A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
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THE METALLURGY OS ANT1MOJNY 1.20<br />
amperes (0*026 to 0*03 ampere per square inch). The necessary<br />
E.M.F. is about 2 volts per bath.<br />
The metal thus obtained is in the pulverulent form or in lustrous<br />
scales, according to the density of the current used.<br />
Koepp's method is to treat antimony sulphide with ferric chloride,<br />
thus :—<br />
6FeCl3 + Sb2S3=6FeCl2+2SbCl3 + S3.<br />
The solution is electrolysed at a temperature of 50° C. between<br />
lead plates. Antimony is deposited upon the cathode and ferric<br />
chloride upon the anode. The current used is 3*7 amperes per<br />
square foot. The use of chlorides as electrolytes precludes the possibility<br />
of the process becoming practical.<br />
Siemens and Halske use as solvent either the sulphides, hydrosulphides,<br />
or polysulphides of the alkalis. When the finely ground<br />
ore is thus lixiviated, a double salt is formed, e.g. with NaHS :—<br />
Sb2S3+6£TaHS=Sb2S3.3Na2S + 3H2S.<br />
The liquor is then led into the cathode division of a bath. The<br />
bath is divided up by diaphragms into series of anodes and cathodes;<br />
the former are made of carbon or platinum, and are closed and made<br />
gas-tight; the latter are made of copper or antimony plates. The<br />
reaction at the cathode end is as follows :—<br />
Sb2S8. SNaaS + 6H = 2Sb + 6KaHS.<br />
In this way, not only is metallic antimony obtained, but also the<br />
NaHS solution is regenerated and used to dissolve more of the sulphide.<br />
Another process by Siemens is to electrolyse a solution of the<br />
double salt formed by treating antimony sulphide with sulph-hydrate<br />
of calcium, barium, strontium, or magnesium. Without the use<br />
of diaphragms, the hydrogen liberated at the cathode end combines<br />
with the sulphur of antimony sulphide, and the antimony is deposited,<br />
while at the same moment the sulph-hydrates of other metals are<br />
formed, to be in turn converted into disulphides by the oxygen<br />
developed in the reaction.<br />
These disulphides are treated with carbon dioxide, obtained by<br />
heating a mixture of the, carbonates and sulphur, the result being<br />
the formation of the carbonates of calcium, barium, strontium,<br />
and magnesium, sulphur and hydrogen sulphide. These, with<br />
the exception of the hydrogen sulphide evolved, are heated in<br />
the absence of air, when carbon dioxide and the caustic alkaline<br />
earths are formed. The carbon dioxide is used to decompose disulphide<br />
solutions, and the basic oxides are treated with the hydrogen<br />
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