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

106 THE METALLURGY OF'ANTIMONY.
Altogether, the process occupies from four to six hours. The combined
action of the charcoal and soda is to separate the antimony from its
oxygen and sulphur compounds, while the gangue is slagged by the
soda, and the foreign metals, if present, are carried into the slag as
sulphides by the action of the sulphide of soda resulting from the
reduction of the Glauber salt by the charcoal. The influence of the
salt added is like that of the Glauber salt and soda, acting as a flux
and as a cover, and in addition carrying the foreign metals present
into the slag as chlorides.
The fuel consumption is 5-6 cwts. per charge, and the loss amounts
to 14 or 15 per cent.
It must be borne in mind that the metal drawn off from the
tapping-hole must be covered over with the slag during its cooling in
FIG. 51.—Front view.
the tapping-pot. When solid, the regulus ie freed from its slag by
hammering.
The following figures were obtained from the working of 830
charges as practised at Siena:—
368,838 lbs. of roasted ore.
268,918
12,641
88,628
38,205
4,409
>t
a
>»
sea salt.
soda ash.
Glauber salt.
slag from previous charges.
iron slag.
The antimony obtained weighed 113,573 lbs.
In New Brunswick the l eduction and the refining are carried out
consecutively in the same operation. The furnace dimensions are :
diameter, 8 feet 6 inches; the depth in the centre is 1 foot 6 inches ;
the beds are built of fire-clay and are concave,