A COMPENDIOUS MANUAL 
- 
OP 
QUALITATIVE CHEMICAL ANALYSIS. 
BY 
CHARLES W. ELIOT and FRANK H. STORER. 
REVISED, WITH THE CO-OPERATION OF THE AUTHORS, 
¥m. RIPLEY NICHOLS, 
of General Chemistry in the Massachusetts Institute} of Technology. 
EIGHTH REVISED EDITION. 
NEW YORK: 
D. VAN NOSTRAND, PUBLISHER, 
23 Murray Street aud 27 Waiike-n’ Street. 
1883. Entered, according to Act of Congress, in the year 1872, by 
C. W. Eliot, F. H. Stoker and W. R Nichols, 
In the Office of the Librarian of Congress, at Washington. PREFACE. 
The authors have endeavored to include in this short treatise 
enough of the theory and practice of qualitative analysis “ in the 
wet way,” to bring out all the reasoning involved in the subject, 
and to give the student a firm hold upon the general manciples 
and methods of the art. It has been their aim to give only so 
much of mechanical detail as is essential to an exact comprehension 
of the methods and to success in the actual experiments. Hence, 
the multiplication of different tests or processes, having essentially 
the same object, has been purposely avoided. For the same reason 
none of the rare elements are alluded to. The manual is intended 
to meet the wants of the general student, to whom the study is 
chiefly valuable as a means of mental discipline and as a compact 
example of the scientific method of arriving at truth. To profes- 
sional students who wish to make themselves expert analysts, this 
little book offers a logical introduction to the subject, an outline 
which is trustworthy as far as it goes, but which needs to be filled in 
and enlarged by the subsequent use of some more elaborate treatise as 
a book of reference. Prof. Johnson, of Yale, has supplied this need 
with his excellent edition of Fresenius’s comprehensive manual. 
The authors believe that they have put into the following pages 
as much of inorganic qualitative analysis as is useful for training, 
and also as much as the engineer, physician, agriculturist, or lib- 
erally educated man needs to know. The book has been written 
for the use of classes in the Institute of Technology, who have 
already studied the authors’ “Manual of Inorganic Chemistry.” It 
Is simply an implement devised to facilitate the giving of thorough iv 
PEEFACE. 
Instruction to large classes in the laboratory. It is the authors’ 
practice to examine their classes orally every four or five exercises, 
in order to secure close attention to the reasoning of the subject. 
With this exception, the subject is studied exclusively in the labor- 
atory, tools in hand. Fifty laboratory exercises of two hours each 
have proved sufficient to give their classes a mastery of the subject 
as it is presented in this manual. 
It is scarcely necessary to say that this little work is a compila- 
tion from well-known authorities, among which may be particularly 
mentioned the works of Galloway, Will, Fresenius, and Northcote 
& Church. 
Boston, April, 1869. 
PEEFACE TO THE EEVISED EDITION. 
In this revised edition, undertaken with the advice and consent 
of the authors, such alterations and additions have been made as 
have been suggested by the use of the book with a number of 
classes in the laboratory. 
w. b. N. 
Boston, July, 1876, TABLE OE CONTENTS. 
Introduction. Qualitative analysis defined. Scope of this manual. PA0B 
Identifying compounds. Division of the subject. ...... 1-3 
Chapter I. Example of the separation of two elements. Division of 
twenty-four metallic elements into seven classes. 4-19 
Chapter II.' Class I. Chlorides insoluble in water and acids. Lead. 
Silver. Mercury 17-20 
Chapter III. Class II. Sulphides insoluble in water, dilute acids and 
alkalies. Mercury. Lead. Bismuth. Copper. Cadmium. The pre- 
cipitation of Classes II and III. .......... 21-23 
Chapter IV. Class III. Sulphides insoluble in water or dilute acids, 
but soluble in alkaline solutions. Arsenic. Antimony. Tin. [Gold 
and Platinum.] 23-36 
Chapter V. Class IV. Hydrates insoluble in water, ammonia-water, 
and solutions of ammonium salts. Simultaneous precipitation of some 
salts which require an acid solvent. Treatment of the precipitate, pro- 
duced by ammonia-water. Chromium. Aluminum. Manganese. Iron. 
Separation of Class IV from Classes II and III. The original condi- 
tion of iron. The use of chloride of ammonium. Interference of or- 
ganic matter 37 46 
Chapter VI. Class V. Sulphides insoluble in water and in saline or 
alkaline solutions. Manganese. Zinc. Nickel. Cobalt. Separation 
of Class V from Class IV. 47-32 
Chapter VII. Class VI. Carbonates insoluble in water, ammonia-water 
and saline solutions. Barium. Strontium. Calcium. Separation of 
Class VI from the preceding classes 33-33 
Chapter VIII. Class VII. Three common metallic elements not com- 
prised in the preceding classes. Magnesium. Sodium. Potassium. 
Table for the separation of the seven classes of the metallic elements. . 39-63 
Chapter IX. General tests for the non-metallic elements. The classes of 
salts treated of. General reactions for acids. Metallic elements to be 
first detected. The barium test. The oalcium test. The .silver test. 
Nitrates, chlorates and acetates. .......... 64-71 
PART I. vi 
CONTENTS. 
PACK 
Chapter X. Special tests for the non-metallic elements. Effervescence. 
Carbonates. Cyanides. Sulphides. Sulphites. Hyposulphites. Chro- 
mates. Arsenites and Arseniates. Sulphates. Phosphates. Oxalates. 
Tartrates. Borates. Silicates. Fluorides. Chlorides. Bromides. 
Iodides. Nitrates. Chlorates. Acetates. ... .... 74-83 
PART n. 
Treatment of substances of unknown composition. General 
observations. Husbanding material. 89 
Chapter XI. Treatment of a salt, mineral or other non-metallic solid. 
Order of procedure. . . . Preliminary examination in the dry way. 
Closed-tube test. Gases or vapors to be recognized. Sublimates. Re- 
duction test. Metallic globules. . . . Dissolving a salt, mineral or 
other non-metallic solid, free from organic matter. Dissolving in water. 
Dissolving in acids. . . . Treatment of solutions obtained. An 
aqueous solution: neutral, acid, alkaline. An acid solution. . . . 
Examination of the solutions for the non-metallic elements. . . . 
Table of solubilities. . . . Treatment of insoluble substances. 
Fusions. Treatment of the fused mass. Decomposition by means 
of carbonate of calcium and chloride of ammonium. Fusion with acid 
sulphate of sodium. Deflagration. ......... 90-129 
Chapter XII. Treatment of a pure metal or alloy. Action of nitric 
acid on metals. Gold test. Platinum test 121-124 
Chapter XIII. Treatment of liquid substances. Evaporation test. Test- 
ing with litmus. Testing for ammonia. ........ 125,129 
APPENDIX. 
Reagents. Acids. Sulphuretted hydrogen. Ammonia-water. Ammo- 
nium salts. Caustic soda. Sodium salts. Potassium salts. Nitrate of 
silver. Calcium salts. Barium salts. Acetate of lead. Lead paper. 
Magnesium mixture. Ferric chloride. Nitrate of cobalt. Sulphate of 
copper. Chloride of tin. Oxide of manganese. Mercury salts. Bi- 
chloride of platinum. Zinc. Solution of indigo. Litmus paper. Starch 
paste. Alcohol. Water. . . . Solutions of known composition. 
. . . Utensils. Reagent-bottles. Test-tubes. Test-tube rack. 
Flasks. Beakers. Glass funnels. Filtering. Filter-stand. Rapid 
filtration. Porcelain dishes and crucibles. Lamps. Blast-lamps and 
blowers. Iron-stand. Tripod. Wire-gauze. Triangle. Water-bath. 
Sand-bath. Blowpipes. Platinum foil and wire. Pincers. Platinum 
crucibles. Wash-bottle. Glass tubing. Stirring-rods. Cutting and 
cracking glass. Bending and closing glass tubes. Blowing bulbs. 
Caoutchouc. Corks. Gas-bottle. Self-regulating generator. Mortars. 
Spatula. *••••• i-xlvi. QUALITATIVE ANALYSIS. 
INTRODUCTION. 
1. Qualitative Analysis, in the widest sense of the term, 
is the art of finding out the elements contained in compound 
substances. The general definition has important limitations 
in practice. In the first place, the art, as commonly taught, 
applies almost exclusively to mineral, or inorganic, substances, 
and touches only incidentally upon the multifarious compounds 
of carbon with hydrogen, oxygen, nitrogen and a few other 
elements, which form the subject-matter of that branch of 
chemical science called organic chemistry. Again, the 
analysis of gases constitutes a distinct branch of analysis, 
requiring methods and apparatus of its own, and therefore 
to be most advantageously studied by itself. These deduc- 
tions made, there remains the analysis of inorganic solids 
and liquids, which is in fact the main subject of qualitative 
analysis in the present technical sense of the term. 
Of the sixty-four recognized chemical elements, only the 
thirty-four most important are embraced in the systematic 
course of this manual. Means of detecting a few other less 
common elements are incidentally given; but most of the 
elements which are so rare as to be at present of little inter- 
est except to the professional chemist or mineralogist are not 
alluded to. 
2. Some previous knowledge of general chemistry is es- 
sential to the successful study of qualitative analysis. It is 
assumed that the student knows something of the common 2 
IDENTIFYING COMPOUNDS. 
§ 3 
elements and of their most important combinations, that he 
is familiar with the principal laws which govern chemical 
changes, and that he possesses a certain skill in the simplest 
manipulations. The tools and operations employed in quali- 
tative analysis are few and simple; but neatness, method in 
working and a vigilant attention even to the minutest details, 
are absolutely essential. As the various substances used or 
produced in the operations of analysis will not be particularly 
described, the careful student will keep at hand some text- 
book on general chemistry, to which he can constantly refer 
to refresh his recollection of the formulae and physical and 
chemical properties of the substances referred to. It should 
be observed that it is often very difficult — in fact, impossible 
in the present state of knowledge — to express in exact 
equations the involved or obscure reactions which occur in 
complex mixtures during the operations of analysis. It is a 
useful exercise for students to write out in equations the 
simpler chemical changes which occur in analysis ; but when 
the attempt is made to put a complex reaction into numerical 
symbols, the equations are apt to express either more than 
we know, or less. 
3. Although the detection of the elements contained in 
compound substances is the ultimate object of analysis, it is 
only by exception that the elements themselves are isolated, 
and recognized in their uncombined condition. An element 
is generally recognized through some familiar compound, 
whose apparition proves the presence of all the elements it 
contains, just as the presence of any word upon this page 
makes it sure that the letters with which it is spelt are im- 
printed there. If, as the result of a definite series of opera- 
tions upon some unknown body, the hydrated oxide of iron 
be produced, no iron having been added during any stage of 
the process, the proof of the presence of iron in the original 
body is quite as certain as if the gray metal itself had been 
extracted from it. If some well-known sulphate, like sul- 
phate of lead, or of barium, for example, result from a series § 4 
IDENTIFYING COMPOUNDS. 
of experiments upon some unknown mineral, it is certain that 
the mineral contained sulphur; provided only that no sulphur 
has been introduced in any of the chemical agents to whose 
action the mineral has been submitted. 
The compounds through which the elements are recognized 
are necessarily bodies of known appearance, deportment and 
properties. They are, in fact, bodies of various, though 
always definite, composition; oxides, sulphides, chlorides, 
sulphates and many other salts, are thus made the means of 
identifying one or more of the elements which they contain. 
The object of the analyst is to bring out from the unknown 
substance, by expeditious processes and under conditions 
which admit of no doubt as to their testimony, these identi- 
fying compounds, with whose appearance and qualities he has 
previously made himself acquainted. As he follows the 
course of experiments laid down in this manual, the student 
will gradually acquire, with the aid of frequent references to 
a text-book of general chemistry, that stock of information 
concerning the identifying compounds which must be always 
ready for use in his mind, and at the same time he will be 
made familiar'with the character of the methodical processes 
which secure a prompt and sure testimony to the elementary 
composition of the substances he examines. 
4. The subject is treated in two parts or divisions, of 
which the first contains a series of experiments to illustrate a 
systematic course of examination for substances in solution, 
when once that solution has been made; while the second 
treats chiefly of the preliminary examination of solids and 
the means of bringing them into solution, and indicates the 
general methods to be pursued in the actual analysis of a 
substance of unknown composition. PART FIRST. 
CHAPTER I. 
DIVISION OF THE METALLIC ELEMENTS INTO CLASSES. 
5. Example of the Separation of two Elements. — Put 
a small crystal of nitrate of silver and a small crystal of 
sulphate of copper into a test-tube (Appendix, § 65), and 
dissolve them in two -teaspoonfuls of water, warming the 
water at the lamp to facilitate the solution. Add to this 
solution a few drops of dilute chlorhydric acid (App., § 3). 
Shake the contents of the tube violently, wait until the curdy 
precipitate, which the acid produces, has separated from the 
liquid, and then add one more drop of chlorhydric acid. If 
this drop produces an additional precipitate, repeat the oper- 
ation until the new drop of acid produces no change in the 
partially clarified liquid. Then, and not till then, has all the 
silver which the original solution contained been precipitated 
in the form of chloride of silver, an unemployed balance or 
excess of the reagent, chlorhydric acid, remaining in the clear 
liquid; this liquid can be readily separated by filtration from 
the curdy chloride. 
Shake the contents of the test-tube, and transfer them as 
as possible to a filter (App., § 70), supported in a 
very small glass funnel (App., § 69), which has been placed 
in the mouth of a test-tube. With a wash-bottle (App., § 81) 
rinse into the filter that portion of the precipitate which 
has adhered to the sides of the first test-tube. When the § 6 
TEE TERM CLASS. — CLASS I. 
5 
filtrate has drained completely frotn the precipitate, set the 
test-tube which has received it aside. Wash the precipitate 
together into the apex of the filter by means of a wash-bottle 
with a fine outlet; and, in order to wash out the soluble 
sulphate of copper which adheres to the precipitate, fill the 
filter full of water two or three times, throwing away this 
wash-water when it has passed through the filter. 
The complete separation of the silver and copper which 
were mixed in the original solution is already accomplished ; 
the silver is on the filter in the form of chloride ; the copper 
is in the clear, bluish filtrate. This speedy and effectual 
separation of the two elements is based upon the fact that 
chloride of silver is insoluble in water and acid liquids, and 
is, therefore, formed when chlorhydric acid is added to a 
solution containing a salt of silver; chloride of copper, how- 
ever, is readily soluble in water and acid liquids, and, even 
if formed by the addition of chlorhydric acid to a solution 
of a compound of copper, would fail to manifest itself by 
appearing as a precipitate. It is, in general, true that when- 
ever, by the addition of a reagent, there can be formed in any 
solution a compound insoluble in the liquids present, this 
compound always separates as a precipitate. Such differ- 
ences of solubility as are illustrated by the case of the chlor- 
ides of silver and copper are the chief reliance of the analyst. 
6. Definition of the term “ Class.” Class I. — In the 
foregoing experiment only two elements have been separat- 
ed. It might obviously be very difficult, if not impossible, to 
find a special reagent for every element, which would always 
precipitate that single element and never any otjier. Chlor- 
hydric acid, for example, which precipitatessilver so ad- 
mirably from any solution containing that element, is capable 
of eliminating two other elements under like conditions. The 
lower chloride of mercury (mercurous chloride or calomel) is 
insoluble in water and weak acids. Chloride of lead is 
sparingly soluble in cold water, and is still less soluble in 
water acidulated with chlorhydric acid. The chlorides of the 6 
DIVISION INTO CLASSES. 
§ 6 
other metallic elements are all soluble in water, and acids 
under the conditions of the analytical process. 
There are embraced in the scope of this manual twenty- 
two of the so-called metallic elements, — elements whose 
hydrates or oxides are said to be basic in their character, and 
are collectively designated as bases : if chlorhydric acid were 
added in proper quantity to a solution imagined to contain 
all these elements, three, and only three, of the twenty-two 
elements would be precipitated as chlorides. After filtration 
and washing, a mixture of chloride of silver, chloride of lead 
and mercurous chloride would remain upon the filter, and all 
the other elements would have passed as soluble compounds 
into the filtrate. Silver, lead and mercury, the three ele- 
ments thus separated from the rest by this well-marked 
reaction with chlorhydric acid, constitute a class, the first of 
several classes into which the metallic elements are divided 
for the ends of qualitative analysis. Each class is character- 
ized by some clear reaction which suffices, when intelligently 
applied, to separate the members of any one class from the 
other classes. The chemical agent, by means of which this 
distinctive reaction is exhibited, is called the general reagent 
of the class. Thus, chlorhydric acid is the general reagent of 
the first class. 
This division of the elements into classes renders it un- 
necessary to find means of separating each individual element 
from all the others. In the systematic course of an analysis, 
the classes are first sought for and separated; afterwards 
each class is treated by itself for the detection of its individ- 
ual members. It is an incidental advantage of this division 
of the elements into classes that, when the absence of any 
whole class has been proved by the failure of its peculiar 
general reagent to produce a precipitate in a solution under 
examination, it is unnecessary to search further for any mem- 
ber of that class. Much time is thus saved, for it is as easy 
to prove the absence of a class as of a single element. The 
full treatment of the first class of elements, comprising, as §§7,8 
DIVISION INTO CLASSES. 
we have seen, silver, lead and mercury, is the subject of 
Chapter II. 
7. Experiment to Illustrate the Division of the Me- 
tallic Elements into Classes. — We proceed to demonstrate 
experimentally the chemical facts upon which rests the divis- 
ion of the other metallic elements into convenient classes. 
Prepare a complex solution, by mixing together in a small 
beaker (App., § 68) a small teaspoonful of each of the fol- 
lowing solutions (App., § 62), viz.: — chloride of copper, ar- 
senious acid in chlorhydric acid, ferrous chloride, chloride of 
zinc, chloride of calcium, chloride of magnesium and chloride 
of sodium. Dilute the mixture thus prepared with its own 
bulk of water. Should any turbidity or precipitate appear, 
add chlorhydric acid, little by little, until the solution be- 
comes clear. This solution is representative ; it contains at 
least one member of each of the classes of elements which 
remain to be defined. It contains no member of the first 
class ; but we may consistently suppose that the members of 
this class have been previously precipitated, as in the fore- 
going experiment (§5), and that an excess of chlorhydric 
acid remains in the liquid. 
8. Definition of Classes II and III. — Pass a slow current 
of sulphuretted hydrogen (App., § 14) from a gas-bottle or 
self-regulating generator through the acid liquid in the beaker. 
This operation must be performed either out of doors or in a 
current of air sufficient to carry the excess of the gas away 
from the operator. A dense, dark colored precipitate will 
immediately appear, and gradually increase in bulk. When 
the gas has flowed continually for five or ten minutes through 
the liquid, remove the beaker from the source of the gas (or 
interrupt the stream of gas if a self-regulating generator be 
employed), stir the liquid well, and blow out the sulphuretted 
hydrogen which lies in the beaker. If after the lapse of two 
or three minutes the liquid smells distinctly of sulphuretted 
hydrogen, it is saturated with the gas, and it is sure that the 
reagent has done its work. If the liquid does not retain the 8 
DEFINITION OF CLASSES II AND III. 
§ 8 
characteristic odor, the gas must be again passed through it 
until saturation is certainly attained. 
In order to obtain still further assurance of the saturation 
of the liquid, it is often well to take the first portions of the 
filtrate of the succeeding paragraph and add a small quantity 
of sulphuretted hydrogen water (App., § 15). If a sufficient 
amount of the gas had not been passed into the liquid,'the 
addition of the sulphuretted hydrogen water would cause the 
appearance of a precipitate. In such a case the filtered por- 
tion must be returned to the beaker and the stream of gas 
again passed through the liquid. 
Pour the contents of the beaker, well stirred up, upon a 
filter which is supported over a test-tube or second beaker. 
Rinse the first beaker once with a teaspoonful of water, and 
transfer this rinsing water to the filter, allowing the filtered 
liquid to mix with the original filtrate. Label* this filtrate 
“ Filtrate from II and III ” (classes), and preserve it for 
later study. 
If any considerable quantity of precipitate has adhered to 
the sides of the original beaker, it may be detached and 
washed on to the filter by means of a sharp jet of water from 
the wash-bottle. The precipitate, as it lies upon the filter, 
must then be washed once or twice with water ; the wash-water 
* The student should at once make it a rule to label every filtrate or 
precipitate which he has occasion to set aside, even for a few moments. A 
bit of paper large enough to carry a descriptive symbol or abbreviation 
should be attached to the vessel which contains the liquid or precipitate. 
Paper gummed on the back or the small labels which are sold already 
gummed are convenient for this use. 
This habit, once acquired, will enable the student to carry on simul- 
taneously without error or confusion, several operations. He may be 
throwing down one precipitate, washing another, filtering a third, and 
dissolving a fourth at the same time, and the four processes may belong to 
as many different stages of the analysis. There will be no danger of error 
if labels are faithfully used ; and a great deal of time will be saved. The 
unaided memory is incapable of doing such work with that full certainty, 
admitting of no suspicion or after-qualms of doubt, which is alone satisfy- 
ing, or indeed admissible, in scientific research. §8 
CLASSES II AND III. 
9 
is thrown away. The washed precipitate consists of a mix- 
ture of sulphide of copper (CuS) and tersulphide of arsenic 
(As3S3). The fact that these sulphides are precipitated under 
the conditions of this experiment proves that the}' are both 
insoluble in weak acid liquors. They are also both insoluble 
in water. But an important difference between the two sul- 
phides nevertheless exists, a difference which affords a trust- 
worthy means of separating one from the other. 
When the water has drained away from the precipitate, open 
the filter upon a plate of glass, and gently scrape the precipi- 
tate off the paper with a spatula of wood or horn. Place the 
precipitate in a small porcelain dish (App., § 73), pour over 
it enough of a solution of sulphydrate of sodium (App., § 23) 
to somewhat more than cover it, and heat the mixture cau- 
tiously to boiling, stirring it all the time with a glass rod. 
The quantity of sulphydrate of sodium to be employed varies, 
of course, with the bulk of the precipitate ; in this case two 
or three teaspoonfuls will probably suffice. It is very undesi- 
rable to use an unnecessarily large quantity of the reagent for 
reasons that will hereafter appear. A portion of the original 
precipitate remains undissolved; but a portion has passed 
into solution. Filter the hot liquid again. The black residue 
on the filter is sulphide of copper, which is insoluble, not only 
in water and weak acids, but also in alkaline liquids. To the 
filtrate, collected in a test-tube, add gradually chlorhydric 
acid, until the liquid has an acid reaction on litmus paper 
(App., § 58). A yellow precipitate of sulphide of arsenic will 
appear as soon as the alkaline solvent which kept it in so- 
lution is destrojmd. The sulphide of arsenic differs from the 
sulphide of copper in that it is soluble in alkaline liquids. 
In this series of experiments copper and arsenic stand, not 
as isolated elements, but as representatives of classes. The 
following common elements have sulphides which are insoluble 
in water, weak acids and alkaline liquids : — Lead, mercury, 
bismuth, cadmium and copper. These elements constitute 
Class II in our system of analysis. The following elements 10 
MERCURY AND LEAD. 
§§8,9 
have sulphides which are insoluble in water and weak acids, 
but soluble in alkaline liquids: — Arsenic, antimony, tin (and 
the precious metals gold and platinum). These elements con- 
stitute Class III. If all the elements of both groups had 
been present in the original solution, one class might have 
been separated from the other by the same process employed 
in the case of the representative elements, arsenic and copper. 
The question may naturally suggest itself, how it happens 
that lead and mercury are included in Class II, when they were 
both precipitated in Class I. The chloride of lead, which is 
thrown down by chlorhydric acid, is not wholly insoluble in 
water ; hence it happens that the lead is not completely pre- 
cipitated in Class I. That portion of the lead which has 
escaped precipitation as chloride in Class I, will be thrown 
down as sulphide in Class II, for the sulphide of lead is in- 
soluble in water, weak acids and alkalies. In regard to 
mercury, it will be remembered that there are two sorts of 
mercury salts, mercurous salts and mercuric salts. The mer- 
curous chloride, Hg2Cl2, (calomel) is insoluble in water; but 
the mercuric chloride, HgCL, (corrosive sublimate) is soluble 
in water. If, therefore, mercury be present in the form of 
some mercurous salt, it will be separated as mercurous chloride 
in Class I. If, on the contrary, it be present in the form of 
some mercuric salt, it will be separated in Class II as mercuric 
sulphide (HgS), for this sulphide is insoluble in water, weak 
acids and alkaline liquids. If a mixture of mercurous and 
mercuric salts be contained in the original solution, mercury 
will appear both in Class I and in Class II. 
The treatment of Class II is fully discussed in Chapter III. 
The separation of Class III and the means of separating the 
members of the class, each from the others, form the subject 
of Chapter IV. 
9. Definition of Class IV. — We now return to the study 
of the filtrate from Classes II and III. Pour the liquid into 
a small evaporating dish, and boil it gently for five or six 
minutes to expel the sulphuretted hydrogen with which the §9 
DEFINITION OF CLASS IV. 
fluid is still charged. To make sure that all the gas ia 
expelled, hold a bit of white paper moistened with a solution 
of acetate of lead (App., § 46) over the boiling liquid; when 
the paper remains white, all the sulphuretted hydrogen ia 
gone. Next, add to the liquid in the dish ten or twelve 
drops of strong nitric acid (App., § 4), and again gently boil 
the liquid for three or four minutes, in order that all the iron 
present may be converted into ferric salts. Then pour the 
liquid into a test-tube, add to it about one third its bulk of 
chloride of ammonium (App., § 19), and finally add annnonia- 
water (App., § 16), little by little, until the mixture, after 
being well shaken, smells decidedly of ammonia. A brownish- 
red precipitate of hydrated sesquioxide of iron will separate 
from the liquid. Pour the contents of the test-tube upon a 
filter, rinse the tube and the precipitate once with a little 
water, and preserve the whole filtrate for subsequent opera- 
tions. 
Two other metals, aluminum and chromium, are precip- 
itated, as iron has here been, by ammonia-water under the 
same conditions and in the same form, viz., as hydrates. 
These three elements, therefore, constitute the fourth class, 
whose treatment forms the subject of Chapter V. The hy- 
drates of these elements are insoluble in water, even in the 
presence of salts of ammonium, such as the chloride of am- 
monium which has been expressly added, and the nitrate of 
ammonium which has been formed during the neutralization 
of the acid liquid. The student may be curious to know 
why the presence of ammonium salts is insisted upon before 
the elements of this class are thrown down by ammonia-water. 
The ammonium salts have nothing to do with the precipita- 
tion of iron, aluminum and chromium ; but by their presence 
they prevent the precipitation, as will be hereafter explained, 
of certain other elements whose hydrates, though but slightly 
soluble in water, are dissolved by solutions of ammonium 
salts. The salts of ammonium are therefore added to keep 
in solution certain other elements which otherwise would 
encumber Class IV. 12 
DEFINITION OF CLASS V. 
§ 10 
10. Definition of Class V.—We now proceed to the 
examination of the filtrate from the precipitate of Class IV. 
Bring this liquid to boiling in a test-tube, and add sulphy- 
drate of ammonium (App., § 17), little by little, to the boiling 
liquid as long as a precipitate continues to be formed. To 
make sure that the precipitation is complete, shake the hot 
contents of the test-tube strongly, and then allow the mixture 
to settle until the upper portion of the liquid becomes clear. 
Into this clear portion let fall a drop of sulphydrate of am- 
monium ; when this drop produces no additional precipitate, 
the precipitation is complete. Filter off the whitish precip- 
itate of sulphide of zinc, and preserve the filtrate for further 
treatment. It sometimes happens that this precipitate refuses 
to settle and leave the upper portion of the liquid sufficiently 
clear to test in the manner described above; in this case a 
small portion of the mixture may be filtered and a drop of 
sulphydrate of ammonium added to the clear filtrate in order 
to determine whether the precipitation is complete. If not, 
the filtered liquid must be returned to the flask and more of 
the reagent added. 
The element zinc, representing a new class of elements, is 
precipitated under the conditions of the above experiment, 
because its sulphide, though soluble in dilute acids, is insolu 
ble in alkaline liquids. The metals manganese, nickel and 
cobalt resemble zinc in this respect, and these four elements 
therefore form a new class, Class V, in this analytical method. 
The representative sulphide of this class was not precipitated 
by the sulphuretted hydrogen when that reagent was em- 
ployed to throw down the members of the Classes II and III, 
because the solution was at that time acid. Again it was 
not precipitated with Class IV by the ammonia-water, because 
the sulphuretted hydrogen with which the solution had pre- 
viously been charged, was expelled by boiling before tha 
ammonia-water was added. The complete treatment of 
Class V forms the subject of Chapter VI. §§ H,12 
DEFINITION OF CLASS VII. 
13 
11. Definition of Class VI. — Add to the filtrate from 
Class V, two or three teaspoonfuls of carbonate of ammo- 
nium (App., § 18) and boil the solution. A white precipitate 
of carbonate of calcium will be produced. After boiling, 
allow the precipitate to settle until the upper portion of the 
liquid is comparatively clear. To this clarified portion add a 
fresh drop of carbonate of ammonium. If this drop produce 
an additional precipitate, more carbonate of ammonium must 
be added, and the boiling repeated. To the partially clarified 
liquid add again a drop of carbonate of ammonium. This 
process of making sure of the complete precipitation of the 
calcium is essentially the same as that prescribed in precip- 
itating the last class, and is, indeed, of general application. 
When the precipitation of the calcium has been proved to be 
complete, filter the whole liquid, and receive the filtrate in a 
small evaporating-dish. Calcium is separated in the form of 
carbonate under these circumstances, because this carbonate 
is almost insoluble in weak alkaline liquids, when an excess 
of carbonate of ammonium is present. The allied elements 
barium and strontium behave in the same way, so that these 
three elements, viz., barium, strontium and calcium, compose 
a new class — Class VI, whose complete treatment is set 
forth in Chapter VII. 
12. Definition of Class VII.—Of the twenty-two me- 
tallic elements, which were to be classified (§6), only three 
remain, viz., magnesium, sodium and potassium. It is ob- 
vious that these three elements could not have remained in 
solution through all the operations to which the original 
liquid has been submitted, unless their chlorides and sul- 
phides had been soluble in weak acids, and their oxides (or 
hydrates), sulphides and carbonates soluble in dilute am- 
monia-water, at least in presence of dilute solutions of 
ammonium salts. It is a fact that all these compounds of 
sodium and potassium are soluble in water, and in weak acid, 
alkaline, and saline solutions; the magnesium would have 
been partially precipitated in Classes IV, V and VI, but for 14 
SEPARATION OF CLASSES. 
§§12,13 
the presence of ammonium salts in the solution. These three 
elements constitute Class VII. 
Evaporate the filtrate from Class VI until it is reduced to 
one half or one third of its original bulk. Pour a small 
part of the evaporated filtrate into a test-tube; add a little 
ammonia-water and a teaspoonful of phosphate of sodium 
(App., § 26), and shake the contents of the tube violently. 
Sooner or later a crystalline precipitate will appear. This 
peculiar white precipitate of phosphate of magnesium and 
ammonium identifies magnesium; but as we have added a 
reagent containing sodium, the filtrate is useless for further 
examination. The liquid remaining in the evaporating-dish 
is then evaporated to dryness, and moderately ignited until 
fuming ceases. All the ammoniacal salts which the solution 
contained will be driven off by this means, and there will 
remain a fixed residue, in which are concentrated all the salts 
of magnesium and sodium which the solution contained. In 
this case we have already proved the presence of magnesium ; 
it remains to indicate briefly the nature of the means used to 
detect the sodium. 
Dissolve the residue in the dish, or a portion of it, in three 
or four drops of water. Dip a clean platinum wire (App., 
§79) into this solution, and introduce this wire into the 
colorless flame of a gas or spirit-lamp (App., § 74). An 
intense yellow coloration of the flame demonstrates the pres- 
ence of sodium. A violet coloration would have proved the 
presence of potassium. Magnesium compounds, when pres 
ent, have no prejudicial effect on these characteristic colora- 
tions. The means of detecting each member of this last 
class in presence of the others will be found described in 
Chapter VIII. 
13. A condensed statement of the classification illustrated 
by the foregoing experiments is contained in the table on 
the next page. All the common metallic elements are em- 
braced in it. The place of the precious metals gold and 
platinum is also indicated. The classification itself would I 13 
CLASSIFICATION. 
15 
Class VII. 
Remaining 
elements. 
Distinguish- 
ed hy special 
tests. 
Mg 
Na 
K 
Class VI. 
Precipita- 
ted as car- 
bonates. 
Ca 
Ba 
Sr 
The Seven Classes of the Metallic Elements. 
Class V. 
Precipitated 
as sulphides 
insoluble in 
alkaline fluids. 
Zn 
Mn 
m 
Co 
Class IV. 
Precipitated by 
ammonia-water, 
usually as hydrates. 
Fe 
A1 
Cr 
[together with cer- 
tain salts which re- 
quire an acid sol- 
vent.] 
Class III. 
Precipitated as 
sulphides insoluble 
In dilute acids, but 
redissolved by 
alkalies. 
As 
Sb 
Sn 
[Au] 
[Pt] 
Class II. 
Precipitated as 
sulphides insoluble 
in dilute acids, and 
not redissolved 
by alkalies. 
Pb 
Hg 
Bi 
Cd 
Cu 
Class I. 
Precipita- 
ted as 
chlorides. 
Ag 
Pb 
Hg 16 
SEPARATION OF CLASSES. 
§§14, 15 
not be essentially different, if all the rare elements were 
comprehended in it. The general subdivisions would be the 
same, although some of them would embrace many more 
particulars. 
14. It is essential to success to follow precisely the 
prescribed order in applying the various general reagents. 
Class I would go down with Class II, were chlorhydric acid 
forgotten as the first general reagent. Class II would be 
precipitated in part with Class IV and in part with Class V 
if sulphuretted hydrogen were not used in its proper place. 
A large number of the members of the first five classes 
would be precipitated as carbonates with Class VI, were they 
not previously eliminated by the systematic application of 
chlorhydric acid, sulphuretted hydrogen, ammonia-water and 
sulphydrate of ammonium in the precise order and under the 
exact conditions above described. It should be noticed that 
all the general reagents are volatile substances, which can be 
completely removed by an evaporation to dryness followed 
by a very moderate ignition. 
15. The series of experiments just completed is merely 
intended to demonstrate the principles in accordance with 
which these twenty-two common elements are classified for 
the purposes of qualitative analysis. The general plan is 
here sketched; the practical details, essential to success in 
the conduct of an actual analysis, will be given hereafter. §§16,17 
17 
CHAPTER H. 
CLASS I. —ELEMENTS WHOSE CHLORIDES ARE INSOLU- 
BLE IN WATER AND ACIDS. 
16. Example of the Precipitation of the Members of 
Class I. — Place in a test-tube five or six drops of a tolerably 
concentrated aqueous solution of nitrate of silver (App., 
§ 62), an equal quantity of a solution of mercurous nitrate 
and two teaspoonfuls of a solution of nitrate of lead. In 
case the solution becomes turbid through the action of car- 
bonic acid dissolved in the water, pour in one or two drops 
of nitric acid to destroy the cloudiness. 
Add dilute chlorhydric acid to the solution, drop by drop, 
and shake the mixture thoroughly after each addition of the 
acid, until the fresh portions of the latter cease to form any 
precipitate on coming in contact with the comparatively clear 
liquor which floats above the insoluble chlorides. Finally, 
add three or four more drops of the acid to insure the pres- 
ence of an excess of it in the solution. 
17. Analysis of the Mixed Chlorides. — The following 
method of separating the chlorides of lead, silver and mer- 
cury, one from another, depends upon the facts : — 1st. That 
chloride of lead, though but little soluble in cold water, dis- 
solves readily in boiling water, while chloride of silver and 
eubchloride of mercury (mei'curous chloride, Hg2Cl2), are as 
good as insoluble in that liquid; 2d. That chloride of silver 
is soluble in ammonia-water; and 3d. That mercurous chlo- 
ride is discolored by ammonia-water without dissolving. 
To effect the separation: — Collect upon a filter the pre- 
cipitate produced by chlorhydric acid, allow it to drain, and 
rinse it with a few drops of cold water. Place a clean test- 
tube beneath the funnel which contains the filter and precip. 18 
SEPARATION OF LEAD. 
§17 
itate, thrust a glass rod through the apex of the filter, and 
wash the precipitate off the filter into the test-tube by means 
of a wash-bottle which throws a fine stream. 
Heat the mixture of water and precipitate to foiling, then 
allow the precipitate to settle and pour off the hot liquor 
upon a new filter, taking care to retain the precipitate as far 
as possible in the tube. To the clear filtrate add two or 
three teaspoonfuls of dilute sulphuric acid. (App., § 9.) A 
white cloud of sulphate of lead will be formed in the midst of 
the liquid. In case the precipitate contains a large 
proportion of chloride of lead, it may happen that 
the hot water will take up so much of it that crystals 
of the chloride will separate from the clear aqueous solution 
as it becomes cold, or that the liquor will be rendered cloudy 
by the deposition of numerous small particles of the chloride. 
Pour a fresh quantity of water upon the precipitate which 
was retained in the test-tube, boil the mixture and, after 
allowing the precipitate to subside, pour the nearly clear 
liquid upon the same filter as before. This operation of boil- 
ing the precipitate with successive portions of water is per- 
formed in order to insure the complete removal of the chloride 
of lead ; the liquid is filtered through the same filter in order 
to retain any particles of the precipitate which fail to settle 
in the tube, but it is not necessary to save this wash-water as 
most of the chloride of lead was obtained in the filtrate from 
the first boiling. 
After the mixed precipitate of chloride of silver and mer- 
curous chloride has been thus boiled with water several times, 
cover it with several teaspoonfuls of ammonia-water, heat the 
mixture to boiling, and pour it upon the filter used in the last 
paragraph: the filtrate is to be received in a clean test-tube. 
The chloi’ide of silver, dissolved by the ammonia-water, will 
pass into the filtrate, while the mercurous chloride suffers de- 
composition, and is converted into an obscure compound of 
mercury, chlorine, nitrogen and hydrogen, which remains 
upon the filter in the form of an insoluble black or gray 
powder. 
Test 
for 
Pb. §§ 17,18 
SILVER AND MERCURY. 
19 
To confirm the presence of silver, add to the filtrate dilute 
nitric acid (App., § 5), until the solution will redden litmus 
paper: the chloride of silver is reprecipitated' un- 
changed as soon as the alkaline solvent is neutral- 
ized. 
To confirm the presence of mercury, the metal itself may 
be set free by heating the dry residue with carbonate of so- 
dium (App., § 24) in a glass tube. To ensure the success of 
this experiment, wash into the lowest point of the filter the 
whole of the black residue. As soon as the last drops of 
liquid have drained from the filter, dry the latter, either in a 
dish upon a water-bath, or by spreading it open upon a ring 
of the iron stand (App., § 76) placed high above a small 
flame of the gas-lamp. When the precipitate is completely 
dry, scrape it from the paper, mix it with an equal 
bulk of carbonate of sodium previously dried over 
the gas-lamp on platinum foil (App., § 79) and 
transfer the mixture to the bottom of a glass tube, No. 4 
(App., § 82), closed at one end. Then wipe out the inside of 
the tube with a tuft of cotton fixed to a wire, or with a 
twisted slip of paper, and heat the closed end of the tube 
for two or three minutes in the flame of a gas-lamp. A sub- 
limate of finely divided metallic mercury will form upon the 
walls of the tube; it will cohere to visible globules when 
scratched with a piece of iron wire. 
18. An outline of the operations described in the forego- 
ing paragraphs may be presented in tabular form, as fol- 
lows : — 
Test 
for 
Ag. 
Test 
for 
Hg. 
The General Reagent (HC1) of Class I precipitates PbCl2, AgCl 
and Hg2Cl2. When the precipitate is boiled with water: — 
PbCl2 goes into 
solution. Con- 
firm presence of 
lead by precipita- 
tion of sulphate 
of lead. 
AgCl and Hg2Cl2 remain undissolved. On 
treating the mixture with ammonia-water: — 
AgCl dissolves. 
Confirm presence of 
silver with nitric 
acid. 
A black compound of Hg 
remains undissolved. Con- 
firm presence of Hg by 
isolating the metal. 20 
CLASS I. 
§ 19 
19. In the actual analysis of a solution of unknown com- 
position, a precipitate might under certain circumstances be 
formed on £ie addition of chlorhydric acid, even in the ab- 
sence of all members of Class I. This might occur in case 
the liquid under examination contained a hyposulphite ; for 
this class of salts is decomposed, with evolution of sulphu- 
rous acid and deposition of sulphur, on the addition of the 
general reagent HC1 of Class I. Some sulphides also are 
decomposed by chlorhydric acid, with deposition of sul- 
phur. A gelatinous white precipitate of hydrated silicic acid 
might also be formed at this stage in certain circumstances, 
as will be explained hereafter (§§ 69 & 86,1, o, a). §§20. 21 
21 
CHAPTER III. 
CLASS II. — ELEMENTS WHOSE SULPHIDES ARE INSOL- 
UBLE IN WATER, DILUTE ACIDS AND ALKALIES. 
20. Example of the Precipitation of the Members of 
Class II. — Place in a small beaker a half teaspoonful 
of a solution of each of the following substances : — mercuric 
chloride (corrosive sub'imate), chloride of bismuth, of cad- 
mium, and of copper, together with two or three teaspoonfuls 
of a cold aqueous solution of chloride of lead. Fill the 
beaker half full of water, and add, drop by drop, enough 
strong chlorhydric acid to redissolve the basic chloride of 
bismuth which the water precipitates. 
Heat the liquid in the beaker nearly or quite to boiling, then 
place the beaker beneath a chimney or in a strong draught 
of air, and saturate the solution with sulphuretted hydrogen 
gas. To determine when enough sulphuretted hydrogen has 
been passed through the liquid, remove the beaker every four 
or five minutes from the source of the gas, blow away the gas 
which lies in the beaker above the liquid, and stir the latter 
thoroughly with a glass rod. If, after the lapse of two or 
three minutes, the liquid still smells strongly of sulphuretted 
hydrogen, it is saturated with the gas and ready to be filtered. 
But in case no persistent odor of sulphuretted hydrogen is 
observed, the gas must be passed anew through the liquor 
until it has become fully saturated. Since some of the sub- 
stances above enumerated are thrown down more quickly by 
sulphuretted hydrogen than the others, it is absolutely neces- 
sary to employ the reagent in excess in order that those mem- 
bers of the class which are least easily precipitated may not 
escape detection. 
21. Analysis of the Mixed Sulphides.—The following 
method of separating the members of Class II depends upon 22 
SEPARATION- OF CLASS II. 
§ 21 
tlie facts : — 1st. That mercuric sulphide is insoluble in hot 
dilute nitric acid, while the other sulphides are converted 
thereby into soluble nitrates. 2d. That sulphate of lead is 
insoluble in acidulated water, while the sulphates of the other 
members of the class are soluble. 3d. That hydrate of bis- 
muth is insoluble in ammonia-water, while the hydrates of 
cadmium and copper are soluble in that liquid. 4th. That 
hot dilute sulphuric acid converts the sulphide of cadmium 
into the soluble sulphate of cadmium while sulphide of copper 
is not affected by this reagent. 
To effect the separation: — Collect the precipitated sul- 
phides upon a filter ; wash the precipitate thoroughly with suc- 
cessive portions of water until the wash-water is no longer acid 
to litmus paper; transfer the precipitate to a small porce- 
lain dish, pour upon it four or five times as much dilute nitric 
acid as would be sufficient to cover it, and boil the mixture 
during two or three minutes, stirring it constantly with a 
glass rod, and adding water or dilute nitric acid at intervals 
to replace the liquid which evaporates. All the sulphides 
with the exception of the sulphide of mercury are decomposed 
and the several elements go into solution as nitrates; the 
sulphide of mercury, mixed with some free sulphur resulting 
from the decomposition of the other sulphides, remains undis- 
solved, as a heavy dark-colored mass. Decant the nitric acid 
solution into a filter, collect the filtrate in a second porcelain 
dish, and evaporate it nearly to dryness in order to drive off 
the greater part of the free nitric acid before examining it for 
the elements supposed to be contained in it. 
The residue insoluble in nitric acid which was left in the 
first dish, is to be washed with water in order to remove the 
adhering solution. This may generally be done by pouring 
water into the dish, allowing the precipitate to settle and then 
decanting the wash-water; it is sometimes necessary, how- 
ever, to collect the precipitate on a filter and wash in the 
ordinary manner. In either case the wash-water is thrown 
away and the precipitate is boiled in the porcelain dish with 
as much aqua regia (App , § 6) as will barely cover it. § 21 
SEPARATION OF MERCURY. 
23 
Dilute the acid solution obtained with an equal volume of 
water, remove from it, by filtration or otherwise, any particles 
of free sulphur which may remain undissolved, and add to it 
almost, but not quite, enough ammonia-water to neutralize 
its acidity. In case of the accidental addition of too much 
ammonia-water, manifested by the appearance of a precipi- 
tate and by the alkaline reaction on litmus, the solution must 
be made just acid by the cautious addition of nitric acid, a 
drop at a time. Place in the slightly acid solution a small 
bit of bright copper wire, and observe that metallic mercury 
is deposited upon the copper as a white silvery coating. After 
the lapse of ten or fifteen minutes, dry the wire upon 
blotting paper, drop it into a narrow glass tube which 
has been sealed at one end, and heat it at the lamp. 
Metallic mercury will sublime, and be deposited as a dull 
mirror upon the cold portions of the glass. By scratching 
the sublimate with the point of a bit of iron wire, the metal 
may be made to collect into visible globules. 
When the greater part of the free nitric acid has, by the 
aforesaid evaporation, been driven off from the filtrate which 
contains the mixed nitrates of lead, bismuth, cadmium and 
copper, transfer the residual liquor to a test-tube, 
mix it with two or three times its volume of dilute 
sulphuric acid, and leave the mixture at rest during 
fifteen or twenty minutes. Sulphate of lead will be thrown 
down as a white powder, plainly to be seen in the test-tube, 
though it would have been scarcely visible in the white dish. 
Collect the filtrate from the sulphate of lead in a small 
beaker, and add to it ammonia-water by repeated small por- 
tions, taking care to stir the liquid thoroughly after each addi- 
tion of the ammonia, until a strong, persistent odor of the 
latter is perceptible. The hydrates of copper, cadmium, and 
bismuth will all be thrown down at first, but the hydrates of 
copper and cadmium will redissolve in the excess of ammonia- 
water, and h}’drate of bismuth will alone be left as an insol- 
uble precipitate. The blue color of the solution is due to the 
presence of copper. If in the case of the actual examination 
Test 
for 
Hg. 
Test 
for 
Pb. 
Test 
for 
Pb. 24 
• SEP ABA TION OF BISMUTH. 
§ 21 
of a solution of unknown composition no precipitate falls on 
the addition of ammonia-water, this does not prove the 
absence of copper and cadmium, as the hydrates may be 
dissolved by the ammonia-water as fast as formed, and thus 
escape observation. 
To prove that the precipitate contains bismuth : — Collect 
it upon a filter, allow it to drain, and dissolve it in the small- 
est possible quantity of strong chlorhydric acid poured drop 
by drop upon the sides of the filter; carefully evaporate the 
acid solution to the bulk of two or three drops, and 
pour it into a large test-tube nearly full of water. 
A dense, milky cloud of insoluble basic chloride of 
bismuth will appear in the water. Since sulphate of lead is 
not absolutely insoluble in water which contains nitric acid, a 
slight precipitate of hydrate of lead might be produced on 
the addition of the ammonia-water even when no bismuth was 
present in the solution. To prove the presence of bismuth, 
the oxychloride must always be carefully tested for. It is to 
be remarked that if the amount of hydrate of bismuth is in 
an}rcase small, considerable care must be exercised in apply- 
ing the confirmatory test. In such a case the basic chloride 
majr appear as white threads marking the path of the heavier 
liquid through the water, and gradually producing more or 
less turbidity throughout the whole mass of the water. 
The blue color of the ammoniacal filtrate from the hydrate 
of bismuth indicates the presence of copper, and when well 
defined is of itself a sufficient proof of the presence of this 
element. But in the absence of a marked blue coloration, at 
this stage, copper should be specially tested for in the man- 
ner described below. 
To separate the cadmium from the copper, proceed as fol- 
lows : — Transfer the ammoniacal filtrate to a glass flask, 
heat it to boiling, and drop into the boiling liquid sulpliydrato 
of ammonium as long as a precipitate continues to be formed. 
In order to be sure that the precipitation*is complete, remove 
the flask from the lamp at intervals, shake it strongly, and 
allow its contents to settle, so that a comparatively clear 
Test 
for 
Bi. § 21 
SEPARATION OF CADMIUM. 
25 
liquid may appear at the top, and into this clear liquid pour 
a drop of the sulphydrate. 
As a general rule, the operations of boiling and agitating 
tend to increase the coherency of precipitates, and to render 
them in some sense granular, so that they separate completely 
from the liquid in which they form, leaving it clear and sus- 
ceptible of rapid filtration. 
Collect the precipitate upon a filter, rinse it once or twice 
with water, and allow it to drain; then transfer the precip- 
itate to a porcelain dish and cover it liberally with dilute 
sulphuric acid (App., § 10), made by mixing one part by meas- 
ure of the strong acid with five parts of water. Heat the mix- 
ture until it actually boils ; then pour the boiling liquor upon 
a filter, and collect the clear filtrate in a beaker. By hot 
dilute sulphuric acid of the prescribed strength, sulphide of 
cadmium is converted into sulphate of cadmium which dis- 
solves in the acid liquid, while the black sulphide of copper 
remains intact. It is essential that the mixed precipitate of 
sulphide of copper and sulphide of cadmium do not remain 
upon the filter for any great length of time; for in such a 
case the sulphide of copper might become partially oxydized 
and dissolve in the dilute sulphuric acid, along with the 
sulphate of cadmium, thus obscuring the test for the latter 
element. 
To prove the presence of cadmium, add ammonia-water to 
the acid filtrate until the liquid is alkaline; then add 
sulphydrate of ammonium, and observe that the 
liquid immediately becomes cloudy from the pres- 
ence of minute particles of sulphide of cadmium of charac- 
teristic yellow color. After some time this precipitate will 
collect at the bottom of the liquid. 
To prove the presence of copper, in case no blue coloration 
was visible in the filtrate from hydrate of bismuth, transfer 
the black precipitate, insoluble in dilute sulphuric acid, to an 
evaporating-dish, dissolve it in a few drops of boiling, concen- 
trated nitric acid, remove and wash the spongy mass of sulphur 
which is set free, neutralize the nitric acid with ammonia- 
Test 
for 
Cd. 26 
THE A TMENT OF CLASS II. 
§§ 21,22 
vrater, acidify the solution with acetic acid (App., § 12), 
transfer it to a test-tube, and add one or two drops of a 
solution of ferrocyanide of potassium (App., § 33). A pe- 
culiar reddish-brown precipitate of ferrocyanide of 
copper will fall in case much copper be present, and 
even when the proportion of copper in the solution 
is extremely small, a light brownish-red cloudiness will be 
produced. 
In the absence of copper, yellow sulphide of cadmium 
would at once be thrown down by the sulphydrate of ammo- 
nium, when this reagent is added to the filtrate from the hy- 
drate of bismuth; and no further evidence of the presence of 
cadmium would be required. 
22. The operations above described may be presented in 
tabular form as follows: — 
Test 
for 
Cu. 
The General Keagent (H2S) of Class II precipitates HgS. PbS, 
Bi2S3, CdS and CuS (as well as members of Class III, which 
are subsequently separated by solution in sulphydrate of sodium). 
The -precipitate is boiled with nitric acid: — 
A residue of 
HgS, mixed 
with S, re- 
mains. 
Confirm 
presence of 
Hg with 
copper wire. 
Pb, Bi, Cd and Cu go into solution as nitrates. 
On adding dilute sulphuric acid to the concentrated 
solution: — 
PbS04 is 
thrown 
down. 
The sulphates of Bi, Cd and Cu remain 
in solution. On adding an excess of 
ammonia-water: — 
Hydrate of 
Bismuth is 
thrown 
down. Con- 
firm Bi by 
precipitat- 
ing the oxy- 
chloride. 
Compounds of Cd and of 
Cu remain in solution. 
Throw down CdS and 
CuS with (NH4) HS, and 
boil with dilute sulphuric 
acid: — 
CdS04 goes 
into solu- 
tion. Con- 
firm pres- 
ence of Cd 
by precipita- 
tion of CdS. 
CuS remains 
undissolved. 
Confirm pres- 
ence of Cu 
by testing 
with ferro cy- 
anide of po- 
tassium. § 23 
SEPABATION OF CLASSES I AND II. 
27 
23. The Method of Separating Class I from Class II has 
already been particularly described in § 6. It should be ob- 
served, however, that even if no member of Class I were 
present in the mixture to be analyzed, it would still be neces- 
sary to acidulate the liquid with chlorhydric acid, before pass- 
ing the sulphuretted hydrogen, in order to prevent the precipi- 
tation of members of Classes IV and V, and to secure the 
complete precipitation of members of Class III. 
The liquid should be watched attentively when the stream 
of sulphuretted hydrogen first begins to flow through it, since 
useful inferences may often be drawn from the various phe- 
nomena which present themselves. 
а. Thus, the formation of a white precipitate which after- 
wards changes to yellow, orange, brownish-red, and finally to 
black, as the liquid gradually becomes saturated with the gas, 
indicates the presence of mercuric chloride. The white pre- 
cipitate at first formed is a compound of chloride and sul- 
phide of mercury (HgCl22HgS), but by the action of succes- 
sive portions of sulphuretted hydrogen, the composition and 
appearance of the precipitate is changed, until it has been 
completely converted into black sulphide of mercury. It is 
important that the mercury should be completely converted 
into sulphide as the compound just mentioned is soluble in 
nitric acid ; the result is rendered more certain if the solution 
be warmed before being treated with sulphuretted hydrogen. 
б. If the precipitate is of a dull red color at first, after- 
wards changing to black, the probable presence of lead is 
indicated; for sulphuretted hydrogen throws down from solu- 
tions which contain much free chlorhydric acid a red com- 
pound of chloride of lead and sulphide of lead, which is 
afterwards decomposed, with formation of the black sulphide, 
when the solution becomes saturated with the gas. 
c. A decided bright yellow precipitate would indicate the 
presence of cadmium, arsenic or tin ; of these three, cadmium 
is distinguished by the fact that its sulphide remains undis- SEPARATION OF CLASSES II AND in. 
28 
§ 23 
solved when the precipitate is treated with sulphydrate of 
sodium to separate the members of Class III. 
But even from solutions which contain no members of 
Classes II or III, yellow-white or milky-white precipitates of 
free sulphur are often thrown down; for sulphuretted 
hydrogen is easily decomposed, with deposition of sul- 
phur, by a variety of oxidizing agents, such as nitric, 
chromic and chloric acids, and solutions of ferric salts and of 
free chlorine. If the solution under examination contained 
much nitric acid, sulphuretted hydrogen would have to be 
passed through it for a long time to destroy the acid, before 
the liquid could be saturated with the gas. In this case the 
sulphur separates as a tenacious mass of dirty yellow color; 
but in most instances, notably when the solution contains a 
ferric salt, the sulphur is precipitated in the form of exceed- 
ingly minute particles, which impart to the solution a pecu- 
liar milkiness or opalescence. These particles are so fine that 
they pass through the pores of filter paper; they cannot be 
removed by filtration. 
If the original solution contains a chromate, its yellow or 
reddish-yellow color will be changed to green by the action 
of sulphuretted hydrogen ; for the chromate is reduced to the 
condition of sesquichloride of chromium : — 
2MCrO4+10HCl+3H2S=Cr2Cl6+3S+2M.Ol2+8H2O. 
The sulphur is set free in the form of the minute white 
particles above described, and remains suspended in the 
green liquid, looking not unlike a green prteipitate. 
d. The immediate formation of a black precipitate indi- 
cates the copper or bismuth, and it is to be ob- 
served that these black precipitates would obscure 
the colors of the §tlier sulphides of the class, and conceal 
them if present. 
e. If no precipitate appears even when the liquid has be- 
come saturated with the gal, the absence of every member of 
Classes II and III is, of course, to be inferred. { 24 
CHAPTER IV. 
CLASS III. —ELEMENTS WHOSE SULPHIDES ARE INSOL- 
UBLE IN WATER OR DILUTE ACIDS, BUT SOLUBLE IN 
ALKALINE SOLUTIONS. 
24:. Example of the Precipitation of the Members of 
Class III. — Place in a small beaker six or eight drops of 
solutions of the chlorides of arsenic, antimony and tin. Pour 
in enough dilute chlorhydric acid to half fill the beaker, and, 
if need be, a sufficient number of drops of strong chlorhydric 
acid to dissolve any cloud of basic chloride of antimony 
which may appear in the liquor. 
Pass sulphuretted hydrogen gas through the solution, in 
the manner described in § 20, until the odor of the gas per- 
sists. Then collect the precipitated sulphides upon'a filter, 
and rinse the precipitate once or twice with water. 
In the analysis of any complex solution of unknown com- 
position which might contain one or all of the members of 
Class III, the sulphides of this class would, of course, all be 
thrown down at the same time as those of Class II. (Com- 
pare §§ 8, 22.) It will be well, therefore, for the sake of 
illustration, for the student to dissolve the present precipitate 
in sulphydrate of sodium in order that he may begin the 
treatment of Class III at the precise point at which this class 
would be encountered in an actual analysis; namely, with 
the sulphides of the class in alkaline solution. To this end, 
allow the washed precipitate to drain, spread out the filter 
upon a plate of glass, scrape the precipitate from the paper 
with a small spatula of platinum, horn or wood, and transfer 
it to a porcelain dish. Pour upon the precipitate two or 
three times as much of a solution of sulphydrate of sodium ANALYSIS OF CLASS III. 
§ 25 
as would be sufficient to cover it, and boil the mixture very 
cautiously, so as to avoid spattering. The precipitate will 
soon dissolve, and no solid matter will be left suspended in 
the solution, excepting a few fibres of the filter paper. It 19 
such a solution as this which in an actual analysis is examined 
for members of Class III. 
25. Analysis of the Mixed Sulphides. — The method 
here given of separating arsenic, antimony and tin depends : 
— 1st. Upon the oxidation of the several sulphides byr means 
of nitric acid and nitrate of sodium, and the conversion of 
arsenic into a compound soluble in water while antimony and 
tin are converted into insoluble compounds; 2d. Upon the 
fact that the tin in the compound thus formed is set free in 
the metallic state when this compound is treated with zinc 
an$.,c]«ilorhydric acid, while the antimony under similar cir- 
cumstances is in part reduced to metallic antimony and in 
part converted into antimoniuretted hydrogen ; 3d. Upon the 
solubility of tin in strong chlorhydric acid. 
To effect the separation ; — Add strong nitric acid to the 
sulphydrate of sodium solution until the reaction is distinctly 
acid; a precipitate forms which consists partly of the sul- 
phides of arsenic, antimony and tin, and partly of sulphur 
from the decomposition of the alkaline sulphydrate. With- 
out heeding the precipitate "which separates, evaporate the 
acid mixture to the bulk of half a teaspoonful; then add solid 
carbonate of sodium very cautiously until further addition 
causes no further effervescence. Then add half a teaspoonful 
of a mixture of equal parts of carbonate and nitrate of sodium. 
Evaporate to dryness with constant stirring, and heat the 
mass until it fuses. Pour out the liquid mass, as far as may 
be possible, upon a bit of cold porcelain, and when it has 
cooled somewhat, transfer it, together with whatever can be 
detached from the dish in which the fusion wras made, to a 
clean mortar and reduce it to powder. Return this powder 
to the porcelain dish and when the dish with its contents is 
perfectly cold pour in several teaspoonfuls of cold water and § 25 
SEPARATION OF ARSENIC. 
31 
allow the mixture to stand, stirring it from time to time, 
until that portion of the fused mass which could not be de- 
tached from the dish has softened and is in part dissolved ; 
finally, filter the solution. By the treatment with nitric acid 
and nitrate of sodium the arsenic of the sulphide of arsenic 
has been converted into arseniate of sodium, a compound 
which is soluble in water and which passes into the filtrate 
together with the excess of nitrate and carbonate of sodium 
and some sulphate of sodium formed during the process. 
The antimony has been converted into antimoniate of sodium 
and the tin into the binoxide; these two compounds, being 
scarcely at all soluble in water, remain on the filter. This 
insoluble residue is examined for antimony and tin in a man- 
ner presently to be described. 
To the filtrate add nitric acid, drop by drop, until the 
liquid shows a faintly acid reaction. If a precipitate appear 
it is probably a hydrate of tin, and its appearance is due to 
the fact that the ignition with nitrate of sodium was conducted 
at so high a temperature that a portion of the nitrate of 
sodium wras converted into caustic soda, and this acting on 
the oxide of tin formed a certain amount of soluble stannate 
of sodium. 
The precipitate, if any appear, is to be filtered olf and 
added to the insoluble residue which awaits examination. 
To one half of the clear filtrate add ammonia-water to alka- 
line reaction, then a few drops of a prepared solution 
of sulphate of magnesium and chloride of ammo- 
nium (App., § 47) and set the mixture aside for 
twelve hours. The formation of a white, crystalline precip- 
itate of arseniate of ammonium and magnesium is evidence 
of the presence of arsenic. 
To the remainder of the filtrate which contains the arsenic, 
and which should contain the smallest possible quantity of free 
acid, add a small quantity of a solution of nitrate of silver. 
On the addition of the nitrate of silver a precipitate generally 
falls even in the absence of arsenic, owing to the fact that 
Test 
for 
As. 32 
SEPARATION’ OF ARSENIC. 
§ 25 
the nitrate of sodium used in the fusion generally contains 
some chloride of sodium, and in order that the arsenic 
present may be converted into arseniate of silver, a small 
quantity of nitrate of silver must be added, over and above 
that necessary to remove the chlorine present. Four or five 
drops of the solution of nitrate of silver (App. § 39) will 
usually suffice. The precipitated chloride of silver is to be 
removed by filtration. 
To the clear filtrate add a solution of acetate of sodium 
(App. § 27), drop by drop, until the mixture smells of acetic 
acid ; a red or brownish-red precipitate of arseniate of silver 
appears. The acetate of sodium is added because the 
arseniate of silver is soluble in nitric acid, and but sparingly 
soluble in acetic acid, unless it is present in considerable 
excess. On the addition of acetate of sodium to the liquid 
containing free nitric acid, there was formed nitrate of 
sodium, and acetic acid was set free. 
Any precipitate supposed to contain arsenic maybe further 
examined by converting the arsenic into a hydrogen com- 
pound by the method known as Marsh’s test. (See Eliot 
and Storer’s Manual of Inorganic Chemistry, pp. 259, 270; 
see also the test for antimony below.) This method is 
applicable to the detection of very minute quantities of 
arsenic. 
The insoluble residue containing antimony and tin, which 
was left on the filter, is washed several times with a mixture 
of equal parts of alcohol and water, and then transferred to 
a test-tube or porcelain dish and warmed with strong chlorhy- 
dric acid. Choose a cork or caoutchouc stopper provided 
with two holes, which fits accurately the mouth of a wide 
test-tube. Fit a small thistle-tube to one of the holes, and 
to the other a short bent tube drawn to a rather fine open 
point. Put a fragment or small strip of zinc (App., § 56), 
together with a bit of platinum foil into the tube, cover with 
water, close the tube with the perforated stopper a,nd, 
through the thistle-tube add strong chlorhydric acid in small § 25 
SEPARATION- OF ANTIMONY. 
33 
successive portions. After hydrogen has been generated 
freely during four or five minutes by the mixture in the 
tube, and all the air originally contained in the latter has 
been expelled, light the gas issuing from the pointed glass 
tube, and pour into the thistle-tube, a portion at a time, the 
mixture of strong chlorhydric acid and the residue containing 
antimony and tin, or the solution if the acid has dissolved 
the residue completely. Hold a cold porcelain dish in the 
flame, taking care to shift the position of the dish frequently 
so that fresh surfaces of porcelain may be exposed to the 
burning gas. If there be really any antimony in the insolu- 
ble residue, antiraoniuretted hydrogen will be evolved, to- 
gether with free hydrogen, and characteristic smoky- Tegt 
black spots or stains of metallic antimony will be for 
deposited from it upon the cold porcelain. To be Sb. 
sure that the spots are really composed of antimony and not 
of arsenic, cover them with a solution of bleaching powder 
(hypochlorite of calcium) ; if they are antimony spots they 
will not dissolve, while arsenic spots dissolve at once. (Com- 
pare Eliot and Storer's Manual, pp. 270, 271.) 
In order not to explode the test-tube on lighting the gas, 
the operator must wait patiently for several minutes, until 
all the air has been expelled from the tube. 
The whole of the antimony is not converted by this means 
into antimoniuretted hydrogen; a portion is reduced to the 
metallic state, and if the evolution has not been too rapid, 
will be found deposited on the platinum foil as a firmly adher- 
ent dark coating or stain. Therefore when the zinc in the 
test-tube is all or nearly all consumed, transfer the contents 
of the tube to a porcelain dish and examine the platinum 
foil for this indication of the presence of antimony. 
In the operation just performed, the tin which existed as 
oxide has been converted into the metallic state, and now 
awaits examination in the porcelain dish. Remove and rinse 
any zinc remaining undissolved and carefully decant from the 
dark spongy mass in the dish, the solution with which it is 
Test 
for 
Sb. 34 
SEPARATION OF TIN. 
§26 
covered and which consists mainly of chloride of zinc. The 
residue is warmed with strong chlorhydric acid, in which 
the tin dissolves. Pour off the solution of stannous chloride 
thus obtained, and add to it two or three drops o/ 
a solution of mercuric chloride (corrosive sublimate) 
(App., § 54). A white or gray precipitate of mer- 
curous chloride (calomel), often mixed with gray metallic 
mercury will be thrown down, for: — 
Test 
for 
Sn. 
2HgCl2-f-SnCl2=Hg2Cl2+SnCl4; and 
Hg2Cl2-|-SnCl2=2Hg+SnCl*. 
To prove that the precipitate really contains calomel, de- 
cant the supernatant liquid, cover the precipitate with ammo- 
nia-water, and heat the mixture to boiling (compare p. 18). 
26. An outline of the foregoing operations may be repre- 
sented in tabular form as follows : — 
The General Reagent (HsS) of Class III precipitates As2S3, 
Sb2S3, and SnS or SnS2, [Au,S3 and [PtS2]. (As well as the 
members of Class II, from which Class III is separated by solution 
in sulphydrate of sodium.) The sulphydrate of sodium solution is 
treated with nitric acid and nitrate of sodium, and the mixture 
evaporated and heated to fusion. The fused mass is treated with 
cold water: — 
Arseniate of sodium 
(with nitrate of so- 
dium, etc.) goes into 
solution. Confirm pres- 
ence of As by magne- 
sium mixture and by the 
silver test. 
Antimoniate of sodium and oxide of tin 
remain undissolved. Reduce with zinc 
and HC1 in presence of platinum foil. 
Antimoniuretted hy- 
drogen is formed and 
antimony spots ob- 
tained. 
Tin is left in the 
metallic state (to- 
gether with some an- 
timony which stains 
the foil). Dissolve 
the tin in HC1 and 
test with HgCl2. 
In the case of mixtures containing gold and platinum (see 
§ 13), as well as arsenic, antimony and tin, the gold and 
platinum would remain with the tin, without interfering in any 
way with the separation or detection of either member of the §27 
SEPARATION OF CLASSES II AND 111. 
35 
class, and when the tin reduced by zinc is dissolved in chlor- 
hydric acid, the gold and platinum would remair undissolved 
(together with some antimony, if present). Since the sul- 
phides of gold and platinum are both black, while those of 
arsenic and tin are yellow or brown, and that of antimony is 
orange, the presence of any considerable quantity of either 
of the precious metals would be indicated by the black color 
of the class precipitate. 
There are excellent special tests both for gold and for plat- 
inum, by which these elements may be detected even in the 
presence of all the other metals. Hence it is most conven- 
ient to make special search for them in the original substance, 
by methods to be described hereafter (§ 96, b.), whenever the 
preliminary examination has given reason to suspect the 
presence of either of them. 
27. The method of separating Class II from Class III 
has been sufficiently described in §§ 8, 24. When members 
of Class II are altogether absent, something may be learned 
from the color of the precipitate produced by sulphuretted 
hydrogen. Thus, — 
An orange colored precipitate indicates the presence of 
antimony; 
A bright yellow precipitate, the presence of arsenic ; 
A dull yellow precipitate, white at first, the presence of 
bisulphide of tin (stannic sulphide). 
A dark brown precipitate, the presence of protosulphide of 
tin (stannous sulphide). 
A black precipitate the presence of gold or platinum. 
When, as a result of the preliminary examination (§ 80, 
III, c), there is reason to suspect the presence of mercury 
as a mercuric salt, sulphydrate of ammonium which has be- 
come somewhat yellow from standing, should be substituted 
for sulphydrate of sodium, because sulphide of mercury is 
rather soluble in sulphydrate of sodium. In the event of the 
analysis of an unknown solution, if on the treatment with 
nitric acid of the solution of sulphides in sulphydrate of so- 36 
SEPARATION OF CLASSES II AND III. 
§ 27 
dium, a black precipitate appear, it may be owing to the pres- 
ence of sulphide of mercury and not to gold and platinum; it 
is therefore sometimes better in such a case to dilute the solu- 
tion with water, filter and treat the precipitate with sulphydrate 
of ammonium. The precipitate remaining undissolved is 
added to the regularly obtained precipitate of Class II, and 
the sulphydrate of ammonium solution added, with a fresh 
portion of strong acid, to the nitric acid solution already ob- 
tained. 
If an abundant supply of the substance under examination 
be at hand, it will often be better to start with a fresh portion 
and make the separation of the two classes with sulphydrate 
of ammonium. 
Sulphide of copper is also somewhat soluble in the sulphy- 
drates of sodium and ammonium, in presence of the sulphides 
of Class III; but enough of this sulphide will always remain 
undissolved to ensure the detection of copper in Class II. 
Since sulphydrate of ammonium often fails to dissolve sul- 
phide of tin, it is not, in general, so fit a solvent for the 
sulphides of Class III as sulphydrate of sodium. In either 
case it is desirable to use no more of the alkaline sulphydrate 
than is necessary, on account of the amount of sulphur which 
it will be necessary to oxidize with nitric acid and nitrate of 
sodium. 
For another method of treading the sulphides of Class III, 
see page 127. § 28 
CLASS IV 
37 
CHAPTER V. 
CLA.SS IV.-ELEMENTS WHOSE HYDRATES ARE INSOLU- 
BLE IN WATER, AMMONIA-WATER AND SOLUTIONS 
OF AMMONIUM SALTS. 
28. The leading fact upon which the separation of this 
class is based is the insolubility of the hydrates of iron, alumi- 
num and chromium in ammonia-water, even in presence of 
solutions of ammonium salts. But these three hydrates are 
not the only substances which are liable to be precipitated in 
an actual analysis when ammonia-water is added in excess to 
a solution previously acid. There are a number of com- 
pounds, soluble in acids, but not in water or in weak alkaline 
liquids, which are thrown down without change when theif 
acid solvent is destroyed. 
It is clear that it is needless to provide in this place against 
the presence of such salts of elements belonging to Classes I, 
II and III. Those elements are already eliminated when the 
fourth class is taken in hand. But if there are any salts of 
elements belonging to the fourth and higher classes which can 
only be kept in solution by a free acid, they will be precipi- 
tated without change in consequence of the neutralization of 
their solvent by the ammonia-water added to precipitate the 
three hydrates above mentioned. Such salts are the phos- 
phates of several members of Classes IV, VI and VII, besides 
a number of oxalates, borates, silicates and fluorides which 
occur so seldom that they need not be particularly considered 
in an elementary treatise. Beside the phosphates, several chro- 
mites and aluminates of members of Classes VI and VII are 
insoluble in ammonia-water, and are often thrown down wholly 
or in part along with the legitimate members of Class IV. 
Manganese also (a member of Class V) is frequently precipb 38 
PRECIPITATION OF CLASS IV. 
§§ 29, 30 
tated in combination with members of Class IV, in the form 
of chromite, ferrite or aluminate of manganese. The general 
scheme for the examination of Class IY, necessarily provides 
for the detection of all the members of the class in the pos- 
sible presence of these extraneous substances. 
29. Example of the Precipitation with Ammonia- 
water. — Pour into a beaker a small teaspoonful of aqueous 
solutions (App., § 62) of sulphate of manganese, common 
alum (sulphate of aluminum and ammonium), chrome alum 
(sulphate of chromium and potassium), and chloride of iron 
(ferrous chloride). As an example of the substances insolu- 
ble in water which might be present in an acid solution, dis- 
solve in a small amount of boiling chlorhydric acid, a 
not very large quantity, say half a gramme, of bone-ash 
(phosphate of calcium), and add the solution to those al- 
ready placed in the beaker. Fill the beaker about one third 
full of water, heat the mixture to boiling and add to it two or 
three drops of strong nitric acid to convert the iron into 
ferric salts. Boil the mixture for a minute or two and then 
add, little by little, ammonia-water to the boiling liquor until 
a distinct odor of ammonia is perceptible after the mixture 
has been thoroughly stirred. 
30. Analysis of the Mixed Precipitate. — The follow- 
ing method of detecting iron, chromium, aluminum (and 
manganese ) in the mixed precipitate which may contain all 
of them, together with phosphates and other compounds of 
barium, strontium, calcium and magnesium, depends: — 1st. 
Upon the oxidation and conversion of the hydrates of man- 
ganese and chromium into manganate and chromate of sodium 
(or potassium) when fused with a mixture of carbonate of 
sodium and nitrate of potassium ; while the hydrate of alum- 
inum under the same treatment is converted, to a greater or 
less extent, into aluminate of sodium, and the compounds of 
barium, strontium and calcium either remain unchanged or are 
converted into carbonates. 2d. Upon the solubility of the 
chromate and aluminate of sodium (or potassium) in water §30 
SEPARATION OF CLASS IV. 
39 
and the insolubility of the carbonates or other compounds of 
barium, strontium and calcium which may be present in the 
fused mass. 8d. Upon the sparing solubility of chromate 
of lead in acetic acid. 4th. Upon the peculiar green color 
of the manganate of sodium (or potassium). 5th. Upon the 
fact that Prussian blue is formed when a solution of ferro- 
cyanide of potassium is added to the solution of a ferric salt. 
6th. Upon the sparing solubility of the oxalates of barium, 
strontium and calcium in dilute acetic acid. 
The details of the treatment of the precipitate produced 
by ammonia-water, are as follows: — Collect the precipitate 
upon a filter, wash it two or three times with water, and then 
dry it either on the filter or by transferring it to a piece of 
platinum foil or to a platinum crucible (App., § 80) and heat- 
ing over the lamp gently so as to avoid spattering. The dry 
precipitate is mixed intimately (best by rubbing in a mor- 
tar) with five or six times its bulk of a dry mixture of equal 
parts of carbonate of sodium and nitrate of potassium (App., 
§36). The mixture is then fused thoroughly by heating it 
over the lamp either on platinum foil or in a platinum cruci- 
ble. If the amount of the mixture be small, a piece of foil 
answers very well; larger quantities may be fused in succes- 
sive portions on the foil, but a small crucible is much more 
convenient. 
If only a manganese compound and no chromium had been 
fused on the foil, the cold mass would have exhibited the 
peculiar bluish-green color of manganate of sodium (or po- 
tassium) owing to the oxidation of a small portion of the 
hydrate of manganese to manganic acid in the presence of 
carbonate of sodium and nitrate of potassium. If only chro- 
mium had been present, the bright yellow color of chromate 
of sodium (or potassium) would have been clearly perceived. 
But from mixtures of the manganate and chromate of sodium, 
(or potassium) in various proportions, different shades of 
green, brownish-green or yellowish-green, will result. When 
iron is present, the red color of its oxide may obscure the 
colors due to manganese and chromium. 40 
SEP ABA TIOK OF CHROMIUM. 
§ 30 
Place the platinum foil or crucible in a porcelain dish, cover 
it with water, and boil the latter until all the soluble matter 
has been dissolved from the foil. Take out the foil, rinse it, 
and throw the contents of the dish upon a filter. The man* 
ganate, chromate and aluminate of sodium pass into the fil- 
trate, along with the excess of the carbonate of sodium and 
nitrate of potassium employed: the filtrate is colored yel- 
low by the chromate, The insoluble residue, in this case, 
consists of the oxides of iron and manganese, together with 
the phosphate of calcium which has not been altered by the 
fusion, and any small portion of carbonate of calcium which 
may have been formed by the decomposition of a part of the 
phosphate. In the case of an actual analysis there might be 
also phosphates, carbonates and other insoluble compounds 
of barium, strontium and magnesium. 
Divide the filtrate from the insoluble residue of the fusion 
into two portions. Carefully add acetic acid, drop by drop, 
to one of these portions until the liquor exhibits an acid re- 
action, and then add to it two or three drops of a solution of 
acetate of lead (App., § 45). An insoluble precipitate of 
chromate of lead will be immediately thrown down, exhibiting 
a bright yellow color if the reagents be all pure. But if, as 
often happens, the carbonate of sodium, employed as the 
flux, is contaminated with sulphate of sodium, the 
yellow color of the precipitate will tend towards 
white, in proportion to the amount of sulphate of 
lead which has gone down together with the chromate. A 
pure white precipitate would be no indication of chromium, 
but only of a sulphate in the reagents. 
Acidulate the other portion of the aqueous solution of the 
fused sodium (and potassium) compounds with dilute chlor- 
hydric acid, add ammonia-water to slight alkaline 
reaction, warm the mixture and leave it at rest for 
at least half an hour or, better, over night. After 
the lapse of some time, a characteristic, gelatinous, colorless 
agglomeration of particles of hydrate of aluminum will ap- 
pear at the top or bottom of the liquid. 
Test 
for 
Cr. 
Test 
for 
AL § 30 
SEPARATION OF ALUMINUM. 
41 
It should be said, that flocks of hydrate of aluminum, when 
diffused through a liquid, are almost transparent enough to 
elude observation. When an acid solution, containing much 
aluminum, is mixed with ammonia-water and warmed, a 
copious precipitate of hydrate of aluminum will appear im- 
mediately, and will often remain floating for some time upon 
the surface of the solution by virtue of bubbles of air en- 
tangled in it. But since it is not easy to convert the whole 
of the alumina in the original precipitate into soluble alurui- 
nate of sodium, by fusion with carbonate of sodium in the 
method above described, the quantity of the hydrate to be 
thrown down at the final test is often very small, and con- 
siderable time must be allowed, in order that every particle 
of it may separate from the solution, and all the particles 
collect into a single mass. 
To confirm the presence of aluminum, collect the hydrate 
in the point of a small filter and allow it to drain. Cut away 
the superfluous paper, place that portion of the filter to which 
the precipitate is attached upon a piece of charcoal, and heat 
it intensely in the blowpipe flame. Moisten the residue with 
a drop of a solution of nitrate of cobalt and again ignite it 
strongly. The unfused compound of aluminum, cobalt and 
oxygen left upon the coal will exhibit a deep sky-blue color 
when allowed to cool. This reaction is useful in distinguish- 
ing the hydrate of aluminum from that of glucinum, an 
element somewhat similar to aluminum though far less 
abundant. Hydrate of glucinum when ignited with nitrate 
of cobalt does not yield a pure blue compound, but only a 
gray mass. 
Return now to the insoluble residue of the fusion with 
carbonate of sodium and nitrate of potassium. If the char- 
acteristic color of the manganate of sodium (or potassium) 
were not distinctly observed at the previous fusion, take 
a small quantity of the insoluble residue and fuse it with 
twice its bulk of a mixture of carbonate of sodium and 
nitrate of potassium upon platinum foil in a strong oxidizing 42 
SEPARATION OF MANGANESE AND IRON. 
§ 30 
blowpipe flame (App., § 78). The peculiar bluish-green 
coloration of manganate of sodium will appear in 
the fused mass, as soon as it has become cold, par- 
ticularly at the edges and thinner portions. In thus 
testing for manganese, it is well to incline the foil, so that por- 
tions of the thoroughly melted mass may flow away from the 
centre of the mixture into thin sheets, in order that the color 
of the manganate may be exhibited in its purity. 
Boil a second small portion of the insoluble residue with a 
little strong chlorliydric acid, dilute the solution with water, 
and add a drop or two of ferrocyanide of potassium. The 
liquid will immediately become colored with Prussian blue, 
an indication of the presence of iron. In case much 
iron be present, the blue color may be too deep to 
be recognized until the liquid has been diluted with 
a large quantity of water. 
Warm another portion of the insoluble residue with a few 
drops of acetic acid, dilute the solution with water and filter 
if anything remain undissolved. To the slightly acid liquid 
add a teaspoonful of a solution of oxalate of ammonium 
(App., § 20). Any compounds of barium, strontium and 
calcium which may have been present in the residue will be 
deposited as oxalates, as the oxalates of these elements are 
but sparingly soluble in acetic acid. In the present case there 
will be a precipitate of oxalate of calcium. Allow the mix- 
ture to stand for some time and finally collect the precipitate 
on a filter, wash, dry and preserve for future examination in 
connection with Class VI. 
In addition to the elements present in the solution which 
has just been analyzed, compounds of magnesium are also 
under certain circumstances precipitated with the hydrates 
of Class IV. In actual practice, thei'efore, the remainder of 
the insoluble residue is examined for magnesium, as follows : — 
Heat the mixture strongly on the platinum-foil so as to ren- 
der the oxides of aluminum and iron as insoluble as pos- 
sible, and then treat with dilute chlorhydrie acid and warm 
Test 
for 
Mn. 
Test 
for 
Fe. §31 
SEPARATION OF CLASS IY. 
43 
gently. "Without regarding the matter which remains undis- 
solved add to the mixture (which contains in solution, along 
with the magnesium, some iron, aluminum, calcium, etc.) a 
teaspoonful of chloride of ammonium, and ammonia-water to 
alkaline reaction. Throw the mixture upon a filter, collect 
the. filtrate, and add it to that originally obtained from the 
precipitate of Class IV": this mixed filtrate will be examined 
in due course (Class VII) for magnesium. In case the whole 
amount of the residue from the fusion of the precipitate of 
the class with carbonate of sodium and nitrate of potassium, 
be but small, it is well to filter the liquid of the preced- 
ing paragraph which contains the precipitated oxalates of 
barium, strontium and calcium, to evaporate the filtrate to 
dryness and iguite to destroy the oxalic and acetic acids. 
The residue is subsequently treated with chlorliydric acid, 
chloride of ammonium and ammonia, filtered and the filtrate 
added to the filtrate from the original Class IV precipitate. 
31. An outline of the foregoing operations may be tabu- 
lated as follows: — 
The General Reagent ([NH4]HO mixed with NH4C1) of Class 
IY precipitates the hydrates of Fe,Cr and Al together with Mn 
(as a chromite, ferrite or aluminate), and various phosphates and 
other compounds of Fe, Cr, Al, Ba, Sr, Ca and Mg. The pre- 
cipitate is dried and fused with Wa2C03 and KN03; the fused 
mass is treated with water and filtered: — 
Divide the filtrate into two 
portions: — 
Divide the precipitate into four 
portions: — 
Yellow color 
of the solution 
indicates Cr. 
Confirm Cr by 
precipitation 
of PbCr04. 
Acidulate with 
HC1 and add 
(NH.f)HO :— 
Colorless floc- 
culent precipi- 
tate proves 
presence of 
Al. 
Test for 
Mn by 
fusing 
with 
U"aa 
C03and 
kno3. 
Test for 
Fe with 
ferrocy- 
anide of 
potas- 
sium. 
Test for 
Ca, etc. ■ 
by pre- 
cipita- 
tion of 
the oxa- 
lates 
from 
acetic 
acid so- 
lution. 
Elimi- 
nate Mg 
by dis- 
solving 
in HC1 
and rc- 
precipi- 
tating 
Class iV 
with 
NH, 
HO 44 
FERROUS AND FERRIC SALTS. 
§ 31,32 
Ill the actual examination of an unknown substance, the 
analysis is somewhat simplified, if the substance be a solid 
soluble in water, or if it be a neutral solution, or if by any 
other means we know that the phosphates, oxalates, etc., men- 
tioned above are absent. The treatment in such a case may be 
simplified by the omission of those operations looking to the 
separation of calcium, barium, etc., from the residue of the 
fusion with carbonate of sodium and nitrate of potassium. 
To determine whether the iron in the substance subjected 
to analysis was originally in the state of a ferric or a ferrous 
salt, test a small quantity of the original solution with a drop 
of ferricyanide of potassium (App., § 34). The formation 
of Prussian blue proves the presence of a ferrous salt. An- 
other small portion of the original solution, tested with a 
drop of a ferrocyanide of potassium, would yield Prussian 
blue in case the solution contained a ferric salt. In applying 
either of these tests, the blue coloration, indicative of iron, 
is alone to be looked for ; no notice need be taken of other 
colorations, or of precipitates formed by the action of the 
ferri- or ferro-cyanide upon the various metallic salts which 
the solution may contain. The possibility that a ferrous salt 
may have been changed into a ferric during the process of 
getting the original substance, if a solid, into solution, must 
not be lost sight of. 
32. Separation of Class IV from Class III. The 
methods of eliminating Classes I, II and III from mixtures 
which contain members of these classes as well as of Class 
IV, have already been described in §§ 6 and 8. 
It is essential to the success of the operation that all the 
sulphuretted hydrogen in the filtrate from Classes II and III 
be expelled, for sulphuretted hydrogen precipitates all the 
members of Classes IV and V from alkaline solutions, and 
the filtrate now in question is, of course, made alkaline when 
ammonia-water is added to it. The conversion of the iron 
into a ferric salt (by means of nitric acid) is necessary be- 
cause ferrous hydrate is somewhat soluble in ammonium-salts, § 32 
FERROUS AND FERRIC SALTS. 
45 
and could not, therefore, be precipitated completely by am- 
monia-water in the acid filtrate from Classes II and III. 
No matter what the condition of the iron may have been in 
the original solution, it is reduced to the state of ferrous salts 
by sulphuretted hydrogen. The filtrate from the precipitate 
produced by sulphuretted hydrogen (the general reagent of 
Classes II and III) should, therefore, be placed in a porcelain 
dish, and boiled, until the steam from it ceases to blacken lead 
paper. After the sulphuretted hydrogen has been expelled, 
three or four drops of strong nitric acid must be added to the 
liquid, and tbe mixture boiled for a moment longer to convert 
the iron into ferric salts. If by accident the student should 
fail to convert the iron entirely to the state of a ferric salt, 
there will be produced a greenish, slimy precipitate of ferrous 
hydrate on the addition of the ammonia-water. Such a pre- 
cipitate must not be confounded with the green hydrate of 
chromium: it should be redissolved in nitric acid and the acid 
solution boiled anew for a few minutes before reprecipitating 
with ammonia-water. 
When all the iron has been converted in the state of a 
ferric salt, a small quantity of a solution of chloride of 
ammonium is added to the boiling liquid, and finally am- 
monia-water, little by little, with constant stirring, until a 
persistent odor of ammonia is perceptible. A large excess 
of ammonia must be carefully avoided, for hydrate of alumi- 
num, being somewhat soluble in ammonia-water, might be 
kept in solution, to the disturbance of the analysis of Classes 
VI and VII. 
It will be remembered that the object of using chloride of 
ammonium is to hold in solution magnesium (of Class VII) 
and the members of Class V. This it does in virtue of the 
fact that the double salts formed by the union of ammonium 
compounds with compounds of the elements in question are 
soluble in water and also in ammonia-water. A considerable 
quantity of the ammonium salt will, of course, be formed in 
any event by the action of the ammonia-water upon the 46 
PRECIPITATE OF CLASS IV. 
§ 32 
chlorhydnc acid in the solution, but it is best to add 
a further portion of the chloride as a precautionary measure. 
The following inferences may be drawn from the color of 
the precipitate produced by ammonia-water: — 
A gelatinous, white precipitate indicates aluminum or some 
one of the oxalates, phosphates, etc., mentioned above. 
A grayish-green or grayish-blue precipitate indicates chro- 
mium. 
A reddish-brown precipitate indicates iron. 
If no precipitate is produced by the ammonia-water, all 
the members of Class IV are absent, and the solution may 
at once be tested with sulphydrate of ammonium, the general 
reagent of Class V. 
When the solution contains much chromium, a small por- 
tion of this element is apt to remain dissolved at first in the 
excess of ammonia-water, and to color the solution pink; but 
by continuing to boil the solution, the color may be made to 
disappear, and the whole of the chromium may be thrown 
down. Care must be taken to replace, by small portions, 
the water driven off by boiling, lest some of the members of 
Class V be converted into insoluble compounds. 
It is to be observed that the legitimate members of Class 
IV cannot be completely precipitated by ammonia-water from 
solutions which contain non-volatile organic substances, like 
albumin, sugar, starch, and so forth, or organic acids (such 
as tartaric, citric, oxalic, or even in some cases acetic acid) 
which form soluble double salts by uniting simultaneously 
with the ammonium and one or more of the members of the 
class. The treatment of substances containing organic mat- 
ter will be explained hereafter. (§ 82.) §§ 33, 34 
CLASS V. 
47 
CHAPTER Vt. 
CLASS V. —* ELEMENTS WHOSE SULPHIDES ARE INSOL- 
UBLE IN WATER AND IN SALINE OR ALKALINE SO- 
LUTIONS. 
33. Example of tlie Precipitation of the Members 
of Class V.—Place in a small glass flask a half teaspoonful 
of aqueous solutions (App., § 62) of the sulphates, nitrates, 
or chlorides of cobalt, nickel, manganese and zinc. Add to 
the mixture five or six teaspoonfuls of a solution of chloride 
of ammonium, as much water, and ammonia-water to alkaline 
reaction. 
Heat the mixture to boiling, and add sulphydrate of am- 
monium to the boiling solution, drop by drop, with frequent 
agitation, as long as a precipitate continues to be formed. 
(Compare p. 12.) In the present case there are special reasons 
why the precipitate should be boiled and shaken, in order to 
make it compact; for the sulphides of Class V, when loose 
and flocculent, are not only easily acted upon by the ah* and 
by dilute acids, but are peculiarly liable to pass through the 
pores of filter-paper, and yield muddy filtrates. 
At the best, these sulphides oxidize rapidly when moist, 
with formation of soluble sulphates which are liable to pass 
through the filters and contaminate the filtrates. The analysis 
of the sulphides therefore be proceeded with imme- 
diately after the precipitation with sulphydrate of ammonium, 
and should be conducted in such manner that no precipitate 
of a sulphide shall ever be left moist upon a filter more than 
half an hour. 
34. Analysis of the Mixed Sulphides.—The detection 
of the several members of Class V depends : — 1st. Upon 
the almost complete insolubility of the sulphides of cobalt 48 
BEPABA TION OF MANGANESE. 
§ 34 
and nickel in cold dilute chlorhydric acid, and the ready solu- 
bility of the sulphides of manganese and zinc in that liquid. 
2d. Upon the solubility of hydrate of zinc, and the insolu- 
bility of hydrate of manganese, in a solution of caustic soda. 
3d. Upon the insolubility of sulphide of zinc in acetic acid, 
in presence of sulphuretted hydrogen. 4th. Upon the pecul- 
iar colors imparted to borax glass by compounds of cobalt 
and nickel dissolved in the glass; and upon certain other 
special tests to be described directty. 
To effect the separation: — Collect the precipitate upon a 
filter, and rinse it once or twice with water; spread open the 
filter in a porcelain dish, and cover it with cold dilute chlor- 
ltydric acid. Scarcely any of the sulphide of cobalt, or of 
nickel, will go into solution, while the sulphides of manganese 
and zinc will be completely decomposed, and dissolved as 
chlorides. 
Filter the chlorhydric acid solution, pour the filtrate into a 
porcelain dish, and boil it strips of moistened lead paper 
held in the steam no long# indicate the presence of sulphur- 
etted hydrogen ; then add caustic soda to the liquid in slight 
excess. A whitish gelatinous preoipitate of hydrate of man- 
ganese, insoluble in caustic soda, will be thrown down, to- 
gether with small portions of the hydrates of cobalt and 
nickel, resulting from the partial decomposition of the sul- 
phides of these metals by the chlorhydric acid, while the 
hydrate of zinc at first precipitated redissolves completely in 
the excess of soda. It is to be observed that precipitation 
should never be effected in a porcelain dish, since a white or 
transparent precipitate is scarcely visible in a white and 
opaque dish. 
To prove the presence of manganese, collect the precipitate 
upon a filter, allow' it to drain, and fuse a small portion of it 
with a mixture of carbonate of sodium and nitrate 
of potassium upon platinum foil in the oxidizing 
blowpipe flame, as dii’ected on p. 42. 
Acidify the alkaline filtrate with acetic acid ; then pass sul 
Test 
for 
Mn. SEPARATION OF ZINC. 
§ 34 
49 
phuretted hydrogen into the liquid. Sulphide of zinc will be 
thrown down as white or dirty white floceulent precipitate. 
To confirm the presence of zinc : — Collect the precipitate 
produced by sulphuretted hydrogen upon a filter and allow to 
drain; transfer it to a porcelain dish, dissolve it in dilute 
chlorhydric acid, and evaporate the solution almost to dryness 
on a water-batli (App., § 77). Dissolve the residue in a few 
drops of water, and without heeding the milkiness which the 
presence of particles of free sulphur may produce in it, pour 
this liquid into a test-tube or three teaspoon- 
fuls of a solution of normal previously 
heated to boiling. A peculiar, 
floceulent precipitate of basic chromate of zinc will 
form in the boiling liquid, and will soon subside to 
the bottom of the tube. The red color of the supernatant 
fluid is due to the formation of bichromate of potassium. 
It is to be observed that in the analysis of mixtures which 
contain no manganese, the precipitate of hydrate of cobalt or 
of nickel, produced by the caustic soda, is usually small and 
sometimes hardly perceptible ; but, no matter how minute the 
precipitate may be, it must always be carefully removed by 
filtration before testing the solution for zinc with sulphuretted 
hydrogen. 
The black residue, insoluble in dilute chlorhjxlric acid, is 
washed with water and tested for cobalt an(| nickel, by heat- 
ing successive sma« portions of it in a bead {§ 89, c.) 
of borax (App., § 25) in the oxidizing lm>wpipe 
flame. If cobalt alone were present, a bright, pure 
blue color would be imparted to the bead. On the other hand, 
if the precipitate was composed solely of sulphide of nickel, 
the borax glass would assume a peculiar reddish-brown color. 
Mixtures of the two sulphides yield beads of various tints, 
according to the proportions of nickel ami cobalt contained 
in them. By adding the precipitate toJ#e borax by repeated 
small portions, and fusing the after each addition, 
it is often possible to obtain first the characteristic color of 
Test 
for 
Zn. 
Tests 
for 
Co&Ni. 50 
SEPARATION OF NICKEL. 
§ 34 
one of the elements, and afterwards tolerably well defined 
indications of the other. 
The blue color of cobalt can usually be made manifest, 
even in presence of much nickel, by heating the borax bead 
in the reducing blowpipe flame (App., § 78). In the reduc- 
ing flame the reddish-brown color imparted by nickel changes 
to gray, while the cobalt blue remains unaltered. 
In any event, one of the two metals will be detected by 
the blowpipe test, and the subsequent operations can be 
limited to searching for the other. 
To prove the presence of nickel, boil the black residue with 
a few drops of aqua regia in the porcelain dish, and evaporate 
the solution almost, but not quite, to dryness. Add to the 
residual acid liquor, little by little, a strong solution of 
cyanide of potassium, until the reaction of the solution be- 
comes decidely alkaline; the cj’anides of nickel and cobalt 
at first thrown down both redissolved easily in an excess of 
cyanide of potassium. Boil the mixture for several minutes, 
adding water bj7 small portions to replace that lost by evap- 
oration. Then add a solution of hypochlorite of sodium 
until the liquid, after shaking, smells strongly of it, and boil 
again. The nickel is precipitated as black hydrated peroxide 
(nickelic hydrate, Ni2H606), while the compound of cobalt in 
solution (cobalticyanide of potassium) is not affected. If 
a light-colored precipitate appears, it may indicate that an in- 
sufficient quantity of hypochlorite of sodium has been added, 
and in the case of a solution actually under examination more 
of the reagent should be added before pronouncing nickel 
absent. 
To confirm the presence of cobalt in case of doubt: — dissolve 
the black residue in a few drops of hot aqua regia, evaporate 
the solution nearly to dryness, pour into the residual solution 
two or three times its own volume of a solution of nitrite of 
potassium (App., § 37), and add to the mixture concentrated 
acetic acid, until the reaction of the li juid is strongly acid. §§34, 35 
SEPARATION OF COBALT. 
51 
Transfer the mixture to a test-tube, and leave it at 
rest during eighteen or tweidy-four hours. A beau- 
tiful, yellow crystalline precipitate of the double 
nitrite of cobalt and potassium will be deposited sooner ot 
later, according to the proportion of cobalt which the solution 
contained. 
On adding caustic soda to the filtrate from the cobalt 
precipitate, hydrate of nickel would be thrown down if pres- 
ent, and the presence of nickel might be confirmed by testing 
this precipitate with borax in the oxidizing blowpipe flame. 
35. An outline of the foregoing operations may be tabu- 
lated as follows: — 
Test 
for 
Co. 
Test 
for 
Co. 
The General Reagent ([NH4]HS) of Class V precipitates CoS, 
NiS, MnS and ZnS. Treat the precipitate with dilute HC1: — 
CoS and HiS 
remain undis- 
solved. 
Test for Co 
and Hi with 
borax glass 
and, if need 
be, with Ha 
CIO or KHO,.1 
i 
MnCl2 and ZnCl2 go into solution. Boil, to ex- 
pel H2S, and add HaHO:— 
Hydrate of manganese is 
precipitated, together with 
traces of the hydrates of 
Co and Hi. 
i Prove presence of Mn by 
The blowpipe test. 
Hydrate of zinc goes 
into solution. Add H2S 
to throw down ZnS. 
Confirm presence of 
Zn by precipitation of 
the chromate. 
36, Separation of Class V from Class IV.—After 
Classes I, II, III and IV have been removed in the manner 
already described (§§ 9, 32), add a single drop of sulphydrate 
of ammonium of good quality (App., § 17) to the filtrate 
from Class IV. If no precipitate is produced, none of the 
members of Class V can be present, and the solution may be 
immediately tested with carbonate of ammonium, the general 
reagent of Class VI. 
If the first drop of the sulphydrate produces a precipitate, 
transfer the mixture to a small flask, heat it until it actually 
boils and add more of the sulphydrate, with the precautions 
enjoined on p. 12 to complete the precipitation. 52 
SEPARATION OF CLASSES IV AND V. 
$ 36 
In case the precipitate produced by sulphydrate of am- 
monium is white, the presence of zinc is indicated. 
If it be flesh-colored, or yellowish-white, and becomes 
brown by oxidation when exposed to the air, the presence of 
manganese is to be inferred. 
In case the precipitate is black, either cobalt or nickel, or 
both these elements, are present. Both of them must be 
sought for, whenever the precipitate exhibits any tinge of 
black at the moment of its formation. 
As the sulphide of nickel is not absolutely insoluble in 
sulphydrate of ammonium, it not infrequentl}' happens that 
the filtrate from Class V is dark-colored, owing to the presence 
of sulphide of nickel in solution. In such case it is well to 
acidify the liquid with chlorliydric acid, and to collect the 
dark-colored precipitate (which consists of sulphide of nickel 
mixed with free sulphur) on a filter, and to test for nickel 
by means of the borax bead. The filtrate must then be made 
alkaline with ammonia-water before testing for Class VI. 
As it is sometimes difficult for the student to obtain satis- 
factory indications of zinc when present in small quantities, 
the following mode of procedure may be adopted. Take 
one half of the alkaline filtrate of p. 48, last line, and treat 
as directed. Acidify the other portion with chlorliydric 
acid. Add one drop of a solution of nitrate of cobalt, then 
a solution of carbonate of sodium as long as a precipitate is 
produced. Boil for three minutes, filter, dry the filter some- 
what, and then burn either on platinum foil or on charcoal. 
In the presence of zinc there remains an ash of a peculiar 
bluish-green color. §§37, 38 
CLASS VI. 
53 
CHAPTER VII. 
CLASS VI.-ELEMENTS WHOSE CARBONATES ARE INSOL 
UBLE IN WATER, AMMO AIA-WATER AND SALINE SOLU- 
TIONS. 
37. Example of the Precipitation of the Members of 
Class VI. — Place in a small beaker a teaspoonful of aque- 
ous solutions of the chlorides or nitrates of barium, stron- 
tium and calcium. Add to the mixture two or three 
teaspoonfuls of a solution of chloride of ammonium, enough 
ammonia-water to produce an alkaline reaction, and finally a 
solution of carbonate of ammonium, drop by drop, as long 
as any precipitate continues to be produced by fresh portions 
of this reagent. To determine this last point, heat the mix- 
ture to boiling at intervals, and after boiling allow it to settle, 
until a sufficient quantity of comparatively clear liquid has 
collected at the top of the mixture to permit the application 
of the test. 
38. Analysis of the Mixed Carbonates. — The separa- 
tion of barium, strontium and calcium, one from the other, 
depends : — 1st. Upon the insolubility of chromate of barium 
in dilute acetic acid, and the solubility of the chromates of 
strontium and calcium in that liquid. 2d. Upon the fact that 
sulphate of strontium is almost absolutely insoluble in acidu- 
lated water, while sulphate of calcium, though rather spar- 
ingly soluble in water, is still sufficiently soluble to be kept 
in solution. (See App., § 30.) 
Collect the precipitate upon a filter, wash it two or three 
times with water, taking care to collect the precipitate at the 
apex of the filter, and dissolve it in acetic acid. The acid 
may be poured into the filter as it rests in the funnel, but SEPARATION OF BARIUM. 
§ 38 
only a few drops should be used, and the filtrate should be 
poured back repeatedly upon the filter, until all the precipi- 
tate has been dissolved. If the portion of acid at first taken 
becomes saturated before the precipitate is entirety dissolved, 
it will be necessary to add an additional small amount. 
Finally rinse the filter with a little water from a wash-bottle 
with small orifice, collect the wash-water with the filtrate, 
and shake the mixture. 
Pour a small portion of the acetic acid solution into a test- 
tube, and add to it a drop of a solution of normal chromate 
of potassium. A pale yellow precipitate falls when barium 
is present, as in this instance ; for chromate of bai'ium is well- 
nigh insoluble in acetic acid, especially in presence 
of saline solutions. In order to separate the whole 
of the barium, pour the contents of the test-tube 
into the reserved portion, of the acetic acid solution, heat the 
mixture to boiling, and add to it chromate of potassium, until 
no more precipitate falls and the supernatant liquor appears 
distinctly yellow, after having been well shaken and allowed 
to settle. Filter the mixture, and proceed to examine the 
filtrate for strontium and calcium. 
If no barium had been present, no precipitate would have 
been produced by chromate of potassium in the small portion 
of liquid first tested, and it would have been unnecessary to 
mix this reagent with the rest of the acetic acid solution. 
Trouble would thus be saved, as will appear below. 
It sometimes happens that chromate of barium is precipi- 
tated in the form of powder so fine that some particles of it 
pass through the pores of the paper and contaminate the fil- 
trate. Now, in order to detect strontium and calcium it is 
absolutely necessary that this filtrate, although of a bright 
yellow color, should be perfectly transparent and free from 
suspended particles of the barium salt. If then the filtrate 
is at all turbid, it must be poured back repeatedly into the 
filter, and again collected in clean tubes, until the last trace 
of cloudiness has disappeared. 
Test 
for 
Ba. § 38 
SEPARATION OF STRONTIUM AND CALCIUM. 
55 
To the filtrate from the chromate of barium add ammonia- 
water to alkaline reaction, and carbonate of ammonium as 
long as a precipitate falls. Heat the mixture to boiling for a 
moment, collect the precipitate upon a small filter, and wash 
it with water, until all the chromate of potassium has been 
removed, and the wash-water runs colorless from the filter. 
Dissolve the precipitate in the smallest possible quantity 
of acetic acid, and mix it with three or four times its volume 
of a solution of sulphate of potassium (App., § 30), made 
of such strength that, though capable of throwing down sul- 
phate of strontium, it cannot precipitate sulphate of calcium. 
Allow the mixture, to stand at rest for two hours or more, in 
order that the white powder of sulphate of strontium Testg 
may separate completely. Then filter, and to the for 
filtrate add ammonia-water to alkaline reaction, and Sr&Ca. 
half a teaspoonful of a solution of oxalate of ammonium. 
A white precipitate of oxalate of calcium will be immediately 
thrown down. 
Since sulphate of strontium is somewhat soluble in a solu- 
tion of chromate of potassium, the filtrate from chromate of 
barium cannot be examined directly for strontium by means 
of sulphate of potassium. The strontium and calcium are 
consequently reprecipitated as carbonates, in order that the 
excess of chromate of potassium may be washed away. The 
operation serves also to collect the strontium and calcium out 
of the mass of liquid in which they have become diffused, and 
to concentrate them to a small bulk. 
It should be observed that, when the proportion of stron- 
tium or calcium in a mixture is small, it often happens that 
the precipitate, produced by carbonate of ammonium in the 
filtrate from chromate of barium, is held in suspension and 
concealed so completely in the yellow liquor, that an unprac- 
tised eye can hardly detect the fact that the liquid has become 
cloudy. That a precipitate has really been formed in such 
cases is easily discovered by throwing a portion of the mix- 
ture upon a filter, and comparing the- efhar filtrate thus ob* 56 
SEPARATION OF CLASS VI. 
§§39,40 
tained with that portion of the mixture which has been left 
unfiltered. 
39. An outline of the foregoing operations may be pre- 
sented in tabular form, as follows: — 
The General Reagent, [!N‘H4]2CC>1, of Class VI precipitates the 
carbonates of Ba, Sr and Ca. Dissolve iu dilute acetic acid, and 
add K2Cr04: — 
BaCrO, 
is thrown 
down 
(IS il 
yellow 
powder. 
Sr and Ca remain in solution. Add and 
(NH4)oC03. Collect and wash the precipitate, and dis- 
solve it in acetic acid. Add dilute K2S04: — 
SrS04 is 
thrown 
down. 
Ca remains in solution. Add oxalate of 
ammonium, to precipitate the calcium as 
oxalate. 
40. Separation of Class VI from the Preceding 
Classes. —After Classes I, II, III, IV and V have been sepa- 
rated in the manner already described (§§ 6 to 10), there will 
still always remain to be examined the filtrate from Class V, 
and sometimes a precipitate (§ 30) composed of oxalates of 
barium, strontium, calcium (and magnesium), — in case any 
salt of these elements, insoluble in ammonia-water, has been 
thrown down with the members of Class IV. 
If such a precipitate has been obtained in the anatysis of 
Class IV, the oxalic acid contained in it must now be de- 
stroyed, the remainder of the precipitate brought into solution, 
and this solution added to the filtrate from Class V, before 
proceeding to precipitate the members of Class VI. To this 
end, ignite the dry precipitate carefully upon platinum foil,— 
by several successive portions if the precipitate is large, — 
taking care that none of the powder is left sticking to the 
paper or lost by dropping it from the foil. At a moderate 
heat the oxalates suffer decomposition, and only carbonates 
or oxides are left upon the foil. Place the foil and the residue 
in a small porcelain dish, and dissolve the residue in boiling 
dilute ehlorhydric acid. Add a few drops of chloride of am* § 40 
SEPARATION OF CLASS VI. 
57 
moniura to the solution, neutralize the acid with ammonia- 
water, pour the liquid upon a small filter and add the filtrate 
to that obtained from Class V. Then add a solution of car- 
bonate of ammonium to the mixture, and boil it in the man- 
ner described in § 37. 
If there be no precipitate of the oxalates from Class IV, 
the filtrate from Class V will, of course, be treated directly 
with carbonate of ammonium, care being taken to add only 
a drop or two of the reagent, at first, to ascertain whether 
any of the members of Class VI are really contained in the 
solution. 
The solution to which the general reagent carbonate of 
ammonium is added, must contain chloride of ammonium, tc 
prevent the precipitation of magnesium as a carbonate, anc 
also ammonia-water, to hinder the decomposition of the car. 
bonates of barium, strontium and calcium by the boiling 
chloride of ammonium. But since the excess of ammonia- 
water and the chloride of ammonium, added to the solution 
before the separation of Class IV, are still contained in it, no 
new quantity of either of them need here be added. 
It is to be remembered, in this connection, that the carbon- 
ates of barium, strontium and calcium are all slightly soluble 
in a solution of chloride of ammonium, and that no precipi- 
tate whatever is produced when carbonate of ammonium is 
added to a weak solution of either of the members of Class 
VI, in case a large quantity of chloride of ammonium has 
been previously mixed with it. On this account it is well in 
an actual analysis to concentrate by evaporation the filtrate 
from the Class V precipitate before adding the carbonate of 
ammonium solution, and in some cases, where a very large 
amount of ammonium salts is present, it is well to evaporate 
to complete dryness and then to ignite in order to drive off the 
ammonium compounds. The residue when cold is dissolved 
in a small quantity of chlorhydric acid ; two or three teaspoon- 
fuls of a solution of chloride of ammonium are added, then 
ammonia-water, and, finally, carbonate of ammonium, as in 
§37. 58 
SEPARATION OF CLASS VI. 
§ 40 
In a solution containing traces of barium or strontium these 
elements might fail to be detected, in case the chlorhydric 
acid employed in the process of separating Classes I and II 
was contaminated with sulphuric acid, or in case the original 
liquid contained nitric acid to oxidize a portion of the sul- 
phur of the sulphuretted hydrogen employed to precipitate 
Class II, or even if the nitric acid, employed to oxidize iron 
in the filtrate from Classes II and III, were added before the 
sulphuretted hydrogen had been expelled. All danger is 
avoided, however, by using pure chlorhydric acid to precipi- 
tate Class I, and expelling the nitric acid from the filtrate by 
evaporating the latter to dryness upon a water-bath, cover- 
ing the residue with pure concentrated chlorhydric acid, again 
evaporating until the mixture becomes dry, and finally dis- 
solving in water acidulated with chlorhydric acid. §§ 41, 42 
CLASS W. 
CHAPTER VIII. 
CLASS VII. — INCLUDES THE REMAINING COMMON ELE. 
MENTS NOT COMPRISED IN THE PRECEDING- CLASSES, 
NAMELY: MAGNESIUM, SODIUM AND POTASSIUM. 
41. The Detection of the Several Members of Class 
VII depends : — 1st. Upon the insolubility of a double phos 
phate of magnesium and ammonium, and the solubility of 
the phosphates of potassium and of sodium; and 2d. Upon 
the fact that compounds of sodium and potassium impart 
peculiar colorations to non-luminous flames, like those of 
alcohol and of a mixture of coal-gas and air. 
Prepare a mixture of a small teaspoonful of solutions 
(App., § 62) of almost any one of the salts of magnesium, 
sodium and potassium, and add to the mixture an equal bulk 
of chloride of ammonium. Pour a quarter of the mixture 
into a test-tube and the remainder into a small porcelain dish. 
Add to the contents of the test-tube two or three drops of a 
solution of phosphate of sodium, and as much ammonia- 
water, and shake the cold mixture at frequent inter- 
vals during one or two hours. A crystalline, white 
precipitate of phosphate of magnesium and ammo- 
nium will appear after a longer or shorter interval, according 
as the original solution was more or less dilute. 
42. Evaporate the contents of the porcelain dish to dry- 
ness, ignite the residue until the chloride of ammonium has 
been completely expelled, — a point which will be indicated 
by the cessation of fuming, — allow the dish to cool, and 
pour into it three or four drops of water. 
Carefully clean the loop on a piece of platinum wire by 
washing it repeatedly with water, and finally holding it in 
Test 
for 
Mg. SEPARATION OF SODIUM AND POTASSIUM. 
§ 42 
the lamp flame until the last traces of sodium compounds are 
burned off, and it ceases to color the flame. W ith- 
out touching the loop with the fingers, dip it into 
the aqueous solution in the dish, and again hold it 
in the flame. A bright yellow color will be imparted to the flame 
by the sodium contained in the mixture ; but the color pecu- 
liar to potassium compounds will be invisible, since the yel- 
low color of the sodium overpowers and conceals it. Dip the 
loop a second time in the solution, and again hold it in the 
lamp flame; but this time look at the flame through a piece 
of deep-blue cobalt glass. This cobalt glass is the ordinary 
blue glass used for stained glass windows ; it is essential that 
the glqjjjLshonld be of moderate thickness, and colored blue 
throughout pilot simply “flashed” with blue. The character- 
istic violet color imparted to a flame by potassium 
compounds will now be visible, for the blue glass 
shuts off completely the yellow sodium light, while 
it permits the free passage of the violet rays. 
Since traces of compounds of sodium and potassium are 
to be found almost everywhere, it is sometimes difficult to 
determine by the foregoing tests whether the substance under 
examination contains one or the other of these elements as an 
essential ingredient, or merely as an accidental impurity. 
It is alwaj’s possible, however, to separate the sodium or the 
potassium from the other members of the class, and to decide, 
by actual inspection of the isolated compounds, whether one 
or both of these substances is contained in really apprecia- 
ble quantity in the substance subjected to analysis. If only 
potassium is sought for, filter the aqueous solution, last 
mentioned, though a very small filter, add to the filtrate a 
drop or two of chlorhydric acid and several drops of a solu- 
tion of bichloride of platinum (App., § 55). A yellow 
crystalline precipitate of cliloroplatinate of potassium will 
separate after some time. Since chloride of ammonium 
would pioduce a similar precipitate, it is, of course, essential 
that the ammoniacal salt should be expelled by ignition be- 
fore potassium is tested for. 
Test 
for 
M Na. 
Test 
for 
- K. §§ 42,43 
ISOLATION OF CLASS VII. 
In case sodium, or both sodium and potassium, be sought 
for, the magnesium must first be got rid of. To this end, 
moisten the dry residue, which contains the chlorides of mag- 
nesium, of potassium and of sodium, with a drop or two of 
water, mix it thoroughly with an equal bulk of red oxide of 
mercury and ignite the mixture until fuming ceases. The 
chloride of magnesium will be changed to oxide, while the 
easily volatile chloride of mercury escapes: — 
MgCl2+HgO=MgO+HgCl2. 
The ignition should be effected beneath a chimney, or in a 
draught of air powerful enough to carry away the poisonous 
fumes of the corrosive sublimate. Boil the 
with a small quantity of water; separate the insoluble oxide 
of magnesium, together with the excess of oxide of mercury, 
by filtration; evaporate the filtrate to a small bulk; throw 
down the potassium as chloroplatinate, collect the latter upon 
a filter, and from the filtrate remove the excess of chloride of 
platinum by means of sulphuretted hydrogen. Filter off the 
sulphide of platinum, and evaporate the filtrate to dryness to 
obtain the chloride of sodium. Or, instead of employing sul- 
phuretted hydrogen, evaporate the filtrate from the chloropla- 
tinate of potassium in a watch glass, at a gentle heat, until the 
liquid begins to become dry at its edges, and then examine it 
with a magnifying glass. Characteristic crystals of chloro- 
platinate of sodium will be seen in the form of long, slender 
prisms or needles of yellow color. 
43. The Isolation of Class VII, by the removal of the 
preceding classes, has been described in § 12. Care must 
alwaj's be taken to concentrate the whole of the filtrate from 
Class VI by evaporation, before testing a portion of it for 
magnesium ; and time enough must be allowed for the mag- 
nesium precipitate to crystallize. The remainder of the 
filtrate from Class VI must be evaporated to dryness and 
ignited, before testing for sodium and potassium, in order 
that the flame reactions of these elements may not be con- 62 
SEPARATION OF CLASSES. 
§ 44 
3 
Add an excess of dilute HC1 to the solution to be examined. 
1 > 
5*73 
Saturate the filtrate with H2S. 
2: ft 
o 2. 
SH 
ft rt- 
Cfi p 
Boil the preciptiate 
with NallS. 
Boil the filtrate, to expel H2S, and add HN03, to oxidize Fe. Then 
add NHi Cl and a slight excess of NH4HO. 
O 
S' 
Qj -i 
The alkaline 
filtrate is tested 
A precip- 
itate indi- 
To the filtrate add a drop of HH»HS. 
Pb 
Ag 
gS 
o & 
? a 
for 
cates 
A precip- 
itate indi- 
To the filtrate add a drop of (NH4)2C03. 
Hg 
(See 
§ 17.) 
Hg 
Pb 
Bi 
Cd 
Cu 
As 
Sb 
Sn 
[Au 
Ptj 
Fe 
Cr 
A1 
Ca3P208 
etc. 
cates 
Co 
Hi 
Mn 
Zn 
A precip- 
itate indi- 
cates 
Ba 
Sr 
Evaporate the residual liquor to a 
small bulk, and test a portion of it 
for Mg (see § 41). 
Evaporate the rest of the solution 
to dryness; ignite and test for Ha 
and K (see § 42). 
(See 
(See § 25.) 
(See § 34.) 
Ca 
§21.) 
(See § 30.) 
(See § 38.) 
TABLE FOR THE SEPARATION OF THE SEVEN CLASSES OF THE METALLIC ELEMENTS. §44 
SEPARATION OF CLASSES. 
cealed or obscured by the vapors of ammonium salts, or by 
the combustion of particles of organic matter derived from 
the various reagents which have been added in the course of 
the analysis. 
44. An outline of the methods employed for separating 
the several classes is presented in tabular form on the opposite 
page. The precautions necessary in the consecutive exami- 
nation of an “ unknown ” solution for the members of the 
various classes have been already given under the several 
classes. 64 
NON-METALLIC ELEMENTS. 
§ 45 
CHAPTER IX 
GENERAL TESTS FOR THE NON-METALLIC ELEMENTS. 
45. The following common elements remain to be consid- 
ered : — Sulphur, nitrogen, phosphorus, carbon, boron, silicon, 
chlorine, bromine, iodine, fluorine, oxygen, hydrogen. It is 
obvious that oxygen and hydrogen cannot be directly sought 
for by any analytical process conducted in the wet way. 
These elements are added to the original matter in the water 
or acid which is used as a solvent. The presence of these 
elements is either inferred from the other results of the 
analysis, or forms the object of direct inquiry in the prelimi- 
nary treatment, — that important part of every analysis which 
forms the main subject of Part II. The remaining elements 
all belong to that class vaguely described as noil-metallic; 
they unite with oxygen, hydrogen, or both these elements, to 
form what are commonly called acids. 
As the metallic elements are recognized through familiar 
compounds, hydrates, chlorides, sulphides, or other, so these 
non-metallic elements are identified by working out of the 
unknown mixture their characteristic compounds. These 
compounds are generally salts. But there is one marked 
difference between the search for the metallic and the search 
for the non-metallic elements in the wet way. In the case of 
iron and mercury it is commonly necessary to determine 
whether the element, if present, exists as a ferrous or ferric, 
as a mercurous or mercuric salt; but as a rule it is true that 
no question usually arises in connection with the determination 
of a metallic element, except the fundamental one of its pres- 
ence or absence in a given solution. The sodium in the three §45 
CLASSES OF SALTS. 
65 
different salts, sulphate, sulphite and hyposulphite of sodium, 
for example, is detected by one and the same method; but, 
when the other elements of these salts are sought for, three 
different reactions will occur according to the varying nature 
of the ingredients other than sodium. A sulphate in solution 
gives one set of reactions, a sulphite another, and a hyposul- 
phite a third. It is important to do more than determine the 
mere presence of sulphur and oxygen. We want to know 
whether the sodium salt be a sulphate, sulphite, or hypo- 
sulphite. Analogous questions arise with regard to other 
non-metallic elements ; there is chlorine both in chlorides and 
chlorates, and carbon both in carbonates and oxalates. 
Arsenic, too, may be present in the form of arsenite or 
arseniate, and these two different kinds of salts exhibit 
many quite dissimilar reactions. 
In the systematic analysis of an unknown substance, the ex- 
amination for the metallic elements by the methods detailed in 
the previous chapter, as a rule, precedes the determination of 
the non-metallic elements. Having ascertained which of the 
metallic elements are present in the substance under examina- 
tion, the analyst tries to identify each class of salts which 
may be present by precipitating, or otherwise making mani- 
fest, some familiar member of that class. Thus he identifies 
sulphates by precipitating sulphate of barium, chlorides by 
precipitating chloride of silver, carbonates by throwing 
down carbonate of calcium, and so forth. The practically 
important inquiry is, how to find means of identifying each 
of the principal classes or kinds of salts. The word “ class ” 
or “ kind ” of salts is used in this connection as a collective 
name for all the salts which may be regarded as derived from 
one and the same acid ; thus all sulphates constitute one class 
or kind, all carbonates another, and so forth. The following 
common classes of salts are those for which more or less per- 
fect means of recognition will be given in this chapter: — 
Sulphates, sulphites, hyposulphites, sulphides, arseniates, ar- 
eenites, phosphates, carbonates, oxalates, tartrates, borates, 66 
TESTING FOR NON-METALLIC ELEMENTS. 
§ 45 
silicates, chromates, fluorides, chlorides, bromides, iodides, 
cyanides, nitrates, chlorates, acetates. 
No system of successive testing and elimination, analogous 
to that already described for the metallic elements, has been 
devised for the non-metallic constituents of salts. There 
arc, indeed, certain so-called general reagents for acids; but 
these reagents are chiefly useful to show the simultaneous 
presence or absence of members of several classes of salts, 
and hardly help towards the identification of any individual 
class, except in cases of the simplest sort, in which only a 
single class of salts is represented. 
It sometimes happens that the preliminary examination 
(§ 80, 81) of the substance to be analyzed leads directly to 
some conclusion as to the class of salts in hand. A 
knowledge of the metallic element or elements present is 
moreover in most cases a great help in the determination of 
the other constituents. It is for this reason that the searoh for 
the metallic elements precedes the examination for the non- 
metallic. A single example will sufficiently illustrate, for the 
present, this important principle, which is of very wide ap- 
plication in qualitative analysis. 
Suppose that the substance under examination is a solid 
which dissolves without difficulty in water and which proves 
to contain barium. From the presence of barium in a com- 
pound soluble in water, it is to be directly inferred that there 
is no sulphate, phosphate, carbonate, oxalate or tartrate in 
the original substance since these barium salts are insoluble 
in water. The list of salts excluded by the demonstrated 
presence of barium would be very long So it ia in greater 
or less degree with many other metallic elements. It is, in- 
deed, no easy matter to make a solution containing even one 
representative of the seven classes into which the metallic 
elements have been divided, because each of these elements, 
except sodium and potassium, when present in a solution 
excludes one or more whole classes of salts. By attending 
to just inferences to be drawn from the quality of the metallic §§46, 47 
THE BABIUM TEST. 
67 
elements, much time will be saved, and the want of a sys- 
tematic procedure in searching for the lion-metallic elements 
will be little felt. The presence of the arsenites and arsen- 
iates, of carbonates, chromates, cyanides, sulphides, sulphites 
and hyposulphites will ordinarily be revealed in the course 
of the search for the metallic elements. 
Before giving the special tests by which the above-men- 
tioned classes of salts are identified, we proceed to describe 
certain general tests which are of value, particularly when 
they give negative results. 
4Q. The Barium Test. — When a solution of chloride 
(or nitrate) of barium is added in suitable quantity to a 
neutral or slightly alkaline solution containing representatives 
of any or all of the following classes of salts, precipitation 
usually occurs, for all these salts of barium are insoluble in 
water and alkaline liquids, if no ammonium salts be pres- 
ent : — 
Sulphates, 
Sulphites, 
Hyposulphites, 
Arseniates, 
Arsenites, 
Phosphates, 
Carbonates, 
Oxalates, 
Tartrates, 
Borates, 
Silicates, 
Chromates, 
Fluorides. 
If the chloride (or nitrate) of barium fail to produce a 
precipitate under the prescribed conditions, the complete 
absence of all the above thirteen classes of salts is at once 
demonstrated, provided that no ammonium salts be contained 
in the original solution. 
47. Illustration of the Barium Test.—Prepare in a 
test-tube a solution containing at once sulphate, phosphate 
and carbonate of sodium ; a very small bit of each salt will 
be sufficient. The solution will be found to be alkaline to 
litmus paper. Add to it chloride of barium (App., § 43), 
little by little, until a fresh addition of the reagent 
no longer produces an additional precipitate. The white 
precipitate consists of sulphate, phosphate and carbonate of THE BARIUM TEST. 
§48 
barium. All the thirteen barium salts which are liable to 
precipitation under these circumstances are white, with the 
single exception of chromate of barium. The yellow color 
of the chromate of barium (§ 38) distinguishes this one pre- 
cipitate from all the rest. If this color is well marked, the 
presence of a chromate in the original solution (which must 
also have been jrnllow) may be inferred with certainty. In 
all other cases, however, the precipitate is white, as in the 
present experiment. The next question is, can anything 
further be learned from this white precipitate ? 
Add to the contents of the test-tube dilute chlorhydric 
acid-, until the liquid has a decidedly acid reaction to litmus 
paper. An effervescence indicates the escape of carbonic 
acid, displaced hy the less volatile chlorhydric acid. The 
bulky precipitate which the chloride of barium produced will 
in part disappear, but a portion of it remains undissolved. 
Filter the contents of the tube. The particles of precipitated 
sulphate of barium are so very fine that they often pass 
through the poses of the paper, necessitating repeated filtra- 
tion through the same filter. To the filtrate add ammonia-water 
until the liquid has an alkaline reaction. A precipitate will 
reappear: the phosphate of barium which was dissolved by 
the chlorhydric acid is reprecipitated as soon as the acid 
solvent is neutralized by ammonia-water. 
48. Of all the barium salts which might, in an actual 
anal}'sis, be precipitated under conditions similar to those of 
the preceding experiment, only one, the sulphate of barium, 
is insoluble in chlorhydric and other strong acids. A separ- 
ation of sulphur from a hyposulphite will not be mistaken for 
a barium precipitate (§ 19, p. 29), The fact that any of thg 
original precipitate remains undissolved by the 
acid demonstrates the presence of a sulphate. The portion 
of the original precipitate which dissolved in the acid, and 
was reprecipitated by ammonia, consisted in this particular 
experiment of phosphate of barium ; but in an actual analysis 
the possible salts represented would be so numerous as to §48 
THE BARIUM TEST. 
69 
make the indication of but little value; on the other 
hand, if ammonia-water causes no precipitation, it must 
not be inferred that the acid of course dissolved nothing, 
for, with the exception of the sulphate, all the thirteen above 
mentioned barium salts are more or less soluble in solutions 
of ammonium salts, and if present in small quantity may 
not be precipitated on addition of ammonia. This is es- 
pecially true of the borate, oxalate, arseniate, arsenite, tar- 
trate and fluoride, and when ammonium salts are known to 
be present, there is really but one perfectly satisfactory indi- 
cation with chloride of barium. The presence of a sulphate 
is revealed by it with certainty, but the results of the other 
tests, if negative, must be received with some distrust. 
It is to be said, however, that if the substance under ex- 
amination is known to be a simple salt and is found to be a 
salt of ammonium, the barium test can hardly fail to give 
a precipitate in alkaline solution, if the unknown compound 
is actually a borate, or phosphate, etc., of ammonium. 
If the original solution be acid, it is necessary to neutral- 
ize it with ammonia-water before the chloride of barium is 
added. If a precipitate is produced, it is necessary to filter 
and proceed with the filtrate. The precipitate may contain 
phosphates, oxalates, etc., as explained in § 28, page 37, and 
this must be ascertained by special tests, §§ 65, 66, 68, etc. 
Even if ammonia-water produce no precipitate, the testing 
is still performed under the disadvantage of the presence of 
ammonium salts. 
If the original solution contained silver or lead salts, or 
mercurous salts, it would be impossible to use chloride of 
barium and chlorhydric acid as reagents; they would throw 
down the chlorides of those metals. Is i irate of barium 
(App., § 44) and dilute nitric acid must then be used. 
The acids added to the precipitate formed by the barium 
salt must be always dilute acids. Chloride and nitrate of 
barium are themselves insoluble in concentrated chlorhydric 
and nitric acids, and if a strong acid were used as a solvent, 
the reagent salt might itself separate from the liquid. 70 
THE CALCIUM TEST. 
§§ 49, 50 
49. The Calcium Test. — Chloride (or nitrate) of cal- 
cium precipitates the same classes of salts as chloride (or 
nitrate) of barium, with the single exception of the chro- 
mates. "When sulphates and all ammoniacal salts are absent, 
or present only in minute quantities, something may be 
learned by testing a neutral or slightly alkaline solution 
supposed to contain representatives of some of the other 
classes of salts enumerated in § 46, with chloride or nitrate 
of calcium. The calcium salts liable to precipitation under 
these circumstances are all soluble in acetic acid, except the 
oxalate and the fluoride. The precipitate produced by the 
calcium reagent is, therefore, treated with acetic acid; if it 
completely redissolves, oxalates and fluorides are most prob- 
ably absent. The presence of notable quantities of ammo- 
nium salts renders this test of uncertain value; because the 
fluoride and many other salts of calcium are soluble in 
solutions of ammonium salts. Since sulphate of calcium is 
sparingly soluble in water and acetic acid, the presence of a 
sulphate, causing precipitation of sulphate of calcium, ob- 
scures the reaction for oxalates and fluorides. Nitrate of 
calcium must be used instead of the chloride whenever silver 
or lead salts, or mercurous salts, are present in the solution 
under examination. 
50. Illustration of the Calcium Test. — Prepare in a 
test-tube an aqueous solution of phosphate, oxalate and tar 
trate of sodium or potassium. A very sm ill quantity of each 
salt will be enough. The solution will be neutral or faintly 
alkaline. Add to this solution a solution of chloride of 
calcium (App., § 42) until the precipitation is complete. 
Collect the white precipitate upon a filter, and, when drained, 
transfer it to a test-tube and treat it with acetic acid. The 
phosphate and tartrate of calcium will redissolve, but the 
oxalate remains untouched. To verify this result, and iden- 
tify each one of the classes of salts present in the original 
solution, special tests, to be hereafter described, must ba 
resorted to. §§ 51, 52 
THE SILVER TEST. 
71 
51. The Silver Test. — Nitrate of silver produces a pre- 
cipitate in neutral or acid solutions -with all chlorides, bro- 
mides, iodides and cyanides, and in neutral solutions with 
most of the classes of salts enumerated in § 46. In order to 
obtain the most comprehensive negative conclusion in the 
case that nitrate of silver produces no precipitate, it is nec- 
essary to operate upon a neutral solution. If, on the addi- 
tion of nitrate of silver to a neutral solution, no precipitate 
appears after the lapse of several minutes, neither chlorides, 
bromides, iodides, cyanides nor sulphides can be present, 
and the absence of sulphites, hyposulphites, carbonates, phos- 
phates, arseniates, arsenites, chromates, silicates, oxalates 
and tartrates may also be inferred with considerable cer- 
tainty. 
52. Illustration of the Silver Test. — Prepare in a test- 
tube a weak solution of chloride of sodium, iodide of potas- 
sium, cyanide of potassium and phosphate of sodium. Add 
nitrate of silver (App., § 39) to this slightly alkaline solu- 
tion, until the precipitation is complete. The dense precipi- 
tate is yellowish-white. Pour dilute nitric acid into the 
mixture, until the solution is strongly acid; shake up the 
contents of the tube thoroughly, and after the lapse of several 
minutes collect the insoluble precipitate on a filter, and 
receive the filtered liquid in a test-tube. 
Neutralize the filtrate with ammonia-water : a yellow pre- 
cipitate of phosphate of silver will reappear. 
Wash the precipitate on the filter thoroughly to free it from 
the superfluous nitrate of silver. Rinse the washed precipi- 
tate into a clean test-tube, decant the water from above it, 
pour over it ammonia-water, and gently heat the mixture. 
The silver precipitate will visibly diminish in hulk, but a yel- 
lowish portion remains undissolved. Filter again, and neu- 
tralize the filtrate v*ith nitric acid; a white precipitate will 
fall. 
This experiment proves that a portion, but not all, of the 
mixed silver salts which are insoluble ir nitric acid, are solu 72 
THE SILVER TEST. 
§ 53 
bio in ammonia-water. The chloride, cyanide and bromide of 
silver dissolve in ammonia-water, the latter with difficulty; 
the iodide remains undissolved. Special tests, hereafter to 
be described, are applied in order to confirm the presence of 
iodine, and to detect each and all of the three substances which 
are liable to be confounded in the white precipitate just men- 
tioned. 
53. In the application of the silver test to the examina- 
tion of a substance of unknown composition, it is, of course, 
most advantageous to work with a neutral solution, as in such 
a case the absence of any precipitate would lead to the infer- 
ence that all the salts mentioned in § 51 are absent: if the 
solution is neutral, the nitrate of silver may be added directly 
to a portion of it. In addition to the classes of salts men- 
tioned in § 51, if the original solution contained any consid- 
erable quantity of a borate, the borate of silver would be 
precipitated under these conditions ; but a small proportion 
of some borate might escape precipitation. If the original 
solution be acid to test paper, add nitrate of silver to a por- 
tion of it in a test-tube, and then pour in upon the liquid 
some dilute ammonia-water, so gently that the two liquids do 
not mix at once. At some layer near the junction of the two 
dissimilar liquids, the fluid must be neutral. If at that layer 
no precipitate or cloud appear, the twelve kinds of salts above 
enumerated are absent. If the original solution is alkaline, 
dilute nitric acid is to be added in precisely the same manner 
as the ammonia-water in the opposite case. The neutral 
layer between the two liquids is attentively observed, and the 
absence of any film or cloud therein justifies the same sweep- 
ing conclusion as that above gh cm. 
Some conclusions may often be drawn from the color of the 
precipitate produced by nitrate of silver. Chloride, bromide, 
cyanide, oxalate, tartrate, and borate of silver are white; 
iodide, phosphate, and arsenite of silver are yellow ; sili- 
cate of silver is yellow or white; arseniate of silver is 
brownish-red; chromate of silver is purplish-red; sulphide §§53,54 
THE SILVER TEST. 
73 
of silver is black. When the silver precipitate is white, 
black, or of some obscure, indecisive color, the operations in 
the wet way at this stage should be directed to proving or 
disproving the presence of chlorides, bromides, iodides, cj- 
anides and sulphides. To this end the portion of the original 
solution which has been already tested with nitrate of silver, 
should be made decidedly acid with dilute nitric acid. Of all 
the silver salts which can be precipitated on the addition of 
nitrate of silver, only the chloride, bromide, iodide, cyanide 
and sulphide can resist dilute nitric acid. If the precipitate 
once formed redissolves completely in nitric acid, no chloride, 
bromide, iodide, cyanide or sulphide was present in the orig- 
inal solution. If, on the contrary, a residue remain, one or 
more of these kinds of salts must have been represented in 
the original solution. If the residue be black or blackish, 
the presence of a sulphide is to be inferred; if it be white or 
whitish, the absence of sulphides and the presence of a 
chloride, bromide or cyanide is to be inferred; if it be dis- 
tinctly yellowish, an iodide is probably present. When the 
liquid under examination contains a ferrous salt, protochlo- 
ride of tin, or any other active reducing agent, metallic silver 
is liable to be precipitated as a dark, heavy powder. Tho 
examination for the met-dlic element will generally have re 
vealed the presence of any such agent. 
It is to be remarked that cyanide of mercury does not give 
a precipitate with nitrate of silver. When mercury has been 
detected in the substance under examination, cyanogen must 
be sought for in other ways (§ 58) than this. 
54. Nitrates, Chlorates and. Acetates. — It is quite 
clear that no method of precipitation whatever will apply to 
nitrates, chlorates and acetates, since no insoluble chlorate 
is known, and, with the exception of some rather ill-defined 
basic compounds, the nitrates and acetates are also all soluble. 
Special tests must be sought for these three classes of salts. 74 
SPECIAL TESTS. 
§§ 55,56 
CHAPTER X. 
SPECIAL TESTS FOR THE NON-METALLIC ELEMENTS. 
55. We now proceed to indicate the most available special 
tests for the non-metallic elements and their commonest com- 
pounds. It is noteworthy that the non-metallic elements 
enter into composition under various forms, which produce, 
with one and the same metallic element, various salts. Thus 
within the narrow range of this treatise, sulphur is to be 
sought in sulphides, sulphates, sulphites and hyposulphites; 
carbon in cyanides, acetates, carbonates, oxalates and tar- 
trates, and arsenic in arsenites and arseniates. The various 
classes of salts will be taken up successively. It should be 
premised that these special tests are sometimes applied to 
the original solution before the precipitation with chloride of 
barium and nitrate of silver, and sometimes during or after 
these more general testings. In the first case, the student is 
seeking guidance in the application of the more comprehen- 
sive tests ; in the latter case, he is trying to confirm results 
already almost sure. 
56. Effervescence. — When a solution containing a car- 
bonate, cyanide, sulphide, sulphite, or hyposulphite, or a 
mixture of represehtatives of some or all of these kinds of 
salts, is treated with chlorhydric acid and then warmed, an 
evolution of gas occurs with more or less effervescence. The 
gases evolved are all colorless; but they all have very char 
acteristic odors except carbonic acid, the gas which escapes 
from a carbonate. A cyanide gives off the pungent odor of 
cyanhydric acid. A sulphide yields sulphuretted hydrogen 
of familiar presence. Sulphurous acid escapes from sulphites H 57, 58 
CAItBONATES. — CYANIDES. 
75 
and hyposulphites alike; but in the latter c ase a deposition 
of sulphur makes the liquor turbid. If only one of these 
gases were present, the effervescence and the odor, or the 
absence of odor, would identify it; but when mixtures are to 
be dealt with, further means of identification are necessary. 
57. Carbonates. — To prove the presence of carbonic 
acid gas, when effervescence has occurred, add chlorhydric 
acid, little by little, to the effervescing solution, until the acid 
is decidedly in excess ; meanwhile keep the mouth of the test- 
tube loosely closed with the thumb to promote the accumula- 
tion of the gas evolved. When the tube is supposed to be 
full, carefully decant the gas into a second test-tube contain- 
ing a teaspoonful of lime-water (App., § 41), taking care 
not to allow any of the liquid to pass over with the gas. 
Mix the lime-water and the gas in the second test-tube by 
thorough shaking. A white precipitate of carbonate of cal- 
cium will be produced, if the gas tested is, or contains, car- 
bonic acid. 
If the effervescence is slight, and the quantity of gas 
evolved seems too small to be decanted in this way, dip the 
end of a dark-colored glass rod into lime-water, and thrust 
the moistened end into the test-tube, bringing it close to the 
surface of the fluid. If the gas be carbonic acid, the lime- 
water adhering to the rod will become visibly turbid. 
The student who desires to see the working of this test 
before having occasion to apply it in an actual analysis, can 
operate upon a morsel of carbonate of sodium dissol> ed in a 
little water. 
58. Cyanides. — When the smell of the gas which es- 
capes from the solution under examination (§ 56), or the 
qualities of the precipitate with nitrate of silver (§ 53), give 
occasion to suspect the presence of a cyanide, the following 
confirmatory test may be resorted to: — Add to the solution 
supposed to contain free cyanliydric acid, or an alkaline 
23’anide, a few drops of a solu iion containing both a ferrous 
and a ferric salt (a solution of ferrous sulphate which has 76 
SULPHIDES. — SULPHITES 
§§ 59, 60 
been exposed, to the air, for example), and a small quantity 
of caustic soda solution. A precipitate forms, which, if 
cyanogen is present, consists of a mixture of Prussian blue 
and the hydrates of iron. Warm the liquid, and add to it 
excess of chlorhydric acid; the hydrates of iron dissolve, 
but the Prussian blue remains undissolved. If the amount 
of cyanogen is small, the hydrates of iron, which of course 
always form, may conceal the Prussian blue until the 
addition of the acid; and in the case of minute quan- 
tities the liquid simply" appears green after the addition of 
cliloi’hydric acid, and it is only after long standing that a 
trifling blue precipitate separates from it. 
This test may be well illustrated by means of a small particle 
of cyanide of potassium dissolved in a teaspoonful of water. 
To detect cyanogen in cyanide of mercury, it is necessary 
to precipitate the mercury as sulphide, by means of sulphur- 
etted hydrogen, and to identify the free cyanhydric acid in 
the filtered or decanted fluid. 
59. Sulphides. — Many sulphides give off sulphuretted 
hydrogen when heated with chlorhydric acid. If the quan- 
tity of gas is so small that its odor is imperceptible, the lead 
paper test (§ 32) should be applied. 
When sulphides are dissolved in nitric acid or aqua regia, 
their sulphur is partly separated in a free state and partly 
converted into sulphuric acid. The free sulphur is identified 
by and texture, and by its behavior when burnt. 
The sulphuric acid in the liquid is detected in the usual 
manner (§ 64). 
60. Sulphites. — All the sulphites evolve sulphurous 
acid, without any deposition of sulphur, when treated with 
chlorhydric acid. The very sharp odor of this gas is enough 
to identify it. 
As has been before stated, nitrate of silver produces in 
solutions of sulphites a white precipitate; but this precip- 
itate blackens when the liquid is boiled, on account of the 
reduction of silver. §§ 61, 62 
HYPOSULPHITES. — CHROMATES. 
77 
When the sulphites are heated with strong nitric acid, or 
other powerful oxidizing agent, they are converted into sul- 
phates without precipitation of sulphur. The sulphates sc 
produced may be identified in the usual way (§ 61). 
61. Hyposulphites. — The hyposulphites disengage sul- 
phurous acid and deposit sulphur when warmed with clilor- 
li3rdric acid. This decomposition is not immediate if the 
solution be dilute. 
The precipitate produced in the solution of a hyposulphite 
by nitrate of silver, dissolves again readily in an excess of 
the hyposulphite. On standing, the precipitate of hyposul- 
phite of silver turns black spontaneously, being decomposed 
into sulphide of silver and sulphuric acid. Heating produces 
this effect almost immediately. 
Hyposulphite of sodium is a good salt from which to get 
the above reactions of hyposulphites. 
62. Chromates. — Chromium is detected during the ex- 
amination for the metallic elements, and the anatyst generally 
obtains pretty certain evidence concerning the actual con- 
dition in which this element enters into the substance 
under examination, whether as chromate or salt of chromium ; 
for the chromates are reduced by sulphuretted hydrogen 
with change of color and deposition of sulphur as stated in 
§ 23. 
To confirm the indications thus obtained, the following tests 
are used: — When acetate of lead (App., § 45) is added to 
a neutral solution of a chromate, yellow chromate of lead 
separates, insoluble in acetic acid, but soluble in caustic 
soda. 
As has been before stated, the purplish-red color of chro- 
mate of silver (§ 53), and the yellow color of chromate of 
barium (§ 48), are valuable indications of the presence of a 
chromate. 
A solution of noimal chromate of potassium is the best 
substance from which to obtain for the first time the reactions 
of the chromates. 78 
ARSENITES. — ARSENIATES. 
§§ 03, 64 
63. Arsenites and Arseniates. — The presence or ab- 
sence of arsenic is determined in the search for the metallic 
elements by the tests already given in the treatment of 
Class III. These tests, however, do not indicate which class 
of compounds (arsenic or arsenious) is present in the solu- 
tion under examination. In whatever form present, the 
arsenic would be precipitated as the tersulphide (As2S3), and 
subsequently converted into an arseniate by fusion with ni- 
trate of sodium. Discriminating tests must therefore be 
applied to the original solution. 
The tests by which an arseniate may be identified have 
already been given (§§ 25, p. 31). It may be remarked fur- 
ther that the presence of this class of arsenic compounds 
is often inferred by the length of time required to saturate 
with sulphuretted hydrogen a solution containing arsenic 
acid or an arseniate. The arsenic acid is first reduced to 
arsenious acid and then precipitated; a separation of sulphur 
accompanies the reduction. 
A solution of an arsenite yields with nitrate of silver a 
yellow precipitate of arsenite of silver under the same con- 
ditions in which an arseniate gives the brownish-red precip- 
itate. The silver test generally serves to distinguish between 
arsenites and arseniates, but circumstances may arise in 
which it would be inapplicable. The following test affords 
further means of discrimination : — 
If to a solution of arsenious acid or an arsenite, caustic 
soda be first added in excess, and then five or six drops of a 
dilute solution of sulphate of copper, a clear bluish liquid is 
obtained, which, upon boiling, deposits a red precipitate of 
suboxide of copper (Cu20), while soluble arseniate of sodium 
is simultaneously produced, and remains in the solution. 
This test is good as a means of distinguishing between 
arsenites and arseniates when no organic matters are con- 
tained in the solution under examination. The qualification 
is necessary, because grape-sugar and many other organic 
substances exercise a like reducing action on copper salts. § 65 
PHOSPHATES. 
64. Sulphates. — The barium test (§§ 46-48) is all suf- 
ficient for the detection of sulphates. The operator should 
make sure that the chlorhydric acid itself contains no sul- 
phuric acid, that an excess of acid is really present, and that 
the solution is tolerably dilute. Concentrated acids and 
strong solutions of many salts impair #he delicacy of the 
reaction. 
65. Phosphates. — When the previous steps of the anal- 
ysisdiave proved that the phosphates present in the solution 
under examination are soluble in ammoniacal liquids, and 
that no arsenic acid or arseniates are present, the following 
test will identify a phosphate or free phosphoric acid. 
Add to the solution to be tested a clear mixture of sulphate 
of magnesium, chloride of ammonium and ammonia-water. 
When a phosphate or free phosphoric acid is present, a white, 
crystalline precipitate of phosphate of magnesium and ammo- 
nium is formed, even in very dilute solutions. Stirring and 
shaking promote its separation. The precipitate dissolves 
readily in acids. 
When arsenic acid or arseniates are present in the original 
mixture, this test for phosphates can still be applied, if all 
the arsenic be previously removed by precipitation as sulphide 
(§ 24). The magnesium mixture can be used in the filtrate 
from the sulphide of arsenic, after it has been boiled to expel 
the sulphuretted hydrogen. 
The preceding test can only be applied when the phosphate 
present is soluble in ammoniacal solutions. The following 
test is of much more general application; it can be used in 
presence of arsenic acid, and is applicable to either neutral 
or acid solutions of phosphates; it is also extremely deli- 
cate. 
When two or three drops of a neutral or acid solution oJ' a 
phosphate (even of iron, aluminum, barium, strontium, cal- 
cium or magnesium [compare § 28]) are poured into a test- 
tube containing four or five teaspoonfuls of a solution of 
molybdate of ammonium in nitric acid (App., § 21), there is OXALATES. — TARTRATES. 
§§ 66, G7 
formed in the cold a pale-yellow precipitate which is apt to 
gather upon the sides and bottom of the tube. If the pre- 
cipitate does not appear in a few minutes, a few drops more 
of the solution to be tested may be added. This precipitate 
is soluble in an excess of phosphoric and other acids; and 
certain organic substances also prevent its formation. A 
yellow coloration of the liquid merely is not enough to prove 
beyond question the presence of a phosphate ; a precipitate 
must be waited for. The yellow precipitate can be easdly 
recognized, even in dark-colored liquids, when it has settled. 
The* solution to be tested must not be heated, nor must it be 
more than blood-warm. 
Phosphate of sodium is the best substance on which to try 
the test for phosphates. 
66. Oxalates.—The precipitation of white, finely-divided 
oxalate of calcium, by all soluble calcium salts from solutions 
of oxalates or oxalic acid, has been already described (§ 50). 
Even the solution of sulphate of calcium gives this reaction 
with oxalates. 
If oxalic acid, or an oxalate in the dry state, be heated in 
a test-tube with an excess of concentrated sulphuric acid, a 
mixture oxide and carbonic acid is set free wTith 
effervescence; the carbonic acid may be identified by the 
lime-water test; and if the quantity operated upon is con- 
siderable, the carbonic oxide may be inflamed at the mouth 
of the tube. 
67. Tartrates. — Tartaric acid and the tartrates, when 
heated in the dry state, char,,and emit a very characteristic 
odor which somewhat resembles that of burnt 
sulphuric acid blackens tartaric acid and the tartratef. This 
is the only class of salts among all those within the scope of 
this treatise, which exhibit this carbonization by sulphuric 
acid. 
To confirm the presence of tartaric acid, or a tartrate, in 
any liquid supposed to contain it, a concentrated solution of 
acetate of potassium is added to the liquid, and the mixture § 68 
TARTRATES. — BORATES. 
81 
violently shaken. The precipitate, when one forms, is a diffi- 
cultly soluble acid tartrate of potassium. The addition of an 
equal volume of alcohol increases the delicacy of the reaction. 
The more concentrated the solution to be tested the better. 
To prepare the required solution of acetate of potassium at 
the moment of use, rub together in a dish half a teaspoonful 
of carbonate of potassium and as many drops of acetic acid 
as will dissolve three quarters of the carbonate; throw the 
mixture on a small moistened filter and use the filtrate. 
Tartaric acid is a good substance from which to get these 
reactions. 
68. Borates. — To confirm the presence of a borate, 
strong sulphuric acid is mixed with the dry substance under 
examination in quantity sufficient to make a thin paste, and 
an equal bulk of alcohol is added to the mixture. The alco- 
hol is then kindled. Boracic acid imparts to the alcohol 
flame a yellowish-green color. The test is made more deli- 
cate by stirring the mixture, and by repeatedly extinguishing 
and rekindling the flame. Copper salts impart a somewhat 
similar color to the flame; but this metal, if present, may be 
got rid of by sulphuretted hydrogen before testing for boracic 
acid. 
If a solution of boracic acid, or of a colorless borate, is 
mixed with chlorhydric acid to slight, but distinct, acid reac- 
tion, and a slip of turmeric paper is dipped half way into the 
liquid and then dried at 100° C., the dipped half slows a 
peculiar red tint. This test is lelicate, but there are a few 
other solutions which impart, not the same, but somewhat 
similar tints to turmeric paper. The yellow turmeric paper 
used for this test is prepared by steeping narrow strips of 
white paper in a filtered tincture of turmeric root. The dried 
paper should 1iave a fine yellow color. The tincture is made 
by digesting one p$rt of bruised turmeric in six parts of 
warm spirts of wine. 
The reactions of borates may be obtained with a fragment 
of borax. 82 
SILICA TES. — FL UOEIDES. 
§§ 69, 70 
69. Silicates. — The silicates of sodium and potassium 
are the only silicates which are soluble in water. The solu- 
tions of these alkaline silicates are decomposed by all acids. 
If chlorhydric acid is added gradually to a strong solution of 
an alkaline silicate, the greater part of the silicic acid separ' 
ates as a gelatinous hydrate. As a rule, the more dilute the 
fluid, the more silicic acid remains in solution. 
If the solution of an alkaline silicate, mixed with chlorhy- 
dric or nitric acid in excess, be evaporated to dryness, silicic 
acid separates ; if the dry mass be ignited and then treated 
with dilute chlorhydric or nitric acid, the whole of the silicic 
acid remains insoluble in the free state, as a gritty, whitish 
powder, while the other substances dissolve. 
A solution o£ chloride of ammonium produces a gelatinous 
precipitate in strong and moderately dilute solutions of the 
alkaline silicates. This precipitate is hydrated silicic acid 
containing alkali. 
A solution of waterglass is the best substance in which to 
study the reactions of the silicates of the alkali-metals. 
70. Fluorides. — If a finely-pulverized fluoride is heated 
with concentrated sulphuric acid in a small leaden capsule or 
platinum crucible, fiuorliydric acid is disengaged. 
Coat with wax the convex face of a watch-glass large 
enough to cover the capsute, by heating the glass cautiously, 
and spreading a small bit evenly over it while the 
glass is hot. Trace some lines or letters through the wax 
with a pointed instrument of wood or horn. Fill the hollow 
of the glass with cold water, and cover with it the capsule 
which contains the fluoride mixture. Heat the capsule gently 
for half an hour or an hour. Then remove the watch-glass, 
dry it, heat it cautiously to melt the wax, and wipe it with a 
bit of paper. The lines or letters traced through the wax 
will be found etched into the A barely perceptible 
etching is made more visible by breathing upon the glass. 
If much silicic acid is present, this reaction fails. 
When a fluoride, naturally combined or artific'glly mixed §71 
FLUORIDES. — CHLORIDES. 
with silica, is heated with strong sulphuric acid, fluoride of 
silicon is evolved. This reaction is available as a test foi 
fluorine. 
A mixture of the supposed fluoride and fine dry sand is 
heated in a short, dr}r test-tube with concentrated sulphuric 
acid. A drop of water, caught in the loop of a clean plati- 
num wire, is held in the mouth of the test-tube. This drop 
of water becomes merely dim, quite opaque, or almost solid 
with silicic acid, according to the quantity of fluoride of 
silicon evolved from the mixture. The gaseous fluoride of 
silicon shows white fumes when it comes in contact with moist 
air. If a considerable quantity of fluoride of silicon be 
evolved from the mixture tested, it can be decanted into 
another test-tube, and there shaken If the 
substance to bevtested for fluorine is klfwvn twBp'itain silica, 
it is, of course, unnecessary to add sand to ijJKp’his method 
applies to all fluorides decomposable by hQfgplphuric acid. 
It is evident that this test reversed can be apP&Fd to the de- 
tection of silica. 
Fluoride of calcium (fluor-spar) is a good material from 
which to obtain these two tests for fluorine. 
71. Chlorides. — The following confirmatory test is ap- 
plied to chlorides in the dry state. 
When a chloride, in powder, is heated in a test-tube with 
black oxide of manganese and strong sulphuric acid, chlorine 
gas is evolved ; this gas is recognized by its odor, greenish- 
yellow color, and reaction with iodo-starch paper. The gas 
evolved by a chloride gives no colored reaction with starch 
alone ; but when a moistened slip of paper, on which a mix- 
ture of starch paste and iodide of potassium (App., § 38) 
has been spread, is held in an atmosphere or current of chlo- 
rine, the paper is colored blue inconsequence of the liberation 
of iodine which the chlorine effects. The yellow color of the 
gas is best seen by looking lengthwise through the tube. 
It is often difficult to obtain black oxide of manganese 
which will not of itself give a reaction far chlorine when 84 
BROMIDES. 
§ 72 
treated with pure sulphuric acid. Instead of this reagen t, pure 
bichromate of potassium in powder may be employed. The 
sulphuric acid used should be diluted with an equal bulk of 
water. The action which takes place is similar, except that 
the chlorine is accompanied by chlorochromic acid (CrC102) 
which in part condenses as a yellow liquid on the sides of the 
tube. The reaction on iodo-starch paper is, however, obtained 
without difficulty. 
Mercurous chloride (calomel) gives no reaction for chlorine 
when treated with binoxide of manganese (or bichromate of 
potassium) and sulphuric acid. The chlorine may be de- 
tected, however, by treating the salt in powder with zinc and 
dilute sulphuric acid. The mercury is reduced to the metallic 
state and into solution as chloride of zinc ; 
in this solutiw%he ctlbrine may be discovered by the ordin- 
72. Broil ;es. — The confirmatory tests for bromides de- 
fend upon thqjwrtting free of bromine itself. 
acm liberates the bromine from all bromides ex- 
ceptraBfc, of silver and mercury. In solutions, the free 
bromine produces a yellow coloration; when set free from 
solid bromides in a long and narrow tube, -the brownish-yel- 
low vapors of bromine condense into a liquid upon the cold 
jvalls of the tube. 
in powder, are heated in a test-tube with 
of manganese (or bichromate of potassium) and 
6trong acid, brownish-red vapors of bromine are 
evolved. If chlorides are also present, the bromine will be 
mixed with chlorine. 
To identify bromine and distinguish it from chlorine, moist- 
ened starch is brought into contact with tire free bromine. A 
yellow or orange-jrellow coloration of the starch marks the 
presence of bromine. To apply this test, thrust a rod smeared 
with starch-paste into the tube which contains the bromine 
vapors; or, when greater delicacy is requisite, perform the 
experiment which is expected to liberate bromine in a very §§ 73, 74 
IODIDES. - NITRATES. 
85 
small beaker, and cover this beaker with a watch-glass to 
whose under side is attached a bit of paper moistened with 
starch paste and sprinkled with dry starch. 
Bromide of potassium is a good substance which to 
study the tests for bromine. 
73. Iodides. — When an iodide, in the solid form or in 
solution, is heated with strong nitric acid, iodine is liberated 
and sublimes in violet vapors. 
Free iodine in vapor is recognized by the deep blue color 
which it imparts to starch-paste. Vapors may be tested by 
bringing into 40itact f?|th them a glass rod smeared with thin 
starch-paste, or a slip of white paper on which the paste has 
been spread. 
The best method of detecting iodine in a is to add 
a few drops of thin, clear starch-paste to the liquid, and then 
set free the iodine by means of nitrite of potassium (App., 
§ 37), as follows : — The cold fluid to be tested is acidulated 
with dilute chlorhydric or sulphuric acid, after the addition 
of the starch-paste, and a drop or two of a concentrated solu- 
tion of nitrite of potassium is then added. A dark blue color 
will be instantly produced. It is essential that the liquid 
should be kept cool, for the blue coloration is destroyed by 
heat. 
Like chlorine and bromine, iodine is liberated by heating 
an iodide with black oxide of manganese (or with 
of potassium) and sulphuric acid. The iodine so 
is readily distinguished by the above tests. 00** 
The student can try all these tests for iodine with ’■& small 
crystal of iodide of potassium. 
74. Nitrates. — The preliminary examination generally 
gives warning of the presence of a nitrate: to confirm the pres- 
ence of a nitrate, one or both of the two following tests may 
be used: — 
If the solution of a nitrate is mixed with an equal volume 
of strong sulphuric acid, the mixture cooled in cold water, 
and a concentrated solution of ferrous sulphate hen cautiously 86 
NITRATES. — CHLORATES. 
§ 75 
added to it in such a way that the two fluids do not mix, the 
stratum of contact shows a purple or reddish color, which 
changes to a brown. If the fluids are then mixed, a clear 
brownish-purple liquid is obtained. The color fades on heat- 
ing. Another way of performing the same test is to drop a 
crystal of copperas into the cold mixture of nitrate and sul- 
phuric acid. There forms around the crystal a dark halo, 
which disappears with a kind of effervescence on the appli- 
cation of heat. It is, of course, essential that the sulphuric 
acid employed for this test should be so free from nitric 
and hyponitric acids, as not itself to give this reaction with 
ferrous sulphate. 
Boil some chlorhydric acid in a test-tube, add to it one or 
two drops dilute solution of sulpliindigotic acid (App., 
§ 57), and the boiling a moment. If the chlorhy- 
dric acid is sufficiently free from chlorine, the resulting liquid 
will be of a faint blue color. If a nitrate, either solid or in 
' solution, be added to this liquid and the mixture be again 
boiled, the liquid will be decoldfczed. This reaction is deli- 
cate ; but there are some other, substances, especially free 
chlorine, which have a like bleaching effect. 
Nitrate of potassium is a suitable material op which to 
illustrate the tests for nitrates. 
75. Chlorates. — The preliminary examination gives 
eof the presence of chlorates. 
l a few particles of a chlorate in the solid form are 
with two or three times as much strong sulphuric 
acid, and the mixture is gently warmed, the liquid becomes 
intensely yellow, and a greenish-yellow irritating gas of pecu- 
liar odor (hypochloric acid, C102) is evolved, which explodes 
with violence at a moderate heat. After this decomposition, 
the gas evolved has the characteristic odor of chlorine. The 
quantity of chlorate operated upon should be very small. 
The solution of a chlorate decolorizes indigo-solution ] re- 
cisely like the solution of a nitrate, under like conditions 
IS 74). § 76 
ACETATES. 
87 
A chlorate is converted by ignition into a chloride, from a 
solution of which nitrate of silver precipitates the chlorine. 
Chlorate of potassium illustrates very well the reactions of 
chlorates. 
76. Acetates.—When acetates are moderately heated 
with strong sulphuric acid, hydrated acetic acid distils from the 
mixture, and may be recognized by its pungent odor. 
When an acetate is heated with alcohol and sulphuric acid 
in equal volumes, acetic ether is formed. The agreeable odor 
of this ether is highly characteristic. 
Hot concentrated sulphuric acid produces no blackening 
with an acetate. 
When a few drops of a solution of ferric chloride (App., 
§ 48), are added to a solution of a neutral acetate, or to a 
solution of an acetate previously neutralized with ammonia, 
the liquid acquires a dark red color, because of the formation 
of ferric acetate. If the liquid contain an excess of the ace- 
tate, a basic acetate of iron is precipitated in yellow flocks 
upon boiling, and the fluid finally becomes colorless. 
Acetate of sodium may be used to show these reactions. 
76a. Oxides and Hydrates. — In case the substance 
under examination is an oxide or a Irydrate, it may in general 
be recognized by the known properties of the oxide or 
hydrate of the metallic element which has been found to be 
present., The hydrates (except of the alkalies) give off water 
when heated, and many oxides and hydrates when heated 
with charcoal in a closed tube give off carbonic acid or car- 
bonic oxide. Peroxides mayr generally be distinguished byr 
their giving off oxygen when heated, or by causing an evolu- 
tion of chlorine when treated with chlorhydric acid. 
salts of most of the oxy-acids, and, indeed, 
substances besides oxides and hydrates, give 
carbonic acid when heated with carbon. This test may 
serve to simple substance, but the presence or 
absence of aiyydltie in a mixture of salts can often be 
determined 6nfys*||P|uantitative analysis. PART SECOND. 
THE ACTUAL EXAMINATION- OF SUBSTANCES OF UN 
KNOWN COMPOSITION. 
77. The substance to be examined may be either solid or 
liquid. We shall consider first the treatment of a solid; 
afterwards that of a liquid. The solid may be a metallic 
substance, that is, a pure metal or an alloy, or it may be a 
salt, mineral, or other non-metallic body. The method of 
procedure differs in the two cases. We shall describe first 
the treatment of a salt, mineral, or other non-metallic sub- 
stance. The two following observations, however, apply to 
all cases. The student should, in the first place, learn as 
much as possible from the external properties of the substance 
to be analyzed, from its color, consistency and odor, if it is a 
liquid; from its color, texture, odor, lustre, hardness, gravity 
and crystalline or amorphous structure, if it is a solid. By 
attentively observing the characteristics or individual peculi- 
arities of every substance which passes through his hands, 
the student will soon learn to recognize many substances at 
sight, — by far the quickest and easiest "way of identifying 
them. Secondly, since the original substance must bo several 
times reverted to in order to complete an analysis, the student 
should husband his stock of the substance to be analyzed, 
never employing the whole of it for any single course of ex- 
periment. It also to reserve a portion for unforeseen 
contingencies. , CLOSED-TUBE TEST. 
90 
§§ 78-80 
CHAPTER XI. 
TREATMENT OE A SALT, MINERAL, OR OTHER NON' 
METALLIC SOLID. 
78. The general course pursued in the analysis of a non- 
metallic solid substance consists, as a rule, in: —1st. The 
preliminary examination, to be presently described; 2d. The 
bringing the substance into solution ; 3d. The examination 
of the solution obtained for the metallic elements according 
to the methods laid down in Part I, Chaps I-V1II; 4th. 
The application of such general and special tests for the 
non-metallic elements as may not have been rendered un- 
necessary by facts observed during the preceding course of 
the analysis. 
A . PRELIMINARY EXAMINATION IN THE DRY WAY. 
79- The preliminary examination in the dry way consists 
essentially of two operations ; the substance is first subjected 
to the influence of heat alone (closed-tube test, § 80) ; and 
afterwards a second portion of the substance, or, in some 
cases, the same portion, is exposed to the influence of heat 
and certain reducing agents (reduction test, § 81). 
80. Closed-Tube Test. — Prepare a hard glass tube 
No. 4 (App., § 82), about three inches long, and closed at 
one end. Let fall into this tube a minute fragment of the 
solid, or a little of its powder. If the substance be used in 
powder, wipe out the tube with a tuft of cotton on a wire, in 
order that the interior walls .of the tube may be clean to 
receive a sublimate. Ileat th£ substance at the end of the 
tube, at first gently in the lamp, but finally intensely at the 
Order of Procedure. § so 
CLOSED-TUBE TEST. 
91 
highest temperature to be obtained with the Bunsen gas- 
lamp, or in the blowpipe flame. The following are the most 
noteworthy reactions with the inferences to be drawn from 
them; it not unfrequently happens that a single substance 
gives several of these reactions. 
I. The substance blackens, and gases or vapors are evolved. 
These vapors often have a disagreeable smell, sometimes like 
that of burnt sugar, paper, or feathers. Sometimes they 
condense in tarry droplets ; water also condenses on the cold 
part of the tube. These appearances indicate the presence 
of organic substances. 
Now the presence of fixed organic matter interferes with 
the detection of many substances, and it must, as a rule, be 
destroyed before the analysis can be proceeded vitliJp The 
method employed is detailed on page 97; no matter 
whether the substance contain organic matter or not, the 
closed-tube test is immediately succeeded by the reduction test. 
Simple blackening is not proof of the presence of organic 
bodies. Some salts of copper and cobalt, for example, 
blacken through the formation of a black oxide. 
When organic matter is shown to be present, the student 
should look particularly, at the proper stage of the analysis, 
for acetates (§ 67) and tartrates (§ 67) ; but he will not 
forget that there are hundreds of organic compounds which 
are not comprehended in the plan of this treatise. 
II. The substance is not carbonized, but vapors or gases 
escape from it. The most important are : — 
a. Aqueous vtipo'‘, which condenses in the upper part of 
the tube. Test this water with litmus paper; if it is alka- 
line, ammonia may be suspected; if acid, some volatile acid 
(H2S04, HC1, HBr, HI, HF1, HN03, etc). 
b. Oxygen, recognized by its relighting a glowing match. 
This gas indicates nitrates, chlorates and peroxides. If the 
heated substance fuses, and a small fragment of charcoal 
thrown in is energetically consumed, the presence of a nitrate 
or chlorate may be assumed. 92 
CLOSED-TUBE TEST. 
§80 
c. Hyponitric acid, recognized by the brownish-red coloi 
of the fumes. It results from the decomposition of nitrates. 
d. Sulphurous acid, recognized by its odor. It not un- 
frequently results from the decomposition of sulphates, sul- 
phites and sulphides. 
e. Carbonic acid, derived from decomposable carbonates, 
and to be recognized by lime-water (§57). 
f. Cyanogen, derived from decomposable cyanides, and to 
be recognized by its odor, and by the blue flame with which 
it burns when there is enough of it to be lighted. 
g. Sulphuretted hydrogen, derived from moist sulphides, 
and to be known by its smell. 
h. Ammonia, resulting sometimes from the decomposition 
of ammoniacal salts. 
III. A sublimate forms beyond the heated portion of the 
tube. The whole of the substance may volatilize. The fol- 
lowing are the commonest sublimates : — 
a. Sulphur, which sublimes in reddish drops. The sub- 
limate becomes solid and yellow, or yellowish-brown, on 
cooling. 
b. Ammonium salts give white sublimates. 
Test a separate small portion of the original substance for 
the salts of ammonium, by mixing it in a small iwst-tube with 
an equal bulk of slaked lime and a few drops of water, and 
heating the mixture. Ammonia, when evolved, may be rec- 
ognized by its smell, and by the white fume produced when 
a rod moistened with a mixture of equal parts of strong 
chlorhydric acid and water is held above the mouth of the 
tube. Unless the original solid is obviously inalterable by 
heat, it should be invariably tested in this way for ammonium 
salts. 
c. Metallic mercury and some of its compounds. The 
metal sublimes in metallic droplets. The two chlorides of 
mercury give sublimates which are white when cold. The 
red iodide of mercury gives a yellow sublimate, The sul- 
phide of mercury gives a dull black sublimate. §80 
CLOSED-TUBE TEST. 
93 
cl. Arsenic and some of its compounds. Metallic arsenic 
gives a black sublimate of metallic lustre. Arsenious acid 
gives a white sublimate which looks crystalline under a mag- 
nifying lens. The sulphides of arsenic give sublimates which 
are brownish-red while hot, but reddish-yellow to red when 
cold ; these sublimates look not unlike that of pure sulphur. 
e. Teroxide of antimony first fuses to a yellow liquid and 
then gives a white sublimate, composed of needle-like crystals. 
/. Oxalic acid gives a white, crystalline sublimate with 
dense fumes in the tube. 
Other reactions besides those just mentioned sometimes 
occur during the examination of a substance in the closed- 
tube : they are, however, of less importance and, in fact, the 
inferences to be drawn from the appearances already indi- 
cated are of very unequal value. Thus the detection of 
organic matter is of importance, because, as lias been stated, 
such matters must generally be got rid of before the 
analysis can be proceeded with. Again the presence, or en- 
tire absence, of ammonium salts should be put beyond doubt 
at this first stage of the examination. Thirdly, the presence 
of mercury, or of mercurous salts, determines the choice of 
the acid solvent in favor of nitric acid, in case water will not 
dissolve the substance under examination (§ 85), and the 
presence of mercuric salts renders necessary the substitution 
of sulphydrate of ammonium for sulphydrate of sodium as 
the solvent for the sulphides of Class III (§ 27). Accord- 
it is useful to get information of the presence of mer- 
cury or its compounds at this early stage of the examination. 
As to the other appearances, they give information which may 
be convenient, but is never essential for the safe conduct of 
the regular course of analysis. Practically the closed-tube 
test may generally be conducted as follows : — 
The substance is introduced into the tube as stated above, 
a strip of moistened litmus paper is folded loosely across the 
mouth of the tube, and the tube heated in the lamp, at first 
very gently. The deportment of the substance is observed 94 
REDUCTION TEST. 
§ 81 
under the gentle heat at first applied and also as the heat 
increases, the appearance of condensed moisture or of other 
sublimate is looked for, and any action of escaping vapors 
on the litmus paper is noted. Meanwhile the tube is occa- 
sionally removed from the lamp, to see whether any peculiar 
odor of escaping gas may be detected. Finally any water 
which may have condensed in the tube is tested with litmus 
paper. The student should note any other appearances, 
whether mentioned above or not, which manifest themselves 
during the examination, as they may serve as corroborative 
tests when the composition of the substance has finall}7 been 
made out with some certainty. 
81. Reduction Test. — Mix a little of the powder of the 
substance under examination (the bulk of a hemp-seed) with 
an equal quantity of carbonate of sodium, and make the mix- 
ture into a pasty ball with a small drop of water. Select a 
piece of dry, well burned, soft-wood charcoal, and cut out of 
it a rectangular block about G inches long, in. wide, and .J 
to f in. thick, having its fiat, smooth surface (6 in. b}7in.) 
at right angles to the rings of growth in the tree. It is this 
surface which is always to be used. A good piece of char- 
coal may be made to serve for many assays by filing off the 
used surface and exposing a new one, but ordinary charcoal 
allows portions of the flux or even small metallic globules to 
run into its pores or into cracks opened by the heat, and can 
rarely be used with advantage the second time. At a quarter 
to half an inch from the end of the piece of charcoal, scoop 
out with a penknife a little cavity of the size of half a pea. 
Place the prepared pellet in this cavity, and expose it for 
several consecutive minutes to the reducing flame of the 
blowpipe (App., § 78). 
Under these conditions, vapors of characteristic odor or 
appearance may be evolved ; some of them will be mentioned 
below. The two objects, however, to which attention is spe- 
cially to be directed, are the residue in the cavity, and the 
incrastation on the charcoal outside of the cavity. § 81 
REDUCTION TEST. 
95 
The following metals may be found as fused metallic glob- 
ules in the cavity; lead, silver and gold are reduced with 
ease, even by an inexperienced operator ; tin and copper with 
some difficulty: — 
a. Gold — a yellow, malleable globule, produced without 
incrustation. 
b. Copper — a red, malleable globule, produced without 
incrustation. 
c. Tin — a bright, white, malleable globule. An incrus- 
tation is simultaneously produced, which is 
faint yellow when hot and white when cold ; 
it immediately surrounds the globule. 
d. Lead — a very fusible and very malleable globule. A 
yellow incrustation is simultaneously pro 
duced. 
e. Silver — a brilliant, white, malleable globule, produced 
without incrustation. 
Two other common metals, bismuth and antimony, may be 
reduced to gray metallic globules, but these globules are 
brittle, and are not liable to be confounded with the malleable 
globules just described. Bismuth gives a yellow incrustation 
which resembles that of lead. 
Common charcoal is itself very apt to show a grayish in- 
crustation of ash round about the heated assay ; this incrus- 
tation remains unaltered or increases, when directly exposed 
to the flame. The student should test each piece of charcoal 
before the blowpipe flame, in order that he may not imagine 
a deposit of ash to be an incrustation derived from the sub- 
stance under examination. 
If a distinct globule has been obtained, it must be picked 
out with a pair of jewellers’ tweezers, and pounded on some 
smooth and hard body to test its malleability. If it is mal- 
leable, replace it upon the charcoal at an unused spot, and 
heat it. strongly with the oxidizing flame. Gold and silver 
globules fuse, but maintain their brilliancy and give no in- REDUCTION TEST. 
§81 
crustation; this proof distinguishes a genuine gold globule 
from a yellow globule composed of an alloy of copper and 
some white metal. A yellow globule composed of oxidizable 
metals tarnishes instantly in the oxidizing flame. A tin 
globule fuses, but its bright surface is instantty 
and a white incrustation of binoxide of tin is produced 
which cannot be driven off by either flame. A lead globule 
is rapidly converted into litharge, a yellow incrustation being 
produced, which volatilizes with a bluish color when touched 
with the reducing flame. A copper globule is blackened by 
the formation of oxide of copper, and the blowpipe flame is 
tinged with green. 
Certain other phenomena may manifest themselves during 
this experiment for the reduction of malleable metallic glob- 
ules. Sulphur, ammonium salts in general, the chlorides, 
bromides, iodides and sulphides of sodium and potassium, 
the chlorides of lead, bismuth, tin and copper, metallic mer- 
cury, arsenic, antimony and zinc, and many compounds of 
these four elements, are liable to pass off in vapors, which 
are often in part deposited upon the coal at a greater or less 
distance from the hot assay according to their volatility. 
With the exception of sulphur, these sublimates are white, 
but when deposited in a thin film upon the black coal they 
have a gray or blue appearance. During the production of 
the arsenic sublimate a peculiar odor is evolved; this sub- 
limate being very volatile is only deposited at a considerable 
distance from the assay. The incrustation produced by zinc 
is distinctly yellow while hot, but turns white on cooling ; it 
settles near the assay and is driven away again with diffi- 
culty. Nitrates and chlorates generally give warning of their 
presence when heated on charcoal by causing deflagration. 
These phenomena, with the exception of the reaction of 
the nitrates and chlorates, are of secondaiy importance ; the 
main object of the experiment is the reduction of the five 
malleable metals above enumerated. We may thus obtain 
knowledge of the presence of gold (for a confirmatory test, § 82 
DESTROYING ORGANIC MATTER. 
see § 96, 6.), a metal not included in our scheme of analysis 
in the wet way. Tin generally gives warning of its pres- 
ence during this experiment; and this warning is of use, 
because it is inconvenient to apply nitric acid as a solvent to 
a substance containing tin, since this reagent converts tin 
into the very insoluble binoxide of tin. The detection of 
copper at this stage is of little advantage. The most im- 
portant fact deducible from the reduction test is the presence 
of either silver or lead. In dissolving an unknown sub- 
stance which proves to be insoluble in water, it is customary 
to try, as the second solvent, clilorhydric acid. The chlor- 
ides of silver and lead being insoluble, or difficultly soluble, 
this acid should not be used as a solvent when either of these 
two metals is present. Nitric acid must be used instead. 
Moreover, if the substance has already given evidence of the 
presence of organic matter (§ 80), porcelain, and not pla- 
tinum, must be used as a support in destroying the organic 
matter, as described in the next section, whenever an easily 
reducible metal is present. 
82. Destruction of the Organic Matter. — As already 
stated in § 80, the presence of fixed organic matter interferes 
with the detection of many substances, and it must, as a 
rule, be destroyed before the analysis can proceed. A por- 
tion of the original substance, sufficient for the regular course 
of examination for the metallic elements, is ignited in a por- 
celain crucible, with free access of air, or better, on platinum 
foil, if the' absence of any easily reducible metal has been 
proved by the reduction test, until all the carbon is burnt out 
of it. This ignition is best performed on successive small 
portions rather than on a large mass at once. 
It is obvious that some inorganic volatile matters may be 
lost during this ignition. Furthermore, some substances, 
especially alumina and chromic and ferric oxides, are made 
very insoluble by ignition. Exceptionally, therefore, the fol- 
lowing process, which is not liable to these objections, is 
employed : — The substance in powder, paste or concentrated 98 
SOLUTION. 
§ 83 
solution, is heated in an evaporating-dish, with strong nitric 
acid, to a temperature just below boiling. To this hot mix- 
ture chlorate of potassium, in small bits, is added gradually 
during several minutes or until the organic matter is all 
destroyed. The solution is then evaporated to dryness on a 
water-bath; the dry residue is moistened with strong chlor- 
hydric acid, the mixture diluted with water, warmed, and 
filtered, if there be any residue. The filtrate is fit for the 
regular course of analysis, except that potassium, having 
been added, must not be tested for in this liquid. The res- 
idue, if any, must be examined for the insoluble chlorides of 
Class I. This process is simply a combustion at a low tem- 
perature. 
The only classes of salts, coming within the scope of this 
manual, which in the closed tube give evidence of the pres- 
ence of organic matter, are the acetates and tartrates. It 
will, of course, be necessary to apply the tests for acetic and 
tartaric acid to a portion of the original substance and not 
to the solution obtained above. But the student will not for- 
get the statement already made in § 80, that the presence 
of organic matter does not necessarily imply the presence of 
either acetates or tartrates. 
B. DISSOLVING A SALT, MINERAL, OR OTHER NON-METALLIC 
SOLID, FREE FROM ORGANIC MATTER. 
83. Before a solid substance can be submitted to the 
systematic course of analysis, it must be brought into solu- 
tion. There is no universal solvent. Different substances 
require different solvents. The four solvents employed in 
qualitative analysis for salts, minerals, and other non-metallic 
solids, are water, chlorhydric acid, nitric acid and aqua 
regia; and these four liquids are to be tried in the precise 
order in which they here stand. Water is always to be tried 
first; to whatever resists water, strong chlorhydric acid is 
applied; if chlorhydric acid fails to dissolve the solid com- 
pletely, nitric acid is tried, and after nitric acid, aqua regia H84, 85 
SOLUTION. 
99 
as the last resort. If for reasons stated in § 81, the prelimi- 
nary examination has shown chlorliydric acid to be unsuitable 
as a solvent, nitric acid is tried immediately after water, and 
lastly aqua regia as before. A solid substance should in- 
variably be reduced to a very fine powder, before being sub- 
mitted to the action of solvents (App., § 91). 
84. Dissolving in Water. — About half a thimbleful of 
the powdered substance is boiled with ten times as much 
water in a test-tube. If an effervescence occurs, as is possi- 
ble with mixtures containing an acid salt (yeast-powders, for 
example), the gas evolved should be carefully tested (§ 56- 
61). If the substance dissolves completely, the solution is 
ready for analysis. When undissolved powder remains in 
the tube after protracted boiling, filter a few drops of the 
liquid, and evaporate a drop or tw'o of the filtrate to dryness 
on clean platinum foil, at as low a heat as possible. If there 
be no residue on the foil, or if the residue be scarcely appre- 
ciable, the substance is practically insoluble in water, and 
acids must be tried as solvents. But if, on the contrary, a 
tolerable residue remains on the foil, decant the liquid in the 
tube into the filter, and boil the powder again with water. 
Persevere with this treatment until it is evident that a part 
of the powder is insoluble in water. The insoluble residue 
in the test-tube is filtered off; the clear filtrates, collected 
together and concentrated by evaporation if of unreasonable 
bulk, are to be labelled “ H20 Sol.” and reserved for the 
regular course of analysis (§86). In this case, and in the 
still more favorable case in which all the substance has dis- 
solved in water, it is a simple aqueous solution which is sub- 
mitted to analysis. 
85. Dissolving in Acids. — The substance which watei 
has failed to dissolve, either in whole or in part, is next boiled 
in a small dish with three or four times its bulk of concen- 
trated chlorhydric acid, unless the tube test (§ 80) or the re- 
duction test (§ 81) has proved the presence of silver, lead of 
mercury; in which case nitric acid is the first acid to be tried, 100 
SOLUTIOX. 
§ 85 
If an effervescence occur, the escaping gas is to be tested, as 
described in §§ 56-61. (See also the last part of § 76a.) After 
boiling the powdered substance with the strong acid, dilute 
the fluid with twice its bulk of water, and repeat the boiling 
if any residue remain undissolved. The acid is diluted be- 
cause, though the substance to be dissolved is best attacked 
in the first instance by strong acid, the salts formed by the 
action of the concentrated acid are more likely to dissolve 
readily in a dilute than in a strongly acid liquor. Not a few 
salts which scarcely dissolve in strong acids, are readily solu- 
ble in the same acids when diluted. If the whole of the 
substance finally dissolves, the solution still farther diluted 
is ready for the transmission of sulphuretted hydrogen (§ 20), 
for it is of course unnecessary to examine it for members of 
Class I. If, on the contrary, an undissolved residue remain 
in the tube, ascertain if anything has dissolved, by carefully 
evaporating two or three drops of the fluid to dryness on 
platinum foil. Should an appreciable residue, in excess of 
that given by two or three drops of the acid employed, re- 
main upon the foil, separate the liquid in the tube from the 
undissolved substance by decantation or filtration. Reserve 
the solution, labelling it “HC1 Sol.” 
Rinse the undissolved powder with water, and then boil it 
in an evaporating dish with three or four times its bulk of 
strong nitric acid. If the original substance contains silver, 
lead or a mercurous salt, acid will not have been 
used, and it will be the residue from the aqueous solution, 
which is now to be boiled with nitric acid. In this case, 
effervescence is to be watched for. If the substance dissolves 
completely in the strong acid, or dissolves, with the exception 
of a light yellow mass of sulphur, which often separates from 
a sulphide, evaporate the liquid to a very small bulk to drive 
off the free acid, dilute the evaporated solution with several 
times its bulk of water, separate the sulphur, if necessary, by 
filtration, and reserve the solution, labelling it “HN03 Sol.” 
If the substance does not completely dissolve in the strong § 85 
SOLUTION. 
101 
acid, dilute the fluid with twice its bulk of water, and repeat 
the boiling. If the dilute nitric acid effects complete solution, 
reserve the solution, labelling it as before, “HTIOa Sol.” If 
neither the strong nor the diluted nitric acid effects the com- 
plete solution of the substance, ascertain if anything has dis- 
solved in the dilute acid by the usual test on platinum foil. 
If an appreciable residue remain on the foil, separate the 
undissolved solid in the dish from the liquid by decantation 
or filtration, and reserve the solution. 
Boil the powder, which has resisted both acids taken singly, 
with aqua regia. If it dissolves completely, evaporate the 
solution to a very small bulk, dilute the evaporated solution 
largely with water, and reserve it for analysis, labelling it 
w Aq. Reg. Sol.” It is useless to look for members of Class I 
in such a solution. If, on the contrary, it does not com- 
pletely dissolve after protracted boiling, test the liquor to see 
if anything has dissolved. If an appreciable residue remains 
on the foil, dilute the acid fluid, filter it, reserve the solution 
labelled as before, and wash the undissolved residue thor- 
oughly with water, to prepare it for further treatment (§ 86). 
Certain silicates, when boiled with concentrated acids, are 
decomposed, and gelatinous silicic acid is separated. This 
happens but rarely, however, in the rapid processes of quali- 
tative analysis; and if it should happen, it is not likely to 
lead the student into error. A residue insoluble in all acids 
will remain; this residue is, or contains, free silicic acid. 
It must not be supposed that it is common to try all four 
solvents on one and the same substance. Water and chlor- 
hydric acid are the common solvents; nitric acid and aqua 
regia are, actually, but seldom resorted to as solvents, except 
for metals (§ 86). It would require some ingenuity to devise 
an artificial mixture which would put to the test all 
bilities of the above-described method of bringing solidsl'kit5 
solution in water and acids. Such mixtures are not met with 
in ordinary experience. It is the object of any method of 
analysis to meet real problems, not artificial complications 
which may be imagined but which do not occur in fact. 102 
AS AQUEOUS SOLUTION. 
§ 8G 
C. TREATMENT OF THE SOLUTIONS OBTAINED. 
88. Since substances which prove to be insoluble in water 
and in acids must be brought into solution by .peculiar 
methods, we proceed to consider first the treatment of the 
solutions already obtained. 
I. An Aqneou3 Solution. —If the student is assured that 
the unknown substance is a simple salt, he may draw some 
trustworthy inferences from the fact that the substance dis- 
solves in water. Of the salts which fall within the scope of 
this manual, the following are practically soluble in water: 
1. All salts of sodium, and all of potassium and am- 
monium, except their double platinum-chlorides. 
2. All nitrates, chlorates and acetates. 
3. Chlorides, bromides and iodides, except those of silver 
and mercury, and the double platinum-chlorides of 
potassium and ammonium. (Mercuric chloride is 
soluble. The lead salts are difficultly soluble). 
4. Sulphates, except those of barium, strontium and 
lead. 
5. Many hyposulphites. 
6. The sulphides of sodium, potassium, ammonium, mag- 
nesium, barium, strontium and calcium. 
7. A few cyanides, oxalates, tartrates and chromates, be- 
sides those of the alkali-metals already mentioned. 
It is obvious that any element of the thirty-six considered 
(n this treatise, may be present in an aqueous solution ; but 
it is also evident from the above list, that a great number of 
salts are absolutely excluded because of their insolubility in 
water. 
If, on the contrary, there is no certainty that the substance 
under examination is not a complex artificial mixture, few 
coiaafrtfsions can be safely drawn from the fact that a part of 
it or the whole of it dissolves in water. 
Test the solution with litmus paper. The solution is eithei 
neutral, acid, or alkaline. § 86 
AN AQUEOUS SOLUTION. 
103 
a. The solution is neutral.— The normal salts of most 
of the metals have an acid reaction. Sodium, potassium, 
barium, strontium, calcium, magnesium, manganese and silver, 
are the only metallic elements which form salts whose solu- 
tions are neutral. Add to two or three drops of the solution 
a drop or two of carbonate of sodium. If a precipitate 
forms, any of the above mentioned elements may be present, 
and are to be tested for in regular course according to the 
methods of Part I; if no precipitation ensues, only sodium 
and potassium can be present, and they may be tested for 
directly, as described in Chap. VIII. 
b. The solution is acid. — The acidity may be caused by 
a normal salt having an acid reaction, or by an acid salt. 
Neither carbonates nor sulphides can be present in an aque- 
ous solution with an acid reaction. The solution is to be 
tested for the metallic elements in the usual manner. 
c. The solution is alkaline. — The alkalinity may be due 
to the hydrates, sulphides, cyanides, or carbonates, of the 
metals belonging to classes VI and VII; to the presence of a 
borate, silicate, phosphate, arseniate or aluminate of sodium 
or potassium; to free ammonia or to carbonate of ammonium. 
If the alkalinity proceed from an alkaline sulphide, the metals 
whose sulphides are insoluble in water and in alkaline sul- 
phides, must be absent. If it is due to the presence of the 
hydrates or carbonates of the metals of classes VI and VII, a 
very large number of substances are excluded. If it proceed 
from ammonia or carbonate of ammonium, all substam.es pre- 
cipitable by these reagents are absent. 
An alkaline solution may obviously contain some substance, 
soluble in an alkaline solvent like caustic soda or sulphydrate 
of ammonium, but liable to immediate precipitation when this 
solvent is destroyed by the addition of chlorhydric acid at 
the first step of the analysis. Thus any sulphide of Class III 
dissolved in caustic soda or in an alkaline sulphide, or com- 
pounds of alkaline hydrates with the hydrates of aluminum, 
einc or chromium, would be precipitated when the alkaline 104 
AN AQUEOUS SOLUTION. 
§86 
solvent was neutralized. Again, the alkaline solution of a 
silicate of sodium or potassium, when neutralized with acid, 
yields a very gelatinous whitish precipitate of hydrated silicic 
acid. From a very concentrated solution of a borate, boracic 
acid separates in colorless, shining, flat crystals, when the 
solution is acidified with cldorhydric acid; but the boracic 
acid thus separated dissolves when the solution is diluted. 
Again, (although, of course, this could not happen in the 
case of an alkaline solution actually made by dissolving a 
solid substance in water) chloride of silver dissolved in am- 
monia-water would be thi'own down by any acid added in 
excess to the solution. (§17, page 19.) 
In view of these possibilities, an alkaline aqueous solution 
should be carefully neutralized with nitric acid, as a prelimi- 
nary measure, before cldorhydric acid is added to it. Effer- 
vescence should be watched for, and, if it occurs, studied as 
directed in §§ 5G-61. Several different cases of precipitation 
may be distinguished, requiring somewhat different treat- 
ment. 
a. If the characteristic gelatinous precipitate of silicic 
acid appears, the acidulated solution must be evaporated to 
dryness and ignited. The silicic acid is thus rendered in- 
soluble. The ignited residue is digested with dilute nitric 
acid and filtered. The filtrate is ready for the usual course 
of analysis. The insoluble residue is silicic acid. 
b. If the glistening, colorless plates of boracic acid ap- 
pear, dilution with warm water will cause them to redissolve. 
c. If a precipitate appear on neutralization, whose color 
or texture proves that it is neither silicic nor boracic acid, 
but some substance insoluble in water and dilute acids, thrown 
down in consequence of the destruction of its alkaline sol- 
ent, the liquid is made slightly acid and then filtered. The 
filtrate is ready for the usual course of analysis. The pre- 
cipitate, rinsed with a little water, is reserved for further 
treatment; it is not properly a substance soluble in water, 
and it must be brought into solution by other methods, here- §§ 86, 87 
AN ACID SOLUTION' 
105 
after to be described. Sometimes a precipitate forms on 
exact neutralization of an alkaline fluid, which redissolves 
when the acid is added in excess. 
II. An acid solution. — Of the three kinds of acid solu- 
tions described in § 85, any one, any two, or all three, may 
be obtained from a single mixture of different solids. There 
is an advantage in knowing that a part of a complex mixture 
is soluble in water, a part in chlorhydric acid, a part in nitric 
acid and a part only in aqua regia ; because this knowledge 
may enable the student, when he has found out all the ele- 
ments of the mixture, to make a more probable guess at the 
manner of their combination in the original mixture, than he 
would otherwise be able to. But it is quite unnecessary to 
keep the three kinds of acid solution apart, when all three 
have been obtained, and to analyze them separately. On the 
contrary, all three should be mixed together, and analyzed in 
one course of testing. It must only be borne in mind that 
when lead, silver, or mercurous salts are present, the nitric 
acid solution of the residue from the aqueous solution, will 
give a precipitate of the insoluble chlorides of Class I, on 
being mixed with a chlorhydric acid or aqua regia solution. 
The student must be careful to use no more acid than is 
absolutely essential. Nitric acid, particularly, is very objec- 
tionable ; because when free it reacts upon sulphuretted 
hydrogen with mutual decomposition, sulphur being set free. 
It has, therefore, been already prescribed to remove the 
greater part of the free acid by evaporation. Sometimes a 
strongly acid solution becomes turbid when merely diluted 
with water. This phenomenon points to the presence of bis- 
muth or antimony. The turbidity will disappear again on 
the addition of chlorhydric acid. 
The mixed acid solutions, after the filtration from any pre- 
cipitated chlorides of Class I, as first mentioned, are submitted 
to the regular course of analysis for the metallic elements. 
87- Examination of the Solutions for the non-metal- 
lic Elements. — A3 has been already stated in § 45, the 106 
TESTS FOE NON-METALLIC ELEMENTS. 
§ §7 
examination for the non-metallic elements invariably follows 
that for the metallic elements. The method of procedure is 
usually as follows: If the substance is soluble in water and 
there is reason to believe that it is not a complex artificial mix- 
ture, but a simple substance, the determination of the metal- 
lic element generally proclaims the absence of certain classes 
of salts, so that it is very seldom necessary to apply more 
than the barium and the silver tests and a few special tests. 
This will best be illustrated by taking two examples. 
Suppose a homogeneous solid, which dissolves readily in 
water, and which proves to contain strontium. Of the classes 
of salts coming within the range of this manual (see p. 65), 
only the sulphide, chloride, bromide, iodide, cyanide, nitrate, 
chlorate and acetate of stroiltium are soluble in water; the 
presence or absence of a sulphide (and probably of a cyanide) 
will have been shown when chlorhydric acid was added to 
precipitate the members of Class I; the silver test will show 
either the presence or absence of the chloride, bromide, 
iodide and cyanide, and these various classes of salts, if any 
are present, must be distinguished by special tests ; special 
tests must also be applied for nitrates and chlorates and also 
for acetates if the substance blackened in the closed tube. 
In this case, then, the silver test is the only general test 
necessary, and the number of special tests could hardly be 
more than four or five. 
Again, suppose the substance soluble in water proves to 
contain a mercurous salt, the only classes of salts to be sought 
for would be the sulphate (to be decided by the barium test), 
the cyanide, chlorate, nitrate and acetate (to be determined 
by special test). 
If the only metallic element found in an aqueous solution 
were sodium or potassium (or the radical ammonium), it 
would be necessary to look for all the classes of salts enu- 
merated on page 65. In this case the barium test would be 
applied first, then the silver test, then such special tests as 
had not been rendered unnecessary by negative evidence § 87 
TESTS FOR NON-METALLIC ELEMENTS. 
obtained from the general tests. The calcium test would also 
be applied if the barium test had made the presence of an 
oxalate, tartrate or fluoride not impossible. 
In the case of an acid solution the conclusions to be drawn 
from the presence of certain metallic elements are not so gen- 
eral, still in the case of simple substances the absence of cer- 
tain classes of salts will generally be made sure. For example, 
a substance under examination, presumptively a simple salt, 
proves to be insoluble in water, soluble in chlorhydric acid 
and to contain nickel. The sulphate, chloride, borate, chro- 
mate, bromide, iodide, chlorate, acetate and nitrate of nickel 
are soluble in water and for this reason are excluded from 
consideration ; the sulphite, hyposulphite, sulphide, arseniate, 
arsenite and carbonate would have revealed themselves in 
the course of the examination for the metallic elements, and 
the only salts to be specially tested for at this point are the 
phosphate, oxalate, tartrate and silicate. If the general and 
special tests fail to indicate the presence of any of the classes 
of salts mentioned on page 65, the substance may be an 
oxide or hydrate. The hydrates give off water when heated 
in a closed tube ; peroxides sometimes give off oxygen under 
the same conditions, and most oxides when mixed with an 
excess of carbon, and heated, give off carbonic oxide, or 
carbonic acid; these gases may be recognized as stated on 
page 80 under oxalates. 
It is evident from what has just been said, that a knowl- 
edge of the solubility of chemical compounds is of great 
value in determining the presence or absence of various 
classes of salts. The student of qualitative analysis should 
always have at hand a copy of some work on general chem- 
istry to which he can turn; but for convenience of reference, 
a table will be found on pages 108, 109, in which are stated 
in a general way the solubilities of the more commonly 
occurring salts. 
It is to be distinctly borne in mind that this table is not 
exhaustive, and is intended merely as a help to the beginner, SOLUBILITIES OF CHEMICAL COMPOUNDS. 
§87 
Table of 
Ah 
[NH.4 ] Sb 
As 
Ba 
Bi 
Cd 
Ca 
Cr2 
Co 
Ca 
Au Fe« [Fes ]' 
Acetate 
Wi 
tv 
U 
u 
TV 
W 
TV 
TV 
TVl 
TV 
TVl 
U 
TV 
TVl 
Arseniate 
A 
w 
U 
u 
(TV) 
(A) 
U 
A 
A 
A 
A 
U 
A 
A 
Arseni te 
U 
w 
U 
u 
(W) 
U 
U 
(W) 
A 
U 
A 
A 
TJ 
A 
A 
Borate 
U 
•W 
TJ 
tj 
(TV) 
A 
(TV) 
(TV) 
A 
(TV) 
(TV) 
V 
A 
A 
Bromide 
TV 
tv 
(W) 
A 
(W) 
A 
TV 
(TV) 
TV 
TV 
TV 
TV 
TV4 
TV 
TV 
TV 
Carbonate 
u 
tv 
u 
TJ 
A 
A 
A 
A 
A 
A 
A 
TJ 
A 
A 
Ch.orate 
tv 
w 
u 
U 
TV 
TJ 
TV 
TV 
TJ 
TV 
TV 
TJ 
TV 
TV 
Chloride 
w 
tv 
w 
A 
TV 
TVl 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
Chromate 
A 
tv 
A 
TJ 
A 
A 
(TV) 
TV 
A 
A 
(TV) 
TJ 
TJ 
A 
Cyanide 
TJ 
tv 
TJ 
U 
(TV) 
TJ 
(TV) 
TV 
A 
A 
A 
TV5 
(A) 
TV 
Fluoride 
I 
IV 
TV 
TV 
(TV) 
TV 
(TV) 
I 
TV 
(TV) 
(W) 
U 
(TV) 
(TV) 
A 
A 
A 
Hydrate 
A 
TV 
A-I 
A 
(TV) 
A 
A 
(TV) 
A 
A 
A 
A 
A 
A 
Hyposulph 
U 
w 
U 
U 
(W) 
A 
TJ 
TV 
TV 
U 
TV 
TJ 
U 
TV 
TJ 
Iodide 
TV 
w 
A 
(TV) 
W 
A 
TV 
TV 
TV 
TV 
TJl 
A 
TV 
TV 
Nitrate 
tv 
TV 
U 
U 
TV 
TVl 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
Oxalate 
A 
TV 
U 
TJ 
A 
A 
A 
A 
TV 
A 
A 
U 
A 
A 
Oxide 
A 
TV 
A 
TV 
TV 
A 
A 
(TV) 
A-I 
A 
A 
A 
A 
A 
Phosphate 
A 
TV 
(TV) 
TJ 
A 
A 
A 
A 
A 
A 
A 
U 
A 
A 
Silicate 
A-I 
TJ 
TJ 
u 
A-I 
U 
U 
A-I 
TJ 
TJ 
A-I 
U 
(A)-I 
(A)-I 
Sulphate 
TV 
TV 
A 
u 
I 
A 
TV 
(TV) 
TV 
TV 
TV 
U 
TV 
TVi 
Sulphide 
U 
TV 
A 
A 
TV 
A 
A 
TV 
U 
A 
A 
A 
A 
TJ 
Sulphite 
w 
TV 
U 
U 
A 
A 
A 
(TV) 
A 
A 
A 
U 
(TV) 
A 
Tartrate 
tv 
TV 
TV 
U 
(W) 
A 
A 
(TV) 
(TV) 
TV 
TV 
(TV) 
TJ 
(TV) 
TV 
Ah 
[NH-t ] Sb 
As 
Ba 
Bi 
Cd 
Ca 
Cri 
Co 
Cu 
Au Fe» 
[Fe2 ]* 
In this table W signifies that the substance is readily 
soluble in water, (W) that the substance is soluble with 
difficulty in water; A and (A) that the substance is 
readily or with difficulty dissolved by acids ; I that the sub- 
stance is insoluble in water or acids; U signifies that the 
compound is either unknown or so uncommon as rarely to be 
met with. §87 
SOLUBILITIES OF CHEMICAL COMPOUNDS. 
109 
SOLUBILI TIES. 
Pb Mg Mn [Hgs p 
Hg« 
El 
Pfc 
K 
Ag 
Ea 
Sr 
Snu 
Sn1’ 
Zn 
TV 
TV 
tv 
(TV) 
TV 
TV 
TJ 
TV 
(TV) 
TV 
TV 
TV 
TV 
TV 
Acetate 
A 
A 
A 
A 
A 
A 
TJ 
TV 
A 
TV 
(TV) 
A 
A 
A 
Arseniate 
A 
A 
A 
A 
A 
A 
TJ 
TV 
A 
TV 
A 
A 
A 
U 
Arsenite 
A 
A 
(W) 
U 
U 
A 
TJ 
TV 
(TV) 
TVs 
(TV) 
A 
U 
A 
Borate 
(TV) 
TV 
W 
A 
(TV) 
TV 
TV 
TV 
(A) 
TV 
TV 
TV 
TV 
TV 
Bromide 
A 
A 
A 
A 
A 
A 
A 
TVs 
A 
TVs 
A 
A 
A 
A 
Carbonate 
W 
TV 
U 
TV 
TV 
TV 
U 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
Chlorate 
(TV) 
w 
TV 
(A) 
TV 
TV 
TV 
TV 
(A)-I 
TV 
TV 
TV 
TV 
TV 
Chloride 
A 
TV 
TJ 
A 
(TV) 
TV 
TJ 
TVs 
A 
TV 
(TV) 
A 
A 
TV 
Chromate 
A 
TV 
A 
U 
TV 
(A) 
(A) 
TV 
A 
TV 
TJ 
U 
TJ 
A 
Cyanide 
A 
(A) 
A 
A 
TV 
(TV) 
TV 
TV 
TV 
TV 
(TV) 
TV 
TV 
(TV) 
A 
Fluoride 
(TV) 
A 
A 
A 
A 
A 
A 
TV 
A 
TV 
(TV) 
A 
A 
A 
Hydrate 
(TV) 
A 
W 
W 
TJ 
TJ 
TV 
U 
TV 
(TV) 
A 
TV 
TV 
TV 
U 
U 
Hyposu' ihltt 
(TV) 
TV 
TV 
A 
A 
TV 
I 
TV 
A 
TV 
TV 
(TV) 
(TV) 
TV 
Iodide 
w 
w 
tv 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
TV 
A 
A 
TV 
Nitrate 
A 
(W) 
(TV) 
A 
A 
A 
TV 
TVs 
(TV) 
TV 
A 
A 
TV 
A 
Oxalate 
A 
A 
A 
A 
A 
A 
A 
TV 
A 
TV 
(TV) 
A 
I 
A 
Oxide 
A 
A 
A 
A 
A 
A 
TJ 
TV 
A 
TV 
A 
A 
A 
A 
Phosphate 
TJ 
I 
(A)-I 
TJ 
TJ 
U 
TJ 
TV 
U 
TV 
A 
U 
TJ 
A-I 
Silicate 
I 
TV 
TV 
TV 
TV 
TV 
TV 
TVs 
(TV) 
TV 
I 
TV 
TV 
TV 
Sulphate 
A 
W 
A 
A 
A 
A 
A 
TV 
A 
TV 
TV 
A 
A 
A 
Sulphide 
A 
(W) 
(W) 
TV 
TV 
A 
TJ 
TV 
A 
TV 
A 
TV 
TJ 
A 
Sulphite 
A 
w 
(TV) 
A 
(TV) 
A 
TJ 
TVs 
A 
TV 
TV 
(TV) 
A 
(W) 
A 
Tartrate 
Pb Mg Mn [Hga p 
Hg» 
Ei 
Pt 
K 
Ag 
Ea 
Sr 
Sn« 
SnT 
Zn 
1 The basic salt is A. 
2 The acid salt is W. 
3 The acid salt is (W). 
4 The -ous salt is A. 
5 The ous salt is I, INSOLUBLE SUBSTANCES. 
§§ 88,80 
who is analyzing comparatively simple substances. In the 
case of complex mixtures the table is of little service. Thus, 
chloride of silver is designated as I, but it would be easy to 
mix chloride of silver and chloride of sodium in such propor 
tions that on treatment with water the whole of the mixture 
would go into solution: so too the chlorides of potassium 
and platinum are readily soluble in water, each by itself, but 
the double chloride of these two elements is so insoluble that 
it is used as a test for potassium (§ 42) and for platinum 
(§ 96). 
D. TREATMENT OF INSOLUBLE SUBSTANCES. 
88. The substances of common occurrence which are 
practically insoluble in water and acids are: — 
The sulphates of barium, strontium and lead. 
Chloride of silver. 
The anhydrous sesquioxides of aluminum, chromium and 
iron, either native, or the result of intense ignition. 
Chrome-iron-ore, a native mineral. 
Some aluminates. 
Binoxide of tin, native, or the result of ignition. 
Silica and many silicates. 
Fluoride of calcium (fluor-spar). 
Besides the substances included in this list, sulphur and 
carbon, or graphite, should, perhaps, be mentioned, because 
they are insoluble; but they will have been detected during 
the preliminary blowpipe examination, and their presence 
allowed for. Bromide, iodide and cyanide of silver are de- 
composed by boiling with aqua regia, and converted into the 
chloride, so that these substances never appear in their proper 
form in the final insoluble residue. 
89. Substances which resist solution in liquids are gen- 
erally liquefied by the action of fluxes at a high temperature ; 
they are fused in contact with some powerful decomposing 
agent, like the carbonate or acid sulphate of an alkali-metal, § 89 
INSOLUBLE SUBSTANCES. 
or the hydrate or carbonate of an alkaline-earth metal. Cer- 
tain preliminary experiments should precede the fusion. 
The insoluble powder is first examined carefully (with the 
help of a lens, if convenient) to ascertain if it is a homo- 
geneous substance of the same color throughout, or a mixture 
composed of dissimilar, variously-colored particles. The fol- 
lowing blowpipe experiments sometimes give decisive indica- 
tions, particularly with homogeneous substances. 
a. The reduction test (§ 81) is repeated with great care, 
looking especially for silver, lead and tin, and applying to 
the globule, if any is obtained, the test for distinguishing 
between these three white metals. This test has already 
been applied to the original substance ; but if this substance 
was a complex mixture containing soluble ingredients, it is 
quite possible that the test should give a more satisfactory 
result, now that all substances soluble in water and acids have 
been removed, than it yielded before. If, however, decided 
indications of the presence of a reducible metal were obtained 
in the first instance, the repetition of the test is, of course, 
unnecessary. If any reducible metal is detected, it is neces- 
sary to use a porcelain crucible for the fusion which it may 
be desirable to make (§ 90) in order to convert the insoluble 
substance into a more manageable form. A platinum cruci- 
ble, which is employed for most fusions, cannot be used with 
safety when the substance to be fused contains any reducible 
metal; for many of the alloys of platinum are extremely 
fusible. 
Sometimes, when the substance under examination contains 
but a small proportion of metal, some metal may be reduced 
during the blowpipe experiment on charcoal, but the detached 
particles may not run together into a single conspicuous 
globule. Since a mistake as to the presence of a reducible 
metal may involve the destruction of a platinum crucible, it 
is best in doubtful cases to operate in a more delicate fashion. 
To ascertain, beyond question, whether any reduced metal has 
been separated in this experiment, moisten the cavity in the 112 
INSOLUBLE SUBSTANCES. 
§ 89 
charcoal with water after the fusion has been finished, cut the 
charcoal out for a little distance, both around and below the 
cavity, and transfer the contents of the cavity and the scraps 
of charcoal to an agate or porcelain mortar. Pulverize the 
whole mass, and then carefully wash away the powdered 
charcoal and all the lighter portion of the mixture. Any 
malleable metal that may have been reduced remains in the 
mortar in little flattened grains or spangles, in which the 
peculiar color and lustre of the metal or alloy are generally 
visible. Sometimes metallic streaks are produced on the 
mortar or pestle by little particles of metal ground between 
them. The student must not mistake glistening particles of 
wet charcoal sticking to the mortar or pestle for metallic 
spangles, and the metal should be thoroughly removed from 
both mortar and pestle by the use of a few drops of warm 
aqua regia, immediately after the experiment is finished, in 
order to avoid errors on a subsequent occasion. 
b. Prepare another pellet of a mixture of equal parts of 
the insoluble powder and carbonate of sodium, adding a little 
charcoal powder to the paste. Fuse this mixture upon char- 
coal in the reducing flame of the blowpipe. Scoop out the 
fused mass and the surrounding charcoal with a penknife, 
place the dry mass upon a bright surface of silver (coin or 
foil), and wet it with a drop of water. If a brown stain be 
produced on tj|| silver, it is evidence of the presence of sul- 
phide ©f sodium in the fused mass. This sulphide results 
from the reduction of a sulphate, and is evidence of the 
presence of a sulphate in the substance tested. The odor of 
sulphuretted hydrogen is often perceptible when the fused 
mass is moistened. The silver coin or foil may be replaced 
by a piece of lead paper, if care be taken not to mistake the 
mere dirtying of the paper for a stain of sulphide ; the silver 
is, however, to be preferred ; it may be cleaned after use by 
treating it with a solution of cyanide of potassium and then 
washing with water. It is obvious that the carbonate of 
sodium used in this test must be so free from sulphate of §89 
INSOLUBLE SUBSTANCES. 
113 
sodium as not itself to give this reaction on silver, after fusion 
on charcoal. Since coal-gas invariably contains traces of 
sulphur compounds, the test cannot be performed with a gas- 
flame ; a candle or lamp flame (App., § 78) must be em- 
ployed. 
It is, of course, possible to apply this test for sulphates to 
the fused mass obtained in (a) ; this second test is in fact 
unnecessary when a decided reaction has been obtained iu 
the first instance. 
c. Make the loop on the end of the bit of platinum wire 
(App., § 79) white-hot in the blowpipe flame, and thrust it 
white-hot into some powdered borax; a quantity of borax will 
adhere to the hot wire; reheat the loop in the oxidizing 
flame ; the borax will puff up at first, and then fuse to a trans- 
parent glass. If enough borax to form a solid, transparent 
bead within the loop does not adhere to the hot wire the first 
time, the hot loop may be dipped a second time into the pow- 
dered borax. 
When a transparent glass has been formed within the loop 
of the platinum wire, touch the bead of glass while it is hot 
and soft, to a few particles of the insoluble powder, and re- 
heat the bead with the adhering powder in the oxidizing 
flame. If the substance dissolves slowly in the borax, and 
the bead has a fine yellowish-green color when cold, chromium 
is probably present. Reheat the bead in the reducing flame: 
if it presents a bright green color both when hot and cold, 
there is no doubt of the presence of chromium. 
It sometimes happens when too much of the substance to 
be tested has been added, that the borax bead becomes so 
dark-colored as to be practically opaque. It may then be 
flattened while soft, by sudden pressure between any smooth 
metallic surfaces, like the flat parts of jewellers’ tweezers. 
If the flattening makes the color of the borax-glass visible, 
nothing more is necessary ; but if the glass is still too dark, 
all the glass outside the loop of platinum may be broken off 
by gentle hammering, and the remaining glass may be re- 
heated and largely diluted by the addition of more borax. 114 
INSOL UBLE SUBSTANCES. — FUSIONS. 
§§89,90 
It is convenient to be informed of the presence of chromium, 
because chromic oxide and chrome-iron-ore are substances 
which it is particularly difficult to decompose effectually by 
fusion. In presence of chromium, no other bead-reaction 
which can be anticipated under the circumstances will give a 
decisive result; but in the absence of chromium, the presence 
of iron may be determined. A suitable quantity of oxide of 
iron causes the borax-bead, heated in the oxidizing flame, to 
look red when hot and yellow when cold. In the reducing 
flame the iron bead becomes greenish, or light brownish- 
green. 
This test is rendered unnecessary if the substance under 
examination be a white powder, or if from other appearances 
the absence of chromium is assured. 
d. The test for fluorine (§ 70) should be applied to the 
original substance, if it has not already been done. 
When all the above-mentioned tests (a-d) give negative 
results, the simplification of the problem is very conspicuous ; 
the substances which may be present are reduced to alumina 
and some aluminates, silica and silicates. Again, in the case 
of a substance evidently homogeneous, if the preliminary 
tests give affirmative results, the indications of the character 
of the substance are almost conclusive. Thus chloride of 
silver, sulphate of lead, chromic or ferric oxide, binoxide of 
tin, or fluoride of calcium, may be satisfactorily identified by 
the preliminary tests alone. 
There are two methods of changing insoluble substances 
into more manageable forms by the application of heat with 
sufficient exactness for the purposes of the qualitative analyst, 
— the method by fusion, and the method by deflagration. 
90. Fusions.—Mix the fine powder of the insoluble sub- 
stance with about six parts by weight of dry carbonate of 
sodium in powder. Both powders must be as fine as they can 
be made, and they must be intimately mixed. Keep the mix- 
ture at a bright red heat, in a platinum crucible (a porcelain § 91 
FUSION OF INSOLUBLE SUBSTANCES. 
H5 
crucible, if a reducible metal has been found in the substance, 
§ 89, a, and fusion is for any reason preferred to deflagra- 
tion) until the mass has been brought to a state of quiet 
fusion (App., § 75). Place the hot platinum crucible, when 
withdrawn from the lamp or fire, on a cold block, or thick 
plate of iron, and let it cool. If a gas blast-lamp be em- 
ployed, the supply of gas may bo interrupted, and the blast 
of air, directed as before, upon the crucible, until it has 
become cold. 
When the green borax bead, and the dark color of the 
insoluble powder, point to the presence of chrome-iron-ore, a 
mixture of three parts, by weight, of carbonate of sodium 
with three parts, by weight, of nitre, may be substituted for 
the six parts of carbonate of sodium alone. 
91. Treatment of the Fused Mass. — When the cru- 
cible has been cooled in the mentioned above, the fused 
mass can generally be removed from the crucible in an 
unbroken lump. Soak the lump in boiling wrater until every- 
thing is dissolved which is soluble in water. If the mass 
cannot be detached from the crucible, the crucible and its 
contents must be soaked in boiling water. 
The aqueous solution of the fused mass is filtered from the 
residue insoluble in water and reserved. That portion of the 
fused mass which boiling water did not dissolve is treated 
with acid, —chlorh3'dric acid if silver and lead be absent, 
nitric acid if either of these metals be present, — and the 
acid solution obtained is treated as will be described. If a 
portion of the fused mass resist both water and acids, the 
insoluble portion may consist of separated silicic acid, or of 
some of the original substance undecomposed by the fusion. 
In the latter case, another and more prolonged fusion is the 
only effectual remedy, although it may often happen that a 
partial decomposition of the insoluble substance will enable 
the analyst to recognize all the elements which it contains. 
The treatment of the aqueous and acid solutions of the last 
paragraph will be best understood if we first consider what 116 
FUSION OF INSOLUBLE SUBSTANCES. 
§ 91 
changes take place in the process of fusion. Suppose that 
the substance in hand is sulphate of barium ; at the high 
temperature of the fusion the barium and sodium change 
places and, instead of sulphate of barium and carbonate of 
sodium, there result carbonate of barium and sulphate of 
sodium: BaS04 + NaC03 = NaS04 -f BaC03. When the 
fused mass is treated with water, the sulphate of sodium 
(with the excess of carbonate of sodium) goes into solution, 
while the carbonate of barium, which is insoluble in water, is 
dissolved by the chlorliydric (or nitric) acid as chloride (or 
nitrate) of barium. Therefore in a case like this, the metallic 
element would be found in the acid solution and the class or 
kind of salt might be determined by applying the test for 
sulphates to the aqueous solution. Again, suppose the sub- 
stance under examination is a double silicate of calcium and 
aluminum. After fusion with carbonate of sodium and treat- 
ment successively with water and acid, a portion of the silicic 
acid will be in the aqueous solution (as silicate of sodium; 
and a portion in the acid solution, while a part may remain 
insoluble; the aluminum will exist partly in the aqueous 
solution (as aluminate of sodium) and partly in the acid so- 
lution (as chloride of aluminum) ; the calcium, which after 
the fusion remained as carbonate, insoluble in water, will havo 
been converted into chloride and will be found in the acid 
solution. Having considered the general nature of the 
changes brought about by fusion with carbonate of sodium, 
we proceed to the statement of the treatment of the aqueous 
and acid solutions of the fused mass. 
a. If the test for sulphates described in § 89, b, on page 
112, has failed to give satisfactory indications, acidify a small 
portion of the aqueous solution with chlorliydric acid, and 
apply the barium test. The carbonate of sodium used in the 
fusion should be free from sulphate. 
b. Acidify another small portion with acetic acid, and 
apply the lead test for chromates (§ 62). In presence of 
sulphuric acid this test will be obscured, but not rendered 
wholly useless (§ 30, p. 40). § 91 
FUSION OF INSOLUBLE SUBSTANCES. 
117 
c, Acidify a third portion with nitric acid, and apply the 
silver test for chlorine. The student must first prove that his 
carbonate of sodium contains no chloride. 
d. If the test for fluorine by the method of § 68 has, for 
any reason, been unsatisfactory, a fourth portion, having been 
concentrated by evaporation in a porcelain dish, and again 
cooled, is acidified with chlorhydric acid, and then left at rest 
until the carbonic acid has escaped. It is then supersatu- 
rated with ammonia, heated, and filtered while hot. The 
filtrate is collected in a bottle ; chloride of calcium is imme 
diately added to it; the bottle is closed and allowed to stand 
at rest. If the original substance contained a fluoride, the 
fluorine will have combined with sodium during the fusion, 
and fluoride of sodium will be contained in the aqueous solu- 
tion. The carbonic acid having been expelled, and alJ sub- 
stances precipitable by ammonia having been removed, the 
chloride of calcium will throw down the fluoride of calcium. 
If a precipitate separates from the liquid in the bottle after 
some time, it is collected in a small filter, dried and examined 
for fluorine by the method of § 68. 
When the tests a-d give negative results, or when by pre- 
vious tests the absence of sulphates, chromates, chlorides 
and fluorides is made certain, the remainder of the aqueous 
solution is added to the acid solution and the mixture is 
evaporated to dryness and ignited ; the residue thus obtained 
is boiled with dilute chlorhydric (or nitric) acid. If the 
dilute acid fails to dissolve the residue completely, the insolu- 
ble portion consists of silicic acid. The solution is examined 
in the usual way for the metallic elements (§ 44), except, of 
course, sodium (and sometimes potassium), which has been 
added in the flux. (See § 92, p. 118). 
When the preliminary examination or the tests a-d show 
the presence of one or more of the classes of salts mentioned 
above, the treatment is slightly different. In that case the 
remainder of the aqueous solution is acidified with chlor- 
hydric acid, evaporated to dryness and ignited; the residua 118 
FUSION OF INSOLUBLE SUBSTANCES. 
§§91,02 
thus obtained is boiled with dilute chlorbydric acid. If the 
acid fails to dissolve the residue completely, the insoluble 
portion consists of silicic acid; the solution may be tested 
for aluminum. (See page 116.) If silicic acid has been found 
in the aqueous solution, the original acid solution of the 
fused mass is evaporated to dryness and ignited ; the residue 
is treated with dilute acid, and the solution after being filtered 
from the silicic acid is examined for the metallic elements in 
the usual manner. It is evidently impracticable in this last 
case to mix the aqueous and the acid solutions, for if the case of 
sulphate of barium (p. 116) be taken as an example, in mix- 
ing the aqueous solution (containing sulphate of sodium) and 
the acid solution (containing chloride of barium), there 
would be an immediate precipitation o$ the insoluble sulphate 
of barium which was the substance to be analyzed. 
tSilicates are by far the most common of insoluble sub- 
stances. A great variety of metallic elements occur in 
insoluble silicious minerals, so that the possible contents of 
the acid solution of the fused mass are very various. The 
evaporation to dryness in order to render the silica insoluble 
is prescribed because the subsequent examination goes or. 
the better for this preliminary removal of silica, which, if left 
in solution, might create confusion by appearing as a precipi- 
tate at almost any stage of the analysis. 
Many silicates contain sodium and potassium. When the 
presence or absence of these alkali-metals is to be determined, 
it is evident that the pulverized silicate must not be fused 
with carbonate of sodium, but with some decomposing flux 
free from alkali. 
92. Decomposition by Means of Cai'bonate of Cal- 
cium and Chloride of Ammonium. — An intimate mixture 
is prepared of one part of the silicate, six parts of pure pre- 
cipitated carbonate of calcium, three fourths part of pul- 
verized chloride of ammonium. This mixture is hca'ted to 
bright redness in a platinum crucible for thirty or forty min- 
utes. 'The crucible with its contents (which should be in a §§ 93,94 
INSOLUBLE SUBSTANCES. 
119 
coherent, sintered, but not thoroughly fused condition), is 
then placed in a beaker, and soaked for half an hour in water 
kept near the boiling point. The contents of the beaker are 
then filtered. The filtrate, containing caustic lime, chloride 
of calcium, and all the sodium and potassium of the original 
silicate as chlorides, is treated with a little ammonia-water, 
and with carbonate of ammonium in slight excess ; the liquid 
is heated to boiling and filtered. This second filtrate is 
evaporated to dryness, and gently ignited to expel the am- 
monium salts. The residue is dissolved in a little water; 
one or two drops of carbonate of ammonium, and a drop of 
oxalate of ammonium are then added; the mixture is again 
heated and filtered; this third filtrate is evaporated to dry- 
ness and ignited; the ignited residue, if there be any, 
consists of the chlorides of sodium and potassium, or of one 
of these two salts. This residue is examined according 
to § 42. 
93. Fusion with. Acid Sulphate of Sodium. — The 
following method may be tried to advantage upon ferric 
oxide, chromic oxide, or chrome-iron-ore, and some very 
refractory silicates. Heat the insoluble substance with three 
or four times its bulk of acid sulphate of sodium (App., § 29) 
in a platinum crucible, until the sulphate melts; then main- 
tain it in the liquid state for half an hour. This operation 
should be performed under a hood. The fused mass is 
treated essentially as before (§91), allowance being made for 
the different nature of the flux. 
94. Deflagration. — The method of fusion just described 
involves the use of a platinum or porcelain crucible, and de- 
mands the heat of a blast-lamp, or strong coal fire. Neither 
crucibles, lamps nor fires are necessary in the method of 
deflagration, which applies the heat inside the mass to be 
fused. This decomposition by deflagration is performed as 
follows: One part, by weight, of the insoluble powder is 
intimately mixed with two parts of dry carbonate of sodium, 
two parts of fine and pure charcoal powder, and twelve parts DEFLAGRATION. 
§ 94 
of powdered nitre. The mixture is put in a thin porcelain 
dish or clean iron tray; the dish, or little tray, is placed 
under a hood, or in the open air, and a lighted match is 
applied to the centre of the heap. The deflagration is com- 
pleted in two or three seconds, and a well-fused mass 
remains. This mass is detached from the cooled dish or 
tray, and boiled with water in a beaker; it is generally very 
porous, and is therefore readily disintegrated by stirring it in 
the hot water with a glass rod. The soluble portion will all 
be extracted in a very few minutes. The residue left by 
water is treated with acid precisely as described in § 91. 
The aqueous and acid solutions of the deflagrated substance 
are submitted to the same operations as the corresponding 
solutions of substances fused in crucibles. A little charcoal 
is generally left undissolved by the acid, and with it any of 
the substance which may have escaped decomposition. The 
mixture of one part, by weight, of powdered charcoal, and 
six parts of nitre, may be kept ready mixed for effecting the 
fusion of insoluble substances. 
The advantages of this process are that it is quick, 
requires only cheap and common tools, and may be applied 
to substances containing reducible metals, as well as to 
any others. It is, of course, inapplicable when sodium and 
potassium are to be sought for in silicates. Chrome-iron ore 
cannot be decomposed in this way. The insoluble sulphates, 
chloride of silver, binoxide of tin, fluorspar, glass, and many 
natural silicates, may be very well treated by this method, in 
spite of its apparent roughness. Ǥ95, 96 
METALS AND ALLOTS. 
121 
CHAPTER XII. 
TREATMENT OF A PURE METAL OR ALLOY. 
95. The elements which are now used in the arts in the 
metallic state, and which therefore may come into the hands 
of the analyst as metals, either pure or alloyed, are silver, 
lead, mercury, bismuth, cadmium, copper, arsenic, antimony, 
tin, gold, platinum, aluminum, iron, zinc, nickel and mag- 
nesium. These metals can all be brought into solution and 
detected in the wet way with ease and certainty. It is there- 
fore not worth while to submit a metal, or metallic alloy, to 
preliminary blowpipe tests, although at need mercury and 
arsenic can be readily detected by the closed-tube test (§ 80), 
and many others, by exposing them on charcoal to the re- 
ducing and oxidizing flame (compare § 81, pp. 95-97). 
A portion of the metal or alloy to be examined should first 
be reduced to as fine a state of division as possible. If it is 
brittle, it can be powdered ; if soft, shavings can be cut from 
it; if tough and hard, it can perhaps be fused, and shaken 
into powder while melted, or granulated by being poured from 
a height into cold water. Filings should be the last resort, 
because of the possibility of foreign admixture of iron. 
96. Action of Nitric Acid oil the Metals.—A small 
quantity of the divided metal or alloy, about the equivalent 
of a pea in bulk, is placed in a flask, covered with concen- 
trated nitric acid, and heated gently under a hood or in the 
open air for half an hour. 
If complete solution ensues, gold, platinum, tin and anti- 
mony are probably altogether absent; they can only be pres- 
ent in tery minute proportion. Any of the other metals 
above enumerated may be present. Transfer the acid solu- 122 
TREATMENT OF ALLOYS. 
§ 9G 
tion to a porcelain dish, and evaporate it almost to dryness ; 
dilute the evaporated liquid with about ten times its bulk of 
water, and proceed with the analysis in the usual wa}r (§ 44). 
If the solution, from which the greater part of the free acid 
has been removed by evaporation, becomes turbid on the 
addition of water, bismuth is doubtless present. In this case 
enough acid must be restored to the solution to clarify it. 
Mercury, if present, will be dissolved to mercuric nitrate. 
If a residue remains undissolved, add a little more acid to 
make sure that the acid is incapable of further action; and 
when this point is settled, test a drop or two of the clear 
liquid on platinum foil, to ascertain if anything has entered 
into solution. If the nitric acid has effected a partial solu- 
tion of the original metal, evaporate the liquid nearly to dry- 
ness, dilute the evaporated mixture with water, filter, and 
submit the filtrate to the usual course of analysis. The 
residue is thoroughly washed with water, to prepare it for 
further treatment. On diluting the evaporated mixture with 
water, a turbidity due to the presence of bismuth may appear. 
The experienced operator will hardly fail to distinguish be- 
tween any such turbidity and a residue insoluble in the nitric 
acid. To avoid mistakes which would lead to the unneces- 
sary addition of acid, it is wrell to take out a drop of the 
nitric acid solution before evaporation and to add it to sev- 
eral teaspoonfuls of water contained in a test-tube. (See 
p. 24.) The absence or presence of bismuth will thus be 
discovered. It will sometimes happen that a white residue 
appears in the nitric acid solution which disappears vThen the 
evaporated mixture is diluted. This is owing to the presence 
of lead : nitrate of lead is rather insoluble in strong nitric acid 
but passes into solution readily when the mixture is diluted. 
Three different cases of insoluble residues may occur, 
readily distinguished by the mere appearance of the residue. 
a. The insoluble substance is non-metallic and white. In 
this case tiu and antimony may be present, but gold and § 96 
TREATMENT OF ALLOYS. 
123 
platinum are probably absent. The white residue may contain 
the insoluble oxides of tin and antimony, or either of them. 
These elements are to be detected by the methods of § 25, or 
by the method described just below (first part of c). 
b. The insoluble substance is metallic, as evidenced by its 
lustre, if it is in visible fragments, or by the weight and gray 
or black color of its powder, if it is in a fine state of divi- 
sion. Such a residue must be either gold or platinum (or 
some of the rare platinum-like metals which lie without the 
range of this manual). The residue is dissolved in aqua 
regia, and evaporated to a very small bulk. 
Test for Gold.—A portion of this evaporated liquid is 
diluted with ten times its bulk of water, and poured into a 
beaker which is placed on a sheet of white paper. A small 
quantity of a solution of protochloride of tin is tinged yellow 
by the addition of a few drops of solution of sesquichloride 
of iron (App., § 48), and then considerably diluted. A glass 
rod is dipped, first into this tin solution, and then into the 
solution to be tested for gold. If even a trace of the precious 
metal be present, a blue or purple streak will be ob- 
served in the track of the rod. If the quantity of 
gold be more considerable a pink tinge will be im- 
parted to the solution, or a purplish precipitate will be pro- 
duced by a sufficient quantity of the tin-solution. This 
“ purple-of-Cassius ” test is applicable to very acid solu- 
tions. 
Test for Platinum. — To another undiluted portion of the 
cooled aqua regia solution, a cold concentrated solution of 
chloride of ammonium is added. The formation of a yellow, 
crystalline precipitate of chloroplatinate of ammonium indi- 
cates the presence of platinum (or of some rare 
platinum-like metal). By adding a little alcohol 
to the liquid, the test is made more delicate. In a 
difficult case, the aqua regia solution might be evaporated to 
dryness with chloride of ammonium, and the residue treated 
with weak alcohol and water, which would dissolve all tha 
Test 
for 
An. 
Test 
for 
Pt. 124 
TREATMENT OF ALLOYS. 
§ or 
ingredients except the chloroplatinate. Upon ignition, chloro- 
platinate of ammonium leaves spongy platinum behind. 
It happens exceptionally in the case of certain alloys, 
especially in the presence of copper, that concentrated nitric 
acid fails to attack them even when it is hot; it is well, 
therefore, before inferring the presence of an insoluble me- 
tallic residue to try the effect of boiling the seemingly insol- 
uble substance in nitric acid diluted with an equal bulk of 
water. 
c. The insoluble residue contains both a white powder and 
a metallic substance. It must then be examined for anti- 
mony, tin, gold and platinum. The following directions 
presuppose the presence of all four metals, — a very rare 
case. 
The residue is treated for the detection of antimony and 
tin, precisely as described in § 25. Gold and platinum 
remain unchanged in the metallic state through the various 
operations. After dissolving the tin in chlorhydric acid 
(page 34, top), the residue is treated again with chlorhydric 
acid to insure the complete removal of the tin, and is then 
washed thoroughly by decantation. The wrashed residue is 
warmed for a quarter of an hour with a solution of tartaric 
acid (App., § 13), and a few drops of nitric acid are added 
towards the close of the digestion. Antimony dissolves in 
this tartaric acid solution; its presence may be verified by 
passing sulphuretted hydrogen through the decanted solution. 
The platinum foil having been taken out of the porcelain 
dish, the metallic residue from the tartaric acid solution is 
thoroughly washed by decantation, dissolved in aqua regia, 
and tested for gold and platinum, as just described in 6, 
above. §§ 97,98 
TREATMENT OF LIQUIDS. 
125 
CHAPTER XIII. 
TREATMENT OP LIQUIDS. 
97. Evaporation Test. — The first step in the examina- 
tion of an unknown liquid is to evaporate a few drops at a 
gentle heat on platinum foil. Attention should be paid to 
the smell of the escaping vapors in order to ascertain if the 
solvent be water or some other fluid, like alcohol, ether, ben- 
zine, or a strong acid. If no appreciable residue remain, the 
fluid is probably pure water, or some other volatile liquid; 
or it is possible that the liquid is some very dilute solution, 
like a spring water, which needs extreme concentration before 
the solid substances dissolved in it can be detected. When 
a residue remains on the foil, the heat is increased, first, to 
ascertain if the dissolved subtances are wholl}’’ volatile, in 
which case only compounds of ammonium, mercury, arsenic 
and antimony, can be present; and, secondly, to ascertain if 
there be any organic matter in the liquid. Carbonization 
or charring with the attendant phenomena (§ 80, I) occurs 
when fixed organic matter is present. If organic matter is 
discovered, it must be destroyed by the second method of 
§ 82, before the analysis can be proceeded with. A vol- 
atile organic solvent can, of course, be got rid of by a simple 
evaporation to dryness. 
98. Testing with Litmus. — The next step is to test 
the solution with litmus-paper. 
а. If it is neutral, and the solvent is water, consult § 86. 
б. If it is acid, the acidity may be due to a normal salt 
having an acid reaction, or to an acid salt, or to free acid. 
No general inferences can be drawn from the acid reaction, 
except that carbonates and sulphides are absent. If dilution TREATMENT OF LIQUIDS. 
126 
§§99, 100 
of the acid fluid produces turbidity, the presence of antimony 
or bismuth may be inferred 
c. If it i3 alkaline, consult §83, c. 
99- By evaporating a portion of the original solution to 
diyness, the dissolved solid is obtained. This solid may 
be subjected to the whole of the preliminary treatment 
prescribed for a salt, mineral, or other non-metallic solid 
(§§ 80, 81) ; but inasmuch as the main object of all prelim- 
inary treatment of a solid is to learn how to get it into 
solution with the least difficulty, it is seldom worth while for 
the analyst to make a solid out of a solution, and thus forego 
the advantage of having the solution already made to his 
hand. 
100. Testing for Ammonia. — A small portion of the 
original solution must always be tested for ammonium salts, 
by heating it in a test-tube with an equal bulk of slaked lime. 
The gas is recognized by its smell and its reaction with 
chlorhydric acid (§ 80, III. b). 
The means of identifying and isolating the rare elements, 
the methods by which minute traces of one substance be 
detected when hidden in proportionally large quantities of 
other substances, as when the impurities of chemicals and 
drugs are exhibited, and the processes to be employed in 
special cases of peculiar difficulty, such as the analysis of 
complex insoluble minerals, or the detection of mineral poi- 
sons in masses of organic matter, must be studied in com- 
plete treatises upon chemical analyse, or in works specially 
devoted to these teclnvcal matters. Such details, however 
valuable to the professional analyst, or expert, would not be 
in harmony with the plan of this manual. § 2oa 
TREATMENT OF CLASS III. 
127 
ANOTHER METHOD FOR THE TREATMENT OP 
CLASS III. 
§ 25a. Analysis of the Mixed Sulphides.— As consid- 
erable difficulty is often experienced, especially by beginners, 
in analyzing the mixed sulphides of this class, the following 
method of treatment is suggested as an alternative. 
To effect the separation : — Add dilute chlorhydric acid in 
small portions to the sulphydrate of sodium solution until the 
reaction is distinctly acid. The sulphides of arsenic, anti- 
mony, and tin, are precipitated, together with some free sul- 
phur. Any large excess of acid is to be avoided lest the 
sulphides of antimony and tin, which are somewhat soluble in 
chlorhydric acid, fail to be precipitated. 
Collect the precipitate on a filter and throw the filtrate 
away. The precipitate is rinsed with water, transferred to a 
test-tube or small flask, covered writh strong chlorhydric acid, 
and gently warmed, not boiled. The yellow' residue is sul- 
phide of arsenic. The antimony and tin pass into the filtrate 
as chlorides. To test for these elements, prepare a small 
hydrogen-generator, as described at the bottom of page 32, 
and test for the elements as indicated on page 33. 
To test for arsenic, transfer the sulphide of arsenic which 
did not dissolve in the strong chlorhydric acid to a small 
flask, add a teaspoonful of strong nitric acid, and wrarm 
gently for several minutes. Then add in small successive 
portions chlorate of potassium, using in all an amount no 
larger than a half-pea. 
When the sulphide of arsenic has entirely dissolved, pour 
the liquid into an evaporating dish and warm gently until the 
chlorous smell has disappeared. This treatment for arsenic 
must be carried on where there is a good draught, and the 
acid must be warmed, not boiled. When the chlorous fumes 
have been driven off, add ammonia-water until the reaction is 
alkaline, filter, if necessary, and to the clear alkaline liquid 128 
TREATMENT OF CLASS III. 
§ 25a 
add a small quantity of a prepared solution of sulphate of 
magnesium and chloride of ammonium, and set the mixture 
aside for twelve hours. The formation of a white crystalline 
precipitate of arseniate of ammonium and magnesium is evi- 
dence of the presence of arsenic. APPENDIX. 
c** Tlioge reagents in the following list, which are marked with the doubla 
asterisk, are rarely employed; a single, small bottle of each of them in the labora- 
tory, will be enough for many students. * Those marked with a single asterisk 
had also better be kept in one or two bottles of sufficient size, rather than be dis- 
tributed to each student, because of their liability to spoil; several of them are used 
in considerable quantities.] 
1. Chlorhydric Acid (Concentrated).—The strong common 
acid prepared by chemical manufacturers, though usually far from 
pure, will answer for most of the purposes of this manual. It must, 
however, be continually borne in mind that the commercial acid is 
usually contaminated with sulphuric acid, and very often with traces 
of arsenic and iron. These impurities may be present in sufficient 
quantity to render the acid unfit for use when these very substances 
are to be tested for in the mixture to be analyzed. 
The yellow color of the commercial acid, though often attributed 
to iron, is really due for the most part to the presence of a peculiar 
organic compound which is soluble in the strong acid. 
If in any experiment doubts arise concerning the character of a 
reagent, a quantity of it, somewhat larger than that which has been 
mixed with the substance under examination, should be tested by 
itself, and the reaction compared with that exhibited in the doubt- 
ful case. If the result of this trial is unsatisfactory, the experiment 
must be repeated with reagents which are known to be pure. 
2. ** Chlorhydric Acid (Pure) may be prepared by distil- 
ling a mixture of fused chloride of sodium and sulphuric acid, and 
collecting the gas in water. (See Eliot and Storer’s Manual of Inor- 
ganic Chemistry, Exp. 49.) 
3. Chlorhydric Acid (Dilute). — Mix 1 volume of the com- 
REAGENTS. II 
REAGENTS. 
§§ 4-13 
raon concentrated acid, or — where special purity is required—of 
the pure strong acid, with 4 volumes of water. 
4. Nitric Acid (Concentrated).— Use the colorless commer- 
cial acid of 1.38 or 1.40 specific gravity. Strong nitric acid of toler- 
able purity can usually be obtained from the dealers in coarse 
chemicals. An acid, which when diluted with five parts of water 
gives no decided cloudiness with either nitrate of silver (absence of 
chlorhydric acid) or nitrate of barium (absence of sulphuric acid) is 
good enough for most uses in qualitative analysis. 
5, Nitric Acid (Dilute). — Mix 1 volume of the strong acid 
with 5 volumes of water. 
0, Aqua regia should be prepared only in small quantities, at 
the moment of use, by mixing in a test-tube one volume of strong 
nitric acid, with three or four times as much strong chlorhydric 
acid. 
7. Sulphuric Acid (Concentrated).— The oil of vitriol of 
commerce will usually be found pure enough for the purposes of this 
manual. 
8. ** Sulphuric Acid (Pure).— Sulphuric acid free from 
chlorhydric acid is necessary in testing for chlorine according to 
§ 71. Such acid may be obtained from the dealers in fine chem- 
icals, but acid purporting to be pure should invariably be tested 
by diluting a portion with a considerable quantity of water and add- 
ing a few drops of nitrate of silver. No turbidity should appear 
after the mixture has stood for some time. 
9. Sulphuric Acid (Dilute) is prepared by gradually add- 
ing 1 part by measure of the concentrated acid to 4 parts of water 
contained in a beaker or porcelain dish; the mixture must be con- 
stantly stirred with a glass rod. When the mixing is finished, the 
liquid is left at rest until all the sulphate of lead, which has sepa- 
rated from the strong acid, has settled to the bottom; the clear 
liquid is then decanted into bottles. 
** 10. Sulphuric Acid (Dilute) for the separation of cop- 
per and cadmium (p. 25). Mix, as described in the preceding sec- 
tion, 1 part of the strong acid with 5 parts of water. 
11. Oxalic Acid. — Dissolve 1 part, by weight, of the commer- 
cial crystals, in 20 parts of water. 
12. Acetic Acid. —The ordinary commercial acid. 
13. Tartaric Acid should be kept in the state of powder, since 
solutions of it slowly decompose. For use, dissolve a small portion 
of the powder in two or three times its volume of hot water. $$ 14-18 
REAGENTS. 
III 
14. Sulphuretted Hydrogen Gas (Sulphydric Acid), is 
prepared as needed, by acting upon fragments of sulphide of iron 
with dilute sulphuric acid in the apparatus described in §§ 89, 90 of 
this Appendix. The apparatus should always be placed either in the 
open air or in a strong draught beneath a chimney. 
15. Sulphuretted Hydrogen Water.— Pass sulphuretted 
hydrogen gas into a bottle of water until the water can absorb no 
more. To determine when the absorption is complete, close the 
mouth of the bottle tightly with the thumb, and shake the liquid. 
If the water is saturated, a small portion of the gas will be set free 
by the agitation, and a slight outward pressure against the thumb 
will be felt. If the water is not fully saturated, the agitation will 
enable it to absorb the gas which lay in the upper part of the bottle, 
and a partial vacuum will be created, so that an inward pressure 
will be felt. 
Since sulphuretted hydrogen water soon decomposes when ex- 
posed to the air, it should always be kept in tightly closed bottles, 
and no very large quantity of it should be prepared at once. A good 
way of keeping the solution is to fill a number of small phials with 
the fresh liquid, cork them tightly, and invert them in water, so 
that their necks shall always be immersed and protected from the 
atmosphere. 
At the moment of using this reagent its quality should always be 
proved by smelling of it, or by adding a drop or two of the liquid to 
a drop of acetate of lead, which should be immediately blackened 
from the formation of sulphide of lead. 
18. Ammonia-Water. — Commercial aqua-ammoniae may usu- 
ally be obtained pure enough for the purposes of this manual. Dilate 
1 volume of the strong liquor with 3 volumes of water. Ammonia- 
water should be free from carbonic acid; when diluted, as above, it 
ought not to yield any precipitate when tested with lime-water. 
17. * Sulphydrate of Ammonium.—Pass sulphuretted hydro- 
gen gas through ammonia-water, diluted as described in § 1G, until a 
portion of the liquid yields no precipitate when tested with a drop 
of a solution of sulphate of magnesium (absence of free ammonia). 
Since sulphydrate of ammonium decomposes after a while, when 
exposed to the air, it is not advisable to prepare it in large quanti- 
ties. In case any doubt arise as to the quality of the reagent, add 
some of it to a drop of acetate of lead. Unless a dense black pre- 
cipitate of sulphide of lead is immediately thrown down, the sulphy- 
drate is worthless. 
18. Carbonate of Ammonium. — Dissolve 1 part, by weight, IV 
REAGENTS. 
§§ 19-22. 
of the commercial salt, in 4 parts of water, and add to the mixture 
1 part, of strong ammonia-water. 
The solution of carbonate of ammonium should be kept in bottles 
made of glass which is free from lead. If kept in fiint-glass bottles, 
the carbonate of ammonium takes up some lead so that when, in 
precipitating the carbonates of Class VI, this reagent is added to a 
solution containing sulpliydrate of ammonium, a dark coloration 
appears in the liquid or obscures the precipitate to the annoyance of 
the operator. 
19. Chloride of Ammonium.—Dissolve 1 part, by weight, of 
the crystallized commercial salt in 10 parts of water. 
20. Oxalate of Ammonium.—Dissolve 1 part, by weight, of 
the salt in 24 parts of water : or, dissolve 37 grms. of crystallized 
oxalic acid in 450 c. c. of water, neutralize exactly with ammonia- 
water and dilute to the bulk of 1 litre. 
21. ** Molybdate of Ammonium.—Digest 1 part, by weight, 
of molybdic acid for some hours in 4 or 5 parts of strong ammonia- 
water, and mix the clear solution with 12 or 15 parts of strong nitric 
acid ; or dissolve 1 part of molybdate of ammonium in 3 or 4 parts 
of weak ammonia-water, and mix the liquid with 12 or 15 parts of 
nitric acid, as before. 
22. Caustic Soda.—Place 1 part, by weight, of the best com- 
mercial caustic soda in a large, stoppered bottle ; pour upon it 8 or 9 
parts of water, and shake the bottle at intervals until the whole of 
the soda has dissolved. Leave the bottle at rest until the liquid has 
become clear, and finally transfer the solution, with a siphon, to the 
small bottles in which it is to be kept for use. The solution thus 
prepared, though pure enough for the uses prescribed in this man- 
ual, is really far from pure. It would be unfit for use in a delicate 
research, because it is usually contaminated with chloride, sulphate 
and carbonate of sodium, and is liable to contain traces of alumi- 
nate, phosphate and silicate of sodium. Since some nitrate of 
sodium is added to it in the process of manufacture, the soda is lia- 
ble to be contaminated with this salt and the products of its decom- 
position, including ammonia. This last impurity is liable to be given 
off when the solution is boiled. 
Caustic potash, as prepared for surgeon’s use, may be substituted 
for caustic soda whenever it can be more readily obtained. The 
potash should be dissolved in about 10 parts of water. 
Since solutions of the caustic alkalies act upon glass rather easily, 
especially when its outer surface or “fire-glaze” has once been re- 
moved, it often happens, when the soda solution is kept in glass- §§ 23-30 
REAGENTS. 
V 
stoppered bottles, that the stoppers become immovably cemented to 
the glass by the silicate of sodium which forms in their necks. This 
difficulty may be avoided by wiping the necks of the bottles dry after 
any of the solution has been poured from them; but it will usually 
be found more convenient to replace the glass stoppers with plugs 
of vulcanized caoutchouc, or better still, with small glass stoppers, 
over the bodies of which short pieces of caoutchouc tubing have 
been stretched. Solutions of the caustic alkalies should be kept in 
bottles made of glass which is free from lead. 
23. Sulphydrate of Sodium. — Dissolve 1 part by weight of 
commercial sulphide of sodium, if it can be obtained, in 8 parts of 
water. Sulphide of sodium may be made by melting together in 
an iron pot or ladle a mixture of dry carbonate of sodium with an 
equal weight of sulphur. This operation does not require a great 
deal of heat and it may be performed over the blast lamp or over 
an ordinary coal fire. Sulphide of potassium is not an available 
substitute for sulphide of sodium. 
24. Carbonate of Sodium. — For most purposes it is essen- 
tial that the sodium carbonate should be free from sodium sulphate. 
Pure dry carbonate may be obtained from the dealers in flue chemi- 
cals or it may be prepared by washing a pound or two of bicarbonate 
of sodium repeatedly, upon a filter, with small quantities of ice-cold 
water, until the original quantity is reduced to a fifth or a sixth of its 
bulk. The powder is then dried, ignited, and kept in well-stoppered 
bottles. 
25. Biborafo of Sodium. — Common borax, powdered, 
23. Phosphate of Sodium, — Dissolve 1 part, by weight, of 
“ common phosphate of soda” in 10 parts of water. 
27. Acetate of Sodium. — Dissolve 1 part of the crystallized 
salt in 10 parts of water. 
2S. Nitrate of Sodium. — Select a clean white sample of the 
commercial salt and keep in the form of a coarse powder. 
29, **Acid Sulphate of Sodium. — Heat a mixture of 1G 
parts, by weight, of Glauber’s salt, and 5 parts of concentrated sul- 
phuric acid, in a platinum vessel, until a portion of the melted mass 
becomes distinctly solid when taken up on a glass rod. Then allow 
the mixture to become cold; remove the cold lump from the plati- 
num vessel, and break it into fragments. Keep the coarse powder 
in a tight, glass-stoppered bottle. 
30. Sulphate of Potassium. — Dissolve one part, by weight, 
»f the crystallized salt in 200 parts of water. A solution of this VI 
BEAGENTS. 
§§ 31-37 
strength contains the same proportional quantity of sulphuric acid 
as is contained in a saturated aqueous solution of sulphate of cal- 
cium. Hence it cannot precipitate the latter when added to soju- 
tions of the soluble calcium salts. 
31. Chromate of Potassium. — (The normal or “neutral” 
yellow chromate.) Dissolve 1 part, by weight, of the salt in 8 parts 
of water. 
32. Bichromate of Potassium. — The pure crystallized salt 
is kept in the form of powder. It must be entirely free from 
chloride. 
33. Ferroeyanide of Potassium. — {Yellow Prussiate oj 
Potash.) Dissolve 1 part, by weight, of the commercial salt in 12 
parts of water. 
34. * * Ferricyanide of Potassium. — (7led Prussiate of 
Potash.) Since the aqueous solution of this salt undergoes decom- 
position, with formation of some ferroeyanide, when kept for any 
length of time, the salt should be kept for use in the form of pow- 
der. The commercial salt is pure enough for analytical purposes. 
A minute fragment of it may be dissolved in water at the moment 
of use. 
35. ** Cyanide of Potassium.—The better sorts of the 
commercial article are pure enough for analytical purposes. It 
should be kept in the solid form in a tightly stoppered bottle. 
When the solution is required, dissolve 1 part of the salt in 4 parts 
of cold water. 
36. Nitrate of Potassium.—Refined saltpetre may be em- 
ployed. It should be kept in the state of powder. 
37. ** Nitrite of Potassium. — Weigh out 8 parts of concen- 
trated nitric acid, mix it with an equal weight of water, aud place 
the mixture in a glass flask provided with a perforated cork and 
gas delivery-tube. The flask should be so large that the mixture 
only half fills it. Throw into the liquid 2 parts of starch, in lumps, 
aud heat the mixture until red fumes of nitrous and hyponitric acids 
begin to be given off; then remove the lamp lest the action become 
too violent. Conduct the fumes into a bottle containing 5 parts of 
potash-lye of 1.27 sp. gr., until the latter is saturated. Then filter 
the saturated liquid, and evaporate it to dryness. For use, dissolve 
1 part of the dry salt in 2 parts of water. 
The nitrite of potassium bought of dealers in fine chemicals is 
often unfit for the uses prescribed in this manual; it can readily be §§ 38-47 
REAGENTS. 
made good, however, by dissolving it in twice its weight of watei 
and saturating the solution with nitrous fumes. 
38. * Iodide of Potassium and Starch Papers, — Dis- 
solve a gramme of pure iodide of potassium (free from iodate) in 
200 cubic centimetres of water. Heat the solution moderately in a 
porcelain dish, and stir into it ten grammes of starch which has 
been reduced to the consistence of cream by rubbing it in a mortar 
with a small quantity of water. Stir the mixture until it gelatinizes, 
taking care not to burn the starch, then allow the paste to cool, and 
spread it thinly upon one side of white glazed paper with a wooden 
spatula. Dry the paper, cut it into strips as large as the little fin- 
ger and preserve it in stoppered bottles kept carefully closed. 
39. Nitrate of Silver. — Dissolve 1 part, by weight, of the 
commercial crystals in 20 parts of water. 
40. ’"Slaked Lime. — Mix common quicklime with half its 
weight of water. Keep the powder in bottles with tight stoppers. 
41. * Lime Water. —Place a handful of slaked lime in a large 
bottle, pour in enough water to almost fill the bottle, cork the latter 
tightly, and shake it at intervals during several days. Decant the 
clear liquid into smaller bottles for use. Refill the large supply - 
bottle with water, and again shake it at intervals. 
42. Chloride of Calcium. — Stir powdered white marble 
into dilute chlorhydric acid until the acid is saturated, and dilute 1 
part of the concentrated solution with 5 parts of water. 
43. Chloride of Barium. — Dissolve 1 part, by weight, of 
the commercial salt in 10 parts of water. 
44. ** Nitrate of Barium. — Dissolve 1 part, by weight, of 
the commercial salt in 15 parts of water. 
45. Acetate of Lead. — Dissolve 1 part, by weight, of “ sugar 
of lead” in 10 parts of water. 
48. * Lead Paper. — Wet strips of white paper in a solution of 
acetate of lead, or better, in a solution of subacetate of lead, and 
dry them in air which is free from sulphuretted hydrogen. Cut the 
dried paper into slips as large as the little finger, and keep the slips 
in tightly stoppered bottles. Or, paper may be slightly moistened 
with a solution of acetate of lead at the moment of use. 
47. Sulphate of Magnesium and Chloride of Ammo- 
nium.— Dissolve 24.6 grammes of Epsom salt and 33 grammes of 
commercial chloride of ammonium in water, add some ammonia- 
water to the solution and dilute the liquor to the volume of a litre. REAGENTS. 
§§ 48-56 
If less than a litre of the reagent is required, the weights above 
given may, of course, be reduced in any desired proportion. Fil- 
ter the solution to separate any precipitate of ferric hydrate or 
other insoluble matters, which may have been present as impurities 
in the components of the mixture, and preserve the clear liquid. 
From a solution thus prepared no hydrate of magnesium can be 
precipitated by ammonia-water; herein consists the advantage of 
the mixture as a test for phosphoric and arsenic acids. 
48. ** Ferric Chloride. — This solution is prepared bypass- 
ing chlorine gas through a saturated solution of iron tacks in 
chlorhydric acid, until a drop of the fluid no longer produces a blue 
precipitate in a solution of ferricyanide of potassium. The solu- 
tion is then heated to expel the excess of chlorine. 
49. ** Nitrate of Cobalt. — Dissolve 1 part, by weight, of 
the crystallized salt in 10 parts of water. 
60. ** Sulphate of Copper. — Dissolve 1 part, by weight, of 
the crystallized salt (blue vitriol) in 10 parts of water. 
61. ** Protochloride of Tin. — This solution is prepared by 
ooiling scraps of tin with strong chlorhydric acid until hydrogen 
ceases to be evolved. The tin must be in excess. The solution is 
diluted with four times its bulk of water acidulated with chlorhydric 
acid, and filtered, if necessary. The clear liquid must be kept in a 
tightly closed bottle containing some bits of tin. 
52. ** Black Oxide of Manganese. — The artificially pre- 
pared pure binoxide of mauganese. 
53. ** Red Oxide of Mercury. — The commercial oxide. It 
should leave no residue when heated upon platinum foil. 
54. ** Chloride of Mercury. — Dissolve 1 part of “corro- 
sive sublimate” in 1G parts of water. 
55. ** Bichloride of Platinum. — Cut a small quantity of 
worn-out platinum foil into very fine pieces and boil them in a porce- 
lain dish, with successive small portions of aqua regia until all the 
metal has been dissolved. Collect the several portions of aqua regif>, 
partially saturated with platinum, in another dish, and evaporate the 
liquid to dryness on a water bath. Dissolve the residue in 10 parts 
of water for use. 
50. Zinc. — The commercial sheet metal, although usually con- 
taminated with lead and cadmium and often containing faint 
traces of arsenic and sulphur, will generally be found pure enough 
for the purposes of this manual. §§ 57-61 
REAGENTS. 
IX 
57. **“ Solution of Indigo” (Sulphindigctic Acid).— 
Pour 5 parts (5 grammes will be ample) of fuming sulphuric acid 
into a beaker, place the latter in a dish of water to keep it cool, and 
stir into the acid, little by little, 1 part of finely powdered indigo. 
When ail the indigo has been added to the acid, leave the mixture at 
rest for 48 hours; then pour it into 20 times its own volume of 
water, filter the mixture and preserve the filtrate for use. Instead 
of 6 parts of fuming sulphuric acid, 12 or 14 parts of the ordinary 
strong acid may be employed; in this case, however, the mixture 
must be heated for several hours on a water-bath. 
5S. Litmus Paper. — Heat 1 part, by weight, of commercial 
litmus with 6 parts of water, upon a water bath for several hours, 
taking care to replace the water which evaporates. Filter, divide 
the filtrate into two equal portions, and stir one half repeatedly 
with a glass rod dipped in very dilute nitric acid, until the color 
appears distinctly red. Pour the blue and red halves into a porce- 
lain dish, and stir the mixture. Draw strips of fine unsized paper 
through the liquid, and hang them on cords to dry. The color of 
the paper thus obtained is not blue but bluish-violet. It turns blue 
when touched with an alkali, and red when exposed to acids, and 
may be used indifferently as a test for either acids or alkalies. 
59. Starch Paste should be prepared, when wanted for use, 
by boiling 30 cubic centimetres of water in a porcelain dish, and 
stirring into it half a gramme of starch which has previously been 
reduced to the consistence of cream by rubbing it in a mortar with 
a few drops of water. 
60. * Alcohol. — Common alcohol of 85 or 90 per cent. 
61. Water. — Clean rain watenwill serve well enough for most 
of the purposes of this manual. In granitic regions the water of 
many lakes, brooks and ponds also is nearly pure. Pure water may 
be obtained by melting blocks of compact ice, or by distilliug ordi- 
nary water in glass or copper retorts and rejecting the first portions 
of the distillate. It should yield no precipitate when tested with 
chloride of barium and nitrate of silver. 
61a. Hypochlorite of Sodium. - The “ chloride of soda " 
of the druggists. § 62 
SOLUTION’S OF KNOWN COMPOSITION. 
62. In case the experiments indicated in Part I are to be per* 
formed by a considerable number of students, it will be found con- 
venient to prepare beforehand a moderate supply of the various 
solutions required in making the known mixtures under the several 
classes. These solutions may be made of the strengths indicated 
below. 
Chloride of Copper.—Dissolve black oxide of copper in 5 
times its weight of a mixture of equal parts of strong chlorhydric 
acid and water. Dilute the resulting solution with 3 times its bulk 
of water. [A single student in performing the experiment, may dis- 
solve a few grains of the oxide in a small quantity of the strong 
acid, and, in general, may make the solutions as needed for use by 
taking a crystal or a small amount of the required substance in 
powder, as the case may be, without regard to the exact amount. It 
is well, however, not to start with such quantities as to make the 
precipitates inconveniently bulky.] 
Arsenious Acid. — Dilute a quantity of chlorhydric acid with 
half its bulk of water and saturate it with arsenious acid at a geutle 
heat. When the solution has become cold, pour off the clear liquor 
from the arsenious acid which has crystallized out. 
Ferrous Chloride. — Treat warm dilute chlorhydric acid (App., 
5 3) with as much iron (wire or filings) as it will dissolve and then 
dilute the solution with an equal bulk of water. [This solution 
should be prepared only in small quantity and kept in a well-stop- 
pered bottle.] 
Chloride of Zinc.—To a quantity of chlorhydric acid diluted 
with an equal bulk of water, ad J as much zinc as the acid will dis- 
solve and then add to the solution 5 times its bulk of water. 
Chloride of Calcium. — Stir powdered white marble or chalk 
mto chlorhydric acid diluted with twice its bulk of water until the 
acid is saturated; filter the solution if necessary. 
Chloride of Magnesium. — Add “magnesia alba” to dilute 
chlorhydric acid until the acid is saturated, then dilute the solution 
with twice its bulk of water. 
Chloride of Sodium. — Dissolve common salt in 10 times ita 
weight of water. § 62 
KNOWN SOLUTIONS. 
Nitrate of Silver. — Dissolve the crystallized salt in 10 times 
Its weight of water. 
Mercurous Nitrate, —Dilute a small quantity of strong nitric 
acid with an equal bulk of water, and to the mixture, warmed over 
the lamp, add more mercury than will dissolve. When action has 
ceased dilute the solution with 5 times its bulk of water and keep in 
a bottle containing a small amount of metallic mercury. 
Nitrate of Lead.. — Dissolve the crystallized salt in 5 times its 
weight of water. 
Mercuric Chloride. — Dissolve corrosive sublimate in 20 times 
its weight of water. 
Chloride of Bismuth, — Dissolve metallic bismuth in aqua 
regia. When the acid is saturated pour off the solution from the 
undissolved metal, dilute it with twice its bulk of water and add 
strong chlorhydric acid to dissolve the precipitated oxy-chloride. 
Or, dissolve the commercial sub-nitrate in chlorhydric acid and 
dilute as before. 
Chloride of Cadmium. — Dissolve the commercial salt in 10 
times its weight of water. 
Chloride of Lead. — Boil dilute chlorhydric acid with an ex- 
cess of litharge and filter the solution when perfectly cold. 
Chloride of Antimony, — Dilute the commercial strong solu- 
tion with an equal bulk of water and add strong chlorhydric acid 
to dissolve the basic chloride which is precipitated. Or, dissolve 
the finely powdered metal in aqua regia and dilute as before. 
Sulphate of Manganese. — Dissolve the crystallized salt in 10 
times its weight of water. 
Common Alum. — Dissolve in 10 times its weight of water. 
Chrome Alum — Dissolve in 10 times its weight of water. 
Bone Ash (p. 3d) had better be kept in powder and dissolved as 
needed, in order that the student may not lose sight of the fact that 
this compound requires an acid solvent. 
Nitrate of Cobalt, — Dissolve in 10 times its weight of water. 
Nitrate of Nickel, — Dissolve in 10 times its weight of water. 
(The chlorides of nickel and cobalt answer equally well and the 
solutions may be made of the same strength.) 
Chloride of Barium. — Dissolve the crystallized salt in 5 times 
its weight of water. 
Chloride of Strontium. — Dissolve the crystallized salt in 0 
times its weight of water. (The nitrate will answer equally well.) KNOWN SOLUTIONS. — UTENSILS. 
§ 63 
Nitrate of Potassium.—Dissolve 1 part of the commercial 
salt in 5 parts of water. 
Sulphate of Sodium. — Dissolve 1 part of Glauber’s salt in 10 
parts of water. 
Phosphate of Sodium. — Dissolve commercial “ phosphate of 
soda” in 10 parts of water as in App., § 26. 
Carbonate of Sodium. — Dissolve 1 part of “ sal soda” in 5 
parts of water. 
Oxalate of Potassium. — Dissolve 1 part of the crystallized 
salt in 5 parts of water. 
Tartrate of Potassium, -r Dissolve tartaric acid in 5 times its 
weight of water and neutralize it exactly with carbonate of potas- 
sium. 
Iodide of Potassium. — Dissolve 1 part of the crystallized 
salt in 10 parts of water. 
UTENSILS. 
63. The implements required by the student of qualitative 
analysis are few and simple. Besides bottles for the reagents enu- 
merated in the foregoing list, and a few small phials for the preser- 
vation of samples of salts and mixtures to be analyzed, there will 
be needed:— 
A dozen test-tubes, 
A wooden test-tube rack, 
A test-tube brush, 
A nest of small beakers, 
2 or 3 glass stirring-rods, 
A small thistle-, or funnel-tube, 
A larger thistle-tube for the gas- 
generator, 
1 stick of No. 7 glass tubing (see 
App., § 82), 
2 or 3 sticks of No. 4 glass tub- 
ing, 
8 small glass funnels, 
A small glass flask, 
A wash-bottle, 
2 small evaporating dishes, 
A procelain crucible, 
1 triangle of iron-wire, 
An iron ring-stand, 
A filter-stand, 
A lamp, 
A gas-bottle for generating sul- 
phuretted hydrogen, 
A common jeweller’s blowpipe, 
A pair of small iron pincers (jew- 
eller’s tweezers), 
A piece of platinum foil, 
A bit of platinum wire. § 64 
REAGENT BOTTLES. 
A small platinum crucible is also 
very desirable, 
A few packages of cut filters, ora 
quire of filter paper, 
A few corks or caoutchouc stop- 
pers, 
A piece of blue cobalt glass (see 
§42). 
64. Reagent Bottles. — The bottles in which reagents are 
kept should be of cylindrical shape, and rather high than wide. 
They should be closed with glass stoppers which fit accurately, but 
are not very finely ground. The stoppers should have upright (not 
mushroom-shaped) heads. Most of the liquid reagents may be 
conveniently kept in narrow-mouthed bottles of the capacity of 6 
fluid ounces; but to avoid the necessity of frequently refilling the 
bottles, it is well to keep the solutions most commonly employed — 
namely, dilute chlorhydric and nitric acids, ammonia-water, chloride 
of ammonium and carbonate of ammonium — in 8-ounce bottles. 
Care must be taken in this case to choose bottles of such shape that 
they can be readily grasped between the thumb and fingers. 
For the reagents which are to be kept in the dry state, wide- 
mouthed bottles of the capacity of 2 or 3 ounces should be chosen. 
Reagent bottles should always be made “extra-heavy,” since, 
from constant use, they are exposed to many blows. The lustrous 
“ flint-glass ” bottles of American or English make are ill suited for 
the preservation of liquid reagents; for such glass is easily attacked 
by many chemical agents, and is therefore likely to render the re- 
agents impure. The German bottles are usually superior to the 
French. They are made of glass free from lead, and have round 
shoulders and well-ground stoppers. The French bottles, though 
made of good glass and sold at a low price, have often such square 
shoulders that it is wellnigh impossible to empty them completely, 
and often difficult to pour out a liquid from them drop by drop. Their 
stoppers, moreover, are usually too finely ground, and are lienee con- 
stantly liable to stick fast. The lettered reagent-bottles recently 
introduced and manufactured by Whitall, Tatum & Co., Philadelphia, 
are excellent in every respect. 
Each reagent bottle should be kept in a particular place on shelves 
before the operator and convenient to his hand. Whenever a re- 
agent is to be used, the bottle which contains it should be grasped in 
the right hand; the stopper should be taken out by pinching it be- 
tween the first and second or third and fourth fingers of* the left 
hand, or by pressing it between the little finger and palm of that 
hand. In either case, the bottle is withdrawn from the stop>per, and 
not the stopper from the bottle. Neither bottle nor stopper should 
be put upon the table; the stopper should be held in the Left hand XIV 
TEST-TUBES. 
§ 65 
as long as the bottle is open. When the reagent has been poured 
out, the bottle is immediately closed, and returned to its place upon 
the shelf. If these apparently trifling particulars are scrupulously 
attended to, no stopper can ever be misplaced, or soiled by contact 
with liquids or dirt on the table; and the bottle will always be 
found in its proper place when instinctively reached for. Moreover, 
the label on the bottle cannot be injured by drops of the reagent, 
since the liquid must necessarily be poured from the back, or blank 
side of the bottle. 
When a stopper sticks tightly in the neck of a bottle, it may 
sometimes be loosened by pressing it first upon one side, and then 
upon the other, with the thumb of the right hand, while the fingers 
of that hand grip the bottle, and the bottle is held still with the 
left hand. Or the neck of the bottle may be immersed in hot water 
for a minute or two, to expand the glass outside the stopper. The 
stopper can then usually be taken out without trouble. The hot 
water may be conveniently applied by pouring a slow stream of it 
from a wasli-bottle upon the neck of the bottle. Another way is 
to heat the neck of the bottle orer a very small flame of the gas or 
alcohol lamp. No matter how the glass is heated, the bottle must 
be constantly turned round and round, in order that each side of 
the neck may be equally exposed to the heat and the risk of crack- 
ing the bottle so be lessened. 
65. Test-tubes are little cylinders of thin glass with round 
■thin bottoms and lips slightly flared. Their length may be from five 
to seven inches, and their diame'-er from one half to three fourths 
of an inch; they should never be so wide that the open end cannot 
be closed by the ball of the thumn. 
Test-tubes are used for heating small quantities of liquid over the 
gas- or spirit-lamp; they may generally be held by the upper eud in 
the fingers without inconvenience; but in case they become too hot 
to be held in this way, a strip of thick folded paper may be nipped 
round the tube, and grasped between the thumb and forefinger just 
outside the tube. 
Two precautions are invariably to be observed in heating test- 
tubes : — 1st. The outside of the tube must be wiped perfectly dry; 
and 2d. The tube must be moved in and out of the flame for a min- 
ute or two when first heated. It should be rolled to and fro also to 
a slight extent between the thumb and forefinger, in order that each 
side of it may be equally exposed to the flame. A drop of water on 
the outside of the tube keeps one spot cooler than the rest. The 
tube breaks, because its parU, being unequally heated, expand un- 
equally, and tear apart. §§ 66-70 
FLASKS. — FILTERING. 
XV 
When a liquid is boiling actively in a test-tube, it sometimes hap- 
pens that portions of the hot liquid are projected out of the tube 
With some force; ths tube should therefore always be held in an in- 
clined position, and the operator should be careful not to direct it 
towards himself, or towards any other person in his neighborhood. 
Test-tubes are cleaned by the aid of 
cylindrical brushes made of bristles caught 
between twisted wires, like those used 
for cleaning lamp-chimneys; the brushes 
should have a round end of bristles. 
60. Test-tube Rack. — Test-tubes 
are kept in a wooden rack, such as is rep- 
resented in Figure 1. When in use, the 
tubes stand upright in the holes of the 
rack; but clean tubes are inverted upon the pegs behind the holes, 
in order that they may be kept free from dust, and that the last por- 
tions of wash-water may drain away from them after washing. 
The rack should be large enough to hold a dozen tubes. Care 
should be taken that the tubes are washed perfectly clean before 
being inverted on to the pegs lest the pegs themselves become dirty. 
67. Flasks. — Small Berlin flasks of two or three ounces capa- 
city are well suited for the purposes of qualitative analysis. These 
German flasks are tough, capable of withstanding sudden changes 
of temperature, ana durable, although their bottoms and sides have 
all the requisite thinness. When a liquid is to be boiled in a flask, 
the flask should be placed upon a support of wire-gauze (App., § 76), 
and sufficiently inclined to prevent any particles of the liquid from 
being thrown out of the neck by the movement of ebullition. 
As with test-tubes and all other glass or porcelain vessels of 
whatever form, the outside of a flask must be wiped perfectly dry 
before exposing it to the lamp. The flame should be moved about 
also beneath the flask, at first, in order that the temperature of the 
latter may be raised equally and not too rapidly. 
68. Beakers are thin, flat-bottomed tumblers with a slightly 
flaring rim. They are bought in sets or nests. A nest in which 
the largest sized beaker has a capacity of about 6 ounces will be 
sufficient for the requirements of this work. 
e9. Clas3 Funnels should be thin and light, and should be 
about 2 or 2.5 inches in diameter. Their sides should incline at an 
angle of 60°. The wider the throat of the funnel the better. 
70. Filtering. — Paper filters are employed in qualitative analy* 
Pig. 1. FILTERING. 
§ 70 
sis to separate precipitates from the liquids in which they hav e been 
formed. A good filtering-paper must be porous enough to fiLter rap. 
idly, and yet sufficiently close in texture to retain the finest powders; 
and it must also be strong enough to bear, when wet, the pressure of 
the liquid which is poured into upon it. Filter-paper should never 
contain any gypsum or other soluble material, and should leave only 
a small proportion of ash when burned. White or light-gray paper 
is to be preferred to colored, since it more commonly fulfils these 
requirements, 
Filtering-paper is commonly sold in sheets, which may be cut into 
circles of any desired diameters for use, according to the various 
scales of operation, and quantities of liquids to be filtered. Or pack- 
ages of “ cut-filters ” may be procured ready-made from the dealers 
in chemical wares. 
As a geueral rule, small filters should be employed in analytical 
operations; the mixture to be filtered should be poured by small 
successive portions upon a filter no larger than is needed to hold 
the whole of the solid matter which is to be col- 
lected. Filters about three inches in diameter are 
well suited for most of the analytical operations 
described in this work, though there are many 
cases where smaller filters are required, and a few 
instances in which filters as large as four inches 
in diameter might be necessary. 
There are two ready methods of preparing filters 
for use. According to the first method, shown in 
Fig. 2, a circle of paper is folded over on its own 
diameter, and the semicircle thus obtained is 
folded once upon itself into the form of a quadrant; the paper thus 
folded is opened so that three thicknesses shall come upon one side, 
and one thickness upon the other, as shown in the upper half of 
Fig. 2; the filter is then placed in a glass funnel, the angle of which 
should be precisely that of the opened paper, viz., 
60°. The paper may be so folded as to fit a funnel 
whose angle is more orless than G0°, but this is the 
most advantageous angle, and funnels should be 
selected with reference to their correctness in this 
respect. 
In the second method of folding filters, the circle 
of paper is doubled once upon itself as before into 
the form of a semicircle, and a fold equal to one 
quarter of this semicircle is turned down on each 
side of the paper. Each of the quarter semicircles 
Is then folded back upon itself, as shown in the lower half of Fig. 3; 
Fig. 2. 
Fig- 3. § 71 
FILTERING. 
the filter is opened, without disturbing the folded portions, and 
placed in the funnel. Filtration can be rapidly effected with this 
kind of filters, for the projecting folds keep open passages between 
the filter and the funnel, and thus facilitate the passage of the liquid. 
That portion of the circle of paper, which must necessarily be 
folded up in order to give the requisite conical form to a paper 
filter, retards filtration in the first manner of folding, but helps it 
in the second. 
A filter should always be moistened with water after it has been 
placed in the funnel, in order that the fibres of the paper may be 
swollen and the size of its pores diminished, before any of the mat- 
ter to be filtered can pass into them. 
Coarse and rapid filtration — as in the preparation 
of reagents — can be effected with paper filters of large 
size, or with cloth bags; also by plugging the neck of 
a funnel or leg of a siphon loosely with tow or cotton. 
If a very acid or very caustic liquid, which would de- 
stroy paper, cotton, tow or wool, is to be filtered, the 
best substances wherewith to plug the neck of the 
funnel are asbestos and gun-cotton, neither of which 
is attacked by such corrosive liquids. 
71. Filter-Stand.— Filters less than two inches in 
diameter may be placed directly in the mouth of a test-tube with- 
out need of even a funnel to support 
them; and in general the funnel which 
holds a filter may be thrust directly 
into the mouth of a test-tube when- 
ever the quantity of liquid to be fil- 
tered is small, if only an ample exit 
be provided for the air in the tube, 
in the manner shown with the bottle 
of Fig. 4. 
But when the quantity of liquid to 
be filtered is comparatively large, or 
the operations to which the filtrate 
is to be subjected require that it 
should be collected in a beaker or 
porcelain dish, the funnel should have 
an independent support. The iron 
ring stand, described in § 7G of this Appendix, may be used for this 
purpose in case of need; but wooden stands of the form repre* 
eented in Fig. 5, adapted expressly for holding funnels, are very 
Fig. 4. 
Fig. 5. FILTRATION. 
§ 72 
convenient and not expensive. The horizontal bar which holds the 
funnel may be flxed at any height on the vertical square rod by 
means of a wedge-shaped key, whose form is shown in the figure. 
A fine-grained wood, which does not swell or shrink much, is desir- 
able for filter-stands. 
In general, care should be taken that the lower end of the funnel 
touch the side or edge of the vessel into which the filtrate descends, 
in order that the liquid may not fall in drops, but run quietly with- 
out splashing. 
72. Rapid Filtration. — Since in the course of an analysis 
much time is consumed in the process of filtration, it is desirable 
that this operation should be made as rapid as possible. A con- 
siderable advantage over the ordinary method may be gained by 
increasing the length of the tube of the funnel by the addition of a 
piece of glass-tubing a metre or so in length and bent as 
represented in Fig. G. When the funnel and the tube are 
filled with liquid, the difference of pressure on the upper 
and lower surfaces is great enough to cause a very sensible 
increase in the rapidity of the filtration. A far more effi- 
cient method of hastening the process of filtration by 
causing a difference in pressure on the upper and lower 
surfaces of the liquid to be filtered, may be made available 
wherever a constant supply of water with a fall of 8 or 10 
feet can be obtained. The details of the process and of a 
convenient form of the apparatus which may be employed, 
will be described presently; the principle of the method 
is as follows : — 
The filtrate instead of being received in a beaker as is 
usual, is received in a flask from which the air is more or less com- 
pletely exhausted. This exhaustion is accomplished by the use of 
a sort of “ water-pump” which is an adaptation of a very simple 
principle. Let a b and c d be two tubes, arranged 
as represented in Fig. 7. If water be allowed 
to flow in a constant stream down the tube a b 
and the amount of supplied be proper'.* 
regulated, that part of the tube a b which is be- 
low the junction with c d will be filled with buh 
bles of air, which is drawn iu continuously 
through c d and dragged down by the falling wa- 
ter; if the tube ate be connected with a closed vessel, the air iu the 
vessel will be gradually exhausted. The efficiency of such a pump 
depends in a measure uppn the relative size of the tubes and the 
Fig. 6. 
Fig. 7. § 72 
FILTRATION. 
amount of water supplied. Various forms of apparatus in which 
advantage is taken of this general principle might be and have been 
devised. As adapted for purposes of nitration the apparatus is 
known as Bunsen’s “filter-pump”; on account of the great advan- 
tage to be gained by its use, the apparatus, and the method of con- 
ducting the filtration will be given in detail. 
A strong glass flask (for the purposes of qualitative analysis, one 
of from 2 to 4 ounces capacity will answer) is furnished with a 
doubly-perforated caoutchouc stopper: through one of the perfora- 
tions is thrust the neck of a glass funnel and through the other a 
piece of No. 7 glass tubing, bent at a right angle. 
This tube serves to connect the flask with the appa- 
ratus designed to effect the rarefaction of the air in 
the flask. If any considerable difference of pressure 
were brought about between the upper and lower 
surfaces of the liquid in the funnel, the filter would 
most likely break and allow the precipitate to fall 
into the flask. This danger is obviated as follows: 
— A funnel is chosen possessing an angle as near 60° as possible, 
the walls of which must be free from inequalities of every sort. 
Into this glass funnel is fitted a second funnel or rather cone of thin 
platinum foil, the sides of which possess exactly the same inclina- 
tion as those of the glass funnel. This platinum cone is made by 
cutting out from a piece of the thinnest platinum foil that can be ob- 
tained, a portion of a circle as represented in Fig. 9, a. For use 
with a funnel two inches in diameter, this circle may conveniently 
have a radius of 1 inch. The foil is then laid upon a piece of 
hard wood and a number of small holes are punched out of it. 
A ready implement for this purpose may be made by grind- 
ing off squarely the point of a common sewing-needle and 
fitting the needle to a wooden handle. When gently tapped 
with a hammer, this punch forces out a small round bit of 
the foil and, by subsequently rubbing the foil on the bottom 
of a mortar with the pestle, any inequalities of surface are 
avoided. When the foil has been annealed by being heated 
to redness in the lamp and allowed to cool, it is bent up 
into the shape of a cone as represented in Fig. 9, 5. This 
cone should have the same angle of inclination as the funnel in 
which it is to be used, and it is desirable that the funnel should be of 
an angle of G0°; still if the funnel be regular in shape, it can be used 
although it varies somewhat from this angle. The cone is best 
fitted to the funnel by the following manipulation. 
Fig. 8. 
Fig. 9. FILTRATION. 
§ 72 
A solid cone of close-grained hard wood, or better of brass (Fig. 
10, a), which has been turned to an angle of G0°, is laid upon the 
platinum foil in such a position that the apex 
of the cone comes at the centre of the circle of 
which the foil forms a part; the foil is then 
folded up and shaped with the fingers so that 
it fits the cone closely. The two edges of the 
foil lap, and if they were soldered in this posi- 
tion the cone would, of course, have an angle 
of 60°. The platinum cone is now inserted in 
the funnel to be used, and opened out a little 
with the fingers, if necessary, so that it fits 
the glass. The funnel should differ so little from 60° that the 
edges overlap each other only slightly more or slightly less than 
when the foil was fitted to the wooden cone.* By means of a 
sharp point make two scratches on the platinum cone, to show where 
the overlapping edges come when the foil is in position, and then 
remove the cone from the funnel. Hold the platinum by means of 
a pair of pincers in the same position that it occupied when in the 
funnel, which is easily done by observing the scratches made. Then 
heat the cone (Fig. 9, b) at the outer overlapping edge, with a blow- 
pipe flame, put on a small amount of powdered borax, heat again, 
then put on a bit of pure gold and heat until the g-old melts and 
solders the two edges together. The cone should be held, the gold 
put on, and the blowpipe-flame directed in such a manner that the 
melted gold will run down towards the apex of the cone and not 
in the contrary direction. After dissolving off' the adhering borax 
with warm wTater, the cone is ready for use. An ordinary paper 
filter, folded according to the first method of App., § 70 is introduced 
into this compound funnel in the usual maimer; when carefully 
moistened and so adjusted that no air-bubbles are visible between 
it and the glass, this filter, when filled with a liquid, will support 
the pressure even of an extra atmosphere without breaking. 
A convenient form of the Bunsen pump is represented in Fig. 11. 
The tubes (ab, be, hh) which are represented in the figure may 
be very conveniently made of quarter-inch lead pipe (see also, p. xxii, 
near bottom) and the bulb-like enlargement at d may also be made of 
Fig. 10. 
* This wooden or brass cone is not essential; the platinum cone could be shaped 
in the funnel with proper care; it is, however, very convenient, especially in a lab- 
oratory where there are a number of students. In procuring such a cone, it is well 
to lay out with a protractor on a piece of thin sheet tin an angle of 60°, to cut this out, 
and then to give the pattern (templet) to the workman employed. § 72 
FILTRATION. 
Fig. n. XXII 
FILTRATION. 
§ 72 
of lead and soldered on to the smaller pipe. The water is supplied 
in not too large amount by the cock a, and as it passes along the pipe 
a b c and into the waste 6 k, it carries with it a continual stream of 
air bubbles dragged through h d. This tube, h d, communicates in- 
directly with the flask F which is not connected immediately with 
the pump; the connection is interrupted by the bottle E, furnished 
with a perforated stopper through which pass three glass tubes. 
One of these tubes connects with the flask F; one (by means of 
caoutchouc tubing) with the lead pipe h; one with the manometer 
m. The object of this bottle E is to prevent the flow of water into 
the flask iF, in case, as sometimes happens, the operator in letting 
on too rapid a stream of water causes it to rise in the bulb d and 
flow over into the tube li h. All the connectors should be of very 
thick caoutchouc tubing tightly fitted and then varnished with a 
strong solution of shellac; the stopper of the bottle E may be treated 
in the same manner. 
The manometer-bottle G is a convenient but not absolutely essen- 
tial addition. It consists simply of a small bottle containing a quan- 
tity of mercury, to the surface of which the atmosphere has access 
through a small glass tube. The tube m dips below the mercury 
and connects with the bottle E. As the air is rarifled in E (and in 
the flask F), the mercury rises in the tube m; this tube may be 
divided into centimetres or inches by means of a file, or it may be 
provided with, or attached to, a paper or wooden scale. 
The amount of rarefaction that can be produced by this means 
depends, of course, upon the head of water accessible, and this will 
be determined by the difference in height between the points b and k, 
the extremity of the waste-pipe. With a fall of 35 ft. it is possible 
to obtain nearly a perfect vacuum, but a fall of 8 or 10 feet is suffi- 
cient for the purposes of qualitative analysis. 
In operating the filter-pump certain precautions should be ob- 
served. Care should be taken that the water be not supplied in too 
large an amount. To this end it is well to have the cock or valve 
so arranged as to make it impossible to let on more water than ex- 
perience shows to be necessary. The greatest effect is produced by 
the smallest amount of water that will drag the air down the pipe 
c k in the form of bubbles, and in order to observe the flow of air it 
is well to make a portion of the pipe k of glass. (For that matter, 
all the pipes may be made of glass tubes joined by thick caoutchouc 
connector; glass tubing of size No. 5 (see App., § 82) will answer; 
and the bulb d may also be biown of glass by a person possessing 
sufficient skill.) In using the pump the water should be let on before H 73,74 
PORCELAIN DISHES. —LAMPS. 
the connection is made with the filtering flask and the flask should 
he removed before the water is shut off.* 
73. Porcelain Dishes and. Crucibles. — Small open dishes 
which will bear heat without cracking, are much used for boiling 
and evaporating liquids. The best evaporating-dishes are those 
made of Berlin porcelain, glazed both inside and out, and provided 
with a little lip projecting beyond the rim. The dishes made of 
Meissen porcelain are not glazed on the outside, and are not so 
durable as those of Berlin manufacture; but they are much cheaper, 
and with proper care last a long time. 
The small Berlin dishes, Nos. “ 00,” “ 0,” and “ 1,” are well suited 
for all the requirements of this work. They will generally bear an 
evaporation to dryness and subsequent ignition over the open flame 
of a gas lamp, — as when ammonium salts are expelled from Class 
VII (§ 41), —but it is well to protect the dish somewhat by placing 
it upon a piece of wire-gauze, rather than to support it upon a sim- 
ple triangle. The Meissen dishes do not so well endure an open 
flame. The cheaper kinds of evaporating dishes, made of “ semi- 
porcelain,” should never be subjected to this severe treatment; 
they are, for that matter, unfit for use in qualitative analysis. 
Very thin, highly glazed porcelain crucibles, with glazed covers, 
are made both at Berlin, and at Meissen near Dresden. In general 
the Meissen crucibles are thinner than the Berlin, but the Berlin 
crucibles are somewhat less liable to crack; both kinds are glazed 
inside and out, except on the outside of the bottom. The Berlin 
Nos. “ 00” and “ 0,” respectively 1 1-4 and 1 1-2 inches in diameter, 
are best suited for the purposes of this manual. As the covers are 
much less liable to be broken than the crucibles, it is advantageous 
to buy more crucibles than covers, whenever it is possible so to do. 
Porcelain crucibles are supported over the lamp on an iron-wire 
triangle; they must always be gradually heated, and never brought 
suddenly into contact with any cold substance while they are hot. 
74. Lamps.— The common spirit-lamp will be understood with* 
out description from the figure (Fig. 12). When not 
actually lighted, the wick must be kept covered with 
the glass cap; for if the wick were exposed to the 
air, the alcohol in the spirit upon it would evaporate 
faster than the water, and the cotton would soon be- 
come water-soaked and incapable of being lighted. 
Whenever gas can be obtained, gas-lamp3 are 
greatly to be preferred to the best spirit-lamps. For 
all ordinary uses, the gas-lamp known as Bunsen’s 
Fig. 12. 
* Bee Note on page xlvi. § 74 
LAMPS. 
burner may be employed. The cheapest and best construction of 
the lamp may be learned from the following description with the 
accompanying figure. (Fig. 13.) The 
single casting of brass a b comprises 
the tube b through which the gas en- 
ters, and the block a from which the 
gas escapes by two or three fine verti- 
cal holes passing through the screw d 
and issuing from the upper face of d, 
as shown at e. The length of the tube 
b is 4.5 c. m., and its outside diameter 
varies from 0.5 c. m. at the outer end 
to 1 c. m. at the junction with the 
block a. The outside diameter of the 
block a is 1.6 c. m., and its outside height without the screws is 1.8 
c. m. By the screw c, the piece a & is attached to the iron foot g, 
which may be 6 c. m. in diameter. By the screw d, the brass tube 
/ is attached to the casting a b. The diameter of the face e, and 
therefore the internal diameter of the tube / should be 8 m. m. 
The length of the tube / is 9 o, m. Through the wall of this tube, 
four holes 5 m. m. in diameter, are to be cut at such a height that, 
the bottom of each hole will come 1 m. m. above the face e when 
the tube is screwed upon a b. These holes are of course opposite 
each other in pairs. The finished lamp is also shown in the figure. 
To the tube b a caoutchouc tube of 5 to 7 m. m. internal diameter is 
attached; this flexible tube should be about 1 m. long, and its other 
extremity should be connected with the gas-cock through the in- 
tervention of a short piece of brass gas-pipe screwed into the cock. 
In cases where a very small flame is required, as, for instance, in 
evaporating small quantities of liquid, a piece of wire gauze some- 
what larger than the opening of the tube / should be laid across the 
top of the tube, and its projecting edges pressed down tightly 
against the sides of the tube before the gas is lighted. In default 
of this precaution, the flame of a Bunsen 
burner, when small and exposed to currents 
of air, is liable to pass down the tube and 
ignite the gas at d. 
A smaller and somewhat cheaper lamp, 
made on the same principle as the ordinary 
Bunsen burner, is represented in Fig. 14. 
The “ tip ” of the burner is cast of brass, 
and the construction will be evident from 
the enlarged section (6). The stand or foot 
Fig.13. 
Fig. 14. § 75 
BLAST-LAMPS. 
XXV 
is the same as shown in Fig. 13, except that the opening for the 
gas is larger. These lamps are excellent where a small flame is re- 
quired, as it is almost impossible for the gas to “back down” and 
ignite at the lower opening. Tips are also made, as shown at c: 
here the upper opening is closed, and the gas issues from smaller 
openings in the sides of the tube forming a •“ rose”; this form of 
burner is of especial service when evaporating a solution in a porce- 
lain dish where it is desirable to heat the liquid equably. Either of 
the tips described may be screwed upon an ordinary gas-burner in 
default of the stand or foot above represented. These burners can 
be procured of M. W. Pierce & Co., Gas and Steam Fitters, Boston, 
Mass. 
75. Blast-lamps and Blowers. — Though well suited for all 
the ordinary operations of the labor- 
atory, the lamps above described are 
incapable of yielding a very intense 
heat. Hence, when the contents of 
a platinum crucible are to be fused 
or intensely heatad, a blast-lamp 
Will be found useful. The best form 
is that sold under the name of Bun- 
sen’s Gas Blowpipe. Its construc- 
tion and the method of using it may 
be learned from the accompanying 
figure; a & is the pipe through which 
the gas enters, c is the tube for the 
blast of air; the relation of the air- 
tube to the external gas tube is 
shown at d; there is an outer slid- 
ing tube by which the form and 
volume of the flame can be regu- 
lated. 
If gas is not to be had, a lamp burning oil or naphtha may be em- 
ployed. Figure 16 represents a glass- 
blower’s lamp, made of tin and suita- 
ble for burning oil. A large wick is 
essential, whether oil or naphtha be 
the combustible. 
For every blast-lamp a blowing- 
machine of some sort is necessary. 
To supply a constant blast it is essential that the bellows be 
of that construction called double. 
Fig. 15. 
Fig. 16. BLOWEBS. 
§ 75 
Fig. 17 represents a very good form of blowpipe-table, made b$ 
J. H. Call, North Billerica, Mass., and costing about thirty dollars. 
The bellows are made of seamless rubber cloth; the table is 0.8 metre 
Fig. 17. 
high, from which the other dimensions may be inferred. A simple r 
form of bellows, and one which can be made by auy carpenter or 
cabinet-maker, is represented' in perspective and in section in 
Fig. 18. 
Fig. 18. The sides of the bellows and of the reservoir are made 
of stout leather. The arrangement of valves will be evident from 
the figure; a constant pressure is ma'itained on the reservoir by 
means of a spiral spring, and the air is delivered through the tube t. 
The rod which is represented in the figure serves si japly as a 
guide. The entire length from a to b may be 0.6 metre. § 75 
BLOWERS. 
Where an abundant supply of water is at command, a Bunsen 
pump of the kind described in App., § 72, but of larger size, may b-* 
used to furnish a blast. The pipe above the enlargment cl (see Fig 
11) is left open to the air instead of connecting 
with a flask as represented in Fig. 11. The 
waste-pipe k passes through the cork of large 
bottle, Fig. 19, of some litres capacity. Through 
the stopper of this bottle there pass also two 
glass tubes; one of them, h, reaches nearly to the 
bottom of the bottle and serves as a siphon; the 
other merely extends through the cork, and to 
it is attached the tube i, to convey the blast to 
any desired point. The water and air which 
together flow down the pipe k b, pass into the 
bottle. When the water is turned on, the 
caoutchouc tube g i is closed for a moment with 
the thumb and Anger. This starts the water 
through the siphon, and immediately a con- 
tinuous and powerlul blast of air rushes out 
through the tube g i, and may be carried directly 
to the blow-pipe. The siphon must be capable 
of carrying off a larger stream of water than that which is allowed 
to enter, so that there shall never be more than 3 or 4 c. m. of water 
in the bottle. 
The efficiency of the blast depends upon the dimensions of the 
tubes and the head of water employed; one of the Bunsen pumps 
in the laboratory of the Institute of Technology used to furnish a 
blast for the blowpipe is made of half-inch lead pipe and there is a 
fall of about 30 feet. It is, however, by no means necessary to have 
so great a fall; a fall of G or 8 feet furnishes an efficient blast, but 
the amount of water used is much larger. 
In default of a blast lamp, platinum crucibles may readily be 
ignited in a fire of coke or anthracite. To this end, place the tightly 
covered platinum crucible in a somewhat larger crucible of refractory 
clay or Hessian ware, and pack the space between the two cruci- 
bles tightly with calcined magnesia, so that the platinum may no- 
where come in contact with the clay. Cover the coarse crucible, 
and place it, with its contents, in the coal fire, in such a manner that 
it may be gradually heated; finally, imbed the crucible in the glow- 
ing coals and urge the draught of the furnace for half au hour. 
The degree of heat to which the contents of the platinum crucible 
may be exposed, in this way, in an efficient fire, is really far greater 
Fig. 19. XXVIII 
§76 
LAMPS. 
than that of the blast lamps above described but the lamps are 
more convenient than the fire. 
The effect of a simple Bunsen’s burner may be greatly increased 
without the use of any blower, by surrounding its flame with a 
cylinder of fire clay, 3 inches in diameter by 4 or 5 inches high, ant 
having walls at least 3-8 of an inch thick. The crucible, or othei 
body to be heated, is hung in the middle of this chimney, and is 
thus exposed not only to the direct heat of the flame, but also to the 
radiant heat from the clay walls which surround it. 
Where no gas is to be had, an alcohol lamp with circular wick, ol 
some one of the numerous forms sold under the name of Berzelius’s 
Argand Spirit Lamp (Fig. 20), 
will be found useful. These 
argand lamps are usually 
mounted on a lamp-stand pro- 
vided with three brass rings 
but the fittings of these lamps 
are all made slender, in order 
not to carry off too much 
heat. When it is necessary 
to heat heavy vessels, other 
supports must be used. 
70. Iron-stand, Tripod, 
Wire-gauze and Triangle, 
— To support vessels over the 
gas-lamp, an iron stand is used 
consisting of a stout vertical 
rod fastened into a heavy, 
cast-iron foot, and several iron rings of graduated sizes secured to 
the vertical rod with binding screws; all the rings may be slipped 
off the rod, or any ring may be adjusted at any con- 
venient elevation. The general arrangement is not 
unlike that of the stand which makes part of the Ber- 
zelius lamp (Fig. 20), although simpler and cheaper. 
As a general rule, it is not best to apply the direct 
flame to glass and procelain vessels; hence a piece of 
iron wire-gauze of medium fineness is stretched loosely 
over the largest ring, and bent downwards a little for 
the reception of round-bottomed vessels; ou this 
gauze, flasks and porcelain dishes are usually sup- 
ported. Crucibles, or dishes, too small for the small- 
est ring belonging to the stand, are conveniently sup- 
ported on an equilateral triangle made of three pieces 
Fig. 20. 
Fig. 21. § 77 
WATEB- AND SAND-BATH. 
of soft iron wire twisted together at the apices; this triangle is laid 
on one of the rings of the stand. An iron tripod,— 
that is, a stout ring supported on three legs, — 
may often be used instead of the stand above 
described, but it is not so generally useful be- 
cause of the difficulty of adjusting it at vari- 
ous heights; with a sufficiency of wooden 
blocks wherewith to raise the lamp or the tripod 
as occasion may require, it may be made availa- 
ble. 
77. Water-bath and Sand-bath. — It is often necessary to 
evaporate solutions, or to dry precipitates at a moderate tempera- 
ture which can permanently be kept below a certain known limit; 
thus, when an aqueous solution is to be quietly evaporated without 
spirting or jumping, the temperature of the solution must never be 
suffered to rise above the boiling-point of water, nor even quite to 
reach this point. This quiet evaporation is best 
effected by the use of a water-bath, — a copper 
cup whose top is made of concentric rings of dif* 
ferent diameters to adapt it to dishes of various 
sizes (Fig- 23). This cup, two thirds full of water* 
is supported on the iron-stand over the lamp, and 
the dish containing the solution to be evaporated 
is placed on that one of the several rings which 
will permit the greater part of the dish to sink 
into the copper cup. The steam rising from the 
water impinges upon the bottom of the dish, and brings the liquid 
within it to a temperature which insures the evaporation of the 
water, but will not cause any actual ebullition. The water in the 
copper cup must never be allowed to boil away. Wherever a con- 
stant supply of steam is at hand, as in buildings warmed by steam, 
the copper cup above described may be converted into a steam-bath 
by attaching it to a steam-pipe by means of a small tube provided 
with a stop-cock. 
An empty tomato-can furnished with rings as above may take the 
place of the copper cup, and, in fact, a cheap but serviceable w ater- 
bath may be made from a quart milk-can, oil-can, tea-canister, or 
any similarly shaped tin vessel, by inserting the stem of a glass funnel 
into the neck of the can through a well-fitting cork. In this funnel the 
dish containing the liquor to be evaporated rests. The can contains 
the water, which is to be kept just boiling. On account of the shape 
Fig. 22. 
Pig. 23. XXX 
BLOWPIPES. 
§ 78 
of the ftmnel, dishes of various sizes can be used with the same 
apparatus. 
When a gradual and equable heat higher than can be obtained 
upon the water-bath is required, a sand-bath will sometimes be 
found useful. A cheap and convenient sand-bath may be made by 
beating a disk of thin sheet iron, about four inches in diameter, into 
the form of a saucer or shallow pan, and placing within it a small 
quantity of dry sand. The dish or flask to be heated is imbedded in 
the sand, and the apparatus placed upon a ring of the iron-stand 
over a gas-lamp. 
73. Blowpipes. — The mouth-blowpipe in its simplest form is 
a tube bent near one extremity at a right angle. Fig. 24, a, repre- 
sents a common form of blowpipe used by jewellers. The blowpipe 
is rendered more convenient by the addition of a mouth-piece and a 
chamber near the right angle for the condensa- 
tion of moisture. Fig. 24, b and c, represent 
different forms of blowpipe thus furnished. 
The cheapest and best form of mouth blowpipe 
for chemical purposes is a tube of tin-plate, 
about 18 c. m. long, 2 c. m. broad at one end, 
and tapering to 0.7 c. m. at the other (Fig. 24, 
6); the broad end is closed, and serves to re- 
tain the moisture; a little above this closed 
end a small cylindrical tube of brass about 
5 c. m. long is soldered in at right angles ; this 
brass tube is slightly conical at the end, and car- 
ries a small nozzle or tip, which may be made 
either of brass or platinum. The tip should be 
drilled out of a solid piece of metal, and should 
not be fastened upon the brass tube with a 
screw. A trumpet-shaped mouth-piece of horn or boxwood is a con- 
venient, though by no means essential, addition to this blowpipe. 
For convenience in cleaning and packing, blowpipes are often made 
in several pieces, as is the one represented in Fig 24, c. 
The blowpipe may be used with a candle, with gas or with any 
hand-lamp proper for burning oil, petroleum or any of the so-called 
burning fluids, provided that the form of the lamp below the wick- 
holder is such as to permit the close approach of the object to be 
heated to the side of the wick. When a lamp is used, a wick about 
1.2 c. m. long and 0.5 c. m. broad is more convenient than a round 
or narrow wick. The wick-liolder should be tiled off on its longer 
dimension a little obliquely, and the wick cut parallel to the holder, 
Fig. 24. $ 78 
BL 0 WPIPE-FLAME. 
in order that the blowpipe flame may be directed downwards when 
necessary (Figs. 25 and 26). A gas flame suitable for the blowpipe 
is readily obtained by slipping a narrow brass tube (£), open at both 
ends, into the tube / of Bunsen’s burner. (See Fig. 13.) This 
blowpipe-tube must be long enough to close the air apertures in the 
tube /, and should be pinched together and filed off obliquely on top; 
it may usually be obtained with the burner from dealers in chemical 
ware. 
To use the mouth blowpipe, place the open end of the tube be- 
tween the lips, or, if the pipe is provided with a mouth-piece, press 
the trumpet-shaped mouth-piece against the lips; fill the mouth 
with air till the cheeks are widely distended, and insert the tip in 
the flame of a lamp or candle; close the communication between the 
lungs and the mouth, and force a current of air through the tube 
by squeezing the air in the mouth with the muscles of the cheeks, 
breathing, in the meantime, regularly and quietly through the nos- 
trils. The knack of blowing a steady stream for several minutes at 
a time, is readily acquired by a little practice. It will be at once ob- 
served that the appearance of the flame varies considerably, accord- 
ing to the strength of the blast and the position of the jet with 
reference to the wick. 
When the jet of the blowpipe is inserted into the middle of a 
candle-flame, or is placed in 
the lamp-flame in the posi- 
tion shown in Fig. 25, and a 
strong blast is forced through 
the tube, a long, blue cone of 
flame, a b, is produced, be- 
yond and outside of which 
stretches a more or less col- 
ored outer cone towards c. 
The point of greatest heat in this flame is at the point of the inner blue 
cone, because the combustible gases are there supplied with just the 
quantity of oxygen necessary to consume them, but between this point 
and the extremity of the flame the combustion is concentrated and in- 
tense. The greater part of the flame thus produced is oxidizing in its 
effect, and this flame is technically called the oxidizing flame From the 
point a of the inner blue cone, the heat of the flame diminishes in both 
directions, towards b, on the one hand, and towards c on the other; 
most substances require the temperature which is found between a 
and c. Oxidation takes place most rapidly at, or just beyond the 
point c of the flame, provided that the temperature at this point is 
high enough for the special substance to be heated. 
Fig. 25. XXXII 
BLO WPIPE-FLAME. 
§§ 78,79 
A flame of precisely the opposite chemical effect may be produced 
With the blowpipe. To obtain a good reducing flame, it is necessary 
to place the tip of the blowpipe, not within, but just outside of the 
flame, and to blow rather 
over than through the mid- 
dle of the flame (Fig. 26) 
In this manner, the flame is 
less altered in its general 
character than in the former 
case, the chief part consist- 
ing of a large, luminous cone, 
containing a quantity of free 
carbon in a state of intense 
ignition, and just in the condition for taking up oxygen. This flame 
is, therefore, reducing in its effect, and is technically called the re- 
ducing flame. The substance which is to be reduced by exposure 
to this flame, should be completely cov- 
ered up by the luminous cone, so that 
contact with the air may be entirely 
avoided. It is to be observed that, 
whereas to produce an effective oxidiz- 
ing flame a strong blast of air is desira- 
ble, to get a good reducing flame, the 
operator should blow gently, with only 
enough force to divert the lamp-flame. 
Substances to be heated in the blow- 
pipe flame, are supported, sometimes ou 
charcoal, and sometimes on platinum foil 
or wire, or in platinum spoons or forceps. 
Charcoal is especially suitable for a support in experiments of re- 
duction. With reference to the choice of charcoal for blowpipe 
experiments, see § 81. The manner of holding the blowpipe is 
illustrated by Fig. 27. 
79. Platinum Foil and Wire. — Pincers. — A piece of plati- 
num foil about 1 1-2 inches long, and 1 inch wide will be sufficient. 
The foil should be at least so thick that it does not crinkle when 
wiped; and it is more economical to get foil which is too thick thar. 
too thin, for it requires frequent cleaning. To keep foil in good 
order it should be frequently scoured with fine moist sand, and in 
case the foil becomes wrinkled it may be burnished by placing it 
upon the bottom of an inverted agate or porcelain mortar and rub- 
bing it strongly with the pestle. 
Fig. 26. 
Fig. 27. § 80, 81 
PLATINUM UTENSILS. 
A bit of platinum wire, not stouter than the wire of a 
email pin and about 3 inches long, will last a long time 
with careful usage. It may be cleaned by long-continued 
boiling in water. A small loop about as large as this O, 
should be bent at each end of the wire. 
When platinum foil is to be heated, it may be held at 
one end with a pair of the small steel pincers known as 
jewellers’ tweezers. A piece of platinum wire, as long 
as the one above described, can be held in the fingers 
without inconvenience, for platinum is, comparatively 
speaking, a bad conductor of heat. Pieces of wire, too 
short to be held, may be made serviceable by thrusting 
one end of the wire into the end of a glass rod or closed 
tube which has been softened in the blowpipe flame. 
80. Platinum Crucibles.—For several of the 
operations of quantitative analysis as now practised, 
platinum crucibles are indispensable, and though not 
absolutely necessary for the profitable study of qualita- 
tive analysis, one of these vessels will often be found conven- 
ient by the student of the elements of analysis. It will be well, 
therefore, for the student, who proposes to continue his chemi- 
cal studies beyond qualitative analysis, to procure a platinum 
crucible once for all. A crucible of the capacity of about 20 cubic 
centimetres will be large enough for most uses; it should be cylin- 
drical rather than flaring, and should be provided with a loose 
cover in the form of a shallow dish. For the purposes of this book, 
however, a small crucible holding 7 or 8 cubic centimetres answers 
every purpose and a cover is not essential. 
No other metal, and no mixture of substances from which a metal 
can be reduced, must ever be heated in a platinum crucible, or upon 
platinum foil or wire, for platinum forms alloys with other metals, 
and these alloys are much more fusible than platinum itself. If 
once alloyed with a baser metal, the platinum ceases to be applica- 
ble to its peculiar uses. 
Platinum may be cleaned by boiling it in either nitric or chlorhy- 
dric acid, by fusing acid sulphate of sodium upon it, or by scouring 
it with fine sand. Aqua regia and chlorine-water dissolve platinum; 
the sulphides, cyanides, and hydrates of sodium and potassium, 
when fused in platinum vessels, slowly attack the metal. 
81. Wash-bottle. —A wash-bottle is a flask with a uniformly 
thin bottom closed with a sound cork or caoutchouc stopper through 
which pass two glass tubes, as shown in Fig. 29. 
Pig. 28, GLASS — TUBING. STIBBING-BODS. 
§ 82, 83 
The outer end of the longer tube is drawn to a 
moderately fine point. A short bend near the Lottom 
of this longer tube in the same plane and direction as 
the upper bend is of some use, because it enables the 
operator to empty the flask more completely by in* 
dining it. By blowing into the short tube, a stream 
of water will be driveu out of the long tube with con- 
siderable force. This force with which the stream is 
projected adapts the apparatus to removing precipi- 
tates from the sides of vessels as well as to washing 
them on filters. For use in analytical operations, it 
is often convenient to attach a caoutchouc tube 12 or 
15 c. m. long to the tube through which the air is 
blown; this flexible tube should be provided with a 
glass mouth-piece, consisting of a bit of glass tubing about 3 c. m. 
long. As the wash-bottle is often filled with hot or even boiling 
water, it may be improved by binding about its neck a ring of cork, 
or winding the neck closely with smooth cord. It may then be 
handled without inconvenience, when hot. 
The method of making a wash-bottle is described in the following 
paragraphs. 
82. Glass Tubing. — Two qualities of glass tubing are used in 
chemical experiments, that which softens readily in the flame of a 
gas- or spirit-lamp, and that which fuses with extreme difficulty in 
the flame of the blast-lamp. These two qualities are distinguished 
by the terms soft and hard glass. Soft glass is to be preferred for 
all uses except the intense heating, or ignition, of dry substances. 
Fig. 30 represents the common sizes of glass tubing, both hard and 
Fig. 29. 
Fig. 30. 
soft, and shows also the proper thickness of the glass walls for each 
size. The numbers rauging from 4 to 8 are best suited for use in 
qualitative analysis. 
83. Stirring-rods. — Cut a short stick of glass rod, No. 8 or 7, 
into pieces four or five inches long (see the next paragraph), and 
round the sharp ends by fusion in the blowpipe flame. § 8-4 
XXXV 
CUTTING AND CRACKING GLASS. 
84. Cutting and Cracking Glass. — Glass tubiug and glass 
rod must generally be cut to the length required for any particular 
apparatus. A sharp triangular file is used for this purpose. The 
stick of tubing, or rod, to be cut is laid upon a table, and a deep 
scratch is made with the file at the place where the fracture is to be 
made. The stick is then grasped with the two hands, one on each 
side of the mark, while the thumbs are brought together just at the 
scratch. By pushing with the thumbs and pulling in the opposite 
direction with the fingers, the stick is broken squarely at the scratch, 
just as a stick of candy or dry twig may be broken. The sharp 
edges of the fracture should invariably be made smooth, either with 
a wet file, or by softening the end of the tube or rod in the lamp. 
(App., § 85.) Tubes or rods of sizes four to eight inclusive may 
readily be cut in this manner; the larger sizes are 
divided with more difficulty, and it is often neces- 
sary to make the file-mark both long and deep. 
An even fracture is not always to be obtained with 
large tubes. The lower ends of glass funnels, and 
those ends of gas delivery-tubes which enter the 
bottle or flask in which the gas is generated, should 
be filed off, or ground off on a grindstone, obliquely 
(Fig. 31), to facilitate the dropping of liquids from such extremities. 
In order to cut glass plates, the glazier’s diamond must be resorted 
to. For the cutting of exceedingly thin glass tubes and of other 
glass ware, like flasks, retorts and bottles, still other means are re- 
sorted to, based upon the sudden and unequal application of heat. 
The process divides itself into two parts, the producing of a crack 
in the required place, and the subsequent guiding of this crack in 
the desired direction. To produce a crack, a scratch must be made 
with the file, and to this scratch a pointed bit of red-hot charcoal, 
or the jet of flame produced by the mouth blowpipe, or a very fine 
gas-flame, or a red-hot glass-rod may be applied. If the heat does 
not produce a crack, a wet stick or file may be touched upon the hot 
spot. Upon any part of a glass surface except the edge, it is not 
possible to control perfectly the direction and extent of this first 
crack; at an edge a small crack may be started with tolerable cer- 
tainty by carrying the file-mark entirely over the edge. To guide 
the crack thus started, a pointed bit of charcoal or slow-match may 
be used. The hot point must be kept on the glass from 1 c. m. to 
0.5 c. m. in advance of the point of the crack. The crack will fol- 
low the hot point, and may therefore be carried in any desired di- 
rection. By turning and blowing upon the coal or slow-match, the 
Fig. SI. MANIPULATION OF GLASS. 
§ 85 
point may be kept sufficiently hot. Whenever the place of experi- 
ment is supplied with common illuminating gas, a very small jet of 
burning gas may be advantageously substituted for the hot coal or 
slow match. To obtain such a sharp jet, a piece of hard glass tube, 
No. 4, 10 c. ra. long, and drawn to a very fine point (App., § 85), 
should be placed in the caoutchouc tube which ordinarly delivers the 
gas to the gas-lamp, and the gas should be lighted at the fine ex- 
tremity. The burning jet should have a fine point, and should not 
exceed 1.5 c. m. in length. By a judicious use of these simple tools, 
broken tubes, beakers, flasks, retorts and bottles may often be made 
to yield very useful articles of apparatus. No sharp edges should 
oe allowed to remain upon glass apparatus. The durability of the 
apparatus itself, and of the corks and caoutchouc stoppers and 
cubing used with it, will be much greater, if all sharp edges are 
removed with the file, or, still better, rounded in the lamp. 
85. Bending and Closing Glass Tubes. — Tubing of sizes 
four to eight inclusive can generally be worked in the common gas- 
or spirit lamp; for larger tubes the blast-lamp is necessary. (App., 
§ 75.) Glass tubing must not be introduced suddenly into the hot- 
test part of the flame, lest it crack. Neither should a hot tube be 
taken from the flame and laid at once upon a cold surface. Gradual 
heating and gradual cooling are alike necessary, and are the more 
essential the thicker the glass; very thin glass will sometimes bear 
the most sudden changes of temperature, but thick glass and glass 
of uneven thickness absolutely require slow heating and annealing. 
When the end of a tube is to be heated, as in rounding sharp edges, 
more care is required in consequence of the great facility with which 
cracks start at an edge. A tube should, therefore, always be 
brought first into the current of hot air beyond the actual flame of 
the gas- or spirit-lamp, and there thoroughly warmed, before it is 
introduced into the flame itself. If a blast-lamp is employed, the 
tube may be warmed in the smoky flame, before the blast is turned 
on, and may subsequently be annealed in the same manner; the de- 
posited soot will be burnt off in the first instance, and in the last 
may be wiped off when the tube is cold. In heating a tube, whether 
for bending, drawing, or closing, the tube must be constantly turned 
between the fingers, and also moved a little to the right and left, in 
order that it may be uniformly heated all round, and that the tem- 
perature of the neighboring parts maybe duly raised. If a tube, or 
rod, is to be heated at any part but an end, it should be held between 
the thumb and first two fingers of eacli hand in such a manner that 
the hands shall be below the tube or rod, with the palms upward, § 85 
MANIPULATION OF GLASS. 
while the lamp-flame is between the hands. When the end of a tube 
or rod is to be heated, it is best to begin by warming the tube or 
rod about 2 c. m. from the end, and thence to proceed slowly to the 
end. 
The best glass will not be blackened or discolored during heating. 
Blackening occurs in glass which, like ordinary flint glass, contains 
lead as an ingredient. Glass containing much lead is not well 
adapted for chemical uses. The blackening may sometimes be re- 
moved by putting the glass in the upper or outer part of the flame, 
where the reducing gases are consumed, and the air has the best 
access to the glass. The blackening may be altogether avoided by 
always keeping the glass in the oxidizing part of the flame. 
Giass begins to soften and bend below a visible red heat. The 
condition of the glass is judged of as much by the fingers as the 
eye; the hands feel the yielding of the glass, either to bending, 
pushing, or pulling, better than the eye can see the change of color 
or form, It may be bent as soon as it yields in the hands, but can 
be drawn out only when much hotter than this. Glass tubing, how- 
ever, should not be bent at too low a temperature; the curves made 
at too low a heat are apt to be flattened, of unequal thickness on the 
convex and concave sides, and brittle. 
In bending tubing to make gas-delivery tubes and the like, atten- 
tion should be paid to the following points : 1st, the glass should be 
equally hot on all sides; 2d, it should not be 
twisted, pulled out, or pushed together dur- 
ing the heating; 3d, the bore of the tube at 
the bend should be kept round, and not 
altered in size; 4th, if two or more bends be 
made in the same piece of tubing (Fig. 32, a), 
they should all be in the same plane, so 
that the finished tube will lie flat upon the level table. 
When a tube or rod is to be bent or drawn close to its extremity, 
a temporary handle may be attached to it by softening the end 
of the tube or rod, and pressing against the soft glass a fragment 
of glass tube, which will adhere strongly to the softened end. 
The handle may subsequently be removed by a slight blow, or by 
the aid of a file. If a considerable bend is to be made, so that the 
angle between the arms will be very small or nothing, as in a 
siphon, for example, the curvature cannot be well produced at one 
place in the tube, but should be made by heating, progressively, 
several centimetres of the tube, and bending continuously from one 
end of the heated portion to the other (Fig. 32, &). Small and thick 
tube may be bent more sharply than large or thin tube. 
Fig. 32. XXXVIII 
MANIPULATION OF GLASS. 
§ 85 
A lamp for bending glass tubing better than the ordinary form of 
the Bunsen burner, is one the tube of which is flattened out so as to 
give a thin but broad flame of the same character as the ordinary 
lamp but in shape more like a bat-wing burner. 
(See Fig. 33.) The tube is placed in this flame 
and turned round and round until it reaches the 
proper temperature; it is then withdrawn from 
the flame and bent. In this way a regular curve 
may be obtained and the sides of the tube do not 
collapse. 
In order to draw a glass tube down to a finer 
bore, it is simply necessary to thoroughly soften on 
all sides one or two centimetres’ length of the tube 
and then taking the glass from the flame, pull the 
parts asunder by a cautious movement of the hands. 
The larger the heated portion of glass, the longer 
will be the tube thus formed. Its length and fineness also increase 
with the rapidity of motion of the hands. If it is desirable that the 
finer tube should have thicker walls in proportion to its bore than 
the original tube, it is only necessary to keep the heated portion soft 
for two or three miuutes before drawing out the tube, pressing the 
parts slightly together the while. By this process the glass will be 
thickened at the hot ring. 
To obtain a tube closed at one end, it is best to take a piece of 
tubing, open at both ends, and long enough 
to make two closed tubes. In the middle 
of the tube a ring of glass, as narrow as pos- 
sible, must be made thoroughly soft. The 
hands are then separated a little, to cause 
a contraction iu diameter at the hot and 
soft part. The point of the flame must now 
be directed, not upon the narrowest part of the tube, but upon 
what is to be the bottom of the closed tube. This point is indi- 
cated by the line a in Fig 34. By withdrawing the right hand, 
the narrow part of the tube is attenuated, and finally melted off, 
leaving both halves of the original tube closed at one end, but not 
of the same form; the right-hand half is drawn out into a long 
point, the other is more roundly closed. It is not possible to close 
handsomely the two pieces at once. The tube is seldom perfectly 
finished by the operations; a superfluous knob of glass generally 
remains upon the end. If small it may be got rid of by heating the 
Whole end of the tube, and blowing moderately with the mouth into 
Fig. 33. 
Fig. 34. § 86 
MANIPULATION OF GLASS. 
XXXLX 
the open end. The knob, being hotter, and therefore softer than 
any other part, yields to the pressure from within, spreads out and 
disappears. If the knob is large, it may be drawn off by sticking 
to it a fragment of tube, and then softening the glass above the 
junction. The same process may be applied to the too pointed end 
of the right-hand half of the original tube, or to any misshapen 
result of an unsuccessful attempt to close a tube, or to any bit of 
tube which is too short to make two closed tubes. When the 
closed end of a tube is too thin, it may be strengthened by keep- 
ing the whole end at a red heat for two or three minutes, turn- 
ing the tube constantly between the fingers. It may be said 
in general of all the preceding operations before the lamp, that 
success depends on keeping the tube to be heated in constant 
rotation, in order to secure a uniform temperature on all sides of 
the tube. 
80. Blowing Bulbs. — Bulb-tubes, like the one represented in 
Fig. 35, are employed for reducing substances capable of forming 
sublimates upon the cold walls of 
the tube. They are readily made 
fiom bits of tubing, in the flame of 
Bunsen’s burner, or in the common 
blowpipe flame. 
If the bulb desired is large in 
proportion to the size of the tube 
on which it is to be made, the walls 
of the tube must be thickened by rotation in the flame before the 
bulb can be blown. The thickened portion of glass is then to be 
heated to a cherry-red, suddenly withdrawn from the flame, and 
expanded while hot by steadily blowing, or rather pressing air, 
into the tube with the mouth; the tube must be constantly turned 
on its axis, not only while in the flame, but also while the bulb is 
being blown. If too strong or too sudden a pressure be exerted 
with the mouth, the bulb will be extremely thin and quite useless. 
By watching the expanding glass, the proper moment for arresting 
the pressure may usually be determined. If the bulb obtained be 
not large enough, it may be reheated and enlarged by blowing into 
it again, provided that a sufficient thickness of glass remain. 
If a bulb is to be blown in the middle of a piece of tubing, the 
thickening is effected by gently pressing the ends of the tube to- 
gether while the glass is red-hot in the place where the bulb Is 
to be. 
It is sometimes necessary to make a hole in the side of a tube ol 
Fig. 35. CAOUTCHOUC. 
§ 87 
other thin glass apparatus. This may be done by directing a pointed 
flame from the blast-lamp upon the place where the hole is to be, 
until a small spot is red-hot, and then blowing forcibly into one end 
of the tube while the other end is closed by the finger; at the hot 
spot the glass is blown out into a thin bubble, which bursts or 
may be easily broken off, leaving an aperture in the side of the 
tube. 
It is hoped that these few directions will enable the attentive 
student to perform, sufficiently well, all the manipulations with 
glass tubes which the experiments described in this manual re- 
quire. Much practice will alone give a perfect mastery of the de- 
tails of glass-blowing. 
87. Caoutchouc.—Vulcanized caoutchouc is a most useful 
substance in the laboratory, on account of its elasticity and because 
it resists so well most of the corrosive substances with which the 
chemist It is used in three forms : (1) in tubing of various 
diameters comparable with the sizes of glass tubing; (2) in stop- 
pers of various sizes to replace corks; (3) in sheets. Caoutchouc 
tubing may be used to conduct all gases and liquids which do not 
corrode its substance, provided that the pressure under which the 
gas or liquid flows be not greater, or their temperature higher, 
than the texture of the tubing can endure. The flexibility of the 
tubing is a very obvious advantage in a great variety of cases. 
Short pieces of such tubing, a few centimetres in length, are much 
used, under the name of connectors, to make flexible joints in ap- 
paratus, of which glass tubing forms part; flexible joints add greatly 
to the durability of such apparatus, because long glass tubes bent 
at several angles and connected with heavy objects, like globes, 
bottles or flasks full of liquid, are almost certain to break even with 
the most careful usage; gas delivery-tubes, and all considerable 
lengths of glass tubing should invariably be divided at one or more 
places, and the pieces joined agai l with caoutchouc connectors. 
The ends of glass tubing to be thus connected should be squarely 
cut, and then rounded in the lamp, in order that no sharp edges 
may cut the caoutchouc; the internal diameter of the caoutchouc 
tube must be a little smaller than the external diameter of the glass 
tubes; the slipping on of the connector is facilitated by wetting 
the glass. In some cases of delicate quantitative manipulations, in 
which the tightest possible joints must be secured, the caoutchouc 
connector is bound on to the glass tube with a silk or smooth linen 
string; the string is passed as tightly as possible twice round 
the connector and tied with a square knot; the string should be § 88 
CA 0 UTGIIO TIC. — CORKS. 
moistened in order to prevent it from slipping while the knot is 
tying. 
Caoutchouc stoppers are much more durable than corks, and are in 
every respect to be preferred, if of proper shape and good quality; 
the common American stoppers are inferior in quality, and being chiefly 
intended for wine bottles, are apt to be too conical. Caoutchouc 
stoppers can be bored, like corks (see the next section), by means 
of suitable cutters, and glass tubes can be fitted into the holes 
thus made with a tightness unattainable with corks ; but these stop- 
pers may be bought already provided with one, two, and three holes. 
It is not well to lay in a large stock of caoutchouc stoppers, for 
though they last a long time when in constant use, they not infre- 
quently deteriorate when kept in store, becoming hard and some- 
what brittle with age. 
Pieces of thin sheet caoutchouc are very conveniently used for 
making tight joints between large tubes of two different sizes, or 
between the neck of a flask, or bottle, and a large tube which enters 
it, or between the neck of a retort and the receiver into which it 
enters. A sufficiently broad and long piece of sheet caoutchouc is 
considerably stretched, wrapped tightly over the glass parts adjoin- 
ing the aperture to be closed, and secured in place by a string 
wound closely about it and tied with a square knot. 
88. Corks.—It is often very difficult to obtain sound, elastic 
corks of fine grain and of size suitable for large flasks and wide- 
mouthed bottles. On this account, bottles with mouths not too large 
to be closed with a cork cut across the grain, should be chosen for 
chemical uses, in preference to bottles which require large corks or 
bungs cut with the grain, and therefore offering continuous chanuels 
for the passage of gases, or even liquids. The kinds sold as cham- 
pagne corks and as satin corks for phials are suitable for chemical 
use. The best corks generally need to be softened before using; this 
softening may be effected by I’olling the cork under aboard upon the 
table, or under the foot upon the clean floor, or by gently squeezing 
it on all sides with the well-known tool expressly adapted for this 
purpose, and thence called a cork-squeezer. Steaming also softens 
the hardest corks. 
Corks must often be cut with cleanness and precision; a sharp, 
thin knife, such as shoemakers use, is desirable for this purpose. 
When a cork has been pared down to reduce its diameter, a flat file 
may be employed in finishing; the file must be fine enough to leave 
a smooth surface upon the cork; in filing a cork, a cylindrical, not a 
tonical, form should be aimed at. XLII 
CORKS. 
§ 88 
In boring boles through corks to receive glass tubes, a hollovr 
cylinder of sheet brass sharpened at one end 
is a very convenient tool. Fig. 36 represents 
a set of such little cylinders of graduated 
sizes, slipping one within the other into a 
very compact form; a stout wire of the same 
length as the cylinders, accompanies the set, 
and serves a double purpose, — passed trans- 
versely through two holes in the cap which 
terminates each cylinder, it gives the hand a 
better grasp of the tool while penetrating the 
cork; and when the hole is made, the wire 
thrust through an opening in the top of the 
cap expels the little cylinder of cork which 
else would remain in the cutting cylinder of 
brass. That cutter, whose diameter is next 
below that of the glass tube to be inserted 
in the cork, is always to be selected, and if 
the hole it makes is too small, a round file must be used to enlarge 
the aperture; the round file, also, often comes in play to smooth the 
rough sides of a hole made by a dull cork-borer. A pair of small 
calipers is a very convenient, though by no means essential, tool in 
determining which size of cutter to employ. A flask which presents 
sharp or rough edges at the mouth can seldom be tightly corked, for 
the cork cannot be introduced into the neck without beiug cut or 
roughened; such sharp edges must be rounded in the lamp. In 
thrusting glass tubes through bored corks, the following directions 
are to be observed: (1.) The end of the tube must not present a 
sharp edge capable of cutting the cork. (2.) The tube should be 
grasped very close to the cork, in order to escape cutting the hand 
which holds the cork, should the tube break; by observing this pre- 
caution, the chief cause of breakage, viz., irregular lateral pressure, 
will be at the same time avoided. (3.) A funuel-tube must never 
be held by the funnel in driving it through a cork, nor a bent tube 
grasped at the bend, uuless the bend comes immediately above the 
cork. (4.) If the tube goes very hard through the cork, the appli- 
cation of a little soap and water will facilitate its passage, but if 
soap is used, the tube can seldom be withdrawn from the cork after 
the latter has become dry. (5.) The tube must not be pushed 
straight into the cork, but screwed in, as it were, with a slow 
rotary as well as onward motion. Joints made with corks should 
always be tested before the apparatus is used, by blowing into the 
apparatus, and at the same time stopping up all legitimate outlets. 
Fig. 38. §89 
GAS- GENERA TORS. 
Any leakage is revealed by the disappearance of the pressure created. 
To the same end, air may be sucked out of an apparatus and its 
tightness proved by the permanence of the partial vacuum. To at- 
tempt to use a leaky cork is generally to waste time and labor, and 
to insure the failure of the experiment. 
89. Gas-bottle. — Figure 37 represents a gas-bottle fitted for 
evolving sulphuretted hydrogen, carbonic acid, and other gases 
which can be prepared without heat. A straight 
glass tube of convenient length is slipped into the 
caoutchouc connector at the right to carry the gas 
into the solution to be tested. The neck of the 
bottle should be rather narrow, since it is difficult 
to obtain tight stoppers for bottles with wide 
mouths, but must nevertheless be wide enough to 
admit a cork, or better a caoutchouc stopper, 
capable of carrying both the delivery and the this- 
tle tubes. 
To prepare, for example, sulphuretted hydrogen 
gas, put a tablespoonful of fragments of sulphide 
of iron in the bottom of the bottle, replace the 
cork with its tubes, and press, or rather twist, it 
tightly into the neck of the bottle; pour in enough 
water through the thistle-tube to seal the lower end of that tube, 
and finally as much concentrated sulphuric acid as would be equal 
to a tenth or a twelfth of the volume of the water. 
At the start it is well thus to mix strong acid with the water in 
the bottle, for the heat generated by the union of the two liquids 
serves to warm the apparatus, and to facilitate the decomposition 
of the sulphide of iron; but it must be remembered that strong 
sulphuric acid is by itself unfit for generating sulphuretted hydro- 
gen, and that the evolution of gas would be checked if much of it 
were added. When the flow of gas ceases, pour a small portion of 
dilute sulphuric acid into the thistle-tube, and repeat this operation 
as often as may be necessary to maintain a constant stream of gas. 
Dilute acid fit for this purpose may be prepared by mixing 1 volume 
of strong sulphuric acid with If volumes of water; — the wate, 
should be well stirred and the acid poured into it in a fine stream. 
In precipitating the members of Classes II and III with sulphur- 
etted hydrogen, the gas delivery-tube should not dip deeper than 
about an inch beneath the surface of the liquid in the beaker. A 
rapid current of gas is useless and wasteful. The best method of 
operating is to pour dilute sulphuric acid into the thistle-tube iu 
Fig. 37. XLIV 
GAS- GENERA TOES. 
$ 90 
such quantity that the bubbles of gas may follow one another 
slowly enough to be counted without effort. 
90. Self-regulating Gas-generator.— An apparatus which 
is always ready to deliver a constant stream of sulphuretted hydro- 
gen, and yet does not generate the gas except when it is imme- 
diately wanted for use, is a great convenience in an active labora- 
tory. The same remark applies to the 
two gases, hydrogen and carbonic acid, 
which are likewise used in considerable 
quantities in quantitative analysis, and 
which can be conveniently generated in 
precisely the same form of apparatus 
which is advantageous for sulphuretted 
hydrogen. Such a generator may be 
made of divers dimensions. The fol- 
lowing directions, with the accompany- 
ing figure (Fig. 38), will enable the 
student to construct an apparatus of 
convenient size. Procure a glass cylin- 
der 20 or 25 c. m. in diameter and 30 or 
35 c. m. high; ribbed candy jars are 
sometimes to be had of about this size; 
procure also a stout tubulated bell-glass 
10 or 12 c. m. wide and 5 or 7 c. m. shorter than the cylinder. Get 
a basket of sheet-lead 7.5 c. m. deep and 2.5 c. m. narrower than 
the bell-glass, and bore a number of small holes in the sides and 
bottom of this basket. Cast a circular plate of lead 7 m. m. thick 
and of a diameter 4 c. m. larger than that of the glass cylinder; on 
what is intended for its under side solder three equidistant leaden 
strips, or a continuous ring of lead, to keep the plate in proper posi- 
tion as a cover for the cylinder. Fit tightly to each end of a good 
brass gas-cock a piece of brass tube 8 c. m. long, 1.5 to 2 c. m. wide, 
and stout in metal. Perforate the centre of the leaden plate, so that 
one of these tubes will snugly pass through the orifice, and secure 
it by solder, leaving 5 c. m. of the tube projecting below the plate. 
Attach to the lower end of this tube a stout hook on which to hang 
the leaden basket. By means of a sound cork and common sealing- 
wax, or a cement made of oil mixed with red and white lead, fasten 
this tube into the tubulure of the bell-glass air-tight, and so firmly 
that the joint will bear a weight of several pounds. Hang the 
basket by means of copper wire within the bell 5 c. m. above the 
bottom of the latter. To the tube which extends above the stop* 
Fig. 38. § 91 
MOB TABS. 
XLV 
cock attach by a good cork the neck of a tubulated receiver of 100 
or 150 c. c. capacity, the interior of which has been loosely stuffed 
with cotton. Into the second tubulure of the receiver fit tightly the 
delivery-tube carrying a caoutchouc connector; into this connector 
can be fitted a tube adapted to convey the gas in any desired direc- 
tion. When many persons use the same generator, each person 
must bring his own tube. 
To charge the apparatus, fill the cylinder with dilute acid to within 
10 or 12 c. m. of the top, fill the basket with fragments of sulphide 
of iron, hang the basket in the bell, and put the bell-glass full of air 
Into its place with the stop-cock closed. On opening the cock, the 
weight of the acid expels the air from the bell, the acid comes in 
contact with the solid in the basket, and a steady supply of gas is 
generated until either the acid is saturated or the solid dissolved; if 
the cock be closed, the gas accumulates in the bell, and pushes the 
acid below the basket so that all action ceases. In cold weather 
the apparatus must be kept in a warm place. For generating sul- 
phuretted hydrogen, sulphuric acid diluted with fourteen parts of 
water is used; for hydrogen, zinc and sulphuric acid diluted with 
four or five parts of water; while for carbonic acid, chalk and muri- 
atic acid diluted with two or three parts of water, should be taken. 
91. Mortars. — Whenever the substance to be analyzed occurs 
in the form of large pieces or coarse powder, it should, as a general 
rule, be pulverized by mechanical means before subjecting it to the 
action of solvents. Mortars of iron, steel, agate or porcelain are 
used for this purpose, according to the character of tbe substance 
to be powdered. 
An iron mortar is useful for coarse work and for effecting the first 
rough breaking up of substances which are subsequently powdered 
in the agate or porcelain mortar. If there be any risk of fragments 
being thrown out of the mortar, it should be covered with a cloth or 
piece of stiff paper, having a hole in the middle through which the 
pestle may be passed. Instead of the common iron mortar, a small 
steel mortar, of the kind called diamond mortars by dealers in chem- 
ical ware, may be used for crushing minerals. Pieces of stone, 
minerals, and lumps of brittle metals may be safely broken into 
fragments suitable for the mortar by wrapping them in strong 
paper, laying them so enclosed upon an anvil and striking them 
with a heavy hammer. The paper envelope retains the broken par- 
ticles which might otherwise fly about in a dangerous manner, and 
be lost. 
The best porcelain mortars are those known by the name of XLVI 
§§ 91, 92 
MOli TABS. — SPATULA. 
Wedgewood-ware, but there are many cheaper substitutes. Porce- 
lain mortars will not bear sharp and heavy blows; they are intended 
rather for grinding or triturating saline substances than for ham- 
mering; the pestle may either be formed of one piece of porcelain, 
or a piece of porcelain cemented to a wooden handle; the latter is 
the less desirable form of pestle. Ungl&zed porcelain mortars are 
to be preferred. In selecting mortars, the following points should 
be attended to, — 1st, the mortar should not be porous; it ought 
not to absorb strong acids or any colored fluid, even if such liquids 
be allowed to stand for hours in the mortar; 2d, it should be very 
hard, and its pestle should be of the same hardness; 3d, it should 
be sound; 4th, it should have a lip for the convenience of pouring 
out liquids and fine powders. As a rule, porcelain mortars will not 
endure sudden changes of temperature. They may be cleaned by 
rubbing in them a little sand soaked in nitric or sulphuric acid, or 
if acids are not appropriate, in caustic soda. 
Agate mortars are only intended for trituration; a blow would 
break them. They are exceedingly hard, and impermeable. The 
material is so precious and so hard to work, that agate mortars are 
always small. The pestles are generally inconveniently short, — a 
difficulty which may be remedied by fitting the agate pestle into a 
wooden handle. 
In all grinding operations in mortars, whether of porcelain or 
agate, it is expedient to put only a small quantity of the substance 
to be powdered into the mortar at once. The operation of powder- 
iug will be facilitated by sifting the matter as fast as it is powdered, 
returning to the mortar the particles which are too large to pass 
through the sieve. 
92. Spatlllse. — For transferring substances in powder, or in 
small grains or crystals, from one vessel to another, spatulae and 
scoops made of horn or bone are convenient tools. A coarse bone 
paper-knife makes a good spatula for laboratory use. Cards, free 
from glaze and enamel, are excellent substitutes for spatuhe. 
Note. — In the place of the “ Bunsen pump ” mentioned in §§ 72 
and 75,may be used, where there is sufficient head of water, “ a jet- 
aspirator ” described by Professor Ricl>ards in the “ The American 
Journal of Science,” VIII T874), p. 412. The laboratories of the 
Institute of Technology and some other laboratories are now fur- 
nished with such apparatus (made of brass, by Thomas F. McGann, 
101 Portland St., Boston), both for ordinary filtration and for driv- 
ing the blast-lamps. INDEX. 
Acetate of Leap, as reagent, vii. 
sodium, as reagent, v. 
Acetates, tests for, 87. 
Acetic acid, as reagent, ii. 
Acid solutions, 103,105. 
Alcohol, as reagent, ix. 
Alkaline solutions, 103. 
Aluminates, precipitated with 
Class IV, 37. 
Aluminum, confirmatory test for, 
41. 
a member of Class IV, 
11, 37. 
precipitated as hydrate, 
11, 38. 
Ammonia-water, as reagent, iii. 
Ammonium-salts, testing for, 92, 
126. 
Antimony, confirmatory test for, 33. 
converted into an insol- 
uble oxide by HN03, 
31, 123. 
see sulphide of. 
globule, brittle, 95. 
a member of Class III, 
10, 29. 
precipitated as sulphide, 
10, 29. 
presence of indicated, 
105. 
spots distinguished from 
arsenic spots, 33. 
teroxide of, as a subli- 
mate, 93. 
Aqua regia, how prepared, ii. 
its use as a solvent, 101. 
Argand spirit-lamp, xxviii. 
Arseniates, test for, 78. 
Arsenic, confirmatory test for,31,32. 
a member of Class III, 10, 
29. 
presence of indicated, 35. 
see sulphide of. 
separation as sulphide, 10, 
29. 
as a sublimate, 93. 
Arsenic acid, tests for, 31, 78. 
Arsenious acid, how distinguished 
from arsenic 
acid, 78. 
as a sublimate, 93. 
tests for, 78. 
Arsenites, tests for, 78. 
Ash of charcoal, 95. 
Barium, a member of Class VI, 13, 
53. 
precipitated as carbonate, 
13, 53. 
precipitated as chromate, 
54. 
salts soluble in ammonia- 
cal solutions, 69. 
test for certain classes of 
salts, 07. 
Beakers, xv. 
Biborate of sodium, as reagent, v. 
Bichloride of platinum, as reagent, 
how prepared, viii. 
Bichromate of potassium, as rea- 
gent, vi. 
Bismuth, confirmatory test for, 24. 
globule, brittle, 95- 
a member of Class II, 9, 
21. 
precipitated as hydrate, 
.24. 
precipitated as sulphide, 
9,21. 
presence of indicated, 28, 
105. 
Blast-lamps, xxv. 
Blowers, xxvi. 
Blowing bulbs, xxxix. 
Blowpipe, xxx. 
how to use, xxxi. 
lamp, xxx. 
Boracic acid, precipitated from an 
alkaline solution, 
104. 
tests for, 81. 
Borates, tests for, 81. 
Borax-bead, how to dilute, 113, 
“ « make, 11?, INDEX. 
Bottles, how to handle, xiii. 
Bromides, tests for, 84. 
Bromine, tests for, 84. 
Bunsen’s burner, xxiv. 
filter-pump, xx. 
Cadmium, a member of Class II, 
9, 24. 
precipitated as sulphide, 
9, 24. 
presence of indicated, 27. 
separation of, 24. 
Calcium, a member of Class VI, 
13, 53. 
precipitated as carbonate, 
13, 53. 
precipitated as oxalate, 
55. 
tests for certain classes 
of salts, 70. 
Caoutchouc stoppers, xli. 
tubing, xl. 
Carbonate of ammonium, as re- 
agent, iii. 
Carbonate of sodium, as reagent, 
how purified, v. 
Carbonates, tests for, 75. 
Carbonic acid, tests for, 75. 
Caustic soda solution, how prepared 
and kept, iv. 
Charcoal for blowpipe use, 94. 
Chlorates, tests for, 86. 
Chloride of ammonium, reagent, iv. 
uses of, 11, 
45, 57. 
Chloride of barium, as reagent, vii. 
Chloride of calcium, as reagent, 
how prepared, vii. 
Chloride of lead, solubility of, 10. 
Chloride of mercury, as reagent, 
viii. 
Chloride of silver soluble in ammo- 
nia-water, 18. 
Chlorides, tests for, 71, 83. 
Chlorhydric acid, as reagent, i. 
its application as 
a solvent, 99. 
Chlorine, tests for, 71, 83. 
Chromate of lead, a test for chro- 
mium, 40. 
Chromate of potassium, reagent, 
vi. 
Chromates, barium test for, 68. 
reduction of by H2S, 
28, 77. 
tests for, 77. 
Chrome-iron-ore, hard to decom- 
pose, 114. 
Chromic-oxide, hard to decompose, 
114. 
Chromites, precipiated with Class 
IV, 37. 
Chromium, a member of Class IV, 
11, 37. 
detected as chromate 
of sodium, 40. 
gives a green borax- 
bead, 114. 
precipitated as hydrate, 
11, 37. 
presence of indicated, 
46. 
Class, term defined, 5. 
Class I, defined, 6. 
how to precipitate, 17. 
Class II, defined, 7. 
how to precipitate, 21. 
Class III, defined, 7. 
Class III, precipitation of, 29. 
Class IV, defined, 10. 
how to precipitate, 38, 45. 
salts precipitated with, 
37. 
Class V, defined, 12. 
how to precipitate, 47, 52. 
Class VI, defined, 13. 
how to precipitate, 53,57. 
Class VII, defined, 13. 
how isolated, 14, 61. 
Clay chimney for Bunsen’s burner 
xxviii. 
Closed-tube test, 90. 
Cobalt, member of Class V, 12, 47. 
blowpipe test for, 49. 
confirmatory test for, 50. 
precipitated as sulphide, 12, 
47. 
presence of indicated, 52. 
Copper, member of Class II, 9, 21. 
confirmatory test for, 26. 
gives blue solutions, 24. 
globule described, 95, 96. 
precipitated as sulphide, 9, 
21. 
presence of indicated, 28. 
Cork-cutters, xlii. 
Corks, xli. 
to force tubes through, xlii. 
Cyanide of mercury, to detect cya- 
nogen in, 76. 
Cyanide of potassium, reagent, vi. 
Cyanides, tests for, 74, 75. 
Cyanogen, tests for, 74, 75. 
Deflagration, 119. 
Dissolving in acids, 99. 
in water, 99. 
Effervescence, what it indicates. 
74. INDEX. 
XLIX 
Elements, identified by compounds, 
2. 
Elements, 34 treated of, 1. 
Etching glass, a test for fluorine,82. 
Evaporation test, applied to a li- 
quid, 125. 
Ferri- and Ferro-cyanides of po- 
tassium, as reagents, vi. 
Ferric chloride, as reagent, viii. 
Filtering, xv. 
Filter-stand, xvii. 
Filtration, rapid, xviii. 
Flasks, xv. 
Fluoride of silicon, a test for fluo- 
rine and silicon, 83. 
Fluorides, tests for, 82. 
Fluorine, tests for, 82. 
to be sought in an insolu- 
ble mineral, 114, 117. 
Folding filters, xvi. 
Funnels, xv. 
Fused minerals, how treated, 115. 
Fusion with acid sulphate of so- 
dium, 119. 
with CaC03 and 1ST H4C1,118. 
with carbonate of sodium, 114. 
Fusions in platinum crucibles, 
xxvii. 
Gas-bottle, xliii. 
Gas-generator, self-regulating, xliv. 
General reagent, defined, 6. 
General reagents for acids, 66. 
General reagents to be used in a 
certain order, 16. 
Glass, bending and closing tubes, 
xxxvi. 
cutting and cracking it, xxxv. 
tubing, xxxiv. 
Gold globule, described, 95, 96. 
insoluble in HNO3, 123. 
a member of Class III, 10, 29. 
presence of indicated, 35. 
purple of Cassius test for, 123. 
Hydrogen, its presence inferred, 
64. 
Hyponitric acid, 92. 
Hyposulphites, tests for, 77. 
Indigo solution, how prepared, ix. 
Insoluble substances, 110. 
Iodides, tests for, 85. 
Iodine, tests for, 85. 
Iodo-starch paper, vii. 
Iron, discrimination between fer- 
rous and ferric salts, 44. 
Hon, to be converted into ferric 
salt, 44. 
Iron, a member of Class IV, 11, 37. 
precipitated as hydrate, 11,37. 
presence of indicated, 46. 
Prussian blue test for, 42. 
reaction in borax bead, 114. 
Iron stand, xxviii. 
Labelling, importance of, 8. 
Lamps, xxiii. 
Lead, belongs to two classes, 10. 
globule described, 95. 
Lead a member of Class I, 6, 17. 
“ “ “ 11,9,21. 
paper, bow prepared, vii. 
precipitated as sulphide, 9,21. 
precipitation rs chloride, 17. 
precipitation as sulphate, 18, 
23. 
presence of indicated, 27. 
the sulphate changed to chro- 
mate, 23. 
Lime-water, as reagent, vii. 
Liquids to be tested with litmus, 
125. 
Litmus paper, how prepared, ix. 
Magnesium, as member of Class 
VII, 13, 59. 
Magnesium, precipitated as phos- 
phate of Mg and 
NH4, 14, 59. 
separation as oxide, 
61. 
Manganate of sodium, 42. 
Manganese, confirmatory test, 42. 
precipitated with Class 
IV, 37. 
precipitation of, as hy- 
drate, 48. 
presence indicated, 52. 
Mercuric chloride, as reagent, viii. 
Mercurous chloride, reaction with 
ammonia-water, 19. 
Mercury, belongs to two classes, 10 
compounds as sublimates, 
92. 
member of Class I, 6, 17. 
member of Class II, 9, 21. 
precipitation as subchlor- 
ide, 17. 
presence of indicated, 27. 
reduction of the metal in 
a closed tube, 19. 
reduction of the metal on 
copper, 23. 
separation as sulphide, 9, 
21. 
as a sublimate, 92. 
Metallic elements, 7 classes of, 15. 
globules described, 94. L 
INDEX. 
Metallic globules tested in oxidizing 
flame, 95. 
Metals, action of HN03 on, 121. 
used in the arts, 121. 
Molybdate of ammonium, a test 
for phosphates, 79. 
Molybdate of ammonium, as re- 
agent, how prepared, iv. 
Mortars xlv. 
Neutral solutions, 103. 
Nickel, blowpipe test for, 49. 
member of Class V, 12, 47. 
precipitated as cyanide, 50. 
precipitated as sulphide, 12, 
47. 
presence of indicated, 52. 
Nitrate of barium, as reagent, vii. 
when used, 69. 
Nitrate of cobalt, as reagent, viii. 
Nitrate of potassium, as reagent, vi. 
Nitrate of silver, as reagent, vii. 
Nitrate of sodium, as reagent, v. 
Nitrates, tests for, 85. 
Nitric acid, action on metals, 121. 
dilute, as reagent, ii. 
strong, as reagent, ii. 
tests for, 85. 
when to be used as a 
solvent, 99, 100,121. 
Nitrite of potassium, as reagent, 
how prepared, vi. 
Non-nietallic elements, how de- 
tected, 64. 
Organic Matter, detection of, 91. 
how destroyed, 97. 
Organic substances hinder the pre- 
cipitation of Class IV, 47. 
Oxalate of ammonium, reagent, iv. 
Oxalates converted into carbonates, 
5G. 
tests for, 80. 
Oxalates, acid as a sublimate, 93. 
as reagent, ii. 
tests for, 80. 
Oxide of manganese, as reagent, 
viii. 
Oxide of mercury, as reagent, viii. 
Oxidizing blowpipe flame, viii. 
Oxygen, how recognized, 91. 
its presence inferred, 64. 
Phosphate of Calcium, presence 
of indicated, 46. 
Phosphate of sodium, as reagent, v. 
Phosphates, precipitated with Class 
IV, 37. 
Phosphates, tests for, 79. 
Phosphoric acid, tests for, 79. 
Pincers, xxxiii. 
Platinum, a member of Class III, 
10, 29. 
crucibles, xxxiii. 
foil, xxxii. 
insoluble in HN03,123. 
presence of indicated, 35, 
test for, 123. 
wire, xxxiii. 
Porcelain crucibles, xxiii. 
dishes, xxiii. 
Potassium, precipitated as cliloro- 
platinate, 00. 
flame-test for, 00. 
a member of Class VII, 
13, 59. 
Precipitates compacted by boiling 
and shaking, 25, 47. 
Preliminary examination of a 
liquid, 125. 
Preliminary treatment, 90. 
of a pure 
metal or 
alloy,121. 
Proto flfloride of tin, as reagent, viii. 
Prussian blue, a test for iron, 42. 
Pulverizing, xlv. 
Qualitative Analysis defined, 1. 
Reagent Bottles, xiii. 
Reagents, i-ix. 
Reducing blowpipe flame, xxxii. 
Reduction test, 81. 
how to perform with 
delicacy, 111. 
Reduction test, to be applied to in* 
soluble substances, 111. 
Salts, kinds of considered, 65. 
soluble in water, 102. 
Sand-bath, xxix. 
Separation of two elements, 4. 
Silicates, alkaline, decomposed by 
acids, 82, 104. 
decomposed by 
chloride of am- 
monium, 82. 
Silicates, the commonest of insolu- 
ble substances, 118. 
Silicic acid, precipitated from an 
alkalire solution, 104. 
Silver, a member of Class I, 6, 17. 
globule described, 95. 
precipitated by reducing 
agents, 73. 
precipitation as chloride, 17. 
salts, insoluble in dilute 
nitric acid, 17. 
salts, sundry, colors of, 72. INDEX. 
Silver, see chloride of. 
test for certain classes of 
salts, 71. 
Slaked lime, as reagent, vii. 
Sodium, crystallization of chloro- 
platinate of, 61. 
Sodium, flame-test for, 60. 
a member of Class YU, 
13, 59. 
Solubilities, Table of, 108, 109. 
Solution of indigo, as reagent, ix. 
Solutions of known composition, x. 
Solvents, the order of use, 98. 
Spatulae, xlvi. 
Special tests for non-metallic ele- 
ments, 74. 
Starch paste, how prepared, ix. 
Starch-test for bromine, 84. 
iodine, 85. 
Stirring rods, xxxiv. 
Stoppers, stuck, how to loosen, xiv. 
Strontium, a member of Class VI, 
13, 53. 
precipitated as carbon- 
ate, 13, 53. 
as sulphate, 
55. 
Sublimates on charcoal while re- 
ducing metals, 96. 
Sulphate of copper, as reagent, viii. 
Sulphate of magnesium, as reagent, 
how mixed, vii. 
Sulphate of magnesium, a test for 
arseniates and phosphates, 31, 79. 
Sulphate of sodium, acid, how pre- 
pared, v. 
Sulphates, barium test for, 69. 
how to detect, 79. 
insoluble, reduced to sul- 
phides, 112. 
Sulphate of potassium, as reagent, 
how prepared, v. 
Sulphide of arsenic, oxidation of, 30. 
Sulphide of tin. oxidation of, 30. 
Sulphides, tests for, 76. 
Sulphides of arsenic, as sublimates, 
93. 
Sulphites, tests for, 76. 
Sulphur, as a sublimate, 92. 
Sulphuretted hydrogen, decom- 
posed by oxidizing agents, 28. 
Sulphuretted hydrogen, how pre- 
pared, iii. 
Sulphuretted hydrogen, how to em- 
ploy it, 7, 21. 
Sulphuretted hydrogen, necessity 
of expelling, 45. 
Sulphuretted hydrogen water, hew 
prepared and kept, lii. 
Sulphuric acid, as reagert, ii. 
Sulphuric acid, tests for, 79. 
Sulphurous acid, 7(5. 
Sulphur, precipitation of, 20, 28. 
Sulphydrate of ammonium, as re- 
agent, iii. 
sodium, as re- 
agent, v. 
Table for Class 1,19. 
II, 26. 
III, 34. 
IY, 43. 
Y, 51. 
YI, 56. 
the separation of the 7 
classes of metallic ele- 
ments, 62. 
Table of solubilities, 108, 109. 
Table of the seven classes of metallio 
elements, 15. 
Tartaric acid, as reagent, ii. 
tests for, 80. 
Tartrates, tests for, 80. 
Test-tube rack, xv. 
Test-tubes, xiv. 
Tin, a member of Class III, 10, 29. 
confirmatory test for, 34. 
converted into an insoluble ox- 
ide by HN03, 31, 123. 
Tin globule, described, 95, 96. 
presence of indicated, 35. 
reduction of by zinc, 33. 
see sulphide of. 
Triangle, xxix. 
Turmeric paper, how prepared, 81. 
Utensils, list of, xii. 
Water, ix. 
Water-bath, xxix. 
Wash-bottle, xxxiii. 
Wire-gauze, xxviii. 
Zinc, a member of Class Y, 12, 47. 
as reagent, viii. 
precipitated as chromate, 49. 
precipitated as sulphide, 12, 
47, 41. 
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Young Engineer. By Wm. Findlay Shunk, C. E., Chief Engineer of 
the Construction of the Metropolitan Elevated Railroad. 
Adams’ Sewers and Drains. 
Octavo. Cloth. $2.50. 
Sewers and Drains for Populous Districts. Embracing Rules and 
Formulas for the dimensions and construction of works of Sanitary 
Engineers. By Julius Adams, C. E. 
MeElroy’s Papers on Hydraulic Engineering. 
8vo. Paper. 50 cents. 
The Hempstead Storage Reservoir op Brooklyn, its Engineering 
Theory and Results. By Samuel McElroy, C. E. 
Spinoza’s Ethics. 
The Ethics op Benedict de Spinoza. Demonstrated after the method 
of Geometers, and Divided into Five Parts. From the Latin ; with an 
introductory Sketch of his Life and Writings. 
8vo. Cloth. $3.00.