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

THE METALLURGY OF ANTIMONY. 107
The operation is thus :—
Roasted ore charged at a time . . .5 cwts.
Cover of Glauber salt 1 cwt.
Coarse, hard wood-charcoal, powdered . 82 lbs.
Before the first charge is made the bed of the furnace must be heated
to redness. The charge generally melts in about four hours, when it
begins to effervesce, with the evolution of carbonic oxide, which escapes
through the layer of slag and burns. The charge is rabbled until
boiling ceases, when it is allowed to settle for half an hour. After
this the charge is allowed to cool by leaving the fire-door open. This is
continued until the slag attains a low red heat and, being in a pasty
condition, is drawn off. Refining materials—27*5 lbs. of Glauber salt
and 11 lbs. of wood-charcoal—are immediately added, and the furnace
is strongly heated. After an hour and a half, when boiling ceases, the
metal and the slag are drawn off together into an iron mould. Care
must be taken to leave at least half an inch of slag as a cover for the
metal, thus preventing the possibility of the metal solidifying before
the mould is filled. As soon as the ingot becomes solidified, the slag—
essentially a sulpho-salt of antimony mixed with sodium carbonate,
containing about 15 per cent, of antimony—is removed and is again
smelted with one-fifth of its weight of iron for subsequent use.
At one of the works in Hungary the refining is said to be combined
with the reduction. In a reverberatory furnace 5 cwts. of
roasted ore are smelted with 10 per cent, of small coal, together with
3 to 6 per cent, of Glauber salt, for twenty hours; after the removal of
the slags thus formed, 22 to 25 lbs. of slag from a previous refining
of antimony are added. The ladling of the metal is commenced as
soon as this is fused.
According to M. Herrenschmidt, the trioxide produced by the
volatilisation method can be reduced in the following way:—An
ordinary reverberatory furnace furnished with condensing apparatus,
as shown in fig. 52, is previously heated before the following charge
is commenced:—
10 parts of the trioxide.
6 parts of crude antimony.
1 part of carbon (charcoal or anthracite).
After six hours the charge must be thoroughly rabbled, with the
result that antimony metal is formed.
The following proportions may be employed:—
80 parts of trioxide.
20 parts of sulphide (crude).
12 to 15 parts of carbon.