantities, amalgams of different  degrees of confift-
 ence.  From the fluid ones, greateft part of the quick-—
 filver may be feparated  by  colature.  Bifmuth  is fo
 far atienuated by mercury,  as to pafs through leather
 with it in confiderable quantity.  It alfo promotes the
 action of  quickfilver upon lead to  a great  degree ; fo
 that mercury united with l,  ^, or  .,%  its  weight of
 bifmuth, diflblves maffes of  lead in a gentle warmth,
 without the agitation,  triture, comminution, or  melt-
 ing heat neceflary   to unite pure mercury  with  lead.
 From thefe properties, this folution of bifmuth in mer-
 cury becomes a  proper folvent for pieces of lead lod-
 ged in the human body.                               J2..„.
  On triturating or digefting amalgams  for a. length Separation,
 of time, a  blackifh or dufky coloured powder arifes of the a-
 to the furface, and  may be readily  wafhed off by wa- malgama-
 ter.   Some of the  chemifts have imagined,  that  the ted meta^-
 amalgamated metal was here reduced to its conftituent
 parts: but pure mercury  is  by  itfelf reducible to a
 powder ofthe fame kind;  and the metallic particles
 in this procefs, united with th'e mercury,  are found to
 be no other than the  metal in its entire fubftance.
 Some metals feparate more  difficultly than others ;
 gold and filver the  moft fo.   Boerhaave  relates,  that
 if the powder whicli  Separates from an amalgam  of
 lead be committed  to  diftillation  with  vinegar  in a
 tall veffel,  the mercury will arife before the vinegar ^
 boils;  that, by a like artifice,  quickfilver may be made
to diftil in a lefs degree of  heat than that-of the hu-.
 man body : but Dr Lewis, though he  made many
 trials,  was never able to fucceed.
  By amalgamation with gold, mercury  may  become Becomes
 exceedingly fixed ;  fo as not to be diffipable by the great- fixed by a--
 eft heat.   Concerning this,  Dr Brandt relates the fol-malgama-
 lowing curious experiment: " Having amalgamated tion with-
 fine gold with a  large  proportion of quickfilver, and £old'
 ftrained off the Superfluous mercury, he  digefted the
 amalgam in a cloSe flopped veffel for two months with
fuch a degree of heat, that a part of the quickfilver
fublimed into the neck of the glafs. The matter be-
 ing then ground  with  twice its weight of fulphur, and
 urged with a gradual fire in a crucible, a fpongy  calx
remained;  which being melted with borax, and after-
 wards kept  in fufion by itfelf for half an hour,  in a
very violent fire, ftill retained fo much of the quick-
filver as to  become brittle under  the hammer, and
appear internally of a leaden colour.  The metal be--
ing again amalgamated with frefh mercury,  the amal--
gam again ground with fulphur, and expofed to an in-
tenfe fire, a  fpongy calx  remained as before.   This
calx being digefted in two or three frefli parcels of
aqua-regia, a fmall  portion of whitifh matter remain- 
'74
C   H    i:   MIST   R    Y.
Pradtkc.
Mercury
»r nyiuk-
(Uvcr.
   1235
Suppofcdto
be convert-
ible into
water.
Dr Lewis's
detection
of thefalfe-
lioodof this
procefs.
ed at hit nndidolvcd.   The p-pi r which covered the
cylindrical glals wherein the digeftion was pcrlen meet,
contracted,  from the  vapours,  a dcip-grtcn circular
fpot m the  middle,  with a Smaller one  at  the  i;de ;
whereas the  aepia-regia digefted  in tiic fame manner
by itfelf, or w ith gold, or with mercery, gave no ftain.
The tint  Solu; :>>.i, on the addition 01 oil of tartar per
dilijuiuui, grew reel as blood ;  on ftanding, it depoli-
'ed, firft, a little yellow calx, like aurum fulminans ; af-
terwards, a bright maiter like line gold ;  and at laft, a
paler precipitate, inclining to green ;  its own deep red
colour and  transparency remaining unchanged.   Be-
ing now committed to diftillation, a colourlefs liquor
arofe; and  the  refiduum, perfectly exliccated, yield-
ed, on cdulcoration, a yellow calx of gold ; which the
alakalinc lixivium had been unable to precipitate. The
fecond folution turned green on  the admixture of the
alkaline liquor,  and let fall a white precipitate, which
turned black and brown.  The feveral precipitates
were calcined with twice their weight of fulphur, and
then melted with four times their quantity of flint, and
twelve of pot-afh, in a fire vehemently excited by bel-
lows.  The fcoria appeared ofia goldencolour,  which,
on pulverization and  edulcoration,  vanifhed.  At the
bottom was a regulus,  which looked bright like the
pureft gold ; but was not perfectly malleable.   Bred..en,
it appeared internally  white; and the white part a-
mounted to at  leaft  one-third its bulk    Befides this
lump of metal,  there  were feveral others, white like
filver, and Soft as lead."
   In Wilfon's chemiftry, we have a  procefs for con-
verting quickfilver into water,  by dropping it by little
and little into a tall iron veflel, heated almoft to a white
heat in the bottom.   Over the  mouth of this veffel
were luted feven aludels ;  and on the top, a glafs alem-
bic head,  with a beak, to which was  fitted a receiver.
The mercury was put  in fo  flowly, that it required
16 hours  for one  pound.  Every time  that a  little
quantity of mercury was put in, it made  a great noiie,
filling  the aludel's  head  and  receiver  with  white
f imes.   When  the velfels were cooled,  a little water
was found  in each of the receivers,  and in the firft
and  fecond  fome  grains  of crude  mercury.  The
whole quantity amounted to 13 ounces and 6 drachms;
which was expected  to prove  a powerful folvent  of
gold and filver: but,  on trial, was found to be in no
refpect different from common  water.  On this ex-
periment Dr Lew is has the following note.
   " The penfibility of converting mercury  into wa-
ter,  or at leaft of obtaining a great quantiiy of water
from mercury,  has not only been believed by feveral
great men in the chemical art,  but  fome have even
ventured  to  aifert that they  have actually made this
change.   Yet,  neverthelefs, they have delivered the
hiltory of this affair with fuch marks,  as feem to make
the reality of the change extremely doubtful.  Mr
Beiyle  (in his tract  of the produciblenefs of Chemical
Principles, annexed  to Sept. Cheveift. p. 235.)  fays,
*< that he once  obtained water from mercury without
udditament, without  being able to make the like ex-
periment fucceed afterwards."   M.  Le Febure, who
;   generally looked upon  as an honeft  practitioner,
directs a procefs fimilar to that above (Wilfon's), for
obt-ining of this mercurial water.  But it is to be fu-
ipectcd, as Mr  Hales very well obferves  (in  his Sta.
                                            2
tical F>p. ntnci.ts,  p. 200.), that Mr Boyle and others Mercury
were deceived  by  lome unheeded circumftauce, when or qtmk-
thcy  thought they obtained  a water from mercury, f*lvf''■ __,
which fhould Item rather to have arifen from the lute
and  earthen veffels made uSc of in the diftillation :
for Mr Hales could not find the leaft Sign of' any nioi-
ftuie upon  diftilling mercury  in a  retort made of an
iron gun-barrel, with  an  intenfe degree of heat;  al-
though he  frequently  cohobatcd the mercury  which
came over into the recipient.   tl In a courfe of chemi-
cal experiments, I repeated Mr Hales's procefs, and
urged  the mercury, which  was let fall by little and
little, through an aperture made in the gun-barrel, with
a moft intenfe degree of heat, without  obtaining any
water; but it being fufpected by a by ftand er,  that  the
mercury in this experiment came  over  before it had
been fufficiently acted  upon by  the fire, by reafon of
the  lownefs of the neck ofthe  diftilling inftrument,
the experiment  w-as varied in the  following manner.
Sixteen ounces  of mercury were heated in a crucible,'
in order to evaporate  any  moifture that might have
been accidentally  mixed with it;  and  an iron gun-
barrel of four feet in length, being placed perpendi-
cularly in a good furnace,  and a glafs-head and reci-
pient fitted to its upper part, the mercury was let fall
by little and little  into the barrel, and the  fire urged
with  bellows.   After   each  injection,  the mercury
made a confiderable noife and  ebullition, and arofe
into the head;  where  it foon condenfed and trickled
down, in the common  form of running mercury, into
the  recipient, without  the  leaft perceptible appear-
ance of any aqueous humidity."                         1237
  Mercury is difficultly amalgamated with regulus of How  to
antimony and copper;  for which fome particular ma- »malgate
nocuvres are required.  Twoof Dr Lewis's receipts for withregu-
         •  , r,      . ,             .     1    1  r •    lusof anti-
uniting quickfilver with copper, we have already given mony
(n°H53.): withregulusofantimony, mercury, he fays,
may be perfectly united, by pouring a fmall Stream of
melted regulus into a confiderable portion of mercury,
made almoft boiling hot.   Another method  directed
by  Henckel, is  to put mercury into an iron  mortar
along with fome water, and fet the whole over the
fire.  When the water boils, a third or fourth part of
melted  regulus  is  to  be  poured in,  and the  mafs
ground with a peftle,  till  the amalgam is completed.
The  ufe of the water, as  Dr Lewis obferves, is to
hinder the mercury from flying off  by the heat of the
regulus: but as the two are by this  means  not  put
together in fo hot  a ftate,  the union is more difficult,
and lefs perfect.  The  lofs of the mercury,  in the firft
procefs, may be prevented by ufing  a large velfel,  and'
covering it with a  perforated iron-plate,  through  the
hole in which the regulus is to be poured.  This me-
thod is likewife applicable to  the amalgamation of
copper.
  With fulphur, mercury  unites very readily,  form-
ing by  trituration, or fimple fufion, a  black powder
or mafs, called Ethiops mineral; which, by careful fub-
limation,  becomes the beautiful red  pigment  called
vermillion.   (See Sulphcr, feet. iv.).                   «
  The extenfive ufe of mercurius  dulcis in medicine Prepara-
has rendered it an object to chemifts to find out fome tionn  of
method of preparing it  with lefs expence and trouble, mercurius
and with more certainty of its effects, than  it can be by <tulcis ,n
the methods hitherto mentioned.  This is nowaccom- l  e m
                                            plifhed way' 
Practice.
CHEMISTRY.
Mercury
of quick-
filver
   i«39
How to
obtain a
perfectly
faturated
folution of
quickfilver
  plifned through the induftry of Mr Scheele,  to whom
  chemiftry in general has been fo much obliged.  His
  method is as follows :
    " Take half a pound of quickfilver,  and as  much
  pure common aquafortis.   Pour  it into a Small  cucur-
  bit with a  pretty  long  neck,  flop the mouth with  a
  little paper, and put it  into warm Sand.   Some  hours
  aSterwards, when  the acid appears no longer  to  act
  upon the quickfilver, the fire is to be augmented So as
  to make the Solution nearly  boil.  This heat is to be
  continued for three or Sour hours, and the veflel now
  and  then  to  be fhaken.   Towards the end, regulate
  the heat in fuch a manner that the folution fhall  gently
  boil for a quarter oS an hour.   In the meantime, dif-
  folve 4^ ounces  of pure common fait in  fix or eight
  pounds of water ; pour this folution,  ftill boiling,  in-
  to a glafs veflel, and immediately aSterwards mix with
  it the  abovementioned Solution of quickfilver,  which
  alSo muft be boiling, in Small quantities at a time, with
  eonftant agitation.  When the precipitate has Settled,
  decant off the clear liquor, and pour hot water again
  on the precipitate,  with, which it is to be edulcorated
  till the water ftanding upon it fliall be  entirely tafte-
  lefs.   Put  the whole,  obtained by  thefe means, toge-
  ther,  filter and dry it in a mild heat."
   On this proceSs it is  remarked, that when the quick-
  filver no longer efferveSces with the acid, one would
  imagine that a Saturation had taken place.  But this is
  far from being  the cafe.   By increafing the heat the
  Solution is ftill able to diffolve a great  quantity ; with
1  this difference, however, that, whereas the quickfilver
  in the  beginning is calcined, a great deal of it aSter-
 wards, in a metallic form, is  diflblved,  as appears
  from  this, that not only no more elaftic vapours a-
 fcend ; but alfo, that with fixed and volatile cauftic al-
 kalies,  a black precipitate is obtained; otherwiSe, when
  the Solution  contains  only  calcined quickfilver, the
 precipitate  is yellow.   If the  black  precipitate'be
 gently  diftilled, quickfilver arifes, and there remains a
 yellow  powder, which is  that part of the metal that
 was calcined  by the nitrous acid.  The fire  muft  at
 any rate be augmented, in order to keep  the mercu-
 rial calx diffolved, the compound of  this metal and
 nitrous acid being extremely apt to cryftallize even in
 the heat.  There commonly remains fome undiflblved
 quickfilver; but it is -always better to take too much
 than too little ; for the  more metal the mercurial  folu-
 tion contains, the more mercurius dulcis is obtained at
 laft.  The quantity here  mentioned ufually produces
 84 ounces  of mercurius dulcis.   The mercurial  folu-
 tion muft be cautioufly poured into that  of  Sea-Salt,
 that no mercury  may follow.   Two ounces of fait
 would  be  fufficient for the precipitation of all the
 quickfilver; butwhenfo fmall a quantity is  ufed, it
 may eafily happen,  that fome Superabundant corrofive
 fublimate may adhere to the precipitate,  which  water
 alone is incapable of entirely feparating.  Among other
 advantages this  method of making mercurius  dulcis
 poffeffes, it is none  of  the leaft,  that the  powder  is
 much finer than any to  which it can be reduced in the
 common way by trituration, however long continued.

                   §8.  Zinc

   This  is a femimetal of  a bluifh white colour.   It is
1240
1241
 the leaft brittle of any of  the femimetals ;  and when
 amply  fupplied with  phlogifton, which may be  done
 by treating it  in cloSe  veflels  with inflammable mat-
 ters, itpofleffes a femiductility, by which it may be flat-
 tened into thin plates. When broken, it appears formed
 of many flat fhining plates or facets, which are larger
 when flowly than when haftily cooled.  When heat-
 ed,  it is very brittle;  and  crackles like tin, only loud-
 er,  when bent.   ExpoSed to the  air, it contracts in
 length of time a yellowifli ruft.  Its Specific  gravity, Deflagra-
 according to Dr Lewis, is  to that of water as 7,V to 1. tion.
 It begins  to melt as  foon as  red-hot ;  but does not
 flow thin till the fire is raifed to a  white heat.   Then
 the  zinc immediately begins to burn with an  exceed-
 ingly bright and beautiSul  flame.  Keptjuftin Sufion,
 it calcines  flowly ; not only  on  the upper  furface,
 but  likewife round  the fides, and  at the  bottom  of
 the  crucible.  If  feveral pieces are jnft  melted  to-
 gether, the  mafs, when grown cold, may be broken
 into the fame number  ;  their union being  prevented
 by a yellowiih calx, with which each piece is covered
 over.   M.  Malouin relates, in the French  Memoirs
 for 1742,  that a  quantity of zinc  being  melted fix
 times,  and the fufion  continued  fifteen hours each
 time, it  proved,  on every repetition, harder,  more
 brittle,  lefs fufible, and lefs calcinable ;  that  after the
 two firft fufions, its colour was grey ;  after the third,
 brown ; and after the fourth, black;  that the fifth
 rendered  it of  a flate-blne  ; and the fixth  of a clear
 violet.
   So violent is  the deflagration of zinc, that the whole Flowers of
 of its calx is fublimed by it, in the  form of light flocks zine-
 of wool ; which,  however,  are eafily reduced to  a
 fine powder.   Thefe are ufed in medicine, and  reck-
 oned an excellent  remedy in  epileptic cafes.   When
 once fublimed,  they are by no  means capable  of be-
 ing  elevated again by the moft  violent heat.  In a
 heat far greater than that  in which they  firft arofe,
 they fuffer  no  alteration ;  in a very  vehement one,
 they melt, according to Henckel, into a femiopaque
 green glafs.  Vitrified with borax, they give a  grey,
 or brownifli, glafs.  Erom  the brightnefs ofthe flame
 of burning zinc,  and the garlic fmell which it is faid
 to emit, fome have concluded that zinc contained the
 phofphorine acid ; which, from fome other circum-
 ftances, is not  altogether improbable.                   I2
   The  flowers of zinc have been thought very diffi- Dr Lewis's.
 eiiltly, or  not at all, reducible  to their metallic form method of
 by an addition of phlogifton.  But Dr Lewis obferves, reducing
 that this difficulty proceeds not from their unfitnefs to be tlieiru
 reftored into the form of zinc, but fromthe volatility of
 the femimetal,  which occafions its being diflipated in
 fumes, if the  common methods are made ufe of.  All
 calces, thefe of iron excepted,  require a greater heat
 for their  fufion than that  in which the metal  itfelf
 melts ; and  as  a full melting heat is the  greateft that
 zinc can  fuftain, it burns and  calcines  the inftant of
its revival, if the air is admitted; and in clofe  veffels
 efcapes, in part at leaft,  through  their pores.  On
mixing flowers of  zinc with  powdered charcoal, and
urging them with a ftrong fire in  a crucible, a defla-
gration and frefh fublimation  enfue : fufficient  marks
that the zinc has  been reduced to its metallic form ;
 for as long as it remains in the ftate of calx, neither
 of thefe  effects can happen.  If the veffel is fo con-
                                             trived 
7«
Zinc.
  fir*
Oilfr-.m
f.OXViTS of
zinc bv Mr
lb' -berg.
   1:44
Another by
Mr Hellot.
  1145
/.inc with
other me-
t ils.
   1246
Materials
I <>r fpecula
   1:47
Pcftagra-
t ..: oiziuc
with other
                            C   II   E    M   I
m\ c>i a» to  exclude the  air, and a: the fine time  to
alb>w the reviving femimetal to runoff from the vehe-
mence of the hear, into a receiver htm cool, the zinc
wdl the re concrete, and be prefcrved in i:s metallic ft ate.
h  is ftill  more etiectually detained by certain metallic
bjJic-, .is copper, or iron ; with which the zinc, when
thus applied, unites  mere  readily and  perfectly than
it  can be made to do by  any other means.
   Ho nberg  pretended  to  obtain  an  oil from  the
flowers ot  zi.:c,  by  diffolving them in  diftilled vine-
gar, and then diftilling the folution  iu a glafs  retort.
At firft a quantity of phlegm arofe;  then the  Super-
fluous  acid;  and at  laft an empyreumatic oil.   This
laft, which  Homberg im igined  to  proceed from the
flowers of zinc,  Newmann \ cry juftly attributes to the
diftilled vinegar.
   An oil of another kind was obtained by  Mr Hel-
lot from the above folution,  by digefting  the  afli-co-
loured refiduum,  which  remained after the  diftilla-
tion, with the acidulous phlegm which  came over, for
eight or ten days;  diftilling the tincture  to dryneSs ;
and repeating the extraction with the diftilled  liquor,
till  the quantity oS dry  extract thus obtained  was
very c viderable.  This  refin-like  matter, diftilled
in a retort with a ftronger  fire,  yielded a yellowifh
liquor,  and a white Sublimate.  The  liquor difcovered
no mark of oil ;  but, upon being paffed  upon the fub-
limate,  immediately diffolved it, and then exhibited
on the furface feveral drops of a reddifh oil.  Some  of
this oil was taken up on the point of a pencil, and ap-
plied to gold and Silver-leaf.  In twenty-four hours
the parts touched appeared,  in both,  equally  diffolved.
   Zinc does not unite  in fufion with bifmuth,  or the
femimetal  called  nickel.  It  unites difficultly with
iron ;  lefs fo  with copper; ealier with the other me-
tals.   It renders iron or copper more  eafily fufible ;
aid, like itfelf, brittle whilft hot, though confiderably
malleable when  cold.   It brightens the colour of iron
almoft into a  Silver hue, and changes  that of copper
iuo a yellow or gold colour.  It  greatly  debafes the
colour of gold ;  and renders near an hundredth part  of
that  moft ductile metal brittle  and untractable.   A
mixture of equal parts of each is very hard,  white,
and  bears a fine polifli;  hence it  is propofed  by Mr
Helbt  for  making  fpecula.  It is not fubject  to  ruft
or tarnilh in the air, like thofe metals whofe bafis  is
copper.   It improves the colour and luftre of lead and
tin,  renders them firmer, and confequently fitter for
Several mechanic uSes.    Tin, with a  Small proportion
oS zinc, forms  a kind of pewter.   Lead will bear an
equal  weight, without  lofing too much of its  malle-
ability.  Maoluin obferves, that  arSenic, which whi-
tens all other metals,  renders zinc black and Sriable ;
that when the mixture is perSormed  in cloSe  veffels,
an agreeable aromatic  odour is  perceived on opening
them ;  that zinc  amalgamated with mercury,  and af-
terwards recovered, proves whiter,  harder and more
brittle  than before, and no longer  crackles on being
bcr.t.                               ,
   Mixtures of zinc with other  metals,  expofed  to a
ftrono- fire, boil  and  deflagrate  more  violently than
zinc by itfelf.  Some  globules of the mixture are ufu-
allv thrown off during  the ebullition, and fome part  of
the metal calci :ied and volatilized by the burning zinc r
                                              1
   S   T    R   Y.                            Practice.
hence this  fubftance has  been called  tnctaliic  1 Ure. nifmuth.
Cold itftlf  docs not entire 1\ leliftits action.  It very
difficultly volatilizes copper ;  and hence the fublimates
obtained  in the furnace.- where braSs is made, or mix-
tures of  copper and  zinc melted, arc  raieh found to
participate  of  that metal.   (fti nthing ct>pptr  and   ia4g
zinc Separately, and then pouring them together, a Cam otic
violent   detonation  inuneiiiatciy  tnn.o,  and  above unitcdwith
half ihe mixture is thrown aboin in globules.          fulphur.
   Zinc does  not  unite  in the lcafl with fulphur, or
with crude antimony,  which Scorify all other fub-
ftances except  gold  and platina; nor with coupon-
tions of fulphur and fixed alkaline fall--, which dillolve
gold itSelS.   With nitre it deflagrates  \kdcnfy.   Its
flowers do  not Senfibly  deflagrate ; yet alkalize double
their weight  oS the Salt more  readily than the zinc   17A9
itfelf.  The alkalinemaSs appears externally greenifh, Nitre alka-
internally oS a purple colour.   It communicates  a  fine lized by
purple to water, and a red  to  vinegar.  The acetous flowers of
tinctureinipidated, leaves a tenacious Subftance which Einc'
Soem runs in the air into a dark red cauftic liquor,  the
alkaheft  of Some oS the pretended adepts.

               §  9.  Bismuth.

   This femimetal, called, alfo tin-glafs, and by fimic
naturalifts  marcaftta ofjicinarun/,  is fomewhat  Similar
to the  regulus of antimony.   It appears to be com-
pofed of cubes formed by  the  application of  plates
upon each  other.  Its colour is lefs white than that of
regulus of antimony ;  and has a reddifh tinge,  parti-
cularly when it is expofed to the air.  In fpecific gra-
vity it approaches to filver;  being nearly  ten  times
heavier than water.  It has no degree  of malleability ;
breaking under the hammer,  and  being reducible by
trituration  to fine powder.  It melts a little later than
tin, and feems to flow the  thinneft  of all metallic
fubftances.   Bifmuth  is femivolatile,  like all  other   I2S0
femimetals.  When expofed  to the fire, flowers  rife Convert-
from it; it is calcined ; and converted into a litharge ible into
and glafs  nearly  as lead is; (See Glass).  It may 1,t|!ar.g*
even be employed, like that metal, in  the purification and £ "*
oi gold and filver by  cupellation.  (See  Refining).
When in fufion,  it occupies lefs volume than in  its fo-
lid ftate  :  a property peculiar to  iron  among the  me-
tals, and bifmuth among the  femimetals.   It  emits
fumes  in the fire as long as it prcServes its metallic
form ; when calcined or vitrified, it proves  perfectly
fixed.                                                J2SI
   Bifmuth mingles in Sufion with all the  metalline Sub- Promotes
Stances,  except regulus of cobalt  and  zinc.  1  he ad-the fufioc
dition  of nickel  or  regulus of  antimony, renders it of all the
mifcible  with the former,  though not with the  latter mctal»>
It greatly promotes the tenuity  as well  as  facility of
the fufion  of all thofe metals with which  it unites.   It
whitens copper and  gold, and improves the colour of
fomc ofthe white metals: mixed inconfiderablc quan-
tity ; it  renders  them all brittle, and of a flaky ftruc-
ture like its  own.  If  nixed  with gold or filver,  a
heat that is but juft fufficient to melt the  mixture,  will
prefently  vitrify a part of the bifmuth ; which, ha-
ving then  no action on tho'c perfect metah, Separates,
and glazes the crucible all roui.d.

                                               £ 10 
Practice.
CHEMISTRY.
77
Regulus of
antimony.
$ io. Regulus of Antimony.
   125a
Appear-
ance of a
ftar on it6
fu.fuce.
   i»53
Sublima-
blc.
  1254
Separation
of the ful-
phur from
antimony.
  1*55
Regulus
eafily mif-
cible with
mercury.
   This femimetal, when pure, and  well fufed,  is of
 a white fhining colour,  and confifts of  laminae applied
 to each other.   When  it  has been well melted, and
 not too haltily cooled,  and its furface  is not touched
 by any hard body during the cooling, it exhibits the
 perfect figure of  a ftar, confiding of many radii ifluing
 from a centre.  This  proceeds from the difpofition that
 the parts of this femimetal have to  arrange themSelves
 in a regular manner,  and is Similar to the cryftalliza-
 tion of falts.
   Regulus of antimony is moderately hard ;  but, like
 other femimetals, it  has  no ductility,  and breaksin
 fmall pieces under a hammer.  It  lofes 1. of its weight
 in water.   The  action of air  and water deftroys its
 luftre, but does not ruft it fo effectually  as iron or cop-
 per.   It  is fufible with a heat fufficient to make it red
 hot;  but  when  heated to a certain degree,  it fumes
 continually, and is diflipated in  yapours.   Thefe fumes
 form what are  called the argentine fowers of regulus
 of antimony, and are nothing but  the eanh of this fe-
 mimetal deprived of  part of its inflammable principle,
 and capable  of being reduced  to  its reguline ftate by
 an union with this principle.
   There  are different methods of  preparing the regu-
 lus of antimony ; but all of them confift  merely in Se-
 parating the Sulphur which this mineral contains, and
 which is united  with the regulus.   It is plain, there-
 fore, that regulus oS antimony may be made by an ad-
 dition oS  any Subftance to crude  antimony in fufion,
 which has a greater attraction for fulphur than the re-
 gulus itfelf has.   For this purpofe, alkaline falts  have
 been  employed,  either  previoufly prepared, or extem-
 poraneoully produced in the procefs, by a deflagration
 of tartar  and nitre.   By  this means,  the fulphur was
 indeed abforbed ;  but the  hepar fulphuris, formed  by
 the union of the fulphur and alkali,  immediately dif-
 folved the  regulus,  fo  that very little, fometimes none
 at all, was to be obtained diftinct from the fcoria.   Me-
 tals are found to anfwer better than alkaline falts, but
 the regulus is feldom or never free from  a mixture of
 the metal employed.   The way of obtaining a  very
 pure  regulus, and in great quantity, is to calcine the
 antimony  in order to  diflipate its  fulphur;  then  to
 mix the calx with inflammable matters,  fuch as oil,
 foft  foap, &c.  which are capable  of  reftoring the
 principle of inflammability to it.   This  method  was
 invented  by Kunckel.  Another, but  more expen-
 five way of procuring a  large yield of very pure regu-
lus, is, by digcfting antimony in aqua-regis, wh;ch dif-
 folves the  reguline part, leaving ttie fulphur untouched,
precipitating the  folution,  and afterwards reviving the
precipitate by melting it with inflammable matters.
  There are confiderable;  differences  obferved in the
regulus of antimony, according to the  different fub-
ftances made ufe of to abforb the Sulphur.  When
prepared  by the  common   methods, it  is found  to be
very difficultly amalgamated with mercury ; but Mr Pott
has difcovered, that a regulus prepared with two or five
parts  oi iron, four of antimony,  and one  of chalk, rea-
dily unites with  mercury  into  an  hard amalgam,  by
bare trituration with water. Marble and quicklime fuc-
 ceed equally well with  chalk;  but clay,  gypfum, or Regulus 0/
 other earths, have no effect.                          antimony.^
   One earthy fubftance, found in lead-mines, and com- '  \~%Tb
 monly called cawk, has a very remarkable effect upon j?.xtempo-
 antimony.  This is found in whitifh, moderately com-raucous re-
 pact and ponderous  maffes;  it is commonly  fuppofed gulus with
 a fpar; hut differs from bodies of this kind, in not be- eawk.
 ing acted upon by acids, (fee  n° 106S).   If a lump of
 cawk, of an ounce or two,  be  thrown red  hot into 16
' ounces of melted antimony, the fufion continued about
 two minutes,  and  the fluid matter poured off,  " you
 will have 15 ounces like polifhed flee), and as  the moft
 refined quickfilver." Phil. Tranf.  n°uo. Dr  Lewis
 mentions his having repeated this  experiment Several
 times with SucceSs :  but having once varied it  by mix-
 ing the cawk and antimony together at the firft, a part
 of the antimony was converted into a very dark black
 vitreous matter, and part Seemed to have Suffered little
 change ; on the furSace oS the maSs Some yellow flowers
 appeared.
   Regulus  of  antimony enters into the compofitions
 for  metallic fpeculums for  telefcopes, and for printing-
 types. It is alfo the bafis of a number of medicinal pre-
 parations; but  many of thefe, whicli  were  formerly
 much efteemed, are found to be either inert, uncertain,
 or dangerous in their operations.  When taken in fub-
 ftance, it is emetic and  purgative, but uncertain  in  its
 operation;  becaufe  it only acts in proportion  to the
 quantity  of folvent  matter it  meets with in the fto-
 mach ; and if  it meets  with nothing capable of  acting
 upon it there, the regulus  will be quite inactive.  For
 thefe reafons,  the only two preparations of antimony
 now retained, at leaft by fkilful practitioners, are the
 infufion oS  glaSs oS  antimony in wine and  emetic tar
 tar.  For making the glafs of  antimony we have the Glafsofan-
 following procefs.   " Take a pound of  antimony; rc-timony.
 duce it to fine powder,  and fet it over  a gentle fire;
 calcine it in an unglazed earthen pan, till it  comes to be
 of an alh colour,  and ceafes to fume : you muft keep it
 continually  ftirring; and if it fhould run  into lumps,
 you muft powder  them again, and then proceed to fi-
 nifli the calcination.  When  that is done,  put the cal^
 cined antimony into a crucible; fet  it upon a  tile in  a
 wind-furnace; put a thin  tile  on the top; and  cover
 it all over with coals.   When it is brought into  fufion,
 keep it So in a  ftrong fire  Sor  an hour:  then  put into
 it an iron rod ; and when  the  melted antimony,  which
 adheres 10  it,  is transparent, pour  it  upon a Smooth,
 hot, marble; and when it is  cold,  put  it up for nfe.
 This is vitrum  antimonii, or ftibium."
   This preparation is more violent  in its effects than
 the pure regulus itSelf;  becauSe it contains let's phlo-
 gifton,  consequently is  fimilar to a regulus  partially
 calcined,  and So more  Soluble.  Hence it is the moft
 proper for infufion in wine, or for  making the tartar
 emetic.   It is obvioufly, however, liable to great un-
 certainties in point of ftrength ; for as the antimony is
 more or lefs ftrongly calcined,  the  glafs will  tinn out
 ftronger or  weaker  in  its  operation, and confequtinly
 all the preparations of it muft  be liable to much unccr-   I2.§
 tainty.   This  uncertainty is   very  apparent in  the Difference
 ftrength of different parcels of emetic tartar: accord-of ftrength,
 ingly Mr Geoifroy found by examination of different"1 tructl<-
 cmetie  tartars, that an  ounce of the weakeft  contain- tartar8'
                         7,                       ed 
per matcri
A for eme
17^                                 r    11   E    M    I
Rugulutored from  :c to90 grains of regulus; an ounce  of mo-
. nimoay. jerate  ftrength  contained  about  108 grains ; and an
         oincc of  the  ftrongeft  kind  contained  154  grains.
         For  their  reafon ,  the author of the Chemical Dic-
         tionary recommends the pulvis  algaroth as the moft
         pro'ei  material for making emetic tartar ;  being per-
   nio   tcctly foluble,  and  always of  an eepial  degree of
 Pnl\;. al- ftrength.   Knctic  tartar,  as he  jufty obScrvc*, ought
gnroth the t0 bc a metallic Salt compofed  of cream of tartar fatu-
molt pro- r.-ted w;:h the regulus of  antimony;  and M. Beaume
         has  fhown fuch  a Saturation to be poflible, and that the
         neutral Salt cryftallizes in the form of pyramids. They
         are  tranfparent while moift ; but by expofiire to a dry
         air, they loSc the water of their cryftallization  and be-
         come opaque.   The preparation of this fait,  according
          to M. Baume, confifts in mixing  together equal parts
          of cream  of  tartar,  and levigated glafs of antimony :
          thefe are  to be thrown gradually into boiling water;
          and the boiling continued till  there is no longer any
          effervefcence, and  the acid is  entirely faturated. The
          liquor is to be filtered; and upon the filter is  obferved
          a certain  quantity  of fulphureous  matter along with
          fomc undiflblvcd parts of the glafs of antimony.  When
       •   the filtered liquor is cooled,  fine cryftals will be form-
          ed in it, which  are a foluble tartar perfectly faturated
          with glafs of antimony.   He obferves, that the diflblu-
          tion is Soon over iS the  glaSs is well levigated, but re-
   1260   quires a long time  if it is o ily grofsly pounded.
 Objection   The trouble of levigating glafs of antimony, as well
 to its ufe. as the  uncertainty of diffolving it, would  render pul-
          vis  algaroth much preferable,  were it not  on account
          of its price ; wdiich would  be a  temptation to thofe
   IZ0I   in  ufe 10 prepare medicines, to fubititute  a  cheaper
 Scheie's  antimonial  preparation  in  its place.   This objection,
 theory of however,  is now in a great meafure  removed  by  Mr
 th, nature Scheele ;  who dem'onftrated  that the pulvis algaroth
 nfpnlvis  js no otilcr than regulus of antimony half calcined  by
          the dephlogifticated marine acid in the corrofive Subli-
          mate made uSe  of for  preparing the antimonial cau-
          ftic.  If therefore  we can fall upon any other method
          of dephlogifticating the regulus,  we fliall then be able
          to combine the marine acid with  it;  and by feparating
          them afterwards, may have the powder of algaroth as
          good as from the  butter of antimony hfelf.   One of
          the methods  of dephlogifticating the regulus is  by
          nitre.   Our author therefore gives  the following re-
          ceipt for the powder in queftion.
            " Take of powdered crude  antimony  one pound ;
           powdered nitre, one pound and a half; which, after be-
          ing well dried and mixed, are to be detonated in an iron
          mortar.   The hepar obtained  in this manner is to be
          powdered,  and a  pound of it to be put into a  glafs
          veflel, on which firft a mixture of three pounds of wa-
          ter  and 1 > ounces of vitriolic acid is  to be poured, and
          afterwards 15 ounces of powdered common  fait are to
          be added ; the glafs veffel is  then to be put in a fand-
           bath,  and kept  in digeftion for 12  hours, during
          which period the mafs is to be conftantly flirred.  The
           folution,  when  cool, is to  be ftrained  through linen.
           O: the  refiduum  one third  ofthe  above menftruum
           is to be poured,  and the mixture digefted and ftrained.
          From this Solution, when it is diluted with boiling wa-
           ter, the pulvis algarothi precipitates, which is to be well
           edulcorated and dried."
            As  r.  uIjs of  antimony, like  other metallic  fub-
■aroth.
His receipt
formi'.:!:^
it cheap.
  S    R   T    Y.                           Praifticc.

fiances, is foluble in liver of Sulphur, it happens, that, Arfenic.
on boiling antimony in an alkaline ley, the l.dt, uniting    Ji6?
with  the  fulphur contained in that  mineral,  forms an c,„it|cnful-
hepar fulphuris, which  diflblves fome of the reguline rhurof>n-
part. If the liquor is filtered, and faturatcd with an acid, timony.iml
the regulus and fulphur will  fall  together in form of a kcrmcinu-
yellowilli or reddifh powder, cMed gold en fulphur cjan-M1
timony. If the ley is fuffered to cool, alikeprecipitationof
a red powder happens. Th\ste(t\scMed kertnes mineral.    J263
   Nitre deflagrates violently with  antimony, conlum- liiaphoro
ing not only its fulphureous part, but alfo the phlogifton tic antimo-
of the regulus :  and thus reduces the whole to an inert ")'•
calx,  called  antimoniinn diaphcrcticum.   If equal parts
of nitre  and antimony  are deflagrated together,  the
fulphureous  part is confumed,  as  well as  part  ot  the
inflammable principle of the regulus.  The metalline
part  melts, and  forms  a  femivitreous mafs of red-    1265
difli colour,  called crocus metalloruve, or liver of anti- Crocus me-
tnony.  It is a violent emetic, and  was formerly ufed "Uomm.
for making inSulions in  wine Similar  to thofe of glaSs
of antimony ;  but is now difufed on account of its  un-
certainty in ftrength.   It is  ftill ufed  by the  farriers:
but the fubftance fold for  it is  prepared with a  far lefs
proportion of nitre;  and  fometimes even without  any
alkaline fait being added  to abforb partof the antimo-
nial Sulphur.  This crocus is of a dull red colour ;  and,
when powdered, affumes a dark purple.

                §  11. Arsenic

   This fubftance, in its natural ftate, has no appearance
of a metal, but much more rcfembles a Salt,  which,
as has been  already obServed, it really is wdicn deprived   1266
of its phlogifton.  When united to a certain quantity Arfenic
of phlogifton, it affumes a metallic appearance;  and found na-
in  this ftate it  is Sound, as Mr Bergman  inSorms us, tural,y >n
in Bohemia, Hungary,  Saxony,  Hercynia, and other rorm
parts;  particularly  at  AlSatia  in  the  mines called
St Murieux.  The maffes in which  it  is Sound are
frequently fhapelefs,  friable, and powdery;  but fome-
times compact,  and divided  into thick convex lamellae,
with  a needle-formed or micaceous furface: it  takes a
p.«';:fh, but foon lofes it again in the air.   When  frefli
 Inyken, it appears compofed of fmall needle-like grains
of a  leaden colour,  foon becoming yellow, and by de-
grees blackifh ; exceeding copper in hardnefs,  though
as brittle as antimony.                                 1267
   Reguline arSenic,  whether found  naturally  or  pre- Regulus of
pared by art,  very readily  parts  with as  much of  its "feme ear-
 phlog-ifton as is fufficient to make it fly efff in a white  ' VT" .
 r  1     1    1 • ami     •             ret   i_i         verted into
 fmoke;  but this ftill retains a very confiderable quan- the  com.
 tity of phlogiftic matter,  asiscvident from its producing -whitekind.
 nitrous  air by  the affufion of nitrous acid,  and  from
 the experiments already related of the preparation  of
 the acid of arfenic. This calx indeed is the form in which
 arSenic  is moft commonly met with.   It is leSs volatile
 than the regulus ;  and  by  Sublimation in  a glaSs veflel
 affumes an opaque  cryflalline appearance  Sroni   be-
 coming  white on the SurSace; bt:t  that which  cryftal-
 lizes in  the bowels of the earth does  not  appear to be
 fubject to any fuch change.                               J2f)i
    White arfenic, though a true metalline calx, may be White ar-
 mixed in fufion with the fame metals which will  unbe fenic may
 with the regulus.  This feems contrary to the general be  mixed
 rule  of  other calces, which cannot be united with any Wlth ?tncI
      2                                        metal 
Pra.ci.ice.
C    H   E    M   I    S    T   R    Y.
Arfenic.
   1269
Solution  of
arfenic in
water.
   1270
Anel in fpi-
rit of wine.
   1271
In vitriolic
acid.
   1272
In marine
acid.
   H73.
Phlogifti-
cated alkali
cannot pre-
cipitate ar-
fenic except
from ma-
tine acid.
 metal in its metalline ftate; but it muft be remembered,
 that by this operation the arSenical calx is  reduced to a
 regulus by the phlogifton oS the metal:  whence, in all
 fufions of this kind, fome feorix rife to the top, confid-
 ing of the calcined metal and part of the while arfenic.
   Eight parts  of  diftilled water diffolve, by means of
 moderate  hear, one  part of  calcined arfenic, and by
 boiling may be  macje  to take  up 15.  The folution
 changes fyrup of violet green,  but   the  tincture  of
 turnfole red.   It  is not changed by  neutral falts, but
 llowly precipitates the folutions of metals, the arSenic
 United  to  the  metallic  calx  falling to  the bottom___
 " It may  be afked  (fays Mr Bergman), whether the
 whole of the arfenic, or only  the arfenical acid, unites
 with the  metallic calx, yielding the  phlogifton to the
 menftruum of the other metal ?"   Certainly fuch  a
 mutual commutation of principles does not appear im-
 probable,  if we confider only thoSe caSes in which the
 menftruum is  vitriolic  or nitrous  acid : but as  iron,
 for example, united with marine acid  (which does not
 attract  the phlogifton of white  arfenic),  as well as
 when it is joined  to the nitrous acid,  is precipitated, it
 would appear  that the whole of the arfenic is united,
 at leaft in  certain  cafes, to the metallic calces.
   One part of arfenic is diflblved by 70 or 80 of  boil-
 ing fpirit of wine.
   ArSenic diffolves partially  in  concentrated vitriolic
 acid, but concretes in the Sorm of cryflalline grains on
 cooling.  TheSe  diffolve  in  water with much greater
 difficulty  than the arSenic itSelS.  On  the  blow-pipe
 they emit a white Smoke, but Sorm into a globule by
 fufion,  which  at  firft bubbles, but Soon grows quiet,
 and  is  but flowly  conSumed even in  a  white  heat.
 This fixity is occafioned  by  the  acid  carrying off the
 phlogifton of the  arSenic, and thus leaving a greater
 proportion of its peculiar acid than what  it naturally
 contains ;  and therefore  the more  frequently the ope-
 ration is repeated, the more fixed the arfenic becomes,
 though  it  is fcarce poflible  to  diflipate the  arfenical
 phlogifton as perfectly  with   this acid as with the ni-
 trous ;  the effects of which  have been already particu-
 larly mentioned.
   The  marine  acid, which  naturally contains  phlo-
 gifton,  diffolves about one-third of its weight of  arfe-
 nic, a great part  of which feparates fpontaneonfly on
 cooling in a ftate of faturation with the acid. This fait,
 which may be had in a  cryflalline form, is much more
 volatile than  the  former, readily fubliming in a  clofe
 veffel with a moderate  heat ; bin is foluble with  diffi-
 culty in boiling water.   It is of a fine yellow colour,
 and  fcarcely differs from  butter  of arfenic, except in
 its degree of  concentration.  The nature of marine
 acid  prevents  it  from difengaging the  arfenical  acid
 from the phlogifton of the femimetal, as will eafily ap-
pear Srom  what has becnTaid concerning that  acid.
The arSenical  acid, however, is eafily made to appear
by tlie  addition oS that oS nitre, as will be underfteiod
from  the directions given by Mr Scheele  for the  pre-
paration of the acid of arfenic.
  Arfenic  is not  precipitated  from  its folution  in vi-
triolic  and nitrous acids by  the phlogifticated alkali,
which  yet very readily precipitates all  other  metals.
From the marine acid, however, it is precipitated by its
means of a  white colour; but unlefs the folution be  very
acid, the addition of mere water will  throw  down  a
precipitate of the fame colour.
   Dephlogifticated marine acid deprives arfenic of its
inflammable principle ;  fo that  in the diftilling veffel
we find water, acid of ArSenic, and marine acid, rege-
nerated.
   ArSenic is diflblved by  its own acid,  and Sorms cry-
flalline grains with it as well as with that of fluor and
borax.    Saccharine  acid diffohes  it likewife,  and
forms  prifmatic cryftals ;  and  a fimilar fait  is  alfo
formed by the acid  of  tartar.   Vinegar,  and the acids
of  vinegar and phofphorus,  form with  it cryflalline
grains, which are fcarcely foluble in water.
   Solutions  of  fixed  alkali   diffolve  arfenic ;  and,
when loaded with  it,  form a brown  tenacious  mafs,
called  liver of arfenic.  The arfenic is partly  precipi-
tated  by  mineral  acids,  though part of it  gradually
lofes its phlogifton, and adheres more tenacioufiy.  So-
lution  made  with  volatile alkali feems to effect  this
decompolition  more   readily, as no precipitation is
made by acids.   Limpid  Solution oS Saline hepar, drop-
ped into a  Solution oS white arSenic,  floats  upon the
Surface in  form of a grey Stratum, which at length di-
ftnrbs  the whole liquor.
   By  the affiftance of heat folutions of arfenic attack
fome ofthe metals, particularly copper, iron, and zinc;
the  folutions of the two laft yielding cryftals  by eva-
poration.   No alteration  is made  on  thefe compounds
by alkaline falts or by acids:  volatile  alkali does  not
difcover the copper by changing the colour ofthe fo-
luiion  blue ; nor does  the phlogifticated alkali throw
down any blue precipitate from the folution of iron.
The reafon of this is the  fuperabundance of phlogifton
in the  folutions;  for  the arfenical acid  takes  up all
metals : when  united  with copper, it  fhows  a blue co-
lour with  volatile alkali ;  and  when united with iron,
it lets  fall a Pruflian blue  in the ufual way •;  but  the
quantity  of phlogifton which converts the  acid into
white  arfenic, prevents the appearance ©f thefe pheno-
mena when the latter is made ufe of.
   Arfenic, either in its calcined or reguline ftate, may
be united  with  fulphur  ;  in  which  cafe it  appears
either  oS a red  or yellow colour, according to  the
quantity oS fulphur with  Which it is  united.   TheSe
compounds  are  Spontaneonfly  produced  by  nature ;
both oS them-Sometimes pellucid and cryflalline ; with
this difference, however,  that the yellow Seems to af-
fect a lamellated,  and the red a cryflalline,  form.
Thefe are called red and yellow orpiment, or realgar and
orpiment  ;  the fpecific gravity of realgar being about
3.225 ; of orpiment, 5.315.   Both  of thefe  fublime
totally  with a moderate  heat,  unlefs when they  hap-
pen to be  mixed with other fubftances.   They  readily
unite with thofe metals which form an union with the
arfenic and fulphur  of which they are compofed.   Sil-
ver  mineralized by fufion with orpiment, forms a fub-
ftance  fimilar to what is called the red ore of that me-
tal.   Iron,  in conjunction witdi  orpiment, affumes  a
white, polifhed,and metallic appearance, fimilar to that
of the  white or arfenical pyrites ;  and by  various
combinations of thefe fubftances  with  metals of  diffe-
rent kinds, many of the natural metalline ores may be
produced.
   Nitre, when treated with mineralized arfenic,  de-
                       ^  2                  tonatcs
   1374
Decompo-
fed by de-
phlogifti-
cated ma-
rine acid.
   1275
Phenome-
na with o-
ther acids.
   1276
Liver of
arfenic.
   1277
Effects lu
metals.
   127S
Unites ea-
fily with
fulphur.
   1279
Realgar
and orpi-
ment.
   1280   .
Phenome-
na with ni-
trous acid. 
i So
CHEMIST    R   V.
Practice.
Arfenic.
   I1M
Buttir of
«: cnic.
   1282
Can fcarce
lit made
to unite
with ma-
rine acid.
   128.I
Oil of ar-
fcnic.
r -nates partly  with the fulphur, and  partly wih  the
phlogifton ni ihe arSenic ;  the alkaline balls of the fait
rithrr  forming  fal  pnlvchrtft with  the  ;.cid  of the
Sulphur, or uniting ui;h ilie alkali, and forming  the
neutral  arfenical  Sab.  By  the addition  <ff fixed al-
kali in proper  quantity, either to 1  p  ment or rerdg.n-,
mid then expofing  the  mixture to a Subliming hcai,
nitre  retains the fulph.ir, but lets go the greateft part
of the atScnic ; the  hepatic mafs, however, retains a
fmall  quantiiy of the latter ; and if there is much al-
kali, fcarce any of the arfenic arifes.
   On diftilling orpiment with twice or thrice it quan-
tiiy of corrofive  Sublimate,  two liquids ariSc which re-
fiffc to unite ;  and at length, on augmenting the heai,
a cinnab-ir arifi s.  A butter of arfenic is found  at the
bottom of the receiver, of a ferruginous brown colour,
but pellucid :  in  the open air it firft  fends forth a co-
pious fume of a white colour,  and then gradually at-
tracts the moifture of the atmofphere, by  which it  is
precipitated.   It is remarkable that it unites fo flowly
with marine acid, that they  feem to repel one another;
nor can they  be made to unite beyond a certain  de-
gree.   By the affufion of  diftilled water, a white pow-
der will be precipitated,  which, though ever  fo well
wafhed, retains fome acidity ; for a  peiriion of butter
of antimony is produced  by diftillation, as is likewife
true of the  pulvis algaroth.  The fmoke  has  a pecu-
lar  penetrating  fmell,  fomewhat fimilar  to  that of
phlogifticated  vitriolic  acid, and  lets fall  white flow-
os.   The liquor  which  fwims above, and which, by
chemical a uhors, has been compared to oil, is yellowifli
and pellucid, feparating a  white  arfenical powder by
the addition of water and fpirit of wine.  It is not
affected by the ftronger acids;  but effervefces, and lets
fall a precipitate, with alkalies.   On  keeping it with a
cucurbit with a  long neck unflepped, white  flowers
gradually concrete round  the orifice, which are lax,
and fometimes approaching  to a cryflalline form.  And
laftly, by fpontaneous evaporation, pellucid cryftals ap-
pear at the bottom of the liquor,  which are foluble in
water with  great difficulty ; but when  diffolved, pre-
cipitate filver from  nitrous acid, and  let fall fome ar-
fenic on  the  addition  of an alkali.   When put  into
limc-wattr, a cloud  flowly Surrounds them : on being
expofed to the fire, they totally Sublime without  any ar-
Senical  Smell,  without decrepitation, or  lofing their
tranfpareney ; but  if ignited phlogiftic matter comes
in contact  with  them, the arSenical Smell inftantly ap-
pears.  No traces of mercury are to  be fonnd  in  this
liqjor by  treating it cither with alkali  or copper ;
not the  llighteft precipitation is  made  by it  on be-
ing-dropped into a folution   of  terra ponderofa  in the
marine acid : f 1  ni all which it apprars, that this liquor
is only a very dilute butter of arfenic,  containing lefs of
the mercury on account of the quantity  of water it
has.  The  butter  contains the acid  in its  moft con-
centrated ftate, and  is therefore  loaded with a larger
quantitv of arfenic : the former liquor will therefore be
obtained in much larger quantity, by  Setting the mix-
ture of corrofive fublimate and arSenic to ftand  a night
in a cellar, or moidencd  with water, beSore it be Sub-
jected to  difti'daiion.   As  the common  marine  acid
can diffolve only a  derermined quantity of the  butter,
it  naturffiy  follows, thai  what remains after complete
faturaiion inou J totally  rdi.lc to mix.    The acid,
however, when too much diJurtff, precipitates 1! e but-  Arfenic.
ter ; but in  proportion  toils  flrengih  it diffolves  .;
greater quantity.                                       1:84
  /Mfenic  mineralized by  fu'phm- is not diflblved by Arfenic mi-
water, but  Is affected by  the different acids, according ncrabied
to the particul ir circuftances  of tach.  Nitrous aeid ty fulPhur'
and  aqua-;e gia act moft  powerfully ; the former foon
deftroys the red col. .11 of ihe  realgar, and converts  it
into yellow orpiment ; its primary action being to cal-
cine the arfenic,  without affecting the yellowuefs of
the fulphur.   It  makes  no change  on  the colour of
orpiment.   Aqua-regia,  by long digeftion,  takes up
the arfenic, and leaves the fulphur at the bottom ; and
hence we may .find out the proportions of the two in-
gredients.   Some  dexterity, however, is neceflary in
performing this operation with accuracy ;  for if,  on
the one hand,  the menftmum  be too weak, part of the
arfenic will remain undiffolved ;  and if,  on the other,
it be too ftrong, part of the fulphur will be decompo-
fed ;  for ftrong nitrous acid is capable of dccompofing
fulphur by  long digeftion, having a greater attraction
for phlogifton than the vitriolic acid  itfelf. The colour
of the refiduum ought to be grey ; for as long as any
yellow  particles remain, it is a fign that fome  of the
arfenic  alfo remains.  If  any  iron be prefent  in the
compound,  it is all diffolved,  by reafon  of the  fupe-
rior attraction of the acid for it, before any of the ar-
fenic is  taken up,  unlefs it fliall have been calcined ei-
ther by the accefs of  air  and  heat  employed in the
operation, or by the too great power of the menftruum.   Iag,
   The  pure regulus of arfenic may be obtained artifi- pUre regtv-
cially from white arfenic,  either by fublimation  with lus of arfe-
oil,  black  flux, or  other phlogiftic  materials;  or by nic»  bow
melting it with double its weight of foap and potafhes; PrePared<
or laftly, by precipitation by means of fome other me-
tal, from orpiment  or fandarack melted with Sulphur
and fixed alkali.    By the firft of thefe  methods it  is
obtained in a cryflalline form, Oetohedral, pyramidal,
or  even prifmatic.  Mr Bergman mentions  a natural   I2g6
regulus of arfenic, named mifpickett  which along with Mifpickcl,
fome fnlphur contaias  a large quanf^y of iron  united-a natural
with the regulus  into a metallic  compound ;  but  tho' "guru* of
the  iron fometimes amounts  to  4  or even   *  of ihcarfcnic"
whole,.it neverthelefs remains untouched by the mag-
net.  When  ignited,  it  fends forth an arfenical fmell,
and foon becomes obedient to the magnet, even though
the operation be  performed on a tile without any ad-
ditional phlogifton ; it melts eafily in an open  fire, and
in clofe veflels the greater pa/t of the regulus Sublimes,
leaving the iron at the bottom.                         12g«
   The  pure regulus of  arfenic is vaftly more volatile Greatvola-
than any other metal,  aud therefore cannot be melted  tility ofthit
It begins to fend  forth a vilible fmoke in 1800 of the femimetal.
Swedilh thermometer, and is capable of inflammation ;
but  in  order  to  inflame  it, ii muft be thrown  into a
veffel  previoufly heated  to a fufficient degree,  other-
wife  it will be fublimed.  The flame is of  an obScure
whiiifh blue, diffufing a white Smoke and garlic Smell.
In clofe veffels it retains its metallic Sorm, and may be
Sublimed of any figure we pleafe.                          g«
   Regulus  of arfenic unites with many  of the metals, Effects of
but deftroys  the malleability  of ihofc  with  which H rej>ulu» of
enters into fulion.   It renders thofe  v ore  tafyoffu  arfenic on
fun which are melted  with diffieffty ly themfelves;0111"11""
but tin, the moft eafily iufiblc of all the metals, be-^1*'
                                              cwnici 
Pratt ice.
CHEMISTRY.
181
Arfenic.
   1289
May be ex-
pelled by
heat from
all the me>
tals with
which it is
united.

   1290
Effects of
it upon al-
kaline
falts and
nitre.
   1291
De compo-
tes corro-
five fubli-
mate.
   1292
Converted
into white
arfenic by
the vitrio-
lic acid.
comes  more refractory  by being united with arfenic.
This metal acquires a permanent and finning whitenefs
by  its union  with regulus of arfenic,  and is able to
retain half its own weight of the arfenical metal.  The
other white  metals become grey  by fufion with this
femimetal, platina only excepted.   Gold  fufed  iu a
clofe veflel with regulus of arfenic, fcarcely takes up yv
of its weight; filver i ; lead '£ ; copper |  ; andiron more
than its own weight.   The magnetic property of  this
laft metal  is deftroyed by a large quantity of regulus,
though  the exact proportion which deftroys it  can
fcarcely be determined,  as fome  of the iron is always
taken up by the fcoria ;  but according to  Mr  Berg-
man, lefs than an equal quantity is  certainly  fiifficient.
BiSmuth  retains r'T of  its weight;  zinc 1; regulus of
antimony 4 ; and  manganefe an equal quantity.  -Nic-
kel and regulus of cobalt take up a large quantity ;  but
how much cannot be determined, as it is next to im-
poffible to procure any of thofe metals in a ftate of per-
fect purity. In  a fufficient degree  of heat, and  by a
triture of feveral hours, regulus of arfenic takes up a-
bout i of its own weight of mercury,  forming an a-
malgam of a grey colour.
  Regulus of  arfenic, by  reafon of its volatility, may
be expelled from all the metals with  which it is unit-
ed ; but,  in flying off, it generally carries along with
it fome of the metals with which it is united,  gold  and
filver not excepted,  if the degree of heat be great and
very fuddenly  applied.  Platina, however,  perfectly
refills the  volatilization;  and  by reafon of its refrac-
tory nature, even retains a portion of the arfenic.
   This femimetal cannot be united  by fufion with alka-
line falts  until the phlogifton is  confiderably dimi-
niihed, and the regulus approaches  to the  nature of
pure arfenical acid.   By  adding regulus therefore to
nitre in  fufion,  a detonation enfues, the phlogifton of
the  former is  totally deftroyed, and the acid uniting
with the alkali  of the nitre  forms a neutral  arfenical
fait, fimilar to  that made with white arfenic and nitre.
By diftillation  with dry acid of arfenic,  the  regulus
fublimes before  it can be acted upon by the acid ;  but
when thrown into the acid  in  fufion, foon takes fire,
and fends forth  a white fmoke:  for the acid,  being in
this inftance deprived of  its  phlogifton, Separates that
principle from the regulus, and unites with it in fuch
quantity as to  regenerate white arfenic;  while on the
other hand, the regulus,  by this operation,  is fo  far
deprived of" its phlogifton as to appear  in  the form of
a calx.  By diftillation  with corrofive Sublimate, a
Smoking butter, and Small quantity of mercurius dul-
cis  and running  mercury, are procured; which happens
in confequence of a double elective  attraction ;  the  re-
gulus of arfenic  yielding its phlogifton  to the bafe of
the  corrofive  fublimate,  which being  thus really cal-
cined, reduces  the  lormer to perfect mercury, while
the marine acid takes  up the calx of arfenic.   The re-
gulus ot arfenic  readily unites with fulphur,  and forms
the fame red and yellow compounds that  have already
been mentioned when fpeaking of  white arfenic;  it is
Soluble, in  hepar Snlphuris, but may be precipitated by
every other metal which can unite  with the hepar.
   Regulus oS arSenic is not affected by the vitriolic a-
cid, uuleSs when concentrated  and  affifted by  heat.
The inflammable part of the regulus which phlogifti-
catcs the acid flics off,  So  that the remainder affumes
the nature of  white arSenic, and exhibits the Same pro-   Cobalt.
perties with menftrua as any other metallic calx: the '    v/
Same holds good with  nitrous acid, except thai it at-
tracts the  phlogifton more vehemently.  Marine acid
has little or no effect except when boiling.              Ii0;5
  Regulus of arfenic precipitates certain metals  diffol- Effects of it
ved in acids, fuch as gold and platina, diffolved in aqua- on metallic
regia, as well  as filver and mercury in vitriolic and ni- Solution.
trous  acids.  Silver generally appears  in beautiful po-
lifhed fpiculse,  like the arbor Dianse; but if the  arte-'
nic be fuffered to ftand long in the nitrous folution but
little diluted, the filver fpiculae are again diffolved, the
arfenic in  the mean time being dephlogifticated.   So-
lutions of  bifmuth  and antimony are fcarcely rendered
turbid.  Iron may be feparated from regulus of arfenic
by digeftion with marine acid, or with aqua-regia ; nei-
ther of which will touch the arfenic, as long as any iron
remains;  but in order to fucceed in this operation, fubtile
pulverifation is neceflary  as well as a juft  quantity and
ftrength of the menftruum.  Heat muft alfo be carefully
avoided.   The regulus  is  alfo diffolved by hepar ful-
phuris and  by fat oils, the  latter  forming with it a
black mafs like platter.

                  §12.   Cobalt.
  Regulus of cobalt,  or more  properly pure  cobalt'
itfelf  (what we have under the  name of  cobalt being
only a calx of the regulus),  is a femimetal of a reddifh
white colour, clofe-grained, fo as to be eafily reducible
to powder, about 7.7 of fpecific gravity, and  forming
itfelf  into  maffes of a needle-like texture, placed upon
one another.   It is Seldom or never found native, but
almoft always calcined and united  with arfenic, the ar-   1294
fenical acid,  fulphur, iron, &c.   The zaffre ufed in Zaffre, a
commerce is an impure and grey calx of cobalt. When calx of cow-
mixed with three  times its weight of pulverifed flints,balt"
and expofed  to  a  ftrong  fire, it  melts into glafs of a
dark  blue colour,  ad\ed fnalt, ufed in tinging  other   1295
glaffes, and in painting.   With three  times its vVeight Smalt,
of  black flux,  a fmall quantityof tallow and marine how pros
fait, it affords  the femimetal known by the improper
name of regulus of cobalt j but the reduction is very   1206
difficult.   For this purpofe a large quantity of flux muft Regulus of
be made ufe of,  asd the crucible  kept a confiderable cobalt diffi-
time in a  white-red heat,  that the matter may become cult t0 re"
very fluid, and that the Scoria may be completely SuSed ducc"
into a blue glaSs,  at which period the cobalt finks in
the form oSa button to the bottom.                      1297
   Cobalt  melts in a ftrong red heat, is very fixed in Properties.
the fire,  and it  is uncertain whether it can be vola-cf cobalt
tilized in cloSe veffels.   When Suffered to  cool flowly, W^J exi
it cryftallizes in needle-fliaped prifins, placed one upon f°at
the other, and united in  bundles, having a  confider-
able  reSemblance to maffes oS bafaltes Separated  Srom
each  other: in order to Succeed in this cryftallization,.
however,  the cobalt muft be  melted in a crucible till it
begins to boil, and, when the Surface  of the metal be-
comes fixed en being withdrawn from  the fire, the vef-
Sel is then to be  inclined ; that which ftill remains fluid
runs out,, and the portion adhering to the lumps form-
ed by the cooling of the furface is found covered with
cryftals.                                                  g
   This  femimetal, expofed  to  the atmofphere,  be- Calcines-
 comes covered with  a  dull pellicle, and  undergoes a fponta-
 fpontaneous calcination,  but  it may eafily  be calcined neoufly in-
                   •                             - in the air. 
CHEMISTRY.
   no9
l'« :ak
fount a
beautiful
bhic glafs.
   I30O
Phenome-
m with vi-
triolic acid
   i,yoi
With ni-
trous aciJ
   I3c:
With ma-
rine acid.
   1 ;cj
With the
ae id «: bo
rux.
in  iry quantity by expofing it in  powder in a (hallow
rew.'., under 1 he muffle of  a  ci jelling  furnace, and
furring it now and then to cxpofe iitfh furfaces 10 the
air.   After  being kept red hoi for fome time,  this
powder lofts its Splendor, increafes in w* igkt,  and be-
comes black, the c ..!x being  convertible,  by a  moft
violent heat,  into a blue glafs.  By fulion it combines
with vitririablc canhs,  forming  wiih  them a beautiful
b ilc gi .Is Ow'.rcmcly iixed in the fire ; whence it  is  of
the greateft ufe in enamel-painting, porcelain-painting,
&c.   The  action ot  terra  ponderofa, magnefia, and
lime,  0,1 cobalt,  is not known.  Alkalies manifcllly
alter it;  but in what refpect  is not known.
   Cobalt difSolves in concentrated  vitriolic acid, when
afllftcd by a boiling heat;  the  acid evaporating almoft
entirely  in the  form  of  fulphureous gis.  The  rcii-
duum is  then  10 be waflied ;  a portion of it diffolves  in
the water, and communicates  a  greenifh colour  to  it
when warm, which changes  to a rofe colour when
cold.  M.  Beaume affirms, that by fufficiently  eva-
porating the  vitriolic  folution of cobalt, two  forts  of
cryftals  are obtained;  one white, fmall,  and  cubical;
the  other greenifh,  quadrangular, fix lines in length,
and Sour in breadth.   TheSe laft  he only conllders  as
the  true vitriol of ceibalt;  the former  being produced
by certain foreign matters  united to it.   The  cryftals
moft commonly obtained have the form of fmall needles,
 in el may be decompofed by fire,  leaving a calx of co-
balt not  reducible by itfelf.   They may likewife be de-
compofed by all the alkalies, by  terra ponderofa, mag-
nefia, and  lime.  According to  Fourcroy,  100 grains
of cobalt, diflblved in the vitriolic acid,  afford, by pre-
cipitation with pure mineral  alkali,  140 grains of pre-
 cipitate; by the  fame  alkali  aerated, 160 grains.  Di-
luted vitriolic acid acts on  ziffirc, and diflblves a  part,
 with which  it forms the fait already defcribed.
   Nitrous acid acts upon the femimetal with  that vio-
■ lencc which  is its general  characterise ;  and the  folu-
 tion,  when nearly faturated, appears either of a  rofy
 brown or bright green colour.   By ftrong evaporation
 it yields a fair in fmall  needles joined together; which
 is very deliquefcent, boils upon hot coals without deto-
 nation,  and leaves a calx oS  a  deep red colour.  It is
 decompofed by the Same Subftances as the former, and
 by excefs of alkali the precipitate difappe irs.
   M iii.uic acid, affifted  by heat,  diflblves cobalt  in
 part, but has no effect upon  it  in the  cold.  It acts
 more ftrongly on z.nlre, forming a folution of a reddilh
 brown,  which becomes green by being heated.   By
 evaporation it yields a very deliquefcent  ft-It  in  fmall
 needles, which  becomes  green  when heated, and is
 Sun after decompofed.  Aqua-regia diflblves  the me-
 tal more eafily  than  the marine acid, but leSs So than
 the nitrous.   The Solution has  been long known as a
fyiKputhlic  Ink.
   Cobalt is not diflblved directly by the acid of borax;
-but when a folution of this (alt is  mixed with  a  folu-
 tion of cobalt in  any  of the mineral acids,  a double
 dec > npuSnion takes place ;  the  alkaline  bafis of  the
 borax uniting with the acid which held  the cobalt  in
 folution ;  and the calx, combining with  the  Sedative
 fait, falls to  ihe bottom iu form  of  an infoluble pre-
 cipitate.
   This  femimetal is  calcined by being heated to igni-
 tion with ni.re.   One part of cobalt, and two or  three
                                                 Practice.

nf dry nitre,  well powdered ard mixed, when thrown  Niekcl.
into a red-hot crucldc; produce Small Scintillations; a
portion of ihe cobalt being converted into a calx of a red
colour, more or lefs deep, and fount hues  e>t  a  yretn.   t;->.t
Sal ammoniac is not  decompofed, by realbn ofthe lit- Vi'itii !  I
tie attraction  there is between ihe metal and muriatic ammoniac.
acid.   M. Bucquet,  wto made  the experiment will; ,..t:^°/.
               11      1   •         • 1    *-   i-i   1  ^ 'th Ittl-
prcn care,  ceuild not obtain a particle of volatile al- , r
kali.  Sulphur dets not unite with it but very difficult-
ly,  and the  com! inaiion  is  promoted  by  liver of  ful-
phur.  Thus a kind of artificial one may be produced,
the grain  of  which  will be finer or cloScr, and  its co-
lour  whiter or  yellower,  in proportion to the quantity
of fulphur in the mixture.   M. Beaume obferves, that
this compound cannot be decompofed by acids, and that
fire cannot deftroy all ihe fulphur.
§13.  Nickel.
1306
  This  was firft difcovered to be a femimetal of a pe- Difcovered
culiar kind by Cronftedt,  in the years  1751 and 1754, by Mr
who procured it in the form of regulus from its ore, but Cronftedt.
without being able to reduce it to a  fuflicieiu degree of
purity ; which indeed has not yet been done by any che-
mift.   M.  Bergman  has  laboured  moft  in  ibis way,
though even he has not reduced it to the purity of other
metallic fubftances.   His experiments were made  with
fome  regulus  made by M. Cronftedt,  and whofe fpe-
cific gravity was to  that of water exactly  as 7.421  to 1.
His attempts to purify it were made,

         I. By Calcination and Scorification.
                                                      1307
  Nine ounces of powdered nickel  were expofed for Effects of
fix hours, in Several portions,  to a  moft  violent hear, calcination
under  the  dome  of an  affay furnace.  Thus the  arfe- Wlth avi°"
nic was  firft  dillipated  with a fetid fmell,  after which
the odour of fulphur became  perceptible;  after this a
white fmoke  arofe  without any fmell of garlic,  and
which, according to  our  author, arofe probably  from
the more  dephlogifticated part of the arfenic which
now began to fublime.  The heaps (we  fuppofe  after
the matter had been poured out of  the difhes, and yet
retaining a great deal of  heat), when hot, began to
fwell, and  green  vegetations arofe from all the furface,
refembling fome kinds of  mofs,  or the filiform lichen ;
a ferruginous afh-coloured  powder remained  at bot-
tom ;  and 0.13 of the whole were diflipatcd during the
operation.   Half an ounce  of this  calx fufed  in a
forge for  four minutes,  along with  three times its
weight of  black flux, yielded a regulus  reticulated on
the furface;  the  areola of a  hexangular figure,  with
very flender ftriae, diverging from a centre, full of lit-
tle  tubercles; it  weighed 0.73 of half an  ounce; was
obedient to the magnet; and,  when fcorified with bo-
rax, left a blackifh glafs.
   By a  fecond roafting the  regulus again emitted  a
garlic  fmell;  afterwards  a vifible  fume without any
fmell, with  vegetations as before.   The roafted  pow-
der, reduced  with  black flux as before,  ftill emitted  a
fmell of  arfenic; but on repeating  the fulion with the
calx and borax,  nothing  but fome obfeure figns of co-
balt appeared.  A  third  calcination feemed  th  have
much  diflipated  the  arSenic,  as it now  emitted but
lhtlc of  that kind of fmell; the vegetations were alfo
gone ; and the matter had rather a ferruginous than  a
                                              green 
Practice.                           C    H    E   M
 Nickel,  green colour.  Nearly the fame phenomenon appeared
■*"        after reduction in a fourth operation.
            On performing  the reduction with lime and borax,
         the regulus,  when firft melted,  loft much of its ferru-
         ginous matter, which  adhered  to the black fcorias;  it
         foon acquired an hyacinthine colour, without any re-
         markable mixture of cobalt, was little obedient to the
         magnet, and  its fpecific gravity was Somewhat dimi-
         niflied,  being now only 7.0828.
            By a fifth calcination, gradually adding  a quantity
         of powdered charcoal  while the matter continued red
         hot, a prodigious quantity of arfenic, imperceptible be-
         fore, flew off in the form of vapour; the arSenical acid
         being thus^ furnifhed with as much phlogifton  as was
         neceffary to make it rife in fume.  The  regulus was
         treated in  this manner until no more arfenical fmoke
         could be perceived; it was now  of a lamellated and
         tenacious texture when reduced, but  ftill diffufed  the
         arfenical odour on  being removed from the fire.   The
         roafting  was therefore repeated a fixth time, and con-
         tinued for ten hours;  the addition of powdered char-
         coal continued to  diffipate the arfenic in invifible  va-
         pours which yet were perceptible by the  Smell;  the
         colour of the metallic calx  was  obfciirely ferrugi-
         nous, with a mixture  of green fcarcely vifible.  On
         reducing the regulus  with  equal parts oS white flux,
         lime and  borax, a Semiductile  regulus was obtained,
         highly magnetic, and Soluble in nitrous acid, to which
         it communicates a deep green colour;  a blackifh maSs
         rejnained, which afterwards become white,  and when
         laid on a burning coal, flies off without any remarkable
         arfenical fmell.  The  regulus being then fix times fu-
         fed with lime and borax, the Scoriae reSembled the hya-
         cinth in  colour,  and the metallic  part was Surrounded
         with a green calx.   The regulus, asbeSore, 'i?as mag-
         netic and Semi-malleable.   Laftly,  it was expoSed  Sor
         14 hours  to a very  ftrong heat; wdien the  powdered
         charcoal was added by degrees  without any  djilipation
         oS arSenic or loSs of weight;  the colour of  the roafted
         powder was ferruginous, with  a very  flight tinge of
         green.   On reduction,  a very fmall globe, ftill mag-
         netic, was found among the Scoriae.

   l3o8                    II. By  Sulphur.
Effects of     Eight hundred parts of Cronftedt's regulus of nic-
|"1f)hurandkel, fufed with fulphur and a fmall quantity of borax,
         yielded a mineralized mafs of a reddifh yellow, whofe
         weight  amounted to 1700.   On expofing one half of
         this to the fire, it began to grow black  ; on  which the
         heat was  augmented until vegetations  appeared; the
         remaining calx weighed 652.   Melting this part with
         borax, and the other  which had not been  expofed to
         the fire,  a  Sulphurated regulus  of a wliitiftvydlow co-
         lour wts obtained, weighing 1102.  The fame regulus,
         calcined  for four hours, was firft covered with vegeta-
         tions, and then, on the addition  of powdered  char-
         coal, diffufed an arSenical odour; the metallic calx was
         green, and weighed 1038.   A whitifh  yellow regulus
         was  obtained  Semiductile,   highly magnetic, and ex-
         tremely  refractory,  weighing 594.  By  fufion with
         fulphur  a fecond time,-it weighed 816;  one half  of
         which roafted to greennefs,  united by means of fire to
         the other half ftill fulphur3ted, weighed 509, and was
         almoft  deprived of  its  magnetic quality.   A calcina-
         tion of  four  hours,  during  which phlogifton was ad-
I    S   T    R   Y.                                 183
 dcd, diflipated a confiderable quantity  of arfenic;  the   Nickel.
 powder put on an afh-colour, Somewhat greenifh, was in *    ^   '
 weight 569;  and by  reduction yielded a regulus whoSe
 SurSace was red, and which, on breaking, appeared of
 a white afh-colour, very  friable,  and weighing  432;
 theSpeciiic gravity 7.173.
   On mineralizing the regulus a third time with Sul-
 phur) adding charcoal as long as any veftige of arSenic
 remained, which required a violent calcination oS 12
 hours,  the remaining  powder was of an afh-green co-
 lour, and weighed  364;   but the  regulus obtained by
 means of a reduction effected by the moft violent heat
 in a forge for three quarters of an hour, was' fo refrac-
 tory  that it only adhered imperfectly  to the fcoria,
 which were of a diftinct hyacinthine colour ; nor could
 it be reduced to a globule by mems of  borax, though
 urged by  the  fame,  vehemence of fire.  The abfolute
 gravity of  this regulus  was 180; its fpecific  gravity
 8.666.  Its  magnetic virtue was very remarkable; for
 it not only adhered  ftrongly to the magnet,  but to any
 other piece of iron;  and  the fmall pieces of it attrac-
 ted one another.  It had  a confiderable ductility,  was
 oS a whitifii  colour, mixed with a kind oS glittering
 red;  diffolved  in volatile alkali,  yielding a blue Solu-
 tion, and a green one in nitrous acid.
  An  hundred parts oS the Same  regulus, beaten out
 imo  thin  plates,  were  covered  by  a calcination of
 four hours, with a cruft apparently martial, having un-
 der  it a green powder,  and within it  a nucleus con-
 futing oS reguline particles ftill  unchanged ; the weight
 being increaSed by 5.   The Sriable matter, reduced to
 powder, put on a brownifh-green colour;  and  after  a
 calcination of  four  hours more, concreted  at the bot-
 tom in form of a friable  black cruft, ftrongly magne-
 tic,  and  weighing  100:   No veitiges of arfenic were
 difcovered by  a Succeeding operation, in which char-
 coal was added ; nor was the magnetic powder deftroy-
 ed,  but the weight was increaSed  to 105, and the co-
 lour Somewhat changed.   By Snfion Sor an hour with
 lime  and borax,  this  powder  yielded  a regulus oS an
 angular Structure, red, Semiductile, and altogether mag-
 netic ;  the  Specific gravity being 8.875.  The Same
 globule diflblved  in aqua-regia, was  precipitated by
 green vitriol,  as iS  it had been loaded with gold ;  but
 the  precipitate  was readily  Soluble in nitrous acid.
 Moft oS  the  reguli Ihowed no Signs of precipitation
 with green vitriol,

            III.  With Hepar  Sulphuris.
                                                      1309
  Fifty-eight  parts of'regulus  of  nickel, which  had Effect of
 been  Sulphurated  before,  being fufed with 1800 parts hepar ful-
 of faline hepar fulphuris, then diffolved in warm water, PllUns-
 filtered thi>ugh paper, and precipitated  by an acid,
 yielded a powder,  which, by  calcination till the ful-
 phur  was driven off,  appeared of an afh-colour, and
 weighed 35.   The infoluble refiduum,  deprived of its
 fulphur by means' of fire, was likewife of an afh-colour,
 and weighed 334.  On reducing this regulus by means
 of the black flux, a friable regulus was obtained, which
 had a very weak  magnetic property ;  but,  on fufion
 with borax', this quality was augmented.  On mixing
 and  melting together  equal parts of calx of  nickel,
 gypfiun,  colophony,  and white  flux,  a powdery, Squa-
 mous,  aud reguline  maSs was  produced ;  which, by
 fufion with borax, afforded a regulus poffeffing the pro-
                                             perties 
184
 Niekr?.
   i^IO
Of nitre.
Nitre ca-
pible of
leparating
all the co-
bale from
«;,-kci
                             C    II    E   M    I

yerties of nkkf.1, but not  entirely dcltitute of cobalt,
which obeyed  the  nug n ,  and did  not part with its
iron  even after  two Solutions in the   nitrous aciJ,
and  various reductions by fulion with borax;  the Sul-
phur was alfo retained wuli great obftinacy.
   On diffolving  rc-Mlus of nickel by fulion,  in hepar
filphurismade  with fixed alkft',  adding  a quantity of
nitre Sufficient only to d elite)/ a Small partof  the ht-
par,  the regulus which had been fufpeuded by it  was
ftp.1r.1tcd, auJ  fell to  the botiom.   On examining this
reg lb s it appeared more pure, and generally dep.ived
of cobd;,  but  ftill confining iron,  in like manner
nickel is a!*vays very diltinctl/ precipitated by regulus
of cobalt, as this latter is attracted more  powerfully by
the hepar fulphuris.  When diffolved by fulion with he-
p n-  fulphuris,  this  femimetal may be precipitated by
adding iron, copper,  tin,  or lead, and even by  cobalt:
the  regulus obtained  is indeed  fcarcely  ever attracted
by rhe magnet; but  we are  not from  thence to con-
clude that it  does not contain  any iron ;  for when  the
heterogenous matte is, which impede its action, are pro-
perl/ rem-wd, it then acknowledges the power of the
magnet very plainly.
                   IV.  By  Nitre.
   One pirt of Cronfledi's regulus was added to twelve
 of nitre  ignited in  a  crucible, and kept  red-hot for
 about an  hour.  Some  weak dailies appeared  firft ;
 then a large  quantity of arfenic was  emitted ;  and,
 laftly, the fides were covered with a blue cruft occafioned
 by  thc'cobalt, a green  matter remaining at bottom.
 This, fufed  again  for an hour, with twelve  parts of
 nitre, tinged the internal  fides of the veffel of a green
 colour;  and, laftly,  a brownifh green mafs, much lefs
 iu epiantity than  in the former  operation,  was left at
 the bottom.   This green matter, treated  in  the  fame
 way for two hours a third time, left a grey fcoria at the
 bottom, which yielded no regulus with black flux.
    Another portion of  the fame  regulus, treated in the
 fame way with nitre, was diffolved, and  became green ;
 yet on being freed by ablution from the alkaline Silt,
 it  yielded no regulus with black flux,  but only Scoria
 of  an hyacinthine"colour  mixed with blue, tinging ni-
 trous acid of a green colour, concreting into a jelly, and
 on evaporatiem leaving a greenifh calx behind.
    Another  portion  of Cronfledi's  regJus was  kept
 Some hours in  the crucible with  16 parts of nitre ; by
 which means  all the arSenic  was firft Separated; then
 the phlogifticated nitrous acid ;  and, hilly, the fides
 of the veffel were penetrated by a kind  ot trreen  efflo-
 reScences.  The maSs, after being walked with water,
 was of a  dilute  green colour,  and tinged borax of  a
 greenilh  brown.  A  green powder was ftill yielded,
 after treating this in the  fame manner with 12 parts of
 ritre ;  and on  reducing it  wiih one-half black flux,
 one-eighth   borax,  and  as  much   lime,  a yellowifli
 white regulus, both  magnetic and malleable, was oh-
  Mined, poifeffihg  ail the  properties  of  nickel.  Its
 fpecific gravity  was 9.000;  the phlogiftic ingredient
 was niVd in  Small  quantity,  that the iron might, if
 poflible, enter the fcoria.
     It bavin ' appeared from this and  fome other  expe-
  riments,  that nitre  was capable of difcovering  the
 fmalleft quantity  of  cobalt  contained 111 nickel  the
 product of the'form:: oprr.-.tions were now iuhjected
   S   T    R    Y.                           Practice.
toits  action.   Then gains  produce^  by repeated fco-   Nb-kel. ^
rilicaiiaii thus l» cunt a Utile blue; that  oiwu.ved  in*"
volatile alkali  (to be ..nciv, ards particularly iiKnlioncd)
difcovered  a confidt-rabie  quantity <>f  cobalt, nor was
there  any one w hich did no; thus u.fcovtr more or Ids
of that ingredient by this trial.
               V.  B) Sal  Ammoniac.                     4
   A calx of nickel, fo  much freed from cobalt that it  Fillet of
did not tinge borax  in the leaft, mixed with  twice  fa.1 ammo-
its  weight of fal  ammoniac,  yielded  by  fublimationniac
with  a ftrong red heat, two kinds of flowers; one,
which rofe higher than the other, was of an afh colour;
the other white.  The botton of  the glafs was  ftained
of a deep hyacinthine colour; the refiduum was divided
into  two  ftrata;  the upper  one yellow,  fcaly, and
fhining like  mofaic gold.  With borax it afforded an
hyacinthine glafs, but not regulus ; and in a Sew days
liquefied in the  air, acquiring a green colour and  the
confiftence oS butter.   The refiduum fhowed the Same
properties  with calx of  nickel;  and the green folution
Ihowed no veftiges of iron wi<h galls, but became blue
with  volatile alkali; which  was  alfo the cafe with  the
flowers.  The lower ftratum contained  a calx, blackifh
on the upper part, but of a ferruginous brown in  the
under, with  a friable and fcarcely magnetic regulus, of
a rcddilh  white.   The blackifh calx yielded anjiya-      >
cii.thine glafs with borax.   Part of  this ftratum  fub-
limed with  twice its quantity  of  fal ammoniac ;  and
 with the fame degree of heat as before,  yielded flowers
 of a  very  fine white, with  a  refiduum  of ferruginous
 brown, greenifh on the upper part towards the  fides of
 the veffel, the bottom being ftained oS  an hyacinthine
 colour as  beSore. Twenty  parts oS Sal ammoniac being
 added to a part of the  inferior ftratum  reduced,  the
 whole was fublimed in a retort;  a  blackifh powder re-
 mained, which became  green by calcination, and of
 an hyacinthine colour  by  fcorification, as did alfo the
 bottom of the containing veffel.  The  fublimaiion  be-
 ing twice  repeated, ufing a double quantity of Sal  am-
 moniac each time, the calx became at length very green,
 diffolving with the fame colour in the nitrous acid,  and
 yielding by  reduction a white,  brittle,  and very little
 magnetic  regulus.  In  all  thefe Sublimations,  it  was
 obServed, that  the volatile alkali rofe firft ;  then Sal
 ammoniac;  and, laftly, a part of  the  marine acid  was
 forced over  by the violence of  the heat.

               VI.   With  Nitrous acid.
                                                       1313
    Having obtained a fait by cryftallization from nickel Effects of
  diffolved in  nitrous acid,  part of this was calcined with antimony.
  charcoal duft in a proper veffel, and during the opera-
  tion  a large quantity of arfenic was diflipated ;  a greyr
  Semiductile, and magnetic  regulus being obtained after
  reduction.  A  brittle regulus was  obtained after a fe-
  cond Solution,  precipitation, and  reduction ; but  by a
  third operation it  became again Semiductile and mag-
  netic.  By  repeating  this proceSs a Scurth  and  fifth
  time, the quantity became So  much  diminiflied  that it
  could no longer  be tried.  In  all thcSe Solutions a
  blackifh refiduum appeared;  which, when  Suffered  to
  remain in the acid, grew white by degrees ;  but when
  edulcorated  and  laid on a burning coal,  exhaled a ful-
  phureous fmoke,  and left a  black  powder foluble  in
  the  nitrous  acid.
                                            VII. By 
^Pradicc.
CHEMISTRY.
185
 Nickel.

   1314
Volatile
alkali.
VII.   By volatile  Alkali.
   1315
Nickel can-
not be ob-
tained in a
ftate of pu-
rity.
   1316
Bergman's
opinion of
the compo-
fition of
nickel.
  Four hundred and eighty-feven parts  of a calx of
nickel, produced by  diffolving Cronftedt's regulus in
nitrous acid, and  precipitating the  folution by  a fixed
alkali, being immerfed  for 24 hours,in a quantity of
volatile alkali,  yielded a refiduum  of  fifty,  having
a blackifh green colour. The Solution, which was blue,
by filtration and inSpiffation yielded  a powder of a light
blue colour,  weighing  282 ;  which,  reduced with
black flux, produced a white, femiductile, and  highly
magnetic  regulus, weighing  35, whofe fpecific gravity
was 7.000.  The  fcorias were  of a  light  red :  but
when mixed  with borax, put on an hyacinthine colour,
and yielded  a regulus weighing 30.  The two  re-
guli united together proved  very refractory ; fo  that
the mafs could not  be melted by  the  blow-pipe, even
with the  addition of borax.   It fent forth  neither  an
arfenical nor fulphureous fmell on ihe addition of char-
coal-duft;  but, on a fucceeding reduction, yielded  hy-
acinthine  fcorias; and the remaining flocculi, diffolved
in nitrous acid, affording a very green folution,  which,
on  the addition of  volatile alkali, yielded a powder of
the fame colour.
   From  50  parts of the blackifh green  refiduum,  13
of  a clear white, brittle, fquamous, and  little magne-
tic  regulus, were obtained, the fpecific gravity of which
was 9.333.   At the bottom  of the veffel was found a
fcoria of an obfeurely blue colour, with the upper part
hyacinthine.   It  was eafily fufed ;  and tinged borax,
firft blue, then of a hyacinth colour, upon which it
became more ftrongly magnetic.  By the affiftance of
heat it diflblved in nitrous acid,  forming a folution of
a beautiful blue colour.  A  black powder at firft float-
ed  in the  liquor, but became  white,  and fell to the bot-
tom.  After  edulcoration it was for the  moft part  dif-
Gpated, with  a fulphureous fmell, on being  expofed to
the fire ;  a little brown-coloured mafs, foluble in vola-
tile  alkali, remaining  at bottom.  This folution was
precipitated  by  phlogifticated alkali, and  a  powder
thrown down of the colour  of calx of nickel, which
foon grew blue with volatile alkali.
   From all thefe experiments it appears,  that nickel
cannot be obtained  in  a ftate of purity by any means
hitherto known.  From every other fubftance, indeed,
it may be feparated, except iron ;  but this refifts  all
the  operations hitherto defcribed,  and  cannot be  di-
miniflied beyond certain limits.  The magnet not only
readily difcovers its prefence, but fome portions ofthe
regulus itfelf  becomes magnetic ;  but  the tenacity
and difficulty  of  fufion, which increafe  the more in
proportion to the number of  operations,  plainly fhow
that there is no hope of feparating the whole quantity,
unlefs we  fuppofe the regulus of nickel itfelf to be  at-
tracted by the magnet; and there is certainly a pof-
fibility that one other fubftance  befides  iron  may be
attracted by the magnet.  The great difficulty, or ra-
ther impofllbility, of obtaining it in a ftate of purity,
naturally  raifes a fufpicion of its not being a diftinct
femimetal, but  a mixture of others blended together ;
and on this fubject  our author agrees in  opinion with
thofe who fuppofe it to be a compound  of other me-
tals.   Indeed,  Mr Bergman  is of opinion, that " nic-
kel, cobalt, and manganefe, are perhaps  no other than
modifications of  iron."  And in order to afcertain this,  Nickel.
he made the following experiments.                     ~^f~
  I. Equal  parts of copper, of the gravity of 9.3243, Experi-
and iron of 8.3678, united by fufion  with black  flux, ments t9
yielded a red mafs, whofe fpecific gravity was 8.5441; compote
and  which tinged nitrous acid firft blue,  then green, nickel arti*
afterwards yellow, and  at  laft of an opaqne brown, ficialljr.
2. Two parts of copper and one of iron had a fpecific
gravity of 8.4634;  the mixture yielding firft a blue,
and then  a green  folution.  3. Equal parts of copper
and  iron, of  the fpecific gravities already mentioned,
with another part of cobalt whofe gravity was 8.1500,
yielded a metal of the gravity of 8.0300, imparting a
brown colour to the folution.   4. Two parts of arfe-
nic of 4.000, added  to one of copper ana  another of
iron, gave a brittle metal of 8.0468,  which formed a
blue folution.   5. One part of copper, one  of iron,
two of cobalt, and two of white arfenic, gave a brittle
regulus of 8.4186; the Solution oS which was brownifh,
and feparated in part fpontaneoufly.   6. One part of
copper, one of iron,  four of cobalt, and two of white
arfenic, formed a mafs of 8.5714.  The folution was
fomewhat more red than  the  former ; and a fimilar
effect  took' place on  repeating the  experiment,  on-
ly that the  fpecific  gravity of  the metal was  now
8.2941.   8.  One part of  iron and four of white arfe-
nic formed a metal which diflblved  with a yellow  co-
lour ;  and, on the addition of Pruflian alkali, imme-
diately let fall a blue fediment.  9. One part of  cop-
per, eight of iron, fixteen of  white arfenic,  and four
of fulphur, united  by fire, on the  addition  of  black
flux,  yielded a mafs  which, though  frequently  calci-
ned  and  reduced,  produced  nothing but brown or
ferruginous calces.  It acquired a greennefs  with ni-
trous  acid; but on the  addition  of phlogifticated al-
kali  depofited a Pruflian  blue.   ic. One part of iron
was diffolved in fix of the nitrous acid, and  likewife
feparated by one  part of copper and one of the calcined
ore of cobalt, in the fame quantity of the fame acid.
The whole of the folution of iron was then mixed with
five  parts of  the folution of copper,  whence a green
and  faturated nickel colour was produced ;  which,
however, on  the addition of three parts of the folution
of cobalt,  became evidently obfeured.  The alkaline
lixivium dropped into this threw down at firft a ferru-
ginous  brown fediment,  the folution  ftill  remaining
green  : afterwards all the blue was  precipitated; by
which at firft all colour was deftroyed, but afterwards
a red  appeared, occafioned  by the cobalt diffolved in
the alkaline fait. The fediment, when reduced, yielded
a regulus  fimilar to copper, and at  the Same time duc-
tile, which tinged both glaSs and nitrons acid of a blue
colour.  IS a Saturated Solution of nickel be  mixed
with  half its quantity of folution of cobalt, the green
colour is much obfeured ;  but four parts of the former,
on the addition of  three of the latter, put off all  ap-
pearances of  nickel.   Sec the article Nickel.
§ 14.  Of Platina.
1318
  The properties of this metal  have not as yet been The hea-
thoroughly inveftigated by chemifts,and there is there- vieftofaU
fore fome  difagreement  concerning them.   Formerly mct*ls-
it was fuppofed  to be  inferior in fpecific  gravity  to
                        A a                  gold i 
186
CHE
   »3'9
Ir'Uuble
i icept l>y
rei^n fub-
flancei.
   13*1
Mr berg-
man's ex-
pcrmu-ntt
                                                       M   I
 I'latina. gold ;  but now is generally allowed to be fuperior in
  ~^   ' that rcfpect  by little lefs than a fourth part ;  being to
         water  in  the  proportion  of 23 to 1  when  perfectly
         freed  from   all  heterogeneous matters.  Mr  Berg-
         man  fys that its  colour  is that of  the pureft fil-
         ver.   The very fmall globules of it are extremely mal-
         leable ; but when ma iy of thefe arc collected together,
         they  can fcarcely t c fo perfectly fufed as to preferve
          the Line degree ot malleability.   They are  not  affec-
          ted by the magnet in  the leaft, nor  can they be dif-
dephlogifti- fn'v: d  in any  lnnple  menftruum excepting  dephlogi-
c..   '.''*"  ftic.ned marine acid.  As  it is  commonly  met  with,
   "•-io   however, platina has  the  form  of  Small grain-, its
Fouul in  pities  of a bluifli black, whole  colour is intermediate
fnwllgn ins betwixt  thofe  of filver  and iron.  Thefe grains are
iaf-rnixtd mixed with  many  foreign  fubftances,  as panicles of
with fo-   g,»ld,  mercury, and blackifh ferruginous, f-ndy grains,
          which by the magnifier appear Scorified.  The  grains
          themfelves,  when examined by a magnifying glafs, ap-
          pear  fonuTnncs  regular, fometimes  round  and  flat,
          like a kind  of button.   When beat on the anvil, molt
          of them  are flattened and  appear ductile ; fome  break
          in p .ces, and on being  narrowly examined  appear  to
          be hoao.v, and particles of iron and a  white powder
          have been found  within them  :  and to thefe  we  mnft
          attribute  the  attraction  of platina by  the  magnet ;
          fince, as we have already obferved, pure platina is not
          attracted by it.
             Mr  Bergman, who carefully examined this metal,
          diffolved  it  firft in aqua-regia compofed of the nitrous
          and   marine acid.    The folution  at firft  exhibits a
 nD.mc" yellow colour,  but on approaching  to  faturation be-
          came red, and the redntfs  increafes  as the  liquor be-
          comes more loaded with metal.   Cryftals are produced
          by evaporation of  a  deep red  colour,  generally  in
          fmall  angular and  irregular grains,  whole true lhape
          tannot be difcovered.   Their appearance is  fometimes
          oqaquc and  fometimes pellucid.   After  thefe are  once
          l'<r%ied, they  arc  extremely difficult of folution, re-
          quiring  much more water than even  gypfum itfelf for
          this purpofe—The folution is not precipitated by vege-
          table fixed alkali, nor does the latter affect the cryftals,
          except very faintly by digeftion with them in a cauftic
          it.v.e.  Aerated mineral alkali takes them up and  grows
          yellow,  but without depofiting  any  thing,  though  it
          decompofes them at laft by evaporating to dryneSs.
 Cryftals of    On the  addition of a fmall quantity of vegetable
 r:.>:.i:.imar fixed alkali,  either mild or cauftic,  fmall red cryftals
 be decom- foluble  in water, and fometimes of an  octohedral fi-
 pofed by  gure,  are  depofited.    They are  decompofed  with
 mincralbut difficulty by the mineral alkali, but  not at all by the
 PPV'ffT vegetable.   If a  larger quantity of fait  is  added   at
 lue fixed al-   »      /-iiir               r      u      1
 kali.  *   firlt>  an > "fallible Spongy matter of a yellow colour  is
          precipitated.   Cryflalline  particles  of the  fame kind
          are thrown  down   by  an alkali faturated either with
          the vitriolic, nitrojs, marine, or acetous acids,  though
          all the platina cannot thus be feparated from the men-
    ,,1;,   ftruum.
 Solution in    Aqua-regia, compofed of nitrous  acid and common
 aqna-rcgia fair, diffolved the metal with equal facility as the for-
 made with n-cr ;  only  the folution was more dilute, and  a yel-
 n,trousaci^ low powder floated on the furface,  a larger quantity
 and tn.t of ^.^ foan^ at ^ bottom.  On adding  vegetable fix-
          ed alkali to the clear  folution, a copious yellow  pow-
          der, foluble in a large quantity of water, was depofited.
ICC.
T3*4
  S   T    R   Y.                             Pratt
A  powder,  of a Similar kind, was precipitated,  tho'   Platina.
more  flowly, and  more of a cryftatline nature;  but  "~  ~
mineral alkali,  though  ufed in much larger qua nifty,
did not make any  alteration.  The collected  powv.tr
was yellow, and agreed in property with that fepara-
ted fpontaneoufly in a former experiment.
  On repeating the  experiment  with nitre and depu-  J" a ll^u"r
rated i; irit of fait,  inftead ot nitrous acid and fea-falt,  compofed
 1    1  •        i'rr 1   j         111    j  i-      „  of nitie and
the platina  was diffolved  into  gold-coloured  liquor,  a  lp;r;t 0f
greenilh  coloured granulated matter falling  to  the bot-  lalt_
torn,  and the finer part of  the  fame riling to the  top.
After faturating the  fuperflnous  acid, a metallic calx,
in Soluble in  water,  was thrown down by the vegetable
alkali.   She green powder is Soluble in water, and is
of the Same  nature with  the  precipitate  thrown  down
by  the vegetable alkali.                                 j^j
   Platina precipitated Srom aqua-regia  by  a  Sufficient  Cryflalline
quantity  of mineral alkali,  the. precipitate wafhed  anc  powder
diffolved in  marine acid, on  ihe addition  of vegetable  Fre^'P,ta"
alkali immediately lets till a cryflalline  powder,  as it  |eui)yVa.8p"
does alfo with nitre and other falts, having the vegeta-  from foju.
hie alkali for their bafis. The cafe is the fame with calx  tion of the
of  platina, diffulved in  vitriolic acid. Nitrous acid  alfo  calx in  ma-
difl'olves ihe calx of  platina,  but docs not yield any di-  rine acid;
ftinct faline precipitate without the affiftance of marine    I32°
acid.—The above  phenomena are likewife produced by  ?ut n°£
the precipitate thrown down by the vegetable alkali af-  fOUJtjon ;,
tcr the faline powder has been depofited.               nitrous a-
   From  theSe  experiments  our author concludes, i.eid.
That the precipitate  which is firft thrown down, on    '3*7
the addition of vegetable alkali to folutions of platina,  This preci-
is a faline  fubftance, and different from  the calx of  j5!43)6 a .
 ,       ,       r~,     ,.   r ..       . .               kind of tr»-
the metal.   3.  That this  faline precipitate is compo   lc falt_
fed of calcined platina, marine acid, and vegetable al-
kali.  3. By means of vitriolic acid, a precipitate ana-
logous to this may  he  obtained, compofed  of  calcined
platina,  vegetable  alkali,  and vitriolic  acid.  4. The
whole folution of platina cannot be precipitated by ve-
getable alkali in form of a  triple fi.lt; but after pafs-
ing a certain limit,  a metallic calx in the ufual way is
produced.                                              ,3a8
   As it  has been denied by Margraaf  and Lewis  that  Whether
mineral alkali is cspable of feparating platina from its  mineral aU
acid, our author was induced  to attend  particularly to^a'icanfc'
this circumftance.   Having therefore  tried ihe com-  Para*e  P1*"
mon folution with mineral alkali, he found that each drop • '"* \°n^u
excited a violent effervefcence, and at  laft that a  yel-
low fpongy matter, affording a  genuine calx of  pla-
tina, was precipitated: this was more fpeedily effected
by ufing the dry  mineral alkali, which had Sallen to
powder  of  itfelf.   To -determine,  however,  the  dif-
ference  betwixt the two  alkalies in a more  accurate
manner, he divided a very acid folution of platina in-
to  two equal parts.   To one of thefe, he added fmall
portions of  the vegetable, and  to the other an equal
weight of pieces  of mineral alkali, waiting  five mi-
nutes after  every addition,  till the effervefcence fhould
fully ceafe.  After  the firft addition, fmall  cryftals ap-
peared ; in the former partly on the furface, and partly r-f^f'
in the bottom;  but  in  the  latter no precipitate could times as
 be obferved until  56  times  the quantity of vegetable much  mi-
 alkali had been added.  The difference,  however, was ntral alkali
 even greater than  what appears from this experiment; "quired to
 for the vegetable alkali was cryftallized,  and therefore Pre<.'Pitate
 charged with  the  water  neceffary to its  cryftallinep    a,aro!
     0                            *          *        vegetablt
                                               form; aUx-jj, 
Practice.
CHEMISTRY.
187
Platina.
          form;  whereas  the mineral alkali was fpontaneoufly
 v—-V-—' calcined :  and though, in equal quantities of thefe two
          alkalies,  the purely  alkaline parts are as 3 to 2, yet
          three parts of vegetable alkali faturated only  1.71 of
          this aqua-regia,  while two  of the mineral alkali took
   1350   up about 2.6.
 Eeffects of   The volatile alkali  firft throws down this metal  in
 the volatile a faline form ; the grains fometimes diftinctly octo-
 alkab.     hedral.   Their colour is red when that of the folution
          is fo, but yellow when the  Solution is  more  dilute.
          After faturating  the fuperabundant acid, the fame al-
          kali precipitates the platina truly  calcined.   This pre-
          cipitate  is diffolved in water, though with  difficulty,
          and may be  reduced to more regular cryftals by  eva-
          poration.   Thefe are diflblved by  the mineral  alkali;
          but hardly  any figns of decompofition are  to be ob-
          ferved, unlefs the yellow folution,  evaporated  to  dry-
          nefs, be again diflblved in water; for then the metal-
          lic calx  refts at the bottom, and  the folution  is de-
          prived of its yellow colour.   The vegetable alkali has
          fcare any effect in this way;  for, after repeated ex-
          ficcation,  the  folution remains clear  and yellow: but
          here probably the fixed alkali takes  the place of the
          volatile;  for in larger quantities,  and efpecially when
          the cauftic vegetable alkali is made ufe of,  the mixture
          Smells of volatile alkali.
 Platina      The  volatile alkali, faturated with any acid,  pre-
partlypre- cipitates the platina in the fame manner as the vege-
eipitated   table alkali in combination with acids : but thefe neu-
by neutral tral falts precipitate only a determined quantity  of pla-
falts.      tjna . for af[er their effect has ceafed, the liquor lets
          fall a pure calx of platina on the addition  of  vegetable
   t*,.*   or volatile alkali.
 Trime falts   The  calx of  platina precipitated by mineral  alkali,
formed by and then  diffolved in any Simple acid, fliows nearly the
 this metal, fame phenomena with volatile alkali as with  the vege-
          table alkali.   "  Whence (fays Mr Bergman) we  may
          conclude, that platina diffolved in acids forms at firft,
          both  with  the volatile  and  fixed vegetable alkali, a
          triple fait, difficult of folution, and which therefore al-
          moft always  falls to the bottom unlefs the quantity of
          water be  very large." Calcareous earth, whether ae-
          rated or cauftic, produces the  fame phenomena  as the
          mineral alkali, without any cryftalliue appearance.
            Platina has been remarkable ever  fince its firft dif-
          covery  for being the moft  infufible fubftance in the
         world.   Meflrs Macquer and  Beaume kept  it in the
thTworl'd.  mo^ violent heat of a glafs-houfe furnace for feveral
          days without perceiving any other alteration  than that
          its  grains adhered Slightly to each other; but the ad-
         hefion was fo flight that they feparated even by  touch-
         ing.  In  thefe experiments the  colour of the platina
         became brilliant by a white heat,  but acquired a  dull
         grey colour after  it had  been heated for a long time.
         They obferved alfo, that its weight was conftantly in-
         creafed; which undoubtedly arofe from the calcination
         of the iron it contained.  Dr. Lewis, after various at-
         tempts  to  fufe platina,  found  himfelf unable  to fuc-
         ceed  even in a fire which  vitrified bits of glafs-houfe
         pots and  Heffian  crucibles.   Meflrs  Macquer  and
         Beaume firft melted this refractory metal with a large
         burning-glafs,  22 inches diameter and  28 inches fo-
         cus.  The power of this Speculum was almoft incre-
         dible, and Sar  exceeded what is related of the lens of
         Tfchirnhaufen or the mirror of Villette.  lis general
  1333
Platina the
moft infu-
fible fub-
ftance in
   1334
Firft melt-
ed by a
burning
mirror.
 effects  are related  under the "articl BuRNixc-Glafs.  Platina.
 And as platina refitted  this intenfe heat more than fix **"   y/   '
 times as long as the moft unfuiible  Subftances Sormerly
 known, it  appears  to  require a fire as  many  times   x ,
 ftronger to melt it.   It  has been Sound, however,  ca- May be vi-
 pable not only oS  SuSion but of vitrification by the e- trifled by
 lectric fire ;  and that it may alfo be melted by fire  ex- electric
 cited by dephlogifticated air:  but M. de Lifle  was  the fire-
 firft who was able  to melt it with the  heat of  a  com-   1336
 mon forge when  expofed to the blaft of a double bel- Its precipi-
 lows in a double crucible.   Thus iis real fpecific gra- *ate fufible
 vity began firft to be  known.   It muft be  obferved, in a com"
 however, that this fufion was not performed on  com- mon or^*'
 mon platina, bat on fuch as had been diffolved in aqua-
 regia  and  precipitated by means  of fal  ammoniac.
 M. Morveau repeated the  experiment,  and from  72
 grains  of  platina  obtained  a  regulus  weighing  504 ;
 which Seemed to have undergone a  very imperfect  fu-
 fion ; for it did not adhere to the crucible or take its
 form, but feemed to be merely platina revived.  Its fpe-
 cific gravity was alfo found to be no  more than  10.045 ;
 but it was nearly as malleable as filver ;  and when it
 had been  fufficiently  hammered, its  fpecific  gravity
 was augmented  to  no lefs than 20.170, which  is more  1337
 than that of  gold  itfelf.  M. Morveau found  that  heThispreci-
 could melt the precipitate with different fluxes, fuch pitate, or
 as a mixture  of white glafs, borax,  and  charcoal, and even croa*
 a  mixture  of white glafs  and neutral arfenical  fait: p.3;tlJ?a' v~
 and that the regulus thus obtained was more complete- affiftance
 ly fufed, but  was not malleable, and obeyed the mag- 0f fluxes.
 net; but the  regulus  obtained  without addition  did
 not fhow this mark of containing iron.   He alfo found,
 that by  means of  the  abovementioned flux  of white
 glafs, borax, and  charcoal, he could melt crude pla-
 tina.   Since  that  lime the fufion of platina has been
 accompliflied by various  chemifts,  and  with different
 fluxes;  and in proportion to the degree  of purity  to
 which  the metal has been reduced,  its fpecific gravity
 has  alfo increafed;  fo that  it is now  fettled  at 23,
 that of fine gold being 19.                                 ,
   Though  Dr  Lewis could not accomplifli the fufion Alloyed by
of platina by the methods  he attempted,  he was ne-Dr Lewis
verthelefs able to alloy  it with other  metals.  Equal with other
parts of gold and platina  may  be melted together  by metals.
a violent fire, and the  mixed metal formed  into  an
ingot by pouring it into a mould.  It is whitifh, hard,
and  may be broken  by a violent  blow;  but when
carefully annealed, is capable of confiderable extenfion
under the hammer.  Four  parts of  gold with one of w^VoU.
platina form a compound much more fufible  than the
former,  and  likewife more  malleable; So that it may
be  extended  into  very thin plates  without being bro-
ken or  even  Split  at  the edges.  Dr  Lewis remarks
alSo, that though in this  caSe it be alloyed with Such a
quantity oS white  metal, it  nevertheless  appears  no
paler than  guineas iffually are, which contain  only
one-twelSth oS Silver.
   Equal parts  of  filver and  platina melted together with fil-
with a violent  fire, form a much  harder and darker-ver.
coloured mafs than filver, which has alSo a large grain,
 though  it  preServes  Some  ductility.  Seven  parts of"
filver with one oS platina form a compound much more
refembling  filver  than  the other; but ftill coarSer-
grained  and leSs white.   From the experiments made
on filver, however, it appears that no perfect union is
                      A a 2                formed 
iS8
CHEMI
 riatina.  formed bctwixt the two;  for after the  mixture has
*   *   ' been kept in fulion for a confiderable time, moft of the
         platina Separates and  falls to the bottom.   Lewis- ob-
         lrrvcd tut filver  melted  with  platina was thrown up
         w  h an explofion againft the fides of the crucible.
            Silver did not appear to be in any degree meliorated
         by its union with this  metal, exc< p ing by the fuperior
   i.«4r   hardnefs  communicated to  it;  but copper feemed  to
 topper   be confiderably improved.   A large proportion of pla-
 c-miu'.er-   lina^ j., i^.j^ as lwo thirds or equal pans,  produced  an
 rr.'.l-edby  hard, brittle, and coarfc-grained compound; but when
 union with a fnalb-r quantity of platina  is added,  as from I to T'-,
 platina.    or even lefs,  a golden-coloured  copper is produced,
          very malleable,  harder,  fufceptible of a  finer  polifli,
          finooiher-grained,  and much lefs fubject  to calcina-
   I34l   tion and rult than  pure copper.
 f.  esmoft    Of all metallic matters, however,  zinc moft  readily
 readily    unites with platina, and is molt effectually diffolved  by
 v.;e-h/.'.nc; fufion.  \\ hen the proportion of platina is confider-
          able,  the  metal is of  a bluifli colour,  the grain clofer,
          without t ami thing or  changing colour in the air, and
          they  have not even the  malleability of  the ftmi-
   1343   metal.
 And with     Platina  unites readily with the compound  metals,
 the com-   Drafs formed of copper and  zinc,  and  bronze  made of
 pi.uud me- COppcr an(j tin_   jn  jjle ]alter it was remarkable, that
           the compound metal  took  up more  platina than both
           its ingredients  Separately  can do.   This  compound
           was bard and capable of receiving a fine  polilh, but is
    1,44    fubject: to tarniih.
 The"com-.   Equal  parts of  brafs and  platina formed a compound
 pound of   very hard, brittle,  capable  of receiving  a fine  polilh,
 brafs and   anj  not fubject to tarnilh.   It is poflible therefore that
 platina a   .^ mjglu l)C ufe(j  t0 advantage as a material for fpecu-
 [«£?f™a"1-'msi a11 ™atcrltlls  for which,  hitherto  difcovered,
 fpcculdms.  have the great inconvenience of tarnilhing in the  air,
     „.,   and that  very quickly.
 Can fcarce    Ph.tina amalgamates with mercury, but  witb much
 be united  greater difficulty  than go'd, which  will alSo Separate
 wit!-, mer-  t!ie quickfilver after  it has been united with  the pla-
 carY'     tini.  The amalgamation of platina does  not  Succeed
           but by very long trituration of the metals  with water,
    1346   as for inftance a  week ;  but if the  trituration be pcr-
 M-'-"T   formed  with  a  mixed  metal compofed  of gold   and
 leaves Pla-   lalina>  the mercury  feizes the gold, and leaves  the
 unto with  Phtin* untouched.  Dr  Lewis propofes this as a me-
   ,U.     thod of  feparating gold from platina;  and it is  ihat
           ufed in Peru, where gold  and platina  are fometimes
           naturally mixed in the ore ; but we do not know whe-
     *W   ther this Separation be quite complete.
 Maybe     Mr Morveau fiicceeded in uniting iron with  platina,
 ""•"if r    though  Dr Lewis could  not accomplifh  this.  The
 cTanJ°cfft latter Succeeded, however, in uniting it  with caft iron.
 iron;     The compound  was much  harder and leSs fubject to
           nut  than pure iron.  It   was alSo   fufceptible of a
     IJ48   much finer poliih.
 And with    Platina  may   be   alloyed  with  tin,  lead,  or  bil-
 tin.lead.or math,  but without any advantage.   To  lead and tin
  r:,:mith.   jt ^ives the property of affuming blue, vmlet, or  pur-
           ple" colours, by being expofed to the atmofphere.
             Dr Lewis could not fucceed ia uniting platina with
   S    T   R    Y.                           Pra&ice-

arfenic ; but M. Schcft'u^affirms,  that  if only  one Platma. ,
twentieth of arfenic be added  to platina when red hot   ,,_,9
in a  crucible,  the two  fubftances will  be  perfectly ]\; ,y be
fufed  and united into  a brittle  grey mafs.  This cxpe- nu-lud ; y
ri'ment  did  not fucceed  with. Mr Margra.f; for he, means d
having  expofed to a violent fire during an  hour a  mix- arfenic.
mrc of  an  ounce of  plaiina with a hilible. glafs,  com-
poScd oS eight ounces  of minium,  two ounces of flints,
and one ounce of  white  arfenic,  obtained a regulus of
platina  well united and  fufed,  weighing  an  ounce
and  32 grains;  the  furface  of  which  was Smooth,
white,  and lhining, and  the internal  parts  grey ; but
which  nevertheless appeared  fufficiently  white when
filed. The experiment Succeeded imperfectly  alfo in the
hands  of Dr Lewis; but  M. Fourcroy  informs  us,
that  " it has Since been repeated, and  that platina is
in fact  very fufible  with  arfenic, but ihat  it remains
brittle.  In  proportion as  the arfenic is driven off by
 the continuance of the heat,  the metal becomes  more
 ductile; and by  this  procefs it is that M. Achard and
 M. de  Min-veau fiicceeded in  making crucibles of pla-
 tina by  melting it a fecond  lime in moulds." (a)         1350
    M. Fourcroy feems  to  deny  that  platina can be Fourcroy
 united  with  mercury, contrary to what  is mentioned demei that
 above.  "  F.acimi ^i'ays  he)  does not unite with mer- j?  ^ited"
 cury, though triturated   for  feveral   hours  with that Jithmer_
• metallic fluid.   It is  likewife  known, that platina re- cury#
 fifts the mercury  ufed in America to feparate the gold.
 Many intermediums, fuch as water, ufed by Lewis and
 Beaume, and aqua-regia by Schcffer, have not been
 found to facilitate the union of thefe two metals.   In
 this  refpect platina  fcems  to refemble.iron, to whofe
 colour and  hardnefs it  likewife in fome meafure ap-
 proaches."  This laft fentence, however, feems very
 little, to agree with what he himfelf had before told us   ^i
 of M. Macquer's experiment of melting platina. " The Inconfifl-
 meutd portions (fays he) were  of  a white  brilliant ent in  his
 colour, in the form  of  a  button; they  could be cut to ?cc?unj
 pieces with a knife." This furely was a very fmall ap- ,ts |»ard_
 proach to tiit hardnefs of  iron;  and  gives  us an idea
 rather  of tft«t confiftence of tin or lead.   " One  of
 thefe muffes was flattened on the anvil,  and converted
 into a  thin plate without cracking or breaking, but it
 became  hard  under the hammer."   In  another expe-
 riment indeed  rhe  button of platina was brittle,  and
 fufficiently  hard to  make deep traces in gel J, copper,
 and-cven iron ;  but this was obtained from precipita-
 ted platina  urged for 35 minutes by  a ftrong blaft  fur-   J35*
  nace.   In an experiment of this kind M. Beaume even rrecipita-
 fucceeded in melting the precipitate along with-  cer- ^itr]fod"bl
  tain fluxes, into a vitriform fubftance by tv/o different M.Bcaumt
 proceffes.   The  precipitate  of  platina, mixed with
* calcined borax, and  a very fufible white  glafs, was ex-
  pofed, for 36  hours, in  the  hotteft  part of a potter's
  furnace;  and afforded   a  greenifh glafs, inclining to
  yellow, without globules of reduced metal.  This glafs,
  treated a fecond time with  cream of tartar,  gypfum,
  and vegetable alkali, was  completely melted, and  ex-
  hibited globules of  platina difperfed through its fub-
  ftance.  M. Beaume feparated them  by  wafhing, and
  found them ductile.  The fame chemift afterwards, to-
                                               gether
(a) For a particular account of this procefs  fee before n° 587. 
Practice.
CHEMISTRY.
not to be
perfect.
 Platina.   gether with M.  Macquer,  expofed precipitate of pla-
v"~v---' tina to the fame burning mirror with which they had
          fufed the metal :  the precipitate exhaled a very  thick
          and luminous fume, with a ftrong fmell of aqua-regia :
          it loft its  red colour, refumed that of platina,  and  melt-
          ed into a perfect brilliant button, which was found to
          be an opaque vitreous fubftance, of an hyacinthine  co-
          lour at its furface,  and blackifh within  ; and may be
          confidered as a true glafs of platina.   It may however
          be obferved, that the faline  matters with which it was
          impregnated  contributed  doubtlefs to  its   vitrificati-
          on.
             "'The orange-coloured precipitate obtained by  pour-
          ing a folution of fal ammoniac into a  folution of pla-
          tina, appears to be a faline fubftance entirely foluble
   *353    'n water-  This precipitate has a valuable  property,
Precipitate difcovered by M. de l'ifle, viz. that it is fufible without
by fal am-  addition in a good furnace or common forge-heat. The
momacfu-  platina nltlted by this procefs is a brilliant, denSe, and
jj  e in a   cloSe-grained button ; but it is not  malleable unlefs it
foree heat. ^as  been expoSed to a very  ftrong heat.   Macquer
          thinks that  this fufion,  like that of  the  grains of
   1354    platina alone,  expofed to the action of a violent fire,
This fufion confifts only in the  agglutination of the foftened  par-
fuppofedby tides ; which being exceedingly more divided and  mi-
Mactmer   nute t]ian tbe grains of  platina, adhere to  and  touch
          each other in a greater number  of points  than  the
          grains ;  and in that manner render the  texture of  the
          metal much  more denfe, though  no true fufion  may
          have  taken  place.  It feems, however,  that if platina
          in grains be capable of fufion by the burning glafs, and
          of becoming confiderably  ductilr, the  precipitate  of
          this  metal, formed  by fal ammoniac may likewife be
          fufed on  account of its  extreme divifion ; and that its
          not being as ductile as  the button of platina fufed by
          the folar  heat, may  perhaps depend on its retaining  a
          part  of the matter it carried  down with it  in precipi-
          tation, of which it may be  poflible to deprive  it by
          fire."
            It  being fo extremely difficult to  bring platina itfelf
          into fufion, one of the  firft attempts to  purify it was
platina by  by cupellation with lead.  Thus the bafer metals would
supell-ation be fcorified ; and,  running through the crucible  along
          with the lead, leave the platina in as great  purity  as
          though it had  been melted  by itfelf.  This  operation,
          however,  was  found almoft equally difficult with  the
          fufion of  the metal by itfelf.  Lewis failed in the ex-
          periment, though he applied the moft violent  heat  of
          the ordinary cupelling funnces.  The vitrification and
          abforption of the  lead  indeed teiok place  as ufual ;
          but in a ihort time the platina became fixed, and  could
          not by any means be rendered fluid.  Meflrs Macquer
          and Beaume fiicceeded by expofing an  ounce of pla-
          tina with two ounces of  lead in the hotteft  part  of  a
          porcelain furnace,  where the  fire  is continued for 50
          hours without intermiffion.   At the end of the opera-
          tion the platina was  flattened  in the cupel ;  its upper
          furface was dull  and rough, and eafily feparated  ;  but
          its under furface was brilliant, and it was found  eafily
          to extend under the  hammer ;  and  on every chemical
          trial was found to be perfectly  pure, without  any  mix-
          ture  of lead.   M.  de IViurvc an likewife  fiicceeded  in
          cupelling a mixture of one drachm  of platina and two
          drachms of lead in M. Macquer's wind-furnace.  The
          cperacion lafted eleven or twelve  hours, and a button
   1355
Attempts
to purify
of platina was obtained which did not adhere to the
cupel,  was uniform,  though rather rough,  and of a
colour refembling tin.' It weighed exactly one drachm,
and was  not at ail acted upon by the magnet.   Thus
it appears that platina may be  obtained in  plates  or la-
mi nas, which may be  forged, and confequently  may
be employed in making very valuable utenlils ; and this
the more efpecially  as Mr Beaume has obferved  that
different  pieces of it may be welded and  forged  like
iron.   After having heated  two pieces of pure cupel-
led platina to whitenefs, he  placed  them one upon the
other,  and ftriking them brifky with a hammer,  found
that they united together as quickly and firmly as  two
pieces of iron would have done.                         j,,g
  The great fpecific gravity of platina has rendered it ofthe pof-
a very definable  matter for fuch as with to adulterate fibility of
the precious metal, and can procure the  platina eafily. adultera-
This,  however, can only be done  in South America, tin£ S°ld.
where platina is met with in plenty.  In  Europe the Wlt PlaU"
fcarcity of platina renders it  a  more valuable object
than even the gold itfelf.  Fears of this fraud,  how-
ever,  have undoubtedly given occafion to the prohibi-
tion oS exporting it.  There  are great differences a-
mong chemifts concerning the quantity of platina that
can be mixed with gold without  deftroying the colour
of the latter.   Dr  Lewis, as  has already been obfer-
ved, informs  us, that  four parts of platina  may be
mixed with one  of gold, and  yet  the mixture be no-
paler  than that for guineas ; while Fourcroy afferts,
that "it greatly alters the colour  ofthe metal,  unlefs
its quantity be very  fmall :  thus, for example, a 47th
part of platina, and all the proportions below that, do
not greatly affect the colour of the  gold."  But  whe-
ther this be the cafe or not, chemiflry has afforded va-
rious  ways  of feparating even the fmalleft propor-
tion of platina from gold ; fo  that there  is now no
reafon to prohibit the  importation of  it to  Europe,
more  than that of any other metal with which gold
can be alloyed.  The following are the  methods by ,, y?5?  ».
  1 • v.   1    1  •        1     °n    ,.,   ,.r      ,J Methods of
which the platina may be  moft readily  difcovered : detecting
I. By amalgamating the fufpected metal with  mercury, this fraud
and grinding  the mixture for  a confiderable time with if it fhoulds
water; by which the platina will be leSt, and the gold bepra&i-
remain united with  the quickfilver.  2. By diffolving fed*
a little of it in aqua-regia,  and precipitating with al-
kaline Salt ;  the  remaining liquor, in caSe the  metal
has been adulterated with platina, will be So yellow,
that it is SuppoSed  a mixture oS one thouSandth  part
would  thus  be found  out.  3. By  precipitation  with
Sal ammoniac, which  throws down the platina but not
the gold.   If mineral alkali be uSed, the  gold will be
precipitated,  but not the platina, unleSs the precipitant
is in  very large  quantity.  4. By  precipitation  with
green vitriol,  which throws down the gold, and leaves
the platina united with the menftruum.                  I5,g-
   All theSe methods,  however,  are not only 2t;er.ded Piatina
with a confiderable deal of trouble, but  in fome  caf.s, moft eafily
for inftance  in fufpected coin, it might not be eligible difcover-
to ufe rhem.   The hydroftatic balance alone affords a alle hJ lts:'
certain method of difcoverinp- mixtures of  met fts with- lrcat  P^C1"*
    1    •     t           r  1  ■          ~,        nc gravity.
out hurting the  texture of their parts.   The  great
fpecific gravity  of  platina would very readily difcover
it if mixed with gold in any  moderate quantity ; and
even in the fmalleft, the gravity of the  mafs could ne-
ver be lefs than that ofthe pureft gold :  which  cir-
                                         cumfta.   n 
190
Manga nef- aimt incr ahi;v
  i;;9
S w l\-mi-
ll ict al af-
f>.nlcd by
niai'.ganefe.

   1360
Properties
• f the com-
mon man-
fancfe trea-
ted with
vitriolic
   1361
Entirely
diffolved
by phlogi-
ftic*: c J vi-
triolic a-
                            CHEMI

                as gold is never  worked whhou:
h>y, wmld be fufficient  to create  a juft lufpicioti ;  ».-
tcr  wh -> fome  of the methods  jlreaelv mentioned
might be tried.  I; is poflible, however, that the hard-
nefs .md ductility of platina might render it more pro-
per f >r a'.ioying gold than even copper or liher, ufually
nude ufe of for this purpofe.

              j 15.  Of Mangaxf.se.

   This fubftance  is now difcovered to afford a femi-
metal diiferent from all others, and likewife  to poffefs
fomc  oilier properties  of  a  very  fingular kind.  Mr
Scheele has inveftigated its  nature  with the utmoft
care ;  and the refult of his inquiries are as follows :
   1.  Two drachms of  levigated  manganefe, digefted
 for feveral days in  a diluted  vitriolic acid, did not ap-
 pear  to be diffolved or diminiflied in  quantity; never-
 theless a  yellowifli white precipitate  was procured by
 Saturating theacid with fixed alkali.   The remaining
 manganefe was not acted upon by more of  the  fame
 acid,  but the  addition of another half ounee nearly
 deftroyed the acidity of the  menftruum when boiled
 upon it.       ,
   2. With  concentrated  vitriolic acid  an  ounce  of
 manganefe was reduced to a  mafs  like honey, and then
 expofed to ihe lire  in a reiort till it became  red-hot.
 Some vitriolic acid came over into the  receiver ; and
 after  breaking the  retort,  a  mafs was found  in it
 weighing 12V  drachms, hard and  white in the in-
 fide,  but  red on  the outfide.  A great part of it dif-
 folved iu diftilled water, on the affulion of  which  at
 firft  it  became very hot.  The refiduum after edulco-
 ration weighed a drachm and an half,  and  was of a
 grey colour.  Being calcined in  a crucible  with  con-
 centrated vitriolic acid  till  no more  vapours arofe, it
 was all  diffolved  by water excepting  one  drachm ;
 which being again calcined  with  the fame acid, an  in-
 Soluble refiduum  oS a  white colour, and weighing on-
 ly half a drachm,  remained.  This  white refiduum
 effervefced with  borax, and melted into a transparent
 brown glafs ;  it likewife effervefced with fixed alkali,
 changing into a brown mafs,  which yielded an hepatic
 fmell with acids, and  became at the fame  time  gela-
 tinous.  The folution obtained by calcination was eva-
 porated and  fet to  cryftallize.   A few fmall cryftals
 of  felenite were firft  depofited,  and afterwards fome
 very fine  large cryftals  of an  oblique parallelopiped
 form, whofe number increafed  as  long as  there was
 any liquid left.   They tailed like  Epfom fait, and  Mr
 Weftfcld fuppofes them to be alum ; but according to
  Mr Scheele, they have no other refemblancc to alum
  than that they contain the vitriolic acid.
    2.  By  phlogifticated  vitriolic acid  the  manganefe
  was entirely  diffolved.   To procure this acid in puri-
  ty,  Mr Scheele dipped Some rags in a Solution of al-
  ka'li  of tartar,   and after  Saturating  them  with  the
  fumes of burning brimftone, put them  into a  retort,
  pouring  on them fome diffolved acid of tartar, luting
  on a receiver which contained levigated manganefe  and
  w iter.   After a  warm digeftion of only one day,  the
  1 .
  and a  little fine  p
  ccous earth, fell to the bottom.
    4.  Two drachms of levigated manganefe, digefted
W'lter.  nilcr * wami  ui^juxu  ~« -..-, --«.----j,  —
liquid of the receiver had become as clear as water,
and a little  fine powder, confifting principally of fili-
   S   T    R   Y.                            Pra<5tice.
for feveral  days with  an ounce of pure  colourlefs .icid Manganefe
of nitre, did  not  appear  to have deprived  i!ic  men- v"
ftruum of  its  acic.uy, 01  to have been affected by it
in any dcgr.e.   The  liquor being diftilled off, and the
product of  ihe diftillation poured back on  the  refi-
duum, a fmall q.iantity of it was  diffolved.   By  a
third  diftillation, aud  pouring  back  the liquor on ihe
refiduum, a complete folution was effected ; and  this
quantity  of acid appeared capable  of diffolving  nine
drachms of the powder.                                tj6i
   5.  The  folution of manganefe  thus faturatcd,  was precipitate
filtered and divided into two equal portions.  Into one and cryf-
of thefe  fome drops of vitriolic  acid were poured, by talsobtain-
which a  fine white powder was thrown down, which, [£ fl^ti.
however, did not  fettle to the bottom for fome hours. on*
It was foluble neither in  boiling water nor in  acids.
The  limpid  folution, by evaporation,  yielded  fome
fmall cryftals of felenite »r gypfum.
   6.  From the other  half of this folution,  after  eva-
poration by a gentle  heat, about ten  grains of  fmall
lhining  cryftals of a bitter tafte were obtained.  On
pouring  fome drops of  vitriolic  acid  into the folution
infpiffated  by gentle heat,  no  precipitation, except-
ing of a little  felenite, enfued ; but as foon as it  was
infpiffated  to  the confiftence of honey, fome fine aci-
cular cryftals, verging towards the  fame centre, began
to form, but grew foft, and deliquefced in  a few  days
after.                                                 1363
   7.  Phlogifticated  nitrous  acid diflblves  manganefe Manganefe
as readily  as the  phlogifticated  vitriolic.  A little le- diffolved
vieated  maneaneSe mixed with Some water  was put in- b7 Phl°g»-
   b   .     &  •          i-i      ,,^1          _  ticated m-
 to a  large receiver,  to which a tubulated  retort was troug acid<
 luted.   Some  ounces of common  nitrous  acid  were
put  into the  retort,  to which fome iron-filings  were
 added, taking care always to clofe the orifice with a
 glaSs  flopple.   The  phlogifticated  nitrous  acid  thus
 paffed over into the receiver, and  diflblved the mau-
 ganeSe in a Sew hours : the Solution was as limpid  a«
 water, excepting only a little  fine filiceous earth.   An-
 other white  precipitate,  Similar  to that produced  by
 adding  vitriolic acid to  the  Solution  in pure nitrous
 acid now  began to fall;  but  in other refpects this  fo-
 lution agreed with the former.                          I304
   8.  An ounce of purified  muriatic  acid  was  poured  Effects of
 upon half an ounce of levigated manganefe; which,  it on fpirit
 after ftanding about an hour,  affumed a  dark brown of fait.
 colour.   A portion  of it was  digefted  with heat in
 an open glafs veffel,  and  fmelled like warm aqua-regia.
 In  a quarter of  an  hour the fmell was gone, and the
  folution became clear and colourlefs.   The reft of the
  brown folution being digefted, to fee whether the mu-
  riatic acid would be faturated with manganefe,  an ef-
  fervefcence enfued,  with a ftrong fmell of aqua-regia,
  which lafted till next day, when the folution was found    j.g.
  to  be faturatcd.   Another  ounce  of acid was poured Entirely
  upon the  refiduum, which was followed  by the fame difmlved
  phenomenon, and the manganefe was entirely diflblved, by thii
  a fmall quantity of filiceous  earth  only   remaining. acid-
  The folution, which was yellow,  being now divided
  into two  portions,  fomc drops of vitriolic acid were
  poured into  the one, by  which  it  inftantly  became
  white, and a fine powder, infoluble in water,  was pre-
  cipitated.  Some fmall  cryftals of felenite  were form-
  ed  by evaporation,  and the refiduum  exhibited  the
  fame phenomenon with  ihofc abovementioned with ni-
                                                trous 
Pra<5tice.
C   H   E    M
   1367
Or in phof-
phoric acid.
Manganefe trous acid,  by evaporating  the other half, fome fmall
*   v    ' fhining angular cryftals were obtained,  Similar to thofe
   1366   procured by means ofthe nitrous acid.
Scarce folu-   9. Very little manganefe was diflblved by fluor acid,
ble in fluor even after feveral days digeftion.  A great quantity
acid>      was required to form a faturated folution.   It had ve-
          ry little tafte, and gave a fmall quantity of precipitate
          with fixed alkali.   But if  a  neutral fait, compofed of
          fluor acid and fal  ammoniac,  be added, a double de-
          compofition takes place,  and the manganefe is precipi-
          tated along with the fluor acid.
             ro.  A drachm of phofphoric acid, digefted with as
          much  powdered  manganefe,  diflblved but litle  of it;
          and, though evaporated to  drynefs, the refiduum tailed
          very acid;  but by adding  more manganefe the acid
          was at  laft faturated.  On  adding  microcofmic  fait to
          a folution of  manganefe, a decompofition  takes place
          fimilar to  that effected  by the combination  of fluor
          acid and volatile alkali.
             11.  Pure acid of tartar  diflblved  manganefe  partly
          in the cold, and  more  effectually  by means of heat.
cid of tar-  The whole, however, could  not  be diflblved,  though
***•       the acid was at laft faturated by adding a great quantity
          of the  mineral.  On adding a folution of foluble  tartar,
          a double decompofition took place.
w^hd'fn-    I2'  Lit£le was diffolved  by diftilled vinegar,  though
cultyin the boiled  on  manganefe ; but after diftilling  fpirit of ver-
acetous.   digris  feveral times upon it, the  acid  at laft became
          faturated.  The  folution,  evaporated to drynefs, left  a
          deliquefcent mafs.   Little or  none of  the  remaining
          manganefe was diffolved  by  concentrated  vinegar,
          though repeatedly diftilled  upon it.
             13.  With acid of lemons  the  whole was diffolved
          with effervefcence,  excepting only fome white  earth.
             14.  Water impregnated with fixed air likewife dif-
          folved manganefe, but parted  with  it on the addi-
          tion of alkali, or  fpontaneoufly  by expofure  to the
          air.
             From thefe experiments Mr Scheele concludes, that
   1368
Partly fo-
luble in a
   1370
 Entirely
 diffolved
 by acid of
 lemons ,-
   1371
 Andby wa-
 ter impreg-
 nated with
 fixed air.   manganefe has a ftrong elective attraction for all phlo-
   137a    giftic  fubftances;   and  that  this attraction becomes
 Hasaftrong ftronger, if there  be prefent  a menftruum which can
           unite with  the phlogifticated  manganefe.   Thus it at-
           tracts phlogifton more powerfully  than even the nitrous
           acid iifelf in the  moift way.   By faturation  with
           phlogifton, manganefe  has the property of lofing its
           black  colour,  and  afluming  a white one, which is
           unufual,  the phlogifton generally  communicating  a
           black or dark colour to the Subftances with which it was
           united.
             That manganefe naturally contains Some phlogifton,
fome phlo- though  but in Small  quantity, appears  Srom evapora-
gifton na-  ting a Solution  oS it in vitriolic acid  to dryneSs,  and
          then diftilling the mats in a glafs retort in an open fire.
          When the  retort begins to melt,  the acid parts fly off
          from the manganeSe in a Sulphureous ftate, leaving the
          former of its natural  black colour.  By diftilling  the
          mafs remaining after  evaporation  of the nitrous folu-
          tion, a  green  volatile nitrous acid  remains, and  the
          black calx of manganefe  remains  as before.  A folu-
          tion of this mineral iu vitriolic or nitrous acid, precipi-
infolublein tatecj by ^xe(j alkali, retains its colour;  but when  cal-
pure acids  cjnej jn tile 0peu  fjre> agajn becomes black.
 t  nl"2'-    ^ lofing its phlogifton, mangyuefe  becomes info-
llon.       \nds\c in pure acids; and therefore the refiduum of the
attraction
for phlogi-
fton.
   1373
Becomes
white by
faturation
with phlo-
gifton .
   1374
Contains
turally.
   1375
Becomes
I    S   T   R    Y.                                  191
 abovementioned  diftillations  cannot be diffolved by Manganefe
 adding more of the vitriolic or nitrous acids: but if that ,"~""v
 which has come  over into the receiver be poured back
 into the retort, a fidution will again take place by rea-
 fon ofthe manganefe reaffuming the phlogifton it had
 parted with to the acid.                                 1376
    On this  principle our  author explains the reaSon oS Partial fo-
 the partial Solutions of this mineral abovementioned. lutions of
 Part of it is diflblved, for inftance, in the vitriolic acid, manganefe
 while the remainder is found infoluble.  This happens en^thhT
 (fays he), " becaufe the undiflblved portion has parted principle.
 with  the  little phlogifton it naturally poffeffed to that
 portion of manganefe  which is taken up by the vitri-
 olic acid  during  the firft digeftion; for without that
 principle  it is infoluble."
    Manganefe attracts phlogifton more ftrongly  when
 combined  with fome  acid than by  itfelf, as appears
 from the  following experiments.                        j*^
    1.  Levigated manganefe, digefted or boiled with  a Strong af-
 folution of fugar,  honey, gum arabic, hartfliorn,  jelly, traction of
 &c. remains unchanged ; but on mixing the pounded rnanganefe
 mineral with diluted vitriolic, or pure nitrous acid, and T.  e" co!n"
 then  adding fome of thefe fubftances,  the whole is dif- acidsfo/
 folved, the black colour vanifhes by degrees, and the phlogifton.
 Solution becomes as limpid as water.   So ftrong is the
 attraction oS manganeSe for phlogifton in thefe circum-
 ftances, that metals, the noble ones  not excepted, ren-   I378
 der it foluble  in  thefe acids in  a limpid  form.   Con-Why the
 centrated vitriolic  acid,  indeed, diffolves manganefe concentra-
 entirely without  any phlogifton.  " It would be diffi- ted acid of
 cult  (fays Mr Scheele)  to comprehend whence the ^fno1 dlf"
 phlogifton in  this cafe  fhould  come,  if we were not ov"man~
 certain that feveral fubftances, which  have a  great without adk
 attraction for phlogifton, can attract it in a red heat, dition.
 Quickfilver and filver, when diffolved in the pureft ni-
 trous acid, really lofe their phlogifton, which is a con-
 stituent part of thefe metals.   This appears from the
 red vapours in which  the  acid arifes;  and  the dif-
 folved metallic  earth cannot be again, reduced  to its
 metallic  form, till  it has acquired the loft phlogifton,
 which is effected either by precipitation with complete
 metals or by heat  alone.  Thus manganefe can attract
 the quantity of phlogifton neceffary for its folution by
 means of concentrated vitriolic  acid  from heat.   It is
 not probable  that  the  concentrated  acid undergoes  a
 decompofition in  this  degree of fire; for if you fatu-
 rate half an  ounce of this acid with alkali of tartar,
 and afterwards calcine in a retort, with a receiver ap-
 plied, an ounce and a half of  powdered  manganefe,
 with an equal quantity of the fame vitriolic acid, then
 diffolve the calcined mafs in diftilled water,  anel like-
 wife wafh well the receiver, which contains fome  drops
 of vitriolic acid, which are alfo to be added to the fo-
 lution, and laftly, add the fame quantity of alkali,
 there will be no mark of fuperabundant acid or alkali.
 Thence  it  may  be concluded,  that the phlogifton in
 the vitriolic acid, if there really exifts any in it, con-
 tributes nothing  to the folution.  But the manganefe
 precipitated by alkali, contains  a confiderable quantity
 of it ; in confequence  of which it  is  afterwards en-
 tirely foluble in acids without any addition.
    " The  effects of volatile fulphureous acid on nunga- Why the
 nefe,  clearly prove what has been aifertedv  The mar- volatile ful-
 ganefe attracts the phlogifton  contained in this ..cid, phureous
 which is  the  caufe of  its great  volatility,  zud winch a<-iddif-
                                             renders.foIv£ai** 
I 92
 M ngir.'
CHEMISTRY.
Pra&ice.
  1.180
rfeiuof
plumed.
         renters  ihe  former folnl-le  in the new  p. re vitriolic
         ac:d.   It (his Solution  be mixed with concentrated  vi-
         triolic acid and diftilled,  no volatile fulphureous acid
         is obtained;  audit it be precipitated  by  means of fix-
         el  vegetable alkali,  vitriolated  tarnr'is obtained ;
         which proves that manganefe has a fironger  attraction
         than  vitriolic acid for phlogifton in the moift  way.
            "  The effects of nitrous acid on this fubftance  are
     iacid fimilar to thofe of vitriolic acid.   Could Spirit oS nitre
on mange- Sultain as grc.n a  degree  of  heat as the concentrated
nefect-   vitriolic  acid, it would alSo entirely diflblve  the man-
         ganeSe by  means of ihe phlogifton attracted by heat;
         but  as this  is not the cafe, it is neceffary to  add phlo-
         gifton in  the manner abovementioned.   The manga-
         neSe  dccompoSes  phlogilfctcd  nitrous  acid, for  the
         fame reafon  ihat ii does the volatile fulphureous acid ;
         and that the  phlogifton of this  acid really  combines
         with   manganefe, is manifeft from this,  that the af-
         fufion of vegetable acid produces no fmell of aquafortis
         by difplacing the phlogifticated acid of  nitre.  By di-
         ftillation with pure vitriolic acid alfo, the  nitrous  acid
         i.- expelled,  not  in a  Smoking ftate, and  of a yellow
         colour,  but pure and colourlefs.
            "  la the teilntion oS manganeSe by means of gum ara-
         bic or fugar, a very coHfiderable  efferveScence  takes
          place, owing to the extrication, or probably  rather the
          production,  of fixed  air from the mixture ;  but with
          phlogifticated acid of nitre no fuch phenomenon takes
          place, becaufe  the manganefe is combined with pure
          phlogifton ;  and if this fhould be again Separated, there
          is no caufe for the production of fixed air.  This  mi-
          neral is alfo diflblved  without effervefcence, by uniting
          it with  nitrous acid and  metals, arfenic or oil of  tur-
          pentine."
            As muriatic acid diflblves manganefe without addi-
 ofphlogif- tion, Mr Scheele  is of  opinion  that this  proves  the
 ton in the  cxiftcnce  of phlogifton in that  acid, as  has already
 muriatic   \yCcll taken   notice  of.  The manganefe digefted in
 aci  prove  ^c  co|j  ^.^  fpjrjt  0f  fa\t ap;umcS  a  dark  brown
          colour;  for  it.is a property of this fubftance  th: t it
          cannot  be  thdblved   into  a  colourlefs  liquor without
          phlogifton,  but  has always a red or blue colour;  but
          with fpirit of fait the  folution is more brown than  red,
          011 account of the fine particles of the manganefe float-
          ing in the liquid.  Here the mineral adheres  but loofely
  ,.Si    to the aeid, fo that it  may be precipitated by water.
 r.xplana-    The  effects of  acid  of tartar  and acid  of lemons
 tion ofthe upon manganefe are likewife explained on the principle
 action of  a]rcady  laid down, viz. the extreme  attraction  this
 acid of tir- {nbitinec has ftir  phlogifton.  Thus it  attracts part of
          that  naturally contained in  thefe acids, dccompofing
          one  part of them, and  being diffolved  by the  other.
          Thisdeftmction  of the  acid is fimilar to that of the
          fugar, gum  arable,  &c.  which render it  foluble in
          nitrous  acid ; for if  a proper  quantity of thefe are
          added, the manganeSe will be diflblved, without a  poS-
          libilkyid recovering the fmalleft particle of the vege-
          table fubftance emplewed ; and if  the folution be frnw-
          ly evaporated and calcined,  there will  not remain the
          fmalleft mark of buroed  Sugar or gum.  During  this
          decompofition,  a pungent vapour ariScs, which, being
          collected,  appears to be  true vinegar.  It is obtained
          in its pureft  ftate from diluted vitriolic acid,  fugar, and
         manganefe.
            Fluor acid diffolves but very little manganefe, owing
         to its precipitating Salt  which envelopes the particles
Ex h .
-<!
tar and
acid of L
mens.
Of n.i-r
ac:*.
of manganeSe, and  prevents  the  Sunhcr action of the Mangancfo
menftruum.  In all precipi-uions of manganefe, how- *"
ever, by means of mild fixed  alkalies, ihe  full qu mtify
is not procured ; becaufe ihe fixed air, detached  from
the mineral, diflblves part of it.                         1 ;*U
   1 i ongh manganefe  decompounds nitre, yet  this F.ti cN of
does not happen  till the  mixture becomes red hot.   It n™1^"^16
phlogifticated manganefe be mixed with an equal quan-on
tity of nitre, and diftilled in  a glafs  retort, the mix-
ture begins to grow black  before the retort becomes
red-hot, but no nitrous  acid  goes over.  By lixivia-
tion, no mark of uncombined alkali*is met with; but
phlogifticated  nitrous  acid is extricated  by  the appli-
cation  of tamarinds, or any  vegetable acid.  Three
parts of phlogifticated manganefe, mixed with one part
of finely pounded nitre,  yields no nitrous acid,  though
the nitre is alkalized as Soon  as the mixture becomes
black in the retort.                                     138$
   Mr  Scheele  proceeds now to another Set of  experi- Experi-
ments upon manganeSe united  with phlogifton.  In nv-nts on
order to procure it in this ftate,  the bell method  is  to"l*^jn
diffove in diftilled  water, and cryftallize the  Salt ob- witi1 phi0-
tained  by  folution  of manganefe in vitriolic acid, and gifton.
then precipitate it with vegetable fixed alkali.  In this
ftate it is white likechalk ; but by calcination in an open
fire, the Superfluous phlogiffon flies off,  and the  calx
regains its ufual black colour.  This change of colour
likewife happens when the precipitation is  made with
cauftic alkalies,  whether fixed or volatile.   The pre-
cipitate, indeed, in  this cafe, is white when kept clofe
from the air, but affumes a brown colour when expo-
fed  to it for any time :  But  when the precipitation is
made  by  mild alkali, the white colour is preferved by
the fixed air, which in  this cafe it alfo contains.   By
diluting the folution with a  confiderable quantity of
water,  and precipitating with cauftic alkali, the  pre-
cipitate is brown from  the very  beginning,  owing  to
the air in the liquid attracting the phlogifton from the
manganefe.  The  precipitate formed by lime-water is
alfo brown ;  but on adding  more of a ftrong folution
of manganefe,  and afterwards precipitating  with cau-
ftic alkali, the powder falls of a while colour ;  becaufe
the air,  being already faturated with phlogifton,  can-
not take up any  more.  The reSults of Mr Scheele's
experiments on this phlogifticated manganeSe are,        1386
   1. An  ounce  of this fubftance diftilled  by  itfelf By diftilla-
in  a glafs retort,  with a ftrong fire, yielded  a  greattionterf**
quantity of fyced air with fome drops of water.   The
refiduum poured warm out of the  retort grew red-hot,
and fet the paper on fire.
   2. On repeating  the experiment with only a drachm
of phlogifticated manganefe,  and tying a  bladder  to
the neck  of a retort,   three ounce-meafiires  of air
came over: the refiduum was of a light  grey  colour;
diffolved in acids without addition of any more  phlo-
gifton; and took fire in that degree of heat  in which
fulphur fmokes, but does not burn.  From thefe expe-
riments, fays Mr Scheele, it is evident, that phlogifton
docs not Separate from manganefe if the accefs of air be
prevented.                                             I3g7
   3. One partof finely powdered manganefe boiled in nodedwitk
four of oil-olive, effervefced vide •:; :b. ■,  and diflblved oil olive.
into a kind of Salve.
   4. On diftilling  a mixture of  finely powdered  man- By'diftiU*-
ganefe and charcoal, with an empty bladder ti.-d to the tion with
mouth of the retort, a  quantityof fixed air was extri- charcoal.
                                                catcd 
Pradlice.
CHEMISTRY.
93
Manga-
nefe.


With ful-
phur.
   1390
By calcina
lion with
•itre.
         cated when the retort began to melt and diftended the
         bladder.*  The refiduum was moftly foluble in diluted
         vitriolic acid,                                    '
           5. On diftilling half an ounce of powdered manga-
         nefe with two  drachms of fulphur, the latter  partly
         rofe into  the  neck of  the  retort, and fome volatile
         acid vapours penetrated  through the lute.   The diftil-
         lation was continued till  the retort began to melt; and,
         on cooling, the refiduum was found to weigh $'-> drachms.
         It was of a yellowifh-grey colour ;  and diflblved in Spirit
         of vitriol with effervefcence,  yielded an hepatic fmell,
         Some Sulphur being alSo  precipitated at the Same lime.
         By  calcination in the open air, the Sulphur w'as diffi-
         pated ; but great part  ot the maSs was rendered Soluble
         on account of its having been penetrated by the acid
         vapour, and fhot into cryftals  as  though it had been
         formally diflblved in volatile  Sulphureous acid ;  and by
         repeating the calcination with more Sulphur, the whole
         became at laft entirely Soluble, and was  reduced  to
         cryftals.
           Finely powdered manganeSe, triturated with nitre and
         ftrongly calcined in a crucible,  unites  with the alkali
         of the nitre, while the acid is  diflipated  in the air.
         The maSs formed by the union of the  manganeSe and
         alkali is oS a dark green colour,  and Soluble in  water,
         communicating alSo a green colour to the  liquid; but
         in a fhort time a fine yellow powder (an ochre oS iron)
         falls to the bottom, leaving the liquor of a blue colour.
         By the addition of water, this folution firft affumes a
         violet colour,  grows afterwards red, and a precipita-
         tion of the manganefe takes  place, which refiimes its
         natural colour as Soon as it has fallen.   The fame pre-
         cipitation takes place on  the addition  of a few drops
         of acid, or by expofure for fome days  to the open air.
         As  for the dark red colour affumed by the folution
         when the precipitate is  about to fall, Mr Scheele con-
         jectures that  the particles of manganefe may naturally
         haye a red colour, which becomes vilible when the fub-
         ftance is diSperSed through a menftruum without being
         perfectly diffolved.
            7. By the  addition of finely powdered  white arfe-
addition of nic to  the alkaline maSs of nitre and  manganefe,  the
         green colour disappears, and the whole becomes white;
         phlogifticated manganeSe being alSo precipitated on the
         addition of water.  This ariSes Srom the more power-
         ful  attraction of manganeSe for the phlogifton  of  the
         arSenic than that of the arSenical acid  itfelf ; and  for
         the fame reaSon, if the mafs be calcined with charcoal,
         or any other  phlogiftic fubftance, a colourlefs folution
         will be obtained.
           8.  ITalf an ounce of phlogifticated  manganefe, di-
         ftillcd in a retort with an equal quantity of  powdered
         fal .".mnioniac, yielded firft a concrete volatile fait, after
         which fome fal ammoniac undecompofed arofe in  the
         neck  oi" the  retort.   Half an ounce of .pure dephlogi-
         fticated manganefe, mixed with two drachms of pow-
         dered  fil ammoniac, yielded alkali in  its cauftic ftate.
         Both reiiduums were foluble in  water  ; which fliows
         that manganefe attracts phlogifton from the volatile
         alkali.
           ;;. On digefting finely powdered manganeSe for fome
         w -eks with pure nitrous acid and fome volatile alkali,
         a great number of a'r-bubbles rife to the top, and the
         volatile alkali is entirely decompofed:  for though the
  I391
With the
arfenic.
   1392
By diftilla-
tion with
fal amtno-
   I39S
By diftilla
tion with
pure ni-
trous acid.
mixture be afterwards diftilled in a retort with the ad- Manga-
dition of quicklime,  not the leaft urinous fmell can be ncfe- •
perceived.  This decompofition is effected by the man-    j,94
ganefe attracting the phlogifton of the volatile alkali; Volatileal-
for that the nitrous acid has no fliare in this, is proved kali de-
by the following experiment.                        ftroyed by
   10. An ounce of well triturated manganefe was di- m*n&™ck
ftilled with half an ounce of fal ammoniac;  and a li- a raui'"f.
quid alkali, fuch as  that obtained from fal ammoniac n_0rf.
and quicklime, was procured.   On repeating this ex-
periment, with the variation only of a bladder inftead
of a receiver, the famckind of air was obtained as that
which rifes to the top of the nitrous mixture.  Though
the emiffion of this air indicated  a  deftruction of the
volatile alkali, our author explains the reafon of its
being ftill  obtained in a cauftic ftate by the phlogi-
fton taken Srom the alkali being more than  Sufficient
to render the alkali Soluble in muriatic acid ; in conSe-
quence of which,  the fuperfluous  quantity combine -
with  the manganefe, and enables it to decompofe the
fal ammoniac iu the ordinary way.  It muft be owned,
however, that his reafoning on this fubject is not en-
tirely fatisfactory,  nor does the account he gives of his
experiments feem entirely conliftent with itSelS.  See
Scheele's  Chem. Effays, Eflay V. § xxxix.               j.gr
   11.  Powdered manganeSe, diftilled with an  equal By diftilla,
quantity  of white arSenic, underwent no change, the tion with
arSenic flying off in its proper form ;  but with an equal arfenic.
quantity  of yellow orpiment, fome volatile fulphureous
acid came over firft,  then a yellow fublimate, and at
laft a little red fublimate arofe.   On  augmenting the
fire by degrees, the orpiment remained  obftinately at-
tached to it.   Similar effects enfued on treating  man-
ganefe with  an equal quantity of  antimony ;  which
likewife  yielded a pungent fulphureous acid, but no
fublimate.   By calcination in the open air thefe com-
pounds are decompofed ; and  the manganefe,  united
with vitriolic acid, becomes foluble in water.           1396
   12. On  diftilling manganefe with an equal quantity With cin-
of finely pounded cinnabar,  a volatile fulphureous acid nabar.
came over firft; then a little cinnabar was fublimed in-
to the neck of the retort ;  and at laft the quickfilver,
which had been the bafis of the cinnabar,  began.to
diftil: the refiduum, being a combination of manga-
nefe  and fulphur,  was fimilar to the compounds al-
ready defcribed.
   13. With an equal quantity of corrofive fublimate, with cor*
manganefe underwent no change ;  but wlien fublimed roftve fub*
with an equal quantity of mercurius dulcis, a corrofive limate.
fublimate,  and then  mercurius dulcis,  arofe into the
neck of the  retort.   The reafon of this is, that the
mercurius  dulcis contains a  portion of phlogifton ;  by
being deprived of which it ceafes to be mercurius dul-
cis, and becomes corrofive fublimate: but by reafon
of the ftrong attraction of manganefe for phlogifton,
the mercurius dulcis parts with that portion which is
neceffary to keep it in its mild ftate, and  thus is con-
verted into corrofive mercury.

        Sect. IV.   Inflammable Subftance}.

   These maybe divided into the following clafles : General
 I. Sulphurs.   2.  Ardent fpirits.   3.  Oils  and fats, divifion.
4. Refins.   6. Bitumens ;  and, 6. Charcoal.   •
                        ^                § 1. Sul- 
>94
CHEMISTRY.
Practice.
tilphor.

1*0
  1400
rryftalli-
aatieiii.
  T40I
Decompo-
fed jy a fu
pcrabun-
rUncc of
phlogifton
             j  I.   5 l' t />  H t r s.
   1. C'vimon fuiphur.   For  the extraction  of this
fubltancc from itb ores, See Sl*lp h or.   The artificial
compoiition  of  it we have already related, n°  715 ;
and have now only to take notice of a very few of its
properties, which come more properly under this Sec-
tion.
   Sulphur, as commonly  ufed in commerce and the
arts, is of a  pale yellow colour, of a difagreeable and
peculiar linell,  which is rendered more fenfible when
it  ik heated or rubbed.  By rubbing,  it receives very
curio is electrical qualities : (See E:  ectricity.)  Its
fpecific gravity  is avilideraMy  greater than  that of
water, though  lefs than eanhs  or ftones.   In clofe
\ ufcls, fulphuris incapable of receiving any altermio'.i.
It  melts with a very gentle heat; and then is Sublimed,
adhering to the capital in Small, very fine, needle-like
cryftals, called flowers of fulphur.  It may thus be Sub-
Jime 1  many  times  without alteration.  \f Sulphur is
expofed to a heat barely Sufficient 10 melt it, and very
flowly  cooled, it cryftalli'cs  in Sorm ot many  ..ecellcs
crodi 1- one another.  Some  of" thefe pointed  cryftals
may alio be obServed in ihe interior parts of the lumps
of Sulphur which have been melted, and caft e;to cy-
lindrical moulds, as they arc com mo nl/ Sold ;  becauSe
the centre ol  tncSe cylinhi-.d rolls  s more  flowly
cooled than the furficc.  Sulphur alfo gives this  needle-
like form to cinnaba.,  anthnmy, atnl many other mi-
nerals containing  it.   S.ilpliur may be decompoSed in
Several ways.    The molt fimple is by burning;  which
we have alrenly taken notice  of,  n° 623.   It  may
al  So be very effectually  decompoSed by mixing ii with
iron filings and water.   In this caSe the phlogifton is
.diflipated, and the acid uniting with the iron forms a
green  \ itried.
   It is very remarkal'r,  that though fulphuris com-
pofed of vitriolic acid and phlo niton,  yet the addition
of more  indammable matter,  1 > tar from  making the
union  ftronger, weakens  it to  a great decree : and
hence we have anotlier method' of decompoling this
fubftance ; namely, by combining it with a large quan-
tity of oil, and  diftilling the compound.
   Sulphur  is capable of-being  e*fily didblved in ex-
pre dedoils, but \ e ry difficultly in effential ones.  Thefe
compofitions  are called balfams  of fulphur; and arc
Sometimes employed in medicine, but are found :o be
of a very heating nature.   They are much ufed by
farriers.   According to Mr  Beaume',  Sulphur cannot
be didblved in oil,  without a heat fiirficient to  melt it.
A  larger quantity is kept diflblved when  the mixture
is  hot, than when cold ; and consequently the Sulphur,
eSpecially if it has been diffolved in a thin  effential ^l,
cryftallizes on coolir i; the mixture.  The fulphur, thus
feparared  from  the oil, is found not to be altered in
any reSpe^t  from *vhat it  formerly was ; but if the
mixture is expofed to a degree of heat capable of en-
tirely decompofing the oil, the fulphur is decompofed
along with  ft, and the fame products are obtained by
difti'ling this mixture to dryntSs, as if a mixture of
p.M-c oil of vitriol and oil were diftilled.   Thefe  pro-
ducts are, firft a portion of oil, when an effential oil
was made ufe of in the compofition  of jhe balfam ;
lina fojnc wiatile fulphureous acid, which is at firft
watery, and afterwards becomes ftronger; along w ith
ill is  acid more oil  arifes,  which becomes  ' >rc  and
nunc thick  towards the  end of the diftillation ;  and
laftly, w he . the retort has been made red hot, nothing
remains but a fixed coal.
  in this procefs we find,  that both the  fulphur and
oil are decompofed.  The acid of the fulphur fcems
to attack  the watery principle of the oil,  while its
phlogifton remains confounded with that of the oil, or
is didipaied  in \apours.   Hence,  though  the vitriolic
acid  in fulphur is concentrated to the utmoft degree,
and perfectly free from water, what rifes in this diftil-
lation is very aqueous, by reafon of the water which
it attracts from the  oil.
  Spirit of wine does not fenfibly act upon fulphur in
its liquid ftate ;  but if both the  fpirit of w ine and ful-
phur  meet in the*ftate of  vapour,  they will then u-
nite,  and a perfect  folution will take place.   By me-
thods of this kind, many combinations might be  ef-
fected, which have been  hitherto thought impoffible.
  Pure  fulphur unites eafily w ith  all metals; gold,
platii:;-, and zinc, excepted.   The compounds, except
that  with mercury, poifefs  a metallic luftre without
any ductility.  The fulphur may be feparated by ex-
pofing the  mixture to a ftrong  fire.  (See Metal-
lurgy,)  or by  diilblving the metalline part in acids.
The fulphur,  however,  defends  feveral of the metals
from  the action of  acids -,  fo that this diifolution fuc-
ceeds but imperfectly.  The reguline part of antimo-
ny is more eafily Separated Srom  Sulphur  by means of
acids than by any other metalliHe Subftance.  Alkaline
Salts  will Separate the fulphur from all metals in Sufion,
but they  unite with it thcinielves, and form a com-
pound equally capable of diilblving the metal.
  Sulphur  united with quickfilver  forms the beauti-
ful pigment called cinnabar, or vermilion; which is fo
much uSed in painting,   that the  making  oS it is  be-
come a diftinct trade. Neumann relates, that in the ma-
king of cimabar by the Dutch method,  fix or eight
parts of quickfilver are made uSe of to one oS Sulphur.
The Sulphur is firft melted,  and  then the quickfilver
is Stirred into it; upon which they unite  into a black
v.y:<i\.  In this part  of the proceSs the mixture is very
apt to take fire ;  of which it gives  notice by fwelling
np to a great degree.  The veffel muft  then be imme-
diately covered.   The maSs being beaten to  powder,
is afterwards to be Sublimed in large earthen  jars al-
moft oS an equal wideneSs from end to end ; thefe  are
hung in a furnace  by a  ftrong rim of iron.  When
the matter  is put in,  the mouth of the veflel is cover-
ed, the  fitt increafed by degrees, and continued  for
feveral hours, till all the cinnabar has fublimed ; care
being taken to introduce  at times  an  iron  rod  to keep
the middle clear; otherwife the  rtuiabar concreting
there, and flopping up  the  paffage would  infallibly
burft the veflels.
  The quantity 01  i.dph'.r directed in the  common
receipts for nuking cinnabar is greatly larger than  the
above; being no lefs thin one-thi» '  >f the quantity
of quickfilver emuloyed : according!; n has been found,
that the fublimate,  v. iih  fuch a large quantity of ful-
phur, turned out of a blackifh colour, and required to
be feveral times fublimed before  it became perfectly
red ; but we cannot help  thinking, that by one gentle
                                        fublimation
Sulphur.
   1402
How folu-
ble in fpirit
of wine.
   M03
Its union
with rm>
tals.
  1404^
Vermilion 
Pra&ice.
CHEMISTRY.
Sulphur.
  T405
Pulvis ful-
   1406
Phofpho-
rus of u-
rhie.
   1407
Mr Mar-
graafc's
procefs for
making.
 fublimation the fuperfluous fulphur might be feparated,
' and the cinnabar become perfectly pure  the  fecond
 time.  Hoffman gives a curious method  of making
 cinnabar without fublimarion: by fhaking or  digelt-
 ing a little mercury with volatile tincture  of fulphur,
 the mercury readily imbibes the  fulphur from the vo-
 latile fpirit, and forms with it a deep red powderrnoc
 inferior in colour to the cinnabar prepared  in thexom-
 mon manner.   Dr Lewis has found the common folu-
 tions of fulphur by alkalies, or quicklime, Lo  have a
 Similar effect.   This cinnabar will  likewife be  of a
 darker or lighter colour, according as the Solution
 contains more or leSs Sulphur.
   Sulphur is a principal ingredient in  gun-powder,
 (See Gun-powder.)   It alio enters the compofition
 of the pulvis fulminans.  This confifts of  three parts
 of nitre, two of the dry alkali of tartar,  and one part
 of Sulphur, well ground together.  If a little quantity
 of this powder is laid on an iron-Spoon or fliovel, and
 flowly heated, it will explode, when it arrives at a cer-
 tain degree of heat, with aftonifhing violence and noiSe.
 The moft probable opinion concerning this  is, that the
 fixed air contained in the alkali is, by the acid vapours
 acting upon and endeavouring to expel it all at once,
 driven off with Such force, that a  loud explofion  is pro-
 duced.
   2. Phofphorus of Urine. This  is a very inflammable
 fubftance, compofed of phlogifton united w ith  a  cer-
 tain acid,  the properties of which we have  already ta-
 ken notice of,  n° 904 et fecj.  The preparation of it
 was long  a Secret,  and only perfectly difcovered by
 Mr Margraaf,  who publifhed it in the Berlin Me-
 moirs in 174?.   This procefs being by far the beft
 and moft practicable, we  fhall content ourfelves with
 inferting it alone.
   Two pounds of fal ammonaic  are to be  accurately
 mixed with four pounds of minium, and the mixture
 diftilled in a glafs retort; by which means a very pe-
 netrating,  cauftic alkaline fpirit will be obtained. The
 refiduum,  after the diftillation, is a kind of pll/t^um
 corneum;  n° 812.   This is to be mixed with nine or
 ten pounds of extract of urine,  evaporated  to the con-
 fiftence of honey.  (Seventy or eighty gaWbns of urine
 are required to produce this quantity of extract.) The
 mixture is to be made flowly in  an  iron pot Set over
 the fire, and the matter frequently  ftirred.  Half a
 pound of powdered  charcoal is then to be added,  and
 the  evaporation continued till  the whole  is reduced
 to a black  powder.  This powder is  to be put  into a
 retort, and urged with a graduated heat,  till  it be-
 comes red  hot, in order to expel all the volatile alkali,
 fetid oil, and ammoniacal fait,  that may be contained
 in the mixture.   After the diftillation, a black friable
 refiduum remains, from which  the phofphorus is to be
 extracted by a Second diftillation  and  a ftronger hear.
 Before it is Subjected to another diftillation, it may be
 tried by throwing fome of it upon hot coals.  IS the
 matter has been well prepared, a Smell of garlic exhales
 Srom it, and a  blue phoSphorical flame is Seen  undu-
 lating along the Surface ofthe coals.
   The matter is to be put into a  good earthen retort,
 capable of Suftaining a violent fire.   Three quarters
 of the retort are to be filled with  ihe matter which is
 to yield the phofphorus, and it is  to be placed in a fur-
nace capable of giving a  ftrong heat.  Mr Margraaf
140*
 divides the matter among fix retorts,  fo that if any
 accident happens to one,  the whole matter is not loft.
 The retorts ought to be well luted to a receiver of a
 moderate fize, pierced with a fmall hole, and half full
 of water ;  and a fmall wall of bricks muft be raifed
 between the furnace and  receiver, in order to guard
 this veflel againft heat as much as poflible.   The re-
 torts are to  be heated by flow degrees for an hour and
 an half;  then the heat is to be increafed till the veflels
 are red hot, when the phofphorus afcends in luminous
 vapours.  When the retort is  heated till between a
 red  and white,  the phoSphorus paffes in drops, which
 faf^and congeal in the water at the bottom of the re-
 ceiver.  This degree of heat is  to be  continued till
 no more comes over.  When a letort contains eight
 pints or more, this operation continues  about five
 hours.
   in the firft diftillation, phoSphorus never paffes pure, Rectlfka-
 but is always of a blackhh colour, by reafon of its car- tion  of
 rying along with it tome part of the coal.  From this, phofpho-
 however, it may be purified by rectification in a fmallrus*
 glafs-retort, to  which is  luted a receiver half Sull of
 water.   A very gentle heat is Sufficient;  becauSe phof-
 phorus, once formed, is very volatile ; and as  the fuli-
 ginous matter was  raifed  probably by the fixed air
 emitted by  the  charcoal in the inftant of its union
 with the phofphorine acid, none of it can  arife in a
 fecond diftillation.
   The pheffphorus is then to be divided  into Small cy-
 lindrical rolls,  which is done  by putting it in glafs-
 tubes immerfed  in warm water ;  for  the phofphorus
 is almoft as fufible as Suet.  It  takes the form of the
 glaSs-tubes ; from which it may be taken out,  when it
 is cold and hardened.   This muft be done under wa-
 ter,  leaft the phofphorus fhould take fire.               T
  This concrete continually appears luminous in a dark Procefs
 place ; and by a very flight heat takes fire, and burns fometimes
 far more vehemently than any other known Subftance. dangcroua
 Hence it is neceffary to be very cautious in the diftil-
 lation of it;  for if the receiver fhould happen to break
 while the phofphorus is diftilling, and a little flaming
 phofphorus fall upon the operator's legs or hands, it
 would burn  its way to the bone in lefs than three mi-
 nutes.  In this cafe, according to Mr Hellot,  nothing
 but urine will flop its progrefs.
  Though phofphorus takes fire very readily by itfelf,
 it does not inflame at all by grinding it with other in-
 flammable bodies, as camphor, gun-powder, or effen-
 tial oils.   In grinding it with nitre, fome luminous
 flafhesare obferved; but the mixture never burns, un-
 lefs the quantity of phofphorus be large  in proportion
 to the nitre : rubbed pretty hard on a piece oS paper or
 linen, it Sets them on fire iSthey are rough, but not if
 they are  fmooth.   It fires written paper more readily
 than fuch as is white, probably from the former ha-
ying more aSperities.  On grinding w ith iron-filings,
 it preScntly takes fire.
  Oils ground with  phoSphorus  appear, like itSelf, Liould"
luminous in  a temperately warm pla:e •,  and thus be- phofpho-
 come a liquid phofphorus,  which may be rubbed on r«5-
the hinds, &c. without danger.  Liquid phofphorus
 is commonly prepared by grinding a little of the Solid
phofphorus with oil oS cloves, or rubbing it firft with
camphor, ?nd this mixture with the oil.   A luminous
amalgam, as it is called, may be obtained, by digefting
                      B b 2                 a fcru- 
Sulphur.
  1411
'vprti-
mcuu on
1' ifpho-
ru- * i-h
l^nt  f
«riae.
  1411
With i f-
I- ntial oils
M.i acid*.
   1413
Mr NLr-
fi.r» ex-
periments
with me-
tals.
                             CHEMI
a Scruple of ioli*{ pho'phoiv.s with hftt'an ounce of oil
of lavcndc:, aud, when the phofphorus begins to eiif-
lolve and the liq.ior to boil, adding a drachm of pare
q ucklilvrr; ihenluilkly Uukiig the glafs for five or fix
iniuutcs till  f..cy unite.
   Rectified fpirit of wine, digefted on phofphorus, ex-
tra is a part of it, So a^ 10 emit luminous flalhes on be-
ing ilropt into  water.  It is  computed that one part
of  phoiphorus  will communicate  this  property  to
600,000 parts oS fpirit.  The liquor is never obferved
 to become luminous of it:elf, nor in any other circum-
 lbncc except that abuvememioncd. By digeftion teu-
 tonic months, the undiffolved phofphorus is reduced to
 a tranfparent oil, which neither emits  light  nor con-
 cretes in  the cold.   By warning with water,  it is in
 fomc meafure revived ; acquiring a thicker confiftence,
 and becoming again luminous, though in aleSs degree
 than at fi.ft.  During this digeftion, the glaSs is very
 apt to burft.
   PhoSphorus is partially diffolved by expreffed oils;
 and totally, or  almoft So,  in  elfei.tial oils and ether.
 V\  V. 1 effential  oils are Saturated  with  it by heat,  a
 part of the phofphorus lcparatcs, on ftanding in the
 cohl, ir! a cyftallizc form.  Concentrated fpirit of fait
 lias 11 > action on it.   In diltillatiem,  the fpirit  rifes
 firft,  and the phofphorus after it unchanged.   Spirit
 ut  nierc  diffolves  it, and  the diflblution is attended
 with great heat and copious red fumes ; fo that great
 part of the fpirit diflils without the application of any
 c\t(!:,il  heat, and  the  phofphorus at laft takes fire,
 explodes, anl burfts  the velfel-..   Oil  of vitriol like-
• wile  diiiolves phoSphorus,  but  not without  a heat
 Sufficient to make theacid diftil.   The diftilled lienor
 is  white,  thick, and turbid ;  the refiduum is a whitiih
 te  lacious maSs,  which deliquates, but  not totally, in
 the air.   Phofphorus itfelf is refolved  into an acid li-
 quor on being expofed two or three weeks to the air,
 i.s inflammable principle Seeming by degrees to bedif-
 lipared.
    Pfiolffhorus has been reported to produce extraordi-
 nary  effects in  the reSolution of  metallic bodies: but
 from the experiments  that have been made with this
 view,  it does not appear'to have  any remarkable ac-
 tion on them ;  at leaft on the precious ones,  gold and
 hher, Sor the reSolution or Subtilization of which it has
 been chie:iv recommended.   The following experi-
 ments were made hy Mr Margraaf.
    1.  A fcruple of tilings of gold  were digefted with
 a drachm of phofphorus for a month,  and then com-
 mitted to diftillation.   Part of the phofphorus arofe,
 and part'remained above  the  gold, in  appearance re-
 fembling glafs : this grew moift  on the admiflion of
 air, and diffolved in water, leaving the gold unaltered.
 Half a drachm  of fine filver,  precipitated by copper,
 being digefted with a drachm of phoSphorus for three
 hours, and  the fire then -increaSed to  diftillation,
 gre.ue ft pan: of the phofphorus arofe pure, and the fil-
 ver remained unchanged   Copper filings being treat-
 ed in the fame manner, and with the fame quantity of
 phofphoric, the phofphorus fublimed as before; Ir,it
 the remaining copper w a-, found to have loft it6 metal-
 lic brig'unefs, and to take fire on the contact of flame.
 Iron filings fuffered no char :e.   Tin filings run into
 granules,  \\hich appeared to he perfect tin.   Filings
«flead did the fame.   The red effx of meiyury, called
R   Y.
Practice.
pi cipitnte perfe,  treated in the fame manner, was to-
tally converted i;:io rum.ing quickfilver.   2. Regu-
lns of antimony faltered no change itltli, but occafion-
ed a  change in thf^.f>nffte:icc  of the phofphorus 1
which, after being eliftillcd from this femimetal,  refu-
ted to congeal, and continued, under water, fluid like
oil-oli\e.   \\ ith  bifmuth there was no alteration.   A
drachm of phofphorus being dih.iled  and cohobated
w ith an equal quantity of zinc, greateft  part of  the
zinc fublimed in form of very light pointed rioters of
a reddifh-vellow colour : thefe flowers*, injected into
a red hot crucible,  took fire, and  run  into a glafs re-
fembling that of borax.  White arfenic, fublimed with
phofphorus,  arofe along with it in form of a mixed red
fublimate.    Sulphur  readily unites with phefphorus
into a mafs which fmells like hepar fulphuris.   This
does not eafily take fire on being  rubbed ;  but expofed
to a moderate dry he..:, it flames violently, and emits a
ftrong Sulphureous rume.  ISphoSphorus is burnt in an
open veflel, a quantity of acid remains  behind ;  and if
a  glaSs bell is held over it,  an acid likewiSe Sublimes
in the Sorm of white flowers.
   2.  Mr  Canton's phofphorus.  This is a Compofition
of quicklime and common Sulphur.  The receipt Sor
making it is as follows.  "  Calcine fome common oy-
fter-lhclls, by keeping them in a good coal-fire for half
an hour ;  let the pureft part of the calx be pulverized
and fitted.   Mix with three parts oS this powder one
part oS flowers of Sulphur.   Let this mixture be ram-
med  into a crucible of about an  inch and  a half in
depth till it be almoft full; and  let it be  placed in
the middle of the fire, where it muft be kept red hot
for an hour at leaft, and then  fet by  to cool: when
cold,  turn  it out  of the crucible ;  and cutting or
breaking  it  to  pieces,  fcrape off, upon trial,  the
brightcft parts; which, if good phofphorus, will be a
white powder.  This kind of phofphorus fhines on be-
ing expofed to the light of the fun, or on receiving an
electrical ftroke.
   4BPhofphorus of Homberg.   This fubftance, which
has the Singular property of kindling fpontaneoufly
when expofed to  the air, was accidentally difcovered
by Mr Homfcerg,  as he was endeavouring to diftil a
clear flavourleSs oil from human excrements. Having
mixed the excrement with alum, and diftilled over as
much  as he could with a red heat,  he was much fur-
prifed at feeing the matters  left in the  retort take fire
upon being expofed to the air, fome days after the di-
ftillation was over.  This induced him to repeat the
operation, in which he met with the fame fuccefs;  and
he then publifhed a procefs,  wherein he recommended
alum and human  excrement for the preparation ofthe
phofphorus.  Since his time, however, the procefs has
been much improved ; and it is difcovered, that almoft
every vitriolic' fait may be fubftituted for the alum, and
moft other inflammable fubftances fir the excrement;
but though  alum is not ahfolutcdy neceflary for  the
fuccefs, it is one of the vitriolic falts that fucceed beft.
The following procefs is recommended in the Chemi-
cal Dictionary.
   Let three parts of alum and one of fugar be mixed
together.   This mixture muft be dried in an iron fho-
vel, over a moderate fire, till it  be almoft reduced to
a blackifh powder or coal; during which  time it muft
be ftirrcd with an iron fpatula.  Any large mafTes muft
                                                 be
Sulphur.
  1414
Mr Can-
ton's phof-
phorus.
  1415
Homberg'e
phofphorus
or pyro-
phorus.
  1416
Beft me-
thod of
preparing. 
Practice.
CHEMISTRY
ic
97
Sulptiur
   1417
Is not in-
jured by
mere ex-
pofure to
light.
   1418
Caufe of
the acccn-
fion.
be bruifed into powder ; and  then it muft be put into
a glafs matrafs,  the mouth of which is rather  Strait
than wide, and fevtn-or eight inches long.  This ma-
trafs is to be placed in a crucible, or other earthen veS-
Sel, large enough to contain the  belly oS the matrafs,
with about a Space equal to that  of a finger all' round
it.   This fpace is to be filled with fand, fo  that  the
matrafs fliall not touch the earthen veffel.   The appa-
ratus is then to  be put into a furnace,  and  the whole
to be made red  hot.   The fire muft be applied-gra-
dually, that any oily or fuliginous matter may be ex-
pelled  ;  after which, when  the matrafs is made red
hot, fulphureous vapours  exhale: this degree of heat
is to be continued till a truly fulphureous flame,  which
appears at the end of the operation, has been feen near-
ly a quarter of an hour : the fire is then to be extin-
gulfhed, and the  matrafs  left to cool, without  taking
it out ofthe crucible; when  it ceafes to be red hot, it
mult be flopped with a cork.  Before  the matrafs is
perfectly cold,  it  muft be taken *ut of the  crucible,
and the powder it contains poured as quickly as pof-
fible into a very dry glafs phial,  with a glafs ftopper.
If we would preferve this phofphorus «. long time,  the
bottle  containing it  muft be  opened as  Seldom as pof-
fible.   Sometimes it  kindles while it is pouring into
the glaSs phial; but  it may  be then  extinguished by
clofing the phial expeditioufly.   A  fmall  quantity of
this pyrophorus laid  on  paper,  and expoSed  to  the
air, immediately takes fire, becomes red like burning
coals,  and emits a Strong Sulphureous  vapour greatly
refembling that which arifes  on decomposing liver  of
fulphur.
   It has been  generally alleged, that the  common
black phoSphorus is impaired by being expoSed  to  the
light;  but Mr Cavallo has discovered the fallacy of this
fuppofition by the following  experiment.   Some por-
tions of the fame pyrophorus were inclofed  in  three
glafs tubes, and immediately Sealed  up hermetically.
On the 22th of May 1779,   two of them were  fu-
fpended from a nail out of a window,  and  the third
was wrapped up in paper and inclofed in a box,  where
not the leaft glimmering of light could enter.  In this
fituation they were left for more than a year ;  after
which one of thofe that  had been  kept out of  the
window was broke,  along with  that which had been
kept in the dark, in the prefence of Mr Kirwan ;  when
the pyrophorus feemed to be equally  good in each
tube, taking fire in about half a minute after  it was
taken out of the tubes, and  expofed to the air on a
piece of paper.
  There are many different kinds of pyrophori : fome
of the moft remarkable of which are  defcribed  under
the1 article Pyrophorus.   Many  theories have been
invented to folve the phenomenon of their accenfion o:i
the contact of air.   This has been thought owing  to
the converlion of the earth of alum into lime, or to a
remainder of the vitriolic acid attracting moifture from
the atmofphere ;  but the formation  of pyrophorus
without either alum  or vitriolic  acid, fhows that  nei-
ther of thefe opinions can be juft.  It is mere probable,
therefore,  that,  the heat is occafioned by the.total dif-
fipation of that aqueous part which is effential to the
coeiftitution of terreftrial fubftances.   In confequence
of this, the water contained  in the atmofphere is not
wffy attracted with avidity, but decompounded by the
matter reduced to fuch a ftate of extreme drynefs.  By
thefe operations it gives out  the  latent heat  contained
in it, and this produces the accenfion in queftion.

               §  2.  Ardent Spirits.

     See Fermentation andDis tillation.

                    § 3.'  Oils.
Oils.
1419
   1. Effential Oils.  Thofe oils are called effential which r.ffcntial
have evidently the fmell of the vegetable  from which oils.
they are drawn.  For the method of procuring them,
fee Distillation.   They are diftinguifhed from all
others by their fuperior volatility, which is fo great as
to caufe them rife with the heat of boiling water.  All
thefe have  a ftrong aromatic Smell, and an  acrid,  cau-
ftic tafte ; in which reSpect alSo they differ  Srom other
oils.   This tafte is thought to proceed Srom a copious Suppofed
and  diSengaged  acid, with which they are all pene- caufe of
trated.  The prefence of this diSengaged acid in effen-rtheir tafte.
tial oils, appears from  the impreffion they  make upon
the corks of bottles in which they  are kept.' Thefe
corks are always ftained of a yellow colour,  and a little
corroded, nearly as they are by nitrous acid.  The va-
pour of thefe oils alfo reddens blue paper,  and converts
alkalies into neutral falts.                             I42I
   This acid is likewife fuppofed to be the cauSe-of their oftheir fo-
Solubility in fpirit of wine.   They are not all equally lubility iu
Soluble in this menftruum, becauSe they do not all con- fpirit of
tain an equal quantity ofacid.  As this acid  is much winc°
difengaged, they loSe a great deal oS it by repeated di-
ftillations,  and  therefore they become leSs and lefs So-
luble on being  Srequently  diftilled.  By  evaporation  -
they loSe their moft volatile and  thin part, in which
the Specific finell  oS the vegetable from  which  they
are extracted  refides  ;  by which loSs they become
thick, and acquire the fmell and confiftence oS turpen-
tine,  and even  oS refins.  In this ftate they are no
longer volatile with the heat  oS boiling water; and, if
diftilled wkh a ftronger fire,  they give  over an oil
which has  neither fmell  nor tafte of the vegetable
whence they were extracted,  but  is entirely empyren--
rnatic, and fimilar to thofe oils procured by diftilling
vegetable or animal fubftances with a ftrong fire.   See
Distillation.                                     1424
   To the clafs of efl'ential oils,  the'volatile  concrete Camphor..
called camphor feems moft properly to belong.  With
them it agrees in its properties of inflammability, So-
lubility in fpirit of" wine,  and a ftrong aromatic fla-
vour.  The only differences between them are,   that
camphor is always in a folid ftate, and is incapable of
decompofition by any number of fublimations.            1423
  It has, however, been found pollible  to  decompofe Decorr.po-
it  by diftillation with certain additions.   By diftilling   _d by cU-
it feveral times along wdth bole,  we obtain a fluid ha- ftl-llftJ0I|
ving the properties of an efl'ential oil,  Soluble in water, Wlt    oe"
and feparating again on the the addition of fpirit of wine.   1424
On diftilling it eight times with dephlogifticated ni- Withce-
trous  acid,  we obtain a fait having the form of a pa-pllJ°Sl11'*
rallelopiped, of an acid and bitter tafte, and changing u nitrou*
the juice of violets and turnfole  red.  This kas  the
properties of a true acid  ; combines with fixed and vo-
latile alkalies into neutral  falts capable of being  cry-
ftallized ;  diffolves copper, iron, bifmuth, arfenic, and
                                            cobalt.. 
'/>                                  C    II    E   M   I

 Oib.    cob.i'.t.  With magnefia it forms  regular  u-yftah, in
   -   '  Some measure refembling bafaltes.   It is dmnigiiilud
         iromthe .«. d e>t  iugjr by not piecipitatiag lime horn
         us Solution in marine .n id, and l--\  forming witn  nag-
         ucfu a white powder foluble in water.
           According to  Nc .mani,  all the camphor made uSc
         of  is  the pcexlucc of two fpecies  ot  trtes;  the one
         growing in Sumatra and Borneo, the  other in J, pan.
         Ofthcie, the Japan kind is  the only one brought into
         FaiojH.   The tree is about the  fizc of a largt  lime,
         iJic Mowers white, and thelruita Small red beriy. All
         parts of the tree  are impregnated with camphor; but
         the roots contain molt, and therefore are cbiei.y  made
         ufe of tor the preparation of this comnmdity: though,
         in want of them,  the wood and  leaves are Sometimes
         mixed.
            The camphor  is extracted  by diftillation with water
         in large iron pots tilled with earthen heads fluffed with
         ftraw;  greateft  part oS the  camphor concretes among
         ihe ftraw, but  pa lies  down into  the receiver among
         the water.  In  this ftate it is Sound in Small  bits like
         gray lalt-pctre,  or common bay-Salt; and requires to
         be purified either by a Second fublimation,  or by diflb-
         luiion in fpirit of wine,  filtration,  and exficcation.   If
         the hrlt method is followed, there w ill  be Some diffi-
         culty in  giving  it the  Sorm  oS  a  perfect  tranfparent
         cake.   A diriie ilty of  tins kind  indeed  always occurs
         in iubliinations ; and the only way  is to keep the  upper
         p.irt of the glafs to fuch a degree of heat as may keep
         liie  fublimate in a half-melted ftate.   Dr  Lewis  re-
         commends the  depuration  of  camphor by  fpirit  of
         wine, and then melting it into a cake in the bottom of
         a glafs.
            Camphor pofl'cffes confiderable  antifceptic virtue*;
         and is a good  diaphoretic, without heating the confli-
         tution ;  with which intention it is often ufed in  medi-
         tinc.   It is likewife employed in fire-works and Seve-
         ral other aits, particularly in nntkiig varnilhes.  See
         Varnish.
u /i4."5^     Tlds f defiance diflblves eafily and  plentifully  in vi-
-rdei.t fi'i- nous fpirits and  in oils ; femr ounces of fpirit ot  wue
iltsanJoil. will eliffdve three of camphor.   On diftilling theni^-
         ture,  the fpirit  rifes firlt, very little camphor coming
          over with it.   This  lhows that  camphor,  however
          volatile it may feem by its fmell, is very far from ha-
          ving the volatility of ether, and confequently is impro-
   1426   pe-rl v clalfedwiih fubftances of that kind.
r:  ) r»-<.i:-    2* F/>:,hyreh:':t!ii-: Oils.   Uiucr this name are com-
?...-... oil*, preliended all thofe oils, from whatever fubftance ob-
         tained, which require a greater heat for their  diftil-
         lation thin that  of boilhng water.  Thefe are partial-
         1. foluble in Spirit of wine, ar.d becomes more and mc re
         lo by repeated diltilbu.ms.  The  empyreumatic oils
         obtained  from animal Sibftances  are at firft more fend
         tl-m thoSe procured Srom vegetables; but by  repeated
         ditnllitions, they become exceedingly attenuated and
         uiLrile,  becoming almoft  as white,  thin, and  vola-
         tile,  21 ether.   They  then acquire a property ofafting
         upon the brain and nervous  Syltem, and of allaying its
         irreguhir movements,  which is common to them v ith
         all other inflammable maners when highly attenuated
         and very volatile , but this kind of oil is particularly
         n-commended in  epileptic and convullive affection;,.
         It is giv ci Srom 4 to  10 or .11 drops:  but, though
         prepared with .  t utmoft care, it ii, very fufceptible of
  S   T   R   Y.                            Pracric*

lofing its whiteaefs,  andeven its  thinned, bjr a fliort    Oil*.
expofure to air ,  w inch proceeds from the almoft  in-   "  *   '
ftiiuuiicous evaporation oi  its moit thin and volatile
[aits, and from the property which  "I clefs volatile
remainder has of acquiring colour,  'lo avoid this in-
co.;ven euce, it muft be put, as Soon as it is nude, into
very clean glaSs bottles with glafs Stoppers,  tno cx-
poicd to the air as  little as pollible.                    rji?
  Ihe  moft  important oblcrvatioiis ennccrning  t!ie How iccti-
mcthod  of making the pure animal oils  are,  firft to llLti-
change  the veflel at  each diftillation,  or at  leaft to
make them perfectly clean ; for a very  fmall quantity
of the thicker and lefs volatile part is luflicient to fpoil
a large quantity of that which  is  more  rectififf.   1.;
the fecond place, Mr Beaume has obferved, that th:i
operation may be greatly abridged,  by taking care to
receive  none but the moft  volatile part  in each  diftil-
lation, and to leave a large refiduum, which is  to be
neglected,  and only  the more  volatile part to be fur-
ther rectified.    By  this method a confiderable quan-
tity of fine oil may be  obtained at three or four diftil-
lations,  which could not otherwife be obtained at fifty
or Sixty.                                              1428
  3. Ar.'nral Fcts.   Though theSe differ confiderably Animal
from one another in their  external appearance, and fat*'
probably in their medicinal qualities,  they  afford, on a
chemical analyfis, products fimilar in quality, and dif-
fering but inconlidcrably in quantity.  They all yield
a larger portion of oil,  and no volatile fait; in  which
refpect they differ from all  other animal fubftances.
Two ounces of hogs's  lard yielded,  according to Neu-
mann, two  drachms of an empyreumatic liquor, and
one ounce five drachms and 50 grains of a clear brown-
coloured oil of a volatile fmell, fomewhat like  horfe-
radifh.   The caput mortuum was of a fliining black co-
lour, aud weighed 10 grains.                           I42)J
  Tallow being diftilled  in the Same manner, two Tallow.
drachms of empyreumatic liquor \v ere  obtained from
two ounces of it;  of a clear brown oil, Smelling like
horfe-radilh, one ounce fix  drachms  and 12  grains.
The remaining coal was of a fhining black colour, and
weighed 18 grains.  A particular kind of acid is now
found to be contained in it.                             I4-0
  The  marrow of bones  differs a  little from fats, Marrow,
when cJiemically  examined.   Femr  ounces  of frefli
marrow, diftilled in the tibial -manner, gave over three
drachms and a fcruple of a  liquor which fmelled like
tallow ;  two Scruples and an halfoS liquor which had
more oSan empyreumatic and  a  fourifh  Smell;  two
ounces and an halSoS a yellowifh-brown,  butyraceous
oil,  which Smelled like horSe-radifh ;  and  fix drachms
and an halS of a blackifh-brown  oil of the  fame fmell.
The caput mortuum weighed four  Scruples.
  All animal fats, when perfectly pure, burn  totally
away without leaving any  feces,  and  have no particif-    I4U
lar  fmell.  In the ftate in which  wc commonly find Rancid oils
them, however, they are exceedingly apt to turn ran- purifitd.
cid, and emit  a moft difagreeable  and noxious  fmell ;
and to this they are peculiarly liable,  when long kept
in a gentle degree of heat.  In this ftate, too, an inflam-
mable vapour arifes from them, which when on  fire is
capable of  producing  cxplofions.    Kcncc, in thofe    s
works where  large beHows are ufed.  they have been
often fuddenly burft by the inflammable vapours ari-
fi;:g from  the rancid  eft  employed for fofiening  the
                                            leather 
Practice.
CHEMISTRY.
199
 Refins and leather.   The expreffed  liiictuous  oils of vegetables
 Balfams.  are, fubjecf to  the fame changes; but from this ranci-
          dity they may all be freed moft effectually, by the fim-
          ple procefs of agitating them  well with water:  which
          is to be drawn off,  and frefli quantities added, till it
          comes off at laft clear and infipid, yithoutany ill fmell.
          The proper inftrument  for performing this operation
          in large is a barrel-churn, having  in it four rows of
          narrow Split deals,  from the centre to the circumfe-
          rence,  each piece fet at obtufe angles to the other, in
          order to give  different directions to the oil and water
          as the churn turns  round, thereby  to mix them more
          intimately.  The churn is to be fwiftly turned round
          for a few minutes ;  and muft  then  be left at reft,  till
          the oil and water have  fully feparated ; which will be
          in 15 or 20 minutes,  more  or lefs, according to the
          fize ofthe churn.  When this water is drawn off, frefh
          Water is  to be put  in,  and  the churn  again  turned
          round,  and this continued  till the  oil is perfectly
          fweet.   If the oil and  water are allowed ro ftand to-
          gether for fome days,  a" gelatinous  fubftance is found
          between them, which is not very eafily mi fcible either
          with Oil or water.   Chalk,  quicklime, and alkaline
          falts, are found alfo capable of taking off the rancidity
          from oils-and fats; but have the inconvenience of de-
          ftroying a part of their fubftance.

                      § 4. Resins and Balsams.

            These  are commonly.reckoned  to be compoSed of
          an effential oil thickened by an acid ; as the effential
          oils themfelves are  found  to  be  convertible into a fi-
          milar fubftance,  by  the exhalation of their more vola-
          tile parts.   True refins are generally tranfparent in a
          confiderable degree, foluble in fpirit of wine, and pof-
   143a    feffed of a confiderable degree of flavour.
Whence      Refins are originally produced by infpiffating the
procured,  natural juices  which flow from incifions made in the
          Stems of growing vegetables,  and  are in that ftate
          called balfams.   The balfams may be confidered as ef-
          fential oils  thickened by lofing fome of their odorife-
          rous  principle, and of their fineft  and  moft volatile
          parts. There are feveralkinds of balfams, which, how7-
          ever, differ from each other only in the fmell and de-
          gree of confiftence ; and  therefore all yield  fimilar
          products on diftillation.  An analyfis of turpentine
          therefore will be fufficient  as an example of the analy-
   1433    fis and natural properties of all the reft.
Turpentine   The true turpentine-tree is found in Spain and the
Chio.      fonthern parts of France, as well as in the ifland of
          Chio and in the Indies.  It is a tniddling-fized ever-
          green-tree, with leaves like thofe ofthe bay, bearing
          purplifh, imperfect  flowers;  and on feparate pedicles
         hard unctuous berries like thofe of juniper.   It is ex-
          tremely  refinous; and  unlefs the refin is difcharged,
         decays, produces fungous excrefcences,  Swells, burfts,
         and dies ; the prevention of which  confifts wholly in
         plentiful bleeding, both in the trunk and  branches.
         The juice is the Chio or Cyprus turpentine of the fhops.
         This fort is quite of a thick confiftence, of a greenifh
         white colour, clear  and tranfparent, and  of Scarcely
   1434    any tafte or Smell.
 Venice.     The kind now called Venice turpentine,  is no other
       # than a mixture of eight parts  of common yellow or
         black rofin with five parts of oil of turpentine.  What
                                                 3
 was originally Venice  turpentine is now unknown. Refins and
 Neumann relates, that  the Venice turpentine fold in J'ailams.
 his country was no other than that prepared from the
 larix tree, which grows plentifully in  Some parts of
 France, as alfo in Auftria, Tyrol, Italy, Spain, &c.
 Of this there are  two kinds ; the young trees yielding
 a thin limpid juice, refembling balfam of copaiba ;  the
 older, a yellower and thicker one.                      1435
   The Strajburg turpentine is extracted from the filver- Strafburg.
 fir.   Dr Lewis takes  notice that Some oS the  exotic
 firs afford balfams, or refins,  fuperior to thoSe obtained
 from  the native European  ones ; as  particularly that
 called bahn ofGileadfir, which is now  naturalized to
 our own climate.   A large- quantity  of an elegant re-
 finous juice  may  be collected from the cones of this
 tree :  the  leaves  alSo, when  rubbed,  emit a fragrant
 Smell; and yield,  with rectified fpirit, an agreeable re-
 finous extract,.                                        1436
   The common turpentine is  prepared from different Common.
 forts of the pine ; and is quite thick, white, and opaque.
 Even  this  is often counterSeited  by mixtures of rofin
 and common exprefl'ed oils.                            I4,-
   All the  turpentines yield a confiderable proportion Phenome-
 of effential oil. From  fifteen ounces of Venice  tur- na on diftii-
 pentine, Neumann obtained, by  diftillation with wa-lation-
 ter, four ounces and three drachms of oil.   The fame
 quantity diftilled, without  addition,  in  the heat of a
 water-bath, gave  but two  ounces  and  an half; and
 from  the refiduum treated with water, only an ounce
 could  be obtained,   The water remaining in the ftill
 is found to have imbibed nothing fromthe turpentine;
 on  the contrary,  the turpentine is  found to imbibe
 part Of the water ; the refiduum and the oil amount-
 ing to a full ounce on the  pound more  than the  tur-
 pentine employed.  When turpentine is diftilled or
 boiled with water till it  becomes folid, it appears yel-
 lowifli ; when  the procefs is further  continued,  of a
 reddifli brown colour :  in  the firft ftate,  it is  called
 boiled turpentine ,■  and in the latter, colophony,  or rofin.
   On diftilling fixteen ounces of turpentine in a re-
 tort with an open fire,  increafed by  degrees, we ob-
 tain firft four  ounces of a limpid colourlefs oil ;  then
'two ounces and  two drachms of a yellowifli one ;
 four, ounces  and  three  drachms of a thicker yellow7
 oil ; and two ounces and one drachm of a dark brown-
 ifh red empyreumatic oil, of the confiftence of balfam,
 and commonly called balfam of turpentine..              T438
   The limpid  effential oil called fpirit of turpentine,  is Effential
 exceedingly difficult of folution in fpirit of wine ; tho' oil difficult
 turpentine itfelf diffolves with great eafe.   One part
 ofthe  oil  may indeed be diffolved in feven parts of
 rectified fpirit; but on  ftanding for fome time, the
 greateft part of the oil fubfides to the bottom,  a much
 greater proportion of fpirit being requifite to keep it
 diffolved.
   2. Benzoin.  This is a very brittle brownifh refin,
 of an  exceedingly fragrant  fmell.  The tree which
 produces benzoin is a native of the Eaft Indies ; par-
 ticularly of Siam and the ifland of Sumatra.   It  is ne-
 ver  permitted  to  exceed the fixth year; being,  after
 this time, unfit for producing the benzoin.   It is then
 cut down,  and  its place fupplied by a young tree rai-
 fed  commonly  from  the fruit.  One tree does not
 yield above three  pounds of benzoin.
   A tree "fuppofed to be the fame with- that which af-
                                               fords
of folutiou.
 14^9
Benzoin. 
I
200
C   M   E    M    I   S   1'   .R    Y.
Pra&ice.
   T44?
Solui 1c i
fpirit of
Mine.
  T44I
flrigiu of
hitumcus.
   I44J
Naphtha.
fords benzoin  h :'c Laft   I:. J i c , i» plentiful alfo in
Yirgiiu  and  Carolina ; from  v  ence  it  has  been
brought into England,  where itgtiv.vs with vigour in
t he eqicn  ground.  The bark and  the leaves have the
f'licli of ben/ion ;  and yield viih rectified fpirit a re-
fill of the fame lmcll ;  but norelin has  been obferved
to iuiic from ii naturally in England, nor has any ben-
zoin been collected from it in America.
   Benzoin diffolves  totally in fpirit  of  w ine into  a
blood-red liquor, leaving  ouly the  impurities, which
commonly  amount to  no  more than a fcruple on an
ounce.  To w ate r, it gives out a portion of faline mat-
tcr of a peculiar kimi, volatile and fublimable in the
fire.  See  984 et /.',/.
   The principal ufe of refins is in the  making of lac-
quer^/, atrnilhcs, ^c.   Sec Varnish.
  »443
Petroleum.
§ J.  Bit
U M F. .V  S.
   These arc inflammable mineral bodies, not fulphu-
 reous,  or  only cafually  impregnated with fulphur.
 They are of various degrees of confiftency ;  and Seem,
 in the mineral  kingdom, to corrcSpond with  the oils
 and refins in the vegetable.
   Concerning the origin of bitumens, chemifts are not
 at all  agreed.   Some chemical writers, particularly
 Mr Macquer,  imagine bitumens to be no other than
 vegetable refms altered in  a  peculiar manner by the
 admixture of fome of the mineral acids in the earth ;
 but Dr Lewis is of a contrary opinion, for the follow-
 ing reafons.
   '< Mineral bitumens are very different in their qua-
 lities from vegetable refins ;  and, in the mineral king-
 dom, wc find a fluid oil very different from  vegetable
 oils.   The mineral oil is changed by mineral acids in-
 to a  fubftance greatly refembling bitumens; and the
 vegetable oils are changed by the fame acids  into Sub-
 ftances greatly reSembling the natural refins.
   '• From bitumens we obtain, by diftillation, the mi-
 neral oil, and Srom refins the vegetable oil,   diftinct  hi
 ihcir qualities as  at  firft.  Vegetable oils  and refins
 have been treated with all  the known  mineral  acids ;
 but have never} i elded any thing Similar to the mine-
 ral bitumens.   It Seems, therefore, as  if the oily pro-
 ducts of the two kingdoms were eifentially and Spe-
 cifically different.  The law s of chemical inquiries  at
 leaft demand,  that we do not look upon  them  any
 otherwiSe,  till  we are  able to produce from  one a Sub-
 ftance Similar to the other.  When this fhall be done,
 and not before, the prefumption that nature effects the
 fame changes  in the bowels of the  earth,  will be  of
 fome weight."
   There is a perfectly fluid, thin bitumen, or mine-
 ral oil,  called naphtha, clear and colourlefs  as cryftal ;
 of a ftrong fmell;  extremely fubtile ; fo light as to fwim
 on all known liquors, ether perhaps excepted : Spread-
 ing to  a vaft furface on  water, and  exhibiting  rain-
 bow colours ;  highly inflammable : formerly made ufe
 of in the compofition of the fuppofed inextinguifhablc
 greek fire.
   Next to this in confiftence is the oleumpetra, or pe-
 trohu.i; which is  groffer and thicker than naphtha,
 ofa yellowifli,  reddr.h, or brownifh colour  ;  but very
 light,  So as to fwim  even on fpirit of wine.   By di-
ftillation, the  pc:roV.-.m becomes thinner  and more
 fubtile, a grels matter Whig left behind ;  it does not,
 however, eafily arife, nor ,k'i.; fi totally lofe its  odour
 by this procefs,  without 1 irticular managements  or
 additions.
   Both naphtha  and petroleum are found plentifully
 in fome  parts of 1'erlia,  trickling through  rocks  or
 fw imming on the furface of  w atcr».   Kempfcr gives
 an account of two Springs  near Baku; one affording
 naphtha,  which it receives in drops from fubterranc-
 ous veins; the other, a blackifh  and more fetid pe-
 troleum,  which comes from Mount Caucafus.   The
 naphtha is collected for making varnifhes ;  the petro-
 leum is collected in pits, and Sent to different places for
 lamps and  torches.
   Native  petrolea  are likewife found in  many diffe-
 rent places,  but are not to be had in  the  fhops ; what
 is fold there for petroleum,  being generally oil of tur-
 pentine coloured with alkanet rootl   The true naph-
 tha is recommended againft  diforders  of  the nerves,
 pains,  cramps, and contractions of the  limbs, &c. but
 genuine naphtha is rarely  or never brought to this
 country.
   There  are fome bitumens, fuch as amber, amber-
 gris, pit-coal, and jet, perfectly folid; others, fuch as
 Barbadoes  tar, of a  middle confiftence between fluid
 and folid.  Turf and  peat  are likewife thought to be-
 long to this clafs.
   1. Amber.  This fubftance melts, and burns in the
 fire, emitting a ftrong  peculiar fmell.  Diftilled in a
 ftrong heat, it yields a phlegm, an oil, and a particu-
 lar fpecies of acid fait.  The diftillation is performed
 in earthen or glafs retorts,  frequently with  the  addi-
tion of fand, fea-falt, coals,  &c. which may break  the
 tenacity of the melted  mafs,  fo  as  to keep it from
 fwelling up,  which it is apt to do by itfelf.  Thefe
 additions, however, make a  perceptible difference  in
 the produce of the diftillation :  with fomc the fait
 proves  yellowifli and dry ;  with others, brownifh or
 blackifh, and unctuous or foft like an  extract: with
 fome, the oil is  throughout  of a dark brown colour ;
 with others, it proves  externally green or greenifh ;
 with elixated afhes, in particular, it is ofa fine green.
 The quantity of oil and phlegm is greateft when coals
 are ufed, and that of fait when fea-falt is ufed.
   The moft advantageous method of diftilling amber,
 however, is without any addition ; and this is the me-
 thod ufed in Pruflia, where the greateft quantities of
 fait and oil  of amber are made.   At firft a  phlegma-
 tic liquor diltils;  then a fluid oil ;  afterwards one that
 is thick and more ponderous ; and laft  of all, an oil
 ftill more  ponderous along with the fait.  In order to
 collect the fait more perfectly, the receiver is fre-
 quently changed ; and the phlegm, and light oil, which
 arife at firft,  are kept by themfelves.   The fait is pu-
 rified,  by  being kept fome time on bibulous  paper,
 which  abfdrbs a part of the oil : and changing the pa-
 per as  long as it receives any oily ftain.  For the fur-
 ther depuration as well as the nature of this fait, fee
 Succinum.
   2, Ambergris.  This concrete, whicli  is only ufed
 as a perfume, .yields,  on diftillation,  products  of a
 fimilar nature to  that of  amber,  excepting that  the
 volatile fait is in much lefs quantiiy.  Sec Amber-
 gris.
 •  3.   Pit-coal. See  the articles Coal and Lithan-
                                            thrax
L'-itumeni.
  1444
Amber.
   1445
Moft ad-
vantage-
oufly di-
ftilled
without
addition.
   1446
Amber-
gris.
 . 1447
Fit-coal. 
CHEMISTRY.
1448
Peat.
  1449
Phenome-
na on diftil-
lation.
Practice.
Bitumen*,  thrax.   This fubftance  yields  by diftillation,  ac-
v—-v---' cording  to the  tranflator of rhe Chemical  Dictio-
          nary,  1. phlegm, or water ;  2. a very acid liquor ; 3.
          a thin oil,  like naphtha; 4.  a thicker oil, refembling
          petroleum, which falls to  the  bottom of the former,
          and which riSes with a violent  fire;  5. an acid, con-
          crete fait;  6.  an un'mflammable earth (we fuppoSe he
          means a piece of charred  coal, or cinder) remains in
          the retort.  The fluid oil obtained from coals is  faid to
          be exceedingly inflammable, fo as to burn upon the fur-
          face of water like naphtha itfelf.
            4.  Peat.  There  are very confiderable  differen-
          ces in this  fubftance, proceeding probably  from the
          admixture of different  minerals : for  the fubftance
          of  peat is  plainly of  vegetable origin ;  whence it is
          found to anfwer for the fmelting of ores,  and   the re-
          duction of metallic calces, nearly in the  Same manner
          as coals of wood.   Some Sorts yield, in burning, a very
          diSagreeable finell,  which  extends to a great diftance ;
          whilft others are inoffenfive.  Some burn into grey
          or  white, and others into red, ferruginous aflies.  The
          allies yield, on elixation, a fmall quantiiy  of alkaline,
          and fome neutral falts.
            The fmoke of peat  does not preferve or  harden
          flefh like  that of wood ; and  the foot into  which  it
          condenfes is more apt to liquefy in moift weather.  On
          diftilling *peat in clofe veffels, there arifes a clear in-
          fipid phlegm ; an acid  liquor, which is f ucceeded by an
          alkaline one ;  and a dark-coloured oil.   The oil has a
          very pungent tafte, and an empyreumatic Smell ;  lefs
          fetid than that of animal Subftances,  but more fo than
          that of mineral bitumens.   It congeals, in the cold,
          into a pitchy mafs, which liquefies in a Small heat: it
          readily catches fire from a candle.; but burns lefs vehe-
          mently than  other oils, and  immediately goes out up-
          on removing the external flame.  It diflblves almoft
          totally in rectified fpirit of wine, imoa dark, brownifh-'.;
          red liquor.
                          \  6.   Charcoal.

 Differences   This is the form to which all inflammable matters
 between  are reducible, by  being fubjeeted to  the moft vehe-
 the coals of ment action of fire in clofe veffels ;  but though all  the
 different  coais are ncarly fimilar to one another  in appearance,
  ubftances. t^ere js  neverthelefs a very confiderable  difference
          among them as to  their qualities.  Thus the charcoal
          of vegetables parts wirh  its  phlogifton very  readily,
          and  is ealily  reducible; to wlvte allies :  charred   pit-
          coal, or, as it is commonly called, coak, much more
          difficultly;  and the  :aals  of  burnt animal fubftances,
          far more difficultly than either ofthe two.  Mr Mac-
          quer acquaints  us,  that  the coal of b.dlock's blood
          parts with its phlogifton  with the utmoft difficulty.
          He kept it very red,  in a fliallow crucible Surrounded
          with charcoal, for fix ho. irs and more, ftirring it con-
          ftantly that it might be all exposed to  the air,  without
          being able to reduce  it to  vhite, or even grey  aflies.
          It ftill  remained very black, and full of phlogifton.
          The coals of pure  oils,  or  concrete oily fubftances,
          and foot,  which is a kind  of coal  raifed during the in-
          flammation of oils, are as  difficultly burnt as animal
          coals.  Thefe coals contain very little  faliiie matter,
          and their aflies furnifh no alkali.  Thefe coals, which
         - are  fo difficultly burnt, are alfo lefs capable of inflaming
          with nitre than others more combuftible; and fome of
    201

Vegetable
and ani-
mal fub-
ftances.
them, in a  great  meafure, refift even the action of ni-
tre itfelf.
   Charcoal is the moft refractory fubftance in nature ;
no  inftance having  been known of  its  ever  being
melted, or fhowing the leaft difpofition to fufion,  ei-   1451
ther by itfelf,  or with additions: hence, charcoal is Charcoal
found to be the moft  proper Support for fuch bodies  as perfectly
are to be expofed to the focus of a large burning glaSs. re ra  or]r'
The only true folvent of charcoal is hepar fulphuris.
By the violent heat of a burning-glaSs,  however, it is
found to be entirely diffipable  into inflammable  air,
without havingany refiduum. See Aerology, n°i2Q.
and Charcoal.
   The different Subftances mixed with different coals,
render fome kinds oS charcoal much lefs fit to be ufed
in reviving metals from their calces, or in fmelting
them originally from their ores.   The coals of vege-
table fubftances arc found to anfwer beft for this pur-
pofe>  See Metallurgy.

   Sect. V. Vegetable and Animal Subftances.

   The only Subftances afforded by vegetables or  ani-
mals, which we have not yet examined, are the muci-
laginous, or gummy ; and the colouring parts obtained
by infufion, or boiling in water; and the calculous con-
cretions found in the bodies of animals, chiefly in,the
human bladder. The colouring matter is treated of under
the article Colour-Making, to which werefer ; and in
this Section fhall only confider the nature ofthe others.

            § 1.  Mucilage4 or Gum.
                                                      145a
   The mucilage of vegetables is  a clear tranfparent Mucilage.
 fubftance, which has  little or no tafte or fmell,  the
 confiftence of which is thick, ropy,  and  tenacious,
when  united  with a  certain  quantity  of fupera-
bundant water. It is entirely and intimately foluble in
water, and contains no difengaged acid or alkali.
   When mucilage  is diffolved in  a large quantity of
 water, it does not fenfibly alter the confiftence  of  the
 liquor: but, by evaporation, the  water  grows more
 and more thick ; and, at laft,  the matter acquires the
 confiftence of gum arabic,  or glue ; and this without
 lofing its  transparency, provided a heat not exceed-
 ing that of boiling water has been  ufed.                 I4^j
   Gums,  and folid  mucilages,  when  wTell dried  and pheuome*
 very hard, are not liquefied in  the fire like refins, but na on di-
 Swell, and emit many fumes ; which are, at firft, wa- ftdlatiom
 tery: then  oily,  fuliginous,   and  acrid.  Diftilled
 in cloSe veffels,  an  aqfceous acid  liquor comes  over
 along with an empyreumatic oil, as from other vege-
 table Subftances;  a  confiderable quantity of coal  re-
 mains, which burns to allies with difficulty.
    Mucilages and gums  are not foluble  either by  oils,
 fpirit of wine, alkalies, or acids, except in fo far as
 they  diffolve  in theSe liquors by means  of the water
 in. which the  alkali or  acid are diflblved.   They  are,
 however, the moft  effectual means of  uniting oil  with
 \yater.  Thice  parts of mucilage,  poured upon one
 parr of oil, will incorporate with it by  trituration or
 agitation ; and the  compound will  be foluble in water*
  Vegetable gums are uSed in medicine, as well  as the
  mechanic  arts ;  bm rhe particular ufes to which  each
  oS them is applicable,  will be  mentioned  under the
  name of each particular gum.
                      C c 
                            CHEMI

  The mucila^eob-.ained fVnu animal fubftances,when
not i >o thick, is called jelly, or gelatinous matter ; when
further infpiifaied, the matter becomes  quite lolid  in
the cold, and is called glue.   If the evaporation is ftill
farther continued, the matter acquires the  confiftence
of horn.
   This gel uinous fubftance feems to be the  only  true
anim.d  one ;  for all  pins ofthe body, by long conti-
nued boili ig,  are reducible to a  jelly,  the hardeft
bonesnot excep.cd.   Animal jelly,  as  well as  vege-
table mucilage, is almoft  iulipid  and inodorous; but,
though it isiiiiucult  to deScribe the difference bctwixt
thcin when apart, it  is very eafily  perceived  when
they are both  together.  Acids and alkalies, particu-
larly the latter, dnlblve animal jellies with great eaSe ;
but ihe nature of thefe combinations is not yet under-
ftood. The other  properties  of this fubftance are com-
mon to it with the  vegetable gums, except only that
the animal mucilage forms a much Stronger cement than
any vegetable gum : and is therefore much employed
for mechanical purpofes, under the name of glue. See
 Glue and Isinglass.
          §  2.  Of the Hum j\ Calculus.

    This Subftance has been repeatedly examined by the
 moft eminent chemifts.   Mr Scheele, as has been re-
 lated n° 9S2, etfeq. has been able to extract an acid from
 it.   His account of it in other refpects is  to the fol-
* lowing purpofe.
    1.  All the calculi  examined, whether flat and  po-
 lithed, or rough and angular, were ofthe fame nature,
 and confided of the fame conftituent parts.
    2.  The diluted  vitriolic acid has no effect upon  the
 calcuhis but the concentrated  acid diffolves it, and by
 ;.;»il .nlion from it  is converted  into the fulphureous
 kind,  leaving a black coal behind.
    ;.  Neither diluted nor concentrated fpirit of Salt had
 anv effect upon it.
    4. U> means of nitrous acid, a new one was  produ-
 ced, and which is poffelfed of fingular qualities, as al-
 ready  mentioned.
    5.' Tne folution of  calculus  in  nitrous  acid  is not
 precipitated by ponderous canh, nor are metallic  folu-
 tions Scniiblv altered by it.
    6. It  is  not precipitated by alkalies,  but  grows
 fomewhat vff lower by a fuperabundance of the latter.
 In a ftrong digefting heat the liquor becomes red,  and
 tinges the fkin of  the  fame colour.  It   precipitates
 creen vitriol of a black colour; vitriol of copper, green;
 nlvcr, grey ; corrofive Sublimate, zinc,aud lead, white.
    7. The folution  is  decompoSed .by lime-water, and
 lets Sail a white precipitate, Soluble in the muriatic acid
 without any  efferveScence : but though  there be an
 exceSs oS precipitate, theliquor ftill remains acid; which
 b ppens alSo with animal earth, and.that oS fluor dif-
 folved in the fame acids. On evaporation to drynefs,
 the matter will at-laft take fire ; but when heated on-
 ly to a dull red heat in a clofe crucible, it grows black,
 Smells like burnt alum, and effervefces with acids; be-
  ing convertible before the blow-pipe into quicklime.
    8. Neither this folution, nor the alkaline mixture,
 is char j;e.'. by the acid of ftigar.
    9. Tne calculus  is not changed  by acid of tartar,
 thoayh it is diffolved even in the cold by alkali, when
 reduced to fuch a ftate of caufticity as not to difcover
 the leaft mark o: aerial acid.   The Solution  is yellow
   S   T    R    Y.                            Practice.

andtaftes fwcctiih ;  and is precipitated by all  the  a-  okulua.
ciels,  even  by the aerial.   It dtcompofes  metallic So-  ^~"~v
lutious, but does  not  prccip'u..u: lime-water; and a
Smell  of volatile alkali 1  produced by a little fuperabun-
dance of alkali in the lo'. ■.11! on.   bry volatile alkali has
no effect upon ihe calculus ; but cauftic volatile  alkali
diflblves it, though a prcity large quantity is required
for this pnrpofe.
   10. Calculus  is likewife diffolved by  digcfting in
lime-water ;  and for this purpole lour oiincts of lime-
water are  required  to twelve grains  of the calculus ;
but the latter is partly precipitated by adding  acids to
the folution.  In this union the lime-water  lofes iu
cauftic tafte.
   11. Calculus  is alSo diffolved entirely by  pure wa-
ter ;  but for this purpofe a large quantity 01  fluid is
required.  Eight grains  of calculus  in  fine  powder
will diflblve by  boiling Sor a fliort time iu five ounces
of water.  The  folution reddens tincture of lacmus,
but does  not precipitate  lime-water;  and  when  ii
grows cold, the greateft part of the  calculus  Separates
in fine cryftals.
   12. On diftilling a  drachm of calculus in  a glafs
 retort, a volatile liquor was obtained refembling harts-
 horn, but  without any oil ; and in the neck of the vef-
 fel was  a  brown fublimate.   On heating the retort
 thoroughly red hot, and then leaving it to cool, a black
 coal was left, weighing 12 grains,  which retained  its
 black colour on a red  hot iron in the open air.  The
 fublimate, which had  fome marks of  fufion, weighed
 28 grains, and became  white by a  new  fublimation.
 Its tafte was fomewhat fourifli, but it had no fmell; it
 was foluble both in water and in fpirit of wine ; but a
 larger quantity of fpirit than of water was requifite for
 this  purpofe.   It did not precipitate  lime-Water, and
 feemed  in fome refpects to agree with the fal  fuccini.    145<j
   From thefe experiments our author concludes, that Hisconclu-
 the  human calculus is neither calcareous  nor gyp-  fionscon-
 feous ;  but confifts of an oily, dry, volatile acid, uni- cerning its
 ted with fome gelatinous matter.   The  calculus is an compofi-
 oily  fait,  in which the acid prevails a little, fince it is non'
 foluble  in pure water  ; and  this folution reddens the
 tincture of lacmus.  That it contains  phlogifton,  ap-
 pears from its folution in cauftic alkalies  and lime-wa-
 ter,  but efpecially from the effect of the nitrous acid,
 by which it  acquires quite  different properties than
 from folution in alkalies; nor  can  it be precipitated
 from this folution.   Theanimal gelatinous fubftance ap-
 pears on diftillation, by which a liquor is obtained refem-
 bling fpirit of hartfliorn, and a fine coal is left behind.    x .*
    13. Calculus is found diffolved in all urine, even in js found
 that of children.  On evaporating four kanncs of frefh univerfally
 urine to two ounces, a fine powder  is depofited as  it in urine.
 cools, and a part  firmly adheres to  the glafs.  The
 precipitated powder reaiily diflblves in a few drops of
 cauftic fixed alkali;  and has in other refpects all  the
 properties of cftclns.   Of the fame nature is the late-
 ritious  fediment depofited by the urine  of thofe who
 labc.;r under an ague.   Mr Scheele SuSpected at firft,
 that there was in this urine Some unknown menftruum
 which  kept fuch a quantity of powder  diffolved, and
  which  might afterwards evaporate by expofure to the
 air ; but  altered his opinion on perceiving that  the le-
  oimentwas equally depofited in clofe vcmls.
    14.  All urine contains fome animal earth combined
  with phofphoric acid ; by the fuperabundance  of w hich
                                                acid, 
Practice.
CHEMISTRY.
203
Calculus.
   1459
Salts, &c.
contained
iu urine.
   1460
Bergman's
account of
the calcu-
lus.
 acid, the  earth  is kept  diflblved ; and by reafon  of
 this fuperabundant acid frefli urine communicates a red
 colour  to  lacmus.   By faturation with cauftic volatile
 alkali a white powder is precipitated;  of which three
 drachms and an half are obtained from four kannes of
 urine.  It is foluble in nitrous acid ;  and on adding
 the vitriolic, fome gypSum is precipitated.   On evapo-
 rating the  nitrous acid, another remained, which pre-
 cipitated lime-water; and when mixed with lamp-black,
 afforded phoSphorus by diftillation ;  whence it is evi-
 dent, that the white powder juft mentioned contained
 lime and phoSphoric acid.
   15.  From theSe experiments Mr Scheele concludes,
 that all urine contains, befides the Subftances  already
 known (viz. Sal ammoniac, common Salt, digeftive Salt,
 Glauber's  Salt, microcoSinic  Salt, Sal perlatum, and an
 oily extractive matter), a concrete acid, or that of cal-
 culus, and animal earth. It is alfo remarkable, that the
 urine of the tick is more acid, and contains more ani-
 mal earth  than that of healthy perfous.  With regard
 to the fal perlatum, it was afterwards difcovered by Mr
 Scheele net to be a peculiar acid, but  only a phofpho-
 ric acid diSguifed by a Small  quantity of  foflil alkali
 united with it.   The analyfis is  confirmed by fynthe-
 fis;  for, by combining foffil alkali  with  phofphoric
 acid, our author obtained a true perlate acid.
   In a fupplement to Mr Scheele's differtation on the
 calculus, Mr Bergman obferves,  that he could not Suc-
 ceed in diffolving it entirely either in pure water or  in
 the  nitrous acid,  though the undiflblved part was the
 leSs  in proportion to the finenefs of  the powder  to
 which the  calculus was reduced.  The undiffelved part
 appears moft conSpicuous,  when Small pieces, or Small
 calculi of  a few grains weight only,  are put into a fu-
 perabundant quantity of menftruum,  and kept in a de-
 gree  of heat very near to that which makes water boil.
 Here it will be obferved,  that the greateft part of the
 piece is diffolved; but that at  the  fame  time  fome
 fmall white fpongy particles remain, which are not af-
 fected either by water,  Spirit of wine, acids, or cauftic
 volatile alkali.  If the liquor  be made  fully to  boil,
 thefe particles divide into white rare flocculi, and be-
 come almoft imperceptible, but without any entire dif-
 folution.   Mr Bergman could  not collect  a fufficient
 quantity of them to determine their nature  with  accu-
 racy ;  only he obferved, that when  expofed to a ftrong
 heat, they  were reduced to a coal which.burns flowly
 to'afhes, and is not foluble in diluted nitrous acid.
   " When calculus  veficae  (fays  he) is  diffolved  in
 nitrous  acid, no precipitation enfues on adding the  acid
 ef fugar ;  whence one is readily induced to conclude,
 that there is no calcareous earth prefent,  becaufe this
 experiment is the  fureft  way  to difcover  it.   But I
 have found, in the variety of experiments  concerning
 elective  attractions, that the addition  of a third  fub-
 ftance, inftead of difuniting two already united,  often
 unites both very  cloSely.   That  the  Same  thing hap-
 pens here 1 had the more reaSon to believe^ becauSe the
 acid of fugar contains fome phlogiftic  matter,  though
of Such a Subtle nature, that, on being burned, it does not
 produce-any Senfible coal;  and  the event of my expe-
 riment has fhown, that I was not miftaken in my con-
jecture,.  In order to afcertain this point, I  burned
 coals ofthe calculus toafhes,  which were quite white,
 and fhowed in every  reSpect the Same phenomena as
linie ;  cauSed fome effervefcence  during their folution
in acids,  united with vitriolic acid inte gypfum, were  Calculus.
 precipitated by the acid of fugar, and w ere partly fo-  v~~^~"
luble in pure water, &c.  Notwithstanding this, there
remains about one-hundredth part of the afhes info-
luble in  aquafortis ; being the  remainder of the fub-
ftance  abovementioned,  which, together  with the
concrete acid,  conftitutes the calculus.  If the calculus
be diflblved in nitrous acid, the Solution filtered and eva-
porated to dryneSs, and the dry maSs calcined to  white-
nefs, a calcareous powder is ilius likewiSe obtained."     l4()I
   As  pure vitriolic acid contains  no phlogifton, our Calcareous
author SuppoSed,  that by dropping it, in its concentra- earth fepa-
ted ftate, into a folution of calculus in nitrous acid, the rated f»orn
calcareous earth,  iSany exifted in it,  would be diScover- nhy vitn-
ed.   In this he was not  disappointed ; for w hen the     aci  '
folution  was faturated, fome Small cryftals  were  thus
immediately Separated.   TheSe, on examination, were
Sound to he gypfum ; and, after being diffolved in di-
ftilled water, were precipitated by acid of fugar.  "VY hen
the  folution of calculus was very much diluted, no
change appeared at firft on the addition of oil  of vi-
triol ; but after a little evaporation,  the abovemen-
tioned cryftals began to appear.   Some calculi of the
bladder or kidneys at leaft certainly contain lime, bur.
Seldom more than one half in an hundred parts,  or one
in 200 parts.                                           «
   By the affiftance of heat, concentrated vitriolic acid
diffolves the calculus with effervefcence, and the folu-
tion is of a dark brown colour.   Oh adding a little wa-
ter,  a kind  of coagulation takes place ; but by adding
more, the liquor again  becomes clear, and affumes a
yellowifli  colour.   Mr  Bergman agrees  withvMr
Scheele in fuppofing that the muriatic acid has no ef-
fect  upon the calculus ; but he is in no doubt whether it
may not  extract fome part of the  calcareous  earth.       x ga
   The red  colour affumed by the folution of calculus Red colour
in aquafortis is remarkable.  A faturated folution dif of the ni-
covers no fmell of nitrous acid,  and if evaporated by trous folu-
itfelf in a large open veflel, the  liquor affumes  at laft tion ac_
a deep red colour, and fcarcely contains any nitrous "unted
acid  :  for, on  the one  hand, paper tinged with lac- °r'
mus  fcarce Shows anyrednefs; and,  on the other, the
colour is deftroyed irrecoverably by  the  addition of
any  acid.   By quick  evaporation the folution at laft
Swells into innumerable  bubbles;  the  foam  grows
redder and redder,  and at laft becomes dark red after
it is  quite dry.  This dry mafs  communicates its co-
lour  to a much larger quantity  oS water than before,
and  diffolves very readily in all acids, even fuch as
have no  action on the calculus;  but they  entirely de-
ftroy the colour,  and  that the  more  quickly in pro-
portion to their degree  of ftrength; even  alum has
this  effect: on account oSthe Small quantity  of loofe acid
it contains.   Cauftic alkalies  alSo diffolve  the colour-
ing matter,  and deftroy it, but more flowly.
  Our author  endeavours to  account for this red co-
lour  produced  by the nitrons aeid,  from the peculiar
nature of that acid and the  effect it has  upon  phlo-
gifton.   In order to obtain it,  a  proportionable  quan-
tity of acid  muft be made ufe of,  and it ought to be
diluted, that there may be no danger of going be-
yond the neceffary limit.  If too much be  ufed, it will
not produce the proper  effect ;  but,  by reafon  of its
fuperabundance, more or lefs, or even the whole, will
be deftroyed in proportion  to the quantity.   By pour-
ing it in' an undiluted ftate on powdered calculus,  it is
                      C c 2                   con- 
204                                 CHEMI
CV  I'n.  converted in  a fe v moments  into mere foam.  The
'    v----acid of calculus is  the more eafily Separated from the
         aqnafoitis by  evaporation, as the latter is rendered
         more  volatile by the inflammable particles ot the fir-
         mer:  alkali added to  them both united  does not pro-
         duce any precipitation ; a circumftance  generally ob-
         it  ved where  two acids are united.   In this caSe both
         in. acids  unite with the alkali,  according  to  the dif-
         ferent laws of their attraction.  The red mafs obtain-
         ed  after deficcation is, however, very  different from
         the concentrated acid, fuch as is contained  in  the cal-
         culus ; foi it is ot a darker colour, and  very deliquef-
         cent : the leaft particle gives a rofe colour to a very
         confiderable quantity  oS water ;  but the muriatic and
         other ftrong acids  always certainly deftroy it;  and,  in
         a  longer  or fliorter time, produce a colourlefs Solu-
         tion.   This  remarkable  change depends,  according
         to our author, more on the action of the nitrous acid
         upon  the  inflammable part, than upon  any thing re-
         maining behind.—Such red fpots as  are produced up-
         on the fkin by the Solution, are  likewiSe produced up-
         on bones, glaSs,  paper,  and other fubftances ; but
         more time  is required for   their  becoming viiible,
         though  this  too may be a little accelerated by means
   i463   oS heat.
Experi-      The following is an abftract of Mr Higgins's expe-
ments of  riments upon  this  Subject.
Mr Hig-     j.  Eight hundred and forty,grains of dry and well
*"■; °£thl3 powdered calculus were introduced into a glafs retort.
lje     It was  taken Srom a  laminated ftone with a fmall nu-
         cleus, which was likewife laminated. The outward cruft
         appeared very porous, but increaSed in denfity towards
         the centre.  By the application of heat,  an elaftic fluid
         w as firft (lowly extricated ; and which, on examination,
         appeared to be compoSed of  equal parts of fixed and
         phlogifticated air.  The laft portions came over very
         faft,  and were attended with an urinous fmell;  and,
         by continuing the diftillation, it became evident that
          fixed and alkaline  air came over together without form-
         ing any union, as they ought,  on the  common prin-
         ciples of chemiftry, to have  done ; though our author
          is  at a lofs  to know why they did  not unite, unlefs
         they  were prevented by the fmall quantity of inflam-
         mable air which came over along with them.
            From the beginning  of the ioth meafure, a black,
         charry,  and  greafy matter began to line the conical
          tube  and air-veflel adapted to the retort;  and as the
          proceSs went on,  the  proportion  of alkaline air de-
          creased,  while that oS the inflammable air was aug-
         mented,  until towards the end, when the laft  nine
         mi afiircs were all inflammable ; aSter which no more
         would come  over, though the  retort was urged with
         ■a white  heat.  On  breaking the  diftilling veffel, a
          black powder wegbing 95 grains was found in  it.   On
         diverting this Sor  an hour in ten ounces  of diftilled wa-
         ter, and  then filtering and evaporating it to two oun-
          ces,  a yellowifli powder was precipitated, but  no cry-
          ft .Is w ere formed after ftanding a whole night.  This
         poweier was then feparated by filtration, and the liquor
         evaporated to one ounce;  during which time more
         powder  was  precipitated.  It was then filtered a fe-
         c nd  time, and the liquor evaporated to half an ounce ;
         when it began to  depofit a white powder,  and to emit
         2 f ibacid aftringent vapour,  not unlike that of vitrio-
         f.c acid.  Th* v.'l.:te'precipitate, when w-fticd and
   S   T    R   Y.                           Pradtice.
dried, amounted only to  one grain, had a fhining ap-  Calcuiu-
pcaiv.ncc,  and felt very foft, not unlike mica in pow- '"
der.  It was not changed, but rather looked whiter
by expofing it  to a  fierce heat for ten minutes.  It
diffolved  in diftilled water without being precipitated
by cauftic volatile alkali.   Mineral alkali, acid of  fu-
gar, and nitrated terra ponderofa, rendered the folu-
tion turbid ; whence our author inferred, that the pow-
der in queftion  was felenite.
   After the feparation of this powder, the remaining
folution was  evaporated to drynefs with a gentle heat.
During the evaporation  it continued to emit fubacid
vapours,  leaving eleven  grains of powder  of a dirty
yellow colour,  having an  aluminous tafte.   To this
powder he added as much diftilled water as was nearly
fufficient to diflblve it; after wKich  it was fet by for
three weeks.   At the expiration of this term feveral
fmall,  tranfparent, and  cubical  cryftals appeared  on
the fide ofthe veflel  above the furface of the folution ;
and thefe likewife had an aluminous tafte.  The whole
was then diflblved in diftilled water,  and  the folution
filtered.   Acid of fugar produced no change in  the
liquor for at leaft five  minutes,  but an  immediate
cloudinefs took place on a mixture with volatile alkali;
and on filtering the liquor it was again rendered turbid
by mineral alkali, though  the cauftic  alkali already
predominated.   Nitrated terra ponderofa threw down
a copious precipitate, and Pruflian alkali difcovered  &
fmall quantity of iron.   This aluminous folution left
a  yellow  fubftance on the filter; which,  when col-
lected  and dried, weighed  only half a grain: it dif-
folved without effervefcence in  nitrous acid ; acid of
fugar caufed no  precipitation, but cauftic volatile al-
kali threw down a precipitate which diffolved in dif-
tilled water.   This folution was  rendered  turbid by
the acid  of fugar and muriated  terra  ponderofa,  but
no effect was  produced by cauftic  volatile alkali or
lime-water.
   The yellow powder firft depofited  by the folution
weighed two grains  and  a half,  and  by expofure to  a
ftrong heat acquired a deep orange colour.   On di-
geftion with diftilled water, the infoluble part was re-
duced to three-fourths of a grain, and appeared to be
iron : while  the foluble  part was found to be nothing
elfe but gypfum.   Our author, however, is of opinion,
that this iron is  impregnated with a fmall portion of
vitriolic  acid, though  not  in fuch quantity as to ren-
der it foluble.
   The charred matter remaining in  the  retort was
reduced by lixiviation with waier to 80 grains. Thefe
were calcined with a red  heat in an  open  fire,  but
could  not be reduced to a  grey powder  in lefts than
three  quarters  of an hour.  When  thoroughly cal-
cined and cold, it weighed only 21  grains, which com-
municated to hot diftilled water a limy tafte,  and gave
it the property of turning fyrup of violets green.   Di-
luted vitriolic acid had  no  effect upon it,  but it was
rendered turbid  by  aerated volatile alkali and acid of
Sugar.  The remainder  when well dried weighed 16-
grains, which diflblved  in  nitrous acid ai firft with  a
little efferveScence ;  and  when this ceaSed, the Solution
went on  very flowly,  until the  whole was taken  up.
Acid of  fugar  made no change m  the liquid, but  the
whole was precipitated by cauftic volatile ?lkali. Pruf-
fian alkali threw down  a grain, or  perhaps  more, of
                                              blue: 
Pra<Sti ce.
CHEMISTRY.
Calculus.
  1464
His ac-
parts.
          blue; the precipitate digefted with diftilled vinegar loft
          a grain and an half, which was thrown down by cauf-
          tic volatile alkali.  The infoluble part being waflied
          and digefted in diftilled water for half an hour,  was
          partly diffolved ; the folution was not affected by cauf-
          tic volatile alkali, but acid of fugar and nitrated terra
          ponderofa  caufed an immediate cloudinefs.   Seven
count of its grains and an half of the powder, which was infolu-
component  ble both in acetous acid and diftilled water, were rea-
          dily taken up by diluted vitriolic acid, and precipita-
          ted by cauftic volatile alkali: the 16 grains laft treat-
          ed,  therefore, appeared to contain, of clay 7' grains;
          of felenite, fix grains ; magnefia,  one  and a half;
          and of iron, one grain.  The proportions of the dif-
          ferent ingredients in the whole  calculus,  therefore,
          according  to Mr Higgins,  are as follows :
                                                    Grains.
              Iron              -            -            2\
              Selenite            -            -          11
              Clay              -            -            n
              Alufn            -             -            8
              Pure  calcareous earth          -             5
              Aerated magnefia         -        -         11
              Charry combuftible fubftance       -     ,  59
  1465
Experi-
ments on
the fubli-
mate ari-
fing from
it on dif-
tillation.
                                     In all    94^
   In this experiment, a darkifh yellow fublimate adhe-
 red to the neck of the retort; the inner part next the
 retort more compact, but the reft of a lamellar fpon-
 gy texture. This fublimate, when carefully colle&ed,
 was found to weigh 425 grains,  and readily diffolved
 in  eight ounces of  hot diftilled water.  A coaly fub-
 ftance was feparated from this folution by filtration,
 which, when wafhed and dried, weighed ten grains,
 and when expofed to a red heat burned with a green-
 ifh flame, emitting white fumes, which fmelledlike vi-
 triolic Sal ammoniac: the refiduum after calcination
 weighed half a grain, and was of a whitifh colour:
 appearing infoluble in diftilled water, but  diffolving
 with efferveScence in nitrous acid.   Acid of fugar cau-
 fed a very fmall precipitation, which did not take place
 until the  mixture had flood for fome time ; but cau-
■ftic volatile alkali inftantly threw down a precipitate,
 which was taken up,  when waflied,  by the acetous a-
 cid.  The quantity was too fmall to be examined with
 greater accuracy ;  but it feemed to poffefs the proper-
 ties of magnefia.   The faline folution had the colour
 pf fmall beer j and,  when evaporated to two ounces, did
 not depofit any fediment, or yield any cryftals.  The
 black-matter with which the conical tube and air vef-
 fel were lined, weighed 28 grains, and adhered fofaft
 to the glafs,  that it was impoffible to collect the whole
 from the fragments of the glafs.  When diffolved in
 diftilled water and filtered, four* grains of coals, fimi-
 lar to that obtained  from the former, were  procured;
 but no figns of cryftallization were obferved after eva-
 poration to one ounce, and fuffering the liquor to ftand
 all night.
   By this treatment the Solution acquired the confift-
 ence of treacle : fo thatit was plainly not cryftallizable,
 and therefore its analyfis was plainly to be  attempted
 after a different method.  It was now put into a tu-
 bulated glaSs retort, together with fix ounces of di-
 ftilled water to wafh it down.  By diftillation in a fand-
 bath. three ounce* of water were procured, which, dif-
fered in nothing from common diftilled water,  but in
being coloured  with a fmall quantity of the folution
from the neck of the retort.   On changing the recei-
ver, about half an ounce of liquor of the fame kind.
came over, after which the diftillation began to be at-
tended with an urinous fmell.   This continued barely
perceptible for fome time ; but when about an ounce
and an half had paffed -over, it became fo very pun-
gent, that our author could no  longer doubt  of its
being in a cauftic ftate.   A fmall  quantity of mild al-
kali, however, adhered to the lower part of the neck.
of the retort, fome of which was  wafhed down by the
diftillation;  fo  that the proportions betwixt the  two
could not be ascertained.  The volatile alkaline folu-
tion in the retort had the colour of fpirit of hartfhorn,
and like it became darker coloured by the contact of
air; on account of the evaporation of part of the al-
kali, and the reft becoming lefs capable of fufpending,
the coaly matter mixed with it.
   After all the liquor had paffed over, and nothing
remained in the retort but a fmall quantity  of black
matter,  the fire was raifed ; and, as the heat increafed,
this black fubftance acquired a white colour, with  a
kind of  arrangement on the furface, which was occa-
fioned by the heat applied to the bottom of the retort
being only fufficient to raife the fait to the top of the.
matter in the retort;  but as  the  fand became nearly
red-hot, white fumes began to appear, which conden-
fed on the upper part of  the retort, and a little way
down the neck.   The  proceSs lafted  until the matter
was nearly red-hot, when the fumes  ceafed, and  no-
thing "more paffed over.   The  fublimate,  when col-
lected,  wras found to weigh 72 grains, a Mack  porous
brittle fubftance remaining on  the bottom of the re-
tort, which weighed 12 grains.  This refiduum, when
expofed to a ftrong heat, emitted  white fumes, with
a flight  alkaline Smell; by which  proceSs it was redu-
ced, with very little appearance of combuftion, to  a
grey powder weighing three grams,  which was acci-
dentally loft.
   Five  grains of this purified fublimate, mixed with-
as much quicklime, emitted no fmell of volatile alkali;
and, when thrown upon a red-hot  iron, emitted white
fumes.  The fame effect was produced by a mixture
of equal quantities of vegetable alkali and fublimate.
The remainder, confuting of 62 grains, was divided
into two equal  parts ;  the one  of which was  mixed
with two ounces of diftilled water, and on the  other
was poured 60 grains of vitriolic acid diluted with
half an ounce of water.   TheSe two mixtures  being
Suffered to remain for fix weeks, feemed to be  but
little acted upon.   That with vitriolic acid was then
put into a fmall matrafs, and boiled on fand for half
an hour with two ounces of diftilled water, when the
whole was taken up..  The folution looked clear, and
depofited nothing on ftanding.  Mild mineral  alkali
had no effect upon it; but mild vegetable alkali threw
down a  copious fediment in white  flocculj,  which was
rediffolved by cauftic alkali, lime-water, and partly by
mild mineral alkali.  Phlogifticated alkali, acid of fu-
gar, and acid of tartar, had  no effect upon it.  The.
other portion of fublimate,  which had been  mixed
with diftilled water,  was very little diffolved ;  but in
pouring it into a matrafs fome fmall round lumps were
obiervable on the bottom of the glafs..  Thefe were
                                               fix. 
zc*                                 CHEMI

Cak-Jut.   fix or feven iii number, fome weighing* whole gi'^in,
'    "     others not more th.. 1 one-half.   They were very hard
          and compact, wiiii a Smooth Surface,  and in figure re-
          :  mbling the nucleus of the  original calculus.   The
          usholc was then put into a  matrafs with about  three
          ounces of water.  On  boiling it on find Sor  three
          ojartcia  of an iw:r,  about  oiu-lulS,  of it was  taken
          lip: the  folution  palled the filter  very  clear whilft
          hot ; but  on cooling  became  turbid, and at hit de-
          pofited white floccnii,  which were redilfolved on the
          addition of cauftic volatile alkali and  lime-water.  It
          turned fyrup ot  violets green;  which, however, our
          author thinks might have been occafioned by its re-
          i.-.ining volatile alkili,  though it had not the fmalleft
          appearance of any fiich impregnation.  He has never-
          theless frequently obferved, that fometimes the pureft
          vegetable alkali .contains volatile alkali, notwithftand-
          ing the various  operations  and degrees  of heat it un-
          dergoes before it can  be brought to the degree of pu-
          riiy at which it is called fait of tartar.
             On filtering  the folution to feparate what had been
          depofited by cooling,  no change was produced in the
          filtered  liquor by mineral alkali; but mild  vegetable
          alkali produced acloudineSs,  which was inftantly taken
          t.p on adding mineral  alkali and lime-water.   Neither
          i'riilfian alkali,  nor the acids of arSenic,  tartar,  Sugar,
          or borax, nor any ofthe three mineral acids, had any
   1466   effect upon it.
Experi-      2.  An hundred and twenty grains  of the  fame cal-
mcuts with cuius were put  into a tubulated glafs retort, and half
nitrous a-  an ounce of ftrong  nitrous  acid poured upon it.  An
*a*       effervefcence immediately  enfued ;  and fome part of
          the extricated aerial fluid being perferved, appeared to
          be fined air mixed with a fmall quantity of nitrous air.
          When the effervefcence ceafed,  a quarter of an ounce
          more of niirous acid was  added.   On  digcfting the
          mixture  upon hot fand for  an hour, it emitted nitrous
          vapour and  nitrous air; but the latter in  very fmall
          proportion.   When  the folution was completed, the
          w hole was poured into a fmall •aatrafs, and gently boil-
          ed  till the Superabundant nitrous acid was nearly ex-
          pelled.   The Solution was of a deep yellow colour and
          turbid ;  but on adding five  ounces more of water, and
          d i^fting it for a quarter of an hour  longer, it  acqui-
          red the colour  and  confiftency of dephlogifticated ni-
          trous acid.   On cooling it became fomewhat turbid,
          and in a Sew days depofited a darkifh yellow powder ;
          which, when Separated, waflied, and dried, weighed
          lktlc  more than a quarter ofa grain, and, on exami-
   j .6?   nation,  was found to be a calx of iron.
 Cryftallizes   Our author being  defirous to know what effect the
on expofure Sin would have upon it, placed it in a window where
•otLcfuu. the Sun  flione full upon it Sor  four hours every day.
          Here a little moifture Seemed daily  to exhale from it,
          the weather being hot,  and the matrafs,  which  had a
          Ihort wide neck, being only covered,  with bibulous pa-
          per to keep out  the  daft.   In  this  fituation, in  the
          courSe of a week, a few very fmall cryftals appeared
          to float upon the fiirfVr.   Thefe in time fell to the
          bottom,  where they  adhered together fo as to form a
          hard concretiem, ftill retaining a cryflalline appearance,
          but lb Small and confufed,  that it was impoffible to di-
          ftinmiilh their fig-ire;  and  this  depofition of cryftals
          continued for a month,  after whicli it feemed to cealc.
          The loluiiun was then filtered to feparate the fait; af»
  S    T   R    Y.                             Pradicc.
tcr which one-half 0! the liquor was evaporated away, Calcuhn. ^
and ihe reft Set in the ulual place for a for might long- ~~""v
cr, but no more  cryftals appeareel.  1 lit fair, which
weighed  three grains,  was men digefted in four ounces
of diftilled water; bit no part feemed to be dillolved.
Three ounces ofthe water were then decanted off,  and
fix drops of vitriolic  acid added  10 the remainder,
which by the help of digeftion  feemed to diflblve the
Salt flowly ;  but on adding half an  ounce  more diftil-
led water,  the whole was readily  taken up.  Acid  of
fugar had no effect  on thi.. folution; but lime-water
rendered it turbid.   The whole was then  precipitated
with  cauftic  volatile alkali, and the folution filtered,
which lilewifc threw down the lime from lime-water.
The precipitate w a.-, then waflied, and diftilled vinegar
poured upon it,  which did not take it up; but it  was
diffolved  by marine acid.  Phlogifticated alkali had no
effect upon it;  and  the acid oS Sugar occafioned very
little  cloudinefs  after  ftanding  three or  Sour hours ,
Srom which our  author fuppofed that  the  matter  was *
phoSphorated clay.
   Tiie Solution, being now free from iron  and phoS-
phorated clay, had a fubacid tafte,  and looked clearer,
though ftill retaining  a yellow caft.  Acid  of fugar
had  no  effect upon  it; but nitrated terra  pondcrofi
threw down a precipitate, as did  likewife the cauftic
volatile alkali.   Mild vegetable alkali cauSed no preci-
pitation ; which our author attributed to the Solution
oS the manganeSe and clay by  the  fixed  air  extricated
from the alkali.  Two-thirds  of the folution  were
then  put into a  fmall glafs retort,  and two  ounces di-
ftilled off', which had no tafte,  but fmellcd very agree-
ably, and not unlike rofe-water.   After  all the liquor
had palled over,  white fumes appeared in the retort,
and thefe were  foon followed by an aerial fluid.  On
collecting fome of this, a  candle w at found  to burn in
it with an enlarged flame.  Nitrous air did not dimi-
nifli it in the leaft ; and  it feemed to be that fpecies
of air into which nitrous ammoniac is  convertible.
No more than 13 or  14  inches of this  kind  of air
conld  be obtained;  and as foon as it ceafed to  come
over, cryftals were, obferved in the lower part of the
neck of the retort.   On augmenting the heat, a white
fait began to fublime and  adhere to the  upper part of
the retort;  the  operation was  continued until the re-
tort was red-hot; but, on breaking it,  the quantity
of fublimate. was fo  fmall, that very little of it  could
be collected ; though,  from the Small quantity obtain-
ed, our  author was  convinced oS its being the Same in
quality with what was obtained in the former analyfis.
The fait which cryftallized in the neck of the retort
was nitrous ammoniac, as appeared from its detona-
tion perf,  &c.   A grey'powder  was left in the bot-
tom of  the retort,  which hot diftilled  water partly
diffolved;  muriated  terra  ponderofa, acid  of fugar,
andvegetable alkali, rendered this folution turbid : but
cauftic volatile alkali had no effect upon  it.  The re-
maining pan of the powder which was left by the  di-
ftilled water,  readily diflblved with tffcrv efe e nee in the
marine  acid,  and w-as prtcq-'taud  by cauftic volatile
alkali ;  the part foluble in dioillcd water appearing to
be gT. pfum, and that foluble in marine acid to be mag-
nefia.
   From all thefe experiments, Mr Higgins conclude*
the compofition of the  human calculus to be vaftly dif-
                                             ferent 
Practice.
CHEMISTRY.
207
 Calculus.

   1468
Higgins's
account of
the confti-
tuent parts
•f calculus.
   1469
Remarks
on the re-
medies pro-
per for dif-
folving it.
ferent from what either Mr Scheele or Mr Bergman
have fuppofed it to  be.   t(  It appears  (fays he), that
the calculus was compofed  of the  following  different
compounds  blended together; viz.  felenite,  alum,
microcofmic fait, mild volatile alkali, lime, and cauftic
volatile alkali, combined with oil,  fo as to form a Sa-
ponaceous mafs ; calx of iron, magnefia combined with
aerial acid,  clay-enveloped by a faponaceous and oily
matter, and the fublimate already defcribed."  Confi-
dering this  to  be the true  ftate of the  calculus iirthe
bladder, the fmall  proportions of clay,  Selenite, mag-
nefia,  and iron, which are  the moft inSoluble of the
ingredients  ;  the great  folubility of microcoSmic Salt
and alum, and the  miScibility oS  lime,  volatile alkali,
and oil, in water ;  tend to fhow, that the Sublimate is
the cementing ingredient.    Indeed, its infolubility in
Water,  and  property oS forming nuclei out of the body,
as  above  obServed, leave no room to doubt  it.   The
proportion of the other ingredients, and very  likely
their prefence, depend upon chance, volatile alkali and
oil excepted ;  therefore this fublimate fhould be the
object of our investigation.
   Mr Higgins concludes  his differtation with  fome
practical remarks concerning the remedies proper for
diffolving the ftone, for counteracting that difpofttion
in the body which  tends to produce it, and  concern-
ing the regimen proper for thofe  who are to under-
go the operation of cutting  for it.   " The  effect of
mild  mineral alkali  (fays  he) on the fublimate, is
well worth  the attention of thofe who may have  an
opportunity of trying its"  efficacy.   Mild mineral al-
kali may  be  taken in large dofes, and continued for
a length  of  time  with impunity  to   the moft deli-
cate conftitutions, only obferving a few  circumftances;
but this alkali, in  a cauftic ftate,  muft very  often  be
attended with mifchievous coufequences.  Befides, if
we confider that it muft enter the mats of blood before
any part can  reach the bladder,  and the fmall portion
of the dole taken Secreted with the urine, and,  laftly,
the action oS cauftic alkali upon animal Subftances ; we
fliall be at  a loSs to know  on what principle cauftic
alkalies have been recommended in  preference to mild.
Soap  itfelf might as well be recommended at  once;
for foon after cauftic alkali is taken, it muft be in a
faponaceous ftate.  Fixed  vegetable  alkali Should  be
avoided, and  the perference given to the other two al-
kalies.   As it is evident that alkalies have no real ac-
tion on the  ftone in the bladder,  though their efficacy
has been experienced in alleviating the diSeaSe when
timely administered, their mode  of action is only ex-
plicable in the following manner : They either prevent
the generation ofthe fublimate in the fyflem, or elSe
keep it in Solution in the maSs of fluids  : and being in
the utmoft degree of divisibility,  its ultimate particles
are capable of paffing through the moft minute emunc-
-tories ;  by which means it is carried off by other Secre-
tions  as well as the  urinary.   Thus urine, not be-
ing faturated with this matter, acts as a folvent on the
ftone ; and  as the moft Soluble parts  are firft waflied
away,  it falls through time into fragments of irregular
furfaces, which by their friction irritate and  in/iame
the bladder, as has been obferved by  feveral practi-
tioners.
   " Allowing that the fublimate is the cementing Sub-
ftance in ihe calculus,  and judging,  from the effects of
alkalies upon it, their modus operandi in the conftitn- Calculus.
tion, it remains now  to inquire  into  the origin of the %~~~~*~"~~'
calculus.   Mr Scheele has found this fublimate  in the
urine of different perfons ;  and hence inferred, that ft
was a common fecretion ; but it  ftill remains to be af-
certained, whether there be a greater  quantity  of it
procured from the urine of patients who labour under
this diforder than in  thofe  v ho do not ?  If this fhould
not be the cafe,  may  not a deficiency of volatile alkali
in the conflitution be the caufe ofthe concretions in the
kidneys,  bladder, &c. ; or, which muft have the fame
effect, too great a proportion of acid, which, uniting
with the alkali, may take up that portion which would
have kept the fublimate in  folution until  conveyed out
of the fyflem by the urinary and other Secretions ;  and
may not this be the phoSphoric acid ?   If this  latter
Iliould be the caSe, an iucreaSe of microcofmic fait muft
be found in the urine; but  if the  former, a decreafe
of the volatile  alkali, and  no increafe of the neutral
fait.  The fmall quantity  of phofphoric acid found in
the  calculus proceeds from the folubility oS micro-
coSmic  Salt.   Do  not volatile alkali and  phoSphoric
acid conftitute a great part  oS the  human frame ?  and
is their not a proceSs  continually carried on  to gene-
rate theSe in the Syftem ? and is  not this proceSs liable
to be retarded or checked by intemperance, &c. which
may vary their quantities  and proportions ?  and may
not a due  proportion of  theSe be neceffary  to a vigo-
rous and Sound constitution  ?  If fo,  no wonder that  an
increafe or deficiency in either or both of theSe fhould
be productive of Several disorders."
   On this Subject, however, our author has not  had
Sufficient leiSure to make  the experiments neceffary for
its elucidation.  Indeed, it feems  not eafy to do fo ;
as, in his opinion,  at leaft 500 would be required for   i47<,
the purpofe.   " That the  urinary  fublimate is prefent Sublimate
in tubercles found in the lungs of perfons who die of °f cakulua
pulmonary confumptions,  and likewife  in  what are found in
vulgarly called chalk ftones, is what I have experienced : canfunT"
but in what proportion, or whether in quantities  SuS- J^^peo,
ficient to caufe the concretion, is what 1 cannot fay ; pie.
for I have  had but a  few grains of each to  examine,
I have every reaSon to SuSpect, that consumptions and
Scorbutic complaints very frequently arife from a fu-
perabundance of this fublimate in the fyflem ; and that
it is chiefly the caufe of the gout and rheumatifm,  and
folely the cauSe oS the ftone  in the bladder.  I  make
no  doubt but  theSe disorders generally  proceed from
obstructions:  and  it is probable, that either a  preci-
pitation of this fublimate in the fyflem,  or elSe  a de-
ficiency of fome other Secretion,  which would hold it
in Sertution until conveyed out of  the body, may be  the
chief cauSe of thoSe obftructions;  and likewife, that
different degrees of precipitation may produce different
fymp oms and diforders.
  " That mineral or volatile alkali  and  bark have
been ufeful in the above  diforders, has been  affirmed
by experienced phyficians;  and I know an inftance
myfelf of mineral alkali and  nitrous ammoniac  being
Serviceable in a  pulmonary complaint of fome  ftand-
ing.
  " WithreSpeet to the ftone, when it acquires a cer-
tain magnitude,  it is abSurd  to  attempt  to  diflblve it
in the bladder, it  waftes fo very flowly ; and during
this time the patient muft Suffer vaft pain, particularly
                                             when 
20J5

V itriolic
«hcr.
                           CHE    M   I
when the ftone  acquires a nigged furface:  therefore
culling for it at once is much preferable.
   " Mineral alkali taken in the beginning of the com-
plaint, and before the ftone accumulates, will no doubt
check its progrefs,  and may in time change that dif-
  S    T   R    Y.                            Practice.

pofition in the habit.  Patients  who  are  cut  for the Niwom
ftone lhould,  1 think, take mineral alkali for fomc tinie acid.
when the wound i» healed, but not before, for  fear
of bringing on a mortification."
E
N
D
X;
Containing fuch DiscovERiEsas have appeared fince the Compilation of the Article,
                 and which could not  be inierted in their proper Places.
   i*7i
Various
methods of
rectifying
vitriolic
ether.
               I.  Vitriolic Ether.

M  Pellf.tier formerly propofed a method of rec-
     • tifying this fluid by  putting manganefe into
the veffels; but as the vitriolated  manganefe might
perhaps communicate fome injurious quality, another
method is propofed by M.  Tingry.   After firft draw-
ing off the ether,  he adds  a diluted folution of volatile
alkali, and avoids as much  as  poflible the diffipation
of the vapours: the ether is then rediftilled.   lt may
afterwards in this  way be waflied  more fafely,  and
with  lefs lofs.  The  little proportion of the ether
which is  feparated in the water, may be again recover-
ed, or the water may be again employed  for the fame
purpofe.   M.  Lunel  propofes  calcined magnefia for
this purpole, as its fait is not foluble ; though perhaps
pure terra ponderofa might be better.

                II.  Nitrous Acid.
   »47»
UrHitf-
gins's ob-
servations
            On this fubject Mr Higgins has feveral curious and
         interefting observations.  "  It is not an  eafy matter
         (fays he),  to afcertain exactly the greateft quantity of
         dephlogifticated air, which a given quantity of nitrous
         acid may contain. I always found nitre to vary, not only
         in its product of phlogifticated and dephlogifticated air,
         but likewife in their proportion to one another.  The
         jnircit nitre will yield,  about the middle of the procefs,
         dephlogifticated air fo pure  as to contain  only  about
         T'_ of phlogifticated air.   In  the beginning,  and near-
         ly about the latter end of the procefs, air  will be pro-
         duced about twice better than common air.  On mix-
         ing  the different products of a quantity of pure nitre,
         it was found that, by expofure to liver of fulphur, 4
         part  was left  unabforbed ;  and this was the  utmoft
         purity in which I obtained  dephlogifticated air from
         nitre.
            "  According to M. Lavoifier, 100 grains of nitrous
         acid  contain 79;  of dephlogifticated air, and  2Qi of
tuent parts phlogifticated air,  which is not quite four to  one.  But
byNl. La- kjs experiments contradict this; for whatever mode he
         adopted to decompofe nitrous acid, it appeared that the
         proportion of dephlogifticated air was nearly as five to
         one of phlogifticated air.
            "  Mr Cavendiffi has proved, that nitrous acid may
         be formed by taking the electric fpark in  a mixture of
         three parts of phlogifticated  air, and Seven  of dephlo-
         gifticated air,  which is but '7 more  of dephlogifticated
         air than nitrous air contains; which may apparently
         contradict M.  Lavoifier's, aswellasmyown, eftimation
         df the propyl tion of  the conilituent principles  of ni-
 I4?j
. aunt of
 confli-
ifier.
  1474
1-v Mr Ca
trous acid, when in its perfeft ftate.  The red nitrons
vapour-contains three parts of nitrous  air and one of
dephlogifticated air, or one of phlogifticated and  three
of dephlogifticated air ; but nitrous vapour may  be
formed with a lefs proportion of dephlogifticated air;
and which, though it may not be  fo condenlible as a
more perSect nitrous vapour, yet will, when in contact
with pure alkali, unite with it, and form nitre, as was
the cafe in the experiment of  Mr  Cavcndifh.   The
common ftraw-coloured nitrous acid contaius more de-
phlogifticated air than the red nitrous acid or vapour;
the proportion appears to be about four to one ;  but
the colourlefs  contains  about five of dephlogifticated
to one of phlogifticated  air.                             147 c
   "  Having once a charge of nitrous and vitriolic acid Method of
iu a  green  glafs retort, I  put it in a fand-pot  to di- obtaining
ftil;  but ihe pot being Small, the edge  came too near c?lourlefe
the retort, about a quarter of an inch  or  more  above °1jF0U8 a"
the charge  ; which,  before  the procefs commenced,
and when it acquired more than the heat of boiling
water, cracked it all  round in that direction.   Being
thus fituated, I was obliged to withdraw the fire,  and,
before the charge  got cold, to ladle it into an earthen
pan.   On introducing it into a frefh retort,  I obtained
from it nitrous acid nearly as colourlefs as water.   The
vitriolic acid ufed in this procefs not being very per-
fect,  the goodnefs of the nitrous acid was attributed to
the purity of the nitre from whence it was diftilled ;
but in another procefs,  though the fame nitre was ufed
with much purer vitriolic acid,  the produce was of an
high ftraw  colour.   On recollecting the  abovemen-
tioned circumftance,  the vitriolic aeid  and nitre were
next  mingled in  due proportion,  and  expofed  in an
earthen pan fet in fand, to nearly the  heat of boiling
water, for half an hour or more, continually expofing
frefh furfaces to the air.  When the charge was quite
cold,  I introduced it into a retort,  and diftilled  as co-
lourlefs nitrous acid as the former.  As no nitrous air
was emitted during digeftion, it  muft have imbibed de-
phlogifticated air from the atmofphere."                   ,
   Mr Prouft found, that ftrong nitrous acid will fet fire How to fet
to charcoal if it be rendered very dry.  He likewife re- charcoal ob
marked,  that charcoal expofed to  the air a few hours fire hy
after calcination, was unfit for the experiment.   Char- rncai18 °f
coal, he obferves, attracts moifture very forcibly.   The n.1'rous a"
firft effect of the charcoal on the nitrous acid,  he ob- C1 '
 ferves, is to withdraw a portion of its  water from it;
 by which it is  rendered highly concentrated,  at the
 fame  time that the condenfation of the water heats  the
 charcoal in a fmall degree, but fufficiently  to volatilize
 a nitrous vapour; which, as  foon as  it  reaches that
 portion of dry charcoal next the humid part,  is con-
                     1                       denfed 
Practice.
CHEMISTRY.
209
   1477
Effecl of
nitrous a
cid on
Mood.
   Nitre,   denfed by it, and generates heat enough to  promote
   —»----' the  decompofition of the nitrous acid.   Hence we fee
          why the experiment  will not  fucceed if the* acid be
          poured on the furface of the charcoal.
            The effect of nitrous  acid  on blood, according to
          Mr Higgins,  is very  fingular.   Two parts of blood
          procured Srefh at  the  butchers, one of ftrong nitrous
          acid, and about one fifth of the whole  of water, were
          digefted in  the heat  nearly  of  boiling  water  (frefli
          portions of water  being  occafionally added until  the
          whole of  the acid was expelled),  when  it acquired
          almoft thccolour, and exactly the tafte, oS bile. When
          mixed with  a large  quantity oS water,  it acquired  a
          fine  yellow colour ; and, on ftanding, depofited a  Sub-
          ftance of a brighter yellow,  though the  Supernatant
          liquor ftill  retained a  yellow  colour and bitter tafte,
          but not So intenSely  as when the precipitate  was Su-
          spended in it.  The different ftages  of this  procefs
          Were well worthy of obfervation.   No nitrous air  was
          produced, and the acid was expelled in the ftate of  a
          white vapour.  The liquor was found to  increafe in
          bittcrnefs as  the  acidity vaniflied. About  the  middle
          of the procefs, the folution firft tafted  acid,  but  was
          quickly fucceeded by  a  bitter fenSation.   It appears
          that  the nitrous  acid  took  dephlogifticated air Srom
          the blood ; for though red  nitrous  acid  was  ufed, it
          was expelled in a perfect ftate.
                          III.   Nitre.

            Though the artificial generation of  the nitrous a-
          cid,  from a  mixture of dephlogifticated  and phlogifti-
          cated air, is now fufficiently underftood, yet we do not
          well know in what manner nature performs the ope-
          ration. Some chemifts,  particularly M. Thouvenal,
          have found,  that putrefaction  favours the  production
          of nitrous  acid.  All animal fubftances,  during their
          decay, give  out  a vaft quantity of  phlogifticated air ;
          therefore, if  dephlogifticated air  be prefent, it will u-
          nite  to the phlogifticated  air in its naScent  ftate,  and
   I478    form nitrous   acid  : but Mr  Higgins has  obServed,  that
Nitregenc- nitrous acid may be generated in plenty where  there is
rated with-no putrid  proceSs  going on.   "The chemical elabo-
outputre-  ratory at Oxford  (fays he) is  near fix feet lower than
          the furface of the  earth.  The walls  are conftructed
          with  common limeftone, and arched over with  the
          fame ; the floor is alfo paved with ftone.   It is a large
          room, and  very lofty.   There are feparate rooms for
          the chemical preparations, fo  that nothing is kept in
          the elaboratory but the  neceflary implements  for con-
          ducting experiments.   There is  an area adjoining it
          on  a  level  with  the  floor, which, though not very
          large, is fufficient  to  admit a free circulation of  air.
          The aflies and fweepings  of  the elaboratory are depo-
          fited in it.   There is a good fink  in the centre of  this
          area, fo that no ftagnated water can lodge there. Not-
          withftanding all  this,  the  walls  of the room afford
          frefh crops of nitre every  three or  four months.  Dr
          Wall, who  paid  particular attention to  this  circum-
          ftance, and who told me it contained fixed vegetable
          alkali, requeftcd I would analyfe it, and let him know
          what it contained.   I found  that two ounces of it con-
          tained fix drachins of nitrated fixed vegetable alkali,  and
          three of calcareous nirre. The nitre firft appears in fmall
          whitifh filaments as fine as cob-web, which, when they
faction.
get a little larger,  drop off';  So that they never acquire
fufficient growth to diftinguifh their figure ro a  naked
eye.  On finding that they contained fixed  vegetable
alkali, I concluded that it  proceeded Sroni mii,ute ve-
getation; but in this I was miftaken  ; Sor I Sound that
they were Soluble  in water,  and that they  detonated
with charcoal at every ftage  of their growth.  Having
fwept this faline  tfflorefcence  from  the wall,  I dug
deep into it, but could not obtain nitre from ir.  When
a part had been white-waftied,  it yielded  nitre,  but
not fo abundantly as a neighbouring Spot which had not
been treated in the Same manner. Hence it is evident,
that nitrous acid may be formed without the affiftancs
oS  putreScent  proceffes  in a ftill damp air,  where
there  is a Subftance to attract it when  half formed,
whereby it is in time brought to perfection. The above
facts moreover prove, that fixed vegetable ajkali  is a
compound."

            IV.   Marine   Acid.
Murine
 acid.
1479
  Mr Higgins informs us,  that he has, with a view Unfuccefi-
to decompofe fea-falt,  mixed it with manganefe in va- ^l at"
rious proportions,  and expofed them in a reverberating temPts t0
r____r.  :_ - —-11 -i-r-j ___-u. r... .1___1____  .  "decompofe
furnace in a well clofed crucible for three hours, to a
fea-falt
heat nearly fufficient to melt caft iron. In the Same man-
ner he treated manganeSe, Salt, and charcoal, as well as
clay, Salt, and charcoal, and Salt and clay alone, with very
little Succef's.  He treated calcined bones, Salt, and char-
coal,  and calcined  bones  and Salr, as well as lime and
Salt, in the Same manner, without effecting any appa-
rent change in the  Salt. He was informed, however, by
Mr Robertfon, apothecary in Bifhopsgaie-ftreet,  that
he had partially alkalized it, by  expofing it with clay
to a fierce heat; but that  Soon  aSter it got into con-
tact with air, it became neutral again.  " IS  common
Salt and litharge ,be SuSed  (Says  Mr  Higgins), it is in
part decompoSed ;  the acid Suffers  no decompofition,
but unites with the lead;  whereby  it acquires, when
the Saline matter is waflied away, a yellow colour.  It is
evident (adds he)  Srom theSe facts, that the  bafis of
marine acid is a combuftible body,  and quite  different
from light inflammable air, charcoal, or any known
inflammable  fubftance; and that it attracts dephlogif-
ticated air with greater  force than any fiibftance hi-
therto discovered.   Though charcoal  will decouypoSe
all  other acids,  except a few,  when  united  to bodies
which will fix them until they acquire a fufficient degree
of heat, yet it has no effect upon marine acid."
   According to Fourcroy,  if alkaline air be confined
by mercury,  and dephlogifticated marine  acid air be
added to  it  (which  muft be done quickly, as the acid
air would diffolve  the mercury),  each bubble produces
a flight detonation,  and furnifhes  a  very amufing fpec-
tacle.                                                 1480
   Though in Britain the  diftillation of the fpirit of Method of
fait with  clay has long been entirely laid  afide for  the diftilling
procefs  with oil of vitriol, yet  it is ftill practifed in [p!nt ?f,
other countries,  and may be effeted in the following  jayWlt
manner:  Having  previoufly decrepitated the  fait,  and
dried the clay,  they are then to be ground, mixed, and
fiftcd together.  The mixture  is  next  to be worked
with a fpatula,  and then  with the hands, until  it is
brought  into a moderately  ftiff and uniform mafs.
                       D d                   This 
210
                                     CHEMI
         This i> 10 be divided into balls abourthe fizc  of a pi-
         pcon's egg, fo that they can pafs through the neck of
         the retort; but before they arc put into the diftilling
         veffel, it is proper to dry them  thoroughly.   The  re-
         torts mull be of  (lone-ware, and  carefully coated, in
         order to prevent  them from breaking with the intenfe
         beat to which they arc expofed.  They are to be filled
         two-thirds fill  of materials,  and the diftillation muft
         be   performed  in  a  rcverberatory  furnace.    The
         receiver at firft  is not luted on,  becaufe that which
         rifes in the beginning of the diftillation, being very a-
         queois, is to be put by itfelf.  When this has come
         over,  another receiver is  then  to be applied, and ce-
         mented with fat lute, and covered with a cloth daubed
         with a mixture of lime and the whites of eggs.  The
         heat is to be  raifed until the retort is red-hot, and con-
         tinued in this degree until the diftillation ceafes.
            Various proportions of clay and  fait have  been re-
         commended  for  this proceSs ;   but it Seems probable
         that  not  leSs than ten  parts of  clay to one of fait, as
         Pott has directed, will be found neceflary.   Inftead of
         the  clay,  fome direct  the  ufe of  bole;  but this is in-
         convenient on account of the iron it contains.  Pow-
         dered talc has  alfo been  recommended, but this is not
         always free from iron; and where a very pure fpirit is
         wanted, there  is a neceffity for having recourfe to oil
         of  vitriol, and  glafs or ftone-ware veflels.   As  the
         marine acid cannot be feparated Srom the  earthy  mix-
         tures  abovementioned,  but by  means  of  moifture,
          M.  Beaume advifes'to  inoiften  the refiduum,  and
         repeat the diftillation, by which  more  acid will be
         obtained.
            As the marine acid has very little action upon phlo-
«narincacid giftic matters,  it cannot therefore  affect oils, either ex-
upon phlo- proffcj or effential, in a  manner fimilar to the vitriolic
        '" or nitrous.   M. Marges, however, has obServed yellow
         cryftals reSembling amber formed  in bottles, containing
          a mixture of oils and marine acid of moderate Strength,
          which had flood  for feveral months.  The little effect
          which the marine acid has upon  thefe fubftances was
         firft  fuppofed to be owing  to its want of phlogifton in
          itftlf; but when it  was  afterwards found,  that, by
          the  application of certain fubftances which have a great
          attraction for phlogifton, the marine acid was render-
          ed  capable of uniting very readffy with inflammable
          matters, the  former theory was abandoned. It was now
          aflcrted,  that the acid,  inftead of containing no phlo-
          gifton, was naturally endowed with a very confiderable
          quantity;  and  that, in its  new ftate, it  was dephlo-
          gifticated  by the fubftances applied.   On the other
          hand, the antiphlogiftians afferted, that no change was
          thus made upon it, farther than  adding a quantity of
          pure air,  which they fuppofe  to be the bafis of all a-
         cids.   On this  fubject, however, M. Cornette main-
          tains, that the marine acid feems  to have  fo little  ac-
          tion upon  inflammable fubftances, merely becaufe it is
          r.caker than the reft;  and likewife  that  it is  often
         previoufly combined with fome inflammable  matter,
         by  which its attraction is  prevented.  He  maintains,
          that if  the marine  acid  be  concentrated in fuch
          a manner as to render its  fpecific  gravity  to  that
          of  water as  19 to 16, it  will then act upon oils with
         heat a-nJ effervefcence, reducing them to  a  black and
         thick fubftance, and even burning them to a  kind of
         loaL  S..;ncex;.'Cii;acntsbavc been made by Mr Haffc,
S    T   R    Y.
Practice.
Effect of
jrjflic mat-
ters
with a view to inveftigate  the action  of the marine
and  vitriolic  acids  upon balfams and oils; for which
purpofe he mixed  two drachms of fmoking fpirit of
fait with one of each of the oily fubftances to be tried.
The  refults  were, that  Canada  balfam  gained  one
fcruple  in weight; balfam  of  capivi 19  grains; fto-
rax, and Venice turpentine, each one fcruple; afphal-
tum  18 grains; but  ihe  effential  oils  of anife-feed,
benzoin, bergamot, coriander, and many others, were
not altered in any degree.  The action of this acid
upon  inflammable matters,  however, is augmented by
its being reduced into the form of air.
   Gmelin relates,  that, by diftilling a mixture  of five
parts of fait, twelve of fpirit of wine, and four of vi-
triolic acid, to which  he had previoufly added one or
two parts of water, he obtained a completely dulcified
fpirit of fait, and an imperfectly dulcified fpirit of vitri-
ol, upon rectifying the liquor.
   Homberg found,  that  glafs  was corroded  by  the
marine acid :  and his obfervation has been confirmed
by  Dr Prieftley ;  who finds  that  its  corrofive pow-
er is augmented by confining the acid in tubes hermeti-
cally fealed.  Its  power  is exerted not only on flint-
glafs,  but even on common  green glafs; though more
powerfully on the former, where it chiefly attacks  the
red-lead ufed in its compofition.  By inclofing  marine
acid gas for fome weeks in a glafs tube expofed to heat,
an incruftation was formed  on the infide, while  the
air was diminiflied to ^ of its original bulk, one half of
which was abforbed by water ;  the other was phlo-
gifticated air.
   The marine acid is generally met with  of  a  yellow
or reddifh co  our, which by Macquer is given as one of
its  characteriftic  marks.   In general,  however, this
colour is thought to proceed from iron;  but Dr Prieft-
ley has found that it may be produced by  many different
fubftances; and his observations have been  confirmed
by Scheele and other chemifts.  The Doctor is of opi-
nion that it  is occafioned  for the moft part,  if not al-
ways, by a mixture of earth ; and he was able to com-
municate it by means of calcined oyfter-fhells, calcined
magnefia,  pipe-clay, or pounded glafs; but not by
wood-alhes, from whence the air had been expelled by
heat.  It was effectually discharged by flowers of zinc,
a coal of cream of  tartar, and by liver of fulphur;  but
he found that the colour which had been difcharged by
liver of fulphur,  would  return by  mere expofure of
the  acid  to ihe  atmofphere, but  not that which had
been difcharged by flow ers of zinc.

           Dephlogifticated fpirit of fait.

   When the action of this vapour upon  any thing is
to be examined, the fubftance mull be put into a bottle
in fuch a manner  as to remain in contact with it ; or
it may be put into a glafs lube,  which is fufpended  and
fixed  to  ihe  flopp-T, and thus introdured  into  the
bottle.—From  its property of deftroying all vegetable
colours, it promifes to be oS very confiderable uSe in the
aris, provided  it could be had in Sufficient quantity,
and cheap.  It bleaches yellow wax, and when proper-
ly a;.plied to linen, will whiten it Sufficiently, and with
out i .';  ry in a Sew hours.  This may  be effected  by
fteeping the linen  for ihat  fpr.ee of time  in water im-
pregnated  with the dephlogifticated marine gas.  It
unites wiih this fluid  rather more eafily than fixed air.
                                              Ber-
   T482
Glafs cor-
roded by it.
   1483
Caufe of
the yellow
colour of
marine
acid.
  1484
F.xpeditious
method of
bleaching
linen. 
Practice.
CHEMISTRY.
2U
 Marine  Berthollet, in order to impregnate water with it with-
  acid.   QUt expofing the operator to  the Sume,  which is ex-
    "    ' tramely diSagreeable, put the  mixture oS marine acid
         and manganeSe  into a retort.   To this he applied firft
         an empty bottle, and  then Several others filled with wa-
         ter, and communicating  with  each other by means of
         bent tubes; Surrounding the  whole with ice.  When
         the water in the bottles was Saturated, the gas became
         concrete, and fell to  the bottom ;  but with ihe fmalleft
         heat it arofe to the top  in bubbles.  The fpecific gra-
         vity of the faturated water was to that of diftilled wa-
         er, when the thermometer was only five degreesabove
         the, freezing point,  as  1003101000.  This impreg-
         nated water is not acid,  but  has an auftere tafte, and
         has the fame action as the gas,  though in a weaker de-
         gree.   Mr Berthollet has obferved, that the addition
         of alkalies  does not prevent,  but rather  promotes, the
         difcharge of colours  ; for which reafon he directs to
         add a fixed alkali to  the impregnated water in which
         linen is to  be fteeped for bleaching.  This is the ex-
         peditious method hinted at under the article Bleach-
         ing ;  but  which has not hitherto come into ufe, prin-
         cipally through the  high price of  the dephlogifticated
         gas.
           The dephlogifticated  marine acid does not difcharge
         all colours with equal eafe.  Thofe of litmus and fyrup
         of violets  are entirely  deftroyed,  and  turned white.
         The colouring  matter of Brazil-wood, and fome green
         parts of plants, retain  a yellow  tint.  The leaves of
         evergreen  plants relift its action for a long time, and at
         laft only acquire the yellow  colour which  they alfume
         by long expofure to the air; and in general the changes
         of colour which vegetable matters fiiffer from this gas,
         are fimilar to thofe which take  place  on long expofure
         to the air ; and by this  operation the gas is converted
         into common marine acid.
            Oils and animal fats are thickened by this gas; and
         by thefe and other inflammable fubftances it is reduced
phlogifhca- t0 j-^g fl.atc of common marine acid.  Light is faid to
        n produce the fame effect.  It  unites with fixed alkalies
         and  calcareous earths, but without any fenfible effer-
         vefcence ;  and  thus they lofe their peculiar tafte  and
         colour.  M. Berthollet  having boiled  in a retort, to
         which a pneumatic apparatus was affixed,  fome of the
         dephlogifticated marine acid liquor with mineral alka-
         li,  thus  obtained   a confiderable  quantity of  elaftic
         fluid,  compofed partly of fixed air,  partly of the air
         contained in the veffels, and partly of air  confiderably
         purer  than that of the atmofphere.  The refult of the
         combination was common fait.   On repeating the ex-
         periment   with lime, no fixed air was obtained ; but
         that whicli came over became gradually more and more
         dephlogifticated.   Volatile alkali, even  when cauftic,
         occafioned  an  effervefcence,  and  emitted a  peculiar
         kind of air, which was neither fixed nor dephlogiftica-
         sed, but ofa peculiar kind.
            Green vitriol is changed to a red by the dephlogifti-
         cated  gas, but  the  colour of blue and  white  vitriol is
         not  affected.   By  the affiftance of light, it acts upon
         phofphorus,  and the refult is phofphoric and  common
         marine acids.   It  does  not  diffolve  ice nor  cam-
         phor; in  which  refpedts it  differs from the common
         marine acid gas.
            On mixing  marine  acid, manganefe,  and fpirit of
         wine, and diftilling  them with a very  gentle heat, little
   1485
Effect of
the de-
phlogiftic
matter,
&c.
air of any kind is produced, but a quantity  of ethereal Aqua- >•■
liquor  very Slightly  acid.  The  proportion  ufed  by regia.____
Pelletier were an ounce and a half of  manganefe, five
ounces of concentrated marine acid, and  three ounces
of fpirit of wine.  "  In this procefs  (Says Mr Kier),
the whole of the  dephlogifticated acid feems to have
united  with the fpirit of wine, and  to have formed
ether.   The  difficulty of combining marine acid with
fpirit of  wine,  fo as  to form an ether, is well known,
and though there have  been  fome approximations to it,
yet the only inftances in which it has been completely
effected, have fucceeded in confequence of the marine
acid being  dephlogifticated;  by which  its action'on
fpirit of wine, as well as on all  inflammable matters, is
greatly increafed."
   M. Pelletier has obferved, that when we put a bit of
phofphorus into  dephlogifticated marine gas, the for-
mer is  immediately diffolved, and  a light is perceived,
the veffel being filled at the fame time with  white va-    T4g-
pours.   He has likewiSe obferved, that fea-falt, with Method of
an excefs of  pure air,  thrown into heated vitriolic a-procuring a
cid produces a fmall detonation.  To make this  fait detonating
in quantity, take, for  inftance, ten pounds of fea-falt,  ?.m.
mixing it with from three to four pounds of manganefe, quantitr.
pour on the mixture ten pounds of vitriolic acid, and di-
ftil with Woulfe's   apparatus.   Pafs  the  difengaged
acid through a folution of fixed vegetable alkali, either
cauftic or otherwife.  A little  more than ten ounces of
the new marine fait with excefs of pure air is obtained,
and a   quantity of fait of Sylvius,  or digeftivc fait.
The fait with excefs of pure air cryftallizes firft,  and
by means of repeated cryftallizations, is entirely  difen-
gaged  from the other.
V.  A$jja Regia.
1488
Marine
ether.
  This acid, which is named from its property of dif- Various
folving gold,  is compounded of the nitrous and ma- ways of
rine acids.   Gold and  platina cannot be  diffolved in PrePannS
any other menftruum, nor C3n regulus of antimony and a<tua"reEia-
tin  be fo eafily diffolved  by any other as  aqna-re-
gia.   It may be made  various  ways.  1.  By adding
the two acids to each other directly.  2. By diffolving
in the nitrons acid fome fait  containing marine acid,
particularly fal ammoniac and common fait.   3.  By di-
ftilling nitrous  acid from  either of thefe falts.   And,
4. In Dr Prieftley's method  of  impregnating marine
acid with nitrous acid vapour.                            i4g„
  The only difference between   thofe liquors  prepared Differences
by the methods abovementioned is, that when fal am- between
moniac or fea-falt are diffolved in the nitrous acid, the {Me aci,i  ■
aqua-regia contains  a quantityof cubic nitre, or nitrons  quors"
ammoniac, which, tho' it cannot much affect the acid as
a folvent,may make a confiderable difference in the na-
ture of the precipitate.   Thus,  gold precipitated from
an  aqua-regia  formed by the pure nitrous and marine
acids, does   not fulminate,  though  it  does  fo  when
precipitated from one made with fal ammoniac.  There
are no eftabliflied rules with  regard to the proportions
of nitrous and marine acids,  or of nitrous acid  and fal
ammoniac, which  ought  to be  employed for the pre-
paration  of aqua-regia.   The  common aqua-regia is
made by diffolving  four ounces of fal ammoniac in 16
ounces of nitrous  acid ; but  thefe  proportions muft be
varied,  according to the  nature of the intended folu--
                       D d 2                   tion. 
212
C   II   E    M    I   S   T    R   Y.
Practice.
  •   -*   tion.   flatir, for inftance, is diffolved  in the greateft
*    -     quantity by  equal parts of the iwo acids;  regulus of
         antimony by  lour parts of i.iirous acid to  <<nc of ma-
         rine ; and, in general, the greater the quantity of  ma-
         rine acid employed in the mixture, the lefs are the im-
         perfect metals, particularly tin, calcined or  precipita-
         ted by it.  A mixture of  two  p.msot  fpirit of nitre,
         and oae of fpirit ot fit,  diflblves nearly an equal weight
         of tin inn a clear  liq !or,  without  forming  any  preci-
         pitate; but,  for this  purpofe,  the operation muft be
         conducted llovilv, and  heat avoided  as much as pof-
         fible.

                           VI.  Bora v.

            In a memoir in Crell's Chemical Annals, by M.
          Tychfon, the author fhews, by different experiments,
   1400   lhat  it may fometimes  be purified  by folution, filtra-
Mcthodtof tion,  and evaporation  only;  but that fometimes  the
j.unfying  operation is  more eafy and effectual  by previous calci-
borai.     nation ; but then  the product  is a little leffened,  cfpe-
          cially if the calcined mafs be not well powdered, and
          then boiled fufficiently in water.  Powder of charcoal,
          he fays, may be fomeiimes  advantageoufly employed
          in the  purification;  but  in general there  is no diffe-
          rence between  the  crude  and purified borax, except
          iu the  addition  of extraneous matters; at  leaft,  as
          the quantity of acids is the  fame,  the addition of mi-
          neral alkali  is ufelefs:  thefe extraneous matters are an
          animal fat,  and a fand compofed of clay, lime, and  a
          martial  earth.  If the oily matter of  un*r be  fepa-
          rated by palling the lixivium through a ftratum of clay,
          as is fuppofed in the  preparation  of  the  cryftals at
          Noiupelicr,  it would Suggeft  a method of  greatly a-
          brid-Miig the procefs ofthe purification of borax.
VII. Acid of  Borax, or Sedative Salt.
1491
   Mtthodsof   On the preparation of this fait Mr Beaume obferves,
   preparing  tjiat a iju]c morc acid ought to be added to  the borax
   the  fed*-  than wju[ is jlllt  fufficient  to faturate its alkaline ba-
P  tivef:llt    pis.   Unlefs this  be done, the  fedative  fait remains
   bo^lx     confounded with the  other  faline matters in the folu-
             ti.m, and of confequence the cryftallization muft be dif-
             tnrbed.   The  fait, though formed in an acidnlated li-
             quor, is eafily deprived of its Superfluous acid by drain-
             ing upon  paper.  It does not cryftallize  as  Soon as the
             ftronger acid Separates  it from  its bafis,  even tho' the
             Solution of borax had been previoufly made as ftrong as
             poflible;  but this delay is occafioned by the  heat  of
             the liquor; for as foon as  it cools, a confiderable quan-
             tiy of cryftals is formed.
               The acid of borax does not  fall into  powder when
             expofed to the air, but rather attracts a little moifture
1  I* proper- from it.   Its tafte is at  firft  fomewhat fourifh,  then
   tici.      cooling and bittcrifli; and laftly, it leaves an agreeable
             fweetnefs on the tongue.   It makes a creaking found,
             and feels a little  rough between the teeth;  and when
             vitriolic  acid is poured upon it, exhales a  tranfient o-
             dour of mufk.  It is foluble, according to  fome  che-
             mifts, in  the proportion of one to 20 in cold water,  or of
             one to eight in boiling water.  Wenzel informs us,
             that 960  grains of boiling water diffolve 434 of the
             fait-while, on the other hand,  Morveau afferts,  that
             he could  diifolvc  no morc ihan 183 grains in a pound
of diftilled  water.  Roufs  informs us,  that fixed airAcidof
prevents the folution of the fait in water; and Morveau, bora* and
that its folubility is much augmented  by cream of  tar- 1,^0°"'
tar.  When previoufly made red hot, it diffolves in wa- ?J    '   r
tcr with a fmell ot  fiffron, and a grey powder  of an
earthy appearance  is precipitated,  which is foluble in
vitriolic and marine acids, and  n;ay be again precipita-
ted in the form of fedative fait.
   Phlogifticated alkali makes  no change  on fedative
fait in folution;  but paper dipped  in  a folution ot it in
vmeyy.ir, and  afterwards  dried,  burns with  a  green
flame.  It  is  capable  of  vitrification,  though mixed
wiih fine powder of charcoal; and with foot unites in-
to a black mafs like bitumen; which, however, is eafi-
ly Soluble  in  water, and  can Scarce be  reduced to
afhes, but partly Sublimes.   By the affiftance of  heat
it diflblves in oils, eSpecially thoSe of the mineral kind j
and  with theSe  it yields  Solid and fluid  compounds,
which gives a green colour to Spirit  of wine.  Rubbed
with phofphorus  it does not  prevent its inflammation ;
but a yellow earthy matter is left behind.   It fcems al-
fo to give to white and red  arfenic a great degree of
fixity, fo as even to become vitrefcible in the  fire ; and
this property it communicates alfo to cinnabar.  When
mixed and heated with powder of charcoal, it forms no
liver of fulphur.

              Sedative Salt combined,
   1. With volatile alkali.   The produce of this is a pe-
culiar ammoniacal fait, which does not evaporate  when
thrown on burning coals, or otherwife intenfely heated,
but  melts into glafs of a greyith colour,  but tranfpa-
rent, which cracks when  expofed  to the air; and, on
diflblution in  water, flioots into  Small  cryftals, which
appear  to have loft none of their  alkaline bafis.  It may
 be decompofed  by the acetons as well as  the mineral
 acids, and by fixed alkalies  and lime.
   2. With magnefia ibis acid flioots into irregular cry-
 flalline  grains  foluble in vinegar and acid of ants;  in
 which liquids they cryftallize like fmall needles joined
 together at right angles.   They are decompofed by all
 other acids, and  likewife  by fpirit  of wine.   In the
 fire, however, they melt eafily without any decompofi-
 tion; and in  the dry way  fedative  fait decompofes all
 the earthy falts formed by  magnefia and any of  the vo-
 latile acids.
    5. With pure earth of alum, fedative Salt forms a fait
 very difficult of folution, when  one  part of  earth  is
 ground with  four times its  weight of fedative fait and
 water. , The fame kind of earth, mixed  with half its
 weight of fedative fait, forms  a hard grey  mafs, refem-
 bling pumice ftone ;  part of which is foluble in water,
 and yields  a mealy  fediment, together with fome Se-
 dative fait unchanged.
    4.  With filiceous earth the fedative fait does not unite
 in the moift  way; but,  on  melting one  part of acid
 with two of this earth, wc obtain a frothy, hard, grey-
  ifh-whitc mafs, from which, however, the acid may  be
  again  procured.
    5. Cold is not acted upon in the wet way  by  acid of
  borax; ncverthelefs Roufs obferved, that when fedative
  fait was melted  with gold-leaf, it did not vitrify, but
  became frothy and hard,  did  not  colour  the  flame  of
  fpirit of wine,  and only a little of  it was  foluble  in
  water in which  icdaiivc fait had  been cryftallized.
                                                   A 
Pra&ice.
CHEMISTRY.
Acidof    A folution of borax in which fedative fait was diflblved,
borax and  did not precipitate  gold.
its combi-    6.  Platina is not precipitated from aqua-regia by fe-
natio"g-  , dative fait.
            7.  Silver is not  affected by melting with  an  equal
          quantity  of  fedative fait; but  the  latter  is  vitri-
          fied  in fuch  a  manner   as   to become  infoluble in
          water.
            8.  Mercury is not  diflblved either in the dry or wet
          way;  but  a  folution of  borax faturated  with  feda-
          tive fait precipitates it in a yellow powder from nitrous
          acid.
            9.  With copper.  On this metal fedative fait acts but
          weakly,  even when  the  folution is  boiling  hot;  ne-
          verthelefs,  as much  ofthe metal is diflblved, as gives
          a little white precipitate on the addition  of  fixed
          alkali ;  but volatile  alkali does not throw  down  a
          blue  precipitate,  nor  turn  the  folution  of that co-
          lour.   The folution of borax  precipitates  all folutions
          of copper in  acids,  and  then the  fedative fait unites
          with  the copper in form of a light green jelly, which,
          after  drying,  is of  very difficult folution  in  water.
          Bergman fays, itisof an agreeable green colour, which
          it preferves after being dried ; and that, when expofed
          to the fire, it melts  into  a dark-red vitreous fubftance.
          "Wenzel  afferts, that by  long  continued trituration of
          copper filings with fedative fait he obtained a folution
          of the metal,  which yielded cryftals on being evaporat-
          ed. With twice its weight of copper in a covered cru-
          cible, an infoluble vitreous mafs was  obtained.
            10. Tin  is not apparently acted upon by boiling with
          fedative fait;  neverthelefs, the folution becomes turbid
          on the addition of an alkali.  By melting  the  calx
          with  half its weight of fedative fait,  we obtain a black
          mafs  like the dark coloured tin ore.   By  rubbing for
          a long time filings of tin with fedative fait and water,
          and afterwards digeftingthe mixture  wiih  heat for one
          day, an hard,  fandy,  and irregularly fhaped fait was
          obtained,  which,  by  diflblution  in  water, yielded
          tranfparent, white,  polygonous cryftals; and a fait of
          of the fame kind was obtained from  the  flag produ-
          ced by melting  equal parts  of fedative fait and tin
          filings.
            n. Lead is not acted upon directly; but, on adding
          a folution of borax to folutions of the  metal in vitriolic,
          nitrous, marine, or acetous acids, the fedative fait unites
          with the lead.  One part of fedative fait with two of
          minium gives a fine, greenilh-yellow, tranfparent, and
          infoluble glafs.
            12. With iron.  The  acid  of borax diffolves this
          metal more eafily than any other. The Solution is amber-
        .,  coloured, and  yields an ochry fediment, with clutters of
          yellow cryftals containing a little iron. The metal is
          precipitated by borax from its Solutions in vitriolic ni-
          trous,  marine, and acetous acids, and the precipitates
          are foluble  in fedative Salt.   A Solution of iron  may
          alfo be obtained by melting this fait with iron filings,
          and lixiviating the mafs.
            13.  Zinc communicates a milky  colour by digeftion
         with folution of fedative fait.   By evaporation it affords
         a confufed faline mafs, and a white earthy powder by
         precipitation with  alkali.  Flowers  of zinc, melted
         with Sedative fait, form a light green inSoluble flag.
           14. Bifmuth, in its metallic ftate, is not acted upon by
         fedative fait, but is precipitated by borax from a  mix-
 ture  of  vitriolic and marine acids, in  form ofa very
 white powder, which keeps  its colour when  expoSed
 to air, and melts in the fire to a white, transparent, and
 permanent glaSs.
   15. Regulus cf antimony  is not acted upon directly,
 but  its calx is  diffolved  when precipitated  by  borax
 Srom a Solution in aqua-regia.
   16. White arfenic unites with  Sedative Salt either in
 the dry or moift way, and Sorms a cryftallizable com-
 pound,  forming either pointed ramifications, or white,
 greyifh.and yellowifli Saline powder.
   17. On regulus of cobalt the acid has no direct action ;
 but  borax precipitates it  Srom  its Solution,  and the
 calx  melts with the Salt into a flag of a bluifh-grey
 colour; and this, bylixiviation and evaporation, affords
 a fedative fait impregnated  with cobalt,  of a  reddifh
 white colour, and of a ramified form.
   18. Nickel is precipitated from its folution,  and  the
 fedative  fait unites  with it into a faline fubftance diffi-
 cult of folution.
   A variety of opinions have  been formed concerning
 the  nature  of fedaiive fait.   M. Beaume and M. Ca-
 det particularly have made a  great number of  experi-
 ments on the fubject; but as none of thefe have led to
 any certain conclufion,  we Sorbear to mention them at
 prefent.   ThoSe oS Meflrs ExSchaquet and Struve have
 indeed  eftablifhed  Some kind of relation between the
 acids of  borax  and phofphorus, and they have  made
 feveral attempts to analize the former, but with little
 fuccefs.   The moft remarkable  of thefe experiments
 are the following.   1. They diftilled,  with a ftrong
 heat, two parts of phofphoric acid evaporated  to the
 confiftence of honey, one of  fedative Salt, and two of
 water.   Towards the end of the diftillation  a  very
 acid  liquor was obtained; and  the  refiduum was  a
 white earth, in quantity above three-Sourths of the Se-
 dative Salt employed, and which, on examination, was
 found to be the filiceous earth ;  the liquor which paf-
 Sed over  into the receiver being Sound  to be  the vo-
 latile phoSphoric acid.  If,   in  this experiment,  tew
 much  phofphoric acid be added, a  greafy matter re-
 mains; and,  if too little, apart of the fedaiive  fait
 will remain undecompofed.   In their attempts  to com-
 pofe borax,  they combined  phofphoric acid  With mi-
 neral alkali,  the refult of which was a compound  re-
 fembling borax  in  many refpects.  When expofed to
 the fire it meks into a very  fufible glafs, which  has a
 mild  tafte,  and feems  neutral, but  on expofure to
 the air, becomes moift  and acid.  On being faturated
 with alkali a fecond time  and vitrified,  it again deli-
 quefces and becomes acid ; and the more  frequently
 this operation is repeated, the  greater  is the refem-
 blance it bears to borax.   In this experiment they fup-
 pofed that the  alkali  was decompofed,  and converted
 into an earth fimilar to that of fedative fait.
  With earthy fubftances the refults were very  re-
 markable.   With  earth of alum a cryftallizable  fait
 was obtained,  which  made paper burn  with a  green
 flame.  Fixed  alkali added  to  a folution of this fait
 precipitates  an  earth, and  the  fait then formed by
 cryftallization refembles borax in feveral properties.—^
 In the dry way the earth  of  alum,  with the phofpho-
ric acid,  melts info a glafs of the fame fufibility as
that of borax, and  like  it is  fixed  in  the fire.  The
folution of this glafs did not cryftallize.   Common
                                                clay
2IJ
Acid of bo"
rax and its
con.binati-
tions.
   1493
Experi-
ments
made to
determine
the nature
of the fe-
dative fait. 
2i4                                 C    II   E    M
Acid of   clay digefted with phofphoric i» id produces  Silky cry-
iniber.    ful; rtirmbling fcdatrvc lair.  \\ hen dried  with their
    ^    mot'.Tei-water, thefc  give a clear glafs, which  when
         united  with  mineral  alk*li,  has  the  tafte  01  borax,
         imcHs in the fame manner, and has the fame tff  ct up-
          on  metals.   \\ ith limt, magnefia, .md terra ponde-
         rofa, this  acid  products 1 alible  glalle-., infduble in
         water, and  whicli   communicate  a green  colour to
         flame.  Earth of  bones  and felenite  mixed  with the
         acid £ive a white, bar■!, fhining glals, like  the  beft
         cryilal, but fufible as the  glafs of beirax,  and  which
         continued  flexible after it had ceafed to be  red-hot.
         Two  parts of gypfum,  with one of phofphoric acid,
         give a mjlk  white   glafs fit for  foldering metals and
         enameling.   In thefe experiments, however,  it muft
         be remembered, that unlefs  the heat be railed very
         quickly, the phoSphoric acid will be evaporated  before
         any fulion takes place.

                       VIII.  Acld of Amber.

            It  was known  to Agricola,  that a particular kind
         of fait could  be obtained from amber by diftillation;
         but neither he,  nor  any fuccecding chemift for fome
         time afcertained its acid properties.  On the contrary,
         fome'erred fofaras  to imagine that it was a  volatile al-
         kali ; bur,  about the  beginning of the prefent century,
         its acidity began to be generally acknowledged.   This
         property indeed difcovers itfelf by  the tafte,  which is
         inanifcftly acid and  empyreumatic, along with the pe-
         culiar  flavour of amber.  According to Scheele, alfo,
         the aqueous fluid which paffes over in the diftillation of
         amber, is an acid  refembling  vinegar both in tafte and
         chemical properties ; and which of confequence ought
         not to be  confounded with  the  true acid of amber,
   1494   which manifefts qualities ofa  very different kind.
Methods     The properties of  fait of amber can  hardly  be in-
of)Hinf.- veftigatcd  until  it has been  purified; for  which, of
mg the i.ilt confequence,  various  methods  have been  propofed.
of amber. pott recommends cryftallization, after  having filtered
         the folution through cott'on-wool, in order  to retain
         the oil.  Canheufcr attempts the purification by dif-
         folving the impure fait in fpirit of wine, then diluting
         with fix times its quantity of  water,  and cryftallizing
         the Salt.   Others recommend Sublimation with com-
         mon Salt or Sand, and Bergman with pure clay.
            The Salt of amber diffolves, by the affiftance of heat,
         in nitrous  and marine acids,  and in the vitriolic with-
         out heat.   In none  of thefe combinations,  however,
         does it either  alter  the diffolving  acidi, or  fuffer any
         alteration itfelf, except that  it  becomes whiter; with
         nitre it detonates  and flies off; and if the quantity of
         Salt eif" amber has been greater than that oS nitre, the
         latter  is alkalized.  Smckar informs  us, that it  expels
         the marine acid from  fal ammoniac, and fublimes be-
         fore that fait; with which it  does not form any  union.
         When fublimed from common f,dt, it does not alter the
         litter in any other refpect than.giving it a darker colour.
         11 precipitates calcareous earth from its folution in vine-
         gar ; and it decompofes fugar of lead ; but the precipitate
         differs from plumbum corneum.  It does not prevent
         the folution of lead in the acids of fea-falt and nitre ; nor
         docs it produce any. fulphureous fmell by calcination
         w;h charcoal.  Hence it appears  that  it is  neither a
         vitriolic,  nitrous,  nor marine acid; and M.  Bourde-
I   S   T    R    Y.                           Pra&ice.
 li.i  muft have been miftaken, when he affirms, that, Acidof
 aiter detonation of this fait with  nitre, he obtained  a amber an 1
 refiduum, which  t..t:cd  like common  fait,  decrcpija- ,M <on,l»-
 tcd in the fire, yielded cryftals ofa cubical form,  p:e- ?* """'  „
 cipitated filver and mercury from the nitrous acid ; and
 thence conclnded  that it was the fame with  acid of
 Sea-Salt.  It is very dear,  as only about half an ounce
 can be obtained from a pound of amber.
             Acid  of  Amber combined,

    1.  With fixed vegetable alkali.   By  faturating fait of
 amber with the fixed vegetable alkali, and  then flow-
 ly evaporating the folution,  we  obtain, according ho
 Wenzel, a light deliquefcent faline mafs; but, accord-
 ing to Stockar, whofe  experiments are confirmed by
 thofe of Mr Keir,  the  folution abovementioned affords
 fhining white tranfparent cryftals  of a  triangular prif-
 matic figure, with the  terminating points  truncated.
 Thefe cryftals readily diflblve  in  water, deliquefce in
 the  air,  and have a peculiarly bitter  faline tafte.  In
 the  fire  they  decrepitate,  melt,  and remain neutral;
 though Wenzel  has  obferved,  that with an  intenfe
 heat they are decompoSed and become alkaline.  TheSe
 cryftals do not change aquafortis  into aqua-regia ; and
 though they precipitate both the Solutions of lead and
 filver, the precipitates are  neither plumbum corneum
 nor  luna cornea.
    2.  With  Mineral alkali.   This combination  produ-
 ces  long three-fided  columnar   cryftals,  intermixed
 with fome that are foliated.  Thefc cryftals do  not de-
 liquefce in the air, and have a  faline, bitter, and Smoky
 tafte.  They are  lefs foluble  than common fait, and
 melt with  more  difficulty  than  nitre.  They  do  not
 become  alkaline  on  burning coals, and, in their other
 properties,  refemble  ihe former.
    3.  With  volatile alkali.  This fait flioots intoacicular
 cryftals,  having  a fharp,  faline,  biuer, and  cooling
 tafte ;  when heated  in  a filver fpoon,  they melt and
 evaporate entirely ; in clofe veffels they fublime. They
 do not precipitate  folution of filver, nor change fpirit
 of nitre into  aqua-regis.  A  powerful antifpafmodic
 remedy is prepared from rectified fpirit of hartftiorn
 and  fait of  amher.
    4.   With lime.   This  flioots into oblong pointed cry-
 ftals, which do not deliquefce in  the air,  and  are fo-
 luble with  difficulty  even in boiling water;  nor, ac-
 cording  to  Mr Stockar  de Neuforn, can they be de-
 compofed by diftillation either with acetous or  marine
 acids.   They detonate by diftillation with  nitrous acid;
 and are decompofed, either in the moift or dry way
 by the vitriolic.   When mixed  with common fal am-
 moniac in  the dry way, they fuffer a decompofition;
 the fuccinated ammoniacal fait flying off and the com-
 bination  of  marine acid  with  lime remaining behind.
    5. With magnefia.  This yields a  white, gummy,
 frothy, faline mafs, which  acquires a ygllowifli colour
 when dried by  the  fire; and, when  cool, deliquatcs
 in the air.   It is  decompofed by  alkalies and  lime, as
 well as by  the vitriolic acid.
    6. With clay.   By  uniting  the acid of amber  with
 an edulcorated precipitate  of  alum with vegetable al-
 kali, Wenzel obtained prifmatic cryftals,  which could
 not be decompofed by alkalies.
    7. IVith ftlver.  The acid of amber has no effect on
                                               filver 
Pra&ice.
CHEMISTRY.
2'5
Acid of    filver in its  metallic ftate ;  but with  its precipitate
amber and forms thin oblong cryftals, radiated and  accumulated
its combi-  Up0I1 one another, from which the filver may be Sepa-
rations.   ^ ratec] by alkalies, by quickfilver, and by copper.
            8. With copper.  By a long digeftion of copper with
          acid of amber a green folution is obtained,  which by
          mixture with common fait is rendered turbid, by vitri-
          olic acid white, and lets fall a green precipitate  on the
          addition of fixed alkali.  Wenzel,  however, could not
          obtain this  precipitation  by  alkalies.    His folution
          yielded groups of green cryftals, gave a cruft of cop-
          per to zinc, and was precipitated by liver of fulphur.
            9. With iron. Wenzel diffolved a precipitate  of this
          metal  in acid of amber, and from the folution obtain-
          ed fmall, brown, tranfparent, and  ftellated  cryftals.
          Zinc precipitated the metal, but not  alkalies.   From
          a flightly  coloured  folution of metallic iron, Pott ob-
          tained, by means of  alkali, a white precipitate, which
          foon  became  yellow, aud at length green, by pouring
          water upon it.
            10. With tin.  Acid of amber  diflblves tin when
          precipitated by  a fixed alkali ; and the folution  yields
          thin,  broad,  and foliated tranfparent cryftals.  Alka-
          lies throw down but little from this folution ; liver of
          fulphur more  ; and lead, iron, or zinc,  nothing.
            II. With lead.  Acid of  amber  whitens the furface
          ef lead in  its metallic ftate, but does not diffolve it  ;
          neither can lead be precipitated from its  folutions in
          nitrous and marine  acids by fait of amber, though this
          is  denied by Pott.  According to Stockar,  however,
          it forms a white precipitate with fugar  of lead.   This
          metal precipitated by an alkali,  and diffolved in acid
          of amber, forms long  foliated  cryftals lying upon one
          another ; from the folution of which the lead may be
          precipitated by alkalies in the  form ofa grey powder,
          and by zinc in its metallic ftate.
            12. Zinc, in its metallic ftate, is readily diffolved by
          the acid of amber ;  and by a  combination  with the
          precipitate  formed by fixed  alkali,  we obtain long,
          flender, foliated cryftals, lying upon one another. The
          folution lets fall a white precipitate on the addition of
          fixed alkali; but this  is denied by Stockar, who fays
          that volatile alkali produces a red precipitate.
            13. Bifmuth.  By  means of heat, Stockar obtained
          a folution of  this femimetal in acid  of  amber,  which
          was decompofed by alkalies.   Wenzel  obtained, from
          a precipitate  of  bifmuth  prepared by  means of fixed
          alkali,  fmall,  flender, foliated,  and yellow cryftals;
          which alkalies  cannot decompofe, though black pre-
          cipitates are thrown down by lead and zinc.
            14.  Regulus of antimony.  Little or none of this fe-
          mimetal,  in  its reguline form, is diflblved in the acid
          of amber ;  but it  attacks  the  precipitate made with
          fixed alkali.  This  folution is  very copioufly precipi-
          tated by liver of fulphur, but not by alkalies.
            The combinations  of this acid with gold, platina,
          nickel, arfenic,  and manganefe, have  either been found
          impracticable, or not  yet attempted ; all  thofe above
          defcribed are non-deliquefcent, and part with their
          acid when expofed to the fire.   The elective attractions
          of this acid, according to Bergman, are Singular, as it
          adheres more ftrongly, not  only to terra ponderoSa and
          lime, but  to magnefia, than  to fixed alkali.
            On  the origin of fait of amber,  Mr  Keir remarks,
          that <{ it  deferves to be confidered as a pure and  di-
ftinct acid.  No proofs have been adduced of its being Acid ef
a modification either of the marine or vegetable  acids,- amber and
as Mr  Cornette and  M. Hermbftadt have  fuppofed.lts ?om^"
The  former, having diftilled  fpirit  oS  Salt with oil of .a lu^  '  ,
lavender, obtained  an acid which fmelled like Salt of   I4t^
amber,  but on examination  was found to retain  the On the  na-
properties of the muriatic acid.  He alfo relates, that, ture of  the
when purifying a  confiderable quantity of  the fait of acid °* alli"
amber which he  had prepared himfelf, fome fea-falt
was feparated, whicli in the diftillation had arifen along
with it.   But this obfervation cannot be juftly applied
to (how  any refemblance betwixt thefe two, any more
than  the fmell in the former cafe could fhow an analo-
gy betwixt it and oil of  lavender.   This mixture  of
fea-falt with acid of amber, however, may readily ex-
plain  the miftake of M. Bourdelin  already mentioned.
M. Weftrumb and M. Hermbftadt  have both laboured
in vain  to convert the  acid of amber into acids of fu-
gar and  tartar by  frequent  diftillations with fpirit  of
nitre ; and their want  of fuccefs confirms the account
already  given,  that the acids of nitre and  amber have
no action upon each other, farther than that the  for-
mer  is phlogifticated or changed into red  fumes, and
the latter becomes whiter. Neverthelefs, if Mr Scheele's
obfervation of the identity of the acid  liquor,  which
comes over in  the diftillation of amber with acetous
acid, holds good, we fhall have the beft reafon yet
given to afcribe the origin of this acid to the vegetable
kingdom ;  and when we confider the  very  different
properties that  are  affumed  by  the  vegetable  acids,
which,  however, are convertible  into  one  another,
no reafon can be drawn from the diverfity  of its pro-
perties with thofe of other vegetable acids, againft its
having a common origin  with  them.  Indeed the na-
tural hiftory of amber, its  fimilarity to  gums and re-
fins, and its involved infects, afford other arguments in
favour of the opinion.
IX.  Acid of Arsenic.
1496
cal acid.
  M.  Berthollet  remarks  upon  Mr Scheele's  pro- M. I'elle-
cefs, that  during  the operation a great quantity  of tier's me-
dephlogifticated  air  is expelled from  the acid.   M.tllod of
Pelletier has found another method of procuring the Focuring
arfenical acid.  He mixes common white arfenic  with *„f *.vjm"
nitrous ammoniac,  and  diftils the mixture.  At  firft
phlogifticated  nitrous acid  paffes over, then the  vola-
tile alkali, and laftly the arfenical  aeid remains in the
retort in form  of  a vitreous  mafs, which deliquefces
into a very denfe acid liquor, reddening fyrup of  vio-
lets, and effervefcing with alkalies.  Mr Macquer had
formerly defcribed this procefs, and obferved, that the
nitrous  acid pafles  over  firft,  and then the volatile al-
kali ; but was  of opinion that the refiduum was no-
thing bin arfenic.   He  mentions a detonation  which
took place in his experiment;  but nothing of this  kind
was obferved  by  M. Pelletier: he only informs us,
that the  nitrous acid was driven over with great vio-
lence, while that of arfenic united with the volatile al-
kali.  M. Berthollet, who has endeavoured  to afcer-
tain the weight gained  by the converfion of fulphur,
phofphorus, and arfenic,  into acids, determines that
of arfenic to be about one-ninth of  the whole.  At rhe
Same time he obferves, that this additional weight does
not diScover the whole weight of the air  contained in
                                                the 
i\()
CHEMIST   R    Y.
Practice.
Aei.'. nf
• 'vlnbt
  the arfenic, as ii had that neceflary to convert  it into
,l c .lx before the operation of converting it into an acid
" was begun.   On  the other hand, M. Bergman  aliens,
  thai onc-fiith of whirr arfenic is phlogifton, and that
  tiiis e dx is converted  into acid merely by being depri-
  ved of its phb.^ii: m.  Thus the fails related by thefe
  two celebrated chemifts differ cnormoufly from one
  another, M. Berthollet affirming that the zrfenic gains
  a ninth  of its original weight  in the procefs of acidi-
  tic.ii ton  ; and M. Bergman,  that  it lefts a fifth partof
  the fame.  M. Berthollet endeavours to reconcile this,
  by  fuppofing  that Bergman had employed  marine acid
  fir the preparation of his arfenical acid, which  is well
  known to cary off with it  fome part  of  moft of thofe
  Subftances with which it is capable of combining ; and
  to  this he attributes the  lofs oS weight in Bergman's
  proceSs.

              IX.  Acid of Molybd.t.xa.
»4>7
 M. lvl'.c-    The opinion oS M* Bergman concerning the metal-
 tier'* cipe- iic nature of the acid of molybdaena has obtained fome
 nments.   confirmation  from the experiments  of M. Pelletier.
          He was not able indeed to obtain any regulus ; but by
          means of oil alone  he procured, by two hours vehe-
          ment  heat,  a fubftance  flightly agglutinated with  a
          metallic luftre, containing fmall round grains ofa grey
          metallic colour, very vifiblc by  the help ofa magnifier.
          Thefe he fuppofes to have been a true regulus of mo-
          lybdaena ;  which  he found to poflefs the following pro-
          perties,   i.  It is calculable by fire into  white calx.
          2.  It detonates with nitre, and the refiduum is a calx
          of molybdaena united with the alkali ofthe nitre. 3. It
          is  converted  into a  white calx  by  means of nitrous
          acid.  4. It yields inflammable air when  treated with
          alkalies in the dry way, and forms peculiar compounds
          with them.   4. It forms regenerated  molybdasna with
          fulphur.  6. It unites, and  forms peculiar fubftances
          with metals.  By uniting it  with  filver, iron, and
          copper, we have friable reguline maffes; and refractory
          powders with lead and tin.
            Our author, in confequence  of his experiments, con-
          fiders molybdaena as  a metallic  fubftance mineralized
          by fulphur ; and  the earth called the acid of molyb-
          drnaasa  calx much dephlogifticatcd, which has  re-
          tained  part of the  air contained in the  nitrons acid.
          He obferves  likewife an analogy betwixt molybdasna
          am! antimony in their chemical refults.  Both of ihem
          yield vitrifiable argentine  flowers by fimilar operations,
          and both are changed into  white earths by nitrous
          *cid ; but  they differ in  the  two  following refpects.
          1.  The  latter eafily gives a Sufible regulus;  but  the
          molybdaena Seems to be the moft refractory of all  the
          femimetals.   2  The calx of regulus of  antimony is
          foluble by  alkalies  in the moift  way, but that of mo-
          lybdoena is not.

                X.  Acid  of Tungsten or Wolfram.
   14'/
IVopeuics    Mr Luvart, who has examined this mineral, gives
of tungften. tj,c  following account of it.   1. It  is infufible by  the
          blow-pipe, though the angles of the pieces into which
          i: is broken  are  thereby remded.   2.  It effervefces
         with microcofmic  fait, and melts before the blow-pipe
         into a  reddifh glafs.  3. With borax it  effervefces ;
 and by She outward flame  ofthe blow-pipe is changed Acid of
 into a reddifli glaSs; by the internal flame intoa green-  tuB^ftew.
 i(h one.   4. Heated by  ufelf in a crucible, it Swelled,  '
 became fpongy,  femivitrified, and was attracted by
 the magnet.   5.  With an equal part of  nitre it deto-
, nated, or  boiled up with a blue flame round the edges,
 and nitrous vapours arofe.  The mafs was  foluble  in
 water, and let fall a white precipitate with acid.   5. It
 melted readily with fixed alkali, leaving a kind of black
 matter  in the  crucible,  and  a fmaller quantity  of
 lighter coloured  fubftance on the filter.   Thefc  rcli-
 duums fhowed a mixture  of iron and manganefe.  6.
 With nitrous acid the filtered folution let fall a  white
 precipitate,  at firft fweet, but afterwards bitterifli and
 fharp, and which caufed a  difagreeable fenSation in the
 throat ; and the acidity of the folution of it  was ma-
 nifeft, by its turning the tincture of turnSole  red.
    Having examined the Subftance by  means of liquids
 in Mr Scheele's way, they obtained the  fame yellow
 powder  which  he  had characterized as the acid  of
 tungften,  along with a very fmall refiduum, which ap-
 peared to  contain a mixture of tin.  Proceeding far-
 ther in the analyfis, they found that wolfram is com-
 pofed of manganefe, calx  of iron, the yellow matter
 called the acid of tungften by Bergman and  Scheele,
 with a very little mixture of quartz and tin, and which
 they confidered as accidental.                           I499
    They now proceeded to examine the yellow matter, ofthe yel-
 fuppofed by the two celebrated chemifts juft  mention- lowmattcr,
 ed to be a Simple acid fait, but which* turned out  very ca|led its
 different  on their inquiries.   In order  to  procure a"cld*>YMf
 quantity of it, they  melted fix ounces of wolfram  with  tlce c'
 as much vegetable alkali,  diffolved  the mixture  in di-
 ftilled water, filtrated the  liquor, and evaporated  it  to
 drynefs.   Thus  they  obtained a white fait;  upon
 which, when  dry,  they poured nitrous acid, and fet
 it to boil  in  a fand-bath ; by which  operation it be-
 came yellow.  They  then decanted the liquor,  pour-
 ing frefh  acid upon the refiduum ; and repeated the
 operation a third time in order to deprive it  of all the
 alkali. The remaining  powder was then calcined in a
 cupelling  furnace under  a muffle, when it  came out
 quite  pure and yellow.   The  properties of it  were
 then found to be as follow.   1.  It is entirely infipid,
 and of the fpecific gravity of 6.12.   2. Before the
 blow-pipe, it  continues  yellow in the exterior flame
 even  though  put on charcoal; but  grows black and
 fwells, though it  does not melt, in the internal flame.
 3. In the  internal  flame it forms a  blue tranfparent
 glafs with microcofmic  fait.   The  colour vanifhes in
 the external flame, but  appears again  in the internal
 one ;  but by a continuance of this operation, it at laft
 lofes its colour fo much  that  it cannot  be recovered.
 4. It  effervefces, and forms a brownifh yellow tranf-
 parent glafs  with borax,  which keeps its  colour in
 both flames.   6. When triturated with water, it forms
 an emulfion which  paffes  through filters without be-
 coming clear,  and continues a long time without any
 depofition.  7. It is infoluble in acids, but  dificlves
 readily in the vegetable alkali both in the moift and dry
 way;  though the produce has always an excefs of alkali.
 8. On adding nitrous  acid  in greater quantity  than
 what is neceffary to  faturate this excefs, a white  pow-
 der falls, which is the fame nub the acidof turgften dif-
 covered by Mr Scheele j but which Meffrs Luyarts will
                                                not 
Pra&ice.
CHEMI
Acid of
tungften.

   1500
No fimple
acid procu
         not allow to be a fimple acid,  though they admit that
         it contains one ; and affirm, that its properties are va-
         rious according to the circumftances of its precipita-
         tion.  The properties of it, as defcribed by them, are
         the following.   1. It is fufible before the blow-pipe,
ruble" from exhibiting the fame phenomena, as the yellow matter.
tungften.  2.  By calcination  in a  little  pot  or teft,  it emits th©
         fmell of nitrous acid, and turns yellow  ; but,  on cool-
         ing,  remains white,  infipid,  and  infoluble ; and this
         refiduum melts by itfelf before the blow-pipe.   3. A
         yellow colour is produced either by vitriolic or marine
         acids;  and  the filtrated liquor affords a neutral fait
         with bafis of fixed alkali,  according to the nature of
         the acid employed.   If the vitriolic acid  is employed,
         and the operation performed in a retort, a quantity of
         niyirous acid paffes over.   4. If, inftead of pouring the
         acid on the fait, it be poured upon its Solution, no pre-
         cipitate will be formed, not even by making the liquor
         boil, if the quantity of acid is  Small; only the  folution
         loSes its  Sweet tafte, and acquires more bitterneSs.  On
         pouring on a large quantity of acid, and  caufing the
         liquor boil,  a yellow precipitate  is formed in every
         refpect fimilar to the yellow matter So often mentioned.
         5.  This Salt is completely diflblved by the boiling with
         vinegar.   On leaving the Solution to cool,  a white
         waxy matter adheres to the fides of the veffel;  which
         being wafhed and kneaded with the fingers, forms an
         adhefive mafs like bird-lime,  having a fat and  greafy
         tafte.  By expofure to the air it acquires  a dark grey
         colour,  lofes its adhefive property, and becomes bitter.
         It diflblves in water ; and gives at firft a fweet,  then a
         bitter tafte,  making  the tincture of turnSole  red.  6.
          On evaporating the alkaline Solution to dryncSs, pour-
         ing acetous acid upon the refiduum, and then making
          it  boil,   the  greater part of  the refiduum,  was dif-
          Solved, and on cooling afforded  feathery cryftals.  TheSe
          when edulcorated had a fweet tafte, though lefs ftrong
          than that of the former fait, which  afterwards be-
         came bitter.  Their folution  turned blue paper red ;
         was precipitated, and became  like an emulfion with fpi-
          rit of wine ;  and the refiduum, which did  not diffolve,
          appeared to be of the fame nature.  The cryftals dif-
          folved in. frefh acetous  acid, and communicated a blue
          colour to the acid; but this gradually  difappcared on
          cooling, and a glutinous matter was depofited  on the
          fides of  the velfel,  which  had the  properties of the
          former fubftance of that fort.   If, in place of  letting
          the folution cool, it  fhould be kept boiling,  the blue
          colour difappears, and nothing is precipitated.   By ad-
          ding fpirit  of wine when the liquor is almoft  evapora-
          ted to drynefs,  a white powder is precipitated ; which
       '   after being edulcorated with frefli fpirit of wine, taftes
          exceedingly bitter, and is very foluble in water.  This
          folution, however, does  not  redden blue paper, nor
          make a  blue  with vinegar.  With vitriolic  acid its
          folution is blue 5 with vitriol of copper it forms a white
         precipitate.   All  thefe falts,  by  calcination,  firft be-
         come blue,  then  yellow,  and laftly white.   7. On
         pouring a quantity of lime-water upon  the folution  of
         the precipitate Sormed  by the  nitrous acid, as well  as
         on thofe obtained by the acetous acid,  white precipi-
          tates were  formed, all of which were a true regenera-
          ted tungften.  Having afterwards impregnated the li-
          quors with fixed air, and boiled them  in order  to pre-
          cipitate  the lim*  morc completely, they found in  the
   S   T   R   Y.                                  217
folutions,  after they were  filtrated and  evaporated to Acidof
drynefs, neutral falts formed of the precipitating acids, tungften.
joined with alkaline and calcareous Safes.  This pro-
ved, that  botn alkali and acid  were concerned in  the
precipitation.   8. (Jn ponringthe vitriolic folutions of
iron, copper, and zinc, a^well as that of marine mercu-
rial fait, alum, and Pruffian alkali, upon the Solution
of the precipitate formed by the nitrous acid, no  pre-
cipitation  eni'ues, and the acetous Salts of copper and
lead give  white precipitates;  hut the  Pruflian alkali
forms no precipitate with the acetous falts.  Hence it
appears that tins Salt is not a  fimple acid, but  rather
a fait compofed ofthe yellow matter, fixed alkali, and
the precipitating  acid;  and its  compofition appears
more fully from the  follow ing •expeiiments  with  the
volatile alkali.
   1. The yellow powder diffolves entirely in volatile
alkali, but without any perfect fatuiation taking place;
and the alkali always prevails.   2. The folution being
fet in a Sand-bath^roducedncedle-like cryftals,  v. hich
had a lharp bitter tafte, exciting a difagreeable  Sen-
fat ion in the throat.  Their folution turned  the tinc-
ture of turn fole red,  and the liquor from which  they
were cryftallized had the fame properties. 3. Having
repeated this operation with different quantities of the
fame  cryftals,  leaving  fome longer on the  fire  than
others, folutions wee obtained, whofe acidity was in
proportion to the time they had remained on the  fire;
but during the operation they all emitted the fmell of
volatile alkali.  By calcination this alkali was entirely
diflipated, and the refiduum was a yellow powder, per-
fectly fimilar to that with which the operation was be-r
gun.   On making ufe of  a  retort for  the operation,
the remaining powder was blue.   4.  This fait precipi-
tates the vitriolic falts of iron,  copper, zinc, and alum,
calcareous nitre, marine mercurial fait; the  acetous
falts of lead and copper; and with lime-water regene-
rates  tungften.   The vitriolic  acid decompounds it,
and forms a blue  precipitate ;  the nitrous and marine
acids produce a yellow ; but no precipitate is occafion-
ed by the Pruflian alkali.
   Having poured nitrous  acid  upon a  portion of the
folution with excefs of alkali, a white powder was pre-
cipitated,  which, after edulcoration, had a tafte at firft
fweet, but afterwards lharp and bitter, and its folution
turned the tincture of turnfole red.  This, on exami-
nation, appeared to be a triple fait formed of  the
yellow powder, volatile alkali,  and the precipitating
acid.
1501
  The following experiments realize the conjecture of a kind of
Bergman, that the acid of tungften is the bafis of a femimetal
particular femimetal.                                procurable
  1. " Having kept 100 grains of the yellow powder fromtUES"
(fays M.  Luyart) in a Zamora crucible well covered, ftcn"
and fet the whole in a ftrong fire for half an hour, it
became a Spongy mafs  of a  bluifli black  colour,  the
furface of which was cryftallized into fine points,  like
plumofe antimony,  and the infide compact, and of the
fame colour.   It was too hard to be broken in  pieces
by the fingers ; and,  when  ground,  was  reduced to
a dark blue colour.
  2, " Having mixed  100 grains ofthe fame powder
with 100 of fulphur,  and put the mixture in a  Zamo-
ra crucible on a ftrong fire for a quarter of an hour, it
came out a dark-blue mafs, which was eafily broke by
                      E e                       the 
                            C   II    E   M
the fingers ,  and the infide prcfented a cryftil!i;v.yon
like needles  as the laft, but tranfparent, aud ofthe
c.ftourof a dark  lapi.^ lazuli.   Tin- v.u\\ weighed 42
 f;rains, and when placed on bjrning coals yielded no
 niell of fulphur.
   1. «' Having put mother \;^z grains of this ;  v\.^ r
n.ti a Zamora crucible, provided with charco.d,  and
v.ill covered, and .Tecdit in a ftrorg rire, where it
remained  an hour ad  a half, we found,  on breaking
t ic cruc i'.dc nfttr it was cool (a), a button, v. hich fell
to powder iutw ecu the fingers.  Its colour  wy.s  dark
brown ; and on examining it with  a glafs, the e  was
fe-cn a  congeries of metallic  globules,  among  w hi;h
fivne were the bignefs of a pin's head, and when broke
had a metallic appearance at the fracture in colour like
ltccl.  It  weighed 60 grains : of courfe there was  a di-
minutionof 49.  Its fpecific gravity was 17.6.  Having
calcined part of it, it became vello,v, with J JJ- increafe
of weight.   ll.ivi:;g put one  portion of this  fubftance
powdered, i;i iligelei it with the  vitriolic  acid,  and
another with the marine aci 1, neither of them fuffered
morc diminution  than  , • ,. of their weight;  then de-
canting the liquor, and examining  the powder'with a
glaf.-,  the grains were ftill perceived ofa metallic a-
Ipevt.   Both the arid liquors  gave a blue precipitate
v ith the Pruflian alkali,  which let us  know that the
fmall diminution  proceeded  from   a portion of iron
which the button had  undoubtedly got from  the pow-
der of the charcoal in which it had  been fet.  The ni-
tron s acid, and aqua-regia extracted likewife from two
other portiems the ferruginous part  ; but befides,  they
converted them into yellow powder, perfectly fimilar
to that which he ufed in this operation.
   4. •" Having put 100 grains of gold and fifty of the
yellow powder in a Zamora  crucible  furnifhed with
charcoal,  and kept  in  a ftrong fire for  three quarters
of an hour,  there came out  a yellow button which
crumbled  in  pieces between  the fingers ;  the infide of
whr.h  fhowed grains of gold,  feparated from others of
a dark-brown colour.  This demonftrated there had not
been a perfect fulion and likewife that  this  fubftance
was more refractory with gold, fince the heat which it
endured was more than fufficient  to have melted it.
The button weighed 139 grains ; of courfe there was a
diminution of  11  grains.    Having put this  button
with lead  in the cupelling furnace, the gold remained
p.:-e iii the  cupel  ; but this  operation was  attended
with confiderable difficulty.
  5. (i  Having made a mixture of platina and yellow
powder in the preceding proportions, and^expofed it
to a ftrong fire, with the Same  circumftances, for an
hour and a quarter, it  produced a button which crum-
bled with eal'e between the fingers, and in which the
o-^ains of platina were obferved to be more white  than
nf lal, and fomc of them changed fenfibly in their fi-
gure.  This button weighed 140 grains,  and of  con-
fequence there had been a lofs of 10 grains.  When
calcined,  it took a yellow colour, with very little in-
creafe of weight ;  and  after wafhing it to Separate  the
p:..y ...,  there remained 118 grains  ofa  black colour.
   S    T   R   Y.                            Practice
Having placed this  portion again to calcine  over a Acidof
ftrong fire in a muffle, it fuffered no fenfible alteration tungf u. ^
ni weight or colour ; for it neither grew  yellow,  mi
took the brown colour ofthe platina, but kept the fame
bl.ck'.efs as before it was calcined.  Ic muft be  attend-
ed to, that in the warnings there was  mn fo much
care taken to collect all the platina as to ,\\ -i\o it of
the yellow co.lo.;r, and for this reafon the .water car-
ried off part of the fine black powder : aria* corrtequent-
lv the increafe which the platina preferved, after being
wafhed and calcined the fecond time, ou^htto be com-
puted more  than the  18 grains  which it  ihowed by its
w eight.
  " Having mixed the yellow powder with other me-
tals in the preceding proportions,  and treated them in
the Same manner,  the reSult was as follows :
  6. " With filver it formed a button ofa whitifh-brown
colour,  fomething fpongy, whicli with  a few ftrokes
of a hammer extended itfelf eafily,  but on continuing
them Splii in pieces.  This button weighed r 42 grains,
and is the moft  perfect  mixture  we  have obtained,
except that with iron.
  7.  "  With copper it gave a button of a copperifh
red, which approached to a dark brown,  was fpongy,
and pretty ductile, and weighed 135 grains.
  8.  "  "\\ ith crude or caft-iron, of a white quality, it
gives a perfect button, the fratture of which was com-
pact,  and of a whitifh brown colour : it was hard,
harfh, and weighed  137  grains.
  9.  "  With  lead it formed a button of a dull dark-
brown,  with very little lnftre; fpongy,  very  ductile,
and fplitting into leaves when hammered : it weighed.
127 grains.
  10. " The button formed with tin was of a  lighter.
brown than the laft, very fpongy, fomewhat ductile,
and weighed r;8 grains.
  11." That with antimony was ofa dark-brown co-
lour,  fhining,  fomething fpongy,  harfh, and broke in
pieces eafily: it weighed  108  grains.
  12. " That of bifmuth prefented a fracture, which,
when feen in one light, was of a dark-brown  colour,
with the luftre of a metal;  and in another appeared'
like earth,  without any lnftre : but in both  cafes one
could  diftinguilh an  infinity of little  holes over  the
whole mafs.  This button was pretty hard, harfh, and
weighed 68 grains.
  13. " Witfc manganefe it gave a  button ofa dark
bluifh-brown colour and earthy afpect;  and on exa-
mining  the  internal part of it  with a lens,  it  refem-
bled impure drops of iron: it weighed 107 grains."

                XI. Acid of Ants.

  Etmuller is among the firft authors who mentions
the exiftence of this  acid, and fpeaks of obtaining it
by diftillation.   Nothing  of its properties, however,
was known, until Margraaf undertook to examine it;
of whofe experiments  we have  an   account  in  the
Memoirs of the Berlin Academy for 1749.   Since  his
time a number of chemifts have profecuted the  fubject
                                                to
  (a)  " The firft time we made thi experiment, we broke the crucible without letting it cool en:irclv ; and
- foon as the matter was in contact with the air,  it took fire, audits dark brown colour  turned  nftumly  yel-
low." 
Prattice.                           C    H    E   M
Acid of   to a confiderably greater length ;  but Mr Keir prefers
ants.   -  the refearches of Arvidfon, Bucholiz, and Hermbftadt,
    v    to the reft.
            The acid in queftion is a natural juice which the in-
         fects difcharge when irritated, and which is very pun-
         gent to the fmell as well as tafte.  Thus it may in-
         ftantly be perceived on turning up  an ant-hill in fpring
   I?02r   or fummer.  The formica: rubra of Linnasus are thofe
Different  inSects which have hitherto fupplied  this  acid. MrAr-
methods of vidfon advifes to collect them ni  the months of June
obtaining  ancj July,  by laying fome  Smooth flicks upon an ant-
tius acid,  jjjjj. which being then  difturbed, the  ants will run
         upon the flicks  in  great numbers, and  may then be
         fwept off into a veffel containing water until it be full.
         Hermbftadt collects them in the fame manner, but into
         a dry bottle, to  avoid the  evaporation of the  Super-
         fluous liquid.  Bucholtz having  moiftened  the infide
         of a narrow necked glafs bottle with honey and water,
       •  funk it into a difturbed ant-hill  until the mouth was
         level with the ground ; on which the infects, allured
         by  the fmell of  the honey, went  into the  bottle, and
         could not get out.
            For obtaining  the  acid,  Margraaf employed diftil-
         lation, with the addition of frefh water.   Thus he ob-
         tained,  Srom 24  ounces oS frefli ants, 11  ounces and
         two drachms of acid, fome volatile alkali, empyreuma-
         tic oil, and a refiduum containing  earth and fixed Salt.
         ArvidSon made uSe of two methods : One confuted in
         diftilling the ants when dry ;  from a pound of which,
         in  this ftate,  he obtained eight ounces of acid befides
         the empyreumatic oil.   His other method was to in-
         clofe, in a piece of linen,  the ants previoufly cleaned
         by  wafhing in water, then to  pour boiling water upon
         them, and to repeat  the operation until it could ex-
         tract no more acid ; which is then obtained by Squeezing
         the linen,  mixing all the liquors, and filtering them.
         Thus from a pound of ants he obtained a quart of acid
         liquor, which tafted like vinegar, but was fpecifically
         heavier.   By diftillation Hermbftadt obtained from a
         pound of dry ants  ten ounces and a half of yellow em-
         pyreumatic liquor, which did not tafte morc ftrongly
         aeid than  the fpirit obtained by  diftilling  wood, on
         which fwam three drachms of a brown fetid oil,  in all
         refpects like that of hartfhorn.  In the retort was left
         a  black  refiduum weighing one  ounce  fix drachms,
         which exhibited figns of containing volatile alkali. By
         diftilling a pound of ants with three of water, according
         to Mr Margraaf's method,  he obtained an acid liquor
         and fome oil in the receiver ;  and from the furface of
         that which remained undiftilled,  he colle&ed a drachm
         and an half of fat oil.
            The fpecific gravity of the acid liquor obtained by
         Mr Arvidfon's maceration  was  1,0011; that of the
         fame liquor,  when diftilled, 1.0075; and of the acid
         concentrated by  freezing,  1.0453.  According to
         Bucholtz,  the acid liquor  thus  obtained  by macera-
         tion did not grow in  the leaft mouldy in the fpace of
         four weeks ; during which it was allowed to reft in
         order to free itfelf perfectly from the impurities it con-
         tained.   MrHermbftadt, however, prefers Margraaf's
         method of diftillation to that of Arvidfon's macera-
         tions, not only as being a more perfect analyfis, but as
         lefs laborious ;  though he  finds fault alfo with  Mar-
         graaf's method,  as diluting theacid too much,  and, al-
         tering it fo that  it hag not the fmell of living ants. He
I   S   T    R   Y.                                  219
  totally difapproves of the method of  diftilling dried Acid of
  ants, as the acid  is thus in a great meafure decom- ants.
  pofed, and the remainder united with  much oil.   To ~~"~v/~~"'
  avoid all thefe inconveniences,  he contrived another
  method, namely, to exprefs the juice ofthe infects ; by
  which means he obtained at once a concentrated liquor
  fit for diftillation.  In this, way he obtained from two
  pounds of dried ants 21 ounces  and two drachms of"
 juice,  which had a pungent and highly acid fmell,  re-
  fembling the vapours of fluor acid ; in tafte reftinbl ng
  concentrated vinegar and acid of tartar; to which laft it
  might be  compared for ftrength of acidity.   By  di-
  ftilling eight  ounces of this expreffed liquor,  he ob-
  tained fix ounces and a half of clear  acid, equal in
  ftrength to a very concentrated vinegar.                 Tj0j
    The acid, when thus procured in purity, has a pun- Properties
  gent, not unpleafant fmell,  a lharp,  cauftic tafte, and ofthe pure
  an agreeable acidity.  It reddens blue paper, fyrup of acid«
  violets, and litmus ; blackens the vitriolic acid, and
  converts part of it into a fulphureous  vapour.   It is al-
  So decompoSed by diftillation with nitrous acid.   Spirit
  of fait likewiSe,  when dephlogifticated, decom} ofes it,
  but not in its ordinary ftate.   It does not form fulphur
  by an union wiih phlogifton,  but products inflamma-
  ble vapours  by  diilblving iron or zihe.   By  the af-
 fiftance ofa gentle heat it diflblves Soot,  but oils with
  much more  difficulty,  and  powder  of charcoal not at
  all.   It does not unite with vitriolic ether; but in di-
  ftilling a mixture of this acid with fpirit of wine,  Mr
  Arvidfon faw fome traces of an ether,  and M.  Bu-
  choltz perfectly fucceeded in making an ether by means
  of it.  It unites with fixed alkali, forming, according
  to M.  Margraaf, a neutral fait, confuting of oblong de-
  liquefcent cryftals,  from which very little acid could
  be procured  by diftillation per fe, but on  adding con-
  centrated oil of vitriol, a very ftrong and pure acid was
  obtained; from a mixture of which with fpirit of wine,
  M. Bucholtz  readily obtained a true ether.   With
 mineral alkali it forms deliquefcent foliated cryftals of
  a faline bitter tafte, and foluble in twice  their weight
 of water.   With volatile alkali it forms an ammonia-
  cal liquor;  which, according to Arvidfon,  cannot be
 brought  into a dry ftate; but Mr Arvidfon fays  he
 has obtained cryftals*>from  it,  though very thin and
 deliquefcent.  Margraaf obtained dry cryftals by uni-
  ting this acid, with chalk or coral;  and Arvidfon ob-
 ferves that this fait is  tranfparent, cubical, or rhom-
  boidal, nondeliquefcent, foluble in eight parts offw7ater,
 of a bitter tafte, and infoluble in fpirit of wine.  No
 acid can be obtained from it by diftillation perfe. From
 a folution of magnefia in this acid, Mr ArvidSon ob-
 tained Some  Saline particles by depofition, and aSter-
 wards an  eflloreSccnce of tranfparent Salt rifing round
 a faline mafs.   This fait had Scarcely  any tafte,  was  '
  Soluble in 17 parts of water, and inSoluble in Spirit of
 wine.   With ponderous  earth the acid formed a clu-
  tter of bitter needle like cryftals, which did not deli-
  quefce, were foluble  in four times  their quantity of
  water, infoluble in fpirit of wine, and when burnt gave
  out a fmell  like  that  of burnt  fugar, leaving a coal
 which effervef ed with acid.   It unites  with  diffi-
  culty  to  the  earth  of alum, and  can   fcarcely  b^
  faturated  with  it.  It  does not  precipitate   filver
  lead, or mercury,  from   their  folution   in  nitron*
  acid ; whence it feems  to have no affinity to the ma-
                        E e 2                  rine 
120
C   H   E    M    I   S   T    R    Y.
Pra&ice.
fed*.
Acid of    r'..T . .-hi : and .;'■ i;  lo" not precipn.re lime Srom the
':l'"x     murine acid,  itfcems to hi. c as little with the vitriolic.
   ,7^    From i  s experiments, however,  Margraafconcludcd,
l!.4tan:fR- -hit th- aid  of aits, in many reflects, though not in
.1 t with   all, has a great alliu;:y with the ace1-  s aciei.  From
il - ...•!.-..» ih s ii is diftinguifhed by forming different compound-,
*''**•      ami likewnc  by h..viiig different  affinities,  it  dii-
          lodges  the  actions  acid alio in all  inftance , and the
          -rfcuical acid. Srom cobalt and  ;iekel.  It has agrcat-
   Tr.-?    tr attraction  Sor fixed alkalies  than  for lime.
lurff.St     A*  a Solvent it afts  but  weakly  upon copper;  not
cb nni-!f. at all,  or very little,  on filver, lead, tin, regains of an-
          timony,  or bii'muth,  but ftrongly on iron or  zinc.  It
          dilTeilveis, however,  the calces of copper, filver,  zinc,
          and lead, without affecting  thofe of tin, regulus of an-
          timony,  or bifmuth.   The calx ofquirkfilver, accord-
          ing to  Margraaf, is  revived by it.  According to Ar-
          vid: in, it cryftallizes  with  iron, zinc, or lead;  docs
          nouactupni the regulus of antimony, of arfenic, co-
          balt, or uicktl; though it diffolves  their  calces as
          well as the precipitate of manganefe.   Gold, mercury,
          and the calx of platina, are not affected by it;  but it
          cryftallizes with thofe of copper, filver, lead, bifmuth,
          and mercury.
             In its ftrength of attraction, the acid  of ants ex-
   ,. ,    cecds thofe of vinegar,  borax,  and the volatile Silphu-
 a. > •  o- reous and nitrous acids.   Infects  armed with flings,
 cured iron as bees, w.ttps, and hornets,  arc likewiSe Said to diS-
 v.ie.oe.-, in- charge a very acid juice when irritated ;  and *•!:•  Bon-
          net has obferved a very ftrong acid ejected by a cater-
          pillar which  hediiti;iguiihes by the name of e; a,.de che-
          nille du fanL a queu founhue.  None of thefc, however,
          have been as yet particularly examined.

                          XII. Acid of Apples.

             That the juices  of unripe fruits contain fome kind
          ofacid has been univerfally known,  and attempts to
          invefticMte the nature  of it  have been  made fome  time
   jko1   ago:  but it is to Mr Scheele that  we owe  the difco-
 Acid of ci- very of the  particular acid now treated of.  He had
 tr-n- how obServed that the juice of citrons contained  a particu-
 lar,..:,.:, laracid; which, by being  r.-ited with lime,  formeda
          Salt  ver/ inSoluole i;i  water; ant',  which there Sore by
          meaus  of fir-.c  could  be readily  feparated  from the
          m.rilagi.ious pm ot  the juice.   By  adding vitriolic
          aei.i to"tbis compound  of lime wiih the acid  juice, al-
          moft in  the f me manner in which he ufed to procure
          the  acid of  tertar,  the lime was again feparated, and
          the pure acid of citrons obtained.  Proceeding in the
          f„ ne maincr with other fruit, he found that an acid,
          a°rcti:ig iu  every rtfpect with  that of citrons,  could
          be procured  from  the juice  of the ribes groffularia.
          E\.:in'miiig  the juice which remained after the Se-
          paration of  the former  acid from  the citrons, he
          fraud  that  it ftill contained another acid ;  which being
          iaturaed with  m ire  calcareous earth, formed  a fait
    T .^   eafily foluble in water,  and therefore remained fufpend-
 /,.  .  -   ed in the jui:c.  To Separate this new f.d:,  he added
 •cid yr.uu- fomc Spirit of wine, by which the Salt was prccipita-
 r-  fr.-m  tcd ;  but fin 'dug that  it ftill  contained much gummy
 ti.^ji-Lc  of juaueT,  he judged that it would I e proper to attempt a
 *""'**     reparation of this jrim beSore he  precipitated the Salt.
          K-.r this purpofe he evaporated fome of the juice ofthe
          riles groffularia to 'he confiftence of honey,  diffolving
the mafs afterwards in fpii it of v, we.   Thus the at'ids, Acid . t
which arc foluble in the fpirit,  were cr.lily fepa:.acd alTlc*-   _,
by filtration  from the infoluble  gam.   lie  then eva-
porated the fpir;t, adding  to  the remainder twice  its
eptantity of water, with as much chalk as was necef-
lary for the Saturation.  The liquor was next  boiled
for two minutes ; during which the infoluble falrrwas
precipitated, and the  liquor  feparated from it by  fil-
tration  contained the folution  of  chalk in  the revr
acid.   To this folution he added fpirit of wine, which
again precipitated  the fait, while  fome faponaceous
and faccharine matters remained diflblved in the fpi-
rit.                                                    uc-9
   Having thus at laft obtained the fait in a ftate of pu- Itsproper-
rity,  he proceeded to  examine its nature ;  and found, tl«»«
i. That fome of it, fpread on his nail,  fiioti dried,
and  affumed the appearance  of varnilh.   2.  It was
very foluble in water, and turned litmus red.  3. \V hen
the folution had flood fome days expofed to air,  it wa»
found  to  have depofited a  number of fmall  cryftals,
which could only be diffolved by a quantity of boiling
water ; and  this  fait was alfo found to be completely
neutralized, fo that,  it yielded  its  calcareous earth to
a fixed  alkali.  4. The fait was decompofed by heat-
ing per fe in a  crucible, aud left a mild  calcareous
earth.  5. The acid was feparated from the earth by
adding  oil of vitriol diluted with water until gypfum
was no longer precipitated, and the new acid was left
difengaged,  fo that  it could be feparated by filtration.
6.  By  this operation, however, all the lime was  not
precipitated; fo that the feparation of the acid was  not
complete.   7.  He obferved that the acid had a greater
attraction for lead than for lime ;  and therefore made
ufe of the method he had formerly  difcovered  for fe-
parating the acid of forrel.   To the  acid he  added a
Solution of fugar of lead ; by which theacid was preci-
pitated along with  the lead,  and the vinegar was  left    !^I0
in the liquor.   To this  precipitate, cleaned from How pro-
thc acetous  acid  by filtration, he added vitriolic acid, cured in
which  expelled  the weaker  vegetable one,  and thus perfect r>»-
left it quite pure and  free  from  any heterogeneous ritV*
mixture.
   The juice of apples, eitherripe or unripe, was found
to contain no acid of cit#ons, but  a large quantity of
the new acid ; which, being thus alone, he could more
erffdy procure by a fingle operation.  The beft method
of procuring this  he found  to be by faturating  the
juice of the apples  with a folution of fixed vegetable
alkali,  and pouring a folution of fugar of lead to that
of the fait juft mentioned.   The  effect of this was a
double decompofition, and  a precipitate of lead com- *
bined with  the new acid.   To the edulcorated  pre-
cipitate he  then added a  dilute vitriolic  acid till he
could no longer perceive any fweet tafte in the liquor ;
for the firft portions ofthe vitriolic acid diffolve a part
of the  calx of lead, and impart a  fweetifh tafte to the
liquor, which is fenfible, notwithftanding its acidity ;
but when the quantity of vitriolic acid is fufficient  to
faturaie the whole ofthe calx, all the metal falls to the
bottom, and the  fweetnefs ceafes;  fo that the acid  isat
orrce obtained pure.                                    T'TI
   The acid of apples is pofTefrcd of the following pro- Trc-pert'"
perties.   1. It cannot be cryftallized, but always re- °bt'*,™dcn
mains  in a  liquid ftate; or, if much evaporated, at- from t^e
tracts ihe moifture of the air.  2.  With fixed alkalies juicc of
                                                     apple* 
Pra&ice.
CHEMISTRY.
Acid of
?pples.
  1514
Produced
from fugar
         of all kinds it forms deliquefcent falts.  3. With cal-
         careous earth it forms fmall irregularly fiiaped cryftals,
         which cannot be diflblvecPbut  in  a large quantity  of
         boiling water ; but if the acid is fuperabundant, the
         fait readily diflblves in lime-water.   4. It is effected by
         ponderous,  earth  in  the fame manner as by  lime.
         5. Earth of alum forms, with the acid of apples, a fait
         not very foluble in water.  6. With magnefia  the acid
         forms a deliquefcent Salt.  7. Iron  is  diflblved into a
         brown liquor, which docs not cryftallize.  8. The fo-
         lution of zinc affords fine cryftals.  9. On other me-
         tals it has no remarkable effects.   From the acid of
         citrons it differs.   1. Theacid of citrons flioots into
         fine cryftals.  2.  The acidof apples can be eafily con-
         verted into that of fugar, which Mr Scheele could not
         accomplifh with that of citrons ; though Mr Weftrnmb
         has fince done it.   3. The fait formed with the citron
         acid and lime is almoft  infoluble  in water ; but that
         with  acid of apples and lime is eafily foluble.  4. Acid
         of apples precipitates mercury, lead,  and  filver  Srom
         their Solution in nitrous acid, and likewiSe the Solution
         of gold, when diluted  with  water; but  the acid of
         citrons does not  alter any of thefe folutions.   c.  The
         acid of citrons feem  to  have a greater  attraction for
         lime than that of apples.
            It is remarkable that this acid is the firft produced in
         the procefs  for  making fugar.  If  a diluted acid of
by mean's of nitre be drawn off from a quantity of fugar until the
nitrous a-  mixture becomes  a little brown, which is a fign that
•"b      all the nitrous acid is  evaporated, the fyrup will be
         found to have acquired  a fourifh  tafte ;  and if,  by
         means of lime, we next feparate all the  acid of fugar,
         another will rtill remain, which diffolves the calcareous
         earth.  When this acid  is  faturated with  chalk,  and
         the folution filtered and mixed with fpirit of wine, a
         coagulation  takes place.  On feparating  the curdled
         part  by means of a lieve,  diffolving it  in water, and
         then  adding fomc vinegar of lead, the clax of lead will
         be  precipitated ;  and if the new acid is then feparated
         from the metal by means of diluted oil  of vitriol,  it
         will be found to poifefs all  the properties of theacid
         of apples, and is indeed the fame.  The fpirit of wine,
         which has been  employed to  precipitate  the  calcare-
         ous Salt, leaves on evaporation a  refiduum of a bitter
         tafte, very deliquefcent,  and fimilar to the Saponaceous
         extract ofthe citron.
   1513      tj^ following are the reSults oS Mr Scheele's ex-
mentvwith periments  with the nitrous  acid upon  different Sub-
nitrous acid fiances.  1. From  gum arabic he  obtained both the
«i various acid of apples and  of fugar.  2. The  fame products
fubftances. were obtained from manna.   3. From  Sugar  of  milk
         he obtained  not only its own peculiar acid, but thofe
         of apples and fugar.  4. Gum tragacanth, during its
         folution in  nitrous acids, lets fall  a white  powder,
         which was found to be the acid of the fugar of milk.
         This gum contained alfo theacid of apples and of fu-
         gar, and a fait formed from  lime and  the acid of ap-
         ples.   5. Starch left an undillblved ma'ter; which be-
         ing  feparated by  filtration,  and wafhed,  refembled a
         thick oil like tallow, which, however, was found to be
         very  foluble in fpirit of wine.  By diftillation he obtain-
         ed from this oily matter an acid fimilar to that of vine-
         gar, and an oil which has the fmell of tallow, and con-
         ceals by cold; and,, befides thefe fubftances, he  found
                                                       221

that ftarch  yielded  the acids- of  rpples  and  fugar. Acid of
6. From the root of  Salephe obtained the acidof ap- ap?1".___(
pies, with a large quantity  of  calcareous faccharine
fait.  7. Extract  of  aloes  indicated the  exiftence of
the acids of fugar and apples,  and loft  the  greateft
part of its bitter  tafte.  During the  digeftion a refi-
nous matter was feparated, which fmelled like flowers-
of benzoin,  and took fire  on being heated in  a re-
tort.  8. Extract of  colocynth was converted  by ni-
trous acid into a refinous fubftance, and fhowed fome
figns  of  containing acid  of fugar. 9. The  extracts
of Peruvian bark and of the other plants examined by
Mr Scheele, gave both the acids of  apples, and fugar.
10. Thefe two acids were likewife obtained from an     ,
infufion of roafted coffee, evaporated to the confiftence
of a fyrup.   11. The fame  products were obtained
from an  extract of   rhubarb,  which yielded alfo  a
refinous   matter.  12. Juice of poppies afforded the
fame  refults.  13.  Extract  of  galls did  the.  fame,
14. The effential oils afforded little or none  of the.
acids ;  but  the  oil  of parfley-feeds   feemed to be
entirely  convertible into  them.   15.  With  a  very
concentrated acid he was able alfo to  decompofe .ani-
mal  fubftances.  From glue  he  thus  obtained finey
cryftals ofacid of fugar, ami  afterwards acid of apples.
Ifinglafs, whites and  yolks of eggs, afforded the  fanne
products.  From all  thefe fubftances,  efpecially the
laft, a fat matter was feparated: but it was remarkable
that the gas, expelled during the  procefs, was com-
pofed of a little fixed air,  a  great quantity  of phlo-
gifticated air, and very little nitrous air,  whereas no
phlogifticated air is  obtained in  the ufual procefs for
preparing acid of fugar.   He obferved  alfo  that in
the procefs for this acid, a fmall quantity  of vinegar
is found in  the  receiver.  He  could not obtain the
acid of  Sigar from the  faponaceous extract of urine ;
but got  inftead of it  a fait, which, when completely
purified, refembled exactly the  flowers of benzoin.
The fame fait is precipitated in  abundance by adding
to the extract of urine  a little  vitriolic or marine
acid; and Mr Scheele had already  remarked that the
fame fait isobtained in the  diftillation of fugar of milk.    iti,t.
   From the various experiments  which have been made.Of ther 1-
on this acid,  it feems, according to Mr Keir, to be in tureof thw-
an intermediate ftate betwixt acid of tartar and acid3"^
oS Sugar.   This, however, ought  not  to  prevent it
from  beinj  accounted  a  feparate and diftinct acid,
otherwiSe we might  confound- all  the vegetable acids
with one another.  Tt approaches more nearly to the
nature of acid  of milk  than of any other.  From this
alfo, however, it  is diftinguifhed, becaufe  the  Salt
formed  by the  union  ofacid of milk with lime is So-
luble in  Spirit oS wine, but  not that  from lime and
the acid of apples.   According to  Mr  Hermbftadt, if
three parts of fmoking nitrous acid be abstracted  from
one part of  fugar, and if the brown acid  mafs which
remains in the reto' t be  diluted  with fix times its
weight  of diftilled water,  and faturated with  chalk,
two compounds will  be  formed ; one confift ing of the
acids of tartar and lime, which  will precipitate ; and
the other of lime and the acid of apples,  which  will
remain  fufpended.  If the  calcareous earth be preci-
tatedfrom this latter folution by adding  acid  of Su-
gar^ a  pure acid  of  apples will  be left in the liquor :
                                                and .
» 
•.id.
   Tils
H.«vv to
crytlalliz:
Ipiriti^
Mindcicri.
   1516
Salt from
the acetous
acid com-
bined with
calcareous
cartli.
   TJI7
\\ ith mag
1.tin.
   IJl8
"With zinc
                            cue
and he f.-.nher informs us, that this acid of apple s may
' e changed  entirely into tholt of fugar and  vinegar,
'••■■ means of ftrong nitrous acid.

              XIII. AciTWS At la.

   It  is generally believed,  that  the  combination oS
this acid with volatile  alkali is  altogether incapable
of cryftallization;  but  Schctfer and Morveau  i.uorm
us, that it may  be reduced into  fmall  necdle-ma-
ped cryftals, w hen  the fpiritus  Mindcreri is  evapo-
rated to the confiftence of a Syrup, and leSt expoSed
to  the cold.   1 he  Salt has  a  very lharp and  burn-
ing title,  but a confiderable quantity  is   loft  during
the evaporation.   Wtllcndoii, by adding his concen-
trated vinegar to volatile alkali,  obtained a  tranfparent
liquor which did  not  cryftallize.  By diftillation it
went over intirtly into the receiver,  leaving a white
fpot on the retort.  A faline tranfparent mafs, how-
ever, appeared in the  receiver under  the  clear fluid.
On feparating it from  the  liquid, and expofing it  to
a gentle heat, it  melted, threw  out  white  vapours,
and in a few minutes  fhot into lharp  cryftals  ru'em-
bling  nitre.  TheSe remained unchanged in  the cold ;
 bui when  melted  with a gentle  warmth,  Smoked and
evaporated.  '1 heir tafte was  firft fliarp and  then
 Sweet.
    The Salt formed by uniting acetous acid with cal-
 careous earth has  a fliarp bitter  tafte, and  fhoots in-
 to cryftals fomewhat refembling ears  of corn.   Thefe
 do not deliquate in the air,  unlefs  the acid has been
 fhperabundant.   They are   decompoSed by diftillation
 per ft, theacid coming over in  white  inflammable va-
 pours  Smelling like acetous ether, Somewhat empy-
 reumatic,  and  condcnling  into  a reddifli brown  li-
 quor.  By rectification this liquor becomes very  vo-
 Utile and  inflammable; on  adding  water,  it acquires
 a milky appearance, and drops oS oil Seem to Swim upon
 the Surface ; a reddifh brown liquor, with a thick black
 oil, remain aSter rectification in the retort.  On mix-
 ing this calcareous Salt with that of Glauber, a double
 decompofition takes  place ; we have a gypSum  and
 the mineral alkali combined  with acetous  acid.   By
 calcination, the mineral alkali may be obtained Srom
 this Salt in a ftate of purity. This acetous  calcareous
 Salt is not Soluble in Spirit of wine.
    On faturating  this acid with magnefia, and evapo-
 rating the liquor,  we  obtain a viScid Saline m*is  like
 mucilage  of gum  arabic, which does not  fhoot  into
 cryftals, but deliqueSccs in  the air.   It has  a  Svv eetifh
 tafte at firft, but is aSterwards bitter.  It is Soluble in
 fpirit of  wine, and parts  with its  acid by  diftillation
 without addition.
    Acetous acid diffolves zinc boih  in  its  metallic and
 cilciform ftate, and even when mixed with other me-
 tals.   By  concentrated vinegar the  zinc is diffolved
 with  great heat,  fulphureous'fmell,  and exhalation of
  inflammable mayer.   By this union we obtain a con-
  cealed mafs, which on dilution  with  water  flioots into
  oblong Sharp cryftals at the firft  cryftallization,  and
  ; yerwards into cryftals oSa ftellatcd form.  From this
  l,quor indeed cryftals  of various forms have been ob-
  tained bv  diti rent chemifts.   Monnet obtained from
  it a pearl-coloured Lit in friable talky cryftals; which
  when thrown on the  coals,  iulum*y.ed a  little  a firft,
M   I    S    T   R    Y.
Practice.
and gave a  bluifli flame, .vd t'.en melted, 1 tiing its Acctm;
acid efcape,  while a yellow calx remained,   Hellot ™fy\
informs us,  that thisfalt  by  diltillation pet fe  in wa-
ter, affords  an  inflammable  liquor, and an oil at firft
yellow and  then  green,  with white  flowers burning
with a blue flame.   Wcftendorf obtained no oil  in this
diftillation,  but Some acetous acid ; a lwcet-talted em-
pyreumatic   liquor  impregnated with  zinc ;  fweet
nowcrs, or  Sublimate, loluble in  water, and burning
wiih  a  green  flame.  On  applying a ftronger heat,
the zinc was fublimed in its metallic form, leavh'.g ■*
fpongy coal  at the bottom  of the retort.  1 he U-iu-
tion gives a green colour to fyrup of violets, lets fall
a white precipitate on the addition of  alkalies or an
infufion of  galls.  It is  not precipitated  by common
fait, vitriolated tartar, vitriolic or marine acids, blue
vitriol,  or corrofive Sublimate ; but  forms a red pre-
cipitate when added to a Solution of gold ;  a white pre-
cipitate with folution of Silver ; a cryflalline  pearly
precipitate  with  lolution of mercury ; and cryftalline
precipitates with folutions  of bifmuth  and tin.  Ac-
acording to Bergman, it is decompofed by acid of ar-
fenic.                                                 *5i9
   Though  regulus  of  arSenic is not foluble in  this Its pheno-
acid, its^calx  may  be  diflblved either in common  or mow with
diftilled vinegar. M. Cadet obtained a Smoking liquor arlcmc-
by diftillation Srom a mixture oS white   arfenic  and
 terra foliata tartari.  This  experiment has been re-
 peated by the chemifts  of  Dijon, and attended with
 the following curious circumftances.   "   We digefted
 (fay they), in a  fand-bath,  five ounces  of  diftilled vi-
 negar on white pulverized arfenic ; the filtrated liquor
 was covered,  during evaporation, with a white faline
 cruft.  Of this fubftance were formed  150 grains ;  on
 which  fixed  alkali appeared to  have no effect, and
 which was at  firft confidered as pure arfenic.  How-
 ever, a cat, which had Swallowed 72 grains of it, was
 only affected w ith vomitings that day  and the next,    J5i9
 and  afterwards  perfectly  recovered.  A Similar dofc vinegar
 was given to a little dog; but .as  he ran away, the fuppofed t«
 effect it  had  upon him could not be difcovered ;  but ^e an antj*
 he  returned  afterwards in good health, and never „£**
 fhowed any uneafinefs :  whence it may be concluded,
 that vinegar is in Some meafure an antidoie a^inft the
 pernicious  qualities of arfenic.
    " On rediffolving  this  faline cruft in  pure  water,
 filtering and mixing it  with liquid alkali, an irregu-
 larly cryftallized fait was formed in k after a few days
 ftanding:   By this fait a yellow precipitate was thrown
 down from the nitrous folution of filver;  whereas the
 folution of arfenic and terra foliata tartari threw down
 a white one.
    " Equal parts of terra foliata  tartari and arfenic, di-
 ftilled in a retort,  gave firft a fmall quantity of limpid
 liquor with a penetrating fmell  of  garlic, and which
 had the property of reddening fyrup of violets^ while
 folution of arfenic in water turns  that  fyrup green.
  The vinegar which now arofe was not faturatcd when
  arfenic, but effervefced ftrongly with fixed alkali, with
  which it became turbid, but did not let  fall any pre-
  cipitate. On changing the receiver, there came over a
  reddifh brown liquor, accompanied with  thick vapours,
  diffufing an intolerable fmell, in which  that of arfenic
  could fcarcely  be  diftinguifhed.   On continuing the
  operation, a black powder Sublimed  into the neck of 
 Practice.                           C   H   E   M
 Acetous   the retort,  together with a'little arfenic in its metal-
 acid,      lie form, and a- matter which  took  fire by a lighted
 "   *-"~"' candle like  fulphur.
            "  The red liquor ftill preferved its property of fmo-
          king though cold ; diftilling at  the fame time its pe-
          culiar and  abominable fetor, from which the apart-
          ment could fcarcely be freed in feveral  days.   This
          liquor does not  alter the colour of fyrup of violets,
          but effervefces flightly with fixed alkali, letting fall
          at the fame time a yellow precipitate, which, however,
          disappeared on an attempt to feparate it by filtration.
 Curious     "  M. Cadet had obferved, that the fmoking liquor
 phofphoric of arfenic did not kindle at the approach of a lighted
 liquor.    candle ;  but that, on pouring it from the receiver into
          another veflel, it had kindled the fat lute with which
          the junctures had  been clofed, and  which  had  been
          dried during  the operation  : but we, being defirous
          of examining more fully the nature of the red liquor
          which collects at the bottom, and has the appearance
          of oil, having decanted that which" fwims on the top,
          and  poured  the remainder on  a  filter  of paper,
          before many  drops  had paffed, there  arofe a  thick
          fmoke forming a column from the veffel to the ceiling ;
          a flight ebullition was perceived at the fides of the vef-
          fel, and a beautiful rofe-coloured flame  appeared for
          a few moments.  The paper filter was burnt at one
          fide, but moft of  it was only blackened. After the flame
          was.extinguiffied, a fat reddifli matter remained : which
          being melted on burning coals, Swelled confiderably,
          emitting a white flame.   It then funk, and left on the
          coal  a black  fpot, which could not be effaced but by
          the moft vehement fire.
            " At the time thefe observations  were  made, the
          liquor had been diftilled for  three weeks, and the bot-
          tle frequently opened.  The inflammability could not
          proceed  from the  concentration of the vinegar : for
          the rofe-colour of the flame, the precipitation of the
          fublimate, and the fixity of  the fpot remaining on the
          coal, evidently fhowed that the  two fubflances were in
          a ftate of combination ;  which is alfo further evinced
          by the lofs  of the  inflammable  property when the li-
          quor was decompofed by fixed alkali.—The  fmell of
          the liquor,  however,  though fo intolerably fetid, was
          attended .with no  other inconvenience  than a  difa-
          greeable' fenfation   in  the  throat,  which further
          ftrengthens the  fufpicion that vinegar is  an antidote
          againft arfenic.
            " The faline brown mafs remaining in the  retort
          was partly diffolved by hot water;  and the filtrated lix-
          ivium was very limpid, but  emitted the peculiar  fmell
          of the phofphoric liquor.   By  evaporation it yielded
          a fait which did  not deliquefce in the air,  of an ir-
          regular fliape; and which being put on burning coals,
          did not fmell  fenfibly of arfenic  ; loft its water of cry-
          ftallization ; and became mealy  and white wShout be-
          ing diflipated  by heat.   On  expofing  the refiduum to
          the air,  it was found next day refolved into a liquor ;
          whence it is probable that moft  of it was compofed of
          cryftallized alkali,  having received from the decompo-
          fition ofthe vinegar  as much fixed air as was necef-
   i$iz   Sary for its cryftallization."
Effect;  of     This acid does not act upon  mercury in its metal-
thc acetous Hc ftate, but diffolves the mercurial calces, as red pre-
acid on    cipitate,  turbith  mineral,  and the precipitate formed
mescury.    x                     '          x
   S    T   R    Y.                                 2zj
by adding fixed alkali to a folution oS mercury in : i- Acetous
trous acid ; with  all which it Sorms white, fhining, acicl-   __f
Scaly cryftals, like thoSe of fedative Salt.                Tj-^
  Vinegar does not act upon filver in its metallic ftate, On Giver.
but readily diffolves the yellow calces  precipitated
from  its folution in nitrous acid by microcofmic fait
and volatile alkali.   By the help  of  a boiling heat al-
fo it  very copioufly diffolves the precipitate obtained
by means of a fixed alkali.  The laft mentioned  folu-
tion  yields  fhining, oblong, needle-fhaped, cryftals,
which are changed to a calx by means of feveral acids,
efpecially the muriatic.   The filver is thrown down in
its metalic form by  zinc, iron, tin, copper, and quick-
filver.                                                1<c24-
  Though the  acetous acid has no effect upon gold in On gold.
its metallic ftate,  yet a folution  of  this metal is de-
compofed by crude vinegar,  which produces both a
metallic  precipitate and  dark violet-coloured powder.
Diftilled vinegar throws down  the gold in its metallic
form.  The precipitate by fixed alkali digefted  with
acetous-acid is of a purple colour.   This, as  well as
fulminating gold,  is diffolved by WeftendorfF's  con-
centrated vinegar ;  the fulminating gold  very  eafily.
The folution is ofa yellow colour ;  and with volatile
alkali affords a yellow precipitate  ; with lixivium fan-
guinis, a blue  one; both of which fulminate.   The
dry fait of gold diffolves in the acetous acid, and pro.
duces oblong yellow cryftals..                           IKZS
  This acid has no effect on fat oils, farther than that on inflam-
when diftilled together,  fome mixture takes place, as mable fub-
the Abbe Rozier has obferved.  Neither does diftil- Stances.
led vinegar act  upon effential oils, though  M. Weften-
dorfFs diftilled vinegar  diflblved about a  fixth part of
oil of roSemary,  and about half its weight of cam-
phor.  The latter folution was inflammable,  and let
fall the camphor on the  addition of water.  The z-
cid diflblves all the true gums,  and fome of thofe cal-
led gum-rcfins, after being long  digefted  with them.
By long  boiling,  Boerhaave obferves,  that it diffolves
the bones, cartilages, flefh, and  ligaments of animals.   j.a<;
  The concentration of this acid may be  effected by Concentra-
combining it with  alkalies, earths,  and metals.   By tion of the
combining it with copper, and then cryftallizing and acetous a-
diftilling  the  compound, we obtain the  acid in  the cid*
higheft ftate of concentration in which  it is ufually
met  with.   To produce this  ftrong  acid, we  have
only  to  diftill verdegris, or  rather  its  cryftals  in
a retort.   The operation muft  be  begun by a  very
gentle fire, which brings over an aqueous liquor. This
is to be  Set afide,  in order to procure the more  con-
centrated acid,, which comes ever with a ftronger fire. .
On changing the receiver, and augmenting the heat,
we obtain a very ftrong acid which comes over partly in
drops, aud partly in white vapours.   It is called radical
vinegar, or Sometimes Spirit oS Venus, and has a  very
pungent Smell,  almoft as  Suffocating as that of volatile
fulphureous acid.   As the laft portions of it adhere
pretty  ftrongly to the metal, we  are obliged to  raife
the heat  to fuch a degree as to make the retort quite
red in order perfectly to feparate them.   Hence fome
part of the mentis raiSed along with the acid, which,
diilblving in the receiver, gives the liquor a greenifh.
colour; but from this it  may be eafily freed by  a Se-
cond diftillauon, when it rifes with a very gentle heat,
                                                and.. 
CHEMISTRY.
Practice.
Of its cr\
         and becomc» extremely white.  Cryftals of verdegris
         afford about one half their weight of radical vinegar;
         but vcrdtgTs iiftlt muchlcL, and ofa more oily qua-
         lity.
            If t1  is acid  be heated in a wide-mouthed pan,  and
         lire applied to  it,  it will burn entirely ..-./ay like fpirit
         of wine.  Tiiis obfervation wc owe to the  coun. de
r.aliiziiion. Lauragais, who has likewife obferved,  that it is capa-
         ble of en lUllization.  This how ever, takes place only
         with the Lit portions which came over, and the cryftals
         appear  in ihe  form of pines or needle*.  The mar-
         quis dc Courtrivon, who  has repeated and confirmed
         the  t.\;-eiime:u of the count dc  Lauragais, fuppofes
         this phenomenon to be owing to a fulphur-like mixture
         of -.ctous acid and phlogifton.  Lconhardi fuppofes
         an analogy between thefc cryftals and the white ialt of
         copper  txptlled at the end of the operation  by  the
         count dc 1^Tone.   This  fait was  at firft very white,
         and fixed on the neck  of  the retort pretty thick;  but
         unlefs  quickly collected,  was foon deftroyed  by  the
          Succeeding vapours.  \\ hen expofed  to the  air, it
          attracts moifture,  and' runs  into  a greenilh  liquid.
          lt is uncommonly light,  and in fuch  fmall quantity,
          that fcuree five or fix grains can be collected  from a
          pound oS verdegris.  Its tafte is acid, auftere, very un-
          pltaliiu and permanent.  It readily and totally  e;ii-
          folves in water, and partially in Spirit of wine,  leaving
          a yellow powder totally lbluble in  volatile alkali,  and
          which  burns w ith a green flame.   From this Salt, \ ola-
          tilc  alkali acquires a blue  colour, and litmus a red
          one ;   and  thus it diScovers  itfelf to be compofed of
          acetous acid and copper.
            Experience has ihown that  radical vinegar differs
          confiderably in its properties from the common  acid.
          It has a greater attraction  for alkalies, forms  with
 pepar and thcm more  perfect combinations,  and is lefs volatile.
 common a- ^  Berthollet obferves,  that when vinegar concentra-
 cetousacid.lCci by froft and radical vinegar, are reduced to equal
          denfities, by adding water to the heavier of the two, they
          differ  very much both  in  fmell  and tafte.   Laffbne
          found,  that radical  vinegar  formed  a cryftallizable
          compound with volatile alkali; and Berthollet has ob-
          ferved the fame w ith regard to fixed vegetable alkali.
          The cryftals of,the latter with radical vinegar  were
          flat, tranfparent, and flexible, flowly deliquefcent in the
          air.    On comparing the falts formed by the two acids,
          he found, that the acetous fait rendered the fyrup of
           violets green ; but its colour remained unaltered with
           that made with radical vinegar.   The latter alfo re-
           quired a ftronger fire to expel  part of its acid ;  it was
           alfo whiter, and had a  lefs acid tafte.  On  pouring
           r ilicabvinegar on the acetous fait, the folution afford-
           ed.  by evaporation and cryftallizaiion, a fait perfectly
           fimilar to that procured  directly from radical vinegar
           and fixed alkali.   On diftilling the mixture, the  radi-
           cal vinegar appeared to have expelled the common a-
           cet'His acid, as the liquor which came over effervefced
           with vegetable alkali, and formed with it a terra foli-
           ata  tartari.
             "  It feems probable (fays Mr Keir), that the  radi-
           cr.l vinegar contains a larger portion of the aerial  prin-
           ciple  than  the common acetous acid ; by which  it un-
           dergoes a change fimilar to that of marine acid,  when
           brought into  that ftate m which it is faid  to be dc-
  Ui8
Difference
between
radical vi-
phlogifticatcd.   This air it may acquire from the me- Acetotw
tal Ik calx, which being; deprived of  its air is reduced *ad*
to its metallic ft ate.   Thole who believe in the phlo« *~
gifton of mtials, may fay that the acid is dtphlogilli-
catcd by imparting its ph'ugiilon  to die metal,  which
is thereby metallized. It apptvi s,  how ever, to be very
diftinct  from common acetous  acid, and  defines  to
have its properties  and compounds farthtr inveftiga-
ted."                                                  ij2<;
  Concentrated acetous acid,  of a great degree  of How to ob-
ftrength may alfo he obtained by diftilling terra folia- tahi it pure
ta tartari with vitriolic acid ; but Lconhardi obferves, from tenx
that the acid thus obtained is always more or lefs con- fohatatar-
laminated with the volatile acid of fulphur.    He ob-
ferves  alfo, that the method propofed of feparating
the fulphureous acid by a Second  diftillation from Salt
of" tartar is not effectual,  becauSe the Sulphureous acid
has lei's attraction for alkalies than the acetous.   Wef-
tendorf recommends the  neutral Salt formed by ace-
tous acjd and mineral alkali, inftead of the terra folia-
ta tartari.   Thus, in the firft place, wc readily obtain
cryftals free from the inflammable matter of the vine-
gar ; and, in confequence of this,  though we  diftil it
afterwards w ith concentrated of! of vitriol, no  fulphu-
reous taint can be produced.   Even  fuppofing this to
be the eafe  (he fays), it may be  removed by a fecond
diftillation from Some mineral alkali.   Mr Keir, how-
ever, obServes, that " probably all the acids difttWed
from acetous Salts by means of the vitriolic, partake
ot the property of that procured by diftilling cryftals
of verdegris ;  and none  of them  can compare with
that from which Mr Louitz -obtained acetous ether
without addition, as a pure concentrated and unalter-
ed vinegar."
XIV. Acid of Benzoin.
I53»
  The properties ofthis acid have been inveftigated by M.  Lich-
M. Lichtenllein, and are as follow,   i.  Expofed to tenftein**
the heat of a candle in a filver fpoon, it melts as clear account of
as water,  without burning, though it is deftroyed by l" Vt0?M"
contact of flame.  2. When thrown upon coals, it eva-
porates, without refiduum, in  a thick  white Smoke.
3. It is not volatile without a confiderable degree of
heat.  4. By very flow cooling its aquerAis  folution
yields large  cryftals, long, thin, and  of a feathery
Shape.  5. It is foluble in the concentrated acids of
nitre and  vitriol, but Separates from them, without de-
compofition,  on the  addition of water.   6.  By the
other  acids it cannot be  diffolved without heat,  and
Separates  from them alfo without any change, merely
by cooling.   7.  It is copioufly diflblved  by fpirit of
wine, and precipitated from it on the addition of wa-
ter.   8.  With alkalies it  forms neutral falts,  very fo-
luble in water,  and of a lharp faline tafte.  With ve-
getable alkali it forms cryftals of a pointed feathery
form : with mineral alkali it  yields larger cryftals,
which fall  into powder on being expofed to  the air ;
and with volatile alkali it  is difficultly cryftallizable in-
to fmall, feathery, and deliquefcent cryftals.  It is Se-
parable from alkalies by the mineral acids.  9. With
calcareous earth it-forms white, fhining,  and pointed
cryftals,  not eafily Soluble, and which have a Sweetifli
tafte  without any  pungency.  10. With magnefia
                                               fmall 
Pra6tice.
CHEMISTRY.
Effects of
nitrous acid
upon it.
  }5W
Acid of
benzoin
procurable
from Peru-
vian balfam
and urine.
 fmall feathery cryftals are  formed, of a  fharp  faline
 tafte, and eafily foluble in  water,   n.  An aftringent
 fait is formed with earth of alum.
   All theSe earthy  Salts are eafily decompofed by the
 mineral acids as well as by alkalies.   The acid of ben-
 zoin itfelf reddens litmus, hut has little effect upon fy-
 rup-of violets.
   Meflrs. Hermbftadt and  Lichtenfteinhave both tried
 the  effects of nitrous acid  upon that of benzoin.  In
 this operation,  however; a great obftacle arofe  from
 the volatility of the  acid of benzoin, which prevent-
 ed it from bearing any confiderable heat  without paf-
 fing over into the receiver.  By repeated diftillations,
 however, the acid oS benzoin, diminiflied in its vola-
 tility, affumed  a darker colour, and  acquired a bitter-
 ifli tafte.  A coal was alSo  left at the  bottom; and, at
 the end ofthe third operation, when the nitrous acid
 had been all drawn off, M.  Hermbftadt obferved that
 fome brown drops came over which  had  the  appear-
 ance oS a dark-coloured transparent oil,  foluble in di-
 ftilled water, emittingacrid fumes, and having a very
 cauftic tafte.   On distilling this acid  liquor a fecond
 time, a yellow faline mafs was obtained,  which,  when
 diffolved in diftilled water, formed a fluid  acid,  which
 precipitated a folution of fugar of lead and lime-water.
 On examining the charred  refiduum left in the retort,
 he obferved, that, after calcination,  fome of the earth
 had been vitrified, while another was ofa foft confift-
 ence, and had  acquired a cauftic  tafte.  From a mix-
 ture of the abovementioned dark-brown acid and fpi-
 rit of wine,  he obtained an  ether, which differed from
 the nitrous inbeing much lefs volatile,  and fuelling like
 bitter almonds.
   From this refiduum Mr Lichtenftein obtained  a re-
 finous fubftance,  to which  he afcribes the volatility of
 the acid of benzoin, as well as the fmell  of bitter al-
 monds already mentioned.
  Scheele failed in  his attempt  to obtain  ether   from
flowers of benzoin and fpirit of wine; but, by adding
a little fpirit of fait, he obtained a kind of ether which
fell to the bottom.   On diffolving  this  in alkalized
fpirit of wine, and drawing off the latter by diftilla-
tion,  he obtained from it a quantity of flowers of ben-
zoin.  From Peruvian balfam alfo  Lehman obtained  a
 quantity of the acid of benzoin.   It  may alfo be pro-
 cured from urine,  either  by precipitation, from the
 faponaceous extract  (a),  or by  repeatedly diftilling
 from it fpirit of nitre,  as in the preparation of acid
 of fugar.  In the urine it is  found combined  with
 votatik alkali,  by which it becomes foluble in fpirit of
 wine.

               XV.  Sebaceous Acid.

  This is faid to have been  firft  difcovered by Mr
 Gruitzmacker,  who publiflied  an account  of   it  in
 1748.   It was afterwards more accurately treated of
by Mr Rhades in 1753.   Its properties were invefti-
gated by Meflrs Segner and Knappe in  1754 ;  and
afterwards more fully by Dr Crell, of whofe difcove-
ries  an  account is  given in the Philofbphical Tranf-
     Vol. IV.
    225
Sebaceous
   1534
Has a re-
markable
power of
attraction.


,   1535
Re mark-
able e-ffeer.
on tin.
   153*
Its effects
on other
fubftances.
 actions for 1780  and 1782.   It is found not  only in
 the  fat of all animals,  but in Spermaceti,  the  butter
 of cocoa,  and probably in other vegetable oils.  In Se-
 veral refpects it feems analogous to the marine acid ;
 but  in others it is remarkably different, particularly
 in precipitating a  folution of corrofive Sublimate,   lt
 is probable, however, that is principles are the Same
 with thofe contained in all other vegetable  and ani-
 mal  acids ;  and this opinion is Supported by w hat hap
 pens on treating tallow in the ufual manner for ob-
 taining acid of fugar ; for thus, not the Sebaceous, but
 the Saccharine acid is Sound to  be produced.   It has a
 very great ftrength of attraction, and by means Of htat
 decompounds even the vitriolic ialts themfelves ; but in
 the moift way is expelled by the three  mineral acids,
 though it  expels all  the  vegetable ones  as wcii as
 thofe of fluor and arfenic.  lis moft rcmarkabJe pro-
 perty is its  effect on tin.   The  filings  of this rut tal,
 eSpecially with the affiftance of heat, arc coirok.ed  by
 it into a yellow powder, and  at the  Same  time give
 out a very fetid fmell.   The Solution, though filtered,
 ftill  continues turbid, and depofits more yellow pow-
 der,  acquiringj.t the Same time a  fine roSe-red co-
 lour.  By adding water to  this  yellow powder,  a
 white deliqueScent Salt may ba obtained, and  a fimi-
 lar one obtained by diffolving a yellow powder pre-
 cipitated  by this acid from folution of  tin  in aqua-
 regia.
   It corrodes lead rather than diffolves it; but diffolves
 a confiderable quantity of minium,  and changes  the
 reft  to a white powder.  This Solution is Sweetifh, and
 is not precipitated  by common Salt.   The metal is
 precipitated by  Sebaceous acid from  the nitrous,  in
 white needle-like cryftals, eafily foluble in water.  A
 like  precipitation  takes place in folution  oS Sugar  of
 lead ;  but the precipitate is ftill foluble in ftrong vine-
 gar,  provided it be not adulterated With oil  of vitriol.
 In its elective attractions it agrees with  the acids  of
 apples and  of fluor, preferring magnefia to fixed al-
 kali.


               XVI. Acid of.>galls.

   Though  it has  for along time been known that
 the infufion of galls has the property of reddening ve-
 getable juices, diffolving iron, and  decomposing liver
 of Sulphur,  thefe effects were generally aScribed to its
 aftringency.  Of late, however, it has been found,
 that  befides this aftringent principle a true acid exifts
 in galls ;  and to this, rather than to the  aftringent
principle, are we to aScribe the properties  of galls  in
ftriking a black with Solution of vitriol, &c.             JS^
  To feparate the acid from the other  matters  con- Method of
 tained in the galls, we muft add fixed alkali to a de- feparating
 coction of them ; by which means the aftringent mat- t^ic ac"*>
 ter will be thrown down, and  the acid remain in the
 liquor joined to the alkali,  the  precipitate,   wafhed
 with clean water,  dried, and rediffolved, blackened a
 Solution oS vitriol but Saintly,  and  no more than what
 may  be SuppoSed to proceed from fome remaining acid,
which could not be abftracted.  This is proved by di-
                         F f               ftilling
  (a) By this is meant urine evaporated to a thick confiftence, and deprived of moft of its falts by Solution in
fpirit of wine. 
»539
i>rotHTt:
<M thisae
   TS40
MrKeir's
objections
r > the opi-
nion son
tnisfub-
                            CHEMI

 ftilling the aftringc.it matter in queftion, when an acid
 liquor comes over,  which has the property of blacken-
 ing  folution of vitriol.  Scheele  has obferved,  that
 when galls in fiihit.mce are expofed to  diftillation,  an
 acid ; i   ;  rifes of an agreeable fmell,  without  oil,
 and afterwards a kind of volatile  fait, which is  the
 true acid of the galls.   Hence he infers,  that this lalt
 is contained read) formed in the galls themfelves;  but
 fo much involved  in  fome gummy or other matter,
 that ii cannot be eafily obtained fepar.utly.
   Tne -id of galls is capable of  being feparated by
 cryftallization.   hi an infufion made with cold water,
 Scheele obServed a Sediment  which appeared to have a
 cryltalline Sorm, and which was acid to the tafte, and
 had  the  property  of blackening  folution of vitriol.
 By expofing the infufion  tor  a  long time to the air,
 and removing from time to time the mouldy fkin which
 grew upon it, a large quantity of fediment was form-
 ed.   On rediffolving this  in warm water, filtering and
 evaporating it very flowly,  an acid fait  was obtained
 in fmall cryftals like fand,  which  had the following
 properties: i.  It tailed acid, effervefced with  chalk,
1 and reddened litmus.   2.  Three parts of boiling  wa-
 ter  didblved  two of the  fait  ;  but 24  parts of cold
 water were required to diffolve one.  3.  It is likewife fo-
 luble in  fpirit of wine;  four parts of which are re-
 quired to diffolve one of the fait when cold, but only
 an equal  quantity  when  affifted by  a boiling  heat.
  4. The fait is  deftructible by  an open fire, melts and
  burns with a picafant fmell, leaving behind a hard 111-
 folub'c coal,  which  does not eafily  burn  to  afhes.
  5.  By diftillation  an acid water is firft obtained with-
  out  any oil : then  a Sublimate,  which  remains  fluid
  while the neck of the retort is hot, and then cryftal-
  lizes.  This fublimateiias the tafte and fmell of flowers
  ef benzoin ; is foluble in  water and in fpirit  of wine ;
  reddens litmus ; and precipitates  metallic Solutions of
  the following colours, viz. gold of a dark brown ; fil-
  ver ofa grey  colour ; copper of a brown ;  iron of a
  black • lead of a white colour ; mercury of an orange;
  bifmuth, lemon-coloured.   The acid of molybdasna be-
  came yellow coloured,  but no precipitate enfued.  So-
  lutions of various kinds of earths were not altered ;
  but lime-water afforded  a  copious grey-coloured  pre-
  cipitate.  6.   By treating this acid with that of nitre,
  in the manner directed for producing  acid of fugar, it
  was changed into the latter.

        XVII. Identity ofthe Vegetable  Acids.

     On- the proofs of the identity of the vegetable acids
  with one another, Mr Keir makes  the following re-
  marks-   "  The  experiments and obfervation s which
  have been made, prove evidently a ftrong analogy be-
  tween the acetous acid,  fpirit of wine, tartar, and acid
  of fugar;  and they feem  to fhow the exiftence of a
  common principle or  bafis in all of them, modified
  either by the addition of another principle not  com-
  mon to all of them,  or by different proportions of the
   fame principle.   None  of the opinions  on this fub-
  ject, however, are quite Satisfactory.  The production
   ofthe  acetous  acid by  treating Spirit of  wine wnh
   other acids, does not prove that  the  acetous acid was
   contained in the fpirit of  wine,  but only  in concur-
   ri  ■ ewith them, that they contain fome common prm-
       ^    r   Y.                            Pra&ice.
       There is no fact adduced to fupport Morvcau's indemity
opium::,  that lixed air is abforbed  during; the  acetous oftheve^
   S
ciple.
fermentation; or that the prefence of this < xcd airis ubto™to
ntetilary.  The decompolition  of all vegetable acids
bv  heat, and the production  theretrom ot fixed and
inriamnuLde gales,  ...ow that thtie acids contain fome
ot the fame principles as thefe  elaftic  fluids  but do   *
not prove that the gale* exilttd 111 the fluids.  \\ c
have good reafon to believe that acetous  acid does not
contain any fixed air already formed ; for it yields none
when vitriolic acid is added  to it, or to foliated earth;
nevertheless,  my  opinion  that vegetable  and animal
acids are, by heat, in a great meafure convertible into
fixed air, Seems  to  be fufficiently  proved by expert--
ments.   Thus Hales has fhown the great quantities of   l5A1
this P-as which tartar yields  on  diftillation.  Berthollet  Quantity
has obtained the fixed and inflammable gaSes from to-  ofthe; d.ne-
liated earth; and Dr Higgins  has verified this experi-  ™ ^ ob_
ment, and deduced the quantities.  From 7680 grains taillcdfrom
of foliated earth, the Doctor obtained.                foliated
3862.994 grains, earth.
i473->G4
1047.6018
 78
182
340

726.9402"
    Cauftic alkali
    Fixed air
    Inflammable air
    Oily matter retained in the re-
       fiduum
    Oil
    Water condenfed
    Deficiency attributed chiefly to
       water
  As  fixed and inflammable  gaSes may be obtained
from every vegetable fubftance by fire, nothing can be
inferred from thefe experiments to explain particularly
the nature of the acetous acid, excepting that it con-
tains fome of the inflammable matter common  to  the
vegetable kingdom,  and eSpecially of the matter com-
mon to vegetable acids ; all which alfo, whenanalyfed,
furnifh large quantities of thefe two gafes.
  « Although we are far (adds our author) from the
knowledge requifite  to give a  complete theory of  the
acetous fermentation, yet it may be  ufiful to explain
the ideas that appear moft probable.  In  all  the in-
ftances that we know of the formation of  acids, whe-
ther effeded by combuftion, as the acids of fulphur and
phofphorus,  or by repeated abftractions of nitrous acid,
as in the procefs for making acid of fugar,  a very fen-    1543
fible  quantity of pure air is abforbed. In the cafe of Airabforb~
combuftion we know, from the weight acquired,  that £-™B
there is a great abforption  of air; and in the latter of ^acidfc
cafe, of acids being produced  by application of nitrous
acid,  as this acid  confifts oS nitrous and pure  air,
and as in theSe operations a quantity of the nitrous gas
is expelled,  there feems but little doubt that there alfo
the pure air ofthe nitrous acid is united with the fub-
ftance  employed in the formation of the new  acid.
 Hence, from all tharwe know, the abforption of air takes
 place in all acidifying proceffes.   But it  alfo  a&ually
 takes place in the acetous fermentation, as has  been
 obferved, particularly by the  Abbe Rozier; and  it is
 generally known, that air is  neceffary to the forma-
 tion of vinegar.  The  next queftion is, What is the
 bafis ?  Aud  from the experiments already related,  of
 forming the acetous acid by means of fpirit of wine,
 it feems' probable, either that this fpirit is the bafis of
 the acetous  acid, or that it  contains this bafis : and
 from  the  convertibility of the acids of tartar and of
                                               fugar 
Practice.
C   H   E   M
   1544
Inflam-.
mable fpi-
rit produ-
ced from
radical vi-
negar.
Identity of fugar into the acetous acid  by the  proceffes  above  de-
the vege-  fcribed,  it feems probable that  thefe alfo contain the
         fame common balls; which,  being united with  a  de-
         termined quantity of pure air,  forms  acid of tartar ;
         with a larger quantity, acidof fugar ; and with a ftill
         larger,  the acetous acid.
            " An inflammable fpirit is Said  to appear  at the end
         of the diftillation  of radical vinegar from  verdigris.
         Now, if the ardent fpirit were contained in  the verdi-
         gris, as  it is more volatile than the acid, it ought to
         come over firft ; but as  it appears only towards  the
         end of the diftillation, it feems  to be formed during
         the  operation ; and I imagine, that the metal, when
         almoft deprived of its acid, attracts fome x)f  the air of
         the remaining acid  ;  and the part or bafis of  the acid
         thus  deprived of its air becomes then an inflammable
         fpirit, and in fome cafes  an oil appears.  But  as   the
         quantity of acid thus  decompofed is very fmall, and
         little air of confequence  remains united with the me-
         tallic part of the verdigris, the copper appears rather
         in a metallic  than calciform ftate after  the  operation.
         But zinc, during its folution in concentrated vinegar,
         decomposes  the acid as  it  does the vitriolic  and other
         ftrong acids, and accordingly inflammable vapours are
         produced ; and what is remarkable, thefe vapours have
         a fulphureous fmell.   Iron  always, during its  folution
         in concentrated vinegar, produces  an expulfion of in-
duced from flammable vapours ;  which, however, do not explode
it.       like  inflammable gas.
   1546      " We muft not imagine that we are yet able to ex-
Ofthe con- plain completely what paffes in the acetous fermenta-
    "f h ^°n> or t^at  t^ie acetous ac^ *s a compound of mere
acetous a-C ^Wn and pure air.    Befides this  combination of fpirit
I   S   T    R   Y.                                  227
  been obServed both by Weftrumb and Scheele.   The Addition
  latter further acquaints us, that he obtained it in ana- to Se(a- *•
  lyfing a tallow  like oil, which remained  undiflblved § 2°'
  upon digefting ftarch in nitrous acid.  As  acid of fu-
  gar alSo may be obtained  from a variety of animal fub-
  ftances, and as  this acid is convertible  into the ace-
  tous we have one reaSon more added to  many others,
  to prove that the matters of vegetable and animal fub-
  ftances are not capable of any chemical diftinction."
  1545
Sulphure-
ous inflam
mable va-
pours pro
acetous a-
cid
          and air, it is obServed, that a precipitation always takes
          place beSore the fermentation is  completed,  of fome
          mucilaginous matter, which  difpoles the vinegar to
          putrefy,  and from which it therefore ought to be care-
          fully feparated.  Stahl affirms, that without  a depo-
          fition of fuch fediment, vinegar cannot be made from
          fugar, wine, or other juice.   Befides the matter that
          is depofited, probably  as  much remains in the liquor
          as can be diffolved therein ;  for, by diftillation, much
          of a fimilar extractive  matter is left  in  the retort.
          What the nature of this matter is, and how it is form-
          ed,  has not yet been  examined.  Though diftillation
          frees rhe acid from much of this extractive fubftance,
          yet we have no reafon to believe that we have  ever ob-
          tained it  entirely free from  inflammable matter; as
          it retains  it even when combined with alkalies  and
          with metals.  When fugar of lead  and other acetous
          falts are diftilled with a ftrong heat, the fubftances re-
          maining in the retort have  been obferved topoffefs  the
          properties of a  pyrophorus;  and this will  happen
          whatever pains have been taken to purify  the  vinegar
          employed.  See the article Pyrophorus.  This  fact
          fhows the exiftence of an  inflammable  matter in this
          acid ; and which may perhaps be  effential in its com-
  ,1-?47    pofition, and neceflary  to its properties.   Although
ed inva-"  fermentation is the uSvil  mode of obtaining: acetous
rious chc   acid, yet  it appears from  the hftances obferved  by
mical pro-  latter chemifts, rljat it is  not effential to its formation,
ceffes.     but  that it is alio formed  in various chemical proceffes ;
          and  the  acid  obtained  bv diftillation from  woods,
          wax, &c. are  very anaWois t^ vinegar,   "tanpears
          alfo on treating the acid of fugar with nitrous acid, as has
XVIII. ADDiTioNto Sect. I. § 20. concerning the volati-
    lity ofa Mixture of Marine and Nitrous Acids.
154S
   This is much lefs fenfible when the acids are weak  Howtode-
than when they are concentrated.   On  mixing  the  Priye a1u.a-
two when moderately fmoking, and which had remain-  regia of its
ed for a long time feparate without occafioning  any  vo a x l y"
difturbance, a vaftly fmoking aqua-regia has been pro-
duced, which would either drive out  the flopple, or
burft  the bottle in warm weather.  On diftilling a
pretty ftrong nitrous  acid from  fal ammoniac,  M.
Beaume obferved, that the vapours which came over
were fo exceedingly elaftic, that notwithftanding every
precaution which could be taken in fuch a cafe,  the
diftillation could not be  continued.   By  letting  this
efcape, however,   Mr Cornette obferved, that  the
diftillation of thefe two fubftances may be carried on
to the end  without  any inconvenience, and  the aqua-
regia will then be no longer troublefome.

        XIX. Test for Acids and Alkalies.
   The general method recommended for difcovering
a fmall quantity of acid or alkali  in any liquid, is by
trying it  with any vegetable blue, fuch  as fyrup of
violets ; when, if  the acid prevails in the liquor,  the
fyrup will acquire a red colour,   more or lefs deep  ac-
cording to the quantity of  acid; or if  the alkali pre-
vail, it will change the  fyrup green in like proportion.    1549
Since the late improvements in chemiftry, however,  the  Inaccuracy
fyrup has  been found deficient  in accuracy, and  the  ofthecom-
infufion  of turnefole,  or  of an  artificial preparation  mou te
called  litmus,  have  been fubftituted inftead of  it.
The infufion of  litmus is blue,  and, like fyrup of vio-
lets, becomes red with acids. It  is fo fenfible that it
will difcover one grain of oil of vitriol though mixed
with 100,000 of water. Unfortunately, however, this
infufion does not change its colour on mixture with al-
kalies ; it  is therefore neceffary to mix it with juft as
much vinegar as will turn the infufion red, which will
then be reftored to its blue colour by being mixed with
any alkaline liquor.   The blue infufion of litmus is al-
fo a. teft of the  prefence  of fixed air in water, with
which it turns red, as it does with other acids.
   The great fenfibility of this teft would leave very
little reafon to Search for any other, were it always an
exact  teft of  the point of faturation  of acids  anff alka-
lies ;  but,  from the following fact, this appears to Mr
Wart  to  be dubious.  A  mixture of phlogifticated  ni-
trous acid with an alkali will appear to be acid by  the
teft of litmus, when other tells,  fuch as the infufion of
the petals of the fcarlet rofe, ofthe blue iris, of vio-
lets, and of other flowers, will fliow the fame liquor to
be alkaline, by turning green fo evidently as to leave
no room to doubt.
   When Mr Watt made this difcovery, the fcarlet  ro-
                       F f2                    fes, 
 22*5

 I tfor a
rids and at
kil.c*.
C   H   E    M    I   S    1    R    Y.
Pra&ice,
   ICO
Red cah-
I- gL an-
fwer* the
purpofe
beft.
   1551
flow to
I re-pare it
f jr ulc*
fcs,.i nlfcvrr.il other rlowcr, whole pct.ils changethcir
colour  by acids .1.1.1  alkalies, were in flower.   Hi-
ving ft.iiucd paper with their juices,  he found that it
was  not affected by the phlogifticated nitrous acid, ex-
cepting in i'i far as it  atled the  part of a neutralizing,
acid  ; but he  found alfo,  that, piper  ftained  in this
manner was muh lefs eafily cite Ted than litmus was;
.mdih.:t, in a lhort time,  it loft  much of  the feniibi-
lity which  it  poil'clfcd at firft ; and having occafion in
winter to repeat fomc experiments in which the phlo-
gifticated nitrous acid was concerned, he found  his
it.iined paper almoft ufelefs.  Searching, therefore, for
fomc other vegetables which might Serve for a  teft  at
all  feafons of the year,  he found the red cabbage to
anfwer his  purpofe  better than any other ;  having
both more feniibility with regard to acids than  litmus,
being naturally blue,  and  turning green with alkalies,
and  red with acids ;  to all which is joined the advan-
tage of its being no farther affected by the phlogiftica-
ted acid of nitre than as it acts  as a real acid.
   T<} prepare this left, Mr Watt recommends  to take
the  frelheft   leaves of the cabbage ; to cut  out  the
large Items, and mince the thin parts oS the leaves very
Small ; then to digeft them in water at about the heat
of 120 degrees for a few  hours,  when they will yield
blue liquor ;  whicli,  if ufed immediately as a teft, will
be found to poffefs great fenfibility: but  as   in  this
ftate it is very apt to turn putrid,  Some of the follow-
ing methods muft be ufed for preferving it.
   1. After hiving minced the leaves,  fpread them on
 paper, and dry them  in a gentle heat; when perfectly
 dry, pnt theniup in  glafs  bottles  well corked ; and,
 when you  want  to  ufe  them,  acidulate  fome water
 with vitriolic acid, and digeft or infufe the dry leaves
 in it, until they give out  their colour;  then ftrain  the
 liquor through a  cloth,  and  add to  it a quantity of
 fine whiting or chalk, ftirring  it  frequently, until it
 becomes of a true  blue colour, neither  inclining to
 green nor purple ; when you perceive that it  has ac-
 quired this colour, filter it immediately ;  otherwife it
 will become  greenifh by ftanding longer on the whi-
 ting.   This  liquor  will depofit a  fmall quantity of
 gypSum, and, by the addition of a little fpirit of wine,
 will keep good for fome  days ; but  will then become
 fomewhat  putrid and reddilh.  If too much  fpirit is
 added,  it  deftroys the colour.   If the liquor is wanted
 ro  keep longer,  it may be neutralized by a fixed alka-
 li inftead of chalk.
    2.  As  thus the liquor cannot  be  long preferved
 wiftiout requiring to be neutralized afrefh juft before
 ft is ufed ; and as  the putrid  fermentation  which it
 undergoes, and perhaps the alkalies or fpirit  of wine
 mixed with it, feem to leffen its fenfibility ;  in order
 topreferve  irs virtues while kept in  a liquid ftate, fome
 frelh leaves  ofthe cabbage, minced  as above directed,
 may be infufed in a mixture of vitriolic acid  and  wa-
 ter, of about the degree  of acidity of vinegar; and  it
  maybe neutralized, as it is wanted,   either by means
 of chalk, or  of the fixed or volatile alkali.   It muft
  be  obServed, however,  ihn if  the liquor has an  ex-
  cefs of alkali, it will foon lofe  its  colour, and become
 yellow ; from which ftate it cannot be reftored ;  care
  ihould  therefore be  taken to bring it very exactly to a
  bine, and not to\:  it verge towards a green.
     3. In this manner, Mr Wart prepared  aredi.if iffm
of violets; which, on being nei t:  :i/.fd, formcda very Volatile
fenfible teft, though he did not know  how long thclc alfcain___,
properties would be preferved; but he is of opinion
that the coloured infufu>;;s of oiher vegetables may be
preferved in the fame manner by  the autifeptic power
of the vitriolic acid, in fuch a manner as to  lolc little
of their original fenfibility.  Paper frefh ftained wiih
thefe lefts, in  their neutral flate,  has fufficient fen-
fibility for many experiments ; but the  alum  and  glue
which enter into  the  preparation of writing  paper,
feem, in fome degree,  to  fix the  colour; and paper
which  is not  fized  becomes  fomewhat tranfparent
when wetted ;  which renders fmall changes of colour
imperceptible.   Where accuracy  is required, there-
fore, the teft fhould be ufed in a liquid tafte.             *55i
  4. Our author has found that  the  infufion of red  Vanouao-
cabbage,  as  well as of various flowers  in  water, a-thcrtelts'
cidulated by   means  oS  vitriolic  acid,  are  apt  to
turn mouldy in the Summer SeaSon, and  likewiSe that
the moulding is prevented by an addition of fpirit of
wine.  He has not been able  to  afcertain  the quan-
tity of fpirit neceffary for this purpofe, but adds  i> by
little and little at a time until the procefs of mould-
ing is flopped.—Very fenfible tefts  are afforded  by
the petals of the fcarlet rofe, and  ofthe pink coloured        £
lychnis treated in the  abovementioned manner.

              XX.  Volatile Alkali.

   MrHiggins claims the firft difcovery of the con-    XSS3 \
 ftituent parts of volatile alkali,  or at leaft of an expe- Volatile al-
 riment  leading to it.   " About the latter  end of kali prepa-
 March  1785  (fays  he),  I found that  nitrous  acid red from
 poured  on  tin filings, and immediately mixed  with n.,jrou*ar
 fixed  vegetable alkali,   generated volatile alkali in  •  an
 great abundance :  fo  fingular  a  fact did not fail of
 deeply impreffing my mind, though at  the time I  could
 not account for it.  About a fortnight after, I  men-
 tioned the circumftance  to Dr  Brocklefby.   1 fe told
 me he was going to meet  fome philosophical gentle-
 men  at Sir Jofeph Banks's, and  defired I  would  ge-
 nerate Some alkali to exhibit beSorethem:  according-
 ly  I did ;  and had the pleaSure of accompanying -him
 thither.  The December  following I mentioned  the
 fa^t to Dr Caulet, and likewife the  copious genera-
 tion of volatile alkali from Pruflian  blue,  vegetable
 alkali,  and water ; on which we agreed to  make a fet
 of experiments upon  the fubject.  At prefent I fliall
 only give an  account  of the following, which  drew
 our particular attention.   Into  a glafs  cylinder, made
 for the purpofe, we charged three parts of alkaline
 air, and to this added  one part of  dephlogifticated air;   jsss
 wc palled the electrical fpark repeatedly in  it,  with- Effects of
 out apparently effecting  the fmalleft  change.  When the electric
 it had received about  100 ftrong.fhocka; la fmall quan- fyarkon it.
  tity of moifture appeared on the fides  of- the  glafs,
  and  the  brafs conductors feemed? to; be.  corroded;
  when we had paffed  60 more fhoc^,«  in.*if, ■  .the  quan
  tity of moifture  feemed to increafe,. and  acquire a
  greenifh colour, -though at this time the column of air
  fuffered no diminution.   On  examining   the  air,  it
  burned w ith  a languid greenifh flame, from,which .we
  inferred that the dephlogifticated air  was'totally con-
  denfed : it ftill retained an alkaline fmell; and the alka-
  line part was not readily abforbed by  water.
                                             " From 
Pra&ice.
C   H    E   M   I
Pruffym
blue.
1556
kali.
           " From Mr Cavendifh's famous difcovery of the
         conftituent parts of water we could  readily account
         for  the loSs of the dephlogifticated air in this experi-
         ment ; but the quantity of water was more than we
         could expect from this : therefore water  muft have
         been  precipitated  from the decompofed  alkali; for
         volatile  alkali,  from  its great attraction to water,
         muft keep Some in Solution even in its aeriform  ftate.
         From the above circumftances it might be expected,
         that a contra&ion of the ^column of air fhould take
True com- place ; but it muft be  confidered,  that the union took
pofition of place gradually in proportion as the alkali was de-
volatile al- compofed; and that, in this caSe, the expanfion muft
         equal the condenfation.  During the fpring of 1786
         I had often  an opportunity of mentioning different
         facts to  Dr Auftin  relating to volatile alkali,  who  at
         that time was too much engaged to pay attention
         to  the  fubject.  In  the end of Auguft 1787,  he
         gave me an account of a fet of experiments which he
         had made, and which actually proved, that  volatile
         alkali confifts of light inflammable and phlogifticated
         airs; not knowing at that time  what Meflrs Houf-
         man and Berthollet had done.  Without depreciating
         the merit of  thefe two gentlemen, Dr Auftin has an
         equal claim to the difcovery, laying afide priority ;  as
         his experiments are as decifive as theirs. Dr Prieftley
         made the firft ftep towards our knowledge of volatile
         alkali."                  •<*>

                       XXI.  Prussian Blue.
S    T
 XXIII.
R   Y.
 New Chemical Nomenclatures.
1557
lutions,
           The acid of this fubftance, as far as it contains an
Woulfe's  acid, is fuppofed to bethat of phofphorus.  Mr Woulfe
teft for mi- propofed a teft of this kind for difcovering iron in mi-
neral wa-  neral waters, which, he obferved, would not be affe&ed
ters.      by acids ;  but the lixivium defcribed by him had the
         bad property of letting fall the  Pruffian blue it con-
         tains in a few weeks.  The precipitate of copper,
         however, treated again with alkali, retained this pro-
         perty upwards of nine months.   The volatile alkali,
         he obferves, is diffolved by the Pruflian acid; and the
         cryftals depofited are  rendered blue  by  the colouring
     g   matter, though the colour  at firft is loft by  the union
Effect of it °f the  alkali with the fubftance  already made.  The
on various metals  were precipitated by this  teft of the following
metallic fo- colours :  Gold of a brownifh yellow, the precipitate
         afterwards becoming of a full yellow ; platina of a deep
         blue, but when quite pure,  of a yellow colour, turning
         flightty green.  Silver in the nitrons acid-was preci-
         pitated ofa whitifh colour; copper from all the  dif-
         ferent  acids was precipitated of a deep brown colour,
         the liquid remaining greenifh ; green vitriol  let fall a
         deep blue powder, leaving a colourlefs lixivium ; fugar
         of lead and muriated tin  gave a white powder ;  nitra-
         ted mercury  a  white  or yellowifli precipitate ;  the
         Illfeld manganefe a brownifh, but that  from Devon-
         shire a  blue, which  firft  became  afh-coloured  and
         then reddifli.   Nitrated bifmuth  afforded  a  white
         precipitate, and the lixivium was (lightly green : mu-
         riated  antimony yielded a white  precipitate, with
         a yellowifli lixivium: vitriolated zinc a whitifh :  co-
         balt in aqua-regia a reddifh white powder :  the pre-
         cipitate of" arfenic and the different earths was com-
         monly white,.
  1559
Bergman's
letter to
Morveau
on this fub-
ject.
  1560
Lavoifier's
explanation
of the new
nomencla-
ture.
                                                       229
                                                   New che-
                                                   mical no-
I. Of that propofed iu \~l%7 by Mejfrs Morveau, Berthol- mencla-
  lett Fourcroy, and Lavoifier.                      tures.

  W h en this nomenclature was firft publifhed, M. La-
voifier.informs us, that  fome blame was thrown upon
the authors'for changing the language,  which had re-
ceived the Sanction of their matters, and been adopted
by them.  In anSwer to this, however,  he urges, that
Mefffs Bergman and Maceper had expreffed a wilh for
Some reformation in the chemical language.  Mr Berg-
man had even written to M. Morveau on the fubject in
the following terms. l( Show no favour to any impro-
per denomination :  Thofe who are already poffeffed of
knowledge, cannot be deprived of it by new terms ;
thofe who  have their knowledge to  acquire, will  be
enabled by your improvement on the language of the
fcience to acquire it fooner."
  The following  is M.  Lavoifiers  explanation of the
principles  on which his new language is  compofed.
il Acids  confift of two  fubftances, belonging to that
order which  comprehends fuch as appear to us to  be
fimple fubftances.   The one  of thefe is the  principle
of acidity,  and common  to all acids; from it therefore
fhould the name of the clafs and genus be borrowed :
The other, which is peculiar to each acid, and diftin-
guifhes them from one another, fhould fupply the fpe-
cific name.   But  in moft of rhe acids,  the two confti-
tuent principles, the acidifying and the acidifyed, may
exift in different proportion, forming different degrees
of equilibrium or faturation;  this is obferved of the
fulpharic and fulphureous acid.  Thefe two ftates of the.
fame acid we have expreffed. by varying the termina-
tion of the fpecific  name.
   "  Metallic fubftances,  after being expofed to  the
compound  action  of air and  fire, lofe their  metallic
luftre, gain an increafe of weight, andaflume an earthy
appearance.   In  this ftate they are,  like acids, com-
pound bodies, confifting of  one principle common.
to them, all, and another peculiar to  each of them.
We have therefore in like manner claffed them under
a generic name,  derived from  the principle which is
common to them all. The name which we have adopt-
ed  is Oxide.-- The peculiar names of the metals from
which  they  are  formed, Serve to diftinguifli  theSe
compounds from  one another.
   " Combftuible Subftances, which,  in acids and me-
tallic oxides, exift as Specific and peculiar principles,
are capable of becoming, in their  turn,  the common
principle of a great number of Subftances. /Combina-
tions of fulphur, were long the only compounds of this
fort known : but of late  the experiments  of Mefffs
Vandermonde, Monge, and Berthollet, have fhown that
coal combines with  iron and  perhaps with various o-
ther  metals ; and that  the  refult of its  combination
with iron are, according to the proportions, fteel, plum-
bago,  ire.   It is  alfo known  from the experiments of
M. Pelletier, that phofphorus combines with many
metallic fubftances. We have therefore arranged thefe
different combinations together under generic names,
formed from  the name of the common fubftance, with
a termination indicating this analogy  ; and have dif-
tinguifhed  them from each other by fpecific names de-
rived from the names of the peculiar fubftances.
                                              " Ic 
230
N rw cl-.c-
C   H   E   M    I   S   T    R    Y.
Tract i
Mr Wieg-
lcb's no-
mencla-
ture.
  "  I. wis fo.md fumewh  t morc difficult to form a no-
menclature for the compounds of thofe  three  fimple
I ibftanccs ;  becaufe they ire fo very numerous, and
ftill  morc, becaufe it is impoffible  to exprefs the na-
ture  of their conftituent principles, without ufing more
compound names.   In bodies belonging to this claf>,
fuch  as neutral Salts for inftance, we had to confider,  r.
the acidifying principle common to them all;  2. the
aciditiablc principle which  pcculiarizes  the  acid;  ?.
the Saline, earthy, or metallic baSe, which determines
the particular Species of the Salt.  We have derived ihe
name of each clafs of falts from that of the acidifiable
principle, common to all the individuals of the  clafs;
and  have then diftinguifhed each fpecies by the name
of the faline, earthy,  or metallic bafe peculiar to it.
  "  As fait, confifting of any three principles, may,
w ithout lofing any of thefe principles, pafs through dif-
ferent ftates by the variation of their  proportions;
our nomenclature would have been defective without
expreffions for thefe different ftates.  We have expref-
fed them chiefly by a change of termination, making
all names of falts in the fame ftate to  end with the
fame termination."

          2. Nomenclature  by M. Wiegleb.

  In Wiegleb's General Syftem of Chemiftry tranfla-
ted by Hopfon, we have another nomenclature formed
on different principles.   In this he gives to fixed ve-
getable alkali  the  name of Spodium, from the  Greek
word <rirc<r&, (afbes).Theminerzl alkali htcaMsnatrum,
the name by which it was anciently diftinguifhed ; and
the volatile alkali ammonium, from fal ammoniac  which
contains  it  in great quantity.  The  compound falts
may  be diftinguifhed into double,  triple,  and quadru-
ple ;  though, in the fcheme given in the work, the firft
divifion is omitted,  as tending only to create confufion.
The  irregular falts, confifting of thofe which are triple
and quadruple, are admitted.  Such as are imperfect
by reafon of an excefs of acid, he fays, are beft deno-
minated by converting the adjective, expreflive of the
bafe, into a participle ; a practice which,  on  many oc-
cafions, though countenanced by the authority of a late
eminent writer, feems aukward and ftiff.   The  excefs
of acid is denominated by the word hyperoxys,  and  a
defect of it by hypoxys.  Hence his  denominations are
formed in the  following manner.
  Salts with excefs of acid.  Cream of tartar, or tarta-
rus fpodatus,  or tartaroxys fpodicus.  Acid vitriolated
lartar, or vitriolum fpodatum, vitrioloxys fpodicus.
  The falts which are imperfect from a  defect of acid
  acum aerocraticum,

Chalk, or calx aerocratica,

Borax, or natrum boracicum.
 have their denominations by mentioning the bafe before New  hc-
 the acid,  and expreffing the former fubftantively, the ndcal no-
 latter adjcctively.  Thus,                           mcncla-
   Salt of" tartar,  aerated vegetable C Oxyfpodium, ae- *urci'<r
     alkali, fpodium aerocraticum, £   rocraticum.
   Aerated volatile alkali, ammoni- X Oxyammonium
                                 \   aerocraticum.
                                 C Oxycalcitis aero-
                                 £   craticus.
                                 COxynatrum bora-
                                \   cicum.
   With refpect to other terms, Mr Wiegleb expreffes
 the acid with which any bafe is combined, by the ter-
 mination cratia, from the Greek upaT©^ (robur), added
 to it;  excepting  only thofe with  the nitrous and mu-
 riatic acids:  and  thefe  (for what reafon does not ap-
 pear) he calls Aponitra and Epiwuria-.  His genera of
 falts are as follow.
   1. Vitriols (Sulphurocratia).  2. Nitres (Aponitra).
 3. Murias (Epimuria).  4.  Boraxes.  5. Fluoricrates.
 6. Arfenicrates.  7. Barylithicrates,  (thofe with acid
 of tungften).   8. Molybdasnocrates.   9. Photocrates,
 (with acid of phofphorus). 10. Electrocrates. 11. Oxy-
 crates, (with the acetous acid) ; or epoxycrates, with the
 aerated acid). 12. Tartars; or, with the acid changedby
 fire,pyro-tartars.   13. Oxalidicrates.  14. Cecidocrates
 (with theacid of galls).  15. Citriocrates.  16.  Meli-
 crates (with the acidof apples).   17. Benzicrates. 18.
 Xylocrates. io.Gummicratcs. 20. Camphoricrates. 21.
 Aerocrates.   22.  Galacticrates.   2?. Gala-melicrates
 (with acid of fugar of milk). 24. Myrmecicrates.  25.
 Cyanocrates  (with  the colouring matter of  Pruflian
 blue).   26. Steatocrates.  27. Bombycicrates.  28. Zoo-
 lithocrates, (with acid of calculus).

   On  the fubject of nomenclatures it is obvious to
 remark, that whatever  may be the defects  of the old
 one, we are ready to be involved in much greater dif-
 ficulties by the introduction of a new one.  Or fup-
 pofing a new language  to  be adopted, where would
 be the fecurity for its permanence ?   That which ap-
 pears moft fpecious at one period, may ftill be fu-
 perfeded by the refinements of another;  and colourable
 pretenfions would never be wanting to fucceffive inno-
 vators.   Hence a continual fluctuation, and  an endlefs
 vocabulary.   As the nomenclature firft abovemention-
ed, however, has attracted no fmall degree of attention,
we fliall here fubjoin a fcheme of it, as well for the fa-
 tisfaction of our readers in general,  as for the gratifi-
cation of thofe in particular who may have imbibed the
 doctrines of its authors.
[Follows The Whole-fleet Table."} 
 ib  it  ing   the   C   H    E   M   I   C   A   L       N   O   M   E   N    C,  L   A    T  U  1   E,
e   MORVEAU,  LAVOISLER,   BERTHOLLET,   and   De   FOURCROY,   in  May 1787.
$To face Tage 55^. •
EDUCED
KY THE
.C.
Seated or vital
                    III.
THE SAME SUBSTANCES  COMBINED
            WITH OXIGENE.
NAMES  NEWLY   IN-
VENTED OR ADOPTED.
Mega
ited air, or at-
ic mephitis.
ANCIENT  MAMEJ.
Water.

The bafeof nitrou3gas.
Nitric acid.
With an excefs of azote.
Nitrous acid.
Carbonic acid.
Sulphuric acid.
With lefs oxigene,
Sulphureous acid.
Phofphoric acid.
   th a /matter propor -
   ion of oxigene,
P^iufphorous acid.  ,
   riatic acid
W th an excefs of oxi-


O.^genated  muriatic
  acid.
l&racic acid.
Water.

'the bafe of nitrous gas.
White nitrous acid.
                     iv.                     |                     v.                      {                    vr.
THE SAME  SUBSTANCES IN AN 0X1-THESE  OXIGENATED   SUBSTANCES THE  SAME  PRIMARY  SUBSTANCES
     GENATED GriZEOUS STATE.         NEUTRALIZED BY  EHE ADDI-    COMBINED WITH OTHER  SUBSTAN-
,MES   NEWIY   IN-    ANC                NAMES  NEWLY   IN-    ANC-ENT NAMES
NTED OR ADOPTED.    """"T »AH«.   VENTED OR ADOI-TED.
Nitrous gas.
Nitrous acid  gas.
Fuming nitrous acid.
Fixed air, or -cretaceous Q,
acid.
Vitriolicaeid.
Sulphureous acid.
Phofphoric acid.
Fuming or "velatiiephof-
  phoric acid.
Marine acid.
Carbonic acid ga*.      Fixed air, mephitk air.
Sulphureous acid gas.'    Sulphureous acid gas.
Meriatic acid gas.      Murine acid gas
Dephlogifticated  marine Oxigenated   muriatic
\
 S> ccinic acid.
Adetous ac.J
  acid.
Sedative fait,
Acid offpar.    ,

Volatile fait of amber.

Diflilled .vinegar.
acid gas.
Fluoric acid gas.
Dephlogifticated marine
  acid gas.
Spathofe gas.
NEUTRALIZED BY EH1
        TION OF  BASES.
VENTED OR ADOPTED.
Nitrate of potalh.
       of foda, &c.

Nitrite of potalh.
ry i_   f of lime.
Ca™°- Jofpotafh,&c
nate.   y r-     «™
         of iron.occ
          of potalh.
          of foda.
          of lime-
Sulphate { of alumin-
          ous earth..
          of barytes.
          of iron, &c.
Sulphite of potalh, &c.
Phofpliate of foda.

Calcareous-phofphate.
Superfatufated  phof-
   phate of foda.
* hofphiteof potath,&c
Muriate of potalh
Muriate of foda.
L'alcarcousmuriate,&c
Ammoniacal muriate.
Oxigenate'd muriate of
   foda, &f.
Borate  fuperfaturated
with foda j or borax.
Borate of foda, Sct.foda
JaturatecLjlJtb the acid.
Fluate orifime, ckc.
Common nitre.
Cubic nitre.
Chalk.
Effervtfcent alkalies.
Ruft of iron, leStc.
Vitriolated tartar.
Glauber fait,
Selenite.
Alum.

Ponderous fpar.
Vitriol of iron, tlfc.
StahV s fulphureous fait.
Phofphoric fait ivitb a
  bafe of natrum.
Earth of bones.
Haupt's fal perlatum.
      CES BUT  NOT AICIDIFIED.

NAMES   NEWLY  IN-
ANCIENT NAMES.
Carbure of iron.
          n ofiron.
Sulphure  L ofantimo.
          3 oflead.
Sulph. hydrogen, gas.
S<jlphure  of potafh. 7
Sulphure  of foda.  $
Alkaline fulphures
  with metals fufpend-
  ed iu them.
Alkaline fulphure with
  carbonaceous  mat-
  ters fufpended in it.
Phofphorifed   hydro-
  genous  gas.
Phofphure of iron.
Febrifuge fait offylvius.
Marine fait.
Calcareous marine fait,
Sal ammoniac.
Common borax.
Fluerfpa
Succinate/ of foda, &c.  —
'of potalh.
 of foda.
Terra foliata tartari.
Mineral terra foliata.
Plumbag*.
Factitious iron pyrites.
Antimony,
Galena.
Hepatic gas.

Alkaline Utters of fulphur.

Metallic  livers of ful-
  phur. ,

Liver of fulphur with
  carbonaceous matters
  fufpended in it.
Phofphoric gas,

Syderite. 
jti txm
Regulus of cobalt.
Regulus of antimony.
Verifiable earth, quartz,
  &c.
Clay, or earth of alum.
Terra ponderofa.
Calcareous earth.
~   li\
Ammoniacal gas.
Alkaline gas.
Oxide of nicies!.
Grey    ? oxide of
Vitreous J cobalt.
Calx of nickel.
Calx of cobalt.
White
( oxide of
  bifmuth.
                       Magiftery of bifmuth, or
                         •white paint.
                       Yellow calx of bifmuth.
                       Olafi of bifmmtb.
                       Diaphoretic antimony,

                       Patvder of Algarstti,

                       Flaivcrs or fnoiu of an-
                         timony.
                       Glafs of regulus of an-
                         timony .
                       Calx of zinc.
SMbjJmated  oxide  of  Flowers  of  zinc, pom
  ^inc
Yfel*

 y  "wfbv  the  ni"
           trous acid,
Cxide  lbyth.em?fi-
yxiue  1    aticacid,
  an"  I  fublimated.
 mony j
       I  vitreous.

dxiefe of  zinc.
'a?  Z oxide of iron.
^ ''bite oxide of tin.

Vbite
Yel
Se<5
  pholix, &c.
Martial athiops,
Aftringent   faffron.  ^Sulphurated  oxuie ot
  Mars.
Caix, or putty of tin.
Alkaline cobaltic       Precipitates of cobalt a-
  oxides.                 Sain ^ff'lved h al'
                         kalies.
Sulphurated  oxide  of  Bifmuth precipitated by
  bifmuth.               liver of fulphur.
Grey   ~\ ~  ,,        Gre3 caiK  °f antimony,
Red    / SuiPhurat"   Kermes mineral.
Oranee f ed oxide of  Golden fulphur.
Vitreous Vantim0ny"   Glafs and liver of anti-
                         mony.
Alkaline oxide  of  an-  Rotrou's folvent.
  timony.

Sulphurated  oxide of  Precipitate  of %inc by
  sine.                  liver of, fulphur  or
                         factitious blende.
 fljite  ~\
 'ef ow  / oxide of
 eA     f   lead.
 itrcousj
:.ed  -\
( Teen / oxide of cop-
     V   Per>
Hue  J
]Jackifti-)       .  ,
. T „    / mercurial
 ellow v.     .,
led    5   °Xlde'
< xide of filver.
< [xide of platina.
< xide of gold.
Cerufe, or "white lead.
Mafficot.
Minium.
Litharge.
Brown calx of copper.
Green  calx  of copper.
  or verdigris.
Mountain blue.
Mthiops per fe.
Turbith mineral.
Precipitate per^fe.
Calx of five r.

Calx of platina.
Calx of gold.
Yellow fulphurated
  oxide of tin.
Sulphurated  oxide  of
lead.
Ammoniacal oxide of
  copper.
Aurum maffivum.
Black C^Ph»rated
XlaJkjoxide of mer-
 "e    Ccury.
Sulphurated oxide  of  —
Mthiops mineral.
Cinnabar.
*r
*
A
          Vegetable fixed alkali of '
             tartar, tsfc.
          Mineral alkali, marine •
             alkali, natrum.
          Fluor, or cauflic volatile
             alkali.
:es in the lower part of this col, cannot be reduced into a gazeous ftate, and not onlif they, but feveral of thofe in the upper part; we have therefore changecj at this place the title of the column, and fubftituted another,

         Denominations  newly appropriated to feveral Subftances,  which are more compound  in their Nature,  yet enter iato new. Combinations withou

                                                                                                                                                                                                ("of potafli.
                                                                                                                                                                                                I.of guaia-
                                                                                                                                                                                                x  cum.
                                                                                                                                                                                       Alcohol <{ of fcam-
                                                                                                                                                                                                 Imoneuin.
                                                                                                                                                                                                 ofmyrrh,
                                                                                                                                                                                                I &c;
	%	3	4
ous	Glutinous matter,		
er.	or gluen.	Sugar.	Starch.
age.	Glutinous matter.	Saceha-	Amylaceous
		rine	matter.
		matter.	-
5	6	7 |l	8
Fixed oil.	Volatile oil.	The aroma, or aromatius principle.	Refin.
Fat oil.	Effential oil.	Spirit us re&or.	Refn.
Extractive matter.
Extra (So-
re fin ous
mattcr.
ExtraStive matter.
"in which the
I  extractive
I  matter pre-
.  dominates.
Refinous  Cin which the
extra&ive < refin "predo
matter.   C  minatcs.
Feculum.
Feculum'.
Alcohol, w fpirit
  of wine.
SpirU afwinc,
   Alkaline tincluxf.
Tincture of guaiacum
•       — fcaifimoni-
  um.
——--~ myrrh, 
                                                       C   231   ]

 TABLE,  fliowing  the  Manner  in which Natural Bodies, confidered  in a  Chemical  View,  may be
    divided  into  ClalTes;  with  their feveral Subdivifions;  their Properties  defined;  and the Manner  in
    which they are obtained, pointed out.

 N AT U R AL  BODIES,   confidered  as the Objefls of Chemiflry,  may   be  divided  into  the following  Clajfes,  viz.
                   i. Salts.   2.  Earths.   3. Metals.  4. Inflammables.  5. Waters.   6.  Airs.

                                                      I.   SALTS.

               These are foluble  in water,  fapid, and not inflammable.   They are either Acids or Alkalies.
 I.  Ac/ds are  diftinguifhed by turning fyrup  of violets  red, or forming  with alkalies neutral  falts; and are  fuppofed to  con-
   fift of dephlogifticated air condenfed,  as their acidifying principle.  The different acids yet known are,
 1.  Vitriolic, fixed.   The moft ponderous of all  fluids next to mercury,  the  moft fixed in the fire, and  the moft powerful as a
   folvent of all the acids.  Obtained chiefly from fulphur by inflammation.
 2.  Vitriolic, volatile.   Obtained alfo  from fulphur -by inflammation; air  being admitted during  the  procefs.   It a&s  lefs pow-
   erfully as a folvent than when in its fixed ftate.
 3.  Nitrous or Aquafortis : a volatile fluid, generally met with of a reddifh colour, and emitting noxious fumes,  when in its con-
   centrated ftate; though this is found not to be eliential to it, but owing to a mixture of phlogifton.   In its pure ftate it is al-
   moft as colourlefs as water,  and fmokes very little.  It is next in ftrength to the vitriolic acid, and obtained chiefly from nitre.
   It confifts of dephlogifticated  and phlogifticated air condenfed, and maybe obtained by taking the ele&ric  fpark for a  long
   time in a mixture of thefe.  By uniting with fome metals it appears to be converted into volatile alkali.
 4.  Muriatic, or fpirit  of fea-falt.   A volatile fluid, generally of a  fine  yellow colour; though this alfo is owing to the admix-
   ture tf foreign fubftances,  generally of iron.  Inferior in power to the former, and  obtained from fea-falt. Naturally this acid
   feems to be in an aerial ftate,  but eafily coiitra&s an union with water.   On mixture with manganefe,  it is wholly converted into
   a yellow, and almoft incondenfible vapour,  called dephlogifticated'fpirit offait; but which, on mixture with inflammable air, re-
   compofes the marine acid.
 j.  Fluor acid.  Obtained from a fpecies of fpar:  has little acid power, but  is remarkable for its property of corroding glafs.
 6.  Acid of borax,  orfedative fait.   Obtained from borax in  the form of fcaly cryftals ; found alfo naturally in fome waters in Italy,
   and in certain minerals in other countries.
 7.  Acetous  acid.   Obtained by  allowing any  fermentable liquor to proceed in the fermentation till paft  the vinous ftate.  It  is
  much lefs corrofive, and lefs powerful as a folvent, than the vitriolic, nitrous, or marine acids.
 8.  Acid of tartar.   Procured from the hard fubftance called -tartar, depofited on the fides of wine veffels.
9.  Acid of fugar.   Found naturally  in the juice of forrel, and procured artificially by means of nitrous acid from fugar and a great
  variety of other fubftances.  Alfumes a dry form.
10. Acid of phofphorus.   Obtained artificially from urine, and in large quantity from calcined bones ; found naturally in fome kinds
  of lead-ore; and in vaft quantities in Spain united with calcareous earth>  AfTumes a folid form, and melts into glafs.
 ir. Acid of ants.   Procured from the animal from which it  takes its name,  by expreffion or diftillation, in a fluid form.
    Acid of amber.   Obtained in a folid form from amber.
    Acid of arfenic.  Obtained from that fubftance by means of nitrous acid.  Is extremely.fixed in the fire.
    Acid of molybdaena.   Procured from that fubftance by means of nitrous  acid.  Refembles a fine white  earth.
    Acidof lapis ponderofus, tungften,  or wolf ram.  Obtained as an acid, perfe,  from this fubftance by Mr Scheele ; but its real aci*
12


14
15
dity is denied by other chemifts.   Is in the form of a yellow powder.
  Acid of milk.  Obtained in a fluid form from that liquor.
  Acid of fugar of milk.   Obtained in form of a white powder, by means of nitrous acid, from fugar of milk.
  Lithifiac acid  Obtained in a folid form from human calculus, by means of nitrous acid.
  Acid of benzoin.   Obtained in a folid form from that gum by fublimation or lixiviation with quicklime.
  Acid of lemons. ■ Obtained trom the juice of that fruit by cryftallization.
  Sebaceous acidt or acid of fat.  Obtained in a fluid ftate from fuet by diftillation.
  Acid of citrons.   Obtained in a fluid ftate from the juice of that and other fruits.^
  Acid of apples*  Obtained in a fluid ftate from the juice of apples and other fruits."
  Acid of forrel.   Obtained in a. folid. form from the juice of that plant; the fame with acid of fugar.
16
17-
18.
19.
20.
21.
22.

24-

II.  Alkalies.   Thefe turn fyrup of violets green, and with acids form neutral falts.  They are,
1.. Fixed vegetable,  or Pot-afh..  Always obtained from the aihes of burnt vegetables.. A deliquefcent fait.
2*. Fixed foffile.  A folid cryftalline lalt, fometimes found  native, as the natrum of Egypt;  and fometimes  by burning fca»
  weed as kelp.
3. Volatile.  Obtained  from fal  ammoniac, from the foot of burning  bodies, and  from the putrefadive fermentation.  It im
  naturally in the ftate.of an invifible and elaftic vapour, conftitating a fpecies of aerial fluid, and confifts of phlogifticated and.
  inflammable air.
                                       Acids, by their union with other  bodies,  form
       Neutral Salts.                Earthy Salts. #
Thefe are always  compofed of  Compofed of an acid joined to
an  acid  and an alkali, and
are of many different kinds,
as may be feen in the fol-
lowing table.
an earthy bafis,  as alum and
gypfum.   See the following
table.
      Metallic Salts.,
Formed of an  acid and  metal.
  The principal of thefe are
  vitriols; the others may be
  feen in the following table-.
     _ Essential Salts.
Obtained from vegetables, and
  contain an acid joined with
  the juices of  the plant in a
  particular manner not to be
  imitated by art. To thefe be-
  long fugar, manna,  honey,
  and others of that fort.
               II. EARTHS. 
z3a                                 CHEMISTRY.                               Table>

                                                   II.  EARTHS.
                                      i
  T;,r - are folid b.)Jirs, not foluble in water, nor inflammable;  and if fufed in the fire, never refume their earthy form r.^ain,
bri take that of gl.>f>.  They are divided into abforbent, cryjuuune, and argitw.cous.

          I.   Ans'.nhtwT Earths arc capable of being united with acids, and are either calcareous, or not calcareous.
                                           a, The calcareous abforbent earths arc,

 r. l.'wiefloiie, or marble.   This is of infinite variety as to colour and texture.   Marble is  the  hardeft and fineft.   Thofe kinds of
  limellonc which feel uncluous to  the touch, are generally impregnated with  clay:  thofe  that feel gritty, or where the lime'
   is hard and weightv, contain fand ; this is the beft for building ;  the other for manure.
 2. C>'alk.   A white,'friable, loft iubftance.  This is much more free of heterogeneous matters than any linicflone, and is eafily
   calcined into quicklime.   It is probably nothing elfe than liincftone fuddenly concreted without being cryftallized.
 3 S. a (bells, are likewife a calcareous earth, and yield a very fine quicklime.  Thei'e are ufed in medicine.
 4. Terra pander   .  A  fine white earth fometimes found  combined with fixed air,  but more commonly with  the vitriolic acid ;
   and forming \\\.'.\ it a very heavy compound, named fpathumponderofuu;.  It is found in mines and veins of rocks.
                              b, The abforbent earths which cannot be reduced into quicklime are,
 I.  Magnefa alba.   A white earth,  ufually  found combined with the vitriolic  acid, and forming bitter purging fait.  It  is likewife
   obtained from the mother-ley of nitre, the afhes of burnt vegetables, ire.
 2. Earth of alum.   A particular kind of abforbent earth,  found in many places mixed with fulphureous  pyrites,  as in Yorkfhire,
   &c.  Clay of any kind may by a particular procefs be converted into this earth.
 3. Earth ojanimals.  '1 his  is obtained by the calcination of animal fubftances, and by precipitation  in the procefs for making
   acid of milk.   It can hardly be converted into glafs;  and is therefore ufed as a  bafis for  white enamels, &c.  It is faid to confift
   ofthe  phofphoric acid united to calcareous earth.

 II   Cryst iLLixE or ViTREsct xt Earths, are hard,  and ftrike fire with fteel;  may be calcined in the fire;  but are not foluble in acids.
                                                      Ofthis kind are,
 1.  Sand and Flint ; found plentifully every where.   With alkaline fubftances they are eafily changed into glafs; and  hence are
   termed vitrefceut.
 2.  Prei.^us  Jicics of all  kinds are  likewife referable to this clafs ;  but they are of a much greater degree of hardnefs and  tranf-
   parency than the others.     _

 III.  Arcillaceovs Earths are digftinguifhed by acquiring a very hard confiftence when formed into a pafte with water, and expofed
                                to a confiderable degre^ of heat; not foluble in acids.   They are,
 1. Common claw   It is of many different colours;  but chiefly  red, yellow, or white.  The pureft  is that which burns White in
   the fire.
 2.  M.dieal boles.  Thefe are of different forts; but are only a purer kind of clay, fometimes mixed with a little iron or other matters.
 3. Lapis  nephriticus, or fieatite.   Thefe are indurated  clays, found in various parts.  They are at  firft  foft and  readily cut; but
   turn extremely  hard in the air.   Many other varieties of  thefe earths might  be mentioned; but as they do not differ in their
   chemical  properties fo much as in their  external appearance, and being all mixed with one another, they more properly be-
   long to the natural hiftorian than the chemift.

                                      III.  METALLIC  SUBSTANCES.

   These arc bodies ofa hard and folid texture ; fufible in the fire,  and reluming their proper form afterwards; not mifcible with
 water, nor inflammable.  They are divided into Metals and Semimetals.
                                        I.  71 Ietals are malleable; and the fpecies are,
 j.  CI.I.   The moft  ponderous and fixed in  the  fire  of all bodies  except platina,  and the moft ductile of any.   It has a yellow
   colour, and is  more commonly  found  in its metallic  ftate  than  any other metal.  It has no proper  ore ; but is found in
   ores of filver,  and almoft all fands contain fome of it.
 2.  Silver is next to gold in malleability and ductility; but lefs fixed in the fire  than  cither it or platina.   It  is  fometimes
   found in its native ftate; but moft commonly in  that of an ore  with fulphur,  fometimes with arfenic, and  afluming different
   appearances.
 3.  Platina.   A white metal ofa greater fpecific  gravity  than gold, and  altogether as fixed  in the fire; the moft difficult to be
   melted of all known fubftances;  refilling the tefts which have ufually been applied for  difcovering the'purity of gold,  fuppofed
   from hence to be the ftniris of the ancients.   Found in South America.
 4. C'.pp.r.   Of a reddifli colour, hard and fonorous ;  admits of being extended  greatly  under the hammer, either hot  or cold.
   Is eiimcult of fufion.   It is generally found  in the ftate of an ore with fulphur.  There are a  great variety  of ores of it,  ex-
   tremely beautiful, blue, red, green, and yellow.                                          ^^V***  ,...  -
 5. Iron.   A grey-eoloured metal, extremely ductile when hot; the lij/hteP of them all except tin.   It is-the only metal certainly
   known to admit ot  being  welded; though  platina is  likewife faid to poffefs fene fhare  of this property.   It is'likcwifc  the
   only one capable of being tempered by  cooling.   It is found ahroft every wjhere ;  and it? ores are infinitely various.
 6 Tin.  A white foft metal, the-lighteft of the whole,  and very ductile.   The ores of  it are generally arfenical,  and afTume a cry-
   fl alliue appearance ;  their colour being moft ufually ofa dark brown,  and fometimes very beautiful*
                                      3                                                                             7. Lead. 
  Tabic.                               C   H    E   M,   I   S    T   R   Y.                                   n3
  7. Lead.   A metal of a dull b1ni(h colour, exceedingly foft and malleable, and very weighty:  Seldom found in its metallic ftate, but
    ufually in an ore with fulphur  or arfenic; but  feldom with  fulphur alone.   The principal ores of it are the cubic, called  galena
    and the glatTy, calledy5>dr.
  8. Mercury or'quickfilver ; formerly  accounted a  femimetal, on account of its  fluidity, but now  reckoned among the moft perfect
    metals.   It is a  white, opaque, metallic body ; fluid, except in a very intenfe degree of cold ;  very heavy, and  eafily  volatilized
    by heat.   Sometimes found in its fluid form, but ufually in a beautiful red ore with fulphur, called cinnabar.

   1                           II.  Semimetals are brittle, and do not ftretch under the hammer.   They are,
  I. Zinc.   A bluifli  white fubftance of a fibrous texture, confiderably  hard and fonorous, with a fmall degree  of dudility ; eafily
    fufed and volatilized.  Its principal ore is lapis calaminaris.
  2. Bifmuth or tin-glafs.   A white ponderous, hard, brittle and  fonorous  body, of a plated texture; eafily fufed and  vitrified.  It
    is only reduced to an ore by arfenic.  Its appearance much the fame with regulus of antimony.
  g. Antimony.  A blackifh  fubftance, of a fibrous  needle-like texture; hard, brittle, and of a confiderable weight; not  difficult  of
    fufion, and eafily convertible  into  glafs.   Its only ore is with fulphur, which is the crude.antimony.
  4. Arfenic.  A bright,  fparkling, whitifh-coloured femimetal;  of a plated texture; very brittle,  and extremely volatile.  It is ge-
    nerally found in the ores of  others metals.
  c. Cobalt.   A brittle  femimetal fufible in a moderate heat, and eafily convertible  into a beautiful blue glafs, called fmalt.   It is
    always obtained from an arfenical ore,  likewife  called cobalt.
  6. Nickel.   A reddifli  white fubftance, of a clofe texture, and very bright; eafily melted, but very difficult to vitrify.

                                    IV.   INFLAMMABLE  SUBSTANCES,

    Are thofe  which continue to burn of themfelves when once fet on fire.   They are divided into oils, fulphur or brim/lone, alcohal
  or ardent fpirits and charcoal.

               I. Oils are thickilh, vifcous fluids, not mifcible with water.  Divided into animal, vegetable,  una* foffile.

                                            a, b,  The animal and vegetable oils are,

    I. Expreffed.  Thefe are of a mild and bland tafte, inodorous, and not foluble  in alcohol.  They are obtained by expreffion, as
    oil of olives, rape-feed, almonds, &c.  Animal fats are of the fame nature, as is alfo wax.
  2. Effential.  Thefe are always obtained by diftillation,  poffefs the tafte and flavour of the fubject from .whence they are drawn,
    and are foluble in alcohol.  Of this kind are oil of cloves, fpike, &c.  The oil of ants is an example in the animal  kingdom.
  3. Empyreumatic^  Thefe  are obtained by a confiderable degree of heat, and  poffefs an acrid tafte and  burnt-like flavour,  as oil of
    hartlhorn.   They are foluble in fpirit of wine.

  c. Foffile oils.   Thefe are found in the earth in their native ftate;  and are called, when pure, naphtha; which  is of  an acrid tafte
    and extremely volatile, not mifcible with alcohol.  A great many  inflammable folfils contain this,  as bitumens, pit-coal, &c.

  II. Sulphur or Brimstone.   This  is a dry friable fubftance, not mifcible with water.  It is found in many mineral fubftances
    metallic ores, &e. but is for  the moft part met with in pyrites. Great quantities of it are found in the neighbourhood of  volcanoes.

  III.  Alcohol or Ardent Spirits.  This is a fluid of an  acrid and volatile nature, mifcible with water; obtained from  fermented
    vegetable juices by diftillation;  as from the juice ofthe grape, malt-liquors, rice, &c.

  IV.  Charcoal.  The refiduum of moft  inflammable matters after undergoing diftillation with a ftrong fire.  A black  fubftance
    acted upon with difficulty by acids;  foluble  in hepar-fulphuris, and entirely diffipable  into inflammable  air  by  a very violent
    heat.  Of great  ufe as fuel,  and efTentially neceffary in metallurgy and  other arts.

                                                       V.   WATER.

                                  A colourlefs infipid fluid  well known.  It is either fimple or mineral.

 1.  Simple,  or pure-rain-water, as it called, though  the  moft homogene ,.;s fluid of this kind with  which we are acquainted, is  not
    perfectly  pure, but always contains a portion of mucilaginous matter, which can never be perfectly feparated.  It is fuppofed
   to confift  of dephlogifticated and inflammable air  condenfed.

 II. MiNERALwaters are thefe  fpring-waters impregnated with faline fubftances;  th£ diverfity of which is exceeding great;  but
    they all agree in having an acid  joined with them.  The moft common forts are  impregnated with iron and fulphur.

                                                       VI. A I R.

»   An invifible and permanently elaftic fluid, is of the following kinds : Dephlogifticated, phlogifticated, fixed or fixable, inflammable
 nitrous  vitriolic acid air, marine acid air, dephlogifticated marine acid, alkaline air,  hepatic air, atmofpherical air.

 I.  Dephlogifticated.  An elaftic fluid naturally extricated in the procefs  of  vegetation;  artificially procured from nitre, minium
    manganefe, water, &c. eminently capable of fupporting flame and animal  life.  One of the component parts of ©ur atmofphere.
                                                                                            G g                      2. Phh- 
-.u
CHEMISTRY.
Tabic.
PbhgiQicatcJ.
                 Produced in ^re.it  quantities during the putrefactive fermentation; obtained alfo  in the calcination of metals and
  other phlogiftic procefls.   Deftroys animal life,  and extinguifhes flame, but  is very  friendly to vegetation.   Is another of the
  continent t\ms"t  our .vn    uie.                                                              ^
\.  Fitel, or fixab/c.  Has its name from the  property of adhering to  certain  bodies,  and fixing itfelf in them.   Confifts of de-
  l liiogifticaictl air united to cbircoal.   I>  obtained by fermentation,  and in all phlogiftic proceffes.   Manifefts the properties of
  aiiaeiJ: cxtingiifhcs flam \ and deftroys  animal life.
4.  Inflammable.  Confifts wholly of charcoal aud a little water nrefiod by heat;  is remarkable for being the lighteft of  all gravi-
  tating fubit ::ices.   Is produced naturally in  mines, and from putrid waters; artificially procured from  certain metallic  folutions,
  !y  puling  the  fleam of  water over red-hot iron;  by diftilling wood, pit-coal, &c. with a ftrong heat; or  by expofing  charcoal
  to the heat of a burning  lens in vacuo.   It extinguifhes flame unlefs it be mixed with a certain  proportion of  atmofphcrical or
   depiilo^n'iic.r.cd air; in which cafe it explodes violently, deftroys animal life, but is friendly to vegetation.
 f.  A..' :i.   Procured artificially in dido ving metallic or other fubftances in the nitrous acid.   On mixture with dephlogifticated
  air  both  the fluids lofe their elaftieity, and a  fmall quantity of nitrous acid is proeluced. It inftantly kills animals, and extinguifhes
  tiinie.   By union with fome  metals is converted into volatile alkali.   In fomc cafes it may  be made to fupport flame, and  even
  ammal life.   I-s property  of condenfing along with phlogifticated air renders it a teft of the falubrity of the  atmofphere.
6. Vitmlic ueid eiir.   Tiie fa;ne with volatile or filphureous vitriolic acid.
7. Marine aud air.   The fame  with marine acid reduced into vapour,  and deprived of moft of  its water.
8. Diphhgijiicated viarim acid.   Suppofed  by  fome  to  be the marine acid deprived of its phlogiftion ; by others to  be the  fame
  acid with an addition of pure air.  It deftroys many kinds of colours; whitens linen, and with  inflammable  air  regenerates
  common marine acid.
rp. Alkaline air.   The fame with pure volatile alkali; is formed by an union of phlogifticated and inflammable air.
10. Hepatic air.  Produced from the decompofition of liver of fulphur by acids,  or in the common  atmofphere. It is inflammable,
  but does  not burn with explofion.
11. A.■<.  ': fu-iical t,ie.  Compofed of dephlogifticated  and phlogifticated air; and  thus  fupports both  animal  life  and  vegetation.
Ti\ BL E,  fhowing   the  feveral  Combinations  that  the  simple  chemical  elementary bodies
   admit  of  with  one  anorlier;  the   Compound  refulting  from  that  Mixture ;  and  the  Manner in
   which  the  Union  is  effected :   With fome  Account of  the  principal  Ufes to  which thefe  are  ap-
   plied in Arts or Manufactures.
A'. B.  This mark
ACIDS.
KARTHS.
put above any word, denotes that there is fome difficulty in the procefs,  or that
           the  union is  not very complete.
ALKALIES.    <!
        VITRIOLIC ACID  may be  combined with the following fubftances,  viz.
    C Nitrous Acid.   A mixture which readily inflames oils.  By folution, generating hear.
    | Muriatic, Vegetable, and all other AciDsyet known.  By folution, generating heat.   But thefe mix-
       tures arc applied to no particular ufe in medicine or arts.
                (Vitriolated tartar.  By folution and cryftallization,  or double elective attraction from a great
                      variety of  bodies.
   Vegetable. <j Nitrum  vitriolatum.  A vitriolated tartar, obtained by diftilling from nitre with the vitriolic
                      acid.
                \^Salpolychreftum.  By deflagrating nitre with fulphur.  There  are many other kinds of vi-
                   triolated tartar,  known  formerly by different  names, and fippofed to  be poflefled of parti-
                   cular properties, but they are now neglected.
 j  Fossile.   Glauber''s fait.   By folution and cryftallization.  Much ufed in  medicine as a gentle purgative.
 (_ Volatile.  Secret aynmoniac.  By folution.  Formerly fuppofed a moft powerful menftruum for metals,  &d
        but without any juft foundation.
                f A corroded calx.  By fimple corrofion.  This  when  perfectly  edulcorated with  water is
                      found to be a true gypfum.
                 Selenites.. By  precipitation  from a very dilute folution  of  chalk in the nitrous acid, bj
                      means of the vitriolic acid.
'Calcareous \ Terra ponderofa.  With this  it  unites in preference to alkalies, forming a very  heavy and in-
   Earth^    <j     foluble fubftance called fpathum ponder of urn.
                 Gypfum or Paris-plafter.  Often found in a native ftate.  May be artificially formed  by  preci-
                     pitating from a  folution  of chalk  in  a very concentrated  nitrous  acid.  Ufed as a ce-
                     ment :  for taking impreffions from medals, &c.
                 Talc  afbeftts, ire.  A native  production which  connot be perfectly imitated by art.  Ufed for
                   holding objects in microfcopes,  making incombuftible cloth, &c.
| Magnesia.  Epfom, or magnefia Glauber's fait.   By folution and cryftallization.   Much ufed in medicine for
(_     the fame purpofes as real Glauber's fait.
                                                                                              EARTHS. 
Table.
EARTHS.
CHEMISTRY.
235
1
METALS.
The fumes which
Lead.
Tin.
L
SEMIMETALS.
in a
dif-
OILS.
SULPHUR*
ALCOHOL.
WATER.
ACIDS.
ALKALIES.
EARTHS.
        Earth  of Alum.  Alum,   By  folution, cryftallization, &c.  Ufed by dyers as a preparatory for taking on
            the colours, papermakers, goldfmiths, &c.
        Earth of Animals, Osteocella,  &c.   By folution.  The mixtures of thefe are not applied to  any
            particular ufe.
        Clay*.   Alum.  By digefting pure clay for fome time  in this acid,  and expofing it for fome time to the  air,
            an alum is produced ; and if the clay is precipitated  from this aluminous concrete, it is found  to he a pure
            earth of alum, foluble in all acids.
        Flint.   A thickifh coagulum.   By digefting the liquor  filices in the vitriolic acid.
        Gold*.   Imperfectly.  By a particular procefs after being feparated from aqua-regia.
        Silver*.  By folution, after it has been precipitated from the  nitrous acid by alkalies.
            arife in this folution are inflammable.
        Copper.  Blue vitriol.  This is fometimes  a native production, but in this way it is never pure.  It is artifi-
              cially prepared by folution in a very concentrated acid, and cryftallizing if.
               f Green vitriol or copperas.  Obtained at large by  particular procefs  from pyrites ;  or by folution, &c.
               j     in a diluted  acid.   This is the bafis of all black dyes, ink, &c.  as it ftrikes a black colour with
        Iron.  <j  •   vegetable aftringents.
               j Salt of fteel.  By calcining the cryftals of green vitiiol till they are converted into a white powder.
               \_Colcothar of vitriol.  By continuing the calcination till it affumes a  brown colour.
               f Saturnus vitriolicus.  A folution in a boiling heat, but is again precipitated when cold.
               ( An indiffoluble concrete.   By precipitation from the nitrons acid.
               Jupiter corrofivus.   By a boiling heat  in a concentrated acid.
                  C Ignis Gehenne, or infernalis of Paracelfus.   By a  boiling heat, and  repeated coctions with frefli
        Mercury.<      acid when it is evaporated.
                  C Turpeth mineral, or mercurius precipitatus  flavus.  By evaporating to drynefs, and  then wafhing
                         with water.
      ("Antimony*.   A metallic fait.   By elective attraction from butter of antimony.
      | Zinc.  White vitriol.  Often found in its native ftate.  Artificially made by folution and cryftallization
      J     diluted acid.  Ufed by painters for drying. *■
      '.Bismuth.  A corroded calx.   By folution in a  concentrated acid.
        Arsenic      -     -    -  By ditto.
      ^Cobalt.  A rofe-coloured mixture.  By folution.  If this is precipitated by a fixed alkali, and again
            folved, the liquor appears of  a beautiful red.
        Expressed.   A blackifh gummy-like mafs.  By folution, generating a confiderable heat.   Native gums  are
            fuppofed to owe their origin to a mixture  of this kind.
        Essential.  A dark-coloured refinous mafs.  A great  heat and violent efFeryefcence being  produced by this
            mixture.  Native refins fuppofed the fame.
        Empyreumatic.  Little known.  By folution.
        Fossile.   A fubftanccrefembling amber.  By folution.
    Here there is no proper union of fubftances ;  but if fulphur is boiled in this acid, it becomes lefs inflammable and
     more fixed than any ordinary fulphur.'
         'Vitriolic ether.  By careful folution and diftillation, the ether being feparated by the addition of water.
          Spiritus vitrioli dulcis.  By folution and diftillation.
          Oleum dulce.  By  continuing the heat after the ether has arifen.
          Oleum anodynum minerale.  By rediftilling the refiduum of the laft with  alcohol.  A medicine much cele-
              brated by Hoffman.
          Sulphur.  By pufhing the heat after the oil comes over.  It is to be obferved that this is produced in every
              combination of this acid with inflammables or metals.
An acidulated  water.   Sometimes, though  feldom, found  ifTuing along with native  fprings.  Applied to  no  particu-
     lar ufe.
           NITROUS  ACID  may be combined with the following Subftances, viz.
        Vitriolic, as above.
        Muriatic.   Aqua-regia.   By folution.   This is the only proper menftruum for gold ; and it is a folution of
            tin in this menftruum which is the bafis of the fcarlet dye.
        Vegetable, and all others.  By ditto.   Thefe compounds have no particular names, nor are applied to any
            particular ufes in medicine or arts.
       Vegetable.  Comrnon nitre.   A native production.  Made artificially by folution and cryftallization.  This
            deflagrates with  oily or  metallic bodies, and is the foundation of gun-powder.
       Fossile.  Cubic nitre.  By folution.
       Volatile.  Nitrous ammoniac.  By  folution.   This differs  from all  the other ammonical  falts, by being
          - foluble in alcohol.
       r             J Deliquefcent cryftals.  By ditto and cryftallization.
            AR o ^. | Baldwin sphofphorus.   By ditto and evaporating to drynefs.
       Earth of Alum, and all other  abforbent earths.  By folution.  The compounds have no names nor any
           remarkable properties hitherto difcovered.
       Crystalline Earths*.   By  folution after precipitation from the liquor filices.
                                              G S 2                                               METALS. 
*-&
C   H    E   M    I    S    T   R    Y.
Table.
METALS.
SEMIMETALS.
OILS.
ALCOHOL,
WATER.
Silver.


CeiTPER.
Ik.
Tr
  Gold*.   Slightly impregnated.  By a boiling heat in clofe vile Is, after the ordinary method of feparating
       filver from gold by the nitrous acid.  It fpontaneoufly fubfides in the air.
            " A fluid folution.   By folution.   fas when diluted with water ftains hair and bones black;  as
                  alfo marble,  agate, jafper, &c. of different colours.
              Sal metallorum.  By folution and cryftallization.
              Cathartkutn !i<eave, lunar cauftic, or lapis if'., na!:s.  By infpifiating the  folution to drynefs.
             A green-coloured folution.   B\  folution.
      s.  A greenifh folution, if a dilated acid is employed ;  if otherwife, it is of a yellowifli colour :  evapora-
       ted to drynefs, it deliquates in the air.
            C A ycllo.v folution.  By diffolving in a diluted acid.   If  much water is added,  the metal ispre-
  Lead.    <     cipitated.
            q  Satumi fuln.iuans. By  infpifTating the folution. This explodes when put upon the fire with greater
              force than nitre, and has been propofed to be ufed as an ingrcJient in gun-powder to augment its force.
         A folution or corroded  calx.  By a careful folution without heat  it remains fufpended ; if  otherwife,
       it falls down in form ofa calx. T iiisis commonly fuppofed to be the compofition ufed in dyeing fcarlet;
       but by miftake : for it is a folution  of tin in aqua-regia that communicates that fine colour to cochineal.
       The fame folution  is the bafis of the powder which tinges glafs ofa ruby colour.   It is  the precipitate of
       gold from ;uj : i-regia by means of tin.
                A limpid folution, intenfely corrofive.   By folution.
                Red precipitate.  By evaporating the folution to drynefs, and then calcining till it becomes red.
                Mercurius corroftvus fufus.   By precipitating from the nitrous acid by fixed alkali.
                White precipitate     -       By ditto with the volatile alkali.
                A greenifh folution.  By ufinj; a concentrated acid.  This might be applied in fome cafes in the
                    art of dyeing ;  but is not yet come into general ufe.
              / MagijLry of bifmuth.   By precipitating from the folution by means of water.  This  has been
                    employed as a cofmetic, but is inefficacious and unfafe.  If mixed with pomatum, this
                    ftains hair of a dark colour without injuring it.
           A corroded folution.  By the dfcdinary means.
                  A colourlefs calx.   By fimple corrofion.
                  Bezoardic mineral. By diftilling from butter of antimony,  after having added the nitrous acid.
                   .Vutimonium diaphoreticum.   By adding nitre to crude antimony, and  deflagrating.
                  Cerufa antimonii.   By deflagrating regulus of antimony with nitre.
             T A red liquor.  By folution either in its calcined or metallic ftate.
             < Rofe-coloured cryftals.  By adding muriatic acid, and allowing it to cryftallize.
             r Green fympathetic ink.   By diffolving thefe cryftals in water.  The folution is red when cold,
                  and green  when warm ; when wrote with, it difappears when dry ;  but when held to the
                  fire it  becomes green;  and again difappears when cold.
             A green-coloured liquor.  By folution.
  Expressed.  A thick bituminous-like lAbftance.  Upon the mixture a confiderable degree of heat is gene-
       rated, and fometimes, though very feldom, actual flame is produced.
  Essenti ;. i..  Ditto.   A more violent heat is generated upon the mixture with thefe oils than any other, and
       with many of them an  actual flame is produced.
  Kmpyreumatic.   This mixture has no name, nor is it applied to any remarkable ufe in arts.
  Fossile.  Ditto.
f A'.'."-cus ether.   By digefting ; the ether arifing to the furface.
( Spiritus nitri dulcis.   By digefting a little, and then diftilling.
Acidulated -eeater.  By folution.
Mercury.
Bismuth,
Zinc.
An rimony
Cobalt.
Nickel,
ACIDS.
ALKALIES.
EARTHS.
 The  MURIATIC  ACID  may be combined with the following Subftances. viz.
 "" Vitriolic and Nitrous.  As in the former part of this Table.
 \ Vegetable, and all others yet known.  By folution :  but as none of thefe mixtures are applied to any par-
      ticular purpofe, we take no notice of them.
 f Vegetable.  Dfe'uve fait.  By folution and cryftallization.
            "Common fait.   Commonly obtained by evaporating fea-water to drynefs ;  or artificially made by
                  mixing the acid and alkali, and cryftallizing.
             Sal gem.   A native foffile fait, found in mines in Poland, Spain, ire ofthe fame nature as com-
                  mon fait, but more  pure.
  Vola n le.   Common ammu-.iac.    Obtained at large by a particular procefs from foot.   Artificially made by
      mixing the acid and alkali, and cryftallizing.
                C Liquid fhell.  By folution. A fubftance whofe effects in medicine have been greatly extolled.
 ("Calcareous.< 01. calcis per deliquium.  By evaporating liquid (hell to drynefs.  It naturally deliquefces.
J               (_ Fixed ammoniac.    By folution and cryftallization.   This fometimes appears luminous in the
 j                     dark when ftruck with a hammer.
 (_Ostfocella, Magnesia, and other abforbents.  By folution :  but the properties or ufes of thefe are not
      kaewn.
                                                                                           METALS.
Fossile. 
Table.
CHEMISTRY.
      237
It  does not
                    'Gold*, A yellow  liquor.  By  boiling a calx of gold (in whatever way obtained) in this acid.
                        v act upon it in its metallic ftate.
                              C A fluid folution.  By  diflblving the ore of filver in this acid.   It does not  act  upon pure me-
                     Silver*.<     tallic filver.
                              £ Luna cornea.  By elective attraction from the nitrous acid.
                     Platina*.  A fluid folution.   With difficulty effected,  after having been precipitated from  aqua-regia
                         by alkalies.
                     Copper.  A green deliquefcent inflammable fait.  By folution and infpifiating to drynefs.
                     Iron.  Tinttura martis aurea.  By  folution.  The iron is  in fome meafure rendered volatile  by the
                         operation.
METALS.        \  T      C A limpid folution.  By a boiling heat, and frequent cohobations with frefli acid.
                           \ Cornea Saturni.  By precipitation from the nitrous acid.                             •
                     Ti n* I ^ corroded powder.  By fimple corrofion.
                          ' \ Butter of tin.  By diftilling from corrofive fublimate.
                                 "A colourlefs cryftalline  mafs,  extremely acrid.   By corrofion, employing  the fumes of a very
                                       concentrated acid.
                                   Mercur.  corrofiv. albus.  By precipitation from the  nitrous acid.
                     Mercury*. <J Corrofive fublimate.   By fubliming from fal ammoniac, common fait, or many other bodies.
                                  Mercurius dulcis.  By refubliming corrofive fublimate with more quickfilver.
                                  Mercurial panacea.   By fubliming corr. fub. nine times, and digefting for fome time in fpi-
                                       rit of wine.
                   "Bismuth*. A folution very flightly impregnated.  By employing a very concentrated acid.
                     Zinc.  A folution of a very flight  yellow colour.
                  j  Arsenic*. Butter of arfenic.  By diftilling corrofive fublimate with arfenic; the arfenic uniting with the
                  1      acid, and leaving the mercury.
                   (Cobalt.   A reddifh  folution.  By the ordinary means.   It becomes green by a gentle heat.
                   (^Nickel.   A green folution.  By the ordinary means.
OILS*.  By folution.  The union here is but imperfect,  nor have they any particular name.
ALCOHOL.  Spiritus falls dulcis.  By digeftion, and afterwards diftilling.  The acid here is never totally dulcified.
WATER.   Acidulated water.   Generating heat by mixture.
SEMIMETALS.
ACIDS.
ALKALIES.
EARTHS.
METALS.
SEMIMETALS.
OILS*.
ALCOHOL,
WATER.   Acidulated water.
            VINEGAR may be combined with the following Subftances, viz.
Vitriolic,  Nitrous, and Muriatic,  as in the above table.  It likewife  unites with all other acids,  gene
    rating heat;  but the properties or ufes of *thefe are not known.
  ("Vegetable.   Regenerated tartar.   By folution and cryftallization.
  < Fossile.  Polychreft of Rochelle.  By ditto.
  £ Volatile.   Spiritus Mindereri   By folution.
  C Calcareous Earth.   Earthy falts.   Not known in medicine or arts.
  £ Magnesia.   Dr Black's purging fait.  By folution.  It  unites with all the other abforbent earths; but the
        properties of thefe mixts are  unknown.
   Copper.  Verdegris. By folution and  cryftallization ; or at large, by ftratifying copper-plates with the hufks
        of the grape.
   Iron.  Sal martis aperiens.  By folution  and cryftallization.
   T       C Cerufe.  By expofing, in certain circumftances, thin plates of lead to the fumes of vinegar.
         '  £ Saccharum Saturni,  By folution and cryftallization.
   Tin*.   This is not properly difTolved; but the acid is evidently  impregnated.   By the  ordinary means of
        folution.
   Mercury* £ A fluid folution.   By employing a precipita;e of mercury from the nitrous acid by alkalies.
              '(_ A red calx.   By long digeftion with fluid mercury.
   'Zinc.  A colourlefs folution of a fweetifh tafte.  By digefting for fome time.
   Antimony*. Vinum benediflum.  This  it  not  a proper folution of the  metal, but the acid is impregnated-
  <}      with an emetic quality.
   Arsenic.  Vinum arfenicum.  By ditto.   A curious phofphoric liquor.
  ^Bismuth.  An auftere ftyptic liquor.  By ftrong coction.
  The union here is imperfect, nor have any of them obtained particular names.
  A mixture much ufed for anointing fprains,  &c.
ALKALIES.

ALKALIES.
    A C I D of   TARTAR  may be combined with the following fubftances t viz.
              C Cream of tartar with excefs of acid.
Vegetable. £ soluble tartar,  when completely faturated.
  Fossile.  Rochelle fait.
I
Volatile
 C A fait very difficult of folmion with excefs of acid.
' \ A beautiful and foluble fait when perfectly faturated,
EARTH. 
EARTH.

METALS.
SKMIMETAL.
                 C   II    E   M   I   S    T   R   Y.
Calcareous.  An indilfolublc felenite.
       per.  A fine green colour for painting.
          A preen aftringent liquid.  Chalybeated tartar.
Kegulus of Antimony.  Emetic tartar.
Tabic.
C Copp
                      ACID of  URIXE  maybe combined with the following fub fiances, viz.
AC IDS of all kinds.   The nature of thefe not known.
                    Fixed Vegetable.   A fait not eafily cryftallized,  the nature of which is not known.
-. j. ...          ! 1 ossile.   A fine cryftallized fait ufed in medicine.
     '   *         j Vo latile.  A glafs-like faline fubftance called microcofmic fait.  The acid is always found in this ftate by
                  (,     evaporating urine.
VITRESCENT  EARTHS.   A glafs of different forts.   By fufion.
                   f Leap*  An inflammable malleable mafs.   By calcining the dry fait with lead.
                   | Tin.   A mafs refembling zinc;  and  inflammable.   By ditto.
                  j Iron   £A iraephofphorus.  By ditto.
METALS.        ■)        £ A bluifli folution.  By employing a watery folution of the acid.
                    Copper.  A  corroded powder,  or green folution.   By a boiling heat in a watery folution  of the acid.
                   [Mercury.   A femi-opaque mafs.   By  fufion with the acid, in its folid form.
                   f7      j A corroded powder, foluble in  water.  By folution in the acid in a watery fituation.
                   I        | A true phofphorus.  By fufion  with the dry acid.
                    a.-^.w^..  C A folution in the  ordinary way.
SEMIMETALS.   \ a*"Mon*.£ -
OILS.
                       t A brilliant ftriated mafs.   By fufion with the dry acid.
            Bismuth.  A mix;ure but little changed in appearance from ordinary bifmuth. By fufion.
            Arsenic.  A whitifh femitranfparent deliquefcent mafs.   By fufion.
          [Cobalt.  A reddifli tincture.   By folution.
Baldwin's phofphorus.  By  diftilling with fubftances that contain oils or inflammable matter.
ALKALIES.
EARTHS.
MI'TALS.
ALKALIES.
EARTHS.
   FLUOR   ACID,  may  be combined with the following Subftances, viz.
Fixed Vegetable.   A gelatinous faline mafs which cannot be cryftallized.   Great part of it is  alfo difli-
    pated by evaporation to drynefs.
Fossile.  A fubftance fimilar to the foregoing.
Volatile.   Lets fall a quantity of filiceous earth, and forms a cryftallizable ammoniacal fait.
Lime-          "1
Magnesia.      >A  gelatinous mstter.
Earth of Alum, j)
Siliceous Earth. After long ftanding, cryftalsof quartz.
Silver        ")   The calces of thefe metals partially diffolved ;  but the properties of the folution un-
Ouicksilyer. 3       known
Copter.  Thccalx eafily foluble, and affording blue cryftals;  the metal only partially fo.
Iron.   Diflblved with violence with  the emiffion of inflammable vapours into an  uncryftallizable liquor.

  A C I D of   SUGAR may be I'.v.bineJ with thefollowing Subftances, viz.
I'ixed Vegetable.   A  fait fcarce capable of cryftallization when perfectly neutral.
Kossile.  A fait difficultly folfible in water.
Volatile.  An ammoniacal fait fhooting into quadrangular prifms.
     .  A kind of felenite from which the acid cannot be feparated by. a burning heat.
     a  Ponderosa.   A  fait formed into angular cryftals, fcarce foluble in water.
Magnesia.  A  white powder inf^khle without an excefs of acid.
          Ai r
A!
"ALS.
rLiME
|  Terr
I  Mag>
[ Earth of
f Gold.
|  Silver.
1
 A yellow pellucid mafs incapable of cryftallization, and liquefying in the air.

The calces of all thefe metals diffolved, but the nitre of the folutions unknown.
SEMIMETAL.
 <J Platina.
 | Quicksilver.J
 [Iron.  D'flolvcd in great quantity, and forming a yellow prifmatic fait eafily foluble in water
Cobalt.  A yellow-coloured fait forming a fympathetic ink with fea-falt.
INFLAMMABLES

         A C ID

ALKALIES.



EARTHS.
   Alcohol.  An ether which  cannot  eafily  be fet on  fire unlefs previoufly heated, and burning with a
       blue flame.
of  B 0 k A X or S E D AT IV E  SALT may be combined with the following Subftances, viz.
  fYssi.E.  B:rax.  A native fubftance,  which may be imitated by art.  It is of great ufe  in promoting the
    fufion of metals <nd  earths.
  Volatile.  An ammoni ;cal fait fhooting into fmall cryftals, and melting by an intenfe heat into a greyifh-
    coloured glr.fi.
C Magnesia.  A fait cryftallizable in vinegar and acid of ants. Decompofed by other acids and fpirit of wine.
£ Earth  of Alum.   In certain proportions a fait difficult of folution;  inotheiy a  hard  mafs'refembling  pu-
    mice-Hone,  vet partially foluble in\Y*rCr-
                                                                                         METALS. 
Tabic.                           CHEMISTRY.                                 239
METAL.
SEMIMETAL.

AIXOHOL.
WATER.
ALKALIES.
EARTHS.
METALS.
SEMIMETALS.
Iron.  An amber-coloured folution yielding cryftals of a yellow colour.
Arsenic.  A cryftallizable compound fhooting into pointed ramifications, or forming a greyiih, white, or yellow
     powder.
A folution with a cbnfiderable heat, which burns with a green flame.
A folution in a confiderable heat.  The other mixtures with this acid not known.

       ACID of  AMBER may be combined with the following  Subftances, viz.
f Fixed Vegetable.  A tranfparent and cryftallizable fait, but deliquefcent.
< Fossile.  A cryftallizable fait not deliquefcent.
£ Volatile.  An ammoniacal fait fhooting into acicular cryftals.
   Lime.  A cryftallizible fait, difficuk of folution  and not  deliquefcent.  Decompofed by common fal am-
       moniac.
   Magnesia.  A gummy deliquefcent faline mafs, not cryftallizable.
   Earth  of Alum.  A prifmatic  fait incapable of decompofition by alkalies.
  Silver.   A fait fliooting into thin oblong cryftals obtained from  the precipitate ;  but no folution cf the perfect
       metal.
  Copper.  A cryftallizable fait of a green colour.
  Iron.  A  cryftallizable fait of a brown colour.
   Lin.  A cryftallizable fait from the precipitate, fcarce to be decompofed by alkalies.
  Le"ad.   A cryftallizable fait from the precipitate.
  Zinc   A cryftallizable fait.
  Bismuth.  A cryftallizable fait from the precipitate, not to be decompofed by alkalies.
  Regulus  of Antimony.   A folution of the precipitate.
ALKALIES.
EARTHS.
METALS.
SEMIMETAL.
The effects  of
    known.
          ACID  of  ANTS  may be combined with the following Subftances, viz.
   Fixed Vegetable.  A cryftallizable fait, deliquefcent in the air.
   Fossile.   A fait of a fimilar nature.
   Volatile.  An ammoniacal liquor, cryftallizable with difficulty.
   Chalk or Coral.   A cryftallizable fait which does not deliquate.
   Magnesia.  A faline liquor fcarcely cryftallizable.
   Terra Ponderosa.  A cryftallizable fait which does not deliquefce.
   Earth of  Alum.  Unites with difficulty, and fcarcely to the point of faturation.  The nature  ofthe com-
     pound not known.
  f Silver*.   By folution.  The calx of filver precipitated from aquafortis by alkalies;  but does not act upon it
  |      in its metallic ftate.
  | Copper.   Beautiful green cryftals.  By diffolving and cryftallizing calcined copper.   It acts flowly upon it in
  )      its metallic ftate.
   Iron.  A cryftallizable fait.  It diffolves this metal with great facility.
   Lead*.  A fait refembling faccharum faturni.   By diffolving the red calx of lead.  But it does not act upon it
        in its metallic ftate.
  Zinc.  Elegant cryftals.  By the ordinary means.
this acid upon  other bodies, or  the ufes to which thefe  combinations might  be applied, are not yet fufficiently
S
ALKALIES.
EARTHS.
METALS.
                     ACID  OF  ARSENIC  may  be  combined with the following Subftances, viz.
                  Fixed Vegetable.   A ponderous fait fhooting into fine cryftals by fuperfaturation with acid.
                  Fossile.   A fait cryftallizable when perfectly neutral.
                  Volatile.  A peculiar kind of ammoniacal fait  parting with the alkali, and decompofing fome of it ia a
                    ftrong fire.
                  Chalk.   A cryftallizable fait fcarcely foluble.
                  Magnesia.  A gelatinous mafs which cannot be cryftallized.
                  Terra Ponderosa.   An infoluble white powder.
                  Copper.  A green-coloured folution.
                  Iron.   A very thick gelatinous folution.
                  Lead.  A folution which cannot be cryftallized.
                  Tin.   A gelatinous folution in the moift way.  A mixture taking fire in clofe veffels in the dry way,
                 fZiNC.   A folution in the moift way, and in the dry, a mixture  taking fire in clofe veflels.
                 | Bismuth.   A partial folution.
SEMIMETALS. { Regulus of Antimony.   A partial folution.
                 J Cobalt.  A partial folution of a red colour.
                 [Manganese.   A partial folution in its natural ftate.   When the manganefe is phlogifticated, a cryftallizable
                    fait may be obtained.
                  Charcoal.  A mixture-taking fire and fubliming when heated in clofe veffels.
                  Oil of. Turpentine, &c.   A thick black fubftance after fome days digeftion.
                  Sulphur.   A red fublimate.
                                                                                                         ALKALIES,
INFLAMMA-
    BLES. 
   %
2.10

ALKALI.
c
 r
II   E    M    I   S   T    R   Y.
Tlblc
•lkalies.

EARTHS.

METALS.

SEMIMETAL.


ALKALIES.

EARTHS.     «


ALKALIES.

EARTHS.

METAL.
SEMIMETAL.


ALKALIES.
            »

EARTHS.




METALS.




SEMIMETALS.




ALKALIES.

EARTHS.
  ACID of  MO L T B D .£ X A >—■ .be united with t)c f-iUmng Subflaic-', viz.
(Fixed Vt getable.   A cryftallizable fait.
\ Volatile.  A neutral Lit, the nature of which is unknown.
         ACID  of  M ILK  may be com^ted veith the f:ll'j:oing Subftances, viz.
f Fixed  Vegetable.  A deliquefcent fait foluble in alcohol.
< Fossile.  A filt of .rfimilar nature.
£ Volatile.  A deliquefcent fait parting with much ofthe alkali by heat.
5 Calcareous  and Argillaceous.  Deliquefcent falts.
£ Magnesia.  A fait more eafily cryftallized, but deliquefcent.
  Copper.   A blue folution, which cannot be cryftallized.
  Iron-.  A brown folution, with the emiffiorfof inflammable air, yielding no cryftals.
  Leap.   An aftringent  fweetifh folution, which does not cryftallize.
 Zinc.   A cryftallizable filt, with the emitfion of inflammable air during the folution.
    ACID of   SUGAR of  MILK may be combined with the following Subftances,  viz.
("Fixed  Vegetable.  A fait very difficult of folution.
-2 Fossile.  A  fait more eafily foluble.
£ Volatile.   A peculiar kind of ammoniac.
Absorbent and Argillaceous.  Infoluble falts.

      ACID  of  APPLES may be  combined with ihe following Sub ft antes, \\t..
Fixed Vegetable,  Fossile, and Volatile.  Deliquefcent falts.
C  Calcareous.  A fait difficult of folution unlefs the acid prevail.
< Magnesia.   A deliquefcent fait.
^ Earth  of Alum.   A fait  very difficult of folution.
Iron.  A brown folution, which does not cryftallize.
Zinc.  A fine cryftallizable fait.
( Fixed, X'i.c
\ Volatile.
s
        ACID of  FAT may be combined with the following  Subftances, viz.
              stable, and Fossile.  Neutral falts of a particular nature.
               A concrete volatile fait.
  Calcareous.  A cryftallizable fait of a brown colour.
) „ ACNES1y<       I  a ijunimy mafs,  which refufes to cryftallize.
£ Earth  ot Alum,  j    b    '     '                  J
 [Silver.  A folution of the calx.
 | Pi atina.  The calx copioufly diflblved, and even  the perfect metal attacked by diftillation to drynefs.
 j Copter.  A green folution, which cannot be cryftallized.
<\ Iron.   A cryftallizable fait, which does not deliquate.
 I Lea;'.  An aftringent folution of the red calx called minium.
 | Tin.  A folution in fmall quantity.
 L Mercury.  A folution by  being twice diftilled from the metal.
  Zinc  Diflblved in its metalline ftate.
  Bismuth.  A folution of precipitate.
  Regulus of Antimony.  A cryftallizable fait, which does  not deliquate.
  Manganese.   A perfect and clear folution.

     ACID of  BENZOIN may  be combined with the following Subftances, viz.
C Fixed Vegetable.  A fait fhooting into pointed feathery cryftals.
^ Fossile.   A fait procurable in larger cryftals.
r Volatile.  A deliquefcent fait fcarce cryftallizable.
C Calcareous.  A cryftallizable fait not eafily foluble.
/ Mag Nisi a.  A cryftallizable fait eafily foluble.
7"*r  FIXED ALKALI, whether Vegetable or  Fossile, can be united with the following Bodies; but the Vegetable is beft known.
ACIDS*- Viirie-lic,  Nitrous, Muriatic, Vegetable;  and acidof Uriire, of Amber,  of Ants, of Borax, &c. as in the former
                  part of this Table.
ALKALIES of all forts.  Theufe^of thefe mixtures are  not known.
                                C Li./u*r filicum.  By fufion with twice their weight of alkali.
                C Crystalline.< C.af.   By  fufion with a much fmaller proportion of alkali.  This is  the  compofition of
EARTHS.      <               C     cryftal  glafs, and all others commonly ufed.
                ? Absorbents.  Argillaceous, and all kinds of  earths.   Glafs.   By fufion ; differing in quality according to the
                      nature of the ingredients.  Glafs is likwife produced with it in fufion with metals.
                C Go i.r*.   After having precipitated it from aqua-regia, it difEolvcs  it if the alkali has been calcined with animal
METALS.      3     fubftances.
                £ Silver' .  After having precipitated it from  the  nitrous acid, it  diffolves k if the alkali-lias been calcined in
                      contact wi:h the fl^ne.
                                                                      2                                   METALS. 
Table.
CHEMISTRY.
2fl
METALS.
SEMIMETALS. << Antimony.
OILS.
SULPHUR.
WATER.

AIR.
   f Tin.   A corroded powder.   By the ordinary means of folution.
   j Copper.   By ditto.
  •^ Lead.  A fluid folution.  By ditto.  This ftains hair black.
    Iron*.   A blood-coloured fedution.  By dropping a folution of iron in the nitrous acid, into an alkaline lixivium.
    Mercury*.  A fluid folution.  After precipitating it from acids ; if the alkali  is in too large proportions, it
         then  diflblves it, efpecially if the alkali has been calcined in contact with the flame.
   "Zinc*.   By folution, after having precipitated it from the nitrous acid.
    Bismuth*.  By folution, after having precipitated it from the nitrous acid.
                  Kermes mineral.   By diffolving antimony in an  alkaline lixivium, filtering, and allowing it to
                      ftand in a cool place till it precipitates.
                  Golden fulphur of antimony.   By diffolving a crude antimony in an alkaline lixivium, and preci-
                      pitating by an acid.
              1 Hepar antimonii.   By deflagrating crnde antimony with nitre.
                  Crocus metallorum.   Is hepar antimonii pulverifed and edulcorated with water.
                  Diaphoretic antimony.  By deflagrating regulus of antimony with nitre.
                 | Antimoniated nitre.  By diffolving diaphoretic antimony in water, and allowing it to cryftallize.
                 1 Magiftery of antimony.  By  precipitating a folution of diaphoretic antimony by adding vinegar.
                 [^Regulus antimonii medicinalis.  By fufing crude antimony with  alkali.   This is  not properly a
                    compound of alkali and antimony, but of another kind.  But as it is a term much ufed, it was
                    proper to explain it.
    Arsenic*.  A metallic arfenical fait.   By a particular elective attraction from regulus of antimony and nitre.
    Expressed.  Soap.  The beft hard foap is made of olive-oil and foffile alkali.  The ordinary white foap of this
         country is made of tallow and potafh;  black foap with whale-oil and potafh.
    Essential.  Saponaceous  mafs.   Beft made by pouring fpirit of wine upon cauftic alkali and then oil, digeft-
         ing and fhaking.
    Empyreumatic.  This mixture diflblves gold when precipitated from aqua regia ;  and  is the bafis of the fine
         colour called Pruffian blue ;  and has various other properties, as yet but little known.
   _Fossile.  This has noname, nor are theproperties well known ; but from fome obfervations that have beenmade
         on  native foapy waters, it is probable thatit would keep linen much longer white than any other kind of foap.
   f Hepar fulphuris.  By injecting alkalies upon melted fulphur.
   ( Lac fulphuris.  By diffolving fulphur in an alkaline lixivium, and precipitating by an acid.
   Alkaline lixivium, when cauftic, or even the ordinary folution  ofmild alkali, is a fluid of great power in wafliing,
      bleaching, &c.
Fixed.  Mild alkali.  This is the general ftate in which alkalies are found ; but if they are rendered cauftic by
      means of quick-lime or otherwife, they again abforb it from the air, or from many other bodies, by elective
      attraction.   When perfectly mild, this alkali may be made to afliime a cryflalline form.
<
         The  VOLATILE  ALKALI,  or SPIRIT  of SAL  AMMONIAC, can be united with thefe Bodies, viz.
ACIDS : Vitriolic,  Nitrous, Muriatic, Vegetable ; of Urine, of Amber, of Ants, &c.
ALKALI, as above.
                  „     #     \ Aurum fulminans.   A powder obtained by precipitating it from aqua regia by volatile alkalies.
                              ( A liquid  folution.  By adding a large proportion of alkali after it has been precipitated from aqua
                                  regia.   This depofites the gold when long expofed  to the air.   The curious vegetation called
                                  arbor Diana is formed by adding mercury to this folution.  A violently fulminating powder ob-
                                  tained by digeftion.
                  Silver*.   A folution. After it has been precipitated from the nitrous acid.  A fulminating powder by digeftion.
                  Platina*.   By folution, after having precipitated it from aqua regia.
METALS.
"A blue-coloured folution.   By the ordinary means.
     with tallow, tinges the flame green.
This when evaporated to drynefs, and mixed
SEMIMETALS.
OILS.
Copper.-^ Sapphire-coloured cryftals.  By cryftallizing the folution.
          | Venus fulminans.  By evaporating the folution to drynefs.
          \^Aqua cerulea fapphirina.  By mixing fal ammoniac, quick-lime,  and thin plates of copper, with
               water, and allowing them to remain a night.
Iron.  By ordinary foluticn.
Lead.   By ditto.
Tin.   The mixts that are produced by thefe metals are little known.
Bismuth*.  By folution, after having precipitated it from the nitrons acid.
Antimony.
Cobalt.  A reddifli liquor.   By folution.
Nickel.  A blue liquor.  By ditto.
Expressed.   Has no name.   By folution.
Essential.   Sal volatile oleofum.  By ditto with fome difficulty, unlefs the alkali is in a cauftic ftate.
Empyreumatic.  A pungent oily fubftance, of  great power in medicine.  The principal one of this kind in
     ufe is fpirit of hanfhorn.
Fossile.  A particular kind of foapy fubftance.
                                                                      2  H               SULPHUR. 
24*
SULPHUR.
ALCOHOL*.
WATER.

AIR.
CHEMISTRY.
Table.
Smoking fpirit <rf  fulphur.   By diftilling fal ammoniac, quick-lime, and fnlphnr.
By diitiiiing alcohol from volatile alkalie?, it acquires a cauftic fiery tafte ;  but tht uplon is net complete.
This folution  might be of ufe in warning or bleaching ;  but, unlefs in particular cafes, would be too cxpenfive.
    It coagulates with alcohol.
Fixed   Mild ve>!.mlc alkali.   The ufual  ftate in which it is found ;  nor has any method yet been difcovered of
    rendering it folid but  in this ftate.
                    EXPRESSED  OILS  may be combined with the following Subftances, viz.
ACIDS : Vitriolic,  Nitrons, Muriatic, Vegetable, of  Urine,  ot Ai  bir, as in the foregoing part ot this Table.
ALKALIES :  Fixed and Volatile, as above.
CALCAREOUS  EARTHS.  A  kind of plafter.  By mixture when in  a canftic  ftate.
                 f Tin*.   Di;to.  By folution when the tin is in the Hate of a calx.
METALS.       ^ Lead*.  Ditto.   By  boiling  the cdx of bad in oils.  This is ufed for cements in water-works.   The com-
                 £     mon white paint is a mixture of thisJcfs perfect.
SEMIMETALS.   Zinc*.  Ditto.   By ditto.
OILS:        Elf  ntiii, Emuyreuniiiiic, and Foffile.  By mixture but their ufes  are not much known.
SULPHUR,   Balfam  of Sulphur.  By  folution in  a boiling heat.
ALCOHOL.  Alter txprcffcd oils arc irccd from foap 01 plafters, they are foluble in alcohol; but not in their ordinary ftate.
(  CorPF.f
(  Lead.
                      ESSENTIAL  OILS  may be combined with ihe following  Subftances, viz.
             r;oiic, Niirous, &c. as above.
              Fixed and Volatile, as rtbi>ve.
                         r.   By folution.
                           By ditto.
OILS of  ,11 kinds.   By folution or mixture.
SULPHUR.  A  b.ilf.m ot  fu'phur.  By folution, imperfectly;  better by  adding effential oils  to the folution made by expreffeJ
                  oils or hepar fulphuris.
                    I  (perfect mixture.   By folution.
                    Aromatic waters.  By diftillation.
WATER.  Diftilled water of the fhops.  By diftilling recent vegetable fubftances with water.
AHDS : V
ALK  \L1K

METALS.
ALCOHOL.
                  EMPYREUMATIC OILS may be combined with the following Subftances, viz.
ACIDS: Vitriolic and Nitron^, as above.
ALKALIES :  Fixed jnd Volatile, as above.
OILS of all kinds.   By mixture.
ALCOHOL.   By folution.   By repeated diftillations the oils are rendered much more fubtile.

                         FOSSILE  OILS  may be combined with the following Subftances, viz.
ACIDS : Vitriolic and Nitrous, as above.
ALKALIES :  Fixed and Volatile, as above.
OILS of all kinds.   By mixture.
SULPHUR.  With fome difficulty, by folution.
ALCOHOL.      -     -      -     By ditto.
                            SU L P H U R  may be combined with the following, Subftances, viz.
ACID*: Vitriolic ; with  the phenomena above defcribed.
ALKALIES :  Fixed and Volatile, as above.
                 'Silver.   A mafs of red-like colour.  By adding fulphur to red-hot filver, and fufing ; fonnd alfo with it in the
                      ftate of an ore.
                 Lead.   A fparkling friable mafs, hardly fufible.   By deflagrating fulphur with lead.  This in a native ftate
                      forms the ore of lead called galea.
                 Copper.   A Black brittle  mafs, eali'y fuf-d.  By adding fiVphur to red-hot copper, or ftratifying with fulphur
                      and fufing.   Naturally in fome  yellow pyrites.
                         TA fpungy-like  drofs, ealily fufible.  By putting fulphur to red-hot iron.  This is alfo found naturally
                               in the common yellow or brown pyrites
                          A fulminating compound.   By  mixing tilings of iron with fu'phur, moiften'mg them with  water, and
                               prefling them hard, they in a  few Injurs b.irii out into flame.  This compofition has been employ-
                               ed for imitating earthquakes.
                         | Croc-is martis.  By deflagrating with iron.
                         | Crocus martis aperiens.  By culcming  the crocus martis in the fire till it afTumes a red appearance.
                         [Crocus martis aftringens.  By pufhinji the heat ftill further.
                         A dark-colo.ired mafs, refembling antimo; y.  By  lufiein.
                              CEthiops mineral.  By heating flowers  of filphur, and pouring the mercury upon it, and ftirring it
                                   well.  Its natural ore  is  called cinnabar.
                  Mercury. -^ Fafiitious  cu.nabar.   By applying  the mere:■;■; and fnlrhur to each othtr  in their pure ftate, and
                                   f ibliming.
                               Cinnabar  of antimony.   By fublimirg corrcfy.y fublimate and crude antir/.ony ; or the refiduum,
                              L    after diftilling butter of antimony.
                                                                                                         SEMIMETALS.
METALS.     -< Iron.
Tin 
Tabic.
CHEMISTRY.
                            243
If in its metalline ftate,  theTulphur
SEMIMETALS.   <
METALS.
                     "Bismuth.  A faint greyifli mafs, refembling antimony.  By fufion
                          feparates in the. cold ; but not fo if the calx has been employed.
                      Antimony.   Crude antimony.  By fufion.
                      Zinc*.   A very brittle, dark-coloured, fhining fubftance.   With foroe difficulty, by keeping it long in a
                          moderate fire, and covering it feveral times with fulphur, and keeping it conftantly ftirred.
                                f Yellow arfenic.   By fufing it with T*o th its weight of fulphur.
                    |            j Red arfenic.  By ditto with ith its weight of fulphur.
                    j  Arsenic. \ Ruby  of fulphur,  or arfenic, or golden fulphur.  By fubliming when the proportions are equal.
                    |            | Orpiment, A natural production; not perfectly imitable by art; Compofed of fulphur and arfenic.
                                [_.   Much ufed as a yellow paint.
                    ^Nickel. Acompound; compact and hard as lead; of a bright metallic appearance; internally yellow. Byfufion.
 OILS :  Exprefl'ed, Efl'ential, and Foffile, as above.
 WATER.  Gas fylveftre.   By receiving the fumes  of burning fulphur in water.   This ought rather to be called a union of  the
                 volatile vitriolic acid  with water.

                    »         ALCOHOL may be combined with the following Subftances, viz1;
 ACIDS: Vitriolic, Nitrous, Muriatic, Vegetable, and of Borax, as above.
 ALKALI* : Volatile, as above.
 METALLIC calces, in fome particular cafes.
 OILS :  Expreffed, Effential, Empyreumatic, and Foffile, as above;
 WATER.  By folution.
                          GOLD may be combined with the following Subftances, viz.
 ACIDS:  Vitriolic*, Nitrous*, and Muriatic*.  In the circumftances and with the phenomena above defcribed.
 ALKALIES : Fixed*, and Volatile*, as  above.
                  fSilver.   By fufion.   And the fame is to be underftood of all the combinations of metals,  unlefs particularly
                       fpecified.
                   Platina.   Ductile, and of a dufky colour.  This has been employed to debafe gold, as it is of the fame fpe*
                       cific  gravity, and  is not difcoverable by the  ufual tefts for discovering the purity of gold;
                   Lead.  A  very brittle mafs.   Gold is rendered pale by the leaft admixture with this.
                   Tin.   A brittle mafs  when the tin is added in confiderable quantity; but the former accounts of this have been
                       exaggerated.
                   Copper.   Paler and harder than pure gold.  This mixture is ufed in all our coins, the copper  being called
                       the alloy.
                   Iron.  Silver-coloured, hard and brittle ; very eafily  fufed.
                   Mercury.  Soft like a pafte called an amalgamum.   By folution; it being in this cafe called  amalgamation •
                       and the fame is to be underftood ofthe folution of any other metal in quickfilver.
                 /"Zinc  A bright  and whitifh compound,  admitting of a fine polifh, and not fubject totarnifh 1 for which quali-
                       ties it has been propofed as proper for  analyfing fpecula for telefcopes.
                 j Arsenic.  Brittle; and the gold is thus rendered a little volatile.
 SEMIMETALS.•< Antimony.  A fine powder for ftaining glafs of a  red colour.  By calcination.
                 | Bismuth*.  A brittle whitifh regulus ;  volatile in the fire.
                 I' Cobalt.
                   Nickel.  White  and brittle.

                              SILVER  may  be combined with the following Subftances, viz.
 ACIDS  : Vitriolic*, Nitrous*, Muriatic*, Vegetable*, and Acid of Ants*, as above.
 ALKALIES:  Fixed*  and Volatile*,  as above.
 fcRYSTALLINE EARTHS and other vitreous matters.  A fine  yellow bpake glafs.   The  fineft yellow paint  for porcelain is
          procured from glafs miked with filver.
                 fGoLD, as above.
                 I Platina.  Pretty pure and malleable.  Difficult of fufion ; and in part feparates When cold.
                 (Lead. Very brittle.
 METALS.     •{ Tin.   Extremely  brittle, as much fo as glafs.
                 j Copper.  Harder  than filver alone.   Ufed in fmall proportions as alloy in coins.
                 (Iron.   A hard whitifh compound.
                 ^Mercury*.  By amalgamation with filver-leaf, or calx of filver  precipitated by copper,  but not by lilts-,
                      This  is ufed for filverjzing on other metals,  in the fame Way as the amalgamum of gold.
                 TZiNC.  Hard, fomewhat malleable, and of a white colour.
                 I Antimony.  A brittle mafs.
SEMIMETALS.^ Bismuth.  A white femi-malleablebody.
                 | Arsenic.   Brittle ; the filver being rendered in part volatile.
                 (_CoBALT.
SULPHUR, as above.
                               LEAD  may be combined with the following Subftances, vh.
ACIDS : Vitriolic, Nitrons, Muriatic,  Vegetable, of Urine, of Ants, as above.
ALKALIES :  Fixed and Volatile, as above.
                                                          H i
"CRYSTALLINE 
I
SEMIMETALS. <
244                                CHEMISTRY.                             Tabic.

CRYSTALLINE  EARTHS.   A thin glafs.  By fufion in a moderate heat.
                 "Gold and Silver, as above.
                  Platina.   Of a leafy or fibrous texture, and purplifh or  blue colour when  expofed to the air.  If a large
                       proportion of platina is ufed,  it feparates in the  cold.
                  Tin.  A little harder than either ofthe metals, and eafily  fufed : hence it is  ufed as a folder for lead ; and it
                       t>rnis the principal ingredients of pewter.  If the fire is long continued, the tin floats on the furface.
 METALS.      -< Copper*.  Brittle and granulated, like tempered  iron or fteel when broke.   By throwing pieces ot apper into
                 i      melted  lead.   The union here is very (light.
                    on*.  An opaque brownifh glafs.  By a great  degree of heat  if the iron has been previoufly reduced to the
                       ftate of a caix ; but never in  its metallic ftate.
                  Merclry*.  By amalgamation.   Effect ed only in a melting heat, unlefs fome bifmuth has been previoufly
                       uuited  with the  mercury.
                  Zinc   Hard and brittle.   By pouring zinc on melted lead.   If the zinc is firft melted, and the lead injected
                       upon it, it then deflagrates.
                  Antimony*.
                  Bismuth.  A grey-coloured femi-malleable body, eafily fufed ; and thence ufed as a folder for lead or tin.
                            C A grey-coloured brittle mafs, eafily fufed, and  extremely volatile.
                  Arsenic. ^ A hyacinth-coloured glafs.  By fufion in  a confiderable heat.   This glafs is  eafily fufed; and is
                            £     a much more po^ erful flux than pure glafs of lead.
                 j Cobalt.  The nature of this compouud is not known.
                 [_Nickel.   A brittle  metallic body.
 OILS :  Expreffed* and Effential, as above.
 SULPHUR, asHbovc.
                                 TIN may be combined with the  following Subftances, viz.
 ACIDS: Vitriolic*,  Nitrous*, Miriatic, Vegetable*, of Urine, as above.
 ALKALIES :  Fixed and Volatile, as above.
 CRYSTALLINE  EARTHS or other vitreous matters.  An opaque white vitreous mafs, which forms the bafis of white enamels.
                  TGoi.d,  Silver, and Lead, as above.
                  1 Platina.  A coarfe hard metal  which tarnifhes in the air.
                  I Copper.  A  brittle mafs.   When the copper  is  in fmall proportions,  it is firmer and  harder than pure tin.
 METALS-      -^     This, in right proportions with a little zinc,  forms bell-metal.
                 | Iron.   A  white brittle  compound.   By heating filings of iron red-hot, and pouring melted  tin upon them.
                       A metal refembling the  fineft filver is made of iron, tin, and a certain proportion  of arfenic.
                  (^Mercury.  This amalgamum forms foils tor mirrors; and forms the yellow pigment called aurum mofaicum.
                       By bc'm- fublimed with fulphur and fal ammoniac.
                  ("Zinc.   Hard and brittle.  When the zinc is in fmall proportions, it forms a very fine kind of  pewter.
                  I Antimony*  Regrrtus veneris.   By elective attraction from copper and crude antimony.
                  j Bismuth.  Briyju, hird, and fonorous, when a fmall proportion of bifmuth is ufed.  This is very eafily fufed,
 SEMIMETALS. «<     and employed as a folder.
                   Aksenic.  A fubftance in external appearance refembling zinc.
                   Cobalt.   By fufion.
                   Nickel.   A brittle metallic mafs.
 OIL : Expreffed*,"as above.
 SULPHUR, as above.
                                COPPER may be  combined with the following Subftances, viz.
 ACIDS :  Vitriolic, Nitrous, Muriatic, Vegetable, of Urine, of Amber, of Ants, as above.
 ALKALIES : Fixed, and Volatile, as above.
                  fGoLD,  Silver, Lead*, and Tin,  as above.
                  | Platina.   A white and hard compound, which  does not tarnifh fo foon as.pure copper, and admits of a fine
  METALS.      J.     polilh.
 Iron.   Harder and paler than copper.   Eafily fufed.
[_Mercu
                         ry*.  A curious amalgam.   Soft at firft, but afterwards brittle.  By triturating mercury with verdigris
                      common fait, vinegar, and water.
                         f Brafs.  Commonly  made  by cementation with diamine.  The larger the proportion of zinc  the
                              paler, harder, and more '->riule is the brafs.
                  Zinc. < Prince's metal, ft,. ALeek, ar.J ot.icr metals refembling gold.   By employing zinc in fubftance in fmall
                              proportions.  Tne beft pmchbecl' ibout i-4thofzinc.
                         ^.S/v/.vr.   A native fubftance, found in Cornwall, confifting of zinc and copper, and ufed  as a folder
SEMIMETALS.^ Antimony.  By fulion.
                  Bismuth.  A palifh brittle mafs.   Somewhat refembling filver.
                 [ Arsen ic.  White copper. ^ By pouring arfenic, fufed with nitre, upon copper in fufion.  If too large a propor-
                 |     tion of arfenic is ufeJ, it makes  the compound black and apt to tarnifh.
                 I Cobalt.  White and  brittle.
                 ^Nickel.  White and brittle, and apt to  tarnifh.
OILS :  EiTential, as above.
SULPHUR, as above.
                                                                                                             IRON 
Table.
CHEMISTRY.
-AS
METALS.
                               IRON may be combined with the following Subftances,  viz.
 ACIDS : Vitriolic, Nitrous, Muriatic, Vegetable, of Urine, of Amber, of Ants, as above.
 ALKALIES :  Fixed*, and Volatile, as above.
 VITRESCENT EARTHS.  A tranfparent  glafs.   In general blackifh ; but fometimes yellow, green, or bine.  The colour is
                      influenced by the degree of heat as well as nature of the ingredients.
    _AT „        f Gold, Silver*, Lead*,  Tin, and Copper, as above.
 Mh 1 ALb.       | Platina.  With caft iron it forms a compound remarkably hard, fomewhat ductile, and fufceptible ofa fine
                       polifh.
                 fZi nc  A white fubftance refembling filver.
                 j Antimony.  The magnetic quality of the iron  is totally deftroyed in this compound.
                 | Bismuth.  In a ftrong  heat, this emitteth flames.
 SEMIMETALS. ^Arsenic.  A whitifh, bard, and brittle compound.  By fufing with foap  or  tartar.  A metal refembling  fine
                       fteel  is made by fufing caft iron with a little arfenic and glafs.
                 I Cobalt.   A compound remarkably ductile.  By fufion in a moderate heat.
                 {^Nickel.   A brittle mafs.
 SULPHUR, as above.
                          M E R C U R Y may be combined with the following Subftances, viz.
 ACIDS : Vitriolic, Nitrious, Muriatic, Vegetable*, of Urine, as above.
 ALKALI: Fixed*, as above.
 MFTAT <J        \ Gold, Silver*,  Lead*,  Tin, and Copper, as above.
 ML     .       | Platina.  The compound refulting from this  mixture is not known.
                 TZinc.  An amalgam.  Soft or hard, according  to the proportions  employed.
                 I  Antimony.   By melting the regulus, and pouring it upon boiling mercury.  By frequently diftilling from,
 SEMIMETALS. ^'      this amalgam, the mercury is rendered much more pure, and then is called animated mercury.
                   Bismuth.  A filverizing for iron.  By putting this amalgam upon iron,  and evaporating the mercury. It has
                       much the  appearance of filver.
                   Cobalt.  By mixing firft with nickel, and then adding mercury.
 SULPHUR, as above.
                              ZINC may be  combined with the following Subftances, viz.
 ACIDS : Vitriolic, Nitrous, Muriatic, Vegetable, of Urine, of Amber, of Ants, as above.
                   Gold,  Silver, Lead, Tin, Copper, and Iron, as  above.
                   Platina  A  hard fubftance.
                   Mercury, as above.
                ^Antimony.   This mixture is applied to no particular ufe.
 SEMIMETALS. ^Arsenic.  A black and friable mafs.
                ? Cobalt.  The particular nature and properties of this mixt is not known,
 OIL :  Expreffed*, as above.
 SULPHUR*, as above.
                          A NT I MO NY may be combined with the following Subftances,  viz.
 ACIDS : Vitriolic*, Nitrous, Vegetable*, and Urinous.  With'the phenomena, and by the means above defcribed.
 ALKALIES :  Fixed and Volatile,  as  above.
 VITREOUS EARTHS.   A thin penetrating glafs ;  which is a powerful flux of metals.
                   Gold, Silver, Lead, Tin*, Copper, and Iron, as above.
                   Ptatina.  A hard mafs.
                   Mercury,  and  Zinc, as above.
                   Bismuth.  A mafs refembling regulus of Antimony.
                   Arsenic.  The nature  and qualities of this mixt arc not known.
                   Cobalt.   Nature unknown.
                _ Nickel.   Ditto.
 SULPHUR, as above.
                          B IS MU T H may be combined with the following Subftances, viz.
 ACIDS : Vitriolic, Nitrous, Muriatic, Vegetable, and Urinous ; with the phenomena, &,c. above defcribed.
 ALKALIES:  Fixed*, and Volatile*,  as above.
 VITREOUS MATTERS.  A yellow glafs.   The ore of Bifmuth  affords with  thefe  a blue  glafs; but this is probably owing to
    fome mixture of Cobalt with it.
                C  Gold, Silver, Lead, Tin, Copper, and Iron, as  above.
                 1  Platina. This mixture changes its colour much on being expofed to the air..
                   Mercury, as above.
                  Antimony, as above.
                  Arsenic.  Nature not known
                  Cobalt*.  By mixing firft with with nickel or regulus of antimony, and then adding cobalt; bat it cannot be
                      united by itfelf.
                   Nickel.   This mixt  is  not known.
 SULPHUR, as above.
                           A R S E NIC may  be combined with  the following Subftances, viz.
ACIDS : Vitriolic, Muriatic*, Vegetable*, and Urinous ; with the phenomena, ire abovementioned.
                                                                                                       ALKALIES.
METALS.
SEMIMETALS.
METALS.
SEMIMETALS. 
246
CHEMISTRY.                             Tabic.
ALKALIFS :  Fixed, and Volatile ; with the phenomena, and by the means mentioned above.
VITREOUS MATTERS.   A glafs which greatly promotes the fufion of other fubfiances.   The arfenic muft firft be prepared by
    didolving and prcci^itaiine from alkalies.
MFTAI S         i Gold, Silver, Lead, Tin, Copper, and Iron, as above.
                  | Platina.
                  1  Zinc, Antimony, and Bifmuth, as above.
SEMIMETALS.   3 Cobalt
I Zt>
■?Coi
£Ni.
                      on k. 1 .
                      ckel.  The phenomena attending thefc mixtures have not been as yet particularly obferved.
SULPHUR, as above.

                           PL  AT I X A may be combined with the j allowing Subftances, viz-
ACIDS :  Muriatic* ;  with the phenomena, &c mentioned above.
ALKALI:  Volatile, as above.
METALS:        Gold, Silver, Mercury,  Tin,  Copper, and Iron, as above.
               C Zinc, Bifmuth, and Arfenic, as above.
SEMIMETALS. 2 Cobalt.
               C Nickel.  The phenomena attending thefe mixtures not yet obferved.

                            COBALT  may be combined with the following Sub fiances, viz.
ACIDS:  Vitriolic, Nitrous, Muriatic, and Urinous ;  with the phenomena, ire. as  above defcribed.
ALKALI :  Volatile, as above.
                              C Safre.   By mixing calcined cobalt with calx of flint, and moiftening them with water, and
EARTHS.     Calx of Flint. ^            preffingthem clofe in wooden tubs.
                              r Smalt.   By vitrifying thefc with the  addition of a little potafh.
KlETALS :       Gold, Silver, Platina, Mercury*, Lead, Tin, Copper, and Iron, as above.
KFMJMETALS  I ZlNC> Antimony, Bifmuth*,_and Arfenic, as above.
fiCKEL.  The properties of this compound not known.
                               NICKEL may be combined with the following Subftances, viz
 ACIDS .-  Nitrous, and Muriatic ;  with the phenomena, ire  as mentioned above.
 ALKALI :  Volatile, as above.
 METALS : Gold, Platina, Lead, Tin, Copper, and Iron, as above.
 SEMIMETALS :  Antimony, Bifmuth, Arfenic, and Cobalt, as above.
 SULPHUR, as above.

                   ABSORBENT  EARTHS may be combined with the following Subftances, Viz.
 ^CIDS :  Vitriolic, Nitrous, Muriatic, and Vegetable ;  with the phenomena, and by the affiftances abovementioned.
 ALKALIES:  Fixed as above.
                C Crystaline.  By this mixture they are both much eafier melted into glafs than by themfelves, but not witli-
 ►CARTHS.      <     out the addition of Pome alkali.
                ? Argillaceous.   This mixture eafily runs into a glafs without any addition.
 WATER.        Lime-water.  By folution.   it is fometimes found flowing out of the earth in fprings ;  and as it always quits the
                      water when expofed to the air, it h there depofed on the banks ofthe ftreams, forming the ftony incruftati-
                      ons called petrifications :  And filtering through the pores of the  earth, and dropping through the roofs of
                      fubterrancous caves, it  forms the curious incruftations foiind hanging from the  roof of fuch places ;  fome-
                      times afliiming forms ftupeuduoufly magnificent.
 AIR.            Fixt.   Lime-ftone.   It is from the quality that quick-lime has of abforbing io  air, again with  it refuming
                      its  ftony  confiftence,   that  it  is fitted  for a cement in building;  and the  great  hardnefs of  the
                      cements  in old buildings is owing to the  air being more perfect\j united  with thefe than in newei
                      works.

 «    CRYSTALLINE or V IT R ESC E NT EARTHS may be combined mith  the following Subftances, viz.
 AACIDS :  Vitriolic*, and Nitrous*; with the phenomena, ire.  as abovementioned.
 ALKALI  : Fixed,  as aboye.
 ABSORBENT EARTHS : as above.
 ARGILLACEOUS EARTHS.  A raafs running into glafs in a moderate heat.
 PETALS :  Lead, Tin, Copper, and Iron, as above.
 WATER.   Although this is not foluble in water by any operation that we are  acquainted with ; yet,  from its cryflalline form, it
     r> probable that it has been once fufpended  ;  and certainly it is fo at this day in thofe  petrifying fprings w;ho/e incruftations are
     of the cryftajline fort.
 SE?»1IMETALS : Antimony, Bifmuth,  Arfenic, and Cobalt, as above.

ARGILLACEOUS  EARTH may be combined  with Abforbent and Cryflalline Earths, as above.   With water it only unites into a
    pai':e of a mechanical nature.                                                                          INDEX. 
Index.
CHEMISTRY.
247
Absolute  heat,  defined,  n°  37.
   Difference  of the abfolute heat of
   different fluids, 46.
Abforption of beat the univcrfel caufe
   of fluidity, 119.   Vapour formed
   by the abforption of  latent heat,
   iao.
Accenfion of  Homberg's  pyrophorus
   explained, 1418.
Atetsas  acid, its  fpecific gravity,  400.
   This acid and its combinations par-
   ticularly treated of,  867.   Procu-
   red by a particular kind of fermen-
   tation, ib  Of it6 combination with
   alkalies, 868.   With  earths,  872
   etfeq.  With metallic fubftances, ib.
   Whether tin  be foluble in it,  879.
   Of its concentration, 881. May be
   cryftallized in form of  a fait,  88a.
   May  be   reduced into an  aerial
   form,  883.   Its combination with
   inflammable bodies, 884.   Produ-
   ces a greater quantity of ether  than
   the vitriolic  acid,  ib.   Acid  of
   milk feems  to be of  the  acetous
   kind,  978.   Whey  may be  con-
   verted into  an acetous acid,  979.
   May  be  almoft entirely deftroyed
   by fire,   IOOI.   Requifites   for
   bringing  it nearer to  the  ftate of
   tartar, 1002.   Weftrumb's  unfuc-
   cefsful attempt to do fo, 1003. Dr
   Crell's opinion of  the poflibility of
   this tranfmutation, 1004.  Method
   recommended  by  him for  trying
   the experiment,  1005.   His expe-
   riments proving that all the vege-
   table acids  may be reduced to the
   acetous,  1006, & feq.   Manga-
   nefe  foluble with  difficulty in  it,
   1369   Procurable from the  refi-
   duum of  vitriolic ether,  2d  722
   Beft  prepared from fugar of  lead
   and oil of vitriol, 882. Mr Dolfufs's
   method of  making  the  acetous
   ether  readily,  884  How  to pre-
   pare it from vinegar of wood, ib
   The  acetous  acid has an  affinity
   with that of ants, 1504.  How to
   cryftallize its combination with the
   volatile alkali,  1515-   Particular
   defcription of the faits formed by
   combining it with calcareous earth,
   I516.  With magnefia, 1517   Its
   phenomena with zinc, 1518  With
   arfenic,  15 9   SuppofVd to be an
   antidote againft that poifon, 1520.
   Produces a  curious phofphoric li-
   quor  with  \t, 2d  957, 1521.   Its
   effects, on  fiiver,    5%$-   Gold,
   1524.     Inflammable   fubftances,
   1525.  Diffolves gunis,gum-refins,
   the flefti and bones of animals, &c.
   ib.  Various  methods  of concen-
   trating it, 1526.   Of its cryftalli-
   zation, 1527.   Difference between
   common  acetous  acid  and radical
   vinegar, 1528.    Mr  Keir's  opi-
   nion concerning them,  1529 How
   to obtain  it from terra foliata  tar-
   tari, ib.
/it-bard's  method of  making crucibles
   from the calx of platina, 387.
             I        N        D


Acid:  Phenomena attending the fo-
  lution of a metal in one, 180.  The
  nitrous  moft  violent in its opera-
  tion,  181.  Vitriolic acid  next to
  it,  182    The marine  acid much
  weaker than  either, except when
  dephlogifticated, 183.   The other
  acids ftill weaker, 184.  Why the
  nitrous acid precipitates a folution
  of  tin or antimony,  200.  Pure
  vitriolic  acid cannot be reduced in-
  to  an aerial  ftate but  by  combi-
  nation with phlogifton, 202  The
  nitrous   acid  ftill more   remark-
  ably changed  by fuch a  combina-
  tion, 203.  The marine  acid  ca-
  pable of  affuming  an  aerial  ftate
  by reafon of  the phlogifton it na-
  turally contains, 205.    Table  of
  the quantity  of  acid taken up by
  various  bafes, 268.   The vitriolic
  acid contains more  fire  than  the
  nitrous or marine,  278.   On  the
  expulfion  of the nitrous by the  di-
  luted vitriolic acid,  28c.  By the
  fame  concentrated,   281.   By a
  fmall quantity  of  dilute  vitriolic
  acid, 282.   On the expulfion of
  the marine acid by the concentra-
  ted vitriolic, 283.  On the decom-
  pofition of vitriolated tartar by  ni-
  trous acid, 28.5.  This fait cannot
  be  decompofed  by  dilute  nitrous
  acid,  287.   Of its  decompofition
  by marine acid, 288.   Requifites
  for the fuccefs of the experiment,
  289.  Why the  marine acid  can-
  not  decompofe   vitriolated  tartar
  previoufly diffolved in water, 290.
  The  decompofitions  of  vitriolic
  ammoniac and  Glauber's fait  by
  this acid never complete, 291.   Ni-
  trous falts decompofed by it, 292.
  Marine  falts  decompofed by  the
  nitrous  acid,  293.   Selenite  can-
  not be decompofed by marine acid,
  and why, 294.  Why the vitriolic
  acid refumes,  on evaporation,  the
  bafis it  had  left, 295.   An excefs
  of acid  requifite to  make metals
  foluble in water, 2;7.   Nitrous
  acid attracts filver more than fixed
  alkali,  301.   Solution  of lead  in
  nitrous acid  decompofed  by  falts
  containing the marine  acid, 312.
  Vitriol of  mercury decompofed by
  marine ac d,  313.    Precipitation
  of  corrofive  fublimate  by con-
  centrated  vitriol.c acid explained,
  315.   Of the  excefs  of acid  in
  the  folution  proper   for   ma-
  king experiments on metallic  pre-
  cipitates,  334.   Iron   and  zinc
  the only metals diffolved by vitrio-
  lic  acid,  337.   N trous  acid dif-
  folves al!  metals, though  it   has
  lefs affinity with them  than  the
  vitriolic or marine,  338    Why
  it cannot diffolve them when very
  concentrated,  339.   In what cafes
  marine  acid  can diffolve  metals,
  and when it cannot,  340.   A triple
  fait formed by marine acid, iron.
       1.        A,


 and regulus of antimony, 366.  A-
 nother by the  fame  acid, regulus
 of  antimony,  and  copper,  367.
 Bifmuth  precipitates arfenic  from
 the nitrous acid, 369. Copper preci-
 pitates it from the marine acid, 370.
 Method of finding the quantity of
 pure acid contained in fpirit of fait,
 376   In other acid  liquors,  378.
 Quantities of acid, water, and  alka-
 li, in digeflive fait, 379.  Mr Kir-
 wan's  method of faturating an add
 exactly with an alkali, 381. Quan-
 tity  of mild and cauftic vegetable
 alkali  faturated by a given quanti-
 ty of marine acid, 382.   Pure  ni-
 trous acid cannot be made to  af-
 fume  an  aerial ftate, 383.   How
 to determine the quantity of  pure
 acid in fpirit of nitre, 384.   Pro-
 portion of acid in fpirit of nitre to
 that in fpirit of fait, 385.  To find
 the fpecific gravity of the pure ni-
 trous  acid, 386.   To  determine
 its mathematical fpecific gravity,
 388.   Of the quantity of real  acid
 contained in it,  389.  Quantity  of
 acid, water,  and  alkali,  in nitre,
 391.   Experiments on  the fpecific
 gravity, &c. of  vitriolic acid, 395.
 Dilution of the  concentrated  acid
 neceffary  for   thefe  experiments,
 396.   How to find the  fpecific
 gravity of pure vitriolic acid,  397.
 Quantity  of acid, water, and  alka-
 li, in vitriolated tartar determined,
 398.   Specific gravity of the ace-
 tous acid, 400.  Why the precipi-
 tates of alum and mercury contain
 a  part of the acid, 408.  How  to
 determine the  quantity  of  pure
 acid in any fubftance, 410.  .Exact
 computation  of  the quantity  of
 pure acid  taken up by mild vege-
table alkali, 418.  Of the quanti-
ties of  acid and water in fpirit of
nitre,  426  Quantity of pure acid
taken  up  by  various  fubftances,
428.   Quantity of  vitriolic  acid
neceffary  to faturate mineral alka-
li, 430.   Of  the fame alkali fa-
turated by dephlogifticated nitrous
acid,  432.     By  marine   acid,
433-    Quantity of  marine  acid
faturated by calcareous earth, 438.
Alum   always  contains an  excefs
of  acid,  448.    Proportion   of
the pure  earth of alum taken up
by nitrous acid,  449.   By  marine
acid, 450.  Quantity  of iron taken
up by the vitriolic acid,  453.  Why
vitriolic air Is produced by diffol-
ving iron  in  concentrated vitriolic
acid, 455.  Ofthe  folution of the
calces of iron in  vitriolic acid,  456.
 Proportion of iron diffolved by the
nitrous acid,  458.  Vitriolic acid
 acts  on iron in a much  more di-
lute  ftate th~n  the nitrous,   461.
 Proportion of this metal taken  up
by the marine acid, 462.  Calces of
iron precipitated of a reddifh colour
from the marine acid, 463.  Of the
 quantity of copper diffolved in the
 vitriolic acid,  464.   Inflammable
 and vitriolic are obtained by diffol-
 ving copper in this acid, 465. Why
 the  dilute vitriolic  acid  will not
 act upon  copper, 566.  Quantity
 of copper diffolved in nitrous acid,
 468.   In marine acid, 469.  Ef-
 fect  of  the  vitriolic  acid  on tin,
 470.  Of the nitrous acid, of the
 marine acid,  of the vitriolic acid,
 on lead, 474.    Of the nitrous acid,
 475.  Scarce foluble in dilute vi-
 triolic acid,  476.   Effects of the
 marine acid upon lead, 477.   Of
 the vitriolic acid  on filver, 478.
 Of nitrous acid on the fame, 479-
 Of the diflblution of filver in the
 marine acid, 480.  The nitrous acid
 cannot, according to  Mr Kirwan,
 diffolve gold, 484.   Effects of the
 vitriolic   acid  on  mercury 485.
 Of the nitrous  acid, 486.   Of the
 marine acid,  2d 486.  Of the vi-
 triolic acid on zinc, 487.   Of ni-
 trous acid  upon it, 488.  Lefs  of
 this femimetal  diffolved by  con-
 centrated  than  by dilute  nitrous
 acid, 489.  Effects of the  marine
 acid on zinc, 490   Vitriolic acid
 can  fcarce diffolve bifmuth,  491.
 Nitrous  acid  diffolves it  readily,
 492.   Marine  acid fcarce acts up-
 on  it, 593.  Effects of vitriolic a-
 cid on nickel, 2d 493.   Of nitrous
 acid,  494   Of  marine  acid, 495.
 Of the  vitriolic  acid   on  cobalt,
 496.   Of  nitrous acid,  497.  Of
 the marine acid, 498   Of vitrio-
 lic  acid on regulus  of  antimony,
 499.   Of nitrous acid,  500.  Of
 the marine acid, 501.   Of vitrio-
 lic acid on regulus of arfenic, 502.
 Of nitrous acid, 503.   Of  marine
 acid, 504.  Quantity of phlogifton
 contained  in it, 509.   Why  the
 marine  acid   acts   fo  weakly,
 510.   How to  diftil  acid  fpirits,
 57£.   Luting  proper  for them,
 577.   Of the vitriolic acid and its
 combinations, 612, et feq.  See Vi-
triolic.  Miftake of Mr Morveau
 concerning the  excefs of acid con-
tained in  alum  detected by Mr
 Kirwan,  642.   This excefs necef-
 fary to render alum foluble in wa-
 ter, 643.   Too great  an excefs
 prevents  the  cryftallization of  the
fait, 681.   This excefs  beft reme-
 died  by  the addition of pure clay
to the liquor. 682, etfeq.  The fu-
perfluous  acid might be advanta-
 geoufly diftilled, 689.   Nitrous a-
 cid and its combinations, 722, etfeq.
 See  Nitrous.   Experiment on  the
 tranfmutation of vitriolic into ni-
 trous acid, 721. Inconciufive,  722.
 Marine acid and its combinations,
 782, et feq. This acid may be de-
 phlogifticated by fpirit of nitre  or
 manganefe, 790.    Mr Scheele's
 method of doing it  by means of
 manganefe, 791.   Properties  of
                  dephlogifticated 
drphlcgiiticitnl mirinc  acid, "91.
A millake of Stahl concerning if
ronverfion  into  nitp < »  acid  .u-
rcuntcd for, 793. See Marine. Fluor
.and difcovered i •  Mr  Margraaf,
i\C. ?l6, *■/ fiq.   M irinc acid pro-
v d to be  different from  that of
fluor, 835.   .And likewife  the  vi-
triolic, 83'). Seeder.   Ofthe a-
cid of Imt't .: d its  combinations,
858—866.  See Bora* and Sal S<-
a'ji.-.Ki.   Of the acetous acid and
its combinations, 867—8?4.  See
 Aittvvi.    Of  the acid  of  tartar,
 885—X?<-.  Sc; ■  -Tjrtjr.  Of the a-
 rid of lugar, X_/>—</0$.   See Su-jr
 srd Saecbarint.   OI the phofpho-
 ric  acid,904—9C7. See  Phf^Utic.
 Of the acid of ants, 2d 907,  908.
 See //*//.  Of the acid of amber,
 909—915.  Purified by marine .1-
 cid, 911.   Elhcts of fpirit of nitre
 on it, 91a.  Of oil of vitriol, 913.
 Ofthe acid of arfenic, 716, et  ftq.
 Nitrous  acid  di coninolcs  arfenic,
 918.  As does alfo dephlogifticated
 marine acid, 919.  Sec Arfenic.  Of
 the acid of molybdaina, 958. et feq.
 Effects  of  the  arfenical acid on
 molybdann,  959.   Nitrous  acid
 acts violently upon it,  960.   See
 I,fr\lJtna.  Of the acid  of lapis
 pon.lcrofus, tungften  or wolfram,
 967, etjeq.  See  'Tungften.   Differ-
 ence between the acids of molyb-
 drra and  tungften,  971.   Why
 Bergman  fuppofed both thefe  to
 be  metallic earths, 972, 973.  Of
 the acid of milk. 974, et fn.  Con-
 tains  the acids  of tartar and fea-
 I ilt, 975.   Ot the acid of fugar of
 milk, 980, 981.  See ALU-   Of the
 acid of  hmcan calculus, 982.   See
  C.i'.ulut.   Of  the acid of benzoin,
  9X4, rt/7.  Scj Flowers and Ben-
 zoin.   Whether the ?.cid  of fugar
 or of tartar is the baCs of the ano-
  malous  vegetable acids,  996.   Dr
 Crell's method of cryftallizing the
 acidof  lemons, 997.   The cryftal-
 Ii;vd  fait cannot be converted into
 acid of lugar, 999.  Product of the
 •icid of tartar by  dry diftillation,
  IOOO. Acetous acid almoft entirely
 deftrudiblc by fire, icoi.  Of  the
 tranfmutation of the  vegetable a-
 cids into the acetous acid, 1002—
 I015. See Ai.tous.  Phenomena re-
 fulting from  the  mixture of acid
 fpirit-i  with  one  another,  1040.
 Solution  of falts promoted by vi-
 triolic  acid,  104'•'.  Terra ponde-
 iou ufually found in  a ftate  of
 combination with this acid,  IC49.
 Effects of marine acid  on aerated
 11 :-a ponderofa,  1 "53.   See Terra
 PtnJercft.   White n -ttcr contained
 in the vitriolic  acid fhown to be
 gypfum,  1059.   Vitriolic  acid ea-
 fily difcoverable  by folution of terra
 ponderofa. 1058.  Marmor metal-
 licum foluble iu very concentrated
 vitriolic aud. 1063  Why the f.uor
 acid  will not diffolve flint directly,
 ID-3. Why the Gliceousearth lar.ic-
t;mc» cunuct be  precipitated by an
acid without the affiftance of he^t,
 1 :*9.  Earth  of flint* precip.uted
       C    II    E    M    I

  by floor acid,  1080.    Neither the
  nitrous nor  marine acid  receffary
  for  the preparation of ..urum ful-
  rnin:.n»,  ill".   Vitriolic ..cid par-
  tially diffolves arfenic, 1271.   Ma-
  rine acid diffolves it  totally, 1172.
  Phlogidicated  a,kali  precipitates
  arf nic from its folution in marine
  acid,  and from  that only, 1273.
  Arfenic  decompofed by  dephlogi-
  fticated marine acid,  1274. Pheno-
  mena of arfenic with nitrous  acid,
  1280.  Butter of arfenic can fcarce
  he made to unite with marine acid,
  1282. Regulus of  arfenic convert-
  ed by the vitriolic acid  into white
  arfenic,  1292.  Phenomena of co-
  balt with vitriolic acid, 1 ,cc. With
  nitrous  acid, 1301.   With marine
  acid, 1302  With the acid  of borax,
  1303.  Efftds of  the nitrous acid
  on nickel, 1313.  Dephlogifticatcd
  marine acid the  only folvent  of
  platina, 1319.   Solution  of  that
  metal in  an  aqua regia  compofed
  of  nitrous arid  and  fpirit of fait,
  1323.  In one compofed of marine
  acid and  nitre,  1324-   Solution
  of  calx of platina  in marine acid
  lets fall a cryflalline powder on the
  addition of vegetable  alkali,  1325.
  But not  that  in the nitrous  acid,
  1526.   Phenomena  of manganefe
  with vitriolic  acid, 1360.   Phlogi-
  fticated vitriolic acid entirely dif-
  lblvc. it, 1361.  And likewife the
  phlogifticated  nitrous acid,  1363.
  Effects of it on marine acid,  1364.
  Entirely  diffolved  by  this  acid
  without  addition,   1365.    Fluor
  acid can  fcarcely diffolve it,  1366.
  Or phofphoric acid, 1367.   Acid
  of  tartar partly  diffolves manga-
  nefe, 1368.  Acetous acid effects
  a  folution with difficulty,  1369.
  Acid of  lemons entirely diffolves
  it,  1370.   As does alfo water im-
  pregnated with  aerial acid,  1371.
  No pure acid  can  diflblvc manga-
  nefe after it has loft its phlogifton,
  I375-   Why  the concentrated vi-
  triolic acid  diffolves  it   without
  addition, 1378.  Why the volatile
  fulphureous acid diffolves  it,  1379.
  Effects  of the nitrous acid  on it
  explained,  1380.     Exiftence  of
  phlogifton  proved  in the marine
  acid,  1381.   Explanation of  the
  efftels of acid of tartar and  of le-
  mons, 1382.  And  of fluor  acid,
  1383.   Effects  of digefting  man-
  ganefe and volatile  alkali with ni-
  trous acid, 1393. An acid fuppofed
  to occafion  the tafte of  effential
  oils, 1420.  A new  one difcovered
  by MrHomberg, 2d  825. See Acids.
  See  alfo Vitriolic,  Nit: ctis, Marine,
  Acetous, Tar/ar, Fluor, &.C.
Acids, one  of the principal claffes of
  falts, 169.   Divided  into mineral,
  vegetable, and  r.nimal, ib.  Their
  different  action  compared   with
  that of alkalies,  171.  Unite  with
  alkalies into neutral falts, fome-
  times with, and fometimes with-
  out, effervefcence,  172.    Change
  the blue colour of  vegetables  to
  red, 173. Different  degrees of their
  S    T    R    Y.

attraction to  ail -.dies,  174.   The
vitriolic  ftrongeft in a liquid ftate,
ib.    Marine  acid ftrongeft  in  a
ftate of  vapour, ib.    The   fixed
acids  ftrongeft when  the  fubjeds
are urged with  a violent heat, ib.
Attraction of the  different  acids
for phlogifton, 175.   The acids 3re
capable  of  forming an union with
metals or earths, 176.  Will leave
a  metal to unite with ?n  earth,
176,177.   And an earth to unite
with   a  mild  volatile alkali, ib.
Will leave a volatile, to unite with
a fixed alkali, ib.  Some will leave
a  fixed  alkali to unite with phlo-
gifton, 175, 178.   Exceptions to
thefe   rules,  179.   Why  precipi-
tates  are fometimes  thrown down
by them, 221.   Explanation of the
decompofitions effected by acids a-
lone, 266.   Quantities of the  dif-
ferent acids taken  up by Various
bafes,  268.  This quantity expref-
five of the  quantity  of attraction
they  have for each of thefe bafes,
269.   "itriolic  falts  decompound-
ed by  the nitrous and marine acids,
275.   Acids unite with alkalies by
giving out fire, and quit themby re-
ceiving it, 286. The attractive pow-
ers of adds to  metals  difficult to be
determined, 296. Proportions of the
different metallic fubftances taken
up by the different acids, 298. Me-
tals have a greater affinity with a-
cids than alkalies, 299, 303.  Ex-
planation of the table of the  affi-
nities to the diftcrtnt metallic fub-
ftances,  316.   An equal quantity
of all  the  mineral acids  taken up
by vegetable  fixed   alkali,  402.
Quantity of this alkali requifite to
faturate the feveral acids, 403.  A-
cids can  never totally  dephlogifti-
cate metallic  earths,  407.    Con-
centrated acids   phlogifticated by
alkalies,  409.    Of the  time re-
quired by mixtures of  the mineral
acids  with water to attain their ut-
moft  denfity, 422.    Of the altera-
tions  of  their denfities by  various
degrees of heat, 423.  Acids can-
not   diffolve  calcined   magnefia
without  heat,  442.   Phenome-
na  of different  acids with in-
flammable fubftances, 518.   Me-
tals foluble in acids,  520.    Calci-
nation and increafe of their weight
by acids, 523.  How to.  diftil the
mineral  acids, 575. Vitriolic, phof-
phoric,  and acetous,  acids, found
in the refin extracted from  the re-
fiduum of  vitriolic ether, 2d 722.
Nitrous,  marine, and phofphoric
acids, capable of expelling the fluor
aeid,  2d 850.  Acids  of fal ammo-
niac and nitre expelled by fait of
amber, 910.  Ofthe anomalous ve-
getable acids,  and the refcmblance
which vegetable  acids in  general
bear to  one  another, 984, et feq.
How  the  anomalous vegetable a-
cids are  divided, 993.  Of  the ef-
fential acids,  994..   Empyrei ir.a-
tic acids, 995.  Whether the  acid
of fugar  or of tart 1  be the bafis of
the vegetable acids, 9^6. Dr Creli'i
                        Index.

   proofs  that all the  vegetable acid«
   may be reduced to one,  which 11
   contained  in  the  pureft  fpirit  of
   wine,  1006.  Phenomena attend-
   ing the diflblution of vitriolic  falti
   in nitrous  or marine acids are not
   neceffary for the  {'reparation of au-
   rum fulminans,  11 1 7.   Copper un-
   dergoes a  change  by  combination
   with  vegetable  acids,  1151.  Co-
   louring matter of Pruffian blue ex-
   pelled by acids,  and then  taken up
   by the  atmofphere, 1177.   Pheno-
   mena  of arfenic  with  different  a-
   cids, 1275. Manganefe  becomes in-
   foluble in  pure acids, by  lofing its
   phlogifton, 1375. See Acids,'Vitri-
   olic, Marine, Vegetable,  &c.
Acids and Alkalies:  inaccuracy of the
   common  tefts for  trying  them,
   1549.   Mr Watt's experiments on
   this  fubject,  ib.   His method  of
   preparing a teft  from cabbage and
   other plants, 1550, et feq.   Abforb
   air during their formation, TJ43,
Adopters, or Aludels, defcribed,  579.
Aerated  terra  ponderofa,  analized by
   Dr Withering, 1057.
Aerial acid: the converfion of dephlo-
   gifticated  air into  it by  means of
   charcoal, a proof of the identity of
   phlogifton  ami charcoal, 151.  De-
   fcription of  the  terra ponderofa
   combined  with  the  aerial  acid,
   1031.    Aerial acid and phlogifton
   fuppofed  to exift in the colouring
   matter Pruflian  blue,  1196.  See
   Fixed Air.
Affinities, quiefcent  and divellent, de-
   fcribed, 267.   Table of the affini-
   ties of the three mineral  acids to
   the different  metals, 298.    Expla-
   nation of this table, 316.   Table of
   the proportional affinities of the
   metallic calces to phlogifton, 330.
   Dr Black's general  table of affini-
   ties, 553.
Affinity   of  the different metals to
   phlogifton, how  determined, 328'
Agents  in chemiftry, how diftinguifh-
   ed from the objects of  it,  22.
Air fupplies inflammable  bodies with
   the heat they emit during combu-
   ftion,  137.  Too great a  quantity
   of air  will diminifh the heat of a
   fire, or even put it out  entirely,
   and why, 159. Only a fmall quan-
   tity of air can   be obtained from
   metals  when calcined, 191.   Dif-
   ferent kinds of it produced  during
   the diflblution of metals, 201  Spe-
   cific gravity of  the different kinds
   of air  according to Fontana,  375.
   Expofure of aluminous ores to the
   air fometimes has  the  fame effect
   with  roafting them, 663.   Vitriol
   deprived of its phlogifton  by expo-
   fure to the air, 687. l,i\ivium fan-
   guinis  lofes   its  colouring  matter
   by expofure to the  air,  1172. This
   colouring  matter taken np  by the
   air after it has been expelled by a-
   cids,  1177.   'hforbed during the
   formation  of acids,  1343.
Air-iukbles produced  in  water du-
   ring  the ad  of  congelation, occa-
   fion  its expanfion   and prodigious
   force,  109.   They arc extricated
                                 fey 
 Index.

  by  a part of the latent heat dif-
  ehargcd  from the  water at  that
  time, no.
Alchemifts :■ the'r labours were of fome
  advantage to chemiftry, 13.
Alchemy  firft  mentioned  by  Julius
  Krraicus Matcrjus, a  writer of
  the 4th century, %. fuppofed to be
  firft  derived  from  the Arabians',
  IO.   The pretenders  to  it  very
  numerous in the beginning of the
  16th  century, 12.
Ahhome's experiments on the effeds
  of  mixing  tin  with gold,  1092,

Alembic, derivation of that word, 5.
Alembroth fal,  made by fubliming e-
  qual  quantities of corrofive' fubli-
  mate  and  fal   ammoniac,  1047.
 , Said to diffolve all  the metals, ib.
  Convertible  by  repeated diftilla-
  tions into  a  fluid that  cannot be
  raifed into vapours by the ftrongeft
  heat, ib.
Algaroth powder, prepared by  preci-
  pitating  butter  of  antimony with
  water, 821.  The moft proper ma-
  terial for the  preparation of  eme-
  tic  tartar,  1239.  Shown by Mr
  Scheele  to be a regulus half calci-
  ned by dephlogifticated marine a-
  cid, 1261.   His  receipt for prepa-
  ring it cheap, 1262.
Alkali lefs attracted by  nitrous  acid
  than  filver,  301.  Metallic earths
  more  ftrongly attraded by  acids
  than^volatile alkali,  303.  Why the
  metallic  earths  feldom  decompofe
  thofe falts that have an  alkali for
  their bafis, 304.  Quantity of  alka-
  li,  acid, and  water, contained in
  digeftive fait; 379.  Mr Kirwan's
  methoi!>of faturating an alkali ex-
  adly with an-acid, 381.  Qiiantity
  of  mild  and cauftic vegetable fix-
  ed  alkali faturatcd   by  a  given
  weight of marine acid, 382. Quan-
  tity of alkali, water, and acid, in
  nitre, 391.   Of  the fame ingre-
  dients in vitriolated tamr,  398.
  Vegetable fixed alkali  takes up an
  equal  qnalitity  of  all the mineral
  acids, 40*.  'Specific gravity of the
  vegetable alkali  determined,  412.
  Quantity of  earth  contained  in
  this alkali, 413.  Of the quantity
  of fixed air contained in oil of tar-
  tar  and dry vegetable alkali,  4T4.
  Quantities of fixed air contained
  in impure vegetable alkali deter-
  mined by Mr  C.ivendifh, 417.  Ex-
  ad  quantity  of  acid taken up  by
  mild fixed alkali, 418.   Mineral al-
  kali how prepared by Mr Kirwan
  for  his experiments,  429.  Of the
  iiuantity of vitriolic  acid  necef-
  lary to faturate  loo grains of it,
  430.   Qiiantity of dephlogiftica-
  tcd nitrous  acid  taken  up by it,
  432.   Of the marine  acid,  433.
  Proportion  of pure alkMi, water,
  and fixed air,  in  cryftallized mine-
  ral  alkali, 434.   Excefs of acid in
  aluminous liquor c:i:mot  be remo-
  ved by mineral  alkali, though it
  may  be  by the vegetable and vo-
       CHE    M

latile kinds,  680.  Vitriolic  acid
combined  with fixed alkali, 628,
629.    With  volatile alkali, 633.
Nitrous acid combined with vege-
table fixed alkali,  740   With  fof-
file alkali, 741  With volatile  al-
kali,  745   Marine  acid combined
with vegetable alkali, 794  With
mineral alkali, ib   With  volatile
alkali, 795   Fluor acid  combined
with  fixed alkali,  4th 850  With
volatile  alkali, 851    Glafs  cor-
roded by the fait  formed from the
union of fluor aeid and volatile  al-
kali,  854  Sedative fait  combined
with  the  vegetable   alkali,   862
With the mineral  alkali, 863  A-
cetous acid combined with  vege-
table alkali,  868   With  mineral
alkali,  869  With volatile alkali,
870   Acid  of tartar  combined
with vegetable alkali, 889 , With
foffil  alkali,  891.    With  volatile
alkali, 892.  Acid of fugar with
vegetable alkali, 899  With foflil
alkali, ib.   Incredible quantity of
volatile alkali fatutated by it,  900
Phofphoric acid with fixed alkali,
906   With  volatile  alkali,   904
Acid of ants  combined  with fixed
and  volatile alkali, 908   Acid of
amber  with fixed  alkalies,   909
With  volatile alkali, ib.   Acjd of
arfenic  with vegetable fixed alkali,
925   With mineral  alkali, 927.
With volatile  alkali,  928  Vege-
table alkali capable  of  being re-
duced into cryftals by means oF fpi-
rit  of wine,. 1017    Without  any
addition into deliquefcent  cr\ ftals,
ib.   Mineral alkali always affumes
a  cryflalline form,   ib.    Change
on  the vegetable  alkali  by  being
united  with fpirit of fak,  1018
Difference betwixt  the  vegetable
and mineral alkali, 1019   The  for-
mer has a greater  attradion  for a-
cids,  ib.  Both of them compofed
of a cauftic fait and fixed air, 1020
Ofthe volatile  alkali, 1030  Of the
method of diftilling it, 1031  Of its
redification, 1032  Combined with
fixed  air,  JO33   Combined with
niftals,  1034   With inflammable
fubft; nccs,  10$ 5  With expreffed
oils, ib    With effential  oils and
fpirit of wine, 1036, 1037   With
fulphur, 1038   Solutions  of cal-
careous earth decompofed  by mild
volatile alkali, 1046  Cauftic  fix-
ed alkali throws down an infoluble
precipitate from folution of terra
ponderofa,  1056   Vegetable  al-
kali precipitates marmor  metalli-
cum  unchanged  from concentra-
ted vitriolic acid,  1064    Volatile
alkali precipitates fi!iceeu«  earth
more completely  than any other,
1074   A triple fait formed by pre-
cipitating this earth with fixed al-
kali,  1075  Siliceous earth diffol-
ved by  boiling in folution of alka-
li, 1076 A remarkable  attradion
bctwixt  fixed  alkali  and filiceous
earth  in  the  dry   way,   107 7
The  ufe  of  volatile alkali orily
I    S    T    R     Y.

   lately  known  in   the   prepara-
   tion  of  aurum fulminans,  1106
   This  alkali   the   caufe  of the
   explofion,   1121    Tt  exhibits  a
   flafh when thrown into a crucible
   by itfelf, 1122  Ufed in the prep i-
   ration of fulminating  filver,  ly" j
   Phlogifticated  alkali,  lofes its pe-
   culiar properties, 1168   Colouring
   matter of Pruffian blue unites with
   volatile alkali, 1182 Forms a kind
   of  ammoniacal  fait with it,  IT86
   Volatile alkali produced  by diftil-
   ling  Pruflian  blue, 1197   Pheno-
   mena on diftilling metallic precipi-
   tates thrown down by Pruflian alka-
   li, 1198  Volatile alkali capable of
   uniting with fixed alkali and phlo-
   gifton fo as to be capable of fuftain-
   ing  a great degree of heat,  1202
   Phlogifticated alkali cannot preci-
   pitate arfenic  except from marine
   acid, 1273   Effeds of volatile al-
   kali  on  nickel, 1314   Mineral
   alkdi capable of decompofing cry-
   ftals of  platina, but not the  vege-
   table  alkali,   1322    Cryftalline
   powder  precipitated   from  folu-
   tion  of calx of platina in  marine
   acid, by^means of vegetable alka-
   li, 1325  But not from the folution
   in nitrous  acid,  1326    Whether
   mineral alkali can decompofe  folu-
   tions of platina, 1328    fifty-fix
   times as much  of  it required for
   this purpofe as of vegetable alkaii,
   1329  Effeds of the volatile alkali
  on folutions of  platina, 1330  Vo-
   latile alkali deftroyed  by manga-
   nefe attrading its phlogifton, 131,4
   See  Alkalies    Wiegleb's   account
   of the  phenomena attending the
   diflblution of copper  in  it, 1035
   Its effeds on dephlogifticatcd fpirit
   of fait,  1485   Higgins firft  difco-
   vered its conftituent  parts, 1553
   Procured it from nitrous  acid and
   tin, ib  Effed of the eledric fpark
 • on a  mixture of it and dephlogifti-
   cated air, 1555    True  compofi-
   tion of it, 1556.
Alkalies ; one of the general claffes of
   falts, 169   Divided into  f.ved and
   volatile, 170   The former fubdi-
   vided into vegetable and  mineral,
   ib  Difference between their adion
   and that of acids, 171  Neutral falts
   form them  by being  united  with
   acids, 172   Vegetable  blues chan-
   ged green by them, 173   Different
   degrees of attradion betwixt them
   and acids,  174   Phenomena at-
   tending  the precipitation «f me-
   tals  by them, 220  Volatile alka-
   lies  particularly apt to form triple
   falts, 274   Why they  precipitate
   the  metals, 300  Metals have  a
   greater  affinity with asids than al-
   kalies, though  the  latter feparate
   them from acids, 299   Why luna
   cornea cannot  be reduced without
   lofs by alkaline falts, 314  Alka-
   lies  phlogifticate concentrated  a-
   cids, 4G9   Proportions ofthe dif-
   ferent ingredients in volatile alka-
   lies, 436  Stone-ware  veffels. ar-
                  I i
                         -     249

   roded l»" cnuf-i: fixed alL?.li<-s, 395
   596   Advantages of ufing clay ra-
   ther  than  alkalies  for abf'Hiinsr
   the fuperfluous acid in alumni''.j'1
   liquor, 683  Solution of filver de-
   compofed with difficulty  by alka-
   lies,  756   How the alkalies are
   procured, I0r6   Differences be-
   tween thft  vegetable and  mineral
   alkalies, 1019    Combinations  of
   them  with  fulphur 1021   With
   expreffed oils, 1026   With effen-
   tial oils, 1027   With  phlogifton,
   1028    Differences between  the
   fixed  alkalies obtained from diffe-
   rent vegetables,  ib   Solution  of
   terra   ponderofa  in marine  acid
   precipitated   by   all the  alkalies,
   whether mild or  cauftic,  IC54
   Alkalies diffolve  lead  by  boiling,
   12x6  Effects «f arfenic  on  alkalies,
   1290    Teft for  them*, and acids,
   1549   See Alkali, Acid, and Acids.
Alkaline falts  See Alkali  and Alka-
   lies   Alkaline ley  improper  for
   extrading   the  flowers  of  ben-
   zoin, 989.
Alfton-Moor in Cumberland,  a kind
   of  aerated terra  ponderofa found
   near that place, 1051.
Aludels, or Adj/ie.s, defcribed,  579.
Alum:  cannot  form  Glauber's fait
   by being diffolved in water along
   with  common fait,  272  Miftake
   of Dr Crell on  this fubjed  cor-
   reded,  ib.    Nor  blue  vitriol  by
   boiling it with copper filings, 349
   Why  its precipitate retains part  of
   che acid, 408  Its earth contains
   26 per cent of fixed air,  446  Pro-
   portions of  the ingredients in  it,
   447   The  fait always contains an
   excefs of acid, 448  Proportion  of
   the earth of alum  taken up by ni-
   trous acid,  449   «>y marine acid,
   450 .Alum  of the ancients diffe-
   rent from ours,  637   The name
   ofRocb-alum derived from Rocco,  a
   city of  Syria, 638   Firft made in
   Europe in  the middle of the  15th
   century, in  Italy,  639   Made  in
   Spain in the 16th century, 640  In
   England and Sweden in the i^th,
   ib.  Its component parts firft difco-
   vered  by iioulduc and Geoffroy,
   641  Found to  contain an excels
   of acid, ib   This denied  by Mr
   Morveau, 642  His miftake dif-
   covered by Mr Kirwan, ib  Info-
   luble  in water when deprived  of
   its  fuperfluous acid, 643   Eafiiy
   calcinable in the fire; after which it
   is called burnt alum, ib   Bergman's
   method  of  finding the  proportion
   of the ingredients it  contains, 644
   Difficulty of  obtaining the  earth
   of alum in  a  pure ftate, 655  Mr
   Bergman's account of the  propor-
   tion of fhe ingredients, 646 Whe-
   ther earth of alum be  a pure clay
   or not, 647  Dr  Lewis's  tj.peri-
   ment,  tending to fliow thi.t  clay
   undergoes  fome  change by being
   converted into earth of alum, !-4cj
   Quantities  of  alum   foluble   in
   warm  and  in  ,v/.i  water, 650
                          Lcrgman'j 
-5°
   Bergman's account  f r J »*- s.vuiifli
   ores  of ».um,  651   ( • 1  poucnt
   parts oil the aluminous fchift, 632
   ll«w changed  by n.fting,  033
   Prefence of pyrites the only rcq:.-
   fitc  for the  produdion  of  alum,
   fn4  Ore* containing alum ready
   u rmed only  to be  met  with  in
   volcanic countries, 6;5   Ores  of
   i." in at  Solfat>rj in It. ly,  036
   Aiul)Ed  by  Mr Bergman, 637
   Hcflian, I'ohcmi.i:),  and  Scan'ai,
   ores, 6j8 Alum,  fulphur,  and vi-
   t ii'l, extracted from the fame ore,
   <-<9  Alum flate found in  •< :i  in
   England,  660   i'ergnian's  dircc-
   t .»ns for  the  preparation of alum,
   l'<\  Ufes of  roafting the ore, 662
   Lzpofure to the air fomevimes ! ..•
   the  fame  effed with roafting, 663
   E.arthy ores unfit for either pur-
   pofe, 664   Mi thod of roafting the
   ore  in  Sweden, 66j  How  often
   the  operation  is  to  be repeated,
   l(d>  Danger  of increafitb, the 1 eat
   t<>.)  much, 667  Rinnuny method
   of ro.iff.-.- the ore at Garphyttan,
   6 j J   Method of burning the hard
   o<,,at Toll a in  Italy, 669  Me-
   thod of cl x.uing the burn :d ore at
   Garphyttan, 670  Heat ami cold
   watcruUi'. for this purpofe in dif-
   ferent phce«,   ib   Diflitnit me-
   thods of elixation,"671   Ninpiiar
   circumftance  by wl.Lh the alum is
   faid to be deftroyed,  672   Of the
   | , 'jc;  Ihciiiyh ofthe lixivium he-
   l. u  it i» committed to  evapor 1-
   ti 1 , 673  Conftrudion of the e-
   v. Mirating veffel, 674   How far
   the  liquor ought  to be evaporated,
   675   Of the  firft  cr\ ionization,
   676   Depuration of the  cryft.:N,
   6'7   Bergman's  remarks  on the
   proper form  of the  coolers, 678
   They ought  to  be  of a  conical
   flv.pc, ib Aluminous  ley conta'ns
   fo much acid that it cannot be cry-
   ft ii.ze-d  without abftrading part
   of the excels,  679   Which may
   be done by the addition  of vege-
   t ibk fixed alkali, or  volatile alka-
   li,  but not by the mineral alkali,
   6^0  Experiments in pre ".if  of th«
   rx.rf; of acid  preventing the cry-
   ftallization of alum, 681  Another,
   fhowing the utility of adding clay
   to the aluminous ley, 682  Advan-
   ce of ufing  it in preference  to
   the  alkalies 6S3   Alum general-
   ly  contamir ated  by  dephlogifli-
   ratcd vitriol, 6^4  Thisdefed re-
   medied  by the  addition of  pure
   clay, 685   Perfed  vtriel  cannot
   be defrayed  by clay, 686   How
   the ]!.i ';  i n  of vitriol may  be
   d. f.oite-'i.  oS-    Epfom fait fup-
   j  :e 1  to  be  producible  from the
   mother liquor of  alum,  688  Su-
   I ;rflu. us acid cf this liquor might
   1 .  -civ,i!t:.geo-ai!y diftilled,  689
   Comfit.anon of arfenical acid with
   .  -th of alum, 938  How to make
   it fhoot into cubical cryftals, 989.
s4. •»/■-.'-   See .-l.rm.
s.,. ■»•  1-,-ii.D  fc-.i k: upia  Italy,
CHEMISTRY.
  039   In  Spain,  Engl. :.el,  and
  Sweden, 640.
Alummtus ires  See Almi
Amalgamation ef fiver :  a -difficulty
  concerning it folved by  Mr Be -g-
  man, 217   Of copper with mer-
  cury, 113;   1>:  Lewis's methods,
  1133  Amalgamation of  mercury
  with different metal<, 1232.
Amber, acid of, 908   Mi   Pott's ex-
  periments on it, 9C9   Requires a
  larger quantity of water for its fo-
  lution,  ib   Rendered   fomewhat
  purer by cryftallization,  ib   Part-
  ly  delhoyed  by  fublimation,  ib
  Forms a neutral fal.ne liquor with
  fixed alkalies which does  not  cry-
  ftallize, ib   Forms an  oily fluid
  with voiatile alkali,  ib   Extri-
  cates the acids of fal ammoniac and
  nitre, 910  Purified by marine  a-
  cid, 911   Does not contain any
  mineral  acid,  ib   Converted al-
  moft entirely  into  a  liquid by di-
  ftillation with fpirit of nitre, 91a
  Moft of it riles in a folid form by
  diftilling wirh oil of vitriol, 913
  Forms  a  loluUon of  qjichlime,
  nioftly refenibmTg the hunt, in ve-
  getable  acids, 914  Its effeds on
  th.- metals, 913   Amber,  by  di-
  dillation, yields an acid fait and oil,
  1444   Difference  in the  produd
  by certain additions fometimes ufed
  in  the  diftillation, ib   Addition
  of  fea-falt produces  the  greateft
  yield of fait of amber, ib  Greateft
  quantities  of amber diftilled  in
  Pruffia, 1443  Diiiilled there with-
  out any addition, ib  The fait pu-
  ril'ud by being kept on bibulous
  piper  t« abforb the oil, ib  Cry-
  it lis refembling it  formed  bv  the
  union of marine acid with pi.l ..u-
  ftie matters,  1481   Method, of
  purifying its  fait, 1494  An acid
  of  another kind paffes over in di-
  ftilling  this fubftance, 1493  Com-
  bination of the fait  with alkalies,
  earths, and metals,  ib   Mr Keir's
  remarks on the nature  of  fait of
  amber, 1495.
An'r.r^vh   yields a produd  on  di-
  ftillation  fimilar to  that  of  am-
  ber, 1446.
America:  method of  mr.king nitre
  there, 726,
Jmn.oniat,  vitriolic,  decompofed  by
  folution of filver,  306   H>v  to
  prepare  this  kind of fal ammo-
  niac,  633    Erroneoufly faid  to
  have powerful effeds on the d.ffo-
  lution  of metals,  ib   Mr Pott's
  experiments  on it, ib Nitrous am-
  moniac, how prepared, 745  Is fo-
  luble in fpirit of wine, ib   Defla-
  grates without  any  addition,  ib
  The principal ingredient in Ward's
  white   drop,  746    Common  fal
  ammoniac prepared from marine
  acid and volatile alkali,  79c  DT-
  folves refins  according to Mr G J-
  lert, ib  Its volatility  dimi: .fhtJ
  by repeated fublimations,  ib   A
  fmall quantity  producible by cii-
  ftuiicg  ka-i'.i: with charcoal,  »«.<.
  ib   Originally  prepared  in  E-
  gypt,  7-96  A method of making
  it de nit bed, ib   Vegetable anuro-
  niac formed of the acetous acid and
  volatile alkali, 870  Can fcarce be
  procured in a dry ftate, ib   Acid
  of common  fil ammonuc extrica-
  ted by acidof amber, 910  And
  by the arfenical acid,  932  Vola-
  tile  fal ammoniac, how  prepared,
  1033  Common fal ammoniac not
  decompofed by regulus of cobalt,
  13.4   Effeds   of  it on nickel,
  1312  Solution  of it  precipitates
  a folution of  platina,  1332  The
  precipitate fufible by a  ftrong forge
   heat, 1333  this fufion  fuppofed
  by   Macqi.er  not to  be perfect,
  1334   Effeds  of manganefe  on
  it, 1392.
Ammoniacal filt, formed by the union
  of the colouring matter of Pruffian
  alkali with volatile alkali,  1186.
r'niiud tartb, ver)  infoluble  in acid:,
  and  iiJuiiMc  in  the fire, 315
  Earth  of  the  foft parts  more  fo-
  luble than  that of  the   hard, ib
  Thi» earth erroneoufly  fuppofed to
  contain phofphoric acid, ib   Ani-
  mal fats  analyfed,  1428   Yield
  a great quantity of oil by diftilla-
  tion, ib   A particular kind of a-
  cid  produced  from tallow,  1429
  How to  redify the empyreumatic
  oil of  animals,  1427  Of animal
  and vegetable fuhilances, 143 1.
Anomalous  earths,  $13   Anomalous
  vegetable  acids,  how divided, 993.
/tntii/iony: why nitrous acid pneipi-
  tatcs a folution  of it,  200  Preci-
  pitates of  it by common and phlo-
  gifticated  alkalies, 246  Of its pre-
  cipitates  with  other  metals, 365
  A triple fait formed by regulus of
  antimony, marine acid, and iron,
  366  Another with  the  regulus,
  marine acid, and copper,  367  Of
  the  folution of the re«ulus in  vi-
  triolic acid, 499   Of  its combina-
  tion with that acid, 709  Corrod-
  ed by  the nitrous  acid, 768  Re-
  gulus of antimony combined with
  marine acid,  821   Of the amal-
  gamation  of it witK mercury, 1237
  Renders  bifmuth  capable of unit-
  ing with the cobalt, 1251 The re-
  gulus particularly  treated of, 1232
  et feq.  Has the  appearance of  a
  ftar on its furface when well made,
  1252   Sublimable into  flowers,
  1253  Different  methods of pre-
  paring the regulus, 1254-  Confi-
  derable differences in  the regulus,
  according to the different fubftan-
  ces  ufed  to abforb the  fulphur,
  1255  O^ l^e regulus made with
  cawk, 1236  The femimetal  ea-
  fily  mifcible with mercury, 1255
  Enters  into  the compofition  of
  fpeculums and printing types, 1236
  Was the  bafis of  many medicinal
  preparations,  now difufed on  ac-
  count of th«ir uncertain operation,
  ib   Glafs  of  antimony, how pre-
  pared, I2-7  M«re violent in its
  iffeOet 1 ....  the regulus  itfelf, ib
                       Index.

  Pi-paratien r>f emetic tartar from
  glafs of antimony aod pulvis alga-
  roth, 1238 etfeq.  See Tartar and
  Algaittb    Preparation of goldcrj
  fulphur of  antimony and licrmes
  mineral,  1263  Diaphoretic  anti-
  mony,   1:64   Crocus   metallo-
  rum,  1265   Batter  of,  Mr  Dol-
  fus's method of prepariiie:  it, 8ar.
Antip^tef>[;:'..irn :  their abfurd  way  of
  explaining the explofion of fulmi-
  nating filver, 1144.
Ants yield  an acid  by  diftillation  or
  infufion in water, 2d  907   Its na-
  ture aud properties,  yc8.
Ants, acid  of, compiles an  ammo-
  niacal  liquor  with volatile alkali
  which cannot be reduced  to a dry
  fait, 908  Cryftallizes  with fixed
  alkalies, ib   And with coral chalk
  or quicklime,  ib    Diffolves  cal-
  cined  copper,  and forms beautiful
  cryftals with it, ib  Makes a pe-
  culiar  kind of faccharum faturni
  with minuni,  ib    lt  effeds  on
  other  nietan, ib   Different  me-
  thods  of  procuring  their  acid,
  13 j*   Properties of the pure acid,
  1303    Has an affinity  with the
  acetous,  1504  Its effeds on me-
  tals, 1305.
J/.i/.j, their  acid treated of,  1306
  Its properties,  1509, 1311   How
  procured  in  ptrfed  purity,  Ijt*
  Pioe'iKed from fu;;ar by means of
  nitrous acid, 1312 Mr Keir's  opi-
  nion concerning its  nature,. 1514.
Aquafortis,  procured by mctfnf of ar-
  fenic ofa blue colour, 739.
Aqua-regia,  beft kind of it for diffol-
  ving gold, 481   Quantity of gold
  taken up  by  it, 482   How  pre-
  pared from nitrous  acid and com-
  mon fait, 788   Of the folution of
  gold in  aqua regia,  1099  Solu-
  tion  of piatina in an  aqua-regia
  con pofed of nitrous  and marine a-
  cieL,  1322   In one  made  with
  r.nriue acid and nitre, 1324   Va-
  t\>>\h   methods  of  preparing   it,
  1488   Differences between the  li-
  quors prepared by thefe methods,
  1489   How  to  deprive  it of  its
  volatility, 1548.
A nuLi alba, a name for mercurius dul-
  cis, 814.
Arabians, the firft broachers of akha-
  my, 10.
Arbtr Diana, how made,' 734.
Ardent fpirits, diffolved  camphor  iu
  great quantity, 1425.
Argand'% Umps, ufed for  lamp-furna-
  ces 611    Doubtful  whether  they
  be preferable for this purpofe to
  Lewis's or not, ib.
Argentine ftoivers , formed of regulUS
  of antimony, 1253.
/♦>.  !ijo'r.-:-i  earth, in what it differs
  fiom  the calcareous, 512   Tobac-
  co-pipe  clay the  purcit  earth of
  this kind, ib.  Abforb colours,  ib.
  Refift  the  utmoft violence of fire
  by themfelves, but melt by a mix-
  ture with chalk, ib.  Combina-
  tion of the argillaceous earth  with
  vitriolic  acid, 637, &c.  See .•;//.,*. 
Index.

Argonauts,  origin  of  the  fable  of
  them, 9.
Arfenic:  Of" its diffolution and preci-
  pitation, 243, 368  Calculation  of
  the quantity of phlogifton contain-
  ed in regulus of arfenic, 318   Pre-
  cipitated by bifmuth from the ni-
  trous  acid, 369   And by copper
  from  the  marine, 370  Quantity
  of vitriolic acid taken up by regu-
  lus  of arfenic,  302   Of nitrous
  acid, 303   Of marine acid,  304
  Compound of  a  particular  kind
  of acid and phlogifton,' 348   U-
  nitts with fulphur, ib.  Is foluble
  in water, ib.  Expels the acid of
  nitre,  ib.  Reafon of this decom-
  pofition, ib.   Phenomena  on  dif-
  tillation with the vitriolic   acid,
  711   Dephlogifticated by the ni-
  trous acid,  770   Of  the adultera-
  tion of corrofive fublimate by ar-
  fenic,  818   Oil an J  butter of ar-
  fenic,  823   Formed  by fubliming
  arfenic with corrofive fublimate,
  ib.  Of the arfenical acid, 916, et
  feq.   See Arfenic, acid of.  A fingle
  grain  of regulus of arfenic  deftroys
  the  malleability  of  an ounce  of
  gold,  1093  Has a great affinity
  with tin,  1219   Methods of fe-
  parating arfenic from tin,   1220
  The  crackling noife of  tin  in
  bending fuppofed to arife from ar-
  fenic,   1221   Arfenic found  in
  fome places of Germany in a me-
  talli<  form,  1266   The regulus
  eafily.^fcnvertible into  common
  white arfenic by diffipating part of
  its phlogifton,  1267   Wrhy the ar-
  fenical calx may  be  mixed  with
  other  metals which will unite with
  it in its reguline ftate,  1268  Of
  the  folution of the calx  in water,
  1269   In  fpirit  of  wine,   1270
  Forms a very  infoluble  and  fixed
  fait  with vitriolic  acid, 1271  Dif-
  folves in large quantity in the ma-
  rine acid and forms a more  vola-
  tile  fait with it, though  difficultly
  foluble in  water, 12; 2   Refcm-
  blancc ofthis folution to butter of
  arfenic, ib.  Phlogifticated alkali
  precipitates'arfenic from  marine a-
  rid,  and from that only, 1273  Ar-
  fenic decompofed  by  dephlogifti-
  cated marine  acid  1274  Pheno-
  mena  exhibited by  it with other
  acids,  1275   Liver  of  arfenic
  formed by  combining  it  with fix-
  ed alkali,   1276  Arfenic  unites
  with fome  metals, and cryftallizes
  with iron and zinc, 1277  Unites
  readily with fulphur,  1278. Com-
  pounds thence refulting,  ib. 1279
  Phenomena exhibited by minera-
  lized  arfenic  with  nitre, 1280
  Butter of arfenic, 1281  This  fub-
  ftance can fcarce be made to unite
  with marine  acid, 1282   Of the
  oil of arfenic, 1283  Ofthe mine-
  ralization of  arfenic  by  fulphur,
  1284  How to prepare pure regu-
  lus of arfenic, 1283   A native re-
  gulus- called  mfpicket, 1286  This
C    H    E    M     I    S    T    R    Y.
  contains a large quantity of iron,
  which  will  not obey  the mag-
  net till the regulus is diflipated, ib.
  Great volatility ofthe reguline ar-
  fenic, 1287   It  deftroys the mal-
  leability of  the metals with which
  it unites, 1288 Maybe expelled by
  heat  from of  all them except pla-
  tina,  1289  Volatilizes all of them
  except platina, ib. Effeds of arfenic
  upon alkaline  falts and nitre, 1290
  Decompofes   corrofive  fublimate
  1291   The regulus converted  in-
  to white arfenic by vitriolic acid,
  1292  Effeds of it on metallic fo-
  lutions, 1293   Platina  may  be
  melted by means of arfenic, 1349
  Effeds of it on manganefe in con-
  jundion with nitre, 1391  Phe-
  nomena on diftillation with man-
  ganefe, 1393.
irfenic,  acid of, firft  difcovered by
  Mr  Scheele,  916  Two methods
  of procuring  it, 917   By means
  of nitrous acid, 918   By  dephlo-
  gifticated fpirit of fait, 919  This
  acid  equally  poifonous with  the
  white  calx, 920  Eafily  refumes
  its phlogifton,  921   Takes  fire
  and  fublimes  inftantaneoufly into
  regulus with  charcoal,  922   Be-
  comes black and  thick with oil of
  turpentine, 923   With  fulphur,
  924  Cryftallizes- into a  neutral
  fait  with  vegetable  alkali,  923
  This fait decompofed and forms a
  regulus with  charcoal, 926 Forms
  a cryftallizable fait when perfectly
  faturated with mineral alkali,  but
  requires an excefs of acid to make
  it cryftallize with the vegetable al-
  kali,  927  Forms likewife  a cry-
  ftallizable fait  with  the volatile
  alkali,  928   Expels the  vitriolic
  acid  from  vitriolated tartar and
  Glauber's fait, 929   And likewife
  thofe of  nitre  and  common fait,
  930,  931 Phenomena on diftilling
  it  with fal-animoniac,  932  De-
  compofes fpathum pondcrofum and
  gypfum : but  cannot expel the flueff
  aeid, 933, 934  Precipitates lime-
  water,  933   Forms a cryflalline
  fait with chalk, 936  But refufes
  to cryftallize  with magnefia, 937
  Or with earth of alum, 938  Does
  not diffolve white clay, 939   Dif-
  folves terra ponderofa, 940  Has
  no effed on gold or platina, 941,
  942  Diffolves  filver  in the dry
  way by a violent heat, 943  Fixes
  quickfilver,  944   Produces  cor-
  rofive  fublimate by  diftillation
  with  mercurius  dulcis,  945   No
  butter of arfenic  obtained by this
  procefs, 946   Diffolves copper, 947
  Forms a very  thick  gelatinous fo-
  lution of iron, 948  Diffolves lead
  in the dry way, 949. And likewife
  tin, 930 Diffolves zinc with effer-
  vefcence, 941   But cannot diffolve
  bifmuth, 932   Nor regulus of an-
  timony, 953   Diffolves cobalt par-
  tially, 934  But not  nickel, 933
  Diffolves a fmall quantity of man-
  ganefe, 936  Converts regulus of
  arfenic into the  white  arfenical
  calx,  937   Strange  phenomena
  from it  and  the  acttous  acid,
  2d 937, 1521  M. Pelletier's me-
  thod of procuring the acid of arfe-
  nic,   1496   Differences  concern-
  ing the weight of the acid fo pro-
  cured, ib.
Afhes   of  different   vegetables,   Dr
  Gmelin's  account of their colours,
  &c.  1089.
Attraction; Fire detained  in bodies
  partly by it, and  partly  by  the
  preffure of the furrounding fluid,
  <;$   of chemical  attradion,  162
  This kind  of  attradion  not  e-
  qually ftrong between  all bodies,
  ib   Different degrees of it betwixt
  the  different acids  and  alkalies,
  174   Attradion of phlogifton fup-
  pofed to be the caufe of caufticity,
  219   Kirwan's definition of che-
  mical  attradion, 260   Difference
  betwixt  it  and   cohefion,   261
  Geoffroy's rule  for  determining
  the degrees, of chemical  attradion,
  262   True method of afcertr.ining
  the quantity of attradion each of
  the acids has for the different ba-
  fes,  263   This quantity expreffed
  by that of the  bafes taken up  by
  the different  acids, 269.  Attrac-
  tion  of metallic calces  to  phlogi-
  fton  determined, 326.
Attracli-ue poivers of different fubftan.
  ces beft expreffed by numbers,  264
  Difficulties in determining the  at>
  tradive powers of  the  different
  acids to metallic fubftances,  296.
Aurum fulminans, its nature and pro-
  perties, 1103   Was known in the
  13th century,  1104  The firft di-
  redions for its preparation given
  by  Bafil Valentine,  1103   The
  ufe of volatile alkali  for this pur-
  pofe but lately known, 1106  Dif-
  ferent accounts of  the increafe of
•  weight in the metal by  being con-
  verted into aurum  fulminans, 1107
  Explodes  with  incredible  force,
  1108  Twenty grains of it more
  than equivalent to half  a pound of
  gun-powder, ib. Does ne>t explode
  in clofe veffels,  1109  The utmoft
  caution neceffary  in managing it
  in the open air, ib, Dr Lewis's ac-
  count  of the  heat  neceffary to
  make it explode,  1110   Explodes
  by fridion fcarce fufficient to occa-
  fion   any   heat,  1111   Tetrible
  accidents  occafioned by it, 1112
  The force of the explofion dired-
  ed equally every way, 1113 Parti-
  culars relating to the. explofion, ib.
  Will not  explode  when moift,
'  1114  Quantity of elaftic vapour
  produced during the explofion, ib.
  Caufe of the explofion  attributed
  to a faline principle, inj   This
  opinion fhown to be erroneous  by
  Mr tiergman, 1116  Why the ful-
  minating property  is deftroyed  by
  trituration  with fixed alkali,   ib.
  The  explofion  rendered more vio-
                               251

   lent by boiling with  fixed alkali,
   ib.  Why the fulminating proper-
   ty is deftroyed by boiling with too
   ftrong a folution of alkali, or with
   concentrated  vitriolic   acid,  ib.
   Neither  the prefence  of nitrous
   or marine acids neceffary  for  the
   produdion of  fulminating  gold,
   1117 The explofion is not occafion-
   ed by fixed air, 1118  How thefui-
   minatingcalxmaybe prepared,ni9
   The  calx moft   readily  thrown
   down by volatile alkali,ib. A ful-
   minating calx produced from folu-
   tion of gold  in  dephlogifticated
   fpirit of fait, ib.   Mr  Bergman's
   theory of the caufe of the  explo-
   fion,  1120  Volatile  alkali  the
   true caufe  of  it  1121   Great
   quantity of elaftic fluid  generated
   by the explofion of aurum fulmi-
   nans, 1123  Why a flight calcina-
   tion deftroys the fulminating  pro-
   perty,  1124   Why  the  calx  will
   not explode in clofe veffels,i 123.
Aurum Mofaic:.-?:, or Mufivum, llOW
   prepared,  1224.
Bacon (Lord), his  opinion of heat
   28, 29.   See Verulam.
Baldwin s phofphorus  prepared  from
   folution of calcareous earth in fpi- -
   rit of nitre, 749.
Balneum arena,  or fand-bath, defcri-
   bed, 378.
Balfmams  of fulphur,  how prepared
   1401  Vegetable  balfams whence
   procured, 1432  May be confider-
   ed as effential oils thickened by the
   diffipation of fome of their more
   volatile parts, ib.  Analyfis of them
   exemplified in turpentine, 143 7.
Barofelen.'u,  a name  for the marmor
   metallicum,  or  combination  of
   terra ponderofa with vitriolic a-
   cid,  1030.
Baft  Valentine,  the firft  who gave
   diredions  for the  preparation of
   aurum fulminans,  1103.
Beaume's  obfervations  on   gypfum
   636  His account of the  forma-
   tion of  fedative  fait ill-founded
   862.  Vitrifies a calx of  platina
   *35»
Beccaria's obfsrvatioos on  phofpho-
   ri,  1083.
Bell-metal,  compofed of  copper and
   tin, 1133 Its fpecific gravity great-
   er  than that of either of the me-
   tals fingly, 113 6.
Belloivs, when to be ufed in chemical
   operations, 608.
Belts: Reaumur's hint concerning an
   improvement in their fhape, ian.
Btnzoin, yields  fragrant acid fait by
   fublimation, 984 The fame obtain-
   ed by lixiviation, 983 Quantity ob-
   tained by both  thefe methods, 986
   Mr Scheele's experiments in order
   to procure all the flowers benzoin
   is capable of yielding,  987,  &c.
   Boiling  with  chalk   infufficient,
   988   Or with alkaline  ley,  989.
   Boiling with lime the beft method,
   990  Scheele's receipt for  for prepa-
   ring the sivwera of benzoin by this
                            Ea«itkwd 
CUE    M    I    S    T     R    V
  i rthud,  «m    Thr   fliTonr  of
  • .rfc floi   •  deftroyed ;>n I rtprc-
  . u ed at j ie jlure.  9yi   1 hi  join
  *   lizcd, 1439  Ai'd of, in\elll-
  gatcd by  Mr  LLr-.tcnftcii',  i.'jO
  1  fcdU  of nitrous acul  iq on  it,
  153I   PiocurJde from  Peruvian
  li'lim and Irem urit:e, 1332.
K ','»j.^'i accfunt of  thr  caufe of
  chcniicil folut.cn,  193 Pifferencn
  l> tween him and K.rwan acvount-
Llcfls of acidof  irfmic upon it,
032   L  convertible rito lithuge
»r\l   glafs,   1: < >   (>  cupir- lefs
fpace when in fufion than wl.cn in
a folid  ftate,  ib.   Mifcible with
all the nu uilic fubftances except eo-
1 alt  atid "'lie, 123 1 Pr«motc-.thc
l-jfion cl all the metal** with wh,ich
it is  mixed,  ib.    Platina may be
alloyed with  it, but without any
advantage, 1348.
cJ for, 433   Ms method of find- Bittern, mkind-rf fait prepared from
                                   it, frequently fupcrlcdcs the ufe of
                                   the true dauber's fait, 632  How
                                   to procure the marine acid from it,
                                   736.
                                   ,' vrens particularly treated of, I44I
                                    V.'hether they  are of a vegetable
                                   or mineral oii<;in. ib.   Macqucr's
                                   opinion  that  tiuy  are only vege-
  ing the [rop<irtion of ingredients
  in alum, 641 I':«  aee>unt  ot  the
  e  antity ' 1 toil, ingredients, O46
  It »accoi...t cf the Swe .ifh ores of
  • :um, 631.  His  analyfis of  the  h
  rrc-at'lolfa in Italy,  637   His
  direction.  I r tfie pceparat-.-.n ol a-
  lum, 661    His  remarks uti  w.o
  piper form of tiic  cooler* for a-
  lam,  ( ■ >•   Conliders  the hpis
  j-ond rolus or :;r r ften as a metal-
  l,c i-rth,  907  lis  opinion con*
  ci ruing the acid,  of  tungften  and
  nulylxkina, 97*   Denies the  1>>-
  lubility « f fihccoui earth in acids,
  ioyb  Form* cry.fals of flint arti-
  ficially,  IQJ2   Shows  the error
  ui  1 hole  who imagine  the  explo-
  fion of aurum  fulminans to be <-c-
  cilii  red by a faline \ linciple, 1116
  I ii-theory of the explofion, 1110
  H * opinion concerning the fulmi-
  natioti cf other cakef,  1126  His
  ■ >pi:.ion concerning  the compofi-
  tion  of nickel, 1316  His experi-
  ment- on  platina,  1321   Letter
  to Muivcau  on the  ii.bjrct of a
  new nomenclature, 1339.
Mtrkts.hout'% opinion of heiu, 36  His
  divifion of it into  fixed and vola-
  tile ,  37.   See  Heat.
Berthollet  difcovers  fulminating  fil-
  ver, 1138  Procure- the  marine
  acid in a folid ft^te, 783  His  new
  fait refembling nitre, 2d 793 How
  to  procure this fait in quantity,
   1487.
>' ■ .-kerf's  tindurc  of  iron,  ad 808
  Miftakrs of chemifts concerning it,
  3d 8c8 True method of preparing
  it, 4th 8c3  Sip pofed  to  abforb
  phlogiflon froi.i   the  fun's ray*,
  51ii  ig8.
Bile:  fome  of  its properties affumed
  by bio.»d when mixed with the ni-
  trous aciJ, 1477-
^ifimmts ■■  Of  it*  precipitation from
  aci I-,  241*  Copper and bifinuth
  prcc jiitatie one another alternat.f
  l;,im  the nitrnux acid,  337   is
  1 arrcly foluble iu vitriolic acid,
  4.'..  Increafes  the faGbility of tin
  au.i lead. 343  A compounlof th:s
  ib.    How  rendered   luminous,
  kSi   .scems to  be ofagvpicous
  n.itirc, ic8i, 10 S3    onaly!i> of
  it, and reafon of its fhining in the
  d.rk, ib.
Borax, compofed of  a pcculir.r  kind
  of acid and minc'^l  alkali,   863
  How prepared in  the  Fall Indies,
  ib.    Of its ftate  when  firft  im-
  port, ci  from the:;ce,  864   H w
  rcSned, ib.  Said  to  be adultera-
  ted during this operation, ib.  This
  denied  by Dr Black,  ib.   Simple
  diffolution and filtration all that is
  neceffary, according to him, for the
  purification, ib.  Its purification ac-
  cording to others,  1490  Has a glu-
  tinous ip-'lity, by  which it gives a
  glofs to lilk, ib.  Its properties with
  acids and various falts, 863.
refin*- altered, ib.  Dr Lewis's Borax,acid of, found in a kind of mi-
ifci
of a  contrary
           for btin
  opinion,  ib.
Bia k, Doctor, his theory of heat, 25
  Experiment? by which he was led
  to the difcovery of latent heat, 41
  Hi*  method  of  calculating  the
  quantity  of heat  produced by tho
  condenfation of vapour,  44   Dif-
  ference  betwixt   his  calculations
  and  thofe of Dr  Ciawf.ird,  31
  Expanfive force of water in free-
  zing explaine d by Dr Black's theo-
  ry of latent heat, 108   His expe-
  riments on the conveihoiiof  wa-
  ter into  vapour,  121  His  obfer-
  vations on  chemical veffe!-,  337
  I iis  direction- for performing the
  operation  of  folution, 363    Dc-
  lcuption of his portable  furnace,
  ad 602  Ii->vc it is adapted to 'he
  various  opciations  of  chemiflry,
  603   Of the  Ir.ting proper for the
  infide  of this  furnace, 604   Me-
  thod of  applying  the  lute,  Cos
  Hi  account of the preparation of  B
  nit'.-,  7:4  His conclufions  con-
  cerning  the  nature of  that  fult,
neral in Germany, 838  Procured
from the fait either by fublimation
or cryftallization,  83 8   Is fixed in
the  fire, and melts into a kind of
                       Index.

  rial for fpcculurm, T344.
F.ming: phenomena of it, 516.  A
  great quantity of water  produced
  from oil by burning, ib.  Part of
  this  probably  from  the| atmof-
  j! ere, ib.
I-i-tier of  antimony compofed of re-
  gulus of antimony and  marine a-
  cid, 821   Becomes fluid by recti-
  fication or expofure to the air,  ib.
  Lets fall the pulvis algaroth by the
  dired affufion of water, ib.   For-
  merly ufed as  a  eaullic, ib.   M.
  Dollfuf.'s  mthod  of  preparing it,
  ib.
Butter of arfenic, prepared  from re-
  gulus of arfenic and  corrofive fub-
  limate,  823   laconic* fluid by re-
  peated  rcdifications, ib.   Is  not
  obtained from white arfenic  and
  couofive  fublimed together,  946
  W'..)  be prepared alfo by fubliming
  oij ii..cut  and corioiivc fublimate,
  1281   Can  fcarcely  be made to
  unite with marine acid, 1282.
glafs by a violent heat, 860  Dif-  Cai>hac.e, an excelici.t teft for acids
folves in fpirit of wine, ib.  Makes
no  change on the colour of  vege-
table  juices, ib.   Mr Bourdcl;n\
experiments  on  its  nature,  861
Mr Cadet's experiments, 862   M
Beaume's opinion that it 1.- produ-
ced  by rancid oils unfatisfae^ory,
ib.   CI  its combination wich  d-
halies  ib.  Forms an unknown fait
with  vegetable  ulkili, ib.    And
borax with the mineral alkali, 863
Its  effeds  on cobalt, ip.3   B.au-
nic's  obfervation? on  the method
of preparing the fedative fait  from
it,  1491   Properties  of the  fait,
I4V2   Its combinations with vo-
latile alkali, earths, and metals, ib.
F-xpcrinunt-. with a view to deter-
mine the nature of the acid, 1493.
:v./...-,  M.  with  Geoffroy,  difco-
vci- the component parts of  alum,
641
lis  method  of making ni- Boullangcr't  opinion  that  the  fluor
  trous ether,  773   Shows  a  me-
  thod  of  making it  without  any
  fpirit of  wim, 777.
Black lead,  a valuable  material   for
  hme ck.mical ^ff-U, 362.
B.!... hing, how performed by  mms
  of  dephiegillicated  fpirit of  L It,
  14^4.
Blood,  ftrangely altered  in its  pro-
  perties by mixture  with  nitrous
  acid,  1477.
B.eth.-ax-e'i experiments to produce a
  change on incr.i.iY by  keeping it
  long  in  a ' entie h.at, and by ;e-
  peated diftillations,  w.thout  fuc-
                                    cefs, 12:9. 1230.
kind luable  in  boiling water,  344 Bohemia:  Bergman's account of the
Diffolved in great quantities by ni-    aluninous ores inthatceuntry,638.
irou* acid,  -05  Volatile alkalies, Bc'ii ;g paint  of  w.tcr  in .vacuo de-
ai\cr pre:ipitjring the metal, take    tcrmined by Mr Boyle, 122  And
.•  up again, ib  The faint thing    by Mr Robinfon <« Ghfgow,  i»j
happons with  fixed alkalies calci-  2L.'. .- camphor iodki tedintoancflen- Brafs  bow   prepared
ni with-inflammable matter, ib.    tialoil by diftdlaton with it, 1423.   and calamine,  1134
Magiftery of bifmuth prepared by  Bolognian fine, a kind of native ph  1-
iddinjf  «-lcr to t':c nitrous folu-    phorus,  icSi    How  firft  Locu-
tion. "66   Neaman'* obferv.  ions    veied,  ib.   7  egr-af's  account
ijiicuniag  i.j*  r-e4 v-tion,  ib.    of  the  a^c; -.  m.v   of  th:: ftone,
  acid is n* other than  the marine
  combined  with   an  earthy  fub-
  ftance, 833   Shown to  be  erro-
  neous by Mr >chec!e, 034.
Bcurdelin's eepcriments on the nature
  of the acid of borax, 861.
Style,  Mr  improves  the  fc-'i.e  of
  chemiiiry, 17   His opinion  con-
  cerning the  number and nature of
  the  elements, 24    Attempts to
  prove that fire  is not an  element,
  ib.  Thar the folid fubftaBce of bo-
  dies is converted into air,  ib.  That
  Water  is  converted  into earth, ib.
  His arguments  incon>lufive, ib.
  His account of the produdion of
  heat, 30   Determ.nes the boiling
  point of water in vacuo, 122   His
  experiment  fhowing the deftrueii-
  bil.ty of gold, 1098 Curious kinds
  of mereury prepared by him, 1227.
                      from  copper
                        May be re-
  duced fo co; per  again by  a long
  continued and violet t h at diflipa-
  ting the  zinc, ib.   A compound of
  y«»; ai.i platina  a prct^r  rnatc-
  or alkalies prepared from it, 1330,
Ci i.-t'» experiments   c 11  the  nature
  ol the acid of Ik 1. v, 862.
Calcj/eci's  eaitbs   Ik 1,111] ofition  of
  vitriolated tartar by their o oih 1 »
  explained, 270  Mr Kirw; 11's ex-
  periments on them,  437    Form
  gypfum with vitriolic acid,  635
  Diffolve in the nitrous acid into an
  acrid liquor  which cannot. I"-' cry-
  ftallized,  747   D.c. nrpofes  .iiis
  acid by frequent diftiilatiwns,  7.54
  Are convertible by it Into  a k.od
  of phofphorus,  749   Form  like-
  wife a phofphorus with the n.;.r;oe
  acid, 797   Their  effeds on the
  folution  of lil ver,  76   form a-
  ftringent  compounds  with the ace-
  tous acid, 871   Decompofe cream
  of  tartar, 807   Have a great  at-
  tradion  for  faccharinc  acid, 900
  Compofe  fluor fpar by being com-
  bined with  its  acid,  831    And
  tungften  with the acid  extraded
  from it,  971.
Calces  of metals;  arguments againft
  the  exiftence of  phlogifton  from
  the  redudion of thofe of the per-
  fed metals without addition, 14Q
   Redudion of metallic calces by  in-
  flammable air, 149  Different  co-
  lours  exhibited  by   them,  192
  Thofe of fome metals, when pre-
  pared by nitrous acid, almoft  to-
  tally infoluble ever afterward--, 1,6
   Why little  or  no elaftic fluid ii
  produced from them, 213  Ot their
   attraction to phlogifton, 326  How
   to find the  fpecific gravity of  the
   different   metallic   calces,   32-
   Whence  their  various  degreck of
   affinity to phlogifton may be  de-
   termined, 328  Calces of  copper
   precipitate  dephloetfticated  folu-
   tions of iron, 343  Solutions of the
   dephlogifticated calces of iron re-
   fufe to  cryftallizu,  457   Cahei
   of iron prccipit ited ofa reddifh co-
   lour from fpirit of fait, 463   Cal-
   ces of ^old  loluble in  the  vitriolic
                                 and 
 Index.

  and nitrous acids, 483   Reafon of
  the increafe of weight in metalline
  calces, 3^4   Bergman's  opinion
 - concerning the fulmination of me-
  tallic calces, 1126  Erroneotis,  ib.
  F.ffeds of  the  colouring matter of
  Pruffian  blue  on  metallic calces,
  1192.
Calcination:   quantity  of phlogifton
  loft by metals during that opera-
  tion, 331   Of the  affinity of their
  calces to   the  deficient part, 332
  Calcination of metals by  fire de-
  fcribed, 52a  Of their calcination
  and increafe  of weight by acids,
  323   Reafon of this increafe, 324
  Solubility of metals increafed  by
  calcination, 343  How to  perform
  the operation  of calcination, 383
  Why a flight  calcination  deftroys
  the explofive  property  of aurum
  fulminans, 1124   Effeds of vio-
  lent calcination on nickel,  1307.
 Calcined metals.  See  Calcination, Cal-
  ces, Calx, and Metal.
 Galculus, human ; Scheele's   experi-
  ments on it,  1433   His  conclu-
  fions  concerning  its compofition,
 "1436  Is  found univerfally in  u-
  rine.  1473    Bergman's   experi-
  ments on it,  1460.   Calcareous
  earth contained in  it feparated  by
  means of  the vitriolic  acid,  1462
  Red colour of the folution in ni-
  trous  acid accounted  for,   1462
  Mr 'Higgin's  experiments,   1460
  His account of its component parts,
  1,463, 1468   Experiments on the
  fublimate arifing from it on diftil-
  lation, 1465   Experiments  with
  nitrous acid,  1466   Cryftalliza-
  tion of the nitrous folution by ex-
  pofure to  the fun,  1467  Remarks
  on the remedies proper for diffol-
  ving the  ftone,  1469  Sublimate
  of calculus met with in confump-
  tive and gouty perfons, 1470  Dif-
  foljition ought not to be attempted
  when the ftone is large, ib.
Calculus : of the acid obtained from it,
  982   All  the calculi produced  in
  the human body of the fame na-
  ture, ib    Diffolved by concentra-
  ted vitriolic,  and  by the nitrous
  acid, but  not by the marine acid,
  ib   The acid of calculus produces
  deep red  fpots on the  fkin, 983
  Affumes a blood-red colour by eva-
  poration,  ib.
Calomel, a name given  to mercurius
  dulcis feveral times fublimed, 814
  Repeated  fublimation no improve-
  ment on the medicine, ib
Calx of the diffolved metal, with va-
  rious degrees of phlogifton,  con-
  tained in metalline  folutions,  214
  Reafons for believing that  metals
  are reduced to  a  calx by folution,
  215   Increafe of  attradion be-
  twixt  the  calx of iron and phlogi-
  fton demonftrated, 342   Calx  of
  iron foluble in lixivium fanguinis,
  1175  Put not when highly de-
  phlogifticated,  1176
Camphor, a.voknilc fubftance  belong-
  ing  to the clafs of effetticl  oils,
         C     II     E    M

   I422  Converted into a true effen-
   tial oil by repeatedly duelling it
   with bole,i423. Intoan acidfalt by
   diftilling it feveral times  with de-
   phlogiilicated fpirit of nitre, 1424
   Effects of this fait on alkalies and
   metals, ib  How diftinguifhed from
   acid of fugar, ib  Account of the
   method  of extrading it  from the
   trees which produce  it,  its  ufes,
   &c. ib.
 Canton's phofphorus,  how prepared,
   1414  Becomes luminous by  ex-
   pofure to the  fun, or the light of
   an eledrical flafh, ib.
 Capacities  of  bodies  for  containing
   heat :  that phrafe explained, 32
   How they are to be  diftinguifhed
   from the temperature' and abfolute
   heat of bodies,  '3   The  capacity
   of a body for containing  heat  the
   fame with the  adion of heat on
   the body, in  Nicholfon'saccount
   of the capacities of bodies for con-
   taining heat, 113.
 Caf-iron  fcarcely decompofes the fo-
   lution of copper, 343.
 Cavallo's method of purifying ether,
   2d  722   Shows that pyrophorus
   is not injured by expofure to light,
   1418.
 Cavendifh, fuppofes heat not to be a
   diftind fubftance, 69   His calcu-
   lation of the quautity of  fixed air
   contained in impure vegetable fix-
   ed alkalies, 417   Shows  that  ni-
   trous acid may be artificially pro-
   duced 'from a mixture of dephlo-
   gifticated  and phlogifticated air,
   2d 722   His opinion concerning
   the nitrous acid, 1474.
 Cauftic alkali,  how  prepared by Mr
   Bergman  for  his  experiments on
   the precipitation  of  metals,  232
   Platina imperfedly precipitated by
   cauftic alkali,  234  Throws down
   a brown precipitate from folution
   of  filver,  233   Corrodes  ftone-
   ware, 393  [396]   Is beft refilled
   by filver,  ib  How to prepare lu-
   nar cauftic, 752   Spirit  of wine
   converted into vinegar and water
   by  repeated diftillations with cau-
   ftic alkali,  1013   The  common
   fixed alkalies compofed of  a cauftic
   fait and fixed  air, IC20   Throws
   down an infoluble precipitate, from
   folution of terra ponderofa, 1036.
 Caufticity  fuppofed to be  occafioned
   by the attradion  of  phlogiflon
   from the fubftance aded upon, 219.
 Catui, a kind of fpar, the fame with
   fpathum ponderofum, forms a re-
   gului of antimony inftantaneoufly,
   1236  Dr  Withering's defcription
   of a fubftance of this kind  found In
   Derbyfhire, 1068.
Cerufs, or White-lead, how prepared,
   873  Observations on  the procefs
  for preparing it, 876   Its poifon-
   ous qualities, ib.
Chalk at firft diffolved, and the folu-
   tion afterwards coagulated, by acid
  of arfenic,  936  Flowers  of ben-
  zoin imptrfeelly extruded by boil-
  ing with chalk, 988.
 I    S    T    R    Y.

 Chalybcatcd tartar, made  by boiling
   cream of tartar with iron, ")$.
 Cbtt'dcfers, chemical, explained, 331
   Some curioufly mark'd on  the in-
   fide of a phial by means of the light
   of the fun-, 736.
 Cbarcit proved  to be the fame with
   phlogifton, 143    Decifive  proofs
   of their identity from  Dr  i'licct-
   ley's experiments, 146   Spirit  of
   wine convertible into charcoal, 147
   Charcoal entirely  diflipated  into
   inflammable air  by the heat of  a
   burning lens  in vacuo, 148  De-
   phlogifticated  air ,converted into
   aerial acid by its union  vviih char-
   coal, 131   Sulphur produced  by
   diftilling concentrated  vitriolic  a-
   cid  with charcoal, 713    Or  by
   Calcining vitriolated  tartar with
   the   fame,  716    Arfenical acid
   takes fire and fublimes into regulus
   with it,  922   Neutral  aricuical
   fait decompofed by it, 926  Char-
   coal diffolved by  liver  of fulphur,
   1023   Phenomena on  diftillation
   with manganefe, 1388   Moft in-
   flammable matters reduced to char-
   coal,   1430   Difference  between
   the coals of different fubftances, ib
   Some coals, particularly  thofe of
   animal  fubftances, can fcirce be
   reduced to afhes,  ib   i.'ullock's
   blood affords a coal of this kind,
   ib   Concrete  oily fubftances,  or
   foot,  burn  with equal difficulty,'
   ib  Some of thefe coals almoft re-
   fift the adion of nitre, ib   This
  fubftance perfedly refradory, 1431
   How let on fire by the nitrous acid,
   1476.
Chemical attraclion particularly treated
  of, 162, etfeq. See AtlraSlion. Kerg-
  man's account of  the caufe of che-
  mical  folution,  193   Kirwan's
   definition of  chemical  attradion,
   260   Difference  betwixt it and
   cohefion, 261   Geoffroy's rule for
   determining  the  degrees of che-
  mical attradion,  262   Chemical
  decompofitions apparently  finale
  are often double,  263   Invention
  of chemical marks and  charaders,
  SSI   New chemical language in-
  vented  by the  French chemifts,
  332   Its ridiculous appearance in
  an attempt to explain the fulmina-
  tion of the calx of filver, 1144 Of
  tables of chemical  affinities  or at-
  tradions, S53  Dr Black's  gene-
  ral tahle  of attradions,  ib  His
  obfervations on chemical veffels,
  337   Good and  bad qualities  of
  glafs  as a material for  thefe vef-
  fels,  338   Of  metals,  360  Of
  earthen ware, 361  Of chemical
  furnaces, 399   Set  Furnaces.
Chemiftry defcribsd,  1  High  anti-
  euiity  of the fcience, 2  Suppofed
  to be founded by Siphons, an  Egyp-
  tian,  3   Mofes thought  to  have
  been well verfed  in chemiflry,  4
  Democritus  taught chemiftry by
  the Egyptian  priefts, ib.  Chemi-
  ftry introduced into medic ne after
  hie time, ib.   Some advantages ac-
               I i •
                              *53
   erucd to chemiftry  from  the  la-
   bours of tin:  alcheniiib, 13   Hi-
   lloiy of chemiftry from the tii-ic-
   i-i Paracelfus,  13   The  ffienc;
   ftudied  by  Lord  Verulam,   16
   Improved by  Mr  '3oy!c, 17  Che-
   miftry emerges from its obfeurity,
   18  Receives  confiderable  advan-
   tages  from the founding  of  the
   Royal Society,  and others of that
   kind,  19   Great  improvements
   made  by chemifls, of various  na-
   tions,  20  Perfed theory of che-
   miflry  defined,  21   Objeds  cf
   chemiftry how  diftinguifhed from
   the agents,  22   Claffification  cf
   tbe objeds, 163  How  far water
   is an objed of ehemiftry, 349  Of
   the different o. nations  in chemi-
   ftry, 334, etfeq:
 Chemifts,  improvements  by thofe  of
   different nations, 18, 1^, 20  How
   divided, 333
 Chio tur^s ,.':ne defcribed, IJ 33.
 Cinnabar: of the diftillation of it from
   manganefe, 1396  See Vermilion.
 Clay: whether the earth of alum is
   to  be  confidered as a pure clay or
   not, 647  Margraaf  demon Urates
   all clay to be compounded of earth
   of  alum and fome other principle
   mechanically mixed,  648   Expe-
   riment of Dr Lewis, which fcems
   to  fliow  that   clay undergoes a
   change by being  converted into
   earth  of alum, 649   fergrr.an's
   experiment to determine the utili-
   ty of adding clay to the leyof alum
   in order to abforb the fuperfluous    j
   acid,  68*   Advantages  of ufing    I
   clay rather than alkalies, 683  De-
   phlogifticated  vitriol  decomposed
   by  clay, 684    But  noj: tbe per-
   fed kind, 683   Clay  ufed in the
   purification of  wines,  886   And
   in that of tartar, ib   Combina-
   tion of  arfenical  acid with clay,
   939   Colouring matter  of  Pruf-
   fian blue  cannot  diffolve   clay,
   1189   Method  of  diftilling fpirit    I
  of fait by means of it, 1480.           I
Cleghorn,  Dr.:  great difference  be-
  twixt his calculations and thofe of
   Dr Crawford,  48   Flis  opinion
   concerning the ufe of thermome-   )
   ters, 72   His hypothefis concern-   j
   ing fire, 74  His  proof that fire   j
   is an elementary fluid, 82.           '
C!^th-printing :  iron lie]uor,  how pre-
  pared for thr.t  purpofe, 873.
Chffus ef t,:irc, a  liquor prepared by
  deflagrating  netre   and  charcoai,
   780.
Coating of glaffes-: lute proper for that
  purpofe, 380.
CoLdt: of its diffolution in  acids, and
   precipitation from  them, 244   Is
   not compofed partly  of iron, 236
   is precipitated by iron, 362  Some
   heterogeneous matter precipitated
   from it by nickel, 363   Solutions
   of cobalt Jet fall a white powder
   on the addition of bifmuth or coo-
   per, 7/4  Of  its folution in vitri-
   olic acid, 496, 710  In  nitrous a-
   cid, 497  In  marine  acid,  498 '
  '                          Foims 
-54
  fr.irn* a rtd f iu'i^n with the Ul-
  tras acid, -69   LMcotrt-ahle  in
  rr.1  by meant  of tl.it  acid, 770
  Form*  a beautiful fympathetic ink
  with marine acid, 811  Diffolved
  by tt.r  acid of .olen.c, 934   ihe
  feiuir.ctal pirtiiu'.arly  defcribed,
  *nd iti  properties  confiderr I, 1293
   h'  calx, call'd  z..jfrt,  defcribed,
   12y4   Rech.eh.n of  the  calx ex-
  tremely difficult, Hy6    !:•■ pro-
   | ci tie* wheu c»pofed to heat, 11/;
   CaUin  «.  fpontaneoufly in ti.  air,
   1298  A beautiful blue giai< form-
  ed  1:0-1 it*  calx, 1299  i'i.110-
   mena of it with vitriolic  acid, i.,oO
   With  nitrous acid,  1301    With
   marine acid,   13.1   With  the
   acidof bou\, 13.3  With  -  ..,
   ib.   With  fal  ammoniac,   1.-^4
   W.th  fulphur,  1303  a!  y  be 1 -
   j  r..-ed from uickei by n.trv, 1311
   *'ntiiod of preparing  a  red lalt
   from it by means of the \itriolic
   acid, 710.
 Cshefem:   difference  bctwixt  it and
   chemical attraction, 261.
 1 Id:  an cxcefhvc degree  of it  at
   (.l-if^ow,  62    Iu   Liberia  and
   Hudfon's Bay,  63   Severity  of
   the cold  in  the'northern n;;iuns
   miti.it. J by the  pieJi.clio.i  of
   i e, £7  Heat, light, cold, and
   electricity, the  effects  of an uni-
   \< rl„l  fluid, 1 ■': .  Particular folu-
   tion of the piiei.on.cna of heat and
   cold, icti  In I  i^ > of bodies ex-
   panding by  cold,  IOJ  Cold fup-
   pofed  to be  a  pofitive fubftance
   from the prodigious expanfive force
   of  w-.'.cr in  freezing,  107   Or
   » nilcn's experiments on cold pro-
   due ^ by  evaporation, 124.
 dour of t.t.-allic folutioi.s c.ai'ed by
   pl.h oijfui, 218  A bcautilul white
   one irom had, 703   A green one
   horn  copper  and  cre.un of tar-
   ti, 8;4  How to  reflect the  co-
   lour of gold, 1130  O; filver, 113 7.
 C \.r,if mailer of  Prullu.i blue in-
   veftigated be Mr  Scheele, 1171
   This matter lie  off from the lixi-
   vium  fanguinis when expokd  to
   the air, 1172  This  effect  luppo-
   p> ict  to be owing to fixed  air  in
   Ihe atmofphere, 1173    The  co-
   louring matter fixed by the addi-
   1 .on oi fome green vitriol  to the
   hiiviutti,  1174  Calx of iron  fo-
   luble in tin  lixivium, 1175  Cut
   1., : when highly, dephlogifticrud,
   1176  The colouring  matter ta-
   ke;, up by the air after  it has been
   •ip-'led by  aculs, Ii7"   Effeds
   • 1 diitilmie tne lixivium with  \i-
   triohc  acid,  1178    Attempts  to
   procure the loioiiinic;  matter by
   itfelf,  11-9   Neutral fait formed
   1  y  i; for o.iffovering iron in minc-
   i-l  waters,  1180  Effeds  of di-
   stilling rhe fait with oil of  vitrio!,
   n8r  The colouring  matter u-
   nites  with  volatile  alkali,   Il8;
   How to free it perfectly from any
   vitriolic  uir.:.  1183  To prevent
   its  efcape through the lute  du.r.i:g
CHEMISTRY.
Index.
1184   Thr  colo-ri"g  C»> *'"''■" of its precipitates, aj8  w*r.y C:>- ve fMi-matt precipitated with-
 di".dl..tio:i
 mailer  liei'her  a:.u  r..ir alk. line,
 1185   forms a kind ct ammoiti-
 acal f.It with v,.'stile alkali,  1186
 Dn.olves  r^.iitiia  alba,  1187
 Wry hale  tc;ra ponderofa, 1188
 D.i'olvis lin.e, tut not  clay, 1189
  I his folution m .t proper  for ma-
 king 1 xpcrirrietits  en  iiK'.al., 1190
  Prccip'.utcs the foiations cf filver
 and qoirkfiiverin  nitrous a.id, and
 of  iron in Died air,  1191  It* ef-
 ( ds   n  the  metallic calces,  1192
 On metalhc  folutions,  11 ;>  Its
  conftitjent p. rts  myelinated by
 exper.  r.-.nt,  1194   Is   of  an in-
 flammable  nature,  1193   Suppo-
  ie-i to  contain  aerial  acid  and
  pbiiigifton,  1196  Irgredicnts  in
  iti  compofition,   1199    I'nfuc-
  cefsful  artenipe-- to \ oduce it by
  volatile alhal.rs in a ihp.ii f..tc,
   [lOO    Slieelfsful  t'l  - i od  With
  l-l ammoniac, fait of  tartar, and
  eiiareor.!,  i::i   Its  volatility de-
  ttno.ed by inanganeie,  1204  Can
  feparate  o:.i,  mercury  and filver
  from thuir l^lutiu:. in nitrous aeid,
   1-03.
Colors of vcg.tables changed by a-
  cul-t an 1  alkalies, 173   Different
  colour^  of  r.u:aii c Calces,  192
  Colours imparted to  various kinds
  of ftone-, by folution of filver, 733
   L'uloiiri oi various kind.* deftroyed
  by  dephlo^ lticated  fpirit .of fait,
  1484.
Comparative beat  of bodies defined,

  4°-            t"
Cempofi, arrificijl, oT Cramer for ma-
  king nitre, 728.
Compound* of two metals fometimes
  heavier than either  of  the ingre-
  dients,  1136  More fufible  than
  either  of them fingly, 342  G:e..t
  fulibility of thufe of tin  and bif-
  muth,   543   Fufibility of  thefe
  ..ugnu-ntcd by the addition of lead,
  ib.   One  fufible  in the heat of
  boiling water, 544   Platina unites
  readily  with compound  metals,
  J 3 4 3 -
Concenttated acids  phlogifticated  by
  alkalies,  409   Concentrated ni-
  trous acid diffolves lefs  metal than
  when  diluted, 489  How to ob-
  tain a very  concentrated  acetous
  acid, 881  Violent  adion of the
  concentrated  nitrous  acid  upon
  molybdxna,  960   Murmer me-
  tallicum foluble  in  concentrated
  vitriolic  acid, 1063   Precipitated
  from  it  unchanged  by  vegetable
  fixed   alkali,  1064   Why  the
  Concentrated  vitriolic  acid  dif-
  folves manganefe  without addition,
   17,78.
CorJenfation  of vapour  produces  a
  great  quantity of heat,  43,  123
  Dr Black's method  of  calculating
  it, 44.
Congealed '.later, the difficulty  with
  which  it melts,  a mean  of pre-
  venting  inLind^ti'.n- in countries
  where   fuow  and   ice  abounds,
it is f.ill'olved by folutions ot filver,
1-.rr.-.iry  ..:iJ  he n,  336    Why
iron and  copper  precipitate  one
another,  341    DcrhLghticatrd
lolutions  of iron  precptcted by
calces cf  copper,  1,43   Lephlogi-
*  icat < the iton \\hich tree pitatcs
it,  7,44   lt< folution  lca;\Jy de-
ci :m-olcd by caft iron, 343   Why
it  feme times  cannot  precipitate
filver, 34S  I re epilations  of mer-
cury J»y it, 333  Precipitations  of
copper  by  nickel, 360   t opper
throwsdjwn a white  powder firm
folutions of cobah,  304  Forms a
triple fait with regulus of antimo-
ny  and  irarine acid,  367   Preci-
pitates regulus of arfenic from the
marine  acid,  370
it diffolved by the
464    Inflammable  ard  vitriolic C>
air produced  from  Us folution in
this  acid, 463   Quantity  of the
u.etal  diffolved by nitrous  acid,
468   l>y marine acid, 469  Forms
blue  vitriol with the vitriolic  aeid,
6y ;   Of its  folution in nitrous a-
ck1, 757   In  the marine  acid, 804
Forr.v. a beautiful green fait  with
acetous  acid,  872   And  \v.th
cream of tartar, 894  Combina-
tion  of arfenical acid with  it,  947
Forms a moft  beautiful blue' fait
with  cauftic  volatile alkali,  1033
Die's not greatly diminifh the duc-
                out  any decompofition  by oil of
                vittioliij  May be decompofed
                by filver in the dry, hut not in the
                moilt  way, 3^6  Of its prepara-
                tion from quickfilver, 814, <•//?.
                Differences of its quality according
                to the different methods by which
                it is pie|  red,  816   Reafon of
                t!ufe i!iti  rences.  ib.  Method of
                making it  at AnilWrdam, ib.   Ob-
                fervations on the diffcre:it method-,
                l 1 -  Of  its adulteration with ar-
                fenic,  818  Yields no  butter of
                arfenic by  fublimation  with  that
                fubftance,  943, 946   Its ufe in the
                prepartion of butter of  antimony,
                821   Of   its   fublimation   with
                manganefe, 1397.
     rt.on  of  Cramer'i artificial  compoft for  ma-
v.tn !ie acid,    kitpj nitre, 728.
i.:/cd, Dr, his explanation of Ir-
vine's  theory  of beat, 36   Dif-
fers pTeatly in his calculations from
Dr cleghorn, 4S  His accounts of
hufible  heat,  49   Diffeis  from
Dr  i>h.ck, 51   His opinion  con-
cerning heat in the abftrad, 34,
His  definition  of  fire,  39   His
method  of  determining the pro-
portional quaiituic >  of  heat   in
bodits,   77   It luflicieBcy of  his
method,   7"   His folution  of a
difficulty  concerning the fectning
difappearancc of hc.t,  86  Infuf-
ficient, 91.
tility  of gold  though  previoufly Cream of tartar, how prepared, 886
alloyed with tin,  1094  Its nature   Analyfed  by  Mr  Scheele,  887
particularly confidered,  1146   Al-   Regenerated, 89c.
ways foftcr than iron,  1147   Will Crell, Dr,  a miftakc of his concern-
not itril.e fire with flint; and there-   ing  the produdion  of Glauber's
fore of ufe to make hoops, &c for   fait  from alum and  common fait
gunpowder cafks, ib.   Itsdudility,   corroded,  272   Hi*  method  of
tenacity, and  fpecific gravity,  ib.
Exploilcs violently by the contad
of moifture when in fufiou,  1148
How granulated, ib*  How calci-
ned, 1149  The  calx exceedingly
refradory ib.  Soluble by all acid
and  other  faline fubftances, and
even by water,  1130   More  fo-
                                   cryftallizing  the acid of lemons,
                                   997   His attempts to bring vine-
                                   gar nearer to the ftate  of  tartar,
                                   1004  His  proofs  that  all  vege-
                                   table acids are to be derived from
                                   one origin, 1006.
                                 Crtcus  metallorum,  how  prepared,
                                   1263.
luble in cold  liquors than in hot, Cronftedt difcovers the new femimetal
ib.  Undergoes  fome  change "hy   called nickel,  1306.
combination with vegetable  acids, Crucibles : of the moft proper material
1131   How  amalgamated  with   for them, 383  Achard's method
mercury,  1132   A curious amal-
gam formed  by mercury and ver-
digris, ib.   Dr Lewis's methods
of amalgamation,  1133   Forms
brafs, prince's metal, «'<c.  by the
addition of calamine or zinc, 1134
Crucibles in which thefc operations
are performed tinged of  a deep
of -making them from calx of pla-
tina,  387   Mr  Pott's directions
for making them, 388  Dr Lewis's
obfervations on their conftrudion,
589   Porcelain probably the fitteft
material for veffels of this  kind,
591   Of  Reaumur's porcelain as
a material for crucibles, 392
  blue colour, ib.  Forms bell-metal Cruft produced by the fluor acid on
  with  a  mixture  of  tin,   1133
  Lewis's obfervations on the fpeci-
  fic  gravity of this and other me-
  tallic  compounds,  1136   White
  copper  made by fufion with an e-
  qual part of arfenic,  1137  A fine
  gold-coloured metal formed by a
  mixture  of  copper and platina,
  1341   Phenomena attending the
  diflblution  of it in volatile alkali,
  i°35-
Copperas.  See Vitriol.
the furface of water, 828   Found
to be  of  the nature  of  filiceous
earth,  829  Scheele's experiments
to determine the  nature  of this
earth,  830   The  fame cruft pro-
duced  from  artificial fluor,  831.
Scheele's opinion that the earth is
formed by the union of the acid
and  water,  832    Contefted by
Meflrs Boullanger, Monnet, &c.
833  Their  opinions fhown to be
wrongous  by  Mr  Scheele, 834
                       Wtigleb's 
Index.

  Weigleb's experiments on the Ori-
  gin of it, 839   Found to proceed
  from the  corrofion of the glafs-
  diftilling  veffel,  840   How  to
  procure  the  acid  free from  it,
  842   None formed  by  mixing
  fand  with a fait  containing fluor
  acid, 844  But a great quantity
  by adding  powdered  green glafs,
  045-
CryHalhne poivder thrown down from
  folution  of calx of  platina  by ve-
  getable fixed alkaK,  1323.
Cryftallization,  in chemiftry :   how
  to  perform  that  operation,  373
  Cryftallization  of  alum  impeded
  by vitriolic acid, 681.
Cryftals of  one kind of  fait,  contain
  none of any other, 573   Fulmi-
  nating cryftals, 1142   Cryftals of
  platina decompofed by the mineral^
  hut not by the  vegetable,  fixed al-
  kali, 1322.
Sullen,  Dr, his experiments on the
  produdion of cold by  evaporation,
  124.
Cupellation : why  lead is ufeful in that
  operation, 331   Attempts to refine
  platina by cupellation, 1333.
Cuprum- ammoniaeale,  how prepared,
  1034.
Decompositions, chemical, are often
  double, though apparently  fingle,
  463   Explanation of  thofe effect-
  ed by acids alone, 266   Decompo-
  fitions of vitriolic falts fuppofed to
  arife from compound forces,  276
  Why decompofitions are fometimes
  incomplete, 403, 406.
Deflagration, an operation in chemi-
  ftry,  how performed,  382.
Democritus  taught chemiftry by  the
  Egyptian priefts,  4  Said to  be
  able to imitate the precious ftones,
  particularly the  emerald, ib,   Was
  probably only acquainted with the
  method of making green glafs, ib.
Denfity  of mixtures, its  increafe ac-
  counted for, 374    How to deter-
  mine the  accrued  denfity of fpirit
  of nitre  mixed with  water,  387.
  Increafe of it in compound fubftan-
  ces,  404.
Dephlogifticated air  converted into ae-
  rial  acid  by charcoal, 131    Ob-
  jedion to the exiftence of  phlogi-
  fton from the total combuftion of it
  in fome cafes, .152.  Little phlogi-
  fton confumed by the combuftion of
  iron in this kind of air, 15 j Ofthe
  dephlogifticated marine acid,  206,
  790, etfeq. 1484  Dephlogifticated
  green vitriolcannot precipitate folu-
  tion of gold, 226 Quantity of mine-
  ral alkali  taken up by  dephlogifti-
  cated nitrous acid, 432  Solution
  of dephlogifticated calx of iron  can-
  not be cryftallized, 457  Dephlo-
  gifticated green vitriol  decompofed
  by clay, 684  Dephlogifticated air
  a material for the  nitrous acid, 2d
  722   How to prepare  the dephlo-
  gifticated  fpiiit  of fait, 790,  791
  Can fcarcely be condenfed into a li-
  quid, 79Z   Its other prop< rties, ib.
  Acid  of  arfenic procured  by its
CHEMISTRY.
  means, 919,  1274  The only fol-
  vent of platina,  1319  Dephlogif-
  ticated fpirit of nitre decompofes
  camphor, 1424.
Dephlogifticated fpirit  of fait:  expedi-
  tious method of bleaching linen by
  means of it, 1484  Effed of it on
  phlogiftic matters, 1483  Effervef-
  ces with cauftic volatile alkali, ib.
  Forms marine  ether with fpirit of
  wine,  i486  Diffolves phofphorus,
  ib.  Method of procuring a detona-
  ting fait in quantity from it,  1487.
Diaholus metallorum, a name for tin,
  on account of  its bad effeds on
  other metals,  1222.
Diaphoretic antimony, how  prepared,
  1264.
Digefter,  Papin's, defcribed, 367  Ef-
  feds of  it producible by long boil-
  ing, ib.
Digeftion, in chemiftry how perform-
  ed,  363.
Digeflivefalt: Quantity of ingredients
  in it, 379, 421   Prepared from ve-
  getable alkali and marine acid, 794.
Dhfotution  of metals:  heat produced
  by that operation, 190.
Diftillation: how  that operation was
  originally performed, 6 Mr Watt's
  experiments  on the diftillation  of
  water in vacuo,  43   Proper me-
  thod of  performing the operation
■ of  diftillation,  374   Phenomena
  on diftillation of inflammable fub-
  ftances,  317   Boerhaave's experi-
  ments on the diflblution of mercu-
  ry,  1230.
Diftilled verdegris, how prepared, 87a.
Divellent affinities explained, 267.
Dolfifs, Mr, his method of prepa-
  ring butter of antimony, 821   His
  procefs for  muriatic  ether,  824
  For  acetous ether, 884.
Du  Fay fuppofes all calcareous  ftones
  to be phofphoric,  1084.
Dyeing: the vitriol formed by  preci-
  pitating  copper with iron lefs pro-
  per for this purpofe than that  made
  after the common method, 344.
Earth:  water fuppofed to be con-
  vertible into  it, 24   Has not the
  charader of an element, 25   Solu-
  ble in acids, 176  Why  the me-
  tallic earths feldom decompofe falts
  whofe bafis is a calcareous earth or
  alkaline  fait,  304   Quantity  of
  earth in vegetable alkali, 413  Dif.
  ficulty in obtaining the pure  earth
  of alum, 643  Lewis's experiment
  to fhow that clay undergoes  fome
  change by  being converted  into
  this  earth,  649   Siliceous  earth
  found in the refin produced  from
  the refiduum of vitriolic ether, 2d
  722   Qiiantity  of filiceous  earth,
  carried  up   by fluor  acid,  847
  Earth of alum  combined with  ar-
  fenicaj acid,  938  Siliceous  earth
  moft completely precipitated by vo-
  latile alkali, XP74  Forms  a  triple
  fait by precipitarion with fixed al-
  kali, 1075  Is diffolved by boiling
  with  alkali,  1076   See  Siliceous.
  Vegetable earth fuppofed by Lewis
  to be  the fame with  magnefia,
  1088  Mr  Gmelin's experiments
  on it, 1089.
Earths how divided, 6th 310  Vitrio-
  lic  acid  combined  with  different
  earths, 635, et feq.   Nitrous  acid
  combined with them, 746 Solution
  of lilver decompofed by calcareous
  earths, 733   Charaders curioufly
  marked by the fun's light on the
  precipitate,  736   Marine   acid
  combined with earths, 797  Fluor
  acid with  them,  832   Acetous
  acid, 871  Acid  of tartar,  893
  Of phofphoric earths, 1081 Earths
  do  not attrad the  colouring mat-
  ter of Pruffian blue, 1169.
Earthen -ware: of its  properties  as a
  material for chemical veffels, 361.
Earthy cruft.  Sec Cruft.
Eaf Indies: of the method  of  pre-
  paring nitre there,  724.
Eau de luce, how prepared,  1037.
Effervefcence attends the  folution  of
  metals,  188.
Edulcoration,  a  chemical  operation,
  how performed, 371.
Edinburgh .- a kind of  ponderous fpar,
  or marmor metallicum, found near
  that city, 1061.
Elaftic fluids extricated during the fo-
  lution of metals, 189 Great quan-
  tity  of  elaftic  fluid generated by
  the  explofion of  aurum  fulmi-
  nans, 1123.
Elaftieity occafioned by heat,  and not
  phlogifton, 209.
ElcBive attratlions, in chemiftry, de-
  fined, 177  Precipitation  of  me-
  tals  by one  another owing to a
  double one, 229.
Eleilric fluid,  in  winter,  the  fame
  with the heat fent  down from the
  fun in fummer, 99.
Eleilric fpark  produces nitrous  acid
  in a mixture,  of dephlogifticated
  and phlogifticated air, 2d 722   Its
  effect on a mixture  of alkaline and
  dephlogifticated air, 1331.
Eleclrical beat, why fo much ftronger
  than that  of  Furnaces,  160  Ca-
  pable of vitrifying platina,  1333.
Eletlricity:  proofs of  the identity  of
  its  fluid  with  fire  and  light,  96
  Connection betwixt it_ and fire or
  heat, 97  Exceffive eledricity  of
  the polar regions, 98  Eledricity,
  heat, light,  and cold,  are to he
  looked upon as the effeds of  one
  univerfal  fluid,  101    Explofion
  of fulminating filver probably ow-
  ing to it, 1146.
Elements; the fuppofition of them the
  origin of alchemy, 23  Mr Boyle's
  opinion of them, 24  Are in their
  own nature invifible, 26.
Emetic tartars:  different degrees  of
  their ftrength as commonly prepa-
  red, 1238    Pulvis algaroth the
  moft proper material for their pre-
  paration,  1239.
Empyreumatic acids produced  by dry
  diftillation of  vegetables are all  of
  one nature, 993  An acid of this
  kind produced from the liquor in
  which  tartarous felenites is boiled,
  1010.
Embyrev-iUicoiti, how rectified, T426.
E.igta.d:  alum-works  when erected
  there, 640.
Engraving 1.11 glafs,  how pe-formed
  by means of fluor acid, 2d 837.
Eolipile  may fometimes be  ufed  tor
  blowing up  fires, 609.
Epfom fait: proportion  of ingredients
  in the common  kind, 443  In ni-
  trous  Epfom,  444    Cannot   be
  found in marine Epfom, 443  The
  true Epfom fait  found in  the ley
  remaining after the  cryftallization
  of alum, 680  Prepared from  the
  bittern of fea-falt, 6jot
Equilibrium of  heat defined,  73.
Effential fait of lemons, a kind of tartar
  extracted from forrel, 883  Effen-
  tial acids produced from the juices
  of vegetables, their properties, 994.
  Phofphorus combined With effential
  oils, 1412 Analyfis of  effential oils
  1419  Their  tafte fuppofed to be
  owing to  a  difengaged  acid, 1420
  Why they lofe their folubility in fpi-
  rit of wine by being  frequently di-
  ftilled, 1421   Converted by ftrong
  heat  into empyreumatic oils, ib.
  A confiderable  quantity yielded by
  all the kinds of turpentine, 1437-
Ether, vitriolic, produced by a com-
  bination of  vitriolic acid and fpirit
  of wine, 717  Mr Beaume's me-
  thod  of making it, 718   Is the
  lighteft of all  liquids, 719   Boils
  in vacuo at 2a0  below o of Fahren-
  heit, ib.  Produces a great degree
  of cold by its evporation, ib   Dif-
  folves gold, ib.   An  inflammable
  fait  produced  by  Wallerius  by
  combining ether with fait of tar-
  tar, 720  This  thought  to  be a
  proof of the tranfmutation of vi-
  triolic into nitrous acid, ib.  The:
  phenomenon otherwife accounted
  for, 72I,1*722  Mr Cavallo's  me-
  thod  of purifying ether,  2d  722
  A refin producible from the refi-
  duum  of its diftillation, affording
  vitriolic, phofphoric,  and  acetous
  acids, Glauber's fait, felenite, iron,
  and  earth of flint, ib.   Nitrous,
  ether produced by combining  that
  acid with fpirit of wine, 773   Dr
  Black's method of making it, ib.
  Mr Woulfe's procefs for procuring
  it in large quantity,  776   Inquiry
  into   the  nature  of  ether,  777
  Made by  Dr Black without  any
  fpirit, ib.  Marine ether how pro-
  duced, 824   Acetous  ether 884,
  Saccharine  ether, 902   Vitriolic
  ether cryftallizes gold,  1129  Dol-
  fufs's method of preparing it with
  marine  acid, 824   With  acetous
  acid  884    Methods of  Pelletier
  and  others  for redifying vitriolic
  ether, I471.
Ethirialfolution of gold,  its properties,
  1129.
Evaporating veffel in alum-works de-
  fcribed, 674.
Evaporation: Dr Cullen's  experiments
  on the production of cold by  it,
  124   Of the method  of  perform-
  ing  that  operation,  in chcadftry, 
^6
C    II    E    M    I    S    T    R    Y.
  371   T.e-a.l vcfiVW nvift pr->p-r f.ir F.'xri air : its  fpecific gravity detcr-
  evjporation* in the large way.  ib.    mined, 411   Ot  the  quantity of
£v/««,ft», one  of the general cff#ds    it  in  vegetable alkali,  414   In
  nfhta', 6t  That rf mererry and    impure vegetable alkali, 417   Of
  f me other  flu.Hs proportional to    t.'i  quantity c,ontiined in mineral
  t    degree* of hi-.it,  ib   Inftru-    alkali,  434  larth of alum con-
  111 •:rn:s for mcifuring t'r expanfion    tain*  a ;reat  quantity,  446   Of
  «-f bo.Iu«,  113  Iufiances of bodies    the quantity of phlogiilon in fixed
  being expand.-d by cold, 103   Ex-    air, 2d 303.  Alkaline fain  com-
  panfion  rf water :n freezing o-    pofed of a cauftic fait and fixed air,
  cafi >ned by the extrication of air-    1020  Is not  the caufe of  the cx-
  bubble*, 10;.                       plofion of aurum fult 1.1 . r.i,  1118
 E :panfn-e fu. • of -.rater  exceffive in    l'.xp< Is the  colouring  matter from
   the ad of lreezing, i~'»  L'lc 1 as   lixivium  fanguinis, 1173  Water
   an argument for the pofitive exift-   impregnate d with it diffolves man-
   ence of cold,  IC7  Explained by    <: itu fe, 13 ~i.
   Dr  1 lack's theory of lit  it  LcU,  Fixe! alkali kfs  attraded by  nitrous
   ro8.                               acid than  filver,  301   Vegetable
 Fitlnfkn of  fulminating  gold vaftly    fixed alkali takes up an equal quan-
   fupcrior  to  th it  of  gunp~>vdcr,   tity of all  the acids,  402   Etad
   1108   A  fmall  di-gr-:-' of  heat    calculation of the quantity of acid
   lufic ef.t  to make th'«  fubftance   taken up by vegetable fixed alkali,
   -•vplfi.lc,   iito   Inflames of its   419  Stoneware corroded by the
   niiic! ievous effeds, ir 12  Its force   cauftic fixed alkali,  393   Fixed
   is not entirely direded downwards.    fal  ammoniac  the fame with a
   II13  Of  the explofion of moift    combination of  the  marine  acid
   aurum fulminans, 1114   Not oc-    and c;Ic.;:toi'- earths,  797   Com-
  cafioncd by a faline principle, 1113,   bination  of fluur acid with fixed
   1116  Nor by fixed air, 1118  Mr   alkali, 4th 830    Fixed alkaline
   Bcrgnan's theory of iti caufe,  1120   falts how procured, loj6   Vcge-
   O.   lone  1 by volatile alkali,  1121    table  alkali cryftallized  in  various
   Explofion  by th?  vapours of  mer-    ways,  1017   Changed by  combi-
   ctn,  1231.                        nation with  marine   acid,  1018
 F. <•: * is, violent, occafioned by heat    Combination of fixed  alkalies with
   luddenly applied,  7Z2.              fnlphur,   icn   With  expreffed
 Fat, acid of;  how procured  from    oils,  1026    With  effential  oi1-,
   fuet,  21I  1015   Salts formed by   1027    With  phlogifton,   10:8
   combining it with alkali.•<, 3d 1013    Differences  obferved betwixt  thofe
   With caiths, ib   With  metals,   obtained from different vLg tables,
   4th 1013.                          ie>i<)    Precipitate   fob,tions  of
 /*.>'; of animals analyfcd,  1428.        tii.i  ponderofa whether in  their
 Fcrn-ertation: milk capable of a com-   mild or  cauftic ftate, 1034   The
   plcte one, 979.                     cauftic fixed alkalies  throw down
 Filings of iron grow hot and  take fire    an infoluble precipitate from thefe
   fpontan evilly with fulghur, 1207.    folutions,  1036  Marmor metal-
 F.rmiats Mntrmus the finl writer on    licum precipitated unchanged from
   alchcpiy, 8.                        oil  of vitriol by mild  vegetable al-
 F,.tering large quantities of wat-.r, a   kali, IC64  A triple   fait  formed
   fchtii: for, 369                    by  fixed  alkalies, filiceous  earth,
 Filtration:  how to perform that ope-    and fluor acid, IC73   The  mine-
   r.vion in ciiemiftry, 308.            ral,  but  not  the  vegetable, fixed
 F-ie fuppofed by Mr Boyle not to be    alkali  decompofes cryftals  of p.i-
   an element p.rfe,  21  The contra-    tina, 13:2.
  ry opinion now  generally  embra-  Flints, earth of,  fuppofed to undergo
  ced,  32   Two general theories of   a tranfmutation by being diffolved
  it in e.hem at ] client, 33  In what    in an alkaline liquor,   1069   This
  ther differ fiom the theory of Joylc    change denied by  Mr  Bergman,
  and Newton, 34  Fire d.tained in    IO70  The fuppofed tranfmut3-
  bodie-.  tut'.v bv attradion  and    tion found to arife from an admix-
  pnrtly 1 y the  preffure of the Ii r-   ture of clay,  1071   Cryftals of
   r.nitiding  fluid, 33   Berkenhout's   flirt produced artificially by  Mr
   divifion of fire into fixed and  vola-   Bergman, icra   Why  the fluor
   tie,  »■»   Pure or  volatile fire de-   acid will not diffolve  flint direcLly,
   h-ribel, 58  Dr Craw ford's dtfini-   1073   Earth  of  flints moft  com-
   tionof fire, 39  Mr Kirwan's opi-   plttely precipitated by volatile al-
   1 i m, 68  Mr Cavtndifh's opinion   kali,  1074   Forms  a  triple  fait
   that it is not a diftinct fubftance,   with  fluor  acid  and  fixed alkali,
   I)  Seem* deftitute of gravity and   i~"i   Di:l  lived  by boiling  in an
   t •■'. in-ttisr, 93  iVoofs of its iJciui-   alkaline  liquor,  1076   Has art-
   ty with  li-iit ai'd eledricity, ,6   niarkable  att:action   for ttlkahne
   Conne?.ioiriK".xt fire and el c-   falts  iu  the  dry way,  IC77   Is
   ric.ry,  o-   Variolic acid  cot.tair.s   very rare and  fpongy when  pr ci-
   more fir  thin the nitrous or ma-   pitated,  1078 Why  the  alkaline
   rine,  278   ..: ds unit: to alkdics   folution  fometimes cannot be pre-
   fer -i.lngout fire, and quit  them   cipitated by zn acid without heat,
   r\ recc.iin'it, 286,  289.            1079  Liquor of flin:s decompo-
                                                           Indix.

  fed by t 'o greit a q.nntity of wa-    its cc>mbination with  fixed  alkali,
  tcr  and by  fluor acid,  i-!o  See    4th  830   With  volatile  alkali,
  Silicc-ur eirti:                        831    With  earths,  832   With
Flores m.utijles, how prepared, 808.     metals 833    Glafs  corroded  by
F.'o-.i-.n of Benzoin, how  prepared,    it  and by the fait produced by iti
  984, tt feq.  bee Betzoin.  Flowers    combination  with volatile  alkali,
  of  zinc prepared  by  the  dcfl.i-    834  Great difficulty of prefcrvi:.;
  gration of  that  femimetal,  1241    this  acid,  833    Golden" veful.,
  Dr Lewis's method  of  reducing    or a phial lined with  oil and wax,
  thorn,  1242  An o.l fuppofed  to    recommended  for this  purpofe,
  be obtained from them by Mr Horn-    836   Dr  Prieftley's method of
  berg, 1243   H's niiftt.ke deteded    converting the fluor acid  into air,
  by Neumann, ib.  Another oil by    837   Retrads  his opinion  of its
  Mr Hellot,  1244  Gold and filver    being only the vitriolic acid altcr-
  leaf diffolved by this oil, ib.   A    ed, ib-  Fluor acid cannot be ex-
  great proportion of-nitre alkalized    pellcd  by  that of  arfenic,  934
  by the flowers of zinc without any    Why it cannot diffolve flint dircd-
  fenliblc deflagration,  1249.           ly» io73   Why it decompofes li-
FIc-a.ij: method  of preparing tefts    quor of flints,  1080   Is fcarce ca-
  for acids and alkalies from them,    pable  rf   diffolving  manganefe,
  1332.                               1366   Explanation of  its  adion
Fluid:  Dr Cleghom's proof that heat    on mnngaucfc, i.yy.
  is occafioned  by one, 82.  Difli-  /"'  xe.. • pi;.tina  and lonie  of its cal-
  culties concerning the nature  and    ces fufible by  their means, 1,537.
  properties of this fluid,  83  Heat  Fontana's account of  the  fpec.lic gra-
  moft  probably the adion  of  an    vity of different kinds of air,  373
  omniprefent fluid,  92    Senfible    An experiment of his confirming
  heat always produced by the con-    thofe of Mr Kirwan,  394.
  vei In :i of a fluid into a  folid, 116   Fofle uUali.   Sec Mmeial.
F'uiditi occafioned by the  abforption  Fuutcroy  denies  thet. platina  can  be
  of heat, 113,  119  Apt oof of this    amalgamated with mercury,  1330
  from  its being  inipoflille to cool    Incoiiliftencc in his account of its
  water below 320 without freezing,    hardnefs, 1331.
  117.                              Fr..---./ity oi  glafs when not well an-
Fluids differ in the degrees of ahfolutc    uealnl, 339.
  heat they contain, 46   The thin-  Frame: of the method of making ni-
  neft fluids  contain  the  greateft    tre there, 731.
  quantityof  heat, 47   Mr Watt's  Freezing: of the prodigious expanfive
  experiments on the evaporation of    power, exerted by water  during
  fluids on i-iit ■'■/,  126    Fluids part    that ad,  106.
  with more  heat  than folid  bodies  Friction makes aurum fulminans ex-
  can, 212.                           plode without any heat,  ntl.
Fluor  acid: why  it can  be reduced  Fulminating  calx of  filver  made  by
  into air without any addition,  207    Kunckel,  736  Fulminating cop-
  Firft difcovered  by Mr  Margraaf,    per,  1033.    Fulminating  gold,
  826  Prepared  by diftilling fluor    1103  See Aurum fulminans.  Ful-
  fpar with oil of vitriol, 827  Forms    minuting filver made  by M. Ber-
  a white earthy cruft on  the furface    tholht,   1138     How  prepared,
  of  water  put  into the  receiver,    1139  See Silver.   1 uiiniiiathig
  828, etfeq  See Cruft.  Fluor aJc!    quickfilver, how prepared, 3d 903.
  proved  to be diftind from that of  Fumes:  nitrous and fulphureous ef-
  fea-falt, 833  And from the  acid    fervefce with  one another,  626
  of  vitriol,  836   Quicklime pro-    Gold not  rendered brittle by the
  ved to be  the  afis of  fluor fpar,    fumes of  tin,  1093.
  837  Miltahe of M. Monnet on  Furnace, a  portable one  defcribed,
  this fubjed, 838  Wiectcb's  ex-    6(5o   Form of Boerhaave's port-
  periments on the earth contained    able furnace,  ib.   Another defcri-
  in  this acid, 839, 840  Mayer's    bed, ib   Dr  Lewis's  portable Fur-
  examination of the acid, 841  How    naces,  601    Objedion  to their
  to procure  the acid free from fili-  _  ufe in fome cafes, 602  Dr Black's
  ceous  earth, 842   Experiments    furnace,  2d  602  How  adapted
  for this purpofe with  an iron di-    to the various operations of  che-
  ftilling veffel,  843   A  fait  con-    miftry, 603   Luting proper for it,
  tait.ing fluor acid forms no cruft    604   Method  of applying  the
  by being  mixed  with  fand, 844    lute,  603    Melting furnace, 2d
  But a  £r at quantity with powder-    005  Mr  Pott's melting  furnace,
  td glafs, 843   Of the  quantityof   (>'.(>  Why in cavity is made of
  filiceous  earth  which  fluor  acid    a  roundifh  form, 607   Lewis's
  carries along with  it, i'-<7   Vio-   lamp, 911  One conftrudedon the
  lent adion of  it upon elafs, 848    principles of  Argand's lamp, ib.
   Mr Wenzel's  experiments on the Furnace;  neceffary for the operations
   fluor acid in a  leaden  retort, 830   of ch miftry, 399,etfeq  Dircdinns
  This acid  procurable by means of   for building  them properly, 610.
   the acids  of nitre,  fea-fajt,  and F.^i-lity of metals increafed  by mix-
   pheffphorus, 2d 850    Appearance   ture,  342   Great  fufibility  of
   and j rtpeitieb of it, 3d 830  Of   mixtures of  tin  -:rA  lifiKuth, 343
                                                                 Inrrea- 
  Index.

    Increafed by the  addition of lead,
    ib.
 Fufion : how to perform  that opera-
    tion in chemiftry, 384   Difference
    betwixt the watery and dry fufion,'
    ib.   Of the crucibles neceffary for
    the   fufion  of  chemical fubjeds,
    583, et feq.  See Crucibles.  Fufion
    of all metals promoted by bifmuth,
    i»51-
 Garphyttan,   in  Sweden :   Rin-
    man's method of  burning  the alu-
    minous  ore  there, 668   Method
    of lixiviating it, 670.
 Gait's,   acid of how feparated  from
    them, 1337   An acid  liquor pro-
*    cured from  them by  diftillation,
    1338   Its properties, 1339.
 Gaftric juice of animals contains phof-
    phoric  acid, 904.
 Geoffroy's rule  for determining the
    degrees  of- chemical  attradion,
    262    His  table  of  affinities, 5S3
    Inveftigates  the conftituent  parts
    of alum, 641  His theory of Pruf-
    fian  blue, 1163.
 Germany;  method of  making  nitre
    in fome parts of it, 730.
 Glafgozu:  a kind of Spathum ponde-
    rofum found in its neighbourhood,
    1060.
 Glafs:  method of engraving on  it by
    means of fluor acid,  2d 837.
 Glafs veffels, when to be ufed by che-
    mifts, 336   Dr Black's remarks
    on the  properties of  glafs  338
    Affords the filiceous cruft obferved
    on fluor acid, 840  Violent adion
    of that  acid on  glafs,  848   Cor-
    roded by it and by the ammoniacal
    fait produced  from  it, 834   Bif-
    muth convertible into glafs,  1230
    How to prepare glafs of antimony,
    I257  A beautiful blue glafs  pro-
    duced by the  calx of  regulus of
    cobalt,  1299.
 Glafs of lead: of  the veffels moft ca-
    pable of refilling its adion,  389.
 Glafs-making: Pliny's account of the
    origin of it, 7.
 Glaffes:  of the  materials  proper for
   coating them, 380.
 Glauber's fal ammoniac prepared  from
   vitriolic  acid and volatile alkali,
   633, Sec Ammoniac.
 Glauber's fait:  Dr  Crell's  miftake
   concerning  its  preparation  from
   alum  and common fait, ^72   Its
   decompofition  by  marine    acid
   never complete,  291   Reafon of
   this decompofition explained,  306
   Quantity of  ingredients in it,  431
   Prepared from vitriolic acid  and
   mineral alkali,  632   Dangerous
   confequences  of miftaking cryftals
   of nitre for it, 743  Produced from
   the refin extraded from the refi-
   duum of vitriolic ether,  2d 722.
Glauber's fpit it of nitre,   734.
CHEMISTRY.
 by green vitriol, 223   But not by
 the -dephlogifticated  kind,  226
 Why it  is precipitated  by folution
 of tin, 227   Various precipitates
 of it, 233  Beft kind of aqua regia
 for diffolving- it, 481  Qiiantity of
 it taken  up  by  aqua  regia,  482
 Its calces foluble in the  vitriolic
 and nitrous  acids,  483  Kirwan's
 opinion  that the metal cannqt  in
 any quantity be diffolved in the
 nitrous acid,  484  Dr  Brandt's
 experiments,  fhowing that it  may
 be fo in clofe veffels, 730   Lewis's
 obfervation on this experiment, ib.
 Solution  of  its calces in  fpirit  of
 fait,  799   Sublimes  along with
 the acid,  ib.  The fublimate  faid
 to  be the material ufed  for the
 blood of St Januarius, 800  Is not
 affeded  in any way by  the arfeni-
 cal acid,  941  Its nature  and  pro-
 perties   particularly  treated   of,
 1089  Unites readily with all the
 metals,  1090  Its  colour  debafed
 by all the metals except copper, ib.
 Said  to  lofe  its malleability re-
 markably  with  tin,  109I   Dr
 Lewis's account of the bad effeds
 of this metal upon it, ib.   Mr Al-
 chorne's experiments in oppofition,
 1092  Gold not rendered brittle
 by the fumes of tin, IC93   Nor by
 the addition of the metal itfelf in
 fmall quantities, ib.   Nor with
 the  addition  of  copper,  1094
 Malleability  of gold entirely de-
 ftroyed by a fmall quantity of re-
 gulus of  arfenic.  1093   Surpri-
 fing tenacity of its parts, 1096   Is
 not liable to ruft 1097  Mr Uoyle's
 experiment to (how its deftrudibi-
 lity, 1098  Of its folution in aqua
 regia,  1099   This folution  of  a
 corrofive  nature, 1100  May be
 cryftallized,  ib.  Of the  precipi-
 tation of the metal from it, 1101
 Separated  from other  metals by
 green  vitriol,  1102   Explodes
 with  prodigious force in fome
 cafes, 1103—1126  See  Aurum ful-
 minans.   Solution of gold by hepar
 fulphuris, 1127  Medical  virtues
 of gold entirely imaginary, 1128
 Solution  in effential  oil not per-
manent,   ib.   Diffolved   perma-
nently in  ether, and cryftallizable
by its means,  1129  Revived from
its folution in aqua regia  by mix-
ing it with fpirit of wine,  ib.   A
method thus  afforded of purifying
it  from  other metals,  ib.  How
 to reftore  its  colour when  loft,
 1130   Mercury fixed by  amalga-
mation  with  gold,  1234   Whe-
ther it  be poflible  to  adulterate
gold with platina, 1336 How to
deted  this fraud if it  fhould be
pradifed, 1337
Gmelin, Dr, his experiments on the dif- Golden  calf:  its diflblution  adduced
  ferences betwixt the alkaline falts   as an inftance of  Mofes's fkill in
  produced from different vegetables,   Chemiftry,  4.
  1029   On the  afhes  of  different Golden fulpbur  of antimony, how  pre-
  plants,  1089  Method of making   pared,  263.
  dulcified fpirit of fait, 1481.       Golden vcff.ls recommended for keep-
Gold: why its folution is precipitated   ing the fluor acid, 856.
 Granulation of copper, how performed,
   1148.       .'
 ■Gravity:  the element of  fire  feems
   to he deftitute of it, 93  Of find-
   ing the fpecific gravity of the dif-
   ferent metallic calces,  327   How
   to find the fpecific  gravity of bo-
   dies, 371   Of  the fpecific gravity
   of fpirit  of fait, 377    How  to
   find that of the ingredients  in di-
   geftive fait, 380  Of the pure ni-
   trous acid,  386  Of its mathema-
   tical  fpecific  gravity,' 38o   Flow
   to conftrud a table  of  the fpecific
   gravities of fpirits of nittre of dif-
   ferent  ftrength,  390    How  to
   find the  fpecific gravity of pure
   vitriolic acid, 397   Of the ace-
   tous acid, 400  Of ftrong vinegar,
   401  Of fixedair, 411   Of fixed
   vegetable  alkali, 412   Mr  Wat-
   fon's account of the fpecific gra-
   vity of fait of tartar,  413    Dr
   Lewis's obfervations on the fpeci-
   fic gravity of  bell-metal and  other
   metallic compounds, 1136
 Green colour produced  from  verdigris
   and cream of tartar, 894.
 Gun-poivder: its  explofive force vaftly
   inferior to  that of  aurum fulmi-
   nans,  1 '08. '
 Gypfum :  proportion of ingredients in
   the natural kind,  439   Formed
   of the vitriolic acid and calcareous
   earth,  63s   Some  differences be-
   twixt  the  natural  and  artificial
   kinds,  ib.   Is foluble in  fome de-
   gree by acids, 636  Convertible
   into quicklime  by a  ftrong  heat,
   ib.  Fufed by a very violent and
   fudden heat, and likewife by the
   addition   of  clay  or  calcareous
   earth,  ib.   Decompofed  by  fixed
   and mild volatile alkalies, ib.  And
   by the acid of arfenic, 933 Found
   in the concentrated vitriolic  acid,
   1039.
Hanover :  method  of making ni-
   tre there,  729.
Huffia :  of the aluminous ores found
   in that country, 638.
Heat, two general theories of,  28
   Lord  Bacon's definition  of it,  29
   Mr  Boyle's opinion, 30  Senti-
   ments of  Sir Ifaac Newton on the
   fubjed, 31  Fire or heat general-
  ly allowed to be an element per fe,
   32  Two other theories inftituted,
   33   In what they differ from the
   former, 34  General account  of
   Dr Black's and Dr Irvine's theory,
   33  Dr Irvine's theory  explained
   by  Dr  Crawford, 36   Abfolute
   heat defined,  37  Great  quantity
   of heat produced by the condenfa-
   tion of vapour, 43, 123 Differ-
   ence of the abfolute heat of differ-
   ent fluids,  46   Thinneft  fluids
   contain the greateft quantity of it,
   47   Crawfords account  of  fen-
   fihle heat, 49   Capacities for con-
   taining heat explained, 32  Craw-
   ford's opinion  concerning heat in
   the abftrad, 34  Dr Bcrkenhqut's
   opinion of  its nature,  36   Heat
   has a tendency to diffufe itfelf e-
                 K k
                             257

 qually over 'loiiies, 60   Is con-
 tained n coniicicrahie quantities i 1
 all  bodies.  61 ■  Its quantity limi-
 ted in all bodies  64   Hxpaniion
 an  univtrfal effed of  hc-t,  63
 Bodies of the fame kind and of
 equal temperature contain quanti-
 ties of heat proportioned to  their
 quantities of matter,  67  Equili-
 brium  of heat defined,  73    Pi
 Crawford's method of <ic termini rig
 the  proportional degrees of  heat,
 7*7   His method  inefficient,  78
 Nicholfon's account of the theories
 of heat,  79   Advantages of the
 dodrine that heat is caufed by  vi-
 bration, 80  Anfwer to Mr Ni-
 cholfon's argument, 81  Dr  Cleg-
 horn's proof that heat is occafioned
 by a fluid,  82  Difficulty arifing
 from the fuppofition that  heat dif-
 fufes itfelf equally,  84   Another
 from the feeming difappearancc of
 heat,  83   Equal  eliflribution  of
 heat promoted by  its abforption
 and evoluton,  89   Heat of the
 torrid  zone thus  mitigated,  90
 Heat moft  probably the adion of
 an omniprefent fluid,  92  Diftri-
 bution  of heat occafioned by the
 adion of the  fun,  94  How heat
 is  produced  by  his rays, <)5   Con-
 nection between  heat  and eledri-
 city, 97 Heat  in fummer becomes
 eledric fluid in winter, 99   Solu-
 tion of the  phenomena of  heat,
 102   Mr Kirwan's theorem for
 finding the point of total privation
 of hsat, 114.  Heat the caufe  of
 the foftnefs  of bodies approaching .
 to  fluidity,  118.   Abforption  of
 heat the univerfal caufe of fluidity,
 120. Heat produced in the burning
 of inflammable bodies comes from
 the air, 137  Too much phlogifton'  .
 prevents the heat of burning bodies
 from being  intenfe,  138   Why
 the folar heat and that of eledri-
 city  are fo intenfe,  160  Table  of
 the  various  degrees of heat, 161
 Heat produced  during the diflblu-
 tion  of metals, 190   Heat and
 not  phlogifton the  caufe of elafti-
eity, 209  Heat  produced in fo-
lution moft probably proceeds  from
the  folvent  liquor,  211   Argu-
ment in favour of  the weight  of
precipitates  being  augmented by
the matter of heat,  249   Experi-
ments to determine the  caufe  of
fome chemical decompofitions from
the degrees  of heat produced by
various mixtures, 277  Alteration
 of the denfity of acids by various
 degrees of heat, 423  Strong fpi-
rit of nitre more expanded by heat
 than weak,  and why,  424   Dila-
 tation  of fpirit of fait by various
 degrees of heat, 427   What me-
 tals  are calcinable, and  by  what
 degrees of heat, 330   Violent ex-
 plofions from the fudden applica-
 tion of heat, 724  Effeds of htat
 on lapis ponderofus, 969  Mercu-
 ry unalterable by  being kept  13
 years in a gentle heat, 1229.
                            Helht 
H* * procure*  from Bowers of <t.nc
  an oil capable  of diffolving  gold
  and filver leaf,  1144-
Mepjr fmtpt »rii firmed  by a combi-
  mfi'in of heed alkaliciaud lulphur,
   1. :t   May be made  cither in the
   u.  i  or dry  way,  ib.   l';r:ly
   dcc«iinj>ofcd by fixed air, ib   En-
   tirely  by acids  i«i:   Effeds of
   the  inflammable  vapour  arifing
   during iudecompofitio':, ib  10:3
   Its phlogifton very rn.h  difpolt-J
   t» fl) off, 1024   Diiulves many
   nit tali, and cha.-co.tl,  1  15. Solu-
   tion of  /old  by it* 111' ails,  1127
   lt« effect- of it  upon nick. 1, 1309.
 Htpatic air contains fulphur,  210.
 Hirmei   'Tttfrnugiftos, the  fame  w.th
   Siphoas, an Egyptian, the founder
   of chemiftry,  3.
 Higgins, Mr. his experiments on hu-
   hunun calculus, 1463,etfeq. His ob-
   fervation son the nitrous acid, 1472
 Method of  obtaining  it  quite  co-
   lourlefs, 1473   Difcovers the true
   compofition of volatile alkali, 1333.
 lLnkerg\   experiments  on  fpecific
   gravities compared with thofe of
   Kirwan,  392  Different refults of
   them  accounted for, 393, 399  An
   oil obtained by Homberg fuppofed
   to come from the flowers of zinc,
   1243  The miftakc difcovered by
   N uni:m,  ib.    How  he  difco-
   vered his pyrophorus,  1413   left
   method of preparing it, 1416  See
   Pyropbtms.  Difcovers that marine
   acid corroilcs glafs, 1481.
 Houfe-paintii;:  a  yellow colour for
   that purpofe, 699.
 J.\nu.nuns, St, a fublimate of  ma-
   rine acid and gold fhown for  his
   blood, 800.
 lit a quantity of  heat  loft in the
   melting  of it, 42.
 "fe.Vv the mucilage of animal fubftan-
   ces, 1434  All of them reducible
   to this by long boiling ib.  Is the
   only   true  animal  fubftance  ib.
   Forms si very ftrong cement, ib.
 Ignited bodies al! equally hot, 128.
 ignition   an univerfal effed  of  fire,
   130   Difterct.ee  betwixt ignition
   ;md inflammation,  132.
 Jl.-x aquifoliu-i  the growth  of that
   plant a fign of aluminous  ores in
   the ground, 639.
 Jnftammal.. and vitriolic acid  air ob-
   tained from folution of copper in
   \itriolic  acid, 463,  471   Inflam-
   mable fubftances,  their nature and
   properties,  516   Principles  into
   which they are refolvcd by burn-
  ing,   1I1.    By  diftillation,  517
  Their phenomena with diflcre:  t
   . y .  318  Some  lingular pro-
  ductions, 519  Vitriolic acid com-
  bined with them,7 -i,etfeq. Nitrous
  acid. 771, rifeq.  Marine acid, 824
  An inflammable  fpirit  entraded
  from  fugar of lead,  878  Inflam-
  mable vapour arifing from the de-
  composition  of  hepar fulphuris,
  ir:.;   Wlatile alkalies combined
  with them, 1033  Of their divifion
  aaddKiweaiiircpcitia»i3/f';<>7 «'•
CHEMISTRY.
Inftjeomablr an ,• metallic  calces  re-
  duced by it, I.; )   Revival ol  lead
  from minium by  it, 324   Quan-
  tity  of  inflammable air produced
  from iron,  454   Why none n
  produced from the nitrous folution
  of iron, 460  Charcoal entirely
  convertible into it,  1431.
Inti.immahle fpiiit produced from ra-
  dical vinegar,   1344    Sulphure-
  ous inflammable vapours produced
  from it, 1345.
Ifammation:  difference  betwixt it
  and  ignition, 132   i>dies decom-
  pounded hut not deftroyed by in-
  flammation,  133.
Ink: a fine fympatnetic one produced
  from folution of cobalt  in fpirit of
  fait, 822 Another by means of vo-
  latile tindure of fulphur and fac la-
  rum faturni,  107,; Blue fympathe-
  tic ink  prepared from cobalt, 822,
Infoluble precipitate thrown down by
  cauftic  fixed alkali from folution of
  terra ponderofa,  1036.
Inundations prevented by the flownefs
  with which concealed water melts,
  88.
lion: objedion  to  the exiftence  of
  phlogifton from the total confump-
  tion of dephlogifticated air iu burn-
  ing  it,  132  Little  phlogifton ex-
  pelled from it by this means,  133
  The  objedion inconclufive,  134
  This metal not reduced to a calx
  by burning in dephlogifticatcd air,
   133   Water  produced  in  the re-
  duction of it by inflammable air,
   I36  Of its precipitates by differ-
  ent  fubftances, 239  Is not an ef-
  fential  ingredient in platina, 234
  Nor  regulus of nickel, 233   Nor
  cobalt  or  manganefe,   236  Why
  folutions of  iron  diffolve  copper,
  336  Iron and zinc the only me-
  tals  diffolved by vitriolic acid, 337
  Why copper and iron  precipitate
  one  another, 341   Increafe of the
  attradion  of calx of iron to phlo-
  gifton  demonftrated,   342   De-
  phlogifticated folutions of iron pre-
  cipitated by calces of copper, 343
  Why a faturated  folution of  filver
  can fcarce be precipitated by iron,
  346   Of the precipitation of  zinc
  and   iron  by one  another,   347
  Iron and  nickel will fcarcely pre-
  cipitate one another, 339  Cobalt
  precipitated by iron, 362  A triple
  fait formed by iron, regulus of an-
  timony, and marine  acid,   366
  Proportion of  iron taken  up by
  the  vitrioh'c  acid,  433  Why vi-
  triolic air is produced by diffolving
  iron in concentrated vitriolic acid,
  433    Solution  of  the calces  of
  iron in vitriolic  acid,  456  That
  of the dephlogifticated calces rc-
  fufe  to cryftallize,  437   Propor-
  tion  of iron diflblved  in  nitrous
  acid, 458    In  the marine  acid,
  462   Calces  of iron affume  a red
  colour when precipitated from their
  folution in the mariue  acid, 463
  Produce green vitriol  by  combi-
  nation with vitriolic acid, 69,6,697
   Precipitate   fpontaneoufly   from
   the vitriolic acid, 698.   Iron con-
   tained in the refin produced  from
   the  refiduum of  vitriolic  ether,
   2d,  722  Cannot  be diffolved by
   concentrated,  though it  will  by
   diluted,  nitrous acid, 739   Dif
   folvcs and  produces inflammable
   air with marine acid, 803   Volati-
   lized by this acid, 806  lt< folution
   ufed in medicine, 807  Combined
   with acetous acid, 873  With acid
   of tartar,  893  With the acid  of
   cikinc,  948  Its n  itc.rc  and pro-
   perties  particularly  treated   of,
   113 -   Has great tenacity of parts,
   113}   Is a combuftible fubftance,
   1139   Is the only  metal capable
   of being welded, 1160  Contrads
   in fufion,  and expands again  on
   becoming cold, Il6l  Is  diflblved
   by all metals except  lead and mer-
   cury,  1162   iecomes  brittle  by
   being immerfed for  fomc time  in
   that  fluid, ib.    Can'  fcarce be
   united  to  zinc,  ib.   Flas a ftrong
   attradion for arfenic, ib.  Is the
   bafis of Pruflian  blue, 1163,  et feq.
   See  Pruffian blue.   Calx of iron fo-
   luble in lixivium  fanguinis,  1175
   Neutral fait for dutovering it in
   mineral  waters, 1180  Precipita-
   ted  oy  the colouring matter  of
   Pruflian blue from its folution  by
   aerial acid, 1191   Nitre  alkaized
   by  it, 1206   Its filings  take fire
   fpontaneoufly  with  fulphur,  1207
   Unites with platina, 134".
Iron liquor for printing cloth,  how
   prepared, 873
Irvine, Dr : a general  account of his
   and  Dr idack's theory of heat,  3s
   H:s theory explained by Dr Craw-
   ford, 36.
Italy :  of the firft alum-works fet up
   there, 639.
Juice, gaftric, yields phofphoric acid,
   904.
Keir,  Mr, his objedions to the doc-
   trines of Mr Kirwan, 2d 310  His
   method of preparing an  alkaline
   ftandard, 4th 310  Of finding the
   fpecific gravity of different liquors,
   3th  310   His  objedions to the
   opiuions concerning the  identity
   of the vegetable acids, 1340.
Kermes   mineral,    how  prepared,
   1263.
Ketley,  in Shropfhire  :  a kind of fpa-
   thum  ponderofum  found  there,
   1060.
Kilpatrick-bills, near  Glafgow:  fpa-
   thum  ponderofum  found  there,
   1060.
Kirivan'%  opinion  concerning  fire,
   68   His theorem  for finding the
   point of total privation  of  heat,
   114   His remarks  on fome expe-
   riments of Dr Prieftley, 323   His
   experiments compared with  thofe
   of Homberg, 392   Different re-
   fults of their experiments  account-
   ed for.  393, 3,9  Kirwan's expe-
   riments confirmed  by one  of  1011-
   tana. 394   Differences with Mr
   Bergman and Lavoilier  accouat-
                        I.NDEX.

  for, 435   Ii of opinion that go'J
  cannot be diffolved in  nitrous «   i,
  484   Miftake of  Morveau  con-
  cerning a fuperabundance ofacid in
  alum accounted for, 641  Objec-
  tions to his  dodrine  conei ruing
  the fpecific gravity, &c. of differ-
  ent fubftances, 2d 310, et feq.  To
  his calculation of  the quantity of
  phlogifton  in fulphur,  6th 310.
Kundel prepares a fulminating calx
  of filver, 736.
Lamp furnace : Dr  Lewis's  de-
  fcribed,  611    Is  not   capable  of
  giving a greater htat than 430°of
  Fahrenheit, ib.
Language :  fpccimen of a  new chemi-
  cal one, 352   Its  ftrange appear-
  ance in attempting to  account for
  the  phenomenon  of  fulminating
  filver, 1144.
Lapis ponderofus confidered as a me-
  tallic earth by Mr lergman, 967
  See Tungften.
Latent heat:  experiments by  which
  Dr Black was led to the difcovery
  of  it,  41  This heat  cannot be
  meafured,  73  Expanfion  of wa-
  ter, in freezing explained  by the
  theory of  latent heat,  108  Air
  bubbles in  ice-produced by part of
  the latent heat of the  water, 110
  Vapour formed by the ablorption
  of heat into a latent ftate, 120.
Lavoificr denies  the  exiftence  of
  phlogifton,  137   His  argHments
  drawn from the increafed weight
  of metals by calcination, 138  His
  theory of inflammation, 139  His
  arguments  from the redudion  of
  the calces of perfed metals with-
  out addition,  140   Difpute be-
  twixt him  and Prieftley, 141  His
  differences  with Kirwan accounted
  for,  435   Account of fomc  of
  his experiments on the increafed
  weight of  metallic folutions, 325
  Confequences deduced by him from
  thefe experiments,  526  Not well
  founded,  327   Account  of the
  conftituent parts of  the  nitrous
  acid,  1473   His new nomencla*
  ture,  1360.
Lead: quickfilver produced from  it
  in certain  cafes,  12, 762  Water
  may be  made fufficiently hot  to
  melt lead,  131  Why the vitrio-
  lic acid cannot ad upon it  with-
  out  a  boiling  heat,   197    Pre-
  cipitates  of lead,   237    Sea-falt
  decompofed  in various ways by
  means of it, 302   In  what  cafes
  folution of  lead is  precipitated by
  other  metals,  3x59   The folution
  in marine  acid decompofed by vi-
  triolic falts,  310   Revival of lead
  from minium by inflammable air,
  324  Why it is ufeful in cupella-
  tion,  331  Precipitation of  it by
  nickel, 360   Veffels  capable  o£
  refifting  the  glafs of lead,  389-
  Lead veflels moft  proper  for the
  preparation of oil  of  vitriol, 627
  cannot be  diflblved in  the vitriolic
  acid,  7j2  A  beautiful white for
  painting in water  prepared Iron*
                           litharge 
Index.
CHEMISTRY.
259
  litharge, nitrous and vitriolic acids,
  703    Diffolves  and  cryftallizes
  with  the nitrous acid, 761   This
  fait decrepitates with great violence
  in the  fire,  762   Becomes  fluid
  like oil byYepeated diffolutions in
  aquafortis, 762  Combination of
  lead with marine acid 811  Plum-
  bum  corneum,  812  Combined
  with  acetous  acid,  874  White
  lead the refult of this preparation,
  873   Obfervations on the procefs
  for making it,  876  Sugar of lead
  prepared  from  acetous  acid  and
  white lead, 877 InfLmmable fpirit
  procured by diftilling this fait, 878
  Combination of lead with the acid
  of arfenic, 949  Great  attradion
  betwixt filver and lead, 1136  Can-
  not be united to iron,  1162   The
  metal particularly treated of,  1207
  etfeq.  The leaft dudile  and tena-
  cious  of all metals, 1208  Sheet-
  lead,  how caft, 1209   Milled lead
  fcarce to be preferrcJ to  this kind,
  12IO   Rendered fonorous by be-
  ing caft into a certain fhape,  1211
  Of its calcination, 1212   Minium
  or red-lead,  how prepared,  I2T3
  Litharge,_i2l4  Phenomena with
  other metals,  12 F3  Remarkable
  way  of uniting with  copper and
  feparating from it again, ib.  So-
  luble  in  alkalies  and oils,  1216
  Of its union with platina, 1348.
Lemons,  effential fait of, a  fpecies of
  tartar extraded  from forrel fold
  under this name, 888  Dr Crell's
  method  of  cryftallizing  the  acid
  of lemons, 997   This acid cannot
  be  converted into acid  of fugar,
  999  Entirely  diffolves manganefe,
  1370   Explanation of the adion
  of the acids of tartar and lemons
  on manganefe, 1382.
Leviiation,  a  chemical  operation,
  how  performed  599  Reaumur's
  porcelain recommended for leviga-
  ting utenfils, ib.
Lewis,  Dr,  his obfervations on the
  making  of crucibles, 390   His
  experiments on Reaumur's porce-
  lain, 393,394   Defcription of his
  portable furnaces, 601   Objedion
  to their ufe  in  fome cafes,  602
  His  lamp-furnace  defcribed,  611
  His experiments to'fhow  that  clay
  undergoes fome change  by being
  converted into  earth of alum, 649
  His diredions for making turbith
  mineral,  706    Fxperiments  on
  the folubility of tin in the  acetous
  acid,  880   His opinion concern-
  ing the earth  of  vegetables, 1088.
  His methods of amalgamating mer-
  cury with copper, 1133.   His ob-
  fervations on  the fpecific gravity
  of bell-metal and other compounds
  of the  metallic kind, 113 6.   His
  obfervation on the crackling noife
  made   by tin  in  bending,  1221
  His detedipn of an erroneous pro-
  cefs in which mercury was fuppo-
  fed to  be converted Into water,
  J236    His method  of  reducing
  the floweis of zinc, 1242   His
  experiments  on  alloying  platina
  with other metals, 1338.
Ley, alkaline, why it is unfit for ex-
  trading  the flowers of benzoin,
  989.
Libavius, fmoking  liquor  of,  how
  prepared, 810.
Lichtenfdns experiments on the acid
  of benzoin, 1330.
Light: proof of its identity with fire
  and eledricity, 96   The effed of
  one univerfal fluid, 101   Charac-
  ters curioufly marked by the fun's
  light on a  precipitatu of filver  by
  calcareous  earth, 736.
Lime the moft proper material for cx-
  trading  the flowers of benzoin,
  991    Cryftallization of the acid
  of lemons prevented by the fmal-
  left particle  of  lime, 998   Terra
  ponderofa  convertible into  a kind
  of lime capable of decompoling  vi-
  triolic falts, 1033   Diffolved  by
  the colouring matter of  Pruflian
  blue,  1189.  How prevented from
  flicking to the bottoms of diftilling
  veffels, 1033
Lime-ivatcr precipitated by the arfe-
  nical acid, 933.
Liquid phofphorus, how prepared, 1410.
Litharge  prepared in the refining of
  filver  with lead,  1214   Almoft
  always contains fome  lead  in  a
  metallic  ftate, ib.   Bifmuth con-
  vertible  into  a fubftance  of this
  kind, 1230.
Lithiftac acid.   See Calculus, acid of.
Lixivium fanguinis  lofes its colouring
  matter by expofure to  the air,
  1172  Calx of  iron foluble  in it,
  H75-
Liver of arfenic formed of alkali and
  arfenic boiled together,  1276.
Lubbock,  Dr, his theory of heat, &c.
  142-
Luna cornea, why it cannot be redu-
  ced without lofs by alkaline  falts,
  314   May be decompofed  by
  mercury,  336   How  prepared,
  802   Its  properties  gave rife to
  the notion of malleable glafs, 803
  How reduced, 1134.
Lunar cauftic, how  prepared, 732.
Lute, proper for lining  furnaces, 605.
Luting, for  acid fpirits,  377.
Maci.ration, in  chemiftry :  how
  to perform that  operation, 398,
Macquer's  theory  of Pruflian  blue,
  1167   Suppofes the  fufion of calx
  of platina by the methods recom
  mended to be imperfed, 1334.
Magnefia  combined with  vitriolic
  acid,  690   With  acid  of  arfenic,
  937   Diffolved  by  the  colouring
  matter  of  Pruflian blue,  1187
  Will not diffolve in acids after cal-
  cination  without  heat,  442   Its
  preparation and properties, 314
  Combined with the nitrous acid,
  749-
Magiftery of bifmuth, 766.
Manganefe:  how  to dephlogifticate
  fpirit of fait by it for the  decom-
  pofition  of arfenic,  919   Combi-
  ned with  the arfenical acid, 936
  Identity  of vegetable acids proved
  from the folution of manganefe by
  the nitrous acid with the addition
  ofacid of fugar, ion  From its fo-
  lution by means of vitriolic acid and
  fpirit  of wine,  II14   Keeps the
  colouring matter  of Pruffian blue
  from rifing,  1204   A  new  femi-
  metal afforded, 1359   Common
  manganefe treated  with vitriolic
  acid,  1360   Is entirely  diffolved
  by  phlogifticated   vitriolic   acid,
  1361  Precipitate and cryftals ob-
  tained from  the  folution,  1362
  Diffolved by phlogifticated nitrous
  acid, 1363   Effeds  of it  on fpirit
  of fait,  I364   See  Dephlogifticated
  and  Marine  acid   Entirely  dif-
  folved  by  marine acid,  1363
  Scarce foluble in fluor  acid, 1366
  Or  in that  of phofphorus, 1367
  Parly diffolves in  acid  of tartar,
  T368   With  difficulty  in the ace-
  tous,  1369  Entirely diffolved by
  acid  of lemons,  1370   And by
  water impregnated  with fixed air,
  1371   Has a ftrong attradion for
  phlogifton, 1372   Becomes white
  by faturation with it, 1373  Con-
  tains  fome  phlogifton  naturally,
  1374  liecomes infoluble  in  pure
  acids by lofing its phlogifton, 1375
  Partial folutions of  manganefe ex-
  plained  on  this  principle,  1376
  Its ftrong attradion  for phlogifton
  when combined with acids, 1377
  Why  it is  diffolv.d by the concen-
  trated acid of  vitriol without ad-
  dition,  1378   Why the volatile
  fulphureous acid diffolves it, 1379
  Explanation of the effeds of ni-
  trous acid  upon it, 1380  Of thofe
  of tartar  and  lemons,  1382  Of
  fluor acid,  1383  Effeds of man-
  ganefe on  nitre, 1384   Experi-
  ments of  manganefe united  with
  phlogifton, 1383, et feq.  By di-
  ftillation  per fe,   1386    Boiled
  with  oil-olive, 1387   By diftilla-
  tion  with  charcoal, 1388  With
  fulphur,   1389   By   calcination
  with  nitre,  1390   With the ad-
  dition of  arfenic, 1391   ly di-
  ftillation with fal ammoniac,  1392
  By digeftion with pure nitrons  a-
  cid,  1393   Deftroys volatile alka-
  li  by  attrading  its  phlogifton,
  1394  Effeds of  diftilling it  with
  arfenic, 1393   With   cinnabar,
  1306  With corrofive  fublimate,
  1397   Ufed for  the  redification
  of ether, 1471.
Margraaf's analyfis of all the differ-
  ent kinds of  clay,  648   His ex-
  periments on the phofphoric acid,
  906   His  method of  reducing
  luna cornea, 1134   His procefs for
  making phofphorus with plumbum
  corneum,  1407 Experiments with
  phofphorus on metals, 1413  Me-
  thod of procuring the acid of ants,
  1302.       '
Marine acid,  the weakeft of the  three
  mineral acids, except  when de-
  phlogifticated,  183   Why it ads
  on fome metals and not on others,
  198   Phenomena exhibited by the
marine acid on account if its na-
turally containing phlogicton,  203
D.ph.ogidicated  marine acid exa-
mined,   206   Vitriolic falts  de-
compofed by a  marine acio,  273
Contains lefs fire than  the vitrio-
lic acid, 278   On its expulfion  by
the concentrated vitriolic acid,  z^-.i
Receives fire  from  the  vitriolic
acid  during  its  expulfion,   284
Decompofes vitriolated tartar,  288
Requifites for the fuccefs of  the
experiment, 289  Cannot decom-
pofe vitriolated  tartar  previoufly
diffolved in water, and why,  290
Decompofition  of Glauber's  fait
and vitriolic ammoniac  by marine
acid never complete, 291  Nitrous
falts decompofed by  marine acid,
292   Cannot  decompofe  felenite,
294   Solution of filver conftantly
decompofed by  falts  containing
marine  acid, 308,  312  Vitriol
of  mercury  decompofed in  the
fame  manner, 313   Nitrous acid
has lefs  affinity with  metals than
the marine 338  In what cafes
marine acid can diffolve metals  and
when it cannot, 340   Forms  a
triple fait with iron and regulus of
antimony,  366   And with  regu-
lus of antimony and  copper, 367
Arfenic precipitated  from marine
acid by  copper, 370  Quantity
of marine  in digeftive fait,  379
Of mild and cauftic vegetable id-
kali faturated by marine acid,  382
Quantity of mineral alkali fatiara-
ted by it,  433   Of the quantity
of marine  acid faturated by calca-
reous earth, 438  Quantity of acid
in  marine felenite, 441  Cannot
be  calculated  in marine  Epfom,
443   Quantity  of earth  of alum
faturated by  marine  acid,  430
Quantity of iron diffolved by it,
462  Calces of  iron  precipitated
from  it  of a reddifh colour,  463
Quantity of copper diffolved by it,,
469  Tin diffolved in marine acid,
473   Lead  diffolved in  it,  477
Of the diflblution of filver in it,
480, 8or  Solution of zinc in  ma-
rine acid,  4jO   Bifmuth  fcarce
foluble  in  it,  493   Solution cf
nickel in it, 493   Regulus of an-
timony fcarce foluble in marine a-
cid,  303   Why  the  marine  acid
ads fo  weakly, 310   Its nature
and combinations with other  fub-
ftances particularly treated of, 782
Moft commonly found combined
with  the mineral alkali, ib.  Why
it is  thought  by fome to be the
fame with the  vitriolic, 783   An
experiment tending  to make this
obfervation  probable,  784   Dr
Prieftley's obfervations cm marine
acid,  783   How  procured   by
means of the vitriolic,  786*  Why
its diftillation  with  copperas does
not Succeed, 787  To procure ma-
rine acid by means of the nitrous,
788   By  diftilling  common   fait
per fe,  989  Marine acid dephlo-.
gifticated by that of nitre, or by 
2^0
C    M    E     M    I    S    T     R    Y.
Index.
 man.'anrfc,  790   Mr  S:heelc'*
 meth >d of dcphlo;  i'lcatnrg t by
 manganefe. 7yi   Piopcrti.cs of it
 when depl.lo^iftictcd, 792   Mi-
 ni e  acid combined with  alk ilnc
 ta.it*. 79^   U ith  v.getable.  fix-
 ed  Jkah,  7^1    With   mineral
 a.kin', *9t  Volatile  alkali, 793,
  7v<i   Combined   with   earths,
  7>7   With  metallic  fuhflanccs,
  79^  Ihflolvc* and Volatilizes the
 calx of gold, ib   With 1.1. cr,  801
  Diffolve'  the  red  filver ore,  ib.
  Form*  Inti.i cornea with  thi»  me-
  tal, 801, 803   With  copper,  84
  With iron, Bos   Volatilizes  this
  in .t.il, 806  The folution of iron
  in this acid ufed  in medicine,  807
  FuM. r...c of iron, and fal ammo-
  niac named ftons  martiales,  808
  Solution of tin, 809  Of great ufe
  in dyeing, ib.  Volatilize* the me-
  tal, and forms wi'h it the fmoking
  1 quor  of  Libaviu-i,  810   With
  Lad, X11   Forms with  it plum*
  bum corneum,  812   With quick-
  diver, 813  Forms with it corro-
  five  fublimate,  814,  et feq.   See
  C.rirftvi.   Volatilizes zinc,  820
  With regulus of  antimony,  821
  See  Butt.r.  Forms a  fine fympa-
  thetic ink with regulus of cobalt,
  8:2   Combined with inflammable
  f.ibflanccs, 824   Marine  ether,
  ib.   Of  its attradion for phlogi-
  fton, 823   lo  not the fame with
  \:Aa,t acid, 8j3  Expels the fluor
  acid, 2d 830   Purifies fait of  am-
  ber, 911   Phenomena on diffol-
  ving vitriolic falts in  marine acid,
  1041  On mixing them with fo-
  hitions of calcareous earth in ma-
  1 me acid, 1042   Of the folution
  of terra ponderofa in it,  K33  Is
  not  neceffary  for  the  preparation
  of auium fulminans,  u 17   So-
  lution  of cobalt  in  marine  acid,
  1302  Effeds of manganefe upon
  it,  17,04  Exiftence  of phlogifton
  in it proved,  1381   Can  fcarcely
  unite with hitter of  arfenic, 1282
  Dephlogifticated  marine acid the
  01.ly folvent of platina,. 1319   U-
  K.1 f.ir diftillatiuii of fpiiit of ni-
  tre,  73 7   Various  methods of ma-
  king marine ether, 824   Method
  of diftilling the acid with  clay,
  1480  Effed of it upon phlogiftic
  natters,   1481   Glafs  corroded
  h\- it, 14S2  Caufe  of its yellow
  coiour,  I483    Effed of the de-
  p! logiftrcatcd acid upon phlogiftic
  matters, 1483   How to m.ike ma-
  rine ether from  the  dephlogiftica-
  ted acid, i486.
Marks, chemical, treated of 55 r.
  Marmcr met.Ill: i. ■?., Withering'* ei-
  I  r.ment* on  it, 1060   Diflblves
  in concentrated vitriolic acid, 1063
  Precipitated from  it  unchanged
  by  vegetable  fixed  alkali,  icf'4
  \\.\-  lie  decompofed in  the  dry
  way by Cdt of tartar, 1063.
"fsrtial vitriol, proci.r-i  by precipi-
  tating copper with iron, lefs fit for
  dyeii.^' than t.ie common,  344.
Marro-v analvfcd,  147,0.
Mathematical  fp.e;!:c  gravity  ex-
  plained,  373   The  mathematical
  fpecific  gravity of fpirit of nitr--
  de:. ruined, 388.
/■tsyer't examination of the fluor  a-
  cid, 841, &c.
Melting furnace  defcribed,  2d 603,
  et feq.   See Fur-tj...
Menftruum, a quantity  of it retained
  by fome j recip tates, 251.
M.-ftiuum f.n- jir.pitu,  a liquor  for
  diffolving gold,  1119.
Al.-.-..rius d-.d.t ,  how prepared from
  corrofive  fublimate.   814,  819
  Preparation of it in the moift way,
  1238.
Mercurius precipitatus per fe, how pre-
  pared, 1228.
Mercurius Trifmegiftus,  the fame with
  Hermes or  Siphoas, an  Egyptian,
  the founder of chemiftry, 3.
Mer.ury, of its precipitates, 236   Its
  folution  in  nitrous  acid decompo-
  fed by vitriolic falts, 311    Vitriol
  of mercury decompofed by  marine
  acid, 313  Why corrofive mercury
  is precipitated  by  oil of  vitriol,
  313   Examination  of Dr  Prieft-
  ley's experiment  concerning  the
  revival of mercury,  322   Why fo
  much of the meul was revived in
  the  Dodor's   e ■cpcriu.ei ts,  323
  Why copper is ihfiolvcd by folu-
  tion of mercury, 336   Precipita-
  tions of mercury by  copper, 333
  Why mercury  and  filver precipi-
  tate one another from the  nitron
  acid,  3S'   Corrofive  1 .blitciate
  cannot  be  decompofed  by  filver,
  though mercury can decompound
  luna cornea,  336   Why precipi-
  tates of  mercury and alum contain
  part of the acid, 4. 3   Of mercury
  diffolved in vitriolic acid, 483, 704
  See Qiickft/ver.  Copper, how amal-
  gamated with mercury,  113 2  Dr
  Lewis's  methods,  113 3   A  cu-
  rious amalgam with verdigris,  ib.
  Cannot be united with iron, 1162
  May be feparated from its fob.tion
  in  nitrous  acid  by  the colouring
  matter  of  Pruffian  blue, 1203
  Ufes of the amalgam of mercury
  and tin, 1223   The metal parti-
  cularly  defcribed,  1223    Is fen-
  fibly heavier  in winter than  in
  fummer, ib.  How  purified, 1226
  Curious mercuries prepared  by  Air
  Boyle, 1227  Is calcined into a red
  powder, by being expofed to acon-
  fiderable degree of heat, and to the
  air at the fame time, 1228   Is  un-
  alterable by a  gentle heat, or  by
  repeated  diftillations,  1229, 1230
  Explofion  by  its  vapours, 1231
  Amalgamated  with different fub-
  ftances,  1232   Separation  of  the
  amalgamated  metal,  1233   Be-
  comes fixed by amalgamation with
  e- ild, 1234  Suppofed to be con-
  \crtible  into  water,  1233   The
  miftake  deteded by  Dr  Lewis,
  1236   How   to amalgamate  it
  with regulus  of  antimony, 1237
  Can fcarce be united with pla-
  tina, 1345   Will leave p'atina to
  unite with gold, 1346.
al/ci'.;.'/.'; ceLe>,  of their  various co-
  lours 192  Metallic  folutions con-
  tain a calx of the metal with va-
  rious degrees of  phlogifton,  214
  Phlogifton the c-afe of their co-
  lour, 218  Some metallic lalu de-
  compofe others,   224   Advanta-
  ges to be derived from the exami-
  nation of metallic  precipitates, 233
  Metallic falts  infoluble in  water
  without en excefs ofacid, 297   Of
  the  attradion of metallic calces to
  phlogifton, 326   Of finding their
  fpecific gravity, 327   Table of the
  proportional  affinities  of  metallic
  calces to phlogifton,  329   They
  can never be totally  dephlogiftica-
  ted by acids, 407  Of their gene-
  ral properties, 3 19   Are foluble in
  acids, 320   Compofed of an earth
  and phlogifton, 32;   Their calci-
  nation and revivicatien, 32a  "in-
  creafe  of weight by  acids, 323
  Reafon  of the increafe of  weight
  in  metallic  calces, 324  Combi-
  nations  of them  with acids.  See
  Aeid and Metals.   Lapis pondero-
  fus fuppofed by Mr Bergman to be
  a  metallic euith, 967   Why  he
  fuppofed ttic  acids e>f  molybd.xna
  and tungllen to be metallic earths
  973  Cli.-inical properties of the
  di.'.ercrt  ii eta'.iic fibftanccs   ii>-
  vcftig itd. 1. h'9,  etfeq.   Effeds
  of the colouring matter of Pruflian
  blue on met. ilic calces. 1192   Its
  e.fed: on metallic folu  ions, 1193.
Mnals may receive  a  valt qu intity
  of  heat more than is fufficient to
  bring them into a ftate of fufion,
  129  The  calces of  the  pcrfed
  ones reducible with ut addition, a
  proof of the  nonexiftence of phlo-
  gifton, 140   Why they w.igh lefa
  iu their metallic than in their cal-
  cined ftate,  130   Combine with
  acids, 176   Separate  from them
  again on the addition of earths or
  alkaline  falts,  177    Phenomena
  attending their folution in acids,
  180  Of their dirt rent degrees of
  folubility,   1^5   Their  folution
  attended  with effervefcen.e,  188
  And heat,  190   Yield little  air
  after they have been calcined,  191
  Why marine acid ads on fome of
  thei* and not on others, 198  Why
  fome metals arc more foluble than
  others,  197   Their  folution* con
  tain a calx of the diffolved metal,
  214  Reafons for believing  that
  this calcination  takes  place, 213
  Why the calces of tht  perfed me-
  tals may be reduced  without addi-
  tion, 216   Phi nomena attending
  the precipitation  of metals by al-
  kaline falts, 2*0  Their  precipi-
  tation by one another owing  to
  a  double elcdive attradiou, 229
  Van; tions in the  order in which
  they prccip-tate one another, 230
  They  contaii different quantities
  of phlogifton, 238  Difliculties in
  determining the  attractive powers
                    2
  of the metal* to acids, 296   Quan-
  tities of the different  metals taken
  up by acid::,  298  Metals  have a
  greater  affinity than-alkalies with
  the acids, 299  Why alkalies  pre-
  cipitate  the  m.tah, r3cxJ    Why
  the metallic earths feldom  decom-
  pofe falts having an earth or a.kali
  for  their  bafis, 304  Explanation
  of the Miblc of affinities of the acids
  to the different metals, 316   Of
  the quantity of phlogifton contain-
  ed  in  the  different  metals,  317
  Quantity of it  loft by metals  du-
  ring calcination, 331    Why the
  metals are  more dcphlogifta ati J
  by  mutual  prcupitation than by
  dired folution, 333  All of them
  diflelved by nitrous acid, 338  In
  what  cafes the marine acid  can
  diffolve  metals, and when  it can-
  not, 340   Mr  Kirw.111'9  experi-
  ments on metals,  431   Beft  me-
  thod  of  diffolving them,   45a
  What metals are  calculable,  and
  with  what  degrees of  heat,  530
  Of  their rufting, 341   Their fu-
  fibility increafed by mixture,  342
  Their folubility increafed by .calci-
  nation,  345    1 !Te6ls  of  fulphur
  on  them, 346   Of their divifion
  into meta'i and femimetals,  547
  Their good and  bad qualities as
  materials for chemical veflels,  360
  Vitriolic fal ammoniac erroneoufly
  fuppor;d to be  a great  folvent of
  met.Is,  (.74   I ffeds of vitriolic
  acid on netals, 691  etfeq.   Ofthe
  nitrous acid, 730   Of the  marine
  acid, 799   Of  the  fluor acid, 833
  Of the acetous, 872  Ofthe acid
  of tartar,  894  Of the acid of fu-
  gar, 90   Ofthe phofphoric acid,
  906   Of  the acid  of amber,  915
  Acid of molybdama has  no fign of
  any metal, 964  Metals diflolvcd
  by hepar fulphuris,  1023   Combi-
  nation of  volatile alkali  with  me-
  i.i's IU34  Their  properties  par-
  ticularly treated, of, 1090  The
  fufion (.'.  all metals promoted by
  bifmuth,  1231   Of the effeds of
  white au.nic on them,  1277  Ef-
  feds of  regulus of arfenic on other
  iretals,   12S8   Combination of
  metsls with fulphur, 1403   Effeds
  of-phofphorus on them, 1413.
Microcofmic fait, how prepared from
  urine,  903   Mr  Margraaf's ex-
  periments on it, 606.
Milk, of its acid, 974  Acquires its
  greateft acidity by  ftanding a fort-
  night, ib.   Scheele's  method  of
  procuring the pure acid of milk.
  976  Properties of this acid, 977
  It feems to be of the acetous kind,
  97b  Milk is capable of complete
  fermentation, 979   How  to  pro-
  cure the acid of fugar of milk, 980.
Milled lead:  rfle  advantages  of ufing
  it in preference to fheet-lead pre-
  carious, 1270.
Mindereri fpirit us ;  how to  cryftral-
  lize it,  1513.
Minium, of  the revival of lead from
  it by inflammable air,  324  How
                                 to 
Index.                                 CHEMISTRY.
261
  to prepare it from the metal, I213.
Mineral t.ikaH, why preferred as  a
  precipitant by Mr Bergman,  231
  Precipitates platina  imperfedly,
  234  An equal quantity of all the!
  mineral acids taken  up by  vege-
  table fixed alkali.  See Acids. How
  to prepare  the mineral alkali for
  experiments on the  precipitation
  of metals, 429   Quantity of it ta-
  ken up by the dephlogifticated ni-
  trous acid, 332  Excefs of  acid *in
  aluminous ley cannot  be removed
  by  mineral alkali,  630   Of its
  combinations  with the different a-
  cids.   See Acetous,,  Marine,  V'f
  triolic,  &c.  Difference between it
  and  the  vegetable  alkali,  1019
  Whether mineral  alkali can fepa-
  rate platina from  its folvent, 1329
  Fifty-fix times as much of  it re-
  quired  to precipitate this metal as
  of vegetable alkali, ib.
Mineral Acids.  See  Acids.
Mineral -waters : Mr  Woulfe's  teft
  for them, 1337.   See Waters.
JMifpickel, a  natural regulus  of arfe-
  nic, 1286.
Mixtures;. the attradivc powers of
  acids determined  by  the  various.
  degrees of  heat excited by them,
  277   Increafed  denfity of  mix-
  tures accounted  for, 374    Timu
  required by mineral acids and wa-
  ter to acquire their utmoft  denfity,
  422   Phenomena refulting from
  mixtures of the different acids, al-
  kalies, and  neutral falts, with  one
  another, 1040, dfeq.
Molybdana,  acid  of, examined, 937
  How to reduce  the  fubftance  to
  powder, 938   Effeds of the acid
  of  arfenic upon it, 939   Violent
  adion of the concentrated nitrous
  acid upon this fuhftance, 960   A-
  cid  of  molybdaEna procurable by
  fire alone,  961   Its chemical pro-
  perties, 962  Is   capable of unit-
  ing  with phlogifton,  963   Shows
  no  fign of containing  any metal,
  964   Properties  of the acid  ob-
  tained  by  nitie,  963   Molybdae-
  na  recemppfed by uniting  its a..id
  with fulphur, 966   Differences be-
  twixt the  acids  uf tungften and
- molybdrena, 971   M.   Pelletier's
  experiments on this acid 1497-
M'ennct's opinions concerningthc fluor
  acid, 833   Shown to be erroneous
  by  Mr Scheele, 834   Miftake of
  Mr  Monnet concerning the bafis
  of fluor fpar, 838.
Morveau's  miftake  concerning  the
  preparation of  Glauber's fait from
  alum dcteded by Mr Kirwan, 642
Mofes fuppofed to be well fkiikd in
  chemiftry, 4.
Mucilage  of   vegetables  confidered,
  1492   Of  animals the fame with
  jelly or glue, 1434
Muriatic.   See Marlr.e.
Naphtha, a fine kind of mineral oil
  defcribed,  :44*-
Neumann's obfervations on the pre-
  paration of tht  magiftery  of bif-
  $iu,th, 766.
Neutral falts compofed of an acid and
  alkali, 172   One  for  difcovering
  iron in mineral waters, 1180  Pla-
  tina may be partly precipitated by
  fome neutral falts, 1331.
Newton, Sir Ifaac, his fentiments con-
  cerning heat, 31.
Nicbolfon'i account of the theories of
  heat, 79   Anfwer  to his argu-
  ment concerning vibration as the
  caufe of heat, 81  His account of
  the  capacities of bodies for con-
  taining heat, occ. 113.
Nickel,  a kind of femimetal, of its
  folution and precipitation, 242  Is
  precipitated "by zinc,  338   Iron
930   Properties of  the acid of
molybdaena obtained by nitre, 963
Alkalized by iron, 1206  And by
the flowers of zinc, 1249  Effeds
of  regulus  of  arfenic  on  nitre,
1290  Effeds  of  it  on  cobalt,
1303  On  nickel,  1310  Is ca-
pable of  feparating all  the cobalt
from  nickel,   1311   Effeds  of
manganefe on  nitre,  1384   Of
phlogifticated manganefe upon it,
1390  M.  Berthollet's  new  fait
refembling it,  2d 793  Method
of  making  it  in quantity, 1487
Generated in foms cafes without
putrefadion, 147 T
and nickel will fcarcely precipitate Nitrous acid, the moft violent of any
  one another, 339  Nickel preci
  pitates copper, lead, and bifmuth,
  360   Throws down fome hetero-
  geneous  mattcr  from cobalt, 363
  Of  its folution  in vitriolic acid,
  493   In  the nitrous acid, 770  Ef-
  feds of acid of arfenic upon it, 05$
  The femimetal particularly treat-
  ed of, 1306  Difcovered  by  Mr
  Cronftedt,  ib.  Effeds of calcina-
  tion with a violent heat upon it,
  1307   Of fulphur and borax, 1308
  Of hepar fulphuris, 1309  Of nitre,
  1310   This fait feparates  all  the
  cobalt in  the   femimetal, 1311
  Effeds of fal ammoniac  upon  it,
  1312   Of nitrous acid,  1313   Of
  volatile alkali, 1314   Nickel  can-
  not be obtained  in a ftate of puri-
  ty,  1313  Bergman's  opinion  of
  its  compofition,  1316   Experi-
  ments to compofe it  artificially,
  13*7-
Nitre : quantity of acid, water, and
  alkali in  it, determined, 391 Why
  it is fo much lighter  than vitrio-
  lated   tartar,  416  The  ingre-
  dients  of which it is.  compofed,
  420   Of the preparation of nitre^
  724   et feq.  rMfcovered in fome
  places  in Podolia  in Poland, 723
  In Spain  and America,  726  Re.
  quifites  for  its  formation,  727
  Cramer's artificial compoft for ma-
  king it,  728   How  prepared  in
  Hanover, 729   In other parts of
  Germany,  730    In  France, 731
  Dr  Black's conclufion  concerning^
  its nature, 732   Suppofed to  be
  the laft effect of putrefadion, 733
  Flow to  procure the fpirit of nitre
  by  means  of vitriolic acid,  733
  Of its redification, 736  Different
  methods  of  diftilling,  737    Its
  ufes, 738  Prepared from  the ni-
  trous acid and veg table fixed  al-
  kali,  740    Cubic nitre  formed
  from this acid and mineral alkali,,
  741   Enumeration of its proper-
  ties and ufes, T41, 743  Danger
  of fivullowing large quantities of
  it, ib.   Is  pur.fiec. by throwing a
  little fulphyr on its furface while.
  melted,  744   Calcareous  nitre,
  747  Heiw alkalized by charcoal,
  779    CTyffus of o't.e,  780    Its
  acid  expelled by that  of phofpho-
  rus, 907   And by that  of  amber,
  910,  And by the acid of arfenic,
in its  operations, 181   Renders
the calces of metals almoft info-
luble, 196   Why it precipitates a
folution of. tin  or antimony, 4.00
Is more obvioufly changed than
vitriolic  by the  addition of phlo-
gifton, 203  Vitriolic falts decom-
pofed by it, 273   Contains  lefs
fire than the  vitriolic  aqid, 278
On the expulfion of it by the vitrio-
lic acid, 280   By a fmall quantity
of dilute vitriolic  acid,  282  Re-
ceives fire from the vitriolic during
its expulfion, 284  Of the decom-
pofition of  vitriolated tartar by it,
28.3   Vitrolated tartar  cannot  be
decompofed by  dilute nitrous acid,
387-  N'frous falts decompofed  by
marine  acid,  292   Marine falts
by  the  nitrous acid,   293   Ni-
trous acid attrads filver  more than
fixed  alkali, 301   Nitrous folu-
tions  of mercury  decompofed  by
vitriolic  falts,   311  Nitrous acid
diffolves all metals, though  it  has
lefs affinity  with  them than  the
vitriolic  or marine, 338   Why
mercury and filver precipitate one
another from the nitrous acid, 355
Regulus of arfenic precipitated  by
bifmuth from the nitrous acid, 369
This acid,  when pure,  cannot  be
made to exift  in an aerial  form,
383   To find  the fpecific gravity
of pure nitrous acid, 386   Quan-
tity  of  mineral alkali taken up  by
dephlogil-icated nitrous acid, 432
C" amity of ingredients in nitrous
felenite,  440  -In  nitrous  Epfom,
444   Of pure earth of alum taken
up by it, 449   Of iron diffolved
by it,  438  Quantity   of nitrous
air  obtained  from this folu-ion,
439   Nitrous  acid cannot ad up-
on iron in fuch a dilute ftate as the
vitriolic, 461    Of copper  diffol-
ved by the nitrous acid,  468  Tin
diffolved by it,  472  Of lead dif-
folved  in nitrous  acid,  476  Sil-
ver with nitrous acid, 479   Calces
of go:d  foluble by it,  483  Can-
not dii olve golJ according to  Mr
Kirwan, 484   Zinc with  nitrous
acid,  488   Lefs metal diffolved
by  concentrated  than   by  diluted
nitr-ius  acid, 489   Effeds  of  this
acid  on  nickel, 494  On regulus
of atitimony,  300  On reguiu -of
arieiiic, ^03  Effervefcence between
 nitrous  and  fulphureous  fumes,
 626  Experiment relating  to  the
 converfion of the vitriolic into  tne
 nitrous acid, 720   Inconclufive,
 72.t  Of  its origin,  2d 722  At-
 trsdion for phlogifton, its  diftin-
 guifhing charaderiftic, 734   How
 to extract, it by means  of the  vi-
 triolic,  733   How  to purify it
 from any  vitriolic  taint, 736   Of
 diftilling it with different  fubftan-
 ces  containing  the  vitriolic acid
 737   Of  its ufes, and the method
 of diftilling  it in the  large way,
 738   Procured of a blue colour by
 means of  arfenic,   739   Of  its
 combination  with  alkaline  falts,
 740   Forms common nitre  with
the  vegetable alkali, ib.    Cubic
 nitre with the mineral, 741,  Ni-
 trous ammoniac with volatile  al-
kali, 743   Of its combination with
earths, 747  Forms calcareous nitre
with  quicklime  or chalk,  ib    Is
decompofed  by  quicklime, 748
 Forms Baldwin's phofphorus with
it, 749   Produces aftringent com-
pounds  with earth of  alum, and
purgative   ones   with  magnefia,
ib.   Of its  combination with me-
tals, 730  Is capable of diffolving
gold in fome cafes, ib.   Diffolves
and  cryftallizes  with filver, 731
 Forms lunar cauftic  with it, 75 a
Diffolves and cryftallizes with cop-
per, 737  Corrodes, and ads vio-
lently upon iron, but fcarcely dif-
 folves it, 739  Diffolves tin  in ve-
ry  fmall  quantity,  760   Forms
 a violently decrepitating fait with
lead, 761    Diffolves  quickfilver
in great  quantity,  763  'Purified
by  diftillation »from this metal,
from vitriolic  or  marine  acids,
 764    Readily  diffolves bifmuth,
 763   And  zinc,  767   Corrodes.'
regulus of antimony, 768   Dif-
folves  cobalt, nickel, and arfenic
 769,  770   Affords  a method  of
 difcovering  cobalt in  ores, 770
Thickens   expreffed   oils,   711
 L'orms ether with  fpirit of  wine,
 773; etfeq.   Of its decompofition
by  phlogifton, 778    Takes  fire
with fomc cffentiil oils, ib.  How
to procure  marine   acid  by  its
 means,  788  Dephlogifticates this
 acid, 790   Fluor acid procured by
its means, *d 830  Effeds  of it
 on  fait of  amber, 912  Arfenic
 decompounded by  it, 918   Vio-
 lent  adion of it  on molybdaena,
 960  Effeds of diffolving vitrio-
 lic falts in it, 1040,  IC42   Forms
 fine  cryftals with terra  ponderofa,
 1066   Is not  neceffary  for  the
 preparation of aurum  fulminans,
 1117  _Effeds  of  it  on  arfenic
 miueralized by fulphur, raSo  Re-. -
 gulus of cobalt combined with it,
 1301   Its effeds on nickel, 1313
 Explanations of  it- effeds on man-
 ganefe, 1380 . Of d.gefting phlo-
 giilictcd. manganefe with pure ni-
 trous  acid,  13^3   Camphor  de-
 compofed by it, 1424  Procurable- 
 I y  iresn* of fpirit of  fu'.t,  73 7
 Movr to procure the dephlogifti-
 catcd kind, 73R, 1 47c   l/ivo.lier's
 accoc. t of the c nftitucnt parts of
 nitrous acid, 14-3   Mr  Cavcti-
 difh'n account, 1474   How to fit
  cl arcoal  on fire by  means o'f it,
  1476   Remarkable effeds of it,
  on blooJ, 1477   Mc Tchcclc's ex-
  ] ■ rioicnts with  it on various i'ih-
  It^nccs, 1313  Volatile alkali I.
  pared from nitrous acid and  t,n,

  Smr.c  lste-   experiments  of  Dr
Pricill y. have fhown, that though
nitrous acid is produced from the d.-
conpofition of dephlogifticated  and
pi ',.gifticated  air, by taking the elec-
tric fpark in the  mixture, it is like-
wife  produced by  the  more rapid
decompofition of combuftion, when
inflammable air is made  ufe  of in-
ftead  of the phlogiilic;.txd kind.  In
this  caff,  though phlogifticr ted air
fhould happen to exift in the> mi. -
ture,  it is not in the leaft affeded by
the  procefs, hut  remains  after the
combuftion of the others,  juft  as it
was; nay, the Dodor obferves, that
1 .•  the addition of phlogifticated air,
tin quantity of nitrous acid produ-
ced  is fo far from being augmented,
that it is much diminifned.   The a-
cid in thefc proceffes always  appears
to  he extremely volatile, infomuch
that fomc part cf it conftatitly cicapc-.
No liquor  -'"jM was condenfed when
the explofioni were made in  quick
fucceflion,  even though the veffel ne-
ver became hotter than the hand.  In
another procefs, the atmofpheric air
was  perfedly excluded,  while the
 pureft dephlogifticated air was pro-
 duced from one of the materials em-
 ployed,  viz.  precipitate  /. r fe.   In
this experiment he found, that a con-
 fidc-abie  quantity  of  fixed  air was
 pro duced,   and that  the water be-
 came acid by the  abforption of it.
 He   concludes,  therefore,  on  the
 whole, that a mixture of dephlogi-
 fticated  and inflammable air always
 produces an acid by coiobuiiion  ; but
 that, when they are in their nafcent
 ftv.. the  aerial  acid  is  generated;
 when both are  completely formed
 p-.vious to the experiment, the ni-
 tres acid  appear*.
 K.iraus air .  Why it does not  unite
   with  water,  -04  Quantity  of it
   produced by folution of iron  in ni-
   trous acid,  439  Quantity of phb-
   gi.lou contained in it, 303.
 Objects of  chemirry,  how diftin-
   guifhed from the sgents, 22   How
   claff.d,  i'y
 0,1 of vitriol precipitates  corrofive
   fublimate from  v..iter, and  why,
   >I3   K • -.» m's experiments  on it,
   393   Why the  diiut on  of it is
   neceffary  in  tl.ffc   experiments
   396   Quantity of fixtd  air  in nil
   01 tartar. 414   Why  oil of vitriol
   ar. ! iron produ> -  vitrio'.i. air, 43 ;
   Combination ol  <■:.  . vitriol .with
   conur.rn oil, ;IJ  Od of -r.'cnic,
       C    II    K    M    I
 I   .v prepared, 8:3   Effeds of oil P<
 of vitriol on fa'.',  of amber,  913
 Effeds ->f mixing oil of turpentine
 with arfenical  .1, 023   Of oil
 of vitriol by diftillation with the
 I i!t compofed of alkali and the co-
 louring  mattcr of  Pruflian blue,
  1191  Oil fuppofed by  Homberg
 to  be obtained  from flowers of
 zinc, 1-43   lhc  miftake difco-
 vered by Neumann, ib.   Another
 capable  of diffolving gold and fil-
 ver  leaf  by Mr Hellot, 12 ',4  Ef-
  feds of oil olive on  man-,atu is
  1387   I'imphor  folulle   in oil,
  1425    yhia   ty  of effential oil'
  oVaincd ini.i  turpentine,  147,7
  This oil vciy difficult of lulu tion,
  1438.
Oils expreff:', thickened  by  nitron
  acid, 771   Effeniial, fired by fpi-
  rit  of nitre,  778   Fixed alkalies
  combined with expreffed oils, 10:^)
  With efienti.il  oils, 10:7    Lead
  foluble  in oils, 12 [6  Of the com-
  bination of phosphorus with clLn-
  tial oils, I412   Chemical proper-
  ties of oils treated of, 14191 et fsq.
   liVcntial cils,  ib.   Empyreumatic
   oils, 1426  How  to purify ran-
   cid oilr,, 1431.
Operations  in  chemiftry  defcribed,
  with directions how to  perform
   ''•c't, 354. ''/•/•
Ores: Bergman's acceunt of the ".-
   luminous  ores in  Sweden, 631
   Alum,  fulphur,  and  vitriol, ex-
   traded  from the fame, 63 9   How
   to difcover cobalt in ores by means
   of the nitrous acid, 7 70.
Orpiment formed of fulphur and ar-
   fenic. 1279.
Oyfth-fblls,  of  thsir phofphoric qua-
   lity, 1087.
Papin's digefter defcribed, 367.
Para.-elfus, account of him, 14  Hi-
   ftory of chemiftry  fince  his time,
   IJ •
Peat analyfed, 1440.
Pelletier,  M. 'his method  of redify-
   ing ether, 1471   His experiments
   on molybdaena, 1497-
Pell'.n, an  obfolete chemical  veffel
   defcribed, 366.
Pcr.iLnd  Hills,  marmor metallicum
   found r.eir them, 1060.
P: y.cr metals.  See Metals.
Peruvian balfar?, yields acid  of ben-
   zoin, 1332.
Petroleum, or rock oil, account of  it,

FLi!t,:"ye/c fal ammoniac, compofed  01
   vitriolic  acid and volatile  alkali,
   633.
 PLLuflc  matters:  effed of marine
   acid upon them, 1481,
 Pblogl.:icated allJi, quantity  of pre-
   cipitate obtained from manganefe
   by it, 237 Phlof illicated air an  in-
   gredient in the it.trous acid,2d. 722
   How   prepared, 1028   Lots  its
   a kalnc properties 1168   Cannot
   pre-eipit.cte arfenic  e>:ccj t from ma-
   t'dcaciil, i:7c5  Phb-ifticat-d  ni-
   trous   acid  djiTelves   manganefe,
   IJ2J.
                                                       Inde,a.
                                   ed,  10C6   Fouvl in vaft qnsnti-
                                   u :\ in the  mineral kingdom, ib.
                                   In vegrtabh• and the giilric juice
                                   of animals, ib.
cination, 138   Fr  .,1  the  r'edue- Phofphoric liqror,  curious  one  from
tion of the calces of perfed metal.   arfenic and vinegar, 2d, 937, 1321.
                                 "h.f-hoift of Baldwin prep r.el from
                                   nitrons acid md  calcareous  earth.
   S    T   R    Y.
I gijhn :  Of it* exigence.  :7, 136
licnicd  by  M.  Lavoitirr,  137
Arguments  againft  it  from  the
increafed weight of metals by cal-
without addition,  140   The  de-
putes on this fubjed muft foon be
entirely decidid, 143   Objcdions
from  its  inviiibibty and fuppofed
want of gravity, 144 Comtnonchar-
coal and phlogifton the finite,  143
Decifive proofs of  its identity from
Prieftley's experiments 146  Too
mv.h phlcgiftcn prevents the her.t
of  a fire frum being  intenfe,  138
Solution  fometimes  promoted by
abrtrading  part  of  the  phlogi-
fton, 186   But totally prevented
by  taking away too much,  as  ex-
emplified    in   manganefe,  187
Hindered by too great a quantity
of  phlogifton,  194   Is  the caufe
of  colour  in  metallic  folutions,
218   Attradion   of  ph'ogifton
fuppofed to be the caufe  of  caufti-
city, 219   Metals contain  differ-
749   Phofphorus   fciutillans,  of
marine acid and calc.rcous  earth,
797   i>o!<  ■ 1 ian phofphorus,  re'li
How  r.-iif'cd luminous,   ic8a
Analyfed,  1083   Phofphorus  ef
urine, 1406  Mr Margraaf's pro-
eel^ for making it,  1407   Redi-
fication of this phofphorus,  1408
The procefs  for making  it fome-
times  d.c.:;-e-inis   1409   Liquid
phofphorus, how prepared,  1410
Experiments with  phofphorus on
fpirit of  wine,  14TI  With effen-
tial oils.indacids, i.\ r2  Mr Mar-
graaf's eveuninents  with it on mc-
ta'.s, 1413   Canton's phofphorus,
1414 Homberg's phofphorus, 1415
etfeq.  Sec Pyrophorus.
M. Pelletier has now difcovered  a
 ent quantities of it, 238   Of  the  method of uniting phofphorus, with-
 phlogifton contained in the differ-  out any  dccompolicioii, with  all the
 ent metals 317   Method of  cal-  met el ,  though he  cautions  againft
 culating this quantity exemplified  the danger with which the procefs is
 in regulus of arfenic, 318   Table  att.tided.  Gold is  phofphorated by
 of the quantities of phhyiP'n in  mixing half an ounce of its calx with
 different metal., 319  Of the at-  an ounce of phofphoric glafsand about
 tradio'n of ine^Hic calces to phlo-  a grain of powdered charcoal; the
 iofto:i,  326   Whence  their  va-  whole is then put into a crucible, tli-
 rVis degrees of affinity to phlogi-  compofition  covered  with  a  little
 lion  1 .ay  be  determined,   328  powdered charcoal,  and a degree of
 Table of  their proportional affini-  heat  fufficient to fufe the gold ap-.
 ties to phlogifton,  329  Quantity  plied.  A great many phofphoric va-
 of it loft  by them during  calcina-  pours arife,  but part  are detained,
 tion, 331    Their affinity  to  the  and unite with the gold which is left
 deficient  part  of their phlogifton,  at the bottom of the crucible.   The
 332   Increafe of the attradion of metal by this operation lofes its co-
 the calx of  irxi to phlogifton de-  lour, becomes  whitifh, breaks under
 monftrated,  342    Quantity  of the  hammer,  and  has  a cryflalline
 phlogifton  contained  in  nitrous appearance.   By continuing the fire
 air, 303   In fixed air, 2d 303  In  ajong time the phofphorus would be
 Vitriolic acid air, 306   In fulprjur, entirely diflipated.   The quantity of
 307 In marine acid air, 309 Attrac- phofphoric glafs  and  charcoal juft
 tion of marine acid for phlogifton, mentioned is fufficient to phofphorate
 825   Union of phlogifton with a- a  whole ounce of platina.  By an
 cid of molybdaena,  963   Is  r:- hour's calcination in a  crucible, the
 markably difpofed to fly off from metal is  converted into a  blackifh
 hepar fulphuris, IC24   Combined mafs refembling filve-r, weighing up-
 with fixed alkalies, 1028   Suppo- wn.rds of an  ounce, and of which
 fed to exift in the colouring matter the lower part confifts of cubical cry-
 of Pruffian blue, 1196  Is ftrong- ilals.  Notwithftanding this change,
 ly attraded by manganefe, 1372 however, the quantity of  phofpho-
 Gives  a  white colour  to manga- rus united with the platina is very
 nefc, 1373  Some phlogifton  na- inconliderable ;  for from  12 ounces
 turally contained in this fubftance, of  the metal, and as much phofpho-
  1374   Proof of its exiftence in the ric  glafs, only  12  ounces and five
 muriatic  acid, 1381  Sulphur de- grains  of the  phofphorated metallic
  compofed by a fuperabundance of m tfs  was  obtained.   It was very
  phlogifton, 1401.                 brittle, but of confiderable  hardnefs ;
Phofphoric acid, found in the refiduum, was not attraded by the magnet, and
  of ether, 2d 722   Expels  that of by expofure  to a  ftrong fire  parted
  fluor, 2d 830  This acid particu- with the phofphorus it had been com-
  larly treated  of, 9C4, et feq.   Ex- bined  with.   He  obferves, that  all
  pels the acids of variolated tartar, the metals lofe  their malleability  by
  nitre, and fea-fdt, 907  Can fcarce- combinni n  with  phofphorus, ex-
  ly diffolve manganefe,, 1367   Of ceptin0 tin and lead;  and  the rcfi-
  pi.ofphoric earthy ic8r, .-'//• 5ur- duum <i the matter which has once
  pnfing phofphoric qual.t; 01 oyfter- phofphorat.d a me cj^willfervc ag ain
  Ihells,  1087   By whom difcover- for the fame purpofe.
                                                                 Tht 
NDEX,
C    II    E    M    I    S    T    R
263
for;: heat,  1333   This fufion flip.
pel j J by Macquer not to be perfcd,
1334   Attempts to purify platina
by cupellation, 1333  Of the pof-
fibility of adulterating gold with
it,  1336   Methods of deteding
ty,  1358.
  The fait formed  by a eombinrtion
of the phofphoric acid with  mineral
alkali is found to be an ufeful purga-
tive, and as fuch is  now brought into
rradice.
  McflW Struve aud  Marquart  are
faid to have difcovered, that the  ga-
ftric juice of animals is compofed of
the phofphoric acid and volatile alka-
li ; and Mr Strive has compofed a li-
quid  from  .thefe  two  ingredients Pliny's account of the origin of glafs-
which ads in a  fimilar manner on a-    making, 7.
limenf&ry matters.                  Plumbum corneum  formed  of marine
Pitcoal analyfed, 1447.                 acid and lead, 812.
Phiina not  partly compofed of iron, Podolia, in  Poland:  nitre found  in
  234    An excellent material  for    the earth in that country, 723.
  chemical veffels, 387 Mr A chard's iV.tr rSe- i the exceflixc  cold  of
  method of making crucibles of its    winter, how mitigated,  98.
  calx, ib.   Effeds of acid of  ar- Poland.  See Podolia.
  fenic upon it,  942   Is the heavieft Ponderous fpar formed of terra ponde-
  of all metals,   1318  Infoluble  ex-    rofa and  vitriolic or aerial  acid,
  cept by  dephlogifticated  marine    1031  Sec Terra ponderofa.   Ana-
  acid, 1319  Found in fmall grains,    fyfis and properties of the aerated
  1320   Bergman's experiments on    kind, 1037.
  it, 13 21  Cryftals of it can be  de- Portable furnaces,boo, etfeq. See Far-
  compofed by the  mineral, but not    n.irei.
  the vegetable  fixed  alkali,  1322 Porcelmr veffels  of ufe  in  chemiftry,
  Soluble in aqua  regia  made  with   363, 391    Reaumur's porcelain
  nitrous acid   and fea-falt,   13:13   recommended,  392
  In one made of nitre and fpirit of   experiments upon it, 393.
  fak,  1324 Solution of the calx in Pott's diredions concerning crucibles,
  marine acid lets  fall a cryflalline   388   His melting furnace defcri
this fraud if it fhould be pradifed, Prefervativcs- ofivoad, 621.
1357   Platina  moft  eafily  difco- Preffure of the furrouding fluid a mean
verable by  its great fpecific gravi-   of retaining fire in bodies, c$.
                                 Prieftley:  difpute betwixt  him and
                                   Lavoificr, 141  Identity of phlo-
                                   em
tions  of, and  by regulus of  anti- gulcillwt a ei'c.recvi rv.".^ .h^p.ived
                                   of its fixedair, 311"   Decompofe*
                                   fpirit of nitre, 748   Is the bafis pf
                                   fluor fpar,  837   Effeds of it on
                                   fait of amber,  947
                                 Quickfilver fometimes produced  f/om
                                   lead, 12,   762   Its  combination
                                   with acids. See Mercury.  How
                                   to obtain a perfectly faturated' fo-
                                   lution of it in nitrous acid, 1293
                                   Quickfilver, fulminating, 3d 903.
      and charcoal given  by his Quiefcent affinities defined, 267
mony, 363   Of and  by arfenic,
368    Of regulus of  arfenic  by
bifmuth,  369   And  by copper,
370   T'hc operation of precipita-
tion defcribed, 370
                                 Radical  vinegar differs from thi
                                    common acetous acid,  1528  In-
                                    flammable fpirit produced from it,
                                    1544-
                                 Rancid oils purified by churning with
                                    water, 1431.
experiments, 323  His method of Realgar,  or red  arfenic,  prepared
procuring the fulphureous vitrio-    from arfenic and fulphur,  1279.
lie acid, 714  His obfervations on Reaumur's  porcelain prepared  by ce-
marinc  acid,  783   Experiments   mentation of green gla/y 59*  Dr
experiments,  146   Kirw..n's
animation of his  experiment con-
cerning the  revival of  mercury,
322  ,Why fo much of the  metal
was  revived  in  his experiments,
323  Kirwan's remarks  on  thefe
powder on the  addition of ve;
table alkali,  1325   But  not  the
nitrous folution,  1326  This pre-
cipitate a kind of" triple fait,  1327
Whether mineral  alkali can  fepa-
rate platina from its folvent,  1328
Fifty-fix times as much  mineral
alkali as of vegetable requifite  for
the precipitation,  1329   Effeds
of the volatile alkali on the  folu-
tion,  1330  The metal  partly
precipitable by neutral falts,  1331
  bed, 606   See Furnace.   His,ob-
  fervations on the decompofition of
  nitrous acid by quicklime,   748
  His experments on the fait of am-
  ber, 909.
Precipitate,  infoluble,  thrown down
  by cauftic alkali from folution of
  terra  ponderofa,  1036    Pheno-
  mena on diftilling metallic preci-
  pitates thrown down  by Pruffian
  alkali,  1198  Precipitate of plati-
  na vitrified by M. Beaume, 1332.
              on converting the fluor acid into a
              kind of air, 837   His experiments
              on the vegetable acid air, 883.
            Privation of heat totally : Mr Kirwan's
              theorem for finding the point of it,
              114.
Dr  Lewis's Pruffian blue, a  preparation of iron,
              1163    Dr  Woodward's  receipt
              for  making  it, 1164
              froy's  theory,  1163
             Lewis's obfervations  on the me-
             thod of making  it, 393   An ex-
             cellent material  for chemical vef-
             fels, ib. And for levigating planes,
             599    His method of  rendering
             lead fonorous, izi£   Hint for an
             improvement of  the fliape of bells.
             ib.
Mr Geof-  Red lead, how prepared,  1213.
 Amufing  Red precipitate of mercury, how prepa-
phenomenon in  the preparation,   red, 764.
1166    Macquer's  theory,  1167 ReduBion of metallic  calces,  without
Some blue produced by the com-   addition,  an argument againft the
mon alkalies, 1170  Mr Scheele's   exiftence, of phlogifton, 140  The
inveftigation of  it,  1171, etfeq.   phenomenon explained, 323.
Pruffian  blue yields volatile alkali Regulus.   See Antimony, Arfnic. and
by diftillation, 1197  Appearances   Cobalt.
on  diftilling   other  precipitates Reid,  Dr, "his  obfervations  on the
thrown down by the  Prufliai-; alka-   temperatures of bodies, 30.
Ii, H98   Appearances on lii'illing Relative heat explained,  38.
Pruffian blue accounted for, 1*03. Refins analyfed, 1432  Are  enly bal-
See Colouring matter.                 fam's thickened by evaporation, ib.
Triple falts formed by this metal, Precipitates, why fometimes thrown Pulvis Algaroth, the moft proper ma- Retort, a chemical veffel, defcribed,
1332  Platina the  moft infufible
fubftance in the world, 1333  Firft
melted by a burning mirror,  1334
May be  vitrified by eledric  fire,
*335  'ts  precipitate fufible  in a
common forge, 1336  This  pre-
cipitate,  or even  crude platina,
fufible by  the  affiftance  of fluxes,
1337  Alloyetl by Dr Lewis with
other metals,  1338   With gold,
1339  With filver,  1340  Cop-
per  confiderably  improved   by
union with it,  1341   It  unites
moft  readily  with  zinc,   1342
down by acids, 221   By the per
fed neutral falts, 222 By a triple
combination,  2,23   Various pre-
cipitates  of gold, 233   Of the
caufe  of  fuch great  variations  in
the weights of precipitates, 248 Pur'fiaeio.i of quickfilver.
Arguments in favour of the weight ry and Quickfilver.
terial  for  emetic  tartar,  1259   57°-
Objedion to  its ufe,  1260   The Rtvivif cation  of metals, how  accom-
objedion removed by Mr Scheele,   plifned, 322.
1261, 1262.  Sec Algaroth.  Pulvis Rinman's method of burning the ores
fulminans, how prepared, 1403.      of alum, 668.
                      See Mercu- Roofing aluminous ores, ufes of it, 662,
                                   et feq.    See Alum.
of  precipitates being  augmented Putrefaction: nitre fuppofed to be the Robinfon, Mr,  of  Glafgow,  deter-
by  the  matter of heat,  249   A   laft effed of it, 733   Not always   mines the  boiling point of water
quantity of the menftruum retain-   neceffary for the produdion of ni-   in vacuo,  123.
ed  by  fome  precipitates,  251   tre, 1478.                        Rocb-ahm,  whence that name is de-
Table of different ones, 259  Why Pyrites,   how  to extrad  green vi-   rived, 638,
thofe  of mercury and alum con-   triol from  it, 619    Its prefence Rochelle fait formed of cream of tartar
tain part ofthe acid, 408.           the only requifite for the produc-   and mineral alkali, 891.  Scheele's
■And with the compound metals, Precipitation .• . phenomena  attending   tion of alum, 634
•1343   The compound of  brafs
and ptatina a proper material for
fpeculums,  1344  It can fcarce be
itnited with mercury, 1345  Is de-
ferted by  mercury when  gold is
added,   1346    May  be  united
with  forged and  caft iron, 1347
And  with  tin, lead,  or bifmuth,
1348  May be  melted by means
of arfenic,  1349  The poffibility
of uniting  it with mercury dented
by Fourcroy,T 330 Inconfiftence in
his account of its hardnefs, 1351
Precipitate ofplatina vitrifiedby M.
Beaume, 1332  The precipitate by
fal  ammoniac fufible in a ftrong
that of  metals  by alkaline  falts, Pyrometer,  an inftrument for meafu-
220  Their  precipitation  by one   ring the expanfion of bodies, 103.
another owing to a double eledive Pyrophorus  of Homberg, 1415   Beft
attradion  229  Ufe of the tables   formed of  alum and fugar, 1416.
and calculations for  knowing a
priori the phenomena of precipita-
                                   method of preparing it, ib.
                                 Royal  Society, when  founded,   19
                                   This  and other focieties of  the
                                   kind has been of great advantage
                                   to chemiftry, ib.
Is not injured by expofure to light,  Rifling cf metals explained,  341   Tin
1417   Theory  of  its  accenfion,    lefs liable to this defed than  iron
tion, 333   Why mutual prec:pita-   1418.                              or copper, 1223.
t'011  dephlogifticates  the  metals Quadruple salts, how formed,273. Saccharine acid,  how prepared,
more  than  dired folution,  335 Quantity  of htat, difficulty of deter-   896  Saccharine,  ether, 902   Is
Precipitations by lead,  332    Of
mercury by copper, 333   Of nickel
by  zinc.  338   Of copper, .lead,
and bifmuth, by nickel,  360   Of
cobalt  by iion,  362    O' f'.rne
heterogeneous  mattcr  from  co-
balt  by nickel, 363    Precipita.
mining  it, 70   It cannot be ufed   not eafily fet on fire, and burns
in the common acceptation of the   with a blue flame, ib.
word with regard to fire,  71  It Saccbarum faturni,  its folution de-
cannot be determined by Dr Cleg-   ftroys that of green  vitriol, 1044,
horn's hypothefis, 76   Is  impof-   and  folution of tin, 1043   How
fible to be determined in any way,   prepared from  lead, 877   An in-
IIZ-                               flammable fpirit v.ojurable from it 
C    H    E    M    I     S    T    R     Y.
       ^1!.;  ,:   *■*
     .: 1.1 ii »' :  .  ijl,lc by means i»f a
    I .»f ar.ts  ur 1  • ■rii rfvirdeyri* 908
.*     'itiiic-i,<%  conn»ofcd of  fal am-
    icaiwc  and  endive  fublimate
   *ce A!i nl.otb.
 * ii .-irno :iac.  Sec Ammoniac.
 SA dig.-lixt-t.  See1 Digefive fait.
 ijl Jinrtt'.cnt,  how  prepared  f-<vn
   aeetout  acid  atid  vegetable  fixed
   alkali,  868.
 S tprun.'a,  prepared from nitre an!
   liophir,  744   Why the  nitre is
   thus ] 'lifted,  ib
 SjI ru/.  1111.   ■>ec Roch.l'e fit.
 e- A fedativus,   >s  : Borax,  acid of.
 »*>-.' volatile oleofum, a preparation*  of
   volatile alkdi,  fpirit of  wine, and
   tfl'cntial oils, 1036.
 Saline mixture prefcribed in f vers, the
   fame with a folution of foluble t..r-
   tir,  889.
 £'-.'.' of vine-ur,  formed from fpirit of
A  purticuUr S.hiele'i mrt'.iod of d.; hlogifticcring
                ipirit of  fait,  791   Dili: nets tiic
                fluor acid, &z6  His opinion that
                the earthy cruft formed by this
                acid proceeds from an u;iion  of it
                with water, 832  Deteds the  er-
                rors of ;  oullangcr and Mounet on
                this fubject, 834  E\phnation  of
                one of his experiments concerning
                this  rruft,  846   His method  of
                anal*.":..: cream of tartar and  ex-
                tracting  its acid puiv,  887  Dif-
                covers the  aeid  of   arfenic,  916
                His method  of analy ling  molyb-
                d.n a,  939  Tungften,  968  His
                mcthod'of procuring the pure acid
                of milk,  976   His receipt for pre-
                paring the flowers of benzoin, ^91
                1 or preparing the pulvis algaroth,
                1262  Difcovers the nature of the
                colouring matter of  Prulli..n blue,
                1171   Method  of preparing Ro-
                chelle fa  t,  89J.
verdegris, 8K2   ElTentitd fait  of Schitter's method of preparing the a-
Ictnotis, a kind of tartar r.arafted   cid of tartar, 888.
Iron forrel fold At it, S08  Frue Sch.f, aluminouc,  component parts  of
fait of lemons cannot be converted   it, (L<2.
                                  Sea-fall, decompofed in various ways
                                    with  lead, 302   Why  the diftil-
  into acid of fugar, 999    Neutral
  lalt f >r difcover'oj; ifon in mineral
  w..trrs, 1182    W'-tfon's  account
  of the fpecific gravity of fait  of
  tartar, ^ 3.
S.i .peln.  'ee' N-re.
Halt  : tfieir g.-.ural properties  con-
  fider.d,  164,   t ftq. are either fu-
  fible or  volatile,  ■' ■   Soluble  in
  water  and cnftulhzab e, ib.  Fheir
  folution  atten ied with an emiffion
  of air-bubbles  fo.netimes miftaken
  for an effervcfcei.ee,  163  Gmc-
                                    lation of it  does not  fucceed with
                                    copperas,  787   It-, a id not  the
                                    fame with that of fluor, 833   Its
                                    acid  cxpe'.ed by that of phofpho-
                                    rus, 907   Mid by acid of arfenic,
                                    9,1   Whitens  filver,  1137    Un-
                                    liiecefsiul  attempts to  decompofe
                                    11, 1479  Meihod of diftilling its
                                    acid  with  clay, I480  Effeds of
                                    the f'p.rit upon  phlogiftic matters,
                                    148  •
 raily foluble in greater quantTy in Sebaceous  acid,  procured  from  a  va-
 hot  th  n in cold  water,  in   bea    variety of fubftances, 1333   Has a
 fait an exception to 'I. i.- rue. <b. Of   remarkable  force  of  attradion,
 their mixture and feparat..>n,  166   1334   Irs effeds on tin,  1333   On
 Hypothefis concerning  their fo-   other fubftances, 1336.
 lut:on,  167   -ire dcftrudible by Secret fit ammonia.-,   Glauber's    See
 r.p. ted folution  and exficcation,   Glauber and Ammoniac.
 iC.-i  Divided iiito acids and alka- Sedative fait.   See E^rax,  acid cf.
 lies,  169   tne  Acid and  Alkali. Sc ^i-.tu's fait.  See Rochelle fait.
 Neutral fait*  formed  by the com- Set.rite.   See Gypfum.  round in the
 binatiou ot thefe  two, 172   Per-   refiduum of vitriolic ether, 2d 722
 fed  and in: . tfed i.tutral frits de-
 fined, ib.   Whv the acids and al-
 k-ilk.« generally efferscfee on inix-
 ti.i c-, ib.  Metui.ic folutions fome-
 timcs difturbed by  neutral  falts, Selenites  tartare'is, compofed of  acid
 222   Triple :e.\l  quadruple  falts,   of tartar aud calcareous earth, 887,
ho-.-,  formed,  273  Vitriolic  falts   893   The  liquor from^ which it
decompofed  by  the nitrous  and   has been extraded affords an em-
marine   rids, &c.  ?ve  Vitriolic   pyreumatic acid of tartar. 1010.
Nitre.u* falts  deccn-.poied by the Semimeial, a new one  procurable from
marine  acid,  ike.   See N.trous.   tungften,  1301.
Wi.y toe  ...etc.Llic  calces feldom Stmlmeuls, one of the general claffes
decoinvofc   the  per fed;   'icutraU,   ol  metallic fubfunces,  547.
'.:i  Ai;oii?al.-js fait- formed from S.-ftHc  h.-at,  Crawfords account of
Wftiy it can;:ot be decompofed by
marine  acid,  294   Quantity  of
ingredients in nitrous felenite, 440
In marine felenite 441.
   the  acetets  acid  and earths, 871
   Of fixci   'Vaiine labs,  1016  See
   A.i  lies.  Nutral falts partly pre-
   cipitate pi..t:na, 1331.
5 and mixed with ff'ur acid,  pro lu-
   ces :'o  earthy cru.l  bv difti.iation,
   8-N-
5.  r.d-p.-.-,  frllh, &.c  how to let them
   in furnaces, 610.
J.  p«i'-. of the aluminous orca found
   i^ ;L-:  ;»un:ry. 6j8.
  it,  49.
Slat-lad,  how made, 1209.   The
  ;.dvantages  of milled lead over  it
  Ver) dubious, J2IO.
Sil.x,  found in the refiduum of vi-
  triolic ether,  2d  722.
Siliceous earth, produces a cruft on the
  Water into which fluor acid is di-
  ft.lled,  829   See Cnfl.  Of  the
  tjUantityof  filiceous earth carried
  .do;.- with  this acid,  847.   Moft
  completely  precipitated from  .t«
  folver.ts  by volatile  alkali,   ic-4
  Diffolved by boiling in fixed  alka-
  line  ley, I076.
Silver:  Why the vitriolic acid cannot
  ad upon it without a boiling  heat,
  197   Difficulty concerning its a-
  i.-.algamation folved  ly Mr i'erg-
  man, 217   Precipitates of it,  233
  Is attraded more than  fixetl alkali
  by nitrous acid, 301   Expl. nation
  of the decompoiition.of vitriolated
  tartar by  folution of  fiiwr,  305
  Of other vitriolic  falts,  306   Its
  folution  always decompofed  by
  marine  falts,  308    Experiment
  explaining the lcjudion of its cal
  ccs per fe, 320  Why copper is dif-
  folved by  fo'ution  of  filver,   336
  Why a faturated folution of filver
  can fcarce be precipitated by  iron,
  346  Why copper  fometimes can-
  not  precipitate filver,  348   Can-
  not   prec.pitate  cop or from  vi-
  triolic acid,  334  Why  it preci-
  pitates  mercury from  the nitrous
  acid, 355  Cannot deeompof-  cor-
  rofive fublimate  except in the dry
  w'av, 336   Of  its  folution in  vi-
  triolic acid, 478  In marine  acid,
  4oe',  801 Of  its combination  with
  vi iiii'c  acid,  691   Has  a ftrong
  attraction   for   mercury  in   this
  ftate, ib.  Combination with the
  nitrous  acid,  731    Volatilized
  by uniting with this acid, ib.   Co-
  lours produced  by  this  folution,
  733   The folution  decompofed,
  733  Is not aded  on by the  arfe-
  nical acid,  943  The  metal  par-
  ticularly treated of, 1131  "Its duc-
  tility inferior  to that of  gold, ib.
  Its colour  and dudility deftroyed
  by fulphur, 1132  Purifed by cu-
  pellation with l"ad,  1133   Redu-
  ced from its combination with ma-
  rine acid, 1134, 1133  11,^ a great
  attradion for  lead, 1136  Whiten-
  ed externally by common fait and
  cream of tartar, 1137  Fulmina-
  ting filver  difcovered by Kunckel,
  736    By  M.  Berthollet,  1138
  How prepared, 1139  Fulm.i..itcs
  by  the  touch  of   any  fubftace,
  whether cold  or  hot, 1140   Dan-
  gerous to fulminate  more than a
  grain at  a  time, 1  41   Cryftals
  formed  by evaporating the liquor
  after the precipitation of  the calx
  explode violently by a touch,  U42
  Cautions to be ufed ir. preparing
  it, 1143   Abfi r.l thecny by which
  the antiphloreiftans attempt to ac-
  count for  this  phenomenon,  1144
  Remarks on  it  and others,  1145
  Electricity  probaby  the  caufe of
  this  phenomenon,   1146   Silver
  precipitated from its  folution in. ni-
  trous acid  by  the colouring matter
  of Pruflian blue, 1191,  1203  Com-
  bination of it  with  platina,  1340.
Sipboas, an Egyptian,  the founder of
  chemiftry, 3.
Smalt produced  from the calx of  co-
  balt and flints, 1293.
Smoking liquor of Libavius  prepared
                        Index.

  from corrofive fublimate aud tin,
    10.
Soap  common,  prepar d   by  com-
  bining fixed alkalies with cxprefT-
  ed  oils,  1026  StarkcyV  foap,  by
  combining them with effentiai oils,
  1027  lb's con.lunation diflici.lt
  to be  effeded, ib.   M  Beauine's
  method  by long trituration of the
  ingredient*,  ib   Dr  Lewis's,  by
  heating  the alkali  red  hot,  and
  mixing it \ ith   the  oil 111 that
  ft;te, ib.  T his foap naturally fub-
  jed  to a decompofition  by the ef-
  florefceiice of Lit,  ib.
$»fne/s,  of bodies,   approaching to
  fluidity caufed by heat, Il8.
SoLr  leal,  why fo  much   more in-
  tenfe than  that of common  fires,
  160.
Sjfutara, aluminous ores found  there
  analyfed by .Mr Bergman, 6$(>,
Solid bodies do  m.t part with fo much
  heat as fluids,  212
Solubility oi  different  metab,  various
  degrees of  it,  18c   Their folubi-
  lity  increafed by calcination,  545.
boluble  tartar,  prepared   by  com-
  bining cream of tartar with vege-
  table fixed alkali,  889  The fame
  with the  faiine mixture prefcribed
  in fevers, ib.
Solution of falts in water, phenomena
  attending   it,  163    Hypothefis
  concerning  it,  167  Salts deftruc-
  tible  by  repeated folutions,   168
  Phenomena attending the folution
  of metals,  180   Sometimes pro-
  moted by abftruding  a portion of
  pbio; ifton,  186   Totally prevent-
  ed by taking a.vay too much, 187
  Solution   of  metals attended  with
  eif< rve-ftence, 188   And the ex-
  trication of various kinds of elaftic
  fluid*, 189    d.trgman's account
  the  caufe  of  chemical  folution
  193   Solution  impeded  by too
  great  a   quantity  of  phlogifton,
  194   Heat  produced in folution
  moft probably proceeds  from the
  folvent liquor,  211   Reafons lor
  believing that  metals are calcined
  by  folution, 213    Why folution
  of gold  is precipitated by ft,  ution
  of tin, 227   Why folution of cal-
  careous  earth decompofes .: Ho-
  late.i tartar,  270   De. ...iipontioii
  of vitriolated tartar by folution of
  filver explained,  303   This  ft Iu-
  tion always decompofed by marine
  f.dts,  308   As  alfo foiution of
  had.* 309.  Solution  of  lead  in
  n.-rn 0 acid decompofed  by vitrio-
  lic  falts,  310  And ntrcus-folu-
  tion  of  mercury,  311    Solution
  of copper fcarcely decompofed by
  caft iron, 343.  Why _ faturatedfo^
  lution of liver can fcarce be pre-
  cipi -ated  by iron,  346   Ofthefo-
  lution of calces of iron in vitriolic
  acid  436   That of the dephlogifti-
  cated calces refufes to  cryfbiuze,
  437  Solution of tin  in vitriolic
  acid  yields  inflammable  dir. 471
  Ho-.v to  perform the chsmio! ope-
  i.u-jii of frvjtion, 364   iciiution
* 
Index.
CHEMISTRY.
265
75 r
 Its
75*
   of  filver  in  nitrous acid,
   Shoots into a corrofive fait, ib
   cryftals  form  lunar cauftic,
   Stains hair, bones, &c of a brown
   or black colour, 733   Imparts va-
   rious  colours  to ftones,  ib.   Cu-
   rious vegetations produced from it,
   734  Several curious circumftances
   attending its decompofition, 733,
   736   Solution of calces of gold in
   marine acid, 799  Of tin in aqua
   regia, 809  This folution  ufeful
   in dyeing, ib.   Is  deeompofed  by
   faccharum faturni,  1043  Calca-
   reous folutions  by mild volatile al-
   kali, ib Solution of falts promoted
   by vitriolic acid, 1048   Solution
   of terra ponderofa a teft of the vi-
   triolic  acid  1038    Solution  of
   flint, 1069   Solution of alkali dif-
   folves filiceous  earth, 1076  Solu-
   tion of gold in aqua regia,  1099,
   tt feq.  In  hepar fulphuris,  1127
   In vitriolic ether, 1129   Solution
   of lime by the colouring matter of
   Pruflian blue, the moft proper  for
   making   experiments  on metals,
   1190  Effeds  of  this mattcr  on
   metallic folutions,  1193   How to
   attain a  perfedly  faturated  folu-
   tion of quickfilver,  1239  Of the
   folution  of  arfenic in water  1269
   Effeds of regulus of arfenic on me-
   tallic folutions,  1293.
Sorrel,  a kind of tartar extraded Spiritus Mindereri
  from it fold for effential fait of le-   it, 1313.
gravity, 377   Proportion of acid  been purified and examined  by Mr
in fpirit of fait to that in fpirit of  Schrikel.   Eight  ounces  and  four
nitre, 383  Dilatation of fpirit of  fcruples of liquid  were obtained  in
fait  by  various degrees  of heat,  this manner from 16 of fine fugar.
427   Effeds of it in the way of  About  fix  drachms  of  water  came
folution in cobalt, 498  How pro-  over firft ;  after which  the acid paf-
cured by means of vitriolic acid,  fed in white vapours, which conden-
786   By nitrous  acid, 788   By  fed in undtuous ftriaj on the  fides  of
   Vegetable  acids  proved from the
   decompofition of this avid,  1008
   Nitrous  acid  enabled by the acid
   of  fugar to  diffolve .manganefe,
   ion  Method  of  procuring the
  acetous acid from it,  882.
Sugar of milk :  how to procure  its
  acid, 9S0.
diftillation of common fait without  the receiver.   It had a  pungent and  Sulphur  dephlogifticated by  nitrous
  addition,  789   Diffolves  and vo- agreeable fmell, and tailed empyreu
  latilizes  the calces  of  gold,   799 matic By repeated diftillations from
  Arfenic  decompofed by dephlogi- pure clay, its fmell became mild, and
  fticated fpirit of fait, 919.          it  acquired  an apparent increafe  of
Spirit of -wine yields  a great quantity acidity.   With vegetable  alkali,  it
  of  water by  being  burned,  134 formed a fait tafting  like that of Syl-
  Convertible  into  charcoal,   147 vices,  and fhooting into needle-like
  Ether produced  by its combination cryftals,  foluble with  difficulty  in
  with  vitriolic acid, 717  Its com- cold water, but not at  all in fpirit of
  bination with  nitrous acid  produ- wine.  It  did not deliquate in the
  ces fpiritus nitri dulcis  and ether, air; but decrepitated in the fire, and
  773,  &c.   Ether with  the marine did not melt on hot coals.  With the
  acid,  824   With the  vegetable mineral  alkali  yellow  cryftals  were
  acid,  884  And with the faccha- formed refembling Rochelle fait  in
  rine acid, 902    Converted  into tafte, eafily folublein water, and not
  acetous acid by digeftion with the deliquating in the air.   Volatile  al-
  acid of tartar, 1013    Enables vi- kali gave  a fharp faline liquor, which
  triolic acid to diffolve manganefe, could not be cryftallized, but left a
  IOI4   Yields  a great quantityof faline mafs on evaporation; and a fimi-
  water by diftillation with  cauftic lar faline mafs was produced by uni-
  alkali, 1013    Diffolves a fmall ting it with calcareous earth.   Mag-
  proportion of arfenic, 1270   How nefia and earth of alum formed gum-
  it  may be  made  to diffolve ful- my compounds.  When concentrated,
  phur,  1402    Diffolves  effential it diffolved the calx of gold, and even
  oils, 1421.                        gold-leaf; but had no effed on fil-
                  how to cryftallize ver, mercury,  or  their calces  With
                                    minium, it  gave  a yellow folution,
   mons, 888,   See Sugar.           Spiritus nitri  dulcis,  how  prepared, which fhot into oblong white cryftals
   ain .-  when alum was firft made    774 Analyfis of its refiduum by Mr of an aftringent tafte.  A blood-red
 S^there, 640  Nitre,  how prepared    Pott, 781  Affords  acetous acid, folution,  which fhot into  green cry-
   in that country,  726.                 1007  And acid  of tartar, 1009.    ftals was  obtained from iron.  Copper
   ar, pouderous,  account  of Dr Wi- Spiritus volatilis fuccinnalus.    See Eau was  diffolved  into a  green  liejuid,
 l^thcrino-'s experiments on it, 1037.    de luce.                            which did not cryftallize.  Regulus of
   ecipc gravity.   See Gravity.        Stahl:  a miftake of  his concerning antimony was alfo diffolved, and the
 Specula, materials proper for  them :   the  converfion of marine into  ni- folution  was  of  a greenifh  colour.
 typropofed  by  Mr Hellot  from  a   trous acid deteded, 793.           Zinc was partly  diffolved   into  a
   mixture  of gold  and  zinc, 1246 Standard fiver: quantity of pure me- green liquor,  and partly corroded.
   A mixture of  brafs  and  platina   tal contained in it,  321.            The  precipitates  wer.e  remarkable.
   propofed by others,  1344.         Star formed on the  furface  of regulus The  cryftals  of iron gave a green
 Spirit of nitre: how to determine the   of antimony,  1232.               precipitate with alkalies, a black or
   quantity of pure acid contained in Steel, fait  of,  the fame  with green dark  blue one with Pruliian alkali,
   it, 384  Proportion of it  to  that   vitriol,  697   How prepared from and a white one  with marine  acid.
   in fpirit of fait, 383"   How to de-   iron, 1207.                        Solution of regulus  let fall a yellow
   termine  the   accrued   denfity on Stills, how to  fet them, 610.         precipitate with fixed  alkali;  with
   mixing fpirit of  nitre with water, Stone -ware  corroded by cauftic alka-  volatile alkali, a powder foluble again
   387    Experiment  to  determine   lies, 393.
   the real quantity of acid  in fpirit Strafburgh turpentine defcribed, 1433.
   of nitre,  389   How  to conftrud  Sublimation, in chemiftry,  how per-
   a  table of fpecific gravities for fpi-    formed,  381.
   rif of nitre, 390  Strong fpirit of Sublimate.   See Corrofive.
   nitre more expanded by heat than  Sugar, acid of, the  fame with that precipitate with infufion of galls, al-
   Weak,  and  why,  424    Exad    of forrel,  2d 903   Acid  of apples '^alies of all kinds whether  fixed, vo-
   quantity of dilatation of  fpirit of   procured from  fugar  by  means of latile, or phlogifticated, as  well as by
   nitre, 42c   Solution of mercury    the nitrous acid, 1312.            the vitriolic acid.  Tin  was partially
   with fpirit of nitre, 426   Quan-    The acid procurable from this fub- diffolved,  and the  folution precipita-
   tity of bifmuth diffolved by it, 492 ftance by means  of  the nitrous, re- ted by  alkalies, and an infufion  of
   Of cobalt, 497   Of regulus of ar- ferobles that  of tartar, in being ca- galls,  but not  by any of the mineral
   fenic,  304  How to prepare  this pable of fuperfaturating the vegetable acids.   Lead  was  precipitated  of a
   fpirit  by  means of oil  of vitriol, alkali, and forming  with it an acid white colour by  vitriolic and marine
   733   By  means of  arfenic,  739 fait  refembling crude tartar.  This acids, and of a grey colour by i.ifu-
   Oils fired  by it,  778   Effeds of is  found naturally exifting  in forrel fion of galls.
   it  on fait of amber, 912.          and  fome  other  plants   There  is, Sugar of  lead.   See Saccharum  and
Spirit of fait:  method of finding the however, another acid  obtained from   Saccharine.   Whether the acid  of
  quantity of pure acid contained in fugar along  with an  empyreumatic   fugar or of  tartar ii  the  bafis of
  it,  376   Of  finding  its fpecific oil,  by dry  diftillation,  which has   vegetable acids,  996  Identity of
                                                                                        JL. 1
   the precipitant;  vitriolic aud ma
rine acids, and  an  infufion of galls,
threw down a white powder, but no
precipitate enfued on adding nitrous
acid
    acid, 193   Exifts  in  hepatic air,
    210   Quantity  of phlogifton'in
    it, 307  Proper method of bt-rn-
    ing it,  308   Deftroys the malle-
    ability  of  metals,  346   How to
    procure the vitriolic acid from it,
    623  Quantity of  the  acid  con-
    tained in fulphur,  ib.   Quantity
    procurable  from  it   624    Me-
    thods of obviating the difficulties
    in the procefs, 623   Effervefcence
    betwixt  the  fumes  of nitre  and
    fulphur,  626   Extraded  from the
    fame ore with alum  and vitnol,
    639  Prepared by combining  the
    vitriolic acid with phlogifton,  713,
    716 Effeds of acid of arfenic up-
    on  it, 924    Molybditna recom-
   pofed by uniting its acid with ful-
   phur, 966   Combined with fixed
   alkalies,  icnr   Its  phlogifton dif-
   pofed to fly  off when fulphur  is
   combined with fixed alkalies, 1024
   Its combination with volatile alka-
   lies, 1038 Effeds of it on  filver,
   1132   Takes fire  fpontaneoufly
   with iron filings, 1207   Cannot
   be united with zinc,  1248  How
   to feparate it from antimony, 1234
   Eafily united  with  arfenic, 1278
   And mineralizes it,  1284   Effects
   of it on  regulus of  cobalt, 1305
   Effeds of it en nickel,  1308  On
   mar.ganefe, 1389    Its nature  and
   properties particularly  confidered,
   1398, et feq.   May be cryftallized^
   I400  Decompofed  by  fuperabun-
   dance of phlogifton, 1^01   How
   it may be-diffolved in fpirit  of
   wine, 1402   Its union with me-
   tals,  .403.
Sulphureous   fumes  effervefce  with
   thofe of fpirit  of nitre,  626   Vo-
   latile fulphureous acid  defcribed,
   713  How procured by  Dr Prieft-
  ley,  7 ! 4   Why this acid diffolves
  manganefe,  1379    Sulphureous
  inflammable vapours procured from
  radical
                                   ical vinegar, 1343.
Solution of zirc gave a white  Sun diftributes trie heat"on the earth
                                94  How heat in produced  by his
                                ra>'s> 95    His lij<ht  blakens  the
                                precipitates of foiution  of  filver,
                                756.
                              Sunffwer contains nitre, 733.
                              Sweden: when alum was  firft made
                                there, 640   Method of roafting
                                the aluminous ores there, 663,  7t

                              Sympathetic ink of a bj[ue colour, 82:.
                              Table of the  different  degrees of
                                heat,  161   Of  different precipi-
                                tate?,  from  Mr  Bergman,  259
                                Of the quantity of acid taken up
                                by different bafes, 268   Coinci-
                                                           dence
•# 
-Jjh
CHEMISTRY.
Index.
  it,  1030    In appearance  when
  combined  with aerial  aeid,  ic.< 1
  Fffcds of fire upon it, 1032   Phe-
  nomena with marine  acid,  1053
  Is prccipitable from it by mild and
  cauftic fixed  alkali,  it 34    Con-
  vertible into lime capable of de-
  compofing  vitriolic  falts,   IC73
  Infoluble precipitate  thrown down
  by cauftic alk.ni,  1036  Analyfis
  and propel ties of the aerated pon-
  derous fpar,  1037   Its folution a
  teft of the prefence of vitriolic  a-
  cid,  1038  Nitrous folution Iy  -j
  into fine cryftals,  1066  A  fmall
  quantity diffolved by the colouring
  matter of Pruffian blue,  1188.
Teft 1 for acids and alkalies:  Inaccu-
  racy  of thofe commonly  in ufe,
  1349   How to prepare one from
  red cabbage and other vegetables,
  1330—1332   Mr Woulfe's tell
  for mineral waters,  1357
 dtrceof this'-ble wi:h'•   rim. «. *  ft has . und it combined with cal-  whirix  cforvefcrd with  acids, and
  .  I  Of the juantit. s of the dif- carcou-. earth in the juice of the roots  weighed 468  grains.   On treating
  ferent metal* t.ktii up In  acids el the/,  t n.m repens, the Uontodon tax-  in the   f.mc manner  a  folution  of
  :<,c:   Table of  the  aflhitic. <i aracum, and China b.iri.  By the aflift-  terra foliata tartari, the liquor began
  ('r -.,iJ»  *o the I'Tere: '. nva'< ancc of  nitrous acid he obtained  it  to change thclynp  of violets  green
  cplained. 316    Of the quant rics alfo from the juice  of grape., mul-  in two months,  and in four the dc-
  of 1 hlr.pB'on in d'fi'ient  mctds, berries, sj pics, pears, orange , ftraw-  compofition feemed  to be complete.
  317  O' th. pr-purtinnil  afiinities b-rries,  and plums;  al'o  from  ho-  At the  end of  a  year  he filtered
  of  metiiii:  1 .....-*  to phlogiston, ney,   fty.ar,  gum  arabic,  manna,  and evaporated the liquor to drynefs,
  32;  Dr ld.ul. » tabi. cf afhn.ticf, fpirit cf  wine,  beech wood,  and  the  by which  procefs he  obtained 432
  f.-j.                             root  of  black hellebore.   In thele  grains   of  fixed  alkali.   The fame
T-il"  ' ar.-lvfed,  T41)              rafts,  where the nitroes acid is made  quantityof terra foliata  tartari  de-
'/.  ■..;  quantityof fixed air in oil ufe  of,  however, it may juhly  be compofed immediately by diftillation,
  cf  tartar, 41 j    Ii»  ic .1  paricu- fuppofed that  the acid  of  tartar is yielded only 36 grains more of alkali.
  lar'.v treated < :', 88;,  et fe-.  Crude  partly at leaft  \ roduced  from it   In  Solution of fait of wood-forrcl fuffered
  tartar di ft ribed, ib.   Purified, r.rd  Sebec'iris procefs  for procuring  the no deeompofition by a fimilar treat-
  then called cream tft.itjr, by boi1-  j ure acid of tartar by means of  cal- ment for two years.   The latter he
  iri; witli  f./rr.e  ef the for  1 ii;d>  careous  tanh,  it  is  advifable  to obferved to be a much more  power-
  ed  clav,  !ft'6     Sche-.ie'b ;.r.a.lyfs  1 ia>.e  ufe  of quicklime rather than ful antifceptic than  tartar; for which
  of cr.am oftsrtar,  ar.d 1: ethod <!  chalk, as by tbi. double the  quantity reafon it feems to relift decompofition
  )  •'.-ni ing the  p".re  acid, 887   So-  of tartar will be decompofed.   An in a proportionable degree.  He fup-
  1  ble  t:i t.r for.r.ed by uniting the  hundred parts of pure tartar contain pofes oil to be the principal caufe of
  veg:cuble fixed a.kifti whh cream  about 23 of vegetable alkali, 43 parts the  deftrudion of  thefe  acids;  and
  id  t.rtj-, 83p   I'ream of mtar  cf acid  employed to faturate that al- the  obvious deficiency of  oil in the Theory of chemiftry defined,  21.
  I. iw rcgi n.-ratc !, 890  Se'gnttte's  kali, and  34 of fuperabuudant acid, faccharine acid,  in  comparifon with Thermometer:  its ufe,  103   Wedge-
  cr  Rochelle fait formed  by com-  By ufing oyfter-fhells well  prepared tartar,  feems  to be the caufe of the     wood's improvement, 104.
  bining  tint  mineral  alial.  with  by boiling  and powdering,  the  cry- want of capacity ih it  to undergo the Thunder  and  lightning:  why  more
  cream of  tartar,  891   Salt formed  ftals of the  acid may he obtained very decompofition juft  mentioned.   A    common in fummer  than in win-
  by the union  of cream  of  tartar  white and  pure. Soiv.c chemifts have remarkable circumftance attends  this    ter, IOO.
  vith volatile rib di, 8; 1   Combi-  imagined that the  vegetable  alkali, fpontaneous decompofition, viz.  that Tin:  why  nitrous  acid precipitates
  ration  of the  acid of tartar  with  does not exift ready formed  in tartar, no air  is either  abforbed or emitted    its folution,  200   Why  folution
  earths, £";',    With  n r. hi- fub-  but that it is produced by fire  or during the whole procefs.  lt is alfo
  li.nees, c\)4   forms a fine ;:icen  mineral acids.  In proof of this  M. worth notice, that in combining acid
  ct.1 o'.ir  with copj cr, in     Ch-dy-  Machi  offers  the following experi- of tartar with fixed  alkalies,  the fait
  be. ted   tartar  \ ith  iron,   893  ments.   On an ounce  of  cream of fuperfaturated with acid or cream of
   Whether this acid or that of fugar tartar were  poured  10 ounces  of tartar is always formed in preference
  is the hr.i'ri of vcpcf.dde acids,  996  boiling  water, and  the mixture al- to the other cMedfoluble tartar. Thus
   i'r dud  of acid of tartar by dry  lowed  to  remain in a jar covered if to  a faturated folution of alkali
  diftillation, 1000   Requifites for with paper and  parchment  in which with cream of" tartar we add another
   bribing vinegir  mr  the  ftate a  ftrall hole  was made w th  a pin. of pure tartareous acid, a white fpongy
   of tartar, ico.'.  Weftrumb's un- At the  end of three months  it  was matter  will be  precipitated  to the
   ft. c  Iriul attempt for this purpofe, confiderably diminiflied;   and  con-  bottom; which, on  examination,  is
   1003   L>r (drill's opinion of the tained  a  quantity  of  thick,  tough, found to be a true tartar.  Any other
   •'  llibility  of   the  tranfmutation, yellow, mucilaginous matter, which acid added to the folution of tartari-
   11..-4   Mctl 0 1 recommended by neither effervefced with acids nor al- fed tartar will in  like manner  pro-
   him  for  attempting the  experi- kr.lies,  and, when  burnt,  the afhes duce a  precipitation of tartar, by cn-
   ment,  1003  Argument  in favour were found to  contain only  a  very gaging  a part  of  the  alkali with
   of the identity of vegetable acids fmall  quantity  of  alkali.   The  ex- which  it was combined ;  and if the
   from  the proere'rion of  an empy- periment was repeated by Mr  Cor- acid of tartar be added to a folution
   reumatic acid  ef tartar  frori the vinus with fome variation.   He kept of any neutral  fait  containing  the
   liouer  in v.hich. ta-tarecus lelenite a folution  ef  cream of tartar  in a vegetable fixed  alkali, as vitriolated
   is  hoibd,  ro.o   From  the  folu- heat between ic° and 300  of Reau- tartar,  fait of Sylvius,  and nitre, a
   t on  of ii-.a;iir-..r.cfe in a mixture cf niur's felt : removing the faline pel- fimilar  precipitation  of  tartar  will
   ri triolic a-id tertireous acid*, 101: licles wh eh  formed on the  furface enfue.  Hence the acid of tartar may
   i-dver  whitened l-\  cram of tar   as fait  as they appeared, and redif- be employed as a teft to difcover the
   nr and  common  fait,   T137  Of  folving  them  in water  By conti- prefence of the  vegetable fixed alka-
   t ic preparation ..f  1 ire tic  tartar,  nuing  the   digeftion   for  feveral li, and to diftinguifh it  from the mi
months,  the liquor became  at  laft neral,  which  has not  that effed.
evidently  alkaline: and he thus ob- Bergman indeed obferves,  that Ro-
   1:7-,  12-8,  et fy.   See E.r.iir.
   . linganeie J'd.ddc in acidof tar-
   t. r,  I 36 X   Explanation  of its ac-  tained 216 grains of a brown alkali chelle fait will do the fame thing;
   • on  upon mangsnefe, 13 c' 2  Schil-  from two ounces of cream of tartar, but it muft be remembered  that this
   |, r\, i.uthodof procuring its  acid,  Mr  Bcrthcilet  expofad   for  nine is prepared with crude tartar, which
   \ •- ;.                              months, to the heat of his laboratory, contains a portion of vegetable alka-
   T ."Ugh the acid of tartar has  been  a folution of two ounces of cream of li, and not with the pure acid.
i-m i-oniy fuppofed a prcJud of the  tartar in  eight ounces of water;  ta- Temperatures:  Dr  Reid's   obferva-
lirous fermentation, vet late expe-  king care to replace the water which    tions concerning,  30.
r.mcrts Lave fhown ti ..t this is not  evaporated,   but without  removing Tena foliata tartari   See Sal diureti-
ihccri..   It  has been found nrt only  the crafts which formed  upon  the    cus   How to prefervc it in a bottle
.;. the juice of the grape-, bi t in that  furface.    At  the end of this time he    without danger of its deliquating,
ni tamarinds, tee berries of the rhus  found that the liquor was no longer    868.
s.i  :ria  and  the  leaves of tKc r. n ex  acid, but began  to turn the fyrup of  Terra ponderofa combined with  acid
    <*.  In thefc  it  is g.v.eTliy  emu-  violets green.  In  18 months it  be-    of  arfenic,  940    Ufually found
bd.  I with the vegetalft fixed  alka-  came ftrongly  alkaline;   and  left,    united with vitriolic  acid,  1049
r, e; with calcarcr* ear* h. Hcrmb-  when c ..po.-a.ttd, an  oily refiduum    Dr Witherirg's experiments upon
of gold is precipitated by folution
of tin, 227   The precipitate con-
fifts  partly of  tin,  228  of  its
precipitates, 240  Why it cannot
be precipitated in its metallic form,
330   Adion  of the vitriolic acid
on tin, 470  Diffolved in  nitrous
acid,  472  Great  fufibility of  the
compounds  of  tin and bifmuth,
343   One  foluble  in hot water,
344   Of  the   compound  formed
by it  and vitriolic  acid, 701   Its
folution  in  marine acid ufeful in
dyeing,  809    Is  volatilized  by
this  acid, and forms  the fmoking
liquor of  Libavius,  810   Of its
combination with the acetous acid,
879   Dr  Lewis's experiments on
this  fubjed, 880   Effeds  of acid
of arfenic  upon it, 930  Solution
of tin deftroyed by faccharum  fa-
turni, 1043   Said to deftroy  the
malleability of gold  remarkably,
1091    Mr  Alchome's  experi-
ments to  determine this point,
1092   Its  fumes  do not render
gold brittle,  1093    Nor the  ad-
dition of  fmall quantities of tin
and   copper,  1094   The metal
particularly treated of, 1216  May
be beat into thin leaves, 1217  Of
its calcination,  1218   Its affinity
with arfenic,   1219   Arfenic fe-
parablc from it, 1220  Dr Lewis's
obfervations on this affinity, 1221
Other metals  injured by tin, 1222
Tin not liable to ruft, 1223   An
ingredient  in  aurum mofaicum,
 1224   Of its  union with  fulphur,
ib.   Readily  unites  with  platina,
 1348  Remarkable effeds of the
febaceous acid upon it, 1335   Vo-
 latile alkali prepared from a mix-
                             ture 
Index.                                CHEMISTRY.                                       267

   ture of it with nitrous acid, 13*3.    able change on copper, 1131  Ve- bable that fimilar acids might be ob- apples  by treating the infuGon with
TinBura martis  made  from  marine    getable fubftances in general confi- tained.   Mr Morveau  has obtained nitrous acid.   If  a pound of Indian
   acid and  iron, 807.                  dered, 1431.                       from galls a icfin  which he fuppofes rhubarb be infufed in hot  water,  a
Tobacco naturally contains nitre,  733.  The folio-wing is a lift of the Vegetables to be  their acidifiable bafe;  and powder fubfidcs,  which  by wafhing
'Tolfa :  method of  burning the  hard   from  •which the induftry of the modern which, along with  pure  air, forms becomes white, weighing then about
   ores of alum there, 669.              chemifls has procured different acids, the  acid of galls.   When  purified, nine drachms, and is found to con-
Torrid zone: heat of it how  mitiga-    -with  the names of the difcovcrers.      this acid  is faid to make a fine and fift of  calcareous earth united with
   ted, 90.                             1  Agave  Americana.   The  juice durable ink.                         the acid of fugar.   Scheele.
Tranfmutation of metals not to be ere-  exfuding from the calyx of this plant   16  Geraninum acidum.   Small  acid   36 Ribes cynofhati.   Acid of citrons
   dited, II   A feeming tranfmuta-  yields acid of tartar and apples.  Mr cryftals Cartheufer.   Said by Hermb- or lemons.  Scheele
   tion  of vitriolic into marine  acid,  Hoffman of Weimar.                   ftadt to be the acid of fugar.            37  Sa.'ep.   Acids  of  fugar  and
   784   Tranfmutation  of earth  of    2 Aloes.    Acid of fugar and ap-   17  Cmfeberries.  Acid of  apples, appks  by treatment with nitrous a-
   flints into fome other,  1069   The  pies.  Mr Scheele.                    Scheele.—Hermbftadt fays  that  they cid.   Scheele.
   miftake  difcovered by Mr Berg-    3 Apples.   A  peculiar acid called contain the acid of tartar alfo.          38 Service  (Morbus aucuparia).   A-
   man, 1070, et feq.  See Flint.       by the  name of the  fruit.   By  ni-   18 Grapes. Their juice well known cid of apples.   Scheele
Triple and quadruple falts, how form-  trous acid that  of  tartar  is  procu- to contain the acid  of tartar  par-   39 Solatium dulcamara.    Acid of
   ed,  273   Volatile  alkali particu-  red.  Mr Scheele and Mr Hermbftadt. tially combined with fixed alkali.     citrons.   Scheele.
   larly adapted for their formation,    4 Barberry.  Acidof  apples, and   19  Grafs-roots.    Saline   cryftals   40 Sorrel 'Rums sacetrfa). Cryftals
   274   Metallic   folutions  fome-  of  tartar.    By  treatment with  ni- from  the  extrad of the juice after of tartar by evaporating  and cryftid-
   times decompofed by a triple com-  trous acid it yields  acid  of fugar. three months Handing.   Thefe were lizing the juice ; and pure acid of tar-
   bination, 223   A triple fait form-  Scheele and Hermbftadt —Hoffman de- foluble in water, and gave  an earthy tar by faturating the acid with chalk,
   ed by marine acid, iron,  and re-  nies that it  contains any native acid precipitate  on mixture with fixed al- and  then  expelling it by means of
   gulus of  antimony, 366  Another  «f  tartar.   By treating it with fpirit kali.  On abftrading the nitrous  a- the vitriolic.   Hermbftadt.   Other che-
   by marine acid,  copper, and  regu-  of  wine and manganefe he obtained cid  from them, and adding a folu- mifts, however, have certainly found
   lus  of antimony, 367   A  triple  an  ether.                            tion of calcareous earth in vinegar, a it to contain the acid of fugar partly
   fait formed  by precipitating filice-    3  Bilberry  (Vaccinium myrtillus). precipitate fell,  which was found  to neutralized with alkali, and which is
   ous earth with fixed  alkali,   1073  Equal parts of the acids of citrons and confift of  acid of tartar  faturatcd capable of being  cryftaliized.  This
   A kind  of  triple fait formed by  apples.   Scheele.                     with lime.   Hermbftadt.               is generally known under the name
   precipitating calx of platina from    6  Bramble   (Rubus  chamamorus).   20  Gum  Arabic.   Acid  of fugar of fait of icood-forrel, and  is manufac-
   the  marine  acid,  1327   Other  The fame with the foregoing. Scheele. and apples.  Scheele.                  tured in  confiderable  quantities in
   triple falts formed by it,  1332.       7 Camphor.  A  peculiar  kind  of   21  Gum tragacanth.  Acids  of fu- Thuringia, Suabia, Switzerland, and
Tubal-Cain: whether to  be account-  cryftallizable acid.   M. Kofegarten.   gar of milk, apples, and fugar.        the Hartz.   It is prepared from  this
   ed a chemift or not, 2.               8 Cherries,  Equal  parts  of acids   22  Hatu  (Cratagus aria).   Equal plant as well  as the  oxalis acctofella.
Tungften particularly examined,  967,  of  citrons and   apples.   Saccharine parts of acids of citrons and apples.   The  plants are bruifed in ftone cr
   et feq.  Confidered as a metallic  acid  by  treatment  with  fpirit   of   23  Honey.  An acid liquor by di- wooden mortars;  the juice is fquee-
   earth   by   Mr  Bergman,   967  nitre.  Scheele,  Hermbftudt, and We- ftillation ; and with fpirit of nitre, the zed through linen  ; and when cleared
   Scheele's method  of analyfing  it, ftrumb—Hermbftadt   fays  that  he acid of fugar.  The diftilled acid has by fettling, is to be boiled to  a pr<-
   968  Effeds of  heat upon it, 969  found acid of tartar alfo.             been faid to diffolve gold.            per confiftence, and clarified with the
   Its chemical properties, 970   Dif-    9 Citrons and lemons.  A particular   24  Lemons    An  acid  the  fame whites of eggs,  or with blood.  It is
   ferences betwixt the acids of tung-  kind of cryftallizable acid.  Scheele    with that of citrons.                 to be ftrained whilft  hot, and then
   ften and  molybdaena,  971   Berg-    10  Coffee.  The  infufion evapo-   23  Leontodon  taraxacum.   Acid  of kept in a cold  cellar    In a few-
   man's  opinion  concerning them,  rated and  treated  with  fpirit   of tartar by treatment with  fpirit  of weeks cryftals  will be formed, from
   972  Why  he fuppofed  the acids  nitre.   Acids of fugar and  apples, nitre.                                which the remaining  liquor muft be
   to be metallic  earths,  973   Its  Scheele.                                 26  Manna.   Acid  of  fugar by poured  off, and by further evapora-
   properties according  to  M.  Lu-    11 Corks.   A yellow  acid by re- treatment with  fpirit of nitre.        tion  will yield more fait.   Savary
   yart, 1498   Of  the yellow matter  peated abftradions of  fpirit of nitre.   27  Mulberries. ' Acid  of  tartar, obtained only  two ounces, and a half
   called its acid  by Mr   Scheele,  With fome of the alkalies and earths Herr bftadt.  A  cryftallizable acid fait of fait  from 23 pounds of the juice.
   I499  No  fimple acid procurable  this acid forms cryftallizable falts by evaporating the  juice.    Angelas  41 Strawberries. Equal parts of the
   from the mineral,  1301   A  new  which do not deliquate, though others Sala.                                acids of apples and citrons.   Scheele^
   femimetal made  from it, 1301.      do.  That with fixed vegetable alka-   28  Oil of olives.   A fait  which  42 avrar.   See the article.
Turbith mineral, how prepared,  703,  li forms needle-like cryftals, foluble fublimed   and  cryftallized,  by re-  43 Sumach  (Rhus coriaria).  Cry-
   706.                              in  water,  vitriolic,  nitrous,  or ma- peated and copious abftradions of the ftuis  of tartar.  Profeffor Tromfdoif
Turpentine:   Appearance of  oil  of  rine acids, but not in vinegar or fpi- nitrous acid.  Weftrumb.              and Son.
   turpentine  with  acid of  arfenic,  rit of wine.   Like the faccharinc  a-   29  Peruvian bark.  Acid of apples  44  Tamarinds.    Acid  of  tartar,
   923   Chio  turpentine  defcribed  cid it has  a  ftrong  affinity to calca- and fugar, by  treating the  extrad  tartar itfelf, with a mucilaginous and
   I433   Venice tuipentine,  1434  reous earth,  which  it feparates from with nitrous acid.  Scheele.            ricrharinc matter.  We.lrumb.
   Strafburgh, 1433   Common, 1436  lime-water,  and forms a greyifh  fa-   30  Prunus fpinofa  et don-.eftica.  A-  .-13 Vaccinium vitis  idaa.   Acid of
   Analyfis of turpentine, 1437  Ef-  line powder,  foluble  in  marine acid, cid of apples.   Scheele.                citrons.  Scheele.
   lential  oil   difficult  of  folution,  but  not in  water, nor even in  its   31  Prunus padus.   Acid  of ci-  46 Wood and bail cf the birch tree.
   1438.                             own  acid.   It exhibits fome  appear- trons.   Scheele.                       From SS  ounces of rhe wood were
Vapour formed by the abforption  ances with metals, which deferve far-   32  Poppy.   Acids of  fugar and obtained 17 ounces of redified acid,
   of latent  heat, l'20    Dr  Black's  ther examination.  Bnignatclli.       apples, by  treating  the  juice  with which  when freed from  an  amber-
   experiments  on the converfion of    12 Cranberry.   {Vaccinium  oxy-  nitrous acid.  Scheele.                 coloured oil  was to the  fpecific gra-
   water into vapour, 121  Heat ex-  cocccs).   Acid of citrons.   Scheele.        33  Rafplerries.   Acids  of  apples vity  of water as  49  to  48, and of
   pelled in great quantity by its  con-    13 Currants, red and zahite.   Acids and citrons.  Scheele.  Aeid  of  tar-  fuch ftrength  that one ounce of it re-
   denfation, 123.                    of  citrons and  apples.   Weftrumb.  tar  by  faturating  the  juice  w ith  quired 23 of  lime-water  for its fatu-
Vegetable colours changed  by  acids  Hermbftadt fays  that they contain  a-  chalk, and then  feparating the earthy  ration.  Chemifts if Dif on.—By allow-
   and  alkalies,  173   Of  vegetable  cid of tartar.                         bafis  by  means of  vitriolic  acid,  ing the: arid diitilled from the hark to
   earths,  313,  1089   Suppofed by    14 Elderberries.   Acid  of  apples.  Hermbftadt.                           remain  at reft for three months,much
   Dr Lewis  to be  the  fame  with  Scheele.                                 34 Rhapontic.  Acid of  tartar by of its oil was feparated ;  by fatura-
  magnefia,  1089    Dr   Gmelin's    13 Galls.   A  peculiar kind ofa-  cryftallizing the juice; of  fugar by  tion  with fixed aihali a dark-coloured
  experiments, ib.  Vegetable ammo-  cid.  Scheele—Mr Kier obferves, that  treating it with  nitrous acid.   Bir.d-  neutral fa'.t was obtained,  which was
  Biac,  870  Vegetable  ether,  884  from other aftringent  matters, efpe-  heir:.                                purified by fufion and fubfequcnt fil-
  Vegetable acids produce a remark-  cially thofe ufed in dyeing, it is pro-    35 Rhubarb.   Acids of fugar and tration  end  t\apcn.tion.   On  fub-
                                                                                                                                         jedinj 
268

icding  the pnrifud fait  to diililia-
tion,  an and arofe,  which had  no
longer  an  e lupyrtumatic fmell, but
rather a flavour of garlic.   Gorttl.nr.
I'rj-rUtions, curious, produced  from
  lolution  of lilvvr, 7*4.
I'em.e tnrpemtin:.   See  Turpentine.
Ver.tignt, h«iA-  prepared, 872   Di-
  ftilled, ib.  Verdigris difMUd, beft
  method  of making it, 872.
Vtrdiier,  a p-cp_iation of copper,
   7 ■" S   Method of   making  blue
   verditer gen. rally unknown, ib.
J'.i •■   -. made by fubliming fulphur
   and mc  .  ry together, 14-.4  Dif-
   ficulty in adjufting the proportions
   o!  the  in redicne-,  ib.   May  be
   made without fublimation  from
   quickfilver a id the  volatile  tinc-
   ture  of  fulphur, ib   Or with the
   folutibn of fulphur  by fixed alkali
   or quicklime, ib.    Is  darker  or
   lighter  according to the quantity
   of fulphur, ib.
 Virulam,  I..>rd,  ftudics and  n-viv.s
   the fcience of chemiftry, 16   Flis
   opinions concerning  heat, 29.
 ViJ'.li, chemical : ofthe  proper ones
   to be ufed, S57,etfeq.  Dr  Black's
   opini.n, ib.   Of  j,l -.ft, $5^  Df
   metal,  360   See  C'-aaiial,  Glafs,
   M1t.1l,  Eartben-tvare,  and  Porce-
   lain.
 Vi.'ration -.  Ni- hoifon's account of the
   advantages attending the fuppoli-
   »ion  that heat is occafioned by it,
   80   Anfwered, 8r.
 I'.riegar:  fpecific gravity .of it when
   ftrongly concentrated, tot   Why
   it may be reduced into at without
   addition,  208   Procurable  from
   the refiduum of vitriolic  ether,  2d
   7:2  Le\\.<y experiment  on the
   foh.b-hty of tin  in th.s  acid, 880
   Whey   convertible   into vinegar,
   979   Requifites  for bringing  it
   nearer  the ft ate  of tartar,  1002
   Weftrumh's attempt- for this pur-
  pofe,  1003    lie  Creli's opinion
  of the  poflibiiity of  the  tranfmu-
   tation,   1004    Method recom-
  mended  by him fin attempting the
  experiment, 1003   Suppofed to be
  an antidote  againft  arlenic, 13 20
   Lhticunce between radical vinegr
  and common acetous aud, 1 •, a -i.
Vis in.-rtt*  : fire lecm* to be deftrfUte
  of it, 93
V.trinl: why folution of gold is pre
  cipitated by the  green kind, 223
  But not  by this, fait  w 1 en dc| hlo-
  "iilicated, 2.6   Ihat   y-r-..cared
  by  jr.cip t tion of  copp.r   witn
  iren  lefs fit  for  dicing  than tie
  common, 344  1 lue v.tnol  can-
  not be  formed by  hoiiing  alum
  and coppr ft' r.^s, 349  Pre. er-
  t.iei  oi Ingicdiei i'i .n biue v triol,
  467  How to or   ft green vi-
  triol fros.i pyr-fts, ...id tri  atltil die
  acid from it, 6a.-, et fef.  Extrac-
  ted from  the  fame ore  with ful-
  phur  aod  : luni,  ' 'O    Alum  is
  j.utr.'i'.y cc^umiii--t . by dephlo-
        C    H    E    M

  gifticated   vitriol,  684    Perfect
  green vitriol cannot be deftroyed
  by  clay, 686    How  to  abftrad
  ti.  phlogifton from it, 6S7   How
  to prepare blue vitriol, 693   Parts
  with  its acid with morc difficulty
  tl an  the  green  kind,  694    Its
  ufes,  603   White  vitriol,  how
  prepared.  708   Why  the diftilla-
  tion of fta-1'alt with copperas does
  nit   fucceed,   787  Green vitriol
  decompofed by faccharum faturni,
  l-~44  Fixes the  colouring matter
  of Pruflian blue, 11:4   flow  af-
  feded by  dephlogifticated  marine
  gas, 1485.
Vitriol, acid of.   See Vitriolic acid.
Vitriolic acid: why ft  cannot ad  on
  lead, filver, &c. without  a  boil-
  ing  heat,  197  Cannot be  redu-
  ced into an aerial form but  by a
  combination with phlogifton, 202
  On   the expulfion of the  nitrous
  acid by  the vitriolic diluted, 280
  By   the fame  in  a concentrated
  ftate, 281   With a  fmall  quan-
  tity of vitriolic acid diluted, 282
  On   the  expulfion  of the  ma-
  rine a.id by  the concentrated  vi-
  triolic,  203    Detompofition  of
  vitriolic ammoniac by marine acid
  never complete,  291   Why the
  vitriolic acid rcfunies on evapora-
  tion  the bafes  it had left, 283
  Decompofition of vitriolic ammo-
  niac by folution of filver explained,
  306   Of  corrofive mercury  by
  concentrated   vitriolic  acid,  313
  tan diffolve no other metals than
  iron and  zinc, 337   Kirwan's ex-
  periments on  the fpecific gravity
  of oil of   vitriol, 383   Why  it
  is neceflary to dilute the acid in
  thele experiments,  396  To find
  its  fpecific  gravity,  397   Quan-
  tity  of acid neceffary  to  f.turate
  pure  mineral  al  -li,  430    Why
  v.triolic  air is  produced by diffol-
  ving iron in concentrated  vitriolic
  acid,  433   Solution  of the  calces
  of iron  in  vitriolic acid,  436  It
  acts 011 iron i.i a much more di-
  lute  ftate  than  the  nitrous, 461
  Proportion of  copper diffolved  by
  vitriolic  acid,  464   Vitriolic air
  obtained from  this folution, 463
  Why tl is  metal cannot be aded
  U'.i .-1 by el.luted vitriolic acid, 466
  .'.ctioa ofthe vitriolic acid  en tin,
  4,C>   O;:  lead, 474   On filver,
  478    O..   mercury, 483    Zinc,
  487    LftcUth,  4;i     Nickel,
  ad 493   Cobalt, 496   Regi.'-.ts
  of antimony,  4y9   Regidus  of
  arfenic, 3c:   Quantity of  ihio-
  giftun in  vitriolic air,  306   This
  acid  and  its  combinations parti-
  cularly treated of, 612, etfeq   Is
  never found naturally  pure, ib.
  How  ratified,  613    Attrads
  moifture from  the air,  614   Pro-
  duces crid  and  hcai according  to
  c.rcumllauees,  613   Coantity  of
  alkali Ltorated  by .t,  bib    '■_-
      S     T    R     Y.

   effeds  on  the  human body, 6tJ
   Diiliculty of procuring it by itfelf,
   618  Diftillation of it from cop-
   peras,  620   Rcdification of the
   acid thus obtained, 622  To pro-
   cure it  from fulphur, 623  Quan-
   tity of acid  contained in it,  ib.
   Quantity produced from it,  6:4
   Methods of obviating the difficul-
   ties in this procefs, 623  Ought
   to  be made in  lead veffels, 627
   Of it= combination with  fixed  al-
   kali,  628   With calcareous earth,
   °35    With  argillaceous  earth,
   637  With magnefia, 690  With
   metals,  691   With inflammable
   fubftances,   712   Bergman's ex-
   periments to fhow that an excefs
   of  this  acid impedes the  cryftalli-
   zation  of alum,  681    Procured
   from  the  refiduum  of   vitriolic
   ether, 2d, 722   Of  its tranfmuta-
   tion into the nitrous  acid,  720
   How to  extrad  the nitrous acid
   by  its means, 734  Whether the
   marine  acid be the fame  with  it,
   783    Experiment   fteming  to
   prove   the   tranfmutation,  784
   Expelled  by  acid  of  fugar,  898
   Effeds  of it on fait of amber, 913
   Diffolves manganefe in  conjunc-
   tion with the acid of tartar, 1012
   Or  with  fpirit  of  wine,  1014
   Expelled  by the nitrous  and ma-
   rine acids,  1041   Promotes  the
   folubility of  falts, 1048   Terra
   ponderofa  ufually found  united
   with  the  vitriolic  acid,   1049
   Unites  with this fubftance  more
   readily  than with alkalies,  1033
   Its prefence  readily difcovered by
   terra  ponderofa, 1038    The oil
   of  vitriol  ufually fold  contains
   gypfum, 1039    Effeds of it on
   arfenic,   1271   Converts  the re-
   gulus into  white  arfenic,  1292
   On regulus of cobalt, 1300.
Vitri'jiatid tartar:  its decompofition
   by calcareous earth explained, 270
   On its  decompofition by nitrous
  acid,  283   l ainiot  be decompo-
  fed by  diluted  nitrous acid,  287
  Decompofed by  marine acid,  280
   Requifites fir the fuccefs of this
  experiment,  289  Cannot be de-
  compofed in  a ftate of folution by
  this acid, 290   Explanation of its
  decompofition by folution  of fii-
  \cr, 333    Why it  is fo  much
  heavier  than  nitre,  416   Of the
  ipjaitity of  ingredients in it, 419
   rio-.v  prepared,  628,  629   Its
  ufes,  631   Decompofed  and  ft 1-
  phur procured from it by calcina-
  tion with charcoal,  716   Its acid
  expelled by that of phofphorus,
  907   And  by the arfenical acid,
  929.
VJatih alkali lefs ftrongly attraded
  than metallic earths by  acids,  303
   M  y be ufed to remove the excefs
  of acid   in   aluminous ley,  680
  Foriris  Glauber's  fal  ammoniac
  with vitriolic acid, 633   Xit.ou-
                        Index.

   ammoniac with  the  nitrous,  74J
   Common fal ammoniac with the
   marine,  793   Vegetable  ammo-
   niac  with the  acetous, 870   A
   fait forming into elegant  cryflali
   with   the  acid   of  tartar,   892
   Its  combination  with  fluor  acid,
   831   Clafs corroded by this fait,
   834   A great quantity of  it fat«-
   rated   by  acid  of  fugar,   900
   Forms microcofmic  fait with  the
   phofphoric acid,  905   Combined
   with acid of arfenic, 928   In its
   mild  ftate decompofes  calcareous
   folutions,  1046   Precipitates fili-
   ceous  earth completely, 1074  Its
   preparation particularly treated of,
   1030, etfeq. Obtained from  various
   fubftances, ib. Proper way of diftil-
   ling it, 1031  How purified, 1032
   Volatile fal ammoniac, how prepa-
   red, 1033   Volatile  alkali  com-
   bined  with  metals,  1034   With
   effential oils  and  fpirit of wine,
   1036,  1037   With fulphur,  1038
   Volatile tindure  of fulphur,  ib.
   Its ufe in  the preparation of aurum
   fulminans but lately known,  1106
   Fhe caufe  of  its explofion,  1121
   Unites with the colouring  mattcr
   of Pruflian blue,  1182  Obtained
   by diftillation from Pruflian  blue,
   1197  Maybe  united  with phlo-
   gifton  and fixtd alkali, fo as to fu-
   ftain a great degree of heat, 120a
   Effeds of it on  nickel,  1314   On
   folution  of platina,  1330   Why
   the volatile fulphureous acid  dif-
   folves  manganefe,  1379  Volatile
   alkali deftroyed by manganefe at-
   trading its phlogifton, 1394.
Volcanic countries  only afford  ores
   containing alum ready made,  63?.
Unguentum  citrinum,  how  prepared,
   772.
Urine, how  the  microcofmic  fait is
   procured  from  it, 903   Alwayi
   contains a  calculous mattcr, 1437
   Why frefh  urine  reddens lacmus,
   1458  Different falts contained in
   »t» U39  Affords the acid of ben-
   zoin, 1332.
Ward's  urop : Nitrous  ammoniac
   the principal ingredient in it, 746.
Water :  Its flownefs in melting when
   congealed,  a  preventative  of in-
   undations, 88   Prodigious force
   exerted by it in  freezing,   106
   Remains  fometimes fluid  though
   cooled below  32  degrees,   117
   Dr 1.lack's  experiments on  the
   converfion  of  water into  fteam,
   ill   It,  boiling  point  in  vacuo
   determined by \\r Boyle, 122  And
   by Mr Robinfon of Olafgow, 123
   May  be  made  fufficiently  hot to
   melt lead,  131   A great  quanti-
   ty of  water yielded by burning
   ft.irit of  wine,   134    Produced
   boo  the deflagration of dephlo-
   gifticated  and  inflammable  air,
   , 3 ?   In the redudion of  iron by
   ii.irimnable air,   136    Why it
   docs not  unite  with nitrous  air,
                                204 
Index.

  204    Cannot   diffolve  metallic
  falts without an excefs of acid, 297
  Quantity  of  it  in digeftive fait,
  379   In nitre, 391  In vitriolated
  tartar,  398   In  fpirit of nitre,
  426   How far  it is an objed of
  chemiftry, 349    Scheme  for fil-
  tering large quantities of it, 369
 'Earthy cruft formed on it by fluor
  acid, 833  See Cruft.   Neutral fait
  for difcovering  iron  in  mineral
  waters, 1180   Mercury fuppofed
  convertible into  it,  1233   The
  miftake difcovered by Lewis, 1236.
Waters, mineral, Mr Woulfe's teft for
  them,1337.
Watt's experiments on  the  diftilla-
  tion  of  water  in vacuo, 43  On
  the evaporation of fluids in vacuo,
  126   His  teft for acids and alka-
  lies, I349  et feq.
Wedge-wood's  improvement  of  the
  thermometer, 104 His ftone-ware
  an improvement in chemical vef-
CHEMISTRY.
269
  fels, 597.
Weight of metals  increafed by calci-
  nation, 323, etfeq.
Wcnzel's experiments on  fluor acid,
  830   Method  of  preparing cry-
  ftals of verdigris, 872.
Weftrumb's analyfis of the refiduum of
  vitriolic ether,  2d 722  His  at-
  tempt to reduce vinegar nearer  to
  the ftate of tartar, 1003.
Whey : chemical properties of it, 970
  Convertible into vinegar, 979.
White: a beautiful white colour from
  lead, 703   White  drop of Ward,
  746   White copper,  how  pre-
  pared, H37-
Weigleb's experiments on fluor acid,
  839   Account  of  the  diftillation
  of nitrous acid by clay, &c. 737
  His  new  chemical nomenclature,
  1361.
Wilfon's experiments  on phofphori,
  1086.
Winch's method of purifying  ether,
   2d 722 Wines, how purified, 886.
Withering's  experiments  on   terra
   ponderofa, 1030.
Wolfram.  See Tungften.
Wood, prefervatives for, 621, 700.
Wood-ward's  receipt for making Pruf-
   fian blue,  1164.
Woulfe's method of procuring nitrous
   ether in laage quantity, 776   Teft
   for mineral waters, 1337.
Yellow colour for houfe-painting,
   699.
York, account of  the  aluminous ore
   found near that place, 660.
Zaffre, a  calx of cobalt,  defcribed,
   1294.
Zinc and  iron, the only metals  dif-
   folved  by vitriolic acid, 337  Of
   theii precipitation by one another,
   347    Precipitates  nickel,   338
   Cannot  precipitate cobalt,  361
   Forms white  vitriol with  the vi-
   triolic  acid,  707  Combined with
   the nitrous acid, 767   With the
 marine acid, 820   Volatilized by
 it, ib.  With acid of arfenic,  931
 Cannot eafily  be  combined  with
 iron, 1162   Its combination  with
 copper, 1134  The  metal parti-
 cularly treated of, 1240   Defla-
 grates violently in  a  ftrong heat,
 ib.   Sublimes into flowers, 124E
 Dr Lewis's  method  of  reducing
 them, 1242  Oil  fuppofed to  bet
 obtained from them by Homberg,
 1243  The  miftake difcovered by
 Neumann, ib.   Another oil by  Mr
 Hellot, capable of diffolving gold
 and  filver  leaf, 1244  Combina-
tion  of zinc with other  metals,
 1243   lts combination with gold
a  proper  material  for  fpecula,
 1246   Its deflagration with other
metals, 1247  Cannot be united
with  fulphur, 1248   Nitre alka-
lyfed by its flowers, 1149  Unites
readily with platina, 1342. 
 
Dobson, Thomas, A system of chemistry..., WZ 270 S995c 1791
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