antimony - Sciencemadness.org

tHE ANTIMONY PREPARATIONS AND THEIR USES. 16l
chloride of antimony. They are then dried and melted with a
certain proportion of antimony sulphide and quicklime, in order to
transform the whole into antimony green. The addition of a small
quantity of quicklime is intended for decomposing the small proportion
of chloride of antimony which may still remain in the
residues.
" 2. Preparation of the Hyposulphite of Lime.—This salt is cheaply
prepared by the action of sulphurous acid upon the sulphide or polysulphide
of calcium, or the oxysulphide. The sulphurous acid is
produced by burning brimstone or roasting pyrites or sulphide of
antimony.
"The polysulphide of calcium is prepared by boiling finely ground
sulphur with newly slaked lime and sufficient water. It is advantageous
to add to this solution of polysulphide a certain proportion
of powdered oxysulphide of calcium, which is the residue of the
lixiviation of crude soda. In the absence of oxysulphide, quicklime
may be added.
" Sulphurous acid, in its reaction upon the sulphide and oxysulphide
of calcium, sets sulphur free and forms a sulphite of lime,
which, in the presence of sulphur and undecomposed sulphide, is soon
transformed into hyposulphite of lime. The reaction is aided by
the elevation of temperature which takes place in the apparatus.
" The liquor is examined now and then to see whether it is alkaline,
neutral, or acid. As soon as it has become slightly acid, it is run
from the apparatus into a large settling-tank, where it generally
becomes neutralised by a certain quantity of undecomposed oxysulphide
of calcium held in it. If, after stirring for some time, the
liquor preserves its acid reaction, sulphide of calcium is added until
complete neutralisation is effected, which is ordinarily made apparent
by a black precipitate of sulphide of iron.
"After settling for some time, the clear liquid is decanted, and
forms a solution of nearly pure hyposulphite of lime. The same
vessel is subsequently used for neutralising the liquors obtained
during the process of manufacture.
" 3. Preparation of Vermilion of Antimony.—The red sulphide of
antimony is prepared with the above solutions of chloride of antimony
and of hyposulphite of lime.
" The apparatus consists simply of several wooden tanks, holding
from 20 to 30 hectolitres each, and raised about 1 metre above the
floor. These tanks are so arranged that they may be heated by
steam, passed through a copper or lead pipe, opening about 2 decimetres
from the bottom, or, what is preferable, through a coil of
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