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

70 THE METALLURGY OF ANTIMONY.
perature is too low the residue will contain too large a proportion
of antimony, part of which at least should go to the liquated
product as crude antimony. It has already been mentioned that
the best size of the pieces of ore is that of walnuts; for, if the
size is in any way smaller, the liquation process is less complete, and
hence the residues are too rich in the sulphide ; furthermore, fine ores
lie so close together as to render the escape of the fused sulphide
difficult.
(a) Intermittent Working.
As a rule, closed furnaces use more fuel and cost more for labour
than open ones (reverberatory), which, on the other hand, lose more
antimony through volatilisation and oxidation than closed ones.
This loss can, however, be eliminated by the use of the condensation
apparatus of Herrenschmidt, to be mentioned later.
The smelting is done in pots, which are either heated directly by
the burning fuel or by the flame coming from a fireplace. In the
liquation in pots, the working is carried on intermittently, while
continuous working is permitted in that of tubes or reverberatory
furnaces, thus economising the consumption of fuel.
a. Intermittent Liquation in Pots in Open Fire.—Pots, being in
direct contact with the fuel, are used at Wolfsberg in the Harz, at
Magurka. Eosenau, and Gross-Gbllnitz in Hungary, at Milleschau in
Bohemia, and at Malbosc
in France. The only merit
of this method is its simplicity,
and for this reason
it can be carried on without
much difficulty at the
mines. If the ores are
rich and fuel (wood or
coal) is cheap at" the mine,
this method can be used
with advantage.
FIG. 3. The pots are made of
fire-clay, and are able to
hold from 11 to 36 lbs. There are in the bottom of each pot four or
five holes, each varying from 0-4 to 0-6 inch in diameter, through which
the molten sulphide escapes. Below these pots rest receivers, made
of burnt clay, for the collection of the liquefied crude antimony.
These receivers are embedded in sand, ashes, or breeze, thus ensuring
the slow cooling of their contents. The pots are arranged in several