James Freeman Sellers.

An elementary treatise on qualitative chemical analysis online

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QUALITAF1V



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INAIY.Sf



MEDICAL




COLLEGE OF PHARMACY



California College of Pharmacy



AN ELEMENTARY TREATISE ON

QUALITATIVE CHEMICAL

ANALYSIS



BY

J. F.jJKLLERS

PROFESSOR OF CHEMISTRY, MERCER UNIVERSITY, GEORGIA



California CoHega of Pharmacy



REVISED EDITION



GINN AND COMPANY

BOSTON NEW YORK CHICAGO LONDON

"K



COPYRIGHT, 1900, 1909
BY J. F. SELLERS



ALL BIGHTS KESEBVED



(.INN & COMPANY PRO-
PRIETORS BOSTON U.S.A.



46
1)



PEEFACE

So many books on analytical chemistry are already in
print that the question may be raised whether it is wise
to add still another to their number ; and therefore the
author desires to present the following reasons which seem
to him to justify the publication of the present work.

Most writers on analytical chemistry have gone either
to the one or the other of two extremes. First, there are
those who, like Fresenius or Prescott and Johnson, have
endeavored to cover the entire field and to include the
whole detail of analytical chemistry. Their works are
indispensable to teachers and to students who make
chemistry a specialty ; but for beginners, who may not
give more than one year of eight or ten hours a week to
the subject, they are faj* too voluminous. On the other
hand, there are those whose ardor for brevity has led them
to the other extreme of condensing their material into
" tables " and " schemes," - by which means they have
magnified the empirical and have minimized the rational
aspect of the subject, to its considerable detriment as a
factor in liberal education.

In order to avoid either extreme the writer presents
this elementary treatise having these features :

1. A course short enough to be digested during the
time allotted in an ordinary college curriculum, but at

39971



IV PEE FA CE

the same time intended to magnify the scientific and
pedagogical nature of analytical chemistry.

2. A course both practical and progressive, practical,
in that the student can master the methods and principles
of chemical analysis, and become a practical analyst ; pro-
gressive, in that the chief aim of the book is to prepare the
student thoroughly for advanced university work.

3. A course selected from the most recent and approved
methods recorded in the best literature and verified by
actual application in the author's laboratory. Among
some of the improved methods are mentioned :

(a) Reddrop's application of normal solutions to quali-
tative analysis. Chemical News, May, 1890.

(b) Hofmann's separation of arsenic, antimony, and
tin, by modification of Marsh's test. Fresenius' Quali-
tative Analysis, 1897 edition, p. 299.

(c) Parr's separation of aluminum, chromium, and iron,
by means of sodium peroxide. This method commends
itself for its accuracy, its briefness and simplicity, and its
certainty in detecting aluminum. Other methods depend-
ing on sodium hydroxide are defective, in that the reagent
itself generally contains aluminum salts ; sodium peroxide,
by reason of its manufacture, does not contain perceptible
traces of such salts. Journ. Amer. Chem. Soc., 19, p. 341.

(d) Fresenius and Support's separation of barium,
strontium, and calcium, by means of the differences of
solubility of their nitrates in ether-alcohol. Fres. Qual.
Anal, p. 160.

(e) Hager's separation of chlorine, bromine, and iodine,
by means of the differences of solubility of their silver salts
in ammonium " sesqui " carbonate. Fres. Qual. Anal., p. 378.



PREFACE V

4. A course free, as is thought wise, from the mechan-
ical schemes in qualitative analysis. To this end, many
of the usual tables of separation are omitted, and in their
place some suggestive hints are given after the list of
reactions for each group. Thus the student is expected
and encouraged to exercise his judgment in selecting
methods of analysis.

5. A course conformable to the modern dissociation
theory of solutions. For example, why is the activity
of certain acids modified by adding the salts of those
acids j or, more specifically, why is the solvent power
of acetic acid decreased by adding some sodium acetate ?

6. A course giving more than ordinary emphasis to
the spectroscope. Though spectroscopy is not chemical
analysis, it possesses superior advantages over the chem-
ical methods in these particulars :

(a) Methods of greater exactness and readiness of
execution.

() Methods superior for the preliminary detection of
the alkali and alkali-earth metals. This is important,
especially when the alkali-earth metals are combined with
phosphoric, oxalic, and hydrofluoric acids.

(c) Methods superior for detecting certain metals, which,
under some conditions, are evasive; e.g., aluminum, man-
ganese, and magnesium.

It is obvious that the study of the theory of solution
and of spectroscopy may either be taken up in the order
of the text or reserved for the last work in the course ;
and also that these subjects may be omitted entirely if
a very elementary course is desired. In the latter case
it would be possible also to omit the discussion of the



Vl PEE FACE

analysis for the metals of the third group in the pres-
ence of phosphoric acid, and those portions of Part II
which are printed in small type.

The discussion of solutions in the brief space available
in this book is necessarily much condensed, and possibly it
is somewhat abstract and uninviting ; but in the author's
opinion its introduction is desirable. Its purpose is to
provide the student of qualitative analysis with the means
for a rational interpretation of many apparently irrational
reactions, and to help prepare him for the next stage of
his chemical education, namely, the study of quantitative
analysis, where the application of the laws of solutions
is more abundant. No other text-book on qualitative
analysis, within the author's knowledge, incorporates
this dissociation theory of solution ; but its adaptability
to qualitative instruction is shown by the fact that during
the past half decade many teachers of the subject have
devoted more or less time in their lectures to the practical
application of the theory.

In the preparation of this book the following literature
has been consulted :

1. Many of the smaller text-books on qualitative analysis,
including Noyes's, Newth's, and Volhard and Zimmer-
mann's.

2. Standard works on general and analytical chemistry,
including Watt's Chemical Dictionary; Roscoe and Schor-
lemmer's Treatise on Chemistry ; MendeleefPs Principles of
Chemistry; Ostwald's and Nernst's works on physical chem-
istry ; Vogel's, Landaur's, and Roscoe's works on spectrum
analysis ; Fresenius' works the latest editions.

3. Memoirs in American and foreign chemical journals.



PREFACE Vll

Grateful acknowledgment is made to Dr. R. W. Jones
of the University of Mississippi, for his painstaking criti-
cism of the manuscript of this little book. The author
learned the chemical alphabet and received much inspira-
tion and encouragement from this excellent teacher.

Appreciative mention also is made of the following gen-
tlemen : Dr. H. C. White of the University of Georgia,
for valuable suggestions as regards the adaptability of the
book to elementary college work; Dr. J. W. Mallet of
the University of Virginia, Dr. J. Stieglitz of the Uni-
versity of Chicago, and Dr. E. Renouf of Johns Hopkins
University, for opinions concerning modern theories of
solution; and Mr. H. V. Jackson of Mercer University,

for general assistance.

J . r . o.

MACON, GA., September, 1900

PREFACE TO SECOND EDITION

THE more important modifications made in this edition
of the book are the appending of 13 pages of reference
notes (see p. 163) and tables, revision of several of the
processes of separation, and correction of a number of
typographical errors.

For criticism and proof reading the author is indebted
to many of his friends, among whom may be mentioned
Professor W. H. Emerson and Dr. G. H. Boggs of the
Georgia School of Technology, Dr. J. P. Montgomery of
the Mississippi Agricultural and Mechanical College, Dr.
Homer V. Black of the University of Georgia, Professor
C. W. Steed of Mercer University, Professor G. P. Shingler
of Emory College, and Professor Alexander Smith of the

University of Chicago.

J. F. S.

MACON, GA., May, 1909



CONTENTS

PART I ANALYTICAL OPERATIONS

CHAPTEU PAGE

I. INTRODUCTION 1

II. THEORY OF ANALYTICAL OPERATIONS .... 5

III. METHODS OF ANALYTICAL SEPARATION .... 26

IV. FLAME COLORATION AND SPECTROSCOPY ... 50
V. LIST AND PREPARATION OF REAGENTS .... 65

VI. SYSTEMS OF ANALYTICAL EXAMINATION ... 73

PART II REACTIONS AND SEPARATIONS

VII. METALS OF GROUP I 77

VIII. METALS OF GROUP II 82

IX. METALS OF GROUP III 100

X. METALS OF GROUP IV 114

XI. METALS OF GROUP V 121

XII. METALS OF GROUP VI 126

XIII. ACIDS OF GROUP I 130

XIV. ACIDS OF GROUP II 141

XV. ACIDS OF GROUP III 148

XVI. THE SYSTEMATIC PROCEDURE OF ANALYSIS . . 151

NOTES 163

INDEX 175

ix



CHEMICAL ANALYSIS

PART I ANALYTICAL OPERATIONS



CHAPTER I

INTRODUCTION

THE science of chemistry is commonly subdivided, for
purposes ,of convenience in reference and teaching, into
several tolerably distinct branches. The usual classifi-
cation is into the main divisions of inorganic and organic
chemistry, each of which may in turn be further divided
into descriptive, theoretical, and analytical chemistry.
Furthermore, analytical chemistry may itself be sepa-
rated into the subdivisions of qualitative and quantitative
analysis ; the -former having for its object the detec-
tion of chemical elements and compounds, and the
latter the relative proportions of such substances.
Analytical chemistry is commonly taught as a dis-
tinct branch, but it is not independent of the other
divisions of the science ; and hence, in all discussions
in this book, both as to theory and manipulation, the
presumption is that the student has, in the beginning
of the course, a fair knowledge of the elements of
general chemistry.

It obviously is essential to success in analysis that
the analyst should have a clear idea of the operations

1



2 CHEMICAL ANALYSIS

involved in his work, as well as of the compounds
with which he is dealing ; and therefore, though both
manipulation and theory are assumed to have been
studied, to some extent in connection with general
chemistry, it is deemed well to review many of the
ordinary operations from the analytical standpoint.
The first part of this book is devoted largely to
such a review ; and it is earnestly recommended that
it be studied closely, and that all of the experiments
there given be carefully performed. It is true that
the time spent on this preliminary work will delay
somewhat the beginning of actual analysis ; but it is
believed that the student will be repaid in the end by
the acquisition of a clearer conception of the work and
of more skill in the manipulation of apparatus.

It should be remembered that it is far easier to form
good habits than to correct bad ones ; and so from the
beginning the attention of the student should contin-
ually be directed to the importance of the following
details which, though simple and apparently insignifi-
cant, are absolutely essential to continued success in
analysis.

CARE OF APPARATUS

(a) Keep all apparatus clean. This can best be done
by cleaning the desk and apparatus before leaving for
the day. Of course this does not apply to apparatus
connected with unfinished experiments.

(b) When vessels containing materials of unfinished
experiments are to be set aside, they should be properly
labeled.



INTRODUCTION 3

(c) Provide towels, clean rags, soap, and a covering
for the clothes, either a long apron or a workingman's
overalls.

(d) Have a place for all reagents and apparatus, and
keep them in their place. Reagents for general use
should not be kept at the individual desks. This is
a source of great annoyance and injustice to one's
neighbors.

(e) Use all care in keeping the reagents pure.
Stoppers should not be placed on the desk while using
the bottles, but held between the fingers. No foreign
pbjects should be dipped into the bottles, nor should
any excess of reagents be poured back into the
bottles.

(/) Use small quantities of reagents. It is best to
add liquid reagents, drop by drop, with frequent
shaking of the test-tube, so that secondary reactions
can be observed.

LABORATORY NOTES

Provide a well-bound notebook for the subject and
use it for nothing else. Keep accurate and methodical
records of all experiments performed. These records
should be made during or immediately following the
performance of the experiment, and not transferred or
erased afterwards. Original notes of an unsuccessful
experiment are more valuable than a well-written
description of a successful experiment, if the latter
is composed in the absence of the experiment.

Some states prescribe by law that chemists, in giving
expert testimony before the courts, shall present only



4 CHEMICAL ANALYSIS

such data as are recorded in the presence of the
experiments.

If desirable the original notes may be written on
alternate lines or pages, and other notes of interpre-
tation added at leisure. But the latter should be
recorded with differently colored ink, or otherwise
distinguished, in order that the original notes be not
confused with subsequent additions.



CHAPTER II

THEORY OF ANALYTICAL OPERATIONS

Nature of Analytical Chemistry. Analytical chemistry
has already been denned as the art of recognizing the
elements, or compounds, which may be present in any
substance ; and, as the nature of the art implies, it
commonly is practiced upon mixtures of one kind or
another. Such mixtures may be mechanical only; and
in such a case, if the elements of the mixture are
sufficiently characterized by their color, crystalline
form, or other external properties, it may be possible
to identify or even to separate them by purely mechan-
ical means. But the mixtures with which the chemist
most commonly has to deal are those in which the
strictly mechanical element plays a minor part. Such
mixtures are produced when, by any appropriate means,
two or more substances are brought into such intimate
contact that they interpenetrate each other even to
their minutest particles the molecules. We bave
examples of mixtures of this class in the air, which
practically is a homogeneous mixture of its constituent
gases and vapors ; in common " solutions," such as
are produced when any suitable material, like salt or
sugar, is treated with some liquid which, like water,
has the power of " dissolving " the material in . ques-
tion ; or in alloys, which are produced when two or

5



6 CHEMICAL ANALYSIS

more metals are united by fusion into a mass which is,
at all points, of uniform composition. Of these mix-
tures, the commonest are the solutions ; and these are
so important, from the standpoint of the analytical
chemist, that it is desirable to spend some time in a
careful study of their properties.

Solution. In a general sense a solution is the prod-
uct of the homogeneous absorption of a gas by a gas,
or of a gas by a liquid, or of a liquid by a liquid, or
of a solid by a liquid; and in recent years the term
"solid solution" has been applied to certain homo-
geneous solid mixtures of which the alloy mentioned
above may serve as the type. But specifically, in
speaking of a solution, we have in mind the liquid
product of the absorption by a liquid, called the
solvent, of a gas, a liquid, or a solid, called the
solute.

It has been found of all gases, and of some liquids,
that they are capable of mixing homogeneously with
one another in all proportions ; but, on the contrary, it
has not been found possible, under ordinary conditions,
to dissolve a gas or a solid in a liquid in any desired
proportion. Sooner or later a point is reached where
the solvent refuses to take up more of the solute ; and
at this point the solution is said to be saturated. In
most cases the application of heat to a saturated solu-
tion will enable it to absorb more of the solute; and
the application of cold will usually result in the sepa-
ration of a part of the material already dissolved. In
such cases we may recover , a portion of the solute by
the mere chilling of its saturated solution; and in cases



THEORY OF ANALYTICAL OPERATIONS 7

where the solute is practically as soluble at low tem-
peratures as at high ones, we may reach the same end
by removing a part or the whole of the solvent by
evaporation. It may be mentioned at this point that
we have still another means of separating the solute
from its solution; viz., by the addition to the solu-
tion of some material which will decrease the solubility
therein of the solute, without changing the identity of
the latter. This process of separation is of considerable
practical importance, and we shall presently have occa-
sion to refer to it again.

Experiment 1

(a) Dissolve 5 grams of potassium nitrate in 25 c.c. of dis-
tilled water, at a temperature of 15-25C. Then add succes-
sive portions of 1 gram each, shaking after each addition until
all has dissolved that the solution will hold at this temperature.
Note the total amount added and then raise the temperature of
the solution to about GO , as hot as the hand can bear without
too much discomfort, and add more of the finely powdered
salt while keeping the solution from cooling. Note the extra
amount which is needed at this temperature to saturate the
solution. Now cool the solution quickly and note the result.
Compare any material which may separate with potassium nitrate.

(7>) Dissolve 5 grams of common salt in 25 c.c, of distilled
water at 15-25. Now add successive portions of ^ gram,
shaking after each addition until the solution is saturated.
Note the total amount dissolved. Raise the temperature as in
the preceding part of the experiment, and see whether it is pos-
sible to dissolve more salt in the hot solution. Allow any un-
dissolved material to settle, and then pour off some of the clear
solution into a clean dry test-tube, and cool as much as pos-
sible. Note the result. Evaporate a portion of this solution
and compare the residue with salt.



8 CHEMICAL ANALYSIS

(c) To about 25 c.c. of a clear saturated solution of common
salt add 50 c.c. of concentrated hydrochloric acid, stirring all
the time. Note the result, allowing the mixture to stand for
some minutes. Pour off the clear liquid from any material
which may have separated, and press a little of the latter be-
tween filter papers, to remove the acid liquor. It will be well
to remove the last traces of acid by washing the residue with a
little saturated brine. Compare the residue with common salt.

It will have been seen, in the performance of these
experiments, that the recovered solute is of the same
character as the original solute. But there are forms
of solution in which this is not the case.

Experiment 2

Dissolve a small piece of zinc in dilute hydrochloric acid and
evaporate the solution to dryness. Compare the residue with
metallic zinc.

Solution of this kind may be called chemical solution, in dis-
tinction from the simple solutions of Exp. 1. It will be seen
that it involves

(1) a compound solvent HC1 + water which itself is a
simple solution ; and a solute, Zn ;

(2) a chemical reaction between the solute, Zn, and one con-
stituent of the solvent, HC1 Zn + 2 HC1 = ZnCl 2 + 2 H in
which reaction the identities of the solvent and of the solute
are changed ;

(3) a simple solution, ZnCl 2 4- water.

Chemical solution is usually the result of the mutual reaction
between

(1) an acid, or a base, and a metal ;

(2) an acid, or a base, and a salt;

(3) an acid and a base.

But it may happen, as when metallic sodium is dissolved in
water, that the phenomenon cannot be classified under any of
these heads.



THEORY OF ANALYTICAL OPERATIONS

Simple solution is often a necessary predecessor of
chemical solution, as has been seen in Exp. 2 ; and, in
general, it prepares the way for chemical action by
placing the reagents in close contact.

Experiment 3

Mix .5 gram of dry potassium iodide with .5 gram of dry
mercuric chloride in a dry mortar, and rub the mixed salts well
together with the pestle. Note the result. Add a little water
and rub again.

Furthermore, simple solution may be necessary to the
continuance of chemical action, in order that the products
of reaction may be removed from between the reagents.

Experiment 4

Add a bit of zinc to 5 c.c. of concentrated sulphuric acid in a
test-tube; leave for a few moments, noting all that happens.
Now transfer the contents of the tube to a dish containing 15-
20 c.c. of water.

When zinc is treated with concentrated sulphuric acid, 1 chemi-
cal action occurs for a short time only, and then ceases entirely.
The explanation is probably this: zinc sulphate, insoluble in
concentrated sulphuric acid, coats the zinc and prevents further
contact of the reagents. The addition of water, in which zinc
sulphate is very soluble, removes the coating and permits chemi-
cal action to go on once more.

Properties of the Solute. So far in our study of the
phenomena of solution, we have considered only those
properties of the solute which are associated with its
solid condition, when, in point of fact, it cannot
properly be called a solute. Let us now see whether
we can discover anything concerning the properties
of the true solute, the body in solution.



10 CHEMICAL ANALYSIS

We have seen that a solution which is saturated
with a given body at one temperature may acquire the
power of dissolving an additional quantity of that body
in consequence of an elevation of temperature, and
that, on the contrary, it may give up a portion of its
solute if its temperature is lowered. That is to say,
if we have a " system " consisting of a limited quantity
of some saturated solution in contact with an excess of
its solute, there will be for any given temperature a
concentration of the solution at which there will be
a condition of equilibrium between the dissolved and
undissolved solute. This condition is entirely analo-
gous to that which is observed when a volatile liquid
is exposed in contact with a limited volume of air or
other gas. In the latter case the liquid will volatilize,
rapidly at first, and afterwards more slowly, until
the concentration of its vapor in the atmosphere to
which it is exposed has reached a certain limit which
will be dependent on the temperature. With a rise in
temperature, more liquid will pass into the state of
vapor; with a fall, a portion of the liquid already
vaporized will be condensed again.

This analogy has been recognized for many years ;
but it is now hardly more than a decade since first its
completeness was fully demonstrated.

Colloids and Crystalloids. 1 It had been shown by
Graham (1842) 2 that certain colloid solutes, whose solu-
tions are not real liquids, but emulsions, cannot pass
through porous membranes 3 such as parchment
and that most crystalloid solutes, whose solutions are
real liquids, readily penetrate such septa. He first



THEORY OF ANALYTICAL OPERATIONS 11

put separate solutions of a colloid and a crystalloid
into separate open cylinders whose bottoms were closed
with parchment, and then suspended the cylinders in
vessels of water so that the membranes were immersed.
After a few hours a large part of the crystalloid had
passed through the parchment into the water in the
outer vessel; and by renewing this water all of the
crystalloid was finally extracted from the cylinder.
From the other cylinder, however, no colloid had
passed out.

Osmosis. Pfeffer, 1 the botanist, in demonstrating and
measuring the internal bursting force of plant cells
(1877), established the fact that crystalloids, though they
do not pass through the so-called " semi-permeable "
membranes, of which protoplasm 2 is a type, do press
strongly against the partition in their futile attempt to
penetrate it. Connecting a mercury gauge and ther-
mometer with a membrane, composed of a porous cell
coated with copper ferrocyanide, and charging this ap-
paratus with saccharine solutions of different strengths,
he found that different concentrations of solution pro-
duced correspondingly different pressures within the
apparatus when the temperature was kept constant,
and that for any given concentration the pressure varied
as the absolute temperature. He showed, therefore,
that the relations of concentration, pressure, and tem-


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