antimony - Sciencemadness.org

THE METALLURGY OF ANTIMONY. 123
acid. The chloride thus formed in solution is treated with water,
which precipitates it as basic chloride; the chloride solution may be
precipitated by hydrogen sulphide.
Rud. Koepp & Co. patented a process to use ferric chloride as a
solvent.
3Fe2Cl6 + Sb2S3= 6FeCl2 + 2SbCl3 + S3.
This reaction goes on better in the presence of hydrochloric acid or
haloid salts.
MacArthur's process is as follows:—The ore is ground small enough
to pass through 20-mesh, and is treated with a solution of sodium
hydroxide of not more than 2 per cent, strength, at a temperature
of 100° C. The filtered solution is precipitated by carbon dioxide
obtained from a lime-kiln. The antimony precipitate obtained is in
the form of a red amorphous sulphide, which is collected in a niterpress,
while the nitrate, containing sodium carbonate, is causticised
by lime from the kiln, ready for further use. The process is therefore
continuous.
Silver-bearing antimonial fahl-ores free from lime can be heated
with Glauber salt and coal in order to convert the antimony into
the double sulphide of sodium and antimony. Sulphur dioxide may
then be used to decompose the leached salt, with the formation of
antimony sulphide and sodium thiosulphate, the former of which
can be treated for antimony in the ordinary manner. Any silver
or copper in the ore would be left behind in the residues from the
leaching process.
Of all the wet processes that have been proposed to treat antimony
ore, especially ore containing gold, that of M. Herrenschmidt seems
superior to all others for practical application on a large scale. The
following is a description of this process * :—
(a) Concentration.—The mineral, ground either in crushing or in
ball mills, is allowed to pass through sieves, the dimension of whose
mesh can only be determined by successive trials. With an endless
belt concentrator, the following products are obtained:—
The concentrates^ to be de-antimonised.
The mixed materials, to be passed back to the concentrator.
The tailing's, to be rejected.
The concentrates consist principally of iron pyrite, mispickel, and
stibnite, as well as all the gold contained in the ore.
* Mapport de MM. Pelatan ct L4vat, Inydnieurs eivils drs Mines, sur le traiUmcnt
de8 minerals auro-antimomeux par le procAdi de M. Hcrrcnschmidt. Paris,
1904 (pamphlet).