antimony - Sciencemadness.org

THE METALLURGY OF ANTIMONY.
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it. The presence of sodium hydrosulphido or of poly sulphides is not
objectionable so long as the proper proportion of sulphur to sodium is
kept (by the addition of soda); that is, every atom of oxidisable sulphur
must be accompanied by an atom of sodium capable of neutralisation.
Antimony glance is best suited for the treatment. For each
molecule of antimony trisulphide there should be present in the
solution three molecules of sodium sulphide; and after the extraction
is complete the concentration should not exceed 12° Baimae* (or 9° to
10°, if hot). To the electrolyte should be added 3 per cent, of
common salt, which not only assists the clearing of the solution by
the separation of dissolved sulphide of iron, but also reduces the
electrical resistance of the solution.
After the ore has been added the whole mass is stirred thoroughly
FIG. 57.
by a current of injected steam for an hour or longer. Air is admitted
from time to time through c on the steam-pipe b.
After two or three hours, when the mass has been sufficiently
heated and stirred, and the insoluble portion of the charge has
settled, the clear solution is drawn off, /, into the leaching vessel, #,
from which it is pumped through the pipe b and the channel i to the
reservoir k. The bell-shaped siphon arrangement, d, is used to
ensure that only the clear liquor is drawn off. From the reservoir,
the liquor is allowed to flow through sxiccessive electrolyte tanks, I;
finally, after being exhausted of its antimony, it flows through the
channel m into the tank n, from which it may be raised for further
circulation, or may be pumped to another part of the works for the
recovery of the thiosulphate, sulphur, or sodium chloride.
The residues from the first extraction are treated with fresh