GIFT F
Harry East Miller
A SHORT COURSE
IN
QUALITATIVE ANALYSIS
BY
J. M. CRAFTS,
FORMERLY PROFESSOR OF GENERAL CHEMISTRY IN THE CORNELL UNIVERSITY.
THIRD EDITION.
REVISED BY
CHARLES A. SCHAEFFER, A.M., PH.D.,
PROFESSOR OF GENERAL AND ANALYTICAL CHEMISTRY IN
THE CORNELL UNIVERSITY.
NEW YORK:
JOHN WILEY & SONS,
15 ASTOR PLACE.
1880.
COPYRIGHT,
1879,
BY JOHN WILEY & SONS.
GIFT OF
i-ffo
This Book is inscribed by the Author
M. ADOLPH WURTZ,
AS A TOKEN OF AFFECTIONATE REGARD, TO A FRIEND AND TEACHER,
AND AS A TRIBUTE OF RESPECT AND ADMIRATION, TO THE
MASTER OF A SCHOOL IN MODERN CHEMISTRY.
M81896
PREFACE TO THE THIRD EDITION.
IN preparing a new edition of this work, the editor has made
no essential alteration of the plan adopted by Professor Crafts
in the previous editions. He has endeavored, however, as far
as possible, to embody the practical results of the great ad-
vance made in both theoretical and practical chemistry within
the past ten years. The few important changes thereby ren-
dered necessary may be briefly specified.
Chapter II., on chemical nomenclature, has been entirely
rewritten. The usefulness of the work has been somewhat ex-
tended by the introduction of several elements not included
in the previous editions, viz. : strontium, cadmium, iodine, and
bromine.
Further changes have been made in the methods of separa-
tion and detection of several of the elements ; more reliable
processes being substituted for those which in the hands of
students were found not to be entirely satisfactory.
The editor desires especially to acknowledge his obligation
to his friend and colleague, Dr. G. C. Caldwell, for numerous
valuable suggestions of which he has availed himself.
ITHACA, December 17, 1879.
PREFACE TO THE FIRST EDITION.
THIS little work was written for the use of a class of stu-
dents in the Cornell University, who take a year's course of
chemistry, including four hours a week of laboratory practice ;
reference was also had to the requirements of the scientific
students in Union College, whose course is nearly equivalent
to that mentioned. The author is indebted to the kindness
of Professor Perkins for many valuable suggestions, and for
the compilation of Tables IV. and V. at the end of the book.
A considerable portion of the introductory part of this book
is devoted to an explanation of the theory of chemical reac-
tions and nomenclature. Many of the standard works on an-
alytical chemistry still use the old notation, and the formulas
to be found in them do not correspond to those used in the
best text-books on general chemistry ; and none of the ele-
mentary works for the laboratory-student supply the want,
often felt by him, of a system of rules, at hand for use at the
moment when he most requires them, namely, when he is
writing the formula of a reaction at his desk in the laboratory
with his tests before him. The author has had these points
in view in writing the two introductory chapters.
It might be objected that the theory of chemical notation
should be found in text-books on general chemistry ; but even
when the student has mastered the rudiments of the science,
as given in any of the best modern works, he will find the
PREFACE. v ii
arrangement of many of them inconvenient for reference,
although it is excellent for instruction, and, moreover, it is by
no means necessary that the study of those works should pre-
cede that of analytical chemistry.
It is quite feasible to commence a course of experiments in
the laboratory concurrently with the study of any of the ele-
mentary text-books on general chemistry, or with the attend-
ance upon lectures, illustrated with the usual experiments.
Chemistry certainly becomes a more attractive study when
the practical and the theoretical present themselves side by
side, so that while the theory explains the experiment, the ex-
periment awakens an interest in the theory ; and no course of
study is more apt to interest the beginner in chemistry than
that of the admirably simple and delicate tests of qualitative
analysis ; tests which illustrate the general laws of the science,
while they have a very direct bearing upon some of the prob-
lems of every-day life.
Analytical chemistry, besides its immediate value as an im-
portant branch of knowledge, cannot be too highly prized as
affording a convenient introduction to the methods of investi-
gation used in an experimental science, and as offering a
means of education of many faculties, which are not easily
developed by school or university training. The importance
of laboratory experiments is awakening every day increased
attention, and the time is fast passing by when chemistry is
taught to persons, who suppose that they have a vocation for a
scientific profession, only by lectures and recitations.
The system of analysis, given in Part III., is founded upon
that of Fresenius, and includes a minute description of all the
steps to be taken in performing tests and directions for pass-
viii PREFACE.
ing from one test to another ; and since these details, which
are required by the beginner, not only become unnecessary,
after a certain familiarity with analytical work has been ac-
quired, but also render the scheme less convenient for refer-
ence, tables similar to those of Will have been added, which
indicate the important tests and leave the experience of the
student to suggest the proper mode of applying them.
The Tables IV. and V. are intended to record a number of
facts in analytical chemistry in a compact form, and to give
an exact conception of what is meant by the insolubility of a
precipitate, and a means of judging of the advantages of dif-
ferent methods of precipitation.
ITHACA, August 19, 1869.
PREFACE TO THE SECOND EDITION.
A FEW changes have been made in the second edition,
which have been suggested by the use of the previous one in
the laboratory and some practical directions have been added,
which are intended to mark out more closely the course of
study which it seems most advisable to follow.
One of the principal applications of analytical chemistry is
to the investigation of minerals, and it may not be out of place
here to recommend to the consideration of instructors and
students the combination of mineralogical work with labora-
tory practice. A convenient order of study is, first to acquire
PREFACE. i x
familiarity with the methods of detection and separation of
bodies in solution, which are given in Part III., and then, be-
fore taking up the analysis of solid bodies, to study their crys-
tallographical and general mineralogical characters from any
elementary work treating of the subject. Turning again to
the general analysis of solid bodies (minerals and technical
products of all kinds), the course should be made as varied
and extended as possible ; and it will be found that the drill
in blowpipe practice and the study of the physical characters
of minerals make an excellent preparation for the preliminary
testing of solids, Part III., and often afford hints which are of
great value in the subsequent performance of the complete
analysis in the wet way.
It is quite possible for a class to complete a course like the
one proposed by working four hours a week for a year in the
laboratory.
ITHACA, 1870^
A SHORT COURSE
IN
ANALYTICAL CHEMISTRY.
PART L INTRODUCTION.
CHAPTER I
THE analytical chemist is not generally required to investi-
gate a large range of substances, and the theory of the com-
position of those bodies which he usually deals with can be
briefly explained.
Elements. The ultimate result of the analysis or de-
composition of all matter is the discovery of a number of sub-
stances which cannot be decomposed, and are therefore called
simple or elementary substances. The table on the next page
contains the names of thirty-six elements. They are chosen
from among the seventy or more elements which have been
discovered, because they are more frequently met with than
the others, and because they are the only ones treated of in
this work.*
* Within the past four years ten new elements have been reported by
their discoverers. How many of these will be substantiated it is at
present impossible to say. On the other hand, very recent investiga-
tions seem to show that at least several of our well-known elements are
really compound bodies. The exact number of elements is, therefore,
especially at the present crisis, very difficult to fix.
I
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SYMBOLS. 3
The task of the analytical chemist is to recognize these ele-
ments when they occur alone, or to separate them from the
compounds of which they form a part, or most frequently to
resolve a compound substance into simpler compounds, and
to isolate the latter in such form that they can be easily re-
cognized. When the different elements are known which
constitute such simpler compounds, the composition of the
complex body from which they were obtained can be deter-
mined.
All compound substances are formed by the union of chem-
ical elements, and a previous study of the manner in which
the elements combine with each other is essential to the suc-
cessful pursuance of analytical investigations.
The language in which chemists express their ideas regard-
ing the chemical constitution of bodies comprises certain sym-
bols or abbreviations, to which a conventional meaning is
attached, and formulas, which are made by grouping symbols
together.
Symbols* The symbols which stand in the table after
the names of the elements are abbreviations, which are used
instead of the names in writing chemical formulas.
Chemical Formulas describe by means of symbols
the chemical constitution of bodies.
Example : HC1 is the formula of hydrochloric acid, and
signifies that it is composed of hydrogen and chlorine.
The Combining Weights are the numbers standing
in the table after the symbols. They are peculiar to each
element, and denote the proportion by weight in which it
unites with other elements. In formulas the symbols stand
for these weights, as well as for the names of the elements ;
thus, in the formula of hydrochloric acid, HC1 signifies that i
part by weight of hydrogen is combined with 35.5 parts by
weight of chlorine.
ELEMENTS COMBINE WITH EACH OTHER IN NO OTHER
PROPORTIONS BY WEIGHT THAN THOSE EXPRESSED BY THE
4 PART /.
COMBINING NUMBERS (OR BY VERY SIMPLE MULTIPLES OF
THEM).
This statement comprises the law of definite proportions
and also that of multiple proportions.
USUALLY THE MULTIPLES OF THE COMBINING NUMBERS, 2,
3, 4, 5, 6, 7, EXPRESS THE PROPORTIONS IN WHICH THE ELE-
MENTS COMBINE WITH EACH OTHER.
Example : Nitrogen combines with oxygen only in the pro-
portions expressed by the formulas : N 2 O, NO, N 2 O 3 , NO 2 ,
and N 2 O 6 , or, referring to the table for the combining num-
bers for which the symbols stand, the following proportions
appear :
2 x 14 parts N unite with 16 parts O.
14 " " " " 16 " "
2 x 14 " " " " 3 x 16 " "
14 " " " " 2 x 16 " "
2 x 14 " " " " 5 x 16 " "
Chemical Atoms* It is supposed that the utmost limit
to which the division of matter could be carried would lead
to its separation into a great number of particles, so small as
to be incapable of further division. With reference to their
quality of indivisibility, such particles of matter are called
atoms (from d, privative, and refAvoD, I cut). Atoms, there-
fore, are the indivisible constituents of matter. It is further
supposed that chemical combination consists in the union of
atoms, or groups of atoms, and chemical decomposition in the
separation of atoms, or groups of atoms ; and a chemical
change supposes a change in the arrangement or grouping of
the atoms of a body involving the destruction of the previous
arrangement.
Atomic Weights. The atomic theory attaches a new
meaning to the combining weights of the elements, and defines
them as the relative weights of atoms. Thus, if the weight of
an atom of hydrogen is i x w (w = a very small unknown
NOTATION. 5
quantity), the weight of an atom of chlorine is 35.5 x w.
Not the absolute weights of atoms, but their relative weights,
have been discovered. The weight of an atom of hydrogen is
taken as a standard, and called i ; hence the weight of the
atoms of other elements are expressed in terms of this unit.
Example, 35.5 for chlorine, 16 for oxygen. With reference
to the above theory, the combining weights are usually called
atomic weights. The full meaning, therefore, of the chemical
formula HC1 is, that the body which it represents consists of
compound atoms, each one containing an atom of hydrogen
and an atom of chlorine. An atom of chlorine weighs 35.5
times as much as an atom of hydrogen, so that the proportion
by weight of each constituent of the body is expressed by its
formula.
Chemical Notation. Any change in the constitution
of bodies, as well as their formation and decomposition, in-
volves what is called a chemical reaction.
A CHEMICAL REACTION may be described as a change in the
arrangement, or the state of combination of the atoms of bodies.
Such a change can be denoted by combining formulas together
in the same way that quantities are combined in common alge-
braic calculations. The signs used are +, , and ='. Coeffi-
cients are only used to multiply the symbols to which they are
joined. When placed on the line, they multiply all the sym-
bols which follow. When placed below or above the line,
they are used to multiply only the symbol, or the group of
symbols in brackets, that immediately precedes them. Brackets
are used to distinguish certain groups of atoms in a compound
from the remaining atoms. The combination of atoms is ex-
pressed by writing their symbols side by side, or by grouping
them together without + or . The sign + expresses that
the bodies connected by it are brought in contact with each
other by addition, but that they are not combined.
Example : Ba(NO 8 ) 2 + CaSO 4 . The formula indicates
that a compound, Ba(NO 8 ) 2 , containing barium, nitrogen, and
6 PARTI.
oxygen, in the proportion of i atom of barium combined with
twice i atom of nitrogen and twice 3 atoms of oxygen, is
brought in contact with a compound [CaSOJ containing cal-
cium, sulphur, and oxygen, in the proportion of i atom of cal-
cium combined with i atom of sulphur and 4 atoms of oxygen.
A reaction is denoted by combining the formulas of the bodies
which take part in it, as in an ordinary equation. The formulas
before the sign ( = ) indicate the state of combination of the
atoms before the reaction ; those after the sign of equality (=)
show the state of combination of the atoms after the reaction.
Example : Ba(NO 3 ) a + CaSO 4 = BaSO 4 + Ca(NO 3 ) 2 .
The equation expresses the result of bringing in contact
the bodies described above, viz. : the formation of new com-
pounds containing barium, sulphur, and oxygen, and calcium,
nitrogen, and oxygen.
CHEMICAL AFFINITY.
The force which impels atoms to unite with other atoms is
called chemical affinity. The quantity or the nature of the
force inherent in the atoms of every substance determines
the chemical properties of the substance. The study of the
results of the action of chemical affinity is the province of
chemistry.
The phenomena which the action of chemical affinity gives
rise to can best be studied under several heads.
Firstly. Chemical affinity may cause the atoms of an ele-
mentary body to unite among themselves. Only the cases of
such action in which the element is capable of assuming the
simplest physical condition of matter, namely, the form of a
gas, have been studied satisfactorily.
The following conclusions in regard to the state of com-
CHEMICAL AFFINITY. 7
bination of the atoms of elementary bodies have been ar-
rived at :
The atoms of mercury and zinc remain separate in the
gaseous state.
The atoms of hydrogen, oxygen, chlorine, bromine, iodine,
nitrogen (and sulphur at a temperature higher than 1000
centigrade) are united in groups of two atoms.
The atoms of phosphorus and arsenic in the gaseous state
unite in groups of four atoms. Sulphur, at a temperature of
500 centigrade, in groups of six atoms.
The formulas for these bodies in a gaseous state are :
Hg HHorH 2 PPPP or P 4 SSSSSS or S 6
Zn OO or O 2 AsAsAsAs or As 4
C1C1 or C1 2
BrBr or Br 2
NN or N 2
SS or S 2
Molecule. At this point a definition of the term mole-
cule is required. A molecule is the smallest particle of a body
which can exist alone.
The molecules of elementary bodies contain one or more
atoms of the same kind. The molecules of compound bodies
contain two or more atoms of different kinds.
A molecule of mercury, hydrogen, hydrochloric acid, or
water is represented by the respective formulas, Hg, H 2 , HC1,
or H 2 O.
Atom. An atom may be further defined as the smallest
particle of matter which can take part in a chemical reaction.
Atoms, therefore, appear while a chemical reaction is going
on, although it is impossible to suppose that a physical sub-
division of matter could be carried further than the isolation
of molecules.
Thus in the reaction : NasS + CuCl 2 = CuS -f 2 NaCl, the
force of chemical affinity breaks up the molecules (Na^) and
8 PART I.
(CuCl 2 ) to form the new ones (CuS) and (NaCl), and during
this reaction the atoms Na, S, Cu, and Cl must be set free
from their combinations, and therefore must exist as atoms.
Secondly. Chemical affinity may combine atoms of a single
element, or groups containing atoms of one or more elements,
with the atoms of another element, or with groups containing
atoms of one or more other elements.
Examples : Hg -f C1 2 = HgCl 2 .
NH 3 + HC1 = NH 4 C1.
The inverse action frequently takes place through the
agency of heat or of some other force, and groups of atoms
(molecules) break up into other groups, which are usually
simpler in constitution than the primitive ones.
Example : Hg(CN) 2 when heated becomes Hg + (CN) 2 .
Thirdly. Chemical affinity may cause compound bodies,
brought in contact with each other, to mutually exchange
some of their constituents ; or an atom or a group of atoms
may substitute itself for another atom or for a group of atoms
in a compound body.
Examples : Na 2 CO 8 + BaCl 2 = BaCO 8 + 2NaCl.
CuSO 4 + Zn = ZnSO 4 + Cu.
THE QUALITY OF THE CHEMICAL AFFINITY inherent in the
atoms of each element determines the part which the element
will play in the different chemical changes mentioned above.
It is usually necessary to study each particular case, in order
to determine the exact result of bringing in contact any two
substances. Empyrical rules, however, defining the nature of
the chemical affinity of the elements and the consequences of
its action, can be given in a few cases. These rules are not
capable of a very strict application, but they serve to indicate,
in most cases, when a number of bodies are brought together
in a reaction, those which will probably combine with each
other. Gold is attacked by acids less readily than the metals
CHEMICAL AFFINITY. 9
of the arsenic group. The difference between the affinities of
the metals which are ranged in the same group in the table
(page 2) is too slight to be of consequence in the application
of rule second.
First. COMBINATION USUALLY OCCURS BETWEEN METALS
AND NON-METALLIC ELEMENTS, LESS READILY BETWEEN DIF-
FERENT NON-METALLIC ELEMENTS, AND LEAST READILY BE-
TWEEN DIFFERENT METALS. See table of the elements, page 2.
The following non-metallic elements, or oxygen compounds
of non-metallic elements, combined with hydrogen form acids,
and combined with metals form salts. STRONG ACIDS sul-
phuric, H 2 SO 4 ; nitric, HNO 3 ; chloric, HC1O 3 ; chlorhydric,
HC1. WEAK - ACIDS sulphurous, H 2 SO 3 ; chromic, H 2 CrO 4 ;
phosphoric, H 3 PO 4 ; boracic, H 3 BO 3 ; oxalic, H 2 C 2 O 4 ; acetic,
HC 2 H 8 O 2 ; fluorhydric, HF ; sulphydric, H 2 S ; cyanhydric,
HCN ; carbonic, H 2 CO 3 ; silicic, H 4 SiO 4 . A metal has a ten-
dency to substitute itself for the hydrogen in a strong acid, to
form a salt with it, in preference to a weak one ; so that a
strong acid usually displaces a weak one from its salts.
Second. THE METALS WHICH STAND LOWEST IN THE TABLE
(page 2) HAVE THE GREATEST TENDENCY TO COMBINE WITH
THE STRONGEST ACIDS.
Example : CuSO* 4- Zn = ZnSO 4 + Cu.
Third. Another rule which sometimes takes precedence of
the second is, that WHEN FROM SOME OF THE CONSTITUENTS
OF DIFFERENT COMPOUNDS IN SOLUTION, AN INSOLUBLE BODY
CAN BE FORMED, THE ELEMENTS WHICH WOULD COMPOSE
SUCH A BODY GENERALLY UNITE WITH EACH OTHER.
Example: Na 2 CO 3 + Ca(HO) 2 = 2NaHO + CaCO 8 . The
compound CaCO 3 is formed in virtue of its insolubility when
the reaction takes place in an aqueous solution.
I0 PART I.
QUANTIVALENCE.
The quality of the chemical affinity of the elements deter-
mines the nature of reactions. The quantity of their chemical
affinity determines the proportions in which the elements com-
bine with each other. The result of the combination of two
or more atoms with each other is the neutralization of the
chemical force which brings them together, so that usually no
force is left in the compound tending to combine other bodies
with it. Thus a molecule of HC1 has no power to combine
further with atoms of H or of Cl. The atoms of some ele-
ments are animated with greater quantities of chemical force
than those of other elements. Thus an atom of oxygen may
unite with an atom of hydrogen, and still be capable of com-
bining with another atom of hydrogen, or with an atom of
chlorine. If an atom of hydrogen has one unit of chemical
force, an atom of oxygen has two units, carbon has four, and
nitrogen has five. The number of units of chemical force re-
siding in an atom is called its QUANTIVALENCE. The table
of the elements, page 2, classifies them, according to their
quantivalence, into monatomic elements, or monads ; and
diatomic elements, or dyads, etc.
Some of the units of chemical force of an element may lie
dormant until developed by the approach of some other force,
which awakens them. Iron, for instance, acts as a dyad when
no element is present to call forth all of its four units of
chemical force. It is worthy of note that in such cases two
units of force generally disappear together, as if they became
dormant by each one neutralizing the effect of the other. It
will be noticed that in the table, page 2, sulphur is placed in
the column of dyads, and also in that of the hexads ; this is
because in many cases four of the six units of chemical force
in sulphur lie dormant, and the element plays the part of a
dyad. In nickel, cobalt, and iron, two of the four units of
Q UANTIVA LENCE. ! x
chemical force frequently lie dormant, and hence these metals
often act as dyads. Only the valence of each element, which
is usually displayed in the kind of reactions which we have to
consider, is shown in the table.
The knowledge of these facts is essential to enable the stu-
dent to write formulas correctly.
Examples: The compound of barium and chlorine must
contain two atoms of chlorine, combined with one atom of
barium. Its formula is BaCl 2 . The greatest amount of oxy-
gen that an atom of carbon can unite with is two atoms.
The formula of the compound is CO 2 . When zinc is substi-
tuted for silver in a compound, one atom of zinc, with its two
units of chemical force or affinity, takes the place of two
atoms of silver, because each atom of silver has only one unit
of chemical force. Thus, in writing formulas, an atom of one
element is equivalent to or takes the place of another element
of the same class. In comparing elements of different classes,
their value in an equation depends upon the number of units
of chemical force which they contain.
TWO MONADS ARE EQUIVALENT TO A DYAD ; THREE MO-
NADS TO A TRIAD, ETC. THREE DYADS ARE EQUIVALENT TO
TWO TRIADS, ETC.
Examples : PbO + 2 HC1 = PbCl 2 + H 2 O.
SiCl 4 + 2H 2 O = SiO 8 + 4HC1.
QUANTIVALENCE OF GROUPS OF ATOMS. When part of the
affinities or units of chemical force of a polyatomic group are
satisfied or neutralized, the residual valences, or those which
remain free, determine the quantivalence of the group.
Example : Nitrogen, a pentad, when combined with three
atoms of hydrogen, is capable of uniting with two other mo-
nads or with one dyad NH 3 can unite with H and Cl to make
NH 4 C1. Moreover, certain groups of elements take part in
many chemical reactions without being broken up, and, so far
as this is the case, they may be considered as playing the part
12 PART L
of elementary bodies in the reactions. Such groups are fre-
quently called radicals, with reference to a theory that they
are the roots of compounds.
The following table, showing the quantivalence of such
groups, will be found convenient in writing formulas :
Monads. Dyads. Triads. Tetrads. Hexads.
HO* SO4 PO 4 SiO 4 Fe 2
N0 8 f S0 3 B0 3 Fe(CN) 6 Cr 2
C10 3 Cr0 4 A1 2
C 2 H 3 O 2 CO 3 Fe 2 (CN) 12
NH 4 C 2 O 4
CN C 4 H 4 O 6
H g2
Examples : Na(HO); H(NO 3 ); (NH 4 ) (HO); Pb(C 2 H 8 O 2 ) 2 ;
* The group HO is a monad, because one of the two affinities of the
oxygen atom is satisfied and nullified by the affinity of the hydrogen with
which it is combined, leaving one affinity free in the oxygen atom.
f The existence of the group NO 3 might seem inconsistent with the
five-atomic character of nitrogen. The explanation is, that four affinities
in the nitrogen atom are used to unite to it two atoms of oxygen, and the
fifth combines with only one of the affinities of a third atom of oxygen,
leaving one oxygen affinity free, which determines the monatomic char-
acter of the group.
\ A similar argument applies to the case of the group SO 4 . Here, sul-
phur being hexatomic, four affinities are used to combine with those of two
atoms of oxygen, while the two remaining affinities of the sulphur atom
are each combined with one in each of the two remaining atoms of oxy-
gen, leaving two oxygen-affinities free.
In the case of Fe 2 , etc., two of the eight affinities, belonging to two
atoms of iron, are used to bind the two atoms together, leaving six free,
and for this reason the group Fe 2 is six-, and not eight-atomic. It may
be noticed that groups of this nature, having free chemical affinities, can
only be found in the case of polyatomic elements, because, when two
monatomic elements combine with each other, no chemical affinity can
be left free. For fuller explanations of the laws of chemical combination,
see Frankland's Lecture Notes for Chemical Students.
QUANTIVALENCE. ! 3
H 2 (S0 4 ) ; Ba (CrO 4 ) ; Hg 2 (C1 2 ) ; H 3 (PO 4 ) ; Fe 2 Cl 6 ; Cr 2 O, ;
A1 2 (HO)..
IN WRITING FORMULAS, THE SYMBOL OF THE ELEMENT, OR
GROUP OF ELEMENTS, HAVING MOST DECIDEDLY THE CHARAC-
TER OF A METAL, IS PLACED FIRST.
Example : NaNH 4 HPO.
I4
CHAPTER II.
CHEMICAL NOMENCLATURE.
WHEN metallic sodium comes in contact with water a reac-
tion takes place, as indicated by the following equation :
Na* + 2 H 2 O = 2NaHO + H 2 .
Each molecule of water is broken up, setting free an atom
of hydrogen and receiving in its place an atom of sodium.
The new body thus formed may then be considered as a mole-
cule of water in which one atom of hydrogen has been replaced
by sodium. Or it may be considered as an atom of a monad
metal united to the monovalent radical HO, known as hy-
droxyl. Furthermore, it may be taken as a type of a numerous
class of bodies, known as METALLIC HYDRATES, all of which
consist of one or more atoms of metal united to an equivalent
amount of hydroxyl, as may be seen from the following
Examples: KHO ; Ca(HO) 2 ; Fe(HO) 2 ; Fe 2 (HO), ; Al,
(HO),
All of the metallic hydrates, when acted upon by a certain
other class of bodies, are similarly affected, as can be shown
by the following equations :
HC1 + KHO = KC1 + H 2 ;
2 HC1 + Ca(HO) 2 = CaCl 2 + 2 H 2 O ;
6HC1 + Fe 2 (HO) 6 = Fe 2 Cl 6 + 6H 2 O ;
HNO 8 + KHO = KNO 3 + H 2 O ;
6HN0 8 + Fe 2 (HO) 6 = Fe 2 (NO 8 ) 6 + 6HO ;
H 2 S0 4 + KHO = KHS0 4 + H 2 O ;
H 2 SO 4 + 2KHO = K 2 SO 4 + 2H 2 O ;
H 2 SO< + Ca(HO) 2 = CaS0 4 + 2H 2 O.
CHEMICAL NOMENCLATURE. ! 5
By inspection of the above equations it will be seen that we
have in the left-hand member of each a metallic hydrate, and
in the right-hand member of each water. Furthermore the
substance indicated first in each equation contains hydrogen,
and when this hydrogen is replaced by the metal of the metal-
lic hydrate the formula of the substance indicated first in the
right-hand member of the equation is obtained.
The original substances containing hydrogen are called
acids, and the compounds occurring first in the right-hand
members of the above equations are salts.
The above we may formulate, then, in the following defi-
nitions :
Acid. An acid is a compound which, when brought into
contact with a metallic hydrate, exchanges the whole or a part
of its hydrogen for the metal of the metallic hydrate ; water
being formed at the same time.
The acids may be divided into two groups.
Firstly, Those which consist of hydrogen united directly to
another non-metallic element as HC1 ; HBr ; HF ; H 2 S.
Secondly, The oxygen acids, or those in which the hydrogen
is united with another non-metal, or with a group, by means of
oxygen, as in HC1O ; HNO a ; H 2 SO 4 . Here the arrangement
of the chemical forces may be shown by the following graphic
formulas : H - O - Cl ; H - O - N O 2 ; H 2 = O 2 --= SO 2 .
Salt . A salt is a compound formed by replacing the hy-
drogen of an acid by a metal.
All compound bodies are susceptible of decomposition by a
current of electricity, and when thus decomposed resolve them-
selves into a positive atom or group, and a negative atom or
group. In writing the ordinary formulas of compounds the
electro-positive atom or group is always placed first, as
+ - + - + - + - +
HC1 ; H 2 ; Na(HO) ; Ba(SO 4 ) ; (NH 4 ) 2 (SO 4 ).
The names of chemical compounds, which are used in works
on analytical chemistry, do not describe their constitution as
16 PART I.
fully as formulas do ; they serve, however, to identify the
bodies and to recall certain principles of classification.
In the ordinary operations of analysis, the only bodies which'
are dealt with are binary compounds (i.e., compounds which
only contain two elements, as KC1 and H 2 O) and ternary com-
pounds, which contain a non-metallic element and oxygen
combined with a metal or with hydrogen, as BaSO 4 , H 3 PO 4 .
In the statement of the rules for the naming of compounds
the subject will be divided under these two heads :
I. BINARY COMPOUNDS. *
a. ACIDS. Two distinct methods are in common use for
naming binary acids. According to the one the name consists
of hydro preceding the root of the name of the other element
and terminates in ic; as, HC1, hydrochloric acid ; HBr, hydro-
bromic acid ; H 2 S, hydrosulphuric acid. By the other method
the characteristic element is indicated first, and the names of
the three acids just mentioned would be, chlorhydric acid,
bromhydric acid, and sulphydric acid.
b. ALL OTHER COMPOUNDS. In determining the names of
binary compounds not acids, if there exists but one compound
of the two elements in question, the positive element takes the
termination ic and the negative ide; as, NaCl, sodic chloride ;
K 2 S, potassic sulphide ; BaO, baric oxide. Or, inverting the
order, they may also be called, respectively, chloride of sodium,
sulphide of potassium, and oxide of barium.
Still another method, and one which has of late been very
generally adopted, is to leave the name of the positive element
unchanged, while giving the termination ide to the negative.
By this method the examples just given would be sodium
chloride, potassium sulphide, and barium oxide.
When two distinct compounds exist, consisting of the same
two elements, as SO 2 , SO 3 , that one which contains the greater
proportion of the negative element is named in accordance
CHEMICAL NOMENCLATURE. ^
with the first method as given above, while the other simply
changes the termination ic of the positive element to ous. SO 2
would then be sulphurous oxide and SO 3 sulphuric oxide.
When a compound exists which contains still less of the
negative constituent than that indicated by the termination
ous y as above, it receives the prefix hypo ; as, N 2 O 3 being ni-
trous oxide, N 2 O is called hyponitrous oxide. Similarly the
prefix per or hyper is used to indicate that the compound con-
tains more of the negative element than the one whose positive
constituent terminates in ic. This prefix is, however, usually
given to the negative element ; as, Mn 2 O 3 being manganic oxide,
MnO 2 is called manganic peroxide.
The prefix sesqui is sometimes used, as in Fe 2 O 3 , the sesqui
oxide of iron.
The relative positions of the several compounds of a series
may be illustrated by the following schedule, in which the plus
sign indicates the root of the positive element and the minus
sign that of the negative :
hypo + ous ide, as XO ;
4- ous ide, as XO 2 ;
hypo + ic ide, as XO 3 ;
+ ic ide, as XO 4 ;
+ ic per ide, as XO 5 .
Unfortunately for the rule, however, the practice of recent
authors varies very widely, so much so that it is the exception,
for example, to find the whole series of oxides of nitrogen
similarly named in any two works on chemistry.
In accordance with the above schedule the following would
be the names of the five members of that series :
N 2 O, hyponitrous oxide ;
NO, nitrous oxide ;
N 2 O 3 , hyponitric oxide ;
NO 2 , nitric oxide ;
N 2 O 5 , nitric peroxide.
l8 PART I.
Instead of these, however, each member of the series has
several different names in common use. For example, the first
compound is known commonly as nitrous oxide ; it is also
called nitrogen monoxide. The second is variously termed
nitric oxide, nitrosyl, nitrogen dioxide, since the molecule is
by some considered to be indicated by the formula N 2 O 2 , and
so on through the whole of the series.
Another striking example of exception to the rule will be
found in the two compounds of carbon and oxygen, CO and
CO 2 . Clearly the former should be called carbonous oxide,
and the latter carbonic oxide. Formerly, however, CO 2 was
considered to be an acid, and was called carbonic acid ; and
in fact it is still so termed in most metallurgical and technical
works, while CO was known as carbonic oxide. Since the
adoption of the present views of the constitution of acids
chemists no longer call CO 2 carbonic acid, and it is therefore
usually named carbonic dioxide, or carbonic anhydride, from
the fact that it may be considered as carbonic acid from which
a molecule of water has been removed (H a CO 8 H 2 O = CO 2 ).
The name carbonic oxide would be inapplicable, since it would
not be perfectly clear whether the compound indicated was
CO or CO 2 . As to CO, it still retains its old name carbonic
oxide in some works, while in others it is termed carbonous ox-
ide, or again carbon monoxide.
Still another source of difficulty to beginners exists in the
fact that many compounds are known by irregular names ; as,
H 2 O, water ; NaCl, common salt ; NH 8 , ammonia, etc.
For the sake of uniformity it would perhaps be well if the
system as shown in the following examples could be adopted :
N 2 O, nitrogen monoxide';
N 2 O 2 , nitrogen dioxide ;
N 2 O 3 , nitrogen trioxide ;
N 2 O 4 , nitrogen tetroxide ;
N 2 O 5 , nitrogen pentoxide ;
or, nitric monoxide, etc.
TERNARY COMPOUNDS. ! 9
Mn 8 O 4 would, according to this plan, be called triman-
ganese tetroxide.
II. TERNARY COMPOUNDS.
a. ACIDS. The elements hydrogen and oxygen are common
to all of this class of acids. They therefore receive their speci-
fic names from the third or characteristic element ; as, HNO 8
is called nitric acid. In case two or more acids occur, consist-
ing of the same three elements united in different proportions,
the prefixes and terminations, as explained under binary com-
pounds, are applied, and in a similar manner ; as,
HNO 2 , nitrous acid ;
HNO 8 , nitric acid ;
H 2 SO 3 , sulphurous acid ;
H 2 SO 4 , sulphuric acid ;
HC1O, hypochlorous acid ;
HC1O 2 , chlorous acid ;
HC1O 3 , chloric acid ;
HC1O 4 , perchloric acid.
b. SALTS. The names of salts express both the metal con-
tained and the acid from which they are derived. The metal
takes the termination ous or ic. The termination of the acid
is changed from ous to tie, and from ic to ate j as,
KNO 2 , potassic nitrite ;
NaNO 3 , sodic nitrate ;
BaSO 4 , baric sulphate ;
FeSO 4 , ferrous sulphate ;
Fe 2 (SO 4 ) 8 , ferric sulphate ;
KC1O, potassic hypochlorite ;
NaClO 2 , sodic chlorite ;
KC1O 8 , potassic chlorate ;
KC1O 4 , potassic perchlorate.
20 PART I.
c. METALLIC HYDRATES. The metal generally takes the
termination /V, as NaHO, sodic hydrate. Where two hydrates
of the same metal exist the one which has the lesser relative
amount of the negative radical takes the termination ous; as,
Fe(HO) 2 , ferrous hydrate ; Fe 2 (HO) 6 , ferric hydrate.
In cases where only one hydrate is formed some authors
prefer to retain the name of the metal unchanged ; as, sodium
hydrate.
CLASSIFICATION OF ACIDS.
The hydrogen of an acid which is replaceable by a metal is
called basic hydrogen.
Those acids which contain in the molecule but one atom of
basic hydrogen are said to be monobasic ; those which con-
tain two such atoms are dibasic ; those containing three are
tribasic, and those containing four, tetrabasic. In hypophos-
phorous acid, H 3 PO 2 , we have an example of a monobasic
acid, since only one of the three atoms of hydrogen is replace-
able. In phosphorous acid, H 3 PO 8 , we have a dibasic acid,
and in phosphoric acid, H 8 PO 4 , we have a tribasic acid, all
three atoms of hydrogen being basic. Pyrophosphoric acid,
H 4 P 2 O 7 , is an example of a tetrabasic acid.
CLASSIFICATION OF SALTS.
Salts are either normal, acid, double, or basic.
A normal salt is one in which the whole of the basic hydro-
gen is replaced by the metal ; as, NaNO 3 ; Na 2 SO 4 ; NaH 2 PO 2 ;
Na, 2 HPO 8 ; Na 8 PO 4 .
An acid salt is one in which some of the basic hydrogen
still remains in the molecule ; as, NaHSO 4 ; NaH 2 PO 3 ;
Na 2 HPO 4 . There can of course be no acid salt of a mono-
basic acid, since, as the molecule contains but one atom of hy-
drogen, if any portion of that element is removed the whole
must be.
CHEMICAL REAGENTS. 21
A double salt is a complex molecule in which either the
basic hydrogen is replaced by two distinct metals, or else the
same metal replaces the basic hydrogen in two different acids.
As examples of the first variety of double salt may be men-
tioned (KCl) 2 PtCl 4 , in which the two metals, potassium and
platinum, replace the hydrogen in hydrochloric acid ; CaMg
(CO 3 ) 2 ; K 2 A1 2 (SO 4 ) 4 . Examples of the second form,
PbS0 4 , 3PbC0 8 ; PbCl 2 , PbCO 3 .
Basic salts are complex molecules which may be consid-
ered as consisting of a normal salt united to the oxide or the
hydrate of the same metal ; as, BiCl 3 , Bi 2 O 3 ; Fe 2 (SO 4 ) 3 ,
Fe 2 (HO) 6 ; (CuCO 8 ) 2 , Cu(HO) 2 .
It will be seen by the foregoing examples how much more
fully the formulas express the composition of bodies than the
names.
The following list of chemical compounds contains the
names and formulas of the substances most frequently used
for testing in the laboratory. These names and formulas
should be committed to memory, and the rules of nomencla-
ture may be studied in their application to them :
Chlorhydric, or hydrochloric Potassic ferrocyanide,
acid, HC1 ; K 4 (FeCy 6 ), or K,Ye(CN) 6 ;
Nitric acid, HNO 3 ; Potassic ferricyanide,
Sulphuric acid, H 2 SO 4 ; K 6 (Fe 2 Cy, 2 ), or K 6 Fe 2 (CN) 12 ;
Sulphydric acid, H 2 S ; Potassic sulphocyanate,
Acetic acid, HC 2 H 3 O 2 ; K(CyS), or KCNS ;
Ammonic hydrate, NH 4 HO ; Calcic hydrate, Ca(HO) 2 ;
Ammonic sulphide, (NH 4 ) 2 S ; Calcic chloride, CaCl 2 ;
Ammonic carbonate, Calcic sulphate, CaSO 4 ;
(NH 4 ) 2 CO 3 ; Baric chloride, BaCl 2 ;
Ammonic chloride, NH 4 C1 ; Baric nitrate, Ba(NO 3 ) 2 ;
Ammonic oxalate, Baric carbonate, BaCO 3 ;
(NH 4 ) 2 C 2 O 4 ; Magnesic sulphate, MgSO 4 ;
22
PART /.
Ferrous sulphate, FeSO 4 ;
Ferric chloride, Fe 2 Cl 6 ;
Cobaltic nitrate, Co(NO 8 ) 2 ;
Plumbic acetate ;
Pb(C 2 H 3 2 ) 2 ;
Argentic nitrate, AgNO 3 ;
Mercuric chloride, HgCl 2 ;
Platinic chloride, PtCU ;
Stannous chloride, SnCl 2 ;
Alcohol, C 2 H 6 O.
After having made himself familiar with the formulas of the
substances with which he tests, the student should write in the
form of an equation the result of the action of each test which
he performs upon a compound under examination.
Ammonic molybdate,
(NH 4 ) 2 Mo0 4 ;
Sodic hydrate, NaHO ;
Sodic carbonate, Na 2 CO 8 ;
Disodic hydric phosphate,
Na 2 HPO 4 ;
Sodic acetate, NaC 2 H 8 O 2 ;
Potassic dichromate,
K 2 Cr 2 O 7 ;
CHEMICAL OPERATIONS.
CHAPTER III.
CHEMICAL OPERATIONS.
Reaction with Test Paper. A small piece of red
or blue litmus paper is dipped in the solution. If it is acid,
blue paper is turned red ; if it is alkaline, red paper is turned
blue.
Turmeric paper is turned brown by alkalies.
Precipitation. When an insoluble body is formed in
a solution and separates (falls) from it, precipitation is said to
take place. Precipitates are gelatinous, as aluminic hydrate ;
flocculent (consisting of flakes), as sulphide of zinc ; or pul-
verulent, as baric sulphate. Usually the particles are less finely
divided, and filtration is easier with precipitates which form in
dilute solutions, particularly in boiling solutions. With some
precipitates, as magnesic phosphate, in very dilute solutions,
the act of precipitation is a slow process of crystallization, and
the formation of a precipitate does not take place until after
several hours.
Filtration is a process by which an insoluble body,
usually a precipitate, is separated from a liquid. It is usually
important to allow a precipitate to settle before filtration ; and
frequently after the clear liquid has been poured upon the
filter it is best to add more water to the precipitate, and to
wait again until it has settled. When the precipitate requires
to be washed, this process may be repeated many times before
the precipitate is brought upon the filter. The precipitate
usually clogs the pores of the filter, so that it retards the flow
of the liquid. A precipitate which has to be washed is finally
brought on the filter by rinsing with the wash-bottle, and it is
24 PART I.
washed by repeatedly filling the filter with water and allowing
it to empty itself. The process should be intermittent, and
the filter should never be kept constantly full during the latter
part of a filtration, when the object is to wash a precipitate
with pure water. Sometimes precipitates which take the form
of a powder are so finely divided as to pass through the pores
of a filter. This can usually be avoided by precipitating in a
dilute solution, and particularly by boiling the solution. Sul-
phur cannot be prevented from going through the filter. Fil-
tration is more rapid with hot than with cold water. Before
commencing a filtration, the filter should be made to fit closely
to the side of the funnel, and it should always be moistened
with pure water.
Decatfltatiovi consists in allowing a precipitate to settle
and in pouring off the liquid above it, in the manner already
mentioned under filtration. This process may or may not be
united with that of filtration. For instance, argentic chloride
settles so completely and quickly that it can usually be washed
simply by repeated decantations.
^Evaporation is usually performed in a porcelain dish.
A few drops of liquid can be evaporated by heating them on
platinum foil. Bits of broken glass or porcelain vessels are
very useful for the same purpose.
The Use of the Blowpipe. An olive oil or kerosene
lamp, with a wick $ in. long and J in. broad, or a Bunsen's
lamp, with the regulator turned to shut off the draught of air,
may be used. If the Bunsen's lamp has no regulator for the
draught, a smaller tube may be introduced into the lamp-tube,
until it rests upon the piece from which the gas issues and
excludes the air. After considerable practice a continuous
stream of air can be forced through the blowpipe by making
the cavity of the mouth the reservoir, into which air is forced
at intervals from the lungs, and is prevented from escaping by
a peculiar contraction of the throat and hanging palate, which
is easily learned ; the breathing goes on through the nose un-
THE USE OF THE BLOWPIPE. 25
interruptedly. The chief difficulty that beginners usually ex-
perience is fatigue of the muscles of the cheeks, which pre-
vents a long-continued effort. Two kinds of flames can be
produced with the blowpipe one containing an excess of air,
consequently of oxygen ; the other containing an excess of
combustible gases, consequently of gases capable of consuming
oxygen or reducing.
The Oxidizing Flame is produced by introducing
the point of the blowpipe one-third through the lamp-flame.
It is a clear blue cone, surrounded and continued at the point
by a colorless flame, intensely hot, and capable of producing
oxidation. The substance should be heated beyond the point
of the blue cone.
TJie Reducing Flame is produced by holding the
point of the blowpipe at the outside of the lamp-flame, and
by blowing somewhat more gently. The flame is much less
pointed and is more luminous than the oxidizing flame. The
substance should be heated at a distance from the point of the
flame equal to one-third of its length, and should be completely
enveloped in the flame. The position of the blowpipe and
the force of the blast regulate the quality of the flame. It is
a difficult matter to produce the true reducing flame, which
should not deposit carbon on the substance heated in it, and
at the same time should contain no excess of oxygen.
The Borax Bead is formed by making a loop -J- in.
in diameter in a piece of platinum wire, heating it red hot in
the blowpipe flame, and touching it to a small piece of borax
while it is hot. The borax, which adheres to the hot wire, is
heated in the blowpipe flame. It at first swells while losing
its water of crystallization, and finally it melts to a clear glass
bead. A finely divided substance can be taken up by touch-
ing the hot bead to it, and it can then be tested as to its solu-
bility in the borax bead, coloring properties, etc., in the blow-
pipe flame.
Heating on Charcoal. Select a good piece of char-
26 PART I.
coal, at least 4 in. long and i in. broad and thick, and smooth
a plane surface in a direction at a right angle with that of the
year-rings. (If heat is applied to a surface parallel to the
planes of the year-rings, the charcoal is more liable to snap
from the expulsion of moisture.) In many cases the charcoal
serves as a convenient support for a substance to be heated ;
in others the reducing agency of the charcoal comes in play.
Substances are also evaporated at a high temperature from the
surface of the charcoal.
Ductility, Malleability, Urittleness are charac-
teristic properties of metals, and metals can be tested with re-
gard to them by pounding with a hammer or by rubbing with
the pestle of a mortar. When a substance which appears to
contain a higher metal is reduced by sodic carbonate on char-
coal, unless metallic globules are at once apparent, the portion
of the charcoal which has been heated should be cut out and
pulverized with water in a mortar, and washed by decantation.
If metallic globules have been formed, they will sink to the
bottom, and after thorough washing, during which the sodic
carbonate is dissolved, and the light particles of charcoal are
floated away, they will appear as globules, if they are hard
like copper ; as brittle grains, if they are brittle like bismuth ;
or as 'flattened disks, when they are ductile like lead, and when
they have been pressed by the pestle against the mortar.
Color of the Flame. If the substance to be tested is
a solid, a small piece of it is brought on a loop of fine platinum
wire, or in a pair of forceps, into the flame of the alcohol or
Bunsen lamp, and the color imparted to the flame observed.
If a substance in solution is to be tested, the platinum wire is
dipped in the solution and is then introduced into the lamp-
flame. If the solution is too dilute to afford a distinct test in
this way, it must be evaporated, and it is usually best to evapo-
rate nearly to dryness, and to take some of the solid residue
for the test.
Tlie Manipulation of Glass Tubing. Glass
CHEMICAL OPERATIONS. 27
softens when a small piece is heated in the flame of an alcohol
lamp, or when a larger piece is heated in a Bunsen lamp, or
with the blowpipe flame or in a blast lamp.
A tube can be bent easily as soon as the glass softens.
It is best only to bend gently at first, then to .heat the adja-
cent part of the tube, and to bend again, and so on, in order
that the sides of the tube may not fall together in bending.
When a glass tube is heated for some time, it contracts and
the sides thicken. By drawing out a tube either immediately
after it has become soft, or after the sides have thickened, a
tapering point of any desired calibre and thickness of glass can
be obtained.
To close the end of a glass tube, draw the tube off while the
glass is as thin as possible, and hold the tapering point in the
flame, and draw the end off again ; in this way a tube with a
pointed closed end is obtained ; by heating the closed end of
the tube, removing it from the flame, rotating it and blowing
in it, while the glass is still red hot, it expands, and a more
rounded end or a bulb can be produced. Glass tubing can be
cut by making a mark at the required place by a few file
strokes, and then by breaking the glass. The ends of glass
tubes cut in this way should be held in the flame till they
become red hot ; in this way the sharp edges become rounded.
PART II.
PART II. is preparatory to Part III., which contains a general
scheme of analysis applicable to compounds of all the elements.
The most important tests are those which are described in Part
III., and a knowledge of them would suffice alone for the pur-
poses of analysis, if the liability to error in chemical manipu-
lations did not make it expedient to employ a variety of tests,
as corroborative evidence, before coming to a conclusion in
regard to the composition of a substance.
It is important that the student should turn to Part III., and
commit to memory the general features of the scheme of
separation for each group, at the time that he is performing
the reactions of the members of the group as they are described
in the following pages. By this means he will make himself
familiar with the important points in which the compounds
with which he has to deal differ from each other, and the
manner in which these differences can be used in analysis ; also
at this stage of his progress it is advisable for him to make
mixtures of compounds of several elements, and to analyze
them according to the directions given in Part III.
The student, keeping in view the reasons for learning the
characteristic reactions of the compounds of each element,
should perform carefully the tests described in Part II., supple-
menting the description by the closest observation of the phe-
nomena as they pass before his eyes. By practice of this kind
he will soon acquire the skill in manipulation necessary for
analytical work. ALWAYS, WHEN A REACTION is PERFORMED,
THE EQUATION DESCRIBING IT SHOULD BE WRITTEN. The for-
28
PART II. 29
mulas of the reagents and the compound operated upon* form
the first half of the equation ; the formula of the precipitate,
which is given in the book, enters into the second half of the
equation and determines the formulas of its other members.
Thus it is known that baric chloride and calcic sulphate give
a precipitate of BARIC SULPHATE, BaSO 4 . (See page 34.)
From the formulas on the labels of the bottles we can con-
struct the equation : BaCl 2 + CaSO 4 = BaSO 4 + X, and by
inspecting the equation we find the unknown quantity X can
only be CaQ 2 . The following case is more complicated : di-
sodic hydric phosphate, ammonic hydrate, and magnesic sul-
phate form a precipitate of MAGNESIC AMMONIC PHOSPHATE,
MgNH 4 PO 4 ; or, putting the statement into formulas, Na^
HPO 4 + NH 4 HO + MgSO 4 = MgNH 4 PO 4 + X. Here X =
Na 2 + H 2 4- O -f SO 4 , and the question arises : How are these
bodies combined ? A slight experience will teach that the rule
2d (page 9) brings the SO 4 and the Na together, and conse-
quently the H 2 and the O ; while an inspection of the tables
of quantivalence (pages 2 and 12) shows that SO 4 combines
with 2Na, and that O combines with 2H ; hence X becomes
Na 2 SO 4 + H 2 O.
The grouping together of the elements or groups of elements
appearing in reactions is not usually a difficult matter, and is
soon learned with practice.
The formulas of the compounds which are most frequently
used in the laboratory stand after the names of the metals and
acids, and can be used in writing equations.
* These formulas should be given in full upon the labels of the bottles
containing the compounds used and the reagents.
TESTS FOR METALS.
GROUP I.
SODIUM, POTASSIUM, AND AMMONIUM.
THERE is no reagent which precipitates all the metals of this
group. The salts of metals of Group I. have a neutral reac-
tion when they contain strong acids like chlorhydric, nitric,
and sulphuric acids. They have an alkaline reaction when
they contain weak acids like sulphydric, boracic, and carbonic
acids.
SODIUM.
NaCl ; Na 2 CO 8 ; NaHO.
Sodium compounds can be recognized by heating them in
the loop of a piece of fine platinum wire in the flame of a
lamp. Sodium colors the flame yellow, and can be recognized,
even when mixed with much larger quantities of other ele-
ments, which alone impart other colors to the flame.
When a liquid is to be tested, it may be evaporated and the
residue brought on the platinum wire, or frequently it is suffi-
cient to dip the wire in the liquid and to bring it into the flame
of the lamp.
No reagent * precipitates sodium compounds.
* Only the reagents spoken of in this book are referred to.
30
POTASSIUM. 31
POTASSIUM.
KC1; K 2 SO 4 .
Potassium compounds color the flame of a lamp violet. A
small admixture of sodium obscures the color of the flame of
potassium, but the sodium color disappears, and that character-
istic of potassium can be observed when the flame is viewed
through a thick glass colored blue with cobalt.
Mix together a sodium and a potassium salt, observe the
yellow color imparted to the flame by the mixture, showing
the presence of sodium, and then examine the flame for the
potassium color through a piece of cobalt glass thick enough
to exclude the sodium flame. Examine a pure sodium flame
with cobalt glass to ascertain that the glass does not allow the
color of the sodium to pass through it, or until the blue color
of the sodium flame can be easily distinguished from the violet
of the potassium flame.*
flatinic Chloride precipitates concentrated solutions
of potassic chloride as a DOUBLE CHLORIDE OF PLATINUM and
POTASSIUM, (KC1) 2 PtCl 4 . No other salt of potassium can be
used for this test. It is best to evaporate the solution to dry-
ness in a water-bath, with a large quantity of platinic chloride,
and to wash the residue several times with alcohol. The
double chloride is left as a yellow crystalline powder, which
gives the potassium flame. The double chloride is slightly
soluble in water, but insoluble in alcohol.
No other reagent precipitates potassium compounds.
* If the glass is sufficiently* thick and intense in color, the light from
the sodium flame is completely excluded. A thinner glass allows a part
of the light to pass through, but it then has a blue color which can be dis-
tinguished after practice from the violet color of the potassium flame,
which passes through the glass with little of its brilliancy diminished.
32 PART H.
AMMONIUM.
NH 4 C1; NH 4 HO.
Ammonium compounds do not color the flame of a lamp.
jPlatinic Chloride precipitates ammonic chloride as a
DOUBLE CHLORIDE OF PLATINUM AND AMMONIUM (NH 4 C1) 2
PtCl 4 . The precipitate forms under the same circumstances,
and has the same aspect and properties as that obtained with
potassic chloride, but it can be distinguished from the latter
by the absence of color imparted to the flame of a lamp when
it is heated in it. It is destroyed at a dull red heat, and a
residue of metallic platinum is left.
Sodic Hydrate, added in excess to ammonic com-
pounds, causes them to give off the smell of AMMONIA GAS,
NH 3 , especially when the solution is heated. AMMONIA GAS
colors moist turmeric paper brown (a delicate test).
No other compound interferes with the application of this
test.
BARIUM.
GROUP II.
BARIUM, STRONTIUM, CALCIUM, AND
MAGNESIUM.
THE chlorides and nitrates of metals of Group II. are soluble
in water. The sulphates of calcium and magnesium are also
soluble. The solutions have a neutral reaction with test-
paper.
Ammonic and Sodic Carbonates precipitate the
metals of Group II. in neutral solutions as CARBONATES. The
carbonate of magnesium is very soluble in solutions of ammo-
nic salts, particularly in ammonic chloride ; therefore no pre-
cipitate of magnesic carbonate is produced when these salts
are present in considerable quantity.
Central "Phosphates (as disodic hydric phosphate)
precipitate the metals of Group II. in neutral or alkaline solu-
tions as PHOSPHATES.
The carbonates and phosphates of metals of Group II. are
soluble in dilute acids, unless the acids themselves are capable
of precipitating the metals.
Sulphydric Acid, Ammonic Sulphide, and
Ammonic Hydrate do not precipitate the metals of
Group II.
BARIUM.
BaCl 3 ; Ba(NO 3 ) 2 ; Ba(HO) 2 .
Sulphuric Acid (dilute) precipitates baric compounds,
as BARIC SULPHATE, BaSO 4 , white powder.
3
34
PART II.
Calcic Sulphate and other soluble sulphates give the
same precipitate with baric compounds.
Baric sulphate is insoluble in acids.
Ammonic Oxalate precipitates baric compounds from
concentrated neutral or alkaline solutions, as BARIC OXALATE,
BaC 2 O 4 , white powder, soluble in acids.
Barium compounds, particularly when moistened with chlor-
hydric acid, color the flame yellowish green.
STRONTIUM.
SrCl 2 ; Sr(N0 3 ) 2 .
Sulphuric Acid (dilute) and soluble sulphates precipi-
tate strontium from its solutions, as STRONTIUM SULPHATE,
SrSO 4 , white powder. The precipitate will not appear imme-
diately unless the solution be concentrated. In very dilute
solutions it may not appear at all, since strontium sulphate is
slightly soluble in water (i part in 6900).
Ammonic Oxalate precipitates strontium compounds
from neutral or alkaline solutions, as STRONTIUM OXALATE,
SrC 2 O 4 , white powder, soluble in acids.
Strontium compounds, particularly when moistened with
chlorhydric acid, color the flame brilliant red.
CALCIUM.
CaCl*; CaS0 4 ; Ca(HO) 2 .
Sulphuric Acid (dilute) and soluble sulphates, except
calcic sulphate, precipitate concentrated solutions of calcium
compounds, as CALCIC SULPHATE, CaSO 4 , white powder. Cal-
cic sulphate is soluble in a considerable quantity of water,
therefore no precipitate is produced in very dilute solutions by
sulphuric acid. It is insoluble in dilute alcohol, therefore
sulphuric acid (dilute), with the addition of a large quantity of
alcohol, precipitates calcic sulphate from even dilute solutions
of calcium compounds.
MAGNESIUM. 2$
Ammonic Oxalate precipitates calcic compounds from
neutral or alkaline solutions, as CALCIC OXALATE, CaC 2 O 4 ,
white powder. The precipitate forms best after standing some
time in a solution to which ammonic hydrate has been added
in excess. Calcic oxalate does not dissolve in acetic acid.
Calcium compounds, particularly when moistened with chlor-
hydric acid, color the flame yellowish red.
MAGNESIUM.
MgCl 2 ; MgS0 4 .
Hydro-Disodic JPJiosphate precipitates magnesic
compounds, to whose solution ammonic hydrate and ammonic
chloride have been added, as MAGNESIC AMMONIC PHOSPHATE,
MgNH 4 PO 4 , white crystalline powder, or white flakes if the solu-
tion is concentrated. This precipitate only appears after the
lapse of some time in very dilute solutions. It is then crys-
talline.
Sodic Hydrate, in excess, precipitates magnesic com-
pounds, as MAGNESIC HYDRATE, Mg(HO) 2 , white powder, when
it is boiled with their solutions. In case ammonic chloride is
present, the boiling must be continued until the odor of ammo-
nia is no longer perceptible.
Mix together the chlorides of barium, strontium, calcium
and magnesium. Add a small quantity of ammonic chloride,
then ammonic hydrate, and finally ammonic carbonate. The
barium, strontium, and calcium will be precipitated as carbon-
ates. Filter, and to the filtrate add hydro-disodic phosphate.
The magnesium will be precipitated as magnesic ammonic
phosphate. Wash the precipitate, consisting of the carbonates
of barium, strontium, and calcium, with water, and pour over it
a small quantity of dilute hydrochloric acid. This will decom-
pose the carbonates, and the chlorides of the three metals will
36 PART II.
be formed, which being soluble will pass through the filter and
can be caught in a test-tube or small beaker. Dilute the solu-
tion with considerable water and add dilute sulphuric acid.
Barium and strontium will be precipitated as sulphates, while
the calcic sulphate will remain in solution. Filter, add am-
monic hydrate to the filtrate until the reaction becomes alka-
line, and then ammonic oxalate. The calcium will be precipi-
tated as oxalate. Wash the sulphates of barium and strontium
on the filter, and then moisten a small particle of the mass with
chlorhydric acid and examine it on platinum wire in the flame.
The yellowish-green color of barium will first appear. After
holding the wire in the flame for a few seconds dip it into
chlorhydric acid and again bring it into the flame. By repeat-
ing this operation several times the barium flame will disappear
and the crimson color, characteristic of strontium, will be very
plainly visible.*
* Processes similar to the above are used for the separation of all the
metals from each other, and care must always be taken to ascertain whether
enough of a reagent has been added to completely effect a precipitation
before the next test is proceeded with in the filtrate, and when a precipi-
tate is to be examined, it must be thoroughly freed by washing from the
solution which adheres to it.
ALUMINIUM. 37
GROUP III.
ALUMINIUM AND CHROMIUM.
THE sulphates, chlorides, and nitrates of metals of Group III.
are soluble in water, and the solution has an acid reaction with
test-paper. Aluminic and chromic alum solutions have a
neutral reaction.
Ammonic Hydrate, Carbonate, and Sulphide
precipitate the metals of Group III. as HYDRATES.
Neutral Phosphates precipitate the metals of Group
III. as PHOSPHATES.
Sulphydric Acid does not precipitate the metals of
Group III.
ALUMINIUM.
A1 2 (S0 4 ) 3 ; A1 2 C1 6 .
Ammonic Hydrate precipitates alum inic compounds
as ALUMINIC HYDRATE, A1 2 (HO) 6 , gelatinous, white flakes.
The precipitate is insoluble in ammonic hydrate and in am-
monic chloride, but dissolves in acids and in sodic hydrate. It
forms best on boiling.
Sodic Hydrate precipitates aluminic compounds like
ammonic hydrate, but an excess of sodic hydrate dissolves the
precipitate so quickly that its formation easily escapes notice.
No precipitate is formed when the solution in sodic hydrate
is boiled.
Solid compounds of aluminium (except silicates), when mois-
tened with cobaltic nitrate solution, and heated with the oxid-
izing blowpipe flame (see page 25) on charcoal, or on a plat-
inum wire, take a blue color.
38 PART II.
CHROMIUM.
Cr 2 (S0 4 ) 3 ; Cr 2 Cl 6 .
Solutions of chromic oxide compounds are green.
Atnmotlic Hydrate precipitates chromic compounds
as CHROMIC HYDRATE, Cr 2 (HO) 6 , gelatinous, dirty green flakes.
The precipitate is insoluble in ammonic hydrate after boiling,
and in ammonic chloride, but dissolves in acids and in sodic
hydrate.
Sodic Hydrate precipitates chromic compounds like
ammonic hydrate, but dissolves them when an excess of sodic
hydrate is present. CHROMIC HYDRATE is precipitated from
its solution in sodic hydrate when the dilute solution is boiled
for some time.
^Blowpipe Reactions. Compounds of chromium
color the borax bead green.
If chromic hydrate, or any solid chromic compound, is
mixed with equal parts of sodic carbonate and sodic nitrate,
and heated red hot on the platinum foil, chromate of sodium
is formed by the oxidation of chromic oxide. Chromate of
sodium dissolves in water with a yellow color. The color is
heightened when an acid is added, and an acid chromate is
formed in the solution.
This reaction is a characteristic test for chromium compounds.
Mix together solutions of chromium and aluminium salts,
add sodic hydrate until the reaction becomes very strongly
alkaline (the precipitate which first forms will dissolve), dilute
with a considerable quantity of water in a small flask, and boil
for several minutes after a dirty green precipitate has formed.
Filter from the precipitate. This precipitate contains all the
chromium. Test it according to Part III. (102). The fil-
trate contains all the aluminium. Test it according to Part
III. (104).
ZINC, MANGANESE, AND IRON. 39
GROUP IV.
ZINC, MANGANESE, IRON, NICKEL, AND COBALT.
THE sulphates, chlorides, and nitrates of metals of Group
IV. are soluble in water. The solutions have an acid reaction
with test-paper.
Ammonic Sulphide precipitates the metals of Group
IV. as sulphides ; if the solution is not neutral, it should be
made so with ammonic hydrate.
Sodic Hydrate and Ammonic Hydrate pre-
cipitate the metals of Group IV. as HYDRATES. The HYDRATE
OF ZINC is soluble in an excess of the precipitant, and the HY-
DRATES OF NICKEL AND COBALT are soluble in ammonic
hydrate.
Sodic Carbonate precipitates the metals of Group IV.
as CARBONATES (ferric compounds as ferric hydrate).
Neutral Phosphates precipitate the metals of Group
IV. as PHOSPHATES.
Sulphydric Acid does not precipitate the metals of
Group IV. when they are in an acid solution. (See Zinc,
page 40.)
SECTION I.
ZINC, MANGANESE, AND IRON.
Metals whose sulphides are soluble in cold dilute chlorhydric acid.
ZINC.
ZnSO 4 ; ZnCl 2 .
Metallic zinc dissolves readily in dilute chlorhydric acid
and sulphuric acid, with evolution of hydrogen.
40 PART II.
The metal melts readily when heated on charcoal with the
blowpipe, and at a high temperature it distils, and the vapor
burns with a bluish-white flame, depositing an incrustation on
the charcoal of OXIDE OF ZINC, ZnO, which is white when hot
and yellow when cold. If the incrustation is moistened with
cobaltic nitrate and heated in the oxidizing flame, it turns
dirty green. By this test zinc can often be recognized in
alloys.
Ammonic SulpJiide precipitates zinc compounds as
the SULPHIDE OF ZINC, ZnS, white, flocculent precipitate. The
sulphide of zinc is soluble in dilute chlorhydric acid, but
not in acetic acid. It is the only white insoluble sulphide.
SulpJiydric Acid precipitates zinc as the SULPHIDE OF
ZINC only when the metal is combined with acetic acid. To
obtain the precipitate, if a stronger acid is present, add sodic
hydrate until the solution has a strongly alkaline reaction, and
then add acetic acid, until the reaction becomes acid, before
treating with sulphydric acid.
Sodic and Ammonic Hydrates precipitate zinc
compounds as the HYDRATE OF ZINC, Zn(HO) 2 , white flakes.
The precipitate dissolves easily in an excess of the precipi-
tants ; and the solution in sodic hydrate is not reprecipitated
when it is boiled.
MANGANESE.
MnSO 4 ; MnCl 2 .
Solutions of manganese compounds have a faint pink color.
Ammonic SulpTlide precipitates manganese com-
pounds as the SULPHIDE OF MANGANESE, MnS, flesh-colored
flakes. The sulphide of manganese is soluble in dilute acids.
Sodic and Ammonic Hydrates precipitate man-
ganese compounds as MANGANOUS HYDRATE, Mn(HO) 2 , white
flakes, which turn brown on exposure to the air. Manganous
IRON. 41
hydrate is insoluble in an excess of the precipitant, but it is
soluble in a large quantity of ammonic chloride.
^Blowpipe Reactions. Manganese compounds color
the borax bead amethyst in the oxidizing flame. If a com-
pound of manganese is heated with a soda bead (which can be
made in the same way as a borax bead in the loop of a plati-
num wire) in the oxidizing flame, it colors it green, in conse-
quence of the formation of manganate of sodium. The same
color is produced when a compound of manganese is heated
on the platinum foil with sodic carbonate and nitrate. On
boiling the green salt with water containing a little alcohol it
is destroyed, the color disappears, and brown flakes of man-
ganic hydrate are precipitated.
IRON (ferrous salts).
FeS0 4 ; FeCl 2 .
Metallic iron dissolves readily in dilute acids, with evolution
of hydrogen.
Ferrous salts in solution have a pale green color.
Oxidizing Agents (as nitric acid and potassic chlo-
rate), when heated with acid solutions of ferrous salts, oxidize
them to FERRIC SALTS, whose color is brownish red, or reddish
yellow, and is more intense than the green color of ferrous salts.
Ammonic Sulphide precipitates ferrous salts as FER-
ROUS SULPHIDE, FeS, black flakes. Ferrous sulphide is soluble
in dilute acids.
Sodic and Ammonic Hydrates precipitate ferrous
compounds as FERROUS HYDRATE, Fe(HO) 2 , at first nearly
white, then bluish green, and, finally, by absorption of oxygen, red-
dish brown. Ferrous hydrate is insoluble in an excess of sodic
hydrate. The presence of a large quantity of ammonic salts
in a solution prevents its precipitation.
Potassic Ferrocyanide precipitates ferrous com-
pounds as POTASSIC FERROUS FERROCYANIDE, K 2 Fe(FeCv 6 ),*
* Cy, cyanogen, is used as a symbol for the group CN.
42 PART II.
bluish white ', turning quickly dark blue, through absorption of
oxygen from the air.
Potassic Ferricyanide precipitates ferrous com-
pounds, as TURNBULL'S BLUE, Fe 8 (Fe 2 Cyi 2 ),* deep blue. This is
the best test for ferrous compounds.
The last two precipitates are insoluble in dilute acids.
JPotassic Sulphocyanate gives no coloration with
ferrous compounds.
IRON (ferric salts).
Fe 2 Cl 6 .
Reducing Agents, as sulphurous and sulphydric acids,
metallic zinc and iron, reduce ferric salts in solution to ferrous
salts when a free acid is present.
The reaction with sulphydric acid is accompanied by a pre-
cipitation of sulphur, Fe 2 Cl 6 + H 2 S = 2FeCl 2 + 2HC1 + S.
A similar reaction takes place with ammonic sulphide and
the other salts of sulphydric acid.
Ferric salts in solution have & yellow color, and they possess
a much stronger coloring power than ferrous salts.
Ammonic Sulphide reduces ferric salts to ferrous
salts, and then precipitates FERROUS SULPHIDE, FeS, black
flakes.
Sodic and Ammonic Hydrates precipitate ferric
compounds as FERRIC HYDRATE, Fe 2 (HO) 6 , red gelatinous
flakes, insoluble in an excess of the precipitants and in am-
monic salts.
Potassic Ferrocyanide produces a precipitate of
PRUSSIAN BLUE, Fe 4 (FeCv 6 ) 3 , deep blue, in a solution of ferric
salts.
JPotassic Ferricyanide colors solutions of ferric salts
deep reddish brown, but produces no precipitate. On the ad-
dition of a reducing agent a deep blue precipitate forms.
. * See note on preceding page.
NICKEL AND COBALT. 43
"Potassic Sulphocyanate gives a deep red color* with
the smallest traces of ferric compounds in acid solutions.
The different behavior with the last three reagents of ferrous
and ferric salts serves to distinguish between them.
^Blowpipe Heaction. Iron colors the borax bead
green in the reducing flame, and reddish yellow while hot, and
yellow while cold, in the oxidizing flame.
Mix together solutions of zinc, manganese, and iron salts ; if
a ferrous salt is taken, add a little chlorhydric acid and boil
the solution for a few minutes with one or two crystals of po-
tassic chlorate, in order to convert the ferrous into ferric salt.
Add sodic hydrate to the solution until the reaction is strongly
alkaline, boil for a few minutes and filter. All the manganese
and iron will be precipitated. Test the precipitate for iron
according to Part III. (101), and for manganese according
to Part III. (102). All the zinc will be contained in the fil-
trate ; test it for zinc according to Part III. (103).
SECTION II.
NICKEL AND COBALT.
Metals whose sulphides are insoluble in cold, dilute chlorhydric acid.
NICKEL.
NiS0 4 ; Ni(N0 3 ) 2 ; NiCl*
Solutions of nickel salts are green.
Ammonic Sulphide precipitates nickel compounds as
the SULPHIDE OF NICKEL, NiS, black flakes. The sulphide of
nickel is insoluble in cold, dilute chlorhydric acid. It dis-
solves readily on boiling, or in a strong acid.
* Potassic sulphocyanate gives the same color with a solution containing
a large quantity.of free nitric acid.
44 PART II.
Sodic and Ammonic Hydrates precipitate nickel
compounds as the HYDRATE OF NICKEL, Ni(HO) 2 , apple green.
The hydrate of nickel is insoluble in an excess of sodic hy-
drate. It dissolves in ammonic hydrate, and the solution has
a blue color.
^Blowpipe Reactions* Nickel colors the borax bead
in the oxidizing flame violet, when it is hot, and a faint reddish-
brown when it is cold. By long-continued reduction in the
reducing flame, or on charcoal, the bead may be obtained col-
orless, but with gray specks of reduced metal in it.
COBALT.
Co(N0 3 ) 2 ; CoCl 2 .
Solutions of cobalt salts, when dilute, are red.
Ammonic Sulphide precipitates cobalt compounds as
the SULPHIDE OF COBALT, CoS, black flakes. The sulphide of
cobalt is insoluble in cold dilute chlorhydric acid. It dissolves
readily on boiling or in a strong acid.
Sodic and Ammonic Hydrates precipitate cobalt
compounds at first as a blue basic salt, which changes to the
pale red COBALTOUS HYDRATE, Co(HO) 2 on boiling. On ex-
posure to the air it becomes brown, through the formation of
cobaltic hydrate. Cobaltous hydrate is insoluble in an excess
of sodic hydrate, but it dissolves in ammonic hydrate, and the
solution is red, tinged with brown.
Blowpipe Reactions. Cobalt compounds color the
borax bead blue, and the color is so intense that a small quan-
tity of cobalt eclipses the color produced by a much larger
quantity of nickel, when the latter is mixed with it. The blue
color does not disappear on reduction, so that when sufficient
nickel is present to hide the color of a small quantity of cobalt
in a bead, the color of the nickel may be made to disap-
pear by a thorough reduction, either on the platinum wire or
on charcoal, so that the blue color characteristic of cobalt can
COBALT. 45
be detected in the bead. If the bead was reduced on char-
coal, it is advisable to remove it from the charcoal and to melt
it on the platinum wire in order to examine its color.
Mix together sulphates of zinc, manganese, and nickel, and
the nitrate of cobalt and ferrous sulphate, add ammonic hy-
drate until a permanent precipitate begins to form, and then
ammonic sulphide * until the metals are completely precipi-
tated as sulphides. Wash the precipitate on a filter and treat
it with cold, dilute chlorhydric acid, in order to separate the
sulphides of nickel and cobalt from the other sulphides. See
Part III. (96).
Test for nickel and cobalt according to Part III. (97) and
(OS).
Test for the other metals in the chlorhydric acid solution
according to Part III. (99), (WO), (101), (102), and
(103).
* In order to precipitate the nickel completely, the solution must not
contain free ammonic hydrate, and the ammonic sulphide must not con-
tain an excess of ammonic hydrate. If these precautions are not observed
a part of the sulphide of nickel dissolves, imparting a brown color to the
solution,
46 PART II.
GROUP F.
SILVER, MERCURY, LEAD, COPPER, BISMUTH,
AND CADMIUM.
THE salts of metals of Group V. with chlorhydric, nitric, and
sulphuric acids, which are soluble in water, have an acid re-
action with test-paper.
Sulphydric Acid and Ammonic Sulphide pre-
cipitate metals of Group V. in neutral or acid solutions as
SULPHIDES. The sulphides of metals of Group V. are insolu-
ble in AMMONIC SULPHIDE and in SODIC HYDRATE, and in dilute
acids, even when heated ; but, with the exception of mercuric
sulphide, they are all dissolved when boiled with strong NITRIC
ACID.
Sodic and Ammonic Hydrates precipitate metals
of Group V. as OXIDES or HYDRATES. The hydrate of lead is
somewhat soluble in an excess of sodic hydrate, and the oxide
of silver and the hydrates of copper and cadmium are readily
soluble in an excess of ammonic hydrate.
Sodic Carbonate precipitates the metals of Group V.
as CARBONATES.
Neutral Phosphates precipitate metals of Group V.
in neutral solutions as PHOSPHATES,
SECTION 7.
SILVER, MERCUROUS COMPOUNDS, AND LEAD.
Metals whose compounds are precipitated as chlorides by chlor-
hydric acid.
MERCUROUS COMPOUNDS. 47
SILVER.
AgN0 3 .
Metallic silver and its alloy with copper dissolve readily in
nitric acid.
Sulphydric Acid and Ammonic Sulphide
precipitate compounds of silver as the SULPHIDE OF SILVER,
Ag 2 S, black flakes.
Chlorhydric Acid precipitates compounds of silver as
the CHLORIDE OF SILVER, AgCl, white flakes, which settle readily
after boiling or prolonged shaking. The chloride of silver dis-
solves readily in ammonic hydrate. It is insoluble in concen-
trated nitric acid, even when it is boiled with it.
Sodic and Ammonic Hydrates precipitate com-
pounds of silver as the OXIDE OF SILVER, Ag 2 O, a grayish
brown powder.
The oxide of silver dissolves very readily in ammonic hy-
drate.
Blowpipe Reactions. Compounds of silver, mixed
with sodic carbonate, are easily reduced on charcoal, by heat-
ing in the blowpipe flame, and a hard globule of metallic silver
is obtained.
MERCUROUS COMPOUNDS.
H g2 (N0 3 ) 2 ; Hg 2 Cl 2 .
Metallic mercury dissolves readily in nitric acid 'to form
mercurous nitrate.
Copper in the form of a thin sheet or wire can be coated
with mercury by immersing it in a solution of mercury con-
taining a free acid. The coating is deposited in a longer or
shorter time, according to the strength of the solution. It
takes the color of mercury when it is rubbed gently with a bit
of cloth or paper. The copper should be cleansed by immers-
ing it in dilute nitric acid solution before it is put in the solu-
tion containing mercury.
48 PART II.
Oxidi&ing Agents, as chlorine, aqua regia, or strong
nitric acid, transform mercurous into mercuric compounds.
Sulphydric Acid and Ammonic Sulphide
precipitate mercurous compounds as MERCUROUS SULPHIDE,
Hg 2 S, black. Mercurous sulphide is not dissolved when it is
boiled with moderately strong nitric acid. It dissolves readily
in aqua regia.
Chlorhydric Acid precipitates mercurous compounds
as MERCUROUS CHLORIDE, Hg 2 Cl 2 , white powder. Mercurous
chloride turns black, but does not dissolve when ammonic hy-
drate is added to it. It is insoluble in dilute acids. It dis-
solves in aqua regia.
Sodic and Ammonic Hydrates give with mer-
curous compounds black precipitates, insoluble in an excess of
the precipitant. (For tests by heating mercurous compounds,
see page 50.)
LEAD.
Pb(C 2 H 8 2 ) 2 ; Pb(N0 3 ) 2 .
Metallic lead dissolves readily in nitric acid.
Sulphydric Acid and Ammonic Sulphide pre-
cipitate lead compounds as the SULPHIDE OF LEAD, PbS,
black. Sulphide of lead is oxidized by strong nitric acid, with
formation of sulphate of lead, white powder y which is insoluble,
unless a very large quantity of nitric acid is present.
Chlorhydric Acid precipitates lead compounds as
the CHLORIDE OF LEAD, PbCl 2 , white. When the solution is
dilute no precipitate is produced. The chloride of lead dis-
solves entirely on boiling with a large quantity of water.
Sulphuric Acid precipitates lead compounds as the
SULPHATE OF LEAD, PbSO*, white powder. Sulphate of lead
is soluble to some extent in chlorhydric and nitric acids, and
it is slightly soluble in water. It is insoluble in a mixture of
alcohol and water. When complete precipitation is required,
it is best to evaporate with an excess of sulphuric acid until
LEAD. 49
all the other acids are driven off, then to dilute with water,
and to add an equal bulk of alcohol.
LEAD, BARIUM, STRONTIUM, CALCIUM, and STANNIC COM-
POUNDS are the only ones precipitated by SULPHURIC ACID.
Sodic and Ammonic Hydrates precipitate com-
pounds of lead as BASIC SALTS OF LEAD, white precipitate.
Basic salts of lead are somewhat soluble in sodic hydrate.
blowpipe Reactions. Solid compounds of lead give,
when heated with sodic carbonate on charcoal, globules of
metallic lead, recognizable by their softness and ductility. An
incrustation of OXIDE OF LEAD, PbO, deep yellow when hot, light
yellow when cold, is formed upon the charcoal, not far from the
place where the substance is heated.
Pure lead, or alloys containing a large amount of lead, when
heated on charcoal, without soda, burn with a blue flame, and
give the PbO incrustation.
Mix together acetate of lead, nitrate of silver, and mercurous
nitrate, add dilute chlorhydric acid until a precipitate ceases
to form on further addition, and filter the liquid. The pre-
cipitate contains all the silver and mercury and a part of the
lead as chlorides. Add to the filtrate an equal bulk of alcohol
and a small quantity of dilute sulphuric acid. All the lead
which it contains will be precipitated. Filter, wash the pre-
cipitate, and test it for lead on charcoal.
Make a hole in the bottom of the filter and wash the pre-
cipitate obtained with chlorhydric acid into a small flask.
Test the precipitate for the remainder of the lead, and for
silver and mercury, according to Part III. (#7), (08), and
(69).
4
PART II.
SECTION II.
MERCURIC COMPOUNDS, COPPER, BISMUTH, AND CADMIUM.
Metals which are not precipitated by chlorhydric acid.
MERCURIC COMPOUNDS.
HgCl 2 .
Snlphydric Acid and Ammonic Sulphide pre-
cipitate mercuric compounds, at first as double salts, which
appear first white, then yellow, orange, and brown, and finally as
MERCURIC SULPHIDE, HgS, black. Mercuric sulphide does not
dissolve when it is boiled with moderately concentrated nitric
or chlorhydric acid. It dissolves readily in aqua regia.
Sodic Hydrate precipitates mercuric compounds at
first as basic salts, reddish brown, finally as MERCURIC OXIDE,
HgO, yellow ; insoluble in an excess of the precipitant.
Ammonic Hydrate precipitates mercuric compounds
as SALTS CONTAINING AMMONIA, white. The precipitate is
insoluble in an excess of ammonic hydrate.
StannoMS Chloride reduces mercuric compounds, and
precipitates them as MERCUROUS CHLORIDE, Hg 2 Cl 2 , white.
After the metals of Group V., Section I., if they are present
have been removed from a solution by the addition of chlorhy-
dric acid, mercuric compounds are the only ones which give a
precipitate in acid solution with stannous chloride.
Reactions with the Aid of Heat. Dry mercurous
and mercuric chlorides form white sublimates when they are
heated in a closed glass tube. All dry compounds of mer-
cury, when they are mixed with dry sodic carbonate, and
heated in a closed tube, give a sublimate of metallic mercury.
The sublimate is at first a faint metallic film, which augments
until drops of mercury appear. If the quantity of mercury is
COPPER.
small, the film may be made to take the form of metallic drops
by rubbing it with a copper wire.
COPPER.
CuSCV, CuCl 2 .
Metallic copper dissolves readily in dilute nitric acid. It
dissolves with difficulty in chlorhydric acid. All copper solu-
tions are blue or green.
Iron OT Zinc precipitates copper from its acid solutions,
either as a metallic coating or as brownish red metallic grains.
If a strip'of zinc and one of platinum are placed in a dilute
acid solution of copper, so that they touch each other, the
platinum is plated with copper.
Sulphydric Acid and Ammonic Sulphide
precipitate cupric compounds as CUPRIC SULPHIDE, CuS, black.
Cupric sulphide is insoluble in dilute acids, but dissolves readily
in strong acids. It is somewhat soluble in an excess of am-
monic sulphide.
Sodic Hydrate precipitates cupric compounds as
CUPRIC HYDRATE, Cu(HO) 2 , light blue. On boiling, CUPRIC
OXIDE, CuO, black, is formed. The precipitate is insoluble in
an excess of sodic hydrate.
Ammonic Hydrate precipitates cupric compounds as
CUPRIC HYDRATE, which dissolves immediately in an excess of
ammonic hydrate. The solution has a very intense blue color.
A valuable test for cupric compounds.
Ferrocyanide of Potassium precipitates cupric
compounds in acid solutions, as FERROCYANIDE OF COPPER,
Cu 2 (FeCy 6 ), reddish brown. This is a delicate test for very
small quantities of copper.
Blowpipe Reactions* Cupric compounds color the
borax bead blue when cold, and green when hot, in the oxidiz-
ing flame. The bead is colored red, and becomes opaque in
ij2 PART II.
the reducing flame. No other metal produces this color-
ation.
When cupric compounds are heated with sodic carbonate
on charcoal, metallic copper is reduced in the form of small
globules, which can be easily recognized by their hardness and
red color.
Copper Flame. Compounds containing copper (alloys
and salts) color the flame of a lamp green, or if chlorine is
present, blue. By moistening a cupric compound with chlorhy-
dric acid the blue color can easily be detected.
BISMUTH.
Bi(N0 3 ) 3 .
Metallic bismuth dissolves readily in moderately concen-
trated nitric acid. It dissolves with great difficulty in chlor-
hydric acid.
Water, Solutions of bismuth, particularly those contain-
ing chlorhydric acid, are remarkable for giving a precipitate
consisting of a BASIC SALT, when water is added to them,
unless they contain a large quantity o free acid. The basic salt
can be dissolved by the addition of an acid. CHLORHYDRIC
ACID precipitates nitrate of bismuth solution as a BASIC CHLOR-
IDE because the basic chloride of bismuth is more insoluble
than the other basic salts. . The precipitate is soluble on the
further addition of chlorhydric acid.
Sulphydric Acid and Ammonic Sulphide pre-
cipitate bismuth compounds as the SULPHIDE OF BISMUTH,
Bi 3 S 8 , black.
Sodic and Ammonic Hydrates precipitate bis-
muth compounds as the HYDRATE OF BISMUTH, Bi(HO) 3 , white.
The hydrate of bismuth is insoluble in an excess of sodic
and ammonic hydrates.
Blowpipe Reactions. Bismuth compounds, mixed
with sodic carbonate, and heated on charcoal, give brittle
CADMIUM.
53
metallic globules, and an incrustation of OXIDE OF BISMUTH,
Bi 2 O 3 , on the charcoal.
The incrustation is orange yellow when hot, and bright yellow
when cold.
CADMIUM.
Cd.
Metallic cadmium dissolves readily in nitric acid, and the
solution contains nitrate of cadmium, Cd(NO 8 ) 2 .
Sulphydric Acid and Ammonic Sulphide
precipitate cadmium compounds as the sulphide, CdS, lemon
yellow. This is insoluble in ammonic sulphide and potassium
cyanide, but readily soluble in hot dilute sulphuric or nitric
acid.
Sodic and Ammonic Hydrates precipitate com-
pounds of cadmium as the hydrate, Cd(HO) 2 , very readily solu-
ble in a slight excess of ammonic hydrate, but insoluble in
sodic hydrate.
When compounds of cadmium are mixed with sodic carbon-
ate and exposed on charcoal to the inner blowpipe flame, the
charcoal becomes covered with an incrustation of yellow or
brownish-yellow oxide of cadmium, CdO.
Mix together mercuric chloride, cupric sulphate, and the
nitrates of bismuth and cadmium, and add sulphydric acid
until the metals are completely precipitated. Filter, and wash
the precipitates with a little water ; spread the filter out ;
scrape the precipitate from it, and heat the precipitate gently
in a porcelain dish with strong nitric acid until red fumes
cease to be given off ; then add a little water and boil for a few
minutes. The sulphide of mercury remains insoluble. Filter
it off and test according to Part III. (89). Test the filtrate
for bismuth, copper, and cadmium according to Part III. (91),
(92), and (93).
54 PART II.
GROUP VI.
TIN, ANTIMONY, ARSENIC, AND GOLD.
THE metals of Group VI. sometimes act as acids, uniting
with metals, and sometimes as metals, uniting with acids.
Their combinations with acids have an acid reaction ; those
with metals which are soluble in water have an alkaline re-
action.
Sulphydric Acid precipitates the metals of Group VI.
as SULPHIDES. The precipitation takes place slowly, particu-
larly in the case of arsenic acid, and it should never be con-
sidered complete unless a current of sulphydric acid gas is
passed through the solution for some time, and it is left to
stand twenty-four hours.
The sulphides of metals of Group VI. are insoluble in dilute
acids, but they are decomposed or dissolved by boiling with
concentrated acids. They are soluble in sodic hydrate and
in ammonic sulphide (the sulphide of gold with difficulty).
TIN.
Sn.
Metallic tin dissolves readily in strong chlorhydric acid on
boiling, and the solution contains STANNOUS CHLORIDE, SnCl 3 .
Tin is oxidized to STANNIC OXIDE, SnO 2 , white powder, by
strong nitric acid. Stannic oxide is insoluble in nitric acid,
but dissolves readily in hot concentrated chlorhydric acid,
and the solution contains STANNIC CHLORIDE, SnCl 4 . Stannic
chloride is also formed by the action of aqua regia on metallic
tin.
STANNOUS COMPOUNDS.
55
Zinc precipitates METALLIC TIN from its solu-
tions in acids as crystalline metallic particles.
^Blowpipe ^Reactions. Compounds of tin are re-
duced, when they are heated with sodic carbonate and potas-
sic cyanide on charcoal ; and METALLIC TIN may be discov-
ered in flattened globules by rubbing the fused mass, taken
from the charcoal, in a mortar with water, and washing several
times by decantation. When the globules are large, they may
be observed on the charcoal during the fusion.
Oxidation by Sodic Nitrate. When a sulphide of
tin is oxidized at the lowest possible temperature by a mixture
of sodic nitrate and carbonate, STANNIC OXIDE, SnO 2 , which
is insoluble in water, is formed. If the oxidation is carried on
at too high a temperature, stannate of sodium is formed, which
is soluble in water.
STANNOUS COMPOUNDS.
SnCl 2 .
Snlphydric Acid and Ammonic Sulphide pre-
cipitate stannous compounds from acid solutions as STANNOUS
SULPHIDE, SnS, dark brawn. Stannous sulphide dissolves with
difficulty in a colorless solution of ammonic sulphide (the
mono- sulphide), and it is scarcely soluble in ammonic hydrate
and carbonate. It is converted into stannic sulphide by a
yellow solution of ammonic sulphide (the poly-sulphide), and
dissolves readily when warmed with the solution. Stannous
sulphide is soluble in sodic hydrate. The sulphides of tin are
precipitated from these solutions, when a dilute acid is added
gradually, until the reaction becomes strongly acid.
Sodic and Ammonic Hydrates and Carbo-
nates precipitate stannous compounds as STANNOUS HY-
DRATE, Sn(HO) 2 , white.
Stannous hydrate dissolves in an excess of sodic hydrate,
56 PART 77.
but it is insoluble in an excess of sodic carbonate and of am-
monic hydrate and carbonate.
Mercuric Chloride changes stannous chloride, SnCl 2 ,
into STANNIC CHLORIDE, SnCl 4 , and a white precipitate of MER-
CUROUS CHLORIDE, Hg 2 Cl 2 , is formed. No other metal in solu-
tion gives this reaction with mercuric compounds.
STANNIC COMPOUNDS.
SnCl<.
Swlphydric Acid and Ammonic Sulphide
precipitate stannic compounds as STANNIC SULPHIDE, SnS 2 ,
light yellow. Stannic sulphide dissolves readily in ammonic
sulphide, and in sodic hydrate, and is precipitated completely
from the solution, when a dilute acid is added gradually until
the reaction becomes strongly acid. Stannic sulphide is nearly
insoluble in ammonic carbonate.
Sodic and Ammonic Hydrates and Carbon-
ates precipitate stannic compounds as STANNIC HYDRATE,
Sn(HO) 4 , white. Easily soluble in sodic hydrate.
Mercuric Chloride does not give a precipitate with
stannic chloride.
Metallic Zinc precipitates TIN as crystalline metallic
particles from stannic compounds in an acid solution, and the
tin can be easily recognized by dissolving the metallic parti-
cles, after they have been washed by decantation. They are
dissolved by heating them with a few drops of strong chlorhy-
dric acid, and the stannous chloride thus obtained gives the
precipitate, above described, with mercuric chloride.
ANTIMONY.
Sb.
Metallic antimony is scarcely attacked by chlorhydric acid.
It is oxidized when heated with moderately strong nitric acid
ANTIMONY. 57
to ANTIMONIC OXIDE, Sb 2 O 5 , which is almost completely inso-
luble in nitric acid, but is readily soluble in hot concentrated
chlorhydric acid. Aqua regia dissolves metallic antimony as
ANTIMONIC CHLORIDE, SbCl 5 .
Water precipitates solutions of antimony containing chlor-
hydric acid, particularly those of antimonious compounds, as
a BASIC CHLORIDE. The precipitation can be prevented, or
the precipitate dissolved by the addition of a sufficient quan-
tity of acid ; for this purpose tartaric acid is the most suitable.
Metallic Zinc partially precipitates METALLIC ANTI-
MONY from its acid solutions, and when a piece of platinum
in contact with a piece of zinc is introduced into solutions of
antimony containing an excess of chlorhydric acid, metallic
antimony is deposited upon the platinum as a dark-brown stain.
No other metal produces the same stain under like circumstances.
Antimoniuretted Hydrogen. To obtain this body,
follow exactly the directions given for obtaining arseniuretted
hydrogen. (See page 59.)
The mirror obtained with antimoniuretted hydrogen consists
of a black, sooty, metallic deposit. It dissolves very slowly in
hypochlorite of sodium. If the deposit is moistened with
yellow ammonic sulphide, an orange-yellow stain appears on the
spot when it is dried. These reactions are unimportant as
tests for antimony, but a knowledge of them is necessary, in
order that they may not be mistaken for evidences of the pres-
ence of arsenic.
^Blowpipe Reactions* Antimony compounds, mixed
with sodic carbonate and potassic cyanide, are quickly reduced,
at a comparatively low temperature, to METALLIC ANTIMONY,
brittle shining grains. The metal is completely volatilized by
a strong heat. Metallic antimony, when heated on charcoal,
burns with a white smoke, and gives an incrustation which is
deposited at some distance from the place heated, and is very
volatile before the blowpipe flame.
Oxidation by Sodic Nitrate. When a sulphide of
5 8 PART II.
antimony is oxidized by a mixture of sodic carbonate and
nitrate, ANTIMONIATE OF SODIUM, Na 3 SbO 4 , insoluble in water,
is formed.
ANTIMONIOUS COMPOUNDS.
SbCl 3 ; KSbOC 4 H 4 O 6 , Tartar Emetic.
Sulphydric Acid and Ammonic Sulphide pre-
cipitate antimonious compounds as ANTIMONIOUS SULPHIDE,
Sb 2 S 8 , orange red. The precipitation should be made in a cold
solution containing tartaric acid and very little free chlorhy-
dric acid. Antimonious sulphide dissolves in sodic hydrate
and in ammonic sulphide, most readily in yellow ammonic sul-
phide, and is precipitated completely from these solutions when
a dilute acid is added gradually until the reaction becomes
acid. It is nearly insoluble in ammonic carbonate. Yellow
ammonic sulphide converts it into ANTIMONIC SULPHIDE, Sb 2 S 6 .
(See below.)
Sodic and Ammonic Hydrates and Carbon-
ates precipitate antimonious compounds as ANTIMONIOUS
OXIDE, Sb 2 O 3 , voluminous white precipitate. The precipitation
only takes place after the lapse of a considerable time in solu-
tions containing tartaric acid. Antimonious oxide is soluble in
sodic hydrate.
ANTIMONIC COMPOUNDS.
SbCl 5 ; Sb 2 6 .
Sulphydric Acid and Ammonic Sulphide pre-
cipitate antimonic compounds in acid solution as ANTIMONIC
SULPHIDE, Sb 2 S 6 , orange red. The precipitation does not take
place immediately ; but first an orange color appears ; and it is
only after passing sulphydric acid for a long time through the
solution that all the antimonic sulphide is precipitated. The
precipitation should be made in a cold solution containing tar-
ARSENIC.
59
taric acid and very little free chlorhydric acid. Antimonic
sulphide has the same properties as antimonious sulphide.
Antimonic oxide, Sb 2 O 5 , plays the part of an acid with bases,
and forms insoluble compounds with SODIUM, and soluble
compounds with POTASSIUM.
Compounds of antimony can best be recognized by the stain,
which they form on platinum, when the metal is precipitated
by zinc from their solutions. (See page 57, Antimony.)
ARSENIC.
As.
Metallic arsenic is readily oxidized to arsenious or to ar-
senic compounds by nitric acid and is dissolved. It is not dis-
solved by chlorhydric acid. Metallic arsenic volatilizes at a
heat below redness in a tube or on charcoal, and produces an
odor like garlic, very characteristic of compounds of arsenic.
The same odor is produced by heating a dry compound of
arsenic on charcoal.
Arseniuretted Hydrogen. To obtain this body,
and to use Marsh's test, provide a 4 oz. flask with a tight-
fitting cork, into which a funnel-tube and a small tube drawn
off to a point and bent at a right angle * are introduced. Fill
it two-thirds full of dilute sulphuric acid, and add several
pieces of pure zinc. A brisk evolution of hydrogen only com-
mences after a few minutes. When that point is reached,
wait five minutes for the expulsion of the air contained in the
flask (without this precaution there is danger of an explosion),
and light the hydrogen issuing from the point of the bent tube.
The opening of the point and the quantity of gas evolved
should be such that the hydrogen burns with a blunt flame
* In order to dry the gas, it is better to fit to the cork a chloride of cal-
cium tube, bent downwards, so that it will not tip the flask over by its
weight, and to adapt to the chloride of calcium tube, by means of a cork,
a suitable jet directed upwards.
60 PART II.
about J in. in length. Hold a bit of porcelain in the flame, in
order to be certain that the reagents employed are free from
arsenic. (See below.) If this is the case, pour a little of an
acid liquid containing arsenic into the funnel-tube, while the
hydrogen flame continues lighted. The flame after a few
moments becomes white, and leaves a black stain of metallic
arsenic upon a cold porcelain object held in it, in the same
way that the flame of a candle would leave a deposit of soot
on a cold surface. The arsenic stain or mirror is shining black
(not sooty black, like antimony). It dissolves quickly in hypo-
chlorite of sodium. When the stain is moistened with yellow
ammonic sulphide solution, and the spot is dried, it is bright
yellow.
Reaction with the Aid of Heat. All dry com-
pounds of arsenic, except some compounds with the higher
metals, when they are mixed with dry sodic carbonate and po-
tassic cyanide, and heated in a sealed tube, give a sublimate
of metallic arsenic, which can be best recognized by breaking
the sealed end of the tube after the formation of the sublimate,
and by heating the sublimate quickly until it begins to volatil-
ize, and by smelling of the upper end of the tube. A smell
of garlic is proof of the presence of arsenic.
ARSENIOUS COMPOUNDS.
As 2 O 8 .
Arsenious oxide is sparingly soluble in water It dissolves
more readily in sodic hydrate or carbonate, or in chlorhydric
acid.
Sulphydric Acid and Ammonic SulpJiide pre-
cipitate arsenious compounds from acid solutions as ARSENI-
OUS SULPHIDE, As 2 S 8 , yellow. Arsenious sulphide dissolves
very readily in sodic hydrate and ammonic sulphide, and it
also dissolves, although less readily, in ammonic carbonate.
ARSENIC COMPOUNDS. 61
It is precipitated from these solutions, when a dilute acid is
slowly added until the reaction becomes acid.
Sodic and Ammonic Hydrates and Carbon-
ates produce no precipitate in arsenious compounds.
ARSENIC COMPOUNDS.
As 2 O 5 .
By heating any compound of arsenic with strong nitric acid,
or by fusing a dry compound with a mixture of dry sodic car-
bonate and nitrate in a porcelain crucible, arsenic acid,
H 3 AsO 4 , or arseniate of soda, Na^AsC)^ is formed. These com-
pounds are soluble in water.
Sulphydric Acid and Ammonic Sulphide do
not immediately precipitate acid solutions of arsenic acid.
The solution (which should contain free chlorhydric acid)
at first becomes yellow, when a current of sulphydric acid is
passed through it, and finally a yellow precipitate is formed ;
reduction to the state of an arsenious compound takes place
slowly, and at the end of several days all the arsenic is pre-
cipitated as ARSENIOUS SULPHIDE, As 2 S 3 , yellow. This opera-
tion may be very materially accelerated by boiling the solution.
See the properties of arsenious sulphide above.
Argentic ^Nitrate produces no precipitate in acid
solutions of arsenic compounds. {When chlorhydric acid is
present a white precipitate of argentic chloride forms, and
must usually, after the addition of an excess of argentic nitrate,
be separated by decantation and filtration.) If sodic hydrate
is added to a clear solution containing arsenic acid, and con-
taining also an excess of argentic nitrate, until a permanent
precipitate forms, and if then acetic acid is added until the
reaction becomes acid, ARGENTIC ARSENIATE, Ag 3 AsO 4 , brick
red, is precipitated. This precipitate is soluble in ammonic
hydrate and in dilute nitric acid.
This is the usual test for arsenic.
62 PART II.
GOLD.
AuCl 8 .
Metallic gold is insoluble in any single acid, but it dissolves
readily in aqua regia.
Ferrous Sulphate solution in considerable quantity
precipitates METALLIC GOLD, Au, purplish-brown powder, from
acid solutions containing gold.
Stan/nous Chloride solution precipitates METALLIC
GOLD, Au, purple flakes, very finely divided, from acid solutions
containing gold. (A very dilute solution of stannous chloride
should be added, drop by drop, to the gold solution.)
Sulphyciric A.d(l gas slowly precipitates gold com-
pounds in acid solutions as SULPHIDE OF GOLD, Au 2 S 3 , brown
flakes. The precipitate is soluble after a long digestion with
yellow ammonic sulphide.
^Blowpipe Reaction. Gold is easily separated from
its compounds with non-metallic elements by heating them on
charcoal. It can be recognized as bright yellow globules.
Gold can easily be separated from the other metals and recog-
nized by its precipitation with ferrous sulphate, or by its insolu-
bility in any single acid.
Mix together solutions containing tin, antimony, and arsenic,
dilute the solution and add a considerable quantity of dilute
chlorhydric acid. Pass sulphydric acid through the solution
for an hour, and set it over night in a warm place. Filter the
precipitate, wash and dry it completely. It contains all the
metals in the form of sulphides ; separate them according to
Part III. (83) and the following tests.
TESTS FOR ACIDS.
GROUP I.
ARSENIOUS, ARSENIC, CHROMIC, SULPHURIC,
PHOSPHORIC, BORACIC, OXALIC, FLUORHY-
DRIC, CARBONIC, AND SILICIC ACIDS.
Acids which are precipitated from neutral or slightly alkaline
solutions by baric chloride.
SECTION I.
ARSENIOUS, ARSENIC, AND CHROMIC ACIDS.
Acids which are precipitated as sulphides or reduced to an oxide
by sulphydric acid.
ARSENIOUS and ARSENIC acids are precipitated as sulphides,
and must always be detected by sulphydric acid.
Arsenic with this reagent plays the part of a metal. (See
pages 60 and 61.)
CHROMIC ACID.
H 2 CrO 4 ; K 2 Cr 2 O 7 .
Solutions containing chromic acid have a yellow color.
Those which have an acid reaction are of a deeper color, and
63
64 PART II.
very concentrated acid solutions are red. Solutions contain-
ing chromic acid can usually be recognized by these colors.
Chromic acid can easily be reduced to chromic oxide (see
page 38) by boiling its solution with chlorhydric acid and
alcohol, or by adding to the solution sulphydric acid or am-
monic sulphide. Therefore, in all solutions to which these
latter reagents have been added, chromic acid is changed to
chromic oxide, and must be looked for among the metals.
JBaric Chloride precipitates chromic acid in neutral
solutions, or in solutions of which the only free acid is acetic
acid (/. e., solutions which have been made alkaline by sodic
hydrate, and acid by acetic acid), as BARIC CHROMATE,
BaCrO 4 , light yellow. Chromium may be discovered in the pre-
cipitate of baric chromate thus obtained, by dissolving some
of it in the borax bead. The green color of chromic oxide
appears, even though very little chromate of barium was con-
tained in the precipitate.
No other acid which precipitates baric chloride gives the same
color in the borax bead.
SECTION II.
SULPHURIC AND SULPHUROUS ACIDS.
Acids which are precipitated by baric chloride in acid solutions,
either immediately or after oxidation.
^Blowpipe Reactions. All compounds containing
sulphur, when they are pulverized, moistened, and mixed with
sodic carbonate, and when the mixture is heated on charcoal,
form sodic sulphide. The sodic carbonate must be heated
until it soaks into the charcoal, then if the portion of the char-
coal which has absorbed it is dug out with a knife, moistened
with water, and laid on a piece of bright silver, the presence
of sulphur may be detected by the appearance'of a black stain
SULPHURIC AND SULPHURO US A CIDS. 65
of sulphide of silver. If no silver is at hand, the sodic sul-
phide can be extracted by soaking with water the portion of
the charcoal which has been heated. The solution, after it has
been filtered, and acidified with acetic acid, gives a precipitate
of SULPHIDE OF LEAD, PbS, black, with a solution of ACETATE
OF LEAD.
For the separation of sulphuric and sulphurous acids, see Part
III. (123) and (124).
SULPHURIC ACID.
H 2 SO 4 ; Na 2 SO 4 .
Baric Chloride precipitates compounds of sulphuric
acid in neutral or acid solutions as BARIC SULPHATE, BaSO 4 ,
white powder. Baric sulphate is insoluble in chlorhydric, nitric,
sulphuric, and the weaker acids. No other acid gives a like
precipitate with BaCl 2 , in acid solutions. COMPOUNDS OF LEAD
AND STRONTIUM and STANNIC OXIDE are the only others precipi-
tated by sulphuric acid.
Calcic Chloride in concentrated solutions gives a pre-
cipitate of CALCIC SULPHATE, CaSO 4 , but calcic sulphate is
soluble in 380 parts of water.
SULPHUROUS ACID.
H 2 SO 8 ; Na 2 SO 8 .
Sulphurous acid, in acid solutions, can be recognized by the
smell of sulphurous oxide which is given off. Sulphurous
oxide is evolved from acid solutions of sulphites when they
are heated.
JZaric Chloride precipitates compounds of sulphurous
acid in neutral solutions as BARIC SULPHITE, BaSO 3 , white
powder. Baric sulphite is decomposed and dissolved by chlor-
hydric and nitric acids. POTASSIC DICHROMATE oxidizes sul-
phurous acid in a solution, made acid with chlorhydric acid, to
SULPHURIC ACID, 2(H 2 CrO 4 ) + 3(H 2 SO 8 ) = Cr 2 (SO*) 8 + 5H 2 O.
5
66 PART II.
Sulphydric Acid decomposes sulphurous acid in acid
solutions with precipitation of sulphur.
2 H 2 S + H 2 SO 8 = S 3 + 3H 2 O.
The Iron Reduction Test. POTASSIC FERRICYAN-
IDE AND FERRIC CHLORIDE, in consequence of the reduction
of the ferric chloride, give a blue precipitate when these so-
lutions are mixed, and a drop of the mixture is held on the end
of a glass rod in an atmosphere containing sulphurous acid.
Sulphydric acid gives the same reaction, and when sulphydric
acid is present it is necessary to add to the solution sufficient
plumbic acetate to precipitate it, before applying this test for
sulphurous acid. This reaction is produced equally well in a
solution ; but there are many other reducing agents which act
in the same manner, but which do not take the gaseous form,
and for this reason it is best to add chlorhydric acid to the
solution, to warm it, and to test the gas evolved for sulphurous
acid with potassic ferricyanide and ferric chloride.
Sulphurous acid is usually recognized by its smell, or ty the
above test.
SECTION III.
PHOSPHORIC, BORACIC, OXALIC, AND FLUORHYDRIC ACIDS.
Acids which are precipitated by baric chloride in neutral solutions ,
but which are not precipitated in acid solutions.
For the tests by which these acids can be most easily detected, see
Part III. (125-128).
PHOSPHORIC ACID.
H 3 PO 4 ; Na 2 HPO 4 .
All the Metals of Groups II., III., IV., V., pre-
cipitate compounds of phosphoric acid in neutral or in slightly
alkaline solutions as PHOSPHATES. The precipitate is soluble
BORACIC ACID. 67
in acids. The phosphoric acid cannot usually be separated
from the metal by treating the precipitate with ammonic
hydrate, and from most metals it can only be partially separ-
ated by a treatment with sodic hydrate or carbonate. MAG-
NESIC SULPHATE solution, to which a solution of ammonic
chloride and of ammonic hydrate is added, precipitates com-
pounds of phosphoric acid as MAGNESIC AMMONIC PHOSPHATE,
MgNH 4 PO 4 , white crystalline powder, soluble in acids but inso-
luble in ammonic hydrate. When the quantity of phosphoric
acid is very small, the precipitate only forms after some time.
This is the best reagent for phosphoric acid in neutral or slightly
alkaline solutions.
Molybdate of Ammonium * precipitates compounds
of phosphoric acid in an acid solution as a yellow crystalline
phospho-molybdate of ammonium. No other acid gives a like
precipitate. The best reagent for phosphoric acid in acid solu-
tions is molybdate of ammonium, when there are bases present
which are precipitated by ammonic hydrate.
Sulphydric acid and ferrocyanhydric acid also precipitate
ammonic molybdate solution. (See Part III., 127.)
BORACIC ACID.
H 8 BO 3 ; Na 2 B 4 O 7 , Borax.
All the Metals of Groups II., III., IV., V. preci-
pitate compounds of boracic acid in neutral or slightly alkaline
solutions as BORATES. The precipitate is soluble in acids.
The precipitation of boracic compounds by metals of these
groups is mostly incomplete, and the acid can be separated
from the metal in almost all cases by treating the precipitate
with ammonia or with sodic hydrate or carbonate.
Flame Test. Boracic acid in dry compounds or in con-
* It is best to pour a few drops of the solution to be tested into the am-
monic molybdate solution, instead of adding the ammonic molybdate to the
solution to be tested.
68 PART II.
centrated solutions imparts a beautiful green color to the flame
of burning alcohol.
In order to perform the test, mix the dry boracic acid com-
pound with a few drops of strong sulphuric acid in a small
evaporating dish, add alcohol, and set the alcohol on fire. Stir
the contents of the dish constantly during the combustion of
the alcohol, and observe the green color, when the alcohol has
mostly burned away.
Turmeric Paper Test.* Boracic acid compounds,
when their solution has been rendered acid by chlorhydric
acid, turn a piece of turmeric paper, which has been dipped in
the solution and completely dried, brownish red. This is the
usual test for boracic acid.
OXALIC ACID.
H 2 C 2 O 4 ; KHC 2 O 4 -
All the Metals of Groups II., III. 9 IV., F. pre-
cipitate salts of oxalic acid in neutral solutions as OXALATES,
except chromic oxide compounds. The precipitate is soluble
in acids, and in the case of many metals the oxalic acid is
removed from the precipitate by ammonic hydrate and by sodic
hydrate and carbonate.
Sulphate of Calcium precipitates oxalic acid and its
salts in a solution to which sufficient ammonic hydrate to
render the solution strongly alkaline, and then sufficient acetic
acid to render the reaction acid, have been added, as CALCIC
OXALATE, CaC 2 O 4 , white powder. No other acid, except fluor-
hydric acid, produces a precipitate under these circumstances, and
calcic fluoride cannot easily be mistaken for calcic oxalate. (See
fluorhydric acid, below.)
Sulphuric Acid (concentrated) decomposes dry com-
pounds, or highly concentrated solutions of compounds of
* If iron is present it is necessary to boil the solution with sodic carbon-
ate in excess, to filter, and to use the filtrate for the turmeric paper test.
FLUORHYDRIC ACID.
69
oxalic acid, with evolution of CARBONOUS and CARBONIC OX-
IDES. Effervescence takes place. H 2 C 2 O 4 = CO +CO 2 + H 2 O.
FLUORHYDRIC ACID.
HF ; CaF 2 ; NH 4 F.
Fluorhydric acid cannot be present in acid solutions in glass
vessels.
BARIUM, STRONTIUM, and CALCIUM salts in neutral solu-
tions precipitate fluorhydric acid as BARIUM, STRONTIUM, or
CALCIUM Fluoride, BaF 2 , SrF 2 , CaF 2 . The two former are
voluminous white precipitates. Calcium fluoride is a gelatin-
ous transparent precipitate, whose formation it is very difficult
to observe.
// is usually unnecessary to test for fluorhydric acid except in
solid substances.
Sulphuric Acid (concentrated) sets fluorhydric acid
free from its solid compounds, and the acid may be recog-
nized by its property of etching glass. To perform the test,
mix the pulverized substance, containing fluorine, with strong
sulphuric acid in a lead cup,* or in a platinum crucible. Pre-
pare a piece of glass by melting wax on it and pouring off all
that does not adhere, leaving a thin coating of wax on the sur-
face ; scratch lines in the wax, laying the surface of the glass
bare ; cover the vessel containing the fluorine compound and
sulphuric acid with the glass, and warm gently. After fifteen
minutes warm the glass, and rub off the wax ; the surface ex-
posed by the scratches will be etched by the fluorhydric acid.
Fluorhydric acid must always be removed, if present, by heat-
ing with strong sulphuric acid, before the other acids of Group I.,
except sulphuric acid and carbonic acid, are tested for in a sub-
stance.
* A lead cup may be made by hammering up the end of a piece of one-
inch lead pipe until it is entirely closed, and by sawing off the pipe i$
inches from the end. Such a cup may be warmed on a sand-bath suffi-
ciently for making the test without danger of melting it.
7 o PART II.
SECTION IV.
CARBONIC ACID AND SILICIC ACID.
Acids which are precipitated by baric chloride in neutral selu-
tion, but which are set free by acids, and which cannot be present
in a' solution that has been evaporated with an excess of an acid.
CARBONIC ACID.
Na 2 C0 3 ; K 2 CO 3 .
Carbonic acid can only be present in considerable quantity
in a solution which has an alkaline reaction.
All the Metals of Groups II., III., IV., V. pre-
cipitate alkaline carbonates.
Every Acid sets free CARBONIC DIOXIDE, CO 2 , from a
solution of a carbonate. An effervescence or the formation of
bubbles can be observed when an acid is added to a solution of
a salt of carbonic acid. Carbonates insoluble in water are also
decomposed by a free acid, carbonic dioxide being evolved.
Carbonic dioxide can easily be recognized by the white
precipitate of CARBONATE OF CALCIUM, CaCO 3 , which the gas
produces in a drop of lime-water,* held in it on the end of a
glass rod.
SILICIC ACID.
K 2 Si0 3 .
Silicic acid combined with bases in a solution is set free by
all acids, and being decomposed into water and silicic oxide
(H 2 SiO 3 = H 2 O + SiO 2 ), the latter often separates as a pre-
cipitate ; frequently, however, it remains for months in a solu-
tion after an acid has been added.
* The lime-water is soon destroyed by the absorption of carbonic di-
oxide from the air, and before using it to test for carbonic acid, the stu-
dent should assure himself that a drop of it gives a precipitate with the
gas evolved from sodic carbonate, to which chlorhydric has been added.
SILICIC ACID. 7I
When silicic oxide, or silica, has been separated from its com-
bination with a base by the addition of an acid, and the solution
has been evaporated completely to dryness, the silica remains
perfectly insoluble when the dry mass is treated with water or
acids to dissolve the bases. This is the characteristic test for
silicic acid.
When silicic acid is present in a solution it is recognized
and separated by the above process before any other tests are
performed.
Many solid compounds of silicic acid are not acted upon by
acids, and can only be brought into solution by the process
described, Part III., XXIII.
The following properties of silicic acid must be considered,
in order to determine whether a body, which has been left in-
soluble after a treatment with an acid, is silica, or some other
compound, which is likewise insoluble :
Silicic acid is precipitated from its solutions by acids in the
gelatinous form, or in the form of amorphous white flakes.
Silica which has been dried always has the latter form.
Silica, after it has been fused with four parts of a mixture
of sodic carbonate and potassic carbonate, forms a glass, which
is entirely soluble in water. When the solution thus obtained
is evaporated with an excess of nitric acid, and the dry mass
is treated with water, no metal should go into solution which
gives a precipitate with sodic carbonate.
PART 77.
GROUP II.
CHLORHYDRIC, BROMHYDRIC, IODHYDRIC, CY-
ANHYDRIC, FERROCYANHYDRIC, FERRICYAN-
HYDRIC, AND SULPHYDRIC ACIDS.
Acids which are not precipitated by baric chloride, but which
are precipitated by argentic nitrate in nitric acid solution.
SECTION I.
CHLORHYDRIC, BROMHYDRIC, IODHYDRIC, AND CYANHYDRIC
ACIDS.
Acids which give with argentic nitrate a white or light yellow
flocculent precipitate, insoluble in dilute nitric acid, and are not
precipitated by salts of iron in acid solution.
CHLORHYDRIC ACID.
HC1; NaCl.
Plumbic, Mercurous, and Argentic Salts are
the only compounds which give, with chlorhydric acid, pre-
cipitates insoluble in nitric acid.
Sulphuric Acid (concentrated) sets free chlorhydric
acid from its compounds. Chlorhydric acid gas precipitates a
drop of argentic nitrate, held on the end of a glass rod in an
atmosphere containing it, as ARGENTIC CHLORIDE, AgCl, white
flakes. Compounds containing cyanhydric, chloric, and hypo-
chlorous acids, produce the same reaction. Chlorhydric acid
gas does not bleach indigo solution. See, however, Part III.
(48).
BROMHYDRIC AND IODHYDRIC ACIDS.
73
Argentic Nitrate precipitates solutions containing
chlorhydric acid as ARGENTIC CHLORIDE, AgCl, white flakes,
turning purple on exposure to light, settling quickly after they
have been shaken. Argentic chloride is soluble in ammonic
hydrate, and completely insoluble in boiling nitric acid (con-
centrated). No other compound of silver except the ferro- and
ferricyanide remains undissolved after this treatment. When
ferro- or ferricyanhydric acid is present in a solution containing
chlorhydric acid, follow the directions given, Part III. (130)
(a), before applying the argentic nitrate test.
This is the usual test for chlorhydric acid.
BROMHYDRIC ACID.
KBr.
Nearly all bromides are soluble in water ; bromide of lead,
however, dissolves very sparingly, and the mercurous and
argentic salts are quite insoluble.
Argentic Nitrate precipitates from solutions of bro-
mides the ARGENTIC BROMIDE, AgBr, white, closely resembling
the chloride, but more difficultly soluble in ammonia ; insolu-
ble in hot nitric acid.
Bromides are decomposed by chlorine, hypochlorites, strong
sulphuric and nitric acids, bromine being set free, which im-
parts a yellow or yellowish-red color to the liquid. On shak-
ing the tube with a little ether or carbonic disulphide the
bromine will be dissolved and impart to the solvent a yellow
or reddish-brown color.
IODHYDRIC ACID.
KI.
The iodides resemble very much the corresponding chlorides
and bromides.
Argentic Nitrate produces in solutions of iodides a
74 PART II.
yellowish-white precipitate of ARGENTIC IODIDE, Agl, very
slightly soluble in ammonia, but soluble in boiling concen-
trated nitric acid.
JVLeTCUTOUS NitTate precipitates yellowish-green MER-
CUROUS IODIDE, Hg 2 I 2 .
jMLevcwT-ic Chloride precipitates brilliant scarlet MER-
CURIC IODIDE, HgI 2 .
Chlorine or bromine water liberates iodine from iodides ; on
shaking with carbonic disulphide the iodine is concentrated in
this liquid, forming a violet-colored solution.
Free iodine imparts a blue color to starch paste. For this
purpose dilute starch paste is added to a solution of an iodide,
and then chlorine water, nitric acid, or sulphuric acid carefully
added to liberate the iodine. If too much chlorine is added
chloride of iodine is formed, which prevents the formation of
the blue color. The chloride of iodine is also produced by
nitric acid in presence of considerable amount of chlorides.
CYANHYDRIC ACID.
HCy; KCy.
The reactions of different classes of cyanhydric acid com-
pounds must be considered separately.
Soluble Simple Cyanides. Cyanides of metals of
Groups I., II., and III. are soluble in water. Cyanhydric acid
is set free from their solutions by even the feeblest acids (acetic
and carbonic). (MERCURIC CYANIDE is soluble in water, but
is not decomposed by alkalies nor by acids, except by sul-
phydric acid ; and the tests described for cyanhydric acid
cannot be applied to it. Sulphydric acid precipitates mercu-
ric sulphide, and sets cyanhydric acid free. )
Insoluble Simple Cyanides. Cyanides of metals
of Groups IV. and V., except mercuric cyanide, are insoluble
in water, and the cyanides of metals of Group V. are not de-
CYANHYDRIC ACID.
75
composed, or are decomposed with great difficulty by acids.
The insoluble cyanides dissolve readily in potassic cyanide, and
the ordinary tests for metals cannot be used with such solutions.
The cyanides can be precipitated from these solutions by the
addition of an acid, with some exceptions, the two most re-
markable of which are described separately. (See Ferro- and
Ferricyanhydric Acids.)
Free Cyanhydric Acid can be recognized by its
smell, which is like that of bitter almonds. (The acid is very
poisonous, and the fumes arising from a solution containing a
considerable quantity of it should be inhaled with caution.)
Argentic Nitrate precipitates soluble compounds of
cyanhydric acid in an acid solution as ARGENTIC CYANIDE,
AgCy, white flakes, which do not settle so readily, when shaken,
as argentic chloride, and which do not turn purple quickly in the
light. Argentic cyanide is wholly decomposed and dissolved
by boiling a few minutes with strong nitric acid. It is also
decomposed, and cyanhydric acid goes into solution, when it is
digested with dilute chlorhydric acid in contact with metallic
zinc.
Prussian Blue Test. When a feebly acid solution
containing cyanhydric acid is mixed with several drops of
ferrous sulphate solution, and with a drop of ferric chloride
solution, and sodic hydrate is added until a precipitate forms,
and the mixture is warmed for a minute, and then acidified
with dilute chlorhydric acid, a blue precipitate, or more frequently
a blue coloration, appears, either immediately or after the addi-
tion of a drop of ferric chloride.
When ferro- or ferricyanhydric acid or both acids are present
(see the following section), they must be removed from the
solution before the Prussian-blue test can be applied. To this
end add to a small quantity of the solution an equal bulk of
dilute sulphuric acid, and dilute with a considerable quantity
of water ; add ferric chloride or ferrous sulphate, or both to-
gether, according as ferro- or ferricyanhydric acid or both
76 PART II.
acids are present, and then add baric chloride until the blue
precipitate appears of a much lighter shade ; shake thoroughly,
and allow the precipitate to settle for a few minutes, and filter.
If only the first few drops run through the filter blue, they
should be thrown away and the remainder of the filtrate taken.
If no clear filtrate can be obtained, add to the filtrate a little
baric chloride and filter again. The filtrate is to be tested as
above by the addition of sodic hydrate, and afterwards of an
acid for cyanhydric acid. A sufficiently capacious flask must
be chosen for the operation. The only object in adding baric
chloride is to facilitate the filtration from the blue precipitate.
Cyanhydric acid is the only acid which gives this reaction under
these circumstances.
SECTION II. .
FERROCYANHYDRIC AND FERRICYANHYDRIC ACIDS.
Acids which give with argentic nitrate colored precipitates,
which are not wholly destroyed on boiling with strong nitric acid,
and which are precipitated by ferrous or ferric salts, and by cu-
pric salts in dilute acid solutions.
FERROCYANHYDRIC ACID.
H 4 (FeCy 6 ) ; K 4 (FeCy 6 ).
Ferrous Sulphate precipitates ferrocyanhydric acid
compounds in acid solutions as POTASSIC FERROUS FERROCY-
ANIDE, K 2 Fe(FeCy 6 ), bluish white precipitate, which quickly
turns dark blue through oxidation by the air.
Ferric Chloride precipitates ferrocyanhydric acid com-
pounds in acid solution as PRUSSIAN BLUE, Fe 4 (FeCy 6 ) 3 , deep
blue.
Ferrocyanhydric acid is the only acid which gives this reaction.
Cupric Sulphate precipitates ferrocyanhydric acid com-
pounds in acid solution as CUPRIC FERROCYANIDE (Cu 2 FeCy 6 ),
brownish-red powder.
SULPH YDRIC A CID. j j
The metals are left as oxides, and the ferrocyanogen is dis-
solved as sodic ferrocyanide, when these precipitates are di-
gested with sodic hydrate.
FERRICYANHYDRIC ACID.
H 6 (Fe 2 Cy 12 ) ; K 6 (Fe 2 Cy 12 ).
Ferrous Sulphate precipitates compounds of ferricy-
anhydric acid in acid solution as TURNBULL'S BLUE, Fe 3 (Fe 2
Cy M ), deep blue.
Ferricyanhydric acid is the only acid which gives this reaction.
Ferric Chloride does not precipitate compounds of fer-
ricyanhydric acid in acid solution. The color of the solution
is deepened.
Cupric Sulphate precipitates compounds of ferricyan-
hydric acid in acid solution as CUPRIC FERRICYANIDE, yellow-
ish-green powder.
The metals are left as oxides, and the cyanogen is dissolved
as sodic ferricyanide when these precipitates are treated with
sodic hydrate.
SECTION III.
SULPHYDRIC ACID.
An acid which gives a black precipitate with salts of lead, silver,
copper, and many others in an acid solution.
No other acid gives a precipitate of the same color with these
metals.
SULPHYDRIC ACID.
H 2 S ; (NH 4 ) 2 S.
Sulphydric Acid is set free from its solutions by all
other acids except carbonic and cyanhydric acid, and it can
be recognized by its smell. The sulphydric acid gas is given
off with effervescence when the solution is concentrated.
7 8 PART II.
The Metals of Groups I. and II. form with
sulphydric acid soluble sulphides, which have an alkaline re-
action.
The Metals of Group IV. 9 when the acid with which
they are combined is neutralized, form with sulphydric acid
INSOLUBLE SULPHIDES, which, with the exception of the sul-
phides of cobalt and nickel, are dissolved by cold dilute chlor-
hydric acid, with evolution of sulphydric acid.
Metals of Groups V. and VI. form with sulphydric
acid insoluble sulphides, which are not decomposed by dilute
acids. (See also Mercury, page 48 and page 50.)
Lead-Paper Test. A piece of paper moistened with
plumbic acetate, and held over a solution from which sulphy-
dric acid is set free by the addition of a stronger acid, is black-
ened. No other acid gives this reaction.
NITRIC AND CHLORIC ACIDS.
79
GROUP III.
NITRIC, CHLORIC, AND ACETIC ACIDS.
Acids which are not precipitated by any metal.
SECTION I.
NITRIC AND CHLORIC ACIDS.
Acids which deflagrate when tested with the blowpipe on charcoal.
NITRIC ACID.
HNO 8 ; NaNOs.
Nitric Acid 9 when concentrated, is readily decomposed
when heated with copper turnings, and red fumes of NITRIC
PEROXIDE, NO 2 , are given off. The reaction can be obtained
with a moderately dilute solution by adding to it concentrated
sulphuric acid. No reaction is obtained with very dilute so-
lutions.
J?errous Sulphate Test. Add a few drops of a solu-
tion containing nitric acid to concentrated sulphuric acid in a
test-tube, and pour upon this solution a layer of cold ferrous
sulphate solution. A brown or red color appears at the line of
separation of the two solutions, arising from the absorption of
nitrous gases by the ferrous sulphate.
This is the characteristic test for nitric acid.
CHLORIC ACID.
KC10 8 .
Sulphuric Acid (concentrated). When a small quan-
80 PART II.
tity of a solid chlorate, or a very concentrated solution con-
taining a chloric acid compound, is added to strong sulphuric
acid, and heat is applied, a peculiar yellow gas (oxides of
chlorine) is evolved, which has a characteristic suffocating
odor, which precipitates ARGENTIC CHLORIDE in a drop of an
argentic nitrate solution, and which bleaches a drop of an in-
digo solution when these reagents are held on the end of a
glass rod in an atmosphere containing the gas.
This is the characteristic test for chloric acid.
Hypochlorous Acid, gives the same reactions as chloric
acid, but that acid is easily set free and evolved from its solu-
tion by dilute sulphuric acid, while chloric acid is not, and
moreover it is usually present only in alkaline solutions.
Chlorhydric Acid in the presence of an oxidizing
agent gives a similar reaction, but the yellow gas evolved
(chlorine) is much less intense in color, and has a different
odor. It is, however, very difficult to distinguish between the
reaction given by chlorine in such a case and that given by
chloric acid compounds.
SECTION II.
ACETIC ACID.
An acid which does not deflagrate on charcoal.
ACETIC ACID.
HC 2 H 8 2 ; NaC 2 H 8 2 .
The Strong Mineral Acids set acetic acid free
from its combinations.
Acetic acid can be recognized by the odor of vinegar pecu-
liar to it.
Sulphuric Acid Test. When an equal bulk of alco-
hol is added to strong sulphuric acid, and a small quantity of
a solution containing a compound of acetic acid is added, and
ACETIC ACID. 8 1
the mixture is heated, a characteristic odor of acetic ether is
given off.
In case gases are given off, which make it difficult to recog-
nize the odor of acetic ether, it is advisable to provide the test-
tube in which the reaction is performed with a tube for distil-
lation,* and to distil a small quantity of the alcohol into an-
other test-tube, to mix the distillate with water, to neutralize it
with sodic carbonate, and to warm it ; the odor of acetic ether
can then be recognized in the liquid which was distilled.
This is the characteristic test for acetic acid.
Argentic and Mercurous Nitrates precipitate
concentrated neutral solutions of acetic acid compounds as
ARGENTIC AND MERCUROUS ACETATES, AgC 2 H 3 O 2 and Hg 2
(C 2 H 3 O 2 )2, white crystalline scales. The precipitates are soluble
in dilute nitric acid, and also in a large quantity of water.
* Bend a 3-16 inch tube, of about one foot in length, at an angle of
about 80, so that one arm shall only be i^ inches long. Fit a cork to
the test-tube, and insert the bent tube in a hole bored through the cork
with a round file,
6
PART III.
PRELIMINARY TESTS WITH NON-METALLIC
SOLIDS.
EXAMINATION IN A CLOSED TUBE.
USE a piece of hard glass tubing three-eighths of an inch
in diameter, closed at one end (see page 26) for this examina-
tion. Introduce the substance, pulverized or in small pieces,
into the tube, wipe the inside of the tube if necessary with a
bit of rolled filter-paper, and heat the substance, gently at first,
but eventually to the highest temperature attainable with the
flame of a Bunsen's lamp or with the blowpipe flame. Ob-
serve carefully the changes which occur.
No Change. The substance contains no organic matter,
(1) no readily fusible body, no readily volatile body, and
no water.
Pass to the Examination on Charcoal (page 85).
Wat er* Substances containing water (usually water of crys-
(2) tallization) deposit a film of moisture in the upper
part of the tube when they are heated. If the water
colors turmeric paper brown, AMMONIA is present.
Organic Matter* Substances containing organic matter
(3) blacken and give off gases when they are heated.
Should the substance contain organic matter it must
be burnt, until the organic matter is completely de-
stroyed,* by heating with the lamp or blowpipe, on
* In some special cases, as in* examinations for mercury and arsenic,
other processes of analysis must be employed, for which larger works must
be consulted.
82
EXAMINA TION OF SOLIDS. 83
platinum foil or on a bit of porcelain, or in a porcelain
dish or crucible, before further analysis, commencing
with the examination on charcoal (page 85), is pro-
ceeded with.
A GAS IS GIVEN OFF.
May be recognized by its property of rekindling
(4) a glimmering match held in the tube.
PEROXIDES, NITRATES, and CHLORATES evolve oxy-
gen.
Nitrates and chlorates also deflagrate on charcoal.
See (14).
Sulphurous Oxide, SO 2 , can be recognized by its smell.
(3) Some SULPHATES of higher metals, and many
SULPHITES, evolve sulphurous oxide when they are
heated.*
SulpTiydric Acid, H 2 S, can be recognized by its smell
(0) and by its property of blackening lead paper. See
(45).
Some alkaline SULPHIDES, containing water, evolve
sulphydric acid when they are heated.
Carbonic Dioxide, CO 2 , can be recognized by its prop-
(7) erty of extinguishing a lighted or glimmering match
held in the tube. See also (41).
Some CARBONATES lose carbonic dioxide when they
are heated.
Hyponitric Oxide, NO 2 , appears as red fumes.
(8) NITRATES of the higher metals evolve hyponitric
oxide when they are heated.
Ammonia, NH 3 , can be recognized by its smell, and by its
* Many sulphides of higher metals give off sulphur in the form of sul-
phurous oxide when they are roasted with . access of air. The sulphides,
finely pulverized, may be heated red-hot in a tube, open at both ends, and
held in an inclined position to favor the draught, and the sulphurous oxide
may be detected by its smell at the upper end of the tube.
84 PART III.
(9) property of turning moist turmeric paper brmvn. Salts
of ammonia, in the presence of alkalies, and some
organic substances, evolve ammonia when they are
heated.
[Better tests for these bodies, with the exception of oxygen,
are given in the following pages, since it is often difficult to
observe the formation of a gas in a small tube ; the phenomena
described above should, however, be looked for when sub-
stances are heated in a closed tube.]
A SUBLIMATE FORMS.
An opinion may be formed of the volatility of the sublimate,
according to the distance from the heated part of the tube at
which it is deposited.
Sulphur sublimes easily and solidifies in reddish-brown
(10) drops, which become yellow or yellmrish-brown on
cooling.
Some METALLIC SULPHIDES give off a portion of
their sulphur when they are heated.
Ammonic Salts form white sublimates. Touch the sub-
(11) limate with a drop of sodic hydrate, or with a bit of
paper moistened with sodic hydrate, and if the smell
of ammonia is given off it consists of an ammonic salt.
Mercury. Metallic mercury sublimes as & grey film, which
(12) augments to form globules when the quantity of mer-
cury is large.
MERCURIC SULPHIDE, HgS, gives a black sublimate,
which becomes ra/when it is rubbed.
MERCUROUS CHLORIDE, Hg 2 Cl 2 , and MERCURIC
CHLORIDE, HgCl 2 , give a white sublimate, which turns
black when it is moistened with ammonic sulphide so-
lution.
Arsenic. Metallic arsenic sublimes and deposits itself as a
(13) brilliant black metallic ring in the tube.
EXAMINA TION ON CHARCOAL. 85
ARSENIOUS OXIDE, As 2 O 8 , forms a white crystalline
sublimate, which turns yellow when it is moistened
with sulphydric acid solution.
ARSENIOUS SULPHIDE, As 2 S 3 , forms a sublimate,
which is reddish yellow when hot, and yelloiv when
cold. It is somewhat less volatile than sulphur.
RECAPITULATION (10) TO (13) SUBLIMATES.
The substance is heated in a closed tube.
WHITE SUBLIMATE ammonic salts (11); mercurous chloride,
Hg 2 Cl 2 , and mercuric chloride, HgCl 2 (12) ; and arsenious
oxide, As 2 O 3 (13).
YELLOW SUBLIMATE sulphur (10) ; and arsenious sulphide,
As 2 S 3 (13).
BROWN SUBLIMATE (while hot) sulphur (10).
REDDISH-YELLOW SUBLIMATE (while hot) arsenious sulphide,
As 2 S 3 (13).
GRAY METALLIC SUBLIMATE mercury (12).
BLACK SUBLIMATE arsenic (13) ; and mercuric sulphide,
HgS, red when rubbed (12).
EXAMINATION ON CHARCOAL.
Hollow out a small cavity in a piece of charcoal (see page
25), and heat a portion of the solid substance with the blow-
pipe flame.
titrates and Chlorates enter into a vivid combus-
tion, called deflagration, when they are heated on
charcoal.
86 PART III.
Potassium and Sodium Salts melt, and some of
(15) them are imbibed by the pores of the charcoal when
they are heated.
Compounds of the Metals of Groups II. and
(16) III., also Zinc Compounds and Silicic
Oxide, remain as a white infusible mass on the char-
coal after heating. Frequently, when heat is first ap-
plied, they melt in their water of crystallization, and
afterwards become solid.
ALUMINIC OXIDE becomes blue, and ZINC OXIDE be-
comes green when they are moistened with cobaltic
nitrate and heated in the oxidizing flame.
Salts of the Metals of Groups IV. and V. leave a
(17) dark-colored residue when they are heated on char-
coal. The oxides of these metals generally assume a
darker color when they are heated. Exceptions : Zinc
and mercury.
Salts of Ammonia and Mercury, also Com-
(18) pounds of Arsenic and Antimony, which
do not contain another metal, volatilize completely
when they are heated on charcoal.
Gold and Silver Compounds, also Oxides of
(19) Lead and Bismuth, give bright metallic globules
when they are heated on charcoal.
FUSION WITH SODIC CARBONATE.
(20) When metals of Groups IV., V., and VI. appear to
be present (see 17), mix a small quantity of the pul-
verized substance with two or three times its bulk of
sodic carbonate in the palm of the hand, moisten with
water, and form the mixture by working it with a knife-
blade into a ball the size of a pea. Place the ball in
a cavity scooped out of a piece of charcoal, and heat
EX AM IN A TION ON CHARCOAL. gy
with the inner blowpipe flame until almost all of the
carbonate of soda has been imbibed by the charcoal.
Many metals are reduced and appear as metallic
globules in the cavity of the charcoal, and those which
are volatile deposit an incrustation of their oxides on
the charcoal. This incrustation is to be looked for at
a greater or less distance from the cavity, according
to the volatility of the metal, and always in the direc-
tion in which the metallic vapors are blown by the
flame.
The physical and chemical properties of the glob-
ules and the color of the incrustations afford means of
recognizing several metals, usually, however, only
when they are not associated with others.
Tron, Cobalt, Nickel, and Manganese Com-
(21) pounds give neither globule nor incrustation.
Gold, Silver, and Copper Compounds give mallea-
(22) ble globules, which can be distinguished by the re-
spective colors of the metals. They give no incrusta-
tion.
Zinc Compounds give no globules, but a white incrusta-
(23) tion, ZnO, near the spot heated. The incrustation is
yellow while hot. It is not volatile in the oxidizing
flame. It becomes green when it is moistened with
nitrate of cobalt, and heated in the oxidizing flame.
Tin Compounds give very ductile white globules.
(24) The incrustation, SnO 2 , produced by tin compounds
is dirty yellow when hot, and lighter when cold. It is
deposited in the immediate vicinity of the cavity, and
it is very difficult to distinguish it from the ash of the
charcoal.
Lead Compounds give very ductile globules.
(25) The incrustation, PbO, is bright yellow when hot,
and pale yellow when cold. It is deposited at a greater
distance than SnO 2 from the cavity. When the blow-
88 PART III.
pipe flame is directed upon the incrustation of PbO
it vanishes, and the flame is colored blue.
Bismuth Compounds give brittle globules. The incrus-
(26) tation, Bi 2 O 3 , is orange yellow when hot, and bright
yellow when cold. It vanishes when the blowpipe
flame is directed upon it, but it does not impart a blue
color to the flame.
Cadmium, Compounds give no globules, but a yellow to
(27) reddish-brown incrustation, very different in color from
that of any other metal.
Antimony Compounds give brittle globules, but metallic
(28) antimony is so volatile that frequently these are driven
off by the heat required for their reduction. Some-
times fumes, arising from* the vapor of antimony, are
visible. The incrustation, Sb 2 O 3 , is white. It is de-
posited at a greater distance than PbO from the cavity,
and it can easily be driven from one place to another
on the charcoal by the heat of the blowpipe flame.
Arsenic Compounds give no globules, but a character-
(20) istic garlic odor. The incrustation, As 2 O 3 , is white,
and it is still more volatile than Sb 2 O 3 .
When the compound contains several metals that can be re-
duced, they alloy with each other, and it is usually impossible
to recognize the metals in the presence of each other by their
physical properties ; also, the incrustation given by one metal
frequently obscures that given by another.
If a sufficient quantity of the metal can be easily reduced,
it is always advisable to treat it with solvents in the manner to
be described under metals. (See page 98.)
Sulphur. The following modification of the fusion with
(30) carbonate of sodium on charcoal is a valuable test to
discover sulphur in baric sulphate and in sulphides.
If a piece of the charcoal which has imbibed the
soda is moistened and laid on a silver coin, a black
stain appears, if the coin is washed after a few minutes,
EXAMINA TION ON CHARCOAL. 89
in case sulphur is present. The charcoal may also be
pulverized and treated with water, and if the solution,
after being filtered, gives a black precipitate with
plumbic acetate solution, sulphur is present. For this
test the flame of a candle, oil lamp, or alcohol lamp
must be used, else the sulphur in the burning gas will
vitiate the results.
RECAPITULATION OF THE EXAMINATION ON
CHARCOAL.
The substance is heated on charcoal.
DEFLAGRATION. Nitrates and chlorates (14).
FUSION. Potassium and sodium salts (15).
WHITE INFUSIBLE RESIDUE. Compounds of metals of Groups
II. and III., zinc salts and silicic acid (10).
DARK-COLORED RESIDUE. Compounds of metals of Groups
IV. and V., except zinc and mercury (17).
COMPLETE VOLATILIZATION. Ammonic and mercuric com-
pounds, and compounds of arsenic and antimony, which
contain no other metal (18).
BRIGHT METALLIC GLOBULES. Silver and gold compounds,
and the oxides of lead and bismuth (19).
The substance is mixed with sodic carbonate and heated on
charcoal.
METALLIC GLOBULES WITHOUT INCRUSTATION. Gold, silver,
and copper (22) ; tin (24).
METALLIC GLOBULES AND INCRUSTATION. Lead (25) ; bis-
muth (26) ; antimony (28).
9 o PART III.
INCRUSTATION WITHOUT GLOBULES. Zinc (23) ; Cadmium
(27). GARLIC ODOR. Arsenic (29).
FORMATION OF SODIC SULPHIDE. All compounds containing
sulphur (30).
PRELIMINARY TESTS WITH METALLIC BODIES.
EXAMINATION IN A CLOSED TUBE.
See page 26.
Mercury. Amalgams containing mercury give a subli-
(31) mate of METALLIC MERCURY when they are heated.
At first a gray film forms in the upper part of the tube,
and, when the amount of mercury is considerable, fine
globules of metallic mercury are formed, which ag-
glomerate and become more distinctly visible when
they are rubbed with a copper wire.
Arsenic* Some metallic compounds, containing ARSENIC,
(32) give a metallic mirror or ring in the upper part of the
tube when they are heated.
EXAMINATION ON CHARCOAL.
Heat a piece, one-fourth as large as a pea, of the
(33) metallic substance in a cavity on a piece of charcoal.
See Part I., page 25. The phenomena to be ob-
served are the formation of the incrustations de-
scribed (pages 87 and 88), the smell of ARSENIC, and
the vapors of MERCURY and ANTIMONY.
COPPER colors the blowpipe flame green, or in the
presence of chlorine blue.
SULPHURIC ACID TEST. 9 !
PRELIMINARY TESTS WITH NON-METALLIC
SOLIDS (continued}.
TESTS WITH THE BORAX BEAD.
If the substance to be tested appears to be the oxide, or an
oxygen-salt of a higher metal (see 17), dissolve some of it in
the borax bead.
Cobalt colors the bead blue in the oxidizing and in the re-
(34) ducing flame.
Copper colors the bead green when hot, and blue when cold,
(35) in the oxidizing flame. It colors the bead red, when
cold, in the reducing flame.
Chromium colors the bead green in both flames.
(36)
Iron* colors the bead brownish red when hot, and yellow when
(37) cold, in the oxidizing flame.
Nickel colors the bead violet when hot, and/0/<? brown when
(38) cold, in the oxidizing flame. The color disappears in
a good reducing flame. (See page 44.)
IVLaifigd'nese colors the bead amethyst in the oxidizing flame.
(39) The color disappears in a good reducing flame.
(40) THE OXYGEN COMBINATIONS OF THE REMAINING
METALS color the bead very slightly or not at all.
CONCENTRATED SULPHURIC ACID TEST.
CONCENTRATED SULPHURIC ACID, with the aid of heat, sets
free other acids from most of their combinations with metals,
and frequently in such a form that they can be recognized by
simple tests. This reaction is not, of course, a method of
separation ; one acid may obscure the test for another, and
the possible cases are so complicated that it would be useless
to attempt to describe them all ; therefore, if the result of the
9 2
PART III.
sulphuric acid test appears doubtful, it is best to reserve judg-
ment of its value until after the tests for acids in solution have
been applied.
The reactions of acids or their salts, when a small quantity
of a solid substance or of a very concentrated solution is added
to a few cubic centimetres of strong sulphuric acid in a test-
tube are described below. Heat should be applied after the
reaction, which takes place at the ordinary temperature, has
been observed.
Carbonic Acid. Effervescence. Carbonic dioxide gas
(41) renders turbid a drop of lime-water held on the end
of a glass rod in the test-tube (see page 70, foot-note).
Carbonic acid is also detected by the chlorhydric acid
test, and in many cases that test is preferable to the
one with sulphuric acid, since oxalic acid does not
give the same reaction with chlorhydric acid. See
(73).
Oxalic Acid. When a dry compound of oxalic acid is
(42) added to strong sulphuric acid, and the mixture
is heated, carbonous oxide and carbonic oxide are
evolved.
The sulphate of calcium test for oxalic acid (125)
is more accurate than that with sulphuric acid.
Cyarihydric, Ferro- and Ferricyanhydric
(43) Acids. Compounds of these acids evolve, when
perfectly dry, carbonic oxide with effervescence when
they are heated with strong sulphuric acid. Usually,
however, a faint odor of cyanhydric acid can be de-
tected. The special tests are more valuable. See
(75), and (133), (134), and (135).
Fluorhydric Acid. When a solid substance or a con-
(44) centrated solution containing fluorine is heated with
strong sulphuric acid, fluorhydric acid is evolved, which
etches glass (see page 69) ; when silicic acid or a sili-
cate is present, fumes of fluoride of silicon, which give
SULPHURIC ACID TEST. 93
a precipitate of silica in a drop of water held over
them on the end of a glass rod, are evolved.
If fluorhydric acid is discovered, the substance
which is to be used for page 104, III., and the follow-
ing tests, must be heated with sulphuric acid in a pla-
tinum vessel until the fluorhydric acid is driven off
completely.
A separate portion can be used for testing for sul-
phuric acid. See (30).
Sulphydric Acid. Compounds containing this acid
(4#) evolve it (often with effervescence) when strong sul-
phuric acid is added to them. Sulphydric acid may be
recognized by its smell and by its property of black-
ening paper dipped in plumbic acetate solution. See
(74) and (129).
Sulphurous Acid. Compounds containing this acid
(40) evolve sulphurous oxide, SO 2 , with effervescence when
strong sulphuric acid is added to them. Sulphurous
oxide, when free from sulphydric acid, and from some
others, can be recognized by its smell. See (7#).
Chloric and Hypochlorous Acids. (See page 80.)
(47) Compounds containing these acids evolve a. yellow gas
on the addition of strong sulphuric acid, even when
the mixture is not heated. The gas can best be recog-
nized by its color, its odor, and its strong bleaching
action on a drop of indigo solution held in the tube
on the end of a glass rod. This gas precipitates nitrate
of silver.
Chlorhydric Acid. Compounds containing chlorhydric
(48) acid evolve the gas, HC1, frequently with efferves-
cence, on the addition of sulphuric acid. The gas
does not bleach indigo solution, but precipitates ni-
trate of silver held on the end of a glass rod in the
tube. Chlorhydric acid, in the presence of an oxidiz-
ing agent, evolves chlorine under the same circum-
94 PART in.
stances. The gas produces the same reactions as are
produced by the gas evolved by chloric and hypo-
chlorous acids, but it can be distinguished from them
by its smell and by its color, which is a less intense
yellow. For special test, see (130).
Hromhydric Acid. Bromides are decomposed by strong
(49) sulphuric acid with evolution of bromhydric acid,
which, if the sulphuric acid is concentrated and in ex-
cess, is partly decomposed, with separation of bromine
and formation of sulphurous oxide. (See also page 73.)
lodhydric Acid. All the iodides are decomposed by
(50) strong sulphuric acid on the application of heat.
Iodine is set free, which escapes in violet vapors and
imparts a blue color to paper moistened with starch.
(See also page 73.)
Nitric Acid. Compounds containing nitric acid in con-
(51) siderable quantity produce reddish fumes when heated
with sulphuric acid in the presence of copper turnings
or of any other reducing agent. The following test
for nitric acid is more delicate : Mix a little of the
powdered substance or solution with strong sulphuric
acid, and pour cautiously upon the acid a solution of
ferrous sulphate. A brown or red color at the line of
separation of the two solutions indicates the presence
of NITRIC ACID, HNO 8 . See (136) (a) for this test
in the presence of ferro- or ferricyanhydric acid.
Acetic Acid gives with sulphuric acid an odor of vine-
gar. The following test is more delicate : Add an
equal volume of alcohol to strong sulphuric acid, and
then add the solid substance or concentrated solution
supposed to contain ACETIC ACID, C 2 H 4 O 2 . If this
acid is present, the odor of acetic ether will be per-
ceptible on heating the mixture. It is well to add
pure acetic acid at the same time to a mixture of sul-
phuric acid and alcohol, in order to compare the odor
SOL UTION OF NON-ME TALLIC BODIES. 95
produced with that observed in the test. If other
gases render the odor of acetic ether difficult to per-
ceive, the precautions described on page 81 must be
observed.
RECAPITULATION OF SULPHURIC ACID TEST.
A colorless gas is given off.
THE GAS is WITHOUT ODOR. Carbonic acid (4:1) ; oxalic
acid (42).
A PUNGENT SUFFOCATING ODOR. Fluorhydric acid (44) ;
chlorhydric acid (48) ; bromhydric acid (40).
AN ODOR OF BITTER ALMONDS. Cyanhydric, ferrocyanhydric,
and ferricyanhydric acids (43).
AN ODOR OF ROTTEN EGGS. Sulphydric acid (43).
AN ODOR OF BURNING SULPHUR. Sulphurous acid (4:6).
AN ODOR OF VINEGAR. Acetic acid (52).
A colored gas is given off.
* The gas has also a peculiar suffocating odor.
YELLOW GAS. Chloric and hypochlorous acids (4:7).
FAINT YELLOW GAS. Chlorine (48).
RED FUMES. Nitric acid with copper (SI).
VIOLET FUMES. lodhydric acid (50).
METHODS OF DISSOLVING NON-METALLIC
BODIES.
Substances to be tested may be divided into three classes.
1st Class : Bodies soluble in water.
To ascertain whether a body is entirely soluble,
take a few grains of the substance, which, when it dis-
solves with difficulty, must be in as finely divided a
96 PART III*
condition as possible, and digest them with a con-
siderable quantity of water in a test-tube. If the sub-
stance does not dissolve completely, boil it for a few
minutes with water. If it still does not dissolve com-
pletely, filter and evaporate a few drops of the filtrate
on platinum foil, in order to see whether anything has
dissolved.
If the substance is partly soluble in water, treat a
considerable quantity in the manner directed above,
repeat the boiling with water once or twice, wash
thoroughly with water, and filter, taking care that as
little as possible of the solid substance goes upon the fil-
ter, and use the insoluble portion for the following test.
A separate analysis should usually be made of the
part of a substance which is soluble, and of that which
is insoluble in water.
If the substance is wholly insoluble in water, it may
be used immediately for the following test. It should
usually be finely pulverized.
2d Class : Bodies insoluble in water, but soluble in chlor-
(54:) hydric acid or in nitric acid or in aqua regia. Digest
a few grains, or a very small quantity of the finely
powdered substance with dilute chlorhydric acid. If
it does not entirely dissolve, boil it with the acid. If
it still does not entirely dissolve, pour off the liquid,
and boil the insoluble substance with strong chlorhy-
dric acid. If the substance is not wholly soluble in
chlorhydric acid, repeat the trial with nitric acid in
the same way, using a fresh portion of the substance.
If the substance is still insoluble, use a mixture of both
.acids (aqua regia).
If sulphur, which may be recognized by its color and
its low specific gravity, or silicic acid, which may be re-
cognized by its peculiar gelatinous aspect, separate out on
the addition of chlorhydric or of nitric acids, the sub-
SOLUTION OF NON-METALLIC BODIES. 97
stance must be considered as soluble, and after filtration
(in case of silicic acid, see 64) the solution must be tested
according to page 104 (///.), or pag'e 107 (VI r .), accord-
ing as nitric or chlorhydric acid has been the solvent.
If the substance is only partially soluble after treat-
ment as above, the insoluble portion must be washed
carefully and separated by filtration from the soluble
portion, and it must be subjected to the tests for the
3d Class. See page 137.
In all cases before proceeding to test the solution
obtained by treatment with acids, it must be so pre-
pared that it will be moderately acid with chlorhydric
acid, and will not contain any free nitric acid, or great
excess of strong acid of any kind. It the solution was
made by the use of dilute chlorhydric acid it is already
in this condition. If nitric acid was used for the solu-
tion the excess must be replaced by chlorhydric acid.
In this case add a quantity of the latter about half
as great as that of the nitric acid used ; evaporate the
liquid almost to dryness in the hood, and add from 25
to 50 c.c. of water to the residue. If the substance
was dissolved in concentrated chlorhydric acid, the
solution should be evaporated down in the same
manner to expel the excess of that acid, and the resi-
due diluted considerably with water. If the addition
of chlorhydric acid should cause a precipitate in the
clear acid solution, or if the residue, after evaporation,
does not dissolve entirely in water, it can only be occa-
sioned by the presence of argentic, plumbic, or mercu-
rous chloride. In this case, after the addition of water,
filter off the insoluble powder and examine for those
metals as directed (OS), (67), (69). Use the fil-
trate for the sulphydric acid test (76).
3(1 Class ; Bodies insoluble in water, and in chlorhydric,
nitric, and nitro-chlorhydric acids (aqua regia).
7
98 PART III.
The tests to be applied to bodies of this class follow
those in the scheme for testing bodies in solution. See
Page 137.
METHODS OF DISSOLVING METALLIC BODIES.
Metals are divided into three classes.
1st Class : Metals which are not attacked by NITRIC ACID.
(50) If the metal does not appear to be entirely soluble
in dilute nitric acid, even after boiling, use strong ni-
tric acid.
GOLD is insoluble, also alloys containing a very large
proportion of gold.
2d Class : Metals which are attacked by nitric acid, and
(57) converted into oxides (white powder], which are inso-
luble in the acid.
TIN and ANTIMONY belong to Class II.
3d Class : Metals which dissolve entirely in nitric acid.
(58) All the remaining metals dissolve entirely in nitric
acid. With metals of this class the solution should be
effected by heating with nitric acid in an evaporating
dish until no more red fumes are given off. Chlorhy-
dric acid should then be added, the greater part of the
acid evaporated, water added, and the solution should
be tested according to (page 104, III.). If the metal
remains partly insoluble, a small portion of it should
be carefully tested by boiling with strong nitric acid,
to see whether it will not dissolve by using a sufficient
quantity of the acid.
An alloy may contain metals of each class, therefore,
after the treatment with nitric acid described in the
last paragraph, if an insoluble residue is found it should
be dissolved in aqua regia, and the solution boiled
until the smell of chlorine ceases to be given off.
Then if the residue had a metallic appearance the solu-
SOLUTION OF METALLIC BODIES. 99
tion must be tested for gold. See (87). If it was a
white powder it must be tested for tin and antimony.
See (86) and (85).
SOLUTION IN CHLORHYDRIC ACID.
(00) Sometimes a test shows that the metallic body can
be readily dissolved in chlorjiydric acid (see ZINC,
page 39, "and IRON, page 41), and in this case the chlor-
hydric acid solution should be preferred, and it should
be tested according to page 107, VI.
TESTS FOR METALS AND
ACIDS.
BODIES IN SOLUTION.
CLASSES I. AND II. (See page 95.)
Sttbstances dissolved in water or in acids.
(The tests I. and II., which follow, are only to be used for
substances dissolved in water, or where the solvent is
unknown.)
I. REACTION WITH TEST-PAPER.
(01) Observe the reaction with litmus paper.
(02) If the reaction is acid, add to a small portion of the
solution sodic carbonate, drop by drop, until the effer-
vescence ceases, and then heat to boiling.
If metals of the 2d, 3d,. 4th, and 5th groups are
present, a precipitate will be formed, except in a few
special cases.
Some idea of the amount of free acid present in the
solution can be formed by observing the amount of
sodic carbonate required to neutralize it.
II. EVAPORATION.
(03) Test one or two drops of the solution by evaporation
on platinum foil (or on a bit of glass or porcelain, if
there is danger of injury to the platinum), to see
whether it leaves a residue.
100
PRELIMINARY EXAMINATION.
If this test shows the presence of solid matter in the
solution, a portion of the latter may be evaporated to
dryness in a small porcelain dish, and some of the tests
for solids, particularly the EXAMINATION ON CHARCOAL
(page 85), and the CONCENTRATED SULPHURIC ACID
TEST (page 91), may be applied to the dry substance
thus obtained. It is best only to use the evaporation
and tests applied to the dry substance, to settle any
doubts that remain in regard to the constitution of the
solution, after the tests usually applied to solutions
have been performed. (See page 104, etc.)
When a solution of unknown origin is presented for
analysis it should always be heated, in order to see
whether a gas is given off that can be recognized by
the tests (page 92, and page 93).
Silicic Acid is usually not present, except in alkaline solu-
tions ; it occurs, however, in small quantities in spring
and river waters, and it may also exist in acid solu-
tions.
Unless silicic acid is known to "be absent it should
be tested for, and removed before making the remain-
ing tests. To this end render the solution acid with
chlorhydric acid, and evaporate carefully to dryness
in a small porcelain dish. Care must be taken not to
heat the dish over the lamp after its contents have be-
come dry. Treat the dry substance with a few drops
of acid, and then boil with water. If there is an inso-
luble residue, it consists of silica, SiO 2 . (See page 71.)
Subject the chlorhydric acid solution to the remain-
ing tests, beginning with page 107, VI. ; and if there
is reason to suspect that the precipitate, left after the
treatment with an acid, contains other substances be-
sides silica, examine it according to page 105, IV.
PART III.
TESTS FOR METALS.
THE following scheme of testing for metals is founded upon
the successive precipitation of a number of groups, which in-
clude all the metals as far as Group II. After the metals of
the higher groups have been removed by precipitation, or have
been found to be absent, those of Group II. are precipitated
successively. Sodium' and potassium are detected by the
colors of their flames in a solution which has been freed from
all the higher metals except magnesium. Ammonia can be
detected in a solution without having reference to its other
constituents.
After the separation into groups has taken place by precipi-
tation with the general reagents, each precipitate, which may
contain one or all the metals belonging to its group, is usually
dissolved, and the further analysis is performed by testing in
the several solutions for all the metals which they may contain.
These special tests sometimes require the separation of the dif-
ferent metals, one after another, in a particular order, while
sometimes a test for a metal may be applied to the solution
without regard to the presence of other metals. In all cases
the conditions requisite for applying the tests will be described.
The general tests must be applied in the following order :
ist, Chlorhydric acid to effect the precipitation of silver and
mercurous compounds, and of lead if it is present in large
quantity. 2d, Sulphydric acid in an acid solution to precipi-
tate small quantities of lead and the metals of Group V., Sec-
tion II., and of Group VI. (From this precipitate the metals
of Group VI. are separated by dissolving them in ammonic sul-
TESTS FOR METALS. IO3
phide.) 36, Ammonic hydrate until the reaction becomes
alkaline, ammonic chloride and ammonic sulphide to precipi-
tate the metals of Groups III. and IV.
Whenever a single metal or a group of metals is precipitated
some of the liquid containing the precipitate must be poured
on a filter, and the first drops of the solution which run x
through must be tested with some of the reagent which was
used to produce the precipitation, in order to ascertain whether
it has been completely effected. Should a fresh precipitate
make its appearance, everything must be poured back from
the filter into the test-tube or flask and more of the reagent
must be added. This operation must be repeated until no
precipitation is produced by the same reagent in the liquid
which runs through the filter. After a little practice it is easy
to estimate how much of a reagent is required to effect a com-
plete precipitation. A surplus over this quantity is called an
excess of the reagent.
When it has been found that a slight excess of the reagent
has been added, the whole of the liquid and the precipitate
together must be poured upon a fresh filter and the liquid
must be allowed to drain off. The liquid is to be tested for
metals of the succeeding groups, and the precipitate must
usually be completely freed from it ; otherwise the separation
has no value. To this end water must be blown on the preci-
pitate from the wash-bottle and allowed to drain off. Care
must be taken not to let the water overflow the edge of the
filter. The washing must be continued until the water which
flows through the filter is proved, either by evaporation on
platinum foil or by the application of tests for the succeeding
groups, not to contain any metal in solution. The last portions
of the wash-water which pass through the filter may be
thrown away, as they contain very little of the substances to
be tested for.
The value of analyses depends upon the care with which
the separation of precipitates from the liquid in which they
104
PART III.
have been formed is executed. For special directions for
filtering, see pages 23 and 24.
When the reaction of a liquid in a test-tube is to be tested,
always close the tube and shake it thoroughly before dipping
the test-paper in.
METALS OF GROUPS VI. AND V.
III. CHLORHYDRIC ACID TEST.
Metals in acid solution.
GROUP V., SECTION I.
In case the solution is known to contain chlorhydric acid, pass to
page 107 (VI.).
If the solution has an alkaline reaction, pass to page 105 (IV.).
(63) Add to a very small quantity of the solution to be
tested a few drops of dilute chlorhydric acid. If a
precipitate forms, continue to add chlorhydric acid,
drop by drop, as long as it seems to increase in quan-
tity, then add a quantity of chlorhydric acid about
equal to that already added.
If no precipitate is formed, or if it is dissolved on
further addition of dilute chlorhydric acid, LEAD IN
LARGE QUANTITY, SILVER, AND MERCUROUS SALTS
ARE ABSENT. Pass to page 107 (VI.).
(06) If a permanent precipitate is formed, it may consist
Of PLUMBIC, ARGENTIC, AND MERCUROUS CHLORIDES.
Most of the succeeding tests for the detection of bases
must be performed in a solution freed from these
metals. Therefore if a precipitate has been observed,
treat a considerable quantity of the solution in the
same way that the small portion was treated, and after
an excess of chlorhydric acid has been added shake
CHLORHYDRIC ACID TEST.
105
the liquid for a minute or two. The precipitate will
then settle in a short time, leaving the solution nearly
clear. The solution should be decanted through a
filter, and the precipitate washed twice by decantation
through the filter with water acidulated with chlor-
hydric acid.
Test the filtrate according to page 107 (VI.).
Lead. Add a small quantity of water to the precipitate^
(67) and boil, then let the precipitate settle, and decant the
clear liquid through the same filter which was used in
(66) into another vessel. Add to the filtrate an equal
bulk of alcohol and a small quantity of dilute sul-
phuric acid. If a white precipitate forms it consists
Of SULPHATE OF LEAD, PbSO 4 .
If lead is found, the precipitate must be washed as
before, with boiling water by decantation, until the
filtrate gives no black precipitate with ammonic sul-
phide. If no precipitate remains after the washing, NO
ARGENTIC OR MERCUROUS SALTS are present. Pass to
page 107 (VI.).
Silver. If a precipitate remains after washing with boiling
(68) water, add to it ammonia, pour the solution through
a filter, and acidify with nitric acid. If a precipitate
forms, it consists of ARGENTIC CHLORIDE, AgCl..
ftfercurous Salts. If a precipitate remains after ammo-
(69) nia has been added, it will have a gray or black color.
The precipitate consists of A MERCUROUS COMPOUND
OF AMMONIA.
IV CHLORHYDRIC ACID TEST.
Metals in alkaline solutions.
(70) Add chlorhydric acid until the reaction becomes
distinctly acid, and if a precipitate forms, wash it
thoroughly with cold water upon a filter until the fil-
I0 6 PART III.
trate is no longer acid to test-paper. Observe whether
sulphydric acid is given off.
If a precipitate is formed with chlorhydric acid, filter
and test the filtrate according &>page 107 (VI.).
(71) If no precipitate is formed, pass to page 107 (VI.).
(a) If the precipitate is white, it may consist of :
Plumbic Chloride. Boil a little of it with water, and
test one portion of the solution for LEAD according to
(07)) and test another portion for CHLORINE by add-
ing nitric acid and argentic nitrate.
Plumbic Sulphate. Test according to (140).
Argentic Chloride. Test according to (141).
(b) If the precipitate is colored it may contain
The Sulphides of Arsenic, Antimony, and Tin.
Test according to page 109 (VIII.).
Sulphur may be precipitated, accompanied by a disengage-
ment of sulphydric acid. The precipitated sulphur
can be recognized by its appearance, and its insolu-
bility in aqua regia.
V. CHLORHYDRIC ACID TEST FOR ACIDS.
See also Silicic Acid (64).
If a solution is acid, many of the following tests,
particularly (73), (74), and (7S), can be applied
by simply heating the solution.
Carbonic Acid is only present in alkaline solutions. CO 2
is evolved with effervescence, when an acid is added,
until the solution has an acid reaction. Hold a drop
of lime-water on the end of a glass rod in the tube ; if
CARBONIC DIOXIDE, CO 2 , is present, a white precipitate
forms. (See page 70, foot-note.) The same test can
be applied to solid carbonates. See also the sulphuric
acid test (41).
The following acids need only be looked for when an
S ULPH YDRIC A CID TEST. ! o 7
odor can be perceived after heating the solution, or after
adding chlorhydric acid and heating.
Cyanhydric Add, in its soluble combinations with
(73) most metals, is set free by chlorhydric acid. It can
be recognized by its smell. See also the prussian blue
test (133),
Sulphydric Acid is evolved from alkaline solutions
(74) (often with effervescence), on the addition of chlorhy-
dric acid, when the solution is heated. It can be re-
cognized by its smell and by the lead paper test.
(See the sulphuric acid test (4#) and the argentic
nitrate test (129).
SulpJlllTOUS Oxide is evolved from alkaline, neutral, or
(7>) slightly acid solutions of sulphites, on the addition of
chlorhydric acid. Mix a little potassic ferricyanide
and ferric chloride, and hold a drop of the mixture on
the end of a glass rod in the tube after chlorhydric
acid has been added and the tube heated. If a blue
color appears, SULPHUROUS ACID is present. If sul-
phydric acid is present add sufficient plumbic acetate
to precipitate it before performing the test. See the
sulphuric acid test (40).
VI. SULPHYDRIC ACID TEST.
Metals in acid solutions.
(76) Add sulphydric acid solution to a small quantity of
the solution to be tested, and warm gently. In case
metals of Group VI. are to be tested for, it is better
to pass sulphydric acid gas into the dilute solution,
made acid with chlorhydric acid. The total precipi-
tation of the metals of Group VI. is frequently only
effected after one or two days.
If no precipitate forms, no metals of Grozips V. and
VI. are present. Pass to page 115 (X.).
I0 8 PART III.
(77) If a precipitate forms observe the color. It may con-
sist Of the SULPHIDES OF LEAD, PbS J BISMUTH, Bi 2 S 8 J
COPPER, CuS ; MERCURY, HgS ; and GOLD, Au 2 S 3 ,
when it is black ; ARSENIC, As 2 S 3 ; TIN (BISULPHIDE),
SnS 2 ; CADMIUM, Cd$>, yellow j TIN (MONOSULPHIDE),
SnS, brown ; ANTIMONY, Sb 2 S 3 or Sb 2 S 5 , orange. The
presence of a black sulphide hides the color of the
other sulphides, so that all may be present when the
precipitate is black.
If only a light, fine, white precipitate, which is not de-
stroyed by acids, is formed, it consists of sulphur, and is
frequently due to the presence of a ferric salt or a chro-
mate in the solution. In case only sulphur is precipi-
tated, pass to page 115 (X.).
(78) If a precipitate forms in a small portion of the solu-
tion, a sufficient quantity for use in all the succeeding
tests for metals must be treated with sulphydric acid
until the metals of Groups V. and VI. are completely
precipitated as sulphides ; and the precipitate thus
obtained must be washed on a filter quickly, with
warm water containing sulphydric acid, until the ad-
dition of ammonic hydrate to the filtrate ceases to
produce a precipitate, and it must then be treated ac-
cording to (79).
Test the filtrate for metals of Groups IV., III., II.,
and I. (See page 115, X., etc.)
VII. SOLUBILITY OF THE SULPHYDRIC ACID
PRECIPITATE IN AMMONIC SULPHIDE.
Add ammonic sulphide to a small quantity of the
precipitated sulphides (76), and warm gently.
If the precipitate dissolves entirely, it consists of the
sulphides of metals of Group VI. Those of Group V.
METALS OF GROUP VI.
109
are absent. Test the remainder of the precipitate accord-
ing to (82) (a).
(80) If a part of the precipitate does not dissolve, add
four or five parts of water, and separate the solution
by nitration from the undissolved precipitate.
The part of the precipitate which is insoluble in ammo-
nic sulphide, after being carefully washed, must be tested
for sulphides of metals of Group V. (See page 112,
IX.)
(81) The ammonic sulphide solution obtained in (80)
may contain metals of Group VI. Add to it gradually
dilute chlorhydric acid until the solution becomes acid,
and observe the color and general appearance of the
precipitate which is produced. It is well to boil the
liquid after the formation of a precipitate.
If only a fine white precipitate forms, which remains a
long time in suspension in the liquid, even after boiling, it
consists of sulphur, and metats of Group VI. are absent,
and the tests described in VIII. can be omitted.
A flocculent precipitate, or one that becomes so on boil-
ing, indicates the presence of metals of Group VI., and
the color of the precipitate shows what metals predomi-
nate. Pass to the following tests :
VIII SEPARATION OF METALS OF GROUP VI.
(82) If the test (page 108, VII.) has shown the presence
of metals of Group VI., and if the precipitate with
sulphydric acid (77) was not entirely soluble in am-
monic sulphide, the whole of that precipitate must be
treated two or three times with ammonic sulphide, as
directed (79), (80), and (81) ; and the sulphides of
Group VI. must be precipitated from the solution, and,
after careful washing, treated as described in (83).
(a) Were the sulphides, precipitated by sulphydric acid,
HO PART III.
wholly soluble in ammonic sulphide (see 79), it is
sufficient to wash and dry the portion of the precipi-
tate (77) which was not treated with ammonic sul-
phide, and to use it for (83)*
(83) Free the precipitate (82) as completely as possible
from water by pressing the filter and its contents be-
tween several thicknesses of filter-paper, remove the
precipitate from the filter and heat it with concen-
trated chlorhydric acid. The sulphides of antimony
and tin will be dissolved, while the sulphide of arsenic
remains undissolved. Collect the residue in a filter,
wash, and dry it at 100, and test for arsenic as fol-
lows :
Arsenic. Place a small portion of the dried residue in a
(84:) small tube closed at one end, and put over it about six
times its bulk of a mixture of equal parts of sodic car-
bonate and potassic cyanide. Heat the portion of the
tube above this mixture, and afterwards the mixture
itself, gently ; if as the result of this any moisture is
deposited in the upper part of the tube, wipe it out
carefully with a rolled-up strip of filter-paper. When
the whole is thoroughly dry, heat the lower part of the
tube with its contents to a red heat. ARSENIC, if
present, is sublimed and deposited on a black or
brownish ring in the upper and cooler part of the
tube.
Antimony. Concentrate the solution of the other two sul-
(85) phides that was filtered from the arsenious sulphide
* By heating the dry precipitate in a glass tube, or with less accuracy,
by heating it before it is dry, on a bit of glass or porcelain, an approximate
test may be made (see 13) ; and in case arsenic sulphide alone is indicated
by the complete volatility of the precipitate, this test is conclusive, and the
remaining tests in the separation of metals of Group V. may be omitted.
The test has little value except when the pure yellow color of the precipi-
tate gives rise to the suspicion that only arsenic sulphide is present.
METALS OF GROUP VI. m
(S3) in an evaporator, put a small piece of zinc in the
concentrated solution, and bring the edge of a piece
of platinum foil in contact with the zinc for a minute
or two. If ANTIMONY is present the portion of the
platinum immersed in the liquid will be stained black
by a thin deposit of that metal.
Tin. Put the rest of the concentrated solution of the sul-
(86) phides in an evaporator with more zinc, collect the
precipitated black flakes that may appear after a time
on a filter, wash carefully, and pour a little concen-
trated chlorhydric acid on the filter. TIN, if present,
will be dissolved, and the solution that passes through
will give a white precipitate, or perhaps a gray one if
much metal is present, with mercuric chloride. (See
page 56.)
Gold. (The analytical chemist usually knows whether it is
(87) necessary to test for gold or not. In ordinary analyses
its presence would be improbable.) When gold is
present, it will be found accompanying the sulphide of
arsenic remaining after treatment with hot chlorhydric
acid (83). Heat a portion of this residue in a por-
celain crucible or on a piece of a broken evaporator
until the arsenic and excess of sulphur have been vol-
atilized. Dissolve the portion which remains in a
mixture of chlorhydric and nitric acids. Evaporate
the solution nearly to dryness, dilute with water, and
add ferrous sulphate solution. The formation of a
brown or purple precipitate of METALLIC GOLD, either
immediately or after heating, indicates the presence
of the metal.
IT2 PART III.
IX. SEPARATION OF METALS OF GROUP V.
(SECTION II.)
(88) If a portion or the whole of the precipitate obtained
with sulphydric acid is insoluble in ammonic sulphide
see (80), free it by careful washing from the liquid in
which it was formed, or from the ammonic sulphide
which was used to dissolve the soluble portion, place
it in a porcelain dish, pour upon it pure concentrated
nitric acid, and heat it gently, if red fumes are given
off, until they cease. In any case, complete the oper-
ation by adding a little water, and boiling the contents
of the dish for a few minutes.
If no part of the precipitate ', or if only yellow particles
of sulphur remain insoluble, mercury is absent. Pass to
(90).
In this test, when the liquid holding sulphur in sus-
pension is boiled, the sulphur melts, and may enclose
particles of black sulphide, which, then become very
difficult to dissolve, and the appearance of the sulphur
may, in such a case, lead to an erroneous conclusion
that mercuric sulphide is present. It is for this reason
that the precipitate is oxiflized with strong nitric acid,
as far as possible at 'a- temperature below its boiling
point, before the sulphides are finally boiled with a
somewhat weaker acid. The same cause makes the
confirmatory test for mercury with stannous chloride
(89) necessary, when there appears to be an insolu-
ble black sulphide.
Mercury. If a black sulphide, HgS, remains insoluble
(89) after the above treatment (88), a MERCURIC SALT is
probably present. Confirmatory test : Boil the black
insoluble sulphide with chlorhydric acid and a little
potassic chlorate in a porcelain dish, and evaporate
until the greater part of the acid is volatilized ; dilute
METALS OF GROUP V. (SECTION II.) 113
with water (it is not necessary to filter), and add stan-
nous chloride. A white precipitate of MERCUROUS
CHLORIDE, Hg 2 Cl 2 , is formed, if mercury is present.
If mercury is present, dilute a few drops of the
nitric acid solution of the sulphides (S3) with water,
and add sulphydric acid. If a black or brown preci-
pitate is formed the solution must be tested for LEAD,
BISMUTH, COPPER, and CADMIUM. Pass to (90). If
the precipitate is yellow, cadmium alone is present
(93). If no precipitate is obtained all of these four
metals are absent. Pass to page 115, X.
LectcL. Add a few drops of strong sulphuric acid to a small
(90) portion of the nitric acid solution of the sulphides
(88) and evaporate until dense, white fumes of sul-
phuric acid appear, and dilute with a considerable
quantity of water. If a white precipitate forms, it
Consists Of SULPHATE OF LEAD, PbSO 4 .
The test can be made more delicate by adding an
equal bulk of alcohol to the solution after it has been
diluted with water. If lead is discovered, treat the
whole of the nitric acid solution of the sulphides in
the same way ; filter and use the filtrate for (91).
^Bismuth. Add ammonic hydrate to alkaline reaction, to
(91) the nitric acid solution of the sulphides, or to the fil-
trate from the lead precipitate, if lead was present.
If bismuth is present it is precipitated as the HYDRATE
OF BISMUTH, Bi(HO) 8 , white. If bismuth is present,
filter and use the filtrate for (92) and (93).
Copper. If copper is present it is dissolved by the ammo-
(92) nic hydrate, and imparts a blue color to the solution.
Cadmium. If the ammoniacal solution obtained in (91)
(93) was colorless, copper is absent, but cadmium may be
present. In this case add sulphydric acid. A yellow
precipitate, CdS, indicates CADMIUM.
If copper is present, neutralize the blue ammoniacal
8
114 PART III.
solution with chlorhydric acid and add sulphydric
acid. This will precipitate both CdS and CuS ; the
former is soluble in hot dilute sulphuric acid. After
washing the mixed sulphides treat the mass with hot
dilute sulphuric acid and filter. Cool the filtrate and
pass sulphydric acid again through the liquid. If
cadmium is present there will be a yellow precipitate of
cadmic sulphide, CdS.
METALS OF GROUPS IV. AND III.
METALS OF GROUPS IV. AND III.
X. AMMONIC SULPHIDE TEST.
(94i) To a small portion of the nitrate from, the precipi-
tate produced by sulphydric acid, or to a portion of
the original solution, if no precipitate is produced in
it by sulphydric acid, add sufficient ammonic hydrate
(free from carbonate) to make the reaction alkaline,
and then, whether a precipitate is formed or not, add
ammonic sulphide. If the solution contains no chlor-
hydric acid, it is necessary to add a small quantity
before neutralizing with ammonic hydrate.
If a black precipitate is formed, it may contain the
SULPHIDES OF NICKEL, NiS J COBALT, CoS ; IRON, FeS ;
MANGANESE, MnS ; and ZINC, ZnS ; and the HYDRATES
OF ALUMINIUM, A1 2 (HO) 6 , and CHROMIUM, Cr 2 (HO) 6 .
If the precipitate is white, flesh-colored, or light green,
it can only consist of the SULPHIDES OF MANGANESE
AND ZINC, and the HYDRATES OF ALUMINIUM AND
CHROMIUM. In this latter case omit (97), (98), and
(101).
If no precipitate is formed no members of Groups III.
and IV. are present. Pass to page 123, XII.
(,9t>) If a precipitate was formed in the above test (94),
treat a considerable quantity of the solution in the
same way, heat the liquid, filter as quickly as possible,
and wash immediately with boiling water, until the
nitrate has no longer an alkaline reaction.
The filtrate must be tested according to page 123, XII.
IT 6 PART III.
SULPHIDES INSOLUBLE IN DILUTE CHLOR-
HYDRIC ACID.
(96) Add to the precipitate (95) cold, dilute chlorhy-
dric acid ; if a black residue is insoluble, it consists of
the SULPHIDE OF NICKEL or COBALT. Filter and
examine the residue on the filter according to (#7)
and (98).
The filtrate must be tested according to (99).
If the precipitate dissolves entirely, or if only a white
residue is left, no NICKEL or COBALT are present. Pass
to (99).
Cobalt* Dissolve a portion of the precipitate, which proved
(97) to be insoluble in cold, dilute chlorhydric acid, in the
borax bead, and expose the bead to the action of the
outer blowpipe flame. If the bead is blue, COBALT is
present. If the bead is brown, NICKEL is present in
large quantity. The bead is blue even when more nickel
than cobalt is present. To test for traces of cobalt in
a nickel bead, detach the hot bead from the wire, heat
it two.or three minutes on charcoal in a good reduc-
ing flame, remove it from the charcoal, and melt it on
the platinum wire in the reducing flame. Even if
only traces of cobalt are present, the bead will be
colored blue.
Nickel. When nickel is present, and when it is nearly free
(98) from cobalt, it can be discovered by the brown color
which it imparts to the borax bead, and the test is
conclusive.
To discover small quantities of nickel in the pres-
ence of considerable quantities of cobalt, dissolve the
precipitate, insoluble in cold dilute chlorhydric acid
(see 90), in concentrated nitric acid, and neutralize
with sodic carbonate. Potassic cyanide is added till
the resulting precipitate has dissolved, and then sodic
METALS OF GROUPS IV. AND HI. II7
hypochlorite till the liquid smells strongly of it, even
after being shaken. It is then boiled. If nickel is
present, a black precipitate of the sesquioxide (Ni 2 O 3 )
is obtained.
SULPHIDES SOLUBLE IN DILUTE CHLORHYDRIC
ACID.
(00) Boil in an evaporating dish the solution which was ob-
tained by the treatment of the ammonic sulphide pre-
cipitate with cold, dilute chlorhydric acid (see 06),
until the smell of sulphydric acid has entirely disap-
peared ; add a few drops of strong nitric acid, and boil
a minute longer, and filter if a precipitate of sulphur
has formed.
If oxalic, phosphoric, and boracic acids are not known
to be absent, pass to page 119, XI.
(100) Add sodic hydrate to the solution obtained in (00)
until the reaction becomes very strongly alkaline, dilute
with water and boil for a few minutes.
If a precipitate forms immediately, or after boiling,
test it according to (101) and (102) ; it may con-
tain the HYDRATES of IRON, Fe 2 (HO) 6 , MANGANESE,
Mn(HO) 2 , and CHROMIUM, Cr 2 (HO) 6 . In this case
filter and test the filtrate, which may contain ZINC and
ALUMINIUM, according to (103) and (104).
If no precipitate forms, pass to (103). The solu-
tion may contain ZINC and ALUMINIUM.
Iron. Put a small quantity of the precipitate (100) on a
(101) watch-glass, dissolve it in a single drop of dilute chlor-
hydric acid, dilute with water, and add potassic sul-
phocyanate. A red color indicates the presence of
IRON.
Manganese and Chromium. Fuse a portion of the
(102) precipitate obtained in (100) on platinum foil with
n8 PART III.
sodic carbonate and sodic or potassic nitrate. A green
mass indicates MANGANESE, owing to the formation of
sodic manganate ; a yellow mass, CHROMIUM, from the
formation of the sodic chromate. A very small quan-
tity of manganese can readily be detected in the pres-
ence of a considerable quantity of chromium by the
green color imparted to the mass. In case of doubt,
however, place the platinum foil in an evaporator, cov-
er it with water, add a few drops of alcohol, and boil.
The sodic chromate will be entirely dissolved, along
with the excess of sodic carbonate, while the sodic man-
ganate will be decomposed, yielding brown flakes of
manganese sesquioxide. These can be filtered through
a small filter, washed thoroughly with hot water, and
fused again upon platinum foil, as before, when the
green color will appear very distinctly. To detect a
small quantity of chromium in presence of excess of
manganese, treat the mass as above with boiling water
and filter. The appearance of a yellow color in the
solution is proof of the presence of CHROMIUM.
Acetate of lead may also be added to the solution,
acidified with acetic acid, and it then takes a deeper
yellow color and becomes turbid, or a yellow precipi-
tate is formed if chromium is present. The formation
of a white precipitate under these circumstances only
indicates that the carbonate of sodium employed con-
tained sulphate of sodium as an impurity.
Zinc. Add sulphydric acid to a portion of the solution in
(103) sodic hydrate, obtained in (100), after it has been
filtered, if a precipitate was formed. If a white, floccu-
lent precipitate forms, it consists of SULPHIDE OF ZINC,
ZnS.
If chromium was discovered in (102), zinc may
also be present in the precipitate obtained in (100).
Therefore, in that case, dissolve a portion of the precip-
METALS OF GROUPS IV. AND III. n 9
itate by boiling with a very little dilute chlorhydric acid,
add sodic hydrate until the reaction is alkaline, acidify
with acetic acid and add sulphydric acid. A white,
flocculent precipitate consists of SULPHIDE OF ZINC,
ZnS.
Aluminium. Add to another portion of the sodic hy-
(104) drate solution, obtained in (100), chlorhydric acid
until the reaction becomes acid, and then ammonic
hydrate until it becomes alkaline, and boil. If a
white, flocculent precipitate forms, it consists of ALU-
MINIC HYDRATE, A1 2 (HO) 6 . This precipitate is at first
gelatinous, and it may easily escape notice ; it is there-
fore best to set the test-tube aside, and to wait a quar-
ter of an hour for the precipitate to settle.
XL AMMONIC SULPHIDE TEST IN CASE PHOS-
PHORIC, OXALIC, AND BORACIC ACIDS ARE
PRESENT.
If PHOSPHORIC, OXALIC, or BORACIC ACID was pres-
ent in the original solution, these acids, together with
the metals of Group II., may be contained, wholly or
in part, in the solution obtained in (99), for the acids
would be precipitated with any of the metals of Groups
II., III., and IV., during the treatment with ammonic
hydrate and ammonic sulphide in (94), and the pre-
cipitates would be dissolved during the treatment with
dilute chlorhydric acid in (96), and consequently the
metals and acids might be contained in the solution
(99). The solution (99) must be tested for phos-
phoric, oxalic, and boracic acids, and freed from them
before the ordinary course of analysis can be pro-
ceeded with.
PllOSpJioric Acid. Use the test (127) with a small
portion of the solution obtained in (99).
120 PART III.
If phosphoric acid is present, use (107) and the suc-
ceeding tests.
If phosphoric acid is absent, use (100) and the suc-
ceeding tests.
In either case first perform the operation described in
the next paragraph.
(103) Before testing for OXALIC AND BORACIC ACIDS it
is necessary to set them free from their combinations
with the metals of Groups II., III., and IV. To effect
this end add sodic carbonate to a small quantity of the
solution obtained in (99) until the reaction becomes
strongly alkaline, and boil for a few minutes and filter.
The metals are precipitated, with the exception of a
portion of the aluminium, and the acids remain in the
solution.
[If no precipitate is formed with sodic carbonate it
* is unnecessary to test further for these metals or acids,
as in that case they cannot be present in the solu-
tion (99).]
Oxalic Acid. Test a portion of the filtrate obtained after
boiling with sodic carbonate for oxalic acid according
to (125).
Itoracic Acid. Test another portion of the same filtrate
for boracic acid according to (128).
If one or both these acids are found \ the whole of the
remainder of the solution obtained in (99) must be treated
with sodic carbonate as in (103), and the precipitate thus
obtained must be dissolved in dilute chlorhydric acid. The
solution must be used for (107) and the succeeding tests,
if phosphoric acid was discovered.
If phosphoric acid is absent, the solution must be used
for (100) and the succeeding tests.
Aluminium. If it was found necessary to treat the solu-
(106) tion obtained in (99) with sodic carbonate according
to (105), the filtrate from the precipitate produced
METALS OF GROUPS IV. AND III. I2I
by sodic carbonate may contain a portion of the alumin-
ium. Add to the nitrate in (103) chlorhydric acid
until the reaction becomes acid, and then ammonic
hydrate until the reaction becomes alkaline. If a
white, flocculent precipitate forms immediately, or after
long standing, it contains aluminium.
Iron. Add a few drops of potassic sulphocyanate to the
(107) solution obtained in (99) ; a red color indicates the
presence of IRON.
(108) Add to the remainder of the solution obtained in
(99), if phosphoric' acid alone is present, or to the
solution obtained in (105), if oxalic or boracic acid
is likewise present, ferric chloride, until a few drops,
treated with ammonic hydrate on a watch-glass, give
a yellow and not & white precipitate ; dilute largely with
water, render the solution alkaline with ammonic
hydrate, and add a considerable excess ; then add
acetic acid until the solution has a slight acid reaction,
and boil for a few minutes in a flask.
The precipitate contains all the IRON, ALUMINIUM,
CHROMIUM, and PHOSPHORIC ACID present in the solu-
tion so treated. Test according to (109) and
(110).
The filtrate contains the MANGANESE, ZINC, and
probably part of the BARIUM, CALCIUM, and MAGNE-
SIUM which were present in the original solution.
The operations described, page 115, X., #;z^page 123,
XII., must be repeated with this filtrate, omitting those
which relate to the separation of NICKEL and COBALT,
and the detection of IRON, CHROMIUM, and ALUMINIUM.
Chromium. Test a portion of the precipitate obtained
(109) in (108) for chromium according to (102).
Aluminium. Boil the remainder of the precipitate ob-
(110) tained in (108) with sodic hydrate, and test the
solution for aluminium according to (104).
I22 PART III.
[The method of precipitation by boiling the acetic
acid solution used in (10S) can be used in all cases
for the separation of aluminium, chromium, and iron
(ferric salts) from the metals of all other groups, except
the Groups V. and VI., and it is preferable to any other,
but it demands more skill in manipulation.]
METALS OF GROUP II.
METALS OF GROUP II.
XII. DETECTION OF BARIUM, STRONTIUM, CAL-
CIUM, AND MAGNESIUM.
Should the filtrate, after removal of the metals of Groups
III. and IV., have a brown color, it can only come from the
presence of nickel, a small quantity of the sulphide of that
metal having been dissolved in the excess of ammonic hy-
drate and ammonic sulphide used. Before proceeding to the
detection of metals of Group II., the nickel must be entirely
removed, and this can be readily accomplished by boiling for
a few minutes and filtering again.
(Ill) To a small portion of the solution, to which the
previous tests have been applied, or to a solution which
has been found to contain no metals of the higher
groups, add ammonic hydrate until the reaction be-
comes alkaline, and then ammonic carbonate, and boil.
(If the solution does not already contain ammonic
chloride, this also must be added, to prevent the precip-
itation of magnesium.)
If a white precipitate forms, it can only consist of
BARIC CARBONATE, BaCO 3 , STRONTIUM CARBONATE,
SrCO 8 , and CALCIC CARBONATE, CaCO 3 .
If no precipitate forms, BARIUM, STRONTIUM, and
CALCIUM are absent ; pass to (116).
If a precipitate was formed with ammonic carbonate,
the whole of the solution must be treated as described
I24 PART In '
above. Filter, wash the precipitate, and test the fil-
trate according to (116). Dissolve the precipitate by
pouring a very little dilute chlorhydric acid on the
filter, and use the solution thus obtained for (112),
(113), (114), and (115).
Barium. To a small portion of the solution in chlorhydric
(112) acid add a considerable quantity of calcic sulphate.
If a precipitate forms immediately, it consists of BARIC
SULPHATE, BaSO 4 .
Strontium. If on the addition of calcic sulphate, as
(113) in (112), a precipitate appears only after some little
time, it consists of STRONTIUM SULPHATE, SrSO 4 .
( 1 14) If BARIUM or STRONTIUM is discovered by means of
calcic sulphate, add dilute sulphuric acid to another
portion of the chlorhydric acid solution. Boil, filter,
and test the filtrate for calcium (11&). Examine
the precipitate on platinum wire moistened with chlor-
hydric acid in the flame. (See pages 26 and 34.)
Barium and strontium can both be detected, even when
a small quantity of one is present with a large quantity
of the other. After placing a small particle of the
precipitate on the loop of the platinum wire the parti-
cle should be repeatedly moistened in chlorhydric
acid and subjected again to the action of the flame.
Where strontium is present in very small proportion
the barium color will, after repeated moistening with
chlorhydric acid, finally give place to the crimson of
strontium. Where, however, the reverse proportion is
found, the detection of barium is not so easy by this
method. In this case add to a portion of the chlor-
hydric acid solution obtained in (111) a solution of
strontium sulphate. A faint white cloudiness appear-
ing after some time indicates the presence of barium.
Calcium. If barium, or strontium, or both, were present in
(115) the precipitate obtained on the addition of ammonic
METALS OF GROUP II. 125
carbonate, add ammonic hydrate to alkaline reac-
tion to the filtrate obtained after precipitation with
dilute sulphuric acid (114), and then ammonic
oxalate. If a white precipitate forms, it consists of
CALCIC OXALATE, CaC 2 O 4 .
If neither barium nor strontium was found, the whole
of the precipitated carbonate (111) must have con-
sisted of calcic carbonate. Confirm by flame reaction,
Page 35.
It is quite possible that owing to the presence of a
large excess of ammonic chloride in the solution, the
calcium may have escaped precipitation by ammonic
carbonate. In this case it would come down as a floc-
culent precipitate in the test for magnesium (116).
To detect calcium under these circumstances filter
the precipitate obtained in (110) and dissolve it in
acetic acid, dilute considerably and add ammonic
oxalate. If calcium was contained in the precipitate
- obtained by hydric disodic phosphate, it will now be
precipitated as the oxalate, which is insoluble in acetic
acid. Filter the calcic oxalate, and to the filtrate add
ammonic hydrate to alkaline reaction, when the ammo-
nio-magnesic phosphate will be re-precipitated.
Magnesium. To the filtrate from the precipitate pro-
(116) duced by ammonic carbonate (111), or to the solu-
tion in which no precipitate was obtained on addition
of that reagent, add sodic phosphate. If a white pre-
cipitate forms (frequently only after the lapse of some
minutes), it consists of the AMMONIO-MAGNESIC PHOS-
PHATE, MgNH 4 PO 4 .
126 PART III.
METALS OF GROUP I.
XIII. DETECTION OF SODIUM, POTASSIUM, AND
AMMONIUM.
Before testing for sodium and potassium, precipitate the
metals of Groups V. and VI. which are present with sulphy-
dric acid, and precipitate those of Groups II., III., and IV.
with a mixture of ammonic carbonate and sulphide, and use
the solution, freed from those metals, for the following tests
(117) and (118):
Sodium. Evaporate the solution to dryness, and drive off
(117) ammonia salts, if any are present, by heat. Sodium,
if present, can be distinguished by the yellow color
which a small quantity of the solid residue held in
the flame of a gas or alcohol lamp imparts to it. See
page 26.
Frequently sodium can be detected in a solution
without evaporation, by dipping a platinum wire in the
solution, and then holding it in the flame.
Potassium can be recognized by the violet color which it
(118) imparts to the flame. The solid residue obtained in
(117) can be tested for potassium in the same way
that it is tested for sodium.
If sodium is also present, its greater coloring power
will obscure the potassium flame, but by looking
through a piece of blue glass at the flame, the violet
color can be distinguished even when sodium is pres-
ent. (The color of the potassium flame is almost the
same as that of the heated wire, while the sodium
METALS OF GROUP I. 127
flame is much more blue, if it is not excluded entirely
by the glass.)
Add to a portion of the original solution a
(HO) few drops of sodic hydrate, and heat.
AMMONIA can be recognized by its smell, or by hold-
ing a piece of moistened turmeric paper or red litmus
paper at the mouth of the test-tube, taking care not to
let it touch the sides, which may be moistened with
sodic hydrate. The turmeric paper will be turned
brown, and the litmus paper blue, if ammonia is
present.
I2 8 PART III.
TESTS FOR ACIDS.
IT is usual to take a fresh quantity of the solution to test
for acids, and generally the tests for metals precede those for
acids, in order that information gained by the first series of ex-
periments may point out the most convenient way of detecting
the acids. Silicic acid, however, is always first precipitated
from a solution as directed, page 101 (64), and the acids no-
ticed under the chlorhydric acid test (page 106, V.) are to be
looked for while that test is applied to the detection of the
metals. Phosphoric, oxalic, and boracic acids interfere with
the ordinary methods of testing for the metals of Groups II.,
III., and IV., and consequently these acids must be tested for
as directed, page 119, XL, during the application of the tests
for the metals of those groups.
In all other cases, when the presence of any metals or acids
in the solution interferes with the performance of the test for
an acid, directions are given under the head of each acid for
removing them.
It is obvious that metals and acids which precipitate each
other cannot be present together in a solution, and that when
certain metals have been found, the number of acids which it
becomes necessary to look for is restricted within limits de-
termined by this consideration. Therefore the knowledge
already acquired of the composition of a solution must be
brought to bear upon the problem of testing for acids.
First, the reaction which the solution gives with test-paper
must be considered, and then the tables IV. and V. must be
ACIDS OF GROUP I.
129
consulted to ascertain what acids can exist in a solution pos-
sessing the observed reaction, together with the metals which
have been discovered.
For instance, if a solution contains lead, and is neutral or
nearly neutral, the only acids which can be present in it are
acetic, chlorhydric, chloric, and nitric. If the reaction is
strongly acid the solution may contain all the acids except
sulphuric, sulphydric, ferro- and ferricyanhydric. Moreover,
the solution cannot contain a large quantity of lead and chlor-
hydric acid at the same time, because the chloride of lead is
only soluble in 135 parts of water.
ACIDS OF GROUP L
Arsenious and Arsenic Acids are always detected
(120) by the sulphydric acid test in searching for the metals.
When these acids are discovered, they must always be
precipitated by sulphydric acid before testing further.
Chromic Acid cannot be present in a solution to which
(121) SULPHYDRIC ACID or AMMONic SULPHIDE has been
added (see page 64). If chromic acid is present in a
solution, it must be contained in the precipitate ob-
tained with baric chloride (122), and can be detected
by heating a small portion of the precipitate in the
borax bead. If CHROMIC ACID, H 2 CrO 4 , is present,
the bead will be colored green. Chromic acid can
often be recognized by the yellow color which it im-
parts to solutions which contain it, and by the yellow
precipitate, PbCrO 4 , which is obtained by adding
plumbic acetate to the neutral or slightly acid solu-
tion.
9
I3 o PART III.
XIV. BARIC CHLORIDE TEST.
Baric nitrate and nitric acid should be used instead of baric
chloride and chlorhydric acid, when lead, silver, or mercurous
salts have been discovered in the solution.
(122) Put a piece of litmus paper in the solution, and if
the reaction is acid, add ammonic hydrate, drop by
drop, until it becomes slightly alkaline. If a precipi-
tate is formed in consequence, add dilute chlorhydric
acid only in sufficient quantity to dissolve it. Add
baric chloride, and if a precipitate forms, it indicates
the presence of ARSENIOUS, ARSENIC, CHROMIC, SUL-
PHURIC, SULPHUROUS, OXALIC, FLUORHYDRIC, PHOS-
PHORIC, BORACIC, CARBONIC, OR SILICIC ACIDS. (Sili-
cic acid cannot be present after the operation (04)
has been performed).
If these acids are absent, pass to the argentic nitrate
test (page 132, XVIIL).
(The baric chloride test is of little value except
when the substance is soluble in water with a neutral
or slightly alkaline reaction, or in case the reaction is
acid, when the metals of Groups II., III., IV., and V.
are absent. The following special tests are more ac-
curate :)
Sulphuric Acid. Acidify (if the solution is not already
(123) acid) with dilute chlorhydric acid, in considerable ex-
cess, and add baric chloride as long as a precipitate
continues to form. (Use nitric acid and baric nitrate
if chlorhydric acid produces a precipitate.) If sul-
phuric acid is present, it is precipitated as BARIC SUL-
PHATE, BaSO 4 , fine white powder. The solution must
not be heated when it is intended to use the filtrate
for the next test.
Sulphurous Acid. To the nitrate from the precipitate
(124) produced by baric chloride, or to the acid solution to
CALCIC SULPHATE TEST. 131
which baric chloride has been added without produc-
ing a precipitate, add potassic dichromate, and boil.
If a precipitate forms, it consists of BARIC SULPHATE,
BaSO 4 , produced by the oxidation of SULPHUROUS
ACID, H 2 SO 3 , contained in the solution. Usually the
CHLORHYDRIC ACID TEST (7<>) is more convenient
and sufficiently accurate.
XV. CALCIC SULPHATE TEST.
If the solution contains metals which are precipitated by
sulphydric or sulphuric acids, they must first be removed by
adding a slight excess of those precipitants and filtering.
Add, if the solution is alkaline, add acetic acid
until the reaction becomes acid ; if it is acid, add sodic
hydrate until the reaction becomes alkaline, and then
add acetic acid until it becomes acid, and test as below
for oxalic acid. If a precipitate forms and does not
dissolve in the acetic acid, add to the original solution
a considerable excess of sodic carbonate, boil, fil-
ter, add to the filtrate acetic acid until its reaction
becomes acid, and test as follows for oxalic acid :
Add calcic sulphate in considerable quantity. If a
precipitate forms, it consists of CALCIC OXALATE,
CaCsO*, white powder. Fluorhydric acid is the only
other acid which precipitates calcic sulphate under
these circumstances, and as the precipitate is almost
transparent and gelatinous, it cannot easily be mistaken
for that produced by oxalic acid.
Acid can only be present in alkaline solu-
(126) tions in glass vessels. If there is reason to suspect
the presence of this acid, add calcic chloride and am-
monic hydrate to the solution, and if a precipitate
forms, collect it on a filter, and examine it for fluorine
according to (44).
132 PART III.
XVI. AMMONIC MOLYBDATE TEST.
Phosphoric Acid. Make the solution strongly acid (if
(127) it is not so already) with nitric acid, and add a small
portion of it to a considerable quantity of ammonic
molybdate solution.* If phosphoric acid is present,
PHOSPHO-MOLYBDATE OF AMMONIUM, yellow crystalline
powder, is precipitated. If the quantity of phosphoric
acid in the solution is very small, the precipitate does
not form until after several hours.
If sulphydric acid is present, it is necessary to heat
the acid solution until it is expelled, before perform-
ing the test. See (136) (a) for this test in the pres-
ence of ferro- or ferricyanhydric acid.
XVII. TURMERIC PAPER TEST.
Boradc Add.\ Strongly acidify the solution (if it is not
(128) already acid) with dilute chlorhydric acid, dip a piece
of turmeric paper in it, and dry the paper by holding
it over the lamp-flame, without charring it. If a red
or brownish-red stain appears upon the paper when it is
dry, it is due to the presence of BORACIC ACID, H 8 BO 8 .
ACIDS OF GROUP II.
XVIII. ARGENTIC NITRATE TEST.
Acidify with nitric acid, if the solution is not already acid,
and add argentic nitrate.
Sulphydric Acid. If a black precipitate is formed, it
(129) must contain ARGENTIC SULPHIDE, Ag 2 S, showing
*See foot-note, page 67. f Ibid., page 68.
ARGENTIC NITRATE TEST. I33
that sulphydric acid was present in the solution. The
precipitate may also contain ARGENTIC CHLORIDE,
BROMIDE, IODIDE, CYANIDE, FERRO- and FERRICY-
ANIDE.
If a precipitate is formed which is not black, it can
only be due to presence of CHLORHYDRIC, BROMHY-
DRIC, IODHYDRIC, CYANHYDRIC, FERROCYANHYDRIC,
and FERRICYANHYDRIC ACIDS.
If no precipitate is formed, none of the above acids are present.
Pass to (137).
Chlorhydric Acid. See also (48). Acidify strongly
(130) with concentrated nitric acid, add argentic nitrate in
excess, shake thoroughly if a precipitate forms, and
allow it to settle, decant the liquid, and pour on the
precipitate strong nitric acid, and boil for five minutes ;
if a precipitate remains undissolved, it consists of
ARGENTIC CHLORIDE, AgCl, if violet. If yellow, of
ARGENTIC BROMIDE. See (132) (a).
See (136) (a) for this test in the presence of ferro-
or ferricyanhydric acid.
IBromhydric Add gives with argentic nitrate a white
(131) curdy precipitate, which darkens on exposure to light,
is insoluble in boiling concentrated nitric acid, and is
not so readily soluble in ammonia as the argentic
chloride. See also (49).
lodliydric Acid gives with argentic nitrate a yellow pre-
(132) cipitate of the iodide which is nearly insoluble in am-
monia. See also (50).
(132) Detection ^/CHLORHYDRIC, BROMHYDRIC, and IODHY-
(d) DRIC acids in presence of each other. Mix the liquid to
be tested with a few drops of dilute sulphuric acid,
then with a little starch paste, and add a few drops of
fuming nitric acid, or a solution of hyponitric oxide
in sulphuric acid, when the blue color characteristic
I34 PART III.
of iodine will appear. (See page 74.) Add now
chlorine water until that reaction has disappeared.
On continuing the gradual addition of chlorine water
the bromine will be set free, and will impart a yellow
or brownish color to the liquid. (See page 73.)
Chlorine in presence of bromine can best be detected
by the following method : Evaporate the solution to
dryness and mix the residue with a little potassic di-
chromate. Place the mixture at the bottom of a clean
test-tube and pour on it a few drops of concentrated
sulphuric acid. On the application of heat dark red
drops Of CHROMYL BICHLORIDE, Or CHROMIC OXY-
CHLORIDE, CrO 2 Cl 2 , will condense in the upper por-
tion of the test-tube. Bromides, under the same
treatment, give a similar result ; but in the latter case
the distillate consists of bromine, which is instantly
. decolorized by a drop of ammonic hydrate. In the
case of chlorides, when the CrO 2 Cl 2 is treated with
ammonic hydrate, it gives a yellow solution, owing to
the formation of ammonic chromate [(NH 4 ) 2 CrOj.
Where the substance to be tested for bromine and
iodine was not soluble in water it should be fused on
platinum foil with sodic carbonate. The mass is then
treated with water and the aqueous solution used for
the foregoing method of separation.
XIX. PRUSSIAN BLUE TEST FOR CYANHYDRIC
ACID.
Cyanhydric Acid. Add to the solution ferrous sul-
(133} phate and a few drops of ferric chloride ; add sodic
hydrate until a precipitate forms (unless the solution
is alkaline and a precipitate forms without the addition
of sodic hydrate), warm for a minute, and add dilute
chlorhydric acid until the reaction becomes acid.
FERRIC CHLORIDE AND FERRO US SULPHA TE TESTS.
135
The appearance of a blue precipitate or a blue color in
the solution is evidence of the presence' of cyanhydric
acid.
See ( 136) (b) for this test in the presence of ferro-
or ferricyanhydric acid.
XX. FERRIC CHLORIDE TEST.
FerrocyanTiydric Acid. Add a little ferric chloride
(134=) to the acid solution. If ferrocyanhydric acid is pres-
ent, a precipitate of PRUSSIAN BLUE, Fe 4 (FeCy 6 )3, deep
blue, is formed.
XXI. FERROUS SULPHATE TEST.
Ferricyanhydric Acid. Add a little ferrous sulphate
(135) to the acid solution. If ferricyanhydric acid is pres-
ent, a precipitate of TURNBULL'S BLUE, Fe 3 (Fe 2 Cyi 2 ),
deep blue, is formed.
(130) If ferro- or ferricyanhydric acid is present, before
(a) performing the tests for PHOSPHORIC ACID (127), and
CHLORHYDRIC ACID (130), the following steps must
be taken : Add dilute sulphuric acid, dilute with
water if the solution is not dilute, add cupric sulphate,
and finally add enough baric nitrate * to render the
precipitate of a decidedly lighter color ; heat almost
to boiling, allow the precipitate to settle for a few
minutes, filter, and use the filtrate for the tests (127)
and (130). In case the test (51) for nitric acid is
to be used take the same preliminary steps ; using
baric chloride in place of baric nitrate.
* Sulphuric acid and baric nitrate or chloride are only added in order to
produce a heavy precipitate of baric sulphate, which carries down with it
the lighter particles of the other precipitates, and renders the filtration
easier.
I3 6 PART III.
(136) If ferro- or ferricyanhydric acid is present, the test
(b) for CYANHYDRIC ACID (133) is to be modified in the
following manner : Dilute with water if the solution is
not dilute, add dilute sulphuric acid, then add, accord-
ing as ferro- or ferricyanhydric acid is present, ferric
chloride or ferrous sulphate, or both, in sufficient
quantity to precipitate the ferro- or ferricyanhydric
acid or both acids ; finally, add baric chloride * until
the color of the precipitate has become decidedly
lighter ; shake thoroughly, allow the precipitate to
settle for a few minutes, and filter. Add to a portion
of the filtrate sodic hydrate until a precipitate forms,
warm gently, and add dilute chlorhydric acid until
the solution becomes acid. The appearance of a blue
precipitate, or of a blue color, is evidence of the pres-
ence Of CYANHYDRIC ACID.
ACIDS OF GROUP III.
ACIDS WHICH ARE NOT PRECIPITATED BY ANY
METALS.
Chloric Acid. See sulphuric acid test (47).
(13V)
Nitric Acid. See sulphuric acid test (SI).
(138)
Acetic Acid. See sulphuric acid test (52).
(139)
*See note, page 135.
INSOLUBLE SUBSTANCES.
CLASS III.
SUBSTANCES WHICH ARE INSOLUBLE IN WATER
AND IN ACIDS.
(See page 97.)
The only substances which are insoluble after the treat-
ment described on page 97 are the following :
Plumbic Sulphate (not absolutely insoluble in acids).
Argentic Chloride (slightly soluble in chlorhydric
acid).
Sulphur.
Carbon.
Baric Sulphate, Silica, and many Silicates,
and some Oxides.
XXII. SOLUTION IN AMMONIC ACETATE AND
POTASSIC CYANIDE.
Plumbic Sulphate. Boil a portion of the substance
(14=0) with ammonic acetate, and test the solution (after fil-
tration, if necessary) with ammonic sulphide. If
LEAD is present, a black color, or a black precipitate is
formed.
Test the solution also for SULPHURIC ACID, accord-
ing to (123).
If lead is discovered, repeat the treatment with am-
monic acetate until no more lead is dissolved.
Argentic Chloride. Digest a portion of the substance,
free from plumbic sulphate with potassic cyanide,
138 PART III.
warm (unless it blackens by warming), and test the so-
lution (after nitration, if necessary) with ammonic
sulphide. A black precipitate indicates the presence
of SILVER. If a black precipitate forms, wash it, dis-
solve it in strong nitric acid, and test with chlorhydric
acid according to (68) in order to confirm the pres-
ence of SILVER.
If silver is present, repeat the treatment with potas-
sic cyanide until no more silver is dissolved.
Sulphur. Test the substance, free from plumbic sulphate
(142) and argentic chloride, for sulphur according to (10).
If the substance is moist, it must be carefully dried by
heating it in a porcelain dish over a water-bath before
applying the test.
If sulphur is present, heat the substance in a cov-
ered porcelain crucible until the sulphur is completely
volatilized.
Carbon. If the substance has a black or gray color, which it
(143) loses when it is heated with the blowpipe on platinum
foil, carbon in some form is probably present. If
carbon is present, the substance, free from plumbic
sulphate, argentic chloride, and sulphur, should be
burnt, until as much as possible of the carbon is de-
stroyed, by heating it red-hot on platinum foil or in a
porcelain crucible.
XXIII. FUSION WITH POTASSIC AND SODIC
CARBONATES AND SODIC NITRATE.
Baric Sulphate, Silicic Acid, and many Sili-
(144) cates, and some Oxides. Mix the finely pow-
(a) dered substance, free from plumbic sulphate, argentic
chloride, and sulphur, and as nearly free from carbon
as possible, with two parts of potassic carbonate, two
INSOLUBLE SUBSTANCES. 139
parts of sodic carbonate, and one part of sodic nitrate ;*
bring as much of the mixture as can be heated at
once on the platinum foil, and heat the under side of
the foil with a blast-lamp until the whole mass is in a
state of quiet fusion. Repeat this operation two or
three times, if much substance is required for the ana-
lysis.
(b) Detach the fused mass from the platinum foil each
time by plunging the foil, while it is hot, in distilled
water. Boil the product of fusion with water, and if
it does not dissolve completely, filter, and wash the
precipitate on the filter with distilled water, rejecting
the washings. Continue the washing until baric
chloride ceases to produce a precipitate in the water
which runs through the filter.
(143) The first filtrate may contain ARSENIC ACID, see
(120), (its occurrence is rare) ; CHROMIC ACID, see
(121) ; SULPHURIC ACID (123), (the tests referred
to above may be applied successively to a single por-
tion of the filtrate) ; FLUORHYDRIC ACID (its occur-
rence is rare), see (126) and (44), and PHOSPHORIC
ACID (127). The two last tests may be applied suc-
cessively to another portion of the filtrate. No com-
pound of these acids, except BARIC SULPHATE, is by
itself insoluble, but insoluble substances sometimes
contain small quantities of the acids. CALCIC FLU-
ORIDE is only decomposed completely by the treat-
ment with sulphuric acid described in (44).
Silicic Add* The principal portion of the filtrate should
(140) be tested according to (04) for silicic acid. After
* The sodic nitrate is added in order to destroy carbon or other reduc-
ing substances. If the substance to be analyzed appears to contain much
carbon, increase the quantity of sodic nitrate. If the substance contains
no carbon, the use of sodic nitrate is usually unnecessary.
140
PART III.
separation of silica the only metals * that can be pres-
ent in the chlorhydric acid solution are LEAD, ALU-
MINIUM, and ZINC. Test for lead by adding an excess
of dilute sulphuric acid and alcohol to the solution.
If a precipitate of PLUMBIC SULPHATE forms, filter.
Test for ALUMINIUM, in the solution, free from lead,
by adding ammonic hydrate in excess. If a precipi-
tate of ALUMINIC HYDRATE forms, filter. Test for
ZINC in the solution, free from lead and aluminium by
adding to the solution containing ammonic hydrate in
excess ammonic sulphide. A flocculent, white precip-
itate Consists Of SULPHIDE OF ZINC.
(14f) If a portion remains insoluble after boiling the fused
mass with water (1.44) (&), dissolve it in chlorhydric
acid. If much silica was discovered (see 146), it
is best to evaporate the chlorhydric acid solution to
dryness, and to proceed as directed in (64).
Test for metals in the chlorhydric acid solution accord-
ing to page 107, VI., etc.
* It is evident that sodium and potassium in insoluble silicates cannot
be detected by this process. All reliable methods for their detection re-
quire the use of platinum vessels and great care in manipulation. Larger
works on analysis must be consulted for such methods,
EXPLANATION OF TABLES.
THE Tables I., II., and III. contain a synopsis of the course
of analysis of bodies in solution given in Part III., and they
are intended as an index to the methods which are there de-
scribed in detail. They may also serve as guides in analytical
work to students who have made themselves acquainted with
the detailed descriptions of Part III.
A skeleton form, similar to that of the tables, should be filled
out with the results of an analysis, and the reactions which oc-
cur on the application of each test should be noted.
The sign ^ placed under the formula of a compound
indicates that it is formed as a precipitate during a reaction.
This sign is used in the following tables, and it will also be
found convenient in noting the results of analyses.
The Tables IV. and V. are intended to indicate the degree
of solubility in water, and in many cases in alcohol, acids, and
alkalies, of the combinations of the metals and acids men-
tioned in Part II.
The properties of a salt are described in the square formed
by the intersection of the column devoted to an acid with that
devoted to a metal.
The Roman numerals standing after the symbols of the
metals indicate their quantivalence, and the formula of a salt is
made by putting the symbol of a metal in the place of the
symbol of an equivalent number of atoms of hydrogen in an
acid. When an acid contains more than one atom of hydro-
gen, several classes of salts may be formed, according as one
or more atoms of hydrogen are replaced by a metal. The
normal or regular salts are those which are formed by the re-
141
142
PART III.
placement of the greatest passible number of atoms of hydro-
gen by a metal.
The descriptions of the tables refer to normal salts, but the
following cases are exceptions, because the salts specified are
more commonly met with in analysis ; and in using the tables
the formulas below must be substituted for those of the normal
salts :
ARSENATES. MgNH 4 AsO 4 ; MnNH 4 AsO 4 ; (Hg 2 )HAsO 4 ;
HgHAs0 4 .
PHOSPHATES. (NH 4 ) 2 HP0 4 ; BaHPO 4 ; CaHPO 4 ; MgNH 4
P0 4 ; MnNH 4 P0 4 ; HgHPO 4 ; Na 2 HPO 4 .
The ARSENATE OF ALUMINIUM probably contains more acid
than the normal salt.
The CHROMATES OF ALUMINIUM and of IRON (ferric chro-
mate) contain a larger proportion of metal than the
normal salts.
ARSENITES. The arsenites referred to in the table have only
two atoms of hydrogen replaced by a metal, except Mg 3
(AsO 3 ) 2 and Ag 3 AsO 3 .
The ARSENITES OF COBALT and MANGANESE contain less than
two atoms of hydrogen replaced by the metal.
BORATES (NH 4 ) 2 B 4 O 7 ; BaB 2 O 4 ; CuB 4 O 7 ; FeB 4 O 7 ; (Fe 2 )
B 3 O 6 ; PbB 4 O 7 ; CaB 2 O 4 ; MnB 4 O 7 ; NiB 4 O 7 ; K 2 B 2 O 4 ;
; Na 2 B 4 O T ; ZnB 4 O 7 .
EXPLANATION OF SIGNS IN TABLES IV. AND V.
Numbers = number of parts of water required to dissolve one part of the
anhydrous salt * at the ordinary temperature,
oo . insolubility.! The sign of infinity indicates that an infinite
quantity of water is required to dissolve the salt,
s. = soluble to a considerable extent in water,
s.s. = slightly soluble,
del. = deliquescent, or capable of dissolving by attracting moisture
from the air.
dec. = decomposed. Examples : dec. = decomposed by water.
dec. = decomposed by acids.
= acids. Example : s. = soluble in acids.
+ = sodic or potassic hydrate. Example : + s. = soluble in so-
dic or potassic hydrate,
am. = ammonic hydrate,
am. cl. = ammonic chloride.
al. = alcohol. Example : al. 00.= insoluble in alcohol.
When no solvent, such as , am., al., etc., is indicated, the signs co.,
s., s.s., and dec. refer to the action of water on the salt.
* The salt without water of crystallization is referred to.
t Most of the salts marked insoluble in the table are not really more insoluble than
salts like baric sulphate, but they are described as insoluble because they are known to
be nearly so, and because the quantity of water required to dissolve them has not been
determined.
143
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TABLE V. EXPLAN
Acetic Acid, HC a H 3 O 2
Arsenic Acid, H 3 AsO 4
Arsenious Acid, )
H,As0 8 . S~~
Boracic Acid, H 3 BO 3 .
Bromhydric Acid.HBr
V^arbonic Acid, H a CO 3
^XfhlorhydricAcid.HCl.
Chloric Acid, HC1O S .
Chromic Acid,H 2 CrO 4
Cyanhydric Acid, HCy
-U
||
^
Fluorhydric Acid, HF.
X
.g
O
K
y
'B
Oxalic Acid, H 2 C 2 O 4 .
y
If
N/Sulphuric Acid, H 2 SO 4
!2
P"
,/Sulphydric Acid, H 2 S.
~1VO 'OOSIONVMd NVS
" '!/! .SH3AVSSV
^!AiI^S
( 2H: ilJLSflf
.Vki Ci'lOW
14 DAY USE
RETURN TO DESK FROM WHICH BORROWED
LOAN DEPT.
This book is due on the last date stamped below, or
on the date to which renewed.
Renewed books are subject to immediate recall.
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REC'D LP
MAY 8 1963
200ef65CD
REC'D LD
OC1 6'65-9pM
4 - 1968
LD
8EC1JLQ. FEB 23 71 -2PM 5 7
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General Library
University of California
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M81896
c.7
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