UC-NRLF
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REESE LIBRARY
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OF THE
UNIVERSITY OF CALIFORNIA
Deceived ^
Accessions No.^,. Shelf JVo.
ELECTRO-CHEMICAL
ANALYSIS.
SMITH.
RlCHTER'S
AUTHORIZED TRANSLATIONS.
BY EDGAR F. SMITH, F.C.S., M.D., PH.D.,
Professor of Chemistry, University of Pennsylvania ; Member of Chemical Societies
of Berlin and Paris, etc.
INORGANIC CHEMISTRY. A Text-book for Students. Third
American, from the Fifth German Edition, thoroughly revised, and
in many parts rewritten. With 89 Illustrations and a Colored Plate
of Spectra. I2mo. Cloth, $2.00
THE CHEMISTRY OF THE CARBON COMPOUNDS, or
Organic Chemistry. A Text-book for Students. Translated from
the Fourth German Edition. Illustrated.
Cloth, $3.00; Leather, $3.50
Prof. Richter's methods of arrangement and teaching have
proved their superiority by the large sale of his books throughout
Europe and America, translations having been made in Russia,
Holland and Italy. They are now used by many of the most
prominent schools and colleges in the United States, by those
giving a high technical education, as well as those who aim to
give but a groundwork in the science of chemistry ; this shows
their wonderful adaptiveness to all grades of teaching.
Upon application, a complete descriptive circular, giving recom-
mendations and examination prices, will be sent free.
P. BLAKISTON, SON & CO.,
PUBLISHERS,
1O12 WALNUT STREET, -' PHILADELPHIA.
ELECTRO-CHEMICAL
ANALYSIS.
BY
EDGAR F. SMITH,
M
PROFESSOR OF ANALYTICAL CHEMISTRY, UNIVERSITY OF PENNSYLVANIA.
WITH TWENTY-FIVE ILLUSTRATIONS.
PHILADELPHIA:
P. BLAKISTON, SON & CO.,
1012 WALNUT STREET.
1890.
Copyright, 1890, by P. BLAKISTON, SON & Co.
PRES8 OF WM. F. FELL <* CO.,
1220-24 SANSOM STREET,
PHILADELPHIA.
PREFACE
In preparing this little volume the author has had
constantly in view the needs of a large class of stu-
dents of analytical chemistry desirous of becoming
acquainted with the methods of quantitative analysis
by electrolysis ; these are daily acquiring greater im-
portance, and being introduced and applied wherever
possible.
The larger texts devoted to analysis have omitted
electrolysis from their pages, thus rendering its special
treatment necessary and desirable.
The plan adopted in the following pages in present-
ing this subject has been to give a brief introduction
upon the behavior of the current toward the different
acids and salts, a short description of the various
sources of the electric energy; its control and measure-
ment ; after which follow a condensed history of the
introduction of the current into chemical analysis, and
sections relating to the determination and separation
of metals, as well as the oxidations possible by means
of the electric agent.
In using this book as a guide, the student is ear-
nestly recommended to perform the determinations of
each metal as indicated in the text. The details have
v
VI PREFACE.
been made sufficiently full, and clear enough, it is
hoped, for the most inexperienced analyst. Additional
skill and valuable experience are acquired with each
trial, so that, when the section treating of separations
is reached, the work there outlined will be performed
without difficulty. Before commencing the determina-
tion of any one metal read, if possible, its literature.
The methods of determination and separation given
preference are not those of any one individual, but
have been selected from all sources after an experience
of many years, care being taken to present only those
which actual tests have shown to be reliable and trust-
worthy.
It has not been considered advisable to include an
outlined electrolytic analysis of alloys and minerals
in the text, inasmuch as the experience gained in per-
forming the analyses already described there will have
given the analyst such a fund of experience that the
course to be pursued in special cases will readily sug-
gest itself.
The author would here acknowledge his indebted-
ness to the various writers on electrolysis, whose
publications he has freely used, to the editors of the
different journals consulted, to friends who have made
kindly suggestions, and to his brother, Dr. Allen J.
Smith, who prepared all the drawings from which the
illustrations of the text were made. S.
University of Pen n a.,
Philadelphia, Sept., 1890.
TABLE OF CONTENTS.
PAGB
INTRODUCTION, 9-10
ACTION OF THE ELECTRIC CURRENT UPON ACIDS AND SALTS, 10-13
OHM, VOLT, AMPERE, ; . 13-14
SOURCES OF ELECTRIC CURRENT
Grenet Battery, Leclanche Cell, Daniell Cell, Meidinger
Cell, Crowfoot Cell, Bunsen and Grove Batteries,
Magneto-Electric Machines, Storage Cells, Ther-
mopile, 14-25
REDUCTION OF THE CURRENT
Rheostat, Resistance Frame, 25-29
MEASURING CURRENTS
Voltameter, Amperemeter, 29-32
HISTORICAL SKETCH, .* . 32-46
SPECIAL PART.
1. DETERMINATIONS OF METALS, 47-89
2. SEPARATION OF METALS, 89-108
3. OXIDATIONS BY MEANS OF THE ELECTRIC CURRENT, . 108-113
INDEX, 115
Vll
IO ELECTRO-CHEMICAL ANALYSIS.
determinations where the ordinary methods yield un-
satisfactory results. This statement is readily con-
firmed on recalling the gravimetric methods usually
employed in the estimation of copper, mercury, cad-
mium, bismuth, tin, etc., etc. That this assertion may
be the conviction of every student of analysis, the
writer would call attention first to the course of the
current in solutions of some of the more frequently
occurring salts; after which will follow a brief account
of the various modes of obtaining the electric current,
how it may be measured and how controlled. Finally,
all the metals, which have been studied electrolytically,
will be taken up in detail, and their various determina-
tions will be followed by a sufficient number of separa-
tions to show, at least in part, how widely the electro-
lytic method of analysis may be applied.
i. ACTION OF THE ELECTRIC CURRENT UPON
ACIDS AND SALTS.
At the At the
Pole. + Pole.
Hydrochloric acid -(- the current = Hydrogen -|- Chlorine.
Copper chloride -f- " " = Cu + C1 2 .
Zinc chloride -f " " = Zn + C1 2 .
Nitric acid -f " " = H -f NO 2 -f O.
In this last case the hydrogen further acts upon more
nitric acid and produces ammonia (NH 3 ) and water.
Lead nitrate -f the current = Pb -f NO 2 + O.
The oxygen liberated here attacks a second molecule of
ACTION OF CURRENT UPON ACIDS AND SALTS. I I
lead nitrate, and produces lead peroxide, Pb(NO 3 ) 2 -j-
O 2 = PbO 2 , which deposits upon the positive elec-
trode.
At the At the
Pole. + Pole.
Copper nitrate -}- the current = Cu -)- (NO 3 ) 2 .
Sulphuric acid + " " = H 2 -f SO 4 .
Secondary changes frequently occur in these de-
compositions ; thus, in the last example the SO 4 reacts
with the water present: SO 4 + H 2 O == H 2 SO 4 -f O,
the oxygen going to the positive electrode. In the
electrolysis of copper sulphate, which is analogous to
sulphuric acid, secondary changes also occur.
At the At the
Pole. + Pole.
Potassium sulphate -|- the current = K 2 -f- SO 4
In this decomposition the liberated potassium acts
upon water, with the liberation of hydrogen and the
formation of potassium hydroxide.
Bourgoin observed the following changes with
formic, acetic and oxalic acids, and their salts :
I. Formic Acid. The decomposition may be ex-
pressed in two equations
(a) CH 2 2 = H + (CHO -f O).
Pole + Pole
(6) 2(CHO -f- O) = CH 2 2 + C0 2 .
The decomposition of sodium formate yields carbon
dioxide and formic acid at the anode, and hydrogen
and sodium hydroxide at the cathode.
12 ELECTRO-CHEMICAL ANALYSIS.
2. Acetic Acid. The electrolysis of the dilute acid
affords ^hydrogen at the negative electrode, and at
the positive electrode a mixture of oxygen, carbon
dioxide and a small quantity of carbon monoxide.
3 Oxalic Acid. The electrolysis of this acid with
a current obtained from four Bunsen cells gave de-
compositions which may be expressed as follows :
C 2 H 2 O 4 .2H 2 O -j- current = 3H 2 -f 2CO 2 -f O 2 ;
Pole. +Pole.
the oxygen reacts upon additional acid :
2C 2 H 2 O 4 + 2H 2 O -f O 2 = 4CO 2 + 4H 2 O,
so that the final products are pure carbon dioxide at
the positive electrode and hydrogen at the opposite
pole. The decomposition of potassium oxalate may
be formulated in the following way :
Pole. + Pole.
the liberated metal and the carbon dioxide then react
further :
2H 2 O -f K 2 = 2KOH -f H 2 and 2CO 2 -f 2KOH = 2KHCO 3 .
When exposed to the same influence ammonium
oxalate yields hydrogen at the negative electrode, and
hydrogen ammonium carbonate at the positive elec-
trode. The latter compound further breaks down
into ammonia and carbon dioxide.
Succinic acid is electrolysed with difficulty. In its
decomposition the products which have generally been
OHM, VOLT AND AMPERE. 13
observed at the positive electrode were oxygen and
the two oxides of carbon. By electrolysing sodium
succinate Kekule obtained hydrogen at the cathode,
and carbon dioxide and ethylene at the anode.
Tartaric acid -f the current gave at
Pole. + Pole.
hydrogen acetic acid, carbon dioxide,
carbon monoxide and oxygen ;
while with potassium tartrate the products were hy-
drogen and potassium at the cathode and acid potas-
sium tartrate, carbon dioxide, carbon monoxide and
oxygen at the anode. An alkaline solution of potas-
sium tartrate gave hydrogen at the cathode and at the
anode, acetic acid, the oxides of carbon, oxygen and
ethane (C 2 H 6 ).
The above examples will suffice to indicate the na-
ture of the decomposition due to the current; they
will assist very materially in understanding the
changes occurring in ordinary electrolytic analyses.
For further particulars in this direction, consult
Tommasi's Traite Theorique et pratique d' Electrochimie.
2. OHM, VOLT AND AMPERE.
These terms may be defined as follows :
The ohm is the unit of resistance. Its value is rep-
resented by a column of mercury I sq. mm. in cross-
section, and 106.2 cm. in length at the temperature
14 ELECTRO-CHEMICAL ANALYSIS.
The volt is the unit of electromotive force (E. M. F.).
It is the E. M. F. which gives a current of one ampere
through a resistance of one ohm.
The ampere is the unit of current. It is the
current which, under an electromotive force of one
volt, flows through a circuit offering a resistance
of one ohm.
V
A-.
O
3. SOURCES OF THE ELECTRIC CURRENT.
The electric energy required for quantitative analy-
sis has been variously furnished by batteries of well-
known types, magneto-electric machines, dynamos,
thermo-piles, and electrical accumulators or storage
cells. A brief description of some of these may be
properly introduced here.
The Grenet cell or Bichromate Battery (Fig. i) con-
sists of two plates of carbon (K) and one of zinc (Z),
movable by means of the handle, a. This is a con-
venient arrangement, as it allows of easy interruption
of the current. The liquid to be used in this cell con-
sists of potassium bichromate (i lb.), strong sulphuric
acid (2 Ibs.), and water (12 Ibs.). In mixing these, the
probable chemical change is :
K,Cr 2 7 + 7 H 2 S0 4 = 2Cr0 3 + K,SO 4 + H 2 O + 6H 2 SO 4 .
SOURCES OF THE ELECTRIC CURRENT. 15
The chemical action in the cell, when the current
passes, may be expressed by the equation :
2 CrO 3 + 6H 2 SO 4
-f
4 -f- 6H 2 O.
The writer found four cells of this type (capacity
two quarts) very serviceable in the electrolysis of solu-
tions of cadmium, uranium, molybdenum and other
FIG. i.
metals. No disagreeable fumes arise from cells of
this class. The electromotive force is about two
volts, and the internal resistance low. The Grenet
cell loses in intensity when used for long periods, but
regains its value when it has remained out of action
for some time.
i6
ELECTRO-CHEMICAL ANALYSIS.
Leclanche cell (Figs. 2 and 3). Two forms of this
cell are in use. In the first, to the left of the
figure, there is a zinc rod, immersed in a solution
of ammonium chloride, and a carbon plate inside
a porous cup, tightly packed with a mixture of
manganese dioxide and broken gas carbon. The
FIG. 2.
FIG. 3.
porous cup is only intended to hold the mixture
in position. There is but one liquid, and that a
strong solution of ammonium chloride. The E. M. F.
of this cell equals 1.47 volts; it decreases rapidly
when sending strong currents. It is inferior to the
Daniell cell when a steady current is desired for
a long period.
SOURCES OF THE ELECTRIC CURRENT. 1 7
The chemical action in cells of this kind Ayrton
expresses as follows :
(Before sending the current)
kC+ I (MnO 2 ) + m (NH 4 C1) + n Zn.
(After sending the current)
k C + (/- 2)(Mn0 2 ) + (m 2)(NH 4 C1) + (Mn. 2 O 3 ) + 2(NH 3 )
+ (H 2 0) + (ZnCl 2 ) + (n - i)(Zn).
The letters k, /, m, n represent indefinite amounts
of the acting substances.
In the modified Leclanche cell the porous cup is
not needed, as compressed prisms of manganese diox-
ide, gas carbon and shellac are used around the
carbon plate.
The Daniell cell (Fig. 4) consists of a glass jar, the
porous cup T, and a cylinder of zinc (Z), the negative
pole. Outside of the porous cup is the sheet-copper
cylinder K. The zinc is the negative electrode, and
the copper the positive electrode. The zinc stands in
dilute sulphuric acid (i : 20), and the copper in copper
sulphate. Zinc sulphate often replaces the sulphuric
acid. The chemical action in the cell is probably :
k (Cu) -f / (CuSO 4 ). /Before sending\ .2 m (ZnSO*) + n (Zn).
\ the current. / *S
o.
(k + i)(Cu) + (/ - i)(CuS0 4 ). /After sendingN (m + i)(ZnSO 4 + ( - i)(Zn).
V the current. ) (Ayrton).
PU
The E. M. F. of this cell is about 1.07. The Meid-
inger (Fig. 5) and Crowfoot (Fig. 6) cells are modifica-
tions of the Daniell, and very serviceable in electrolytic
i8
ELECTRO-CHEMICAL ANALYSIS.
FIG. 4.
SOURCES OF THE ELECTRIC CURRENT. \g
work when currents of low intensity are desired. In
the sketch of the Meidinger cell, G is a large glass
jar; g t a small glass vessel, in which stands the copper
cylinder, K (-f- P). Z ( P) is a cylinder of zinc.
B contains the supply of copper sulphate crystals.
The current from either of these batteries remains
quite constant for long periods. The cells themselves
do not require much attention. Haifa dozen of either
of these forms will do nearly all the electrolytic work
of an ordinary laboratory. The "Crowfoot" form
can be readily and cheaply prepared. Rejected acid
bottles, after removing the neck and upper portions,
answer well as jars.
If currents of greater E. M. F. are required, the
Bunsen (Fig. 7) or Grove cell (Fig. 8) should be used.
* In the former there is zinc in dilute sulphuric acid, or
a mixture of potassium bichromate and sulphuric acid,
and a carbon plate in a cup of nitric acid. It is a less
expensive cell than the Grove, as platinum is not
employed. It is not so readily handled, and con-
sumes more nitric acid. Its electromotive force is
somewhat less than that of the Grove form. In the
latter there is a strip of* platinum (P) in concentrated
nitric acid (in the porous cup, x)~ and zinc (ZZ) in
dilute sulphuric acid (one pint acid and ten pints
water). The E. M. F. is 1.93 volts. When acting,
X 2 O 4 is set free ; this can be in a measure suppressed
by adding ammonium chloride to the nitric acid.
The chemical changes occurring in the Bunsen and
20
ELECTRO-CHEMICAL ANALYSIS.
Grove cells are very similar. Ayrton expresses them
as follows :
(Befor^ current is sent)
A(Pt) +/(HN0 3 ).
(After sending current)
* (Pt) + (/ 2 )(HN0 8 ) + (N 2 O 4 ) + ( 2 H 2 0).
FIG. 7.
The internal resistance of the Grove cell is small.
To obtain good results both the Bunsen and Grove
cells require constant attention.
SOURCES OF THE ELECTRIC CURRENT. 21
In amalgamating the zincs in any of the preceding
batteries, first allow them to remain o,ver night in very
dilute hydrochloric acid, then immerse in mercury,
and with a wet cloth rub the latter into the metal.
This should be done once a week, when the cells are
in daily use. For further information upon batteries,
consult Ayrton's Practical Electricity.
Magneto-electric machines, and dynamos have been
used to some extent in electrolytic decompositions,
but a detailed description of their construction will
not be given. This may be found in Classen's
Analysis by Electrolysis, pp. 21-35 (Herrick's transla-
tion).
Thermo-piles have also been used to furnish cur-
rents for electrolytic work. Their use has been
objected to upon the ground that the currents afforded
by them are rarely strong enough for the greater num-
ber of determinations and separations, and again they
are easily broken and difficult to repair. The forms
generally met with are those recommended by Cla-
mond and Noe.
The Clamond thermo-pile is pictured in Fig. 9. I
is a perspective view of the same ; 2 represents a ver-
tical section, and 3 a basal section, showing the bars
and armatures. The elements consist of bars of a zinc
and antimony alloy, and a strip of sheet-iron. These
are arranged in circles, as indicated in 3 ; they are
placed one above the other. In 3, B represents the
bars of zinc and antimony alloy, while the tinned
22
ELECTRO-CHEMICAL ANALYSIS.
SOURCES OF THE ELECTRIC CURRENT. 23
sheet-iron plates are marked L. The sheet-iron serves
to conduct the current from one element to the other;
hence, these strips rest upon the bars B. Heat ex-
pands the latter, and in consequence renders the con-
tact more intimate. The single elements, as well as
the circles of elements, are separated from each other
by plates of asbestos (see r in 2). The cylinder itself
consists of a series of such circles. The welded points
of the bars are all directed to the centre of the cylin-
der. The gas flames are prevented from coming in
immediate contact with them by the asbestos lining
of the cylinder. As gas is employed to furnish the
necessary heat, in the middle of the cylinder will be
observed a clay tube (A) provided with apertures (2
and 3). The gas enters through the Giroud regulator
C (i and 2), which makes it possible to maintain a
uniform temperature, and a constant current. From
C it is conducted to A, through 7", into which air is
admitted by suitable apertures. The mixture of air
and gas burns at the openings in A. Additional
air is supplied through D. Light the gas jets from
above, after removing the cover. The poles of each
ring of elements end in binding screws, thus en-
abling the operator to connect any number of them,
depending upon the external resistance (Z. f. a. Ch.,
15, 334)-
When in excellent condition, thermo-piles are said
to yield a current equivalent to 400-500 c.c. oxy-
hydrogen gas per hour. Those persons who may
24 ELECTRO-CHEMICAL ANALYSIS.
desire fuller information upon this type of battery are
referred to the following
LITERATURE: Z. f. a. Ch., 14, 350; 17, 205; Ding. p. Jr., 224,
267; Z. f. a. Ch., 18, 457; 25, 539.
The best source of electric energy, for electrolytic
purposes, is unquestionably the storage cell (Fig. 10).
FIG. 10.
The illustration represents a cell of the Julien type.
It contains nineteen alternating plates of lead and lead
dioxide. Each of these is five and three-fourths inches
square. The exciting liquid is sulphuric acid of sp.
gr. 1.2. The E. M. F. of such a cell is a little more
than two volts. The current is very constant.
Cells of this kind can be charged from primary
REDUCTION OF THE CURRENT. 25
batteries, or better, by means of a dynamo. In any
community where electric lighting is employed it is
possible to have the charging done at little expense,
and in factories where there is always sufficient power,
a small dynamo could easily be arranged for this pur-
pose, so that almost any number of cells could be kept
in condition for work. The iron estimations required
by any establishment could be rapidly and accurately
made with three cells of this type ; little attention
would be demanded from the chemist. While storage
cells can be used in almost every description of elec-
trolysis, there are a great many cases where economy
would suggest the use of the cheaper batteries, e.g.,
the Crowfoot. Consult the following literature upon
storage batteries:
Proceedings of the Royal Society, June 2Oth, 1889; Transactions of
Am. Inst. Mining Engineers (Electrical Accumulators, Salom), Feb.,
1890.
Having thus briefly described the more important
current-producers, the means of regulating the current
may be next considered.
4. REDUCTION OF THE CURRENT.
When a battery gives a current that generates 10
c.c. oxy-hydrogen gas per minute, and work is to be
done which can easily be performed by an expenditure
of energy not exceeding 3 c.c. oxy-hydrogen gas per
minute, it will become necessary to reduce the strong
c
26
ELECTRO-CHEMICAL ANALYSIS.
current. Persons acquainted with practical physics
will promptly suggest the resistance coils found in
physical laboratories, as suitable for this purpose.
They are, on the whole, quite satisfactory, and have
been thus utilized, although simpler and more con-
venient current-reducers have made their appearance
FIG. ii.
in recent years. A few of these later appliances may
be mentioned :
i. The current may be sent through a solution
(saturated) of zinc sulphate, contained in a large glass
cylinder, about 22 cm. long and 8.5 cm. in diameter.
In one experiment the current is passed from a to b
(Fig. T i), and in the next from b to a. " The rod b,
REDUCTION OF THE CURRENT. 2/
with one zinc pole, is pushed toward the zinc pole a,
until the current reaches the desired strength." It is
well to amalgamate the zincs from time to time. We
are indebted for this piece of apparatus to Classen,
who has also described another simple rheostat (Fig.
12) (Ben, 21, 359). In this apparatus the current
enters at a, travels the German silver resistance ;/, and
returns through b to the battery. In the performance
of electrolytic depositions the platinum vessels, serv-
ing as negative electrodes, may be connected with any
one of the binding-posts from 1-20. This makes it
possible for the analyst to execute eight different de-
terminations at the same time. To show the influence
of this apparatus, a current from five Bunsen cells,
generating 68 c.c. oxy-hydrogen gas per minute, was
allowed to act upon copper solutions contained in six
vessels. The current at binding-post I was found to
be equal to 3.75 amperes; at 2, it equaled 2.617
28
ELECTRO-CHEMICAL ANALYSIS.
P^JG. 13.
MEASURING CURRENTS. 29
amperes; at 3, 2.085 amperes; at 4, 1.911 amperes,
etc., until at 20 it was only 0.098 of an ampere.
To better understand these figures it should be re-
membered that an ampere equals 10.436 c.c. oxy-
hydrogen gas per minute, or it is equivalent to a
current which will precipitate 19.69 mg. of metallic
copper, or 67.1 mg. of metallic silver in one minute.
For a larger form of apparatus somewhat similar to
that described above see Ber., 17, 1787.
The writer has for some time employed a much
simpler current-reducer, which has the advantage of
cheapness and ready construction to recommend it.
It consists of a light wooden parallelogram, about six
feet in length. Extending from end to end, on both
sides, is a light iron wire, measuring in all about 500
feet (Fig. 13). With the binding-posts at a and b, and
a simple clamp, it is possible to throw in almost any
resistance that may be required. It answers all prac-
tical purposes.
LITERATURE. v. Klobukow, Jr. f. pkt. Ch., 37, 375; 40, 121.
5. MEASURING CURRENTS, VOLTAMETER,
AMPEREMETER.
In every analysis by electrolysis it is advisable that
the strength of the acting current should be known.
The simplest and most convenient apparatus for this
purpose is the Bunsen voltameter (Fig. 14). The
inner tube a, containing sulphuric acid of sp. gr. 1.22,
3O ELECTRO-CHEMICAL ANALYSIS.
stands in a large cylinder of water to cool it. The
liberated hydrogen and oxygen are collected over
water in the eudiometer tube R ; p and p r are platinum
electrodes. In all accurate experiments the volume
of gas should always be reduced to o and 760 mm.
FIG. 14.
pressure. Some chemists substitute a galvanometer
(tangent or sine) for the voltameter. The deflection
of the needle by the current measures the strength of
the latter. " In order to express in terms of chemical
action the deflection of the needle, it is placed in the
MEASURING CURRENTS. 3!
same current with a voltameter, and the deviation of
the needle is observed, as well as the volume of elec-
trolytic gas (reduced to o and 760 mm. pressure),
which is produced in a minute. Placing the volume
equal to v, the quotient ~ - gives the standard value
for the galvanometer. If this standard value is de-
FIG. 15.
noted by R, the strength I, of a current, which pro-
duces the deviation a, is I = R tan. a."
The writer has found the amperemeter of Kohl-
rausch (Fig. 15) very satisfactory, especially in cases
where strong currents are employed. In this instru-
ment the current travels through an insulated wire
32 ELECTRO-CHEMICAL ANALYSIS.
surrounding a bar of soft iron. The latter, in its
magnetized state, attracts the needle C, attached to a
spiral. C moves over a graduated face (in amperes),
and its deflection gives at once the strength of the
current in amperes.
In electrolytic work of any kind it is advisable
that the apparatus intended to measure the current
strength should be in the circuit during the entire
decomposition, for it is only in this way that we can
expect to effect separations without encountering un-
pleasant difficulties. It is necessary to know just what
energy is required, and then to so regulate the current
that the same is approximately maintained throughout
the entire determination.
Before taking up the description of the details to
be observed in the electrolytic precipitation of indi-
vidual metals, it may not be uninteresting to briefly
trace the history of the introduction of the electric
current into chemical analysis.
6. HISTORICAL.
Although the early years of this century show con-
siderable activity in electrical studies, the efforts were
mainly directed to the solution of the physical side of
electrolysis. To Gaultier de Claubry probably be-
longs the credit of having first (1850) applied the cur-
rent to the detection of metals when in solution. His
efforts were wholly directed to the isolation of metals
HISTORICAL. 33
from poisons by depositing the same upon plates of
platinum. When the precipitation was considered
finished the plates were removed, carefully washed,
and the deposited metals brought into solution with
nitric acid, and there tested for and identified by the
usual course of analysis. The current was evidently
very feeble, as the time recorded as necessary for the
deposition varied from ten to twelve hours. Gaultier
considered this method reliable in all instances, but
especially recommends it for the separation of copper
from bread. In testing for zinc he employed a strip
of tin as anode, but states that a platinum plate will
answer as well.
In Graham-Otto's Lehrbuch der Chemie (1857) it
is stated that the oxygen developed at the positive
electrode readily induces the formation of peroxides ;
. . . that lead and manganese peroxides are de-
posited, from solutions of these metals, upon the posi-
tive electrode of the battery ; . . . that the point of
a platinum wire, when attached to the anode of a cell,
is therefore a delicate means of testing for manganese
and lead. In the same text the oxidizing power of
the anode is nicely shown by the following simple ex-
periment : A piece of iron, in connection with the
positive electrode of the battery, is introduced into a
V-shaped glass tube containing a concentrated solu-
tion of potassium hydroxide, while a platinum wire
running from the negative electrode projects into the
other limb of the vessel. In a short time ferric acid
34 ELECTRO-CHEMICAL ANALYSIS.
appears around the anode, and is recognized by its
color.
C. Despretz (1857) described the decomposition of
certain salts by means of the electric current, and
remarked that, while operating with solutions of the
acetates of copper and lead, he expected both metals
would be deposited upon the negative pole, and was
much surprised to find that the lead separated as oxide
upon the anode at the same time that the copper
was deposited upon the cathode. The results were
the same when experiments were conducted with
the nitrates and pure acetates. With manganese no
deposition took place upon the negative electrode, but
a black oxide appeared at the opposite pole. Potas-
sium antimonyl tartrate gave a crystalline metallic
deposit of antimony at the cathode, and upon the anode
a yellowish-red coating, supposed to be anhydrous
antimonic acid. Bismuth nitrate yielded a reddish-
brown deposit at the positive electrode. Despretz
concludes his paper by stating that although the facts
were few in number, yet they were new in so far as
they concerned lead, antimony and manganese ; and,
furthermore, that the separation of copper from lead
by the current was almost perfectly complete.
Three years later (1860) Charles L. Bloxam recom-
mended the process of Gaultier for the detection of
metals in organic mixtures, although it may not be
improper to add that Smee (1851), in his work on
electrometallurgy, asserts that Morton was the first
HISTORICAL. 35
person to employ the electric current for the isolation
of metals from poisonous mixtures. However this
may be, the fact remains that Bloxam did use the
current quite extensively for this purpose, and while
he claims no quantitative results for the method, the
apparatus employed by him and his subsequent work
in this direction deserve great credit.
To detect arsenic electrolytically Bloxam made use
of a glass jar, four cubic inches in capacity, closed
below by parchment, which was tightly secured by
means of a thin platinum wire. In the neck of the
jar was a large cork, through which passed a glass
tube bent at a right angle. This tube was intended
to serve as a means of escape for the gases liberated
within the jar. The platinum wire from the negative
electrode was also held in position by the cork. The
portion of the wire within the jar was attached to a
platinum plate dipping into the arsenical mixture con-
taining dilute sulphuric acid. The jar with its contents
stood in a wide beaker, filled with water, into which
dipped the positive electrode of the battery. Under
the influence of the current, metals like antimony,
copper, mercury and bismuth separated upon the
platinum plate of the negative electrode, while arsine
was liberated and escaped through the exit-tube into
some suitable absorbing liquid. To ascertain what
metal or metals had separated upon the cathode,
the plate attached thereto was removed, after the
interruption of the current, and treated with hot
36 ELECTRO-CHEMICAL ANALYSIS.
ammonium sulphide. Upon evaporating this solution
an orange-colored spot remained if antimony had been
previously present. If a metallic deposit continued
to adhere to the foil the latter was acted upon by
nitric acid to effect the solution of the remaining
metals.
J. Nickles (1862) precipitated silver with the current
obtained from a zinc-copper couple. The positive
electrode consisted of a piece of graphite, taken from
a lead-pencil, while a thin, bright copper wire consti-
tuted the negative electrode. The silver separated
upon this. The current was very feeble, for hydrogen
was not liberated at the cathode. Nickles also sug-
gested the reduction of large quantities of silver from
the solution of its cyanide by this means. To obtain
the silver he advised using a cylindrical cathode con-
structed from some readily fusible alloy, so that after
the reduction was finished, the other metals might be
easily melted out and leave a silver plate. Copper,
lead, bismuth and antimony were separated electro-
lytically, by Nickles, from textiles.
In 1862 A. "C. and E. Becquerel resumed their
electro-chemical investigations, first begun some thirty
years previously. Their experiments seem to have
been aimed chiefly toward the reduction of metallic
solutions upon a large scale, caring not for the quanti-
tative estimation of metals, but seeking rather a rapid
and satisfactory technical isolation process.
Wohler (1868) found that when palladium was
HISTORICAL. 37
made the positive conductor of two Bunsen cells, and
placed in water acidulated with sulphuric acid, it
immediately became covered with alternating, bright,
steel-like colors. He regarded the coating as palladium
dioxide since it liberated chlorine when treated with
hydrochloric acid, and carbon dioxide when warmed
with oxalic acid. Black amorphous metal separated
at the cathode. Its quantity was slight. Under
similar conditions lead also yields the brown dioxide,
and the same may be said of thallium. Osmium, in
its ordinary porous form, at once becomes osmic acid.
When caustic alkali is substituted for the acid the
liquid rapidly assumes a deep yellow color, while a
thin deposit of metal appears upon the cathode.
Ruthenium behaves similarly when applied in the
form of powder. Osmium-iridium, a compound de-
composed with difficulty under ordinary circum-
stances, immediately passes into solution when brought
in contact with the positive electrode of a battery
placed in a solution of sodium hydroxide, and imparts
a yellow color to the alkaline liquid. A black
deposit of metal slowly makes its appearance upon
the negative pole.
The experiments, thus far described, are qualitative
in their results. The first notice of the quantitative
estimation of metals electrolytically was that of Gibbs
(1864), when he published the results he had obtained
with copper and nickel. Luckow, in alluding to this
work a year later (1865), says : " I take the liberty to
38 ELECTRO-CHEMICAL ANALYSIS.
observe that so far as the determination of copper is
concerned, I estimated that metal in this manner
more than twenty years ago, and as early as 1860
employed the electric current for the deposition of
copper quantitatively in various analyses." It was
Luckow who proposed the name Elektro-Metall Ana-
lyse for this new method of quantitative analysis.
According to this writer the current may be applied
as follows :
1. To dissolve metals and alloys in acids by which
they would not be affected unaided by the electric
current.
2. To detect metals like manganese and lead
(silver, nickel, cobalt) ; separating them in the form
of peroxides ; also manganese as permanganic acid.
' 3. To separate various metals, e.g., copper and
manganese from zinc, iron, cobalt and nickel.
4. To deposit and estimate metals quantitatively,
in acid, alkaline and neutral solutions.
5. For various reductions, e.g., silver chloride, basic
bismuth chloride and lead sulphate, in order that the
metals in them may be determined. To reduce chro-
mic acid to oxide, e. g., potassium bichromate acidu-
lated with dilute sulphuric acid.
These applications embrace nearly all that has since
been accomplished by the aid of the current. In the
same article to which Luckow calls attention to the
facts recorded above, he describes minutely the method
HISTORICAL. 39
pursued by him in the precipitation of metals. Refer-
ence to these early experiments will show with what
care and accuracy every detail was worked out.
Luckow also announced " that all the lead contained
in solution was deposited as peroxide upon the posi-
tive electrode, and might be determined from the
increased weight of the latter." This observation
was fully confirmed by Hampe and, later, by W.
C. May.
Wrighfson (1876) called attention to the fact that
if solutions of copper were electrolysed in the presence
of other metals, the latter greatly influenced the sepa-
ration of the former. For example, with copper and
antimony, the deposition of the copper was always
incomplete when the antimony equaled one-fourth to
two-thirds the quantity of the former. Notwithstand-
ing, a complete separation of the two metals can be
effected when the quantity of the antimony is small.
A somewhat similar behavior was noticed with other
metals. The deposition of cadmium, zinc, cobalt and
nickel was apparently not satisfactory.
Lecoq de Boisbaudran (1877) electrolysed the potas-
sium hydroxide solution of the metal gallium, using
six Bunsen elements with 20-30 c.c. of the concen-
trated liquid. The deposited metal was readily de-
tached when the negative electrode was immersed in
cold water, and bent slightly.
The unpromising behavior of zinc solutions, ob-
served by Wrightson, was fortunately overcome by
40 ELECTRO-CHEMICAL ANALYSIS.
Parodi and Mascazzini (1877), who employed a solu-
tion of the sulphate, to which was added an excess of
ammonium acetate. Lead was also deposited in a
compact form from an alkaline tartrate solution of this
metal in the presence of an alkaline acetate.
After Luckow's experiments upon manganese, little
attention appears to have been given this metal until
Riche (1878) published his results. While confirming
the observations of Luckow, he discovered that manga-
nese was not only completely precipitated from the
solution of its sulphate, but also from that of the
nitrate, thus rendering possible an electrolytic sepa-
ration of manganese from copper, nickel, cobalt, zinc,
magnesium, the alkaline earth and the alkali metals.
Riche recommended that the deposited dioxide be
carefully dried, converted by ignition into the proto-
sesquioxide and weighed as such. According to this
chemist, the one-millionth of a gram of manganese,
when exposed to the action of the current, gave a
distinct rose-red color, perceptible even when diluted
tenfold.
In zinc depositions Riche gave preference to a
solution of zinc- ammonium acetate containing free
acetic acid.
Luckow was the first to mention that the current
caused mercury to separate in a metallic form, from
acid solutions, upon the negative electrode. F. W.
Clarke (1878) used a mercuric chloride solution,
feebly acidulated with sulphuric acid, for this purpose.
HISTORICAL. 41
The deposition was made in a platinum dish, using
six Bunsen cells. Mercurous chloride was at first pre-
cipitated, but it was gradually reduced to the metallic
form. J. B. Hannay (1873) had previously recom-
mended precipitating this metal from solutions of
mercuric sulphate, but gave no results.
Clarke, also, gave some attention to cadmium ; his
results, however, were not satisfactory. A few
months later the writer (1878) succeeded in depositing
cadmium completely and in a very compact form
from solutions of its acetate. Upon this behavior
Yver (1880) based his separation of cadmium from
zinc. Furthermore, the writer found (1880) that the
deposition of cadmium could be made from solutions
of its sulphate, contrary to an earlier observation of
Wrightson. At the same time copper was completely
separated from cadmium by electrolysing their solu-
tion in the presence of free nitric acid.
A very successful determination of both zinc and
cadmium was published by Beilstein and Jawein in
1879. They employed for this purpose solutions of
the double cyanides.
Heinrich Fresenius and Bergmann (1880) found
that the electrolysis of nickel and cobalt solutions
succeeded best in the presence of an excess of free
ammonia and ammonium sulphate.
Their experience with silver demonstrated that
the best results could be obtained with solutions
42 ELECTRO-CHEMICAL ANALYSIS.
containing free nitric acid, and by the employment
of weak currents.
The writer showed (1880) that if uranium acetate
solutions were electrolysed the uranium was com-
pletely precipitated as a hydrated protosesquioxide ;
and further, that molybdenum could be deposited as
hydrated sesquioxide from warm solutions of am-
monium molybdate in the presence of free ammonia.
Very promising indications were obtained with salts
of tungsten, vanadium and cerium.
In a more recent (1880) communication from
Luckow, to whom we are indebted for much that is
valuable in electrolysis, is given a full description of
his observations in this field of analysis, from which
the following condensed account is taken. While it
relates more particularly to the qualitative behavior
of various compounds, its importance demands careful
study.
When the current is conducted through an acid
solution of potassium chromate the chromic acid is
reduced to oxide, whereas, if the solution of the oxide
in caustic potash be subjected to a like treatment
potassium chromate is produced. Arsenic and
arsenious acid behave similarly. The same is true
also of the soluble ferro- and ferri-cyanides and nitric
acid. In the presence of sulphuric acid, ferric and
uranic oxides are reduced to lower states of oxidation.
Sulphates result in the electrolysis of the alkaline
HISTORICAL. 43
sulphites, hyposulphites and sulphides, and carbonates
from the alkaline organic salts. In short, the current
has a reducing action in acid solutions, and the
opposite effect in those that are alkaline. In the
electrolysis of solutions of hydrogen chloride, bromide,
iodide, cyanide, ferro- and ferri-cyanide and sulphide,
the hydrogen separates at the electro-negative pole,
and the electro-negative constituents at the positive
electrode. Cyanogen sustains a more thorough de-
composition, the final products being carbon dioxide
and ammonia. In the electrolysis of ferro- and ferri-
cyanogen, Prussian blue separates at the positive
electrode. In dilute chloride solutions hypochlorous
acid is the only product, whereas chlorine is also
present in concentrated solutions. In alkaline chloride
solutions chlorates are produced as soon as the liquid
becomes alkaline. In the iodides and bromides iodine
and bromine separate at the positive electrode, while
bromates and iodates are formed when metals of the
first two groups are present. Potassium cyanide is
converted into potassium and ammonium carbonates.
Concentrated nitric acid is reduced to nitrous acid ;
however, when its specific gravity equals 1.2, this does
not occur, at least not when a feeble current is used.
Dilute nitric acid alone, or even in the presence of
sulphuric acid, is not reduced to ammonia. If, how-
ever, dilute nitric acid be present in a copper sulphate
solution undergoing electrolysis, copper will separate
upon the negative electrode and ammonium sulphate
44 ELECTRO-CHEMICAL ANALYSIS.
will be formed. Solutions of nitrates, containing .sul-
phuric acid, behave analogously. Phosphoric acid
sustains no change. Silicic acid separates as a white
mass, and boric acid, in crystals uniting to arborescent
groups, at the positive electrode.
In the Ber. d. d. chem. Gesellschaft for 1881 (Vol.
14, 1622), Classen and v. Reiss presented the first of
a series of papers upon electrolytic subjects, which
continued through subsequent issues of this publica-
tion. Their early work was devoted to the precipita-
tion of metals from solutions of their double oxalates.
They also elaborated excellent methods for antimony
and tin. Many very serviceable forms of apparatus,
intended for electrolytic work, were devised and de-
scribed by them, and it must be conceded that through
the activity of the Aachen School electrolysis acquired
more importance in the eyes of the chemical public
than it ever before possessed. The details of the
more important methods proposed by Classen and
his co-laborers will receive due mention under the
respective metals.
At the same time with and quite independently of
Classen, Reinhardt and Ihle proposed the double oxa-
lates for the estimation of zinc electrolytically ; and
in this connection it may not be improper to mention
that as early as 1879, two years prior to the publica-
tion of Classen's first communication, Parodi and Mas-
cazzini (Gazetta chimica italiana, Vol. 8) announced
that antimony and iron could be deposited completely
HISTORICAL. 45
and in compact form by electrolysing the solutions
of the sulpho-salts of the former and the chloride
of the lattter in the presence of acid ammonium
oxalate.
In 1883, Gibbs recommended placing solutions of
mercury, tin and cobalt in a beaker glass, on the
bottom of which was placed a layer of mercury,
which served as the negative electrode. Knowing
the combined weight of the beaker and mercury, the
increased weight, after precipitation and removal of
the liquid, will give the quantity of metal under
examination. This method is not applicable in the
case of antimony and arsenic.
Three years later (1886) Luckow recommended a
very similar procedure for the estimation of zinc.
Moore (1886) also published new data upon the
estimation of iron, cobalt, nickel, manganese, etc., full
notice of which will appear under these metals.
The most recent publications relating to electrolysis
are those of Brand, who succeeded in effecting sepa-
rations by utilizing solutions of the pyrophosphates of
different metals, and those of Smith and Frankel, who
have made an extended study of the double cyanides,
and found thereby a number of very convenient
methods of separation heretofore unrecorded. The
results are given in detail in the following pages.
The preceding paragraphs give a brief outline of
what has been accomplished in the field of analysis by
46 ELECTRO-CHEMICAL ANALYSIS.
electrolysis ; for further information consult the fol-
lowing
LITERATURE. Jahrb., 1850, 602; C. r., 45, 449; Jr. f. pkt. Ch., 73,
79; Chem. Soc. Quart. Journ., 13, 12; Jahrb., 1862, 610; Ann., 124,
131; C. r., 55, 18; Ann., 146, 375; Z. f. a. Ch., 3, 334; Ding. p. Jr.
(1865), 231 ; Z. f. a. Ch., 8, 23; n, I, 9; 13, 183; Am. Jr. Sc. and
Ar. (3d ser.), 6, 255; Z. f. a. Ch., 15, 297; Ber., 10, 1098; Annales
de Ch. et de Phy., 1878; Am. Jr. Sc. and Ar., 16, 200; Am. Phil. Soc.
Pr., 1878; Z. f. a. Ch., 15, 303; Am. Ch. Jr., 2, 41; Berg-Hutt. Z.,
37, 41; Z. f. a. Ch., 19, i, 314, 324; Am. Ch. Jr., i, 341; B. s. Ch.
Paris, 34, 18; Ber., 12, 1446; 14, 1622, 2771; 17, 1611, 2467, 2931;
18, 168, 1104, 1787; 19, 323; 21, 359, 2892, 2900; Jr. f. pkt. Ch.,
24, 193; Z. f. a. Ch., 18, 588; 22, 558; 25, 113; Chem. News, 28,
581 ; 53, 209. And the following will be found worthy of careful
study: Ann., 36, 32; 94, i; Z. f. a. Ch., 19, I ; Berg-Hutt. Z., 42,
377; Z. f. a. Ch., 22, 485.
SPECIAL PART.
i. DETERMINATION OF THE DIFFER-
ENT METALS.
COPPER.
LITERATURE. Gibbs, Z. f. a. Ch., 3, 334; Boisbaudran, B. s.
Ch., Paris, 1867, p. 468; Merrick, Am. Ch., 2, 136; Wrightson,
Z. f. a Ch., 15, 299; Her pin, Z. f. a. Ch., 15, 335 ; Moniteur Scien-
tifique [3 ser.], 5,41 ; Ohl, Z. f. a. Ch., 18, 523; Classen, Ber., 14,
1622, 1627 ; Classen and v. Reiss, Z. f. a. Ch., 24, 246; 25, 113;
Riche, Z. f. a. Ch., 21, 116; M akin tosh , Am. Ch. Jr., 3, 354;
Rudorff, Ber., 21, 3050; Luckow, Z. f. a. Ch., 8, 23.
Dissolve 19.6 grams of pure copper sulphate in
water, and dilute to I litre. Place 50 c.c. of this solu-
tion (= 0.25 gram of metallic copper) in a clean plati-
num dish, previously weighed. Connect the dish with
a battery, whose current is sufficiently strong to effect
the complete precipitation of the copper in the course
of ten or twelve hours. The apparatus may be
arranged as in the accompanying sketch (Fig. 16),
page 48.
A is an ordinary filter stand, upon the base of which
is fixed a binding-post, x, to which is attached a heavy
copper ring for the support of the platinum vessel. It
47
4 8
ELECTRO-CHEMICAL ANALYSIS.
DETERMINATION OF METALS COPPER. 49
is in connection with the negative electrode of the bat-
tery. The arm, y t has been shortened, and at its
extremity there is a second binding-screw,/; the lat-
ter holds the positive pole (a heavy platinum wire
bent into a flat spiral at its lower end), and the copper
wire from the anode of the battery (the copper plate
in a " Crowfoot " cell). It will be noticed that the
current passes through the vessel, B (a Bunsen volta-
meter), in which acidulated water is undergoing de-
composition, the resulting gases being collected in d.
Their volume serves to measure the strength of the
acting current. Copper is very readily precipitated
from solutions containing free nitric or sulphuric acid.
Hydrochloric acid should never be present.
Having arranged the apparatus as just described,
add 9-10 drops of concentrated nitric acid to the solu-
tion of the electrolyte ; cover the vessel with a perfo-
rated watch crystal during the decomposition. To
ascertain when the metal has been completely precipi-
tated, add water to the dish ; this will expose a clean,
platinum surface, and if in the course of half an hour
no copper appears upon it, the deposition may be con-
sidered as finished. Or, a drop of the liquid may be
removed, and brought in contact with a drop of
ammonium hydroxide or hydrogen sulphide, when, if
a blue coloration or black precipitate is not produced,
the deposition can be considered ended.
As the precipitation has been made in an acid solu-
tion, the current should not be interrupted until the
50 ELECTRO-CHEMICAL ANALYSIS.
acid liquid has been removed, for in many cases the
brief period during which the acid can act upon the
metal will be sufficient to cause some of the latter to
pass into solution. To obviate this, siphon off the
FIG 17.
acid liquid. The sketch (Fig. 17) shows how this can
be done. A rubber tube of small diameter may be
substituted for the glass siphon. As the acidulated
water is conveyed away by the latter, pour distilled
DETERMINATION OF METALS COPPER. 51
water into the dish. Empty the platinum dish twice
in this way ; the current can then be interrupted with-
out loss of copper. Finally, disconnect the dish, wash
the deposit with hot water and then with alcohol. Dry
the precipitated copper at a temperature not exceed-
ing 1 00 C; an air-batH, an asbestos plate, or warm
iron plate will answer for, this purpose. Do not weigh
the dish until it is perfectly cold, and has attained the
temperature of the balance-room.
In the ordinary precipitations of copper from dilute
nitric or sulphuric acid solution a current, giving
0.3-0.5 c.c. oxy-hydrogen gas (electrolytic gas) per
minute, will be amply sufficient. The deposition can
also be made in a platinum crucible, or the copper can
be precipitated upon the exterior surface of the same.
This is sometimes convenient. Place the liquid under-
going electrolysis in a beaker glass (capacity 100-250
c.c.), and suspend the crucible in it (Fig. 18); support-
ing it there by a. tight-fitting cork, through which
passes a stout copper wire, w, in connection with the
negative electrode of a battery. The positive electrode
is a platinum plate projecting into the liquid. The end
of the decomposition may be learned by pressing down
upon w, or by adding water to the solution in the
beaker. No further appearance of copper on the newly
exposed platinum indicates the end of the precipita-
tion. Raise the crucible from the liquid, wash the
copper with water, then detach the vessel carefully
from the cork, and dry as already directed.
52 ELECTRO-CHEMICAL ANALYSIS.
Instead of using either of the suggestions first
offered, substitute the apparatus of Riche (Fig. 19) if
convenient. This consists in suspending a crucible
within a crucible. The sides of the inner vessel are
perforated so that the liquid will maintain uniform
FIG. i 8.
FIG. 19.
concentration. It is practically the same as the device
just described above.
Copper can also be precipitated from the solution of
ammonium-copper oxalate. To this end the copper
solution (sulphate or chloride) is treated with an ex-
cess of a saturated solution of ammonium oxalate,
care being taken that the entire volume does not
DETERMINATION OF METALS COPPER.
53
exceed 170200 c.c. A current liberating 0.10.2 c.c.
oxy-hydrogen gas per minute will answer for the
deposition, which will require about twelve hours. If
the double oxalate solution be heated to 70, and
held at that temperature, the decomposition will be
finished in five hours at the most. Use ferrocyanide
FIG. 20.
of potassium to learn whether all the metal has been
precipitated. Wash and dry as already instructed.
Riidorff obtained excellent results with the follow-
ing conditions: 0.1-0.3 gram of metallic copper in 100
c.c. water, to which were added 2-3 grams of potas-
sium or ammonium nitrate, and 10 c.c. of ammonium
54 ELECTRO-CHEMICAL ANALYSIS.
hydroxide. A current giving 0.5 c.c. oxy-hydrogen
gas per minute will throw out the copper from this
solution.
Moore advises dissolving the recently precipitated
copper sulphide, obtained in the ordinary course of
analysis, in potassium cyanide; and, after the addition
of an excess of ammonium carbonate, electrolyses the
warm (70) solution.
In the analysis of commercial copper Luckovv em-
ployed the apparatus pictured in Fig. 20. The beaker
(a) contains the electrolyte, and. the metal is precipi-
tated upon the cylinder of platinum (ti). It is a very
satisfactory device for almost any kind of electrolytic
work.
Foote (Am. Ch. Jr., 6, 333) has also described a
very excellent improvement in the apparatus intended
for the electrolytic precipitation of copper.
CADMIUM.
LITERATURE. Ber., 11,2048; Smith, Am. Phil. Soc. Pr., 1878;
Clarke, Z. f. a. Ch., 18, 104; Beilstein and Jawein, Ber., 12,
759; Smith, Am. Ch. Jr., 2, 42; Luckow, Z. f. a. Ch., 19, 16;
Wright son, Z. f. a. Ch., 15,303; Class en and v. Reiss, Ber.,
14, 1628.
Cadmium can be determined electrolytically as
readily as copper. Prepare a solution of the chloride
or sulphate of definite strength. Remove 50 c.c. to a
suitable, weighed platinum vessel. Add one gram of
DETERMINATION OF METALS CADMIUM. 55
pure potassium cyanide ; dilute with water to 150-200
c.c., and then connect with five or six " Crowfoot "
cells in the same manner as directed under copper.
Introduce the voltameter as there indicated. It is well
to commence the decomposition in the evening, and
by morning the metal will be fully deposited. A
current yielding 0.3 c.c. electrolytic gas per minute
will precipitate 0.2 gram metal in this time. To ascer-
tain whether the precipitation is complete, raise the
level of the liquid in the platinum dish. In washing,
it will not be necessary to siphon off the supernatant
liquid ; it can be poured off, after interruption of the
current, without loss of metal from re-solution. Wash
the deposit with cold and hot water. Dry upon a
warm iron plate (temperature not exceeding 100 C.).
Cadmium may also be precipitated from a solution
of its sulphate containing a small amount of free sul-
phuric acid (2 c.c. H 2 SO 4 , sp. gr. 1.09 for o.i gram
cadmium). When operating with a solution of this
character, use a current generating 5 c.c. electrolytic
gas per minute. Two Bunsen cells will answer,
although it may be necessary to reduce the current to
some degree ; this can be accomplished by introducing
one of the resistances described on pages 26 and 27.
Arrange the apparatus as under copper. The pre-
cipitation takes place at the ordinary temperature.
Cadmium can also be deposited quite readily, and
in a crystalline form, from its acetate solution. In
this case the liquid, containing an excess of free acetic
50 ELECTRO-CHEMICAL ANALYSIS.
acid, is heated to 70-80 during the decomposition.
The apparatus can be arranged as in Fig. 21. The
platinum dish is placed in a water bath, and the current
made to pass through R (resistance frame) and V
(voltameter). An asbestos plate may be substituted
for the water bath. The current should give I J^-2
c.c. of oxy-hydrogen gas per minute. This will insure
the precipitation of 0.12-0.15 gram of cadmium in
five to six hours. When the precipitation is completed,
detach the dish, wash the deposited metal first with
DETERMINATION OF METALS MERCURY. 57
warm water, then with absolute alcohol, and finally
with ether. Dry upon a moderately warm plate.
If desired, the metal can also be precipitated from
the solution of the double oxalate of ammonium and
cadmium (see Copper).
In the usual course of gravimetric analysis cad-
mium is obtained as sulphide. To prepare it for elec-
trolysis dissolve the same in nitric acid, and after
expelling the excess of the latter, add a small amount
of potassium hydroxide (sufficient to precipitate the
cadmium), and follow this with an excess of potassium
cyanide (i to 2 grams). Proceed further as already
directed.
MERCURY.
LITERATURE. Ber., 6, 270; Clarke, Am. Jr. Sc. and Ar., 16, 200;
Classen and Ludwig, Ber., 19, 323; Hoskinson, Am. Ch. Jr., 8,
209; Smith and Knerr, ibid.; Smith and Frankel, Am. Ch. Jr.,
n, 264.
In preparing solutions for experimental purposes,
use either mercuric nitrate or chloride. A current
equivalent to 0.5-1.0 c.c. electrolytic gas per minute
will precipitate 0.3 gram of mercury from such solu-
tions (add a slight amount of free nitric acid) in twelve
hours. The deposit will be drop-like in appearance.
Even in the presence of considerable free nitric acid
it has been found that a current of 4 c.c. electrolytic
gas per minute will suffice to precipitate as much as
o.io gram of metal in 30 to 45 minutes. In such cases
E
58 ELECTRO-CHEMICAL ANALYSIS.
the acid liquid must be removed before the interrup-
tion of the current occurs.
A mercuric chloride solution, feebly acidulated
with sulphuric acid, gradually yields its metal to
a current, giving 56 c. c. oxy-hydrogen gas per
minute. Always wash the deposited metal with cold
water.
From experiments made in this laboratory the writer
prefers and would especially recommend solutions of
the double cyanide of mercury and potassium for the
electrolytic deposition of mercury. A current of 0.2
c.c electrolytic gas per minute will precipitate from
0.10-0.20 gram of metal in twelve hours. This pro-
cedure requires no further attention after it is once
set in operation. The deposit is always compact,
and gray in color. Use water only in washing it,
for alcohol seems to detach some of the metallic
film. The quantity of alkaline cyanide present may
vary from 0.26-2.6 grams (KCN) for every gram of
mercury.
In general analysis mercury is frequently obtained
as sulphide. Its determination in this form requires
time and exceeding care. As a substitute for this the
writer would advise the solution of the sulphide in
acid, and after neutralizing the excess of the latter
with caustic alkali, add an excess of pure potassium
cyanide, and electrolyse as above indicated. It is best
to use a platinum dish as the negative electrode, and
a platinum spiral (p. 49) for the anode. Dry the
DETERMINATION OF METALS BISMUTH. 59
deposit on a moderately warm plate, or over sulphuric
acid. " Crowfoot " cells are well adapted for decom-
positions of this kind.
BISMUTH.
LITERATURE. Luckow, Z.f. a. Ch.,ig,i6; Classen and v. Reiss,
Ber., 14, 1622; Thomas and Smith, Am. Ch. Jr., 5, 114; Moore,
Ch. News, 53, 209; Smith and Knerr, Am. Ch. Jr., 8, 206;
Schucht, Z. f. a. Ch., 22, 492; Eliasberg, Ber., 19, 326; Brand,
Z. f. a. Ch., 28, 596.
Prepare a solution of definite value as directed
under the preceding metals. To a portion of it add
an excess of a cold ammonium oxalate solution, and
act upon the mixture with a current of o.io c.c. oxy-
hydrogen gas per minute. Those who have employed
this method find that the deposit is not very adherent,
and great care must be taken to expose as large a pla-
tinum surface as possible. If metallic particles do sepa-
rate, collect them upon a small filter and weigh alone.
Eliasberg advises bringing the solution of the metal
into a weighed platinum dish, and then adding 10 c.c.
of a potassium oxalate solution (i 13). Heat is applied,
and solid ammonium oxalate is introduced until com-
plete solution ensues. Dilute to 170-180 c.c., and
warm to 70-80 C, while the current acts. The latter
should be so feeble that the liberation of gas in the
voltameter is scarcely perceptible. In sixteen hours
the greater portion of the metal will have separated,
60 ELECTRO-CHEMICAL ANALYSIS.
and then oxalic acid is added to distinct acid reaction.
As soon as the metal is fully precipitated, interrupt the
current and wash the deposit with water. Take special
pains in drying, so that the metal does not oxidize.
Experiments made in this laboratory demonstrate
that by electrolysing the sulphate, an alkaline citrate
solution, or one containing free citric acid, the bis-
muth will be rapidly and completely precipitated. In
some cases the deposits were made in small platinum
crucibles, while others were thrown upon the exterior
surface of the crucibles arranged as under Copper. If
peroxide should separate upon the anode in the electro-
lysis of citrate or sulphate solutions of bismuth, it will
disappear before the decomposition is fully ended.
Heat is not required. The best results were obtained
with solutions of the sulphate, containing free sul-
phuric acid. For example: 0.1542 gram of bismuth,
as sulphate, 3 c.c. sulphuric acid (1.09 sp. gr.), and 150
c. c. of water, required a current giving 3 c.c. oxy-
hydrogen gas per minute, for a period of three hours,
to effect the complete separation of the metal. The
latter was quite compact and offered no difficulty in
washing with water and alcohol. An air-bath was
used for drying purposes.
Moore recommends the following method : add
sufficient tartaric acid to the bismuth solution to
prevent the precipitation of a basic salt, then, after
rendering the solution slightly alkaline with ammon-
ium hydroxide, add a considerable excess of glacial
DETERMINATION OF METALS BISMUTH. 6 1
phosphoric acid, so that the solution has a strong acid
reaction. The current should give 0.33-0.50 c.c.
electrolytic gas per minute, at first, but this must be
increased at last to 7.5 c.c. per minute. The deposit
at the beginning of the deposition is loose, but
gradually becomes hard and compact.
Brand's recommendation consists in adding to a
somewhat dilute acid solution of bismuth from four
to five times as much sodium pyrophosphate as will
be necessary to form the double salt. Ammonium
carbonate is then carefully introduced until the re-
action of the liquid is distinctly alkaline, when 35
grams of ammonium oxalate are added. The total
dilution should be about 200 c.c. The electrolysis is
commenced with a current giving o.i-i.o c.c. electro-
lytic gas per minute, although toward the close it will
be necessary to increase the same to 2-3 c.c. per min-
ute. By following these instructions 0.2500 gram of
bismuth can be precipitated in twelve hours. When
considerable quantity of metal is present in solution a
feeble current should be used at first. If the peroxide
appears upon the anode in the course of the decompo-
sition, redissolve it in a few drops of a concentrated
solution of oxalic acid. However, this should not be
done until there is no further separation of metal upon
the cathode. The final reduction is ascertained by
testing with hydrogen sulphide. The metal is said
to sustain a superficial oxidation, hence it is converted
into oxide and weighed as such.
62 ELECTRO-CHEMICAL ANALYSIS.
LEAD.
LITERATURE. Luckow, Z. f. a. Ch., 19, 215; Riche, Ann. de
Chim. et de Phys. [5 ser.], 13, 508; Z. f. a. Ch., 21, 117; Classen,
ibid., 257; Hampe, Z. f. a. Ch., 13, 183; May, Am. Jr. Sc. and Ar.
[3 ser.], 6, 255, also Z. f. a. Ch., 14, 347 ; Parodi and Mascazzini,
Ber., 10, 1098 ; Z. f. a. Ch., 16, 469; 18,588; Riche, Z. f. a. Ch., 17,
219; Schucht, Z. f. a. Ch., 21, 488; Tenney, Am. Ch. Jr., 5, 413;
Smith, Am. Phil. Soc. Pr., 24, 428.
The metal may be obtained by electrolysing so-
lutions of the double oxalate(see Copper and Cadmium),
the acetate, the oxide in sodium hydroxide, or the
phosphate dissolved in the latter reagent. A current
of o. I 0.2 c.c. electrolytic gas per minute, is sufficient
for this purpose. While the metal separates well from
either one of these solutions, difficulty is experienced
in drying the deposit, for the moist metal almost in-
variably suffers a partial oxidation, thus rendering the
results high. The deposit can be dried, without oxid-
ation, in an atmosphere of hydrogen, but for the in-
experienced operator this procedure offers little satis-
faction. It is, therefore, better to utilize the tendency
of lead to separate, from acid solutions, as the dioxide.
For trial purposes make up a definite volume of lead
nitrate. Electrolyse several portions (= o.i gram lead
each) in a platinum dish connected ivith the anode of a
battery, giving 0.1-0.2 c.c. electrolytic gas per minute.
In order that the lead may be precipitated wholly
as dioxide upon the positive electrode and none in
metallic form upon the cathode, it is necessary that
DETERMINATION OF METALS SILVER. 63
the solution being analyzed should contain from ten
to twenty per cent, of free nitric acid. This quantity
of acid is required when lead alone is present in so-
lution. In the presence of other metals the complete
deposition of the lead as dioxide occurs with even
less acid (eight per cent.). At the end of the precipi-
tation siphon off the acid liquid, and wash in the dish,
then dry the deposit at 1 10 C, and weigh. Reference
to the literature shows that May preferred, after dry-
ing the deposit, to carefully ignite it and finally weigh
as lead oxide (PbO). This deportment of lead affords
an excellent method by which to separate it from
other metals, e.g., mercury, copper, cadmium, silver,
and all those soluble in nitric acid, or those which, in
a nitric acid solution, are deposited upon the electro-
negative pole of a battery.
The analysis of an alloy of lead, bismuth and
copper can be most satisfactorily made by employing
electrolytic methods (see Separations).
SILVER.
LITERATURE. Luckow, Ding. p. Jr., 178, 43, Z. f. a. Ch., 19,
15; Fresenius and Bergmann, Z. f. a. Ch., 19, 324; K rut wig,
Ber., 15, 1267; Schucht, Z. f. a. Ch., 22, 417; Kinnicutt, Am.
Ch. Jr., 4, 22.
The experiments of Luckow showed that this metal
could be deposited from solutions containing as high
as eight to ten per cent, ef free nitric acid. The
64 ELECTRO-CHEMICAL ANALYSIS.
deposit was spongy, and there was a simultaneous
deposition of silver peroxide at the anode. This was,
however, prevented by adding to the solution some
glycerol, lactic or tartaric acid. A voluminous mass
was also obtained from silver solutions, containing an
excess of ammonium hydroxide or carbonate, and per-
oxide appeared at the same time upon the anode.
Fresenius and Bergmann, who have given the elec-
trolysis of acid solutions of silver particular study,
observed that the tendency of the metal to sponginess
is most marked when the electrolyte is concentrated,
and acted upon by a strong current. In a dilute
liquid, the current being feeble, the deposit was com-
pact and metallic in appearance (free acid should be
present). From neutral solutions, although very
dilute, the metal is separated in a flocculent condition
by the feeblest currents. Therefore, to obtain results
that would answer for quantitative analysis, the fol-
lowing conditions were adopted : The total dilution
of the solution was 200 c.c. ; in this there was 0.03
gram .04 gram silver, and 36 grams of free nitric
acid. The poles were separated about I cm. from
each other, while the current gave 100-150 c.c. elec-
trolytic gas per hour.
In the experiments of Fresenius and Bergmann,
apparatus similar to that in Fig. 22 was employed.
It has some decided advantages. Both spiral (a) and
cone (b) are constructed of platinum. The metallic
deposition, it will be understood, occurs upon the
DETERMINATION OF METALS SILVER. 65
cone, the sides of which are perforated, so that a uni-
form concentration of liquid is preserved throughout
the decomposition. When liquid electrolytes contain
much iron, it is essential that the oxygen liberated
within the cone should be equally distributed over its
outer surface. This is made possible through open-
ings. The shape of the cone also prevents loss from
FIG 22.
the bursting of the bubbles, arising from the platinum
spiral in connection with the anode.
Krutwig advises adding a large excess of ammo-
nium sulphate to the silver solution, previously made
alkaline with ammonium hydroxide, and employs a
current giving 150 c.c. electrolytic gas per hour, but
after half an hour the latter is increased to 300 c.c. of
66 ELECTRO-CHEMICAL ANALYSIS.
gas per hour. In this way, o.i gram of silver is
precipitated in two hours.
The writer's experience has chiefly been with solu-
tions of silver containing an excess of alkaline cyanide
(l gram KCN for 0.2-0.3 gram silver). With these
peroxide separation does not occur, and a very weak
current will precipitate 0.15-0.20 gram metal in ten
ho.urs from a cold solution. The precipitation can
be made either in a platinum dish or crucible as
cathode.
Chlorine, bromine and iodine can be indirectly
estimated electrolyttcally by first precipitating them
as silver salts, then dissolving the latter in potassium
cyanide, and exposing "the resulting solution to the
action of a current from three to four " Crowfoot "
cells.
Luckow reduced silver chloride by placing it in a
platinum dish, serving as the negative electrode, cov-
ered it with dilute sulphuric or acetic acid, and allowed
the positive electrode to project into the solution.
Four Meidinger cells were strong enough to reduce
o.i gram silver chloride in ten minutes. The deposit,
while spongy, was adherent. It was washed with
water and then thoroughly dried to insure the absence
of any acid. (See the reference to Kinnicutt's experi-
ments ; also Prescott and Dunn, Jr. An. Ch., 3, 373.)
DETERMINATION OF METALS ZINC. 6/
ZINC.
LITERATURE. Wrightson, Z. f. a. Ch., 15, 303; Parodi and
Mascazzini, Ber., 10, 1098, Z. f. a. Ch., 18,587; Riche, Z. f. a. Ch.,
17, 216; Beilstein and Jawein, Ber., 12, 446, Z. f. a. Ch., 18, 588;
Riche, Z. f. a. Ch., 21, 119; Reinhardt and Ihle, Jr. f. pkt. Ch.,
[N. F.], 24, 193; Classen and v. Reiss, Ber., 14, 1622; Gibbs,
Z. f. a. Ch., 22, 558; Luckovv, Z. f. a. Ch., 25, 113.
Much has been written upon the electrolytic esti-
mation of zinc. The personal experience of the writer
inclines him to give preference to the method sug-
gested by Parodi and Mascazzini. They recommended
that the metal be present in solution as sulphate ; its
quantity may vary from o. 1-0.25 gram. To it add 4 c.c.
of a solution of ammonium acetate, 20 c.c. citric acid,
and dilute to 200 c.c. with water. The electrodes are
then introduced into the liquid, their distance apart
being not more than a few millimetres. The precipi-
tation can be made in a beaker glass, using a weighed
platinum cone (Fig. 22) as the cathode. The current
for this purpose should give 250-300 c.c. electrolytic
gas per hour. When the precipitation of metal has
ended, which may be ascertained by removing a small
quantity of the liquid with a capillary tube and bring-
ing it in contact with a drop of a solution of potassium
ferrocyanide, remove the bulk of the liquid with a
siphon. Wash the deposit with water and alcohol.
There is no danger of oxidation during the drying
process. It will be discovered on dissolving the pre-
cipitated zinc that a considerable quantity of the metal
68 ELECTRO- CHEMICAL ANALYSIS.
remains unattacked, but this can be removed by gently
heating the residue with air contact, then fusing it
with potassium bisulphate.
Beilstein and Jawein add sodium hydroxide to the
solutions of zinc nitrate or sulphate, until a precipitate
is produced, and dissolve it in potassium cyanide.
The decomposition is carried out in a rather large
beaker glass, the cathode being either the platinum
cone already described (p. 65), or a rather large plati-
num crucible suspended from a cork (p. 52), perforated
by a copper wire, touching the inner surface of the
crucible. Four Bunsen cells (usual size) are sufficient
for the precipitation. Wash the deposit as instructed
above.
Reinhardt and Ihle have objected to nearly all the
methods which have been proposed for the electrolytic
estimation of zinc. They say of the Beilstein and
Jawein method .... that the results are fairly good,
.... but a strong current is necessary, otherwise the
precipitation of the zinc is slow and incomplete, ....
the positive pole diminishes in weight very appreciably,
.... finally, working with potassium cyanide is very
unpleasant. The writer's experience has proved that
a current considerably less than that which Beilstein
and Jawein first recommended will throw out all the zinc
in the course of a night, and further that the anode
is not appreciably affected. The method suggested
by Reinhardt and Ihle is, however, very excellent
and deserves trial by all interested in the electrolytic
DETERMINATION OF METALS - ZINC. 69
estimation of zinc. Its essential features, taken from
their publication, are these: Mix the solution of
zinc sulphate or chloride, neutral as possible, with an
excess of neutral potassium oxalate, until the pre-
cipitate, which appears at first, redissolves. A current
giving 90 c.c. electrolytic gas per hour will answer for
complete precipitation.
The immediate decomposition of the zinc oxalate
is into zinc and carbon dioxide (two molecules), and
the potassium oxalate into carbon dioxide (two mole-
cules) and potassium ; the latter then reacts with the
water, so that while an abundant liberation of hydrogen
occurs at the cathode, the alkali simultaneously set
free is converted into acid potassium carbonate by the
carbon dioxide at the anode :
K 2 C 2 4 = (Zn + ^KOU + H 2 ) + 4 CO 2 .
Cathode. Anode.
Therefore, just as long as zinc oxalate is being
decomposed, considerable evolution of gas is notice-
able at the positive electrode, and when this dimin-
ishes, and occasional bubbles escape, the decomposi-
tion is complete, and the deposition of metal may be
considered finished.
Free oxalic acid, or any other acid, is not injurious
if there is a sufficient quantity of potassium oxalate
present. Nitric acid, however, free or combined, should
70 ELECTRO-CHEMICAL ANALYSIS.
be avoided ; it gives rise to ammonium salts, which
prevent the zinc from separating in a dense form. The
acid potassium carbonate produced during the decom-
position offers great resistance to the current ; it is,
therefore, advisable to add potassium sulphate to the
solution to increase its conductivity. Reinhardt and
Ihle recommend the following solutions for use in
decompositions like that just described: 166 grams of
potassium oxalate in I litre of water; 250 grams of
potassium sulphate in I litre of water, and a solution
of oxalic acid saturated at 15 C.
Experiments, (i) 40 c.c. of a solution of zinc sul-
phate (= 0.181 2 gram metallic zinc), to which were
added 50 c.c. of potassium oxalate and 100 c.c. of
potassium sulphate, were electrolysed with a current
giving 109 c.c. of electrolytic gas per hour. After
five hours the current was interrupted. The precipi-
tated zinc weighed 0.1814 gram. (2) 2.1867 grams
brass (containing tin, copper, lead and zinc) were dis-
solved in nitric acid and the tin determined in the
usual gravimetric way. Its quantity was found to be
0.04 per cent. In the filtrate, containing nitric acid,
lead and copper were determined simultaneously by
electrolysis (the copper separated upon the cathode
and the lead as dioxide upon the anode) :
Found /-- 8 5# Pb and 64.60 # Cu.
1 \ 0.85 64.62
The acid liquid was siphoned off from the deposits,
DETERMINATION OF METALS ZINC. /I
evaporated to dryness with sulphuric acid, neutral-
ized with caustic potash, and then to this (100 c.c. in
volume) solution were added 50 c. c. of a solution
of potassium oxalate and 100 c. c. of a solution of
potassium sulphate. The zinc found equaled 34.50
per cent.
When using this method employ a stout platinum
wire, wound to a spiral at the one end, for the anode,
and a platinum cone for the cathode. To avoid the
peculiar spots which electrolytic zinc shows upon a
platinum surface, it will be best to first coat the nega-
tive electrode with copper (5 grams). In dissolving
the precipitated zinc, use rather dilute nitric acid.
The copper layer will be but slightly attacked, and
after washing and drying will serve for further depo-
sitions. Wash the zinc deposit with water, alcohol
and ether ; dry in a desiccator. Oxidation is liable to
occur if an air bath be used for the drying.
Riche employs " a solution of the acetate with an
excess of ammonium acetate, obtained by supersatu-
ration with ammonia, and acidifying with acetic acid."
This method affords good results, as may be seen
from the following determination : 0.4736 gram of zinc
sulphate was dissolved in 200 c.c. of water, to which
were added three grams of sodium acetate and ten
drops of ordinary acetic acid. The current gave 3 c.c.
of electrolytic gas per minute. After two hours o. 1063
gram of metallic zinc was obtained, the required
quantity being 0.1072 gram.
72 ELECTRO-CHEMICAL ANALYSIS.
Moore seems to have obtained exceedingly satis-
factory results by precipitating a solution of zinc
sulphate with sodic phosphate, then adding an excess
of ammonium carbonate, and after dissolving the pre-
cipitate in potassium cyanide, the solution was elec-
trolysed at a temperature of 80 with a current giving
rooo c.c. electrolytic gas per hour. The metal was
deposited upon a silver-plated electrode.
A very convenient stand for electrolytic work and
suitable in the zinc depositions has been described by
v. Malapert (Z. f. a. Ch., 26, 56), and since conve-
niently modified by Herrick (Jr. An. Ch., 2, 167).
NICKEL AND COBALT.
LITERATURE. Gibbs, Z. f. a. Ch., 3, 336; Z. f. a. Ch.,n, 10; 22,
558; Merrick, Am Ch., 2, 136; Wrightson, Z. f. a. Ch., 15, 300,
3 3>3335 Schweder, Z. f. a. Ch., 16,344; Cheney and Richards,
Am. Jr. Sc. and Ar. [3], 14, 178; Ohl, Z. f. a. Ch., 18, 523; Luckow,
Z. f. a. Ch., 19, 16; Bergmann and Fresenius, Z. f. a. Ch., 19,
314; Riche, Z. f. a. Ch., 21, 116, 119; Classen and v. Reis, Ber.,
14,1622,2771; Schucht, Z. f. a. Ch., 21, 493; Kohn and Wood-
gate, Jour. Soc. Chem. Industry, 8, 256.
These metals are precipitated from solutions of their
double cyanides, double oxalates, and sulphates mixed
with alkaline acetates, tartrates and citrates, or from
ammoniacal solutions. The latter seem best adapted
for nickel depositions, the presence of ammonium
sulphate or sodium phosphate being favorable to the
precipitation.
DETERMINATION OF METALS NICKEL, COBALT. 73
Fresenius and Bergmann, who have carried out a
series of experiments with nickel and cobalt, give the
following as satisfactory conditions : 50 c.c. nickel
solution (=0.1233 gram nickel), 100 c.c. ammonia
(sp. gr. 0.96), io c.c. ammonium sulphate (305 grams
of the salt in I litre of water), 100 c.c. of water; sepa-
FIG. 23.
ration of the electrodes j~~X cm. : time, four hours.
Current, 300 c.c. electrolytic gas per hour. The nickel
found was 0.1233 gram. Apparatus suitable for the
decomposition just described is represented in Fig.
23. The metal is deposited upon the weighed plat-
inum cone in the beaker glass, C. The vessel is covered
F
74 ELECTRO-CHEMICAL ANALYSIS.
with a glass lid having suitable apertures for the posi-
tive and negative electrodes. As soon as the blue-
colored liquid becomes colorless, an indication that
the metal is completely precipitated, remove a few
drops and test with a solution of potassium sulpho-
carbonate. If the latter causes only a faint rose-red
coloration the deposition of metal may be considered
complete. It is not advisable to interrupt the current
or to remove the cone from the electrolysed liquid
until the latter has been replaced by water. This is
effected by the vessels to the left of the figure : A
is an aspirator, filled with water ; B is air-tight and
empty; x is a doubly bent tube extending to the
bottom of C. Open p and the liquid in C is gradually
transferred to B. Add fresh water in C. Ammonium
chloride should not be present in the solution under-
going electrolysis.
The statements upon nickel also apply to cobalt.
An experiment, taken from the article of Fresenius
and Bergmann is here given as a guide in determin-
ing cobalt: 50 c.c. of cobalt sulphate ( 0.1286 gram
cobalt), 100 c.c. of ammonia, 10 c.c. of ammonium sul-
phate, 100 c.c. water; current, 300 c.c. electrolytic gas
per hour ; separation of electrodes, ^-^ cm. Time,
five hours. The deposited cobalt weighed 0.1286
gram.
Use potassium sulpho-carbonate to test when the
metal is fully reduced ; it gives a wine-yellow colora-
tion with even the most dilute solutions of cobalt salts.
DETERMINATION OF METALS MANGANESE. 75
When too little ammonia is present in the electro-
lyte the results are bad ; too much of this reagent
retards the deposition of the cobalt.
When precipitating these metals from the solutions
of their double oxalates, the conditions should be
similar to those indicated under Iron (p. 78).
The writer has electrolysed cobalt compounds con-
taining an excess of an alkaline acetate (see Zinc) with
perfectly satisfactory results, and would recommend
such solutions for this particular metal.
MANGANESE.
LITERATURE. Z. f. a. Ch., ix, 14; Rich 6, Ann. de Chim. et de
Phys. [5th sen], 13, 508; Lu cko w, Z. f. a. Ch., 19, 17 ; Schucht,
Z. f. a. Ch., 22,493; Classen and v. Reiss, Ber., 14, 1622; Moore,
Ch. News, 53, 209 ; Smith and Fran kel, Jr. An. Ch., 3, 385; Ch.
News, 60, 262; Brand, Z. f. a. Ch., 28, 581.
The electric current causes this metal, when in solu-
tion as chloride, nitrate or sulphate, to separate as the
dioxide upon the anode (see Lead). In a solution of
nitric acid, the hydrogen set free reduces the acid to
oxides of nitrogen and, finally, to ammonia. Hence,
when the liquid becomes alkaline or only slightly acid,
peroxide will also separate upon the cathode ; it will
be necessary to remove this by means of a strip of
paper, and ignite the same along with the greater bulk
of dioxide, weighing all finally as Mn 3 O 4 . As long
as manganese alone is present in the solution, this
76 ELECTRO-CHEMICAL ANALYSIS.
separation at both electrodes will not cause a serious
result; but in electrolysing a nitric acid solution con-
taining manganese, magnesium or aluminium, the re-
sults will be high. For this reason a solution of the
sulphate, slightly acidulated with two to six drops of
sulphuric acid, is preferable for electrolytic purposes.
Riche advises connecting a platinum crucible or dish
with the anode of a battery, warming the solution,
during the deposition, upon a water-bath (7O-9O),
and then electrolyses with a current generating
3 c.c. of oxy-hydrogen gas per minute. Arrange
the apparatus as directed under Cadmium. As
soon as the manganese has been fully precipitated
as dioxide, the current is interrupted, the deposit
washed with water, and should any of the dioxide
become detached, it must be caught upon a small
filter, then dried, ignited and weighed, together with
the adherent dioxide, which is changed to Mn 3 O 4
before weighing. In the presence of large quantities
of iron, this precipitation is unsatisfactory ; therefore,
first remove the iron with barium carbonate. Tartaric,
oxalic and lactic acids retard the formation of manga-
nese dioxide. The same is true of phosphoric acid.
Potassium sulphocyanide also prevents its formation,
and, if added to solutions in which dioxide is already
precipitated, it causes the same to redissolve.
The apparatus devised by Herpin (Fig. 24) can be
well applied in the decomposition of manganese salts.
It consists of a platinum dish, A, resting upon a tripod,
DETERMINATION OF METALS MANGANESE.
77
B, in connection with the cathode of a battery. The
upper portion of the dish is so constructed that it
will support an inverted glass funnel, D. Any loss
from the bursting of bubbles is prevented by this
FIG. 24.
means. The anode is a platinum spiral C. In esti-
mating manganese it must not be forgotten to connect
the dish with the anode of the battery employed for
the decomposition.
78 ELECTRO-CHEMICAL ANALYSIS.
IRON.
LITERATURE. Wrightson, Z. f. a. Ch., 15, 305; Parodi and
Mascazzinl, G. Ch. ital., 8; also Z f. a. Ch., 18, 588; Luckow, Z.
f. a. Ch., 19, 18; Classen and v. Reiss, Ber., 14, 1622; Moore,
Ch. News, 53, 209; Smith, Am. Ch. Jr., 10, 330; Brand, Z. f. a.
Chem., 28, 581.
In the historical sketch p. 44, it was mentioned
that Parodi and Mascazzini found that iron could be
precipitated from solutions of its double oxalates.
This suggestion has since been greatly elaborated by
Classen, and by him applied to many other metals.
Following the recommendation of this chemist the
iron salt is placed in a weighed platinum dish con-
nected with the cathode of a battery, and to this are
added 1 3 c. c. of a solution of potassium oxalate
(i 13), and 25 c. c. of water. 3-4 grams of ammo-
nium oxalate are next introduced into this liquid and
dissolved by the aid of heat, and the entire solution
then diluted to 200 c. c., and electrolysed with a cur-
rent generating 12 c. c. of electrolytic gas per minute.
It is necessary to increase this toward the end of the
reduction, to insure the complete deposition of the
metal. Test the clear liquid, acidulated with hydro-
chloric acid, with potassium sulphocyanide. The
solution should be hot (70) during the decomposi-
tion. The deposited iron has a steel-gray color; it
should be washed with water, alcohol and ether.
Avoid the presence of chlorides and nitrates. By
DETERMINATION OF METALS IRON. 79
carefully complying with the conditions recommended
by Classen good results are sure to follow. To show
that persons with but little experience can obtain
satisfactory results the two following determinations,
made by a student, are given : A quantity of ferric
ammonium sulphate (= 0.0814 gram iron) was dis-
solved in 200 c. c. 'of water, and to this were added
eight grams of ammonium oxalate. The solution
was heated to 80, and in two hours, with a current
of 15 c. c. electrolytic gas per minute, 0.0814 gram
of iron was obtained. In a second experiment, the
quantity of iron was doubled (= 0.1628 gram iron),
while the ammonium oxalate was 1 1 grams, tempera-
ture 66 and the current 10 c. c. electrolytic gas per
minute. The precipitated iron weighed 0.1619 gram
instead of 0.1628.
The writer found the following procedure admirably
suited for iron determinations: 10 c. c. iron solution
( 0.0300 gram metal), 20 c. c. sodium citrate (28
grams in % litre) with a little free citric acid, then diluted
with water to 150 c. c. Current, 12 c. c. electrolytic
gas per minute. In four hours 0.0303 gram iron was
precipitated from the cold solution. The deposit was
washed as already directed. In several determina-
tions aluminium and titanium were present with the
iron, but the latter was precipitated free from the other
two.
A third method, originated by Moore, advises that
glacial phosphoric acid (15% acid) be added to the
8O ELECTRO-CHEMICAL ANALYSIS.
distinctly acid solution of ferric chloride or sulphate,
until the yellow color fully disappears, then a large
excess of ammonium carbonate added and gently
warmed until the liquid becomes clear. On electrolys-
ing the hot (70) solution by a current equal to 1200
c. c. electrolytic gas per hour, the iron is rapidly and
completely deposited at the rate of 0.75 gram per hour.
The end of the decomposition is recognized by test-
ing a portion of the solution with ammonium sulphide.
Wash the deposit as already directed.
URANIUM.
LITERATURE. Luckow, Z. f. a. Ch., 19, 18; Smith, Am. Ch.
Jr., i, 329-
For electrolytic purposes use the acetate or any of
the salts to which an alkaline acetate has been added
in large excess, together with a few drops of free acetic
acid. The dish in which the deposition is made is
placed upon a water-bath, and connected with the
negative electrode of a battery giving 2-3 c.c. of elec-
trolytic gas per minute (see Cadmium). Heat the
liquid to 70 throughout the entire decomposition.
The uranium separates as yellow uranic hydroxide
upon the cathode; by the continued action of the
current it changes to the black hydrated protosesqui-
oxide. As soon as the solution becomes colorless,
interrupt the current, and quickly pour the clear liquid
upon a small filter, to catch any detached particles of
DETERMINATION OF METALS THALLIUM. 8 1
oxide. Wash with a little acetic acid and boiling
water ; dry, ignite and weigh as Ur 3 O 4 (Ur s O 8 ). This
method affords an excellent separation of uranium from
the alkali and alkaline earth metals.
THALLIUM.
LITERATURE. Schu cht, Z. f. a. Ch., 22, 241, 490; Neumann ,
Ber., 21, 356.
This metal separates as sesquioxide, from acid solu-
tions, upon the anode, while from ammoniacal liquids it
is deposited partly as metal and partly as oxide. From
oxalate solutions, and from its double cyanides it sepa-
rates only as metal, when the current is feeble. How-
ever, difficulty is experienced in drying the deposit
without having it oxidized. In this respect it is even
more troublesome than lead. Neumann utilizes the
current to separate the metal, dissolves the latter in
acid and measures the liberated hydrogen ; from its
volume he calculates the quantity of thallium origi-
nally present. For suitable apparatus to carry out
this method, consult the literature cited above.
82 ELECTRO-CHEMICAL ANALYSIS.
PLATINUM, PALLADIUM, MOLYBDENUM,
GOLD, ETC.
LITERATURE. Luckow, Z. f. a. Ch., 19, 13; Classen, Ber., 17,
2467; Schucht, Z. f. a. Ch., 22, 242; Smith, Am. Ch. Jr., i, 329;
Hoskinson and Smith, ibid., 1,90; Smith and Keller, Am.
Ch. Jr., 12, 252.
The solutions of platinum salts, slightly acidulated
with sulphuric acid, and acted upon by a feeble cur-
rent, give up the metal as a bright, dense deposit upon
the dish, frequently so light as to be scarcely dis-
tinguished from the latter. In using platinum vessels
for this purpose, first coat them with a rather thick
layer of copper, upon which afterward deposit the
metal. Wash the deposit with water and alcohol.
In ordinary gravimetric analysis, potassium is
frequently estimated as potassio-platinum chloride,
K 2 PtCl 6 . This operation requires time and care.
Rather dissolve the double salt in water, slightly acidu-
late the solution with sulphuric acid, and electrolyse
with one Bunsen cell. The deposit will be black
and spongy if the current is too strong. From the
quantity of platinum found calculate the potassium.
The following facts have been taken from Classen's
article (see Literature) : A platinic chloride solution,
containing 0.6 gram platinum, was diluted to 200 c.c.
with water and electrolysed. In five hours 0.4581
gram platinum had separated. When mixed with
ammonium oxalate 0.0996 gram platinum was pre-
DETERMINATION OF METALS PALLADIUM. 83
cipitated in two hours. From a solution, feebly acidu-
lated with hydrochloric acid, four Meidinger cells
precipitated 0.737 gram platinum in the course of
twenty-four hours. On dissolving 0.5 gram ammonio-
platinum chloride in 100 c.c. water and mixing with
ammonium oxalate the current from one Bunsen cell
precipitated 0.208 gram platinum in five hours. 0.6042
gram potassio-platinum chloride was dissolved in 150
c.c. of water, acidulated with thirty drops of dilute sul-
phuric acid (i : 6), and in six hours gave 0.2017 gram
platinum to the action of the current; 0.5015 gram
of the same salt gave 0.0956 gram metal in two
hours; while 0.4545 gram of the double chloride
dissolved in 100 c. c. water, and not acidulated, gave
0.0688 gram platinum in three hours.
PALLADIUM can be deposited in the same manner as
platinum. The use of a feeble current gives a bright
metallic deposit ; otherwise it is spongy.
It has been recently discovered, in this laboratory,
that this metal can be rapidly and fully precipitated
from ammoniacal solutions of palladammonium chlo-
ride, by a current liberating 0.7 c.c. electrolytic gas per
minute. Palladammonium chloride, Pd(NH 3 Cl) 2 , is
prepared by adding hydrochloric acid to an ammonium
hydroxide solution of palladious chloride. To show
the accuracy of this method several actual determina-
tions are here introduced: (i) A quantity of the
double salt (= 0.2228 gram palladium) was dissolved
84 ELECTRO-CHEMICAL ANALYSIS.
in ammonium hydroxide; to this solution were added
20-30 c.c. of the same reagent (sp. gr. 0.935), and 100
c.c. of water. A current, giving 0.9 c.c. electrolytic
gas per minute, acted upon this mixture through the
night, and deposited 0.2225 gram palladium. (2) In
another experiment, with conditions similar to those
just mentioned, excepting that the quantity of the
palladammonium chloride was doubled, and the current
reduced to 0.7 c.c. electrolytic gas per minute, the
quantity of metal precipitated equaled 0.4462 gram
instead of 0.4456. Oxide did not separate upon the
anode. The deposit, when dry, showed the same
appearance as is ordinarily observed with this metal
in sheet form. It was washed with hot (70) water,
and dried in an air-bath at no-ii5. It is best to
deposit the palladium in platinum dishes previously
coated with silver.
WHEN the electric current acts upon ammoniacal,
or feebly acid solutions of ammonium molybdate, a
beautiful iridescence appears ; as the action continues
this assumes a black color, and the deposit becomes
more dense. It is the hydrated sesquioxide, which is
precipitated ; after washing with hot water it is dried,
carefully ignited to molybdic acid, and weighed. The
precipitation can take place in a platinum crucible, in
connection with the cathode of a battery liberating
3-4 c.c. of electrolytic gas per minute. The tempera-
ture of the solution should not fall below 70 ; its
DETERMINATION OF METALS TIN. 85
volume may vary from 25 c.c.-i25 c.c. Three hours
were required for the precipitation of 0.0329-0.1000
gram of oxide.
GOLD is best deposited from solutions of its double
cyanides.
THE facts relating to the electrolytic behavior of
vanadium, tungsten and osmium are, at the present
writing, few in number and will not be given here.
TIN.
LITERATURE. Luckow, Z. f. a. Ch., 19, 13; Classen and v.
Reiss, Ber., 14, 1622; Gibbs, Ch. News, 42, 291 ; Classen, Ber.,
!7, 2467; 18, 1104.
Tin may be deposited either from a solution of its
chloride, or from that of ammonium tin oxalate. It
is advisable not to use potassium oxalate in the electro-
lysis, for then a basic salt is liable to separate upon the
anode. Three to four grams of ammonium oxalate
will be sufficient for the decomposition. The current
should liberate 3 c.c. electrolytic gas per minute.
When electrolysing acid tin solutions do not interrupt
the current until the free acid is first removed ; this is
not necessary when operating with oxalate solutions.
Classen has published a great deal of very valuable
information upon the electrolysis of this metal, and
has discovered that a tin solution, containing an excess
86 ELECTRO-CHEMICAL ANALYSIS.
of ammonium sulphide, largely diluted with water,
yields a quantitative deposition of the metal when
exposed to the action of a current from two Bunsen
cells. In dilute sodium or potassium sulphide solu-
tion the tin precipitation is incomplete, and whenever
such conditions exist, the sodium or potassium salt
must be converted into ammonium sulphide. To this
end the liquid is mixed with about 25 grams of ammo-
nium sulphate, free from iron, and the solution then
carefully warmed in a covered vessel until the evolu-
tion of hydrogen sulphide ceases ; after which the
liquid is heated to incipient ebullition for fifteen min-
utes. Allow it to cool, dissolve any sodium sulphate
which may have separated by the addition of water,
and electrolyse with a current of 9-10 c.c. oxy-hydro-
gen gas per minute. The tin separates in a gray, dense
layer. Wash it with water and alcohol. At times
sulphur sets itself upon the tin deposit ; this is diffi-
cult to remove, but can be detached, after washing the
deposit with alcohol, by gently applying a linen hand-
kerchief.
DETERMINATION OF METALS ANTIMONY.
ANTIMONY.
LITERATURE. Wright son, Z. f. a. Ch., 15, 300 ; Parodi and
Mascazzini, Z. f. a. Ch., 18, 588; Luckow, Z. f. a. Ch., 19, 13 ;
Classen and v. Reiss, Ber., 14, 1622; 17,2467; 18,1104; Lecre-
nier, Chemiker Zeitung, 13, 1219; Chittenden, Pro. Conn. Acad.
Sci., Vol. 8.
Antimony, when precipitated from a solution of its
chloride, or from that of antimony potassium oxalate,
does not adhere well to the cathode. It is deposited
very slowly from a solution of potassio-antimony
tartrate. Its deposition from a cold ammonium sul-
phide solution is satisfactory, but the use of this
reagent for this purpose is not pleasant, especially
when several analyses are being carried out simulta-
neously. For this reason potassium or sodium sul-
phide has been substituted. The alkaline sulphide
used must not contain iron or alumina.
The antimony solution, mixed with sodium sulphide,
is largely diluted with water. A more rapid reduction
follows in consequence of the dilution. A current
giving 2-3 c.c. of electrolytic gas per minute will pre-
cipitate o.i gram of antimony in four or five hours.
To ascertain when all the metal is deposited incline
the dish slightly, thus exposing a clean platinum sur-
face. If this remains bright for half an hour the pre-
cipitation is finished. In separating antimony from
the heavy metals, e. g., lead, it happens that alkaline
sulphides containing polysulphides are used, or are
55 ELECTRO-CHEMICAL ANALYSIS.
produced. To remove these Classen proposed adding
to the antimony-polysulphide mixture, already in a
weighed platinum dish, an ammoniacal solution of
hydrogen peroxide, and warming the same until the
liquid becomes colorless. When this is accomplished,
even if a precipitate has been produced, add, after
cooling, 10 c.c. of a concentrated solution of sodium
monosulphide, and electrolyse with a current of 1.5-2
c.c. electrolytic gas per minute. Wash the deposit
with water and alcohol.
Lecrenier writes as follows relative to the preceding
method: The precipitation is all that one can desire,
providing the solution of the sulpho-salt is absolutely
free from polysulphides ; otherwise, it is incomplete.
The antimony sulphide, obtained in the ordinary
course of analysis, always contains sulphur, and this
must be eliminated. To remove the various incon-
veniences connected with the method add 50-75 c.c.
of a 20 per cent, solution of sodium sulphite to the
solution after the addition of the excess of sodium
sulphide, then heat the liquid to complete decoloriza-
tion ; allow to cool, after which the current is con-
ducted through the liquid. This can rise to 5 c.c. per
minute without impairing the result ; but it is not best,
as the precipitated metal is then not very coherent.
It is better to use a current giving not more than half
of the above volume of electrolytic gas per minute.
When the quantity of antimony does not exceed
0.2 gram the deposit will be adherent and free from
SEPARATION OF METALS. 89
sulphur ; wash with water, alcohol and ether. Sulphur
will separate upon the anode, despite the presence of
an excess of sodium sulphite. This, however, does
not affect the result.
ARSENIC.
LITERATURE. Luckow, Z. f. a. Ch., 19, 14; Classen and v.
Reiss, Ber., 14, 1622; Moore, Ch. News, 53, 209.
A successful method for the complete deposition of
arsenic is not known. The current, acting upon the
chloride, causes complete volatilization of the metal
in the form of arsine. Its separation from oxalate
solutions is incomplete; nor do the sulpho-salts
answer for electrolytic purposes.
2. SEPARATION OF THE METALS.
Electrolysis, to be of value, must not only furnish
the analyst with methods suitable for the complete
deposition of metals, but it should, in addition, enable
him to separate metallic mixtures. The data given
in the preceding pages will serve for this purpose, but,
as special treatment is required in some instances, a
brief outline of a series of separations will be indi-
cated.
90 ELECTRO-CHEMICAL ANALYSIS.
COPPER.
We recall, first of all, that this metal can be de-
posited electrolytically from solutions in which free
nitric acid is present (p. 51). This behavior renders
the separation of copper from cadmium possible (Am.
Ch. Jr., 2, 42). Place the solution containing the two
metals in a beaker glass of 200 c. c. capacity ; suspend
(p. 52) a weighed platinum crucible in the liquid,
and precipitate the copper upon it. The total dilution,
during the decomposition, should not exceed I5<DC. c.
As much as 5 per cent, of nitric acid can be present ;
the current should give 0.5 c. c. electrolytic gas per
minute. When all the copper is precipitated, washed,
dried and weighed (p. 51), make the residual liquid
alkaline with sodium hydroxide, and add sufficient
potassium cyanide to redissolve the precipitate. Elec-
trolyse as directed (. 55). Copper and cadmium
can also be separated in solutions of their double
alkaline cyanides (Jr. An. Ch.,^, 385). Five to six
grams of potassium cyanide should be added for every
0.2-0.4 gram of metal. Do not work with less than
200 c. c of liquid, and the current should not exceed
0.28 c.c. of electrolytic gas per minute. Under these
conditions the cadmium is deposited, while the copper
remains dissolved. Very recent experiments, made
in this laboratory, show that also in the presence of an
excess of free sulphuric acid the current will precipi-
tate copper free from cadmium: e.g., 0.1975 gram of
SEPARATION OF METALS COPPER. 9 1
metallic copper, and 0.1828 gram of cadmium, both as
sulphates, were dissolved in 20 c. c. of water ; to this
were added 10 c. c. of sulphuric acid, of 1.09 sp. gr.
and 100 c. c. of water. The current gave 0.30 c. c.
electrolytic gas per minute. The precipitated copper
weighed 0.1976 gram; it contained no cadmium.
It is not possible to separate these metals when
present together in an oxalate solution.
The precipitation of copper in nitric acid solutions
further enables us to separate it from iron, aluminium,
chromium, cobalt, nickel, zinc, the alkaline earth and
the alkaline metals, though it would perhaps be better
to execute the separation from the first six in a solu-
tion containing free sulphuric acid. From mercury,
silver and bismuth the copper cannot be separated in
the presence of nitric or sulphuric acid. For the elec-
trolytic separation of copper from mercury see p. 97.
Its separation from bismuth has only recently been
made possible by combining the behavior of copper
in the presence of an excess of alkaline cyanide, and
that of bismuth where it exists as a double citrate in
an alkaline solution (p. 60). Add 3-4 grams of citric
acid to the bismuth solution, so that upon the later
addition of sodium hydroxide to alkaline reaction a
precipitate is not produced. Into this liquid introduce
the cyanide copper solution, and electrolyse with a
current giving 0.15 c.c. electrolytic gas per minute.
In a solution of copper and lead, containing 5 per cent,
of nitric acid, the former will be deposited completely
92 ELECTRO-CHEMICAL ANALYSIS.
at the cathode, while the latter is fully precipitated as di-
oxide at the anode (p. 62). This course is adopted when
separating these metals in alloys or minerals (p. 63).
The separation of copper from manganese should
be conducted in solutions containing a slight excess
of sulphuric acid. While the copper is deposited as
such upon the cathode, the manganese separates upon
the anode as dioxide (p. 76). A platinum foil may be
used as anode in this separation. Another method,
applicable here, is based on the observation that man-
ganese remains dissolved in the presence of phos-
phoric acid, while the copper is deposited in its usual
form. For example, 0.1770 gram copper and 0.1500
gram manganese, both as sulphates, were treated with
30 c.cr of sodium phosphate, of sp. gr. 1.0388, and 10
c.c. phosphoric acid, of sp. gr. 1.347, trien diluted to
1 50 c.c. with water and electrolysed with a current
giving I c.c. of electrolytic gas per minute. The pre-
cipitated copper weighed 0.1765 gram. Manganese
did not separate, even as dioxide. (See Am. Ch. Jr.,
12, 329.)
The deposition of copper in the presence of anti-
mony is yet unsatisfactory. When the latter does not
exceed j of the quantity of the first, no fault can be
found with the separation (p. 39, and Wrightson, Z. f.
a. Ch., 15, 297).
As to the separation of copper from arsenic, Classen
remarks (Ber., 15, 297), that when the arsenic exceeds
0.20 per cent., the deposited copper is more or less
SEPARATION OF METALS COPPER. 93
dark in color, and the result will be high. Some
chemists have advised that after the copper deposit
has been dried, it should be heated to volatilize the
arsenic ; the residual cupric oxide is redissolved and
its solution again electrolysed. This procedure will
be satisfactory when arsenic is present in traces, other-
wise it is worthless. The arsenic in copper ores can
be entirely removed by evaporating their acid solution
with bromine, when it will be expelled as bromide.
The copper results are then satisfactory.
McCay (Chemiker Zeitung, 14, 509) has observed
that when the current from 4-6 Meidjnger cells is con-
ducted through a potassium arsenite solution, made
distinctly alkaline with ammonium hydroxide, this
salt sustains no change. With copper, under like con-
ditions, the separation of the metal is quantitative.
Upon this behavior he bases a very excellent separa-
tion of these two metals. The only care necessary is
to see that not too much ammonia is employed. In
this laboratory like results were obtained, but prefer-
ence has since been given to the following course :
Add the copper solution to that of the alkaline arsen-
ite or arsenate, and follow it with a solution of potas-
sium cyanide until the precipitate first produced is
just dissolved; the liquid will then show a slight
purple tint. A current of 0.25 c.c. electrolytic gas
per minute, precipitates the copper quite rapidly
under these conditions ; the deposit will contain no
arsenic (Am. Ch. Jr., 12, 428).
94 ELECTRO-CHEMICAL ANALYSIS.
When antimony, arsenic and tin are associated with
copper, treat the sulphides with sodium sulphide.
The resulting alkaline sulphide solution can then be
employed for the separation of the first three (p. 102),
while the insoluble copper sulphide may be dissolved
and treated as described on page 54.
CADMIUM.
The methods already described under copper are
sufficient for the separation of cadmium from this
metal. A solution containing free nitric acid is used
for the separation of cadmium from silver, mercury,
lead and bismuth ; the latter is also separated from it
by using a solution in which there is a slight excess
of sulphuric acid (p. 60). When these metals have
been removed from their solution, neutralize the
excess of acid with potassium hydroxide, add a slight
excess of potassium cyanide and electrolyse the liquid
for the estimation of the cadmium, as directed on
page 55-
When there is an excess of but 2 c.c. of sulphuric
acid, of sp. gr. 1.09, cadmium can be precipitated
(p. 55), and thus separated from iron, aluminium, chro-
mium, zinc, cobalt, nickel and manganese (the latter
deposits at the same time as dioxide upon the anode,
p. 76). Another method which serves for the separa-
tion of cadmium from either zinc or cobalt, consists
in having these metals in solution in the form of
SEPARATION OF METALS CADMIUM. 95
double cyanides with the alkaline cyanides. The
volume of the aqueous solution should be at least
200 c.c. ; to this add 4^ grams of potassium cyanide,
and electrolyse the liquid with a current giving 0.30
c.c. electrolytic gas per minute (Am. Ch. Jr., n, p.
352). Cadmium cannot be separated from nickel by
this method.
Under the special methods given for the estimation
of cadmium (p. 55) it was mentioned that it separates
well from solutions of the acetate. Yver (B. s. Ch.
Paris, 34, 18) has employed this behavior to separate
cadmium from zinc. The method is this : the metals
are converted into acetates by the addition of 2-3
grams of sodium acetate to their solution, followed
by several drops of free acetic acid. This liquid is
then exposed to the current from two ordinary Daniell
cells. Heat (70) the solution during the decomposi-
tion. The precipitated cadmium contains no zinc.
Three to four hours are necessary for the reduction
of 0.18-0.210 gram of cadmium. Remove the zinc
from the filtrate by the method of Riche (p. 71).
Smith and Knerr (Am. Ch. Jr., 8, 210) have tried this
separation, and recommend that the current should
not exceed 0.10.2 c.c. of electrolytic gas per minute.
It is also essential that the liquid be held at a nearly
uniform temperature (70) during the reduction. The
dilution of the liquid should not exceed 100 c.c.
The same chemists also (Am. Ch. Jr., 8, 210)
found that upon electrolysing a solution of these two
96 ELECTRO-CHEMICAL ANALYSIS.
metals, to which 3-4 grams of sodium tartrate and
tartaric acid had been added, with a current of 3-4
c.c. electrolytic gas per minute, tKe cadmium was
deposited completely from the warm solution, and
contained no zinc.
Eliasberg (Z. f. a. Ch., 24, 550) has also proposed
a method for the separation of cadmium from zinc :
Dissolve the metallic oxides in hydrochloric acid,
evaporate their solution to dryness, add 8-10 grams
of potassium oxalate, and 2-3 grams of ammonium
oxalate, diluting finally to 100 c.c. ; heat "to boiling
and electrolyse the warm (not boiling) liquid with a
current equal to 0.15 c.c. electrolytic gas per minute.
Cover the vessel in which the decomposition is made.
Six to seven hours' will be required for the com-
plete deposition of 0.15 gram of metal (cadmium).
The electrolytic separation of these two metals is also
possible in a solution of their phosphates, dissolved
in phosphoric acid (Am. Ch. Jr., 12, 329).
To separate cadmium from antimony and tin it is
necessary to have recourse to the usual method of
analysis, the solubility of the sulphides of the first
two in alkaline sulphides. A direct separation of
cadmium from arsenic is possible, but that the cad-
mium may be precipitated absolutely free from
arsenic, the latter must be present in the solution as
an arsenate. Upon adding two grams of potassium
cyanide to such a solution, and electrolysing the same
with a current equal to 0.3 c.c. of electrolytic gas per
SEPARATION OF METALS MERCURY. 97
minute, the cadmium will be completely precipitated
in ten hours. The reduction is made in cold solu-
tions (Am. Ch. Jr., 12, p. 428).
MERCURY.
This metal is deposited quite rapidly from solutions
containing free nitric acid (p. 57), hence under such
conditions it may be separated from cadmium, iron,
aluminium, chromium, zinc, nickel, cobalt, barium,
strontium, calcium, magnesium and the alkalies. When
lead and mercury are exposed, in a solution of nitric
acid, to the action of the current, they are deposited
simultaneously, the lead as dioxide at the anode
(p. 62), and the mercury as metal upon the cathode.
Manganese and mercury are separated to the best
advantage in solutions containing free sulphuric acid
(p. 76). Mercury cannot be separated in the electro-
lytic way from silver and bismuth. From copper, as
long as the quantity of this metal does not exceed 20
per cent, of that of the mercury, the separation can be
made in a cyanide solution (Jr. An. Ch., 3, 254). As
an example, it may be stated that 0.1833 gram mer-
cury, as chloride, and 0.0259 gram copper, as sul-
phate, with 1.5 grams potassium cyanide, were diluted
to 200 c.c. with water, and then electrolysed in the
cold, with a current giving 0.32 c.c. of electrolytic gas
per minute. At the end of sixteen hours 0.1833 gram
mercury had separated.
98 ELECTRO-CHEMICAL ANALYSIS.
More recent experiments, made in this laboratory,
prove that mercury may be readily separated in the
same way from zinc, nickel and cobalt. The quantity
of alkaline cyanide to be used in these separations
may vary from three to four grams, although when
cobalt is to be separated from mercury good results
will not be obtained if more than three grams of potas-
sium cyanide are present for 0.30.4 gram of metal.
The current should not exceed 0.8 c.c. of electrolytic
gas per minute (Am. Ch. Jr., 12, 104).
In separating mercury from tin and antimony, pre-
pare their sulphides, and digest these with ammonium
sulphide, dissolving out the first two. The residual
mercury sulphide is then dissolved in aqua regia, and
after neutralizing the excess of acid with an alkaline
hydroxide, potassium cyanide is added in sufficient
quantity to form the double cyanide, which is then
electrolysed as described, p. 58. Mercury is separated
from arsenic similarly to cadmium from this metal,
although it is immaterial whether the arsenic exists
in the solution as an arsenite or arsenate (p. 96).
BISMUTH.
At present there is no satisfactory electrolytic
method known for the separation of this metal from
mercury, silver and lead. Its separation from cad-
mium is effected in solutions containing free sulphuric
acid (5-10 c.c. of sp. gr. 1.09), p. 60. This course will
SEPARATION OF METALS LEAD. 99
also serve to separate it from iron, manganese, zinc,
nickel, cobalt, aluminium, chromium, uranium, mag-
nesium and the alkaline metals (p. 60). The method
of Eliasberg (p. 59) may also be used for the separa-
tion of bismuth from zinc, nickel, cobalt and uranium.
In separating bismuth from those metals the sulphides
of which are soluble in alkaline sulphides, it is neces-
sary to have the usual gravimetric course precede the
electrolytic reduction.
LEAD.
The deposition of lead as dioxide upon the anode
(p. 62) in the presence of at least five per cent, of
nitric acid affords a method for its separation from
mercury, silver, copper, cadmium, iron, chromium,
aluminium, zinc, nickel, cobalt, uranium, the metals
of the alkaline earths and the alkaline metals. It
will be remembered, of course, that some of these
metals separate as such upon the cathode simultane-
ously with the lead upon the anode. Lead, in some
respects, is much like manganese, from which it can-
not be separated electrolytically. Its deposition re-
quires no special description, as the conditions already
described upon p. 63 are to be observed in the per-
formance of the separations just indicated. Lead, tin,
antimony and arsenic are separated as directed under
the preceding heavy metals. Follow the ordinary
gravimetric course.
Lead dioxide, like manganese dioxide (p. 76), is
IOO ELECTRO-CHEMICAL ANALYSIS.
not separated from solutions containing an excess of
an alkaline sulphocyanide, and, if already precipitated
as dioxide, will redissolve upon the addition of the
sulphocyanide.
SILVER.
To separate silver and copper electrolytically, mix
equal quantities of the two metals, in the form of
nitrates, with four and one-half grams of potassium
cyanide, dilute to 200 c.c. with water, and electrolyse
with a current, giving 0.15-0.80 c.c. electrolytic gas
per minute (Am. Ch. Jr., 12, 104). As much as 0.2
gram of silver will be deposited in 1214 hours. If
desirable, expose the filtrate containing the copper to
the action of a stronger current (3 c.c. O-H gas per
minute) ; as soon as the excess of alkaline cyanide is
decomposed, the copper will be deposited in a dense
and brilliant coating. Proceed as directed (p. 94) in
separating silver from cadmium. There is no known
electrolytic method for the separation of silver from
mercury. It is true both can be precipitated from a
nitric acid solution (pp. 57, 64), their joint weight
determined, after which the mercury can be expelled
by heat and the silver residue be re-weighed.
There is no electrolytic method known for the
separation of silver from bismuth. The separation of
silver from lead is made in a nitric acid solution (p.
64). A similar solution is used to separate it from
the metals of other groups.
SEPARATION OF METALS SILVER. IOI
When antimony, tin and silver are present together,
digest their sulphides with sodium sulphide, which
will bring the antimony and tin into a proper condition
to effect their separation electrolytically (p. 102). The
insoluble silver sulphide is dissolved in nitric acid,
and, after the excess of the latter is expelled, potas-
sium cyanide is added in excess and the resulting
liquid electrolysed in the cold, with a feeble current.
The silver is deposited as a dense coating, and may
be washed with hot water.
It is possible to separate silver from arsenic in the
presence of three grams of potassium cyanide, pro-
viding the arsenic exists in the solution as an arsenate.
A current, giving 0.30 c.c. electrolytic gas per minute,
will be sufficient for the metallic reduction. Deter-
mine the arsenic in the residual liquid by the usual
gravimetric method (Am. Ch. Jr., 12, p. 428).
The course just described (above) for the separation
of silver from copper will answer admirably for the
same purpose with silver, zinc, nickel and cobalt. Not
more than three grams of potassium cyanide are re-
quired for 0.2 gram of each metal. The total dilution
should not be less than 200 c.c., and the current not
stronger than 0.3 c.c. electrolytic gas per minute.
102 ELECTRO-CHEMICAL ANALYSIS.
Much credit is due Classen and his co-laborers for
valuable data upon the electrolytic separation of the
following metals :
ANTIMONY FROM TIN.
The sulphides (or residue from a solution of the
metals) are placed in a weighed platinum dish, and
covered with 60 c.c. of sodium monosulphide, to which
is added one gram of sodium hydroxide. If imme-
diate solution does not occur, apply heat, then cool.
Conduct a current of 1.5-2.0 c.c. of electrolytic gas
per minute through this mixture. When the reduc-
tion is finished, pour off the liquid into a second dish.
Treat the antimony deposit as already directed (p.
87). To prepare the tin solution for electrolysis, pro-
ceed as described (p. 86) for the conversion of the
sodium into ammonium sulphide (Ber., 17, 2245 ; 18,
1 1 10).
ANTIMONY FROM ARSENIC.
These metals, or compounds of the same, are evapor-
ated to dryness with aqua regia, the residue dissolved
in 23 c.c. of water ; concentrated sodium hydroxide is
added so that there will be one gram of alkali present
in the liquid, and finally add 60 c.c. of sodium mono-
sulphide. Electrolyse as in the separation of anti-
mony from tin (Ber., 19, 323).
If antimony, arsenic and tin are present together,
SEPARATION OF IRON FROM MANGANESE. 103
the arsenic is expelled from their solution by the
Fischer-Hufschmidt method (Ber., 18, 1 1 10), and the
separation of the tin and antimony made as already
directed on the preceding page.
In general analysis phosphoric acid is frequently
precipitated as tin phosphate. The latter, of course,
contains oxide of tin. Dissolve the precipitate in
ammonium sulphide. On electrolysing the solution
the tin is precipitated, and the filtrate will contain all
the phosphoric acid; this can be estimated in the
usual way (Classen). By observing this suggestion
the determination of the phosphoric acid in a separate
portion of the material will not be required.
IRON, MANGANESE, ZINC, NICKEL, COBALT, ALU-
MINIUM, CHROMIUM AND PHOSPHORIC ACID.
Electrolytic methods for the separation of these
metals are not either so numerous, nor so thoroughly
worked out as with the metals already considered.
Their separation from the heavy metals has been out-
lined under these, and it only remains to describe the
courses which may be pursued with this group of
metals when present together.
Concerning the separation of iron from manganese,
it should be remembered that objections have been
offered to the suggestion of Classen (Ber., 18, 1787),
hence to obtain results at all satisfactory it is advisable
to carry out the separation exactly as given by this
IO4 ELECTRO-CHEMICAL ANALYSIS.
chemist : " If a solution of the double oxalates of iron
and manganese is subjected to electrolysis, without
the previous addition of a great excess of ammonium
oxalate ..... it is impossible to obtain a
quantitative separation of the two metals, because the
manganese dioxide carries down with it considerable
quantities of ferric hydroxide. The complete sepa-
ration of the metals is possible only when the sepa-
ration of the dioxide is delayed till most of the iron
is precipitated." The electrolysis in the cold is not
favorable ; the large amount of ammonium carbonate,
or ammonia formed in the decomposition of the ex-
cessive ammonium oxalate dissolves the precipitated
dioxide. " The rapid dissociation of ammonium oxa-
late when heated, however, gives a simple means of
delaying, or entirely preventing, the formation of a
manganese precipitate during the electrolysis." The
solution containing the two metals is treated with 56
grams of ammonium oxalate, and while hot is acted
upon with a current giving 1 5-20 c.c. of electrolytic
gas per minute. Treat the iron deposit as directed
on p. 78. Boil the liquid, poured off from the iron,
with sodium hydroxide, to decompose the ammonium
carbonate present, after which add sodium carbonate
and a little sodium hypochlorite. The manganese
is precipitated as dioxide, and finally weighed as the
protosesquioxide. Nickel and manganese are sepa-
rated from each other in a similar manner. Cobalt
and zinc, when present with manganese, are separated
SEPARATION OF IRON FROM ZINC. IO5
from it by a current of 10 c.c. oxy-hydrogen gas per
minute, acting in the cold. Oxalic acid is added
toward the end of the reduction to redissolve any
separated manganese dioxide.
To separate iron from zinc, add 1-3 c.c. of a solu-
tion of potassium oxalate (i : 3) and 3-4 grams of
ammonium oxalate to their solution, and electrolyse
the liquid with a current liberating 10-12 c.c. electro-
lytic gas per minute. The zinc is deposited first, and
no difficulty is experienced, providing its quantity is
less than one-third that of the iron present. Classen
provides for this condition by adding a weighed
amount of pure ferrous ammonium sulphate in excess.
The same chemist precipitates iron and cobalt simul-
taneously from their double oxalate solution (condi-
tions as above), takes the combined weight of the
metals, dissolves them in acid and determines the iron
by titration ; the cobalt is found by difference. Nickel
and iron are also deposited together (same as cobalt
and iron) as an alloy, which is weighed, then dissolved
in concentrated hydrochloric acid, the iron oxidized,
and the ferric solution titrated with a stannous chloride
solution. It will be observed that an electrolytic
separation of zinc from cobalt and nickel, and 'the
latter from each other is wanting.
The writer would recommend the following course
in separating the metals of this group : Separate the
iron from the manganese, zinc, nickel and cobalt, by
precipitation with barium carbonate. Dissolve the
H
IO6 ELECTRO-CHEMICAL ANALYSIS.
iron precipitate in citric acid, and electrolyse the
solution according to the directions given upon page
79. The filtrate, containing the zinc, manganese,
nickel and cobalt, together with a little barium salt,
is carefully treated with just sufficient dilute sulphuric
acid to remove the barium. After filtering, electrolyse
the filtrate in a platinum dish, connected with the
anode of a battery, yielding 35 c.c. of electrolytic
gas per minute. A weighed piece of platinum foil
will answer for the cathode. The manganese is de-
posited as dioxide (p. 76) ; the other metals remain dis-
solved and can only be separated by one of the usual
gravimetric methods. This course proved quite satis-
factory in the analysis of the mineral franklinite, where,
after having obtained the iron and manganese as
described, the zinc was also determined electrolytically
in the liquid poured off from the manganese deposit.
If the solution containing these two metals be very
slightly acid with sulphuric acid, they can be precipi-
tated simultaneously the zinc at the cathode, and
manganese dioxide at the anode.
Iron can be further separated, in citrate solution,
from aluminium, chromium and titanium (p. 79).
The deposition should occur in a cold solution, with
a current, liberating 12 c.c. electrolytic gas per minute.
This method will also serve to separate iron from
chromium and phosphoric acid. Classen separates
iron, cobalt, nickel and zinc from manganese, chromium
and aluminium by electrolysing their hot oxalate solu-
SEPARATION OF MERCURY AND PALLADIUM. IO/
tion in the presence of a large excess of ammonium
oxalate. The first four are deposited as metals, while
the manganese dioxide upon the anode has carried
with it some chromium, and should be dissolved, and
the manganese reprecipitated by sodium hydroxide
and sodium hypochlorite (p. 104). The main solu-
tion from the metals is digested until the excess of
ammonia is expelled, when the aluminium hydroxide
is filtered off; the chromate solution, then reduced
with hydrogen sulphide in the presence of an acid, is
precipitated with ammonium, hydroxide. In all cases
where it is necessary to add oxalic acid to redissolve
the aluminium hydroxide, or manganese dioxide, the
acid should be introduced without the interruption of
the current. When phosphoric acid is present with
the iron and manganese it will be found in the liquid
(oxalate) from which the metals have been previously
precipitated, and may be removed as ammonium
magnesium phosphate.
Little can be said relative to the separation of the
rarer metals ; further investigation is required in this
direction.
Quite recent experiments, made in this laboratory,
show that mercury and palladium can be separated if
present together in a solution containing not less than
3 grams of potassium cyanide for 0.2-0.4 gram of the
metals. The current necessary here may vary from
IO8 ELECTRO-CHEMICAL ANALYSIS.
0.08 c.c. 0.22 c.c. electrolytic gas per minute. Not-
withstanding that cadmium and silver are easily
precipitated from their double cyanide solutions, it is
impossible to separate them from palladium. In fact,
they appear to hasten the deposition of the latter
metal.
Mercury, silver and cadmium, furthermore, can be
separated from solutions containing excess of alkaline
cyanide together with tungstic and molybdic acids,
without carrying down any of the latter. The con-
ditions most favorable for these separations are
perfectly similar to those just given above (pp. 96, 98,
101) for the separation of these metals from arsenic
(Am. Ch. Jr., 12, p. 428).
3. OXIDATIONS BY MEANS OF THE
ELECTRIC CURRENT.
When natural sulphides, e.g., chalcopyrite, marca-
site, etc., are exposed to the action of a strong current
in the presence of a sufficient quantity of potassium
hydroxide their sulphur will be quickly and fully
oxidized to sulphuric acid (Jr. Fr. Ins., April, 1889,
Ber., 22, 1019). The metals (iron, copper, etc.) orig-
inally present in the mineral separate as oxides and
metal on dissolving the fused alkaline mass in water.
This method of oxidation eliminates many other
disagreeable features of the old methods. Its rapidity
OXIDATIONS BY MEANS OF CURRENT. 1 09
and accuracy entitle it to the following brief descrip-
tion :
Place about 20 grams of caustic potash in a nickel
crucible i^ inches high and i%& inches wide. Apply
heat from a Bunsen burner until the water has been
almost entirely expelled, when the flame is lowered so
that the temperature is just sufficient to retain the
alkali in a liquid condition. The crucible is next
connected with the negative pole of a battery, and the
sulphide to be oxidized is placed upon the fused
alkali. As some natural sulphides part with a portion
of their sulphur at a comparatively low temperature,
it is advisable to allow the alkali to cool so far that a
scum forms over its surface, before adding the
weighed mineral.
The heavy platinum wire, attached to the anode,
extends a short distance below the surface of the
fused mass. When the current passes a lively action
ensues, accompanied with some spattering. To pre-
vent loss from this source, always place a perforated
watch-crystal over the crucible. After the current
has acted for 10-20 minutes interrupt it. When the
crucible and its contents are cold place them in about
200 c.c. of water, to dissolve out the excess of alkali
and alkaline sulphate. Filter. Invariably examine
the residue for sulphur, by dissolving it in nitric acid
and then testing with barium chloride. The alkaline
filtrate is carefully acidulated with hydrochloric acid,
and after digesting for some time, is precipitated with
1 10 ELECTRO-CHEMICAL ANALYSIS.
a boiling solution of barium chloride. When the
hydrochloric acid is first added, care should be taken
to observe whether hydrogen sulphide or sulphur
dioxide is liberated. If the oxidation is incomplete
sulphur also makes its appearance as a white tur-
bidity. The caustic potash employed in these oxida-
tions should always be examined for sulphur and
other impurities. As it is difficult to obtain alkali
perfectly free from sulphur compounds, a weighed
portion should be taken and its quantity of sulphur
deducted from that actually found in the analysis.
The arrangement of apparatus employed in the
oxidations just outlined is represented in Fig. 25.
The crucible A is supported by a stout copper wire
bent as indicated, and held in position by a binding
screw attached to the base of a filter stand. The arm
of the latter carries a second binding screw holding
the platinum anode in position. While the platinum
rod is generally the positive electrode, it is best to
make it the negative pole for at least a part of the
time during which the current acts. This is advisable
because in many of the decompositions metals are
precipitated upon the sides of the crucibles, and can
readily enclose unattacked sulphide, so that by revers-
ing the current (the poles) any precipitated metal will
be detached, and the enclosed sulphide be again
brought into the field of oxidation. Cinnabar is a
sulphide which has a tendency to mass together, and
it could only be decomposed and its sulphur thor-
OXIDATIONS BY MEANS OF CURRENT.
112 ELECTRO-CHEMICAL ANALYSIS.
oughly oxidized by reversing the current every few
minutes. To reverse the current use the contrivance
C\ this is nothing more than a square block of wood
fastened to the top of the table T, by a screw or nail.
The four depressions (x) in it contain a few drops of
mercury, into which the side binding screws (a) pro-
ject. The mercury cups are made to communicate
with each other by a cap of wood, D, carrying two
metallic wires, which pass through it and project a
slight distance on its lower side. By raising the cap
and turning it so that the wires are vertical (J) or
horizontal (*->), the crucible or the platinum wire
extending into the fused mass can be made the anode
or cathode in a few seconds. E is a Kohlrausch
amperemeter (Fig. 15), and R the resistance frame
( Fi g- 13)-
Storage batteries furnish the most satisfactory cur-
rent for work of this character. In the sketch the
cells stand beneath the table ; the wire from the anode
passes through a hole in the table top, and is attached
to one of the binding posts of the block C, while the
positive wire is attached to a binding post at the end
of the table top, and from here it passes to the resist-
ance frame R y where it is fixed by an ordinary metal-
lic clamp.
For most purposes the strength of current need not
exceed 11.5 amperes per minute; however, it may
be necessary occasionally to increase it to 4 amperes
per minute. Pyrite, FeS 2 , is even then not completely
OXIDATIONS BY MEANS OF CURRENT. 113
decomposed. This particular case requires the addi-
tion of a quantity of cupric oxide equal in weight to
the pyrite, and a current of the strength last indi-
cated before all of its sulphur is fully converted into
sulphuric acid.
By increasing the number of crucibles it will be
possible to conduct at least from four to six of these
decompositions simultaneously, and by using a volu-
metric method for estimating the sulphuric acid, a
sulphur determination can easily be executed in forty
minutes.
Experience has demonstrated that 0.1-0.2 gram of
material will require about 20-25 grams of caustic
potash.
The arsenic in minerals is rapidly oxidized to
arsenic acid by this method.
Chromite also seems to be rapidly decomposed
when subjected to this treatment. Several quantita-
tive experiments have been carried out, and the
results obtained were very satisfactory.
INDEX.
AMPERE, 14
i* Amperemeter, 31
Anions, 9
Anode, 9
Antimony, determination of, 87-89
separation from arsenic, 102
bismuth, 99
copper, 92, 94
lead, 99
mercury, 98
silver, 101
tin, 102
Arsenic, determination of, 89
separation from antimony, 102
bismuth, 99
cadmium, 96
copper, 92
lead, 99
mercury, 98
silver, 101
tin, 103
D ATTERY, Bunsen, 19
*-* Crowfoot, 17
Daniell, 17
Grenet, 14
Grove, 19
Leclanche 16
Meidinger, 17
storage, 24
Bismuth, determination of, 59-61
separation from aluminium, antimo-
ny, arsenic, cadmium, chromium,
cobalt, iron, manganese, nickel,
tin, uranium, zinc, 98-99
separation from copper, 91
CADMIUM, determination of, 54-57
^ separation from aluminium, anti-
mony, arsenic, bismuth, cobalt,
iron, manganese, mercury, nickel,
silver, tin, uranium, zinc, 94-97
separation from copper, 90
molybdenum and tungsten,
108
Cathions, 9
Cathode, 9
Cobalt, determination of, 72-75
separation from bismuth, 99
cadmium, 94, 95
copper, 91
iron, 105, 106
manganese, 104
mercury. 97, 98
silver, 101
Copper, determination of, 47-54
separation from aluminium, 90, 91
antimony, 92, 94
arsenic, 93
bismuth, cobalt, iron lead,
nickel, uranium, zinc, 91
cadmium, 90
manganese, 92
mercury, 97
silver, 100
tin, 94
Current, action upon compounds, 10
ELECTROLYSIS, defined, 9
"OLD, determination of, 85
LJISTORICAL account, 32-46
IRON, determination of, 78-80
separation from aluminium, 106
bismuth, 99
cadmium, 94
cobalt, 105
copper, 91
lead, 99
manganese, 103
mercury, 97
nickel, 105, 106
silver, 64
zinc, 105
INDEX.
EAD, determination of, 62-63
' separation from aluminium, 99
antimony, 99
arsenic, 99
cadmium, 99
cobalt, 99
copper, 91, 99
iron, 99
mercury, 97, 99
nickel, 99
silver, 99, 100
uranium, 99
zinc, 99
AGNETO-machines, 21
M
Manganese, determination of, 75-78
separation from aluminium, 105, 106
bismuth, 99
cadmium, 94
cobalt, 106
copper, 92
iron, 103, 105
mercury, 97
nickel, 106
zinc, 106
Mercury, determination of, 57-59
separation from aluminium, cad-
mium, copper, iron, lead, 97
antimony, arsenic, tin, 98
from cobalt, nickel, zinc, 97, 98
molybdenum, 108
palladium, 107
tungsten, 108
Molybdenum, determination of, 84
separation from cadmium, mercury
and silver, 108
NICKEL, determination of, 72, 75
separation from aluminium, 106
bismuth, 99
cadmium, 94
cobalt, 94, 95
copper, 91
iron, 105, 106
lead, 99
manganese, 106
mercury, 97, 98
silver, 101
O HM ' '.3
^-s Osmium, 37
Oxidations by means of the current, 108
DALLADIUM, determination of, 83
separation from mercury, 107
Platinum, determination of, 82, 83
Phosphoric acid, separation, etc.,
103, 107
R
ESISTANCE coils and frames,
26, 27, 28
SILVER, determination of, 63-67
separation from aluminium, copper,
iron, lead, manganese, uranium,
100
antimony, arsenic, cobalt,
nickel, tin, zinc, 101
cadmium, 94
molybdenum and tungsten,
1 08
Sulphur, oxidation of, 108, 109
'TANGENT galvanometer, 30
Thallium, determination of, 81
Thermo-electric pile, 21
Tin, determination of, 85, 86
separation from antimony, 102
arsenic, 103
bismuth, 99
cadmium, 96
copper, 94
lead, 99
mercury, 98
U
RANIUM, determination of, 80
fOLT, 14
Voltameter, 29
'7INC, determination of, 67-72
^ separation from aluminium, 106
bismuth, 99
cadmium, 94, 95, 96
copper, 91
iron, 105
lead, 99
manganese, 106
mercury, 97, 98
silver, 101
JUST PUBLISHED.
FUEL AND ITS APPLICATIONS,
BY E. J. MILLS, D.SC.,F.R.*., AND F. J. ROWAN, C.E., ASSISTED
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the student, without embarrassing him with a flood of
theory and involved statements. They have been pre-
pared by well-known men, who have had large experience
as teachers and writers, and who are, therefore, well
informed as to the needs of the student.
Their mechanical execution is of the best good type
and paper, handsomely illustrated whenever illustrations
are of use, and strongly bound in uniform style.
Each book is sold separately at a remarkably low
price, and the immediate success of several of the
volumes shows that the series has met with popular
favor.
No. 1. SURGERY. 236 Illustrations.
A Manual of the Practice of Surgery. By WM. J.
WALSHAM, M.D., Asst. Surg. to, and Demonstrator of
Surg. in, St. Bartholomew's Hospital, London, etc.
228 Illustrations.
Presents the introductory facts in Surgery in clear, precise
language, and contains all the latest advances in Pathology,
Antiseptics, etc.
" It aims to occupy a position midway between the pretentious
manual and the cumbersome System of Surgery, and its general
character may be summed up in one word practical." The Medi-
cal Bulletin.
" Walsham, besides being an excellent surgeon, is a teacher in
its best sense, and having had very great experience in the
preparation of candidates for examination, and their subsequent
professional career, may be relied upon to have carried out his
work successfully. Without following out in detail his arrange-
ment, which is excellent, we can at once say that his book is an
embodiment of modern ideas neatly strung together, with an amount
of careful organization well suited to the candidate, and, indeed, to
the practitioner." British Medical Journal.
Price of each Book, Cloth, $3.00 ; Leather, $3.50.
THE NEW SERIES OF MANUALS.
No. 2. DISEASES OP WOMEN. 15O Illus.
NEW EDITION.
The Diseases of Women. Including Diseases of the
Bladder and Urethra. By DR. F. WINCKEL, Professor
of Gynaecology and Director of the Royal University
Clinic for Women, in Munich. Second Edition. Re-
vised and Edited by Theophilus Parvin, M.D.,
Professor of Obstetrics and Diseases of Women and
Children in Jefferson Medical College. 150 Engrav-
ings, most of which are original.
" The book will be a valuable one to physicians, and a safe and
satisfactory one to put into the hands of students. It is issued in a
neat and attractive form, and at a very reasonable price." Boston
Medical and Surgical Journal.
No. 3. OBSTETRICS. 227 Illustrations.
A Manual of Midwifery. By ALFRED LEWIS GALABIN,
M.A., M.D., Obstetric Physician and Lecturer on Mid-
wifery and the Diseases of Women at Guy's Hospital,
London; Examiner in Midwifery to the Conjoint
Examining Board of England, etc. With 227 Illus.
" This manual is one we can strongly recommend to all who
desire to study the science as well as the practice of midwifery.
Students at the present time not only are expected to know the
principles of diagnosis, and the treatment of the various emergen-
cies and complications that occur in the practice of midwifery, but
find that the tendency is for examiners to ask more questions
relating to the science of the subject than was the custom a few
years ago. * * * The general standard of the manual is high ;
and wherever the science and practice of midwifery are well taught
it will be regarded as one of the most important text-books on the
subject" London Practitioner.
No. 4. PHYSIOLOGY. Fourth Edition.
321 ILLUSTRATIONS AND A GLOSSARY.
A Manual of Physiology. By GERALD F. YEO, M.D.,
F.R.C.S., Professor of Physiology in King's College,
London. 321 Illustrations and a Glossary of Terms.
Fourth American from second English Edition, revised
and improved. 758 pages.
This volume was specially prepared to furnish students with a
new text-book of Physiology, elementary so far as to avoid theories
which have not borne the test of time and such details of methods
as are unnecessary for students in our medical colleges.
" The brief examination I have given it was so favorable that I
B'aced it in the list of text-books recommended in the circular of the
niversity Medical College." Prof. Lewis A. Stimson, M.D.,
3^ East 33d Street, New York.
Price of each Book, Cloth, $3.00; Leather, $3.50.
THE NEW SERIES OF MANUALS.
No. 5. ORGANIC CHEMISTRY.
Or the Chemistry of the Carbon Compounds. By Prof.
VICTOR VON RICHTER, University of Breslau. Au-
thorized translation, from the Fourth German Edition.
By EDGAR F. SMITH, M.A., PH.D. ; Prof, of Chemistry
in University of Pennsylvania; Member of the Chem.
Socs. of Berlin and Paris.
" I must say that this standard treatise is here presented in a
remarkably compendious shape." y. W. Holland, M.D., Professor
of Chemistry, Jefferson Medical College, Philadelphia.
" This work brings the whole matter, in simple, plain language,
to the student in a clear, comprehensive manner. The whole
method of the work is one that is more readily grasped than that of
older and more famed text-books, and we look forward to the time
when, to a great extent, this work will supersede others, on the
score of its better adaptation to the wants of both teacher and
student." Pharmaceutical Record.
" Prof, von Richter's work has the merit of being singularly
clear, well arranged, and for its bulk, comprehensive. Hence, it
will, as we find it intimated in the preface, prove useful not merely
as a text-book, but as a manual of reference." The Chemical
News, London.
No. 6. DISEASES OP CHILDREN.
SECOND EDITION.
A Manual. By J. F. GOODHART, M.D., Phys. to the
Evelina Hospital for Children ; Asst. Phys. to
Guy's Hospital, London. Second American Edition.
Edited and Rearranged by Louis STARR, M.D., Clinical
Prof, of Dis. of Children in the Hospital of the Univ.
of Pennsylvania, and Physician to the Children's Hos-
pital, Phila. Containing many new Prescriptions, a list
of over 50 Formulae, conforming to the U. S. Pharma-
copoeia, and Directions for making Artificial Human
Milk, for the Artificial Digestion of Milk, etc. Illus.
" The author has avoided the not uncommon error of writing a
book on general medicine and labeling it ' Diseases of Children,'
but has steadily kept in view the diseases which seemed to be
incidental to childhood, or such points in disease as appear to be so
peculiar to or pronounced in children as to justify insistence upon
them. * * * A safe and reliable guide, and in many ways
admirably adapted to the wants of the student and practitioner."
American Journal of Medical Science.
Price of each Book. Cloth, $3.00 ; Leather, $3.50.
THE NEW SERIES OF MANUALS.
No. 6. Goodhart and Starr : Continued.
" Thoroughly individual, original and earnest, the work evi-
dently of a close observer and an independent thinker, this book,
though small, as a handbook or compendium is by no means made
up of bare outlines or standard facts." The Therapeutic Ga-
zette.
" As it is said of some men, so it might be said of some books,
that they are 'born to greatness.' This new volume has, we
believe, a mission, particularly in the hands of the younger
members of the profession. In these days of prolixity in medical
literature, it is refreshing to meet with an author who knows both
what to say and when he has said it. The work of Dr. Goodhart
(admirably conformed, by Dr. Starr, to meet American require-
ments) is the nearest approach to clinical teaching without the
actual presence of clinical material that we have yet seen." New
York Medical Record.
No. 7. PRACTICAL THERAPEUTICS.
FOURTH EDITION, WITH AN INDEX OF DISEASES.
Practical Therapeutics, considered with reference to
Articles of the Materia Medica. Containing, also, an
Index of Diseases, with a list of the Medicines
applicable as Remedies. By EDWARD JOHN WARING,
M.D., F.R.C.P. Fourth Edition. Rewritten and Re-
vised by DUDLEY W. BUXTON, M.D., Asst. to the Prof,
of Medicine at University College Hospital.
" We wish a copy could be put in the hands of every Student or
Practitioner in the country. In our estimation, it is the best book
of the kind ever written. 'N. Y. Medical Journal.
No. 8. MEDICAL JURISPRUDENCE AND
TOXICOLOGY.
NEW, REVISED AND ENLARGED EDITION.
By John J. Reese, M.D., Professor of Medical Jurispru-
dence and Toxicology in the University of Pennsyl-
vania ; President of the Medical Jurisprudence Society
of Phila. ; 2d Edition, Revised and Enlarged.
" This admirable text-book." Amer.Jour. of Med. Sciences.
" We lay this volume aside, after a careful perusal of its pages,
with the profound impression that it should be in the hands of every
doctor and lawyer. It fully meets the wants of all students
He has succeeded in admirably condensing into a handy volume all
the essential points." Cincinnati Lancet and Clinic.
Price of each Book, Cloth, $3,00 ; Leather, $3.50.
6 STUDENTS' TEXT-BOOKS AND MANUALS.
ANATOMY.
Macalister's Human Anatomy. 816 Illustrations. A new
Text-book for Students and Practitioners, Systematic and Topo-
graphical, including the Embryology, Histology and Morphology
of Man. With special reference to the requirements of
Practical Surgery and Medicine. With 816 Illustrations,
400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50
Ballou's Veterinary Anatomy and Physiology. Illustrated.
By Wm. R. Ballou, M.D., Professor of Equine Anatomy at New
York College of Veterinary Surgeons. 29 graphic Illustrations.
I2mo. Cloth, i.oo; Interleaved for notes, 1.25
Holden's Anatomy. A manual of Dissection of the Human
Body. Fifth Edition. Enlarged, with Marginal References and
over 200 Illustrations. Octavo. Cloth, 5.00; Leather, &oo
Bound in Oilcloth, for the Dissecting Room, $4.50.
" No student of Anatomy can take up this book without being
pleased and instructed. Its Diagrams are original, striking and
suggestive, giving more at a glance than pages of text description.
* * * The text matches the illustrations in directness of prac-
tical application and clearness of detail." Ne^v York Medical
Record.
Holden's Human Osteology. Comprising a Description of the
Bones, with Colored Delineations of the Attachments of the
Muscles. The General and Microscopical Structure of Bone and
its Development. With Lithographic Plates and Numerous Illus-
trations. Seventh Edition. 8vo. Cloth, 6.00
Holden's Landmarks, Medical and Surgical. 4th ed. Clo., 1.25
Heath's Practical Anatomy. Sixth London Edition. 24 Col-
ored Plates, and nearly 300 other Illustrations. Cloth, 5.00
Potter's Compend of Anatomy. Fourth Edition. 117 Illus-
trations. Cloth, i.oo; Interleaved for Notes, 1.25
CHEMISTRY.
Bartley's Medical Chemistry. Second Edition. A text-book
prepared specially for Medical, Pharmaceutical and Dental Stu-
dents. With 50 Illustrations, Plate of Absorption Spectra and
Glossary of Chemical Terms. Revised and Enlarged. Cloth, 2. 50
Trimble. Practical and Analytical Chemistry. A Course in
Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem-
istry in the Phila. College of Pharmacy. Illustrated. Third
Edition. 8vo. Cloth, 1.50
JH&" See pages 2 to j for list of Students' Manuals.
STUDENTS' TEXT-BOOKS AND MANUALS. 7
Chemistry : Continued.
Bloxam's Chemistry, Inorganic and Organic, with Experiments.
Seventh Edition. Enlarged and Rewritten. 330 Illustrations*
Cloth, 4.50 ; Leather, 5.50
Richter's Inorganic Chemistry. A text-book for Students.
Third American, from Fifth German Edition. Translated by
Prof. Edgar F. Smith, PH.D. 89 Wood Engravings and Colored
Plate of Spectra. Cloth, 2.00
Richter's Organic Chemistry, or Chemistry of the Carbon
Compounds. Illustrated. Cloth, 3.00 ; Leather, 3.50
Symonds. Manual of Chemistry, for the special use of Medi-
cal Students. By BKANDRKTH SYMONDS, A.M., M.D., Asst.
Physician Roosevelt Hospital, Out- Patient Department; Attend-
ing Physician Northwestern Dispensary, New York. i2mo.
Cloth, 2.00 ; Interleaved for Notes, 2.40
Tidy. Modern Chemistry, ad Ed. Cloth, 5.50
Leffmann's Compend of Chemistry. Inorganic and Organic.
Including Urinary Analysis and the Sanitary Examination of
Water. New Edition. Cloth, i.oo; Interleaved for Notes, 1.25
Muter. Practical and Analytical Chemistry. Second Edi-
tion. Revised and Illustrated. Cloth, 2.00
Holland. The Urine, Common Poisons, and Milk Analysis,
Chemical and Microscopical. For Laboratory Use. 3d
Edition, Enlarged. Illustrated. Cloth, i.oo
Van Niiys. Urine Analysis. Illus. Cloth, 2.00
Wolff 's Applied Medical Chemistry. By Lawrence Wolff,
M.D.,Dem. of Chemistry in Jefferson Medical College. Clo.,i.oo
CHILDREN.
Goodhart and Starr. The Diseases of Children. Second
Edition. By T. F. Goodhart, M.D., Physician to the Evelina
Hospital for Children ; Assistant Physician to Guy's Hospital,
London. Revised and Edited by Louis Starr, M.D., Clinical
Professor of Diseases of Children in the Hospital of the Univer-
sity of Pennsylvania; Physician to the Children's Hospital,
Philadelphia. Containing many Prescriptions and Formulae,
conforming to the U. S. Pharmacopoeia, Directions for making
Artificial Human Milk, for the Artificial Digestion of Milk, etc.
Illustrated. Cloth, 3.00; Leather, 3.50
Hatfield. Diseases of Children. By M. P. Hatfield, M.D.,
Professor of Diseases of Children, Chicago Medical College.
i2mo. Cloth, i.oo; Interleaved, 1.25
Day. On Children. A Practical and Systematic Treatise.
Second Edition. 8vo. 752 pages. Cloth, 3.00; Leather, 4.00
9&~ See pages 14 and rf for list of f Quiz- Compends f
8 STUDENTS' TEXT-BOOKS AND MANUALS.
Children: Continued.
Meigs and Pepper. The Diseases of Children. Seventh
Edition. 8vo. Cloth, 5.00; Leather, 6.00
Starr. Diseases of the Digestive Organs in Infancy and
Childhood. With chapters on the Investigation of Disease,
and on the General Management of Children. By Louis Starr,
M.D., Clinical Professor of Diseases of Children in the Univer-
sity of Pennsylvania; with a section on Feeding, including special
Diet Lists, etc. Illus. Cloth, 2.50
DENTISTRY.
Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50
Flagg's Plastics and Plastic Filling. 3d Ed. Preparing.
Gorgas. Dental Medicine. A Manual of Materia Medica and
Therapeutics. Third Edition. Cloth, 3.50
Harris. Principles and Practice of Dentistry. Including
Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery
and Mechanism. Twelfth Edition. Revised and enlarged by
Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00
Richardson's Mechanical Dentistry. Fifth Edition. 569
Illustrations. 8vo. Cloth, 4.50; Leather, 5.50
Stocken's Dental Materia Medica. Third Edition. Cloth, 2.50
Taft's Operative Dentistry. Dental Students and Practitioners.
Fourth Edition, too Illustrations. Cloth, 4.25 ; Leather, 5.00
Talbot. Irregularities of the Teeth, and their Treatment.
Illustrated. 8vo. Cloth, 1.50
Tomes' Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00
Tomes' Dental Surgery. 3d Edition. Revised. 292 Illus.
772 Pages. Cloth, 5.00
DICTIONARIES.
Gould's New Medical Dictionary. Containing the Definition
and Pronunciation of all words in Medicine, with many useful
Tables etc. ^ Dark Leather, 3.25 ; ^ Mor., Thumb Index 4.25
See last page.
Cleaveland's Pocket Medical Lexicon. 3ist Edition. Giving
correct Pronunciation and Definition. Very small pocket size.
Cloth, red edges .75 ; pocket-book style, i.oo
Longley's Pocket Dictionary. The Student's Medical Lexicon,
giving Definition and Pronunciation of all Terms used in Medi-
cine, with an Appendix giving Poisons and Their Antidotes,
Abbreviations used in Prescriptions, Metric Scale of Doses, etc.
24010. Cloth, i.oo; pocket-book style, 1.25
KiT See pages 2 to 5 for list of Students' Manuals.
STUDENTS' TEXT-BOOKS AND MANUALS. 9
EYE.
Arlt. Diseases of the Eye. Including those of the Conjunc-
tiva, Cornea, Sclerotic, Iris and Ciliary Body. By Prof. Von
Arlt. Translated by Dr. Lyman Ware. Illus. 8vo. Cloth, 2.50
Hartridge on Refraction. 4th Ed. Cloth, 2.00
Meyer. Diseases of the Eye. A complete Manual for Stu-
dents and Physicians. 270 Illustrations and two Colored Plates.
8vo. Cloth, 4.50; Leather, 5.50
Fox and Gould. Compend of Diseases of the Eye and
Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae.
Cloth, i. oo ; Interleaved for Notes, 1.25
ELECTRICITY.
Mason's Compend of Medical and Surgical Electricity.
With numerous Illustrations. 12010. Cloth, i.oo
HYGIENE.
Parkes' (Ed. A.) Practical Hygiene. Seventh Edition, en-
larged. Illustrated. 8vo. Cloth, 4.50
Parkes 1 (L. C.) Manual of Hygiene and Public Health.
i2mo. ' Cloth, 2.50
Wilson's Handbook of Hygiene and Sanitary Science.
Sixth Edition. Revised and Illustrated. Cloth, 2.75
MATERIA MEDICA AND THERAPEUTICS.
Potter's Compend of Materia Medica, Therapeutics and
Prescription 'Writing. Fifth Edition, revised and improved.
Cloth, i.oo; Interleaved for Notes, 1.25
Biddle's Materia Medica. Eleventh Edition. By the late
John B. Biddle, M.D., Professor of Materia Medica in Jefferson
Medical College, Philadelphia. Revised, and rewritten, by
Clement Biddle, M.D., Assist. Surgeon, U. S. N., assisted by
Henry Morris, M.D. 8vo., illustrated. Cloth, 4.25; Leather, 5.00
Headland's Action of Medicines. 9th Ed. 8vo. Cloth, 3.00
Potter. Materia Medica, Pharmacy and Therapeutics.
Including Action of Medicines, Special Therapeutics, Pharma-
cology, etc. Second Edition. Cloth, 4.00 ; Leather, 5,00
Starr, Walker and Powell. Synopsis of Physiological
Action of Medicines, based upon Prof. H. C. Wood's " Materia
Medica and Therapeutics." 3d Ed. Enlarged. Cloth, .75
"Waring. Therapeutics. With an Index of Diseases and
Remedies. 4th Edition. Revised. Cloth, 3.00; Leather, 3.50
4&- See pages 14 and ij for list of f Quit- Compends f
10 STUDENTS' TEXT-BOOKS AND MANUALS.
MEDICAL JURISPRUDENCE.
Reese. A Text-book of Medical Jurisprudence and Toxi-
cology. By John J. Reese, M.D., Professor of Medical Juris-
prudence and Toxicology in the Medical Department of the
University of Pennsylvania ; President of the Medical Juris-
B-udence Society of Philadelphia; Physician to St. Joseph's
ospital ; Corresponding Member of The New York Medico-
legal Society. 2d Edition. Cloth, 3.00; Leather, 3.50
Woodman and Tidy's Medical Jurisprudence and Toxi-
cology. Chromo-Lithographic Plates and 116 Wood engravings.
Cloth, 7.50; Leather, 8.50
OBSTETRICS AND GYNAECOLOGY.
Byford. Diseases of Women. The Practice of Medicine and
Surgery, as applied to the Diseases and Accidents Incident to
Women. By W. H. Byford, A.M., M.D., Professor of Gynaecology
in Rush Medical College and of Obstetrics in the Woman's Med-
ical College, etc., and Henry T. Byford, M.D., Surgeon to the
Woman's Hospital of Chicago ; Gynaecologist to St. Luke's
Hospital, etc. Fourth Edition. Revised, Rewritten and En-
larged. With 306 Illustrations, over 100 of which are original.
Octavo. 832 pages. Cloth, 5.00 ; Leather, 6.00
Cazeaux and Tarnier's Midwifery. With Appendix, by
Munde. The Theory and Practice of Obstetrics ; including the
Diseases of Pregnancy and Parturition, Obstetrical Operations,
etc. By P. Cazeaux. Remodeled and rearranged, with revi-
sions and additions, by S. Tarnier, M.D., Professor of Obstetrics
and Diseases of Women and Children in the Faculty of Medicine
of Paris. Eighth American, from the Eighth French and First
Italian Edition. Edited by Robert J. Hess, M.D., Physician to
the Northern Dispensary, Philadelphia, with an appendix by
Paul F. Munde, M.D., Professor of Gynaecology at the N. Y.
Polyclinic. Illustrated by Chromo-Lithographs, Lithographs,
and other Full-page Plates, seven of which are beautifully colored,
and numerous Wood Engravings. Students' Edition. One
Vol., 8vo. Cloth, 5.00; Leather, 6.00
Lewers' Diseases of Women. A Practical Text-Book. 139
Illustrations. Second Edition. Cloth, 2.50
Parvin's Winckel's Diseases of Women. Second Edition.
Including a Section on Diseases of the Bladder and Urethra.
150 Illustrations. Revised. See page 3.
Cloth, 3.00; Leather, 3.50
Morris. Compend of Gynaecology. Illustrated. In Press.
Winckel's Obstetrics. A Text-book on Midwifery, includ-
ing the Diseases of Childbed. By Dr. F. Winckel, Professor
of Gynsecology, and Director of the Royal University Clinic for
Women, in Munich. Authorized Translation, by J. Clifton
Edgar, M.D., Lecturer on Obstetrics, University Medical Col-
lege, New York, with nearly 200 handsome illustrations, the
majority of which are original with this work. Octavo.
Cloth, 6.00; Leather, 7.00
Landis' Compend of Obstetrics. Illustrated. 4th edition,
enlarged. Cloth, i.oo; Interleaved for Notes, 1.25
t Pages 2 to 3 for list of New Manuals.
STUDENTS' TEXT-BOOKS AND MANUALS. 11
Obstetrics and Gynacology : Continued.
Galabin's Midwifery. By A. Lewis Galabin, M.D., F.K.C.P.
227 Illustrations. Seepages. Cloth, 3.00; Leather, 3.50
Glisan's Modern Midwifery. 2d Edition. Cloth, 3.00
Rigby's Obstetric Memoranda. 4th Edition. Cloth, .50
Meadows' Manual of Midwifery. Including the Signs and
Symptoms of Pregnancy, Obstetric Operations, Diseases of the
Puerperal State, etc. 145 Illustrations. 494 pages. Cloth, 2.00
Swayne's Obstetric Aphorisms. For the use of Students
commencing Midwifery Practice. 8th Ed. 12010. Cloth, 1.25
PATHOLOGY. HISTOLOGY. BIOLOGY.
Bowlby. Surgical Pathology and Morbid Anatomy, for
Students. 135 Illustrations. i2mo. Cloth, 2.00
Davis' Elementary Biology. Illustrated. Cloth, 4.00
Gilliam's Essentials of Pathology. A Handbook for Students.
47 Illustrations. i2mo. Cloth, 2.00
*** The object of this book is to unfold to the beginner the funda-
mentals of pathology in a plain, practical way, and by bringing
them within easy comprehension to increase his interest in the study
of the subject.
Gibbes' Practical Histology and Pathology. Third Edition.
Enlarged. i2mo. Cloth, 1.75
Virchow's Post-Mortem Examinations. 2d Ed. Cloth, i.oo
PHYSIOLOGY.
Yeo's
dents
's Physiology. Fourth Edition. The most Popular Stu-
nts' Book. By Gerald F. Yeo, M.D., F.R.C.S., Professor of
Physiology in King's College, London. Small Octavo. 758
pages. 321 carefully printed Illustrations. With a Full
Glossary and Index. See Page 3. Cloth, 3.00; Leather, 3.50
Brubaker's Compend of Physiology. Illustrated. Fifth
Edition. Cloth, i.oo; Interleaved for Notes, 1.25
Stirling. Practical Physiology, including Chemical and Ex-
perimental Physiology. 142 Illustrations. Cloth, 2.25
Kirke's Physiology. New i2th Ed. Thoroughly Revised and
Enlarged. 502 Illustrations. Cloth, 4.00; Leather, 5.00
Landois' Human Physiology. Including Histology and Micro-
scopical Anatomy, and with special reference to Practical Medi-
cine. Third Edition. Translated and Edited by Prof. Stirling.
692 Illustrations. Cloth, 6.50; Leather, 7.50
" With this Text-book at his command, no student could fail in
his examination." Lancet.
Sanderson's Physiological Laboratory. Being Practical Ex-
ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00
Tyson's Cell Doctrine. Its History and Present State. Illus-
trated. Second Edition. Cloth, 2.00
Hff- Set pages 14 and 15 for list of 'Quiz-Commends f
12 STUDENTS' TEXT-BOOKS AND MANUALS.
PRACTICE.
Taylor. Practice of Medicine. A Manual. By Frederick
Taylor, M.D., Physician to, and Lecturer on Medicine at, Guy's
Hospital, London; Physician to Evelina Hospital for Sick Chil-
dren, and Examiner in Materia Medica and Pharmaceutical
Chemistry, University of London. Cloth, 4.00
Roberts' Practice. New Revised Edition. A Handbook
of the Theory and Practice of Medicine. By Frederick T.
Roberts, M.D. ; M.R.C.P., Professor of Clinical Medicine and
Therapeutics in University College Hospital, London. Seventh
Edition. Octavo. Cloth, 5.50 ; Sheep, 6.50
Hughes. Compend of the Practice of Medicine. 4th Edi-
tion. Two parts, each, Cloth, i.oo; Interleaved for Notes, 1.25
PART i. Continued, Eruptive and Periodical Fevers, Diseases
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver,
Kidneys, etc., and General Diseases, etc.
PART n. Diseases of the Respiratory System, Circulatory
System and Nervous System ; Diseases of the Blood, etc.
Physician's Edition. Fourth Edition. Including a Section
on Skin Diseases. With Index, i vol. Full Morocco, Gilt, 2.50
Tanner's Index of Diseases, and Their Treatment. Cloth, 3.00
PRESCRIPTION BOOKS.
Wythe's Dose and Symptom Book. Containing the Doses
and Uses of all the principal Articles of the Materia Medica, etc.
Seventeenth Edition. Completely Revised and Rewritten. Just
Ready. 321110. Cloth, i.oo; Pocket-book style, 1.25
Pereira's Physician's Prescription Book. Containing Lists
of Terms, Phrases, Contractions and Abbreviations used in
Prescriptions Explanatory Notes, Grammatical Construction of
Prescriptions, etc.., etc. By Professor Jonathan Pereira, M.D.
Sixteenth Edition. 32mo. Cloth, i.oo; Pocket-book style, 1.25
PHARMACY.
Stewart's Compend of Pharmacy. Based upon Remington's
Text-Book of Pharmacy. Second Edition, Revised.
Cloth, i.oo ; Interleaved for Notes, 1.25
SKIN DISEASES.
Anderson, (McCall) Skin Diseases. A complete Text-Book,
with Colored Plates and numerous Wood Engravings. 8vo.
Just Ready. Cloth, 4.50; Leather, 5.50
Van Harlingen on Skin Diseases. A Handbook of the Dis-
eases of the Skin, their Diagnosis and Treatment (arranged alpha-
betically). By Arthur Van Harlingen, M.D., Clinical Lecturer
on Dermatology, Jefferson Medical College ; Prof, of Diseases of
the Skin in the Philadelphia Polyclinic. 2d Edition. Enlarged.
With colored and other plates and illustrations. 12010. Cloth, 2.50
Bulkley. The Skin in Health and Disease. By L. Duncan
Bulkley, Physician to the N. Y. Hospital. Illus. Cloth, .50
JKS~ See pages 2 to 3 for list of New Manuals.
STUDENTS' TEXT-BOOKS AND MANUALS. 13
SURGERY.
Caird and Cathcart. Surgical Handbook for the use of
Practitioners and Students. By F. MITCHELL CAIRO, M B.,
F.R.C.S., and C. WALKER CATHCART, M.B., F.R.C.S., Asst. Sur-
geons Royal Infirmary. With over 200 Illustrations. 400 pages.
Pocket size. Leather covers, 2.50
Jacobson. Operations in Surgery. A Systematic Handbook
for Physicians, Students and Hospital Surgeons. By W. H. A.
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