A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

THE ANTIMONY PREPARATIONS AND THEIR USES. 167
This pigment can be produced thus :—
Finely powdered sulphate of baryta . .2 parts.
Native sulphide of antimony . . . . 1 part.
Powdered charcoal . . . . . . 1 ,,
This mixture is calcined in a crucible of clay or graphite for several
hours up to red heat. The crucible should remain closed until it
becomes cold, because the carbonaceous matter contained in it might
become inflamed, with explosion, if it remained open. The calcined
mass is then boiled in water, and the insoluble residue—the sulphide
of barium and calcium—is used in the mixing of the material for
another operation. The filtered liquid has a pale-yellow colour.
Dilute sulphuric acid is then added to it until the orange colour is
entirely precipitated. The colour thus produced is mixed with blanc
fixe. If a purer orange hue is desired, the solution of sulpho-antimonite
of barium is boiled with \ part of sublimed sulphur. The sulphoantimonite
of barium is then transformed into sulpho-antimonate,
which has a composition analogous to that of Schlippe's salt.
A yellowish orange colour is obtained when, a dilute solution of
sulpho-antimonate of sodium is treated with a mixture consisting
of 1 kilo, of quicklime, dissolved in 25 litres of cold water, 1 kilo, of
sulphate of iron protoxide, 1 kilo, of sulphate of zinc, and alum in
amount varying according as the colour is required to be of a more
yellowish or less red hue.
(i) Orange-red Sulphide of Antimony.—The patent of MM.
Leclaire and Barruel is to the following effect:—1 part of natural
Sb^Sg is pulverised and dissolved, with the aid of heat, in 7 parts of
hydrochloric acid at 20° Be. The hydrogen sulphide given off from
the first operation is condensed in a solution of milk of lime. When
all the sulphide is dissolved, the acid solution of antimony chloride is
poured into stoneware vessels which have holes at different heights.
The liquor is diluted with water until it becomes turbid and a white
precipitate appears. Then this is put into demijohns and is submitted
to a stream of hydrogen sulphide. The liquor is occasionally
stirred with a wooden stick, and the vessels covered to prevent the
escape of the hydrogen sulphide, which is, however, led to a solution of
milk of lime by means of tubes, and is absorbed therein. The sulphide
thus obtained is washed and dried in a stove-room heated to from
40° to 50° C, but not higher; otherwise it loses much water and turns
black.
(?) Miscellaneous Pigments.—(a) A yellowish-red pigment can
be obtained by melting a mixture of 8 parts of the oxide with 2
parts of the sulphide together. This is known as crocus.