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quantity of manganese passing in the filtrate be not disregarded
( 109, 1, a). The bases may also be precipitated with
ammonium carbonate instead of with sodium carbonate (65) ;
in fact it deserves the preference.


Precipitate boiling with sodium carbonate, wash the pre- 109
cipitate- with boiling water, dry, and ignite. If sufficient
zinc is present, the precipitate will consist of ZnO -f- a?Mn a O 8 .
Weigh off a portion of the precipitate and in it determine the
manganese as in 72. If insufficient zinc is present, proceed
as in 72 JV. B. Regarding the small quantity of manganese
passing into the filtrate see 109, 1 a.


Determine both metals as in 110, 1, &, and 2, and 111, 110
1, &, dissolve the reduced metals in hydrochloric acid with
the addition of some nitric acid, evaporate the solution repeat-
edly with hydrochloric acid to dryness until all the nitric acid
has been expelled, and in the solution of the chlorides then
determine the cobalt according to 111, 3, the nickel being
found by difference. The method is applicable only in the
presence of small quantities of nickel, and gives only fair

*Annal. de Cliem. u. Pharm., LXXXVII, 261.

666 SEPARATION. [ 161.

13. Indirect Method.


Of the many indirect methods proposed, but which are 111
now seldom resorted to since the introduction of volumetric
methods, I will give only the following : Dissolve in hydro-
chloric acid in a current of carbonic acid, add an excess of
gold and sodium chloride, stopper the flask, and allow the
precipitated gold to subside. Then filter, and determine the
gold as in 123. Determine the total quantity of iron in the
filtrate or in another portion of the substance. The calcula-
tion is readily made if it be remembered that 2 eq. of precipi-
tated gold are the equivalent of 6 eq. of ferrous chloride (or
oxide) thus: 6FeCl a + 2AuCl, = 2Au + 3Fe a Cl, (H. EOSE).



As these metals are found together in the analysis of most
silicates, and also in many other cases, I devote a separate para-
graph to the description of the methods which are employed
to effect their separation.

1. Method based upon the employment of Barium Car-
bonate (particularly applicable in cases where the mixture con-
tains only a small proportion of calcium).

The solution should contain no free chlorine, and the iron 112
should be all in the form of ferric salt. Precipitate the iron
and aluminium by barium carbonate * (54 and 76), dissolve the
precipitate in hydrochloric acid, throw down the barium with
sulphuric acid, filter, and estimate the iron and aluminium
according to one of the methods given in 160, by preference
104, at least when the quantity of aluminium is not too small.

To the filtrate from the barium -carbonate precipitate add
hydrochloric acid, heat, throw down the barium with sulphuric

* Before adding the barium carbonate, it is absolutely indispensable to ascer-
tain whether a solution of it in hydrochloric acid is completely precipitated by
sulphuric acid, so that the filtrate leaves no residue upon evaporation in a
platinum dish.

161.] BASES OF GROUP IV. 667

acid, added just in excess. Filter off the precipitate, wash till
free from soluble sulphate, concentrate if necessary, precipitate,
and determine the manganese as sulphide ( 109, 2). To the
filtrate add hydrochloric acid, heat, filter off the sulphur, pre-
cipitate the lime with oxalate of ammonia, and finally separate
the magnesia from the alkalies by one of the methods given

2. Method based upon the application of Alkali Acetates
or Formates.

Kemove by evaporation any very considerable excess of acid 113
which may be present, dilute, add sodium carbonate * until the
fluid is nearly neutral, then sodium acetate (or sodium formate)
and precipitate iron and aluminium, observing all directions
given in 85. Wash the precipitate well, dissolve in hydrochloric
acid, precipitate the solution with ammonia (45), dry, ignite,
and weigh. Dissolve in .concentrated hydrochloric acid and
determine the iron volumetrically with stannous chloride, as
in 113, 3, 5, or digest it with 16 times its weight of a
mixture of 8 parts sulphuric acid and 3 parts water, or fuse
it for a long time with potassium bisulphate, dissolve in
water, and determine the iron volumetrically as in 113,
3, a. The difference gives the quantity of the aluminium.
If any silicic acid remains behind on dissolving the pre-
cipitate, it is to be collected on a filter, ignited, weighed,
and deducted from the alumina. The filtrate contains the
manganese, the alkali-earth metals, and the alkalies. Pre-
cipitate the manganese with ammonium sulphide ( 109, 2),
boil with hydrochloric acid and filter off the sulphur, precipi-
tate the calcium, after addition of ammonia, with ammonium
oxalate, and lastly, after removing the ammonium salts by igni-
tion, precipitate the magnesium from the hydrochloric acid
solution of the residue with ammonium sodium phosphate.
However, if it is intended to estimate the alkalies, the magne-
sium must be separated by one of the processes in 153, 4. This

* In cases where it is intended to estimate the alkalies in the filtrate, ammo-
nium salts must be used instead of the sodium salts. If, however, it is
intended to precipitate manganese subsequently with bromine, ammonium
salts must not be introduced into the solution.

668 SEPARATION. [ 161.

method is convenient, and gives good results, especially in the
presence of much iron and little aluminium. Since aluminium
is not precipitated by alkali acetates or formates with the same
certainty as iron, it is necessary to test the weighed manganese
sulphide for aluminium.

[This method is to be recommended when manganese is pres-
ent with iron, or with iron and a moderate proportion of alumin-
ium. If, however, the amount of aluminium is large in propor-
tion to the iron, it is difficult to precipitate it completely with
sodium acetate. Instead of precipitating manganese with
ammonium sulphide it may be separated from calcium and
magnesium by precipitation with bromine. Add aqueous solu-
tion of bromine to the filtrate from the iron precipitate with-
out previous concentration of the filtrate, unless its volume
exceeds 600 or 700 c.c., and proceed according to 159, 72, d.

3. Method based upon the application of Ammonium Sul-
phide. .

Mix the fluid in a flask with ammonium chloride, then with 114
ammonia, until a precipitate just begins to form, then with
yellow ammonium sulphide, fill the flask nearly up to the top
with water, cork it, allow to settle in a warm place, filter, and
wash the precipitate consisting of iron and manganese sulphides
and aluminium hydroxide without interruption with water
containing ammonium sulphide. Separate the calcium, magne-
sium, and alkalies in the filtrate as in 113. Dissolve the precipi-
tate in hydrochloric acid, and separate the aluminium from
the iron and manganese according to 77 or 78, and then the
iron from the manganese, say by 82 or 85.

The following method is particularly suitable in cases
where no manganese is present, or only inappreciable traces:

4. Method lased upon the application of Ammonia.

a. The solution must contain all the iron in the state of a 115
ferric salt. Add a relatively large quantity of ammonium
chloride, and observing the precautions indicated in 45
precipitate with ammonia. The precipitate contains the whole
of the iron and aluminium ; at most an inappreciable amount
of the latter remains in solution if the free ammonia has been
almost but not entirely driven off by heat, if the solution was


diluted sufficiently, and if enough ammonium chloride was
present. It may also contain small quantities of calcium and
magnesium and a little manganese. It is well, therefore,
usually to redissolve the washed precipitate in hydrochloric
acid, and reprecipitate with ammonia. In this way the pre-
cipitate will be obtained free from alkali-earths and manganese.
Wash the precipitate completely, dry, ignite, and treat accord-
ing to 113. If silicic acid, remains undissolved, it is to be
determined and deducted. The solution filtered from the
aluminium and ferric hydroxide is concentrated by evaporation,
and the manganese is precipitated and determined according
to 109, 2, as sulphide; the alkali-earth metals and alkalies
in the filtrate are determined according to 113. The weighed
sulphide of manganese is .digested with dilute hydrochloric
acid ; any residue that may remain is fused with potassium
bisulphate, dissolved in water, and tested for aluminia.

5. Precipitate the aluminium, iron, and calcium by add- 116
ing ammonia and ammonium carbonate and oxalate, decant,
and filter. Dissolve the precipitate in hydrochloric acid, add
pure tartaric acid to prevent the aluminium and iron from
being precipitated, and then precipitate the calcium with
ammonia as an oxalate. In the solution separate the iron and
aluminium as in 77; and in the first filtrate the magnesium
arid alkalies according to 18. Should sulphuric acid be pres-
ent in the first filtrate, remove it by means of barium chloride,
then separate the alkali-earths from the alkalies by evaporat-
ing with oxalic acid, igniting, and treating the residue with
boiling water, and finally separate the barium from the mag-
nesium as in 29 (E. MITSCHEKLICH ; LEWINSTEIN *). As alu-
minium in the presence of ammonium oxalate is only grad-
ually precipitated on warming (PisANi), the liquid must be
digested for some time with heat before the first filtration;
and as the precipitate always contains a portion of the magne-
sium, I would advise that, after separating the iron from the
aluminium, the filtrate from the latter, as well as the alumina
itself, be tested for magnesia. If weighable quantities of
manganese are present, the method is inapplicable.

*Journ. f. prakt. Chem., LVIII, 99.

670 SEPARATION. [ 161.

c. Precipitate with ammonia, digest for some time with 117
heat, and until the greater part of the excess of ammonia has
been expelled, filter, carefully and thoroughly wash the pre-
cipitate, ignite, and add to the residue, without reducing it to
powder, at least ten times its quantity of anhydrous sodium
carbonate, cover the crucible and heat the mixture in a blast-
lamp or other suitable flame (an alcohol-lamp with double
draught is not sufficiently powerful) until no further decom-
position of the sodium carbonate is observed, for at least 45
minutes. Now add some caustic potassa to the fused mass, and
boil it with water (heat in a silver dish) until thoroughly ex-
tracted ; if a green color indicates that sodium manganate is
present add a few drops of alcohol, wash the precipitate by
decantation and filtration, first with water containing potassa,
then with pure water. Dissolve the precipitate in hydro-
chloric acid, add a few drops of alcohol, and heat in order to
more readily reduce the manganese chloride, and finally add
ammonium acetate to separate the iron from the portions of
manganese, calcium, and magnesium which were contained in
the ammonia precipitate, and which may be estimated sepa-
rately or together with the main quantities according to 113.
The aluminium is determined in the alkaline solution as in 78.

5. Method based on the Decomposition of the Ni-
trates (DEVILLE).

This method assumes that the bases are present as nitrates 118
only. Proceed first as in 46. The nitrous acid evolved dur-
ing the heating of the nitrate is no indication of the total de-
composition of the ferric or aluminium nitrate, because these
vapors may also be due to the conversion of manganous nitrate
into manganese dioxide. When all vapors cease to be evolved,
and the substance acquires a uniform black color, interrupt the
heat. After treatment witli ammonium nitrate there remains
in solution the nitrates of calcium, magnesium, and the alka-
lies, while the residue will contain aluminium, iron, manga-
nese dioxide, and if much manganese is present small quan-

*Journ.f. prakt. Chem., LXIV, 378.

161.]* BASES OF GROUP IV. 671

titles of alkaline earths. (That under certain circumstances
some manganese dissolves has already been stated in 71 ; this
trace is found with the magnesium, from which it is finally

DEVILLE recommends the following methods to further
effect the separation :

a. Heat the precipitate with moderately strong nitric acid
until the iron and aluminium are. dissolved, leaving the man-
ganese dioxide as a pure-black residue, which is ignited, and
the sesquioxide then weighed. Evaporate the solution in a
platinum crucible, ignite the residue, and weigh the mixture
of ferric oxide, alumina (and possibly some manganese sesqui-
oxide). Now treat a portion according to 91, and thus find
the alumina. If manganese was present, the iron cannot be
determined by difference. DEVILLE, therefore, evaporates the
solution of the chlorides (92) with sulphuric acid, ignites
gently, and treats the residual mixture of ferric oxide and
manganous sulphate with water to remove the manganese salt.
(In case too strong a heat has been applied, in which case the
manganous sulphate may also have been decomposed, moisten
the residue with a mixture of oxalic and nitric acids, add a
little sulphuric acid and repeat the ignition.)

b. From the filtrate precipitate first the calcium with
ammonium oxalate and then separate the magnesium as in
153, 4. In the presence of manganese this method is not to
be recommended.

6. Method which combines 4

Precipitate with ammonia (45), decant, filter, wash, 119
remove the still moist precipitate so far as possible from the
filter, dissolve the remainder in nitric acid and transfer this to
the dish to effect solution of the bulk of the precipitate, pro-
ceed according to 118, and mix the fluid separated from the
ferric oxide and alumina (and which contains small quantities
of magnesium, possibly also traces of calcium) with the main
filtrate. This method is to be recommended when manganese
is absent. The estimation of aluminium is best effected by
determining the total weight of the ferric oxide and alumin-
ium, and then determining the iron volumetrically (104). If

672 SEPARATION. [ 161.

on dissolving the precipitate of ferric oxide and alumina there
remains any silica, this must be deducted.

Supplement to the Fourth Group.
To 158, 159, 160.


It has already been stated, in 114, that uranium in uranyl 120
compounds cannot be completely separated from the alkalies
by means of ammonia, as the precipitated ammonium uranate
is likely to contain also fixed alkalies. The precipitate should
therefore be dissolved in hydrochloric acid, the solution evapo-
rated in the platinum crucible, the residue gently ignited in a
current of hydrogen gas (Fig. 83), the chlorides of the alkali
metals extracted with water, and the uranous oxide (UO a )
ignited in hydrogen in order to weigh it as UO a , or in the
air, whereby it is converted into uranous uranate, U(UO 4 ) a .
Instead of dissolving the precipitate in hydrochloric acid
and treating the solution as directed, you may .heat the
precipitate cautiously * with ammonium chloride and treat the
residue with water (II. ROSE). Uranium may be completely
separated from the alkalies also by ammonium sulphide,
as II. ROSE found. REMELEf has examined this subject
with great care and recommends the following method of pre-
cipitation : The solution being neutral or slightly acid, add an
excess of yellow ammonium sulphide and keep nearly boiling
for an hour to convert the first-formed precipitate of uranium
oxysulphide entirely into a mixture of uranous oxide and sul-
phur. The fluid, at first dark from presence of dissolved
uranium, will now appear yellow and transparent. Filter off
the precipitate containing all the uranium and wash it with
cold or warm water, first by decantation, finally on the filter.
It is well to mix a little ammonium sulphide or chloride with

Strong ignition would occasion the volatilization of uranium chloride,
\ Ztitechr.f. analyt. Chem., iv, 379.

161.] BASES OF GROUP IV. 673

the water, as when pure water is used the last filtrate is apt to
be turbid. The dried precipitate is roasted and then converted
into uranous uranate by ignition in the air, or into uranous
oxide by ignition in hydrogen ( 114).

FK. STOLBA * recommends separating uranyl from alkalies 121
by means of hydrosiliconuoric acid with the addition of alcohol.
Treat the substance with a sufficient quantity of 3- to 5-per
cent, aqueous silicofluoric acid and warm gently. As soon as
the yellow powder has disappeared, allow to cool, add 3 to 4:
volumes of 75- to 80-per cent, alcohol, mix, allow to settle in
the dark, or at least in a place not exposed to direct sunlight,
filter, wash with alcohol until the washings are absolutely free
from acidity, and determine the alkali volumetrically accord-
ing to 97. 5. Direct sunlight renders the alcoholic solution
cloudy, an insoluble uranium silicofluoride precipitating. If
the uranyl is to be estimated also, evaporate the alcoholic liquid,
heat the residue with an excess of sulphuric acid to expel
the hydrosilicofluoric acid, dissolve the residue in water with
the addition of some nitric acid, filter, and in the filtrate
determine the uranyl according to 114.

This method is also applicable for the analysis of uranyl-
alkali salts soluble in alcohol. It should be remarked here
that moderate quantities of hydrochloric or nitric acid do not
noticeably interfere, while sulphuric acid, by causing a pre-
cipitation of alkali sulphates, gives too low an alkali value.

From barium, uranyl may be separated by sulphuric acid ; 122
from strontium and calcium, by sulphuric acid and alcohol.
Ammonia fails to effect complete separation of uranyl from
the alkali-earth metals, the precipitate always containing not
inconsiderable quantities of the latter. In such precipitates,
hoWever, the uranium and the alkali-earth metals may like-
wise be separated by gentle ignition with ammonium chloride
and treatment of the residue with water.

Uranyl may be separated from strontium and calcium also 123
by precipitation with ammonium sulphide by the method given
above in the separation from the alkalies. As carbonates of the
alkali-earth metals may be coprecipitated, treat the washed pre-

* Zcitschr. f. analyt. Chem., in, 71.

674 SEPARATION. [ 161.


cipitate of uranous oxide and sulphur in the cold with dilute
hydrochloric acid which will not dissolve uranous oxide.
Ammonium sulphide will not answer for the separation of
uranium from barium (REMELE*).

Magnesium may be separated from uranyl not only by 124
ammonium sulphide in presence of ammonium chloride, but
also by ammonia. Add enough ammonium chloride to the
solution, heat to boiling, supersaturate with ammonia, continue
boiling till the odor of ammonia is but slight, filter the hot fluid,
and wash the precipitate, which is free from magnesium, with
hot water containing ammonia (H. HOSE). It is always well to
test the uranous oxide obtained by ignition in hydrogen for
magnesium by treating with dilute hydrochloric acid.

Aluminium is best separated from uranyl by mixing the
somewhat acid fluid with ammonium carbonate in excess. The
uranyl passes completely into solution, while the aluminium
remains absolutely undissolved. Filter, evaporate, add hydro-
chloric acid to resolution of the precipitate produced, heat till
all the carbonic acid is expelled, and precipitate with ammonia

( H4).

Uranyl is best separated from chromium (W. GiBBsf) by
adding to the solution soda in slight excess, heating to boiling
and adding bromine water, when the chromium is rapidly
converted into chromic acid. Filter the solution containing
sodium chromate from the precipitate which has a deep orange-
red color and consists of a compound of soda and uranic oxide
mixed with some uranyl chromate. Wash the precipitate with
hot water containing a little soda, dissolve it in hot nitric acid,
boil the solution a few minutes to drive off any nitrous acid, and
precipitate the chromic acid according to 130, I., , ft with
mercurous nitrate (according to GIBBS at a boiling heat). The .
filtrate now contains the whole of the uranium, of course in
presence of mercury.

The separation of uranyl from the metals of the fourth 125
group may be based simply on the fact that ammonium carbonate
prevents the precipitation <f nranvl, but. not that of the other
metals by ammonium sulphide. Mix the solution with a
mixture of ammonium carbonate and ammonium sulphide, allow

* Zeitichr.f. analyt. Cfiem., IV, 883. ^ Ib. t xn, 310.


to subside in a closed flask, and wash the precipitate with, water
containing ammonium carbonate and ammonium sulphide.

Remove the greater part of the excess of ammonium car-
bonate from the filtrate by a very gentle heat, acidify with
hydrochloric acid, warm, filter off the separated sulphur, and
throw down the uranium either by ammonium sulphide (see
above, Separation of Uranium from the Alkalies] or by
heating with nitric acid and then adding ammonia (H. ROSE,*
REMELEf). The method is not so suitable in presence of nickel,
as a little of this metal is very liable to pass into the filtrate
on precipitation with ammonium carbonate and ammonium

Ferric iron may be also separated from uranyl by means of
an excess of ammonium carbonate. The small quantity of iron
which passes with the uranium into solution will fall down on
allowing the solution to stand for several hours, or it may be
precipitated with ammonium sulphide, before the uranium is
thrown down (PisANiJ).

From nickel, cobalt, manganese, zinc, and magnesium
the uranyl may also be separated by barium carbonate. The
fiuid, which should contain a little free acid, is mixed with the
precipitant in excess, and allowed to stand in the cold for 24
hours with frequent shaking (76).

From cobalt, nickel, and zinc, uranyl may also be separated 126
(GIBBS and PEKKINS) by taking the neutral or slightly acid
solutions of the chlorides, adding sodium acetate in excess and
a few drops of acetic acid, and passing a rapid current of hydro-
gen sulphide for half an hour through the boiling fluid. The
uranium remains dissolved while the other metals are precipi-
tated. I should advise testing the filtrate with a mixture of
ammonium carbonate and ammonium sulphide to see if any
nickel, cobalt, or zinc remain in solution.

* Zeitschr.f. analyt. Chem., I, 412. \ Compt. rend., LII, 106.

f lb., iv, 385. Zeitschr. /. analyt. Chem., in, 334.

676 SEPARATION. [ 162.

Fifth Group.





INDEX. (The numbers refer to those in the margin.)

Silver from the metals of Groups I. IV., 127, 128.
Mercury (in mercurous and mercuric compounds) from the

metals of Groups I. IV., 127, 129.
Lead from the metals of Groups I. IV., 127, 130.

" manganese, 142.
Bismuth from the metais of Groups I. IV., 127, 140.

" manganese, 142.

Copper from the metals of Groups I. IV., 127, 131, 132,

133, 134, 135.

Copper from zinc, 136, 137.
" manganese, 142.

iron, 138.
" nickel, 139.

Cadmium from the metals of Groups I. IV., 127.
" zinc, 105.

" manganese, 142.

A. General Method.


Principle : Hydrogen Sulphide precipitates from Acid
Solutions the Metals of the Fifth Group, but not those of the
first Four Groups.

The following points require especial attention in the execu
tion of the process :

a. To effect the separation of the metals of the fifth group 1
from those of the first tlnve groups, by means of hydrogen
sulphide, it is necessary simply that the reaction of the solution
should be acid, the nature of the acid to which the reaction is
due being of no consequence. But, to effect the separation of
the metals of the fifth group from those of the fourth, the
presence of a free mineral acid is indispensable ; otherwise zinc
and, under certain ciiviiinMances, also cobalt and nickel may be

162.] BASES OF GEOUP V. 677

{3. But even the addition of hydrochloric acid to the fluid

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