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

122 THE METALLURGY OF ANTIMONY.
obtained can be treated with bisulphide of sodium or bisulphide of
calcium; or it can be melted in a crucible with sufficient sulphur to
convert nine-tenths of the metal into sulphide, while the remaining
one-tenth contains all the gold. This alloy of antimony and gold
can be treated with nitric acid so as to extract all the gold.
II. EXTRACTION BY WET METHODS.
There have been many wet processes proposed for treating poor
ores or liquation residues, but none have been practicable on a large
scale.
Haremann has devised a process of extracting antimony from
antimonial lead ores by roasting the crushed ore with alkaline
carbonate and carbon. The result is a double sulphide of alkali
and antimony, which, on being lixiviated, yields the precious
metal and lead. The antimony is precipitated as a sulphide
by the addition of an acid, preferably sulphuric acid, with the
formation of an alkaline sulphate which can be recovered for
future use.
N. W. Edwards proposes to treat gold- and silver-bearing antimony
ores by lixiviation with a 7 per cent, solution of calcium sulphide,
preferably cold, in large vats provided with stirring apparatus.
The resulting reaction is that the antimony is dissolved as
sulphide, while the gold is left behind with the residues. The
gold thus obtained can be recovered by any of the ordinary
methods. The solution obtained above is then drawn oft* and
is treated with carbonic acid obtained by burning Hrno. The
calcium is precipitated, as carbonato, by the carbonic acid, and
is filtered off. Upon the further treatment of the solution by
carbonic acid, the antimony sulphide is finally precipitated. TKo
hydrogen sulphide evolved during the reaction may bo used to
regenerate calcium sulphide solution by bubbling it through milk
of lime.
According to Hargreaves, finely powdered ore can bo treated with
hot hydrochloric acid. Lime is used to neutralise the solution, which
is then to be treated with zinc or iron for precipitation of the
antimony. The precipitated metal is to be washed successively with
antimony chloride solution, hydrochloric acid, and water, and then
fused with potash in crucibles.
Smith's method is similar to the one just described.
Hering also proposes to treat liquation rosirtuos by hydrochloric