ELEMENTS 
OF 
QUALITATIVE AND QUANTITATIVE 
CHEMICAL ANALYSIS 
/ 
BY 
G. C. jCALDWELL, 8.5., Ph.D., 
PROFESSOR OP AGRICULTURAL AND ANALYTICAL CHEMISTRY IN CORNELL UNIVERSITY; 
AUTHOR OF AGRICULTURAL CHEMICAL ANALYSIS; MANUAL OF INTRODUCTORY 
CHEMICAL PRACTICE; MANUAL OF QUALITATIVE ANALYSIS. 
SECOND EDITION, REVISED AND ENLARGED. 
PHILADELPHIA: 
P. BLAKISTON, SON & CO., 
1012 WALNUT STREET. 
1892. Entered according to Act of Congress, in the year 1892, by 
. P. Blakiston, Son & Co., 
in the office of the Librarian of Congress, at Washington. 
Press of Wm. F. Fell & Co., 
1220-24 Sansom St., 
PHILADELPHIA. PREFACE. 
In this work the author has brought together what has already 
been published, separately, in the “ Manual of Qualitative 
Chemical Analysis,” by himself and Dr. S. M. Babcock, and 
the “ Notes on Chemical Analysis,” by himself alone; he has 
added thereto much matter on qualitative analysis, all of Parts 
111 and IV on quantitative analysis, and nearly all of Part V. 
Of course no such work as this can be satisfactorily prepared 
without frequent reference to the standard treatises of Prescott 
and Johnson, and of Fresenius, in one of which the whole 
subject of qualitative analysis is very thoroughly treated, and 
in the other both qualitative and quantitative analysis. The 
author would acknowledge his indebtedness to these works, 
while claiming for himself at least some novelty in the arrange- 
ment of the matter, as well as in some of the matter itself, in 
this attempt to prepare a book that is much needed in his own 
laboratory. 
Also, for valuable suggestions in the revision of the work for 
the second edition, he is indebted to Professor Dennis, and 
Instructors Chamot and Preswick, of the University. 
Certain modifications in the spelling of chemical terms, 
adopted after careful consideration by the chemical section of 
the American Association for the Advancement of Science, are 
used in this second edition. TABLE OF CONTENTS. 
INTRODUCTION. 
PART I. 
THE PROCESSES OF ANALYTICAL CHEMISTRY AND SOME OF 
THE PRODUCTS OF ITS OPERATIONS. 
Chapter I.—Solution and Solids from Solution. 
The solvent agents used ; physical solution ; chemical solution ; table of 
solubilities; solution of metals; solubility and temperature; solubility 
of salts in acids; comparative range of solvent power of different 
solvents; saturated solutions; solution of gases or vapors; solids from 
solution, by cooling of saturated solutions; by removal of the solvent 
agent. 
Chapter II.—Acids, Bases, Salts. 
The terms defined; anhydrids; normal salts; acid salts ; basic salts. 
Chapter 111.—Oxidation, Chlorination, Reduction. 
The terms defined; conditions under which oxidation or chlorination may 
take place ; reduction defined ; conditions under which reduction may 
take place ; the reactions of oxidation and reduction, with free oxygen ; 
nitric acid; aqua regia; potassium chlorate and hydrochloric acid; 
bromin ; chromic acid ; sulfuric acid ; changes in valence accompany- 
ing oxidation or chlorination or their reverse. 
Chapter IV.—Metathesis. 
Term defined ; conditions under which it takes place; important law of; 
several kinds of metathesis made use of; on some of the products of 
metathesis; metathesis requires time. 
Chapter V.—Writing Equations. 
Requirements for the correct writing of an equation; structural or graphic 
formulae of compounds ; valence of elements and compounds ; table of 
elements and hypothetical compounds entering into the equations for 
the reactions of chemical analysis; special signs attached to the equa- 
tion; additional directions; common errors in writing equations; 
writing the history of a substance in equations. 
v VI 
TABLE OF CONTENTS. 
Chapter Vl.—The Manipulations of Analytical Chemistry in 
General. 
Making solutions; fluxing; evaporation, ignition, acidification, alkaliza- 
tion, neutralization; adding a reagent in excess; precipitation ; how 
precipitates are described; digesting; boiling; filtration; washing 
precipitates; dissolving precipitates; cleanliness in the laboratory; 
rapidity of work. 
PART 11. 
SYSTEMATIC COURSE OF QUALITATIVE ANALYSIS. 
Chapter Vll.—The Mode of Procedure in General. 
Introduction ; the grouping of the substances ; the sulfids, how produced, 
and important characteristic properties, solubility, oxidation, chlorina- 
tion, reduction; the hydroxids, how produced, when the action of the 
reagents normal, and when not, solubility; the final tests, place of in 
the course of analysis, two classes of; order of arrangement of the 
work; tabular view of the course of analysis. 
Chapter VIII.—The Solution of Substances. 
Solution of non-metallic substances; of metallic substances ; treatment of 
insoluble substances. 
Chapter IX.—The Acidigens (or Acids). 
Solubility of compounds, reactions, and systematic course for their detec- 
tion. 
Chapter X.—The Systematic Course for the Separation and De- 
tection OF THE BaSIGENS (OR METALS). 
The silver group; occurrence, reactions and detection of the members of 
the group, and explanations of the chemistry of the work; the tin 
group, ditto; the copper group; the iron group; the aluminum group; 
the calcium group ; the potassium group. 
PART 111. 
PART 111. 
THE OPERATIONS OF QUANTITATIVE ANALYSIS. 
Chapter XL—Methods of Measuring, in Gravimetric Analysis. 
Introduction; the balance described; its proper care and use ; the weighing 
of the substance for analysis; the manipulations of weighing; the 
weighing of the products of the analysis. 
Chapter XlL—Measuring in Volumetric Analysis. 
Standard and normal solutions defined; determination of strength of 
measuring solutions; the instruments for measuring, measuring flask, TABLE OF CONTENTS. 
pipette, burette; cleaning these instruments; chromic acid cleaning 
mixture ; calibration of graduated instruments; special precautions for 
use of these instruments. 
Chapter Xlll.—Seven Important Operations of Quantitative Work. 
Weighing the substance; preparation of the solution ; the precipitation ol 
the substance, for gravimetric estimation ; fdtration, and use of suction ; 
washing the precipitate ; the asbestos filter, in Gooch crucible; prepara- 
tion of precipitate for weighing, by ignition. 
Chapter XlV.—Miscellaneous Matters. 
Determination of specific gravity of liquids, by specific gravity pipette; 
calculations of results of analysis; the quantitative note book ;■ special 
maxims for the young analyst. 
PART IV. 
EXAMPLES FOR PRACTICE IN QUANTITATIVE ANALYSIS. 
Chapter XV.—lron and Sulfur Trioxid. 
Iron, gravimetric method ; products of the analysis described ; the process 
for the determination; volumetric method, process described ; prepara- 
tion of standard solution of dichromate; assay of limonite; sulfur 
trioxid; product of the analysis described; process for the determination. 
Chapter XVl.—Acidimetry and Alkalimetry. 
The principles of these methods of determining free acid or base; the 
indicators used ; preparation of the standard solutions, and determina- 
tion of their relative strength ; determination of absolute strength of the 
acid by silver nitrate; actual determination of free acids and bases. 
Chapter XVII.—Lead, Phosphorus Pentoxid, and Calcium. lod- 
OMETRY. 
Lead, products of the analysis described; the process for the determination; 
phosphorus pentoxid, product of the analysis described; the process for 
the determination; calcium, by a gravimetric and a volumetric method, 
principles of the methods; product of the analysis described ; prepara- 
tion of the standard solution; the processes for the determination, 
lodometry; principles of this method of volumetric analysis; prepa- 
ration of the solutions; determination of antimony. 
Chapter XVlll.—Analysis by Electrolysis. 
Separation of copper and silver; determination of the silver and copper 
by electrolysis; determination of silver as chloride. 
PART V. 
MISCELLANEOUS MATTER. 
List of apparatus for qualitative work. 
Lists of apparatus for quantitative work, for shorter course, and for full 
course. TABLE OF CONTENTS. 
Special directions concerning the use of apparatus. 
List of reagants used, arranged in the alphabetical order of their full names, 
and also in the alphabetical order of their formulas. 
Directions in regard to the preparation of reagents. 
Table of atomic weights. 
Tables showing per cent, of NH3, S03 HCI, N.205 and lIN03, in solutions, 
different specific gravities. 
Table of comparison of weights and measures. 
Course of laboratory work in chemistry. 
Index and glossary. INTRODUCTION. 
At Cornell University a large number of students in some of 
the technical courses are required to take an elementary course 
of practice in chemical analysis, including both qualitative and 
quantitative work, after having had the elements of general 
chemistry in this University or elsewhere. 
There are many comprehensive and excellent works on 
chemical analysis in general, and on particular branches of 
chemical analysis, with which every special student of chemistry 
is acquainted; but these works are too large and expensive for 
any but the professional chemist. There are also numerous 
smaller works on the general subject. But in such of these as 
the author has met with no special chapters are devoted to the 
enlightenment of the student beginning this study, on the 
chemistry of the operations of qualitative and quantitative 
analysis in general; he must, therefore, be referred to the larger 
works for this important information. 
Consequently either every beginner, whether his proposed 
course be thorough or elementary, must possess the works of 
Fresenius, or some other treatise of equal scope on the subject, 
or else copies of these works must be placed in the laboratory, 
for reading or reference,—many copies, if the number of.students 
is large. Each plan has its manifest disadvantages. 
In these considerations the author finds the reason for the pub- 
lication of this little volume, for the convenience of his own 
students,—that they may have always at hand such full details as 
to the chemistry and manipulation of these operations that they 
are called upon to perform, many of which are entirely new to 
them, that they need never be at a loss as to what to do, or how 
to do it, or why they do it, if they will read with care what is 
here given. When the work laid out in this book is mastered, 
the student who wishes to go further in general or special direc- 
tions will find himself prepared to use the general or special 
treatises on chemical analysis, for no one of which this introduc- 
tion can be taken as a substitute. 2 
INTRODUCTION. 
Chemical analysis is studied usually because the student expects 
to make some application of it in his business or profession ; in 
so far it is a practically useful study. But beyond this it has, as 
does the study of every branch of science, its special disciplinary 
value. It enforces the importance of attention to even small 
details in manipulation; the student learns, if he is capable of 
learning anything by experience, that the only sure way to suc- 
cess in any part of the work is by the closest following of the 
directions given him, at least till he has proved, by conclusive 
results of his own experiments or observations, that there is a 
better way; but this better way must in its turn be followed no 
less precisely. 
No one of the analytical processes in use is absolutely perfect; 
it is this that makes accuracy and precision in the manipulation 
of so much the greater account. Such discipline as this practice 
affords of the hand, eye, and judgment is useful in many of the 
professions for which the first special training is given in the 
University. 
Chemical analysis comprises two kinds : 
Qualitative analysis, by which we ascertain what chemical ele- 
ments or compounds a substance contains. 
Quantitative analysis, by which we ascertain how much of one 
or more of its constituents the substance contains. 
The chemistry and manipulation common to both kinds of 
analysis is treated in Part lof this work. The systematic course 
of qualitative analysis follows in Part 11. In Part 111 a descrip- 
tion is given of some of the special operations of quantitative 
analysis, and in Part IV the special examples for practice com- 
prised in this short course are described and explained. Finally, 
in Part V, lists of apparatus and reagents are given, with some 
instructions concerning their proper use, and several Tables for 
reference. PART I 
THE PROCESSES OF ANALYTICAL CHEMISTRY, 
AND THE 
PRODUCTS OF ITS OPERATIONS. 
CHAPTER I. 
SOLUTION AND SOLIDS FROM SOLUTION. 
i. The getting of substances into solution, and getting them 
out of solution into the solid form, are fundamental operations 
of analytical chemistry with which the student has to deal more 
than with any others, especially in the earlier stages of his work. 
Some general acquaintance with the principles and methods of 
the solution of substances is essential at the very outset. 
2. Solution :—The solvent agents used. The more important 
solvent agents used in chemical analysis are, besides water, 
aqueous solutions of hydrochloric acid, nitric acid, and acetic 
acid, of the alkaline hydroxids, KOH, NaOH, or NH4OH, of 
alkaline sulfids, especially ammonium sulfid, and alcohol, 
ether, and carbon disulfid. 
3. Since all these acids and alkaline solvents consist largely of 
water, a substance that is insoluble in water cannot, so long as it 
is the same chemical substance, be dissolved by any one of them. 
Therefore when a substance that is insoluble in water is dissolved 
with the aid of a solution of an acid, such as the hydrochloric 
acid of the laboratory, or of an alkaline hydroxid, or an alkaline 
salt, such as a sulfid or a chlorid, some chemical change must 
precede such solution. On these grounds two kinds of solution 
may be distinguished, physical solution and chemical solution. 
4. Physical solution is the resultant solely of the mutual action 
of physical forces among the particles of the solid and of the 
liquid, the final result of which is the disappearance of the solid 
3 4 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 5-6. 
as a separate substance, visibly distinct from the liquid; it 
becomes completely merged in the liquid, but suffers no chemical 
change; on removing the solvent, in any way that does not 
chemically affect the substance dissolved in it, as by evaporation, 
this substance reappears possessing the same chemical properties 
as before. This is the kind of solution that is commonly effected 
by water. 
5. Chemical solution involves a chemical alteration of the sub- 
stance dissolved, and the production of a new substance that is 
soluble. It may take place with water alone, when the substance 
is an oxid that can form a soluble hydroxid. CaO is probably 
insoluble in water, but Ca(OH)2, formed as soon as this oxid is 
brought in contact with water, is slightly soluble. We cannot 
say that we know whether K2O is soluble or insoluble in water; 
for in the instant of contact between the two KOH is formed, 
which is very soluble. 
Most commonly, it is a more active agent than water, which 
serves to bring about the solution by chemical change, such as 
an acid or an alkaline solution ; and if the excess of acid or 
alkali, remaining after the solution is completed, be wholly 
removed, leaving nothing but water, the solution still continues 
undisturbed, which is evidence that a new substance has been 
formed, soluble in water; and it has been formed by chemical 
changes affecting the solvent agent as well as the substance dis- 
solved, as illustrated by the following equations ; 
CaC03 + 2HCI == CaCl2 + H2O + C02. 
Ca3(P04)2 + 4HCI = CaH4(PQ4)2 + 2CaCl2. 
3Pb + BHNO3 = 3Fb(NQ3)2 + 4H20 + 2NO. 
as2S3 + 3(NH4)2S == 2(NH4)3AsS3. 
The substances whose formulas are underlined are new sub- 
stances, which are soluble in water. 
6. Table of solubilities. Some acquaintance with the solu- 
bility of the chemical compounds met with in the ordinary work 
of chemical analysis is very helpful to the student. In the fol- 
lowing Table, Win the square corresponding to any salt indi- 
cates easy solubility in water, w sparing solubility, wa solubility 
in water only when £t least slightly acidified, A insolubility in 
water but solution by moderately dilute mineral acids, and I 
insolubility in water or dilute acids. Slight trace of solubility 
in water or dilute acids, or solubility or insolubility in acetic SOLUTION AND SOLIDS FROM SOLUTION. 
5 
TABLE 
I- 
-SOLUBILITIES 
Aluminum. 
Ammonium. 
Antimonous. 
j Barium. 
A 
3 
s 
H 
Cadmium. 
Calcium. 
Chromium. 
Cobalt. 
Copper. 
\ Gold. 
Ferrous. 
j Ferric. 
j Lead. 
a 
d 
'cfl 
CL) 
a 
Ci/) 
c3 
s 
Manganese. 
, Mercurous. 
Mercuric. 
1 
% 
r* 
CJ 
s 
Platinic. 
Potassium. 
Silver. 
Sodium. 
Stannous. 
Stannic. 
Strontium. 
Zinc. 
Acetate, 
W 
W 
W 
W 
w 
W 
W 
W 
W 
W 
W 
W 
W 
w 
W 
w 
w 
w 
VV 
w 
VV 
VV 
W 
W 
W 
Arsenate, 
A 
W 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
VV 
A 
VV 
A 
A 
A 
A 
Arsenite, 
W 
A 
w 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
w 
A 
VV 
A 
A 
Borate, 
A 
vv 
A 
A 
w 
A 
A 
A 
A 
A 
A 
A 
w 
A 
. . 
A 
vv 
A 
VV 
A 
A 
A 
Bromid, 
W 
w 
\va 
W 
wa 
w 
VV 
W 
W 
VV 
W 
W 
W 
w 
w 
W 
I 
.VV 
W 
W 
w 
I 
VV 
VV 
W 
W 
W 
Carbonate, 
A 
w 
A 
A 
A 
A 
W. 
A 
A 
A 
A 
A 
A 
A 
A 
A 
w 
A 
vv 
A 
A 
Chlorate, 
W 
w 
VV 
W 
W 
W 
VV 
W 
VV 
W 
w 
W 
W 
W 
VV 
W 
VV 
w 
VV 
w 
VV 
VV 
Chlorid, 
W 
w 
wa 
W 
wa 
W 
w 
w 
W 
W 
w 
w 
w 
w 
W 
w 
I 
w 
w 
VV 
w 
I 
vv 
wa 
W 
w 
w 
Chromate, 
w 
A 
A 
A 
A 
W 
A 
A 
W 
w 
A 
w 
W 
A 
w 
A 
w 
A 
vv 
A 
w 
w 
Cyanid, 
, 
w 
w 
w 
A 
vv 
A 
A 
A 
A 
A 
A 
w 
A 
vv 
A 
vv 
1 
w 
vv 
A 
Ferricyanid, 
w 
w 
I 
w 
I 
I 
I 
w 
w 
w 
I 
i A 
I 
w 
I 
w 
A 
A 
w 
A 
Ferrocyanid, 
w 
w 
I 
w 
I 
I 
I 
I 
A 
w 
A 
A 
I 
w 
I 
w 
A 
A 
vv 
A 
Fluorid, 
A 
vv 
W 
A 
w 
w 
A 
w 
w 
w 
w 
w 
w 
A 
A 
VV 
vv 
w 
w 
VV 
w 
W 
VV 
A 
w 
Hydroxid, 
A 
w 
. . 
w 
A 
A 
W 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
w 
w 
A 
A 
A 
A 
lodid, 
w 
wa 
vv 
wa 
W 
w 
W 
W 
wa 
A 
W 
VV 
w 
W 
W 
A 
A 
W 
vv 
I 
vv 
W 
wa 
w 
VV 
Nitrate, 
VV 
w 
w 
wa 
w 
w 
W 
W 
vv 
W 
W 
vv 
W 
W 
wa 
w 
VV 
vv 
w 
vv 
vv 
wa 
wa 
w 
VV 
Oxalate, 
A 
w 
A 
A 
A 
A 
1 A 
w 
A 
A 
A 
W 
A 
W 
A 
A 
A 
A 
w 
A 
w 
A 
w 
A 
A 
Oxid, 
A 
A 
A 
A 
1A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
w 
A 
w 
A 
A 
A 
A 
Phosphate, 
A 
w 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
w 
A 
w 
A 
A 
A 
A 
Sulfate, 
W 
w 
wa 
I 
wa 
W 
W 
W 
W 
W 
W 
VV 
I 
W 
W 
w 
wa 
VV 
w 
w 
w 
W 
VV 
I 
W 
Sulfid, 
w 
i 
w 
i 
I 
w 
I 
I 
I 
A 
A 
I 
W 
A 
I 
i 
A 
I 
w 
I 
w 
I 
I 
VV 
A 
Sulfite, 
w 
w 
1 A 
A 
A 
A 
A 
A 
A 
A 
1 
1A 
A 
A 
A 
A 
A 
A 
A 
vv 
A 
w 
A 
A 6 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 7-3. 
acid is not taken account of, nor solubility or insolubility of 
other than normal salts (§ 15), except when, as in the case of 
many carbonates, for example, basic salts are those ordinarily 
met with. 
An examination of this Table shows at once that all normal 
nitrates and acetates, and all the salts of the alkaline metals 
(potassium, sodium) are soluble. Other similar general conclu- 
sions can be deduced by the student himself, which, once 
familiarly learned, will be very useful in working out equations. 
Of solubility in strong acids, but not in dilute, the following 
instances are specially important: nearly all insoluble sulfids are 
soluble in concentrated nitric acid ; many insoluble silicates are 
decomposable by concentrated hydrochloric acid, with solution 
of the bases. 
7. Solution of metals. As to the solubility of the commonly 
occurring metals, it is to be noticed that all are absolutely in- 
soluble in pure water; that those of the aluminum and iron 
groups are soluble in hydrochloric or sulfuric acid, with evolu- 
tion of hydrogen, and with the formation of chlorids or sulfates ; 
they are soluble in nitric acid, with the formation of the usual 
products (§ 24 b); that the rest, except gold and platinum, are 
dissolved by nitric acid, forming solutions except in cases of 
antimony and tin, that gold and platinum are attacked by aqua 
regia or any mixture evolving free chlorin. 
8. Miscellaneous considerations, a. Solubility and tempera- 
ture : The solubility of salts is in most cases much greater in 
hot than in cold solvents. 
b. Solubility of salts in acids. A salt that is perfectly soluble 
in water may be insoluble in strong acid ; the salt, if separated 
out or precipitated in the acid, usually takes a somewhat crystal- 
line form, often to the confusion of the young analyst; on the 
addition of sufficient water, solution takes place readily. For 
instance, barium chlorid, which is easily soluble in water, is not 
soluble in strong hydrochloric acid; hence, if barium carbonate 
is dissolved in too strong a solution of the acid, the chlorid is 
apt to appear as a crystalline deposit. 
c. Comparative range of solvent power of different solvents. 
In the operations of chemical analysis, the solubility or insol- 
ubility of substances is utilized in, more particularly, water, 
alcohol, mineral acids, organic acids, and solutions of alkaline 
hydroxids or hydrates, or alkaline solutions as they are com- 
monly called. Of these, water has by far the widest range of §9-] 
SOLUTION AND SOLIDS FROM SOLUTION. 
7 
solvent power; it may, in fact, be called the solvent upon which 
we depend in nearly all cases for solution of substances: a 
chemically active agent does not dissolve, but, as has been 
already shown, only makes new compounds that are soluble 
in water. For this preparatory work, hydrochloric and nitric 
acids have the widest range of action ; comparing these two 
acids, it may be observed that while nitric acid will dissolve nearly 
all substances that are dissolved by hydrochloric acid, it will, in 
virtue of being an oxidizing agent (§ 20), dissolve many sub- 
stances that hydrochloric acid will not dissolve, such as some 
metals and their sulfids. 
d. A saturated solution. For each substance and each neutral 
solvent in which it is soluble, there is a definite limit to the 
amount of the substance that can be dissolved at a given tem- 
perature ; when this limit is reached the solution is said to be 
saturated. When the temperature of such a solution falls, or, in 
a very few cases, is raised, or when any of the solvent is removed, 
a portion of the substance separates out in the solid form. When 
thus separated it is more or less crystalline. Therefore, when a 
crystalline deposit appears in a solution, for no other apparent 
reason than a possible change in one or both of these conditions 
mentioned above, it can be re-dissolved either by adding more 
of the solvent, usually only water being required, or by raising 
the temperature. 
e. In the case of chemical solution, the quantity of the sub- 
stance dissolved is dependent on the quantity of water present to 
dissolve the new substance formed, and also, in accordance with 
the laws of stochiometry, on the quantity of the chemically 
active, solvent agent present. So far as this active agent is con- 
cerned, it is independent of the temperature, except that, as 
chemical action is stronger at high than at low temperatures, the 
solution will proceed more rapidly if the mixture of substance 
and solvent is heated. 
g. Solution of gases or of vapors. Some of the reagents used 
in chemical analysis are solutions of gases or vapors in water, 
such as hydrochloric acid and ammonia; and some reactions 
that are made use of in the analytical work depend to some 
extent on such solution. 
As in the solution of solids in water, there is a definite limit 
to the amount of the gas dissolved for any given temperature ; 
but the amount dissolved increases, instead of diminishing, as 
the temperature falls, and increases also as the pressure of the 8 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 10-I I. 
particular gas dissolved increases on the surface of the liquid, or, 
in other words, as the proportion of that gas increases in the 
air to which the dissolving liquid is exposed. 
From what has been stated above, except when a solution of a 
gas is very dilute, that is, has but a very little of the gaseous 
substance in it, if the solution is warmed a portion of the sub- 
stance will escape; or, if a strong solution is poured from a 
closed vessel into an open dish, or even if the stopper of the 
bottle containing it is left out, the gas will escape. 
Other reagents in common use are solutions of substances that 
are volatile only at moderately elevated temperatures, or of 
vapors, such as bromin water. On heating such a solution the 
substance dissolved will escape in part, and the more rapidly the 
lower the temperature at which it assumes the vaporous form. 
In a solution containing a mixture of such substances, the more 
volatile one may be almost entirely expelled by heat, while a 
large portion of the other still remains; thus nitric acid or hy- 
drochloric acid may be removed from a solution by heating it 
for a sufficient length of time with a large excess of sulfuric 
acid. 
io. Solids from Solution :—There are many ways by which 
the reverse of solution of solids can be accomplished ; some of 
these have been referred to in the preceding sections. 
The cooling of saturated solutions. This is of little account in 
analytical work. In a few cases, when the cooling is slow, the 
crystalline form assumed by the solid may be a convenient 
means of identifying it or confirming results of other tests. 
ii. The removal of the solvent agent. This may be accom- 
plished in three ways. 
a. By its slow escape, as it passes into vapor by simple ex- 
posure to the air. This takes place readily with the chemically 
inactive solvents, water, alcohol, common ether, petroleum ether, 
and carbon disulfid. The process is of little use in analytical 
work, except when, as also in the case of slow cooling of satu- 
rated solutions referred to in the preceding section, the solid 
obtained may exhibit some characteristic crystalline form that 
will aid in its identification. Such an operation is best applied 
to a small quantity of the liquid in a watch glass, and it is usually 
necessary to examine the deposit with the microscope. 
b. By the rapid removal of the solvent by the aid of heat. 
This is a very important analytical process, for it often becomes 
necessary to obtain the product of some operation, or series § 12.] 
of operations, in the solid form, expeditiously : see Evaporation, 
Chap. YI. 
ACIDS, BASES, SALTS. 
9 
c. By the removal of an active solvent through neutralization. 
Many precipitates are soluble in acids, and some are soluble in 
solutions of alkaline hydroxids or salts, forming new, soluble 
compounds; on neutralizing the acid or the base, or decompos- 
ing the solvent salt by an acid, the original substance is precip- 
itated again, in some cases; in other cases, another substance is 
formed, of the same qualitative composition, but different quan- 
titative composition. The solution of ammonium magnesium 
phosphate in acid and the effect of the neutralization of the acid 
by ammonia, also the solution of aluminum hydroxid in sodium 
hydroxid and the result of the neutralization of the alkali by 
acid, are good illustrations of the first mentioned kind of action. 
See aluminum and magnesium in the aluminum and calcium 
groups, Chap. X. The precipitation by acids of the sulfids 
of arsenic, tin, and antimony from their solutions in ammonium 
sulfid, illustrates the second kind of action; see the tin group, 
Chap. X. 
b. By the formation, through chemical action, of a new insolu- 
ble compound containing at least one of the constitutents of the 
substance dissolved. This method of obtaining solids from solu- 
tion, which is of fundamental importance in analytical chemistry, 
will be more fully considered in Chapter IV, on Metathesis. 
CHAPTER 11. 
ACIDS, BASES, SALTS. 
12. A solution made in any of the ways described in Chap. I 
may contain acids, bases, or salts. 
For our present purposes, an acid may be defined to be a body 
always containing (r) hydrogen, (2) a so-called electro-negative 
or acidigenic (acid-generating) element, such as chlorin, sulfur, 
phosphorus, and (3) sometimes oxygen; its hydrogen being 
replaceable by an electro-positive or basigenic (base-generating) 
element or compound, such as potassium, calcium, magnesium. 
An acid may, however, contain, in the place of one of the reg- 
ular acidigenic elements, an element usually basigenic, as iron, ELEMENTS OF CHEMICAL ANALYSIS. 
or manganese in manganic or permanganic acid. The presence 
of an acid in solution is indicated by the reddening of blue 
litmus paper. 
13. A base is a body containing (1) a basigenic or base-form- 
ing element or compound, such as potassium, ammonium, cal- 
cium, or iron, and (2) the hypothetical hydroxyl, HO, this 
hydroxyl being replaceable by an acid minus its basic hydrogen. 
The presence of a base in solution is indicated by the blue color 
given to red litmus, or the brown color given to turmeric. 
By the abstraction of the elements of water from one or two 
molecules of an acid or a base, the so-called anhydrids are pro- 
duced : these anhydrids are also called oxids, with the prefixes 
di, tri, tetra, pent, used to indicate the number of atoms of oxygen, 
when more than one atom is present. 
Thus:— 
2HN03 = N205 (nitrogen pentoxid) -j- H2O. 
H2S04= S03 (sulfur trioxid) -f- H2O. 
2KOH = K2O + H2O. 
Ca(OH)2 = CaO + H2O. 
14. A salt is the body formed when the hydrogen of an acid 
replaceable by a basigenic element or compound, or the hydroxyl 
of a base replaceable by an acid minus its basic hydrogen, is so 
replaced. 
Thus:— 
KOH + HCI = KCI + H2O. 
2NaOH + H2S04 = Na2S04 + 2H20. 
It will be seen that in all cases where a salt is formed by the 
mutual action of a base and an acid, water is produced from the 
hydrogen of the hydroxyl and a part or all of the oxygen. 
Salts may also be formed by the direct union of acidigenic and 
basigenic oxids. 
A most characertistic property of an acid and a base, respect- 
ively, is this tendency to react with each other, and, neutralizing 
each other’s marked properties, to form a salt. 
15. Of salts there are several kinds. A normal salt is one in 
which the basigenic element or compound is substituted for all 
the replaceable hydrogen of the acid; for example, K2S04, 
NaN03, Al2 (So4)s. 
16. An acid salt is one of an acid having more than one re- 
placeable atom of hydrogen, in which less than the whole num- 
ber is replaced by a basigenic element; for example, KHS04; 
NaH2P04, compared with Na3 P04. §§l7-20.] OXIDATION, CHLORINATION, REDUCTION. 
11 
17. A basic salt is one, following the same line of definition, 
in which only a part of the hydroxyl of a base having more 
than one molecule thereof is replaced by an acid minus its 
hydrogen, or in which there is a smaller number of molecules of 
the acidigenic part of the salt, as compared with the basigenic 
part, than in the normal salt; for example, PbOHN03, 
Pb2020HN03, compared with the normal salt Pb (N03)2; 
Bi(OH)2NO3, BiOCl, compared with the normal salt 8i(N03)3. 
Basic salts are often difficultly soluble, when normal salts of 
the same acid are soluble, and sometimes cause the analyst 
much trouble: thus, while solubility in water is an eminent 
characteristic of all normal nitrates, many basic nitrates are in- 
soluble in water. 
18. A double salt is defined as one containing with one 
acidigen two basigens, as KNaS04, KPtC!fi. 
CHAPTER 111. 
OXIDATION, CHLORINATION, REDUCTION. 
ig. These processes play an important part in the operations 
of chemical analysis, and a clear understanding of their nature, 
and of the conditions under which they take place, is essential 
to intelligent work. 
Oxidation is the addition of oxygen to a substance, in chem- 
ical combination : chlorination is the addition of chlorin to a 
substance in chemical combination ; the reverse of either of these 
operations is reduction. 
20. Conditions under which oxidatio?i or chlorination may take 
place. 
a. The substance must be one capable of taking oxygen or 
chlorin into chemical combination. Such substances are all 
the basigenic elements, in the list in the Table, § 37, whether 
these elements are in the free state, or combined with sulfur as 
sulfids. In the latter case the sulfur is displaced by the oxygen 
or chlorin. Moreover, several of these elements are met with 
in ordinary analytical work in combination with more than 12 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 20. 
one proportion of oxygen or chlorin, as shown in the following 
table:— 
FeO, FeCl2; Fe203, FeCl3 
NiO, NiCl2; Ni203, NiCl3 
CoO, CoCl2; Co203, CoCl3 
Cr203, CrCl3; Cr03 
MnO, MnCl2; Mn203, MnCl3; Mn02; Mn03; Mn207 
Cu20, CuCl; CuO, CuCl2 
Hg,O,HgCI; HgO, HgC!2 
Au20, AuC12; Au203, AuC13 
As203, AsC13; As205 
Sb203, SbCl3; Sb205, SbCl5 
SnO, SnCl2; Sn02, SnCl4 
Therefore any one of these elements, although already in com- 
bination with oxygen or chlorin, may possibly combine with an 
additional quantity. 
Further, in our analytical work, we may meet with compounds 
of certain acidigenic elements with oxygen in different propor- 
tions. Such elements are nitrogen, sulfur, and carbon. 
b. There must be an oxidizing or chlorinating agent. Such 
agents, as used in analytical work, are especially nitric acid and 
free chlorin. The free oxygen of the air, or the oxygen dis- 
solved in water, may oxidize. Hydrochloric acid alone may 
act as a chlorinating agent on the metallic elements, but without 
ever carrying the chlorination higher than the first stage, if there 
be more than one with the metal in question; when this acid 
chlorinates, in this sense, its hydrogen is set free. 
Fe + 2HCI = FeCl2 + 2H. 
Also, when an oxid is dissolved in hydrochloric acid a chlorid 
is formed, but hydrogen is not set free. 
In compounds of bromin and chlorin with oxygen, the union 
is a feeble one, and these compounds may serve as active oxidiz- 
ing agents. Such are chlorates (KCIO3), and hypobromites 
(NaßrO). See § 24, d and e, for examples. 
Any element capable of combining with oxygen or chlorin in 
more than one proportion may yield compounds in these higher 
proportions, which themselves become oxidizing or chlorinating 
agents, when brought into contact, under the requisite condi- 
tions, with a substance capable of being oxidized or chlorinated. 
4FeSO4 + H2Mn04 + 3H2504 = 2Fe2(S04)3 + MnS04 + 4H20. OXIDATION, CHLORINATION, REDUCTION. 
Iron is changed from a ferrous to a ferric salt, and manganese 
is reduced from manganic acid to a manganous salt. 
c. In case the oxidizing agent is the acid constituent of a salt, 
it must usually be set free by an excess of another and a stronger 
acid before action will take place in solution. Hence, a nitrate 
in solution in water, as sodium nitrate or silver nitrate, is not an 
oxidizing agent as free nitric acid is; further, nitric acid, as 
formed free in an aqueous solution, is usually too much di- 
luted to act as an oxidizing agent. Potassium chlorate in solu- 
tion does not oxidize till an excess of concentrated hydrochloric 
acid or other stronger acid is added. To get oxidizing action 
from potassium dichromate strong acid must be added in excess. 
These substances may, however, act as oxidizing agents with- 
out such assistance, when fused. 
d. Usually, heat favors oxidation or chlorination, as it does 
chemical action generally. 
e. When an element can take more than one degree of oxida- 
tion or chlorination (see list in a of this section) the higher 
oxid or chlorid will commonly be formed (or a salt correspond- 
ing with the higher oxid), if the oxidizing or chlorinating agent 
be in excess to a considerable extent, and especially if its action 
be aided by heat. If the element itself is in excess, so that, as 
in the case of a solution of a metal by nitric acid, and especially 
if the acid be not very strong and the operation be conducted 
without heat, and a portion of the metal remains undissolved 
when the action of the acid has ceased, the lower oxid or chlorid 
is more likely to be formed. These rules as to chlorination 
apply, however, only to cases where the work is done by free 
chlorin, and have nothing to do with the simple solution of 
metals in hydrochloric acid. 
In cases where an element, or one of its compounds, is 
attacked by free chlorin in the presence of water, and the chlorid 
of this element cannot exist under the conditions of the attack, 
but the oxid or a compound of the oxid can exist, this oxygen 
compound may be formed, the oxygen being derived from the 
water present. 
As2S3 + 10CI + 8H20 == 2F13 As04 + 10HCI + 3S. 
21. Reduction. This operation, the reverse of oxidation or 
chlorination, takes place under conditions the reverse of those 
required for oxidation or chlorination. 
a. The compound must be one that is capable of giving up 14 ELEMENTS OF CHEMICAL ANALYSIS. [§ 22. 
oxygen or chlorin under the given conditions. Such compounds 
are any of those formed with oxygen or chlorin by the basigenic 
elements, and by certain acidigenic elements And as an element 
may combine first with one quantity of oxygen or chlorin, and 
then with an additional quantity (§ 20 a), so in reduction under 
certain conditions, a part of the acidigenic element may be with- 
drawn, and under the same conditions continued in force, or 
under other more powerfully active conditions, another portion 
may be withdrawn. 
2HgCl2 + SnCl2 = 2HgCI + SnCl4 
2HgCI -f" SnCl2 = 2Hg + SnCl4 
PtCl4 + SnCl2 = PtCl2 + SnCl4 
PtCl2 +2H =Pt + 2HCI 
b. There must be a reducing agent. This may be any element 
having under the given conditions a stronger attraction for the 
oxygen or chlorin in combination, than is exerted by the other 
element in the compound ; or it may be a compound of one of 
these elements with oxygen or chlorin in a lower proportion, that 
is capable of combining with more than one proportion. (§ 20 a). 
22. A reducing agent excelling all others in the scope and 
power of its action is nascent hydrogen, or hydrogen taken just 
at the moment when it is liberated from combination, as when zinc 
is dissolved in dilute sulfuric acid. Further, hydrogen compounds 
in which the hydrogen is rather loosely bound, and especially if 
associated with elements that are themselves capable of oxidation, 
are a strong reducing agent; sometimes the other element of the 
compound is set free. 
AsHs + 6AgN03 + 3H20 ■= 6Ag + H3As03 + 6HN03. 
Oxalic acid, H2C204, sulfurous acid, H.2S03, and hydrogen 
sulfid, often occur as agents of reduction in analytical work; 
carbon dioxid and water, sulfuric acid and water, and free sulfur 
being the products from the reducing agents in the several 
cases. 1 
As to the hydrogen, it may be observed in general that when- 
ever any oxidation, chlorination, or reduction is taking place, and 
there is any hydrogen in the substances engaged, it is very likely 
to appear in H2O or HCI in the products of the action ; the 
bond of union between hydrogen and oxygen, or between 
hydrogen and chlorin, is one of the strongest in chemistry; 
consequently the tendency to form one or the other of these §§ 23-24.] OXIDATION, CHLORINATION, REDUCTION. 
compounds, whenever there is any opportunity so do so, is very 
powerful. 
6H2C204 (oxalic acid) -f~ 2KMn04 -f- 2H2S04 = 8H20 I2C02 
+ K2S04 + MnS04. 
Free hydrogen not nascent is a strong reducing agent when 
aided by heat. Also at higher temperatures, a red heat or above, 
carbon is a powerful reducing agent, carbon monoxid or carbon 
dioxid being the product. 
23. Except when oxidation or chlorination is effected directly 
by free oxygen or chlorin, these processes and reduction go hand 
in hand; the simultaneous presence, and the co-operation, of 
both a substance capable of oxidation or chlorination, and 
a body capable of yielding oxygen or chlorin, are essential. 
Commonly, the existence together in a solution is impossible of 
a substance in the free state that is capable of acting as an oxid- 
izing or a chlorinating agent under the existing conditions, and 
of a substance capable of taking up oxygen or chlorin. 
Since, as is usually the case in analytical operations, oxidation 
or chlorination of one substance implies reduction of some other 
substance,' the same general conditions that are favorable for one 
operation are favorable for the other. 
24. The reactions of oxidation and reduction. 
a. With free oxygen. When oxidation results from the action 
of free oxygen of the air, or the oxygen dissolved in water, as 
when moist and freshly precipitated ferrous sulfid is oxidized to 
the sulfate, the reaction needs no explanation. 
b. With nitric acid; products of the oxidation. Water is 
always formed by the union of the hydrogen of the acid with a 
part of its oxygen. 
When metals or their sulfids are treated, a nitrate of the 
metal is nearly always formed ; in a very few cases, as with 
antimony and tin, for example, oxids that are insoluble in the 
excess of acid are produced. All such exceptions to the general 
rule that nitrates are formed are mentioned where they occur. 
In the treatment of a sulfid the sulfur is either set free or 
oxidized to sulfuric acid (see sulfids, Chap. YII). 
Products of the reduction. The nitrogen of the decomposed 
nitric acid may be evolved as ammonia, NH3, free nitrogen, 
nitrogen monoxid or nitrous oxid, N2O, nitric oxid or nitrogen 
dioxid, N202, or NO, nitrogen trioxid, N2Os, or nitrogen tetroxid, 
N204, or N02. If the nitric acid is in excess and a boiling heat ELEMENTS OF CHEMICAL ANALYSIS. 
is used, the product is nearly all NO : but excess of reducing 
agent, a very dilute acid, and a low temperature favor the form- 
ation of NH3 at the other extreme. Under certain conditions 
hydrogen may be set free, although, as the presence of nascent 
hydrogen and nitric acid together is incompatible, such condi- 
tions can occur but rarely. In general, NO, a colorless gas, is 
formed in analytical work, which in contact with the air takes 
up oxygen, forming N203 and N02, the latter appearing as 
brown fumes. 
The following diagram illustrates the manner in which HN03 
may be supposed to be broken up in the oxidation of substances, 
or in the production of nitrates of the metals, with NO as the 
product of the reduction 
In oxidation. 
Formation of nitrates. 
H - O -O - 1 N= O 
H- O -O- N= 0 
H-(CT - O - N= 0 
H- O -O- N= O 
H- O |-0- N= 0 
H- I O -Or- N= O 
It wilb be seen that in simple oxidation 2 molecules of 
HN03 yield 3 atoms of oxygen : and that, in order to get the 
product H2O, which is always formed, the number of molecules 
of HN03 taken must always be 2 or some multiple thereof; and 
that the number of atoms of oxygen used for the oxidation 
must always be 3or some multiple thereof. Observe, also, that 
just half of the oxygen of the HN03 consumed goes to oxidize 
the metal, and the other half appears in the H2O and NO. 
It is also shown that in the formation of nitrates, 4 molecules 
of HN03 yield 3 molecules of the hypothetical N03; and that, 
in order to get the product H2O, the number of molecules of 
HN03 used must be 4 or some multiple thereof, and the number 
of molecules of N03 used directly in the production of, and 
appearing in, the nitrate in the right hand member of the equa- 
tion must be 3 or some multiple thereof. 
3Sn + 4HNO3 = 3SnO2 + 2H20 + 4NO. 
3Pb + BHN03 = 3Pb(NO3)2 + 4H20 + 2NO. 
c. With aqua regia (3 parts cone. HCI, 1 part cone. HN03). 
These acids react with each other as follows: 
3HCI + HN03 = NOC12 + Cl + 2H20, 
or 3HCI + HNOs = NOCI + 2CI + 2H20. 
The products vary according to the existing conditions. OXIDATION, CHLORINATION, REDUCTION, 
The reaction is aided by heat, and takes place only very 
slowly between moderately dilute acids. These compounds of 
nitrogen, oxygen, and chlorin, or nitrosyl chlorids, are gaseous 
and very unstable; they are dissolved by that part of the acid 
still undecomposed : when the solution is saturated their produc- 
tion ceases. If a metal is put into this solution, action (chlorina- 
tion) takes place, these compounds being decomposed and sup- 
plying chlorin, while oxids of nitrogen escape; the solution 
being then no longer saturated with these gases a fresh quantity 
is formed: thus the operation goes on, as long as these 
chlorinating products are consumed by a body capable of chlori- 
nation. It is especially the production of this abundance of free 
and nascent chlorin that makes aqua regia such a powerful 
chlorinating agent. 
The products of the action of aqua regia are, therefore, a 
chlorid of the metal attacked, and water, and, for the reduction, 
lower oxids of nitrogen, probably nitric oxid for the most part. 
d. -Potassium chlorate and hydrochloric acid. This mixture 
gives when heated a greenish yellow gas, a mixture of chlorin 
and chlorin dioxid. 
KCI0S + 2HCI =CI + C 102 + KCI + H2O. 
The chlorin dioxid is very unstable, giving nascent chlorin 
and oxygen by its decomposition. The mixture is, therefore, a 
very efficient chlorinating agent: in the presence of water it 
may act also as a strong oxidizing agent. 
The products of the action of this mixture on substances 
capable of oxidation or chlorination are oxids and chlorids of the 
basigenic element. 
e. JSromin. This acts as an oxidizing agent in the presence 
of water, by reason of its strong attraction for hydrogen, and the 
generally greater stability of the oxids than of the bromids. 
Being much more soluble in concentrated hydrochloric acid than 
in water, this acid solution is often used in preference to an 
aqueous solution. Hydrobromic acid and oxygen are the pro- 
ducts of the reaction with water, in the presence of a substance 
capable of oxidation. 
Dissolved in solutions of potassium or sodium hydroxid it 
yields a mixture of hypobromite, KBrO or NaßrO, and bromite, 
KBr02 or Na Br02, powerfully oxidizing substances: a bromid 
of the alkaline metal is the product of the reduction. 
CH4N20 (urea) + 3KBrO = C02 -f 2H20 + sKBr + 2N. 
2 ELEMENTS OF CHEMICAL ANALYSIS. 
f. Chromic acid. In a solution of a chromate containing free 
acid, the chromic acid is liberated from its base, and acts as 
an oxidizing agent, or chlorinating in the presence of hydro- 
chloric acid. 
Salts containing chromium as a basigenic constituent are the 
products of the reduction. 
2H2Cr04 + 6HC! -f- 3H2S = 8H20 + 2CrCl3 + 3S. 
g. Sulfuric acid. This when concentrated and hot may act as 
an oxidizing agent, sulfurous acid being the product of the reduc- 
tion, and a sulfate of the metal oxidized. As under e above, the 
carbon and hydrogen of organic substances may be oxidized in 
this way, but the nitrogen nearly always appears in the form of 
ammonia. Kjeldahl’s exceedingly useful method of determining 
nitrogen in organic compounds is based on this reaction. 
25. Changes in valence accompanying oxidatioii or chlorination, 
or their reverse. Thus far, these operations have been regarded 
only as involving the addition or removal of oxygen and chlorin ; 
other important changes, as in valence, may, however, take place 
simultaneously, supposing that more than one valence be allowed 
to the same element. The higher degrees of valence are found 
in the higher grades of oxidation or chlorination. Illustrations 
will be found in the Table, § 37, where the same element is 
given in more than one group. The student should notice the 
very marked changes in chemical properties that sometimes 
accompany such changes in valence. 
CHAPTER IV. 
METATHESIS. 
26. Constant use is made in chemical analysis of the kind 
of chemical change designated as metathesis, from the Greek, 
meaning to set over. 
Conditions under which metathesis takes place. 
a. Metathesis takes place as a rule only between substances 
that are liquefied either by solution or fusion. Only under such 
conditions is there that closeness of contact, and freedom of mo- 
tion among the particles of the substances acting on one another, 
which permits or facilitates chemical change. § 27-] 
METATHESIS. 
19 
In the case of exceptions to this rule, which are to be found 
in the course of the qualitative work, it will be noticed that at 
least one of the substances engaged is in solution, while the other 
is often freshly precipitated and moist, when it may reasonably 
be supposed to exist in a much more porous condition, exposing 
a larger surface to attack by the dissolved reagent, than when 
even in the finest powder of the previously dried substance. 
W or wa in the Table of Solubilities, § 6, may be taken as 
indicating sufficient solubility for a precipitating reaction ; and 
such a reaction will be given, provided that the reagent used is 
capable of giving it in any solution of the substance. 
b. That one and the same elementary or compound substance 
exhibits unequal attraction for different elementary or compound 
substances is an important fundamental principle of chemistry, 
which the student learns very early in his study of the science. 
But the formation or decomposition of chemical compounds, or, 
in other words, the kind of metathesis that takes place, is some- 
times powerfully modified by conditions quite independent 
of the relative forces of attraction that make or break these 
compounds. 
27. The following law illustrates this statement, and at the 
same time bears a very important relation to the operations of 
analytical chemistry. 
On bringing together a substance from the acidigen column, 
Table, § 37, and one from the basigen column, if a substance 
can be formed by their union that is insoluble in the medium 
of contact, or one that is gaseous at the temperature of contact, 
such union will take place; or such changes will take place in 
the arrangement of the constituents of compounds containing 
these substances as may be necessary to produce the new insol- 
uble or gaseous compound. 
It is above all upon the unfailing operation of this law that the 
success of the work of the analytical chemist depends; if, for 
instance, he could not rest assured beyond all doubt of the cer- 
tainty of the reaction expressed by the following equation : 
Na2S04 + BaCI2 = BaSO* + NaCl2, 
or, that in a solution prepared in a certain definite manner a 
barium salt would always react with a sulfate, yielding a precipi- 
tate of barium sulfate, and at least almost completely removing 
the sulfuric acid from the solution, no dependence could be 
placed on the reliability of his qualitative or quantitative results, 20 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 28-29. 
where the detection or quantitative estimation of either barium 
or sulfuric acid is concerned. 
28. In cases where insoluble compounds cannot be formed by 
interchange of the constituent parts of the substances brought 
together, it may be supposed that new compounds are neverthe- 
less formed, even though there may be no visible changes. If, 
for instance, the substances brought together in solution were, 
instead of those in the above equation, sodium sulfate and 
ferric chlorid, a part of the chlorin may go to the sodium and a 
part of the sulfuric acid to the iron, so that four salts, Na2S04, 
FeCl3, NaCl, Fe2(S04)3 exist in the solution instead of the two 
original ones, or instead of only one salt, as in the secqnd mem- 
ber of that equation. Evidence of such change is found in 
certain color reactions, as, for instance, the deep red color which 
results from the reaction between a ferric salt and a sulfocyanate, 
(§ 92): no insoluble substance is formed, but there must be, 
nevertheless, a partial interchange of acids and bases. Moreover, 
when a new compound can be formed by interchange of the con- 
stituents, or by metathesis, that is partially or slightly soluble in 
the medium of interchange, a portion of the new compound will 
be precipitated, while the rest may remain in solution as such, 
and we will have also some of the original, undecomposed salts; 
thus, with the first letters of the alphabet, used as coefficients, 
representing known quantities and the last letters unknown 
quantities: 
aCaCl2 + bK2S04 = uCaS04 -f zKCI + vCaS04 + yCaCl2 + xK2S04. 
Calcium sulfate is slightly soluble in water, and while one 
portion is precipitated, another will remain in solution, together 
with a portion of the original calcium salt. 
Such will be the result, as may now be readily understood, 
if the conditions under which a complete precipitation is to be 
made are not carefully fulfilled: errors may follow, which may 
be especially serious in quantitative work, and often in qualita- 
tive analysis as well, and which the student is too prone to 
attribute to the fallibility of the reaction instead of his own 
want of care. 
29. If, as a result of the metathesis, one of the new substances 
produced be an acid, or any other solvent agent that will dis- 
solve the other possible product of the metathesis, of course the 
conditions are not fulfilled, according to the law stated above,. § 3°-] 
for the production of that substance, and there may be no visible 
evidence of its production. 
METATHESIS. 
21 
FeCl3 + H3P04 = FeP04 + 3HCI 
may not be a correct representation, since FeP04, though in- 
soluble in water, is soluble in hydrochloric acid ; but the following 
is correct:— 
FeCl3 + (NH4)3PO4 = FeP04 + 3NH4CI. 
A precipitate may be formed in the first case, however, since 
the small quantity of HCI set free can make only a very dilute 
acid liquid, perhaps insufficient to keep the phosphate from 
separating out. 
30. Several kinds of metathesis are made use of in analytical 
work. Between two salts giving : 
a. An insoluble new salt; 
NaCl + AgN03 = AgCl + NaNOs. 
b. No insoluble salt, but at least a partial exchange of acids 
and bases, and some evidence of the exchange visible to the 
senses; 
FeClg + 3NH4CNS = Fe(CNS)3 (deep red solution) -)- 3NH4CI. 
A more nearly correct equation would, however, be similar to 
that in § 28, but without any precipitation at all. 
Between an acid and a salt giving : 
c. An insoluble salt, insoluble in water, but possibly not in 
the new acid produced, unless very dilute; 
Hg N03 + HCI = HgCl + HN03, 
But 
CaCl2 + H2C204 -f 2HCI =no visible reaction, possibly. 
d. A gaseous product. 
K2C03 + 2HC2H302 = 2KC2H302 + C02 + H2O. 
Between anhydroxid and a salt giving : 
e. Metallic hydrates or hydroxids, insoluble : 
AICI, + 3NaOH = AI (OH), + sNaCI. 22 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 31-33- 
f. Insoluble salts into which the basigenic element of the 
hydroxid enters:— 
Ba(OH)2 + K2S04 = BaS04 + 2KOH. 
g. A gaseous product: 
NH4CI + KOH = KCI + NH3 + H2O. 
31. Metathesis is not completed instantaneously, although it 
may set in the moment that the substances reacting upon one 
another are brought together. If a slightly soluble salt is the 
product, this slight solubility may retard the completeness of 
the separation, or prevent it altogether ; but if time is allowed, 
the separation may be carried much further than at the beginning 
of contact, and it may in the end be quite complete. Instances 
in illustration of these points will be met with in the course of 
the analytical work that follows, where directions are given to 
allow the mixture of reagent and solution of substance to stand 
for several hours, in order that the desired reaction may be 
obtained or completed. 
CHAPTER V. 
WRITING EQUATIONS. 
32. All the chemical changes that take place in the operations 
of chemical analysis, and upon which these operations are based, 
are comprised under these three heads of (1) solution, (2} oxida- 
tion and reduction, and allied processes in which chlorin, bromin, 
iodin or sulfur may take a part, like that taken by oxygen, and 
(3) metathesis. 
The working out of chemical equations explaining these 
changes may be justly regarded as a valuable test of the student’s 
insight into their chemistry; the writing of these equations is an 
important part of his study of chemical analysis, and it may be 
made to give some intellectual zest to what would otherwise be 
little more than mere machine work. 
a. A knowledge of the formulas of the substances originally 
acting upon each other. 
33. The correct writing of an equation requires : 
b. A knowledge of the products of this action. §§ 34-35-] 
WRITING EQUATIONS. 
c. A balancing of the equation so that its two members shall 
be equal in respect to kind and number of atoms, without in- 
cluding any substances, elementary or compound, whose presence 
is impossible or unreasonable under the existing conditions, and 
in which every simple or compound hypothetical body in- 
cluded shall have its supposed combining power or valence 
satisfied. 
23 
The information under a is given in the text-books, or often 
on the labels of the bottles; that under b is usually partly given 
in the description of the reaction ; what is not thus explained 
must be worked out under the general rules to be found in this 
text-book or in other works. 
The law stated in § 27 can be usefully applied, in combination 
with the study of the table of solubilities, in the working out of 
this part of the problem, where it becomes necessary to decide 
whether any reaction will take place. 
The work under c is accomplished by the application of prin- 
ciples laid down in this or other text-books. Under this head 
it is important to understand some of the principles upon which 
formulas are constructed. 
34. Structural or graphical formulas of compounds. The or- 
dinary formula of a compound shows only the relative and most 
reasonable number of atoms of each of the elements composing 
it. In the structural formula an idea is presented to the eye of 
the manner in which the component elements may reasonably be 
supposed to be grouped together, as illustrated by the following 
examples : 
In these formulas each element is supposed to have a certain 
combining power, measured in terms of a monovalent- atom, 
which is called its valence ; this is shown in the formula by the 
number of dashes connected with its symbol, or by Roman 
numerals in small type above and to the right of it; the valence 
of each of the elements in the second plan of the formula of 
potassium sulfate is indicated with perfect clearness by the 
method first stated. 
35. The true valence of many of the metallic elements is not 
yet settled : and this whole matter of valence should be strictly 24 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 36-37* 
regarded as merely a working theory, and one which can be 
made useful in the study of chemical equations. 
In the following Table the apparent valence is assigned, in 
such unsettled cases, that corresponds with the most generally 
adopted formulas of the compounds of these elements. To silver 
the valence one is assigned, which is apparent in the formulas 
AgCl, AgN03, Ag2S04, etc., although there are reasons for re- 
garding it as a dyad metal with a valence of two. Lead is prob- 
ably a tetrad element, but the formulas of all its common salts 
can be and are constructed on a dyad basis: the same may be 
said of barium, strontium, etc. Iron is regarded by many as 
dyad in ferrous compounds and tetrad in ferric compounds, while 
others regard it as tetrad in both. Again, more recent researches 
tend to show that it is triad in the ferric compounds, instead 
of tetrad ; although the question is, perhaps, not yet fully set- 
tled, the simpler formulas on the triad basis are given in the case 
of iron, and of some other elements also, in regard to which the 
same view is at least permissible. 
36. In the equations of the more simple forms of metathesis 
certain groups of elements are invariably transferred from one 
member of the equation to the other, apparently without being 
broken up in the actual course of the changes involved in the 
reaction; thus, in the equation 
K2S04 + 8a(N03)2 = BaS04 + 2KN03. 
S04 and NOs changes places; in the structural formula for 
K2SO, (§ 34), it is seen that the group S04 is dyad ; so in the 
structural formula for sodium nitrate Na-O-N 02, the group 
-0-N 02 is monad; if, in writing equations for. metathesis 
the student supposes these and similar acidic groups to be broken 
up he is very likely to end his work in confusion. Hence, for 
his purposes in equation writing, the most practical course is to 
regard these groups as actually transferred from one basigen to 
another, and as bearing the valence indicated by the composition 
of the compounds containing them. But he must not forget 
that they are purely hypothetical groups which have not been 
isolated, or proved to exist as such in any chemical compound 
apparently containing them. 
37. For assistance in explaining by equations the reactions 
that take place in the course of ordinary qualitative analysis, the 
following classification is given of elements, and of certain hypo- 
thetical compounds of which examples were mentioned in the 
preceding section. §§ 38-39-] 
WRITING EQUATIONS. 
In any product of the ordinary metatheses of chemical analysis 
there will be at least one basigen and one acidigen, but not 
necessarily only one atom or molecule of each : very rarely will 
there be more than one acidigen (see basic salts § 17) ; more often 
there will be more than one basigen, provided that the acidigen 
is more than monovalent (see acid salts § x 6), as illustrated 
in the following formula of sodium ammonium phosphate : Na 
NH4HP04. 
25 
Basigens (base-forming'). 
Acidigens (acid-forming) 
MONAD. 
H, K, Na, NH4, Ag, Hg(ous), 
Cu. 
Cl, I, Br, F, OH, N03. C 103, Cy, 
(or CN), CyS (or CNS), C 2H302. 
DYAD. 
Ba, Sr, Ca, Mg, Zn, Mn, Fe(ous), O, S, S03, S04, C03, C 204, Cr04 
Ni, Co, Ft, Hg(ic), Cd, Cu, Pb. Si03, Sn03, C 4H406. 
Au, Bi, Fe. 
TRIAD. 
P04, AsOs, As04, Sb04, C 6H507, 
Fe(CN6) (in ferricyanid). 
TETRAD. 
FeCy6 (or Fe(CN)6) (in ferrocyanid). 
Sn, Pt. 
DYAD OR TETRAD. 
TRIAD OR PENTAD 
Sb, As, 
38. In order that a chemical equation shall exhibit at a glance 
as much as possible of the nature of the products formed, the 
sign y is always to be put underneath the formula of an 
insoluble compound precipitated, and the sign A over the 
formula of any gaseous product evolved. In the case of the 
solution of a substance originally insoluble in water, effected by 
any active solvent agent, by which a new compound soluble in 
water is formed, the special, new, soluble product of the solution 
is to be indicated by a straight line under its formula. See 
equations, § 5. 
39. In writing equations it must be remembered that water 
is always present when the reactions are obtained in the wet way, 
that is in solutions, and that water can always be incorporated 
into the equation if necessary for reasonable results. 2 6 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 40. 
Also, when solution is made by an acid, an excess of the acid 
is always supposed to be present, and the possible effect of such 
excess must be regarded, such, for instance, as its tendency to 
form salts with oxides (§ 40 c). 
Also, that any soluble salt of an acid will give the same reac- 
tion as will the acid itself, but will not, of course, act as a solvent, 
like the free acid. Thus NaCl and HCI give the same charac- 
teristic product with silver salts. 
40. Providing against some of the common errors in writing 
equations, a. An equation written is to be regarded as repre- 
senting some chemical change of which there is sensible proof, 
such as the disappearance of a solid as it passes into solution by 
an acid, a case of oxidation or an allied process, or of reduction, 
a precipitate formed, or a gas evolved, or a change of color of 
the liquid. Metatheses may take place, and doubtless do when 
there is no plain evidence of it presented to the senses (§ 28) : 
but they are not such as are expressed by the ordinary equations 
explaining the operations of chemical analysis. The student 
must be able to give one of the above reasons for every equation 
that he writes. Failure to meet this requirement is a very com- 
mon source of error. 
b. As a result of the metatheses made use of in analytical 
work, in the wet way, it is not common that the metals them- 
selves appear as precipitates ; they of course never exist as such 
in a solution, for they are not soluble; it is only their com- 
pounds that are soluble. Therefore an equation that leaves a 
metal in a free state, and at the same time unprecipitated, 
cannot be a correct one. 
c. The oxids of the metals do not exist as such, in a free 
state, in a solution, since every oxid which is capable of forming 
a base soluble in water, immediately on contact therewith forms 
such a base. 
K2O + H2O = 2KHO. 
CaO + H2O = Ca(OH)2. 
Nor do the oxids, whether in solution or insoluble, exist as 
such in the presence of an excess of a free acid, provided that 
they are capable of yielding soluble salts with that acid ; any 
explanation of a metathesis which results in this condition of 
things must therefore be incorrect. 
d. It is more common to meet with the acidigenic elements 
in the elementary form, as the products of metathesis or other 
operations of analytical work; they may be in solution, as in the § 41-] 
WRITING EQUATIONS. 
case of bromin or chlorin, or precipitated, as iodin or sulfur, or 
gaseous, as chlorin. 
27 
e. The anhydrids of the acids, such as N205, S03, correspond- 
ing to the oxids of the bases, cannot exist in a free state, in an 
excess of water, provided that they are capable, as is the fact in 
most cases, of forming a soluble acid : for such an acid will be 
immediately formed on contact with the water, and will go into 
solution. 
f. Of course an acid and a base cannot exist free in the same 
solution ; whichever is in excess, or present in quantity more 
than sufficient to combine with all of the other, will take it all 
up to form a salt, no matter whether the salt so formed be 
soluble or insoluble. In this connection it is to be remembered 
that a hydroxid or hydrate (Chap. VIII) answers to the definition 
of a base (§ 13). 
g. In writing equations a reagent added is always to be con- 
sidered, as in the actual use of it, in excess, more or less above 
what is required of it for the actual work of precipitation or 
solution: and in completing an equation the possible effect of 
such excess must be taken into account; as, for example, when 
the reagent is a strong base, like KOH or NaOH, and an acid is 
one of the products of the reaction. Other illustrations of this 
principle occur in some of the equations given out. 
41. Students are too ready to extricate themselves from some 
difficulty in completing an equation, by indicating some chemical 
element which they cannot dispose of readily in any other way, 
as left in the free state; and usually, as the element so left free 
is often a very active one, as oxygen, chlorin, hydrogen, etc., 
this is done in direct violation of well established chemical laws. 
Some common errors of this kind are noticed in the preceding 
paragraphs with reference to some of the elements and to some 
compounds. A few other elements need mention in this con- 
nection. 
a. Oxygen. Except by the action of the electric current this 
element is left in the free state only when liberated from com- 
pounds containing it loosely held in combination, such as 
nitrates, chlorates or other compounds containing both chlorin 
and oxygen, and many of the metallic oxids, especially higher 
oxids where more than one is formed with the same metal—and 
in the absence of any substance with which it can combine at 
the temperature of liberation, such as metals especially of the 
potassium, calcium, aluminum, and iron groups, and some lower 28 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 41. 
oxids where more than one is formed with the same metal (§ 20), 
or any of the reducing agents mentioned in § 22, to which might 
be added hydrogen sulfld. 
This liberation of oxygen very rarely takes place except by 
heating the dry substance or mixture of substances, the temper- 
ature required for such liberation being in nearly all cases above 
the boiling point of water or of any aqueous solution. Free 
oxygen is therefore so very rarely a product of metatheses taking 
place in solution, that such a result would always be specially 
stated in the description of the metathesis. 
This statement as to the liberation of oxygen from its com- 
pounds does not refer to cases where it is withdrawn from oxid- 
izing agents, that readily yield it at temperatures within the 
boiling point of solutions, when bodies are presented that are 
capable of combining with it under such conditions : no free 
oxygen appears, however; the element simply passes, so far as 
our observation extends, from one compound into another. 
b. Chlorin. This element is set free ; 
x. By heating, in the dry condition, certain chlorids of metals 
of the copper and tin groups. 
2. When a substance containing chlorin and one containing 
loosely bound oxygen are brought together; and in case the 
chlorin is in the form of a stable salt, the cooperation of a 
strong acid is necessary. The common method of making 
chlorin, with Mno.2 and HCI illustrates the principle. For 
other illustrations see § 24 c, d, and f. 
But chlorin canot appear in the free state simultaneously with 
any body that will readily combine with it, like a metal, or hydro- 
gen, or a compound containing hydrogen loosely bound, as hy- 
drogen sulfid, or in the presence of any other sulfid, of which it 
at once takes the metal, or in the presence of water and an easily 
oxidizable substance, such as a sulfite or any organic substance. 
c. Hydrogen. When this element appears in the free state, as 
the result of a chemical reaction, and evolved from a liquid, it 
is the product: 
1. Of the action of certain metals of the first and second 
groups on water, these metals having such an exceedingly strong 
attraction for oxygen as to be able to take it from this most 
stable compound. 
2. Of the action of certain metals, as zinc, aluminum, or tin, 
on an aqueous solution of an alkali (KOH, NaOH), the metal 
displacing the hydrogen. §42.] 
WRITING EQUATIONS. 
29 
3. By the substitution, in a solution of an acid, of a metal for 
the hydrogen. The common method of preparing hydrogen by 
means of zinc and H2S04 is a familiar illustration of this prin- 
ciple. 
It will be seen that a common reaction characterizes all these 
methods : regarding water as a compound of the hypothetical sub- 
stance hydroxyl, HO, with hydrogen (HO -)- H = H - O - H) 
the hydrogen which appears may be always considered as this 
second atom of the element, as shown in the following equa- 
tions, illustrating each mode of production above mentioned : 
H-O-H + K equals KOH + H. 
2KOH -)- Zn equals K2 = 02= Zn -f- 2H. 
H2 = 02 = S = 02 -j- Zn equals Zn = 02 = S= 02 -f- 2H. 
It must not be forgotten that hydrogen in the moment when 
it is set free is in its nascent state and possessed of powerful 
reducing properties; and that, therefore, it cannot appear in 
the second member of the equation if there is present at the same 
time any oxidizing or chlorinating agent, or any of the sub- 
stances in the list in § 20 a, that readily give up oxygen or 
chlorin (or bromin or iodin). 
d. Nitrogen. Although this is not, like the elements already 
considered, powerfully active, and eager to enter into chemical 
combination, still it is set free from solutions only under certain 
conditions, occurring so rarely in ordinary analytical work, as 
always to receive special mention in the account of the reaction 
yielding it. 
e. Bromin and lodin. The same may be said as to the ap- 
pearance of these elements in the free state that was said of 
chlorin. 
f. Sulfur is very often set free in the reactions of sulfids, ap- 
pearing as a very fine powder, or turbidity: its appearance in 
the right-hand side of the equation is therefore allowable, and in 
this respect it differs strikingly from the other elements noticed 
above. 
42. Good practice is obtained in writing equations, as well 
as a better acquaintance with the chemistry of the analytical 
work, by writing out, in equations, the history of each sub- 
stance in its passage through the special course in which it is 
tested for. Taking, for example, calcium in the scheme for the ELEMENTS OF CHEMICAL ANALYSIS. 
calcium group, the solution brought there contains all its basi- 
gens in the form of their chlorids, as a consideration of the pre- 
ceding schemes will show. The first reagent added that affects 
the calcium is (NH4)2CO3, by which the carbonate is precipi- 
tated ; this, then, would be the first step in the history, to be 
shown by an equation. 
These carbonates are next dissolved in HC2H302, and the 
next equation would show the action of this acid on calcium 
carbonate. K2Cr04 has no action on the calcium in this solu- 
tion, and therefore the next step to be shown is the precipitation 
again by(NH4)2C03; next comes the solution of this precipi- 
tate in HCI, then the action of (NH4)2C204 on the salt of cal- 
cium in this solution, giving the final test. Thus it takes five 
equations to express the history of calcium, in its passage through 
the course for its detection. 
CHAPTER VI. 
THE MANIPULATIONS OF ANALYTICAL CHEMISTRY. 
43. Making Solutions. The suitable preparation of a solution 
for analytical purposes is not so unimportant a matter as on first 
thought it might appear to be. There is a certain degree of 
strength, or concentration of the solution that is most suitable 
for the work to be done with it, which may be different in 
different cases. 
Of substances soluble in water, there are few that will not 
dissolve in ten times their weight of the solvent. A solution of 
such concentration is not unsuitable, as a general thing, either 
for reagents, or as a solution of a substance to be analyzed. As to 
reagents, however, it is better that some should be much more 
dilute, and others stronger; for such cases directions will be 
given where they are needed. 
A substance to be analyzed in the wet way, that is by treatment 
with the reagents in solution, must first be brought into solution 
itself. For this purpose, only three reagents are in common use : 
distilled water, hydrochloric acid, and nitric acid, the acids being 
either dilute or concentrated. In general the presence of strong 
acid in a solution to be analyzed is to be avoided, as liable to §§ 44-45-] 
MANIPULATIONS. 
31 
interfere with the success of subsequent operations; the young 
analyst needs especially to bear this in mind. If strong acid is 
required for the actual solution of the substance, the excess of it 
must usually be removed by evaporation nearly to dryness; 
water is then added to the residue in such quantity as to make a 
solution of about the right strength. For the details of the 
operation of getting the substance into solution for analysis, see 
the directions given in Chapter VIII. 
44. Fluxing. Some substances can be brought into solution 
only after a metathesis has been produced between them and 
certain reagents in a state of fusion. Sodium and potassium 
carbonates are used for such reagents. A soluble salt of the 
acid of the insoluble substance and the alkali metal is formed, 
while the carbon dioxid either escapes, or forms carbonates 
of the basigenic elements in the insoluble substance, or is 
disposed of in both ways. None of these new compounds being 
insoluble in acids, the original substance can by this means be 
brought entirely into solution for analysis; with this exception, 
however; in the silicates we have a large class of insoluble 
substances; when the flux obtained with these compounds 
is treated with water and acid to dissolve it, a portion of-the 
silica immediately appears in an insoluble form ; but it is entirely 
separated from the basigenic elements with which it was origin- 
ally combined, and the condition of insolubility of the substance 
is broken up. 
In order that this operation of fluxing shall be entirely suc- 
cessful, three conditions must be fulfilled : 
The insoluble substance must be very finely pulverized in an 
agate mortar, till the powder does not feel gritty under the pes- 
tle ; this proper pulverization requires much patience. The 
powder must be most carefully mixed with a large proportion of 
the reagent, not less than three or four times its own volume. 
This mixture must be kept in a state of fusion for not less than 
fifteen to thirty minutes. The fusion is best performed in a 
platinum vessel of some kind ; porcelain might itself be attacked 
by the flux ; the heat of a blast lamp is necessary. 
45. Evaporation. This operation comes into use very often 
in analytical work, to make a solution more concentrated, or 
to free it from some ingredient that would interfere with opera- 
tions to follow, or to get a solid from the substance held in 
solution. 
Evidently, the larger the surface exposed for the escape of 32 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 46-47- 
vapor, in proportion to the mass of the liquid, the greater the 
rapidity of the evaporation ; and since the rate of evaporation 
is more rapid, the less there is of the vapor of the solvent in the 
air over the surface of the liquid, the more frequently this air, 
more or less laden with the vapor, is replaced by fresh air, the 
faster the evaporation will proceed. The porcelain evaporator 
is the utensil most frequently employed for this purpose ; in 
such a shallow dish the surface is large, and the vapor-laden air is 
readily removed by air currents passing over. A flask or a nearly 
covered beaker is most unsuitable for evaporation, for plain 
reasons ; if the flask is laid over on its side evaporation will 
proceed more rapidly than if it is upright; or, if, while upright, a 
continuous current of air is forced into it, the evaporation will 
proceed quite satisfactorily. 
46. In all quantitative work there must be no loss of substance. 
From the surface of a boiling liquid, even if the boiling is very 
quiet, minute particles of the solution are constantly projected 
upward and obliquely, some of which will fall outside of the 
dish, unless the surface of the liquid is much below its rim; 
therefore, in all work of this kind evaporation must be con- 
ducted without boiling the liquid, unless it is in a deep beaker, 
or in a flask laid on its side; in this last case the projected par- 
ticles strike the upper side of the flask, and are soon washed back 
again by the condensed vapor flowing down. 
As the evaporation nears the end, and some of the solid matter 
is deposited, the sputtering of the thickened liquid may become 
so violent that small masses of the substance may be projected 
out even from a deep beaker. Even in qualitative analysis, 
where the loss by the boiling of the liquid may be disregarded, 
this closing part of the operation must be conducted with care ; 
more loss may be suffered than can be afforded ; and, moreover, 
particles of the substance thrown out may fall into solutions near 
by, and thus do serious damage to other work. 
47. Ignition. A residue left by evaporation, or a precipitate, 
must sometimes be subjected to a stronger heat than is attainable 
in a solution, that is it must be ignited. This operation must be 
performed in a crucible, or, if the quantity is small, on a plati- 
num foil. It cannot be done in an evaporator without risk of 
breakage. Therefore, when the residue from an evaporation is 
to be ignited, with a spatula transfer it to the crucible while it is 
still in a pasty condition, dry it over a direct, low flame, and then 
proceed with the ignition, gently or strongly, as maybe directed. §4B.] 
MANIPULATIONS. 
33 
48. Acidification, alkalization, neutralization, adding a reagent 
in excess. It is often directed that a solution shall be made 
acid, alkaline, or neutral before proceeding further. With refer- 
ence to acidification, this does not mean that the liquid shall be 
made strongly acid, unless specially so stated, but rather that, 
if alkaline or neutral, acid shall be added slowly, and with con- 
stant stirring, or mixing in some other way, only till the reaction 
is clearly acid to the test paper; and the same is true as to 
making a solution alkaline. The proper mode of procedure, 
therefore, is to add the reagent in small portions at a time, care- 
fully mixing each portion as added, and frequently applying a 
drop of liquid to the test paper; when the reaction indicates an 
excess of the reagent, a little more may safely be added, in order 
to be sure of enough. The mode of procedure is similar for 
making a liquid alkaline. Since ammonia is the reagent com- 
monly used for this purpose, the careful mixing is all the more 
essential, as it is lighter than water or any solution of salts or 
acids, and will tend to float on the surface of such a solution ; on 
dipping the test paper into the liquid, or taking a drop out on a 
glass rod and touching it to the paper, the reaction might be 
strongly alkaline, even with a strongly acid liquid in the lower 
part of the tube. When this reagent is used to neutralize acidity, 
as soon as the liquid smells strongly of it, after the thorough 
mixture has been made, one can be sure that the liquid is alka- 
line. When a solution made alkaline by an excess of an alkaline 
carbonate, Na2C03, K2C03, or (NH4)2CO3, is to be made acid, 
as soon as the addition of the acid does not cause decided effer- 
vescence, due to the escape of carbon dioxide, the same precau- 
tions being taken as to the careful mixing in of each portion of 
acid added, the condition of acidity is probably reached ; but in 
any case the final test with litmus paper should never be omitted. 
One can never afford any uncertainty in regard to the matter. 
When the liquid to be treated is in a test tube, the mixing can 
be most easily done simply by pouring it back and forth from 
one tube to another. 
Addition of a reagent in excess. Directions are often given to 
add a reagent in excess; but unless the desired excess is specially 
stated to be large, which is rarely the case, it is not meant that a 
great quantity of it is to be added. If it is an acid or an alkali 
that is added, it should be known, by the use of test papers, 
when it is first in slightest excess, as directed above; then the 
further addition of a quantity of the reagent equal to about one- 34 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 49~5°- 
tenth of the volume of the solution, will usually suffice. If it 
is a precipitating reagent that is added, then it should be known 
when the precipitation is first complete ; then a further addition 
of one-tenth, as above described, will be sufficient. 
49. Precipitation. This operation, the eduction of a solid 
substance from solutions, as the result of some metathesis, is the 
most important one in analytical chemistry. The reagent used 
is commonly called the precipitant. 
Qualitative analysis consists almost entirely in the production 
of precipitates for one purpose or another, and generally under 
certain prescribed conditions. In order that the result sought 
for shall always be obtained, the conditions prescribed in each 
case must be fulfilled—such as neutrality, or acidity, or alkalinity 
of the solution, precipitation with heat or without, with time 
given for the reaction to be completed or not. Especially in 
quantitative analysis, the conditions under which the precipita- 
tion is to be made, are usually very precisely indicated, since in 
that kind of work the completeness in the reaction is of the 
utmost importance. 
But this matter of completeness of precipitation is in many 
cases of no less importance in qualitative analysis, as in the 
separation of groups of substances from one another, or of 
removing one substance from the solution that may interfere 
with the detection of another. Therefore, in the very beginning 
of his work, whether such beginning is made in qualitative or 
quantitative analysis, the student has to learn to be careful in 
the preparation of his solutions for precipitation, and in the 
management of the precipitation itself. 
50. Description of precipitates. Precipitates are distinguished 
as having this or that color, or, as to structure, as being crystal- 
line, pulverulent, or flocculent. 
A crystalline precipitate is usually characterized by the 
property of sinking rapidly to the bottom and leaving a com- 
paratively clear supernatant liquid. Sometimes a precipitate is 
so finely crystalline as to show only a glistening shimmer 
when present in very small quantity in a liquid that is gently 
disturbed. Precipitates that take the crystalline form will 
usually appear sooner if the liquid is strongly agitated ; some- 
times such agitation is almost necessary to start their formation, 
as in precipitation of morphia by ammonia. 
A pulverulent precipitate is very fine, usually not settling 
quickly nor leaving a clear, supernatant liquid. One that is §§ 51—53-3 
MANIPULATIONS. 
35 
pulverulent, if produced quickly and in large quantity, may be 
plainly crystalline if formed slowly and in small quantity, 
as may be seen sometimes in the formation of the precipitate of 
ammonium magnesium phosphate. The more insoluble a pre- 
cipitate is in the liquid in which it is produced, the more it 
inclines to the pulverulent rather than crystalline character; 
but even some of the most insoluble precipitates, as barium 
sulfate, will, if produced only in traces, exhibit the glistening 
appearance above mentioned, as indicating crystalline structure. 
51. A flocculent or flaky precipitate, sometimes defined as 
woolly-looking, never presents this glistening appearance, how- 
ever slowly formed. It settles slowly, and occupies much more 
space than a crystalline or pulverulent precipitate. It is often 
separated from the liquid by filtration only with difficulty. It is 
sometimes translucent, so that, if at the same time colorless, 
it is almost invisible till gathered together in masses; of this 
character the precipitate of aluminum hydroxid is an example. 
Precipitates will usually collect together and settle to the 
bottom more quickly, and be more easily filtered out, if the 
liquid containing them is hot. 
52. According as a precipitation is made simply for the 
detection of a substance in a solution, by the appearance under 
the prescribed conditions, of a precipitate of a certain form or 
color, or is made for the separation of one or more substances 
from others, the manner of making it differs. In the former 
case, the first appearance of the precipitate suffices, and any fur- 
ther addition of the reagent is useless, except when there is 
necessity for getting a large quantity of the product for confirma- 
tory tests. But in the other case, the addition of the reagent 
must be continued as long as a precipitate is formed; and this 
cessation of further precipitation must be determined beyond all 
doubt by adding a few drops of the precipitant, either to the 
supernatant liquid clarified by standing for the precipitate to 
settle, or to a portion of the liquid filtered from the precipitate ; 
sometimes it is necessary to give time for the completion of the 
reaction, even after no further precipitation is shown by testing 
as above. 
53. Digestion. In order that a chemical reaction, and espe- 
cially an operation of solution or precipitation, shall be com- 
plete, it is often necessary to leave the substance and reagent in 
contact for a time. This is commonly called digestion. 
Usually heat is applied, but not always; in this case we speak of 36 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 54-55* 
digestion in the cold. Digestion at a boiling temperature is 
sometimes specified ; but this is too often incorrectly con- 
strued as vigorous boiling, while it means only that the liquid 
shall be kept just at the boiling temperature. 
54. Boiling. Rapid boiling of liquids is required only when 
they are to be quickly evaporated, or some product is to be dis- 
tilled off. It is very rarely necessary in qualitative work, and is 
to be avoided unless specially called for. 
A clear liquid can usually be boiled without any trouble, in a 
beaker, flask, or evaporator; but in a test tube, especially if 
half full or more, the vapor does not escape in a continuous 
stream of small bubbles, but in very large ones, often, which are 
formed suddenly, and are very likely to propel a part of the 
liquid before them in their escape. 
When any solid matter is mixed with the liquid, and especially 
if the liquid is strongly alkaline, boiling without spurting is still 
more impracticable in a test-tube, and should never be at- 
tempted ; even in a flask, beaker, or evaporator it is not easily 
managed, and must be carefully watched, particularly when the 
quantity of liquid is small as compared with that of the solid 
by holding the lamp in the hand, and, with the flame very low, 
moving it in and out under the dish, without the intervention 
of a sand bath, thus keeping the mixture just at the simmering 
point, the whole object of the operation may be accomplished 
without danger. When there must be actual boiling for a time, 
as in the treatment of the precipitated chlorids of the silver 
group with water to dissolve out the lead chlorid, it is advisable 
to hold the flask by the test-tube holder and keep its contents 
in rapid motion by a movement of the hand in a small circle. 
55. Filtration. It is usually necessary, after having made a 
precipitate, to separate it from the liquid, in order to perform 
some further operation with it. For this purpose, paper filters 
already cut are now supplied in every laboratory. To fit a filter 
in the proper manner, first fold it over so as to form a semicircle, 
and then again, forming a quadrant; then open this quadrant 
in such a way that when it is pressed down into a funnel there 
is a continuous lining of the paper on the sides of the funnel 
of three thicknesses half way round and one thickness on the 
other half. The filter should always be about half or a third of 
a centimeter smaller than the funnel when thus fitted into it. In 
preparing for the filtration, push the filter, opened as above 
described, down till its apex is in the throat of the funnel, and §§ 56~58-] 
MANIPULATIONS. 
37 
hold it there with the finger while wetting it with a jet of water 
from the wash-bottle; then* by gentle pressure with the finger fit 
it snugly to the walls of the funnel throughout. Time should 
be taken to carefully adjust the filter in this manner for every 
filtration. 
56. Decantation before filtration. Filtration can often be 
made more quickly if the liquid is first digested at a gentle heat 
till the precipitate has settled, and the supernatant liquid is then 
carefully decanted off before putting the mass of the precipitate 
on the filter. If the work is qualitative and nothing further is 
to be done with the liquid, the decantation can be made at once 
into the sink; otherwise it should be made into the filter. 
57. Washing precipitates. It is usually important to com- 
pletely free a precipitate from the substances in solution in the 
liquid from which it has been filtered, and with which its 
pores are filled. 
This washing may sometimes be partially done with advantage, 
by repeating the above described process of decantation, two or 
three times, pouring boiling water over the precipitate, stirring 
it up well and decanting again after a little time, and so on, and 
finally washing once or twice after the precipitate has been put 
on the filter. When, however, it is crystalline pulverulent, and 
filters quickly, it may as well be thrown on the filter at once and 
washed there. In all cases use hot water, unless otherwise 
directed, for with this the washing is sooner finished; and 
use only distilled water. 
In qualitative work the washings need not be saved; but they 
often must be preserved in quantitative work. 
The completion of the washing may be tested for in two ways : 
first, by evaporating a drop of the washings to dryness on a 
watch glass, at a gentle heat; no residue, or in qualitative work 
only a slight one, should be left on the spot where the drop was: 
second, by testing about a cubic centimeter of the washings for 
some substance which one may know to be in the solution, and 
for which there is some very delicate test. Such a substance is 
a chlorid, which is usually present in qualitative solutions, from 
the hydrochloric 'acid that has been added in some previous 
operation; the silver test for chlorin, after acidification of the 
liquid with nitric acid is exceedingly delicate. 
58. Dissolving precipitates. This often necessary operation, 
especially in qualitative work, may be done simply by dropping 
the solvent over the precipitate in the filter, when heat or 38 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 59~60. 
digestion is not required; when two or three cubic centimeters 
of the solvent have run through, this may be again poured through 
the filter, if the solution is not complete, thus avoiding the use 
of a large excess of acid. If the precipitate must be removed 
from the filter, take the latter from the funnel by slipping the 
spatula under it, open it on the piece of window glass that is in 
the set of apparatus, and scrape the precipitate off with the 
spatula. 
59. Cleanliness in the laboratory. Reasonable cleanliness of 
apparatus and work table is much more conducive to good re- 
sults than the extreme slovenliness that is often seen. Every 
piece of apparatus must be clean within before a liquid is put 
into it that is under treatment for analysis; if not clean, then 
the constituents of the dirt that was on the walls of the vessel 
are liable to be added to the solution, and to be reported as a 
part of the substance analyzed. Unless a piece of glassware is 
clean on the outside, it cannot be known whether it is clean on 
the inside. The cleaning is never more easy than immediately 
after the apparatus has been used ; and it is liable to be more 
difficult if put off for days. 
Therefore, the student should never leave the laboratory for 
the day without having first cleansed every soiled piece of 
apparatus that is not in actual use, finishing the operation by 
rinsing each piece off with a little distilled water. By the use 
of a little strong hydrochloric or nitric acid, pouring the same 
portion from one piece to another, intractable dirt may often be 
dissolved. While the student is at work his table should be 
kept neat, everything spilled by accident or otherwise being at 
once washed off with a sponge and an abundance of water. 
If acid comes in contact with the clothing, the spot should as 
soon as possible be saturated with a few drops of ammonia. 
Strong nitric acid on woolen cloth makes a permanent yellow 
stain unless immediately neutralized ; sulfuric acid if not 
neutralized, even if dilute at first, becomes more and more con- 
centrated by the slow evaporation of the water, and finally the 
cloth is corroded; hydrochloric acid leaves only a red stain, 
easily removed by ammonia. 
60. Rapidity of work. Much time will be spent in accom- 
plishing little work, unless the student. is always careful to keep 
as many operations in progress as he can manage without making 
mistakes. Early in his course of practice he should seek in this 
way to make the best possible use of his time in the laboratory. §6o.] 
MANIPULATIONS, 
39 
The teacher’s estimate of the proficiency of the student must be 
based on the amount of good work accomplished in the amount 
of time that is given to the practice. Therefore, there should 
never be any idle waiting for a precipitation, tedious filtration, or 
any other slow operation to be completed ; some other operation 
should be started. If the work is qualitative, two substances can 
be carried along at once; or, the constituents being separated 
into groups if the analysis is one covering the entire course, two 
or more groups can be worked along together. In many ways 
the student who is really in earnest, meaning to do the best that 
he can with his time, can get over much more ground without 
slighting any part of his work, than he will if he gives this mat- 
ter of rapid work no serious thought. If every stage of the work 
is properly labeled, trusting nothing to the memory, none of the 
mistakes need be made that might seriously lessen the gain in 
progress. PART 11. 
THE SYSTEMATIC COURSE OF QUALITATIVE 
ANALYSIS. 
CHAPTER VII. 
THE MODE OF PROCEDURE IN GENERAL. 
61. Introduction. This course in qualitative analysis is, in 
many respects, similar to that of Fresenius. The same grouping 
of substances is followed, although under different names; the 
name of a familiar member of each group applied to it is more 
easily remembered, and conveys somewhat more of meaning 
than a mere number. Usually the methods of separating the 
members of each group from each other, and of detecting them, 
are the same as those given by Fresenius. But the work is much 
abridged, in order that it may be completed in a reasonably 
satisfactory manner in the short time that can be allowed for the 
study in some of the University courses, and to make it possible 
for the student in these courses to devote a little attention to 
quantitative analysis, some knowledge of which may be of more 
importance to him than a fuller acquaintance with qualitative 
methods. To the student who intends to make a special study 
of chemistry, the full course given in Fresenius, or in Prescott 
and Johnson, is none too extended; and for guidance in the 
more difficult parts of the analysis, he must refer to these com- 
prehensive works. 
Whatever is peculiar to the course of analysis given here, has 
been thoroughly tested by practical use for many years in the 
chemical laboratory of Cornell University. This experience has 
shown that with strict following of the directions laid down, the 
careful student will from the beginning commit but few errors, 
and will readily learirhow to make a correct analysis of any mix- 
ture containing the more commonly occurring elements. 
40 § 62.] 
MODE OF PROCEDURE. 
41 
62. The grouping of the substances tested for. The substances 
that are tested for in all ordinary schemes of qualitative analy- 
sis are of two classes, the acidigenic and the basigenic elements 
or groups, or, as they are called in other works, the acids and 
bases. Of the acidigens, or acids, a small number can be asso- 
ciated together by their common property of being precipitated 
in a neutral solution, as barium salts; and another group con- 
sists of those that give a precipitate with silver nitrate in a solu- 
tion acidified with nitric acid. In other words, the barium salts 
of the members of the group first mentioned are insoluble in 
water, and the silver-salts of the members of the other group 
are insoluble in dilute nitric acid. 
But this grouping has no such significance as there is in the 
grouping of the basigens, as the student will understand much 
more clearly after he has completed his qualitative work; neither 
the barium nor the silver group of acidigens is separated out by 
itself, in any scheme of analysis, for the purpose of testing for 
each member of the group in the precipitate thus obtained. 
The analysis for the acids consists mostly of a succession of inde- 
pendent tests applied to the original substance, or to a solution 
of the substance prepared by boiling with sodium carbonate, so 
as to have only sodium salts in the solution to be worked with. 
The only use of this grouping is to determine by a single brief 
test whether any acid of one or the other group is present, thus 
making it possible in some cases to omit the whole series of the 
tests required to prove the presence or absence of the several 
members of one or both groups. On the other hand, a very im- 
portant part of the analysis for the bases consists in their separa- 
tion into six groups: the members of each one of these groups 
being allied in so far as they possess at least one common prop- 
erty, as to insolubility of certain of their compounds in water or 
in acids of different degrees of dilution, by which they may be 
thus brought out together. Each group is then, perhaps, subdi- 
vided, sometimes by difference in respect to solubility in some 
other active agent than an acid ; and, finally, each member of 
the group is so far isolated as may be necessary to make a final 
confirmatory test for its presence or absence. 
The substances thus brought out of the solution in company 
are often not at all chemically allied ; consequently the analytical 
grouping is in some cases not so sharply defined as to avoid all 
overlapping of groups. While this measure of unlikeness may 
facilitate the sub-grouping of elements, on the other hand, when 42 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 63-65. 
members of the same group are closely allied, their separation 
and identification may be very difficult; of this, nickel and 
cobalt, in the iron group, furnish a striking example. 
The whole course of the analysis is thus divided into eight 
principal stages, of which the examination for the acidigens or 
acids is the first. See Table at end of this chapter. 
With reference to the basigens we have three classes of com- 
pounds that are commonly made use of for grouping purposes, 
namely, chlorids, sulfids, and carbonates. Of these the sulfids 
are so important in analytical work as to be worthy of the 
special consideration of their more important properties. 
THE SULFIDS. 
63- These may be produced by fusion of metals with sulfur, 
or by the action of hydrogen sulfid or of solutions of soluble 
sulfids on metallic salts in solution. 
They are distinguished : 
a. For their different degrees of solubility in (x) water, (2) 
acids, (3) other solvent liquids. 
b. For their different degrees of susceptibility to oxidation. 
64. Solubility of the sulfids. Most of the sulfids of the 
basigens are insoluble in water, only those of the potassium 
and calcium groups being soluble. 
c. For their variety of color. 
The sulfids of the iron group of metals differ much in solu- 
bility in dilute acids, as the behavior of nickel, cobalt, and zinc 
sulfids shows, in the course of the separation of the members of 
this group from one another. 
The sulfids of the metals of the aluminum group are in their 
nascent state decomposed by water, forming hydroxids and 
hydrogen sulfid. 
All the remaining sulfids are insoluble, not only in water but 
in at least moderately strong mineral acids; some of them are 
insoluble even in strong acid, and the metal contained in them 
can be brought into solution only through attack by strong 
oxidizing agents. 
Thus, it is seen, we have every grade, from easy solubility of 
the alkaline sulfids in water, to insolubility in the strongest acid 
of sulfids of some metals of the copper and tin groups. Hence, 
in part, the great importance of the sulfids in analytical chem- 
istry. 
65. Certain elements (tin group) are capable of forming with § 66.] 
MODE OF PROCEDURE. 
43 
oxygen a lower oxid that is basigenic and a higher oxid that is 
acidigenic. Similar compounds are formed in which sulfur takes 
the place of oxygen; and, as nearly all salts of the alkaline 
metals are soluble, we may have soluble alkaline salts of these 
metals in which all the oxygen is replaced by sulfur, as, for 
instance, (NH4)3Aso3, ammonium arsenite, and (NH4)3AsS3, 
ammonium sulfarsenite. Remembering that the formulas of the 
oxygen salts of the acids formed from these elements are as 
follows, it is easy to see the relation of the sulfo-salts of the tin 
group to them : M3As03; M3As04; M3Sb04; M2Sn03. Min 
these formulas stands for any monad basigen. 
These sulfo-salts are readily formed by simple treatment of the 
solutions of compounds of these elements, or their freshly pre- 
cipitated sulfids, by solutions of alkaline sulfids, especially such 
as have an excess of sulfur, as (NH4)2SX, for example. Hence, 
the easy and nearly complete separation by means of ammonium 
sulfid of the tin group elements from those of the copper group. 
It is worthy of notice that, in this treatment, the action of the 
(NH4)2SX on the antimonous and stannous sulfids corresponds in 
its character to one of oxidation ; for, from these “ ous ” sulfids 
there is formed the sulfo-salt corresponding to the antimoniate 
or the stannate, and the sulfid precipitated by acid from the 
solution of the sulfo-salt is antimonA or stanmV sulfid. 
66. Oxidation of the sulfids. In the sulfids we have two 
elements both of which are capable of combining with oxygen, 
but the metal usually more eagerly than the sulfur. In nearly 
all cases a nitrate of the metal is formed, if nitric acid is used as 
the oxidizing agent; if the nitrate is not formed it is either 
because of the production of a higher oxide of the metal not 
basigenic, or because, the sulfate of the metal being insoluble, 
that is formed, to the entire or partial exclusion of the nitrate. 
If the metal is capable of forming more than one oxid and 
series of salts, whether it be the lower or the higher oxid depends 
upon the conditions of the oxidation ; if the sulfid is in excess 
and no heat is employed, a nitrate of the lower oxid may be the 
product; ordinarily an excess of acid and heat are employed, 
yielding a salt of the higher oxid. Nickel and cobalt sulfids 
are exceptions, giving only the lower oxid salts. 
The sulfur of the sulfids is mostly set free as a precipitate, 
which in a hot liquid is liable to fuse together in small globules 
that resist oxidation with much obstinacy. Even when the sul- 
fate of the metal is soluble, some of the sulfur is oxidized to sul- 44 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 67-69. 
furic acid, and some of this sulfate is formed together with the 
nitrate which is the chief product. However, it is usual in writing 
the equations for these reactions to assume, unless it is otherwise 
stated, that all the sulfur is set free, and only nitrate of the 
metal formed, at least in the first part of the reaction, as illus- 
trated in the following equation : 
3PbS + BHNO3 - 3Pb(NQ3)2 + 4H20 + 2NO + 3S. 
Occasionally a sulfid is so susceptible to oxidation as to suffer 
change by simple exposure to the oxygen of the air, or to the 
free oxygen dissolved in the water used to wash the precipitate. 
67. Chlorination qf the sulfids. When a sulfid is attacked in 
the presence of water by reagents setting chlorin free, oxidation 
may be the result by oxygen from decomposed water; but, 
especially if the chlorin be in excess and heat is applied, chlorin- 
ation may also take place; and if the metal forms more than 
one chlorid the higher one is produced. Most of the sulfids are 
converted into chlorids by simple treatment with more or less 
concentrated hydrochloric acid, with evolution of hydrogen sul- 
fids ; but this is metathesis rather than chlorination; in the 
latter case, as in oxidation, sulfur is set free. 
68. Reduction of sulfids. Just as oxids may be reduced by 
nascent hydrogen, which takes the oxygen to form water, so sul- 
fids, subjected to the same treatment (with zinc and sulfuric 
acid), may be reduced, H2S being formed instead of H2O, and 
set free. Thus some sulfids may be decomposed that are with 
difficulty broken up in other ways. 
THE HYDROXIDS (OR HYDRATES). 
69. By the action of solutions of hydroxids on salts of other 
metals in solution, a class of reactions is produced of great im- 
portance in analytical work ; the normal product of the reaction 
is a hydroxid of the metal acted upon. 
Regarding this action as normal in all cases where with all 
three of the alkaline hydroxids, KOH, NaOH, andNH4OH, insol- 
uble hydroxids are produced of normal composition, such as 
Fe(OH)2, Zn(OH)2, Al(OH)3, it is strictly normal with the metals 
of the aluminum group, and those of the iron group except cobalt, 
which yields a basic salt; with some metals of' the copper and 
tin groups the result is more or less irregular ; only with bis- 
muth, cadmium, copper, and tin (ous) is it fully normal, but in § 7°-] 
MODE OF PROCEDURE. 
45 
the case of copper only when the reagent is added just to satura- 
tion : with lead and thehydroxids, KOH, NaOH, it is regu- 
lar, but NH4OH yields basic salts, PbOCl2, or Pb3020HN03, 
according to the acid of the lead salt. With silver, Ag20 
is precipitated, and with salts of mercury and the fixed alkalies 
in excess, Hg20 or HgO : with NH4OH, compounds are pro- 
duced in which a part or all of the hydrogen of the NH4 is re- 
placed by mercury; these new compounds play the part of a 
basigenic body, like the ammonium, and remain in combination 
with the acid of the mercury salt. Example, 
N No3 N g2g Cl, NHg2N03) 
according as Hg is monad (mercurous) or dyad (mercuric). 
With arsenic compounds, soluble salts of the alkaline metals 
are formed, arsenites and arsenates, and of course no precipi- 
tates ; with antimonous compounds, Sb203 is precipitated ; with 
antimonic compounds, soluble antimoniates are formed, or an 
insoluble antimoniate, NaSb03: with stannic salts (stannates), 
stannic acid, H3Sn03, is precipitated. With gold only NH4OH 
gives a precipitate, and that has a peculiar composition, (NH3)2 
Au203. Platinum in the form of chlorid gives with KOH and 
NH4OH insoluble double chlorids, of great value in the quanti- 
tative estimation of potassium and ammonium, 2KCI.PtCl4and 
2NH4CI.PtCI4: NaOH gives a precipitate of Na2Pt03. 
The reactions with the hydroxids are seen to be more and 
more varied as we pass up to the tin group, where the elements 
tend to yield acidigenic oxides even in their lower degrees of 
oxidation; and the reaction in such cases has little analytical 
value. 
70. Solubility of the hydroxids. All the normal hydroxids are 
insoluble in water, except those of the potassium group, and of 
barium, strontium, and calcium of the calcium group; all are 
soluble in dilute acids, forming salts of the acids used. 
Most of them when freshly precipitated are soluble in solutions 
of either KOH, NaOH, or NH4OH ; but only one, Zn(OH)2, is 
soluble in both a fixed and a volatile hydroxid, meaning by the 
latter ammonium hydroxid. New compounds are produced by 
this solution, differing so widely in form for different metals, 
that no general formula can be given for them ; some of these 
formulas are given later. 
Owing to this property of the hydroxids, we may have 46 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 71-74- 
two metatheses produced by one reagent, an insoluble product 
being formed first, which is afterward dissolved by an excess of 
the precipitant, with the formation of a second new compound 
that is soluble in water. 
71. Behavior when heated. All the hydroxids, except those 
of the potassium group, are decomposed by heat, with the 
formation of an oxid of the metal, and water. In some cases 
this decomposition takes place even in boiling water. 
THE FINAL TESTS. 
72. One after the other, the presence or the absence of each 
substance to be tested for is proved by a final characteristic test, 
after it has been, if present, more or less completely isolated. 
Some of the reactions of these tests are so unique that they can 
be made in the presence of all the other members of the group, 
or even in the original solution, without regard to anything else 
that may be present: this is the case with many of the tests 
for the acids after they have been separated from all the bases 
except the alkalies by the transposition with sodium carbonate. 
The final tests for gold, platinum, copper, and iron are excellent 
illustrations of such as are not interfered with by the presence 
of other members of the groups to which they severally belong. 
73. In these final tests we have two general classes of reac- 
tions : 
a. Color reactions, among which are some of the most deli- 
cate, marked, and unmistakable in use. Often nothing can 
interfere with their production. We may get them in : 
(1) solution products; 
(2) precipitates from solution ; 
(3) fusion products, on the foil or in the borax bead ; 
(4) flame tests. 
b. Precipitates without any marked color, usually white. 
The main safeguard against error, in the interpretation of 
results in such cases, is to have the conditions under which the 
precipitates are obtained, precisely as laid down in the direc- 
tions for obtaining them. 
THE COURSE OF ANALYSIS. 
74. Order of the arrangement of the work. Beginning with the 
acidigen group, Chap. IX, the student reads over the description 
of the reactions of the first acid taken up, and writes out the 
equations explaining those reactions ; he then tries the reaction or §74-] 
MODE OF PROCEDURE. 
47 
reactions given in italics ; that is, to a small quantity, one or two 
cubic centimeters, of a solution containing a salt of the acid 
under consideration, in a test tube, he adds a small quantity of 
the reagent, precisely in the manner described in the account of 
the reaction, and compares the results obtained with the descrip- 
tion of the result that should be obtained ; only in this way can 
he become so acquainted with the reactions described, that he 
will surely recognize them when he may meet with them again 
in the actual analysis of an unknown substance. The italicized 
reactions are those specially characteristic of each substance, 
made use of each time that it is tested for; a thorough, personal 
acquaintance with them is therefore of great importance. The 
other reactions come into use only in the separation of sub- 
stances from one another, or as occasional confirmatory tests in 
doubtful cases. 
This work having been carefully performed with every sub- 
stance in the group, the student then makes a mixture contain- 
ing all the substances of which he has tried the characteristic 
reactions, and proceeds to analyze it according to the directions 
for the analysis for acids, § 85. 
To simplify this part of the work with respect to the large 
group of the acids, by reducing the number of tests to be made 
in one solution, a mixture containing salts of only the barium 
group may be analyzed by itself, then a mixture containing only 
the silver group, with nitric acid added, and finally a mixture of 
the organic acids. 
In doing this work he should get, clearly and unmistakably, 
the final, characteristic, reaction of every substance; if he does 
not, he should repeat so much of the work as may be required to 
bring out this reaction; evidently he is not prepared to take up 
the analysis of a substance whose composition is unknown to 
him, if there is any possible constituent of it which he should 
find, but cannot even when he has put it in himself and knows 
that it is present. 
The student should then study carefully the explanation of the 
chemistry of the work on the acidigens in § 84. He is not fully 
prepared to do the best that is possible for him, in the analysis 
of an unknown substance, till he has learned the reasons for all the 
steps of the work, and is fully posted as to the special precautions 
that may be necessary to avoid errors. 
Being then ready for the actual analysis of an unknown 
substance, this work is first done for the acidigens only; when 48 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 76- 
the required proficiency has been attained, the student passes 
on to the first group of the basigens or metals, those precipitable 
by silver nitrate from a solution acidified with nitric acid, going 
through with the same series of preliminary operations and 
study, before analyzing the unknown substances containing the 
members of this group, and so on through all the groups in 
succession. Here, however, the work with his own solution 
begins with sub-section b of the section headed, “Preparation 
and Analysis of the Silver Group Precipitate,” and follows this 
and sub-section c, headed “Analysis of the Silver Group Pre- 
cipitate,” with its table, to the end. Then comes the study of 
sub-section a of the same section on the chemistry of the analysis. 
The same course is followed with each of the other groups fol- 
lowing. Finally comes the test of the thoroughness with which 
the several groups have been studied, in the analysis of sub- 
stances in which the presence or absence of all the members of 
all the groups has to be proved. The following tabular view of the 
complete course of analysis of a substance may be useful as a 
general guide in this part of the work. 
CHAPTER VIII. 
THE PREPARATION OF THE SOLUTION OF THE SUBSTANCE. 
76. As nearly all the work of the analysis, for both acidigens 
and basigens is done with solutions?, the matter of the suitable 
preparation of these solutions is a very important one. 
The solutions for the acidigens. 
Cl. To 1 gm. of the original substance, finely powdered, add 
15 c.c. of a concentrated solution of Na2C03 and boil ten 
minutes, replacing the water as it evaporates, dilute to 30 c.c. 
and filter if a residue remains. 
This solution or filtrate contains all the acids of the substance 
except possibly phosphoric, hydrofluoric and silicic acids; mark 
it A, and test separate portions for the other acids as directed in 
§B5. 
b. Acidify a small portion of A with H2S04. The formation 
of a yellow or orange ppt. shows the presence of metals of the TABLE II. 
75. General View of the Full Course of Analysis of a Substance. 
1,—The original substance is: 
2.—Metallic. 
4. Non-metallic. 
3.—There need be no tests for acids, nor 
for metals of the potassium group, nor for 
metals of the calcium group, except Mg. 
Prepare a solution for analysis (as directed 
in Chap. VIII) and pass on to xo, below. 
5.—Test for 
H2S,as direct- 
ed in the acid 
group, Chap. 
IX. 
6.—Test for 
C02, I IF and 
H3P04, as di- 
rected in Chap. 
IX. 
7.—Boil with cone, 
solution of Na2C03, fil- 
ter and test the filtrate 
for the remaining acids, 
as directed in Chap IX. 
8.—Test for 
NH4, as direct- 
ed in the potas- 
sium group, 
Chap. X. 
9.—Prepare the 
solution for the rest 
of the analysis, as 
directed in Chap. 
VIII. 
10.—To the solution of the substance, whether metallic or non-metallic, add HC1, if not already present, and filter. 
ix.—Precipitate. 
12.—Filtrate: add H2S and filter. 
Silver group. 
All white. 
PbCl2. 
AgCl. 
HgCl. 
13. Precipitate. 
14.—Filtrate: add NH4OH and (NH4)2S and filter. 
(a) Sulfids of the tin 
group, soluble in (NH4)2SX. 
SnS, brown. 
SnS2, yellow. 
Sb2S3, orange. 
As2S3 yellow. 
Au2S, Au2S3, black 
or brown. 
PlS2, black. 
(b) Sulfids of the copper 
group, insoluble in 
(NH4)2SX, soluble 
in HNOs. 
PbS, black. 
CuS, “ 
Bi2S3> “ 
CdS, yellow. 
HgS, black, insoluble in 
HN03. 
15.—Precipitate. 
16.—Filtrate: add (NH4)2C03 and filter. 
(a). Sulfids of the iron 
group, insoluble in 
cold HC1. 
CoS, black. 
NiS, “ 
Ditto, soluble in cold HC1. 
FeS, black. 
MnS, flesh colored. 
ZnS, white. 
(b). Hydroxids of the 
aluminum group 
soluble in cold, 
HC1. 
Al(OH)3, white. 
Cr(OH)3, green. 
17. Precipitate. 
18.—Filtrate: divide in two portions. 
Carbonates of the 
calcium group, 
except Mg, 
all white. 
CaC03. 
BaCOjj. 
SrCOs. 
19.—Portion 1. 
20.—Portion 2. 
Add Na2HP04. 
Precipitate, 
MgNH4P04, 
white. 
Soluble salts of the 
potassiui?i group. 
KC1. 
NaCl. ELEMENTS OF CHEMICAL ANALYSIS. 
Sn group; in such case acidify a large portion of A with H2S04; 
filter, and boil the filtrate in a beaker or an Erlenmeyer flask 
until H2S is entirely removed, which may be determined by 
holding a piece of moistened lead-paper in the escaping vapor 
at the mouth of the flask. Mark this solution B, and reserve 
also for § 85. 
77. The solutions for the basigens. 
The substance is metallic. 
To about half a gram add 2 c.c. of HNO;!* and warm until 
the substance is entirely dissolved or until no further change is 
observed, even when more HNO:i is added. 
a. The substance is entirely dissolved, either at once or upon 
addition of water and boiling. 
Gold, platinum, tin, and antimony are absent, except when 
present in alloys with very large proportions of soluble metals, 
when some of these metals may be completely dissolved. Take 
the solution to § 87 b. 
h. The substance is not completely dissolved, a white residtie 
remaining even when boiled with water. Sn, Sb and As may 
be present, the residue consisting of Sn02 or Sb204 and Sb205, 
and possibly As205. 
Dilute with water and filter. Heat the insoluble residue with 
HCl*; if it is not all dissolved decant the liquid carefully 
through a filter, after adding about its volume of water to it, so 
that the strong acid shall not cut through the paper, boil the 
residue with water, decant this off into the same filter, and 
repeat the treatment with HCI. Test the united solutions, 
thus obtained, for As, Sb and Sn, after removal of the excess of 
strong acid as directed in 82 § 89, c, then taking the solution to 
37> b. 
Evaporate a drop or two of the filtrate from the treatment 
with HNO:i in a above (the first filtration mentioned in &) on 
a watch glass; if a residue remains, showing that the liquid 
holds something in solution, take it to § 87, b, testing, in the 
following course for the Sn group, only for those members of the 
group not found in the above residue. 
C. A metallic residue remains in a 9 undissolved. Treat it 
* When the formula of an acid is given in this heavy type, concentrated acid 
is indicated, otherwise dilute acid. §7B-] 
PREPARATION OF SOLUTIONS. 
51 
with aqua regia (§ 24, c,) and test the solution for Au and Pt, 
as in 36 § 89, c. 
Treat the filtrate from this residue, as directed for the filtrate 
under h9 above. 
The substance is non-metallic. 
78. a. Make a preliminary test, with about one-fifth gm. of 
the substance, as follows: add 2 c.c. of water and heat to 
boiling ; if a residue remains, add to the contents of the tube a 
few drops of HCI and heat again; if a residue still remains 
allow it to settle, pour off the clear liquid and add to the residue 
1 c.c. of HCI and warm. If a solution is not obtained in this 
way, repeat the experiment with another portion of the sub- 
stance, using HN03 instead of HCI. If neither of these 
methods gives a clear solution, treat a third portion with aqua 
regia (a mixture of one part of HNO:i and three parts of HCI). 
In a few cases, where the addition of acid causes a ppt., it is 
necessary to remove the portion soluble in water before treat- 
ment with acids. If a solution is obtained by any of the above 
methods, treat about 1 gm. of the substance by the same method, 
and take the solution to § 87, b. 
If in the above tests, there is an insoluble residue which is 
white and gelatinous, and remains for some time suspended in 
the liquid, it will probably consist of Si02 from silicates that 
have been decomposed by acids; in this case evaporate the solu- 
tion, with the residue, to complete dryness, moisten with a few 
drops of HN03, add 10 c.c. of water, boil and filter; this 
residue, if white and gritty, consists of Si02. Take the filtrate 
to § 87, b. 
h- A reaction obtained in the aluminum group for A 1 might 
be misleading unless in every case of the solution of a mineral 
by acid, the silica possibly present is not removed by this 
evaporation to dryness before proceeding with the analysis: an 
error might also be made in the test for P203. Therefore, in 
important cases the silica should be removed here. 
C. If H2S was found in the tests for acids, a residue of sulfur 
may remain; this will be yellow, will float on the liquid and 
when heated on a crucible cover will first melt, then burn with a 
blue flame emitting the odor of S02. 
d. If the substance is not affected by the above treatment, 
it must be treated as directed in § 79 for insoluble substances; 52 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 79* 
or if a residue remains that is not white and gelatinous (Sio2) 
and is not sulfur, this residue must be so treated. 
79. The substance is non-metallic, and wholly or 
partially insoluble. 
Cl. The only substances of ordinary occurrence that are not 
dissolved by the treatment described in § 78, are C, S, AgCl, 
Agßr, Agl (possibly PtCl2, and Pbl2), PbS04, BaS04, SrSO* 
[CaSOJ, Si02, many silicates and a few oxids and fluorids. If 
in the tests for acids no HI, HBr, HCI, HF, or HtS 0± is found, 
the insoluble substance is generally either a silicate or an oxid 
[or chrome iron]. In this case pass to c. 
If either of the above mentioned acids is found add to the resi- 
due obtained in § 78, or to the original substance if wholly insol- 
uble, 5 c. c. of a mixture of equal parts of HCI and water, and 
a piece of Zn and warm gently; if the Zn or the residue is 
blackened after a few minutes, PbS04, or a salt of silver may be 
present; let the action continue till no further change is observed 
and decant the liquid, rejecting it, wash the residue by decanta- 
tion, add HN03, heat as long as any action appears to take 
place, as indicated by the evolution of reddish fumes, and filter, 
if solution is not complete. 
6. Filtrate. Test for Ag and Pb as in § 87, b. 
C. Residue. Mix the dry and very finely powdered residue 
(See § 44) obtained above, or the residue referred to in § 78, d, 
or a portion of the original substance, if it was wholly insoluble, 
and contains no lead or silver salts, with 4 or 5 parts of a flux 
composed of about 4 parts of Na2C03 and 1 part of KN03, and 
fuse on platinum foil, in several separate portions ; heat gently at 
first over an ordinary burner, and then with full flame, so man- 
aging the operation as to lose no substance by boiling over; 
then heat over the blast lamp for about ten minutes, or till 
bubbles of gas are no longer set free; the mass should fuse to a 
liquid ; if not, more flux should be added and the heating over 
the blast lamp be repeated. Put the foil in an evaporator with 
water, and digest (§ 53) till the fused mass is completely disinte- 
grated ; fuse the second portion of the mixture of substance and 
flux, and so on, digesting all the fused masses in the same por- 
tion of water; finally, filter. 
d. Filtrate. Acidify with HCI and evaporate in the hood 
to co77iplete dryness, moisten the residue with a few drops of HCI, THE ACIDIGENS OR ACIDS. 
evaporate to dryness again, and moisten again with HCI, add 
20-25 c- c- °f water, and heat. A white residue, gritty under 
the glass rod indicates Si02. 
Filter, reject the residue, and take the filtrate to § 87, b. See 
also filtrate from e, below. 
e. Residue from filtration at end of c. Wash thoroughly 
with hot water, add about 5 c. c. of HCI, and evaporate in 
the hood to complete dryness; moisten the residue with HCI, 
add 20-25 c. c. of water, heat and filter, rejecting the residue if 
white. This filtrate may be put with the filtrate from d, if no 
ppt. appears on mixing small portions of them together. Take 
the mixture, or the two solutions separately if they cannot be 
mixed, to § 87, b. 
f. If the residue from the above filtration is black, and 
therefore appears to be unaffected by the fluxing, fuse it with 
7-8 parts of KHS04 (potassium bisulfate), to which a little borax 
may be added; the fused mass thus obtained is to be treated as 
directed for the fused product in c above. 
CHAPTER IX (A). 
THE ACIDIGENS OR ACIDS. 
DESCRIPTION. 
80. The barium group : Solubility of compounds, and reactions. 
Carbon dioxid ; C02:—An odorless gas, slightly soluble in 
water, forming probably carbonic acid, H2C03. 
All normal carbonates except those of metals of the potassium 
group are insoluble in water. 
All carbonates are decomposed by dilute acids, C02 being set 
free with strong effervescence. 
Reaction:—When Ca( OId)2 in solution (lime water) is ex- 
posed to CO-i gas, the solution is made turbid by the formation of 
CaC03; on longer exposure the turbidity may disappear, owing 
to the solution of the carbonate in the excess of C02. 
Sulfuric acid; H2S04:—All sulfates except PbS04, BaS04, 
SrS04, and CaSO4, are readily soluble in water; CaS04, is 
soluble in about 400 parts of water, and in HCI; the other 
three are nearly insoluble in all acids. 54 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ B°- 
PbS04 is decomposed by Zn and HCI, Pb being set free; all. 
of these insoluble sulfates are transposed by fusion with Na2C03, 
carbonates of the metals and Na2S04 being formed. All sulfates 
except the native barium sulfate (heavy spar) are similarly 
transposed by boiling with a cone, solution of Na2C03. 
Reaction :—BaC/2 ppts. immediately from solutions containing 
H.fOx, or sulfates, barium sulfate,BBaSt pulverulent, white, 
heavy and very insoluble. Traces or even more than traces 
may not be precipitated from a solution containing ammonium 
nitrate or normal citrates, as well as from solutions acid with free 
HCI or HN03. 
Sulfurous acid ; H2S03:—S02, sulfur dioxide is a gas pos- 
sessing a suffocating odor, and soluble in water. 
Sulfites except of the potassium group are mostly insoluble in 
water. 
They are transposed by boiling with cone, solution of Na2C03, 
Na2S03 and carbonate of the base being formed. 
Reaction :—A 02 reduces ferric to ferrous salts, and therefore 
causes a blue ppt. in a mixture of Fe CL, and K-,FeCyr>, since ferric 
salts give no ppt. with K3BeCy6, while ferrous salts do. 
Oxalic acid ; H2C204:—Oxalates except those of metals of 
the potassium group are mostly insoluble in water; all are 
soluble in dilute mineral acids. 
Oxalates except of the aluminum and iron groups are readily 
transposed by boiling with cone, solution of Na2C03; they are 
decomposed by ignition, but without blackening. 
Reactions:—Pb(C2H302)2 ppts. from solutions of oxalates 
PbC204 white, pulverulent, insoluble in HC2H302, and in 
NH4OH, soluble in HN03. 
CaSOi ppts. from neutral or acetic solutions of. oxalates, 
calcium oxalate, Ca C 2 04, pulverulent, white, soluble in HCI or 
HNOi} insoluble in HCH?,O2. 
Chromic acid; H2Cr04:—Chromates, except those of the 
potassium group, are mostly insoluble. Solutions of normal 
chromates are yellow, of acid chromates yellowish-red. All 
chromates are colored. 
Reactions:—When a solution of a chromate is acidified with 
HCI and boiled after the addition of alcohol, aldehyd, C 2H40, 
and a green solution of CrCl3 are obtained; this solution with 
NH4OH gives Cr(OH)3, greenish ppt. provided that, as just 
directed, the alcohol was added after the HCI. § Bo.] 
THE ACIDIGENS OR ACIDS. 
55 
If to a solution of a chromate, acidified with HCI, and con- 
taining no other oxidizing agent than the chromate, KI is added, 
iodin is set free, which colors CS2 violet, if this reagent is shaken 
up with the liquid. This reaction is exceedingly delicate. 
If a sohition of a chromate is added to a mixture of lead acetate 
and ammonium acetate acidified with acetic acid, a yellow ppt. 
PbCrOx, appears, at once, or after standing a short time if the 
chromate solution was very dilute; the ppt. is insoluble in 
acetic acid, slowly soluble in HN03, soluble in NaOH ; no other 
acids present as normal salts interfere with the test. 
Boric acid ; H3B03:—Borates except those of metals of the 
potassium group are insoluble in water, but soluble in acids. 
Borates are decomposed by H2S04, with liberation of the acid, 
and are transposed by boiling with Na2C03. 
Reaction;— Boric acid liberated by a stronger acid, such 
as H2S04, imparts a green color to the flame of burning alcohol, 
particularly when the alcohol is nearly burned away. 
Hydrofluoric acid; HF:—Fluorids except of the metals 
of the potassium group are mostly insoluble or difficultly soluble 
in water. 
Any fluorid in solution will quickly corrode the surface of 
glass with which it comes in contact. 
Reaction:—H,SO4 liberates from a- fluorid HF, a gas which 
corrodes glass. 
Phosphoric acid; H3P04:—All normal phosphates, except 
those of the potassium group, are insoluble in water, but are 
readily soluble in dilute mineral acid. 
Reaction : Oi ppts. immediately or in a very short 
time from solutions containing or phosphates, and 
HNOi, ammonium phospho-molybdate, pulverulent, partly ad- 
hering strongly to the sides of the tube, lemon-yellow, readily 
soluble in NH, OH. 
Silicic acid ; H2Si03:—Silicates, except those of the potas- 
sium group containing an excess of alkali, are insoluble in 
water or acids. 
Silicates are transposed by fusion with Na2C03, and some are 
decomposed by strong acids with the liberation of the silica in a 
gelatinous form. 
Reaction : When a solution containing silicic acid or a silicate 
is evaporated to dryness with HCI, the silicate is decomposed, and 
Si O2 remains as an insoluble gritty powder. 56 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 81. 
81. The silver group : solubility of co77ipounds, and reactions. 
Hydrosulfuric acid ; H2S :—An ill-smelling gas, slightly 
soluble in water. 
All sulfids except those of metals of potassium and calcium 
groups are insoluble in water. FeS, MnS, and ZnS are soluble 
in cold HCI, with evolution of H2S. NiS, CoS, CdS, Bi2S3, 
CuS, PbS, and Ag2S are soluble in hot HNO;„ nitrates of the 
metals being formed and the sulfur partially oxidized to H2S04 
and partly set free, and giving in the case of PbS insoluble, white 
PbS04. Sulfids of arsenic, tin and antimony are decomposed 
by hot HN03, oxids of the metals, H2S04 and S being formed. 
The sulfids of mercury are not decomposed by HNOs. 
Most of the sulfids that are not attacked by dilute acid are 
decomposed by such acid in the presence of metallic zinc. 
Reaction:—IfS gas, liberated by HCI or H2SOi} with 
the aid of Zn if necessary, blackens paper moistened with 
Rb(QH3OP)3. 
Hydriodic acid ; HI ;—The iodids closely resemble the 
chlorids in solubility (see below under hydrochloric acid). 
lodids are transposed by boiling with a cone, solution of 
Na2C03. 
Reactions ;—AgNOa ppts. immediately fro7n solutions of iodids 
acidified with HN03, silver iodid, Agl, flocculent, yellow, insol- 
uble in NH^OHand in (NH4)2CO3, and decomposed by Zn and 
H2S04; it is not decomposed by ignition to low redness. 
In a solution of an iodid co7itai7ii7ig free acid the addiiio7i of a 
little K2 Cr Ox causes the liberatioti of free iodi7i. Chlorin causes 
the same liberation. 
CS2 i7i a solution contai7iing free iodin will dissolve the iodin 
if the mixture is well shaken, and be colored violet. 
Hydrobromic acid ; HBr :—Bromids closely resemble chlorids 
in solubility (see below under hydrochloric acid). 
Bromids are transposed by boiling with Na2C03, and are 
deco77iposed by chlori7i with liberation of Br. 
Reactions :—AgN03 ppts. i77wiediately fr.0771 solutions of bro- 
mids acidified with lIN03 silver bromid, Agßr, flocculent, 
yellowish-white, soon darkening in the light, slightly soluble in 
NH4OH, and insoluble in (NH4)2CO3; it is decomposed by Zn 
and H2S04, the metal being set free, but is not decomposed by 
ignition to low redness. 
CS2 added to a solutio7i contai7iing free Br will dissolve it if the 
77iixture is well shaken, and take a yellow or orange color. §Bl.] 
THE ACIDIGENS OR ACIDS. 
57 
Hydrocyanic acid ; HCy:—Simple cyanids of metals of 
the copper and iron groups, except HgCy2 are insoluble, of 
the potassium, calcium and aluminum groups, are soluble in 
water. 
Soluble cyanids are readily decomposed by dilute acids, HCy, 
a colorless and very poisonous gas being liberated. Cyanids are 
transposed by boiling with Na2C03. 
Reactions :—AgN0:i ppts. immediately from solutions of cyo7l- 
- acidified with HNO3 silver cyanid, AgCy, fiocculent, white, 
soluble with decomposition in boiling HNOs, and soluble in 
and in (NH4)2CO3, It is decomposed by Zn and 
H2S04, and also by ignition to low redness, metallic silver 
remaining. 
(NHi)2Sx exposed to HCy gas for a few minutes gives, in solu- 
tion, ammonium sulfocyanate, NHV CyS; if the drop of solution 
is evaporated to dryness and the residue moistened with FeClz, 
Fe( CyS)3, deep red, will be formed. 
Hydroferrocyanic acid; H4FeCy6:—Ferrocyanids, except 
those of metals of the potassium and calcium groups, are mostly 
insoluble in water, and in acids. 
Reactions:—FeSOx gives immediately with acid’’solutions of 
potassium ferrocyanid,potassium ferrous ferrocyanid K.,FeFe Cy6, 
fiocculent, light blue, which, on expo store to air or treatment by 
HNO,, becomes by oxidation ferric ferrocyanid (.Prussian blue'), 
FefFeCy6)3, dark blue, insoluble, and decomposed by NaOH 
with the formation of ferric hydrate, Fe(OH)3, reddish brown. 
Ferrocyanids are transposed by boiling with Na2C03. 
Fe Cl3 gives in solution of ferrocyanids, FefFe Cy6)3 
Hydroferricyanic acid; H6(FeCy6)2 or H3FeCy6:—lnsolu- 
bility the ferricyanids are similar to the ferrocyanids. 
Ferricyanids are transposed by boiling with cone, solution of 
Na2C03. 
Reactio?is\—FeS O, gives immediately, in acid solutions of 
ferricyanids, ferrous ferricyanid, FefFeCy6)2 fiocculent, dark 
blue, decomposed by NaOH, as above, giving ferrous hydrate. 
FeClz gives tio ppt. with ferricyanids, but a darkening of the 
liquid. 
Hydrochloric acid ; HCI:—Chlorids, except AgCl, FIgCl 
and PbCI2, are soluble in water. PbCl2 is slightly soluble in 
cold water, and readily soluble in hot water ; AgCl and HgCl 
are insoluble in dilute acids. 58 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 82-83. 
Chlorids are transposed by boiling with cone, solution of 
Na2COs. 
Reaction :—AgNO:. ppts. immediately from solutions of chlorids 
acidified with UNO,. silver chlorid, AgCl, flocculent, white, soon 
darkening in the light, soluble in and in (NH4)2CO3 ; it 
is decomposed by contact with Zn and H2S04, Ag being depos- 
ited, but is not decomposed by ignition to low redness. 
82. The oxidizing acids, solubility of compounds, and reactions. 
Nitric acid ; HN03:—All normal nitrates are soluble in 
water. 
Nitrates are decomposed, with liberation of the nitric acid, by 
sulfuric acid, and are transposed by boiling with a cone, solu- 
tion of Na2C03. 
Reactions :—ln presence of H ,SO, and a reducing agent the 
liberated HNOs is decomposed, with the formation of nitric oxide, 
NO ; if the reducing agent is FeS04 and the liquid is cold, 
(FeSOp.pVO is formed, giving a blackish-brown solution. HBr, 
HI, H3FeCy6 H4FeCy6 and H2Cr04 interfere. 
If a drop of phenyl-sulfuric acid is put on a dry nitrate and 
after a few minutes two or three drops of strong Nil, OH are 
added, a bright yellow color appears, ammonium nitro-phenylate. 
The reaction is exceedingly delicate. Chromates interfere. 
Chloric acid ; HCI03;— All chlorates are soluble in water. 
Chlorates are decomposed by ignition, with liberation of their 
oxygen, and by H2SOt and are transposed in boiling Na2C03 
solution. 
Reactions:—-Na.fi 0± in an acidified solution of a chlorate, by 
taking up a part of the oxygen of the chloric acid sets free chlorin 
or some compound thereof, bleaching indigo solution. 
With H2S04 a chlorate gives off an offensive greenish-yellow 
product, which partly dissolves in the acid, coloring it green- 
ish-yellow. The experiment should be performed in a watch- 
glass with a very small quantity of the substance. 
S3- The organic acids (except oxalic'), solubility of compounds, 
and reactions. 
Acetic acid; HC2H302:—All acetates are soluble. On ig- 
nition the dry salts are decomposed and blackened by separa- 
tion of carbon with evolution of odorous products. 
Reactions:—When heated with H ,SO, and a little CJlfi, 
acetic ether, CtHh C 2HA Oz, very volatile, is formed, possessing a 
peculiar, pleasant odor. § 84.] 
ANALYSIS FOR THE ACIDIGENS. 
59 
When a neutral acetate and Fe Clz are mixed together the solu- 
tion assumes a deep red color, not removed by Hg Clt, but it disap- 
pears when the liquid is boiled after much-dilution. 
Tartaric acid; H,2C4H406:—Tartrates of the alkali metals 
are soluble, but only sparingly so in the case of some acid tar- 
trates ; other tartrates are partly soluble and partly insoluble in 
water, those of , metals of the aluminum and iron groups being 
mostly quite soluble. 
Tartrates are transposed by boiling with Na2C03 and are de- 
composed on ignition, turning black and giving off th.e odor of 
burnt sugar. 
Reactions:—With Pb(C2H3O2)2 tartrates give PbC4H406, white, 
soluble in NH4OH free from carbonate. With acidi- 
fied with HC2H302, concentrated neutral solutions of tartrates give 
hydrogen potassium tartrate, KHC±H± Oe, white, crystalline, insolu- 
ble in alcohol. Boric acid interferes with this test. 
Citric Acid ; H3C6H507:—Citrates of the alkali metals are 
readily soluble in water, those of the calcium group metals are 
insoluble, the others are mostly soluble. 
All citrates are decomposed on ignition, with separation of 
black carbon, and evolution of odorous products of the decom- 
position. 
Reaction:—Pb{ CJd. 02)2 in solutions of citrates ppts. lead 
citrate, Rb f C 6H5 0-)2, white, amorphous, soluble i?i NH4 OH free 
from carbonate; on digestion for several hours with water or 
HC2H302 it becomes crystalline. 
CHAPTER IX B. 
THE ANALYSIS FOR THE ACIDIGENS. 
84. Notes on the chemistry of the analysis. 
With regard to the course for the detection of the acids so 
much of the work consists in the mere application of final tests, 
which are sufficiently explained under the description of the 
reactions for the acids, or elsewhere, that little remains to be 
made clear. 
The transposition in a § 76 with Na2C03 is made in order to remove from the solution all bases except those of the alkaline 
metals; these, giving only soluble salts with all the acids, will 
themselves give no precipitates or reactions with any of the 
reagents used, that might confuse or mislead the analyst, or inter- 
fere with his work. 
ELEMENTS OF CHEMICAL ANALYSIS. 
The tin group metals if present in the alkaline solution that 
was prepared in (a) would be precipitated on acidification in 
12 and cause difficulty. 
It must not be overlooked in making this group test, in 
1 following, that the liquid while containing an excess of 
Ba(OH)2 may slowly become turbid by absorption of carbon 
dioxid from the air. 
Since the treatment with acid in 1, in the course of analysis 
following, expels the carbon dioxid of the original substance, as 
well as of the Na2C03 used for the transposition of the acids into 
sodium salts, this acid must be tested for in every case, whether 
a ppt. is obtained for the barium group or not. 
H2S is also a reducing agent: by metathesis with the lead 
acetate it gives insoluble PbS, and is thus removed, in 4. 
Chlorates and ferricyanids are, like chromates, oxidizing 
agents in the presence of free acid ; hence the iodin test cannot 
be used as confirmatory of the lead test, in the presence of those 
compounds, in the test for chromic acid in 7. 
This precipitate for P205 in 10, by molybdate, is more insolu- 
ble in a liquid containing HN03, if it is not too strong, than in 
other acids. 
It is soluble to some extent in solutions of phosphates; hence 
the method of making the test which secures always an excess of 
the reagent, in 10 d. 
Compounds of arsenic and phosphorus are much alike, and 
both arsenic and phosphoric acids give lemon-yellow precipitates 
with molybdate; hence the removal of members of the tin group 
in 10 h. 
Ferrocyanid and molybdate react, giving a flocculent brown 
precipitate, which might mask the yellow phospho-molybdate, 
if only a little of it were precipitated. Zinc ferrocyanid is in- 
soluble in dilute HN03 while the phosphate is soluble, and the 
former is thus removed in 10 C. 
Sulfites also give H2S with zinc and free acid; hence they 
must be removed before making the test for H2S with these 
reagents, as in 13. 
In the reaction in 14 the HI produced from the iodide by the §B5-] 
ANALYSIS FOR THE ACIDIGENS. 
61 
stronger HN03 becomes a reducing agent, its hydrogen reducing 
the chromic acid of the chromate, while its iodin is set free. 
Solution A must be used in the test for HCy in 16 because 
HCy was expelled from Bby the H.2S04 added. The (NH4)2S, 
which would give a black precipitate with the FeCl3, added later, 
is decomposed by the evaporation to dryness; in this evapora- 
tion, if the dry residue be heated too strongly the sulfocyanate 
itself will also be decomposed. 
The laboratory solution of ammonium carbonate contains 
free NH4OH, which, according to the required conditions of this 
operation, should not be present: hence the treatment with 
C02, in the separation of AgCl from Agßr in 19 b. 
While the fused residue of AgCl, Agl, and Agßr is acted upon 
by Zn and H2S04 in the same manner that these salts are acted 
upon when freshly precipitated, it is not so acted upon by 
NH4OH and (NH4)2CO3; hence the freshly precipitated salts 
must be prepared again, after this decomposition of the salts in 
the fused products, as directed in 19 C. 
The tests for citric and tartaric acids are satisfactory only 
when very carefully performed, and even then are not easily ob- 
tained unless the solution contains at least a moderate quantity. 
85. The course of analysis : 
1. To 3 c. c. of A from § 76, in a small beaker or flask, add 
HCI very slowly and with constant stirring, till there is no 
further effervescence, and the solution is slightly acid ; boil thor- 
oughly, cool, and add Ba(OH)2 till the liquid is slightly alka- 
line, and with care to expose to the air as little as possible. 
The Barium group :—Preliminary test for this group. 
The liquid remains clear; none of the Ba group of acids need 
be tested for except C02. A slight turbidity, remaining after 
the acidification of the liquid (§ 48), may be due to traces of 
sulfuric acid, sulfates being very commonly present as impurities 
in many ordinary chemicals. 
2. Carbonic acid :—To a portion of the original substance 
add HCI. If solution with effervescence takes place, test the gas 
evolved with a drop of lime water in the open end of a small tube. 
If no other acids of the barium group are present to 14. 
8. Sulfuric acid:—To 2 c.c. of A (§ 77) add HCI till acid 
and then BaCl2 in excess. 62 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 85- 
4. Sulfurous acid :—Acidify a portion of A with HCI, warm 
and immediately expose to the gas in the tube in the open end 
of a small tube, a drop of mixture pf FeCl3 and K3FeCy6. If 
H2S is present a little Pb(C2H3O2)2 should be added to A before 
acidifying with HCI. 
5. Preliminary test for the presence of either of the three or- 
ganic acids, acetic, tartaric, or citric :—Carefully ignite about 
0.5 gm. of the original substance on a crucible lid, heating only 
for a moment at a time, at first gently, then more strongly, 
removing the test repeatedly from the flame to observe the odor, 
and any appearance of smoky products of combustion, or forma- 
tion of a carbonaceous residue; if none of these results are per- 
ceived, these acids are absent, except at the most in very small 
quantities. 
6. Oxalic acid :—(a) No indication of organic acids was 
observed in s—Acidify5—Acidify a portion of A with acetic acid, and add 
CaS04. 
(P) Organic acids are present.—Acidify 3 c.c. of A with 
dilute HC2H302 (1 of acid to 4 of water), add 8-10 c.c. of 
neutral Pb(C2H302)2, filter, wash the ppt, with dilute alcohol 
(equal parts of 95 per cent, alcohol and water), transfer to a 
small beaker and add about 8 c.c. of NH4OH, mix well and 
filter, saving the filtrate for 23. 
Wash the contents of the filter with dilute NH4OH, treat it in 
a beaker with 1-2 c.c. of HN03, pass H2S through the liquid 
and filter. Neutralize the filtrate with NaOH, acidify with 
HC2H302 and add CaS04. 
7. Chromic Acid;— Acidify a portion of A with HC2H302 
and add to it about 2 c.c. of the lead and ammonium acetate 
mixture. 
8. Boric acid :—Evaporate 2 c.c. of A to dryness, moisten 
the residue with H2S04, add 2 c.c. of alcohol, set the mixture 
on fire, and stir it, while burning, with a glass rod. If copper 
is absent, as indicated by the absence of any greenish or blue 
color in the original solution, the original substance may be used 
directly for this test. 
9. Hydrofluoric acid :—To the finely pulverized substance, 
in a small platinum or leaden cup, add enough H2S04 to make 
a thin paste, and cover the dish with a piece of Bohemian glass 
coated with wax except where the coating has been removed by 
writing through it down to the glass with a pointed wooden §B5-] 
63 
ANALYSIS FOR THE ACIDIGENS. 
pencil; heat the dish gently for an hour, warm the glass till 
the wax is melted, and rub it off with filter paper. The etched 
lines to be looked for may need to be brought out by breathing 
on the clean glass; they should reappear after the glass has been 
rinsed off, dried, wiped, and breathed upon again. 
10. Phosphoric acid ;—Dissolve a small portion of the orig- 
inal substance in HN03 with the aid of heatv add its volume of 
water to the liquid. Filter if solution is not complete, evapor- 
ate the solution nearly to dryness, and dissolve the residue in a 
little water. 
(ft) No members of the Sn group of metals were found in (77 It), 
and no is present; add 0.5 c.c. of this solution to 4 
c.c. of (NH4)2 Mo04. 
(b) Members of the Sn group of metals were found, but no 
is present; remove these metals by heating the solution 
and passing H2S through it till no further precipitation is pro- 
duced by the reagent, boil to remove all H2S, and test the 
cooled solution with (NH4)2M004, as above directed. Or the 
test for this acid may be deferred till the work in § 89 c has been 
completed, when, if no As has been found, the test for H3P04 
may be made as above, with the original solution; if As is found 
in § 89, c, a portion of the filtrate from the group precipitation 
by H2S may be used for the test, after first heating it with a 
few drops of HN03. 
(c) is present: add ZnS04 to the solution, freed 
from Sn group metals if originally present, as long as any fur- 
ther precipitation takes place, filter and test the filtrate as above 
with (NH4)2M004. 
11. Silicic acid:—Evaporate a portion of A to complete 
dryness, after acidification with HCI, and dry thoroughly at a 
gentle heat; moisten the residue with HCI, and after a little 
time add HCI and digest for a short time. For the detection of 
Si02, in an insoluble substance, see § 79. 
12. Preliminary test for the silver group of acids:—Acidify a 
small portion of B (or of Aif there is no B) with HN03, and 
add AgN03. The formation of a white or whitish precipitate 
indicates the presence of either HCI, HBr, HI, H4FeCy6 or 
HCy. In ordinary cases a mere turbidity may be taken as indi- 
cating traces of HCI only, and the other acids precipitated by 
silver nitrate may be regarded as absent, unless there be special 
reasons for searching for any of them. A colored precipitate 64 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 85. 
may contain also H3FeCy6 or H2Cr04. A black precipitate will 
be due to the presence of H.2S. If no precipitate appears all 
these acids are absent from this solution. H,S may be present 
in the original substance, in sulfids that were not transposed in 
§ 76. Pass on to 13. 
18. Hydrosulfuric acid :—To a portion of the original sub- 
stance in a test tube add HCI and warm gently. If solution 
with effervescence takes place, test the gas evolved with moist- 
ened lead paper. If a colored residue remains after this treat- 
ment, it may contain sulfids, although no reaction for H2S was 
obtained as above; in such case, warm the contents of the tube 
until all action ceases, to insure removal of S02 that may be 
present, add a piece of zinc, and repeat the test with lead paper. 
Should no reaction for H2S be now obtained, and a residue still 
remain, remove the Zn and wash the residue several times with 
water, to remove soluble sulfates, add to it HNOs and warm till 
red fumes are no longer set free, dilute with 5 or 6 parts of water, 
filter if not clear, and add BaCl2 to the filtrate. A white ppt., 
BaS04, shows that a sulfid or free sulfur was present in the sub- 
stance. If the other members of the Ag group are absent, pass 
on to 20. 
14. Hydriodic acid :—To 2 c.c. of B (or of A if there is 
no B) add 2 c.c. of HN03, 3 drops of K2Cr04 and 1 c.c. of 
CS2; bring the last mentioned reagent into contact with every 
part of the solution by thorough shaking ; if ferrocyanid or 
ferricyanid is present (see below), this shaking should be gentle, 
in order not to flour the liquid. 
15. Hydrobromic acid;—(a) HI was not found hi the pre- 
ceding test; to the same test add 0.5 c.c. of moderately strong 
chlorin water, and mix thoroughly by shaking. Too much 
chlorin may itself color the CS2. 
(b) HI was found in the preceding test; filter out the colored 
CS2 through a wet filter, add 2 c.c. of the chlorin water, mix 
well, add 0.5 c.c. of CS2 and mix again thoroughly by shaking. 
16. Hydrocyanic acid :—To a small portion of A add H2S04 
till acid, and in the open end of a small glass tube expose a drop 
of (NH4)2SX to the gas evolved; the tube may be supported by 
means of a perforated cork that rests in the top of the test tube. 
After exposure for 15 minutes, evaporate the drop of (NH4)2SX 
to dryness, on a crucible cover, by a very gentle heat, and 
moisten the residue with FeCl3. §B5-] 
ANALYSIS FOR THE ACIDIGENS. 
65 
17. Hydroferrocyanic acid:—Acidify a portion of B (or 
of Aif there is no B) with H2S04 and add a drop of FeCI3. In 
case HI is present the same reaction will, however, be obtained 
from H3FeCy6. HI acting as a reducing agent would change 
FeCl3 to FeCl2; but in any ordinary analysis an iodid and a 
ferricyanid would rarely be found together. 
18. Hydroferricyanic acid;—Dissolve x gm. of iron filings 
in H2S04, thus preparing a fresh solution of a ferrous salt, and 
add a drop of the solution to a portion of B (or of A if there is 
no B) that has been made acid with H2S04. It must be ob- 
served that even in the absence of ferricyanid a light blue ppt. 
will be formed if H4FeCy6 was found in 17, which will be 
changed to dark blue on addition of a few drops of HNOs. 
The ferrous solution must be used at once, as it oxidizes rapidly 
in the air, becoming unfit for use. 
For the more difficult separation and identification of ferro- 
and ferricyanid, when occurring together, see Prescott and John- 
son, or Fresenius. 
19. Hydrochloric acid :—lf no HI, HBr, H4FeCyG or HCy 
has been found, and a white precipitate was obtained in 12, it 
can be due to HCI only, and no further test need be made for 
this acid ; the precipitate may be black, owing to the presence 
of H2S, and still contain HCI :in this case treat it with am- 
monia, filter, and acidify the filtrate with HN03; a white pre- 
cipitate indicates HCI. 
If HI, HBr, H4FeCy6 or HCy has been found make a por- 
tion of B (or of A if there is no B) acid with HN03, add 
AgNOs, shake well, decant the liquid, and wash the ppt. twice 
with water by decantation, and test it as follows: 
(a) HI only was found.— Digest the ppt. for a few minutes 
with NH4OH, filter and acidify the filtrate with HN03. A white 
ppt. shows HCI. 
(6) HBr is present and HCy is absent.—Add to the ppt. 2 
c.c. of (NH4)2CO3, pass C02 through the mixture for a short 
time and digest, shaking occasionally, for fifteen minutes, filter, 
and acidify the filtrate with HN03. A white ppt. shows HCI. 
(c) HCy, HFe Cy6 or HAFeCy& is present.—Put the ppt. into 
a porcelain crucible, dry by gentle heat, ignite to low redness 
and allow to cool; put a piece of Zn in the crucible in contact 
with the ppt., add a little H2S04 and allow the action to con- 
tinue an hour; pour off the liquid, add to it AgN03, and test 66 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 85. 
the ppt., as directed in (jo) or (&), remembering that in the ab- 
sence of HI and HBr the formation of a white ppt. with AgN03 
is a sufficient test for HCI. 
20. Nitric acid :—lf A contains no chromate, evaporate a 
drop of it to dryness on a crucible lid, at a very gentle heat, 
cover the residue with a drop of phenyl-sulfuric acid, warm 
gently, and allow the action of the reagent to continue five min- 
utes, special care being taken, by tipping the lid this way and 
that, that every part of the residue is brought into complete con- 
tact with the reagent; then add two or three drops of NH4OH. 
The yellow color to be looked for may be transient, but more 
NH4OH will make it permanent. 
If A does contain chromate, nearly bdt not quite neutralize it 
with HCI, add Pb(C2H302)2 in slight excess, that is till precipita- 
tion is quite complete, filter, evaporate a drop of the filtrate on 
a crucible lid, then another drop on this residue, wet the last 
residue with a drop of water, and test with phenyl-sulfuric acid 
as above. If the solution to be tested is a very dilute dne, as a 
sample of water, several drops may be evaporated one after the 
other on the same spot. 
21. Chloric acid :—To the solution colored light blue with 
indigo solution add a little H2S04, and then, dropwise, Na.2S03; 
observe whether the color is discharged. The H2S04 test should 
be made, to confirm this result, if affirmative. 
No reaction was obtained for organic acids in 5. Pass on to 
the silver group, § 87. 
22. Acetic acid :—To a small portion of the aqueous extract 
of the original substance, or of A after neutralization with dilute 
acid, add 1 c.c. of H2S04 and a little alcohol, warm the mix- 
ture for a moment, then cool it in a stream of cold water, and 
observe the odor while shaking the tube gently; to be sure of 
the reaction, and of not mistaking it for the odor of nitric ether 
if HN03 should be present, a comparison test should always be 
made at the same time, with sodium acetate, H2S04and C 2H60, 
in another tube. 
If HCy is present, this test might be dangerous, and only the 
FeCl3 test should be used. 
23. Tartaric acid :—Pass H2S through the filtrate saved in 
6 b, heat the liquid gently to remove NH4OH, filter, add about 
x c.c. of strong HC2H302, a volume of KC2H302 solution about 
equal to the volume of the liquid, and a volume of alcohol THE SILVER GROUP. 
about equal to twice the whole, shake well, and allow to stand 
an hour. 
24. Citric acid :—Evaporate the filtrate from the final 
ppt. obtained in 23, till the C 2H60 is removed, and add 
Pb(C2H3O2)2; if a ppt. appears test its solubility in NH4OH. 
CHAPTER X. 
BASIGENS, OR METALS 
86. The Silver Group : forms of occurraice and reactions. 
Silver ; Ag:—May be met with as metal, alone or in alloys, 
or as silver salts. 
Reactions :—HCI ppts. immediately from neutral or acid solu- 
tions of silver salts, silver chlorid, AgCl, flocculent, white, soon 
darkening in the light, insoluble in hot as well as in cold water, 
insoluble in dilute acids, soluble in NHxOH, as (dVHs)3AgCI, 
from which it is re-precipitated by acids. This ppt, is often so 
fine that unless flocculated by strong agitation it passes easily 
through the filter. 
HoS ppts. immediately from all solutions, silver sulfid, Ag2S, 
flocculent, black, insoluble in (NH*)2SX and dilute acids, solu- 
ble in moderately dilute HN03. 
Lead ; Pb :—May be met with as metal, alone or in alloys, as 
insoluble oxids or as lead salts. 
Reactions:—HCl ppts. from not too dilute, cold solutions of lead 
salts, lead chlorid, Pb Cl,, pulverulent or crystalline, white, soluble 
in boiling water, and separating, crystalline, from this solution, 
on cooling. 
K,CrO, ppts. from neutral solutions, PbCrOx, yellow, slightly 
soluble in acetic acid, very slightly soluble in HN03, easily 
soluble in solution of KOH or NaOH. 
H2S ppts. immediately from all solutions lead sulfid, PbS, 
flocculent, black, insoluble in and in cold dilute acids, 
soluble in hot moderately dilute HN03; insoluble, white PbS04 
is formed if HN03 is used to dissolve it. 
HISOx ppts. in a short time, and immediately if its volume of 68 
[§ 87- 
ELEMENTS OF CHEMICAL ANALYSIS. 
alcohol is added to the liquid, lead sulfate, PbSOi} pulverulent, 
white, less soluble in H2S04 than in pure water. 
Mercury ; Hg :—As mercurous salts. 
Reaciioiis :—HClppts. immediately from solutions of mercurous 
salts, mercurous chlorid, HgCl, pulverulent, white, insoluble in 
hot as in cold water, and in cold acids, not dissolved by NHX Old, 
but blackened, NH.2Hg2CI being formed. 
H2S ppts. immediately mercurous sulfid, Hg2S, flocculent, first 
white if HgN03 was in the solution, then, after long continued 
action of the H2S, black; this black sulfid is insoluble except 
in aqua regia, forming then HgCl2. , 
87. Preparation and analysis of the silver group precipitate. 
Cl, The chemistry of the work on this group. 
The members of this group are precipitated as chlorids from a 
solution made somewhat acid by HN03; the lead chlorid is 
separated from the others by making use of its solubility in hot 
water, and the silver chlorid is then obtained by itself, by means 
of its solubility in NH^OH. 
As the grouping work of the course begins thus with the pre- 
cipitation of its members as chlorids by HCI, it is evident that 
if the solution was originally made with this acid it is therefore 
present in the clear liquid, and no members of the group can 
also be present unless the acid was concentrated and no water 
has been added. 
Many substances (Prescott and Johnson § 547), are held in solu- 
tion by an alkaline liquid, the free alkali or the alkaline salt, to 
which the alkaline reaction of the liquid is due, acting as a 
chemical solvent (§ 5). New soluble salts are formed, by the 
production, generally, of feeble acids, in which the metal of the 
compound dissolved acts as an acidigen, yielding soluble salts 
with the alkaline base: such salts are decomposed by stronger 
acids with the reprecipitation of the substance dissolved, which 
is sometimes redissolved by an excess of the acid, and sometimes 
not. Hence, by the addition of HCI to a solution having an 
alkaline reaction, compounds of elements belonging to other 
groups may be precipitated together with the chlorids of this 
group, which, besides perhaps being in the way here, might be §B7-] 
THE SILVER GROUP. 
69 
missed where they should be tested for; therefore this test for 
alkalinity must be made as in 26. Nitric acid will also precipi- 
tate these compounds not properly belonging in the HCI pre- 
cipitate, but only one member of this group, the other two 
remaining undisturbed, to be thrown down by HCI in the proper 
manner ;• the one possibly precipitated, silver, will be found in 
its place on following out the course of treatment laid down in 
26, a. 
Since, as above stated, some of the foreign compounds pre- 
cipitated are redissolved on the addition of acid beyond the 
point of neutralization, leaving the solution clear and in a proper 
condition for the HCI precipitation, there should be certainty 
that enough acid has been added for this purpose, while at the 
same time any great excess is avoided. 
The products of this group precipitation may contain a little 
antimony oxychloride (§ 89), if much antimony is present; this 
will not, however, interfere with the examination of the precipi- 
tate for this group, nor will this element be missed in Table 111, 
since this precipitation is only partial. 
The weak points in the work of this group, which the student 
should bear in mind, are the imperfect insolubility of the PbCl2 
in cold water, its rather sparing solubility in hot water, and the 
slight solubility of AgCl in strong HCI or solution of alkaline 
chlorids. 
h. Preparation of the silver group precipitate. 
25. If HCI was used in making the solution, and it is clear 
when cold, or HCI was used, and the solution remains clear 
when diluted with two or three times its volume of cold water, 
pass on to § 87 b. 
If not clear when cold, as when hot, or after such dilution, 
proceed as in case a ppt. is obtained in 26 h, below. 
26. If the substance is already in solution when received, or 
is made with water only, test it with litmus paper; if found to 
be alkaline pass to (a) ; if acid or neutral, to (&). 
(a) The solution is alkaline. Add HN03 till acid ;if no ppt. 
forms pass to (b); if a ppt. is formed and does not dissolve on 
adding more acid, filter, examine the ppt. by § 78, and examine 
the filtrate as directed in (&). ELEMENTS OF CHEMICAL ANALYSIS. 
(h) The solution is acid or neutral. Add a few drops of 
HCI; if no ppt. appears pass to § 89, h. If a ppt. is formed 
continue to add HCI till it no longer increases, shake vigor- 
ously, allow the ppt. to settle and decant the liquid through a 
filter. If much Sb is present in the original substance this ppt. 
may possibly contain a little Sb405Cl2 (see above.) Reserve the 
filtrate for the tin and following groups, § 89, h. 
C, Analysis of the Silver Group Precipitate. 
TABLE III. 
27. Wash the precipitate \Vith cold water, by decantation, till the wash 
water is no longer acid, then boil it with about 10 or 20 c.c. of water, and 
filter while still boiling hot. 
28. Filtrate. 
29. Residue. 
To a portion add 
K2Cr04. A yellow 
ppt. or turbidity in- 
Add about 5 c.c. of NH4OH, shake thoroughly 
and filter if solution is not complete. 
dicates Pb. 
30. P'illrate. 
31. Residue. 
Acidify with 
HN03. A white 
ppt. indicates Ag. 
This, if there is any of it, is 
blackened by the treatment 
with NH4OH. Hg, as mer- 
curous salt, is indicated. THE TIN GROUP. 
88. The Tin Group: forms of occurrence,properties, and re- 
actions. 
Gold; Au :—To be met with as pure metal or in alloys, and 
as soluble chlorid. 
Reactions:—Gold is soluble in aqua regia, forming yellow 
AuC13. 
H2S ppts. from cold acid solution Au2S3, black, from hot solu- 
tions Au2S, brown ; both sulfids are slowly soluble in (NH4)2SX 
as (NH4)3 AuS3 and repptd. from this solution by acids as Au2S3. 
H, C, especially in presence of {Nlf)., C, 0+ ppts. from not 
too acid solutions of gold, metallic gold, brown to violet, very fine 
powder, which rubbed with a knife on a hard surface shows the 
color and lustre of gold. 
Sn Cl2, to which a little chlorin water has been added to convert 
a smallportion of the stannous to stannic salt, gives in solutions of 
gold a purple red ppt. or coloration, or sometimes violet or brown- 
ish-red (purple of Cassius), insoluble in HCI. 
Platinum ; Pt. :—To be met with as metal, alone or in alloys, 
and as soluble chlorid. 
Reactions :—Platinum is soluble in aqua regia, forming soluble 
PtCl4. H2S ppts. from acid solutions of platinum salts, slowly 
unless the solution is hot, PtS2, blackish-brown, soluble slowly 
and with difficulty in (NH4)2SX, and repptd. from this solution 
by acids. 
SnCL reduces platinic salts to platinous salts, which dissolve 
in HCI, giving a deep red color. 
Arsenic; As:—To be met with as, (1) arsenous oxid, 
As406, slightly soluble; (2) as sulfids, As2S2 realgar, As2S3, orpi- 
ment, or As2S5, all insoluble ; or (3) in arsenites, M*3As03 or 
arsenates M3As04, both mostly insoluble ; or (4) as a gaseous 
compound with hydrogen, AsH3 very poisonous. 
Reactions:—H2S ppts. from acid solutions immediately arsen- 
ous sulfid, As2S3, flocculent, light yellow, soluble in (NH4)2SX 
forming (NH4)3AsS3 (variable), and repptd. from this solution 
by acids as As2S3, insoluble in HCI, but dissolved by digestion 
with fully concentrated hydrochloric acid and KCI03 (potassium 
chlorate) forming H3AsG4. 
With Zn and H,SOt solutions containing As yield arsenous hy- 
dride, As/f a colorless gas, which conducted into a solution of 
* M stands for any monad basigen. 72 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 88. 
AgNO?> causes the separation of Ag, black ppt., while the As re- 
mains in solution as H3As03. HN03 is also formed, but no NO 
as when HN03 is itself the oxidizing agent. The oxygen for 
this oxidation appears to come from the water present. 
To make this test, a hydrogen generator is required, consisting 
of a small flask provided with a two-hole rubber stopper; 
through one of these holes a funnel-tube passes, and extends 
nearly to the bottom of the flask ; a short tubs in the other hole, 
bent at a right angle, is connected by a rubber tube with the 
glass delivery tube that conducts the gas evolved in the flask into 
the solution of AgN03. Put two or three small pieces of granu- 
lated zinc into the flask, while holding it in an inclined posi- 
tion, so that the zinc will glide down the side, and not fall 
directly on the thin bottom, perhaps breaking it; put in also a 
piece of clean platinum foil, add about 10 c.c. of H2S04, or so 
much that the mouth of the funnel tube will be immersed, carry 
the delivery tube into about 10 c.c. of AgN03, in a test tube, 
and then add the solution containing the arsenic, or to be tested 
for arsenic, very slowly. The gas from the generator should 
never be allowed to escape except through the silver solution, if 
there is any possibility that arsenic is present. 
Compounds of arsenic, and especially the sulfid, when heated in 
a bulbed tube of hard glass with a perfectly dry mixture of sodium 
carbonate and potassium cyanid, are reduced, and the arsenic is 
volatilized and deposited as a black, lustrous ring on the cooler 
part of the tube. To make this test, proceed as follows; put a 
small quantity of the perfectly dry substance in the bulb of the 
tube, and cover it with a mixture of equal parts of dry Na2C03 
and KCy; the bulb should be so large, or the quantity of sub- 
stance taken so small, that the bulb will not be more than half 
filled. Heat the bulb gently, and with a twisted piece of filter 
paper wipe out any moisture that may collect on the inner walls 
of the tube; this drying must be very thoroughly done; now 
heat the bulb strongly, and for some time if no black deposit 
appears at once. 
Antimony; Sb ;—May be met with (i) as metal, alone or in 
alloys; (2) as insoluble sulfids, Sb3S3, and Sb2S5; (3) as oxids, 
Sb406 and Sb204, insoluble, acting feebly acidigenic or basigenic, 
and Sb205, acting only acidigenic and forming mostly insoluble 
compounds ; (4) in combination with Cl as SbCl3, or SbCl5; or 
(5) in a gaseous compound with hydrogen, SbH3. 
Reactions:—Metallic antimony is oxidized by HNO:, to §BB.] 
THE TIN GROUP. 
73 
Sb204 and Sb205, white, soluble in HCI and, when freshly pre- 
cipitated, in tartaric acid. 
H2S ppts. immediately, from acid solutions containing anti- 
mony, antimonous sulfid, Sb2S3, flocculent, orange yellow, solu- 
ble in (NH4)2SX forming (NH4)3SbS4, and repptd. by acids from 
solution as Sb2S5. Both sulfids are soluble in hot HCI forming 
SbCl3. 
H2O added in large quantity to a solution containing SbCl3 
ppts. basic salt or oxychlorid, variable, but mostly Sb405Cl2, pul- 
verulent, soluble in tartaric acid, and converted into antimonous 
sulfid by H2S passed through water in which it is suspended. 
With Zn and IfSO{, in the hydrogen getterator, solutions con- 
taining antimony yield metallic antimony, deposited as an adherent 
black coating on platinum foil kept itt contact with the zinc ; this 
deposit is insoluble in HCI, soluble in HNO,; at the same time 
that this deposit is formed a part of the antimony yields antimonous 
hydrid, SbHz a colorless gas, which in a solution of AgNO. gives 
SbAg3 black ppt. The tnore rapid the evolution of hydrogen, the 
more Sb is liable to be carried off as Sblf. 
Tin ; Sn :—May be met with (i) as metal, alone or m alloys, 
(2) as insoluble oxids, SnO or Sn02, one acting basigenic, the 
other basigenic or acidigenic, (3) as insoluble sulfids, SnS or 
SnS2, and (4) as soluble chlorids, SnCl2 or SnCl4. 
Reactions:—HN03 oxidizes tin to Sn02, white, which at 
once forms with the water raetastannic acid, HIOSn5O15, variable, 
insoluble in acids. HCI dissolves tin as SnCl2, soluble. 
H2S ppts. immediately from not too strongly acid solutions 
containing stannous salts, stannous sulfid, SnS, flocculent, dark 
brown, soluble in (NH4)2SX forming (NH4)2SnS3, and reprecipi- 
tated by acids as SnS2. From solutions of stannic salts H2S ppts, 
stannic sulfid SnS2, flocculent, white at first, while the stannic 
salt is in excess, then yellow, soluble in (NH4)2SX with formation 
of the same compound as in the solution of SnS. SnS and SnS2 
are soluble in hot HCI, forming SnCl2 and SnCl4, respectively. 
With Zn and H2S <94 solutions containing tin give Sn, gray ppt. 
deposited mostly on the zinc, and not adhering either to this or to 
the platinum foil if deposited thereon. 
HgCh gives with solutions of stannous salts, mercurous chlorid, 
HgCl, pulverulent, white first and becoming grayish with excess 
of stannous salt. 74 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 89. 
Bg. The preparation and analysis of the tin group precipitate. 
ft. The chemistry of the work o?i this group. 
For the separation of the members of this group from those 
that follow, use is made of the insolubility of their sulfids in 
moderately strong hydrochloric acid. Since the sulfids of the 
metals of the copper group are equally insoluble in acids, both 
groups are precipitated together by this reagent. The two 
groups are then separated by means of the solubility of the 
sulfids of the tin group in (NHJ2SX (ammonium sulfid with 
excess of sulfur). When this solution is treated with excess of 
dilute acid, the metals of the tin group are again precipitated as 
sulfids. Separate and special tests being made in the original 
solution for gold and platinum, only arsenic, antimony and tin 
remain to be tested for in this second precipitate. For the sepa- 
ration of these elements use is made of their different behavior 
with nascent hydrogen, especially in the presence of metallic 
platinum ; the first passes off as a gaseous compound, AsH3, and 
is taken up by a silver solution ; the second is mostly precipi- 
tated as an adherent coating on the platinum ; the third is precipi- 
tated as a loose metallic deposit, or loosely adhering to the zinc ; 
both the second and the third therefore remain in the generator. 
In this Table the grouping by sulfids first comes into effect, 
and so far as it takes place here depends upon the solubility in 
dilute acid of sulfids of metals to be tested for in the iron and 
aluminum groups, and the insolubility of those to be precipitated 
here. But a study of the properties of these sulfids will show 
that they are more or less soluble in strong mineral acids when 
hot, and in aqua regia ; hence, especially as the precipitation 
must be made in a hot liquid, the directions for the careful prep- 
aration of the solution as to its acidity. 
Furthermore, since these sulfids are soluble in solutions of the 
fixed alkaline hydroxids by the formation of oxygen salts of 
these bases, such as K3As03, and in solutions of alkaline sulfids 
forming soluble sulfo-salts (§ 65), and since, if the solution con- 
tained free alkali at the start, the first portions of H2S added 
would be taken up to form these sulfids of the alkaline metals, 
acidity in the beginning is also an essential condition. Also, 
some of these sulfids are not readily precipitated in a neutral 
solution, as will appear on writing the equation for the precipita- 
tion of arsenic or antimony from neutral solutions of salts of the 
alkaline metals in which they take the part of acidigens. 
The fact that Sb405Cl2 and BiOCl, if precipitated in the course §B9-] 
THE TIN GROUP. 
75 
of the preparation of the solution, may be left undissolved is an 
interesting illustration of the principle (§ 26 a) that metathesis 
may sometimes take place between substances when one of 
them is in the solid condition ; that these oxychlorids cannot be 
allowed to remain as such in the later work of the course will 
become evident on careful study of the steps that follow, which 
result in confining antimony to this course and sending bismuth 
to the next, and comparison of the solubility of these oxychlor- 
ids and of the four corresponding sulfids. 
The tests for gold and platinum in 86, Table IV, exhibit a 
nice distinction between the power of different reducing agents; 
oxalic acid reduces only the former, while SnCI2 reduces both. 
In order that the color of the reduced gold may not interfere 
with the sharpness of the other reaction, it must first be removed. 
Concentrated HCI serves to dissolve any platinum that might be 
precipitated in the test for gold, in the presence of the ammo- 
nium salt added, as 2NH4CI.PtCl4. 
The group precipitation must be made in a hot solution as in 33 
below, chiefly on account,of the possible presence of arse mV salts. 
Under the reactions of arsenic it will be seen that only As2S3 is 
precipitated by H2S from any solutions containing this element; 
therefore, if the arsenic is not already in the form of 
salts, reduction must take place before precipitation; such reduc- 
tion by H2S requires the aid of heat, about 70°, and consider- 
able time, even perhaps twelve to twenty-four hours; previous 
treatment with a more active reducing agent, as H2S03, greatly 
shortens the time required for complete precipitation. 
Under the reactions for mercuric salts, considered in connec- 
tion with the first step in sub-grouping taken in § 91 c, will be 
found another reason for keeping the solution under the influ- 
ence of H2S for a considerable time. 
The use of yellow ammonium sulfid, (NH4)2SX, in 34, which 
is necessary for the separation of members of this group on 
account of the difficult solubility of tin and antimony sulfids in 
the normal, colorless (NH4)2S, has this disadvantage, that the 
CuS which should pass over to §gic, is soluble in it; but this 
sulfid is almost completely precipitated again on boiling the 
solution. 
The constitution of the compounds formed in this solution of 
the sulfids is explained in § 65. 
In the re-solution by concentrated acid of the sulfids pre- 
cipitated from the (NH4)2SX solution, as in 37«, the use of the 76 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ s9- 
strong oxidizing agent, KCI03 in presence of HCI, is likely to 
carry at least a portion of the elements combined with the sulfur 
up to their highest degree of chlorination ; this makes more 
striking the illustration furnished here of the reducing power of 
nascent hydrogen, all the antimony, tin and arsenic being 
reduced to the elementary form ; then, by further action in the 
same direction, all of the arsenic and a part of the antimony 
are carried off as gaseous products in combination with hydro- 
gen. 
The sharp separation of arsenic and antimony is a difficult 
matter ; any one of several methods will give satisfactory results, 
as will this one, as given in 37b, if carefully executed, but 
otherwise failure is likely to be encountered. In this method 
arsenic may possibly remain in its reduced form in the generating 
flask, or by misfortune in the opposite direction all the antimony 
may be carried as SbH3 out of the generator. By the slower 
production of hydrogen in the first part of the operation, the 
deposition of a certain portion of the antimony on the platinum 
foil is secured, when it will be safely fixed, having passed the 
nascent state; a subsequent more rapid evolution of gas secures 
the transfer of at least the largest part of the arsenic to the 
test-tube. 
Tin cannot leave the generator under any conditions. 
82. Before proceeding further with the analysis the solution 
must be so prepared that it will be moderately acid with HCI, 
and it is better that it should not contain free HN03 or strong 
acid of any kind; if the solution was made with water and then 
acidified with HCI, or made with dilute HCI, it is already in this 
condition ; pass to 83. If HCI was used for the solution, 6or 
7 parts of water may be added, then pass to 33. If HNO:i was 
used in preparing the solution, evaporate the liquid nearly to 
dryness, in the hood, add to the residue 1 c. c. of HCI and 10 
c. c. of water; if a white ppt. forms on addition of water it 
probably consists of Sb405Cl2 or BiOCl (see § 89 a). 
b. Preparation of the group precipitate. 
33. Reserve about 5 c. c. of the solution for the tests for gold 
and platinum, and through the rest of it pass a slow current of §B9-] 
THE TIN GROUP. 
77 
H2S for at least 15 minutes, or till no further precipitation is 
produced by the reagent, or no further change appears in the 
color of the ppt. For this important group precipitation the 
liquid must be hot in the beginning ; and if the operation requires 
much time for its completion the liquid should be heated as often 
as may be necessary to keep it hot; finally, on filtering, the first 
portions of the filtrate should be heated nearly to boiling, and 
tested with H2S for complete precipitation. 
If no ppt. is formed, or only one that is white, very fine and 
plainly only sulfur, pass on to the iron group, § 93, h (see 
Table II). 
If a colored ppt. is formed, filter and wash thoroughly with 
hot water till a drop of the washings received in a little AgN03 
in a test tube gives at the most only a slight turbidity. Reserve 
the filtrate for following groups, beginning with the iron group, 
§93 b. See also Table 11. 
34. Precipitate. Digest a small portion in an evaporator 
with (NH4)2SX : if it dissolves completely, only metals of the Sn 
group are present in this ppt., and the remainder of it may be 
used in the analysis for these metals, as directed below (37 Cl) ; if 
a residue remains undissolved, metals of the Cu group are also 
present: in this case pour off the (NH4)2SX and test it with HCI 
as in 35; if no metals of the Sn group are shown to be present, 
take the remainder of the ppt. to § 91, h9 for the analysis of the Cu 
group. If metals of both groups are present, the whole of the 
ppt. must be treated as above, with (NH4)2SX and the mixture 
boiled and filtered. Reserve the insoluble residue for the Cu 
group. 
35. Filtrate. Dilute with 3or 4 parts of water and acidify 
with HCI; if only a fine, white, or faintly yellowish ppt. appears 
that remains suspended in the liquid it consists of sulfur from the 
(NH4)2Sx, and As, Sn, and Sb are absent; pass on to the Cu 
group. A colored ppt. that is flocculent, or becomes so on warming, 
may contain the sulfids of these metals: filter, rejecting the 
filtrate, and take the precipitate to Table IV, following. 78 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 89 
C. Analysis of the Tin Group Precipitate. 
TABLE IV. 
36. Filter a small portion of the solution, reserved in 33 for this purpose, if 
not clear, and add to the filtrate i c.c of (NH4)2C204 and of H,C204, boil and 
let stand ten minutes; a brown or violet ppt. indicates Au. The result may 
be confirmed by the other reactions given for this metal. 
If Au was found, filter, wash the ppt. with 0.5 c.c. of HC1 and add SnCh 
to this filtrate; a red color shows Pt. If no Au was found add SnCl2 directly 
to a small portion of solution 33. 
37 (a) Transfer the ppt. brought from 34 or 35 to an evaporator, add 5 c.c. of 
fully concentrated hydrochloric acid and warm; if the ppt. does not dissolve 
remove the lamp, add a small crystal of KClCb and digest till the sulfids are 
dissolved, or the residue is at least decolorized. Filter if a residue (sulfur) 
remains, add to' the filtrate 5 c.c. of FeS04 and 5 c.c. of H2S04, and proceed 
as follows. 
(6) Into the hydrogen generator, described under the reactions of arsenic and 
prepared for use as there directed, pour this solution very slowly, only a few 
drops at a time, till all has been added ; if before this the zinc is wholly dis- 
solved, lift the cork of the flask for a moment and drop in another piece ; be 
sure that the platinum is in contact with the zinc during the whole operation, 
which need be continued only for a few minutes after the last portion of the 
solution has been added. 
Contents of the Generator. 
Contents of the Test-tube. 
The loose ppt. 
The fixed ppt. 
40. If no black ppt. is form- 
ed As and Sb are both absent. 
38. Pour the contents of the 
generator into a filter, pick out 
the pieces of zinc, and rinse 
whatever adheres loosely to 
them and to the platinum foil 
into the filter with the jet of the 
wash bottle, and then with the 
same jet collect the contents of 
the filter down into the apex of 
the cone; when the water has 
fully drained out, carefully re- 
move the filter from the funnel,, 
tear off that part containing the 
solid matter, and warm this 
very gently with about two c.c. 
of HC1, till all action ceases, 
add about its volume of water 
to the liquid, filter into a small 
test tube, and to the filtrate add 
HgCl2. A white or grayish 
ppt. shows Sn. 
39. If the platinum foil is 
blackened, and remains black 
after treatment with HC1, 
antimony is probably present; 
to confirm the indication wash 
the residue insoluble in HC1 
in 38, together with the foil, 
with water, add a few drops 
of HN03 and 2 c.c. of tar- 
taric acid, heat nearly to 
boiling, dilute with an equal 
volume of water and add to 
the solution H2S. An orange 
ppt. shows Sb. If this ppt. 
is black, owing to the possible 
presence of Cu, heat it with 
two c.c. of tartaric acid for a 
few minutes, filter, and apply 
the H2S test to the filtrate. 
If a black ppt. appears, filter, 
rejecting the ppt., to the fil- 
trate add HC1 as long as a 
ppt. is formed, heat just to 
boiling and filter, pouring the 
filtrate through the filter a 
second time to insure complete 
removal of AgCl, and to the 
filtrate add H2S. A yellow 
ppt. shows As. In the pre- 
sence of a large proportion of 
Sb, and little As, this ppt. may 
be so colored by Sb2S3 that 
the indication for As is uncer- 
tain. In such case collect the 
ppt. on a filter, wash it down 
into the apex of the cone, dry 
it thoroughly in the drying closet, 
remove it from the filter, and 
test it for As by heating in the 
bulbed tube with Na2C03 and 
KCy. § 9°-] 
THE COPPER GROUP. 
79 
90. Forms of occurrence and reactions. 
THE COPPER GROUP. 
Copper ; Cu :—To be met with as metal, alone or in alloys, as 
oxids, insoluble, and as copper salts. 
Reactions:—H2S ppts. immediately from all solutions contain- 
ing copper, cupric sulfid, CuS, flocculent, black, insoluble in 
cold dilute acids, slightly soluble in (NH4)2SX, soluble in hot 
HN03 and in KCy (potassium cyanid) solution. 
JVHi OH ppts. immediately cupric hydroxid, Cu( OH)2 floccu- 
lent, greenish-blue, soluble in excess of the precipitant forming a 
dark blue liquid; the formulas of the double compound of NH3 
and copper salts, causing this blue color, vary with the nature of 
the acid of the copper salt used, and other conditions. 
Cadmium; Cd:—To be met with as metal, alone or in alloys, 
and as cadmium salts. 
Reactions :—H,S ppts. immediately from solutions containing 
cadmium, cadmium sulfid, CdS, flocculent, yellow, insoluble in 
cold dilute acids and in (NH4)2SX, soluble in hot HN03, insolu- 
ble in KCy. 
NH4OH ppts. cadmium hydroxid, flocculent, white, soluble in 
excess of precipitant. 
Bismuth; Bi:—To be met with as metal, alone or in alloys, 
or as bismuth salts. 
Reactions:—H2S ppts. immediately from all solutions con- 
taining bismuth, bismuth sulfid, Bi2S3, flocculent, black, insoluble 
in cold dilute acids and in (NH4)2SX, soluble in hot HN03. 
NH4OH ppts. bismuth hydroxid, Bi(OH)3, flocculent, white, 
insoluble in excess of precipitant, soluble in dilute acids. 
H, O added in large quantity to concentrated solutions containing 
bismuth and a moderate quantity of HCI causes the formation of 
bismuth oxychlorid, BiOCl, lustrous white, soluble in strong 
acid. 
Mercury; Hg;—To be met with as metal, alone or in alloys 
(amalgams), and as mercurous or mercuric salts. 
Reactio7is :H2S ppts. immediately from all solutions con- 
taining mercuric salts, mercuric sulfid, HgS, flocculent, black 
finally when precipitation is complete; color at first may be 
white, and pass through yellow, orange, and brown to black; if 
the mercury was originally present as nitrate, long continued 
action of the H2S may be necessary to convert it completely into 
the black sulfid. The black ppt. is insoluble in (NH4)2SX, and ELEMENTS OF CHEMICAL ANALYSIS. 
is soluble only in aqua regia, forming HgCl2. The lighter 
colored ppt. consists of compounds of HgS with the original 
salt, the HgS predominating more and more as the action of the 
H2S is continued. 
SnCl2 in presence of HCI gives mercurous chlorid, HgCl, pul- 
verulent, white or gray. The darker color is due to reduction of 
some HgCl to metal, by the excess of SnCl2. 
gI. The preparation and analysis of the copper group precipitate. 
Cl. The chemistry of the work on this group. 
In the ordinary course of a complete analysis of a substance 
possibly containing members of all the groups, the members of 
this group are already separated from those of the other groups, 
in the residue insoluble in (NH4)2SX, brought from the preparation 
of the precipitate for the tin group. If, as when working on 
this group by itself, as in the usual preliminary practice, the 
original substance is at once examined for this group, or if the 
substance is known to contain only members of this and following 
groups, the solution of it is prepared and treated with H2S, as 
directed in § 89 b, and the members of this group are then 
obtained in the same form as in the insoluble residue from 84 in 
that section. 
From this precipitate the mercury is separated by the insolu- 
bility of its sulfid even in concentrated HN03. In the solu- 
tion containing the other members of the group, copper and 
cadmium are separated from bismuth by the solubility of their 
hydroxids in NH4OH, and the copper is finally separated from the 
cadmium by the insolubility of its sulfid in KCy. 
In the ordinary course of a complete analysis of a substance, 
we have at the opening of this group analysis, sulfids precipi- 
tated in 88 and insoluble in (NH4)2SX; also, possibly, lead from 
26 b, for reasons explained at the close of § 28. By the re- 
agent applied here in the very beginning, the first step in the 
sub-grouping of the members of this group is effected. The 
continuance of the red fumes indicates continuance of oxidation 
of sulfids, and their cessation is evidently, in the simultaneous 
presence of HgS and other black sulfids of this group, the 
only easily observed indication of the complete solution of § 91-] 
THE COPPER GROUP. 
81 
all that can be dissolved by the acid from this mixture of 
sulfids; incomplete solution might result in missing one or more 
of the substances to be tested for under 42 to 45, Table Y. 
For the removal of lead, if still present, in 42, Table V, ad- 
vantage is taken of a more insoluble precipitate than the chlorid ; 
and if any still escapes precipitation it may be arrested by the 
NH4OH added later, so that its troublesome presence in filtrate 
43 should never occur with proper care in the previous manipu- 
lation. 
Because lead may thus be present in the precipitate by NH4OH, 
the formation of that precipitate is not of itself sufficient proof 
of the presence of bismuth. 
For copper we have one of those characteristic color tests 
which might as well be applied in all ordinary cases to the origi- 
nal solution, if, indeed, the presence of this substance is not 
sufficiently betrayed by the blue or greenish-blue color of that 
solution, or of the nitric acid solution made in 41. 
By the addition of KCy the cuprammonium compound in the 
deep blue solution, yielded by NH4OH with the copper, is broken 
up by the formation of new compounds into which cyanogen 
enters, the color is destroyed, and we have a solution in which 
the excess of KCy prevents the formation of CuS, and, its color 
being much lightened, the cadmium precipitate can be more 
easily distinguished in it. 
For bismuth we have a reaction in 45 that is peculiar, in that 
the precipitate is apparently made by so general a solvent as 
water; it is due to the tendency of normal salts of bismuth to 
decompose when added to a large quantity of water, forming 
basic salts (§ 17), Some of these salts, and especially the oxychlo- 
rid, are quite insoluble in water; but as they are readily soluble in 
acids, the reason for the use of but little acid may be understood, 
and also, although for another purpose, for the precaution noted 
in 42 of adding sufficient H2S04 in the precipitation of lead; 
the reason for evaporation to a very small bulk is also indicated, 
since in the evaporation of an acid solution the free acid is more 
or less completely expelled. 
Since the conditions requisite for the production of this oxy- 
chlorid are the presence together of a bismuth salt and HCI in 
certain proportions, and a sufficient degree of concentration of 
the solution, the precipitate may appear, as well as the similar 
one, Sb405Cl2, in the group precipitation of the Ag group; but 
only in case of much more caution in adding HCI than the [§ 91- 
82 
ELEMENTS OF CHEMICAL ANALYSIS. 
student usually shows ; and, as it is altogether likely that only a 
part of these metals would be thus precipitated in any case, the 
occurrence of such a precipitate would do no other harm than 
to lead to the inference that, having a group precipitate, then 
certainly one or more of the members of the group ought to 
be found in it. 
h. The preparation of the copper group precipitate. 
In the course of a complete analysis of a substance, this pre- 
cipitate is already prepared. In the case of practice on this 
group precipitate alone, the precipitate is prepared as described 
in 82 and 33 under the tin group. § 91-] 
83 
THE COPPER GROUP. 
C. The Analysis of the Copper Group Precipitate. 
TABLE 
V. 
41. Heat the precipitate in an evaporator with about 3 c.c. of 
HN03, with constant stirring and boiling, till red fumes are no 
longer evolved, add its volume of water to the mixture, and filter. 
42. Filtrate. 
46. Insoluble 
residue. 
Test a small portion for Pb with alcohol and H2S04 (see 
reactions of Pb, $ 86); if Pb is found treat the whole of the 
solution with alcohol and H2S04, with care to add the acid in 
excess, that is, more than enough to ppt. the Pb, so as to prevent 
possible precipitation of Bi, and filter, to remove the Pb. To 
this filtrate or to the remainder of filtrate 415 if Pb is absent, 
add NH4OH till strongly alkaline. A white ppt. indicates 
bismuth, but its presence should be confirmed as below. If 
this ppt. is formed filter. 
Dissolve in 
aqua regia, with 
aid of heat, and 
add to the solu- 
tion SnCl2. 
A white or gray 
ppt. shows Hg 
present as mer- 
curic salt. 
Pass on to the 
43. Filtrate. 
45. Precipitate. 
iron group, §$ 92 
and 93. 
If this filtrate is blue, the presence of Cu 
is indicated. 
Dissolve in a 
little HC1; eva- 
porate the solu- 
44 (a). Copper is 
absent. 
To a portion of the 
solution add (N H4)2S. 
A yellow ppt. indi- 
cates Cd. 
44 (fc). Copper is 
present. 
To a portion of the 
solution add KCy 
till the blue color 
disappears. Then 
add (NH4)2S. 
A yellow ppt. in- 
dicates Cd. 
tion till only a 
few drops re- 
main; add a little 
of this solution to 
a test-tubeful of 
water. 
A white ppt. or 
turbidity i n d i - 
cates Bi. 
If no insoluble 
residue in 41, 
pass on to the 
iron group, | | 92 
and 93. 
A black ppt. obtained here for Cd may be 
due to the presence of Pb or Hg; in the 
latter case because the element was not 
completely converted into black sulfid in 
33 ; filter, wash the ppt., put it with the 
filter into an evaporator and boil with 
H2S04, filter again and add to the filtrate 
H2S. A yellow ppt. shows Cd; but if the 
ppt. is still black, owing to presence of HgS, 
it must be boiled with HC1, which will dis- 
solve the CdS if present; the solution is 
then to be diluted, and tested with H2S. 84 
[§ 92- 
ELEMENTS OF CHEMICAL ANALYSIS. 
92. Forms of occurrence and reactions. 
THE IRON GROUP. 
Nickel ; Ni:—To be met with as metal, alone and in alloys, 
and as nickel salts. 
Reactions : ppts. from neutral or alkaline solutions 
nickel sulfid, NiS, flocculent, black, insoluble in cold HCI, sol- 
uble in hot HN03; somewhat soluble in excess of the precipitant, 
giving a brown solution. 
NH4OH and NaOH ppt. nickelous hydroxid, Ni(OH)2, floc- 
culent, green, soluble in NH4OH ; it is oxidized by Br in pres- 
ence of NaOH to Ni(OH)3; when this compound, nickelic 
hydroxid, is boiled with NH4OH it is reduced, with evolution of 
nitrogen, to Ni(OH)2, and dissolved. 
To the borax bead nickel compounds give a brown color. 
To make this test, heat the clean loop of the platinum wire in 
the lamp flame, and then quickly dip it into powdered borax; 
fuse this mass in the flame, heating gently at first till the effer- 
vescence becomes moderate, and finally to redness; if the bead 
is thin, dip it into the borax again while hot, and fuse again, 
and repeat till a full oval bead is obtained ; then heat it again 
with a small quantity of the substance to be tested adhering to 
it, till the bead is clear. If too much substance is taken the 
bead may be opaque; in such a case break it, and fuse a part of 
it in a new bead. 
Cobalt; Co;—May be met with as metal, and as cobalt 
salts. 
Reactions :—(NH4)2S ppts. from alkaline or neutral solutions 
cobalt sulfid, CoS, flocculent, black, insoluble in cold HCI, 
soluble in hot HNOs; it is not soluble in excess of (NH4)2S. 
NH.tOH and NaOH ppt. cobaltous hydroxid, Co(OH)2, with 
properties similar to those of nickelous hydroxid ; but the corres- 
ponding cobaltic hydroxid, Co(OH)3, is not reduced by boiling 
with NH4OH. 
To the borax bead cobalt compounds give a deep blue color ; the 
test is very delicate. 
Iron; Fe;—To be met with as metal, ferrous and ferric 
oxids, insoluble, and as ferrous and ferric salts. 
Reactions :—Ferrous salts. HNOs oxidizes ferrous to ferric 
salts. 
(NH4)2S ppts. immediately from alkaline or neutral solutions 
ferrous sulfid, FeS, flocculent, black, turning grayish on expos- § 92-] 
THE IRON GROUP. 
85 
ure to the air, by oxidation and separation of sulfur, soluble in 
dilute mineral acids. This oxidation of the sulfid leads to the 
formation of FeS04, and finally a basic ferric salt, Fe20(S04)2. 
NF[4OH and NaOH ppt. ferrous hydroxid, Fe(OH)2, dirty 
green, changing to reddish-brown, Fe(OFf)3, on exposure to the 
air. BaC03 does not ppt, this hydroxid, except from solutions 
of the sulphate. 
KiFeCys and F3FeCy6 give blueppts. (see reactions of hydro- 
ferrocyanic and hydroferricyanic acids). 
KCySgives no reaction. 
Ferric salts.—H2S reduces ferric to ferrous salts, with sepa- 
ration of sulfur, but in alkaline solutions ppts. FeS. 
(NH4)2S ppts, from neutral or alkaline solutions ferrous sulfid, 
FeS (see ferrous reactions), with separation of sulfur. 
NH4OH or BaC03 ppts. ferric hydroxid, Fe(OFI)3, flocculent, 
reddish-brown, soluble in acids. 
K4FeCy6 ppts. from neutral or acid solutions Fe4(FeCy6)3 (see 
hydroferrocyanic acid reactions). K3FeCy6 gives no ppt. 
KCyS gives ferric sulfocyanate, Fe(CyS)s, soluble, deep red; 
this test is very delicate. 
Manganese ; Mn :—To be met with in alloys, as oxids and 
as salts of manganese. 
Reactions:—(NH4)2S ppts. from neutral or alkaline solutions 
manganous sulfid, MnS, flocculent, flesh colored, changing to 
brown on exposure to the air by oxidation, soluble in dilute 
acids, including FfC2H302. 
NH4OH ppts. a part of the manganese in a solution as 
manganous hydroxid, white, turning brown on exposure to the 
air by oxidation to MnOOH, The rest of the manganese, 
remaining at first in solution as an ammonium salt, is gradually 
pptd. on standing exposed to the air, as this second hydroxid. 
BaC03 does not ppt. this hydroxid in the cold except from 
solutions of MnS04. 
Fused with Na2 COs and KNO, compounds of manganese give 
a dark green color to the fused mass, by formation of sodium 
manganate, Na2Mn04. 
Zinc; Zn :—To be met with as metal, as oxid, and as zinc 
salts. 
Reactions : ppts. from neutral or alkaline solutions, 
zinc sulfid, ZnS, white, soluble in cold HCI, slightly soluble in 
hc2h3o2. 86 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 93- 
NH,OH ppts. zinc hydroxid, Zn(OH)2, flocculent, white, 
soluble in excess of precipitant, as (NH4)2ZnO2, repptd. on 
boiling as Zn(OH)2. 
BaC03 does not ppt. this hydroxid, except from solutions of 
the sulfate. 
93. Preparation and analysis of the group precipitate. 
This group precipitate contains also the members of the 
aluminum group that may be present, precipitated as hydroxids. 
a. Chemistry of the work on this group. 
The nickel and cobalt are separated from all the other mem- 
bers of both groups by the insolubility of their sulfids, in HCI 
of such dilution as will readily dissolve the other sulfids and the 
hydroxids. These two sulfids being then dissolved by stronger 
acid, the metals are separated, if separation is necessary, by the 
different behavior of their tri-hydroxids with ammonia, after 
they have been converted into nickelic and cobaltic salts by 
treatment with bromin. 
After the conversion of the iron into a sesquioxid salt by 
treatment of the group precipitate with HN03, it is then sepa- 
rated, together with the aluminum and chromium, from the 
manganese and zinc by precipitation of the three as hydroxids 
by barium carbonate. This precipitate is used later for the tests 
for aluminum and chromium. 
We bring to this course a rather strongly acid solution charged 
with H2S. It contains all the bases of the potassium, calcium, 
aluminum, and iron groups, and the acids that were combined 
with these bases originally, except such as would be expelled on 
the treatment with strong acids, or converted by the reducing 
H2S into other forms. 
The first operation of the group precipitation, in 47, in the 
course of analysis following, consists in adding in 
slight excess for the purpose of saving the (NH4)2S, to be 
added later, from decomposition by the acid present; but even 
if this were not done, and the (NH4)2S were added at once, 
the final condition of the solution would be the same, namely, 
decidedly alkaline. The oxalates, phosphates, borates, silicates, 
and fluorids of the calcium group metals are insoluble in an § 93-] 
THE IRON GROUP. 
87 
alkaline liquid. The possibility is therefore evident of entirely 
missing metals of that group in their proper place, in the filtrate 
from the group precipitation for this table, if the solution is made 
alkaline while these acids are present. 
Considering in this course only two of these acids, that are 
perhaps most likely to be in the way in an ordinary qualitative 
analysis, one of them is removed at once by gaseous products of 
its oxidation. The other, not being so easily removed, has to be 
provided for as in 53 a. For the course of operations to be 
followed in case H3B03, HF, or H2Si03 is also present, the 
student is referred to larger works, such as Fresenius, or Prescott 
and Johnson, 
Having evaporated the solution and ignited the residue, for 
the removal of the oxalic acid, ammonium salts are no longer 
present; but NH4CI is necessary to prevent the precipitation of 
magnesium as hydroxid, and the consequent danger of missing 
it in its proper place. 
The addition of ammonia here will precipitate a small portion 
of the members of this group as hydroxids; but a study of the 
work that follows, and comparison of the solubility of hydrox- 
ids and sulfids of the members of this group, will make it clear 
that these hydroxids cannot be left as such after the treatment 
with (NH4)2S without leaving the way open to serious errors; 
that, nevertheless, the precipitate formed by NH4OH can be left 
undissolved indicates another case of metathesis where only one 
of the reacting substances is in solution. 
All of the sulfids precipitated are quite insoluble in (NH4)2S 
except the NiS, which is slightly soluble; on this account any 
unnecessary excess of the reagent should be avoided. 
Two of the sulfids, FeS and CoS, are liable to be oxidized to 
sulfate on exposure to the air, or even perhaps by the oxygen 
dissolved in water (§ 66) : washing, as directed in 48 following, 
sefves to avoid the error that one might fall into, if such oxida- 
tion were permitted, these sulfates being soluble in water. 
In the solution of such portion of the precipitate as is dissolved 
by HCI, the iron, in whatever form it was originally, is present 
now as a ferrous salt: but both for its final test and its precipita- 
tion by BaC03 in 53 h, it must be in the ferric form : only those 
hydroxids corresponding to the so-called sesquioxids, having the 
general form M 203 in which M 2 represents two atoms of a triad 
metal, are precipitated by BaC03 under the conditions of the 88 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 93- 
treatment by that reagent: hence the treatment with HNOs in 
52, Table VI. 
The separation of the P205 from the metals of the calcium 
group is effected (53 Cl) on the following principle. In the 
presence of enough of the ferric salt to combine with all the 
P205 present, forming FeP04, on making the solution exactly 
neutral, all of this acid will be precipitated, while metals of the 
second group remain in solution. The exact neutrality is most 
easily secured by the presence of BaC03, a portion of which is 
decomposed by any free acid present, with the formation of a 
neutral barium salt. 
Provision of sufficient ferric salt is secured by its addition till 
the red precipitate is obtained by ammonia : ferric phosphate is 
white: as long as there is not enough iron present to satisfy all 
the P205, only white FeP04will be precipitated by the NH4OH ; 
as soon as there is more than enough, the excess not going down 
as white phosphate is precipitated as reddish-brown hydroxid. 
This condition of the solution having been secured, the 
neutralization is nearly effected with (NH4)2CO3, to save BaC03; 
but it must be left slightly acid, for any precipitate by excess of 
(NH4)2CO3 might contain metals to be tested for under 54 and 
following sections; then the BaC03 completes the neutralization 
for the precipitation of the phosphates, besides doing its other 
work of throwing down the aluminum, iron, and chromium as tri- 
hydroxids. 
Here again is an illustration of a metathesis in which one of 
the substances taking part in the reaction is a solid : and it is 
not, as in other cases previously noted, necessarily freshly pre- 
cipitated. 
When a liquid is added to a liquid, the two may be at once 
intimately mixed by agitation, and the conditions are right for 
the reaction to proceed without further external assistance, the 
two substances being in intimate contact throughout; but in this 
treatment with BaC03 the heavy solid soon settles to the bottom 
after agitation, and the desired reaction can go on directly only 
at the surface of contact between the particle's of the reagent and 
that part of the solution at the bottom of the flask, and indirectly 
in the rest of the liquid by the slow process of diffusion. Hence 
the importance of frequent agitation and considerable time for 
the full completion of the reaction. 
Since, if P205 is present, the metals of the calcium group are § 93-] 
THE IRON GROUP. 
89 
to be tested for in the filtrate from the precipitate by BaC03, 
and since for all the work of precipitation of iron, aluminum, and 
chromium actually done by this reagent a corresponding quantity 
of BaCl2 passes into solution, as will appear on writing out the 
equation for the reaction, barium cannot of course be tested for in 
this filtrate. Therefore a small portion of the solution is so pre- 
pared in 58 af by taking advantage of the solubility of Ba3(P04)2 
in acetic acid and the insolubility of the chromate, to get a 
solution in which barium can be tested for at once. Any part 
of the precipitate formed in the first part of this operation, and 
insoluble in acetic acid, would consist of phosphates of iron, 
aluminum, and chromium. 
J). Preparation of the iron (and aluminum) group precipitate. 
46. (a) Oxalic acid is absent: pass to 47. (6) Oxalic acid 
is present; add to the solution a little HN03 and evaporate to 
complete dryness, in the hood, moisten the residue with HN03, 
dry by gentle heat, and ignite gently; dissolve this residue with 
a little hot HCI, filter if not clear, and add 2 c.c. of NH4CI 
and 25 to 30 c.c. of water. 
47. Add NH4OH till slightly alkaline, then whether a ppt. is 
formed or not add (NH4)2S and heat the mixture nearly to boil- 
ing. If no ppt. appears pass on to the Ca group, § 97, b. If a 
ppt. does appear, filter and reserve the filtrate for the Ca group, 
§ 97> 
48. Precipitate. Wash immediately and very thoroughly 
with hot water to which a little (NH4)2S has been added. ELEMENTS OF CHEMICAL ANALYSIS. 
C. The Analysis of the Iron Group Precipitate. 
TABLE VI a. 
Treat the ppt. either on the filter 
or after removal from 
it (see § 58) with 5 to 15 c.c (according to quantity of ppt.) 
of dilute HC1 (1 cone, acid to 10 of water), with special care 
to bring all parts of the ppt. in contact with the acid, by 
stirring. Filter if necessary, and reserve filtrate for Table 
VI b. 
49. Residue. 
Any residue remaining here should be black; if it is not, 
it must be treated with more HC1 as directed in 48. If black 
it may consist of NiS and CoS. If the filtrate 47 has a deep 
brown color Ni may safely be put down as present in the sub- 
stance analyzed. 
If the borax bead is colored blue by fusion with a portion 
of this residue Co is also present; if only a light brown or a 
nearly colorless bead is obtained Co is absent. If Ni and Co 
are found by these tests, pass on to Table VI b. 
If the filtrate 47 is not brown, or 
if in testing for cobalt 
with the borax bead the color was so 
dark a brown owing to 
the presence of much nickel that the cobalt color might have 
been masked, proceed as follows. 
To the residue 49 in an evaporator, add HC1 and a few 
drops of HN03, boil, in the hood, till the liquid is nearly 
evaporated, add NaOH till strongly alkaline and then a quan- 
tity of bromin solution equal to the volume of the liquid in 
the dish, boil for a few minutes and filter, rejecting the 
filtrate; wash the ppt,, return it to the evaporator, add 
NH4OH, boil again, and filter if a residue remains. 
50. Filtrate. 
61. Residue. 
Add H,S. A black ppt. indicates 
Test for Co with borax 
Ni. 
bead. 
A mere slight brown coloration may 
Pass on to Table VI b. 
be due to Co, if its presence in con- 
siderable quantity is indicated by the 
bead test. THE IRON GROUP. 
C. Analysis of the Iron Group Precipitate, concluded. 
TABLE VI b. 
52. 
Filtrate from Residue 49. 
Boil to expel H2S, add a few drops of HNO:) and boil again. 
To a small portion of this solution add NH4CNS. A red color 
shows Fe. A slight tinge of red is given by very small traces of 
iron, the test being very delicate. 
53 a. Phosphate is present. 
58 b. Phosphate is not present. 
To a small portion of the 
solution add NH4OH till 
alkaline, then acetic acid 
till acid, filter if a ppt. ap- 
pears, and test the filtrate 
for Ba with K2Cr207 and 
H2S04, as in Table VIII. 
To the remainder of the solu- 
tion (52) add FeClg till a 
drop gives a brownish red 
ppt. with NH40H and pro- 
ceed as in 58 b, the P205 
being now removed. 
Concentrate the solution to a small bulk, nearly 
neutralize it with (NH4)2C03, (if a permanent 
ppt. forms on addition of (NH4)2COs, it must be 
redissolved with a drop of FIC1), transfer to a 
small flask, add about to c.c. of BaCG3, shake the 
mixture occasionally, after several hours filter, 
and reserve the contents of the filter for the Al 
group, Table VIII, after washing two or three 
times with hot water. 
54. Filtrate. To a portion add acetic acid 
and then H2S. A white ppt., soluble in HC1 
shows Zn. 
55. Evaporate another small portion carefully 
to dryness in the platinum cup, and fuse the 
residue with a mixture of equal parts of Na2C03 
and KN03. A bluish-green color in the fused 
mass shows Mn. • 
Phosphate was present, 
I 
• 
56 (lf and Mn and Zn 
also present. 
56 b, and Mn and 
Zn not present. 
To the remainder of the 
filtrate from the ppt. by 
BaCOs in 53 b add NH4- 
OH and (NH4)2S, warm 
and filter; with filtrate 
pass to 56 c. 
There being no Mn 
or Zn to remove, by 
(NH4)2Sas in 56 a, 
take remainder of fil- 
trate from ppt. by 
BaCO, in 63 b to 
56 c. 
66 c. Filtrates 66 a (or 63 b). 
Add to the filtrate from the ppt. by (NH4)2S 
in 47, and reserve for \ 96 b, remembering in the 
analysis of the Ca group ppt. that Ba has already 
been tested for. 92 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 94-95- 
THE ALUMINUM GROUP. 
94. Forms of occurrence and reactions. 
Aluminum ; A 1:—To be met with as metal and in salts. 
Reactions :—NH±OH, (NllfS or Fa CO3 ppts. aluminum 
hydroxid, A!( flocculeni or gelatinous, white, slightly soluble 
in soluble in NaOH as Al{ONa)3, solution not repre- 
cipitated on boiling, soluble in dilute acids. 
Chromium ; Cr:—To be met with as oxid and as salts of 
chromic oxid, or of chromic acid. The acid is always reduced 
to the oxid by H2S. 
Reactions ; (NH4)2S or BaC03 in solutions of salts of 
the oxid ppts. chromic hydroxid, Cr(OH)3 flocculent, green : 
the ppt. is slightly soluble in excess of NH4OH, and is soluble 
in NaOH as NaOOCr: Cr(OH)3 is reprecipitated from this 
solution on long boiling, more easily in the presence of ammon- 
ium salts. 
95. The analysis of the aluminum group precipitate. 
a. The chemistry of the work on this group. 
For the separation of the two metals of this group, advantage 
is taken of the easy oxidation of chromic oxid compounds to 
chromic acid compounds, and also of the precipitation of chro- 
mic hydroxid on boiling its solution in sodium hydroxid, 
while aluminum hydroxid is not precipitated under similar con- 
ditions. The reactions of chromic acid are very delicate, so 
that the above oxidation makes it easier to detect the chromium. 
The Al(OH)3 in the precipitate by BaC03 is dissolved out by 
NaOH, made as it is wanted and in the tube in which it is to do 
its work, by the action of Ba(OH)2 on Na2C03. This solution 
takes place in accordance with the reactions of aluminum; the 
succeeding treatment with HCI breaks up the compound, 
Al(ONa)3, that is in solution, and in this solution now contain- 
ing no free NaOH the precipitation of Al(OH)3 takes place by 
NH4OH in the usual manner. 
Sodium hydroxid, so entirely free from impurities that it will 
not of itself give a reaction similar to this for aluminum on treat- 
ment with HCI and NH4OH, is difficult to make and to keep in 
good condition; hence its preparation for this test as wanted, §95-] 
THE ALUMINUM GROUP. 
from materials that are much more easily obtained free from 
those impurities, such as aluminum compounds or silicate, which 
would impair the reliability of the test. 
93 
C, The Analysis of the Aluminum Group Precipitate. 
TABLE VII. 
57 a. Iron was not found 
in Table VI in more than 
traces, and phosphate is not 
present. 
Make a preliminary test for 
A1 and Cr as follows ; Dissolve 
a small portion of the precipi- 
tate obtained with BaC03 in 
53, in a little HC1, add H2S04 
as long as a ppt. is formed, heat 
just to boiling, and filter; a 
slight turbidity in the filtrate 
will do no harm. To about 
3 c.c. of this filtrate, in a io 
cm. test tube, add NH4OH 
very slowly from a dropping 
tube, holding the point of the 
tube close to the surface of the 
liquid, so that the specifically 
lighter reagent will fall gently, 
and float on the solution tested. 
At the zone of contact between 
the two liquids there appears :— 
58. Iron was found in Table VI in 
more than traces, or phosphate is present. 
59 a. Fuse a 59 b. To another 
portion of the ppt. portion of the ppt. 
by BaCOg in 53 in. an evaporator, 
with about three add about half a 
times its bulk of a gram of Na2C03, a 
mixture of equal quarter of a gram 
parts of Na2C03 of Ba(OH)2, and 
and NaNOg,in the 10c.c. of water, boil 
platinum cup. The and filter, rejecting 
fused mass will the ppt.; acidify the 
usually be yellow filtrate with HC1. 
if much Cr is pre- To about 2 or 3 c.c. 
sent. Extract it of this solution, in 
with hot water, fil- a 10 cm. test tube, 
ter, acidify the fil- add NH4OH slowly 
trate with HC2H3- from the dropping 
02, and test for tube, holding the 
chromic acid with point of the tube 
the lead and am- close to the surface 
monium acetate of the liquid, so that 
mixture, 7, | 85, b. the specifically 
A yellow ppt. indi- lighter reagent will 
cates, as present in fall gently, and float 
the original sub- on the solution to 
stance, either in the be tested. A floc- 
form of a chromate culent, white ppt. at 
or of a salt of the zone where the 
chromic oxide, Cr. two solutions meet 
shows Al. 
57 b. No pre- 
cipitate. 
57 c. A pre- 
cipitate. 
Even after a few 
minutes. 
A1 and Cr are 
absent. Pass to 
the Ca group. 
Treat the 
rest of the 
group precipi- 
tate as direct- 
ed under 58. 94 
ELEMENTS OF CHEMICAL ANALYSIS 
[§ 96* 
96. Forms of occurrence and reactions. 
THE CALCIUM GROUP. 
Barium ; Ba ;—To be met with as barium salts 
Reactions :—(NH4)2C03 ppts. from neutral or alkaline solu- 
tions barium carbonate, BaC03, flocculent, afterward pulveru- 
lent, or crystalline, white, easily soluble in acids. 
K2Cr04 ppts. from acetic acid solutions, if not too dilute and 
only weakly acidified, barium chromate, BaCr04 yellow, soluble 
in HCI. In order that this precipitation shall be certain, if but 
little barium is present, it is important that the quantity of free 
acetic acid be small in comparison with that of the potassium 
chromate. 
Jd.,S O, ppts. from all solutions, except possibly such as contain 
but little of the element, and are strongly acid (see reactions of 
sulphuric acid, § 80), barium sulfate, BaSOy, pulverulent, white, 
very insoluble. 
Soluble phosphates or oxalates ppt. from alkaline solutions 
the corresponding barium salts. 
Strontium ; Sr :—To be met with only as strontium salts. 
Reactions :—(NH4)2C03 ppts. from neutral or alkaline solu- 
tions strontium carbonate, SrCOs, resembling BaC03. 
CaSOy ppts. slowly from neutral solutions strontium sulfate, 
SrSOy, pulverulent, white. 
K2Cr207 gives no ppt. in acetic acid solutions. 
Soluble phosphates or oxalates ppt. from alkaline solutions 
the corresponding strontium salts. 
Calcium ; Ca :—To be met with as oxid or in salts. 
Reactions:—(NH4)2C03 ppts. in neutral or alkaline solutions 
calcium carbonate, CaC03, flocculent first, afterward crystal- 
line, white, readily soluble in acids. 
(NHP)t C 2 0A ppts. from neutral or alkaline solutions calcium 
oxalate, Ca C 2 Oy, pulverulent, white, soluble in dilute mineral 
acids, insoluble in acetic acid. 
K2Cr207 gives no ppt. in acetic acid solutions. Soluble phos- 
phates ppt. from alkaline solutions calcium phosphate Ca3(P04)2, 
white. 
Magnesium; Mg:—May be met with as metal, as oxid, or 
as salts of magnesium. 
Reactions:—(NH4)2C03 and (NH4)2C2Q4 do not ppt, magne- 
sium from solutions containing enough NH4CI. 
Na2HFOi ppts., often slowly, from solutions made alkaline by § 97-] 
NH± OH, ammonio-mag7iesium phosphate, crystal- 
line, white, soluble in acids; it often adheres to the walls of the 
tube, especially along the lines where the end of a glass rod has 
been drawn with some pressure ; this may 7iot beco77ie visible, if the 
ppt. is abundant, till the co7itents of the tube are poured out. 
THE CALCIUM GROUP. 
95 
97. The preparatio7i and analysis of the calciu77i group precipitate. 
a. The che77iist7y of the work. 
The barium is separated from the calcium and the strontium 
by the greater insolubility of its chromate in acetic acid, the 
strontium from the calcium by the much greater insolubility of 
its sulfate in water, and the magnesium from all the others by the 
formation of a double carbonate of magnesium and ammonium, 
soluble in solution of ammonium chlorid. 
The solution brought to this point, 60 below, contains in addi- 
tion to the members of the calcium and potassium groups that 
may have been present in the original substance, a considerable 
quantity of NH4CI, and perhaps other ammonium salts. The 
presence of this salt is useful, since it lessens the danger of pre- 
cipitation of MgCOs by the grouping reagent. On the other 
hand, all the carbonates which it is desired to precipitate here 
are slightly soluble in solutions containing NH4CI, so that the 
action of the grouping reagent is thereby rendered more or less 
imperfect; and it is well in the work of preceding groups to 
avoid the use of any unnecessary quantity of HCI, which must 
afterward be neutralized with NH4OH in 47, thus charging the 
solution excessively with this salt. 
The precipitate by (NH4)2CO3 being dissolved by acetic acid in 
6i, Table VIII, it is at once ready for the next step in the 
separation. The BaCr04 being slightly soluble in the acid, the 
separation from strontium and calcium is not perfect if an 
unnecessary excess of the acid is used in making the solution. 
In the separation of strontium from calcium in 63 to 65, Table 
VIII, we have to deal again with an imperfect action of the 
reagents used : the SrS04 is slightly soluble in water and in 
HCI: this is implied by the statement, under the reactions for 
this element, that it is precipitated slowly by CaSO,t. If much 
water is present, or, in other words, the solution is very dilute, 
and much more if it is more than weakly acid, and at the same 
time the conditions are such that only a little SrS04 can be 
formed, the salt may remain entirely in solution : the condition 96 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 97- 
last mentioned would be fulfilled, if but little of either strontium 
or of H2S04 were present: CaS04 is but sparingly soluble in 
water, and we can have at the most but a very dilute solution of 
the reagent: therefore the second of these last two conditions is 
fulfilled. Hence the double reason is plain for the evaporation 
of the solution as prescribed in 68, and also for the addition of 
but little water to the residue. The reason is also plain, from 
the foregoing, for the direction that the test in 64 be allowed to 
stand several minutes. 
As 1,000 parts of water are required to dissolve one ,part of 
SrS04, and only 400 parts of water for one of CaS04, while the 
oxalates are about equally insoluble, and are undistinguishable 
from each other in appearance, the reason for the treatment with 
K,S04, much more soluble than CaS04 and therefore yielding a 
stronger solution of the reagent, is apparent: even if, owing to 
the concentration of the solution, some CaS04 should also be 
precipitated, enough would always remain in solution for the 
final test. 
For reasons explained in the foregoing paragraphs, traces of 
any one of these three metals might be missed in following this 
scheme of separation : for a method of treatment in such a case 
the student is referred to Fresenius or Prescott and Johnson. 
Either the trace of barium, strontium, or calcium that may re- 
main unprecipitated by the group reagent, as explained above, 
yielding a flocculent precipitate with Na2HP04, in 66, or the 
formation of Mg(OH)2 by the NH4OH, owing to an insufficient 
quantity of NH4CI in the solution, may, in case the precipitate 
for magnesium is slight, make it flocculent instead of crystalline 
as it should be. By taking advantage of the fact that BaS04 and 
CaC204 are much more insoluble than the carbonates, a solution 
can be prepared, if the above-mentioned difficulty is encountered, 
that is practically free from those metals, although it may still 
contain traces of strontium. (Fresenius 1880, p. 296.) 
I). The preparation of the calcium group precipitate. 
60. If the filtrate brought from the Fe group (47) is brown 
with Ni in solution, boil and filter again ; to this filtrate add 
(NH4)2CO3 as long as a ppt. is formed, and then somewhat more 
to be sure of an excess of the reagent, and warm. If no ppt. 
appears, pass to 66. If a ppt. is formed, filter, and reserve both 
precipitate and filtrate for Table VIII. § 97-] 
THE CALCIUM GROUP. 
97 
C. The Analysis of the Calcium Group Precipitate and Filtrate. 
TABLE VIII. 
61. Precipitate. 
66. Filtrate. 
1 
Dissolve the precipitate, on the filter, by pouring a 
small quantity of acetic acid over it, two or three times, 
using the same portion of acid; all of it should be 
dissolved. To a small portion of the solution add 
K2Cr04; if no precipitate is formed Bais absent,and 
the remainder of the solution is used for the Sr and Ca 
j tests. 
A precipitate is formed : add the reagent to the 
| remainder of the solution, and filter. 
Divide in two 
portions, and re- 
serve the larger one 
for Table IX. To 
the other portion 
add Na2HP04 and 
NH4OH, draw the 
end of a glass rod 
with some pressure 
over the inner walls 
of the tube along 
three or four lines, 
and set aside for 
several hours. A | 
white ppt., crystal- 
line if only small in 
quantity, and in any 
case adhering along 
the lines traced by 
the rod, after the 
contents of the tube 
are poured out, in- 
dicates Mg. 
, 62. Precipitate. 
63. Filtrate. 
Dissolve this 
yellow precipi- 
tate in HC1, and 
add to the solu- 
tion a few drops 
of H2S04. A 
white ppt. shows 
Ba. The white 
color may not 
come out plainly 
till, after allow- 
ing the ppt. to 
settle, the liquid 
is decanted off, 
and the ppt. 
I washed with a 
little water. 
Make alkaline with NH4OH and 
add (NH4)2COs. If no ppt. ap- 
pears Sr and Ca are absent, and this 
solution need be tested no further. 
If a ppt. is formed add more 
(NH4)2C03 till the precipitation is 
complete, filter, rejecting the filtrate, 
wash the ppt. with water, dissolve 
it on the filter with HC1, evaporate 
the solution almost or quite to dry- 
ness, and dissolve the residue in a 
little water. Divide this solution 
into two portions. 
64. Portion I. 
65. Portion 2. 
Add CaS04, 
heat to boiling, 
and let stand ten 
minutes. A fine 
white ppt. shows 
Sr, 
If Sr was found 
in portion I add 
K2S04, warm and 
filter,rejecting the 
ppt.; to the fil- 
trate, or directly 
to this portion if 
Sr is absent, add 
NH4OH till al- 
kaline and then 
(NH4)2C204. A 
white ppt. shows 
Ca. 
7 98 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§§ 98-99- 
THE POTASSIUM GROUP. 
98. Forms of occurrence and reactions. 
Potassium ; K :—To be met with commonly only as hydroxid, 
or as potassium salts. 
Reactions :—Sodio-cobaltic nitrite, (NaNO2)3 • C0(N02)3, ppts. 
from neutral solutions containing potassium, potassio-cobaltic 
nitrite, (KN02)3.C0(N02)3, pulverulent, yellow. 
Sodium; Na :—To be met with commonly only as hydroxid 
and as sodium salts. 
Reactions:—Compounds of sodium give no ppt. containing 
that element, which furnishes a satisfactory test for the metal, 
and is practicable for use by the student. 
Held in the platinum wire loop, in the flame of a Bunsen burner, 
sodium compounds color the flame yellow. 
This test is so delicate, and sodium is so widely diffused, and 
common in occurrence, at least in traces, as an impurity in the 
reagents and other materials of the laboratory, that there is 
little difficulty in getting this reaction in nearly every substance 
analyzed. Just before using the wire for the test it should be 
dipped in HCI and heated in the flame till it gives no color 
thereto. 
Ammonium ; NH4;— To be met with only as ammonium 
hydroxid or salts, or as ammonia gas, NH3. 
Reactions :—NaOH decomposes ammonium salts, setting free 
ammonia gas, NHA which colors red litmus paper blue, or yellow 
turmeric paper brown. 
99. Chemistry of the analysis of this group. 
a. No separation is made of the members of this group from 
each other, sodium and potassium being tested for in portions 
of the same residue, and ammonium in a portion of the original 
substance. 
Bringing from the analysis for the calcium group a solution 
containing much ammonium salts, the first operation performed, 
preparatory to the analysis for this group, gives us a residue not 
encumbered with the considerable quantity of ammonium salts 
in the filtrate from 60, and we can thus get a surer test for 
sodium. Furthermore, as might be inferred from the great 
similarity between potassium and ammonium, in all the reactions 
with which the easy volatility of the salts of the latter does not § 99-] 
THE POTASSIUM GROUP. 
99 
interfere, it is necessary to have ammonium salts entirely re- 
moved before a reaction with (NaNO2)3 • C0(N02)3 can be safely 
taken to indicate potassium. 
b. Preparation of the substance for the analysis. 
67. Evaporate the solution brought from 66 Table VIII -to 
dryness, in the hood, and ignite the residue gently as long as 
white fumes are given off, to remove ammonium salts. 
C. The Analysis for the Potassium Groicp. 
TABLE IX. 
68 a. Portion I. 
68 b. Portion 2. 
69. Original Sub- 
stance. 
Introduce on a platinum 
wire a small portion of the 
residue into the flame of a 
Bunsen burner. If the 
flame is colored a bright 
yellow, Na is present. 
In order to gain any approxi- 
mate idea of the proportion of 
j Na present, account should be 
taken of what has already been 
found in the substance, the 
quantity of the residue left after 
the ignition just made, and of 
! the probable proportions of K 
and Mg in this residue, and 
I finally of the intensity and per- 
! sistence of the Na flame reaction. 
Dissolve the larger 
portion of the resi- 
due in a little water, 
add to this solution 
three or four drops 
of sodio-cobaltic ni- 
trite, and let stand 
for a few minutes. 
A yellow ppt. shows 
K. 
To a small por- 
tion of this add 
NaOH and warm 
gently. 
If the vapors 
evolved change 
moistened turmeric 
paper from yellow 
to brown, NH4 is 
shown. 
If it was necessary to fuse the original substance 
with Na2C03 in Table E, in order to get it into solu- 
tion, prepare a solution for the above tests for Na and 
K as follows : mix I part of the finely pulverized sub- 
stance with 6 parts of precipitated CaCOs arid yf part 
of NH4C1, and heat to bright redness in a small 
platinum crucible for 30 minutes. Cover the crucible 
with water in a beaker and heat to near boiling for 
30 minutes, filter, add a little NH4OH to the filtrate, 
and proceed further as in 60, 67 and 68. PART 111. 
THE OPERATIONS OF QUANTITATIVE 
ANALYSIS. 
CHAPTER XL 
THE BALANCE AND ITS USE. 
ioo. Introduction. Quantitative chemical analysis has for its 
object the determination of one or more of the constituents of 
a substance whose qualitative composition is wholly or partially 
known. It is ultimate analysis when the elementary constituents 
of the substance are determined, as the carbon and hydrogen of 
sugar: it is proximate analysis when some or all of the com- 
pounds supposed or known to exist in the substance are deter- 
mined, as the sulfur trioxid of a sulfate, or the calcium oxid in 
marble, or the sugar and fat in milk. 
Its results are obtained by careful measurements, as is the case 
with all accurate determinations of quantity. From a measured 
portion of the substance the constituent to be determined is 
converted into some new form, in which it is capable of measure- 
ment, and into which it can be completely transposed, or at least 
very nearly so. In the quantitative analysis of a solid, or the 
determination of the substances in a solution, there are two 
general modes of procedure, called gravimetric and volumetric 
analysis. 
Gravimetric analysis. The substance to be determined is 
usually converted into some compound that is (i) insoluble in 
the liquid medium in which it is made, (2) has a perfectly defi- 
nite and well known composition, and (3) is of such a character 
that it can be finally obtained in a form in which it can be 
weighed without difficulty. The quantity of the substance 
sought is then calculated by simple stochiometric methods. 
Volumetric analysis. To a solution containing the substance 
to be determined, a solution is added containing another sub- 
100 THE BALANCE AND ITS USE. 
stance, that gives with the first a definite reaction; and this 
addition is made under such conditions that it can be sharply- 
decided when all of the first substance has been acted upon, and 
just what volume of the solution of the second substance was 
required to complete the reaction. The strength of this reacting 
solution being known, and also the exact nature of the chemical 
change that it produces, so that the same can be expressed by a 
chemical equation, the quantity of the first substance can be 
calculated from the quantity of the second substance required. 
In setting out with the quantitative analysis of a substance, it 
must first of all be accurately known how much of it is taken for 
the analysis. In some laboratories for instruction, it is the 
practice to give to the beginner carefully measured quantities 
of a solution of a substance to be determined; in others an in- 
definite quantity of a solid is given to him, from which he weighs 
out his own portions for analysis. But even in the first case he 
very soon has to use the balance to weigh the products of his 
operations; therefore, weighing on the chemical balance natur- 
ally comes up first for explanation. 
ioi. The balance. When the beam of the balance is swing- 
ing, its knife-edges rest on polished agate surfaces; the sharp- 
ness of the knife-edges and the polish of the agate must not be 
impaired, if the balance is to maintain its sensitiveness and ac- 
curacy. To be more sure of this preservation of the good con- 
dition of the instrument, the knife-edges are always lifted off the 
agate plates, and kept so all the time when the weighing is not 
actually going on. The arrangement by which the beam is raised 
or lowered is controlled by a small, milled-edge wheel on the 
outside of the balance, in front. The working parts of the bal- 
ance are inclosed in a glass case not only to protect them from 
injurious fumes, but also to exclude currents of air that might 
affect the swinging of the beam, and the indications of the needle 
as its point moves to and fro over the scale in front of the post. 
In order to make this exclusion more complete just when it is 
most essential, namely, when one is making the last adjustment 
of the weights so as to exactly counterpoise the object weighed, 
this final adjustment is effected by means of the rider, that can 
be placed at any desired position on the right hand arm of the 
beam, by means of a hook on a rod sliding through a socket, 
near the top of the end of the balance case ; the balance can 
therefore be entirely closed while this rider is used. 
The weights. When the equilibrium is established between 102 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 102. 
substance and weights, this rider gives by its position on the 
beam, the milligrams and fractions thereof, of the total weight, 
or what appears in the written expression of the weight as the 
third and fourth decimals. The number on the beam nearest to 
the left of the rider gives milligrams (third decimal) and the rel- 
ative distance between the rider and this number and the next 
following one indicates tenths of a milligram. The beams of 
some balances are graduated for milligrams and tenths, of others 
only to milligrams and halves ; in this latter case the tenths must 
be estimated by the eye. 
The brass weights in the weight box give the grams, the 
number of grams indicated by each weight being stamped on it. 
The larger weights of foil, of which there are always four, 
stamped 0.5, 0.2, 0.2, 0.1, or 0.5, 0.2, 0.1, o.x, give decigrams, 
expressed by the first decimal, and by the same number and 
relative denominations of smaller foil weights the centigrams are 
given, occupying the place of the second decimal in the total 
weight. In some cases the number of milligrams is stamped on 
these foil weights, as 500, 200; or 50, 20, and so on. 
102. The proper care and use of the balance. The strict 
observance of the following rules and precautions is important. 
a. All movements of the beam should be slow, and so moder- 
ate in extent that the needle does not swing much beyond the 
fifth d ivision on either side of the zero mark. No sharp impulse 
should be given to this movement, either by quick raising of the 
beam rests, or by making any changes in the weights or on the 
other pan, while the beam is off its supports, or by touching the 
beam, while swinging, with the rider hook, or by attempting to 
move the rider over more than a small portion of one of the 
divisions. At the moment when the beam is to be actually lifted 
off the agate plates, the needle should be close to the zero point; 
this is easily brought about by causing the supports of the beam 
to follow its movement as it swings towards this position, without 
allowing them to touch it; then, just as the needle points to zero 
the beam is lifted easily without any jar. 
b. The greatest care should be taken that nothing comes in 
contact with the substance-pan but clean and dry pieces of 
apparatus. Of course the weighing may be worthless if any- 
thing weighable is detached from the object weighed and left on 
the pan, if another weighing of the same object is to be made 
that bears any relation to this first weighing. If the substance 
so left behind is acid, the pan is liable to be corroded and seriously damaged. Such a plain precaution as this would seem 
to be superfluous; but every teacher who has had experience 
with beginners in quantitative work, has now and then met with 
an exhibition of such a degree of thoughtlessness, it might 
almost be called stupidity, in the handling of delicate instruments, 
as would hardly be supposed possible. 
THE BALANCE AND ITS USE. 
c. Paper should never be used to weigh a substance in. It is 
more or less hygroscopic, and may therefore itself change in 
weight during the weighing. For a similar reason, substances 
that are themselves hygroscopic, or liquids that may lose weight 
by evaporation, must always be weighed in well closed vessels. 
d. Never weigh a piece of apparatus while warm, nor directly 
after wiping it off; if necessary to wipe it with chamois skin, as 
may be with a piece of glass apparatus, let it stand in the balance 
for a few minutes before weighing. 
e. Never touch the weights with the fingers, but only with the 
forceps provided for the purpose. Always use the greatest care 
to return each weight to its proper place in the box. 
f. If the balance is properly adjusted, and the weights on its 
pans are equal, the needle will stand at zero when the supports 
are slowly lowered till the beam is free. Also, if the beam is 
made to vibrate, so that the needle will move, to five divisions 
to the left for instance, on swinging over to the right side, it 
will fall a little short of five divisions; on moving back again to 
the left it will not go quite so far as it did on the right side, and 
so on till it finally settles at zero when the vibration ceases. In 
actual weighing, this vibration method is always followed, 
because much quicker than to wait till the beam comes to rest. 
103. It is usually desirable to take approximately a certain 
quantity of a substance that is to be analyzed ; this quantity is 
sometimes specified in the directions for the determination to be 
made; when not mentioned, from 300 to 500 mgms. may be 
considered as a suitable quantity, if the constituent to be 
determined forms a fairly large proportion of the substance; if, 
on the other hand, it forms but a very small part, as only a few 
hundredths of a per cent, for example, a larger quantity of sub- 
stance must be taken, perhaps as much as four or five grams; in 
such a case, if a small quantity is taken the error resulting from 
unavoidable imperfections in the method of analysis, or from 
want of experience, or both, may be so large in proportion to 
the amount of the constituent weighed or otherwise measured, at 
the end of the analysis, as to render the determination of little 104 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 104. 
value; if the quantity of this constituent carried through all the 
operations of the analysis is much larger, errors of equal mag- 
nitude will count for much less in relation to the quantity of 
substance determined, and will vitiate the result in a much 
smaller degree. 
On the other hand, unnecessarily large quantities of substance 
are undesirable, for errors of other kinds may be introduced, 
and the manipulations may require a longer time. Therefore 
the quantity of substance to be taken should always be carefully 
considered on beginning an analysis. 
104. When the substance to be weighed is not at all hygro- 
scopic, the following method of weighing out accurately an 
approximate quantity is convenient. Get the weight of a watch 
glass; make the sum of the weights on the weight-pan that of 
the quantity of substance to be taken plus that of the watch 
glass; turn down the beam-supports till the needle takes a posi- 
tion one or two divisions to the left of zero ; then, while holding 
the beam there, slowly pour the substance from the tube into the 
watch glass, till the needle swings over to the other side; the 
glass contains a little more than the quantity desired; proceed 
now to get the exact weight of the substance in the usual manner. 
A hygroscopic substance must be weighed in a weighing tube; 
the quantity to be taken for the analysis is then to be poured 
into the vessel in which the first treatment is to be made, and 
the tube is weighed again. If the hygroscopicity is only moder- 
ate, first weigh out the quantity desired, on ordinary scales 
capable of weighing down to decigrams, pour this quantity into 
the weighing tube, and mark the space it occupies; then fill the 
tube to the same mark with a fresh portion of the substance, 
weigh, empty the entire contents of the tube into the vessel in 
which the first treatment is to be made, and weigh again. 
A convenient pair of weighing tubes is made from two test 
tubes, one of which will just fit into the other; cut the rim off 
the smaller tube and draw out the larger one about midway of 
its length, and seal up and round out the bottom so as to make 
a tube of about half the length of the other; this serves as a cap 
that will sufficiently exclude the moisture of the air from the 
substance within. 
Never, unless specially directed to do so, weigh out any par- 
ticular quantity of a substance, such as exactly one gram or two 
grams; the last part of such a weighing, consisting, as it must, 
of abstracting minute quantities of the substance from the con- THE BALANCE AND ITS USE, 
tents of the glass on the substance-pan, or adding some of the 
substance thereto, till the desired weight is obtained, consumes 
much more time than the usual method, and no important 
advantage is gained. 
For assistance in measuring by the eye approximately the 
quantity of the substance to be taken, it may be observed that 
so much of a dry powder of average specific gravity as can be 
piled on a five-cent piece will weigh from 0.8 to 1.2 grams. 
In pouring a substance from the weighing tube into a beaker, 
hold the latter in an inclined position and pour the substance 
down the side, so that if the substance is specifically light, and 
in a fine powder, none of it will be lost; and, finally, tap the 
tube gently on the rim of the beaker, to dislodge into the 
beaker any particles adhering loosely to the lip. 
105. The operation of weighing. On seating himself at the 
balance, the student first ascertains whether its arms are in 
equilibrium, by setting the beam in oscillation, and observing 
the swing of the needle; this movement of the beam need not 
be made to extend beyond five divisions from zero, and can be 
started easily by dropping the rider on the beam for an instant 
near the fulcrum; if it does not swing as it should with the arms 
in equilibrium, that is at a uniformly decreasing rate on each 
side, raise the beam-supports, and brush off the pans with the 
camel’s hair brush in the balance case; if the equilibrium is not 
then restored, the attention of the instructor in charge of the 
balances should be called to the matter; the beginning student 
must not attempt to correct the fault himself. 
When the balance is in order put the object to be weighed, on 
the left-hand pan. If the weight is quite unknown, it is to be 
settled, first of all, what the largest collection of gram weights is, 
that is too small. For example, suppose the whole weight is 
20.56 grams, and that, being quite sure that it is less than 20 
grams, one begins with a 10-gram weight; he will then go on, 
adding one weight after another, till 19.99 grams is put on the 
pan before the error in judgment is suspected ; ten weights have 
been taken from the box, only to have to put them back and 
begin over again. But if one had begun with a 20-gram weight, 
and then added in succession the 10, 5, 2, and 1 gram weights, 
finding each one too heavy, it is thus settled that the highest 
number of whole grams that is too small is 20; having started 
right with the brass weights, one proceeds in the same way with 
the decigram foil weights, and then with the centigram weights; ELEMENTS OF CHEMICAL ANALYSIS. 
the same number of weights will be handled as in the first case 
supposed, but this time one has proceeded steadily towards the 
desired end. 
The beam supports must be raised between each change of 
weights on the pan, but they need be lowered, each time, only 
far enough to allow the needle to swing out one or two divisions, 
showing plainly whether the last weight added was too small or 
too large. 
Too great care cannot be exercised in recording the weights. 
In the first place, this record should always be made in the lab- 
oratory record book, and never on loose slips of paper. Sec- 
ondly, the reading should be made twice; to this end the 
student should learn the arrangement of the weights in the box, 
so that one reading can be made by the vacant places there ; the 
second reading is made on the weights as they are returned from 
the balance to the box. These two readings, by such different 
methods effectually check one another. In order that the first 
method shall be reliable, it is evident that each student using 
the balance should carefully return every weight to its proper 
place in the box ; there is little danger of any mistake in this 
respect, except as to the foil weights. Where many are using 
the same balance, the only safe reading is the second one, that 
of the figures stamped on each weight. 
106. When a substance is to be weighed after ignition, which 
in this case is usually the product of an analysis, this weight is 
nearly always taken in a crucible or dish of porcelain or plati- 
num. This crucible or dish must always be weighed before it 
receives the substance ; and before being weighed it must be 
ignited, so that it shall be subjected to the same treatment that 
is given to it while the substance is ignited in it. 
After every such ignition, the vessel, while still warm, is trans- 
ferred from the platinum-wrapped triangle, which is always used 
for supporting it on the ring of the lamp-stand, to the desicca- 
tor, This transfer, as well as that from the desiccator to the 
balance-pan, is always to be made with the crucible tongs, never 
with the fingers. 
The desiccator, a shallow, glass jar, with a ground glass cover, 
contains some powerful absorbent of moisture, as calcium chlo- 
rid, or sulfuric acid soaked up by pumice stone; in the dry air 
of this closed jar, the substance can absorb no moisture while 
cooling. If sulfuric acid is used as the absorbent, there should 
be no more of it than can be taken up by the pumice stone; if § 107-] 
MEASUREMENT IN VOLUMETRIC ANALYSIS. 
107 
otherwise, and it stands as a liquid in the bottom of the vessel, 
a sudden jar, as when the desiccator is set down heavily on the 
table, or is quickly moved in any way, may cause some of the 
liquid to spatter up on to the bottom of the crucible; this may 
then come in contact with the balance-pan, and cause serious 
damage. 
The desiccator should be uncovered only while putting some- 
thing into it or taking something out. 
CHAPTER XII. 
MEASUREMENT IN VOLUMETRIC ANALYSIS. 
107. The standard of measurement. In this mode of analysis 
(§ 100) the quantitative measurements are made partly by 
weight, and partly by liquid volume. The weighing is confined 
mostly to the substance taken for the analysis. 
In gravimetric analysis, the unit of measurement is the gram; 
in volumetric work it is partly the gram and partly the cubic 
centimeter; in the gravimetric method we take such and such a 
weight of substance, and get such and such a weight of precipi- 
tate, the product of the analysis. In the volumetric method we 
also take a certain weight of substance, for the analysis, but our 
measurement of the result is made in cubic centimeters, although 
this is afterwards calculated in weight. In the gravimetric work 
the gram weight, with its sub-multiples and multiples, answers 
for all the measurements; but in volumetric work there are 
many solutions by which we measure, and therefore many 
analytical values of the cubic centimeter. 
It is evident that anything used for a measure must itself have 
a known value. Some of the solutions used for measuring do 
their work by oxidizing the substance in solution whose quantity 
it is desired to measure ; others act by neutralizing its acidity or 
its alkalinity,-others by precipitating it out of the solution ; the 
more of the substance to be measured there is in the solution, 
the larger the volume of the oxidizing, neutralizing, or precipi- 
tating solution will be required for the work. We must, then, 
be able to determine two things with accuracy; how much 
oxidizing, neutralizing, or precipitating power there is in one cubic centimeter of the measuring solution ; and, secondly, the 
exact point at which we have added just enough of the measur- 
ing solution to complete the reaction ; this is usually accomplished 
with the aid of some reagent called the indicator, that gives 
some sharp color reaction. For the determination of the 
strength of the measuring solution we must generally use a gravi- 
metric process of some kind. 
ELEMENTS OF CHEMICAL ANALYSIS. 
108. Standard and norttial solutions. A solution whose 
strength has been determined for the purpose of volumetric 
analysis is called a standard solution ; when the standard of the 
solution bears a certain definite relation to the molecular weight 
of the active agent that it contains, it is called a normal solution, 
which is thus defined: a normal solution is one of which one 
liter contains a quantity of the substance, expressed in grams, 
chemically equivalent to one gram of hydrogen. 
Volumetric analysis may be divided into three kinds. 
a. Analysis by neutralization, or saturation, in which the 
quantity is measured of a solution of known strength of an acid 
or a base, that is required to neutralize the unknown quantity of 
a free base or acid. 
b. Analysis by precipitation, in which the quantity is measured 
of a solution of known precipitating power, that is required to 
precipitate the unknown quantity of a substance from a solution. 
c. Analysis by oxidation or reduction, in which the quantity 
is measured of the reagent of known oxidizing or reducing 
power, required to oxidize or reduce the unknown quantity of the 
substance to be determined in this way. 
Standard solutions for use in volumetric analysis are usually 
solutions of acids, bases or salts; one important solution contains 
the elementary substance, iodin, for its active ingredient, and 
another contains hydrogen peroxid, which do not belong to any 
of these classes. A standard solution of an acid or a base is 
used mostly for the determination of free bases or acids in 
solution; or an acid may be used for the determination of the 
basic part of a salt, whereof the acid is one that can be com- 
pletely and easily expelled, by the acid used, as in the case of 
carbonates, A standard solution of a salt may be used as a 
precipitant, either by its basic or its acidic part, or as an oxidiz- 
ing or reducing agent. 
That part of the reagent, of any one of these kinds, which 
reacts with the substance to be determined is the active constituent 
of the solution. If the reagent is an acid, the acidic part of the MEASUREMENT IN VOLUMETRIC ANALYSIS. 
formula of the acid represents the active constituent; if a base, the 
basic part of the formula represents the active constituent. If the 
reagent is a salt, and the reaction is the precipitation of some 
constituent of the solution acted upon, the active constituent of 
the standard solution is that part of the salt that enters into the 
precipitate formed. In the same manner, if the action of the 
standard solution is oxidizing, then that part of the substance in 
the solution which actually produces the oxidation, whether 
directly or indirectly, is the active constituent of the solution. 
If the action is one of reduction, that constituent of the solution 
which is carried to a higher degree of oxidation or chlorination 
is the active constituent. 
In the following equations, representing reactions of neutraliza- 
tion and precipitation, the active constituent in the reagent, or 
that part of the reagent containing it, is italicised. 
2KOH + H2S£4 = K2S04 + 2H20. 
2HCI + jßa{pH)2 = Ba<Z\ + 2H20. 
NaCl + 4^NOs = Ag^Oi -f- NaNOg. 
Equations illustrating the action of oxidizing agents will be 
found further on. 
In tile formulas of these acids, bases, or normal salts, acting 
as neutralizing or precipitating reagents, the valence of the 
active constituent, shown by the number of atoms of hydrogen 
in the acid, replaceable by a metal to form a salt, or of hydroxyl 
in the base, or by the valence of the non-active part of the salt, 
gives, directly or indirectly, the number of atoms of hydrogen 
to which that quantity of the active part of the reagent repre- 
sented by its molecular weight is equivalent. In H2S04, the 
acidic and really active constituent is sulfur trioxid, S03: this 
can be contained but once in the formula of the acid, hence S03 
is equivalent to H taken twice; or, expressed in molecular 
weight, 80.06 of S03 is equivalent to 2 of H, or 80.06 grams of 
S03 is equivalent to 2 grams of H. Hence, according to the 
definition of a normal solution, a liter of a normal solution of 
H2S04 should contain 40.03 grams of S03; and the number 
of grams of H2S04 containing this weight of S03 is given by 
half the molecular weight of H2S04, or 49.03. It is evident, 
however, that we need not thus resolve the sulfuric acid into its 
component parts to learn what its ultimate active constituent is, 
the S03. The acidigenic part of its formula is the S04; it is 
equivalent to H2 in that formula; therefore, we learn directly ELEMENTS OF CHEMICAL ANALYSIS. 
that the molecular weight represented by the ordinary formula 
must be halved to get the figure for the weight of H2S04, ex- 
pressed in grams, for a liter of a normal solution. So a liter of 
a normal solution of Ca(OH)2 must contain the number of grams 
expressed by the figure for half its molecular weight: we need 
not stop to consider that the really active constituent is the CaO ; 
that this is equivalent to H2; that its molecular weight must be 
halved, and, consequently the molecular weight of Ca(OH)2; 
to consider that (OH)2 is equivalent to H2 shows us at once the 
more direct course that can be taken. 
If a normal solution of a salt is to be made for a precipitant, 
consider first whether it is the basic or acid part of the salt that 
comes into action in the use of the solution. For example, a 
normal solution of potassium chromate, K2Cr04, is wanted as a 
precipitant by its chromic acid. The formula of the salt shows 
that the acidigenic constituent is bivalent, and is therefore 
equivalent to H2; hence the figure given by half the molecular 
weight of the salt, expressed in grams, represents the weight of 
the salt to be taken for a liter of a normal solution. 
But the dichromate, K2Cr207, may also be used as a precipi- 
tating reagent; this is not a normal salt, and the rule given 
above applies only to normal salts. The equation for the re- 
action of this substance, with a barium salt for example, shows 
that a molecule of it has twice the precipitating power of a 
molecule of the normal chromate. 
28a(C2H302)2 + K2Cr207 + H2O = 2BaCr04 + 2KC2H302 + 2HC2H302. 
8a(C2H302)2 + K2Cr04 = BaCr04 + 2KC2H302. 
The acidigenic part of this salt in one molecule is therefore 
equivalent to H4. 
Passing now to oxidizing agents the same general rule can be 
applied to them. The following equation represents the oxidizing 
action of KMn04 on ferrous oxid: in order to show more 
plainly the course of the oxidation, the acid necessary to form 
salts with the oxids, and to hold them in solution is omitted. 
2KMn04 -(- loFeO = 5Fe203 + K2O + 2MnO. 
This equation shows that two molecules of the permanganate 
give up 05 for oxidizing work: 05 is equivalent to H10: or 
315.34 grams of KMn04 is equivalent to 10 grams of hydrogen ; 
and, calculated in this way, on the basis of the actual working 
effect of two molecules of the salt, a liter of a normal solution of MEASUREMENT IN VOLUMETRIC ANALYSIS. 
it contains 31.5 grams. Likewise, one molecule of potassium 
dichromate gives up in oxidation three atoms of oxygen, as 
shown by the following equation, in which also, for greater 
plainness, the hydrochloric acid, or some other acid necessary 
to hold the products in solution, is omitted. 
K2Cr207 + 6FeO 3Fe203 -f- Cr203 -J- K2O. 
03 is equivalent to H6: hence the figure expressing grams of 
K2Cr207 in a liter of a normal solution of this salt, when used as 
an oxidizing agent, is given by one-sixth the weight of a mole- 
cule of the salt. 
In these cases, therefore, as in those of the neutralizing or the 
precipitating reagents, the equivalency to hydrogen of the actually 
working part of the reagent in a molecule of it, is taken as the 
basis for the calculation in making up normal solutions. 
Other standard solutions are used in technical practice, which 
Mohr calls empirical solutions, and of which he gives this example. 
A standard acid may be so made that it contains in 100 c.c. the 
quantity of the active constituent required to saturate one gram 
of pure Na2C03; then, in assaying a sample of soda ash, exactly 
one gram is taken, and the number of cubic centimeters required 
to neutralize the sodium oxid gives, at once, the per cent, of 
Na2C03 in the sample. But this relation of acid required to 
pure salt in the sample would hold good for sodium carbonate 
only; another standard acid must be made for potassium car- 
bonate, and another for calcium carbonate, and so on. Such a 
solution is useful, therefore, only where one substance is to be 
assayed with it, and by one and the same kind of a reaction. 
These definitions and explanations should enable the student 
to formulate the rule for the calculation of the required weight 
of substance for any normal solution. 
A normal solution of full strength is usually too strong for 
actual use; it will not measure with sufficient closeness. In 
order to measure length or weight as closely as we desire, in 
accurate work with small quantities, we have to use a smaller 
measure than the meter or the kilogram. In gravimetric work 
we weigh in grams, and sub-multiples and multiples of the gram. 
In like manner we reduce our normal solutions to half normal, 
or one-tenth normal, containing in a liter one-half or one-tenth 
of the quantity of substance required for a normal solution; 
such solutions are designated as ~, and so on. ELEMENTS OF CHEMICAL ANALYSIS. 
In the use of these solutions it is better to take such a quantity 
of the substance for analysis, that not less than about 40 c.c. of 
the chief standard solution will be required for each determina- 
tion made with it. 
The temperature of any standard solution should be approxi- 
mately the same at all the several times when its strength is 
determined, and when it is used for analytical purposes; the 
temperature of a comfortable room is a convenient one to 
maintain; therefore, if a solution has been standing so long in 
a cold room as to have fallen much below this point, it should 
not be used till it has become warmed to about the right degree. 
109. The special instruments used in volumetric analysis. These 
are pipettes, burettes, measuring flasks, and graduated cylinders. 
The pipette may be simply a graduated tube, showing cubic 
centimeters and fractions thereof; or it may consist of a short 
piece of wide tube* connecting two longer pieces of narrow 
tube, when it is intended to measure only one fixed quantity, as 
5, 10, 25 or 50 cubic centimeters : this capacity is indicated by 
a mark on the stem of the instrument. To use the pipette im- 
merse the point in the liquid to be measured, and with the 
mouth draw the liquid up till it rises a little above the mark ; 
then quickly close the mouth of the tube with the ball of the 
index finger, and with the mark on the stem at the level of the 
eye, looking towards a window or a bright wall, raise the end of 
the finger just enough to let the liquid flow out slowly, and 
finally drop by drop, till the lowermost part of the meniscus and 
the mark on the neck coincide-; take off the drop that may 
adhere to the point by touching it on the side of the glass, and 
then let the liquid flow out by its own gravity into the vessel 
destined to receive it, the point of the pipette being held 
against the side of the glass : then allow the pipette to drain in 
this position for about a minute. 
The burette, a long graduated tube, is closed below by a 
rubber tube about three centimeters long, carrying a short glass 
jet at its lower end, and a small glass ball within ; on grasping 
the tube around this ball between the ends of the thumb and 
index finger, and pinching it in such a manner as to draw it out 
to one side and away from the ball, a passage is opened for the 
liquid in the burette, and the rate of flow can be easily regulated. 
The rubber tube should be pushed up on the burette-point till 
the ball in it is close to the opening of the burette, and the end 
of the delivery tube in the rubber tube should also be close to MEASUREMENT IN VOLUMETRIC ANALYSIS. 
the ball. The size of the ball should be so adapted to the size 
and elasticity of the rubber tube that, while making a tight 
closure, still no such effort is required to open it that it cannot 
be held open as long and as much as may be necessary, without 
painfully straining the fingers. 
The burette is filled at the top through a funnel, till the liquid 
rises above the zero mark, then the valve below is quickly 
opened as wide as possible, so that the air in the rubber tube 
and jet will be completely displaced by the liquid, quite to the 
point of the jet; the liquid is then allowed to flow out, slowly, 
till the lower part of the dark zone of the meniscus, or the line 
on the burette-float if one is used, coincides with the zero line 
on the burette; the reading of the amount of liquid delivered for 
any purpose is taken in a similar manner. In delivering a 
large quantity of liquid at once and rapidly, a minute should be 
allowed for the walls of the burette to drain before the reading 
is taken. 
The measuring flask has a mark on its neck indicating its 
capacity. It is often used when it is desired to make a certain 
volume of a solution of a substance, in hand for analysis; ali- 
quot parts of this solution are then taken out with a pipette, for 
the further treatment. The volume of the whole solution being 
known, as well as that of each part taken out, the results ob- 
tained with each portion can be calculated to the whole amount 
of substance taken in the beginning for analysis. 
T}ie graduated cylinder. This is a cylinder of uniform diam- 
eter, on a foot, not graduated to less than one cubic centimeter; 
measurements made with it are not so accurate as with the meas- 
uring flask or pipette, because the diameter of the column of 
liquid where the reading is taken is so much greater. 
When the liquid flows from a pipette or burette, it should 
leave no streaks on the walls, showing more adhesion in one 
place than in another; in such case the readings cannot be accur- 
ate. Such irregularity in the flow is caused by dirt of some kind 
on the glass, usually oily matter; this can be removed most 
easily by means of a strong oxidizing agent, as chromic acid. 
Directions will be found in Part V, under the head of reagents, 
for the preparation of this solution and for its use. 
no. The calibration of graduated instruments. Successful 
work in volumetric analysis requires that the instruments used be 
correctly graduated. The testing of their graduation is called 
calibration. Not only should the correctness of the several parts ELEMENTS OF CHEMICAL ANALYSIS. 
of the burette and the graduated pipette be tested, but also that 
of the total capacity of each instrument, as the full pipette and 
the measuring flask, and their relations to one another. To the 
beginner in quantitative analysis, taking only the course in Part 
IV of this work, the calibration of his burette, 25 c.c. pipette, 
and 250 c.c. measuring flask is of most importance. 
Calibration of the burette. After it has been properly cleaned, 
fill it to the zero mark with distilled water at a temperature of 
about 200, run out exactly 10 c.c. into a light weighing flask, 
previously weighed with a small watch glass over its mouth, 
and weigh on a balance sensitive to centigrams ; nothing is 
gained by weighing more accurately than this. Run in another 
10 c.c. and weigh again, and so on till the lowest 10 c.c. 
has been weighed. Repeat, and take the average for each 
10 c.c. 
For the correct scale of reading for this calibration, for 1 c.c. 
on the burette scale put down in your note book one-tenth of 
the weight of the first 10 c.c; for 2 on the burette scale, two- 
tenths of that weight, for 3, three-tenths, and so on ; then when 
xo on the burette scale is reached the corrected number will be 
the same as the weight of the first 10 c.c., if the calculations 
have been rightly made. Proceeding in the same manner, for 11 
on the burette scale, add to the corrected number for 10 c.c. 
on the burette scale, one-tenth of the weight of the second 10 
c.c., and so on. If the deviation for any 10 c.c. is less than 
0.05 gram, the graduation of that part of the burette is suf- 
ficiently accurate, and no correction need be made. 
To calibrate the pipette, weigh its contents, delivered exactly 
as has been directed ( § 109) into the same weighing flask that 
was used in the calibration of the burette. Then calibrate the 
measuring flask by means of this pipette, delivering it ten times 
filled into the flask, and repeating the operation till results agree 
closely. If the mark on the neck of the flask does not coincide 
very nearly with the lowest part of the dark zone of the menis- 
cus at the level of the liquid, when the flask is thus filled, a new 
mark should be made for this calibration by putting on a short, 
narrow strip of a gummed label, at the proper place. Now, 
with the aid of this measuring flask and pipette, one can get 
exactly one-tenth of the weight of a substance taken for analysis 
and brought into solution, this solution being made up to 250 c.c. 
in the flask, or one-tenth of the soluble part of it if not entirely 
soluble. MEASUREMENT IN VOLUMETRIC ANALYSIS. 
in. Special directions for the use of these graduated instru- 
ments. When it is desired to get a certain volume of a solution 
of a substance, as 250 c.c. for example, in the measuring flask, 
and heat can be used with advantage, always treat the substance 
first in another flask, or in a beaker, with not more than half 
this volume of the solvent. When the solution is completed, or 
when carried as far as it can be if the substance is not wholly 
soluble, with a funnel in the mouth of the measuring flask pour 
this solution into it, and carefully rinse the flask or beaker into 
it with distilled water; then pour in more water cautiously 
almost to the mark on the neck, and finally, holding the flask in 
a vertical position, with the mark on a level with the eye, let 
water drop in from a pipette, or a dropping tube, till the mark is 
reached; close the flask tightly with its glass stopper, or with a 
soft cork, and mix its contents by repeated inversion. After 
this, while the solution is being used for the analysis, the flask 
should be uncorked only while some of its contents is being 
withdrawn. 
If the solution has stood for some time undisturbed, it is well 
to mix the contents, except when there is some special reason 
for not doing so, by inverting the flask two or three times, before 
taking out a portion for analysis. If two or three portions are 
to be used take all of them out at the same time; if but one is 
taken, and the pipette is laid on the table while the analysis of 
that portion is carried through, some of the solution on the point 
of the pipette will evaporate, leaving a solid deposit there ; this 
cannot be washed off without danger of getting a little water 
into the pipette; of course the pipette must not be dipped 
into the liquid in the flask with this deposit still on it, or with 
water in it. 
Always after using a pipette rinse it out, finally with distilled 
water, and dry it; do the same with a burette when through with 
the use of it for a particular solution, or when the work must be 
left for some time. Only when clean and dry are these instru- 
ments ready for use. 
Never attempt to fill a burette at its mouth otherwise than 
through a funnel; without this precaution, some of the liquid 
may flow down on the outside; if it is a solution of any salt the 
water will evaporate, leaving a deposit on the glass that will ob- 
scure the readings; or if a beaker containing a solution to be 
analyzed should happen to be under the burette, some of the ELEMENTS OF CHEMICAL ANALYSIS. [§§ 11 2-113. 
overflowing solution might drop into it, and the analysis would 
be ruined. 
Always close the mouth of a burette carefully, on leaving a 
standard solution in it that you expect to use again in a short 
time; if the work will not be continued within a very few days, 
it is better to empty the solution out an.d clean and dry the 
burette. 
CHAPTER XIII. 
SEVEN IMPORTANT OPERATIONS OF QUANTITATIVE WORK. 
112. Every gravimetric analysis brings into use seven import- 
ant operations namely, weighing of the substance and the 
product of the analysis, the preparation of the solution, precipi- 
tation of the new compound, filtration, washing of the precipi- 
tate, preparation of the same for weighing, usually by ignition, 
and the calculation of the result. 
The first, sixth and seventh operations are peculiar to quanti- 
tative analysis; the others are common to both qualitative and 
quantitative work, and they differ in manipulation in the two 
cases only in this one respect, but a very important one, that 
they must be carried through in such a manner as to involve 
neither loss of any of the substance that is under manipulation, 
nor the addition of any foreign matter to it that will make it 
other than the chemically pure product, of definite chemical 
composition, which the process requires to be weighed, when 
these manipulations are completed. 
The first operation has been fully described (Chap. XI). To 
what has already been given in Part I concerning the other 
operations, the following considerations are added as bearing 
specially on the two conditions emphasized above. 
113- The solution of the substance. The liquid in which the 
solution is being made must not be boiled, unless special direc- 
tions are given to that effect; if boiled, it must be in a beaker 
covered with a beaker cover, or if in a flask, with the flask turned 
over on its side and securely supported in that position. If any 
gas is given off during the solution, as in the treatment of a 
carbonate with an acid, the beaker must also be covered, and the §§ 114-115-] SEVEN IMPORTANT OPERATIONS. 
117 
reagent causing the effervescence should be added slowly and 
with constant stirring. The conical Erlenraeyer flask, which 
can be covered with a small watch glass, is most suitable for such 
solution. When the solution is completed in such cases as these 
requiring the covering of the vessel, the cover and the sides of 
the beaker should be thoroughly rinsed down with distilled 
water, after the solution is completed. Unless otherwise directed, 
the volume of the solution when ready for the analysis may well 
be about 150 c. c., unless otherwise directed, and it should never 
be strongly acid unless so directed. 
114. The precipitation. In this operation, two important 
points are to be looked after: the precipitate must be obtained 
in the best possible condition for easy filtration and washing, 
and the precipitation must be beyond all doubt complete. If a 
Table of the strength of the reagents used is given (see Part V) 
it is easy to calculate how much of the precipitant will be 
required in any given case, if the composition of the substance 
given out for analysis is approximately known, and it is assumed 
to be a chemically pure substance; the calculated quantity 
having been added, and then one or two cubic centimeters 
more, it may be safely considered as sufficient; and yet it is 
better even in such a case to make the test for complete precipi- 
tation, either in the supernatant liquid, partly clarified by the 
settling of the precipitate, or in a small filtered portion. 
The special directions given in many cases for the preparation 
of the solution, and the management of the precipitation, often 
have reference to the first condition, and should be closely fol- 
lowed. In general, it may be said that precipitates made in hot 
solutions, and with the gradual addition of the precipitant, 
stirring it in as fast as added, and the avoidance of a large excess 
of the precipitant, will lead to better results than the reverse 
methods. 
115. The filtration. If, as is usually the case, the filter on 
which the precipitate is collected is to be ignited, the filter is 
burned with it; the filters used in quantitative work leave a 
small but uniform weight of ash, which is deducted from the 
total weight of the product. Full directions for fitting the filter 
have already been given (§ 55) ; it is much more essential for 
the attainment of the best results that those directions should be 
followed in quantitative work. The filter should never be filled 
to within less than about three millimeters or one-eighth of an 
inch, of the rim. It is usually best, for rapid and clear filtration, -[§ TIS- 
118 
ELEMENTS OF CHEMICAL ANALYSIS. 
to have the liquid hot, and to decant off into the filter the 
supernatant clear or partially clear liquid, before transferring the 
precipitate. 
Occasionally a filtrate from a fine precipitate is at first clear, 
while the later portions are turbid; therefore in the case of such 
precipitates it is well to throw out the filtrate from time to time, 
as long as it is clear; then, if turbidity appears only a small 
portion instead of the whole has to be re-filtered. The vessel 
for receiving the filtrate should be perfectly clean at the begin- 
ning, so as to be prepared for a second filtration if it becomes 
necessary. 
On proceeding to the filtration, hold a glass rod (with the 
straight end downwards), against the lip of the beaker, with 
its end well into the filter, and slowly pour the liquid down this 
rod, thus preventing it from running under the lip of the beaker; 
when the filter is full, draw the rod upwards for a little distance, 
while still in contact with the lip, and the drop of the liquid, 
with perhaps some of the precipitate suspended in it, that is 
liable to form under the rod and lip, will be taken off on the rod. 
If a beaker is nearly full, pouring from it without having some of 
the liquid run down the side will be very difficult, even with the 
rod against the lip; this matter of the proper size of the beaker 
must therefore be thought of before making the precipitation. 
The loosening of every particle of the precipitate from the 
sides of the beaker, and the transfer of these last portions to the 
filter, are sometimes difficult. A short piece of rubber tube 
slipping tightly on the end of a glass rod, and projecting just a 
very little beyond it, is commonly used to loosen a strongly 
adhering precipitate; or, an eighth of a filter may be folded 
into a wad, and with a few drops of water in the beaker, 
rubbed over the surface of the glass, under the end of the rod 
pressed down on it firmly, and finally dropped into the filter; 
another eighth of a filter may be used in the same manner, if 
necessary; this method has the advantage, which is of importance 
in some cases, that if any of the precipitate adheres strongly to 
the swab, it is not lost, as it would be if the rubber tube were 
used. 
Sometimes a very fine precipitate, such as barium sulfate, 
crawls up the sides of the beaker, apparently as fast as it is 
washed down ; in such a case, get as much of it as possible down 
into the bottom of the beaker with a continuous current from 
the jet of the wash-bottle ; then, holding the beaker between the SEVEN IMPORTANT OPERATIONS. 
thumb on one side, and the second and third fingers-on the 
other, lay the rod across the top, and hold it there with the 
index finger; all the pouring from the beaker can now be done 
with this hand ; and while the beaker is still inclined over the 
funnel, a jet of water from the wash-bottle can be directed into 
it, and all over the sides and bottom, which will immediately 
flow out into the funnel, carrying with it in this continuous 
stream all of this fine precipitate ; the jet-tube of the wash- 
bottle being connected with the main tube by rubber, making a 
flexible joint, by means of the index finger of the hand holding 
the wash-bottle, pushing the jet-tube upwards, the stream can be 
directed even against the upper sides of the beaker while still 
flowing down the rod into the filter. 
This transfer of the precipitate is completed only when the 
inside of the beaker is perfectly clean, the outside being clean 
also in order that one may plainly see anything adhering to the 
inner walls. 
116. Filtration by suction. The assistance of suction to 
hasten filtration is much used in quantitative work. It is applied 
in two ways, with paper filters, and with asbestos filters. 
The paper filter is usually supported by a perforated platinum 
cone in the throat of the funnel; when the filter is crowded 
down snugly against this cone, its rim should touch the sides of 
the funnel at all points of its circumference; if it does not, the 
opening of the funnel is too wide, and another one should be 
taken, or the filter should be folded with a wider opening, which 
is easily done. When the filter is put into the funnel and wetted 
as described in § 55, special pains must be taken to fit it down 
against the cone and against the glass above the cone, every- 
where from the apex of the cone to the rim of the filter ; creases 
made in the paper in doing this will do no harm ; but wherever 
the paper is not directly backed up by the platinum or the glass, 
it will probably be torn when the suction is turned on, and some 
of the substance will pass through. Only slight suction should 
be used at the beginning of the filtration, and more, later, when 
the filter is well covered with the precipitate; without care in 
this regulation of the suction much time may be lost on account 
of spoiled work. By the use of filters whose points have been 
dipped in nitric acid of sp. gr. 1.42, and afterwards washed with 
water till the acid is all removed, the use of the platinum cone 
can be dispensed with. 
When the suction is in use, it should never be turned off 120 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 1 *7* 
entirely, till first disconnected from the filtering bottle; other- 
wise the water at the suction-pump, which is commonly attached 
to the water supply at each student’s table, may rush back into 
the bottle, and the work may be spoiled. Strong bottles or 
flasks specially made for the purpose must always be used to 
receive the filtrate : never use an ordinary flask. Flasks of the 
conical, Erlenmeyer form, with a lateral tube for connection 
with the suction are now provided, and are very serviceable. 
It is advisable to start every paper filtration in filters carefully 
fitted into the cones, or treated with HNOs, so that suction may 
be applied later if desirable. 
117. Washing precipitates. Upon the thoroughness with which 
the precipitates are washed depends in largest measure the fulfill- 
ment of the second requirement for successful work stated in 
§ll2. When the filtration is completed, the precipitate and 
the filter are saturated with a solution containing all the products 
of the reaction by which the precipitate was made, as well as, 
sometimes, other substances that one needed to add to make the 
precipitation as perfect as possible : and so far as these are not 
volatile at the temperature of the burning of the filter, they will 
remain and add to the weight of the product. It must not be 
forgotten, therefore, that it is the filter as much as the precipitate 
in it that needs washing. 
Hot water, unless proscribed, should always be used for this 
washing, to save time; the jet should be made to play all over 
the filter, from as near the rim as possible down, till the contents 
are covered with water, or till the filter is about two-thirds filled; 
when all this has drained out, repeat the addition of water; the 
washing will be sooner completed with several small quantities 
of water, than with as many larger quantities. 
The first spurt of water from the wash-bottle is apt to be so 
strong as to cause spattering of the precipitate up on the sides of 
the funnel above the filter; this maybe avoided by first filling 
the whole delivery tube and jet with water, while the jet is 
pointed in another direction; then, while the tube is full, pinch 
the rubber tube between the jet and the main tube, direct the 
jet into the filter, and release the pressure on the rubber tube 
while the blowing in at the mouth tube is continued. Also, 
while the delivery tube is thus held full of water, if the wash- 
bottle is held in a much inclined position with the jet pointing 
downwards, the delivery tube becomes a siphon by which the 
water can be run into .the filter fast or slow at pleasure, by inclin- § nB.] 
SEVEN IMPORTANT OPERATIONS. 
121 
ing the flask more or less; by letting the flow run dropwise on 
the rim of the filter for a few rounds, that more difficult part ot 
the washing may be facilitated ; but this must be done with care 
in the case of very fine precipitates, lest they begin to crawl up 
on the glass. 
If channels are formed in the precipitate by shrinkage, while 
it is being washed on the filter, these are to be broken up, most 
easily by stirring the precipitate with a glass rod. This shrinkage 
will happen only in the case of somewhat gelatinous or very 
flocculent precipitates, such as ferric hydroxid, and it is best to 
wash these largely by decantation before putting them on the 
filter—pouring considerable water over the precipitate in the 
beaker, after as much as possible of the liquid in which the 
precipitation was made has been poured off through the filter, 
without removing much of the precipitate, stirring it vigorously, 
pouring this liquid off after partial settling of the precipitate, 
and repeating the operation several times. 
There should be no guess-work as to the question of the com- 
pletion of the washing of the precipitate; in every case a test 
should be made from time to time in a cubic centimeter of the 
washings, for that substance in the solution for which there is the 
most delicate as well as simple qualitative reaction. If, for 
instance, we know that the solution contains a chlorid and a 
nitrate, as the delicate test for the former by silver nitrate is more 
simple than the very delicate test for the latter, given under nitric 
acid in § 81, we would use the former test; and when we can no 
longer get any reaction with silver nitrate in the washings acidi- 
fied with nitric acid, we can usually assume that, together with 
the chlorids thus proved to be washed out, nitrates and all other 
salts are removed. The test may be made in another way, by 
the evaporation of a drop of the washings to dryness on a clean 
watch glass; if no residue remains, the washing is complete. 
118. The asbestos filter. For this, instead of a funnel, a large 
platinum crucible is used (the Gooch crucible) with perforated 
bottom, or a porcelain crucible without bottom, except a narrow 
ledge to support a perforated platinum disk (the Caldwell-Gooch 
crucible). The crucible is put in a funnel with short, perpen- 
dicular sides, the upper edge of which is covered with a ring of 
sheet rubber, in such a manner that as soon as the suction is 
turned on, and the crucible is pressed down gently, this rubber 
makes a tight joint between it and the rim of the funnel. 
To prepare the filter, while the crucible is pressed down in this 122 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ nB. 
manner and the full force of the suction is turned on, pour on a 
very little of the asbestos pulp, shaken up with very much water; 
then pour in a little more, down a glass rod, the end of which 
is held close to the bottom of the crucible, so as to leave the 
first coating over the perforated bottom undisturbed; a third or 
fourth portion may be added; but the layer of asbestos should 
be no thicker than moderately heavy filter paper, and uniformly 
distributed over the whole surface; the finer the precipitate to 
be collected, such as barium sulphate or calcium oxalate, the 
greater the care that must be bestowed on the preparation of the 
filter. After it has been properly made, wash it with water 
poured in on a glass rod the end of which is close to the asbestos, 
till the washings are clear; the washings must be frequently 
poured out of the filtering bottle, in order that one may be able 
to determine when the last washing is free from fibers of asbestos. 
The crucible and filter is then to be dried and ignited over a 
low, direct flame, the lamp being held in the hand so that the 
flame can be made to play evenly and lightly over the whole 
crucible, and not merely impinge forcibly against the bottom ; 
the drying flame should be applied very gently at first, by 
moving it in and out, under and around the crucible; the 
ignition, later, is complete as soon as the bottom of the crucible 
has reached a dull redness, unless higher heating is specially 
directed. 
When this filter is to be used, first turn on the suction and 
then put the crucible in its place in the funnel, moisten the 
filter with a few drops of water, and proceed with the filtration, 
always having the end of the glass rod well down in the crucible. 
When the washing is completed the crucible and contents can be 
dried and ignited in the same manner as directed for the treat- 
ment of the filter before the filtration. 
This method of filtration is so useful and so widely applicable, 
especially with the cheaper porcelain crucible, that the student 
should learn to use it very early in his course. If a thin plat- 
inum jacket is made for the crucible, fitting it just a little 
loosely, the ignition can be made as satisfactorily as in a plat- 
inum crucible; and as the platinum can be spun much thinner 
than would be practicable for a crucible, with this arrangement 
one can have all the advantages of a platinum Gooch crucible at 
much less cost. Any worker in platinum can make the jacket. 
In using it lay two or three long, slender fibers of asbestos in 
the jacket before putting the crucible into it, to avoid danger § IT9-] 
SEVEN IMPORTANT OPERATIONS. 
123 
of adhesion between the two if the ignition must be made at a 
high temperature. 
119. Preparation of the precipitate for weighing. In case the 
asbestos filter is used it is a very simple matter to prepare the 
precipitate for weighing, as has already been explained. If the 
precipitate is collected on paper the operation is less easy. 
The precipitate must first be dried for a few hours in the dry- 
ing chamber provided for this purpose 3 to this end cover the 
funnel with a common filter, on which your name and the num- 
ber of the anaylsis have been written 3 this filter must be about 
a centimeter larger than the funnel, and be folded down tightly 
over the edge, so that it will stay in place ; the moisture will 
easily escape through the porous paper. To put this cover on 
so that it will remain in place, set the funnel in the funnel- 
holder, lay the filter on the edge of the funnel, and hold it in 
position by pressing it down on this edge with the finger-ends 
and thumb of one hand 3 then with the index finger of the other 
hand fold the edge of the filter down over the edge of the 
funnel at one point on the circumference, and while holding 
this fold in place with this finger, with the thumb make the next 
fold tightly over the first one 3 move the index finger to this 
second fold and hold it in place, and at the same time tucking 
it under a third fold laid over it by the thumb 3 while doing 
this, this side of the funnel is gradually moved round and away 
from the operator 3 at no time is the pressure of the fingers of the 
other hand to be released. Each fold is to be drawn down as 
tightly as possible without tearing the paper. 
Meanwhile the crucible is to be ignited and weighed, if this 
has not already been done (§ 126). In this ignition adjust the 
height of the crucible above the lamp so that about two-thirds 
of a flame ten centimeters long will be below the crucible 3 
there should of course be no deposit of carbon from the lamp 
flame on the crucible : if there is it must be burned off before 
putting the crucible in the desiccator. 
To guard against any possible loss of the precipitate in trans- 
ferring it to the crucible, the operation is to be performed over 
glazed paper 3 this paper should be in four pieces 3 one (a) 
about 37 by 50 centimeters, one (b) about 22 by 25 centimeters, 
and two small pieces, (c, d,) each about 14 by 22 centimeters: 
these pieces can be cut out of a sheet of the ordinary size. 
All these pieces should be trimmed smooth at the edges 3 this 124 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 119- 
paper should never be on the table except when in actual use for 
the transfer of the precipitate to the crucible. 
Lay the largest piece of paper a on the clean, dry table, on 
that the piece b, and on that the piece c, and finally on that 
the crucible. In a place where there are no strong currents of 
air, touching the filter only on the outside, press and rub it 
together gently, where the precipitate is, g.ll the time holding it 
over the glazed paper, and empty as much as possible thereof 
into the crucible ; then carefully open the filter completely ; it 
will be seen that, the precipitate is entirely confined to one half 
of it; with the other half towards you take hold of the rim of 
it with the thumbs and second fingers of both hands, bring the 
two quarters of the other half together by means of the index 
fingers pressing upwards on the outside, and then by a back- 
ward and forward motion of the right and left halves of the filter 
rub the inside surfaces together, and thus loosen as far as possi- 
ble those portions of the precipitate that still adhere to the 
paper ; change the positions of the index fingers about, so as to 
rub different parts of the filter together, and then empty it into 
the crucible; now that as much as possible of the precipitate 
has been transferred to the crucible, fold in that edge of the filter 
over which the precipitate was emptied, so that no particles 
loosely adhering to it shall drop off and be lost in subsequent 
operations, fold the filter up again as it was originally, roll it up 
and wind the long piece of platinum wire (in a glass tube handle) 
about it, as much as may be necessary to keep it together; hold 
the roll with the closed end downwards directly over the cru- 
cible, touch the lower end with the lamp flame, and lower it at 
once into the crucible ; when the burning and glowing have 
ceased, raise it a little above the crucible and let the flame play 
on any unconsumed parts, thus burning the filter as completely 
as possible in this free access of air, before the remains drop out 
of the wire; a gentle tapping of the wire on the edge of the 
crucible will then detach any particles adhering to it. 
If all this work has been carefully and skillfully done, very 
little of the precipitate will fall outside of the crucible ; set the 
crucible aside on the other small piece of paper d, and gather all 
visible particles of the precipitate from sheet a on to sheet c on 
which the crucible stood ; then putting c on a gather whatever is 
on b on to c\ then, setting the crucible and the piece it is now on, 
on b, transfer what has been collected on cto the crucible. By SEVEN IMPORTANT OPERATIONS. 
conducting the operation in this manner the direct transfer of 
precipitate to the crucible is always done from a small piece of 
paper, and more easily than from a large one; and each part of 
the operation is conducted over a sufficiently large piece of paper 
so that no particles are likely to get out of sight; if any do not 
move readily on the glazed paper, they can be pushed along to the 
edge by means of the platinum wire; this is better than a brush 
or a feather, for adhesion to either of these is quite as easy as to 
the paper, if not more so. 
Now set the crucible in the platinum-wrapped triangle on the 
lamp ring, and put the glazed paper away in its drawer. Cover 
the crucible, and ignite it at first gently and afterwards to full 
redness, or as much as may be directed in any special case ; remove 
the cover, lay the crucible on its side with its mouth towards one 
of the twisted arms of the triangle, and the cover partly on this 
arm and partly on the crucible, and so far down as to leave its 
mouth about two-thirds uncovered; some access of air is thus 
provided for the combustion of the small remnant of carbon that 
usually remains; apply the full heat of the lamp to the bottom 
of the crucible, this being set high enough so that about two- 
thirds of the length of the flame is below it. When no further 
change appears to take place in the contents of the crucible put 
it in the desiccator to cool. 
In a few cases there is no danger of any reduction of the sub- 
stance to be weighed, by contact with the burning organic matter; 
then the filter and contents maybe put at once into the crucible, 
and at first gently ignited with the cover on ; after the filler is 
thoroughly charred the ignition is continued in the partly covered 
cruci bje, as described above. In other cases the precipitate is so 
easily reduced that it must receive special treatment after the 
ignition, to restore it to its normal condition ; it is better to 
collect such precipitates on the asbestos filter. 
120. Calculation of the results of the analysis. In the calcula- 
tion of these results, two important ideas are specially prominent: 
first, the product of the analysis, that is weighed, rarely consists 
of that substance alone for the determination of which the 
analysis was made, or in the same form in which it existed in the 
compound subjected to analysis. If, for example, we seek to 
determine phosphorus in cast iron, we finally weigh it as mag- 
nesium ammonium phosphate, a form of combination totally 
different from that in which it existed in the iron. Secondly, 
the result is nearly always to be given in percentage, or parts 126 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ I 21. 
per hundred parts of the substance analyzed ; only by comparing 
results thus calculated can they be checked against one another, 
since different quantities of substance are in nearly all cases 
taken for the several determinations that are made. 
In order to be able to make the first part of the calculation, 
it is essential that the chemical composition of the product of 
the analysis weighed be accurately known, so that its formula 
can be written ; as one way of verifying this formula, the equa- 
tion for the reaction by which the precipitation is made should 
always be written out by the student. Knowing the formula of 
the substance weighed, the amount of the substance sought is 
calculated by stochiometric rules. Make the molecular weight 
of the product of the analysis, or substance found, the first term 
of a proportion; the atomic or the molecular weight of the sub- 
stance sought, according as this substance is elementary or com- 
pound, taken as many times as it occurs in the formula of the 
compound weighed, the second term; the weight of substance 
found, the third term; the fourth term will be the amount of 
substance sought, for the determination of which the analysis 
was made. With this result, and the weight of substance taken 
for analysis, the percentage of the substance determined in the 
substance analyzed is calculated. 
In the larger works on analytical chemistry, Tables are given 
for facilitating this calculation, to which the advanced student 
will usually refer; but the beginner should make it without such 
aid till he is thoroughly familiar with the methods, and can 
understand the principles upon which these Tables are con- 
structed. 
CHAPTER XIV. 
MISCELLANEOUS MATTERS. 
121. The determination of the specific gravity of solutions. 
When a solution contains only one substance, the relation be- 
tween the specific gravity of the solution and the quantity of the 
substance in it can be determined and put in the form of a 
Table; this Table can then be used for ascertaining the per 
cent, of this substance in any solution of it, whose specific 
gravity is known. A number of such Tables are given in the MISCELLANEOUS MATTERS. 
larger text-books on analytical chemistry, as well as in many 
smaller books devoted exclusively to Tables of various kinds. In 
these Tables, the figure in the column under the formula of the 
substance in the solution, against any specific gravity figure, 
gives the number of grams of the chemical substance having 
that formula, in 100 parts of the solution having that specific 
gravity. If the substance column is headed S03, it is the num- 
ber of grams of sulfur trioxid in 100 parts of the solution of 
the acid of the specific gravity found ; if the substance column 
is headed PTSCb, it is the number of grams of this chemical 
compound in 100 parts of the acid of the specific gravity found, 
and so on. 
The approximate determination of the specific gravity of a 
liquid, by means of the areometer. The use of this instrument 
depends upon the principle that a body floating and partly 
immersed in a liquid displaces exactly its own weight of the 
liquid. If the liquid is a solution, and increase of the quantity 
of the substance in the solution makes the liquid specifically 
heavier, the floating body will not sink so deep, and vice versa. 
The graduated scale on the stem of the instrument enables one to 
measure the extent of the immersion ; this scale being so made as 
to indicate the specific gravity corresponding to the extent of 
immersion, we have thus a very quick method of making a deter- 
mination of the specific gravity of a liquid with sufficiently close 
approximation to the truth to answer for many purposes. 
The reading is taken where the stem of the instrument meets 
the surface of the liquid. It is well to learn to read the scale 
before putting the areometer into the liquid. Take the liquid 
at the temperature of about 150 C., in a cylinder longer than the 
areometer, and with an inner diameter of at least about a centi- 
meter greater than the bulb of the instrument. 
122. The accurate determination of the specific gravity of a 
liquid. This determination is made by comparing the actual 
weights of equal volumes of the liquid and of water, at the 
same temperature. Many forms of apparatus are used for this 
purpose. The special points to be looked after are, (1) exact 
equality of volumes of the two liquids weighed, (2) exact 
equality of their temperatures at the time the volumes were 
measured, and (3) absolute security against any loss of these 
measured volumes by evaporation till the weighings are made. 
The specific gravity pipette is a convenient instrument for 
making this determination. In this instrument the volume of 128 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 122. 
liquid to be weighed is that which will fill the space from the 
point a, to the mark con the stem. The weight of this volume 
of distilled water is to be determined first: although 150 C 
is the temperature usually adopted, 20° is nearer 
the ordinary temperature of the room, and is 
therefore more easily maintained during the ma- 
nipulation. 
Drying and weighing the pipette. Remove the 
rubber tube, lay the pipette in the drying closet, 
and when it is hot connect it with the air blast. 
Then weigh it with rubber tube and screw-clamp 
on, the tube being pushed quite down to the 
bulb d and the clamp being close above the end 
of the stem of the pipette. This lube should 
slip easily on the glass tube ; if it does not, wet 
the latter a very little over its whole surface. By 
the platinum wire loop, which goes with the 
pipette, hang it on the left arm of the balance, 
and put a small watch glass on the pan under- 
neath, to protect the pan if any of the liquid 
should drop from the.pipette during the weighing. 
Filling the pipette. With water; fill a large 
beaker with tap water, bring its temperature to 
200, and suspend in this, by means of a copper 
wire triangle over the mouth, your smallest 
beaker, filled with distilled water: as soon as this 
water has taken the temperature of 20° immerse 
the point of the pipette in it, and with the 
clamp s open just enough, and no more, to admit 
of suction through the rubber tube, by means of 
another rubber tube from the tube m to the 
mouth, slowly draw the water up, while seated at the table so 
that the eye is nearly at the same level with the upper part of 
the instrument; as the liquid approaches e fill very slowly, and 
at the instant when this space is full close the clamp, the screw 
of which is all the time held between the thumb and finger of 
the right hand, while the stem of the pipette above the bulb d 
is held by thumb and finger of the other hand. Screw up the 
clamp as long as it yields to the pressure, but not any longer; 
it is easy to break it by screwing unnecessarily tight. Now 
detach the tube m, and with the point of the pipette still in the 
water, grasp the rubber tube by the part that is on the stem MISCELLANEOUS MATTERS. 
between the clamp and the bulb, and carefully raise this tube by 
a somewhat spiral movement, till the liquid is drawn up exactly 
to the mark c; if it is drawn higher the pipette must be 
emptied, dried, weighed and filled again. 
Remove the pipette from the liquid, by a quick movement of 
the finger around the point take off the adhering drop, and then 
by further raising of the rubber tube draw the liquid up a little 
and thus away from the point; now, any slight expansion of the 
liquid while being weighed will not cause any to drop out, and 
also the point can be wiped dry without danger of removing 
any of the liquid. If the clamp was properly closed the con- 
tents of the pipette will remain perfectly stationary. If any of the 
liquid does drop out, before the weighing is completed, or even if 
a drop collects about the point, the pipette must be emptied, dried 
and refilled. Duplicate and closely agreeing results must be 
obtained, both when the pipette is filled with water, and when 
filled with the liquid whose specific gravity is to be determined. 
When the pipette is to be laid aside, slip the rubber tube off, 
and open the clamp. 
This instrument may also be used very conveniently for accur- 
ate weighing of small quantities of a liquid. When thus used 
it must be filled at least up to the stem at e; if only partly filled, 
the liquid is apt to drop out on account of changes in the 
volume of the air in the upper part of the bulb. The size of 
the bulb must therefore correspond to the quantity of liquid to 
be weighed. In emptying the pipette, force out the last drops 
of the liquid by closing the upper end of the rubber tube on the 
stem with the thumb and finger, and then quickly compressing 
the tube just above the stem. 
123. The use of platinum ware. Ignitions are so much more 
easily, quickly, and satisfactorily made in platinum than in porce- 
lain crucibles, that every student intending to make chemistry 
his special work should own his own crucibles, and will be ex- 
pected to procure either these or platinum jackets for the porce- 
lain Gooch crucible. 
Platinum is attacked by free chlorin. Therefore it should 
never be allowed to come in contact with any mixture contain- 
ing free HCI and HN03, or with any salts of these metals under 
such conditions that their acids can be set free, as, for instance, 
in the presence of free H2S04; nor should any other mixture 
that can evolve chlorin be allowed to come in contact with the 
crucible under conditions that make such evolution possible. ELEMENTS OF CHEMICAL ANALYSIS. 
At ignition temperatures platinum should not come in contact 
with any easily fusible metal, or with any mixture of a salt of 
such a metal and a reducing agent. 
After a platinum dish or crucible has been used for an igni- 
tion, the outside should be polished down by rubbing with sea 
sand on the moistened fingers till the surface is bright. If by 
this treatment the surface of the platinum is scratched, the sand 
is not suitable for this use, its grains not being sufficiently 
rounded by attrition. 
124. The quantitative note book. This book is to be provided 
by the student for recording all the notes of the work done in 
the quantitative laboratory. In it are to be made the original 
entries of the results of the qualitative analysis of the substance, 
if such analysis is required ; a brief statement of the method of 
determination followed ; answers to the questions on the method, 
if such are given out; all the figures of the weighings, or the 
volumetric readings ; and the calculations and results. In short, 
it is required, in the author’s laboratory, that a full and orderly 
record of every analysis shall be given in this book, ready 
for inspection at any time. The manner in which it is desired 
that these records shall be entered is illustrated below. 
Before beginning the actual work of the analysis, the written 
questions are to be answered, if any are issued. The student is 
not prepared to make a successful quantitative determination till 
he understands the reason for every step in the work and every 
precaution mentioned ; hence this requirement. When, as in 
more advanced work, questions are not given, he should still 
study the directions no less carefully, and work out the equation 
for every unfamiliar reaction. 
The beginner in this work will find the needed information 
for the answers to the questions under the description of each 
determination, or in Part II on qualitative analysis. The more 
advanced students will need to consult the larger works in the 
chemical library, such as those of Fresenius. In his quantita- 
tive analysis, that author describes the properties of the products 
of the determinations under the running title “ Forms ; ” the 
manner of making the determinations under the title “ Deter- 
mination and under the title “ Separation,” the special 
methods of separating the substances from one another, when 
present together in a mixture or compound, preparatory to their 
determination. Answers to questions or inquiries, not indicated 
under any of these heads, must be sought for in other works of 
reference in the library. MISCELLANEOUS MATTERS. 
This note book is the property of the student. If neatly and 
honestly kept, and for the time given to the practice showing a 
large amount of work, with good results and few errors, and full, 
intelligent and carefully written notes and references on the 
work, it may be more useful than any letter of recommendation, 
by the evidence it gives of the actual quantity, kind, and quality 
of the work accomplished as a student. 
125. Sample pages of records of a gravimetric determination. 
Substance No. xo (magnesium carbonate). 
Received March 15th, 1890. 
Found: 
Qualitative Analysis (if called for). 
Mg. 
Co2. 
Quantitative Analysis. 
Determination of Mg : 
Method: 
(Give here all references consulted.) 
Answers to questions (if called for, or suggested by the work). 
I. 
2. Etc. 
Mg; Det. 1. 
Det. 2. 
Vial + s, 5-6643 
Less s, 4-8231 
Subst. 
.8412 
Cr ppt. 16.8794 
Cr. 16.2486 
Ppt. .6308 
Less ash, .0006 
.6302 
Calculation of results 
Det. 1. 
Mg2P207 : 2Mg = .6302 ; x 
222.6 : 48.6 = .6302 : x 
Det. 2. 
x x too 
= Per cent. Mg. 
.8412 
(Work the above calculations out by logarithms, putting all 
the figures down here.) 132 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 126. 
A volumetric determination; iron by dichromate. 
The record should be about as follows, with such modifications 
as may be necessary in individual cases. 
Give first all the preliminary matter as indicated at the head 
of the preceding page. 
Det. i. 
Vial + s, 6.7304 
“ less s, 5.8613 
Det. 2. 
Subst., .86gi 
St. sol. required, 15.6 c.c. 
1 c.c. = 0.01713 gm. Fe. 
15.6 X 0.01713 x 100 
= per cent. Fe. 
(Work this out by logarithms, giving all the figures here.) 
If two or more constituents of a substance are determined, 
making a complete analysis, sum up the work as follows:— 
Summary of results on feldspar. 
I. 11. 111. 
AIA 64.13 64.25 
K2O 18.40 18.21 18.56 
Si02 16.91 16,80 
99.44 99.26 
126. Miscellaneous maxims. The best economy of time is 
secured by doing the work as carefully as possible, from first to 
last. All analytical processes are affected more or less by condi- 
tions beyond control, none of them being absolutely perfect. 
The> strict observance of all known rules and precautions is there- 
fore the more essential for the best success in the work. The student 
who values his time cannot afford to disregard a single one of 
the general directions and precautions for the management of 
his work, given in the preceding pages, or of the special direc- 
tions and precautions given in the description of each determina- 
tion, Repetition of work made necessary by poor results hastily 
obtained consumes more time than is required to do the work 
carefully in the first instance, and, moreover, makes the record 
poor. 
Be always on the watch to exclude from the work in hand, 
in all its stages, the accidental addition to it of any substance, 
solid or in solution, that does not belong there, or the loss of 
any of the substance to be weighed or measured. MISCELLANEOUS MATTERS. 
Make duplicates of every determination, and further repetitions 
if results do not agree on the first two. A single determination 
is of little value till confirmed by another giving practically the 
same result. In the case of every analysis undertaken, the 
student should consider that he is to learn for himself, as 
correctly as he can, what the actual proportion is in the 
substance of the constituent that he is called upon to determine, 
or the actual composition of the substance as a whole if that is 
required, before making any report. This knowledge he has 
not gained if the results that he has obtained are discordant. 
Many students make the mistake in this matter of supposing 
that if the first two determinations do not agree sufficiently well, 
another two must be made, and then perhaps even another two. 
An analytical method is worth little if only by carrying through 
two analyses simultaneously, concordant results can be obtained. 
The right course is this; the first two determinations do not 
agree; if the work has been done with reasonable care one of 
them is probably correct; make one more determination to 
ascertain which one of the first two is correct. But if the first 
two results and this third are all widely apart and otherwise 
incorrect, it is fair to presume that the student is working 
carelessly, and that he must reform his ways of working in 
general, paying more scrupulous attention to the general direc- 
tions for quantitative work in Part 111 of the text-book, or to the 
special directions given for each determination. After reading 
this matter over again, carefully, he may as well begin anew on 
the analysis that has made him so much trouble. 
Be orderly, and scrupulously clean. There is no excuse what- 
ever for slovenliness and disorder in respect to apparatus or 
work-table. Better work can surely be done under a neat and 
orderly system than otherwise. 
Avoid use of unnecessarily large quantities of reagents. Avoid 
the use of unnecessarily large beakers or flasks; when precipi- 
tates are to be filtered from them, the larger the vessel the 
larger the surface to be washed in transferring the precipitates to 
the filter. 
Be sure that your solution is of about the right degree of con- 
centration before beginning any operation with it; it may be 
too late after reagents are added. 
Without careful planning of the work, very much time is 
easily spent in accomplishing but little. In estimating the 
capacity of a student in the laboratory, account must be taken 134 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 126. 
of the amount of work done, as well as of its quality. Celerity 
is important, as well as accuracy, in all kinds of laboratory 
practice. Always keep as many determinations in progress as you 
can without confusion, so that you will be busily occupied with 
some manipulation or study in connection with your work, 
either that in hand or that to come, during all your laboratory 
time. A slow filtration will not go on any more rapidly for 
your watching it. Ignite and weigh your crucibles in any 
moments of leisure; then, kept in the desiccators, they will be 
ready for use just when wanted, and you will not be obliged to wait 
for your turn at the balance before you can go on with the work 
at your own table. PART IV. 
EXAMPLES FOR PRACTICE IN QUANTITATIVE 
ANALYSIS. 
CHAPTER XV 
THE DETERMINATION OF IRON AND OF SULFUR 
TRIOXID. 
127. The determination of iron. 
The gravimetric method. In the gravimetric determination of 
iron, it is nearly always weighed as ferric oxid, after precipita- 
tion as ferric hydroxid. 
Iron may be precipitated from its solutions as ferrous or as 
ferric hydroxid, according to its state of oxidation in the solu- 
tion precipitated. Ferrous compounds in solution, or in the 
solid form and freshly precipitated, tend to pass rapidly into 
ferric compounds on exposure to the air; solutions of the 
chlorid oxidize more rapidly than those of the sulfate. The 
ferric compounds are much more stable than the ferrous com- 
pounds, and they are therefore better adapted for quantitative 
precipitation. 
Ferric hydroxid, Fe(OH)3, is insoluble in water and in dilute 
solutions of alkaline hydroxids or of ammonium salts, easily 
soluble in acids. If precipitated with the alkaline hydroxid, 
not in excess, a basic salt (§ 17) is obtained; if, on the other 
hand, the alkali is in excess, some of it adheres to the pre- 
cipitate with great tenacity, and is difficult to remove unless 
volatile. 
On ignition the hydroxid is converted to oxid ; if only super- 
ficially dried before the ignition, there may be loss of particles 
of the substance thrown out of the crucible by the sudden forma- 
tion of steam from the inclosed moisture. 
Ferric chlorid, volatile at the temperature of the ignition, can 
135 136 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ I2§- 
be formed by reaction between ferric hydroxid and ammonium 
chlorid. 
Ignited ferric oxid is not easily soluble in acids. 
The operation. To the solution, not less than about 200 c. c. 
in volume, better in a porcelain dish than in a beaker, add 
in small excess, heat almost to boiling, let settle, decant into 
the filter, add boiling water, and stir well; let settle and decant 
again ; wash in this way two or three times, then transfer the 
whole of the precipitate to the filter, and wash with hot 
water. Dry it thoroughly before ignition. 
Give the results as Fe. 
128. The volumetric method. The ready passage of iron from 
one state of oxidation or chlorination to the other, and the 
delicate qualitative tests that can be used to show when this con- 
version is complete, combine to provide several very satisfactory 
volumetric methods for the determination of this element. The 
permanganate method and the dichromate method are more 
commonly used; in both of these the iron is first completely 
transformed by reducing agents into the ferrous condition, and 
it is then ascertained how much of a standard solution of the 
oxidizing agent is required to convert it to the ferric condition. 
If permanganate is used, the highly colored oxidizing agent 
itself is its own indicator, a single drop of it perceptibly color- 
ing a large quantity of solution, while the products of its decom- 
position when reduced and held in solution are nearly colorless. 
The only objection to this method is its unreliability in solu- 
tions containing HCI; a reaction takes place between the HCI 
and the KMn04, by which chlorin is set free, the manganese 
compound being changed to manganous chlorid; although chlorin 
should ordinarily chlorinate ferrous salt to the ferric condition, 
it will not readily in so dilute a solution of the iron salt as must 
be used in this process. 
Since HCI is a much more convenient solvent of iron ores 
than H2S04, the dichromate method, in which the presence of 
even a large excess of this acid does no harm, is the better one 
for general purposes. 
In this method the reducing agent used to convert all the iron 
to the ferrous condition, before the treatment with oxidizing 
solution, is stannous chlorid; the excess of it is removed by 
mercuric chlorid, the presence of a moderate quantity of which 
in the solution does not affect the result. The chromic acid is 
converted in this operation to chromic chlorid. The indicator used is potassium ferricyanid. This may some- 
times contain ferrocyanid, which can be changed to the ferri- 
cyanid by treatment of the solution with chlorin, the excess 
of which must be removed by boiling. 
IRON AND SULFUR TRIOXID. 
The preparatio7i of the standard solution. To 5 grams of pure 
K2Cr207, approximately weighed on the reagent-shelf scales, add 
about 500 c.c. of water in a beaker, and heat the mixture on the 
hot plate till solution is complete; cool the solution, transfer it 
to a one-liter glass-stoppered bottle, fill the bottle up to the 
shoulder, and mix the contents thoroughly. 
Weigh out two portions of about 150 mgms. of clean piano 
wire, whose contents of pure iron should be determined if not 
known (ordinarily very nearly 99.6 per cent.), dissolve the wire in 
small, covered beakers, in about 40 c.c. of HCI with the aid of 
a gentle heat; to the hot solution add a little SnCl2 dropwise and 
with constant stirring, till the yellow color that may have been 
present at first is entirely removed, and with care to add only a 
small excess; dilute to about 150 c.c., cool quickly, add at once 
HgCl2, of which about 20 c.c. will usually suffice ; the precipitate 
should be white; next proceed without delay with the addition 
of the K2Cr207 from a burette, till no reaction appears with the 
K3FeCy6 after the test drops have been in contact for half a 
minute. 
Time will be saved, and some useful practice gained in 
stochiometrical calculation, by figuring out in advance the 
probable quantity of the standard solution that will be required, 
and then running the solution in at once up to within 5 c.c. of 
this amount, with constant and rapid stirring, before making any 
tests. When first beginning to make the tests, from 0.5 to 1 c.c. 
of the standard solution can be added between them; but as the 
end is approached the quantit}' should be diminished till, close to 
the end. it should be only a tenth of a cubic centimeter at once. 
At this part of the operation, also, when the proportion of ferrous 
iron in the solution has become very small, somewhat larger 
drops of it should be taken out for the tests. 
To make these tests conveniently, put some of the solution of 
K3FeCy6 in a test tube, and set this tube in a small beaker of 
ivater; put a drop of the solution under analysis on a porcelain 
plate, by means of the stirring rod, and with a dropping tube 
bring a small drop of the indicator in contact with it; put the 
dropping tube in the water in the beaker, thereby rinsing it for 
the next test. In order that the progress of the reaction can be r§ 129-130. 
138 
ELEMENTS OF CHEMICAL ANALYSIS. 
followed, toward the end of the operation, in the gradual weak- 
ening of the color in the tests, drops as nearly alike in size as 
practicable should be taken for all tests, except at the close as 
above noted, from both solutions ; and, in order that the 
strength of the solution of the indicator in all the drops shall 
be about the same, the water should be blown out of the drop- 
ping tube each time before taking up a fresh portion of this 
reagent. 
When the operation is completed with both solutions of the 
iron, calculate the value of 100 c. c. of the solution in Fe as a 
factor for permanent use. Two determinations of this factor 
should agree within 2 mgms., if the work has been carefully 
done. 
For every determination of iron in a substance make the solu- 
tion acid with 40 c. c. of HCI, and dilute it afterward as in 
this operation of standardizing the solution. If it is a ferric 
compound that is analyzed, more SnCl2will of course be re- 
quired than in the treatment of the above solution of the iron 
wire. 
129. Assay of limonite. Supposing the ore to have been pre- 
viously ignited to remove organic matter, which must not be in 
the solution, proceed as follows : 
To a weighed portion of about 3 grams add 100 c. c. of HCI, 
and boil gently in a covered beaker, in the fume closet, till the 
residue is entirely changed to a gray sand. Rinse the cover into 
the beaker, and make the volume of the solution up to 250 c. c. 
in a measuring flask (§ in). Measure out three portions of 25 
c. c. each into beakers, add to each about 10 c. c. of HCI, and 
proceed in the same manner as in the standardization of the 
dichromate, beginning with the addition of the SnCl2; use the 
first determination only as an approximate one, adding a cubic 
centimeter of the dichroraate between each test. Proceed in the 
same manner with another weighed portion of the limonite. 
Report the result in Fe, giving the average of the last two 
determinations on each weighed portion. 
130. The deter)7iination of sulfur trioxid. Sulfur trioxid in 
salts is always determined by precipitation as barium sulfate. 
One part of this salt requires 400,000 parts of water to dissolve 
it ; it is appreciably more soluble in acids, even if dilate, and 
its solubility increases with the strength of the acid. Alkaline 
nitrates in the solution hinder its complete precipitation. 
The precipitate is very fine, and often causes trouble by pass- ACIDIMETRY AND ALKALIMETRY. 
ing through the filter, especially if made in a cold solution and 
filtered at once ; a clear filtrate is more easily obtained if HCI 
or NH4CI is present in the solution. The precipitate readily 
carries down with it other substances present in the solution, 
especially nitrates, and it is almost impossible to remove some 
of these foreign matters, even with hot water or dilute acids ; if 
nitrates are present they must first be converted into chlorids by 
repeated evaporation of the solution to dryness with HCI. 
Barium sulfate can be ignited to redness without change, but 
if the heat is carried up to whiteness, it loses S03. At a red 
heat in the presence of reducing substances it passes readily into 
the sulfid. 
The operation. To the well diluted solution, acidified with 
HCI and heated nearly to boiling, add a hot solution of BiC12 
slowly and with constant stirring, as long as a precipitate is 
formed, and with some care to avoid any large excess of the 
reagent; let the liquid stand, still kept hot but not boiling, till 
the precipitate has nearly settled, decant the supernatant liquid 
into the filter, pour about 100 c. c. of boiling water over the 
precipitate, let settle and decant again, and repeat till the wash- 
ings give no notable reaction for chlorids; then transfer the 
whole of the precipitate to the filter, complete the washing, and 
dry and ignite in the usual manner, after careful separation of 
the precipitate from the filter. When the ignition is completed 
and the crucible cooled, moisten the contents very slightly with 
H2S04, dry over a very low flame, and then ignite gently. Give 
the result as S03. 
CHAPTER XVI. 
ACIDIMETRY AND ALKALIMETRY. 
131. This kind of analysis, as the names imply, is the deter- 
mination of an acid or an alkaline substance, and as commonly 
understood it refers to their determination by volumetric methods. 
It can be directly applied to acids only when in the free state and 
soluble in water, and only indirectly to their determination in 
salts. Bases can be determined by the alkalimetric methods, 
when free, and also when in the form of carbonates. 
The method consists simply in the addition of a standard solu- [§ 131- 
140 
ELEMENTS OF CHEMICAL ANALYSIS. 
tion of a base to the solution containing the acid to be deter- 
mined, or in the addition of a standard solution of an acid to 
the solution of the base to be determined, till the point of neu- 
trality is reached ; or the addition of a standard acid in excess 
to the carbonate, and, when the salt is completely decomposed, 
determining by means of the standard solution of the base how 
much acid was used in excess; this subtracted from the total 
quantity of acid used gives the quantity required to form a neu- 
tral salt of the basigenic constituent of the carbonate. 
Any base or acid soluble in water can be used for standard 
solution. The most convenient solutions for general use are 
an solution of ammonia, and an ■— solution of hydrochloric 
acid. The presence of carbonic acid, dissolved in the liquid in 
which an alkalimetric or acidimetric determination is made, is 
usually objectionable, because it may interfere with the distinct- 
ness of the color reaction of the indicator used to show when the 
neutral point is reached. Potassium and sodium hydroxids 
absorb carbon dioxid from the air much more readily than am- 
monium hydroxid does; furthermore, they act more rapidly on 
the glass of the bottles or the burettes. A fifth normal solution 
of HCI can be heated up to boiling without loss of strength; 
even a tenth normal solution of NH3 cannot be heated without 
escape of ammonia; but as there is never any occasion in this 
work to heat a solution containing an excess of standard am- 
monia, this is no objection to its use. 
The indicators most employed are litmus, cochineal, and 
methyl orange ; as the preparation of a really serviceable solution 
of litmus is difficult, it is used mostly in cases where the others 
do not give a sharp reaction, as in the titration of organic acids. 
Although the calculation of an acidimetric or alkalimetric de- 
termination is somewhat easier if the solutions are exactly one- 
tenth and one-fifth normal, when but small quantities are 
required, as for this practice, it is not advisable to take the time 
for their preparation; it is more convenient to make solutions 
approximating closely to the desired strength, by the aid of areo- 
metric specific gravity determinations, and Tables, and then to 
determine their exact strength by other means. 
If, however, it is desired to make a solution whose strength is 
exactly equal to that of a normal solution, or to some aliquot 
part of such strength, proceed as follows. Prepare the first, 
approximately correct solution in such a way that it shall surely 
be somewhat too strong. Determine its exact strength in § i32-] 
ACIDIMETRY AND ALKALIMETRY. 
141 
accordance with the special directions given; calculate the 
quantity of the active constituent of the reagent in 1000 c. c. 
of this solution ; calculate the number of cubic centimeters of 
this solution, which really contains that quantity of the active 
constituent of the reagent, required to make 1000 c. c. of solu- 
tion of the correct strength; then 1000 minus this volume gives 
the quantity of water that must be added to this quantity of 
the solution to make xooo c. c. of a solution of the correct 
strength. 
For example; it is desired to make an exactly -2- solution of 
silver nitrate, silver being the active constituent. The first solu- 
tion is prepared as directed above, and when its strength is 
determined it is found to contain 22.5 grams of silver per 1000 
c.c., 21.58 grams being the correct quantity ; the solution is too 
strong. Then 
22.5 : 1000 : : 21.58 : 951.1. 
1000 951.1 = 48.9. 
Therefore, on adding to 951.1 c.c. of the solution, which 
quantity contains the right quantity of silver for 1000 c.c. of 
an f solution of the nitrate, 48.9 c.c. of water, we shall have 
1000 c.c. of an ± solution of the reagent. 
Since of these two solutions above mentioned, for alkalimetry 
and acidimetry, the hydrochloric acid is the more stable one, 
more care is usually given to the determination of its absolute 
strength than of the ammonia: the strength of the latter can 
be verified from time to time by comparison with the acid. 
132. Preparation of the standard solutions. With the aid of 
the areometer (§ 121), and the specific gravity Tables in 
Part V, determine the strength of the shelf NH4OH, and the 
HCI of the laboratory. Then prepare a liter of an approxi- 
mately one-tenth normal solution of ammonia by measuring 
out the proper quantity of the reagent with the graduated 
cylinder into a one-liter measuring flask, filling the flask up to 
the mark with water, and mixing thoroughly by repeated inver- 
sion of the flask. Transfer this solution to a liter glass stoppered 
bottle; the bottle should be rinsed out with distilled water but 
not necessarily dried before using it. In like manner prepare 
a liter of an approximately one-fifth normal solution of hydro- 
chloric acid. 
The determination of the relative strength of the acid and the 
alkali7ie solutions. Fill one burette with one solution and 
another burette with the other; run 10 c. c. of the acid into a 142 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 133- 
small beaker, add enough of the indicator (about 0.5 to 1 c. c. 
of cochineal or litmus, or three or four drops of the methyl 
orange) to give a decided color to the solution, put the beaker 
on a large sheet of white paper in a good light, and run in 
ammonia with constant stirring, till the proper change of color 
appears, produced by, at the most, two or three drops of the 
solution ; if it is feared that too much may have been added, 
0.1 to 0.2 c. c. of acid maybe run in to restore the original 
color; then add ammonia again. By repeating this operation, 
several times back and forth, the point of neutralization can be 
very acccurately determined. If sharp results are not obtained 
with one indicator, try another. Note the total quantities of acid 
and ammonia used, and repeat the operation with 25 c. c. por- 
tions of acid till closely agreeing results are obtained. Finally, 
calculate the quantity of acid required to neutralize one cubic cen- 
timeter of ammonia solution and the quantity of ammonia 
solution required to neutralize one cubic centimeter of the acid 
solution. If all the preliminary measurements and the rest of 
the work have been carefully performed, the acid should prove 
to be very nearly twice as strong as the ammonia. 
133. The determination of the absolute strength of the solution 
of acid. This determination is made by precipitation with silver 
nitrate, and weighing the chlorid obtained. 
The precipitate of AgCl is white, and mainly flaky, while a 
part of it remains quite persistently in a finely divided form that 
passes easily through the filter; but on vigorously shaking or 
stirring the liquid containing the precipitate, the fine portion 
becomes attached to the flocculent part, and the liquid clears 
more readily on standing, especially if it is hot and contains 
AgN03, in excess, instead of HCI. It is very insoluble in 
water and in HN03, soluble in traces in HNOs, more soluble in 
HCI; it is appreciably soluble in solutions of other chlo- 
rids, and of nitrates, including silver nitrate; much excess of 
this last mentioned reagent should therefore be avoided in the 
precipitation. 
On exposure to sunlight, and especially the direct rays, it 
turns violet, losing chlorin, and forming Ag2CI; the change is 
superficial, but it may affect the weight of the product if 
allowed to go too far. When gently ignited it fuses to a yellow- 
ish liquid, without decomposition. 
The operation. Procure a 130-150 c. c. Erlenmeyer flask, a 
good cork that when properly softened fits tightly in its mouth, § *33-] 
ACIDIMETRY AND ALKALIMETRY. 
143 
and a small piece of black cloth to protect the precipitate from 
the light. To 25 c. c. of the standard solution in this flask, add 
about xc. c. of HN03, 75 c. c. of water, and then AgN03, 
slowly and with constant agitation of the solution by moving 
the flask gently in a small circle, while resting on the table, till 
the reagent is in slight excess. 
Since it is very necessary that this excess of the reagent should 
be present, and the reaction be completed before the precipitate 
is collected together in the manner described below, time will 
be saved by making a preliminary calculation of the quantity of 
silver nitrate required ; see §ll4. This is easily done, since the 
strength of the standard solution is very nearly known, and that 
of the reagent is given in § 147. The precipitate settles so 
slowly that it is very difficult to determine in the usual manner 
when enough of the precipitant has been added. 
Cork the flask, wrap it in the black cloth and shake the con- 
tents vigorously for about five minutes; by this operation the 
precipitate is flocculated, and it will settle very quickly, leaving 
a supernatant liquid that must be entirely free from turbidity; 
if it is not, the shaking must be repeated. The filtration should 
not be attempted till a perfectly clear supernatant liquid is 
obtained. 
When all is ready for the filtration, by a quick movement of 
the flask while held in the hand, throw some of the clear liquid 
up against the cork, and repeat this till the particles of the pre- 
cipitate adhering to the cork and the neck of the flask are com- 
pletely rinsed down; transfer the precipitate at once to the care- 
fully prepared and rather thick Gooch filter; the mass on the 
filter becomes very compact and somewhat fissured; stir and 
break it up fine, with the rod, with care not to penetrate so far 
as to disturb the asbestos, and wash with cold water containing 
about one hundredth of its volume of HNOs, till fifteen or 
twenty cubic centimeters of the washings give no turbidity with 
two or three drops of HCI. If during the washing the wash- 
water becomes turbid, it must of course be passed through the 
filter again ; it is well to empty the filtering flask frequently, as 
mentioned in § 115, so that at no time will it be necessary to 
filter again more than a small quantity of liquid. If any fissures 
appear in the mass on the filter during the washing, close them 
in the same manner as at first. 
Dry the precipitate for two or three hours at no°-i2o° ; then 
ignite it, at first very gently for a few minutes, with crucible [§ 133- 
144 
covered, and then more strongly till it just begins to fuse. This 
last part of the operation should be performed with the crucible 
uncovered, so that its progress can be closely watched ; the cru- 
cible should be laid as far over on its side as possible, and the 
lamp, with a high flame turned on, should be moved in and out 
under the side of the crucible till fusion begins, not only in de- 
tached portions of the chlorid in that part of the crucible directly 
exposed to the flame, but also on the edges of the main mass of 
the substance on the asbestos. 
ELEMENTS OF CHEMICAL ANALYSIS. 
A better way is to hold the crucible by the tongs, in a still 
more nearly horizontal position, and by a motion of the hand 
and arm turn it over and back, so that it will be heated on dif- 
ferent sides while holding it in the flame; thus danger of over- 
heating any portion of the chlorid is more easily avoided. When 
the crucible is thus heated on its sides and only when in a hori- 
zontal position, or nearly so, and the flame is not at any time 
allowed to impinge directly against the bottom, the fused chlorid 
will not run through or around the asbestos to the platinum 
disk. 
Repeat the operation with other portions of the acid till con- 
cordant results are obtained. The fused silver chlorid can be 
loosened from the asbestos and the disk of platinum by digestion 
with HCI while in contact with pieces of zinc. 
Now calculate the mgms. of HCI in one cubic centimeter of 
the standard acid : and, knowing the exact relation between this 
acid and the standard ammonia, calculate the absolute strength 
of this alkaline solution, or the number of milligrams in one 
cubic centimeter. Next, for practice, calculate the value of 
one cubic centimeter of the acid in sodium carbonate, potas- 
sium carbonate and calcium carbonate, and the value of one 
cubic centimeter of the ammonia solution in sulfur trioxid 
and nitrogen pentoxid. It now remains to test the accuracy 
of this work in the preparation of these standard solutions, by 
the analysis of test substances. 
If the substance is a carbonate, add water, which will 
dissolve it if an alkaline carbonate; add the indicator, and 
then standard acid very slowly and with constant stirring, till 
plainly in excess, with the substance itself entirely dissolved. 
If it is a carbonate insoluble in water, this solution in the acid 
will take place rather slowly, especially towards the end, unless 
a large excess of acid is used, which is unadvisable. 
Before titration back with ammonia in the case of a carbon- LEAD, PHOSPHORUS PENTOXID AND CALCIUM. 
ate, the solution should be heated just to boiling, in a covered 
beaker, and kept boiling gently for about five minutes. The 
cover and sides of the beaker are then rinsed down with water, 
and the liquid cooled. 
In all this work be careful not to dilute the solution of the 
substance to be determined, too much ; the volume should not 
exceed 100 c. c. when the liquid is ready for the titration, and 
should be within 75 c.c. if practicable. 
CHAPTER XVII. 
THE DETERMINATION OF LEAD, PHOSPHORUS PENTOXID 
AND CALCIUM. lODOMETRY. DETERMINATION OF 
ANTIMONY. 
134. The determination of lead. Lead is most conveniently 
determined as lead sulfate. This salt is nearly insoluble in 
water, more insoluble in water containing sulfuric acid, much 
more soluble in H.2S04 and HNOs, and in water containing 
ammonium salts in solution, especially the nitrate, acetate or 
tartrate ;it is insoluble in alcohol. Ignited, at a red heat it is 
unchanged, but at a white heat gives off S03; it is easily reduced 
at ignition temperatures in contact with incompletely burned 
combustion products, the metal separating out; the filter upon 
which it has been collected cannot, therefore, be wrapped in 
platinum wire for the ignition (§ 123). 
The operation. To the solution, which should not be concen- 
trated, add H2S04 in slight excess ; if nitric acid or a nitrate is 
possibly present, evaporate the solution down nearly to dryness 
on the water-bath, leaving the beaker uncovered; when taken 
from the bath, the liquid should not give any odor of nitric acid. 
If hydrochloric acid or a chlorid is possibly present, the solution 
must receive the same treatment. These obstacles to complete 
precipitation of the lead as sulfate being removed, add about 50 
c.c. of water to the residue in the beaker, and after stirring well 
add about 100 c.c. of alcohol; let the mixture stand for a few 
hours, filter, wash with alcohol, and dry. Transfer as much of 
the precipitate as possible from the filter to a crucible, in the 
usual manner and ignite gently. Fold the filter up and burn it 
directly in another crucible, heating at first very gently with the 
xo 146 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ x 35- 
cover partly on, and complete the ignition in the usual manner ; 
when the crucible is cool moisten its contents with HN03, 
evaporate to dryness at a gentle heat, moisten the residue with 
H2S04, dry and ignite gently. Add the two weights of substance 
obtained and calculate the result as Pb. 
For a somewhat shorter method, requiring but one weighing of 
substance, and much more careful manipulation, but permissible 
only where there are no currents of air, see Fresenius, § 52. 
135. The determination of phosphorus pentoxid. Phosphorus 
pentoxid is nearly always weighed as magnesium pyrophosphate, 
Mg2P207, after precipitation as magnesium-ammonium phosphate, 
MgNH.tPO4.6H2O. This salt forms a white, crystalline powder, 
slightly soluble in water, easily soluble in acids, less soluble in 
water containing ammonia, less insoluble if ammonium chlorid 
is also present, easily soluble in acids. Excess of magnesium 
sulfate increases the insolubility in ammoniated water, but unless 
much ammonium chlorid is present, magnesium hydroxid, or a 
basic magnesium sulfate is liable to be precipitated also; excess 
of sodium phosphate diminishes the solubility of the precipitate. 
Heated to ioo° the water of crystallization escapes, and on 
ignition, the ammonia also; too rapid heating, producing a 
sudden evolution of the ammonia, may cause a loss of sub- 
stance mechanically. The pyrophosphate is white or grayish, 
often quite dark in color, unchanged at a white heat, easily 
soluble in acids. 
The operation. To the solution containing in 75 c. c. about 
500 mgms. of phosphorus pentoxid, as nearly as can be esti- 
mated from previous knowledge of the composition of the sub- 
stance to be analyzed, add about 5 c. c. of ammonia, or till in 
excess, and then with constant stirring and care not to touch 
the side of the beaker with the rod, add the magnesia mixture 
drop by drop, most conveniently from a burette, at the rate of 
about a drop per second ; 20 c. c. of the reagent will usually be 
sufficient, if the quantity of the substance present has not been 
underestimated. Let the mixture stand three or four hours before 
filtering. Filter and use water containing one-fourth its volume 
of ammonia for cleaning the beaker and washing the precipitate ; 
wash till the chlorin reaction disappears, or is at least no stronger 
than is given by a few drops of the washing solution added to 
half a cubic centimeter of silver nitrate acidified with HNOs. 
It is often necessary to complete the ignition over the blast- 
lamp, if a nearly white residue cannot be obtained by the LEAD, PHOSPHORUS PENTOXID AND CALCIUM. 
ordinary treatment; after one ignition over a Bunsen lamp, if 
the product is not white or nearly so, moisten it with a drop of 
HN03, and dry very carefully over a low flame, then ignite 
strongly over the blast-lamp and weigh ; if the residue is still 
not nearly white, repeat the treatment with HNOa and the igni- 
tion, and weigh again; if the loss in weight is null, or insignifi- 
cant, do not carry the operation any further, but report the result 
obtained, with a statement of the condition of the precipitate. 
Give results as P205. 
136. The determination of calcium. For the determination of 
calcium it is usually precipitated as the oxalate; with this pre- 
cipitate four courses may be taken. It may be dried at ioo° till 
the weight is constant, the product then having the composition 
given below; it may be ignited very carefully and weighed as 
carbonate, or ignited very strongly and weighed as oxid; its 
complete conversion into carbonate without carrying a little of 
it on to the oxid is somewhat difficult; and it is even more 
difficult to convert a large quantity of the oxalate completely 
into oxid. 
Therefore another course, which is open to none of these 
objections is described here, namely, the volumetric method, 
with potassium permanganate ; this reagent causes the conversion 
of all the oxalic anhydrid into carbon dioxid, as the result of a 
process of oxidation in the mixture in which the reaction is made 
to take place. 
Calcium oxalate, CaC204.2H20, forms a white, very fine, 
crystalline precipitate, insoluble in water, and in solutions of 
alkaline chlorids, easily soluble in mineral acids; ignited, it 
passes into the carbonate at a moderate heat, and into the oxid 
at a high heat. 
The precipitation. To the hot solution, of about the average 
degree of dilution,.and containing, as near as may be estimated 
from previous knowledge of the composition of the substance to be 
analyzed, about 100 mgms. of calcium, add ammonia till in 
moderate excess, and (NH4)2C204 with constant stirring, till no 
further precipitation takes place, and let the mixture stand for 
several hours in a warm place. 
Decant the clear liquid into a weighed Gooch filter, with as 
little disturbance of the precipitate as possible, wash several times 
with hot water by decantation, and finally transfer the precipitate 
itself to the filter; wash the precipitate till no further reaction is 
obtained for oxalic acid in a test with 5 c. c. of the washings. [§ 137- 
148 
Unless a very carefully prepared filter is used, and all these 
directions are followed, there may be difficulty in getting a clear 
filtrate. 
ELEMENTS OF CHEMICAL ANALYSIS. 
Dry the crucible and contents to constant weight, at ioo° 
C., and calculate the result as Ca. 
137. Volumetric determination of the calcium in this precipitate. 
Make an approximately solution of KMn04 (see § 108), 
and standardize it by means of ferrous oxide in the form of 
ammonium ferrous sulfate, FeS04. (NH4)2 S04 -p 6H20, taking 
carefully weighed portions of about 1 gram each. Dissolve 
the salt in about 200 c. c. of water, add at once about 10 c. c. 
of H2S04, and, with the beaker on a white tile or plate, add the 
permanganate from a glass-stoppered burette, dropwise, and with 
constant stirring. At first the color of each drop disappears 
immediately, and then more and more slowly; towards the end 
of the operation, add the drops very slowly, with stirring between 
each, till the color disappears; the end point is reached as soon 
as the last drop added gives to the whole of the solution an 
unmistakable faint reddish tinge. This color may be permanent 
only for a very few moments, but nevertheless the ferrous iron is 
completely oxidized, and the reaction is completed. Repeat 
till closely agreeing results are obtained. 
The equation is given in the section above referred to, for the 
reaction between the ferrous oxid and permanganate. In the 
actual operation, the ferrous oxid is present in the form of sul- 
fate, and in the presence of the FT2S04 added we have sulfates in 
the right-hand member of the equation instead of oxids; but 
this does not affect the process of oxidation in any other way 
than to facilitate it. The equation shows that ten atoms of Fe 
in the form of ferrous salt are converted into ferric salt by the 
oxygen yielded by two molecules of KMn04. 
From the formula of the ferrous salt used, calculate the 
quantity of Fe in the weight of salt taken, and then from the 
results of the titration calculate the exact strength of the KMn04 
solution. Then calculate the value of one cubic centimeter of 
this solution in CaC204; for the equation for this reaction 
between the KMn04 and CaC204, take five molecules of the 
oxalate and two of the permanganate, with the necessary 
quantity of H2S04; the products of the reaction are calcium 
sulfate, manganese sulfate, potassium sulfate, carbon dioxid and 
water; then calculate the quantity of calcium in this quantity of 
calcium oxalate, and thus obtain the value of 1 c.c. of the § 138-] 
lODOMETRY. 
149 
permanganate in calcium. Or the value of the permanganate in 
Ca can be calculated directly, without first calculating its value 
in calcium oxalate. 
Now determine the quantity of calcium oxalate in the pre- 
cipitate obtained and weighed above, by the same kind of an 
operation as that performed in standardizing the permanganate ; 
to this end, transfer the precipitate with the asbestos to a beaker, 
add about 100 c.c, of water, and 50 c.c. of H2S04, warm to 
about 6o°, and then titrate with permanganate. 
Give the result in Ca. 
138. lodometry. 
This method of volumetric analysis depends upon the action 
of iodin as an indirect oxidizing agent. In the presence of 
water hydriodic acid is formed, while oxygen in its nascent state 
acts on any oxidizable substances present. 
H2S03 (sulfurous acid) -j- I 2 -f- H2G = H2S04 -(- 2HI 
KgAs03 (potassium arsenite) -j- I 2 -f- HzO = KaAs04 -f- 2HI 
If the substance combined with the hydrogen is not readily 
oxidized it may be set free. 
H2s +I2 = 2HI + S 
lodin may be set free in a solution of potassium iodid by a 
substance capable of displacing it from its combination with the 
metal. 
KI + Cl = KCI + I 
The extreme delicacy of the reaction of free iodin with starch, 
and the sharpness of its reaction with thiosulfate, give the means 
for measuring the quantity of free iodin in a solution with excep- 
tional accuracy. 
The reaction with sodium thiosulfate is as follows : 
2Na2S2Os -J- I 2 = Na2S4Os (sodium tetrathionate) -)- aNal. 
The preparation of the solutions. 
lodin in potassium iodid. For 500 c.c. of an solution dis- 
solve about 12 gms. of potassium iodid in about 200 c.c. of 
water; weigh out about 6 gms. of powdered iodin in a covered 
watch glass, and at once put it into a glass-stoppered measuring 
flask, rinsing the glass into the flask with some of the iodid solu- 
tion ; add the remainder of this solution, and shake up the contents 
of the flask frequently till the iodin is completely dissolved, using 
no heat; make the solution up to 500 c.c. with water, and mix ELEMENTS OF CHEMICAL ANALYSIS. 
as usual. If a larger quantity of the solution is made it should 
be put into a number of 250 c.c. bottles, nearly filled ; in this 
manner it may be kept unchanged in strength for a long time. 
Sodium thiosulfate. Dissolve 12.4 gms. of the pure and well 
crystallized salt in 500 c.c. of water, previously boiled to expel 
C02 in solution. If this solution is kept in a cool, dark place, 
its strength will remain unchanged for a considerable time. 
The starch solution. To about a gram of powdered starch add 
about 100 c.c. of water with constant stirring, and heat the mix- 
ture, with continued stirring, to boiling; let cool, and pour off 
the nearly clear liquid from the sediment. The solution is not 
permanent, and should be fresh when used. 
Standardizing the iodin solution against the thiosulfate. To 20 
c.c. of the latter solution, run from a burette into a beaker, add 
three to four c.c. of the starch solution, and then iodin solution 
from a glass-stoppered burette, slowly and with constant stirring, 
till the whole of the liquid is colored blue by the last drop added. 
Repeat till closely agreeing results are obtained. 
The standard of the iodin solution. Break up some crystals of 
pure sodium thiosulfate to a coarse powder, dry this over sulfuric 
acid for a short time, then pulverize the effloresced residue very 
fine, and dry it for several days over sulfuric acid, with a watch 
glass containing pieces of potassium hydroxid to absorb any 
carbon dioxid that might be present and act on the salt. Take 
about 200 mgms. of the powder for each test, dissolving it in 
about 20 c.c. of water. Calculate the iodin in one c.c. of the 
solution. 
139. Determination of antimony, in the form of antimojious 
oxid. 
Sb203 +I, + Na20 == Sb205 + 2NaI. 
The oxidation must take' place in an alkaline solution, and in 
the presence of a large excess of alkaline carbonates. Fresenius 
gives the following directions, which are to be found also in 
Fleischer’s Titrirmethoden. 
Dissolve a quantity of the substance containing about 100 
mgms. of antimony in about 10 c.c. of a solution of tartaric acid 
(one to ten), add sodium carbonate till the solution is nearly neutral, 
and about 20 c.c. of a cold saturated solution of sodium bicar- 
bonate, then the starch, and finally the iodin solution, dropwise 
and with constant stirring, till the whole of the liquid assumes a 
briefly permanent blue color; that the color disappears after a ANALYSIS BY ELECTROLYSIS. 
little time is not to be taken as an indication that more iodin 
solution is required. Fleischer commends the usefulness of this 
determination, since antimony can be precipitated as tersulfid 
from any of its compounds; and after dissolving the precipitate 
in HCI, boiling out the hydrogen sulfid, adding tartaric acid 
and the alkaline carbonates as above directed, the solution is 
ready for the titration. 
CHAPTER XVIII. 
ANALYSIS BY ELECTROLYSIS—SEPARATION AND DETER- 
MINATION OF SILVER AND COPPER. 
140. Method 1 (Classen’s). Silver oxalate, precipitated by 
(NH4)2C204 is insoluble in excess of the precipitant, while copper 
oxalate is soluble. The two metals are separated by this reaction 
and subsequent filtration, the silver oxalate is dissolved in potas- 
sium cyanid, and each solution is electrolyzed separately. 
The re-solution of the copper oxalate in excess of the reagent 
is easy, but since the silver oxalate settles very slowly, it is 
difficult to decide when the precipitation is complete, and when 
the addition of the ammonium oxalate in excess really begins, or 
when, in the solution colored bluish-green by the dissolved copper 
salt, the undissolved residue consists only of the white silver salt. 
It is better, therefore, to estimate by calculation, or ascertain by 
experiment, how much of a cold saturated solution of the pre- 
cipitating reagent is required to effect a complete reaction : any 
excess of the reagent does no harm. For a solution containing 
about 500 rngms. of copper and silver together, 60 to 70 c. c. of 
the saturated oxalate solution will be enough, even if copper 
predominates very largely; the larger the proportion of silver, 
the less oxalate will be needed. 
Classen's arrangement of electrodes consist of a platinum dish 
for the cathode, with vertical sides, holding about 225 c.c., 
and for the anode a platinum disk 4.5 cm. in diameter, pierced 
with several holes 5 mm. in diameter, and fastened to a stout 
platinum wire. These electrodes are supported on a stand, with 
a glass post carrying a brass ring for the dish and a short rod 
for the disk, with binding screws for connection with the bat- 
tery. The wire fastened to the anode passes through a small 152 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ Uo- 
hole in the centre of a cover-glass; the platinum dish is filled 
with the solution to such a level that, when the cover is in 
place, the lowest part of its convex surface is in contact with the 
liquid directly over the anode, and for an area a little larger than 
that of the anode ; thus all spattering of the liquid on to the 
cover from the bubbles of gas evolved at the anode is avoided, 
and also the consequent necessity for rinsing the cover into the 
dish towards the close of the operation. 
The most convenient source of the current is a storage battery. 
The analysis. Dissolve about 500 mgms. of the alloy in di- 
lute nitric acid, evaporate almost to dryness on the water bath, 
add 15 c.c. of water, evaporate again almost to dryness, and 
add 50 c.c. of water to the residue. A clear solution, contain- 
ing very little free acid, should result. To this add 60-70 c.c. 
of a cold, saturated solution of ammonium oxalate, allow the 
precipitate to settle, filter, and wash first with ammonium ox- 
alate, and then with cold water. 
Dissolve this silver oxalate in a solution of pure potassium 
cyanid, transfer the solution to the weighed platinum dish, 
make its volume up as directed above, and precipitate the 
silver with a current corresponding to 0.2 to 0.5 c.c. of oxy- 
hydrogen gas per minute. Before disconnecting always ascertain 
whether the precipitation is complete ; for this purpose add to 
the contents of the dish enough water to raise the level of the 
liquid about 2 mm., and then allow the current to flow half an 
hour longer ; if no silver is deposited on the walls of the dish 
above the level of the first solution, the precipitation is com- 
plete. Confirm by testing with HCI. 
Remove the cover-glass and anode, pour out the liquid in the 
dish quickly, and wash the deposit first with water; holding a 
wash-bottle mouth lowermost, and with the outer arm of the 
mouth tube nearly horizontal and very near the inner rim of the 
dish, direct the stream of water from the mouth-tube on to the 
inside of the dish above the deposit, while revolving the dish in 
such a manner as to bring this impact of the water in an oblique 
direction against the whole circumference of the rim ; pour this 
water out, and repeat the operation three times. Then wash 
three times with strong alcohol in the same manner. Remove 
the last portions of alcohol by blowing into the dish while held 
in the hand, dry for an hour in the desiccator, and weigh. 
Determination of the copper. Evaporate the filtrate and 
washings from the silver oxalate down to about 150 c.c. if the ANALYSIS BY ELECTROLYSIS. 
volume is much larger than this, transfer at once to the weighed 
platinum dish, add 20 c.c. of a cold saturated solution of am- 
monium oxalate, and electrolyze with a current of the same 
strength as above. Test for complete precipitation as directed 
for the silver determination, and also by taking out about one c.c. 
of the liquid with a small pipette and applying the ferrocyanide 
test. When precipitation is complete wash and dry the dish, as 
directed above, and weigh. 
141. Method 2. Precipitation and determination of the silver 
as chlorid and the copper by electrolysis. In this method the 
less expensive platinum foil electrodes can be used, the cathode 
being about cm. and the anode cm. 
Dissolve a quantity of the substance containing 250 to 300 
mgms. of the metals in water, or in HNOs if the substance is 
metallic. In this last case evaporate the solution down till 
fumes of nitrous acid are no longer evolved, add about 75 c.c. 
of water and then HCI as long as a precipitate is formed ; 
make this addition and carry out the subsequent operations as 
directed for the estimation of HCI in § 133. The liquid will 
not clarify so readily as in that operation, HCI being in excess 
instead of silver nitrate. 
Since the filtrate is to be used for the estimation of the cop- 
per, none of it or of the washings are to be lost; as is usual in 
the separation of substances from one another preliminary to 
their quantitative estimation, the filtrate and washings must be 
concentrated by evaporation. 
142. The determination of the copper. The solution must be 
free from HCI or chlorids, and contain nitric acid as its only 
free acid, except that a very little free sulfuric acid is permissi- 
ble. If HCI has been added in any previous operation, or the 
salt is a chlorid, add to the concentrated solution about 20 c. c. 
of HN03 and evaporate to dryness on the water bath. Take up 
the residue with a little water and about 20 c. c. of HN03, of 
1.2 sp. gr., in a beaker of about 250 c. c. capacity, heating a 
short time if necessary to get complete solution, with the beaker 
covered, and finally add 180 c. c. of water. 
Shape the electrodes into a curved form so that they will fit 
evenly against the sides of the beaker containing the solution, 
clean them of any organic matter by heating to redness for a 
moment in the lamp-flame, and lay them in the desiccators; do 
not handle the broader parts with the fingers after they have been 
thus cleaned. Only the larger electrode of each pair is to be weighed, unless there is reason to suppose that a little lead may 
be deposited on the other as Pb02, as in the analysis of brass. 
In weighing, suspend the electrode, by the loop in its platinum 
wire, on the hook over the balance pan. 
ELEMENTS OF CHEMICAL ANALYSIS. 
Put the electrodes in the beaker so that they nearly touch the 
bottom, bend the platinum wires over the edge of the beaker, 
thus suspending each one in its place, and make the connections 
with a current corresponding to three to four c.c. of oxyhydrogen 
gas per minute. Cover the beaker during the electrolysis. 
From twelve to twenty-four hours will be required for the com- 
pletion of the electrolysis, with 250-300 milligrams of copper in 
the solution. When the solution appears quite colorless, rinse 
the cover into the beaker, add a little more water so as to raise 
the level of the liquid by about half a centimeter, stir gently to 
mix in the added water, and after one or two hours observe 
whether any copper is deposited on that part of the electrode 
freshly immersed ; if not, confirm the test by adding ammonia 
to about five c. c. of the liquid till in slight excess, then acetic 
acid till acid, and then K4FeCy6; there should be no red precipi- 
tate or coloration. 
The deposition of the copper being complete, slowly raise the 
electrode out of the liquid while it is still in the circuit, rinsing 
it off on both sides with water as it is raised, finally leaving only 
one corner immersed; then lift it quite out, and rinse off this 
corner ; finally rinse off with alcohol, and dry as directed in 
Method 1. 
In the place of an ordinary beaker, one with a lateral tubulure 
near the top is often used ; the washing of the electrode is done 
by conducting a small stream of water to the bottom of the 
beaker, till the overflow through the tubulure is no longer acid ; 
then the current can be discontinued without danger of redissolv- 
ing any of the copper. PART V 
LISTS OF APPARATUS AND REAGENTS, SPE- 
CIFIC GRAVITY AND OTHER TABLES. 
143. The qualitative set of apparatus. 
One apparatus, Marsh (flask, funnel-tube, rubber cork, con- 
ducting tube, and platinum foil) ; one bottle, glass-stoppered, 
60 c.c., with AgN03; one bottle, glass-stoppered, with alco- 
hol; one crucible, porcelain, No. 8; one evaporator, 
porcelain, 70 mm. ; one package of 50 filters, 7 cm. ; one 
package of 100 filters, 9 cm. ; one finger cap, rubber; two 
flasks, conical (Erlenmeyer), 60 c.c. ; two flasks, conical 
(Erlenmeyer), 100 c.c.; one flask, ordinary, flat bottom, 60 
c.c. ; one forceps; three funnels, 50 mm. opening ; one 
mortar and pestle; one lamp with 60 cm. of 6 mm. rubber 
tube; one piece plain glass, 10 x 10 cm, ; one platinum 
cup and wire; two 10 cm. rods of glass; one sand bath ; 
one spatula of horn ; one sponge; one stand, of iron, 
with rings; six test-tubes, 10 cm. long ; twelve test-tubes, 
15 cm. long; one test-tube holder; one test-tube rack; 
one test-tube brush ; three tubes, bulbed for arsenic test; 
one tube, dropping, drawn out at one end; one tube, with 
loop, for C02, H2S03, and HCy tests; one wash-bottle; 
one watch-glass, 28 mm. ; one wire triangle. 
144. Directions concerning the use of this apparatus. This set 
of apparatus comprises all that is essential for the work in quali- 
tative analysis. Some of the pieces will, of course, be broken 
sooner or later, and may perhaps have to be replaced many 
times during the term. The student is advised to keep his set 
always full; there is nothing superfluous in it, and it is mis- 
taken economy to attempt to carry on the work with any pieces 
wanting. 
The Marsh apparatus is used only in the test for arsenic in 
the course for the tin group. 156 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ 144- 
Use the evaporator only for evaporating liquids ; set it directly 
over the lamp without the intervention of a sand-bath, not more 
than a centimeter above the mouth of the lamp tube, and turn 
the gas down so low that the flame will not rise higher on the 
outside than the level of the liquid within. 
Use the crucible for heating the residues from evaporations; 
see § 47 on ignition. 
The finger cap is convenient for protecting the skin from con- 
tact with corrosive liquids, when it is necessary to close the 
mouth of a test-tube, to be inverted for mixing its contents. 
Always use smaller filters when only small quantities of a sub- 
stance are to be filtered out. 
The flasks can be heated over a direct flame, with the same 
precautions as given above for heating evaporators. Consult 
§§ 53» 54, on digestion and boiling. 
Keep the forceps entirely from contact with solutions that you 
are analyzing, lest you may report copper and zinc incorrectly. 
To light the lamp, turn on the full flow of the gas, and not 
till after it is lighted turn it down to the desired point ; a flame 
from five to seven centimeters high is the most suitable for ordi- 
nary work, and should always be used except when special di- 
rections are given for a lower or a higher flame. Be particularly 
careful in turning the flame down very low, that it does not 
“strike down” and burn at the little jet by the air inlets; 
when this has taken place, the gas burns also at the mouth of the 
tube with a pale, light-colored, slender flame, and not with an 
almost colorless, somewhat bulging flame, without light, as it 
should; when burning in this way the whole lamp may become 
hot and burn the fingers if touched; it is to avoid this that the 
directions are given as above for lighting the lamp. The only 
way to set the matter right when the lamp is burning in this 
way, is to shut the gas off entirely and light it again in the manner 
directed above. 
Keep your platinum cup bright and clean; fuse a little potas- 
sium bisulfate in it, and soak the fused mass off with hot water 
when it cannot be cleaned by heating with HCI. 
Do not bring the horn spatula in contact with strong acid or 
alkaline liquids, or the sponge in contact with strong acids. 
See §54 about heating liquids in test-tubes. Do not have any 
acid in the test-tube when cleaning it with the brush. 
Put only sand enough in the sand-bath to fill it about one- 
third. Put only distilled water in the wash-bottle. APPARATUS, REAGENTS, ETC. 
145. The apparatus for quantitative work. 
The smaller of the two sets of apparatus given below is issued 
to students taking only the short course of quantitative work 
laid out in Part IV, and occupying about one hundred and ten 
hours of actual practice. The other set is issued to those taking 
a longer course and working more hours. 
There is occasional use for some expensive pieces of apparatus, 
especially by students taking the longer course of work, which 
are not included in these sets. In the author’s laboratory these 
can be obtained, for such temporary use, of the supply clerk, 
checks being in all cases deposited for each piece ; any piece of 
apparatus drawn on check is to be returned, as soon as the special 
work for which it was required is completed, and the check is to 
be reclaimed. Checks missing at the end of the term may be 
charged for at a rate much above their actual cost, since, under 
this system, they may represent apparatus of great value ; there- 
fore it behooves the student to look after them carefully. 
146. The smaller quantitative set of apparatus. 
Twenty apparatus checks; seven beakers (one 30 c.c., four 
200 c.c., two 300 c.c.); six beaker covers (two 62 mm., four 
So mm.) ; five bottles (one 60 c.c. with AgNOs, one 250 c.c. with 
alcohol, two 1000 c.c., flat stoppered, one 500 c.c., wide mouth) ; 
two burettes, 50 c.c. graduated in c.c., with rubber tube, 
glass ball, and jet; two burette floats ; two crucibles, porcelain, 
No. 7; one crucible, Caldwell-Gooch, with perforated plati- 
num disk; one crucible tongs; two desiccators, with glass cov- 
ers and triangles; two evaporators, no mm.; fifty filters (25 
for quantitative filtration, 25 common) ; three flasks (one 60 
c.c., two 250 c.c., conical, with lateral tube and rubber stopper, 
for suction filtration) ; one forceps ; five funnels (four, usual form, 
50 mm., one cup-shaped for the Gooch crucible) ; one lamp, 
Bunsen, with 60 centimeters of 6 mm. rubber tube; one sheet 
glazed paper, cut (see § Ix 9) ; one pipette, 25 c.c., with mark on 
neck; one white plate; four rods of glass; one spatula, horn ; 
one thermometer ; two triangles, platinum-wrapped ; one tube, 
dropping, drawn out at one end; ninety centimeters rubber 
tube, 3 mm.; three test-tubes, 10 cm.; one tube, graduated; 
one wash-bottle (flask with rubber cork and tubes) ; two watch- 
glasses, 38 mm. ; one wire, platinum, in glass handle; one 
Y-tube. 158 
ELEMENTS OF CHEMICAL ANALYSIS. [§§ 147-148. 
Also, one iron rod with two lamp rings, one rod with funnel 
holder, and one with burette holder, all for the fixed iron stand 
on the table. 
147. The larger set of apparatus. 
Twenty apparatus checks; seven beakers (one 30 c.c., four 
200 c.c., two 300 c.c.); ten beaker covers (two 62 mm., six 
80 mm., two 95 mm.) ; ten bottles (one 60 c.c. with AgN03, one 
250 c.c., with alcohol, one 1000 c.c. with distilled water, one 
500 c.c., wide mouth, two 250 c.c., two 500 c.c., flat stopper, 
two 1000 c.c., flat stopper); two burettes, 50 c.c. gradu- 
uated in with jet, rubber tube, and glass ball; two burette 
floats; two cones, platinum, for suction filtration; four 
crucibles, porcelain (two No. 7 ordinary, two No. 6 Cald- 
well-Gooch, with perforated platinum disks); one crucible 
tongs; one cylinder, 100 c.c., graduated; two desiccators, 
with glass covers and triangles; six evaporators (two no mm., 
two 145 mm., two 180 mm.); one hundred filters (twenty-five 
ordinary, twenty-five 7 cm., and fifty 9 cm. for quantitative 
filtration); seven flasks (one ordinary 60 c.c., two 500 c.c. 
Erlenmeyer, with lateral tubulure for suction filtration, two 
Erlenmeyer, 250 c.c., two ditto, 400 c.c.; one forceps; eight 
funnels (six ordinary, 50 mm. opening, two cup-shape for 
Gooch crucible; one lamp, Bunsen, with 60 centimeters of 6 
mm. rubber tube; one mortar and pestle ; one sheet paper, 
glazed, cut (see § 119); four pipettes (one 10 c.c., pne 25 c.c., 
one 50 c.c., each with mark on neck, one 10 c.c., graduated) ; 
one white plate; eight rods, glass, 15-18 cm. long; one spatula, 
horn; one thermometer; two triangles, platinum-wrapped; 
one dropping-tube; ninety centimeters of 3 mm. rubber tube ; 
twelve test-tubes (six 10 cm., six 15 cm.) ; one test-tube brush ; 
one test-tube holder; one test-tube rack ; one test-tube, gradu- 
ated ; two wash-bottles (one 250 c.c., one 500 c.c.) with rubber 
corks and tubes complete; four watch-glasses (two 35 mm., 
two 50 mm.); one pair of weighing tubes, made from two test- 
tubes; one Y-tube; one wire, platinum, in handle; one wire 
gauze, xo cm. square ; also, one iron rod with two lamp rings, 
one rod with funnel holder, and one with burette holder, all for 
the fixed iron stand on the table. 
148. List of the reagents used in the work described in this 
book, arranged in the alphabetical order of their full names and APPARATUS, REAGENTS, ETC. 
giving, when practicable, the number of grams to be taken for 
1000 c.c. of solution. In the case of those given in italics, refer 
to § 150 for special directions for making the solutions. 
Acetic acid, HC2H302. 
Alcohol, C 2HSOH or C 2H60. 
Ammonia alum. 
Ammonium carbonate, (NH4)2CO3. 250 
Ammonium chlorid, NH4CI. 100 
Ammonium ferrous sulfate (NH4)2SO4.FeSO4 + 6H20. 
Ammonium hydroxid, NH,OH. 
Ammonium molybdate, (NH4)2M004. 
Ammonium oxalate, (NH4)2C204 -f- H2O. 75 
Ammonium sulfid, (NH4)2S 
(or, with excess of sulfur, (NH4)2SX). 
Aqua regia, 3 HCI, 1 HN03. 
Barium carbonate, BaC03. 
Barium chlorid, BaCl2 + 2H20. 75 
Barium hydroxid, Ba(OH)2. saturated solution. 
Borax, Na2B^07 -f- ioH20. 
Bromin (solution), Br. 
Calcium carbonate, CaC03. 
Calcium hydroxid, Ca(OH)2 
(or milk of lime). saturated solution. 
Calcium sulfate, CaS04 -f- 2H20. saturated solution. 
Carbon dioxid 
(or carbonic acid), C02, 
Carbon disulfid, CS2. 
Chlorin (water), Cl. 
Chromic acid cleaning mixture. 
Cochineal, tincture of. 
Ferric chlorid, FeCl3. 
Ferrous sulfate, FeSOt -f- 7H20. 
Hydrochloric acid, concentrated, HCI. 
Hydrochloric acid, dilute, HCI. 
Hydrosulfuric acid, or hydrogen sulfid, H2S. 
Indigo solution. 
lodin solution. 
Iron filings, Fe. 
Iron wire, piano. 
Lead acetate, Pb(C2H3O2)2 -j- 3H20. 100 
Lead acetate and ammonium acetate. 
Lime water. saturated solution. ELEMENTS OF CHEMICAL ANALYSIS. 
Litmus solution. 
Magnesia mixture. 
Mercuric chlorid HgCl2. 50 
Methyl orange, indicator. 0.5 
Nitric acid, concentrated, HN03. 
Oxalic acid, H2C204 -J- 2H20. 100 
Phenyl-sulfuric acid. 
Potassium acetate, KC2H302. saturated solution. 
Potassium bisulphate, KHS04. 
Potassium chlorate, KCI0S 
Potassium chromate, K2Cr04. 100 
Potassium cyanid, KCy, or KCN. 50 
Potassium dichromate, K2Cr207. 50 
Potassium ferricyanid,K3FeCy6, or K3Fe(CN)6. 10 
Potassium ferrocyanid, K4FeCy6 or K4Fe(CN)6 -j- 3H20. 50 
Potassium iodid, KI. 50 
Potassium nitrate, KN03. 
Potassium permanganate, KMn04. 
Potassium sulfate, K2S04. 100 
Potassium sulfocyanate, KCNS or KCyS. 50 
Silver nitrate, AgNOs. 50 
Sodio-cobaltic nitrite, (NaNO2)3 C0(N02)3. 
Sodium carbonate, Na2C03 4- ioH20. 200 
Sodium hydroxid, NaOH. 150 
Sodium phosphate, Na2HP04 -(- i 2H20. 75 
Sodium thiosulfate, Na2S203. 
Sodium sulfite Na2S03. 100 
Stannous chlorid, SnCl2. 
Starch. 
Sulfuric acid, concentrated, H2S04. 
Sulfuric acid, dilute, H2S04. 
Tartaric acid, H2C4H406. 100 
Zinc (metallic), Zn. 
Zinc, sulfate, ZnS04 + 7H20. 100 
149. List of such reagents as are usually named only by their 
formulas, in the description of the analytical work, arranged in 
the alphabetical order of their formulas. 
AgN03, silver nitrate. 
BaCl2, barium chlorid. 
BaC03, barium carbonate. 
Ba(OH)2, barium hydroxid. APPARATUS, REAGENTS, ETC. 
CaC03, calcium carbonate. 
Ca(OH)2, calcium hydroxid or lime water. 
CaS04, calcium sulfate. 
C 2HSOH, or C 2H60, alcohol. 
Cl, chlorin (water). 
C02, carbon dioxid, or carbonic acid. 
CS2, carbon disulfid. 
Fe, iron (filings). 
FeCl3, ferric chlorid, 
FeS04, ferrous sulfate. 
HC2H302, acetic acid. 
H2C4H406, tartaric acid. 
HCI, hydrochloric acid, concentrated. 
HCI, hydrochloric acid, dilute. 
H2C204, oxalic acid. 
HNOj, nitric acid, concentrated. 
HNOs, nitric acid, dilute. 
H2S, hydrogen sulfid. 
H2S04, sulfuric acid, concentrated. 
H2S04, sulfuric acid, dilute. 
HgCl2, mercuric chlorid. 
KC2H302, potassium acetate. 
KCI, potassium chlorid. 
KCI03, potassium chlorate. 
K2Cr04, potassium chromate. 
K2Cr207, potassium dichromate. 
KCy, or KCN, potassium cyanid. 
KCyS, or KCNS, potassium sulfocyanate. 
K3FeCy6, or K3Fe(CN)6, potassium ferricyanid. 
K4FeCy6, or K4Fe(CN)6, potassium ferrocyanid. 
KHS04, potassium bisulfate. 
KI, potassium iodid. 
KMn04, potassium permanganate. 
KNO3, potassium nitrate. 
K2SO4, potassium sulfate. 
NaC2H3O2, sodium acetate, 
Na2C03, sodium carbonate. 
Na2HP04, sodium phosphate. 
NaN03, sodium nitrate. 
(NaNO2)3Co(NO2)3, sodio-cobaltic nitrite. 
NaOH, sodium hydroxid. 
Na2S03, sodium sulfite. 162 
[§ IS°- 
ELEMENTS OF CHEMICAL ANALYSIS. 
Na2S203, sodium thiosulfate. 
NH4CI, ammonium chlorid. 
NH4CNS, ammonium sulfocyanate, 
(NH4)2CO3, ammonium carbonate. 
(NH4}2C2O4, ammonium oxalate. 
(NH4)2 Mo04, ammonium molybdate. 
NH4OH, ammonium hydroxid. 
(NH4)2S, ammonium sulfid. 
(NH4)2Sx, ammonium sulfid, with excess of sulfur. 
Pb(C2H302)2, lead acetate. 
SnCI2, stannous chlorid. 
Zn, zinc (metallic). 
ZnS04, zinc sulphate. 
150. Special directions for thepreparatioti of reagents or sola 
tions. 
The strength of the acids. Hydrochloric acid:—Only for the 
solution of the precipitated sulfids of the metals of the 6th group 
is acid of full strength (about 1.2 sp. gr.) required. For ordinary 
use, this acid diluted with its volume of water is sufficiently 
strong; this moderately diluted acid is indicated by the heavy- 
faced symbol HCI, and is about x.i sp. gr. 
For dilute hydrochloric acid, indicated by HCI, add to the 
fully concentrated acid eight parts of water. 
Nitric acid:—For the concentrated acid for ordinary use, 
indicated by HN03, add to the fully concentrated acid its vol- 
ume of water, making an acid of about 1.2 sp. gr. 
Sulfuric acid:—For the dilute acid, H2S04, add one part of 
ordinary concentrated acid, H..SOt, to four parts of water. 
Ammonium carbonate:—Dissolve 250 gms. of the salt in a 
mixture of 200 c.c. of ordinary aqua ammonia and 800 c.c. of 
water. 
Ammonium hydroxid:—The solution for laboratory use should 
have a specific gravity of about 0.96. 
Ammonium molybdate :—For two litres of solution take 1300 
c.c. of water; to 200 c.c. of NH4OH add 300 c.c. of this water, 
and dissolve 100 gms. of molybdic acid in this diluted ammonia. 
To 500 c.c. of fully concentrated nitric acid add the rest of 
the water, and to this add the ammoniacal molybdic solution, 
slowly and with constant stirring; let the whole stand in a 
warm place 48 hours, and decant off the clear solution for 
use. § is° ] 
163 
Ammonium sulfid:— Pass H2S through ordinary ammonia 
water till the solution gives no precipitate with MgS04, and to 
700 c.c. add 300 c.c. of NH4OH. For the sulfid indicated by 
fNH4)2Sx dissolve sulfur in this solution to saturation. 
APPARATUS, REAGENTS, ETC. 
Bro?7iin solution :—To a solution of 50 gms. of potassium 
bromid in 500 c.c. of water, add bromin till no more is dis- 
solved when the mixture is well shaken. 
Cochineal, tincture of:—Digest 3 grams of cochineal for a 
long time in 250 c.c. of a mixture of 3 to 4 parts of water and 
1 part of alcohol, and filter, or decant. If the solution to be 
titrated is heated when this indicator is used, the presence of 
free carbonic acid does not appreciably mask the change of 
color. 
The chromic acid cleaning mixture:—To about 150 c. c. of 
warm water in a beaker add about 40 grams of ordinary 
powdered K2Cr207; when all the salt is dissolved, cool the 
solution and pour it slowly and with constant stirring into 
about 230 c. c. of H2S04. When the mixture is cold transfer 
it to a 500 c. c., wide-mouth, glass-stoppered bottle; any por- 
tion of it once used for cleaning can be poured back into the 
bottle. Shake it up when about to pour it into a vessel to be 
cleaned, for the red crystals are the most effective part for 
cleansing purposes. As it is a strongly corrosive liquid, any of 
it dropped on the table should be at once washed off with much 
water. It is to be used only for cleaning glass ware that cannot 
be cleaned by ordinary treatment with water, or with a little hot 
HCI, and then with water ; it is never to be used for cleaning 
beakers, flasks, or evaporators, unless they have had some 
organic matter in them, such as fat or oil, that water will not 
remove. 
To clean a burette, put it mouth downward into the bottle 
containing the mixture, and, opening the ball valve in the rubber 
tube, slowly suck the liquid up, with as much of the red precipi- 
tate of chromic acid as possible, to within three or four centi- 
meters of the rubber tube ; on letting the valve close the liquid 
will stand at that height, and can be left undisturbed as may be 
desired, with the simple precaution to so support the burette 
that it cannot upset the bottle by its weight. On rinsing the 
burette out afterward, take off the rubber tube; the cleaning 
mixture should never come in contact with that. 
To clean a pipette, attach a short piece of rubber tube to the 
mouth, and with the point in the cleaning mixture in the bottle, 164 
ELEMENTS OF CHEMICAL ANALYSIS. 
[§ Is°- 
cautiously draw the liquid up to the mark on the neck; then 
pinch the rubber tube tight while closing its open end with a 
short piece of glass rod. 
Ferric chlorid:—For this solution use the ammonio-ferric 
chlorid, which is not so deliquescent as the ferric chlorid itself, 
dissolving roo gms. in a litre of water. 
Ferrous sulfate:—This solution should be freshly prepared; 
or if kept on the shelves it should be acidified with H2S04 (100 
gms. FeS04, 500 c. c. water, sc. c. H2S04), and should always 
be kept acid, and have a little undissolved iron in it. 
Indigo solution;—To 5 parts of fuming sulfuric acid, add 
slowly and with constant stirring one part of finely pulverized 
indigo, in a beaker immersed in cold water ; let the mixture 
stand 48 hours, the beaker being covered, then pour it into 
twenty times its volume of water, mix and filter. 
Lodin solution:—In 500 c. c. of water dissolve 18 gms. of 
potassium iodid, and then 7 gms. of iodin. 
Lead acetate and ammonium acetate:—Acidify with acetic 
acid a mixture of equal parts of solution of lead acetate and a 
ten per cent, solution of ammonium acetate. 
Litmus solution:—Boil the litmus three or four times with 85 
per cent, alcohol, and finally filter. Wash the insoluble residue 
once with a little water, by decantation, and then digest it with 
hot water and filter. Divide this extract in two portions. Just 
barely acidify one portion with H2S04, make the other portion 
very weakly alkaline with NaOH solution, and mix the two 
portions together. The solution will keep better if in a loosely 
stoppered bottle. A few drops of a solution of salicylic acid in 
20 to 30 parts of alcohol added to 100 c. c. of the litmus solu- 
tion will preserve it completely from mould. 
Magnesia mixture:—Dissolve 100 grams of MgCl2 and 200 
grams of NH4CI in 400 or 500 c. c. of water, add 400 c. c. of 
ammonia, sp. gr. .96, make the solution up to one liter, let 
stand several days in a closed bottle, and decant off the clear 
liquid from any precipitate that may have separated out. 
Phenyl-sulfuric acid:—Dissolve one part of carbolic acid in 
four parts of H2S04, and add two parts of water. 
Sodio-cobaltic nitrite:—Dissolve 100 gms. of sodium nitrite 
in 300 c.c. of water, add acetic acid to feeble acid reaction, and 
10 gms. of cobaltic nitrate ; let the solution stand for several 
hours and filter if not clear. Since the reagent decomposes 
slowly, it is better not to make a large quantity at once. If it APPARATUS, REAGENTS, ETC. 
loses its precipitating power for potassium, the addition of more 
sodium nitrite will restore its efficiency. 
Stannous chlorid:—To a saturated solution of tin in hot HCI 
add four parts of water and a few pieces of granulated tin ; the 
solution should always have an excess of tin and a slight quantity 
of free acid in it. 
As to the important matter of the purity of these reagents, pure 
nitric and hydrochloric acids will be found on the reagent 
shelves, except that there may be slight traces of sul- 
furic acid in the latter, and of hydrochloric acid in the 
former; pure ammonia is supplied also. The quality of the 
other reagents will be as good as practicable, but the student 
should form the habit of testing them in cases where any im- 
purities that they might contain, such as chlorid or sulfate, 
would affect his results. Fresenius gives, in his works on quali- 
tative and quantitative analysis, a full account of the tests that 
should be made. It may sometimes occur that a reagent is not 
perfectly clear, in which case some of it should be filtered for 
use, especially in quantitative work. ELEMENTS OF CHEMICAL ANALYSIS. 
151. TABLE OF ATOMIC WEIGHTS. 
These atomic weights are taken from a revised table by F. W. Clarke, and 
issued December 6th, 1890; the rare elements are omitted. The full table, as 
stated by the revisor, “ represents the latest and most trustworthy results, 
reduced to a uniform basis of comparison with Oxygen == 16.” 
Name. 
Symbol. 
Atomic 
Weight. 
Name. 
Symbol. 
Atomic 
Weight. 
Aluminum, , . 
A1 
27. 
Manganese, , . . 
Mn 
55- 
Antimony, . . 
Sb 
120. 
Mercury, .... 
Hg . 
200, 
Arsenic, . . . 
As 
75- 
Molybdenum, . . 
Mo 
96. 
Barium,.... 
Ba 
137- 
Nickel, 
Ni 
58.7 
Bismuth, . . . 
Bi 
208.9 
Nitrogen, .... 
N 
14-03 
Boron, .... 
B 
11. 
Oxygen, .... 
0 
16. 
Bromin, 
Br 
79-95 
Phosphorus, . . , 
P 
31- 
Cadmium, . . . 
Cd 
112. 
Platinum, .... 
Pt 
195- 
Calcium, . . . 
Ca 
40. 
Potassium, , . . 
K 
39 11 
Carbon, .... 
C 
12. 
Selenium, . . . 
Se 
79- 
Chlorin, . . . 
Cl 
35-45 
Silicon, .... 
Si 
28.4 
Chromium, . , 
Cr 
52.1 
Silver, 
Ag 
107.92 
Cobalt, .... 
Co 
59- 
Sodium, .... 
Na 
23-05 
Copper, .... 
Cu 
63-4 
Strontium, . . . 
Sr 
87.6 
Fluorin, 
F 
19. 
Sulfur, 
S 
32.06 
Gold, .... 
Au 
197-3 
Tellurium, . . . 
Te 
125. 
Hydrogen, . . 
H 
1.007 
Tin, 
Sn 
119. 
lodin, .... 
I 
126.85 
Titanium, . . . 
Ti 
48. 
Iron, ...... 
Fe 
56. 
Tungsten, . . . 
W 
184. 
Lead, .... 
Pb 
206.95 ' 
Uranium, . . . 
U 
239.6 
Lithium, . . 
• Li 
7.02 
Zinc, 
Zn 
65-3 
Magnesium, 
Mg 
24-3 
Zirconium, . . . 
Zr 
90.6 167 
§§ 152_153-] 
APPARATUS, REAGENTS, ETC 
152.—Table giving grams of NH3 in 100 c.c. of solution of 
NH4OH, of different specific gravity, at 150 C. 
(Lunge and Wernik : Zeit. ang. Chemie, 1889.) 
Specific 
Gravity. 
Grams NH3 
in 100 c.c. 
Specific 
Gravity. 
Grams NH3 
in 100 c.c. 
Specific 
Gravity. 
Grams NH3 
in 100 c.c. 
.960 
951 
•932 
16.81 
.904 
24 39 
.958 
10.03 
•930 
17-34 
.902 
24.94 
•956 
10.54 
.928 
17.86 
.900 
25.50 
•954 
n.07 
.926 
18.42 
.898 
26.05 
•952 
H-59 
.924 
18.93 
.896 
26.60 
.950 
12.10 
.922 
19-47 
•894 
27-15 
.948 
12.62 
.920 
20.01 
.892 
27.70 
.946 
1313 
.918 
20.56 
.890 
28.26 
■944 
i3-65 
.916 
21.09 
.888 
28.86 
.942 
14.17 
.914 
21.63 
.886 
29.46 
.940 
14.69 
.912 
22.19 
.884 
3°-I4 
•938 
15.21 
.910 
22.74 
.882 
30-83 
•936 
iS-74 
.908 
23.29 
•934 
16.27 
.906 
23-83 
153.—Table giving grams of S03 in 100 c.c. of solution of 
different specific gravity, at ,is° C. 
(Lunge and Isler: Zeit. ang. Chemie, 1890. p. 129.) 
Specific 
Gravity. 
Grams S03 
in 100 c.c. 
Specific 
Gravity. 
Grams S03 
in 100 c.c. 
Specific 
Gravity. 
Grams S03 
in 100 c.c. 
1.08 
10.3 
i-35 
494 
1.6l 
91-3 
I.IO 
12.9 
1.36 
5°.9 
1.62 
93-o 
I.II 
14-3 
M7 
52.5 
I.63 
94-7 
1.12 
15.6 
1.38 
54-i 
X.64 
96.4 
II3 
16.9 
i-39 
55-7 
1.65 
98.1 
1.14 
18.3 
1.40 
57 3 
i .66 
99.8 
II5 
19.6 
1.41 
S8.9 
1.67 
101.6 
I.l6 
21.0 
1.42 
60.4 
1.68 
103.4 
1.1? 
22.4 
1-43 
62.0 
1.69 
io5-3 
1.18 
23.8 
1.44 
63.6 
1.70 
107.1 
1.19 
25-3 
i-45 
65.1 
1.71 
108.9 
1.20 
26.8 
1.46 
66.7 
1.72 
110.8 
1.21 
28.2 
1.47 
68.3 
i-73 
112.7 
1.22 
29.7 
1.48 
69 9 
i-74 
114.6 
1.23 
31-2 
1.49 
7M 
i-75 
116.5 
1.24 
32-7 
150 . 
73-i 
1.76 
118.5 
1-25 
34-i 
M1 
74.8 
1.77 
120.4 
1.26 
35-6 
i-52 
76.4 
1.78 
122.8 
1.27 
37 0 
i-S3 
78.1 
1.79 
125.2 
1.28 
38.5 
i-54 
79-7 
1.80 
127.7 
1.29 
40.0 
i-55 
81.3 
1.81 
i3°-5 
1.3° 
41.6 
1.56 
82.9 
1.82 
133-8 
*•31 
43-2 
i-57 
84-5 
1.83 
137.6 
1.32 
44-7 
1.58 
86.1 
1.84 
I43-6 
M3 
46.2 
i-59 
87.7 
i-34 
47-9 
1.60 
89-5 ELEMENTS OF CHEMICAL ANALYSIS 
154.—Table giving grams of HCI in 100 parts of hydrochloric 
acid of different specific gravity, at 150 C. (Ure.) 
Specific 
Gravity. 
Grams HC1 
IN IOO PTS. 
Specific 
Gravity. 
Grams HC1 
IN IOO PTS. 
Specific 
Gravity. 
Grams HC1 
IN IOO PTS. 
I.0259 
5-3 
1.0859 
17-53 
I-I473 
29.77 
1.0298 
6.12 
1.0899 
18.35 
I-I5I5 
30.58 
I-°337 
6-93 
I.O939 
19.17 
I-IS57 
3 MO 
1-0377 
7-75 
I.0980 
19.98 
I-I599 
32.21 
1.0417 
8.56 
I.1020 
20.80 
1.1641 
33-03 
1-0457 ' 
9-38 
I 1061 
21.6i 
1.1681 
33-85 
I.0497 
10.19 
1.1102 
22.43 
1.1721 
34.66 
1-0537 
11.01 
1-1143 
23.24 
1.1762 
35-48 
1-0577 
11.83 
1.1185 
24.06 
1.1802 
36.29 
1.0617 
12.64 
1.1226 
24.87 
1.1846 
37-H 
1.0657 
13.46 
1.1267 
25.69 
1.1875 
37-92 
1.0697 
14.27 
1.1308 
26.51 
1.1910 
38-74 
1.0738 
15-09 
I-I349 
27.32 
1.1946 
39 55 
1.0778 
15.90 
1.1389 
28.14 
x.1982 
40.37 
1.0818 
16.72 
1.1431 
28.95 
. 
1.200 
40.78 
155•—Table giving grams of N205 and HN03 in 100 c.c. of 
nitric acid of different specific gravities at 150 C. 
(Lunge and Rey : Zeitschrift fur angewandte Chemie, 1891, p. 16.) 
Specific 
Gravity. 
Grams 
n2o5 
IN 
IOO C.C. 
Grams 
HN03 
IN 
IOO C.C. 
Specific 
Gravity. 
Grams 
n2o5 
IN 
IOO C.C. 
Grams 
HN03 
IN 
100 C.C. 
Specific 
Gravity. 
Grams 
n2o5 
IN 
IOO C.C. 
Grams 
HN03 
IN 
IOO C.C. 
1.02 
3-3 
3-8 
1.X9 
3i-5 
367 
1.36 
67.1 
78.3 
I 03 
4.9 
57 
1.20 
33-3 
38.8 
1-37 
69.8 
81.4 
I.04 
6.4 
7-5 
1.21 
3S-1 
40.9 
1.38 
72.5 
84.6 
i.05 
8.1 
9.4 
1.22 
36-9 
43-° 
i-39 
75-3 
87.9 
1.06 
97 
if-3 
I.23 
387 
45-2 
1,40 
78.3 
91.4 
1.07 
11 3 
13.2 
I.24 
40.7 
47-5 
1.41 
81.6 
95-2 
1.08 
12.9 
15.1 
1.25 
42.7 
49.8 
1.42 
84.9 
99.1 
1.09 
M-S 
16.9 
1.26 
447 
52.1 
i-43 
88.5 
103.2 
1.10 
16.1 
18.8 
1.27 
46.7 
54-4 
1.44 
92.1 
107.5 
1.11 
17-7 
20.7 
1.28 
487 
56.8 
i-45 
96.1 
112.1 
X 12 
I9-5 
227 
I.29 
50.8 
59-3 
1.46 
100.1 
116.8 
I 13 
21.1 
24.6 
I.30 
52-9 
61.7 
i-47 
104-5 
X21.9 
1.14 
22.8 
26.6 
I-3I 
55-1 
643 
1.48 
109.2 
127.4 
; I-I5 
24.5 
28,6 
1.32 
57-3 
66.9 
1.49 
114.4 
*33-5 
1.16 
26.2 
30.6 
i-33 
597 
69.7 
1-50 
121.0 
141.1 
1.17 
27.9 
32.6 
1-34 
62.1 
72.5 
1.18 
29.7 
347 
i-35 
64.5 
75-3 § 156.] APPARATUS, REAGENTS, ETC. 
169 
156. Comparison of measures and weights, 
Directions are often given, especially in the 
qualitative work, to add a certain volume of 
a liquid to a substance or solution under treat- 
ment. The adjoining figure represents the 
actual size of the 10 centimeter test-tubes usu- 
ally issued to the students in the author’s 
laboratory ; with the aid of this graduation 
in cubic centimeters, a close approximation to 
any desired quantity of liquid is easily made. 
Approximate Relations Between English and Metric Weights and 
Measures. 
I Kilo, equals 
1 Gram “ 
1 Gram “ 
1 Liter “ 
1 Liter “ 
I Meter “ 
2.2 lbs. av. 
15.4 grains. 
I lb. av. equals 
I grain “ 
1 oz. av. “ 
1 quart “ 
I fluid oz. “ 
I inch “ 
454 grms- 
-64.8 mgms. 
28.35 Srms- 
-946 c.c. 
0.035 oz. av. 
2.1 pints. 
33.8 fluid oz. 
39.4 inches. 
30 c.c. 
Inches X S 
= centimeters. 
2 
2.54 cm. 
Centimeters V 2 . , 
— = inches. 
5 [§ 157- 
170 
ELEMENTS OF CHEMICAL ANALYSIS. 
Course of Laboratory Work in Chemistry. 
157. The following course of quantitative analytical work, for 
special students of chemistry at Cornell University, is so planned 
as to give practice in the greatest variety of manipulation, and 
also of difficult processes, as is possible in the time allowed for it. 
It follows the introductory course given in this book. 
(1) Limestone, complete analysis. (2) Sugar by the volumetric 
and by the gravimetric method. (3) Nitrogen in organic sub- 
stances, by the Kjeldahl method. (4) Milk, complete analysis : 
total solids, fat, sugar, proteids, ash. (5) Butter; water, vola- 
tile and insoluble fatty acids, iodin equivalent, by Hiibl’s 
method, melting point. (6) Water, sanitary examination ; total 
solids, free and albuminoid ammonia, chlorids, nitrates, nitrites, 
oxygen consumed, oxygen dissolved. (7) Potassium in a salt. 
(8) Phosphorus pentoxid in a salt, by the molybdate method. 
(9) Urine; urea by hypobromite, phosphorus pentoxid, by the 
volumetric uranium method, chlorin by Volhard’s volumetric 
method. 
(10) Feldspar, complete; silicic oxide, aluminum oxide, potas- 
sium oxide, calcium oxide, etc. (n) Nitrogen pentoxid, by 
modified Kjeldahl method, by method of Pelouze and Fresenius. 
(12) Organic ultimate analysis; carbon and hydrogen in a solid, 
and in a volatile liquid; sulfur, chlorin : nitrogen by the absolute 
method. (13) Iron and steel; phosphorus by the molybdate- 
magnesia method, and by titration of the molybdate precipitate 
with permanganate; manganese, by the Williams method ; car- 
bon, by the chromic acid method. (14) Chemical toxicology, 
inorganic; detection and determination, in a mixture with 
organic matter, of arsenic, and one other substance from the 
following list: antimony, lead, copper, mercury, cyanogen, 
phosphorus. 
(15) Chemical toxicology, organic; detection, in mixture with 
organic substance, of two alkaloids selected from the follow- 
ing list: atropine, aconitine, brucin, coniine, morphine, narco- 
tine, nicotin, strychnin, veratrin, (16) Tannin in tanning 
materials, or indigo, analysis for valuation ; by two methods. 
(17) Alloys, two from the following list: type metal, solder, 
bronze, Wood’s metal, tin and lead, bismuth and lead, phosphor 
bronze. (18) Complete analysis of two minerals selected from 
the following list: beryl, chromite, franklinite, cassiterite, spha- 
lerite, chalcopyrite, wavellite, celestine, bornite, stibnite, molyb- § 157-] 
APPARATUS, REAGENTS, ETC. 
171 
denite, lepidolite, rutile, fahlerz, strontianite, wolframite, petalite, 
boronatrocalcite. 
(19) Separations; nickel and cobalt; arsenic, antimony and 
tin. (20) Wine, or tobacco, or food substance, complete analysis; 
in wine, alcohol, extract, sugar, free acid, tannin, glycerine; in 
tobacco, nicotin, nitrate, ammonia; in food or fodder, ash, 
proteids, ether-extract, fiber, nitrogen-free extract, non-albumi- 
noid nitrogen. (21) Analysis by electrolysis; separation and 
determination of copper and manganese, copper and lead, copper 
and nickel, antimony and tin. 
In connection with this work, and partly following it, instruc- 
tion is also given in gas analysis, and the use of the micro- 
scope, spectroscope, colorimeter, polariscope, and refractometer, 
in chemical analysis. INDEX. 
Acetic acid, in qualitative analysis, 58, 66. 
Acid, defined, 9 
Acidification, operation of, 33. 
Acidimetry, 139. 
Acidigenic elements and groups, list of, 25. 
Acidigens, or acids, notes on the chemistry 
ot the analysis for, 59. 
Acids, barium group, solubility of com- 
pounds and reactions, 53 ; analysis of, 61; 
organic group, ditto, ditto, 58, 66 ; oxi- 
dizing group, ditto, ditto, 58, 66; silver 
group, ditto, ditto, 56, 63. 
Alkalimetry, 139. 
Alkalization, 33. 
Aluminum in qualitative analysis, 92, 93 ; 
—- group of basigens, forms of occur- 
rence and reactions, 92; analysis for, 
92; notes on chemistry of analysis for, 
92 ; 
Ammonia, standard solution, preparation, 
141; determination of strength of, 144 ; 
solution, Table of specific gravity, 
167. 
Ammonium, in qual. analysis, 98, 99 ; 
carbonate, as reagent, 162 ; hy- 
droxid, reagent, preparation, 162; 
magnesium phosphate, as quant, ppt., 
146 ; molybdate, reagent, prepara- 
tion, 162 ; sulfid, reagent, prepa- 
ration, 163. 
Antimony in qual. analysis, 72-78; deter- 
mination by iodometry, 154. 
Apparatus, qualitative set, 155; directions 
for use of, 155; quantitative set, 
larger, 158 ; smaller set, 157. 
Aqua regia, oxidation and chlorination by, 
16. 
Areometer, principle of, 127. 
Arsenic in qual. analysis, 71, 78. 
Asbestos filters, 121. 
Assay : the testing of a metal or an ore to 
determine the proportion of its valu- 
able constituents. 
Atomic weights, table of, 166. 
Balance, description and use of, 101-103. 
Barium, in qual. analysis, 94, 97 ; sul- 
fate, as quantitative ppt., 138. 
Base, defined, 10. 
Basigenic elements and groups, list of, 25. 
Bismuth in qual. analysis, 79, 83. 
Boiling of liquids, loss in, 32 ; how to conduct, 
36. 
Boric acid, in qual. analysis, 55, 62. 
Bromin, conditions under which set free, 
29 ; oxidation by, 17; solution 
as reagent, 163. 
Burette, calibration, 114; use of, 112. 
Cadmium, in qual. analysis, 79, 83. 
Calcium, in qual. analysis, 94, 97 ; determi- 
nation of, 147; group, forms of 
occurrence and reactions, 94; analysis 
of 95 ; notes on chemistry of analysis, 
95; oxalate, as quant, ppt., 147; 
oxidation of by KMn04,148. 
Caldwell-Gooch crucible, 121; platinum 
jacket for, 122. 
Calibration; the determination of the rela- 
tive values of the different parts of a 
scale. 
Calibration of graduated instruments, 113. 
Carbonate, analysis of by alkalimetry, 144. 
Carbon dioxid, in qual. analysis, 53,61. 
Chloric acid, in qual. analysis, 58, 69. 
Chlorination, defined, 11 ; conditions of, n ; 
reactions of, 16. 
Chlorin, conditions under which set free, 28. 
Chromic acid cleaning mixture, 163. 
Chromium in qual. analysis, as acidigen, 54, 
62 ; as basigen, 92, 93. 
Chromic acid, oxidation by, 18. 
Citric acid in qual. analysis, 58, 67. 
Cleaning mixture, chromic acid, 163. 
Cleanliness in laboratory, 38. 
Cobalt in qual. analysis, 84, 90. 
Cochineal tincture, reagent, 163. 
Copper, determination by electrolysis, 153 ; 
in. qual. analysis, 79,83 ; group, 
forms ot occurrence and reactions, 79 ; 
analysis for, 83; notes on chemistry of 
analysis for, 80 ; separation from 
silver, 151. 
Cylinders, graduated, 113. 
Decantation, 37. 
Desiccator, ic6. 
Digestion, 35. 
Electrolysis, determination of copper by, 
153; of silver, 152. 
Elements and groups of same; basigenic 
and acidigenic, Table of, 25. 
Effervescence; foaming or bubbling of a 
liquid, due to the rapid setting free of a 
gas in it. 
Equation, chemical, correct writing of, 22 ; 
common errors in, 26; signs of, 25. 
Ferric chlorid, reagent, preparation, 164. 
Ferrous sulfate, reagent, preparation, 164. 
Ferrous and ferric hydroxids, in quant, 
analysis, 135 
Filters, quantitative, 117; strengthened 
by treatment with HNO3, 119. 
Filtration, 36; quantitative, 117 ; by 
suction, 119; in Gooch crucible, 121. 
Fluxing, 31. 
Formulas, graphic or structural, 23. 
Gases, solution of, 7. 
Gooch crucible, 121. 
Gold in qual. analysis, 71, 78. 
Graduated instruments, directions for use 
of, 115. 
Gravimetric analysis, definition of, 100. 
Grouping of substances, qualitative, 41. 
Groups of elements, acidigenic and basi- 
genic, 25. 
Hydriodic acid in qual. analysis, 56, 64. 
Hydrobromic acid in qual. analysis, 56, 64. 
Hydrochloric acid in qual. analysis, 57, 65 ; 
determination of, gravimetric, 142 ; 
standard solution of, preparation, 
141, and determination of absolute 
173 174 
INDEX, 
strength, 142; as reagent, prepara- 
tion, 162 ; Table of specific gravity 
of, 168. 
Hydrocyanic acid in qual. analysis, 57, 64. 
Hydroferricyanic acid, in qual. analysis, 
57, 65. 
Hydroferrocyanic acid, in qual. analysis, 
57. 65. _ 
Hydrofluoric acid, in qual. analysis, 55, 62. 
Hydrogen, conditions under which set free, 
28. 
Hydrosulfuric acid, in qual. analysis, 56, 
64. 
Hydroxids, properties, 44. 
Hygroscopic, tending to absorb moisture. 
Hygroscopic substance, weighing of, 104. 
Ignition of residues from evaporation, 32 ; 
of quantitative ppts., 123. 
Indicator; in volumetric analysis, the sub- 
stance employed to show when the re- 
action is completed. 
Indicators, 140. 
Indigo solution, reagent, preparation, 164. 
lodm, conditions under which set free, 29. 
lodin solution, reagent, preparation, 164. 
lodometry defined, 149 ; preparation of 
solutions for, 149 ; determination of 
antimony by, 150. 
Iron, in qual. analysis, 84, 91; determi- 
nation of, gravimetric, 135, ditto volu- 
metric, 136; group, forms of occur- 
rence and reactions, 84 ; analysis of, 
go; —— notes on tbe chemistry of the 
analysis for, 86. 
Lead, acetate and ammonium acetate mix- 
ture as reagent, preparation, 164. 
Lead, in qual. analysis, 67, 70 ; determi- 
nation, 145; sulfate, properties as 
quant, ppt., 145. 
Limonite, assay of, 138. 
Litmus solution, preparation, 164. 
Magnesia mixture, reagent, preparation, 
164. 
Magnesium in qual. analysis, 94 97 ; py- 
rophosphate, as quant, ppt., 146. 
Manganese, in qual. analysis, 84, 91. 
Manipulations of analytical chemistry, 30. 
Maxims, special, for quantitative work, 132. 
Measuring flask, 113; how to use for 
making certain volume of a solution, 
ttS- 
Measurement in volumetric analysis, stand- 
ard of, 107. * 
Measures and weights, comparison of, 169. 
Meniscus ; the curved surface of a liquid 
caused by capillarity. 
Mercury in qual. analysis, 68, 70, and 79, 
83. 
Metals, solubility of, 6. 
Metathesis, defined, 18 ; kinds of, 21. 
Neutralization, 33. 
Nickel in qual. analysis, 84, 90. 
Nitric acid, in qual. analysis, 58.66; 
oxidation by, 15 ; as reagent, pre- 
paration of, 162; Table of specific 
gravity of, 168. 
Nitrogen, conditions under which set free, 
29- 
Normal solution, defined, 108. 
Note-book, quantitative, 130. 
Oxalic acid, in qual. analysis, 54, 62. 
Oxidation, defined, n ; conditions of, 
11 ; reactions of, 15. 
Oxygen, conditions under which set free, 27 ; 
free, oxidation by, 15. 
Pheynl-sulfuric acid, reagent, preparation, 
164. 
Phosphoric acid, in qual. analysis, 55, 63; 
anhydrid, determination, 146. 
Pipette, 112; calibration of 114; 
measuring out several portions with, 
115; specific gravity, 128. 
Platinum, in qual. analysis, 71, 78; 
ware, use and care of, 129. 
Potassium, in qual. analysis, 98, 99; 
group, forms of occurrence and reac- 
tions, 98; notes on analysis of, 98; 
chlorate, oxidation and chlorina- 
tion by, 17; dichromate, standard 
solution of, 137; permanganate, 
standard solution of, 148. 
Precipitation, 34 ; quantitative, testing 
for completeness of, 117. 
Precipitates, description of, 34; dissolving 
of, 37 I washing of, 37,120. 
Precipitates, quantitative, 117; ignition of, 
125 ; preparation for weighing, 123 ; 
removal of from beaker, 118 ; transfer 
to crucible, 123 ; washing of, 120. 
Qualitative analysis, order of arrangement 
of work, 46; course of, tabular view, 49. 
Rapidity of work, 38, 133. 
Reaction; the chemical change produced 
by a reagent. 
Reagent; the chemical substance used to 
take part in producing some desired 
chemical change, in chemical analysis. 
Reagents, addition of in excess, 33; list of 
in alphabetical order of full names, 159, 
ditto in alphabetical order of formulas, 
160 ; purity of, 165. 
Records of quantitative work, 131. 
Reduction, defined, 13; agents of, 14; 
conditions of, 13 ; reactions of, 14. 
Residue : that portion of a substance that 
is left after treatment of it with a sol- 
vent in some prescribed manner, or 
after igniting it. 
Results of quantitative determinations; cal- 
culation, 125; recording of, 130. 
Salt, defined, 10; acid, basic, normal, 
10, 11; solubility in acids, 6. 
Silicic acid, in qual. analysis 55, 63. 
Silver, in qual. analysis, 67, 70; group 
of basigens, forms of occurrence and 
reactions, 67 ; analysis of, 68 ; notes on; 
the chemistry of the analysis, 68 ; 
chlorid, as quantitative precipitate, 142 
determination, 152,153 ; separation from 
copper, 151, 153, 
Sodio-cobaltic nitrite, reagent, 164. 
Sodium, in qual. analysis, 98, 99. 
Solids, obtained from solutions, by cooling 
of saturated solutions, 8; ditto, by 
removal of solvent agent, 9. 
Solubilities, Table of, 5. 
Solubility of salts in acids, 6. 
Solution, 3 ; chemical, 4 ; deter- 
mination of specific gravity of, 126 
of gases and vapors, 7; making 
of, 30 ; physical, 3; relation of 
specific gravity to amount of substance 
contained, 126 ; relation to tempera- 
ture, 6, 7 ; of substance for quali- 
tative analysis, 48; ditto, for quanti- 
tative analysis, 116. 
Solutions, Tables of relative specific gravity 
and contents explained, 126. 
Solvents, different solvent power compared, 
6. 
Specific gravity of solutions, by areometer, 
126; ditto, by specific gravity pipette,. INDEX. 
Stochiometry ; the application of the laws 
of chemical combination in fixed pro- 
portions, in chemical calculation. 
Standard solutions defined, 108 ; use of, 
112. 
Stannous chlorid, reagent, preparation, 165. 
Strontium in qual. analysis, 94, 97. 
Substance for analysis, quantitative, quantity 
taken, 104. 
Suction filtration, 119. 
Sulfids, properties of, 42. 
Sulfuric acid, in qual. analysis, 53, 61; 
as reagent, preparation of, 162 ; 
Tables of specific gravity of, 167. 
Sulfuric trioxid, determination of, 150. 
Sulfurous acid, in qual. analysis, 54, 62. 
Tests, final, qualitative, 46. 
Tin, in qual. analysis, 73, 78; group, 
forms of occurrence and reactions, 71; 
analysis of, 78; notes on the chemistry 
of the analysis, 74. 
Titration: in volumetric analysis, the act 
of adding the standard solution to the 
solution of the substance under analysis, 
for the purpose of determining how 
much of it is required to react upon the 
substance to be estimated. 
Valence of the elements, 23. 
Vapors, solution of, 7. 
Volumetric analysis, definition of, too. 
Wash-bottle, how to use, 120. 
Washing, quantitative precipitates, 120. 
Weighing, directions for, 103-106; 
records of, 106 ; tubes, 107. 
Weights, atomic. Table of, 166; set 
of, for balance, described, 102 ; and 
measures, compared, 169. 
1 
Zinc, in qual. analysis, 89, 91.