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EXAMINATION OF WATER.






    LEFFMANN AND BEAM. 
     PROGRESSIVE EXERCISES
                 IN
PRACTICAL  CHEMISTRY.
                 BY
   Henry Leffmann and William Beam.

         i2mo.  Illustrated.  $1.00.
A  COMPEND  OF  CHEMISTRY,
        INORGANIC AND ORGANIC.
               INCLUDING
     URINARY  ANALYSIS.
                  BY
            Henry Leffmann.

   especially adapted to students in medicine
             and dentistry.

          Third Edition.  Revised.
 Price $1.00.  Interleaved, for taking Notes, $1.25.
P. BLAKISTON, SON & CO. 
Examination of Water
SANITARY AND TECHNICAL PURPOSES.
HENRY LEFFMANN, M. D., Ph.D.,
PROFESSOR OF CHEMISTRY IN THE WOMAN'S MEDICAL COLLEGE OF PENNSYLVANIA,
    IN THE PENNSYLVANIA COLLEGE OF DENTAL SURGERY AND IN THE
       WAGNER FREE INSTITUTE OF SCIENCE; PATHOLOGICAL
           CHEMIST TO THE JEFFERSON MEDICAL
               COLLEGE HOSPITAL.
WILLIAM BEAM, M.A.,
DEMONSTRATOR OF CHEMISTRY IN THE PENNSYLVANIA COLLEGE OF DENTAL
     SURGERY ; ASSOCIATE OF THE SOCIETY OF PUBLIC ANALYSTS
          OF GREAT BRITAIN; FORMERLY CHIEF
               CHEMIST B. t. O. R. R.
'*/
M-Q-, frJ-'
SECOND EDITION, REVISED AND ENLARGED, WITH
           ILLUSTRATIONS.
          PHILADELPHIA:
P.  BLAKISTON,  SON & CO:,
       IOI2 WALNUT STREET.
 
WAA
U4<i5e
Copyright, 1890, by P. Blakiston, Son & Co.
^f^S
Hirllfi.VrE
PRESS OF WM. F. FELL « CO.,

 1220-24 SANSOM STREET.

   PHILADELPHIA. 
PREFACE.
  In the period that has elapsed since the publication of
the  first edition of this work, many  processes for water
analysis have been proposed, and we have  included in the
present revision such of these  as seem to us of substantial
value. . In particular we may mention  the methods recom-
mended  by the Chemical Section of the American Associa-
tion for the Advancement of Science,  and  the application
of the Kjeldahl process to the determination of the organic
nitrogen.  The adoption of the former methods will serve
to secure uniformity in analytical  data, while it  is to be
hoped that chemists generally will investigate and report
on the latter, in  order  that a basis for the interpretation
of results may be obtained.
  No material change has been made in the description of
the general Quantitative Analysis, in which we have followed
to a large extent  the  methods  indicated by Fresenius,
selecting those best adapted to technical purposes.
  We  have  extended  considerably the   section   on  the
Biological Examinations, although we  have seen no reason
to change the opinions  expressed in the former edition as
to the  value of these results.   It would  be impossible to
overestimate  the  importance of bacteriology, in etiology,
pathology and  general  biology, but until  pathogenic  mi-
crobes are more clearly  indicated  and  described,  the
                           v 
VI
PREFACE.
methods will be of little use in  dealing with the problem
of the determination  of the sanitary and technical value of
water supplies.
  In the  chapter on the Purification of Water we have
described  in  some detail a few of the important systems,
especially  the Anderson iron  process, the  efficiency  of
which  we  have had ample opportunity to  observe  by
experiments  on a comparatively  large  scale,  extending
over several months.
  The  favorable reception accorded to  the first edition,
both by journals  of  acknowledged  authority, and  by
chemists of extended experience in  this  department,  has
indicated  that  the work is not without usefulness  in  the
field to which it is devoted.                      H. L.
                                              W. B.
    71 j Walnut St.
         December, i8go. 
CONTENTS.
                                                           PAGES
History of Natural  Waters.
         Classification — Rain  Water — Surface Water—Subsoil
           Water—Deep Water,..............9-15

Analytical Operations.
     Sanitary Examinations:—
         Collection and Preliminary Examination—Total Solids—
           Chlorine—Nitrogen  in  Ammonium Compounds  and
           in Organic Matter—Nitrogen as Nitrates—Nitrogen as
           Nitrites — Oxygen-consuming  Power — Phosphates—
           Dissolved Oxygen—Poisonous  Metals,......IO_53
     Technical Examinations :—
         General Quantitative Analysis—Spectroscopic Analysis—
           Specific Gravity,...............53-69

Interpretation of Results.
     Statement of Analysis,................70-82
     Sanitary Applications—Action of Water on Lead, ....    83

Biological Examinations,..............'  . 85-96

Purification of Drinking Water,..........98-107

Identification of Source of Water,........ 107-110

Technical  Applications.
         Boiler Waters—Purification  of Boiler Waters—Sewage
           Effluents..................111-118

Analytical Data.
        Factors for Calculation—Conversion Table—Oxygen Dis-
           solved in Water—Rain and Subsoil Waters—Schuylkill
           Water—Artesian Waters—City Supplies,  .... 119-125
                               vii 
i 
EXAMINATION   OF  WATER.
   history  of  natural  waters.
  Pure water is  an artificial product of the laboratory.
Natural waters always contain foreign matters in solution
and suspension, varying from mere  traces to very large
proportions.   The properties, effects and  uses of water are
considerably modified by these ingredients, and the object
of analysis  is to ascertain  their character and  amount.
Since  these are  largely  dependent  on the history of  the
water, a  classification based  on this  will be  convenient.
We may distinguish four classes of natural waters:—
  Rain Water.—Water  precipitated from the atmosphere
under any conditions, and therefore including  dew, frost,
snow and hail.
  Surface Water.—All collections of  water in free contact
with the atmosphere, as  in streams, seas, lakes, or ponds.
  Subsoil or Ground Water.—Water  not in free  contact
with the atmosphere, percolating or  flowing through soil or
rock at moderate  distance  below the  surface, and derived
in large part from  the rain or surface water of the district.
  Deep or Artesian Water.—Water  accumulated at con-
siderable  depth  below the surface,  from  which the subsoil
water  of  the district has been excluded by difficultly per-
meable strata.
  Rain Water, when  gathered in the open country and
      b                  9 
10
HISTORY OF NATURAL WATERS.
in the latter period of a long rain or snow, is the purest
form of natural water.   When collected directly, it con-
tains but  little solid matter, this consisting principally of
ammonium  compounds and  particles of organic matter,
living and dead, gathered from the  atmosphere.  In  dis-
tricts near the sea an appreciable amount of chlorides will
be present.   It is obvious that a  prolonged rain will  wash
out the air, but since storms are usually attended by wind,
fresh portions of air are continually flowing in, and thus the
water never  becomes perfectly pure.  Rain water collected
in inhabited districts is usually quite  impure.
   Surface  Water.—Rain water in part flows  off on the
surface, and gains in the proportion of suspended and dis-
solved  matters, the former being found in large amount
when the rainfall is  profuse.   The wearing action of water
is dependent on  the amount  and character  of  these  sus-
pended materials.   From the higher levels of a watershed,
the streams, more or less in the form of torrents, gather into
larger currents, and reaching  lower  levels become slower
in movement, and deposit much of the  suspended matter.
By admixture of the waters from  widely separated districts
the character and amount of the dissolved matters are much
modified.   An action of this kind is seen in the watershed
of the Schuylkill River.   This stream rises in the anthracite-
coal region  of Pennsylvania, and receiving much refuse
mine-water becomes impregnated with iron salts and free
mineral acid, being then quite unsuitable for drinking or
manufacturing purposes.  In its course of about one hundred
miles,  it  passes over an extensive limestone district,  and
receives several large streams highly charged with calcium
carbonate.  The result is a neutralization of the acid, and a
precipitation of the iron and much  of the calcium.   The river 
SUBSOIL WATER.
II
becomes purer, and at its junction with the Delaware River
at Philadelphia, it contains neither free sulphuric nor hydro-
chloric acid, only traces of iron, and  but a small amount
of calcium sulphate.   In this manner there  is produced  a
soft water, superior to that of the river near its  source, or
to the hard waters of the middle Schuylkill region.
   It is obviously impossible to  establish close  standards of
composition for surface  waters.  In the case of rain water,
falling on the surface of undisturbed, unpopulated territory,
the amount of solids dissolved will be small, and will consist
principally  of  carbonates  and  sulphates.  The water of
lakes and rivers is,  however, in part derived from  springs,
which may proceed from great depths,  and thus  introduce
substances not easily soluble in surface water, nor derivable
from the soil of the district.
   The exposure to light and air which surface water under-
goes, results in the absorption of oxygen and loss of carbonic
acid, together with the  oxidation  of the  organic matter.
The diminution of  the  rapidity  of  the  current  permits
the deposition of the suspended  matters,  and this occurs
especially as the river approaches the sea, not only from
the retarding influence of the tidal wave, but from the pre-
cipitating action of the  salt water.  The  investigations of
Carl Barus,  published in Bulletin No. 36, U. S. Geological
Survey,  have shown  the  decided influence  of  sodium
chloride in accelerating the subsidence  of fine particles.
   Subsoil  Water.—Water  which penetrates the  soil,
passes  to various depths, acccording to the  porosity and
arrangement of  the strata.   As a rule, it descends until it
reaches but  slightly pervious  formations, upon the level of
which it accumulates.  In the upper layer of soil it dissolves
mineral and organic ingredients, and becomes impregnated 
12
HISTORY OF  NATURAL WATERS.
with microorganisms, through  the agency  of which  the
organic matter undergoes important transformations.   The
water constantly accumulating, gradually flows along the
incline  of the impervious stratum, or  through its fissures,
and may either pass downward or emerge in the form of a
spring.
  The proportion of water which may be held by any rock
or soil is often much larger than would  be at first supposed.
T. Sterry Hunt  states that a square mile of  sandstone ioo
feet thick will contain water sufficient to sustain a flow of a
cubic foot a minute for more than  thirteen years.
  Much difference is observed in  the composition of sub-
soil waters, but as a general rule they contain but a limited
amount of mineral substances, and a very small proportion of
organic matter.   In populated districts, however, a marked
change is. produced  through admixture with water contain-
ing animal and vegetable products in various stages of decom-
position.  It is  especially the organic  matter containing
nitrogen that is  of  importance.  To this class belong all
those  compounds  forming  tissues that  are intimately
associated with  vital action;   also  many  characteristic
excretory  products. These bodies are  mostly  unstable,
and  as soon as their  vitality  ceases  begin  to  decom-
pose, partly  by  oxidation,  partly by  splitting  up  into
simpler forms; these changes being in most  cases brought
about by microorganisms.  Among the products noticed in
the early stages of such decay, are  substances which possess
close analogies to the organic bases or alkaloids, but more
susceptible  of decomposition.   They are generally present
in minute amount,  but are not infrequently very active in
their physiological effect. From the most recent researches it
seems probable that the  pathogenic power of many micro- 
SUBSOIL WATER.
r3
 organisms rests not upon any mechanical or other action of
 the  germs themselves, but upon  the  alkaloidal  principles
 which they produce and excrete.  As a group these bodies
 are known as the " ptomaines."   Nitrogen is an  invariable
 ingredient.  The ultimate results of  the processes of de-
 composition  depend  largely on  circumstances.   When
 organic matters containing nitrogen are subjected to  the
 action of oxidizing  agents, such as alkaline potassium per-
 manganate or  chromic acid, some of the  nitrogen is con-
 verted into ammonia.   A similar result occurs in all waters,
 but a considerable portion of the  organic matter may also
 suffer further oxidation and in association with the  mineral
 substances present form nitrites and  nitrates, especially the
 latter.  This conversion is called  "nitrification."   The
 conditions under which it occurs have been carefully studied
 by Warrington, Munro and others.
   Nitrification  takes place under the influence of  microbes,
 the habitat of which does not extend more than a few yards
 below the surface of the soil.  Percy and Grace Frankland
 have isolated and described a bacillus with active  nitrifying
 powers.   It is  a very short, almost spherical form, which
 grows in ammoniacal  culture-fluids and in meat-broth,  but
 does not grow  in the usual gelatin-peptone mixture, except
 when  previously  cultivated  in  meat-broth.  The  nitri-
 fying action  is probably exerted only upon the ammonium
 which is formed from  the organic matter.   The presence
 of some substance capable of neutralizing acids is necessary
 to continuous  action.   Calcium and  magnesium carbon-
ates  fulfill  this function.  Nitrates  are  the final result of
this action ; nitrites are present at any given time  only in
small  quantity.  Denitrification,  that is,  the reduction
of nitrates and nitrites  to ammonium, takes place under 
M
HISTORY OF  NATURAL WATERS.
the influence of microbes, and is especially apt to occur
when considerable quantities of decomposing organic mat-
ter are introduced.  Percy and Grace  Frankland have
described several species  of bacilli  which have active  de-
nitrifying powers.   Among these are Bacillus  liquidus, B.
vermicularis and B. ramosus.   A partial reduction some-
times occurs, and a notable proportion of nitrites is found,
but in the presence of actively decomposing organic matter,
such as that in sewage, a complete reduction, even to  the
liberation of nitrogen, may occur.
   Deep Water.—Water which penetrates  the fissures of
the fundamental rock formations may pass to great depths,
and by following the lines of the lowest  and least perme-
able strata may be transported to points far removed from
those at  which it was originally collected.   The chemical
changes thus induced  include most of those  which take
place at higher points, but the increase of pressure  and
temperature confers increased power.  Carbonic acid will
accumulate under  conditions favorable to the solution of
calcium, magnesium and  iron  carbonates, and  iron and
manganese oxides  may be converted into carbonates and
then dissolved.  Sulphates are  reduced to  sulphides, and
these subsequently, by the action of carbonic acid, yield
hydrogen sulphide.  Organic  matter, living  and dead,
plays an important part, determining the reduction of ferric
compounds  to ferrous, and of the sulphates to sulphides,
and  is itself converted ultimately  into  ammonium com-
pounds, notable quantities of which are often found in deep
waters.   Further, it is found that nitrates and  nitrites  are
present only in small amount,  except  from  certain strata
rich  in organic matter.   In some cases the water acquires
very high temperature,  and dissociation  of  rocks  occurs, 
DEEP  WATER.
15
with solution of considerable amounts of silicic acid, which
is ordinarily but sparingly soluble in water.
  Masses of water thus accumulated under heat and pres-
sure may find their way to the surface either through natural
fissures, or be reached by borings.   The mineral springs,
highly charged with solid matters, and the artesian waters,
are obtained in  this way.
  While no absolute unchangeable line can be drawn be-
tween deep and  subsoil waters, yet it will in most cases be
found  that the  deep water of a given district,  whether
obtained  through  natural  or  artificial  channels,  will be
decidedly different in composition  from the subsoil or sur-
face water  of the same,  and that the  rocks  passed through
in such cases will be characterized  by one or more strata,
difficultly  permeable to water,  and therefore preventing
direct  communication.   The characteristic differences be-
tween  surface, subsoil, and  deep waters are  clearly indi-
cated in the table of analyses made by us  as given in the
Appendix.
  The fact that  mere depth is not  the  essential difference
between the two classes of  waters is shown by comparison
between the composition of the water from the well at
Barren Hill, on the northern border of Philadelphia county,
and the deep well at Locust Point,  Baltimore.  The former
is a dug well, 130 feet deep; the latter  is an  artesian bor-
ing of 128 feet, which in its descent  passes  through four
feet of solid  rock.  The deeper  well is evidently  supplied
by  subsoil  water.   The  artesian  well, though located 100
yards from a brackish sewage-laden estuary, evidently de-
rives no water from it. 
ANALYTICAL  OPERATIONS.
SANITARY EXAMINATIONS.
Fig. i.
   COLLECTION AND  PRELIMINARY EXAMINATION
                     OF SAMPLES.
                    Great care must  be  taken  in collect-
                  ing  water samples, in order to secure a
                  fair  representation of the supply and to
                  avoid  introduction of foreign matters.
                  The five-pint green glass stoppered bot-
                  tles used for holding acids are suitable
                  for containing the  samples.   The con-
                  tents of one such bottle will suffice for
                  most sanitary or technical examinations.
                  Fig. i shows a bottle encased  in wood,
                  and  known under  the  name of  the
                  "Penn Demijohn,"  which  we  have
                  found  very convenient  for transporta-
tion.   It  is  provided  with a hinged lid which can  be
securely  fastened by a  padlock.  The green glass  stop-
pered bottles may also  be fitted  to such an arrangement.
Stone jugs, casks or metal vessels must not be employed.
The bottles used must be thoroughly rinsed several times
with the water to be examined, filled and the  stopper tied
down, or  fastened  by stretching a rubber finger-cot  over
the stopper and lip.  If corks are used, they should be new
and thoroughly rinsed.   No  wax, putty, plaster or similar
material should be used.
                         16
 
SANITARY  EXAMINATIONS.
17
   In taking samples from lakes, slow streams or reservoirs,
it is necessary to submerge the bottle so as to avoid collect-
ing any water that has been in immediate contact with the
air.
   In the examination of public water  supplies, the sample
should  be  drawn  from a hydrant in direct connection
with the main, and not from a cistern, storage  tank or dead
end of a pipe. In the case of pump-wells, a few gallons of
water should be pumped out  before taking  the  sample, in
order to remove that which has been standing in the pipe.
   In all cases care should be  taken  to fill the vessel with as
little agitation with air as possible.
   It is important that with each sample a record be made
of  those surroundings and conditions which  might influ-
ence the character of the water, particularly in reference to
sources of pollution, such as proximity to cesspools, sewers
or manufacturing establishments.  The character and con-
dition of the different strata of the locality should be noted
if possible.
   Determinations of nitrogen existing as ammonium com-
pounds, and as organic matter, and of oxygen-consuming
power, should be made upon  the sample  in  the original
condition, whether turbid or clear, but all other estimations
should be made upon the clear liquid.  Turbid waters may
be clarified by standing or by filtration ; for the  latter pur-
pose Schleicher &  Schiill's extra heavy No. 598 paper is
the best.  In  many cases the suspended matter cannot be
entirely removed by filtration, and  subsidence must be re-
sorted to.  The use of a small  quantity of alum, as described
in the section  on the purification of water, will sometimes
be applicable as a rapid means of clarifying water samples.
For [the quantitative determination, the sediment from a 
18             ANALYTICAL OPERATIONS.
known volume of the water is collected on a tared filter,
dried at 1120 F., and weighed.
  The water from newly-dug wells is generally turbid and
the determinations are best made after filtration, but the
results will be unsatisfactory, showing a higher proportion
of organic matter than will be found when the supply be-
comes clear.
  The following  methods of determining color and odor
have been adopted by the Society of Public Analysts  of
Great Britain :—
  Color.—A colorless glass tube, 2 feet long and 2 inches
in diameter, is closed at  each end with a disc of colorless
glass. An opening for filling and emptying the tube should
be made at one end,  either by cutting a small segment off
the glass disc, or  cutting out a  small segmental  section of
the tube itself before the disc is  cemented  on.   A good
cement for such purposes is the following :—

         Caoutchouc,..........  2 parts.
         Mastic,.............  6   "
         Chloroform,...........100   "

  The ingredients are mixed and  allowed to stand for a
few days.  The cement should be used  as soon as solution
is effected, as it becomes viscid on standing.
  The tube must be about half filled with the water to be
examined, brought into a horizontal position, level with the
eye, and directed toward a brightly illuminated  white sur-
face.  The comparison of tint has to be made between the
lower half of the tube containing the water under examin-
ation, and the upper half containing air only.
  Odor.—Put  about 150 c. c. of the water  into a clean,
wide-mouth  250  c. c.  stoppered bottle, which  has been 
SANITARY EXAMINATIONS.
19
previously rinsed with the same water ; insert the stopper
and warm the water in a water-bath to  ioo° F.   Remove
the bottle from the  water-bath, and shake it rapidly for a
few seconds ;  remove the stopper and immediately note if
the water has any smell.   Insert the stopper and repeat the
test.
  In  a  polluted water the odor will sometimes give  a clue
to the origin of the  pollution.
  Reaction.—The determination  of reaction is usually
made by the addition of a neutral solution of litmus to the
water.  If an acid reaction is obtained the water should be
boiled in order to determine if it is due to carbonic acid.
Some of the more delicate indicators,  such  as phenol-
phthalein and  lacmoid,  may be used with advantage for
these  tests.   The latter possesses the advantage  that it is
unaffected by carbonic acid,  but detects  even traces of free
mineral acid.   It is  neutral, also, to many normal metallic
salts, such as ferrous sulphate, which are acid to litmus. Fer-
ric salts, however, are acid to lacmoid.  Its color changes are
the same as  those of litmus, i. e., red with acids  and blue
with alkalies.
  Phenolphthalei'n is best applied to the  detection of weak
acids,  such  as carbonic  acid and the organic acids.   In
acid and neutral solutions it is colorless—in alkaline, deep
red.  Nearly  all waters contain carbonic  acid, and will
therefore  bleach a  solution of  phenolphthalem which has
been reddened by a small amount of alkali.

                    TOTAL SOLIDS.
  A platinum  basin holding 100 c. c. will be found con-
venient for this determination.    This should weigh  about
45 grams.  It should be kept clean and smooth  by frequent 
20
ANALYTICAL OPERATIONS.
burnishing with  sand, a little  of which should be placed
in the palm of the hand, moistened,  and the dish gently
rubbed against it.  Very fine sea sand with round, smooth
grains is the only kind suitable  for this  purpose.   Coarse
river sand, tripoli, or other rough  scouring powders, must
not  be employed.  If proper care is  taken, the lustre of
the metal will remain unimpaired indefinitely, and the  loss
in weight will be trifling.  The inner surface  can generally
be  cleaned  by treatment with  hydrochloric acid, rinsing
and, if necessary, burnishing.  Neglect of these precautions
will soon  lead  to serious damage to  the dish.  A small,
smooth slab of iron or marble is convenient to  set it on
while cooling.  When being heated over the  naked flame
the  dish  should  rest  on a  triangle of iron wire, covered
with pipe-stems.  The dishes of pure nickel have not been
found by us  to be  satisfactory substitutes  for  those of
platinum.
  Platinum-pointed forceps should be used in handling the
dish.  The  platinum  terminals  may be  kept bright  and
          Fig. 2.           clean by the use of sand.
                           The low-temperature  burner,
                         used as shown  in Fig. 2, will be
                         found a very convenient  substi-
                         tute for  the  water-bath and  hot
                         air oven. The inlet pipe is very
                         short and soon becomes  so  hot
                         as to injure the rubber tube.  To
                         avoid this it may be lengthened
                         by means of a piece of }i inch
                         gas-pipe,  or the junction may be
wrapped with a rag, the ends of which dip into water.  By
capillary attraction the rag is kept moist and cool.
 
SANITARY EXAMINATIONS.
21
   The determination of total solids is made by evaporating
50 or 100 c. c. of the water in the platinum basin, which has
been previously heated almost to redness, allowed  to  cool
for ten minutes, and weighed.  The operation is conducted
at a moderate heat.  When  the residue  appears  dry, the
heat may  be increased slightly for some  minutes.   The
above method will  answer in most cases.  In waters of ex-
ceptional purity it may be advisable to use larger quantities,
such as 250 c. c.   When  the residue contains deliquescent
bodies, the determination will  not be  accurate, and when
bodies are present which take up much water of crystalliza-
tion, the residue will  need to  be strongly heated, if  con-
trol figures  are  to be obtained.   This  determination of
total solids is described in connection with the technical
examinations.
   After  the  weight of the residue  is  obtained,  the  dish
should be cautiously heated to low  redness, and the efftct
noted.   Nitrates and nitrites, calcium  and magnesium car-
bonates, and magnesium chloride are decomposed ; ammo-
nium salts are driven  off;  potassium  and  sodium chlo-
rides are  also  driven off  if  the  temperature  is high.
Organic  matter  is at first  charred, and by continued heat-
ing burned off.   When the quantity of nitrates is consider-
able, slight deflagration may be observed, or the produc-
tion of  red  fumes of nitrogen dioxide.  The organic
matter, in  decomposing,  not infrequently develops odors
which  indicate  its  character or source.  These  are more
satisfactorily observed,  when a rather  large quantity, say
250 c. c, is evaporated at a low heat, preferably on a water-
bath.
   In water of high  organic purity, the  residue on heating
will  give no appreciable   blackening nor odor,  while in 
22
ANALYTICAL OPERATIONS.
forest streams charged with vegetable matter  derived from
falling leaves, very decided blackening without unpleasant
odor will be noticed.  The loss  of weight  after  heating
cannot  be taken  as  a measure  of the  organic  matter,
except when present in relatively large amount.

                      CHLORINE.
Solutions Required:—
  Standard Silver  Nitrate.—Dissolve about 5 grams of
pure recrystallized  silver  nitrate  in distilled water,  and
make the solution up to 1000 c. c.  The amount of chlorine
to which this is equivalent may be determined as follows:
Several grams of pure sodium chloride are finely powdered
and heated over a Bunsen burner for five minutes, not quite
to redness.  When cold,  0.824 gram is dissolved in water
and the solution made up to 500 c. c.  25 c. c.  of this should
be treated as below, and  the amount of  silver solution re-
quired noted.   Each c. c. of the sodium chloride solution is
equivalent to .001 gram chlorine.
  Potassium Chromaie.—5 grams of potassium chromate are
dissolved in 100 c. c. of distilled water. A solution of silver
nitrate is added until a permanent red precipitate is  pro-
duced, which is separated by filtration.
Analytical Process: —
  If a preliminary test shows the  chlorine to be present in
considerable amount, the determination  may be made on
100 c. c. of the water without concentration.   If, however,
there is but little present, 250 c. c. should be  evaporated to
about  one-fifth, and the determination  made on the con-
centrated liquid after cooling.
  The water is  placed in a porcelain dish or  in a beaker
standing on  a white  surface, a  few  drops  of potassium 
SANITARY  EXAMINATIONS.
23
chromate solution  added,  and  standard silver  nitrate
solution run  in from a burette until a faint  red  color of
silver chromate remains permanent on stirring.  The pro-
portion of chlorine is then calculated from  the number
of c. c. of silver  solution added.  For greater accuracy a
second determination may be made, using as a comparison
the liquid first titrated, the red color  having been pre-
viously discharged  by a few drops of  sodium  chloride
solution.
  The water  should always be as nearly neutral as possible
before titration.   If acid, it must be neutralized by the
addition of some precipitated calcium carbonate.

  NITROGEN IN AMMONIUM  COMPOUNDS AND IN OR-
                    GANIC  MATTER.
  The nitrogen  in ammonium compounds, and a part of
that in the organic matter, is determined by a process
of distillation first  developed  fully by Messrs. Wanklyn,
Chapman and Smith.   It depends upon the conversion of
the nitrogen  into  ammonia  and subsequent estimation in
the distillate.
  Apparatus Required:—
  Distilling Apparatus.—That shown in  Fig. 3 has been
found to'be the most convenient.   The  still consists of a
Bohemian glass retort of about 1000 c. c. capacity.  The
beak of the retort should incline slightly upward, to prevent
contamination by splashing.   At about two  inches from
the end it should be bent at  a right angle, and drawn  out
so as to enter the condensing worm for about  an inch, and
terminate beneath the level of  the water.   Glass worms are
apt to crack, and it is more satisfactory to use  one  of block
tin.  A piece of rubber tubing is drawn over the junction. 
24
ANALYTICAL OPERATIONS.
A rapid current of cold water should be maintained through
the condenser.  The heat is applied by means of the  low-
temperature burner, the iron ring of which is removed so
that  the  retort rests directly on  the gauze.  With  this
arrangement the heat is  under perfect control,  and the
danger of fracturing the glass is reduced to a minimum.
  Cylinders for Comparison-Color Tests, about 2.5 cm.  in
diameter and holding  100 c. c, made of colorless glass.
Solutions Required :—
  Sodium Carbonate.—50 grams of pure sodium carbonate 
                SANITARY EXAMINATIONS.             25

are strongly heated, dissolved in 250 c. c. of distilled water,
and the solution boiled down to 200  c. c.
   A?nmonium-Free  Water.—If the distilled water of  the
laboratory gives a reaction with Nessler's reagent, it should
be treated with sodium carbonate, about  one grain to  the
liter, and boiled until about one-fourth  has been  evapor-
ated.  Ammonium-free water  may be obtained  by distill-
ing  in a retort, water made slightly acid  with sulphuric
acid.
   Standard Ammonium Chloride.—Dissolve  0.382 gram of
pure dry  ammonium chloride  in 100 c. c. of ammonium-
free water.  For  use, dilute 1 c. c.  of this  solution with
pure water to 100 c. c.  1 c. c. of  this dilute solution con-
tains .00001  gram of nitrogen.
   Nessler's Reagent.—Dissolve  35  grams  of  potassium
iodide in 100 c. c. of water.  Dissolve  17  parts of mer-
curic chloride in 300 c. c. of water.  The liquids  FlG
may be heated to aid solution,  but must be cooled
before use.   Add  the mercuric chloride solution
to that of the potasssum iodide, until a permanent
precipitate is produced.   Then dilute with  a  20
per  cent, solution  of sodium  hydroxide to 1000
c. c, add mercuric chloride solution until a per-
manent precipitate again forms and allow to stand
until clear.  Nessler's and other reagents are best kept in
glass-capped  bottles,  Fig. 4, in which the pipette may re-
main when not in use.  The solution improves by keeping.
   Alkaline Potassium Permanganate.—Dissolve 200 grams
of potassium hydroxide, in sticks,  and 8 grams of potas-
sium permanganate, in a liter of distilled water.
   The solution is boiled until  about one-fourth is evapo-
rated ;  then  made up  to a  liter   with  ammonium-free
       c
 
26
ANALYTICAL OPERATIONS.
water.   Since it will still  furnish some ammonia, it is ne-
cessary to determine the amount.   Fox recommends to dis-
till 50 c.c. with 500 c. c. of absolutely ammonium-free water,
best  twice distilled  with sulphuric acid, and note  the am-
monia  obtained.  This quantity  should be deducted in
each analysis.
Analytical Process :—
   The retort and condenser are thoroughly rinsed with am-
monium-free water, 500 c.  c. of the water to be tested in-
troduced, about 5 c. c. of the sodium carbonate  solution
added to render the water alkaline, and a piece of  pumice-
stone heated  to redness and  dropped in while hot.  The
water is  then boiled gently until  the distillate  measures
50 c.c.   The  distillate is  transferred to one of the color-
comparison  cylinders and  2 c. c. of  the Nessler's reagent
added.  A yellowish-brown  color is produced, the intensity
of which is  proportional to the amount of NH3,  present.
The  full color is developed in five  minutes.  This  color is
exactly  matched by introducing  into  another cylinder
50 c. c. of ammonium-free water,  some  of  the  standard
ammonium chloride solution, and 2 c. c.  Nessler's reagent,
as before.   According as the color so produced is deeper
or lighter than that obtained from the water, other compari-
son liquids are prepared containing smaller or larger pro-
portions of the ammonium chloride, until the proper color
is produced.
  The   distillation   is  continued,  successive  portions of
50 c. c.  each collected, and tested until no reaction occurs
with Nessler's reagent.  The  sum of  the figures  from the
several distillates gives the total nitrogen obtainable as
"free ammonia," so-called.
  If the quantity of ammonia is sufficient  to cause a precipi- 
SANITARY  EXAMINATIONS.
27
 tate, the color comparison cannot be accurately made.  In
 most cases this will not be of serious moment, as the quan-
 tity will be beyond the allowable limit.   If accurate deter-
 mination be desired, it may be made by dividing the  first
 distillate into two equal parts, nesslerizing one of these,
 and then, if necessary, diluting the second part with ammo-
 nium-free water and nesslerizing this.
   Occasionally the evolution of ammonia continues indefi-
 nitely,  and  may  even increase with  successive  distillates.
 This is due, not to  ammonium compounds  existing as
 such, but to decomposition of certain nitrogenous bodies,
 especially urea.  In this case, it is not advisable  to prolong
 distillation beyond the fourth or fifth distillate, but to pro-
 ceed to the  following part of the process.
   The residue in the retort serves for the determination of
 the nitrogen which is convertible into ammonia by alkaline
 potassium permanganate—the so-called  "albuminoid am-
 monia" of Messrs. Wanklyn, Chapman and Smith.
   50 c. c. of alkaline permanganate solution are added to
 the retort, the distillation resumed, and the nitrogen esti-
 mated in each 50 c. c. as before, deducting that yielded by
 the permanganate.
   It is the practice of some analysts to mix the distillates
 of each of the above operations,  and thus make determina-
 tions merely of the total nitrogen in  each case.  By  so
 doing valuable information  may be lost, since it has been
 pointed out by several observers, notably Mallet and Smart,
 that  important information maybe gained by observing the
rate  of evolution  of  the  ammonia.   Mallet has further
pointed out that  many  waters  may  contain substitution
ammoniums which may pass over before  the  addition of the
alkaline permanganate, but not  be correctly measured by 
28
ANALYTICAL OPERATIONS.
nesslerizing.   To avoid this source  of error, he suggested
that  two determinations be made on each sample, one as
above described and the other by the addition  of alkaline
permanganate without  previous distillation.  In this man-
ner a higher figure will often be obtained than  the sum of
the figures from the two distillations by the other process.
  Since small quantities of ammonium  compounds  and
nitrogenous matters are everywhere present, the greatest
care  should be exercised in order to avoid their introduc-
tion  in  any way during the course of the analysis.   All
measuring vessels, cylinders,  etc.,  should be  thoroughly
rinsed before using.
  The Chemical Section of the American Association for the
Advancement of Science recommends the following method
for the application of the "ammonia process,"  embodying
the results of recent investigations :—
   "  200 c.  c. of distilled water, together  with  10 c. c. of
the sodium carbonate solution, are distilled down to about
100 c. c. in the retort in which the  analysis is  to be  con-
ducted, and the last portion of 50 c. c. nesslerized to assure
freedom from ammonia.  Then 500 c. c. of the water to be
examined are added and the distillation is carried on at such
a rate that about 50 c.  c. are collected in  each  succeeding
ten minutes, and until a 50 c. c. measure  of  distillate is
obtained containing only an inappreciable quantity of am-
monia.   In nesslerizing, five minutes are to be  allowed for
the full  development of color; after this, no change takes
place for many hours.
   "Now throw  out the contents  of  the  retort,  rinse it
thoroughly, put in 200 c. c. of distilled water and 50  c. c.
of the permanganate solution, distill down to about 100  c. c,
and  nesslerize the last  portion of 50 c. c, to make sure of 
SANITARY  EXAMINATIONS.
29
Fig. 5.
 freedom from ammonia; add another  portion of 500 c. c.
 of the water under examination and proceed with the dis-
 tillation and nesslerizing as with the first portion.
   "The  difference  between the  'free' ammonia of the
 first operation and the total ammonia of the second,  is to
 be taken as the  'albuminoid' ammonia."
   For nesslerizing and  other color comparisons,
 many  forms of apparatus  have been  proposed.
 One of the simplest is that  devised by Hehner,
 shown  in  Fig.  5.  It consists of a  graduated
 cylinder with a stopcock near the base, by which
 the liquid can be drawn down at will.  Two such
 cylinders may be used, one for the nesslerized dis-
 tillate, the other for the comparison liquid.   The
 darker  liquid is drawn out  until  the  tints are
 equal,  when the relative volumes  remaining will give the
 data for calculation.
   Another convenient form of color comparator
 is shown in Fig. 6.  It consists of a box black-
 ened inside, and supported so as  to permit a
 movable mirror  to  be mounted underneath.
 The box is perforated at both ends to  receive
 graduated tubes  holding 60 c. c.  A projecting
 rim shades the  ends of the tubes  from extra-
 neous light.
   In practice the Nessler reagent is mixed with
 50 c. c. of the distillate, and poured into one
of the tubes.  The usual comparison color  is
made up and transferred  to  the other tube.
The darker liquid is poured into the vessel in
which it was originally prepared and then poured
slowly back into the tube until the colors are equalized.
Fig. 6.
fcM\
 
3°
ANALYTICAL OPERATIONS.
  This apparatus permits the use of amber glass as a stand-
ard color in place of the  comparison liquid.   Very rapid
and sufficiently accurate  determinations  can be made by
this means.  The amber glass is standardized as follows:—
  One of the tubes is nearly filled with clear water, and the
glass placed across the top, the mirror being so adjusted
that the light is thrown directly up the tube.  The equiva-
lent of  the color so produced  is carefully determined by
nesslerizing, in the adjoining tube, a known amount of am-
monium chloride.  The glass is used as a comparison color
by placing it, as before, on the top of one  of the tubes filled
with clear water, and pouring into the other tube the dis-
tillate mixed with Nessler's  reagent  until the colors  are
equalized.
  For example: If the glass is equal  to 1.5 c. c. standard
diluted ammonium chloride solution, and  in a given experi-
ment, the tube must be filled to 40  c. c. with the  liquid
to be determined (50 c. c. of distillate and 2 c. c. of Ness-
ler) then
  40 : 52 : : 1.5 :  1.95.   1.95 is the number  of c.c. of
ammonium chloride solution to which the 50 c. c. of distil-
late are equal.

             TOTAL ORGANIC  NITROGEN.
  Several processes for the  determination of the organic
nitrogen in water, based on those in use in ordinary organic
analysis, have been devised.   That of Frankland and Arm-
strong requires complex and extensive apparatus and spe-
cial skill, has been  shown also  to be liable to inaccura-
cies, and has not come into extended use.
  The ease and certainty with which the nitrogen of most
organic bodies may be converted into ammonium sulphate 
SANITARY  EXAMINATIONS.
31
by boiling with sulphuric acid, offers a means of determina-
tion free from the objections  of former methods.   The
method introduced by Kjeldahl for general organic analy-
sis, was first successfully applied to water analysis by Drown
and Martin {Technology Quarterly, 11, 3).
  In their  original process 500 c. c. was concentrated  to
about 300 c. c, and the distillate nesslerized for determin-
ing the nitrogen existing as ammonium compounds.   The
organic nitrogen is then determined in the residual water.
Owing to the fact that in many waters the organic matter
is   decomposed by boiling, there is liability  to  under-
estimation  of the nitrogen.  We prefer, therefore, to de-
termine at  once the  total  unoxidized nitrogen, and  esti-
mate,  without  distillation, on  a separate  portion of the
sample, the nitrogen that exists in ammonium compounds.
Our procedure is as follows :—
Reagents  Required:—
   Concentrated Sulphuric Acid.—This should be as free as
possible  from nitrogen.  It can be  obtained  containing
only 0.015 nigra, in 10 c. c.
  Sodium Hydroxide Solution.—The white granulated caus-
tic  soda sold  for household use  will  answer;   350 grams
are dissolved in water and made up to 1000 c. c.
  Sodium Carbonate and Hydroxide Solution.—25 grams of
each are dissolved  in 250 c. c.  of distilled water, and the
solution boiled down to 200 c. c, to free it from ammonium.
Analytical Process:—
  Determination of Nitrogen Existing as Ammonium.—200
c. c. of the water are placed in  a stoppered bottle, 2  c.  c.
each of  the solutions of sodium carbonate  and  sodium
hydroxide added, the stopper inserted, the solutions mixed
and allowed to stand for an hour  or two.  A filter is pre- 
32
ANALYTICAL OPERATIONS.
pared by inserting a rather large plug of absorbent cotton
in a funnel.  This should be washed with  ammonium-free
water  until  the  filtrate gives no  color   with  Nessler's
reagent.   The  clear  portion  of the sample is drawn  off
with a pipette and run through the filter, the first portions
being rejected,  since it is diluted  by the water retained in
the cotton.  The filtration is rapid,  and when ioo c. c. of
the liquid  have passed through it is nesslerized.  If but
little  ammonium is  present, a narrow tube about 60 centi-
meters long should be used for observing the color.
   Estimation of the Total Organic and Ammoniacal Nitro-
gen.—500 c. c.  of the water are placed in a round-bottomed
Bohemian glass flask, 10 c. c. of concentrated sulphuric acid
added, and a piece of pumice-stone is heated to bright red-
ness and dropped in while hot.  The liquid is boiled until
the acid is colorless  or very  pale,  the boiling  being
continued for nearly an hour  from this point.  The flask
is then removed from the flame, allowed to cool, and about
250 c. c. of ammonium-free water added.   50 c.  c. of the
sodium hydroxide solution should be placed  in the distil-
ling apparatus, Fig. 3, about 250 c.c. of water added, a piece
of red-hot pumice-stone dropped in and the liquid distilled
until  the distillate is free  from ammonium.  It is best to
distill until the retort  contains  not more than 100 c. c.
The sulphuric  acid  solution  is then poured in slowly, by
means of a funnel the stem of which  touches the side of the
retort, so that the two liquids do not mingle.  The stopper
of the retort is inserted, the liquids mixed  by  gentle agita-
tion,  and distilled.   If much  ammonium  is  present it is
advisable to distill the first  portion into about 10 c. c. of
very dilute (1:  1000) sulphuric acid, a piece of glass tube
being connected to the condensing worm so that  the lower 
SANITARY  EXAMINATIONS.
33
end dips below the surface of the  liquid.   The  distillates
are collected and nesslerized in the usual way.
  A blank experiment should be made to determine the
amount of ammonium in the  sulphuric acid.

               NITROGEN AS NITRATES.
Solutions Required:—
  Phenolsulphonic Acid.—37  c. c. of strong sulphuric acid
are added to 3 c. c. of water and 6 grams of pure phenol.
  Standard Potassium Nitrate.—0.722 gram of  potassium
nitrate, previously heated to  a temperature just  sufficient
to fuse it, are dissolved in water, and the solution made up
to 1000 c. c.   1 c. c. of this solution will contain .0001
grm. of nitrogen.
Analytical Process :—
  A measured volume of the water is evaporated just to dry-
ness in a platinum or porcelain basin. 1 c.  c. of the phenol-
sulphonic acid is added and thoroughly  mixed  with the
residue by means of a glass rod.   1  c. c. of water is added,
three  drops of strong sulphuric  acid, and  the dish gently
warmed on the  water bath.   The liquid  is then  diluted
with about 25 c. c. of water,  ammonium hydroxide added
in excess, and the solution made up to 100 c. c.
  The nitrate converts the phenolsulphonic acid into picric
acid, which  by  the action of the  ammonium hydroxide
forms ammonium picrate ;  this  imparts to the solution a
yellow color, the intensity of which is proportional to the
amount present.
  One c. c. of the standard solution of potassium nitrate is
now similarly evaporated in  a platinum  basin, treated as
above, and made up to 100 c. c.   The color produced  is
compared to that given by the water, and one or  the other 
34              ANALYTICAL  OPERATIONS.
of the solutions is diluted until the tints  of the two agree.
The comparative  volumes of the liquids furnish the neces-
sary data for determining the amount of nitrate, as the fol-
lowing example will show :—
  The solution from  10 c. c. is diluted to iooc. c.; i c. c.
of the standard,  equal to .0001  of N, requires, after treat-
ment,  dilution to 200 c.  c.  to match the color.   Then
200 : 100 : : .0001 : x. x. = .00005 = N.  in 10 c. c. =
.005 N. in 1000 c. c.
  Since ammonium picrate solution keeps well in  the dark,
a good plan is to make a solution, equivalent to, say, ten
milligrams of  nitrogen as  nitrate  per liter, to which  the
color obtained from the water may be directly compared.
  The results obtained by this method are accurate.  Care
should be taken that the same quantities of phenolsulphonic
acid are used for the water and for the comparison liquid.
  With subsoil and other waters probably containing  much
nitrates, 10 c. c. will be sufficient; but with river and spring
waters, 25 c. c. may be used.   When  the  organic matter is
sufficient to color the  residue,  it will  be well  to purify the
water by addition of alum and subsequent filtration, before
evaporating.
  The following is the process for determining nitrogen as
nitrates (and nitrites) recommended  by the Chemical Sec-
tion of the A. A. A.  S.   It depends  upon conversion into
ammonium  by the copper-zinc couple, and subsequent
nesslerizing.
  Take two wide-mouth glass-stoppered bottles, each  hold-
ing 250 c.c. and a piece of sheet zinc as long  and about as
wide as the bottles are deep from the  shoulder down ;  clean
the zinc by dipping in dilute acid  and washing with  water
and make it into a loose coil by rolling it round a piece of 
SANITARY EXAMINATIONS.
35
glass tube.  Immerse it in a 1.4 to 1.8 per cent, solution of
cupric sulphate in ammonia-free water, and  leave it there
until its surface is well covered with a continuous layer  of
the black copper; lift it out carefully, cover it in a beaker
with  successive portions  of ammonia-free water,  lifting
it  out and draining  each  time,  and  at  once  put  it
into one of the  bottles  of acidified water,  prepared  as
follows :—
   Make  500 c. c. of the water to be examined distinctly
acid with oxalic acid added  in fine powder, with constant
stirring,  so that  it shall dissolve readily, and pour half of
the liquid into one of these 250 c. c. bottles, and half into
the other, and leave them, stoppered, in a warm place for
twenty-four hours.   Then nesslerize both  samples, decant-
ing off the portions as wanted, from the precipitated  earthy
oxalates, and using double the  usual  quantity  of Nessler's
solution, since the free oxalic  acid has to  be neutralized
first by  the alkali  of the  reagent.  The  proportion  of
ammonia may often  be  so large  in the  water in  which
the reduction is made, by  the  copper-zinc  couple,  that
only five or ten c. c. can be taken for each test, and made
up to 50 c. c. by  the addition of ammonia-free water.  The
difference between the results with  the  two  portions  of
water, gives the amount of nitrogen due to the oxidized
nitrogen compounds in the water examined.

               NITROGEN AS NITRITES.
   The following is Ilosvay's modification of Griess's  test.
It  has the advantage  over the  original method,  that the
color is developed more rapidly, and the solutions are not
so  liable  to change. 
36
ANALYTICAL OPERATIONS.
Solutions Required :—
  Para-amidobenzenesulphonic Acid {Sulphanilic Acid).—
Dissolve 0.5 gram in 150 c. c. of diluted acetic acid, sp.
gr.  1.04.
  a-amido-naphthalene Acetate.—Boil 0.1  gram  of solid
a-amido-naphthalene (naphthylamine) in  20 c. c. of water,
filter  the  solution through  a plug  of washed absorbent
cotton,  and mix the filtrate  with  180 c. c. of diluted acetic
acid.  All water  used must be free from nitrites, and all
vessels  must  be rinsed  out with such water  before  tests
are applied, since appreciable quantities of nitrites  may be
taken up from the air.
  Standard  Sodium  Nitrite.—0.275  gram  pure silver
nitrite are dissolved in pure water, and a  dilute solution of
pure sodium  chloride added until the precipitate ceases to
form.   It is then diluted with pure water to 250 c. c, and
allowed to stand until clear.  For use 10  c. c.  of this solu-
tion are diluted to 100 c. c.   It is to be kept  in the dark.
  One c.  c. of the dilute  solution is equivalent to .00001
gram nitrogen.
  The silver  nitrite is prepared thus : A  hot concentrated
solution of silver nitrate is added  to  a concentrated solu-
tion of  the purest sodium  or potassium  nitrite available,
filtered  while hot and allowed to  cool.  The silver  nitrite
will separate  in fine needle-like  crystals, which are freed
from the mother  liquor by filtration  by the aid of a filter
pump.  The  crystals are dissolved in the smallest possible
quantity of hot water, allowed to cool and again separated
by means  of the pump.   They are then  thoroughly dried
in  the  water-bath, and preserved in a  tightly-stoppered
bottle away from the light.   The purity  may be tested by 
                SANITARY EXAMINATIONS.             37

heating a weighed quantity to redness  in a tared porcelain
crucible and noting the weight of the metallic silver.   154
parts of AgN02 leave a residue of 108 parts Ag.
Analytical Process : —
  25 c. c. of the water are placed in one of the color-com-
parison cylinders.  By means of a pipette, 2 c. c. each of
the solutions of sulphanilic  acid  and amido-naphthalene
acetate are dropped into the water.  It is convenient to
have a pipette for each solution, and to use it for no other
purpose.
  One c. c. of  the  standard  nitrite  solution is placed in
another clean cylinder, made up with nitrite-free  water to
25 c. c. and treated with the reagents as above.
  In the presence of nitrites  a pink color is produced.  At
the end of five minutes the  two  solutions are compared,
the colors equalized by diluting the darker, and the calcu-
lation  made as  explained under the estimation of nitrates.
  The reactions consist in the conversion of the  sulphan-
ilic acid into  diazo-benzene  sulphonic anhydride,  by the
nitrite present; this compound is  then in  turn converted
by  the amido-naphthalene into azo-a-amido-naphthaiene-
parazobenzene  sulphonic acid.  The last-named body gives
the color to the liquid.

             OXYGEN-CONSUMING POWER,
  All organic materials being more or  less  easily oxidized,
several methods have been suggested for determining the
oxygen-consuming  powers  of waters  by  treatment  with
active  oxidizing agents.   These  methods are,  however,
limited in value.  The  organic  matters  in  water differ
much in character  and condition, and their oxidability is
subject to much variation, according  to the circumstances 
38              ANALYTICAL OPERATIONS.

under  which the test is made.   Nevertheless, as a high
oxygen-consuming power certainly indicates departure from
purity, some additional evidence may be  obtained.  Potas-
sium  permanganate  is  especially  suitable.  The test  is
usually made by introducing a known  amount of the per-
manganate into  the water, which has been rendered acid,
and measuring after a definite period the  proportion which
has been decomposed.
  It must  not  be  overlooked that if a water  contains
nitrites, ferrous  compounds, or sulphur  compounds other
than sulphates, the proportion of oxygen  consumed will be
greater than that required for the organic matter.  It has
been  proposed,  in  order to  remove  the nitrites  before
applying the permanganate,  to take 500 c. c. of the water,
add 10 c. c.  of  the dilute sulphuric acid, boil for twenty
minutes,  allow to cool, and then treat with permanganate.
Since, however,  the amount of nitrites, if appreciable, can
be directly determined, it  is  more  satisfactory  to deduct
from the oxygen consumed  the amount  required to con-
vert the  nitrites present into  nitrates, and the remainder
will be that required for the other oxidizable  ingredients.
14 parts of nitrogen existing as nitrite require 16 parts of
oxygen for conversion  into nitrate.  Similarly, 112 parts
of iron in a ferrous compound  will  require 16 parts  of
oxygen for conversion to the ferric  condition.
  Of the following  methods the first is due in the main to
Dr. Tidy, has been  improved  by Dr. Dupre, and is ap-
proved by the Society of Public Analysts of Great Britain :—
Solutions Required:—
  Standard Permanganate.—.395 gram pure potassium per-
manganate are dissolved in distilled water, and the solution
made up  to 1000 c. c.  1 c. c. is equal to. 0001 gram oxygen. 
SANITARY EXAMINATIONS.
39
  Diluted Sulphuric Acid.—Add 50 c. c. of pure sulphuric
acid to 100 c. c. of  water, and then add solution of potas-
sium  permanganate  until a  faint pink color is  obtained,
which is permanent when  the  liquid  is  heated  to  8o°
Fahrenheit for four hours.
  Potassium Iodide.—10 grams  of the pure salt recrystal-
lized  from alcohol are  dissolved in  100 c. c. of distilled
water.
  Sodium  Thiosulphaie.—1 gram of the pure crystallized
salt dissolved in 2000 c.  c. of distilled water.
  Starch Indicator.—1  gram of clean starch is   mixed
smoothly with cold  water  into  a thin  paste, then  poured
gradually into about 200 c. c. of boiling .water, the  boiling
continued for one minute, the liquid allowed to settle,  and
the clear portion used.   It is best freshly prepared.
Analytical Process: —
  Two determinations are made, one,  of the oxygen con-
sumed in fifteen minutes, which  is considered to  represent
the nitrites, sulphides or ferrous  compounds,  and the other
of the oxygen consumed by four hours' action.   Both de-
terminations are made at a temperature of 8o° F.   Three
glass-stoppered  bottles, of about 350 c. c.  capacity,  are
rinsed with strong sulphuric acid, and then  with water.   In
one is placed 250 c.  c. of pure distilled  water as a  control
experiment, and in each of the others 250 c. c. of the water
to be  tested.   The bottles are stoppered, and brought to a
temperature of 80 F.; 10 c. c. of the dilute sulphuric acid
and 10 c. c. of  the standard  permanganate  are added to
each  and the  stoppers  again replaced.   At the  end of
fifteen minutes one sample  of water is  removed  from  the
bath,  and two or three drops of the potassium iodide solu-
tion added  to  remove  the pink color.  After  thorough 
40
ANALYTICAL OPERATIONS.
admixture, the thiosulphate solution is run in from a burette
until the yellow  color is nearly  destroyed, a few drops of
the starch solution added, and the addition of the  thiosul-
phate continued  until the blue color is quite discharged.
If the addition  of the  thiosulphate solution   has  been
properly conducted, one drop  of the permanganate solu-
tion will restore  the blue color.
  The other bottles are maintained at 8o° F. for four hours.
Should the pink  color disappear  rapidly in the bottle con-
taining the water under examination, 10 c. c. of the per-
manganate solution must be added to each bottle, in order
to maintain a distict pink color.   At the end  of four hours
each bottle is removed  from the bath, two or three drops
of potassium  iodide added,  and the titration  with thiosul-
phate  solution conducted  as just described.   The  calcu-
lation is most conveniently made as follows: —
  0 = number of c. c.  required for the control experiment.
  b = number of c. c. required for the water under exami-
    nation.
  c = available O in permanganate (.001 for 10 c. c.)
  x = oxygen consumed by water.
  Then,  a  : a-b : :  c : x.

  The following  method is recommended by the Chemical
Section of the American Association  for the Advancement
of Science:—
  " Prepare a solution of potassium permanganate contain-
ing o. 1 mgm. of available oxygen to  one c. c. and a solu-
tion of oxalic acid of such  strength as to decompose the
permanganate solution,  volume  for volume,  the strength
being re-determined from time to time.   The water used
for making these  solutions should be purified, by distillation
from alkaline permanganate. 
SANITARY  EXAMINATIONS.              41
     "To 200 c. c. of water to  be examined, in a 400 c. c.
  flask, add 10 c. c. of dilute sulphuric acid (1 : 3) and such
  measured quantity of the permanganate as will give  a per-
  sistent color; boil ten  minutes, add, if necessary, more
  permanganate in  measured quantities so as to maintain the
  red color; remove the flask from the lamp, add 10 c. c. of
  oxalic acid  solution to  destroy  the  color,  or  more if
  required by the excess of permanganate, and then add per-
  manganate, drop by drop, till a  faint pink tint  appears.
  From the total quantity of permanganate  used  deduct the
  equivalent of the oxalic acid used, and from the remainder
  calculate  the milligrams of oxygen consumed by the oxid-
  izable organic matter in  the water."
     The oxygen-consuming power may also be indirectly
  estimated by the  action of the organic matter  upon silver
  compounds.   H. Fleck's method  {Fresenius' Quantitative
  Analysis, English  edition, vol. 11, p. f2f~)  depends upon
•  the reduction produced  by boiling the water with alkaline
  solution of silver thiosulphate and estimation of the unre-
  duced silver.  A. R. Leeds (lond., Edin. and Dub. Phil.
  Mag., July, f88j) gives a method  by treating the  water
  with  decinormal  silver  nitrate,  exposing  to  light until it
  settles perfectly clear, and estimating the reduced silver in
  the deposit.
     These methods are open to practically the same objections
  as in  the use of  permanganate, and do not seem to possess
  any  decided  advantage.   Qualitative  results  of  some
  interest  may  occasionally be  obtained  by the  following
  method :  2 c. c. of a one per cent, solution of silver nitrate,
  rendered  decidedly alkaline by ammonium hydroxide, are
  added to 100 c. c. of the water in a stoppered bottle,  which
  is then placed in  full sunlight  for two hours.  Waters con-
         D 
42              ANALYTICAL  OPERATIONS.
taining but little organic matter will not show at the end of
this period any appreciable tint.   The following results will
show the character of the test:—

    Schuylkill water.............no color.
        "      "  with 0.02 c. c. urine, .  .  . red-brown.
               "  with o.oi c. c. urine, .  .  . deep brown.
              "  with 0.25 gram raw sugar, . no color.
    Well water, not perfectly pure, but
               not unfit to drink,.....faint black.
      "    "  markedly contaminated,  .  .  . black ppt. almost
                                          immediately.
    Water from a small stream, quite pure ... no color.

                      PHOSPHATES.
Solutions Required: —
  Ammonium Molybdate.—Ten  grams of molybdic anhy-
dride are dissolved in 41.7 c. c. of ammonium hydroxide, sp.
gr.  0.96, and the solution is poured slowly, and with con- .
stant  stirring,  into  125  c. c. of nitric acid, sp. gr. 1.20,
and allowed to stand in a warm place for several days, until
clear.
Analytical Process:—
  500 c. c. of the water are slightly acidified with nitric acid,
and evaporated to about 50 c. c.  A kw  drops of dilute
solution of ferric chloride are added and  then ammonium
hydroxide in slight excess.   The  precipitate, which con-
tains all the phosphate, is filtered off and  dissolved on the
filter  by the  smallest  possible  quantity  of hot  dilute
nitric acid.  The filtrate  and washings should not exceed
5 c. c;  if more, they must be evaporated to this bulk.   The
liquid  is  heated  nearly  to  boiling, 2 c. c. of ammonium
molybdate solution added, and  the liquid kept moderately 
SANITARY  EXAMINATIONS.              43
warm for half an  hour.   If  the quantity of precipitate is
appreciable, it is collected on a small weighed filter, washed
with distilled water, dried at ioo°  F. and weighed.  The
weight  of the precipitate multiplied by 0.05 gives the
amount of P04.   If the quantity is not sufficient to collect
in this  mariner, it is  usually reported, according  to cir-
cumstances, as  "traces," " heavy traces," or "very heavy
traces."
                      SUGAR-TEST.
  This  method was proposed by Heisch for the detection
of a fungus supposed  to be  peculiar to sewage.  It con-
sists  in adding  to  the  water  a  small  quantity of sugar, in
which the fungus grows with great rapidity.   The  test is
applied as follows  :—
  A  stoppered  bottle of about 100 c. c.  capacity is  rinsed
thoroughly with the water to  be tested, filled with the clear
water, about half a gram of pure crystallized sugar  added
and the stopper inserted.  The bottle is placed in a strong
light, and kept at a temperature of about 8o° F.   At the
end  of  several hours it is examined for the fungus, which,
in a good side light, with the bottle  against a dark back-
ground, is generally easily visible as  a distinct turbidity.
If examined under a power  of 250 diameters, it is found
to consist of small spherical  cells, having in most cases a
bright nucleus.  After the lapse of some days these gradually
group themselves  together something like grapes;  they
next spread out into strings,  with a surrounding wall con-
necting the cells together; the original cells then seem to
break  and  leave  apparently tubular threads   joined  by
branches.  In the  more marked cases  the development of
the  fungus is  accompanied  by a distinct odor of butyric
acid.   Hydrogen sulphide and other  gases are  also some- 
44             ANALYTICAL OPERATIONS.
 times formed.  These odors do not generally appear until
 after twenty-four hours or longer.   Heisch concluded that
 the cells thus developed were distinct  evidence of sewage
 contamination, but such microorganisms are found in all
 waters that have been  exposed even  momentarily to air,
 and Frankland has shown that their  development  under
 these conditions is due to the presence of phosphates.  He
 found  that the addition even of minute traces of a phos-
 phate, either as sodium phosphate, white of egg, or animal
 charcoal, at once determined  the growth  in  saccharine
 liquids  which,  before, exhibited  no tendency to develop
 them.
                 DISSOLVED OXYGEN.
  The method here given, a modification of Mohr's,  was
 proposed by Blarez.  Our experiments indicate that it  is
 rapid and satisfactory.
 Solutions Required:—
  Sodium Hydroxide.—40 grams of pure sodium hydroxide
 to the liter.
  Ferrous-Ammonium  Sulphate.—40  grams   dissolved  in
about a liter of water, and acidified with  a  few drops of
concentrated sulphuric  acid.
  Decinormal Potassium Permanganate.—3.156 grams dis-
solved  in a  liter of distilled water.  The accuracy of this
solution should be determined by titration with a known
weight of ferrous-ammonium sulphate.  One c. c. should
be  equivalent to  .0392 grm.  ferrous-ammonium sulphate
(.0008 gram of oxygen).
  The apparatus employed (shown in Fig.  7) is a globular
separator, of about 250 c. c. capacity.   Above the bulb  is
a caoutchouc stopper  carrying a  cylindrical funnel,  of
about  12 c.c.  capacity, terminating  in a  tube, y$  inch 
                SANITARY EXAMINATIONS.             45

calibre, sharply contracted at the  outlet to a capillary
opening.   The  tube  should  project about  ^ inch below
the stopper.  The exact capacity of the  appa-
ratus is measured as follows :  The bulb is com-
pletely filled  with   water  and  the  stopper
inserted;   the   level  of  the  water will rise
slightly in the funnel  tube,  and  should  be
brought down  to its outlet by drawing a little
off at the stopcock,  after which the water is
run into a graduated measure  and its volume
noted.
Analytical Process :—
   35  c.c.  of mercury and 10 c. c. of sodium
hydroxide solution  are  put into  the  bulb,
and  then  sufficient of the water  to be tested
to fill  it.   The  funnel stopper is  inserted  and  the water
which rises  into  the funnel brought  into the bulb  by
cautiously  running out  at  the stopcock,  mercury,  the
volume of which should be  noted.   The  exact  volume
of water used is thus known.   Five c. c. of the  ferrous-
ammonium sulphate  solution are poured into the  funnel,
brought into the bulb  by running out mercury, and the
liquid thoroughly mixed'by giving the apparatus a gyratory
movement.   After standing five or six minutes the  oxygen
will  be completely absorbed; 10 c. c.  of the diluted  sul-
phuric acid  are now added  by the same  method.  On
agitating the bulb the contents become  clear. The watery
liquid is then transferred to a beaker and titrated with deci-
normal  permanganate.  A volume  of water equal  to that
used in the test  is poured into another beaker, 10  c.  c. each
of the sodium hydroxide and diluted sulphuric acid added,
and then  5 c.  c. of ferrous-ammonium  sulphate solution.
 
46
ANALYTICAL OPERATIONS.
The resulting liquid is  titrated with permanganate.  The
weight of oxygen corresponding  to the difference between
the two titrations gives the weight of dissolved oxygen in
the liquid employed.   From this  should be subtracted as
correction the amount of oxygen  dissolved by a volume of
water equal to that of the sodium hydroxide solution used.
This is found by reference to the table in  the appendix.
The amount of dissolved oxygen in the sulphuric acid  has
no appreciable effect.
  Nitrates do  not  appear to impair the accuracy of this
method, and  the interfering action of  nitrites and other
reducing compounds is avoided by the control experiment
as detailed.
  It is perhaps  hardly necessary  to add that the  exact
temperature  of  the water  is to  be noted at  the time of
collection of the sample.
  In transferring to the bulb, the  water should be agitated
as little as possible in  contact with  the air, in  order to
avoid the absorption of  oxygen.   A siphon should  be
used for this purpose, the lower end being allowed to reach
to the bottom of the bulb.
  The following modification is suggested as being  especi-
ally suitable for poorly oxygenated 'waters :  An accurately
stoppered bottle, the exact capacity of  which is  known
(about 500 c. c. is a convenient  size),  is completely filled
at the source with the water to be  examined, and the stop-
per inserted so as to drive out  all  air.   The stopper is  re-
moved in the  laboratory,  50 c. c. of the water  drawn off
with a pipette, and  the  water  covered  immediately with a
layer of gasoline previously purified by shaking up  several
times with  a solution  of  potassium  permanganate  and
diluted sulphuric acid, and washed several times with water. 
SANITARY  EXAMINATIONS.
47
The sodium  hydroxide, ferrous-ammonium  sulphate and
sulphuric acid are introduced into the water by means of
burettes to which long glass delivery tubes are  attached.
The titration with potassium permanganate  is conducted
in the same way.   The  liquid is mixed from  time to time,
as the solutions are added, by means of a glass rod.   In
this way the air may be completely excluded throughout
the entire operation.  The amount of water titrated is, of
course, equal to the whole  capacity of the bottle, less the
50 c. c. removed  by the pipette.
   The control experiment on an equal volume of the water,
and the correction for  the oxygen added with the sodium
hydroxide  solution, are made as detailed  above.
   Dupre has  employed the determination of free oxygen
for the estimation of the proportion of oxygen-consuming
microbes.  The principle of the method is that pure water,
if kept in a closed bottle, will neither gain nor lose oxygen
in any length of time, but if  organisms capable of causing
absorption of oxygen are  present, the quantity will de-
crease.
   The experiment is carried  out by  placing a  sample, of
the water  in  a clean bottle, and  vigorously  shaking  it to
saturate with  air.   A clean 250 c. c.  bottle is completely
filled with  the water, tightly stoppered, and maintained at
a temperature of  68° F. for ten days ;  the free oxygen re-
maining is then determined.

                  POISONOUS METALS.
   In this class are included barium, chromium, zinc, arsenic,
copper and lead; jna?iganese and iron also, though not usually
classed in  this  group, are  objectionable  when  present  in
notable amounts. 
48
ANALYTICAL OPERATIONS.
  Barium is rarely present, and only in water containing
no sulphates.   It can be detected and estimated by slightly
acidifying  the water with hydrochloric  acid, filtering if
necessary, and adding solution of calcium sulphate.   The
precipitated barium sulphate is collected  and weighed in
the usual way.
  Chromium is rarely present, but may be looked for in
the waste  waters of dye works and similar sources.   To
detect it, a considerable volume of the water is evaporated
to dryness with addition  of a small amount of potassium
chlorate and nitrate, transferred to a porcelain crucible and
brought to quiet  fusion;  any  chromium  present will be
found in the residue in the form  of chromate.  The fused
mass, after cooling, is boiled with  a  little  water, filtered,
the  filtrate rendered slightly  acid  with  hydrochloric
acid, and a solution of hydrogen dioxide  added.  In  the
presence  of chromium a transient  blue color will appear;
by adding a little ether, and shaking the mixture the color
will pass into the ether, and on standing will  form a blue
layer on the surface of the water.
  Zinc is best detected  by the  test  described by  Allen.
The water is rendered slightly ammoniacal, heated to boil-
ing, filtered, and the clear  liquid treated with  a few drops
of potassium  ferrocyanide; in  the presence  even of  the
merest trace of zinc a white precipitate will be produced.
  Arsenic is most readily detected by Reinsch's test. One
liter of the water  is rendered  slightly alkaline by sodium
carbonate, free from arsenic, and evaporated nearly to dry-
ness in a porcelain basin.   2 or 3 c. c.  of water strongly
acidulated  with hydrochloric acid are placed in a small
test-tube,  about ^ square centimeter  of bright copper
foil  is added, and the  liquid  boiled  gently for  a  few 
SANITARY EXAMINATIONS.
49
moments.   If the copper remains bright, showing that the
reagents contain no  arsenic, the water-residue  is acidified
with hydrochloric acid, added to the contents of the test-
tube, and the liquid again boiled for  several minutes.  If
arsenic be present, a steel-gray stain  will appear on the
copper.   The slip is removed, washed with distilled water,
thoroughly dried  by pressure  between filter paper, inserted
into a narrow glass tube closed at one end, which has been
previously dried by heating nearly to redness.   The tube is
gently heated at the point at which the copper rests; the
arsenical  deposit will sublime and  collect on  the cooler
portion of the tube, in crystals which the microscope  shows
to be octahedral.
  Since small amounts  of  arsenic frequently occur  in
reagents and in glass  vessels, care  must be taken to  avoid
such  sources of  error.  Sodium  carbonate  solution may
contain arsenic dissolved from the glass bottle  in which it
is kept.   It is best, therefore, to use the solid carbonate for
rendering the water alkaline,  and to determine  its freedom
from arsenic before use.
  Iron is detected by the addition of a drop of ammonium
sulphide to the water in  a tall glass cylinder.   Ferrous sul-
phide is formed, having a greenish-black color, instantly
discharged by acidifying the water with dilute hydrochloric
acid.  A  still better test is the  production of a blood-red
color, with potassium sulphocyanate, due to the formation
of ferric sulphocyanate.  The water should  be first boiled
with a few drops  of nitric  acid, to convert the  iron to the
ferric condition, cooled, and  a drop or two of the solution
of potassium sulphocyanate added.   The test is very deli-
cate.   Either of the  above tests may be made quantitative 
5°
ANALYTICAL OPERATIONS.
by matching the color produced in ioo c.  c. of the water
with  that obtained from  a known weight of  iron.  The
method with potassium sulphocyanate is preferable, as it is
more delicate and there are fewer interfering  conditions.
The following is the  method as  elaborated by Thompson
and described in Sutton's "Volumetric Analysis: "—
Solutions  Required:—
  Standard Ferric Sulphate.—0.7 gram ferrous ammonium
sulphate are dissolved in  water  acidified  with sulphuric
acid, and potassium permanganate solution  added until the
solution turns a very  faint pink color.  The  solution  is
diluted  to a liter.  1 c. c. contains 0.1 milligram iron.
  Diluted Nitric Acid.—30 c. c. concentrated nitric acid
diluted  with water to about 100 c. c.
  Potassium Sulphocyanate.—5 grams of the salt dissolved
in about 100 c. c. water.
Analytical Process:—
  About 100 c. c. of the water are evaporated to small bulk,
acidified with hydrochloric acid,  and just sufficient  dilute
potassium permanganate solution  added to  convert all the
iron to  the  ferric  condition.  The  liquid  is  evaporated
nearly to dryness to  drive off excess of acid, then diluted
to its original volume, 100  c.  c.   In two   tall  glasses
marked  at  100 c. c, 5 c. c. of the nitric acid and fifteen
c. c. of  the sulphocyanate solution are placed.   To one of
these a  measured volume of the treated water is added and
both vessels filled up to the mark with distilled water.   If
iron is present, a blood-red color will be produced.   Stand-
ard iron solution is added to the second vessel until the color
agrees.   The amount  of water which is added to the first
glass will depend upon the quantity of iron it contains ; 
SANITARY EXAMINATIONS.
51
not more should be used than will require two or three c. c.
of the standard to match it, otherwise the color will be too
deep for comparison.
  Manganese.—The  following method is  described  by
Wanklyn in his treatise on water analysis.  About one liter
of the water is evaporated to small bulk, nearly neutralized
by hydrochloric acid and  treated with a few drops  of a
solution of hydrogen dioxide.   The formation of  a brown
precipitate indicates the presence of manganese.   The test
is very delicate.   The precipitate may be collected  on
a filter,  the filter ashed, and the residue fused with a mix-
ture of sodium carbonate  and potassium nitrate.  Green
potassium manganate will be produced, which, when boiled
with  water, will give  a bright  red solution of potassium
permanganate.  The quantitative determination   is  given
elsewhere.
   Lead may  be readily detected by adding to the water in
a tall glass cylinder a drop of ammonium sulphide ; brown-
ish black lead sulphide is formed, which does not dissolve
either by acidulating the  water  with  dilute hydrochloric
acid (distinction from  iron) nor  by the  addition  of about
one c. c.  of a strong  solution of potassium cyanide (dis-
tinction  from copper).   S. Harvey (Analyst, April, 1890)
gives the  following method for detecting lead in water:
250 c. c. are placed in  a  conical  precipitating jar, about
o. 1  gram  of  crystallized potassium dichromate  is added
and dissolved  by agitation.   The same volume of  lead-free
water is treated in the same manner, and the two  solutions
placed side by side.  Water containing 0.3 parts  per mil-
lion,  will show a turbidity in fifteen minutes, which will be
rendered  more  distinct by  contrast with the clear  water
alongside.   By allowing the jar  to stand for about twelve 
52
ANALYTICAL OPERATIONS.
hours undisturbed, the precipitate will  settle and  will be-
come still more distinct.   No other metal likely to be pres-
ent in water will give a similar reaction.
  In  the absence of copper, the  amount  of lead present
may be determined as follows :  A solution is prepared con-
taining 1.6 grams of lead nitrate to the liter; one c. c. of
this contains one milligram lead,   ioo c. c. of the water to
be tested are placed in a  tall glass vessel, made acid by the
addition  of a  few drops of acetic acid and  five  c. c. of
hydrogen sulphide added.  In a similar vessel ioo  c. c. of
distilled water are placed, together with the same quantities
of acetic acid and hydrogen sulphide, and sufficient of the
standard  lead solution to match  the tint in the first cylinder.
The amount of lead in the water under examination is thus
known.
  Copper is  detected in the  same  manner as lead by
acidifying the water with acetic acid and adding hydrogen
sulphide  water.   The precipitate is distinguished from lead
sulphide by the fact that  the color is discharged on the
addition  of  about  one c. c. of  a strong solution  of pure
potassium cyanide.  It  may be further  confirmed by the
addition  to another portion of  the  water of  a solution of
potassium ferrocyanide.   In the presence of even a very
small amount of copper, a mahogany red color is produced.
  In the  absence of lead, copper  is estimated in the same
way as that  metal, using, however, a  standard solution of
copper for the  comparison liquid.  This is  made by dis-
solving 3.929 grams of crystallized copper sulphate in one
liter of  water.   One c.  c.  of  the solution  contains one
milligram copper.
  If both lead and copper are present, a large quantity of
the  water should  be evaporated to  small bulk, and the 
TECHNICAL EXAMINATIONS.
53
metals separated and estimated by any one of the ordinary
laboratory methods.
  The following table, prepared by A. J. Cooper, indicates
the comparative delicacy of some of the ordinary tests for
the detection of poisonous metals in water :—
Metal.	Reagent.	Depth of Liquid, 3^ inches.	Depth of Liquid, 14^ inches. Cylinder enclosed in opaque tube.
Copper . . . Zinc . . . . Arsenic . . Lead . . . .	K4Cy6Fe NH4HO H2S NH4HS H2S K2Cr04 H2S	1 part of metal detected in 4,000,000 of water. 1,000,000 " 4,150,000 " 2,500,000 " 3,600,000 " 4,000,000 " 100,000,000 "	1 part of metal detected in 11,750,000 of water. 1,950,000 " 15,660,000 " 7,520,000 " 5,875,000 " 196,000,000 "
            TECHNICAL EXAMINATIONS.

         GENERAL QUANTITATIVE ANALYSIS.
   Silica, Iron,  Aluminum,  Manganese,  Calcium,
and Magnesium.—One liter of the water acidified with
hydrochloric acid is evaporated  to complete  dryness, best
in a platinum dish, the residue  treated  with  hydrochloric
acid and water, and the separated silica filtered, washed,
dried, ignited in a platinum crucible and weighed.
   To the filtrate, previously boiled  with a few drops  of
strong nitric acid, slight excess of ammonium hydroxide is
added, the liquid  boiled  several minutes,  the  precipitate
collected, washed thoroughly with  boiling water, dried,
ignited and weighed.   It consists of Fe203 and A1.203.  It
also contains all  the  phosphates and some  manganese if
much is present in the water. In such cases the precipitate 
54
ANALYTICAL  OPERATIONS.
before drying is re-dissolved in  hydrochloric  acid and
neutralized with  a dilute solution of ammonium carbonate
until the water almost becomes  turbid.  It is then boiled
and  the precipitate, now free  from manganese,  washed,
dried, ignited and weighed.   The iron may be determined
by dissolving the precipitate  in strong hydrochloric acid
and employing the colorimetric method described on page

  If no  manganese or only  traces are present, the filtrate
from the iron is mixed with sufficient ammonium chloride
to prevent the precipitation of the magnesium, ammonium
hydroxide,  and then ammonium oxalate added in quantity
sufficient to precipitate the calcium  and to convert  all the
magnesium into oxalate, and thus hold it in solution. The
precipitate  contains all  the calcium and some of the mag-
nesium.  If the magnesium is present only in relatively small
quantity the  amount carried down  may be  disregarded ;
otherwise a second precipitation  should be made as follows:
The solution  is allowed  to stand until the precipitate has
subsided; this will require some hours.   The  supernatant
liquid is  poured  off through a filter, the precipitate  washed
by decantation, then dissolved in hydrochloric acid, water
added, then ammonium  hydroxide and a small quantity
of ammonium oxalate.  After  the  calcium  oxalate  has
thoroughly  subsided it is filtered off, washed and dried.   If
quite small  in amount it is placed with the filter in a weighed
platinum crucible,  ignited over the  Bunsen burner for a
short  time, and  then  over the blast lamp for  from five  to
fifteen minutes.   The calcium is thus obtained in the form
of oxide, which  is allowed  to cool in the desiccator and
weighed.   The weight thus obtained multiplied by 0.7142
gives the weight of calcium.   When the amount of precipi- 
TECHNICAL EXAMINATIONS.
55
tate is large, it is better to remove  it from the filter, and
heat it just short of redness until it assumes a grayish tint.
It then consists of  calcium carbonate.   To this is added
the ash of the filter.   The weight of the calcium carbonate
multiplied  by 0.4 gives the weight of calcium.
   The filtrates are  mixed, slightly acidified with hydro-
chloric acid,  concentrated and cooled, ammonium hydrox-
ide and sodium phosphate added  in excess, stirred briskly
and allowed  to stand  in the  cold for about twelve hours.
The  precipitated  ammonium  magnesium  phosphate  is
brought upon a filter, that adhering to the sides of the ves-
sel being dislodged by rubbing with a glass rod tipped with
a piece of clean  rubber tubing.   It is washed with a solu-
tion made by mixing one part of the ammonium hydroxide
of 0.96 sp. gr. with three parts of water.  The precipitate is
dried, transferred  to a  platinum  crucible,  the filter ashed
separately and added  to it, and the  whole  heated at first
gently and then  to intense redness for several  minutes.
After  cooling, it is  weighed.   It consists of magnesium
pyrophosphate ; the weight multiplied by o. 2162 gives the
weight of magnesium.
   Manganese,  if present in appreciable quantity, is sepa-
rated before  the precipitation of the calcium, as follows:
The filtrate from the iron precipitate is slightly acidulated
with hydrochloric acid, concentrated, and  the manganese
precipitated as sulphide by colorless or slightly yellow solu-
tion of ammonium sulphide.   The flask, which should be
nearly full, is stoppered, allowed  to  rest in a moderately
warm  place until  the  precipitate  has thoroughly settled,
filtered, washed with dilute ammonium sulphide water and
purified by dissolving in a small  quantity of hydrochloric
acid and reprecipitating with ammonium sulphide.  It  is 
56
ANALYTICAL OPERATIONS.
filtered off, washed  as  before, dried, placed in a weighed
porcelain crucible, covered with a little sulphur and ignited
in a current of hydrogen introduced into the crucible by a
tube passing through a hole in the cover.   The pure man-
ganese sulphide  thus  obtained  is allowed to  cool and
weighed.  The weight  multiplied by .63218 gives mangan-
ese.
   Sulphates.—500 c. c. of  the  clear water are slightly
acidulated with  hydrochloric acid, heated  to boiling, and
barium chloride  solution added in moderate excess.   The
precipitate is allowed to subside completely, collected upon
a filter, washed  thoroughly, dried and incinerated.   It is
BaS04; the weight  multiplied by 0.412 gives S04.  If the
proportion of S04 is very low, it will be advisable to  con-
centrate the water to one-fifth or one-tenth  its  bulk before
precipitating.
   Control.   Potassium,  Sodium  and Lithium.—
From 250  to  1000 c. c.  of the water, according to the
amount of solid  matters present, are evaporated to dryness
in a platinum dish, and the residue heated  in an air-bath
to about 3600 F., until  the weight becomes constant.   This
determines  the total solid matter in solution.
   The residue is treated with  a small amount of water and
sufficient dilute sulphuric acid to decompose the salts pres-
ent.  The dish should then be covered  and placed upon the
water-bath  for five  or  ten minutes, after which any liquid
spurted on the cover is washed  into  the  dish, the whole
evaporated to dryness and heated to redness. A few  drops
of ammonium carbonate solution should then be mixed with
the residue, and  the ignition repeated to insure the removal
of the last portions  of  free acid.   In the majority of  cases
the only basic  elements present in considerable quantity 
TECHNICAL EXAMINATIONS.
57
are calcium, magnesium and  sodium.  The sodium may be
determined  indirectly, therefore, by  calculating  from the
amount of Ca and Mg found, the calcium and magne-
sium sulphate in the residue,  and subtracting  this  sum,
together with  the silica, from the total residue.
   If potassium or potassium and lithium, also, are to be
estimated,  the filtrate from  the  precipitation of the S04
may be used, provided that sufficient of the water has been
used for the estimation.  For the determination of potas-
sium and sodium in ordinary well and river waters, not less
than one liter should be employed.  When lithium is to be
determined, it is generally necessary to use at least  two or
three liters.   In any case, as  the alkalies are to be weighed
as chlorides, it is advisable to precipitate the sulphates by
addition of barium chloride.   Unless the sulphates  are to
be estimated  in this  portion, it is unnecessary to remove
the precipitate of barium sulphate so formed.
   The  water  is evaporated to about 200 c. c, thin, pure
milk of lime added in slight excess—generally from  two to
three c. c. will be sufficient—to the hot liquid, and the heat
continued for several minutes.  It is then washed into a 250
c. c. flask, disregarding  the insoluble portion adhering to
the dish,  which, however, should  be thoroughly washed,
and  the washings  added  to  the flask.  After cooling, the
flask is filled up to the mark with distilled water, thoroughly
mixed,  the  precipitate  allowed to  settle, and  the  liquid
filtered  through a  dry filter.   200 c. c.  of the filtrate are
measured  into another 250 c. c. flask, ammonium carbonate
and ammonium oxalate added, filled with water  up to the
mark, mixed, allowed to settle, filtered through a dry filter,
200  c. c.  of the filtrate  measured off and  evaporated to
thorough  dryness  in  a platinum  crucible,  heating very
       E 
58
ANALYTICAL OPERATIONS.
cautiously at the last stages to avoid loss by spurting.  The
low-temperature burner  is suited for this purpose.  The
crucible  is now covered and  cautiously heated to dull
redness,  cooled and  weighed.   The  residue  consists  of
potassium,  lithium  and  sodium  chlorides.    It  contains
sometimes, also, traces of magnesium, which may be  re-
moved by  treating  again with lime and with  ammonium
carbonate and oxalate.   It is frequently of  advantage, in
evaporating these saline solutions, to  add, when  the  solu-
tion becomes concentrated, several c. c. of strong hydro-
chloric acid.  This precipitates the greater portion of the
salts  in  a finely granular condition,  and renders loss  by
spurting less liable to occur.
  If potassium and  sodium chlorides only are present, they
can be readily estimated  by dissolving the weighed residue
in water, determining the total  chlorine by  titration with
silver nitrate and potassium chromate, and applying the fol-
lowing rule : " Multiply  the quantity of chlorine in the
mixture by 2.1035,  deduct from the product the sum of the
chlorides, and multiply the remainder by 3.6358 ; the pro-
duct expresses  the quantity of sodium chloride contained
in the mixed chloride."
  The results by this method  are not accurate  if either
the potassium or the sodium  is present in  relatively  small
amount.   In such cases  the  following procedure may be
resorted to. The weighed chlorides are dissolved  in a small
quantity of water, an excess of a concentrated neutral solu-
tion of platinum chloride added, evaporated  nearly to dry-
ness  at  a low  heat on the water bath, some 80  per  cent.
alcohol  added, allowed to  stand, the  clear liquor decanted
off on a small filter and  the residue washed in this way sev-
eral  times  by fresh small portions of 80 per  cent, alcohol. 
TECHNICAL EXAMINATIONS.
59
The precipitate is then washed on to the filter with alcohol,
washed  again with  80 per cent, alcohol, thoroughly dried
and transferred  as  far as possible to a watch glass.   The
small  portion on the filter is dissolved off and the solution
placed in a weighed platinum dish and evaporated to dry-
ness.   The main portion on the watch glass is then added,
and the whole dried to a constant weight at about 2600 F.,
cooled and weighed.  The weight thus found multiplied by
•3°557 gives the weight of potassium  chloride.   This sub-
tracted  from the combined weight of the chlorides gives
the weight of sodium  chloride.
  Lithium, if present, is best separated before the treatment
with platinum chloride.   The  following method, devised
by  Gooch, gives good results :  To the concentrated solu-
tion of the weighed chlorides,  amyl alcohol is added  and
heat applied, gently at first, to avoid  bumping, until  the
water disappears from the solution and the point of ebulli-
tion becomes constant at a  temperature which is approxi-
mately  that  at  which the alcohol boils (2700  F.),  the
potassium  and  sodium chlorides are deposited and  the
lithium  chloride is dehydrated and  taken  into  solution.
The liquid is then cooled  and  a drop or two of strong
hydrochloric acid added  to reconvert traces of lithium hy-
droxide in the deposit, and the boiling continued until the
alcohol  is again free from water.  If the amount of lithium
chloride be small, it  will be found in the solution and the
potassium chloride and sodium chloride in  the residue,
excepting traces which can be allowed for.  If the lithium
chloride exceed ten or twenty milligrams the liquid may be
decanted, the residue washed with amyl alcohol, dissolved
in a few drops of water and treated as before.  For  wash-
ing, amyl alcohol previously dehydrated by boiling is to be 
6o
ANALYTICAL OPERATIONS.
used, and the  filtrates are to be measured apart  from the
washings.  In filtering,  the Gooch filter with asbestos felt
may be used with advantage, applying gentle pressure by
the aid of the filter  pump.   The crucible and  residue are
ready for weighing after gentle heating over the  low-tem-
perature burner.   The weight of the insoluble chlorides is
to be corrected by adding .00041 for every ten c. c. of amyl
alcohol in the filtrate, exclusive of  the washings, if only
sodium chloride  be  present; .00051 for  every ten c.c. if
only potassium chloride, and  .00092 in  the presence of
both these chlorides.
  The filtrate and washings are evaporated to dryness in a
platinum  crucible heated with sulphuric  acid, the excess
driven off, and the residue ignited to fusion, cooled and
weighed.  From the weight is to be subtracted, for each ten
c. c. of filtrate, .0005, .00059, or -00109, according as only
sodium chloride,  potassium chloride, or both were present
in the  original mixture.
   Hydrogen Sulphide.—The following method is  taken
from Sutton's  " Volumetric Analysis : "—
Reagents Required :—
   Centinormal Iodine.—Dry, commercial  iodine is inti-
mately mixed with one-fourth its weight of pure potassium
iodide and  gently heated between  two  clock-glasses by
resting the lower on a hot plate.   The iodine sublimes in a
perfectly pure  condition.  It is allowed to cool under the
desiccator, 1.265  grams weighed out, together  with 1.8
grams  of pure  potassium iodide, dissolved  in about 50 c. c.
of water and the  solution made up exactly to a liter.  The
liquid  must not be heated, and care should be taken that
no  iodine vapor is lost.   One c. c. is equivalent to .00017
H2S.   The solution is best preserved in stoppered bottles, 
TECHNICAL EXAMINATIONS.
6l
which should be completely filled  and kept  in  the  dark.
It will not even then keep very long, and should be standard-
ized by titration with a weighed  amount  of pure sodium
thiosulphate, which should be powdered previous to weigh-
ing, and pressed between filter paper to absorb  any mois-
ture.   50 c. c. of the iodine solution, when of full strength,
will require 0.124 gram of sodium thiosulphate.
  Starch Indicator.—See page 39.
Analytical Process:—
  10 c. c, or any other necessary  volume  of  the iodine
solution, is measured into a 500 c. c. flask, and the water
to be examined added  until the color disappears.  5 c. c.
of starch liquor are then added and the iodine solution run
in until the blue color  appears;  the  flask is then filled to
the  mark with distilled water.   The  respective  volumes of
iodjne  and starch solution, together with the added water,
deducted from the 500 c.  c. will show the volume of water
actually titrated by iodine.  A correction  should be made
as follows for the excess of iodine required  to produce the
blue color:   5 c.  c. starch solution are made up with dis-
tilled  water  to  500 c. c, iodine  run in until  the  color
matches that in the test, and the volume of iodine solution
so  used  subtracted  from the figure obtained  in the first
titration.
  Hardness.  COs in Normal Carbonates.—Waters
containing considerable quantities of calcium and magne-
sium salts are said  to be hard.  Since the  solution of cal-
cium and magnesium carbonate in water depends partly upon
the  presence  of  carbon  dioxide, boiling precipitates the
greater portion of the carbonates, the result being to diminish
the  hardness, /. e., soften  the  water.  Magnesium and cal-
cium sulphates and  chlorides are  not precipitated in this 
62
ANALYTICAL OPERATIONS.
way.  Hardness,  therefore,  is  divided  into  two classes,
temporary  and permanent,  the  former being that  which
may be removed by boiling.   The process here described
is due to Hehner.
Reagents Required:—
  Standard Sodium Carbonate.—1.06  grams of  recently
ignited  pure  sodium carbonate are dissolved in water  and
the solution diluted to 1000 c. c.   1 c. c. =.00106 gram
Na2C03, equivalent to .001 gram CaC03.
  Standard Sulphuric Acid.—1 c. c. of pure concentrated
sulphuric acid is added to about 1000 c. c. of water.  50 c. c.
of the  standard  sodium carbonate are  placed in  a porce-
lain dish, heated to  boiling,  a few drops  of a solution of
phenacetolin  or lacmoid added,  and  the sulphuric acid
cautiously run in from a burette until the proper change of
color occurs.  From the  figure thus obtained, the extent
to which the acid should be  diluted in order to make  1 c. c.
of the sodium carbonate equivalent to 1 c. c. of the acid may
be calculated.  The proper amount of water is then added
and the solution verified by again titrating.
Analytical Process:—
   Temporary Hardness.—100 c. c. to 250 c. c. of the water
tinted with the indicator are  heated to boiling, and the sul-
phuric acid cautiously run in  until the color change occurs.
Each c. c. required will represent one part of  calcium  car-
bonate or its  equivalent per 100,000 parts of the water.
  Permanent Hardness.—To  100 c. c.  of  the   water is
added an amount of the sodium carbonate solution more
than sufficient to decompose the calcium and magnesium
sulphates, chlorides and nitrates present; usually a bulk
equal to the water taken will  be more than sufficient.   The
mixture is evaporated  to dryness  in a  nickel or platinum 
TECHNICAL EXAMINATIONS.
63
dish, and the residue extracted with distilled water.  The
solution is filtered through a very small filter, and the filtrate
and washings titrated hot with sulphuric acid as above ;  or
25 c. c. of distilled water may be poured on  the  residue,
and the  solution obtained filtered through a dry filter, the
filtrate measured and titrated.   The  difference   between
the number of  c. c. of sodium carbonate used  and the
acid required for the  residue  will give  the permanent
hardness.
   If the  water  contains sodium or potassium carbonate
there  will be  no permanent  hardness, and  there will  be
more  acid required  for the filtrate than the equivalent of
the sodium  carbonate  added.   From  this  excess  the
quantity of  sodium  carbonate in the water may be deter-
mined.
   Since any alkali carbonate  in the water would  be erro-
neously  calculated  as temporary hardness by the direct
titration, the equivalent, in terms of calcium carbonate, of
the alkali carbonate present should be deducted  from the
figure given by the titration in order to get the true tempo-
rary hardness.
   The total C03 in normal carbonates is given by the direct
titration of the water with dilute  sulphuric acid.  One c. c.
of the acid is equivalent to .0006 gram of C03.
   Free  Carbonic Acid.—The following process, due to
Pettenkofer, is  taken  from Sutton's  "Volumetric Analy-
sis " :—
   A stoppered bottle of known capacity, about 150 c. c,
is filled at the source  by submergence, or, if taken from a
faucet, by allowing the stream to run in with full force for
some minutes, the nozzle being inserted into the neck of
the bottle.  50  c. c. of the water are then quickly removed 
64
ANALYTICAL OPERATIONS.
by  a pipette, and  the following solutions  immediately
added :  3 c. c. of a saturated solution of calcium chloride
and 2 c. c. of a saturated solution of ammonium chloride ;
45 c. c. of clear  calcium hydroxide  solution of  known
strength are added, the flask well corked, the liquids  mixed,
and set aside  for at least twelve hours, to allow the calcium
carbonate formed  to  settle  and  become   crystalline and
insoluble.  An aliquot part  (50 to 100 c.  c.) of the clear
liquid is then drawn off and titrated with decinormal acid,
using phenacetolin 6r  lacmoid as indicator, and from  the
amount required the entire proportion of calcium hydroxide
unacted upon can be  determined.   This  being deducted
from  the amount originally added, and   the  remainder
multiplied  by .0022,  will give  the  weight of carbonic
acid in  the water  in  excess  of that  existing  as   normal
carbonates.
  Boric Acid.—Detection.—Add to one liter of the water
sufficient sodium carbonate to render it distinctly alkaline.
Evaporate  to dryness, acidify with hydrochloric acid,
moisten a slip of turmeric paper with the liquid, and dry it
at a moderate heat.  In the presence of boric acid the paper
will assume a distinct  brown-red tint.
  Estimation.—The  following  method for  determining
boric acid is due  to Gooch, and  has been found very
satisfactory.  One liter or more of the water is rendered
alkaline, if necessary, by sodium  carbonate and  evapo-
rated to dryness.  The residue is transferred as completely
as possible by the aid of slight excess of acetic acid to
a flask attached to a condensing apparatus,  arranged as
in Fig.  8.  About 1  gram of  pure quicklime  is  heated
in a  platinum crucible  over  the  blast   lamp  for from
five to fifteen minutes, to decompose any hydroxide or 
TECHNICAL EXAMINATIONS.
65
Fig. 8.
 
66
ANALYTICAL OPERATIONS.
carbonate, allowed to cool in the desiccator, and weighed.
It is then introduced into the Erlenmeyer flask, slaked by
the addition of a few c. c. of water, and the flask attached
to the lower end of the condenser, as shown (Fig. 8).  The
terminal tube of the condensing apparatus should dip into
the milk of lime.  The  hemispherical copper basin contains
paraffin, which is heated to a temperature of about 2500 F.
The bath is then raised so as to immerse the entire bulb of
the flask, and the liquid distilled to dryness.  The bath is
then lowered, and when  the flask  and  its contents have
somewhat cooled, 10 c. c. of methyl alcohol are introduced
by  means of the stoppered funnel tube, the bath  raised
again,  and the liquid  again distilled  to dryness.   This
manipulation is repeated until  six portions  of  10 c. c. of
methyl  alcohol have been  distilled  off.   The boric  acid
will distill over and be  fixed by the lime.  The contents of
the Erlenmyer flask are concentrated and transferred com-
pletely to the same crucible in which the lime was heated.
Any portions  adhering to the  sides of the flask or  to the
tube may be dissolved by a little acetic acid.  The material
in  the crucible is cautiously dried and heated over the blast
lamp for ten minutes,  allowed to  cool  in  the  desiccator
and weighed.  The increase  in weight represents boric
anhydride, B203.

            SPECTROSCOPIC EXAMINATION.
  For  the ordinary spectroscopic  examination of a water
a simple apparatus will suffice.   The arrangement figured in
the cut (Fig. 9) is a small direct-vision spectroscope, held
in  a universal stand, with Turquem's adjustable burner as
the source  of heat.  The entire apparatus does not  cost
over $15.00, and will be found  convenient and efficient. 
TECHNICAL EXAMINATIONS.
67
Fig. 9.
  For the examination, a liter or more should be evapo-
rated nearly to dryness,  a little hydrochloric acid being
added near the end of the
process, the residue  placed
in a narrow strip of plati-
num  foil  having the sides
bent  so as  to retain the
liquid, and heated  in the
flame.  While  this method
will  be sufficient  in many
cases, a far better plan  is
to separate the  substance
sought for in a state of ap-
proximate purity and then
examine with  the spectro-
scope. Very small traces of
lithium, for instance, may
be detected as follows : To
about a liter of  the water
sufficient sodium carbonate
is added  to precipitate all
the  calcium and  magne-
sium, and the liquid boiled
down to  about one-tenth
its bulk;  it is  then filtered, the filtrate rendered slightly
acid with hydrochloric acid and  evaporated to  dryness.
The  residue is  boiled with a  little alcohol, which  will dis-
solve out the lithium chloride.  The alcoholic solution is
evaporated to  dryness, the residue taken  up with a little
water and tested in the flame.
  In  order to  identify with  certainty any line which  may
be obtained, it is only necessary to  hold  in  the  flame at
 
68
ANALYTICAL OPERATIONS.
the same time a wire which has  been dipped in a solution
of  the  substance  supposed  to  be present,  and  to note
whether the lines produced by it and the material  under
examination are identical.

                  SPECIFIC  GRAVITY.
  In  the  great majority of cases the  determination of
specific gravity is not essential.   Ordinary river, spring and
well waters contain such small proportions of solid matter
that it is usually the practice  to take a  measured volume
and to assume its weight to be  that of an equal  bulk of
pure water.   If the proportion of solids  be high, a  deter-
mination  of  the specific gravity  may be desirable.   For
this purpose the specific gravity bottle may be used.   This
consists merely of  a small flask provided with a finely per-
forated  glass  stopper.   The  bottle is weighed first alone,
then filled with  distilled water  at 6o° F., and finally with
the water  under examination at the same temperature.   In
filling the  bottle, the  liquid is first  brought  to the proper
temperature, the bottle completely filled, the stopper in-
serted,  and the excess of  water, forced  out through the
perforation and around the sides of the  stopper, carefully
removed  by  bibulous  paper.   The  weight of  the  water
examined  divided by the weight of the equal bulk of dis-
tilled water at  the same  temperature gives the  specific
gravity.
  Another method, and one which  gives  very satisfactory
results,  is  by the use of a plummet.  This  may convenient-
ly consist  of a piece of thick  glass rod of  about  10 c. c. in
bulk, or of a test-tube weighted with mercury  and the open
end sealed in the flame.  The plummet is  suspended  to the
hook of the balance by means of a fine platinum wire and 
TECHNICAL EXAMINATIONS.
69
its weight ascertained.   It is then immersed in distilled
water at 6o° F. and the loss in weight noted.   The figure so
obtained is the weight  of a bulk of water equal to that of
the plummet.  This having been determined, the specific
gravity of any water may be  found by immersing in it the
plummet and noting the  loss  in weight.   This, divided by
the loss suffered in pure water, gives the specific gravity. 
    INTERPRETATION  OF RESULTS.

            STATEMENT OF ANALYSIS.

  The composition of water is generally expressed in terms
of a unit of weight in a definite volume of liquid, but much
difference  exists  as  to  the standard used.  The decimal
system is  very  largely employed,  the  proportions being
expressed in milligrams per liter,  nominally parts  per  mil-
lion ;  or in centigrams per liter, nominally parts per hund-
red thousand.   Not  infrequently  the figures are given in
grains per imperial  gallon of 70,000 grains, or the U. S.
gallon of  58,328 grains.   Much more  rarely grains per
quart, parts per thousand,  per cent, or other inconvenient
ratios are  employed.  In  this work the composition  is
always expressed in parts per million.  This ratio  is practi-
cally equivalent  to milligrams per liter,  except in cases of
waters very rich in solids, a liter of  which weighs notably
more  than one million milligrams.  Factors for converting
the different ratios are given at the end of the book.
  From the analysis of a water it is rarely possible  to ascer-
tain the exact arrangement of the elements determined, but
it is the custom  to assume arrangements  based  upon the
rule of  associating  in combination  elements having the
highest affinities, modifying this system  by any inferences
derived from the character or reactions of the water itself.
It has been demonstrated that, even in the case of mixtures
of salts producing no insoluble substances, partial inter-
                          7o 
STATEMENT OF  ANALYSIS.
71
change of the basylous and acidulous radicles takes place.
In a solution of sodium chloride and  potassium  sulphate,
sodium sulphate  and potassium chloride will be  found, as
well as the original salts.   When the conditions are ren-
dered  more complex by the addition of other  substances,
it is obviously impossible  to determine  the  exact arrange-
ment.   In view of these facts, it is preferable to  express
the composition of a water by the proportion of  each  ele-
ment  or radicle  present.   In this way a water containing
K.,S0o will be expressed  in terms  of K and S04,  respec-
tively.  In the case of bodies like C02 and Si02, which may
possibly exist free in the water, their proportion is expressed
as such.  It frequently occurs that the characteristics of
some of the compounds in a water are sufficiently marked
to indicate their presence, and there can be no objection
to suggesting in connection with the analytical statement,
the inferences which may  thus be drawn.
  The organic  matter, or its derived  products, are best
stated  in  terms of the  nitrogen which they contain, thus
permitting a comparison of the  different stages of decom-
position.   It is inadvisable to  represent the  amount of
unchanged organic matter in  terms of  oxalic acid, as has
been suggested, or to express the nitrogen in terms of albu-
min, or any other supposititious compound.

               SANITARY APPLICATIONS.
  Judgment upon the analytical results from a given sam-
ple of water  depends upon the class to which it belongs,
and  to the particular influences to which it  has been sub-
jected. A proportion of total solids which would be  sus-
picious in  a rain  or river water, would be without signifi-
cance  in that from an artesian  well.   On the other hand, a 
72
INTERPRETATION OF  RESULTS.
subsoil water of unobjectionable character would contain a
proportion of nitrates which would be inadmissible in the
case of a river or deep water.   Location has also  much
bearing in the case; subsoil waters near the sea will  be
found to contain, without invoking suspicion, proportions
of chlorine which would be  ample to condemn the same
sample if derived from a point far inland.   Hence the im-
portance of recording at  the time of collection, all ascertain-
able information as to the surroundings and probable source
of the water.
  Color, Odor and Taste.—Water of the highest purity
will  be  clear, colorless,  odorless,  and  nearly tasteless.
While in some cases a decided departure from this standard
may give rise to suspicion, analytical  observations are
necessary to decide the point.   Water highly charged with
mineral matters will possess decided taste, vegetable  mat-
ters  may communicate  distinct color;  but, on  the  other
hand, it may be  highly contaminated with dangerous sub-
stances and give no indications to the senses.  Well-waters
occasionally become offensive  in  odor,  from penetration
of tree  roots.  The odor often recalls that of hydrogen
sulphide.   Sulphides are, indeed, often  formed in  such
cases by the abstraction of  oxygen from  sulphates under
the   influence  of microbes.   Such waters are  often  used
without apparent injury,  but it is probable that if direct
pollution  occurs, the danger would be  enhanced by the
presence of the  vegetable matter.  Miquel has described
a bacillus,  under the name  B.  sulphydrogenus, which pro-
duces hydrogen  sulphide readily.  Some of the common
putrefactive bacilli  doubtless have this power also, largely
through the influence of the hydrogen liberated by them.
In  waters  containing hydrogen  sulphide, species of beg- 
SANITARY APPLICATIONS.
73
giatoa,  especially B. alba, thrive, and  decomposing the
sulphide, become  impregnated with sulphur.  Natural sul-
phur waters frequently contain these organisms, as do, also,
waste-waters containing sulphide.
  Total Solids.—Excessive proportions of mineral solids,
especially of marked physiological  action, are  known to
render  water  non-potable,  but  no  absolute maximum or
minimum can be assigned as the limit of safety.    Distilled
water and  waters very highly charged with mineral matter
have been  used for long periods without ill effects.  The
popular notion  that the so-called  hard  waters conduce to
the formation of urinary calculi is not borne out by surgical
experience  nor  statistical  inquiry.   Many urinary calculi
are composed of uric acid, and  are the results of disorders
of the general nutritive functions.
  Sanitary authorities have fixed an arbitrary limit of total
solids of about  six hundred parts  per million, but many
artesian waters in constant use  exceed this.  An  instance
is found in the well on Black's Island, near Philadelphia,
given in the table of analyses, which contains nearly twelve
hundred parts per million, is very agreeable in taste, and
has been  in constant  use  for some  years by a number of
persons without injury.   The assertion that water to  be
wholesome must contain an appreciable proportion of total
solids is also not demonstrated by clinical experience.  A
discussion of the effects of special mineral ingredients, e. g.,
magnesium sulphate, ferrous  carbonate,  etc.,  belongs to
general therapeutics.
  The odor produced on heating the water residue is often
of much use  in detecting contamination.   Odors similar
to those produced by heating glue,  hair, rancid fats, urine,
or other animal  products, will give rise to grave suspicion.
       F 
74
INTERPRETATION OF RESULTS.
On the other  hand, a more favorable judgment may be
given when  the odor recalls those given off in the heating
of non-nitrogenized vegetable  materials,  such as  wood-
fibre.
   Poisonous Metals.—The proportion of iron in water
constantly  used  for drinking purposes should not much
exceed  three parts per million.   Lead, copper, arsenic
and  zinc must be considered dangerous in any amount,
though it appears that zinc and copper, being least cumu-
lative, are rather less objectionable in minute  amount than
the others.   Concerning the  limit of safety with  mangan-
ese and chromium very little is known, but their presence
in appreciable quantity must be  looked upon with  sus-
picion.
   Chlorides and Phosphates.—Chlorides—principally
sodium  chloride—and  phosphates are abundantly distrib-
uted in rocks  and  soils, and find their way into natural
waters ; but while the former are freely soluble, and remain
in undiminished amount under all conditions to which the
water is subjected, all but minute amounts of  the latter are
either precipitated or  removed  by  the action of living
organisms.   Surface and subsoil  waters ordinarily contain
but  a few parts  per million.  Both chlorides and phos-
phates  being  constant and characteristic ingredients of
animal excretions, it is obvious that  an excess  of them in
natural  waters, unless otherwise accounted for, will suggest
direct contamination.   Proximity to localities  in which
sodium  chloride is abundant, such as the  sea  or salt de-
posits, will deprive  the figure for the chlorine of diagnostic
value, nor can any indication of sewage or other danger-
ous pollution be inferred from high proportion of chlorine
in deep waters.  Further, it has  been shown that the pro- 
SANITARY  APPLICATIONS.
75
 portion of chlorine in uncontaminated waters  is tolerably
 constant, while  in  water subjected  to the infiltration of
 sewage, the chlorine undergoes marked variation in amount.
 In most  cases, therefore, a correct judgment can only  be
 attained  by comparison with the average  character of the
 waters of the  same type in the district, and by examination
 at intervals of the water in question.
  As regards phosphates, Hehner, who  has  published a
 series of analyses, states that the presence of more than 0.6
 parts per million—calculated as P04—should be  regarded
 with suspicion.   On the other  hand, the absence of phos-
 phates affords no positive proof of the freedom  from pollu-
 tion.   The application of Heisch's test will often afford
 additional information on  this point.   F. E. Lott, who
 has applied this test  in  the examination of a number  of
 waters, fully confirms  Dr. Frankland's statement that the
 development is due to phosphates, and draws the following
 conclusions: —
  Any water which undergoes  butyric fermentation when
 simply treated with cane sugar and kept at a temperature of
 8o° F., may be at once condemned as unfit for domestic use.
  The single  fact of a water not undergoing butyric fer-
 mentation is no proof of its purity.
  A water which remains  clear  under this  treatment would
 certainly be less likely to be contaminated by sewage than
 one which becomes  milky, and the possibility  of unoxid-
 ized sewage matter being in a  water  which remains quite
 clear is very doubtful.
  The butyric ferment is not perceptibly influenced  by the
presence  of abnormal amounts of chlorine, ammonia, nitro-
genous matter, sulphates or nitrates, but is a very accurate
indicator of the presence of phosphates. 
76           INTERPRETATION  OF RESULTS.
  Nitrogen from Ammonium Compounds.—Ammo-
nium compounds are usually the results of the putrefactive
fermentation  of nitrogenous organic matter ; they may also
be the product  of the reduction of nitrites and nitrates
in presence of excess of organic matter.  In  either case,
therefore, they suggest contamination.   Deep  waters often
contain an excess of ammonium compounds, derived, in
large part, from the reduction of nitrates.   Their presence
here is hardly  ground  for adverse judgment,  since  the
water, even though originally contaminated, has undergone
extensive  filtration and  oxidation and its organic matter
converted into bodies presumably harmless.   Such waters,
indeed, usually  show only traces of unchanged  organic
matter.
  Rain water often contains  large  proportions of ammo-
nium compounds; but here, also, the fact cannot condemn
the water, since it does  not  indicate contamination with
dangerous organic matter.
  The evolution of ammonia in the distillation of rain water
often continues indefinitely, the larger portion passing over
in the first distillates, but  small  quantities  being present
even after the distillation has been much prolonged.  The
same continuous evolution  of ammonia is noted  in waters
containing urea, but in this  case  a  larger proportion  is
collected in  the earlier distillates, nearly all coming over
before one-half the  water  has been  distilled.  Fox gives
the  following  figures as ratios obtained  in  the analysis of
two samples, one of rain water collected  from a roof  and
therefore impure, and the other of a water containing
urine :— 
SANITARY  APPLICATIONS.
77
                 RAIN WATER.  URINE WATER.
                 , .  .  .35      .38      parts per million.
                  .  .  .25      .14
                 ...  .12      .065       "       "
                 ...  .09      .035
                 ...  .09
                 ...  .04
                 ...  .03

                      .97      .620

   Nitrogen by Alkaline Permanganate (Nitrogen of
"albuminoid  ammonia").—A large yield of ammonia by
boiling with  alkaline  potassium  permanganate will, of
course, point  to  an excess of nitrogenous organic matter.
The inferences to be drawn  depend  upon the origin and
condition of the organic material.   If animal, the water
may at once be condemned as  unsafe.  Waters containing
excessive  amounts  even of vegetable matter are not free
from objection, since they have frequently caused persistent
diarrhoea.   If  the organic matter, whether   animal  or
vegetable, is in a  state of active decomposition, it is doubly
objectionable.  Mallet has called attention to the fact that
such  waters, as a  rule, yield  ammonia  rapidly, whereas
non-decomposing material  yields  it but  slowly, and  he
points out the importance, therefore,  of noting  the  rate at
which the ammonia collects in the distillate.
   Dr.  Smart has observed that water containing fermenting
vegetable matter  is colored yellow by boiling with sodium
carbonate, and that  when Nessler's reagent is added to the
distillate, a  greenish, in  place of  the ordinary  yellowish-
brown color is produced.  He applies  this fact  in con-
junction with the determination of the oxygen-consuming
1st distillate,
2d
3d
4th    "
5th    "
6th
7th    " 
78           INTERPRETATION  OF RESULTS.
power  (Tidy's  process)  and the  rate of evolution of the
ammonia by alkaline permanganate as follows: —
  A water  yielding  ammonia slowly by alkaline perman-
ganate,  contains  recent  organic   matter;  of   animal
derivation, if the  oxygen-consuming  power  is  low;  of
vegetable, if high.
  A water yielding ammonia more rapidly by alkaline per-
manganate, shows decomposing organic matter ;  of animal
origin, if the oxygen-consuming  power be  low  and there
be no interference  with the Nessler reaction ; of vegetable
origin, if the oxygen consumed  be  high, and if a yellow
color be produced  in the water by sodium carbonate, and a
greenish color in the nesslerized distillate.
  Inferences as to  the  source of  the organic matter can
usually be drawn from the amount of chlorine and nitrates
present.  If the chlorine be  high  /. e., in  excess  of the
average of the district,  it may be  inferred that the material
is, in great part, of animal origin. In this case, the nitrates
will  either be  high or entirely  absent, according as the
contaminating matter has passed through soil or  enters the
water directly.
  A large amount of vegetable matter will, as a rule, show
itself by the color it  imparts to the water.
  Wanklyn gives the following standards:—
    High purity,..........oo  to .041 per million.
    Satisfactory purity,  .......041 to .082  "    "
    Impure,...........over .082.
In the absence of  ammonium  compounds, he does not
condemn a water unless the nitrogen by permanganate ex-
ceeds .081 per million;  but  a water yielding 0.123 parts
per million  of  nitrogen  by  permanganate  he condemns
under all circumstances. 
SANITARY  APPLICATIONS.
79
  Total  Nitrogen.—Drown  and Martin's results with
surface waters indicate that the  total nitrogen obtained by
their process is about twice that obtained by alkaline per-
manganate. Our own experiments accord with this. Further
observation on different waters  and by different observers
will be  required to determine the value to  be assigned to
the figures obtained  by  this  method.  This  method  is
especially  suitable  for studying the effects of  filtration,
storage, etc., on the nitrogenous organic matter in water.
  Nitrogen as Nitrites.—Nitrites are present in water
as the result either of incomplete nitrification of ammonia,
or the reduction of already formed nitrates, under the in-
fluence  of reducing  agents or  microbes.   Since  they are
transition products,  their  presence in water  is usually evi-
dence  of existing fermentative changes, and, further, may
be taken as indicating  that the  water is unable to dispose
of the  organic  contamination.   When, however, the con-
ditions are such that oxidation  cannot  take  place, nitrites
may persist for  a  long time.  This sometimes occurs in
deep waters in  which fermentative changes have long since
ceased,  but oxygen is  not available.   These contain  not
infrequently small amounts of nitrites, to which the same
degree of  suspicion  cannot  be  attached.   When nitrites
are found in these waters, the possibility of  their introduc-
tion from polluted subsoil water, through defective tubing,
must  not  be  overlooked.  Rain water,  also,  sometimes
contains nitrites derived from  the air, and  therefore  not
indicative  of  any putrefactive  change.  The  presence of
measurable quantities of nitrites in river or  subsoil  water
is sufficient ground for condemnation.
  Nitrogen as Nitrates.—Nitrates are the final point in
the oxidation  of  nitrogenous   organic matter, especially 
8o
INTERPRETATION OF RESULTS.
animal  matters.  Rain  water  and that  from  mountain
streams and  deep  wells, except  from cretaceous  strata,
generally contain only traces, but river and subsoil  waters
will always contain  appreciable  amounts,  unless some re-
ducing action, such as recent sewage pollution, is at work.
When, therefore, a water contains  enough mineral matter
to demonstrate  its percolation through soil, and at the same
time is free from nitrates or contains only traces, the oc-
currence of a destructive fermentation may. be inferred.
These cases are not  uncommon among well waters, and the
samples are generally turbid from suspended organic matter.
Decided departure, either by  increase or  decrease, from
the proportion  of nitrates usual in the same class of water
in any district may be taken as evidence of contamination.
   Oxygen-consuming  Power.—Sanitary  authorities
differ very  much as  to the significance of this datum.  At-
tempts have  been made to fix maximum limits for  the
various types  of water, and also to gauge the character and
condition of  the organic  matter by observing  the rate at
which  the  oxidation takes place, but no  positive conclu-
sions  can   be given.  In  general, it may be said that a
sample  which has high  oxygen-consuming power will be
more  likely to  be unwholesome  than one which is low in
this respect; but the interferences are so numerous, and the
susceptibility  to oxidation of different organic matters of
even the same  type, is so different, that the  method  is at
best  only of accessory value.  It is especially suitable for
consecutive determinations on the same supply.
  The following proportions are given by Frankland and
Tidy  as the basis  of  interpreting  the  results of  this
method :— 
STATEMENT  OF ANALYSIS.
8l
                            OXYGEN ABSORBED IN THREE HOURS.
    High organic purity,.......05    parts per million.
    Medium purity,........0.5 to 1.5   "  "    "
    Doubtful,..........1.5 to 2.1   "  "    "
    Impure,.........over 2.1        "  "    "

  For the method with acidified permanganate at the boil-
ing heat, the German chemists, who employ it largely, re-
gard  an absorption of 2.5 parts of oxygen  per million as
suspicious, and some sanitary authorities have fixed 3.8 parts
of oxygen per million as the highest permissible limit.
  Dissolved  Oxygen.—Full  aeration of water is favor-
able to  the destruction of organic matter; a decided dimi-
nution in  the quantity of dissolved oxygen may show excess
of such  matter  and of microbic life.  Gerardin has pointed
out that this diminution  is associated with the development
of low  forms of vegetable life, and Leeds has recorded
similar facts.   These changes are more likely to take place
in still waters, and are frequently accompanied by disagree-
able odor and  taste.  In cases in which stored waters be-
come unpalatable, these facts should be borne in  mind.
  Dupre has given the  following as the basis  for  interpret-
ing the results of his adaptation  of the  determination of
dissolved oxygen :—
  " A water which does not diminish in its degree of aera-
tion during a given period, may or may not contain organic
matter, but  presumably  does not  contain  growing organ-
isms.   Such organic matter as it may be found to contain
by chemical  analysis need not be considered as dangerous
impurity."
  " A water \yhich by itself,  or after  the addition of
gelatin  or other  appropriate cultivating matter,  consumes
oxygen  from the dissolved air, at  lower temperatures, but 
82
INTERPRETATION OF  RESULTS.
does not consume any after heating for, say, three hours at
1400  F.,  may be regarded  as  having  contained  living
organisms, but none of a  kind able  to survive exposure to
that temperature."
   " A water which by itself, or after addition  of gelatin or
the like, continues to absorb oxygen from the contained
air after heating  to 1400 F.,  may be taken as containing
spores or germs able to survive that temperature."
   Hardness.—The degree of hardness has but little bear-
ing on the sanitary value of water, but  is important  in
reference to its use for general household  purposes, in view
of the soap-destroying power which hard  waters possess.
USUAL  ANALYTICAL  RESULTS  FROM
    UNCONTAMINATED WATERS.
            Parts per million.
	Rain.	Surface.	Subsoil.	Deep.
Total solids,....... Chlorine,..... Nitrogen by permanganate, as NH4, .... " " nitrites, . . . " " nitrates, . . .	5 to 20 Traces to i .08 to .20 .20 to .50 None or traces Traces.	15 upward 1 to 10 •05 to .15 .00 to .03 None .75 to 1.25	30 upward 2 to 12 .05 to .10 .00 to .03 None 1.5 to 5	45 upward Traces to large quantity .03 to .10 Generally high None or traces .00 to 3
 
ACTION  OF WATER ON LEAD.
83
             ACTION OF WATER ON LEAD.
  The almost  universal use of lead pipes  for  conveying
water, and the  facility with which some waters corrode
and dissolve  the metal, make it  a question of moment to
determine  the cause of this action and to devise means for
its  prevention.    The subject  has  received  considerable
attention within the last few years, and the conditions which
determine  corrosion are now fairly understood.  As a rule,
it is found that waters free  from mineral matter dissolve
lead with  facility, especially in  the presence of oxygen.
Some  very soft waters are entirely without action,  and
this was unexplained until a few years  ago, when Messrs.
Crookes, Odling and Tidy found that the action was con-
trolled by the amount of silica contained  in  the water.
They found that those soft waters which,  when taken from
the service pipes, contained a notable  quantity  of  lead,
gave, on the average, three parts of silica per million; in
those  in which  there  was no   lead,  the  silica present
amounted  to 7.5  per million and  in those  in  which the
action was intermediate, 5.5 parts per million.  That it
was really  the silica that  conditioned the  corrosion, was
confirmed  by laboratory experiments.   They also  found
that the most effective way of silicating a water is by passing
it over a mixture of flint and limestone.  The reason for
this was pointed out later by Messrs. Carnelly and  Frew,
who showed that while calcium carbonate and silica both
exert  a protective  influence,  calcium  silicate  is  more
effective than either, and further, that  in almost all  cases
in which corrosion took place it was greater in the presence
of oxygen.  This  is particularly the case with potassium
and ammonium nitrates and with calcium hydroxide.  The 
84            INTERPRETATION OF  RESULTS.

reverse is true of calcium sulphate, which is more corrosive
when air is excluded.  Their experiments also show that the
presence of calcium carbonate or calcium silicate, altogether
prevents corrosion by potassium and ammonium nitrates.
  As the result of an elaborate series of experiments, Miil-
ler concludes, that while chlorides, nitrates and  sulphates
all act upon lead  pipes, no  corrosion  takes  place  in the
presence of sodium acid carbonate, and that calcium car-
bonate, by taking  up carbonic acid, acts in the same way.
This latter conclusion  is at variance with the observations
of Carnelly and  Frew, who found that calcium carbonate
is equally effective when carbonic acid is excluded.   Miil-
ler also states that surface waters, contaminated by sewage
and containing large amounts of ammoniacal compounds,
will dissolve lead under all circumstances.
  Allen has shown that  water containing free  acid, in-
cluding sulphuric acid, acts energetically upon lead.   This
is not  surprising in view of  the  later  experiments, which
prove that even calcium sulphate is corrosive.  Later, W.
Carleton-Williams found that even in the presence of free
acid, corrosion may be prevented by the addition of suffi-
cient silica.   His experiments also confirm  the view gener-
ally held, that soluble phosphates protect lead to a marked
degree.
  The  following is a summary of the more important ob-
servations  on this subject:—
  Corrosive:  Free acid or alkalies, oxygen, nitrates, par-
ticularly potassium and ammonium nitrates,  chlorides and
sulphates.
  Non-corrosive and preventing  corrosion by the above :
Calcium carbonate, sodium  acid  carbonate,  ammonium
carbonate, calcium silicate, silica and  soluble phosphates. 
SANITARY APPLICATIONS.
85
              BIOLOGICAL EXAMINATIONS.
   In a comprehensive sense  the living organisms of water
include representatives of all the  great groups of animals
and plants.  The presence of any of the higher orders of
organic forms may be taken  as an indication of moderate
purity, as these are absent from very foul water.   From an
analytical point of view, observation is limited to the deter-
minations  of those forms which are  inappreciable to the
unassisted eye.  As far as regards  some of the moderately
complex organisms, such  as  the minute crustaceans, algaa,
desmids, and even  the amoebae, it may be said  that while
some general inferences as to the  character and  history of
the water may be  deduced  from  an  identification of the
specific forms, no definite  sanitary  signification can  be
attached to them.  The ova  of the entozoa might in some
cases be detected  by careful search, and would  indicate
recent  pollution of a highly dangerous character.
   Cohn  (Beitr. z. Biol.  d.  P/ianz.) regards chlorophyll-
producing  plants (diatoms and green algas),  together with
the infusoria that feed upon them, and species of entomos-
traca (Daphnia and Cyclops), when  present in only moderate
amounts,  as  indicating water not very  rich  in  dissolved
organic matter.  Species  of  Cladothrix,  Crenothrix and
Beggiatoa,  which are among the  larger  bacteria, and fre-
quently appear as branching  forms,  indicate  suspended
organic matter; while  dissolved organic matter  in a state
of active  decomposition  is indicated  by the presence of
ordinary bacteria (Bacilli, Spirilli), etc.
   Cladothrix dichotoma withdraws iron  from water, and
fixes it, causing obstructions  in  iron water pipes.   Creno-
thrix Kiihniana,  Rabenhorst, is seen in  water containing
iron and sometimes causes a disagreeable odor. 
86
BIOLOGICAL EXAMINATIONS.
  The number of the higher forms present in any sample
will depend very much upon the point at which it is  col-
lected, they being more numerous  in the neighborhood of
large  plants  and at  the bottom  and  sides of  streams.
Under our present  knowledge, no pathogenic power  can
be assigned  to  the  higher forms of organic life, except
entozoa, but their bodies after death  may indirectly con-
tribute to the rapid increase of the bacilli proper, by serving
as food.
  Instances of  the  introduction of  the ova  of entozoa
into the human  system by means  of  water  are  doubtless
very common, and cases have been reported.   One of the
most striking of these was the anaemia  occurring among
the workmen in the  St. Gothard tunnel, which was found to
be due to the  ingestion of the ova of a parasitic animal, An-
                                chylostomum duodenale.
                                  Culture  Media.—
                                For bacteriological  ex-
                                aminations, culture
                                media  prepared with
                                gelatine  or  agar-agar,
                                are generally used.  In
                                special  cases  potatoes
                                and  blood - serum  are
                                employed.   In all cases
                                solutions  and  vessels
                                must   be   thoroughly
                                sterilized.  This is most
                                easily accomplished in
                                the Arnold steam steril-
                                izer, shown in  Fig.  10.
                                It consists of a copper
boiler, A,  in  the form of an inverted funnel, which com-
37759392 
SANITARY APPLICATIONS.
87
municates with the sterilizing chamber.   A double casing
is so arranged  that the condensed steam falls  into the pan
B and  returns to  the boiler.   This pan  should be about
half-filled with water before starting.   We have found this
apparatus  suitable  not only for all sterilizations, but  also
for preparing solutions and for hot filtrations.
   Mcat-extract-peptone-gelatin :—

        Water,.................1000 c.c.
        Meat extract  (Armour's),.........    5 grams
        Gelatin  (best  French),..........150   "
        Peptone (Merck's, dry),.........   10   "
        Glucose (best),.............    2   "

   The  materials are dissolved by  heat  and  the solution
rendered slightly alkaline by  the addition of sodium  car-
bonate  or trisodium phosphate, added by small portions,
stirring  between each addition, and testing the liquid by
placing a drop of it on red litmus paper.  When the alka-
line reaction  appears, the liquid is filtered through good
filter  paper, the funnel and beaker being  placed  in the
sterilizer, and a gentle steaming maintained  in order to
keep the gelatin liquid.
   In place of meat  extract, a solution may be made as fol-
lows : macerate 500 grams of  finely minced lean meat in
1000 c.c. of water,  for twenty-four hours, at  a temperature
not over 45 °  F.    Strain the liquid,  add  five  grams of
common salt  and  the  peptone, gelatin  and glucose,  and
render feebly alkaline, as before.
   Agar-agar Mixture.—When cultures are to be conducted
at a temperature above 68° F., agar-agar must  be used as
gelatinizing ingredient.   The solution is prepared as given
above, except  that only 15 grams of agar-agar must be 
88             BIOLOGICAL EXAMINATIONS.

used and a much longer time will  be required for its solu-
tion.   The operation  can be  facilitated by soaking the
agar-agar for twelve hours in a  strong solution of common
salt, or by the following treatment, which was first described
by Mace:—
  20 grams of agar-agar, cut fine, are steeped  in 500 c.c. of
water, containing six per cent, of hydrochloric acid, with
occasional stirring.   It is then well washed, and placed for
a similar period in the same amount of water, to which six
per cent, of ammonium hydroxide has been  added.   It  is
again washed thoroughly and added to 1000 c.c. of boiling
water.   It  dissolves at once.   The  peptone, gelatin  and
salt can then be added, the mixture rendered feebly alka-
line and filtered in the sterilizer.
  Agar-agar Gelatin.—To secure  the advantages of both
agar-agar and gelatin, a solution may be made by dissolv-
ing 50  grams of  gelatin  and  7.5 grams of agar-agar in  a
liter of  water, adding the peptone, etc. in the usual pro-
portions, rendering alkaline, filtering and sterilizing.  The
proportions of agar-agar and gelatin must be adhered to
closely or the gelatinization may be lumpy and incomplete.
  Potato Culture.—Cultivation  on  potatoes is an important
method of distinguishing  the  Bacillus typhosus.   Large,
sound  potatoes  should be  selected, thoroughly  washed,
and cut into  disks about  5  cm.  in diameter and 1  cm.
thick.   These are placed in glass boxes  (pomade boxes)
which  have lids with ground joint, and heated for about
one-half hour in  the sterilizer.   Another method  is to cut
out cylinders with the aid  of  an apple-corer, or largest
size cork-borer, slice these obliquely, and place  them in
test-tubes,  which are then closed  with cotton plugs,  and
sterilized.   The latter method does not give a large sur- 
SANITARY  APPLICATIONS.
89
face,  but the growth  of any  inoculation may be  easily
watched.
  Collection of Samples.—Bacteriological examinations
are of little value unless promptly made on samples that
have  been collected with precautions against  contamina-
tion.  The inoculation of the culture medium is best done at
the source.   If this is not possible, glass stoppered bottles
holding about 200 c.c, which have been thoroughly steril-
ized,  with stoppers in place, in a hot air oven  at 3000 F.,
must  be used for collection.   They should be rinsed  on
the outside with  water,  dipped  below the  surface,  the
stopper withdrawn, and again inserted when  the bottle is
full.  If  these  are  to be transported  any distance they
should  be packed  in  ice.  For delivering the measured
volume of water, a  pipette  sterilized in the hot-air oven
should be used.
  Culture  Manipulations.—For  the  estimation and
isolation of microbes in  water, we may employ either the
original  plate culture of Koch, Esmarch's "roll culture,"
or a modification that we have used in our own work,  which
may be designated " bottle culture."
  Plate  Culture.—Test-tubes containing about ten c.c. of
nutrient jelly  are  plugged with  cotton and  steamed for
fifteen minutes in the sterilizer on two successive days.   In
filling the tubes, care must be  taken that none of the jelly
touches the upper  part, where it can come in contact with
the cotton plug.  After sterilization,  the tubes should  be
put aside for  a few days, to  determine if all  spores are
destroyed.  If no  development of microbes  takes  place
in this time, the jelly is ready for use.   It should be melted
at a low temperature in  a water-bath, the cotton plug re-
moved with a twisting motion and a measured volume of
       G 
9o
BIOLOGICAL EXAMINATIONS.
water introduced by means  of a sterilized pipette.   The
plug  is immediately replaced  and  the  liquids mixed by
shaking, taking care not to soil the  cotton.  The quantity
of  water  to be  added will  depend on  the number  of
microbes  supposed to be present.   If the amount is  pro-
bably quite small, i c. c. should be taken ;  if it is probable
that a  large  number  is  present,  i c. c.  of the  sample
should be diluted to 10 c.c. with sterilized water, and i c.c.
of this mixture used.   In most cases  it will be well to make
several cultures, using different proportions of water. After
the jelly and water have been  mixed the  liquid is poured
out on  a  glass plate  and allowed to set.   The principal
difficulty  in the method arises  from the liability to con-
tamination from  the  air during  this part  of the process.
The glass  plates should, of course, be thoroughly sterilized.
                     They are  usually  set  upon  glass
                     benches,  and  placed in a so-called
                     moist chamber, which  consists of
                     two  cylindrical  glass  dishes,  one
                     fitting  within  the other (Fig.  n).
                     The  benches and  plates are placed
in the inner dish.  To hasten the setting of the jelly, it  is
necessary  that  the plates should be cold, and it will be best
to have them resting in a level  position on a flat tin bottle
filled with ice water,  or, if ice  is not at hand, a recently
prepared  mixture of  one part  of ammonium nitrate with
two parts  of water.   The coated  plates must be protected
from dust  while  being cooled,  and as  soon  as  possible
must be transferred to  the moist chamber, which, as well
as the benches, should have  been  previously thoroughly
washed  with recently  boiled water.   The bottom should
be covered with a sheet of moist filter paper.   The plates
 
SANITARY  APPLICATIONS.
91
are kept in the chamber for several days.  Each living
microbe that is capable of  growing  in the  jelly will
become the centre of a colony of its own kind, which will
soon become visible to the naked eye.   The  number  of
colonies may  be counted  as soon  as they  are distinct.
When the  number  is very large, an  approximate counting
may be made by means of a glass  plate with  lines ruled so
as to divide it into a considerable number of equal squares.
This is placed over the culture, and the number of colonies
in several of the squares counted,  the result  averaged and
multiplied  by the number of squares  that  the  entire culture
covers.
   Roll  Culture.—Instead of  pouring the jelly on a plate,
it  may be spread in a uniform layer on the inner wall of the
test-tube, taking care not to  allow it to touch  the cotton.
The jelly may be rapidly hardened by rolling the tube  in
contact with ice.  The method avoids all danger of contam-
ination with dust  and is  very simple  in manipulation,
but  is open to the objection that when bacilli  are present
which liquefy the gelatine, as will generally be the case, the
fluid will run down and inoculate other portions of the layer.
   Bottle Culture.—To avoid  the  disadvantage  of  the
above methods, it will  be found convenient to  employ flat
rectangular bottles of  the form  known technically as  the
"Blake" Bottle.   Those of 8  or 10  ounce capacity are
the best, and  it is well to select such as have as uniform a
thickness of glass as possible.   They should be thoroughly
cleaned and sufficient of the jelly put in to form a thin layer
on one  of the broader sides when the  bottle is  placed
horizontally.  The mouth is  then  closed by  a cotton-plug
and  the bottle sterilized as described  in connection with
plate culture.  To make a culture, the jelly is melted at a 
92             BIOLOGICAL EXAMINATIONS.

low temperature, the measured volume of water added,
the cotton  plug replaced, and  after mixing, the bottle is
placed in a horizontal position for the usual time.
  General Character of the Microbes  in Natural
Waters.—The microorganisms of natural waters are prin-
cipally  included  in  the genera bacillus and  spirillum,
especially the  former.   Micrococci  and  moulds are rare,
and when they appear on  the  culture plate,  are generally
due to contamination by dust.
  Microbes are distinguished according  to the conditions
favorable to their growth, as follows :—
  Saprophytic.  Growing on dead matter.
  Parasitic.  Growing only on  living  matter.
  Aerobic.  Requiring  free oxygen.
  Anaerobic.   Not requiring free oxygen.
  When the organism possesses the power of adapting itself
to different conditions, the  term facultative is applied;
when  it can grow only under special  conditions, the term
obligatory is applied.
  Thus,  the Bacillus butyricus is  unable to develop  in
contact with free oxygen; it is an obligatory  anaerobe.
The B. typhosus can grow either on dead or living matter,
and though growing best in  presence of free oxygen, can
also grow in  the absence of it.   It  is, therefore, a faculta-
tive saprophyte, and a facultative anaerobe.
  Microbes are also differentiated by  the effect which they
produce  upon  the culture medium.   Some species rapidly
or slowly liquefy the jelly with evolution of foul smelling
gases; others—chromogenic microbes—produce character-
istic colors.   Many do  not produce any positive modifica-
tion,  and for  purposes of distinction  it is usual  to transfer
portions of the colonies to other culture media.  Thus the 
SANITARY APPLICATIONS.
93
B. typhosus causes neither liquefaction nor coloration, but
gives a distinct growth on potato.  Such special cultures
are obtained by taking up a  portion of the colony on the
end  of a wire which has  been just sterilized by heating to
redness, and inoculating the  prepared  medium.
   Cultivation in Absence of  Oxygen.—Several of the most
frequently  occurring microbes  are  obligatory anaerobes,
and will  grow, therefore, only in an atmosphere deprived
of free  oxygen.   Carbon dioxide has been  found  to  act
unfavorably upon  their development.   The most suitable
atmosphere is one  of  pure hydrogen.    Cultivation  in
such an atmosphere may be  secured  by  constructing the
moist  chamber so  as to permit its being filled with
hydrogen and sealed, or by the use of Liborius'  tube,
Fig.  12.
   The tube  is charged with nutrient jelly,     fig. 12.
plugged  with cotton,  sterilized,  inoculated
with the material to be tested, the jelly main-
tained in a liquid  condition  by  a very gentle
heat and  a current of pure hydrogen  passed
through  the  side tube until all air  is  ex-
pelled.   The  test-tube and side  tube are then
sealed quickly at  the narrow  portions, in
the blow-pipe flame,  and the  jelly allowed  ^^
to solidify.
  Staining.—The differentiation of the various species  of
microbes may also be  accomplished by staining with vari-
ous aniline colors.  These methods are, however,  more
generally applicable  to pathological work, that is, to the
staining of microbes in tissues;  but one of the methods is
here  described, as it is frequently referred to in bacterio-
logical literature.
 
94             BIOLOGICAL EXAMINATIONS.
   Gram''s Method of Staining (as given by Crookshank).—
Place a few drops of pure aniline in a test-tube three-fourths
full of water, and shake  thoroughly.   Filter the emulsion
twice, collect some of the perfectly clear filtrate in a watch-
glass and add, drop by drop, a concentrated alcoholic solu-
tion of gentian violet, until precipitation appears.   Stain
sections in this for about  twenty minutes, then  place them
in a solution prepared as  follows : —

       Iodine,..............o.l gram
       Potassium iodide,.........0.2 "
       Water,..............30.0 grams.

Allow them  to remain until dark brown.    Decolorize  by
placing in alcohol. This  process gives blue or bluish-black
microbes  in a background tinged faintly yellow.
  Indol Reaction.—Indol, C8H7N, more properly indine, is
a weak  base, which is a  product of the  growth  of many
species of microbes, and the detection of it  may, therefore,
be utilized as a  differentiation test.   S. Kitasato (Zeit.f.
Hyg. vn, 518) gives the  following method  for  performing
the test:—
  Ten c. c.  of an alkaline-peptone-meat infusion  (without
gelatin),  which has been previously inoculated with the mi-
crobes to be tested, and kept for twenty-four hours at blood
heat, are treated  with 1 c. c. of solution of pure potassium
nitrate (0.02 grm. in 100 c. c.) and then with a few drops
of concentrated sulphuric acid.   In the presence of indol
a rose or  deep-red color is  developed.   Spirillum cholerce.
gives  the reaction strongly;  S. Finkleri feebly;  Bacillus
typhosus does not give it.
  Inferences from Culture.—Several difficulties inter-
fere with the  interpretation  of bacteriological  cultures. 
SANITARY  APPLICATIONS.
95
All natural waters contain microbes, the proportion being
subject  to great variation, without corresponding variation
in sanitary quality.   Many of the forms are harmless in
any  proportion.   Their number  is subject  to  rapid in-
crease for a brief  period after collection of the sample, and
may be greatly modified by  incidental conditions  during
storage or transportation, so that little value can be attached
to quantitative determinations, except  when made without
appreciable delay.  The culture fluids used, and the condi-
tions under which the cultivation takes place, do not suffice
for the development of all the  forms  present.  The culti-
vation ought to be extended over many days and  different
samples of the same water tried with various nutritive media
and  at  various temperatures, to secure  a full knowledge of
the microbes present.
   As an indication of the insufficiency of these methods, it
may be mentioned  that Miller has described six  species
of microbes occurring  in the  human  mouth, not  one of
which will  grow in any form  of culture medium at present
known.
   While, then, these examinations are  as  yet of uncertain
value in the determination of the potability of water, they
have been  of  much value in determining the effects and
usefulness of certain conditions to which water  is subjected.
In these studies the method is sufficiently  free from  fallacy
to make the results  trustworthy.  By it, it has been shown
that  filtration  at  first greatly  diminishes the number of
microorganisms, but subsequently, owing  to the fouling of
the filter,  and partly  to  the penetration  of successive
colonies of microbes through  the pores  of the filter, the
filtrate   becomes  richer  in  microbes   than  the  unfiltered
water.   When  suspended mineral  matters  are caused  to 
96
BIOLOGICAL EXAMINATIONS.
settle, a large proportion of the microbes is carried down;
but if  the  water thus purified is not soon removed, the
microbic life again  develops, it  may be  even in greater
amount than was originally present.  The storage of water
at first increases and then diminishes the number present.
The presence of  free acid, even  of  carbonic   acid, is
decidedly inhibitory  to  their  development.   When  mi-
crobes essentially foreign to the water are introduced they
are often soon  destroyed, apparently under the  influence
of  those forms  naturally  present, and therefore,  better
adapted to existing conditions;  but this is by no means
always the case, some of  the  more virulent  pathogenic
organisms having high resisting power.
   Max  Holz (Zeit. f. Hyg., vm,  159)  gives a method of
preparing a potato-gelatin,  in which he finds  the typhoid
bacillus to grow  freely.   If such a culture^ medium  be
treated with 0.05 per cent, of pure phenol, it is found that
the growth of moulds  and liquefying bacilli  is prevented
while the growth of the B. typhosus is merely somewhat
delayed. 
SANITARY APPLICATIONS.
97
CULTURE  PHENOMENA OF  SOME OF THE  MORE IM-
                  PORTANT MICROBES.
                Compiled from Mace and others.
	ACTION ON	ON POTATO.	RELATION	REMARKS
	GELATIN.		TO OXYGEN	
Bacillus butyricus, .	Liquefies.		Anaerobe.	Produces butyric acid.
Bacillus chlorinus,	Liquefies.		Aerobe.	Produces a green color.
Bacillus cceruleus, . .	Liquefies.	Dark bluish film.	Aerobe.	Produces blue color.
Bacillus coli-com-				
mune,......	Does not	Yellowish-	Aerobe.	Not colored by
	liquefy.	green film.		Gram's method.
Bacillus erythro-				
	Does not liquefy.	Reddish film.	Aerobe.	
Bacillus flavus, . . .	Liquefies.		Aerobe.	Forms a yellowish deposit.
Bacillus fluorescens				
liquefaciens, . . .	Liquefies.	Glistening yellow film.	Aerobe.	Strong green fluo-rescence.
Bacillus fluorescens				
putidus, . ...	Does not liquefy.		Aerobe.	Greenish fluores-cence.
Bacillus subtilis, . .	Liquefies	Cream-col'd	Aerobe.	Occurs in hay in-
	slowly.	film.		fusion.
Bacillus typhosus, . .	Does not	Thin, glairy	Facultative	Not colored by
	liquefy.	film, harsh and resist-ing.	anaerobe.	Gram's method; does not give indol reaction.
Bacillus violaceus, . .	Liquefies	Brownish	Aerobe.	Violet color pro-
	rapidly.	film.		duced only in the presence of oxy-gen ; reduces ni-trates to nitrites.
Micrococcus aquatilis,	Does not liquefy.		Aerobe.	Colonies white and crenate.
Micrococcus prodigio-				
	Liquefies.	Blood red. Old cultures have green-ish lustre.	Aerobe.	Generally intro-duced from the air.
Spirillum cholerae,	Slowly	Grows only	Obligatory	Not colored by
	liquefies.	at moder-ately high temperature, as a thin brownish film.	aerobe.	Gram's method. Gives indol re-action.
Spirillum Finkleri, .	Liquefies	Grows at or-	Aerobe.	Gives indol re-
	rather	dinary tem-		action feebly.
	rapidly.	perature as a gray film with white ragged margin.		
 
98
PURIFICATION OF  WATER.
         PURIFICATION OF  DRINKING WATER.
  The most obvious method of purifying water  is by dis-
tillation.  The process is too expensive for general use, but
is especially adapted for water intended for pharmaceutical
or chemical purposes.  It has also been used for supplying
vessels at sea and in tropical localities in which the natural
waters may be contaminated  with malarial or other germs.
The majority of microbes are killed by short exposure to a
temperature of 2120 F. ;  hence, water may be purified, on
a small scale, by simple boiling.  Freezing does  not have
the  same effect, many microbes retaining vitality for a long
while in ice.
  The self-purification of water, that  is the destruction of
organic matter and  pathogenic microbes, by reason of the
development of  the  ordinary microbes  of putrefaction,
occurs satisfactorily  only  in  alkaline  waters,  hence, acid
effluents check this process.   The addition of lime in suffi-
cient  amount  to give  a  slightly alkaline reaction will be
beneficial.
  The methods  in general  use  for  purifying  water are
simple filtration and the  removal of the impurities by ap-
propriate chemical agents.
  Filtration.—For household purposes forms of carbon,
stone  and sand filters are used, which yield clear filtrates,
but  permit, sooner or later, the transmission of microbes.
The suspended matter  in the water gradually  accumulates
on the surface of the filter, and causes a  great increase in
the  number of the microbes, some species of which appar-
ently  grow through the pores of the filter, and are  carried
into the  filtrate.  The following  are among the more ef-
ficient forms of household filters:— 
SANITARY APPLICATIONS.
99
Fig. 13.
Fig. 14.
   Bischof Spongy-Iron Filter.—The construction of this is
shown in Fig. 13.  The spongy iron
is obtained by reducing  haematite,
at a temperature below  the fusing
point of iron.
   It rests on a  layer of pyrolusite
(manganese  dioxide), below which
is an  asbestos bag  having a short
tube with perforated cap.   This is a
very efficient form, removing much
            of the dissolved organic
            matter,  and practically
            all the suspended matter,
            including the microbes.
              Chamberlain -Pasteur
            Filter.—This consists of
            tubes of unglazed biscuit-ware,  the  number
            depending on the size and required delivery of
            the  filter.   Fig. 14  shows the
            arrangement for continuous fil-
            tration by attaching the tube to
            the  faucet.   Fig. 15 shows  a
form adapted to simultaneous cooling and
filtration.  The observations of Pasteur and
others  have  shown  that  this is a  highly
efficient  filter, yielding for a considerable
time a filtrate entirely sterile.   It requires
occasional cleaning, since, after continuous
use,  the microbes  may pass through  the
pores,  probably  by  a  process of growth.
An occasional  boiling  of  the tubes  in  water would  be
sufficient to overcome this difficulty.
Fig. 15.
 
ioo
PURIFICATION OF WATER.
  Fig. 16 shows a form of sand filter  which is used in the
laboratory of  Professor Kemna, at Antwerp.   A  moder-
                            ately wide and stout tube  is
                            passed  to the bottom of a
                            tall jar, and the intervening
                            space filled  to the depth of
                            about  twenty-five centime-
                            ters with fine sand,coarse sand
                            and gravel, as shown.  The
                            exit tube consists of a siphon,
                            the outer  leg of  which does
                            not quite  reach to the level
                            of the surface of the sand,
                            the inner leg reaching to the
                            bottom of the jar.  The flow
may be controlled by a  stop-cock attached to the outer
leg.   The object of this arrangement  is  to prevent  the
water level being drawn to or below the level of the sand.
The filter should be supplied from a reservoir by means of
a siphon, the exit tube  of which is curved upward,  in
order to prevent disturbing  the  deposit which collects on
the surface of the filter.
  The filter  may be cleaned by removing  the  siphon and
sending a slow current of water down the  wide tube until
the deposit  upon the surface of the sand is washed out.
The apparatus  is especially suited  for  laboratory experi-
ments on filtration.
  For the purification of drinking water on a large scale,
sand filter beds have been found  to be  efficient; but the
best results are obtained only under proper supervision.
  Numerous determinations of the efficiency of sand filter-
ing basins have been made by bacteriological and chemical
C««i . . . . 
                SANITARY APPLICATIONS.             IOI

methods.   It has been found that, at the start, a large pro-
portion of  the  organic matter, dead  and  living, passes
through;  but that as filtration proceeds, the surface of the
sand becomes covered with a close deposit, which acts both
as a means of retaining suspended impurities and, by  its
active  microbic life, destroys the organic matter in a man-
ner analogous to  that occurring  in  soil.  The water thus
becomes practically free from  microbes, but after a time
these gradually penetrate the pores of the filter and appear
in the  filtrate.  Increase of pressure  will hasten this effect.
   Bertschinger  (Jour.   Soc.  Chem.  Ind.,  Dec.  1889;
abstract)  has published  observations on  the efficiency of
the sand filters in use at  the Zurich Public Water-works.
The filtering material rests on a brick grating, and consists
of the  following layers,  commencing at the bottom :—
   5 to 15 cm. of coarse gravel, 10 cm. of garden gravel,
15 cm. of coarse sand  and 80  centimeters  of fine sand.
As soon as the diminution in pressure of water, due to the
resistance of the filter, is from  60 to  80 cm., the filter is
cleaned by allowing the water to run off and  removing the
top layer of sand to a depth of 2 cm., as this  is found to
contain the whole of the mud.   The filter  is then  filled
up with filtered water from below,  and  washed by allowing
this to overflow.  After filtration has  recommenced, the
first portion of the filtrate is rejected.    Two of the filters
are arched over; these  require cleaning once in seventy-
seven days ; the others once in forty-eight  days.  As soon
as the layer of fine sand has been reduced to  the thickness
of 50 cm., fresh sand is substituted  or more added, until
the depth is again  80 cm.  Among the conclusions reached
are the following :—
  Under normal conditions  the  filtered water is free from 
102
PURIFICATION OF  WATER.
 microbes, although a  few are taken  up again in the later
 stages of the filtration.
   After  cleaning  the  filter, the water  which first passes
 through  is not  in  normal  condition.   It contains many
 microbes, the efficient  layer of scum not having had time to
 collect on the sand, though  the  chemical purity of  the
 water is satisfactory.
   When the filters have not been  used for some time,  the
 water which first passes through them contains more bac-
 teria  than usual, owing  to their  rapid multiplication  in
 stagnant water, but its chemical  purity is not materially
 different from the normal filtered water.
   Precipitation  Methods.—The  observations  of  Dr.
 P. F. Frankland and others, have established the following
 points: —
   " Organized matter is, to a large and sometimes to a most
 remarkable extent, removable from water by agitation with
 suitable solids in a fine state of division, but such methods
 of purification are unreliable.
   " Chemical precipitation is attended with a large reduc-
 tion in the number of microorganisms present in the waters
 in which the precipitate is made to form and allowed  to
subside.
   " If subsidence either  after agitation or after  precipita-
tion be continued too long, the organisms first carried down
 may again become redistributed throughout the water."
  It is essential, therefore, that the  liquid be  filtered  as
short a time after the precipitation as possible.
  A  small  quantity  of alum added to  water is decom-
posed with the formation of a flocculent precipitate of  alu-
minum hydroxide, which settles comparatively rapidly, and
carries down with it all.suspended matters, as well  as a large 
SANITARY APPLICATIONS.
103
proportion of the dissolved organic matters.  Waters which
contain such an excess of organic matter as to be distinctly
colored, may usually be made quite clear and colorless by
this treatment.   Two grains  of alum to the  gallon  will
suffice for  the purpose, but  if very rapid  subsidence is de-
sired  more may be added.
  Several systems of filtration now in extended use employ
this precipitation  method in conjunction with filters of small
area,  the  necessary flow being obtained by increased pres-
sure.   The Hyatt  and  National systems belong to  this
class.  The differences between the various forms are chiefly
in  the mechanical  arrangements for supplying the water
and for cleaning the filter.  The material is generally sand
or  coke ;  the cleaning is performed at short intervals, by
means of reverse  currents of water.   The alum solution is
introduced as needed by automatic apparatus.
  These filters are efficient, and are suitable for the purifi-
cation of water for manufacturing establishments, and when
large basins are not available.

  The addition of an iron salt to water containing carbon-
ates, is attended with decomposition and the formation of
a precipitate of ferric hydroxide.  This  reaction has been
employed with great advantage as a means of purification.
One  of these methods was by passing the water  through
spongy iron, then aerating to precipitate the iron,  and  filt-
ering through sand.   The method is very efficient, but the
spongy iron gradually chokes  by oxidation, and  becomes
useless.  This difficulty is removed by the use of iron bor-
ings or punchings, contained in an iron cylinder (Anderson
and Ogston, Proc. Inst.  Civ. Eng. Vol. 81), which is rotated
while the water passes  through ;  the iron is brought into 
io4
PURIFICATION OF  WATER.
thorough  contact  with the water, and there is  sufficient
abrasion to keep its surface clean.
  The apparatus as practically employed is shown  in Fig.
17. It consists of a  cylinder rotating in a horizontal position,
attached to the internal periphery of which are short curved
shelves, arranged at equal distances.  Fipes enter the hollow
trunnions  to admit and discharge  the water.  As it enters
the cylinder, the water strikes against a circular distributing
plate, and is caused to flow radially through a narrow an-
nular space,  to prevent the formation of a central current
along the axis of the purifier.   The inner  end of the out-
let pipe carries an inverted bell-mouth which catches  the
fine  particles of the iron  carried  forward by the   water,
and causes them to fall again to the bottom of the cylinder.
Sufficient  borings  or  punchings   to one-tenth   fill  the
cylinder are introduced, and the purifier is then completely
filled with water, and set  in motion, the rate of rotation
being about  six feet per  minute at the periphery.  The
effect of the  rotation is to scoop up the iron particles and
to shower  them down through the flowing water.
  The effect  is  due mainly to the formation of  ferrous
carbonate, through the action of the  carbonic acid of the
water.  On issuing into the open air, this is gradually con-
verted by oxidation into  the insoluble ferric  hydroxide,
which carries down much  of the organic matter and sub-
sequently  oxidizes  and destroys it.   Temporary  hardness
is also decreased by the abstraction of the  carbonic acid
and  consequent  precipitation of calcium  and  magnesium
carbonates.
  The time of contact with the iron depends upon  the
purity of the water.  For Antwerp water, which is purified
by this means, the maximum effect  is accomplished  in 3.5 
Jm$	^TT
JaSi ! f'	ffjr^
	
X.1	'!T"ifi'!i-
105 
106            PURIFICATION OF WATER.
minutes.   After leaving the cylinder,  the water is passed
through sand filters. Analytical examinations show the efflu-
ent water to be of high organic purity and practically sterile.
  Cast-iron borings are  much  more  readily acted upon
than steel punchings.   The latter suffice in operating upon
water rich in dissolved organic substances, carbon dioxide
and  suspended matters,  while the former are  especially
suited  for treatment  of water comparatively pure, and,
therefore, less active.'
  For determining the most advantageous method of treat-
ing any water supply, laboratory  experiments may be made
as follows:—
  A strong wide-mouth bottle holding  about 2000  c. c, is
charged with one-tenth its bulk of clean borings or punch-
ings, filled completely with water and shaken for four min-
utes, in such manner that the iron particles are continuously
showered  through the liquid.   The water is then aerated
by agitating it in a large,  thoroughly clean glass-stoppered
bottle.  With some (e.g.,  peaty)  waters, it will be  of
advantage to allow about 200  c.  c. of air to remain in the
bottle in  which the shaking with iron  is performed, occa-
sionally removing the stopper to renew the  air.   (Con-
tinuous aeration during treatment  is provided  for in  the
apparatus used on the large scale).  The liquid  is allowed
to stand from a few minutes to  four hours, depending on the
rapidity with which the iron separates, and is  then filtered
through  the  sand  filter  (page  100),  or through a well-
washed cotton plug inserted in the neck of a funnel.  Sat-
isfactory  purification  as  regards ammonium  compounds
cannot be obtained, but with  proper attention to cleanliness,
the figures for total organic nitrogen, nitrogen by perman-
ganate, and oxygen consuming power will be trustworthy. 
SANITARY APPLICATIONS.
I07
  The following results were obtained by us in the treatment
of  Delaware river water  at  Lardner's Point  pumping
station, Philadelphia.   The purifier was capable of deliver-
ing 100,000 gallons per 24 hours.   All figures are in parts
per million.
  September, 1890.
                              Before Treatment.  After Treatment.
        Nitrogen as ammonium,       .04          .03
           "     as permanganate,     .27          .09
  November, 1890.
        Nitrogen as ammonium,       .084         .034
           "     by permanganate,    .091          .049
           "     as nitrites,          traces.        none.
  A sample of Schuylkill  water treated in the laboratory,
and  the reduction of total  organic nitrogen determined,.
gave the following figures :—
                              Before Treatment.  After Treatment.
        Total organic nitrogen,      0.36         0.118.
  Sample of water from the Mississippi river at Memphis
Tenn.
                              Before Treatment.  After Treatment.
        Oxygen absorbed at 2I2°F.,   2.88          0.36

     IDENTIFICATION OF THE SOURCE OF WATER.
  The determination of the course of underground streams,
and  of communications between  collections of water, is
often an important practical problem.  In geological and
sanitary surveys, valuable information may occasionally be
gained.  The method  generally pursued when connection
between water at accessible points is to be detected, is to
introduce at one point some substance not naturally exist-
ing  in  the water,  and capable  of recognition in small 
io8
IDENTIFICATION OF  SOURCE.
amount.   Lithium compounds are among the best for this
purpose.   They are not  frequent  ingredients of natural
waters, and are  easily recognized by  the  spectroscope.
Lithium chloride is the most suitable.   The quantity to be
employed will vary with circumstances.   It scarcely needs
to be stated that  the waters under examination should be
carefully  tested for lithium before using the method.
   When  the lithium method is inadmissible, recourse must
be had to other substances of distinct  character, such as
strontium chloride, but this possesses the disadvantage that
a considerable amount may be rendered insoluble, and thus
lost in the ordinary transit through soil.   Recently, use has
been made of organic coloring  matters of high tinctorial
power, one  of the  most suitable of which is fluorescein,
C20H12O5, a derivative of benzene.  This will communicate
a characteristic and intense fluorescence to many thousand
times its  weight of water.  An entire river may be colored
by a few  kilograms.  By its use an underground communi-
cation was demonstrated to exist between the Danube and
the Ach,  a small  river which flows  into the  Lake of Con-
stance.   The coloration is only distinct in alkaline liquids.
Other colors,  such as aniline red, may be employed.   For
detecting leakage from  cesspools  and  cisterns, sanitary
inspectors occasionally employ water colored by Prussian
blue.
   A  more important feature of the problem in a sanitary
point of  view is the determination of the source of a given
current or collection of water, when such source is inaccessi-
ble.  Problems of this character are not infrequent in large
cities in which the systems of water supply and drainage are
defective, thus giving occasion to accumulations of water
in cellars and  similar places.  Often, in these cases, no ex- 
SANITARY APPLICATIONS.
I09
tended explorations can be made, by reason of the adjacent
buildings and conflicting property interests, and  the ques-
tion may arise whether the water proceeds from a leaky hy-
drant, drain, sewer, or subsoil current.   It  is obvious that
in the case of the collection  of water in a cellar from causes
other  than  surface washings or entrance of rain,  it must
have passed through some distance of soil, and in built-up
districts will  almost certainly be  charged with  organic
refuse.   To correctly interpret the results, it will be neces-
sary to know  the general character of the subsoil water of
the district and the composition of the public supply.   As
a rule, the transmission of water through moderate distances
of soil will not materially increase the mineral constituents.
Hence, if the sample contains an excess of dissolved mat-
ters as compared with the water  supply of the district, it
may reasonably be inferred that it is derived from a drain,
sewer, or subsoil current.
   In  these investigations it  will generally be sufficient to
determine  the  total  solids, odor  on  heating,  chlorine,
nitrates and nitrites.   The following figures are from some
results obtained in investigations  made in association with
Mr.  Chas.  F. Kennedy, Chief Inspector to the  Board of
Health of this city :—
                                    CELLAR WATER.
                   CITY SUPPLY.  No. I.     No. 2.     No. 3.
    Total solids,.....115     140     661       640
    Odor on heating, . . .faint     faint     strong    urinous
    Chlorine,......   4       6.4     77.0      128.0
    N as nitrates,  ....   0.7     1.0      3.5     none
    " " nitrites,  ....  none    present   present    none

  Sample No. 1 was taken from a cellar in which a small
amount of water had  been almost constantly present for a 
no
IDENTIFICATION OF  SOURCE.
long time, and of which the source could not be ascertained.
The results of analysis led to the  view that since it  resem-
bled in composition the city supply, it  was derived  from  a
leaky hydrant pipe.  The parties  in  interest  were not in-
clined to accept this opinion, but the  examination  of the
condition  of  the hydrant on an adjacent property showed
a leak, which being repaired the water  ceased to appear in
the cellar.   In this case it was found  that the water had
passed through twenty-two feet of earth.  In the %econd case
the sample- is seen to be very impure, and it was suggested
that it was derived directly from a leaky drain, which upon
exploration proved to be the case.  In the third sample, the
high chlorine, strong urinous odor and absence of nitrates
and nitrites  pointed unmistakably to  recent and profuse
contamination with sewer water.
   Occasionally the analytical results will be ambiguous, and
it  is advisable to make examinations  of more  than one
sample,  since accidental circumstances, rain-fall, etc., may
affect the composition of the water.
   Instances of the contamination of water by unusual sub-
stances are occasionally noted, and these sometimes afford
a clue to the source of  the water.  Among the instances
of this kind within our own experience  may be noted the
contamination with petroleum  and with soap.  In  the
former case it was evident that the contamination was from
a -leaky pipe  connecting  two refineries.  In the latter  it
was shown to be derived  from an adjoining building used
as a laundry. 
TECHNICAL APPLICATIONS.
Ill
             TECHNICAL APPLICATIONS.
   Boiler  Waters.—The  main  conditions affecting  the
value of a water for steam making purposes are its tendency
to cause corrosion and  the formation of scale.   Corrosion
may be due to the water itself, to the presence of free acids,
or to substances which  form acids under the influence of
the heat to which the water is subjected. Pure water, e.g.,
distilled ^.ter, exhibits a powerfully corrosive action upon
iron.  The dissolved oxygen which all waters contain also
aids in the corrosion, and especially when accompanied, as
is usually  the case, by  carbonic  acid.   There is always
greater rusting at the point at which the water  enters  the
boiler, since there the gases are driven out of solution and
immediately attack the metal.  This is an evil that obtains
with all waters, and it is not customary, in making examina-
tion for technical purposes,  to  determine the  amount of
these bodies.  In water that  has had free access to air, the
oxygen in solution is a  tolerably constant quantity, and it
is sufficient to note the  temperature and refer to the table
of amounts of  oxygen  dissolved  in water.   The  corro-
sive  action of  oxygen  and carbonic  acid  is  especially
noticeable  in  waters  that are comparatively pure, such as
those derived from mountain springs.  This was  repeatedly
observed by one of us  in the examination of  the  waters
used for the locomotives of the Baltimore and Ohio railroad.
The waters which caused the most corrosion were mainly
those  containing small quantities of solid matter, the full
amount of oxygen and considerable carbonic acid, but  no
other acid or acid-forming body.
   Free acid, other than carbonic acid,  is not often  found
in water, and  if present renders  the  water unfit for use, 
112
BOILER WATERS.
unless it be neutralized.  Mine waters are the most likely
to contain free acid, sulphuric acid being generally present.
Sometimes the acidity is due  to organic acids.  These act
very injuriously on iron.   Allen gives an example of this
in the water supplied to Sheffield, Eng., which he found
to contain an organic acid in amount equivalent to from
3.5 to 10 parts of sulphuric acid per million.
  Magnesium chloride is frequently present in waters, and
if in considerable quantity may be very harmful. ^At a tem-
perature of 3100 F., corresponding to an effective pressure
of four atmospheres/magnesium chloride reacts with water
to  form  magnesium  oxide  and  hydrochloric  acid,  the
latter attacking the boiler, especially at the water line.   If
there is present at the  same time  considerable calcium
carbonate the  evil  may  be  somewhat  lessened, but  as
Allen has  pointed out, and as we also have noticed,  there
may still be corrosion, so that the presence of more than a
small quantity of the salt, say a grain or two to the gallon,
may be considered objectionable.   Allen remarks that the
presence of a  certain amount of sodium chloride  may
prevent this decomposition,  the two chlorides  combining
to form a stable double salt.   The  addition, therefore, of
common salt to a water containing  magnesium chloride
may act  to diminish corrosion, a point which will bear
further investigation.
   It has not  been determined how far  the presence of
nitrites, nitrates and ammonia affects the quality of water
for steam-making purposes;  but it is more than  probable
that they act harmfully, especially the nitrates, which are
frequently present in large amount.
   Scale is composed of matters deposited from the water
either by the decompositions induced by the  heat or by 
TECHNICAL APPLICATIONS.             113
concentration.   When  the  deposit  is  loose it is termed
sludge or mud, and usually consists of calcium  carbonate,
magnesium oxide and a small amount of magnesium  car-
bonate.  The magnesium oxide is formed by the decompo-
sition of the  magnesium carbonate and chloride.  This
fact was first pointed out by Driffield (J. Soc. Chem. Ind.,
vi, 178).
  The formation of sludge is the least objectionable effect,
since it rnay readily be  removed  by " blowing off," pro-
vided  that care is previously taken to  allow the  flues to
cool down so that  when the water  is removed the heat of
the flues may not bake the deposit  to a hard mass.  Waters
containing calcium sulphate  form  hard  incrustations diffi-
cult  to remove and causing great loss  of fuel by inter-
fering with the transmission  of the heat to the water.  It
not only forms a  hard incrustation in itself, but  becomes
incorporated with  the mud and renders it  also hard.   The
hard scale will also contain  practically all the silica  and
the iron and aluminum  present in the  water, besides  any
matters originally held in suspension.
  It follows from the  above  that a water only temporarily
hard, will, if care is taken in  the management of the boiler,
cause the formation merely of a loose deposit of sludge—
temporary hardness being due in the main to calcium  and
magnesium carbonates.   A  water  permanently hard  will
probably form a hard  scale, since such hardness is -usually
due to  calcium sulphate.
  In accordance  with  these principles, the analysis of a
water for steam-making  purposes may include the determi-
nations of free acid, total solid residue, S04, CI,  Ca, Mg,
temporary and permanent hardness.  In cases in which the
qualitative  tests show but small amounts of S04 and CI, 
114
BOILER WATERS.
the analysis may be limited to the determinations of the
temporary and permanent hardness.
  It has  been pointed out in  an  earlier chapter that it is
not possible to deduce from the analytical result the exact
forms  in which the various elements  are  combined, but
since it is known that at the high temperature ordinarily
reached  in  boilers definite chemical changes occur, it is
safest to  exhibit  the  maximum amount of  corrosive and
scale-forming ingredients which the water  under these cir-
cumstances  could  develop.  Thus, since calcium sulphate
is practically insoluble in  water above  212° F., the pro-
portion of calcium sulphate may be regarded  as such as
would  be formed  by the  total quantity of calcium or the
total quantity of S04, according to which is  present in the
larger amount.   Similarly,  as the decomposition of magne-
sium chloride is  induced by the  high temperature of the
boiler, the  analytical statement should indicate the maxi-
mum proportion of this compound obtainable from  the
magnesium and chlorine  present.   These rules cannot ap-
ply absolutely to  waters rich  in  alkali carbonates, since
these would neutralize any acid  formed from the magnesium
chloride, or even prevent its formation, and would prevent
to a large extent the formation  of calcium sulphate.  Much
remains to be determined concerning the  effects  of the
high temperature and concentration to which boiler waters
are subjected.
  Purification of Boiler Waters.—The  problems pre-
sent  in the treatment of  boiler  waters are  usually  the
removal of the calcium carbonate and  sulphate, and mag-
nesium carbonate  and  chloride.   Both  carbonates  are
appreciably  soluble in pure water.   About  one  grain of
calcium carbonate to the gallon is  usually stated to be the 
TECHNICAL APPLICATIONS.
1*5
proportion dissolved, but it has been pointed out by Allen
that solutions can be obtained containing twice this amount.
If the water contains carbonic acid it will take up a much
greater proportion of the carbonates, but in this case they will
be deposited from the solution by boiling. This has been ac-
counted for by supposing the existence of soluble bicarbon-
ates, which  are decomposed by the boiling.   Nearly all of
these carbonates can be thrown out of solution by any means
that will deprive the water of the carbonic acid.   Sodium
hydroxide is usually the best for the  purpose, and  should
be added  in quantity just sufficient to form normal sodium
carbonate.  If there are present  in the  water calcium and
magnesium  chlorides and  sulphates, these also will be de-
composed and precipitated by  the  sodium  carbonate  so
formed.   If the amount  of sodium carbonate formed is not
sufficient  to decompose all  of  these bodies, a  sufficient
quantity should be added with  the  sodium hydroxide  to
effect  the complete  decomposition.   The  precipitate  is
allowed to settle or filtered off.
  In cases in which the feed-water is heated before it enters
the boiler, it  may only be necessary to add  to  the  water
sodium carbonate in quantity sufficient  to decompose  the
calcium and magnesium  chlorides and sulphates,  since the
heat alone will suffice to  throw down the carbonates.
  Care should be taken  in  these precipitations that no
more sodium hydroxide  is added than  is required for the
precipitation, since any excess would  tend to corrode the
boiler.
  Clark'sprocess consists in treating the  water with calcium
hydroxide (lime-water).   This precipitates the calcium and
magnesium  carbonates by  depriving  the water of its free
carbonic acid.   It  has, of course, no effect  upon the cal- 
n6
BOILER WATERS.
cium sulphate.   It is to be noted  that the proportion of
calcium hydroxide which is to be added must be calculated
from  the  amount of free  carbonic acid existing  in  the
water, and not  from the amount of carbonates to be re-
moved.  The precipitate will usually require at least twelve
hours for complete subsidence, but after three or four hours
the water will be sufficiently clear for some purposes.  If a
filter press is used, as in Porter's process, the time required
for clarification  is very much shortened.   Another advan-
tage of this process is the use of a solution of silver nitrate,
in order to determine more conveniently the proportion of
calcium hydroxide which is to be employed.  The lime is
first slaked  and dissolved in  water, and  the water to be
softened run in and thoroughly mixed with it.   From time
to time small portions  are taken out and  a few drops of  a
solution of silver nitrate added.  As long as the lime  is in
excess a brownish coloration  is produced.   When this has
become quite faint, and just  about  to disappear, the addi-
tion of the water is  discontinued, and, after a short time,
the water is filtered by means of the press.

   Soluble phosphates added to  a  water,  precipitate com-
pletely in  a flocculent condition any calcium, magnesium,
iron or aluminum.   This reaction can  be best applied by
using the tri-sodium  phosphate (Na3P04 -f- i2H20), which
is now a  commercial  article.   By reason of  the facility
with which this substance loses a portion of its sodium to
acids,  it acts not only as a precipitant to the above mate-
rials, but will neutralize any free mineral acid present in the
water.  From evidence submitted by those who have used
the process on the large scale, it appears that  not only is
no hard scale formed, but that scale already existing prior 
TECHNICAL APPLICATIONS.
117
to its use is gradually disintegrated and removed with the
sludge.   Experiments  indicate that no injury results from
an excess of the material;  but the economical employment
of the  method, especially with very hard waters, can only
be based upon a correct analysis, and an estimation of the
phosphate  required for the  precipitation.   In many cases
the composition of the water will  be such that a partial
precipitation will be sufficient.

   Waters rich  in  ferrous  compounds  may be purified by
thorough aeration  and filtration, the iron  being separated
as ferric hydroxide.   Simple filtration through a bed of
manganese dioxide will accomplish the same purpose.
   General Technical Uses.—In regard to the quality
of water for technical  other than steam-making purposes,
such  as brewing,  dyeing,   tanning,  etc.,  no  detailed
methods or standards can  be laid down.  The nearest
approach to purity that can  be secured in the supply will
be  of  the  greatest advantage.  The  more objectionable
qualities will be large proportion of organic  matter, espe-
cially if it  distinctly colors  the water, excessive hardness,
and notable amounts of iron  or free mineral  acid.  It is
stated  by Bell (Jour. Soc. Chem., Ind.) that one part  per
million of  iron will  render water unsuitable for bleaching
establishments.  It has been noted that a large proportion
of active microbes is injurious in the manufacture of indigo.
In artificial ice making, a very pure water  must  be used if
a clear and colorless product  be desired.   Any suspended
or dissolved coloring matter will be concentrated by  the
freezing and appear in the  bottom or centre of the mass.
The Antwerp water, purified by the Anderson process, is 
n8
SEWAGE EFFLUENTS.
used with entire satisfaction for the manufacture of artificial
ice in that city.
   The examination  of  sewage effluents and waste waters
from manufacturing establishments is to be conducted upon
the same principles  as  for ordinary supplies, but especial
attention must be  given  to the presence  of poisonous
metals, and  free mineral acids.   The  latter interfere with
the normal self-purification of the water.   For the nitrogen
determination,  the Kjeldahl  process will be  found more
satisfactory than that by alkaline permanganate. 
ANALYTICAL  DATA.
FACTORS FOR CALCULATION.
Parts per   100,000   X
         1,000,000   x
          100,000   x
         1,000,000   x
         1,000,000   X
Grains"  Imp. gallon  -5-
          t<    <<
         U. S.   "
A1203,  .
AgCl,  .
BaS04,
BaS04,
BaS04,
B203,  .
CaO,   .
CaCOs>
Fe203,  •
KC1,   .
Mg,P207,
Mg2P207,
MnS,  .
NaCl,  .
7     = Grains per Imperial Gallon
07    =   "    "     "     "
583   =   "    "   U. S.
058   =   "    "     "     "
00833 = Av- pounds per 1000 U. S. Gal.
7     = Parts per   100,000
07    =   "   "   1,000,000
583   =   "   "    100,000
058   =   "   "   1,000,000
534	= Al
2473	= CI
588	= Ba
J373	= S
412	= so4
3M3	= B
7H3	= Ca
.40	= Ca
■7	= Fe
•524	= K
.2162	= Mg
.856	= P04
.632	= Mn
394	= Na.
119 
Cn +. Co to i-i O no 00--I OnCm +nU m m o^O 00^1 Oni/i 4^ Co	to «	FARTS PER MILLION.
		CO JO • >
I.WOjMHhhO^O'OOO OO^t On ONCn Cn 4* 4*- Co to to w ui NO Co ^J "-1 On O -£■ OONM "UHOOJ OOtO On O 4>- no Co ^J O to 4^ OnOOO 104* On 00 O to 4* On 00 O 104^ OnOOO to 4*	« o ON 00	S 2 r ^ 2! f°
		2 <n •0 w *
■<! On OnUt 4^4>-Oo to ii i-i b NO *b 00--J --J CNCn 4^ 4* Co to to ux oo i-i 4^. -~a O Co OnnO to 4* 00 ~ 4*- -J O Co Onno NUi 00m	- o 4- «-4	AINS ER GAL.
 MMM»Nj)klM»f)MIOjJjOIOlOMMMHNHMMM

*b  00--J "-J ON OnCti 4* 4^ Co Co  to  to  m  O O NO NO  00--1 *J ON ONCn Vyi
 0 4n  00 to On »« Cn NO Co ^] to  O\04>  OCCo --1  -Ui'0 4> 00 to  OO
 0  to -(*• ONOOO  to 4*  ONOOO  to 4^  ONOOO to +.  OnOOO to 4"  OnOC
WOjOJU(»)WOJ(rilOMt)»MNIOIOMM|OMNtOM  mhh

UiiojNK>«bb>bbo 00-<r  °ONCn On 4^. Oj CO  tO  «  !h O *b  00 00
 O Co  OnnO to en  OOh^si QCo  On^O to Cn 0Om*vj  O <" On^O  to
t"1 *3 >
C W fO
O * H
•   >
p 5
y -a
~ w > 
TABLE  OF  DISSOLVED OXYGEN.
121
Diudin's Table of Oxygen  Dissolved by  Water at Various
  Temperatures, extended to Give the Weight of Oxygen
    Per Liter.  Corrected to o° C.  and  760mm.  Pressure.

                                  CUBIC INCHES OF      MILLIGRAMS
 TEMPERATURE       TEMPERATURE  OXYGEN PER GALLON     OF OXYGEN
 FAHRENHEIT.       CENTIGRADE.     (7000O GRAINS).       PER LITER.
     41°......5-00°.....2.IOI......10.84
     42 ".  '.  '.  '. '. .   5-55.....2.074......IO-72
     43......6.11.....2.048......10.57
     44......6.66.....2.022......10.45
     45......7.22.....1.997......10.30
     46......7-77.....J-973......lo-l&
     47......8-33.....»-949......IO°6
     48......8.89.....1.927......9-94
     49......9.44.....i-9°5......9-83
     50......10.00.....1.884......9-72
     51......10.55.....1 864......9-DI
     52......11.11.....1844......9.51
     53......11.66.....1.826......9.42
     54    .....12.22.....1.808......933
     55  [.....12.77.....1.791......9-24
     56......13-33.....x-775......9-15
     57......13.89.....1.760......9.08
     58......14-44.....!-746......9-DI
     59    .....15.00  ..... I-732......8.94
     60......15-55.....i-7'9......8.87
      61......16.11.....1.706......8.80
      62  ...... 16.66.....1.695......8.74
      63  [.....17.22.....1.683......8.68
      64  !.....17-77.....x-674......8-64
      65      .... 18.33.....I-667......8.60
      66  1  1 ...  . 18.89.....I-66°......8-56
      67......19.44.....1-652......8.52
      68......20.00.....1.644......8.48
      69  !  ! !  .  .  . 20.55.....1.639......8-45
      70......21.1 I.....1-634......8.43
  The table is calculated for a barometric pressure of 760 mm., and would require
 corrections for  variations from  this, but such corrections are mostly within the
 limits of experimental error.
I 
122     ANALYSES OF RAIN AND SUBSOIL WATERS.
ANALYSES OF RAIN AND SUBSOIL WATERS.
PARTS PER MILLION.
	From.	19 "5 w "n 0 H	c u	c	X	6 z,	z
Rain water. Subsoil water.	Bellefonte—collected by Prof. Wm. Frear, after long rain. Wynnewood—pool fed by underground spring. Wynnewood—well about 150 yards from above. Wynnewood—well pol-luted by farm-yard drain-age ; about 500 yards from pool. Pump - well in densely populated district. Highly contaminated. Newly dug well in popu-lated district. Highly con-taminated. Well at Barren Hill, 130 feet deep.	5 65 60 1120 620 470	none 6.20 4.00 16.00 5700 120.00 120.00	0.148 0.032 0.024 0.208 1.00 0.08 undet.	0.280 0.024 0.016 0.028 3.120 2.00 undet.	none none none none O.OI 0.03 traces	none 2-3 3-5 14.2 33-° 16.0 22.0
 
RESULTS FROM SCHUYLKILL RIVER—Parts per Million.
Samples taken from hydrant at 715 Walnut Street.
1888.	State of Weather.	Condition.	Total Solids.	Nitrogen by KMn04.	Nitrogen as NH4.	Nitrogen as NO,.
Sept. 17.	Continued rain.	Turbid.	160	.06	.048	None.
" 18.	Continued rain.	Muddy.	160	.09	.020	"
" J9-	Clear.	Turbid.	140	.108	.004	Trace.
" 20.	"	"	150	.124	None.	Faint trace.
" 21.	"	Less turbid.	150	.132	"	None.
" 22.	"	Very muddy.	180	.180	"	Faint trace.
" 24-	"	Turbid.	140	.100	"	None.
" 25.	"	Slightly turbid.	130	.092	"	"
" 26.	'*	Slightly turbid.	120	.068	.01	
" 27.	"	Very slightly turbid.	no	.056	None.	"
*' 28.	"	Very slightly turbid.	105	.052	"	"
" 29.	"	Nearly clear.	"5	.052	.008	"
Oct. 1.	"	It n	140	.052	.012	
" 2.	»	" "	125	.044.	None.	"
" 3i	<«	" "	120	.080	.016	"
" 4-	"	Clear.	120	.084	.008	"
" 5-	"	"	120	.092	.012	
6.	Rain.	"	120	x6o	.012	"
8.	• •	Turbid.	150	.108	.008	"
" 9-	Clear.	Slightly turbid.	130	.088	.008	"
" 10.	"	Almost clear.	12s	.056	.010	"
" 11.		Clear.	US	.044	.010	
 
ANALYSES OF  ARTESIAN WATERS.
         MILLIGRAMS  PER LITER.
	Philadelphia.						Baltimore.	Indiana.
	•et/3 n ■B a OMI o	> < •a c c 0 rt ho ■2 S N S3	•s! y?«	0 s «l U	T3 i2 cert "Si 0 u 0	c s	*. a '0 3 0	u a >>
Condition, .... Reaction..... SiO,....... so4,...... P04)...... CO, (combined), . CI,...... H2S,...... Mn,........ Fe,....... Ca,....... Mg,....... Na,....... K,........ Nby KMii04, . . " as NH4, . . . " " X()„, . . . "" no;, . . .	Clear. Alkaline. 36.00 61.80 0.24 64.91 89.21 9.80 54-57 15-27 54-13 4.14 0.032 0.248 Trace. Trace.	Clear. Alkaline. 34-5° 36.26 0.31 no.17 91.77 Trace. 7.70 44.28 7.98 84.13 8.54 Not det. Not det. None. Trace.	Slightly turbid. Alkaline. 35.00 9.90 0.31 54.80 108.50 5-7° 50.00 12.60 32.46 4.10 0.048 0.034 None. None.	Clear. Alkaline. 24.00 25.84 Trace. 78.84 206.01 1.80 528 125.00 30.70 72 -34 Traces. 0.048 0.032 0.02 2.00	Clear. Alkaline. 29.00 15.24 Trace. 108.64 172 00 4-32 101.42 22.27 55-83 6.28 0.015 0.004 Trace. 1.00	Clear. Alkaline. 19.50 102.36 0.38 50.64 554-48 1.05 53-57 6.48 37863 Trace. 0.148 0.132 None. None.	Clear. Alkaline. 4.00 4.10 4.68 25 0.86 0.012 0.044 None. None.	Clear. Alkaline. 190.2 0.035 0.315 None. None.
* We are indebted to Mr. Wm. Glenn, Chemist of the Baltimore Chrome Works, for this sample. 
ANALYSES OF WATER  SUPPLIED TO CITIES.      125
Table showing the Relative  Purity of the Water  Supplied
        to Cities, from the Determinations made in
                  June, 1881, by A. R. Leeds.
Parts per million.
Total solids,  ....
  "   hardness, . .  .
Chlorine,......
Oxygen -consuming
  power,......
Nitrogen by KMn041
Nitrogen in a m m o-
  nium compounds. .
Nitrogen as nitrites.
    "   " nitrates.
2 a. T3	0 >	c 0 0	U >>	e 0 0	c 0 oi c 15	0 0 <A
J3	£	«	1—>	85.0	115.0	
I43-0	118.0	60.0	93-o			100.0
44.O	33-°	22.7	32.0	21.0	48.0	550
3-°	3-5	5-5	2-35	3'5	2.70	i-95
4.6	8.1	4-i3	9-5	17.7	6.00	7-9
•'4/	.221	.067	•344	.496	.221	.188
.008	.022	.006	■039	.108	O.49	•°93
None.	None.	None.	None.	None.	None.	None.
1.51	1 84	2.69	2.01	2.75	1.84	1.39
 
 
INDEX.
 A CIDS, action on lead, 84
•**•  Actinic method for organic matter,
       41
Action of water on lead, 83
Aeration of water, 81
Agar-Agar, 87
Albuminoid ammonia, 26, 72
Alkali carbonates, determination of, 61
Alkaline permanganate, 25
Allen, on boiler waters, 112
------, lead in water, 84
------, sulphuric acid in water, 112
------, test for zinc, 58
Alum, action of, 102
------, use of,  102
Aluminum, determination of, 53
------, in  scale, 91
Amido-naphthaiene, 36
Kmmonia, albuminoid, 26
------,free, 25
------, free water, 25
------, from rain water, 75
------process, 26
Ammonium chloride, standard, 25
------molybdate, 42
------picrate solution, 34
Analysis, statement of, 70
Analytical operations,  16
Anderson  and Ogsten,  purification of
  water, 103
Animal matter, 73
Antwerp water, purification of, 104
Artesian water, 9, 14
------waters, composition of, 124
Arsenic,  detection of, 48
------, effect of, 73
TDACILLI, species of, 97
■^  Bacillus typhosus, culture of, 96,

      •  97
Bacteria in water, 85, 97
Bacteriological examination, 85
Barium, detection and estimation of, 48
Barren Hill well, 15, 122
Barus, Carl, suspended matters in water,
  n
Basin, platinum,  19
Bicarbonates in water, 115
Biological examinations, 85
Black's Island well, 73, 124
Blarez' oxygen process, 44
Boiler mud, 113
------water, in
------water, points to be determined in,
        "3
------------, purification of, 114
------------, statement of results from,
               "4
Boric acid estimation, 64
Bottle culture, 91
------for test solution, 23
Burner, low temperature, 20
 f ALCIUM bicarbonate, 115
 ^------carbonate, action in boiler
              waters,  113
 ------------, solubility of, 115
 ------compounds, removal of, 115
 ------, determination of, 54
 ------hydroxide for. purifying  water,
        "5
 ------sulphate, insolubility of, 113
 ------sulphate, action in boiler  water,

        113
 Carbonates, action on lead, 84
 ------, determination of normal, 61
 Carbon filters, 98
 Carbonic acid, action of, 14
 ------------, free, determination of, 63
 -------------, effect on microbes, 93
 Carleton-Williams, lead in water, 84
 Carnelly and Frew, lead in water, 84
 Caustic soda, use of, in boiler water, 115
 Cellar waters, examination of, 109
 Chlorine, determination of, 22
------, significance of,  74
Chromium, detection of, 48
City supplies, 125
Clarifying water, 17, 102
Clark's process for purifying water, 115
Color comparators, 29
------, determination of, 18
------, significance of, 72
Comparison cylinders, 29
127 
128
INDEX.
Control determination, 21, 56
Conversion of ratios, 119, 120
Cooper, A. J., delicacy of tests, 53
Copper, detection of, 52
------, effects of, 73
------sulphate, standard, 52
Corrosion of boilers, m
Crookes, Odling and Tidy, lead in water,
  83.
Cultivation of microbes,  86
Culture media, 86
D1
   kEEP water, 14, 74, 124
     Demijohn for water samples, 16
Dibdin, table of dissolved oxygen, 121
Distilled water, wholesomeness of, 73
Driffield, composition of boiler mud, 113
Drown and Martin, nitrogen determina-
  tion, 31
Dupre, dissolved oxygen, 47, 81
■pERMENTATION, butyric, 25
■*■    Ferrous   ammonium   sulphate,
        standard, 44
Ferric sulphate, standard,  50
Filter paper, 17
Filters, BischofFs, 99
-----, Pasteur-Chamberlain, 99
-----, sand, 100
-----, spongy iron, 99
Filtration, effect of, 101
Fleck's silver method, 41
Fluorescein, use of, 108
Forceps, platinum, 20
Frankland, purification by precipitation,
  102
------and Tidy, standards of purity, 80
------nitrifying bacillus, 13
      ■ ammonia, 25, 76
Frew and Carnelly, lead in water, 83


   GALLON, Imperial, 70
     -----, U. S , 70
Gelatin culture media, 86
------, liquefaction of, 92
Gerardin, dissolved oxygen, 81
Gooch, method for borates, 64
■------, method for lithium, 59
tTARDNESS, determination of, 62
      ------, permanent, 62
------, temporary, 62, 114
Hard scale, 113
------water, sanitary relations of, 82
------water, softening of, 115
Hehner, limit of phosphates, 73
Hehner's  cylinders  for color compari-
          son, 29
Hehner's method for hardness, 62
Heisch's test, 43
History of water, 9
Hunt, T. Sterry, water in rocks, 12
Hyatt filter, 103
Hydrogen sulphide,  titratiqn of, 60
IDENTIFICATION  of source   of
■*■  water, 107
Imperial gallon, 70
Interpretation of results, 70
Indol reaction, 94
Iodine, centinormal, 60
Iron, action of, in purification, 104
------compounds, solution by water, 14
------, determination of, 50, 53
------, significance of, 73
TZJELDAHL method, 31
■**•  Koch's culture method, !
TACMOID, use of, 19
  '  Lead, action of water on, 83
Lead, determination of, 51
------, nitrate, standard, 52
------, significance of, 73
Leeds' actinic method, 41
------dissolved oxygen, 81
Lime, purification of water by, 98,
Lithium compounds, use of, 108
------, detection of, 67
------, separation of, 59
Litmus, use of, 19
Locust Point well, 15, 124
Lott, F. E., Heisch's test, 74
TUTAGNESIA in boiler sludge, 114
AVJ-  Magnesium, determination of. 55
Magnesium  chloride,  decompositions
          and effects of, 114
------compounds, removal of, 115, 116
Mallet, ammonia process, 76
Manganese, detection of, 51
------, determination of, 55
Microbes, table of, 97
Mineral springs, 14
Mine water, 112
Miiller, lead in  water, 84
TSTAPHTHYLAMINE, 36
■*•'   National filter, 103
Nesslerizing, 29
Nessler's reagent, 25
Nickel dish, 20,62
Nitric acid, diluted, 50
Nitrification, 13
Nitrates, action  in boilers, 112 
INDEX.
129
Nitrates, determination of, 33
------, formation of, 13
------, significance of, 78
Nitrites, determination of, 35
------, formation of, 13
------, significance of, 77
Nitrogen in ammonium compounds, 26,
        3!.74
------as nitrites, 35
------as nitrates, 33
------by permanganate, 75
------, oxidation of, 13
------, total organic, 30
 f"\DOR, determination of, 18
 ^   ------ from residue, 21
------, significance of, 72
Odling,  Crookes and Tidy,  lead  in
  water, 83
Organic matter, 12, 21, 71
------------, action of, 14
------------, oxidation of, 40
------in water, 86
------, precipitation of, 102
Oxygen consumed, 37
-------consuming microbes, 97
-------consuming power, 37
------, amount of, dissolved,  121
------, dissolved, determination of, 44
------, dissolved, effects of, 81, 111


   PARA - AMIDO - BENZENE- SUL-
     PHONIC acid, 36
Pasteur-Chamberlain filter, 83, 99
Permanganate method, 37
------standard, 37, 44
Pettenkofer's method for free carbonic
  acid, 63
Phenacetolin, use of, 62
Phenolphthalein, use of, 19
Phosphates, action on lead, 84
------, determination of, 42
------, significance of, 73
------, use of, in purifying water, 117
Phenol-sulphonic acid, 33
Plate culture, 89
Platinum, preservation of, 20
Plummet for specific gravity,  68
Poisonous metals, detection of, 47
-------------, significance of, 69
Polluted waters, characters of, 67-77
Porter's  process for purifying water, 94
Potassium determination, 52
------chromate solution, 22
------iodide solution, 39
------nitrate, standard, 33
Potassium permanganate, alkaline, 25
------permanganate, decinormal, 44
Potato culture, 88
Preliminary examination, 16
Ptomaines, 12
Pure water, corrosive action of, in
Purification of boiler water, 114
------of drinking waters, 98
TD AIN water, 9, 80, 122
     Ratios, conversion of, 119, 120
Reaction, 19
Residue, charring of, 21
Results, statement of, 70
River water, 9, 10, 80, 123, 125
Roll culture, 91
Q ALT, action on boiler waters, 112
^   Samples, collection of, 16
Sand filters, 100
Sanitary application, 71
-----  examinations, 16
Scale,  112
Schuylkill River water, composition of,
  10, 123
Sewage, action of, 14, 80
—----fungus, 43, 79
Silica, action of, in water, 83
------, determination of, 53
------in scale, 112
Silicates, action on lead, 84
Silver  nitrate, standard, 22
------------, test in Porter's  process,
        116
------nitrite, preparation of, 36
------test for organic matter, 41
Sludge, 113
Solids, total, determination of, 19
Solids, significance of, 73
Sodium and potassium, separation of, 58
------carbonate, solution of, 25
------------, standard, 62
------------, use of in  boiler waters,
              "5
------chloride, standard, 22
------, determination of,  58
------hydroxide, solution, 31
------nitrite, standard, 36
------thiosulphate, 39
Source of water, tracing of, 107
Smart, C, nature of organic matter, 75
Subsoil waters, composition  of, 12,  122
Specific gravity, 68
Spectroscope, 67
Spectroscopic examination, 67
Spongy iron filters, 99
Staining, 93
Starch indicator, 39
Sterilizer, 86
Storage,  effect of, 95
Subsidence, promotion of, 17, 192
Subsoil water, 9, n, 122
Sugar test, 42
Sulphanilic acid, 36 
13°
INDEX.
Sulphides, formation of, 14, 72
Sulphuretted hydrogen,  determination
  of, 14, 60
Sulphuric  acid, diluted, 31, 39
------------, standard, 62
Surface water, composition of,9, io, 123
Suspended matters, 10, 11
npASTE,significance of, 72
 ■*■   Technical examinations, 53
Tests for metals, delicacy of, 53
Thompson, estimation of iron, 50
Tidy's permanganate process, 38
Tidy and Frankland, standard of purity,
          , 79
-----,  Odling and  Crookes,  lead in
           water, 83
Tri-sodium phosphate, use of, for  puri-
  fication, 116
T JNCONTAMINATED waters, 82
^"'  Urea, decomposition of, 75
Urine in water, 75
U. S. gallon, 70
V
EGETABLE matter, 21, 76
  Vegetable growth in water, 81
\X7ARINGTON, R., nitrification, 13
 " *   Water, amount of, in  rocks, 12
Wanklyn, standards of purity, 77
Wanklyn's albuminoid ammonia  pro-
           cess, 23
-----test for manganese, 51
'INC, detection of, 48
'   -----, effect of, 72 
 
 
CATALOGUE No. 7.
DECEMBER, 1890.
      A  CATALOGUE
                 OF

Books  for  Students.
             including the
      ? QUIZ-COMPENDS ?
CONTENTS.
PAGE			PAGE
New Series of Manuals, 2,3,4,5		Obstetrics. .	. IO
Anatomy,	6	Pathology, Histology,	. II
Biology,	11	Pharmacy, .	. 12
Chemistry, .	6	Physiology, .	. I 1
Children's Diseases,	7	Practice of Medicine,	. 12
Dentistry,	8	Prescription Books,	. 12
Dictionaries,	8	PQuiz-Compends ?	M, 15
Eye Diseases,	8	Skin Diseases,	. 12
Electricity, .	9	Surgery,	• '3
Gynaecology,	10	Therapeutics,	■ 9
Hygiene,	9	Urine and Urinary Org	ans, 13
Materia Medica, .	9	Venereal Diseases,	• '3
Medical Jurisprudence,	10		
	__	___	
published by
   P. BLAKISTON, SON & CO.,

Medical Booksellers, Importers and Publishers.

 LARGE STOCK OF ALL STUDENTS' BOOKS, AT
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 Practical  Therapeutics,   considered  with  reference  to
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 No. 8.  MEDICAL JURISPRUDENCE AND

            TOXICOLOGY.

     NEW, REVISED AND ENLARGED EDITION.

 By John J. Reese,  m.d.,  Professor of Medical Jurispru-
   dence and  Toxicology in the University  of Pennsyl-
   vania ;  President of the Medical Jurisprudence  Society
   of Phila.;  2d Edition, Revised  and Enlarged.

  " This admirable text-book."—Amer.Jour. of Med. Sciences.
  " We  lay this  volume aside, after a  careful perusal of its pages,
with the profound impression that it should be in the hands of every
doctor and lawyer.  It fully meets the wants of all students.....
He has succeeded in admirably condensing into a handy volume all
the essential points."—Cincinnati Lancet and Clinic.

     Price of each Book, Cloth, $3,00;  Leather, $3.50. 
6     STUDENTS' TEXT-BOOKS AND MANUALS.
                      ANATOMY.
Macalister's Human Anatomy.  816 Illustrations.  A new
  Text-book for Students and Practitioners, Systematic and Topo-
  graphical, including the Embryology, Histology and Morphology
  of Man.  With special  reference to the  requirements  of
  Practical  Surgery and Medicine.  With 816 Illustrations,
  400 of which are original.   Octavo.    Cloth, 7.50; Leather, 8.50
Ballou's Veterinary Anatomy and Physiology.  Illustrated.
  By Wm.  R. Ballou, m.d., Professor of Equine Anatomy at New
  York College of Veterinary Surgeons.  29 graphic Illustrations.
  121110.                  Cloth, 1.00; Interleaved for notes, 1.25
Holden's  Anatomy. A manual of Dissection  of the Human
  Body.  Fifth Edition.  Enlarged, with Marginal References and
  over  200  Illustrations.  Octavo.      Cloth, 5.00; Leather, 6.00
     Bound in Oilcloth, for the Dissecting Room, $4.50.
  " No student of Anatomy can  take up this book without being
pleased and instructed.  Its Diagrams  are original, striking and
suggestive, giving more at a glance than pages of text description.
*  * * The text matches  the illustrations in  directness of  prac-
tical application and clearness of detail."—New York Medical
Record.
Holden's Human Osteology.  Comprising a Description of the
  Bones, with Colored Delineations  of  the Attachments of the
  Muscles.   The General and Microscopical Structure of Bone and
  its Development.  With Lithographic Plates and Numerous Illus-
  trations.  Seventh Edition. 8vo.                  Cloth, 6.00
Holden's Landmarks, Medical and Surgical. 4th ed.  Clo., 1.25
Heath's Practical Anatomy.  Sixth London Edition.  24 Col-
  ored  Plates, and nearly 300 other Illustrations.      Cloth, 5.00
Potter's Compend of Anatomy.   Fifth Edition.  Enlarged.
  16 Lithographic Plates.   117 Illustrations.
                        Cloth, 1.00; Interleaved for Notes, 1.25

                     CHEMISTRY.
Bartley's  Medical Chemistry. Second Edition. A text-book
  prepared specially for Medical, Pharmaceutical and Dental Stu-
  dents.  With 50 Illustrations, Plate of Absorption Spectra and
  Glossary of Chemical Terms.  Revised and Enlarged.  Cloth, 2.50
Trimble.  Practical and Analytical Chemistry.  A Course in
  Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem-
  istry in the Phila. College of  Pharmacy.  Illustrated.  Third
  Edition.  8vo.                                     Cloth, 1.50
       *S"" See pages 2 to 5 for list of Students' Manuals. 
STUDENTS' TEXT-BOOKS  AND MANUALS.     7
                   Chemistry:—Continued.
Bloxam's Chemistry, Inorganic and Organic, with Experiments.
  Seventh Edition.  Enlarged and  Rewritten.  330 Illustrations.
                                     Cloth, 4.50; Leather, 5.50
Richter's  Inorganic  Chemistry.  A text-book for Students.
  Third American, from Fifth German Edition.  Translated by
  Prof. Edgar F. Smith, ph.d.   89 Wood Engravings and Colored
  Plate of Spectra.                                 Cloth, 2.00
Richter's  Organic Chemistry, or Chemistry  of the Carbon
  Compounds.  Illustrated.            Cloth, 3.00;  Leather, 3.50
Symonds.  Manual of Chemistry, for the special use of Medi-
  cal Students.  By Bkandreth  Symonds, a.m.,  m.d.,  Asst.
  Physician Roosevelt Hospital, Out-Patient Department; Attend-
  ing Physician Northwestern Dispensary, New York.  nmo.
                        Cloth, 2.00; Interleaved for Notes, 2.40
Tidy.   Modern Chemistry.  2d Ed.               Cloth, 5.50
Leffmann's  Compend of Chemistry.  Inorganic and Organic.
  Including Urinary Analysis.  Third Edition.  Revised.
                        Cloth, 1.00;  Interleaved for Notes, 1.25
Leffmann and Beam.  Progressive Exercises in Practical
  Chemistry.  i2mo.  Illustrated.                  Cloth, 1.00
Muter.   Practical and Analytical Chemistry.   Second Edi-
  tion.  Revised and Illustrated.                    Cloth, 2.00
Holland.  The Urine, Common Poisons, and Milk Analysis,
  Chemical  and  Microscopical.   For  Laboratory Use.   3d
  Edition, Enlarged. Illustrated.                    Cloth, 1.00
Van Niiys.   Urine Analysis.  Illus.             Cloth, 2.00
Wolff's Applied  Medical  Chemistry.   By Lawrence Wolff,
  m.d., Dem. of Chemistry in Jefferson Medical College.  Clo., 1.00

                      CHILDREN.
Goodhart and Starr.  The Diseases of Children.  Second
  Edition.  By J. F. Goodhart, m.d., Physician to the Evelina
  Hospital for Children;  Assistant Physician to Guy's  Hospital,
  London.  Revised and Edited by Louis  Starr, m.d., Clinical
  Professor of Diseases of Children in the Hospital of the Univer-
  sity of Pennsylvania;  Physician to the Children's  Hospital,
  Philadelphia.   Containing  many Prescriptions and  Formulae,
  conforming to the U. S. Pharmacopoeia, Directions for making
  Artificial Human Milk, for the Artificial Digestion  of Milk, etc.
  Illustrated.                         Cloth, 3.00; Leather, 3.50
Hatfield.  Diseases  of Children.  By M. P. Hatfield, m.d.,
  Professor of  Diseases  of Children, Chicago Medical College.
  Colored Plate.  i2mo.           Cloth, 1.00; Interleaved, 1.25
Day.   On Children.  A  Practical  and  Systematic Treatise.
  Second Edition.  8vo.  752  pages.    Cloth, 3.00; Leather, 4.00
     1&~ See pages 14 and IS for list of ? Quiz- Compends.' 
8     STUDENTS*  TEXT-BOOKS  AND MANUALS.
                    Children:— Continued.
Meigs  and  Pepper.  The  Diseases of Children.   Seventh
  Edition.  8vo.                     Cloth, 5.00; Leather, 6.00
Starr.  Diseases of the Digestive Organs in Infancy and
  Childhood.  With chapters on  the Investigation of Disease,
  and on the  General Management  of Children.  By Louis  Starr,
  m.d., Clinical Professor of Diseases of Children in the Univer-
  sity of Pennsylvania.   Illus.   Second Edition.       In Press.
                     DENTISTRY.
Fillebrown.  Operative Dentistry.  330 Illus.     Cloth, 2.50
Flagg's Plastics and  Plastic Filling.   3d  Ed.    Preparing.
Gorgas.  Dental Medicine.  A Manual of Materia Medica and
  Therapeutics.  Third Edition.                     Cloth, 3.50
Harris. Principles and Practice  of  Dentistry.  Including
  Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery
  and Mechanism.   Twelfth Edition.  Revised and enlarged by
  Professor Gorgas.   1028 Illustrations. Cloth, 7.00; Leather, 8.00
Richardson's  Mechanical Dentistry.   Fifth Edition.   569
  Illustrations.  8vo.                 Cloth, 4.50;  Leather, 5.50
Sewill.  Dental Surgery.  200 Illustrations.  3d Ed.  Clo., 3.00
Stocken's Dental Materia Medica. Third  Edition. Cloth, 2.50
Taft's Operative Dentistry. Dental Students and Practitioners.
  Fourth Edition.  100 Illustrations.    Cloth, 4.25 ;  Leather, 5.00
Talbot.   Irregularities of the  Teeth, and their Treatment.
  Illustrated.   8vo.   Second Edition.                Cloth, 3.00
Tomes' Dental Anatomy.   Third Ed.  191 Illus.  Cloth, 4.00
Tomes' Dental Surgery.   3d Edition.  Revised.   292 Illus.
  772 Pages.                                      Cloth, 5.00
■Warren. Compend of Dental Pathology  and Dental Medi-
  cine.  Illustrated.              Cloth, 1.00;  Interleaved, 1.25

                   DICTIONARIES.
Gould's New Medical Dictionary. Containing the Definition
  and Pronunciation of all  words in  Medicine, with many  useful
  Tables etc.  % Dark Leather, 3.25 ;  J£ Mor., Thumb Index 4.25
Cleaveland's Pronouncing Pocket Medical  Lexicon.  31st
  Edition.  Giving  correct Pronunciation and Definition.  Very
  small pocket size.   Cloth, red edges .75 ; pocket-book style, 1.00
Longley's Pocket  Dictionary.  The Student's Medical Lexicon,
  giving Definition and  Pronunciation of all Terms used in Medi-
  cine, with an Appendix giving Poisons and Their Antidotes,
  Abbreviations used in Prescriptions, Metric  Scale of Doses, etc.
  241110.                    Cloth, 1.00; pocket-book style, 1.25
       KS'See pages 2 to 5 for list of Students' Manuals, 
STUDENTS' TEXT-BOOKS  AND MANUALS.
                          EYE.
Arlt.  Diseases of the Eye.   Including those of the Conjunc-
  tiva, Cornea, Sclerotic, Iris and Ciliary Body.   By Prof. Von
  Arlt. Translated by Dr. Lyman Ware. Illus.  8vo.  Cloth, 2.50
Hartridge on Refraction.  4th Ed.                Cloth, 2.00
Meyer.  Diseases of the Eye.  A complete Manual for Stu-
  dents and.Physicians.  270 Illustrations and two Colored Plates.
  8vo.                               Cloth, 4.50; Leather, 5.50
Fox and Gould.  Compend  of Diseases  of   the Eye and
  Refraction.  2d Ed.  Enlarged.  71  Illus.  39  Formulae.
                        Cloth, 1.00 ;  Interleaved for Notes, 1.25

                    ELECTRICITY.
Mason's Compend  of Medical  and Surgical Electricity.
  With numerous Illustrations.   i2mo.               Cloth, 1.00

                        HYGIENE.
Parkes' (Ed. A.)  Practical  Hygiene.  Seventh  Edition, en-
  larged.  Illustrated.  8vo.                        Cloth, 4.50
Parkes' (L. C.) Manual of  Hygiene and  Public  Health.
  i2mo.                                          Cloth, 2.50
Wilson's  Handbook  of Hygiene  and  Sanitary  Science.
  Sixth Edition.  Revised and Illustrated.           Cloth, 2.75

MATERIA MEDICA AND THERAPEUTICS.
Potter's Compend of Materia Medica, Therapeutics and
  Prescription Writing.  Fifth Edition, revised and improved.
                        Cloth, 1.00; Interleaved for Notes, 1.25
Biddle's  Materia Medica.   Eleventh Edition.  By the late
  John B. Biddle, m.d., Professor of Materia Medica  in Jefferson
  Medical  College, Philadelphia.  Revised, and rewritten,  by
  Clement  Biddle, m.d., Assist. Surgeon, U. S. N.,  assisted  by
  Henry Morris, m.d. 8vo., illustrated.  Cloth, 4.25; Leather, 5.00
Headland's Action of Medicines.  9th Ed.  8vo.  Cloth, 3.00
Potter.  Materia   Medica,  Pharmacy  and  Therapeutics.
  Including Action of Medicines, Special Therapeutics,  Pharma-
  cology, etc.  Second Edition.        Cloth, 4.00; Leather, 5.00
Starr, 'Walker  and Powell.  Synopsis  of  Physiological
  Action of Medicines,based upon  Prof. H. C. Wood's " Materia
  Medica and Therapeutics."  3d Ed.   Enlarged.      Cloth, .75
Waring.   Therapeutics.  With an  Index of  Diseases  and
  Remedies.  4th Edition.  Revised.   Cloth, 3.00: Leather, 3.50
     Jt&- See pages 14 and /j for list of f Quiz- Compends f 
10    STUDENTS'  TEXT-BOOKS AND  MANUALS.
          MEDICAL JURISPRUDENCE.
 Reese.  A Text-book of Medical Jurisprudence and  Toxi-
   cology.  By John J. Reese, m.d., Professor of Medical Juris-
   prudence  and  Toxicology in the Medical  Department  of the
   University of  Pennsylvania;  President of the Medical Juris-
   prudence  Society of Philadelphia;   Physician  to  St. Joseph's
   Hospital; Corresponding  Member of The New York Medico-
   legal Society.   2d Edition.          Cloth, 3.00; Leather, 3.50
 Woodman and Tidy's Medical Jurisprudence  and Toxi-
   cology.  Chromo-Lithographic Plates and 116 Wood engravings.
                                     Cloth,  7.50; Leather, 8.50

      OBSTETRICS AND GYNECOLOGY.
 Byford.  Diseases of Women.  The Practice of Medicine and
   Surgery, as applied to the Diseases  and Accidents  Incident to
   Women.  By W. H. Byford.A.M., m.d., Professor of Gynaecology
   in Rush Medical College and of Obstetrics in  the Woman's Med-
   ical College  etc., and Henry T. Byford, m.d., Surgeon to the
   Woman's  Hospital  of Chicago ;  Gynaecologist  to  St. Luke's
   Hospital, etc.   Fourth Edition.  Revised,  Rewritten and En-
   larged.  With 306 Illustrations, over  100 of which are original
  Octavo.  832 pages.                 Cloth,  5.00 ; Leather, 6.00
Cazeaux and  Tarnier's Midwifery.  With  Appendix, by
  Munde. The Theory and  Practice of Obstetrics ; including the
  Diseases of Pregnancy and Parturition, Obstetrical Operations,
  etc.  By P.  Cazeaux.  Remodeled and rearranged, with revi-
  sions and additions, by S. Tarnier, m.d., Professor of Obstetrics
  and  Diseases of Women and Children in the Faculty of Medicine
  of Paris.   Eighth American, from the Eighth French and First
  Italian Edition.  Edited by Robert J. Hess,  m.d., Physician  to
  the Northern Dispensary,  Philadelphia, with an appendix by
  Paul F. Munde, m.d., Professor of  Gynaecology at the N. Y.
  Polyclinic.  Illustrated by  Chromo-Lithographs, Lithographs
  and other Full-page Plates, seven of which are  beautifully colored'
  and  numerous  Wood  Engravings.   Students'  Edition.   One
  Vol.,8vo.                           Cloth, 5.00; Leather, 6.00
Lewers' Diseases  of Women.  A Practical Text-Book.  139
  Illustrations.  Second Edition.                     Cloth, 2.50
Parvin's Winckel's  Diseases of Women.  Second Edition.
  Including a Section  on Diseases  of the  Bladder and Urethra
  150  Illus.   Revised.   See page 3.      Cloth, 3.00 ; Leather, 3.50
Morris.  Compend of Gynaecology.   Illustrated.   Cloth, 1.00
Winckel's Obstetrics.  A Text-book on Midwifery, includ-
  ing the Diseases of Childbed.  By Dr. F. Winckel, Professor
  of Gynaecology, and Director of the Royal University Clinic for
  Women, in  Munich.  Authorized  Translation, by J. Clifton
  Edgar, m.d., Lecturer on  Obstetrics, University Medical Col-
  lege, New York,  with nearly 200 handsome illustrations the
  majority of which are original with this work.  Octavo.    '
                                    Cloth, 6.00 ; Leather, 7.00
Landis*  Compend  of Obstetrics.   Illustrated.   4th edition
  enlarged.              Cloth, 1.00;  Interleaved for  Notes, 1.25

         «*=• See pages 2 to 5for list of New Manuals. 
STUDENTS' TEXT-BOOKS  AND MANUALS.    11
            Obstetrics and Gynecology :—Continued.
Galabin's  Midwifery.   By  A. Lewis  Galabin,  m.d.,  f.r.c.p.
  227 Illustrations.  See page 3.         Cloth, 3.00; Leather, 3.50

Glisan's Modern Midwifery.  2d Edition.         Cloth, 3.00
Rigby's Obstetric Memoranda.  4th Edition.       Cloth, .50
Meadows'  Manual  of Midwifery.  Including the Signs and
  Symptoms of Pregnancy, Obstetric Operations, Diseases of the
  Puerperal State, etc.  145 Illustrations.   494 pages.  Cloth, 2.00
Swayne's Obstetric Aphorisms.   For the use of Students
  commencing Midwifery Practice.  8th Ed.   i2mo.  Cloth, 1.25


  PATHOLOGY.   HISTOLOGY.  BIOLOGY.
Bowlby.  Surgical  Pathology and Morbid Anatomy,  for
  Students.  135 Illustrations.  i2mo.              Cloth, 2.00

Davis' Elementary Biology.  Illustrated.         Cloth, 4.00
Gilliam's Essentials of Pathology.  A Handbook for Students.
  47 Illustrations.  i2mo.                           Cloth, 2.0c
  ***The object of this book is to-unfold to the beginner the funda-
mentals of pathology in a  plain,  practical way, and  by bringing
them within easy comprehension to increase his interest in the study
of the subject.
Gibbes' Practical Histology and Pathology.  Third Edition.
  Enlarged.  i2mo.                                Cloth, 1.75
Virchow's Post-Mortem Examinations.  2d Ed. Cloth, 1.00


                     PHYSIOLOGY.

Yeo's Physiology.  Fourth  Edition.   The most Popular Stu-
  dents' Book.  By Gerald F.  Yeo, m.d., f.r.c.s., Professor of
  Physiology  in  King's  College, London.  Small Octavo.   758
  pages.   321  carefully  printed Illustrations.    With  a  Full
  Glossary and Index. See Page3.     Cloth, 3.00;  Leather, 3.50
Brubaker's  Compend   of  Physiology.   Illustrated.  Fifth
  Edition.               Cloth, 1.00;  Interleaved for Notes, 1.25
Stirling.  Practical Physiology, including  Chemical and Ex-
  perimental Physiology.  142 Illustrations.          Cloth, 2.25
Kirke's Physiology.  New 12th Ed.  Thoroughly Revised and
  Enlarged.  502 Illustrations.          Cloth, 4.00; Leather, 5.00
Landois' Human Physiology.  Including Histology and Micro-
  scopical Anatomy, and with special reference to Practical Medi-
  cine.  Third  Edition.   Translated and  Edited by Prof. Stirling.
  692 Illustrations.                    Cloth, 6.50; Leather, 7.50
  " With this Text-book at his command, no student could fail in
his examination."—Lancet.
Sanderson's Physiological Laboratory-  Being Practical Ex-
  ercises for the Student.  350 Illustrations.  8vo.     Cloth, 5.00
Tyson's Cell Doctrine.  Its History and Present State.  Illus-
  trated.  Second Edition.                          Cloth, 2.00

     *S* See pages 14 and 15 for list of f Quiz-Compends t 
12    STUDENTS'  TEXT-BOOKS  AND MANUALS.
                       PRACTICE.
Taylor.  Practice  of Medicine.  A Manual.. By  Frederick
  Taylor, m.d., Physician  to, and Lecturer on Medicine at, Guy's
  Hospital, London ; Physician to Evelina Hospital for Sick Chil-
  dren, and  Examiner  in  Materia Medica  and Pharmaceutical
  Chemistry, University of London.                  Cloth, 4.00
Roberts' Practice.   New  Revised Edition.  A  Handbook
  of the  Theory and  Practice  of Medicine.  By Frederick T.
  Roberts, m.d. ;  m.r.cp., Professor  of Clinical  Medicine and
  Therapeutics in University College Hospital, London. Seventh
  Edition. Octavo.                    Cloth, 5.50 ;  Sheep, 6.50
Hughes. Compend of the Practice of Medicine.  4th Edi-
  tion.  Two parts, each, Cloth, 1.00;  Interleaved for Notes, 1.23
  Part i.—Continued, Eruptive and Periodical  Fevers, Diseases
of the  Stomach, Intestines, Peritoneum, Biliary  Passages,  Liver,
Kidneys, etc., and  General Diseases, etc.
  Part ii.—Diseases  of  the Respiratory System,  Circulatory
System and Nervous System; Diseases  of the Blood, etc.
  Physician's Edition.  Fourth Edition.  Including a Section
    on Skin Diseases. With Index.  1 vol. Full Morocco, Gilt, 2.50
From John A. Robinson,  M.D., Assistant to Chair of Clinical
  Medicine, now Lecturer on Materia Medica, Rush Medical Col-
  lege, Chicago.
  " Meets with my  hearty approbation as a substitute for the
ordinary note books almost universally  used by medical students.
It is concise, accurate, well arranged and lucid,   .  .  .  just the
thing for students to use while studying  physical diagnosis and the
more practical departments of medicine."

             PRESCRIPTION  BOOKS.
Wythe's Dose and Symptom Book.  Containing the  Doses
  and Uses of all the principal Articles of the Materia Medica, etc.
  Seventeenth Edition.  Completely Revised and  Rewritten.  Just
  Ready.  32mo.           Cloth, 1.00; Pocket-book style, 1.25
Pereira's Physician's Prescription  Book.  Containing  Lists
  of Terms,  Phrases,  Contractions and Abbreviations used in
  Prescriptions  Explanatory Notes, Grammatical Construction of
  Prescriptions, etc., etc.   By Professor Jonathan  Pereira, m.d.
  Sixteenth Edition.  32mo.  Cloth, 1.00; Pocket-book style, 1.25

                     PHARMACY.
Stewart's Compend of Pharmacy.  Based upon Remington's
  Text-Book  of Pharmacy.  Third Edition, Revised.  With new
  Tables,  Index, Etc.      Cloth, 1.00;  Interleaved for Notes, 1.25
Robinson.   Latin Grammar  of  Pharmacy  and  Medicine.
  By H.  D.  Robinson, ph.d., Professor of Latin Language and
  Literature,  University of Kansas, Lawrence.   With  an  Intro-
  duction  by  L.  E. Sayre, ph.g., Professor of Pharmacy in, and
  Dean of, the Dept. of Pharmacy, University of Kansas.  i2mo.
                                                  Cloth, 2.00
                  SKIN DISEASES.
Anderson, (McCall) Skin Diseases.   A complete Text-Book,
  with Colored  Plates and numerous  Wood Engravings.  8vo.
                                     Cloth, 4.50; Leather, 5.50
        %g- See pages 2 to 5 for list of New Manuals. 
STUDENTS* TEXT-BOOKS AND  MANUALS.    13
                  Skin Diseases:—Continued.
 Van Harlingen on Skin Diseases.  A Handbook of the Dis-
   eases of the Skin, their Diagnosis and Treatment (arranged alpha-
   betically).  By Arthur Van Harlingen, m.d., Clinical Lecturer
   on Dermatology, Jefferson Medical College ; Prof, of Diseases of
   the Skin in the Philadelphia Polyclinic. 2d Edition.   Enlarged.
   With colored and other plates and illustrations. i2mo. Cloth, 2.50
 Bulkley.  The Skin in Health and  Disease.  By L. Duncan
   Bulkley, Physician to the N. Y. Hospital.  Illus.     Cloth, .50

         SURGERY AND  BANDAGING.
 Jacobson. Operations in  Surgery.  A Systematic Handbook
   for Physicians, Students and Hospital Surgeons. By  W. H. A.
   Jacobson, B A., Oxon. f.r.c.S. Eng.;  Ass't Surgeon Guy's Hos-
   pital ; Surgeon at Royal Hospital for Children and Women, etc.
   199 Illustrations.  1006 pages.  8vo.  Cloth. 5.00; Leather, 6.00
 Heath's Minor Surgery, and Bandaging.  Ninth Edition.   142
   Illustrations.   60 Formulae and Diet Lists.          Cloth, 2.00
 Horwitz's  Compend  of  Surgery,  Minor „ Surgery and
   Bandaging,  Amputations, Fractures, Dislocations, Surgical
   Diseases, and the Latest Antiseptic Rules, etc., with Differential
   Diagnosis and Treatment.  By Orville Hokwitz, b.s., m.d.,
   Demonstrator of Surgery, Jefferson Medical College.  4th edition.
   Enlarged and  Rearrangecf.  136  Illustrations and  84  Formulae.
   i2mo.    Cloth,  1.00 ; Interleaved for the addition of Notes, 1.25
   *** The new Section on Bandaging  and Surgical Dressings, con-
 sists of  32 Pages  and 41 Illustrations.  Every Bandage of  any
 importance is figured.   This, with  the Section  on  Ligation of
 Arteries, forms an ample Text-book for the Surgical Laboratory.
 Walsham.  Manual of Practical Surgery.  For Students and
   Physicians.  By Wm. J. Walsham, m.d., f.r.c.s., Asst. Surg.
   to, and Dem. of Practical Surg, in,  St. Bartholomew's  Hospital,
   Surgeon  to Metropolitan Free  Hospital,  London.   With 236
   Engravings.  See Page 2.            Cloth, 3.00; Leather, 3.50

      URINE,  URINARY ORGANS, ETC.
 Holland.  The  Urine, and  Common  Poisons and  The
   Milk. Chemical and Microscopical, for Laboratory Use.  Illus-
   trated.  Third Edition. i2mo.  Interleaved.       Cloth, 1.00
 Ralfe.   Kidney Diseases and Urinary Derangements.   42 Illus-
  trations.  i2mo.  572 Pages-                       Cloth, 2.75
 Marshall and Smith.  On the Urine. The Chemical Analysis of
  the Urine. By John Marshall, m.d.,  Chemical  Laboratory, Univ.
  of Penna; and Prof. E. F. Smith, ph.d. Col. Plates. Cloth, 1.00
 Thompson.   Diseases  of  the  Urinary Organs.   Eighth
  London Edition.   Illustrated.                      Cloth, 3.50
 Tyson.  On the Urine.  A Practical Guide to the Examination
  of Urine.  With  Colored Plates and Wood Engravings. 6th Ed.
  Enlarged. i2mo.                                Cloth, 1.50
Van Niiys, Urine Analysis.  Illus.               Cloth, 2.00

             VENEREAL DISEASES.
Hill and Cooper.   Student's Manual of Venereal Diseases,
  with  Formulae. Fourth Edition.   i2mo.         Cloth, 1.00
     49s See pages 14 and is for list of * Quiz- Compends f 
NEW AND REVISED EDITIONS.
PQUIZ-COMPENDS?

 The Best Compends for Students' Use

     in the Quiz Class, and when Pre-

          paring for Examinations.

Compiled in accordance with the latest teachings of promi-
     nent lecturers and the most popular  Text-books.

  They form a most complete, practical  and exhaustive
set of manuals, containing information  nowhere else  col-
lected in such a condensed, practical shape.  Thoroughly
up to the times in every respect, containing many new
prescriptions and formulae, and over two  hundred  and
fifty  illustrations, many of which have been drawn  and
engraved specially for this series. The authors have had
large experience as quiz-masters and attaches of colleges,
with exceptional opportunities for noting  the most recent
advances and methods.

     Cloth, each $1.00.  Interleaved for  Notes, $1.25.

No. 1.  HUMAN ANATOMY, " Based upon Gray." Fifth
  Enlarged Edition, including Visceral Anatomy, formerly
  published  separately.   16   Lithograph  Plates,  New
  Tables and 117 other Illustrations.   By  Samuel O. L.
  Potter, m.a., m.d., late A. A. Surgeon U.  S. Army.  Professor
  of Practice, Cooper Medical College, San Francisco.
Nos. 2  and 3.  PRACTICE OF MEDICINE.  Fourth Edi-
  tion.   By Daniel E. Hughes, m.d., Demonstrator of Clinical
  Medicine in Jefferson Medical College, Philadelphia. In two parts.
  Part I.—Continued, Eruptive and Periodical Fevers, Diseases
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver,
Kidneys, etc. (including Tests for Urine), General Diseases, etc.
  Part II.—Diseases of the Respiratory System (including Phy-
sical  Diagnosis), Circulatory System and Nervous System;  Dis-
eases of the Blood, etc.
  *#* These little books can be regarded as a full set of  notes upon
the Practice of Medicine, containing the Synonyms, Definitions,
Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each
disease, and including a number of prescriptions hitherto unpub-
lished.
No.  4.   PHYSIOLOGY, including  Embryology.  Fifth
  Edition. By Albert P. Brubaker, m.d., Prof, of Physiology,
  Penn'a College of Dental Surgery;  Demonstrator of Physiology
  in Jefferson Medical College, Philadelphia.  Revised, Enlarged
  and Illustrated.
No. 5.  OBSTETRICS.  Illustrated.  Fourth Edition.  By
  Henry G.  Landis, m.d., Prof, of Obstetrics and Diseases of
  Women, in  Starling Medical College, Columbus, O.  Revised
  Edition.  New Illustrations. 
    BLAKISTON'S  PQUIZ-COMPENDS?

 No.  6.   MATERIA  MEDICA, THERAPEUTICS  AND
   PRESCRIPTION WRITING.  Fifth Revised Edition.
   With especial  Reference to  the Physiological Action of Drugs,
   and a complete article on Prescription Writing.  Based on the
   Last  Revision of the U. S. Pharmacopoeia, and including many
   unofficial remedies.   By Samuel O. L. Potter, m.a.,  m.d.,
   late A. A. Surg. U. S. Army; Prof, of  Practice, Cooper Medical
   College, San Francisco.  Improved and Enlarged, with Index.
 No. 7.  GYNAECOLOGY.  A Compend of Diseases of Women.
   By Henry Morris, m.d., Demonstrator of Obstetrics, Jefferson
   Medical College, Philadelphia.  4s Illustrations.
 No. 8. DISEASES OF THE EYE  AND REFRACTION,
   including Treatment and Surgery.  By L. Webster Fox, m.d.,
   Chief Clinical Assistant Ophthalmological Dept., Jefferson Med-
   ical College, etc., and Geo. M. Gould, m.d. 71 Illustrations, 39
   Formulas.   Second Enlarged and improved Edition.  Index.
 No. 9.  SURGERY, Minor Surgery and Bandaging.  Illus-
   trated.   Fourth  Edition.   Including  Fractures,  Wounds,
   Dislocations, Sprains, Amputations and other operations ; Inflam-
   mation, Suppuration,  Ulcers, Syphilis, Tumors, Shock, etc.
   Diseases  of the  Spine,  Ear, Bladder, Testicles, Anus, and
   other Surgical Diseases.  By  Orville Horwitz, a.m.,  m.d.,
   Demonstrator  of Surgery, Jefferson Medical College.  Revised
   and Enlarged.   84 Formulae and 136 Illustrations;
 No. 10. CHEMISTRY.  Inorganic and Organic.  For Medical
   and Dental Students.  Including Urinary Analysis and Medical
   Chemistry.  By Henry Leffmann, m.d., Prof, of Chemistry in
   Penn'a College of Dental Surgery, Phila. Third Edition, Revised
   and Rewritten, with Index.
 No. 11. PHARMACY.  Based upon " Remington's Text-book
   of Pharmacy." By F. E. Stewart, m.d., ph.g., Quiz-Master
   at Philadelphia College of Pharmacy.  Third Edition, Revised.
 No. 12.  VETERINARY ANATOMY  AND PHYSIOL-
   OGY.  29 Illustrations.   By  Wm. R. Ballou, m.d., Prof, of
   Equine Anatomy at N. Y. College of Veterinary Surgeons.
 No. 13. DENTAL PATHOLOGY AND DENTAL MEDI-
   CINE.  Containing all the  most noteworthy points of interest
   to the Dental  student.  By Geo. W. Warren,  d.d.s., Clinical
   Chief, Penn'a College of Dental Surgery, Philadelphia.  Illus.
 No. 14. DISEASES OF CHILDREN.  By  Dr. Marcus P.
   Hatfield, Prof,  of Diseases of  Children,  Chicago Medical
   College.  Colored Plate.

   Bound in Cloth,  $1.   Interleaved, for the Addition of Notes, $1.25.

   B@°* These books are constantly revised to keep up with
 the latest teachings and discoveries, so  that they contain
 all the new methods and principles.  No series of books
 are so  complete in detail, concise  in  language, or so  well
printed and bound.   Each  one forms a complete  set of
 notes upon the subject under consideration.
Illustrated Descriptive Circular Free. 
JUST PUBLISHED.
           GOULD'S  NEW
Medical  Dictionary
      G0MPAGT.

      GONGISE.

     PRACTICAL,

     ACCURATE,

'fft COMPREHENSIVE
OS;:!
S|  UP TO DATE,
It contains Tables of the Arteries, Bacilli, Gan-
  glia,  Leucomai'nes,  Micrococci, Muscles,
     Nerves, Plexuses,  Ptomaines,  etc.,
        etc., that will be found of great
            use to the  student.
Small octavo, 520 pages, Half-Dark Leather,  .   #3.25
With Thumb Index, Half Morocco, marbled edges, 4.25
   From J. M. DaCOSTA, M. D., Professor of Practice and
Clinical Medicine, Jefferson Medical College, Philadelphia.
   "Ifind it an excellent work, doing credit to the learning and
discrimination of the author." 
 
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