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phide to the wash-water, and keep the filter as full as possible with
the same. We guard against the filtrate running through turbid,
by adding gradually decreasing quantities of ammonium chloride to
the wash-water (at last none). (Expt. No. 40.) On igniting the
precipitate mixed with sulphur in a stream of hydrogen the
anhydrous sulphide remains. If we have gently ignited during
this process, the product is light green; if we have strongly
ignited, it is dark green to black. Neither the" green nor the
black sulphide attracts oxygen or water quickly from the air
(II. EOSE). The anhydrous sulphide is also readily soluble in
dilute acids.


Mn .... 55-00 63-17

S 32-07 36-83

87-07 100-00

f. Anhydrous manganous sulphate, produced by exposing the
crystallized salt to the action of heat, is a white, friable mass,
readily soluble in water. It resists a very faint red heat ; but
upon exposure to a more intense red heat, it suffers more or less
complete decomposition oxygen, sulphur dioxide, and sulphur
trioxide being evolved, and protosesquioxide of manganese re-
maining behind. Ignited with sulphur in a stream of hydrogen it
is transformed into sulphide (II. EOSE).


xtiU'if MnO 71-00 47-00

' Ua < O " ' SO 3 . . . 80-07 53-00

151-07 100-00

g. Ammonium, manganese phosphate. GIBBS* says that this
precipitate is insoluble in boiling wnter, but I have not found this
to be the case. My results are that 1 part dissolves in 32092 parts
of cold w;itM-, in 20122 parts boiling water, and 17755 parts of
water containing ^ of ammonium chloride. It has the formula

*Sillim. Amer. Journ. (n), 44, 216.


NH 4 MnPO 4 -f- II 2 O. It presents pale pink scales of pearly
lustre, which sometimes turn reddish on the filter. On ignition it
is converted into manganese pyrophosphate.

h. Manganese pyrophosphate is the white residue left on the
ignition of the preceding.


_ n

\PO<g>Mn~ P *> J^

284 100


Nickel is precipitated as HYDROXIDE, and as SULPHIDE. It is
weighed in the form of NICKELOUS OXIDE, of METALLIC. NICKEL, or

a. Nickelous hydroxide forms an apple-green precipitate,
almost absolutely insoluble in water. "When precipitated from a
solution of the chloride or sulphate, it retains some of the acid
even after long washing (TEICHMANN*). It is also very difficult to
remove the last traces of alkali. It dissolves with some difficulty
in ammonia and ammonium carbonate, far more readily in the
presence of an ammonium salt. From these solutions it is com-
pletely precipitated by excess of potassa or soda; application of
heat promotes the precipitation. It is unalterable in the air ; on
ignition, it passes into nickelous oxide.

l>. Nickelous oxide is a dirty grayish-green powder. When
obtained by heating the nitrate to redness, it always contains some
nickelic oxide, and requires very strong and protracted ignition for
conversion into the pure green nickelous oxide (W. J. RUSSELL).
It is insoluble in water, bult readily soluble in hydrochloric acid.
It does not affect vegetable colors. It suffers no variation of
weight upon ignition with free access of air. Mixed with am-
monium chloride and ignited, it is reduced to metallic nickel
(H. ROSE) ; it is also easily reduced by ignition in hydrogen or
carbon monoxide.


M . . . 58-7 78-58

O 16-0 21-42

74-7 100-00

*Annal. d. Chem. u. Pharm., CLVI, 17.

190 FORMS. [ 79.

c. Metallic nickel obtained by the reduction of nickelous oxide
with hydrogen has the form of a gray powder, or if the heat lias
been very strong, and it lias melted, it is lustrous and white like
silver. It is unaltered in weight by ignition in hydrogen ; when
ignited in the air it is superficially oxidized. It is attracted by
the magnet. It is dissolved slowly by hydrochloric acid and dilute
sulphuric acid, and readily by moderately strong nitric acid.

d. Anhydrous nickelous sulphate obtained by evaporating a
solution of the chloride, nitrate, &c., with sulphuric acid is yellow,
soluble in water to a green fluid. The hydrous salt may be
rendered anhydrous without loss of acid by cautious heating in a
platinum dish, but at low redness it begins to blacken at the edges
and loses acid (F. GAUHE*).

e. Ilydrated nickelous sulphide, prepared in the wet way,
forms a black precipitate, insoluble in water. I must make some
observations on its precipitation.f In order to precitate the nickel
from a pure solution completely and with ease, ammonium chloride
must be present ; it is not enough to add ammonium sulphide
alone. A large quantity even of ammonium chloride produces no
injurious effect. In the presence of free ammonia, on the con-
trary, some nickel remains in solution. In this case, the super-
natant fluid appears brown. As precipitant, colorless or light-
yellow ammonium sulphide containing no free ammonia should 1 >e
used, a large excess must be avoided. If the directions given are
adhered to allowing to stand 48 hours the nickel may be pre-
cipitated by means of ammonium sulphide, from solutions con-
taining only THTTF OTTT ^ * ne oxide. As the precipitate is liable to
take up oxygen from the air, being transformed into sulphate, a
little ammonium sulphide is mixed with the wash-water, to which
also it is advisable to add ammonium chloride (less and less at
last none); the filter should be kept full (Expt. No. 41). Brown
filtrates, containing nickel sulphide in solution, may be freed from
the latter by acidulation with acetic acid, and boiling some time.
The sulphide falls down, and may now be filtered off. It is very
sparingly soluble in concentrated acetic acid, somewhat more
soluble in hydrochloric acid. It is more readily soluble still in
nitric acid, but its best solvent is nitro-hydrochloric acid. It loses
its water upon the application of a red heat ; when ignited in the
air, it is transformed into a basic compound of nickelous oxide
with sulphuric acid. Mixed with sulphur and ignited in a stream

* Zritofhr. f. analyt. Cfom., iv, 190. \Journ. f. prakl. Chem., LXXXII, 251.


of hydrogen, a fused mass remains, of pale yellow color and me-
tallic "lustre. Tins consists of Xi a S, but its composition is not
perfectly constant (F. GAUHE *). On heating a solution of a nickel-
ous salt with an excess of sodium thiosulphate in a sealed glass
tube at 120, all the nickel will be precipitated in the course of
half an hour as a sulphide (2MC1 2 + 2Na 2 S 2 O 3 = Ni.S + 2NaCl
+ Ka,S 3 O 6 ). The sulphide so obtained is black, and unchange-
able in air ; it may be readily washed, is almost unaffected by
hydrochloric or dilute sulphuric acid, and it may be converted
into nickelous. sulphate by dissolving it in nitric acid and
evaporating the solution with sulphuric acid (W". GIBBS f).
[Nickel may be precipitated as a sulphide, dense in form, easy
to wash, and not readily oxidizing by contact with air, by proceed-
ing as follows : To the solution, which should be concentrated and
contain a liberal quantity of ammonium salts, add ammonia (if
necessary) to alkaline reaction, then acetic acid to slight acid reac-
tion, also ammonium or sodium acetate, .and heat to boiling.
Transmit H 2 S gas through the boiling solution. Since much free
acetic acid prevents complete precipitation, it is necessary some-
times when much nickel is present to partially neutralize once or
twice the acid set free during the process.]


Cobalt is weighed in the PURE METALLIC state, or as COBALTOUS
SULPHATE. Besides the properties of these substances, we have to
study also those of COBALTOUS HYDROXIDE, of the SULPHIDE, and of


a. Cobaltous hydroxide. Upon precipitating a solution of a
cobaltous salt with potassi, a blue precipitate (a basic salt) is
formed at first, which, upon boiling with potassa in excess, exclud-
ed from contact of air, changes to light red cobaltous hydroxide ;
if, on the contrary, this 7 process is conducted with free access of
air, the precipitate becomes discolored, and finally black, part of
the cobaltous hydroxide being converted into cobaltic hydroxide.
But the hydroxide prepared in this way, retains always a certain
quantity of the acid, and, even after the most thorough washing

* ZeitscJir. f. analyt. Chem., iv, 191.
f Ib. , in, 389.

192 FORMS. [ 80.

with hot water, also a small amount of the alkaline precipitant.
The latter, however, is not enough to spoil the accuracy of the
results (II. ROSE, F. GAUHE*). Cobaltous hydroxide is insoluble
in water, and also in dilute potassa ; it is somewhat soluble in very
concentrated potassa, and readily in ammonium salts. When dried
in the air, it absorbs oxygen, and acquires a brownish color. By
strong ignition it is converted into cobaltous oxide (even if some
higher oxide had formed from boiling or drying in the air) ; if
cooled with exclusion of air, as in a current of carbon dioxide,
pure light.brown cobaltous oxide will be left ; if cooled, on the
contrary, with access of air, it is more or less changed to black
protosesquioxide (cobaltoso-cobaltic oxide) (W. J. RussELi/f-). By
ignition in a current of hydrogen, metallic cobalt is left, from
which any traces of alkali may now be almost completely removed
by boiling water.

b. The metallic cobalt obtained according to a, or by igniting
the chloride or the protosesquioxide (produced by igniting the
nitrate) in hydrogen is a grayish-black powder, which is attracted
by the magnet, and is more difficultly fusible than gold. If the
reduction has been effected at a faint heat, the finely divided metal
burns in the air to protosesquioxide of cobalt, which is not the
case if the reduction has been effected at an intense heat. Cobalt
does not decompose water, either at the common temperature,
or upon ebullition except sulphuric acid be present, in which
case decomposition will ensue. Heated with concentrated sul-
phuric acid, it forms cobaltous sulphate, with evolution of sulphur
dioxide. In nitric acid it dissolves readily to cobaltous nitrate.

c. Cobalt sulphide, produced in the wet way, forms a black
precipitate, insoluble in water, alkalies, and alkali sulphides. "With
regard to its precipitation,^: this is effected but slowly and im-
perfectly by ammonium sulphide alone; in the presence of am-
monium chloride however, it takes place quickly and completely.
Free ammonia is not injurious ; it is all one, whether colorless or
yellow ammonium sulphide is employed. If the directions given
are observed, cobalt may be precipitated from a solution contain-
ing no more than TnroVor f * ne protoxide. In the moist con-
dition, exposed to the air, it oxidizes to sulphate. In washing it,
therefore, water containing ammonium sulphide is employed, and
the lilter is kept full. It is ad\ i>alle also to mix a little ammo-

* Zeitte/tr.f. analyt. Chem., iv, 54. \ Ib. t u, 471.

\ Journ. f. prakt. Chem., LXXXII, 262.


nium chloride with the wash- water, but its quantity should be
gradual fy decreased, and the last water used must contain none.
It is but sparingly soluble in acetic acid and in dilute mineral
acids, more readily in concentrated mineral acids, and most readily
in warm nitro-hydrochloric acid. Mixed with sulphur and ignited
in a stream of hydrogen, we obtain a product which varies in
composition according to the temperature employed. The residue
is therefore not suited for the determination of cobalt (II. ROSE).
Cobalt can be precipitated as sulphide completely in the presence
of a very small amount of free acetic acid by hydrogen sulphide,
or by heating with an excess of sodium thiosulphate in a
sealed tube (W. GIBBS, Zeitschr.f. analyt. Chem., in, 390), in
the same manner as nickel (see 79, e). Cobalt sulphide may be
converted into cobaltous sulphate by heating in the air, moistening
with nitric acid, evaporating with sulphuric acid and igniting.

d. Cobctltous sulphate crystallizes, in combination with 7 aq.,
slowly in oblique rhombic prisms of a fine red color. The crystals
yield the whole of the water, at a moderate heat, and are con-
verted into a rose-colored anhydrous salt, which bears the applica-
tion of a low red heat without losing acid. At a stronger heat the
edges become black and some sulphuric acid escapes (F. G-AUHE*).
It dissolves rather difficultly in cold, but more readily in hot water.


^ (K _CoO . 75-00 48-37
U 2 < Q - -so, 80-07 51-63

155-07 100-00

e. Tripotassium cobaltic nitrite. If a solution of a cobalt salt
(not too dilute) is mixed with excess of potassa and then with
acetic acid till the precipitate is redissolved, and a concentrated
solution of potassium nitrite previously acidified with acetic acid is
added, first a dirty, brownish precipitate forms which gradually
turns yellow and crystalline, especially on the application of a
gentle heat (K. W. FISCHER-^). The composition of this precipi-
tate corresponds to the formula (KN"O t ),Co 1 (N"O t ), + aq =
CoK 3 (NO 2 ) 6 + aq. (SADTLER). Dried at 100 its composition is
somewhat variable (STROMEYER, ERDMANN^:). It is" decidedly

* Zeitschr.f. analyt. Chem., iv, 55. \Pogg. Ann., LXXII, 477.

J Journ. f. prakt. CJiem., cxvn, 385.

194 FORMS. [ 81

soluble in water, less in potassium acetate whether neutral or
acidified with acetic acid, not in potassium acetate to which some
potassium nitrite has been added, not in potassium nitrite, nor in
80-per cent, alcohol. On washing with water or solution of potas-
sium acetate, unless potassium nitrite is added, nitric oxide is con-
stantly evolved in small quantities. It is decomposed with separa-
tion of brown cobaltic hydroxide, with difficulty by solution of
potassa, with ease by soda or baryta. On being moistened with
sulphuric acid and ignited (finally with addition of ammonium
carbonate) it leaves 2(CoSO 4 ) + 3(K 2 S0 4 ), but there is a diffi-
culty in driving off all the excess of acid without decomposing the
cobaltous sulphate. The yellow salt is soluble in hydrochloric
acid ; potassa precipitates the whole of the cobalt from this solu-
tion as hydroxide.


Iron is usually weighed in the form of FERRIC OXIDE, occasion-
ally as SULPHIDE. We have to study also the FERRIC HYDROXIDE,


a. Ferric hydroxide, recently prepared, is a reddish-brown
precipitate, insoluble in water, in dilute alkalies, and in ammonium
salts, but readily soluble in acids ; it shrinks very greatly on
drying. When dry, it presents a brown, hard mass, with shining
conchoidal fracture. If the precipitant alkali is not used in excess,
the precipitate contains basic salt ; on the other hand, if the alkali
has been used in excess, a portion of it is invariably carried down
in combination with the ferric hydroxide, on which account
ammonia alone can properly be used in analysis for this purpose.
Under certain circumstances, for instance, by protracted heating of
a solution of ferric acetate on the water-bath (which turns the
solution from blood-red to brick-red, and makes it appear turbid
ly reflected light), and subsequent addition of some sulphuric acid
or salt of an alkali, a reddish-brown hydrated ferric oxide is pro-
duced, \vhich is insoluble in cold acids, even though concentrated,
and is not attacked even by boiling nitric acid (L. PEAN DE ST.

Closely allied to ferric hydroxide are the highly basic salts
obtained by mixing dilute cold solutions of ferric salts, best ferric
chloride, with much ammonium chloride, cautiously adding am-

*Journ.f. prakt. Chem., LXVI, 137.


monium carbonate till the fluid on standing in the cold instead of
becoming clear turns more turbid if anything, and then boiling.
The precipitates, thus produced in the fluid which still retains its
acid reaction, contain the whole of the iron present and play an
important part in analytical separations. They should be washed
with boilino; water containing ammonium chloride, being 1 soluble to

O O o

a slight extent in pure water. They are not suitable for ignition,
as ferric chloride might occasionally escape from them.

1. Ferric hydroxide is, upon ignition, converted into ferric
oxide. If the hydroxide has been superficially dried only, the
violent escape of steam from the lumps is likely to occasion loss;
but if it has been dried as much as possible by suction and still
remains moist, it may be ignited without fear of loss. Pure ferric
oxide, when placed upon moist reddened litmus-paper, does not
change the color to blue. It dissolves slowly in dilute, but more
rapidly in concentrated hydrochloric acid ; the application of a
moderate degree of heat effects this solution more readily than
boiling. With a mixture of 8 parts concentrated sulphuric acid
and 3 parts water, it behaves in the same manner as alumina. The
weight of ferric oxide does not vary upon ignition in the air;
when ignited with ammonium chloride, ferric chloride escapes.
Ignition with charcoal, in a closed vessel, reduces it more or less.
Strongly ignited with sulphur in a stream of hydrogen, it is trans-
formed into ferrous sulphide.


Fe 2 111:8 69-96

O/ 48-0 30-04

159-8 100-00

c. Ferrous sulphide, produced in the wet way, forms a black
precipitate. The following facts are to be noticed with regard
to its precipitation.* Ainihonium sulphide used alone, whether
colorless or yellow, precipitates pure neutral solutions of ferrous
salts, but slowly and imperfectly. Ammonium chloride acts very
favorably ; a large excess even is not attended with inconvenience.
Ammonia has no injurious action. It is all the same whether the
ammonium sulphide be colorless or light yellow. If the direc-

* Jo-urn. /. prakt. Chem., LXXXII, 268.

196 FORMS. [ 81.

tions given are observed, iron may be precipitated by means of
ammonium sulphide, from solutions containing only TFlr J innr of
ferrous oxide. In such a case, however, it is necessary to allow to
stand forty-eight hours. Since the precipitate rapidly oxidizes in
contact with air, ammonium sulphide is to be. added to the wash-
water, and the filter kept full. It is well also to mix a little
ammonium chloride with the wash-water, but the quantity should
be continually reduced, and the last water used should contain
none. In mineral acids, even when very dilute, the hyd rated
sulphide dissolves readily. Mixed with sulphur, and strongly
ignited in a stream of hydrogen, anhydrous ferrous sulphide re-
mains (H. HOSE).


Fe 55-90 63-54

S 32-07 36-46

87-97 100-00

d. When a neutral solution of a ferric salt is mixed with a
neutral solution of an alkali succinate, a cinnamon-colored pre-
cipitate of a brighter or darker tint of a basic ferric succinate is
formed, Fe(OH)C 4 H 4 O 4 , succinic acid being set free. From the
nature of this precipitate it must follow that, in its formation,
one equivalent of succinic acid (using an excess of ammonium
Buccinate) must be liberated, as follows :

Fe,(SO,), + 3(NII.)AH.O. + 2H.O

= 2Fe(OH)C,H.O. + 3(NII,),SO 4 + H.-O.H.O..

The free succinic acid does not exercise any perceptible sol-
vent action upon the precipitate in a cold and highly dilute solu-
tion, but it redissolves the precipitate a little more readily in a
warm solution. The precipitate must therefore be filtered cold,
if we want to guard against re-solution. Formerly the precipi-
tate was erroneously supposed to consist of a normal salt, de-
composable by hot water into an insoluble basic and a soluble acid
compound. Basic ferric succinate is insoluble in cold, and but
sparingly soluble in hot, water, containing for every equivalent of


succinic acid, II a *C 4 H 4 O 4 , from 18 to 30 equivalents of
Fe a O 3 . * It dissolves readily in mineral acids. Ammonia,
especially if warm, deprives it of the greater portion of its acid,
leaving compounds which are highly basic ferric succinates

e. If to a solution of a ferric salt, sodium carbonate be added
in the cold, till the fluid contains no more free acid, and in con-
sequence of the formation of basic salt has become deep red, but
remains still perfectly clear, and then sodium acetate be poured
in and the mixture boiled, the whole of the iron will be precipi-
tated as basic ferric acetate.

The precipitation is successfully effected in this operation by
having the ferric salt solution sufficiently dilute, that the free
acid be properly neutralized, and that sufficient sodium acetate be
added. The duration of boiling is of little consequence ; when
proper proportions have been used, one boiling-up suffices. Of
course it is understood that all the iron must be ferric. Instead
of sodium carbonate or acetate the corresponding ammonium salts
will answer also. The precipitates may, as a rule, be filtered off
and well washed without any ferric oxide passing into the filtrate ;
at times, however, the reverse may happen. I should advise not
to boil longer than is necessary to precipitate, then filter while
hot, and to add to the boiling wash-water some sodium- or ammo-
nium acetate ; this can cause no inconvenience, because the pre-
cipitate is usually redissolved in hydrochloric acid, and reprecipi-
tated with ammonia water.

f. Instead of the sodium- or ammonium acetate used in 0, the
corresponding formates may be used. The basic ferric formate
obtained in this case is more easily washed than the basic acetate

* Chem> Centralblatt, 1861, 3.

198 FORMS. [ 82.



Silver may be weighed in the METALLIC state, as CHLORIDE, SUL-

a. Metallic silver, obtained by the ignition of salts of silver
with organic acids, &c., is a loose, white, glittering mass of metallic
lustre; but, when obtained by reducing silver chloride, &c., in the
wet way, by zinc, it is a dull-gray powder. It fuses at about 1000.
Its weight is not altered by moderate ignition. It may, however,
be distilled by the heat of the oxy hydrogen flame (CHRISTOMANOS*).
It dissolves readily and completely in dilute nitric acid.

I. Silver chloride, recently precipitated, is white and curdy.
On shaking, the large spongy flocks combine with the smaller
particles, so that the fluid becomes perfectly clear. This result is,
however, only satisfactorily effected when the flocks have been
recently precipitated in presence of excess of silver solution (com-
pare G. J. MULDER f). Silver chloride is in a very high degree
insoluble in water, and in dilute nitric acid ; strong nitric acid, on
the contrary, does dissolve a trace. Hydrochloric acid, especially
if concentrated and boiling, dissolves it very perceptibly. Accord-
ing to PIERRE, 1 part of silver chloride requires for solution 200
parts of strong hydrochloric acid and 600 parts of a dilute acid,
composed of 1 part strong acid and 2 parts water. On sufficiently
diluting such a solution with cold water the silver chloride is pre-
cipitated so completely that the filtrate is not colored by hydrogen
Milphide. Silver chloride is insoluble, or very nearly so, in con-
centrated sulphuric acid; in the dilute acid it is as insoluble as in
water. In a solution of tartaric acid silver chloride dissolves per-
ceptibly on warming; on cooling, however, the solution deposits
the whole, or, at all events, the greater part of it. Aqueous solu-
tions of chlorides (of sodium, potassium, ammonium, calcium, /inc,

* Zeitscfir. f. analyt. Chem., vn, 299.

f Die Silberprobirmethode, translated into German by D. Cim. GRIMM, pp.
19 and 311. Leipzig : J. J. Weber. 1859 .

82.] BASES OF GROUP V. 199

&c.) all dissolve appreciable quantities of silver chloride, especially
if they sfre hot and concentrated. On sufficient dilution with cold
water the dissolved portion separates so completely that the filtrate
is not colored by hydrogen sulphide. The solutions of alkali and
alkali-earth nitrates also dissolve a little silver chloride. The solu-
bility in the cold is trifling ; in the heat, on the contrary, it is very
perceptible. A strong solution of silver nitrate dissolves it slightly,
especially in the heat ; but I have found it insoluble in a moder-
ately dilute cold solution of lead nitrate. The action of mercuric
salts upon it is remarkable. When well washed and treated with a
very dilute solution of mercuric chloride it becomes white if pre-

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