er, a hot blast is used on
highly sulphuretted copper ores, a concentration of 8 of ore into 1 of
matte is obtained, with a consumption of less than one-third the fuel
which would be consumed in smelting the charge had the ore been
previously calcined. A great impetus to pyritic smelting was given by
the investigations of W. L. Austin, of Denver, Colorado, and both at
Leadville and Silverton raw ores are successfully smelted with as low a
fuel consumption as 3 of coke to 100 of charge.

Two types of pyritic smelting may be distinguished: one, in which the
operation is solely sustained by the combustion of the sulphur in the
ores, without the assistance of fuel or a hot blast; the other in which
the operation is accelerated by fuel, or a hot blast, or both. The
largest establishment in which advantage is taken of the self-contained
fuel is at the smelting works of the Mt. Lyell Company, Tasmania. There
the blast is raised from 600 deg. to 700 deg. F. in stoves heated by
extraneous fuel, and the raw ore smelted with only 3% of coke. The ore
is a compact iron pyrites containing copper 2.5%, silver 3.83 oz., gold
0.139 oz. It is smelted raw with hot blast in cupola furnaces, the
largest being 210 in. by 40 in. The resulting matte runs 25%. This is
reconcentrated raw in hot-blast cupolas to 55%, and blown directly into
copper in converters. Thus these ores, as heavily charged with sulphur
as those of the Rio Tinto, are speedily reduced by three operations and
without roasting, with a saving of 97.6% of the copper, 93.2% of the
silver and 93.6% of the gold.

Pyritic smelting has met with a varying economic success. According to
Herbert Lang, its most prominent chance of success is in localities
where fuel is dear, and the ores contain precious metals and sufficient
sulphides and arsenides to render profitable dressing unnecessary.

_The Nicholls and James Process._--Nicholls and James have applied, very
ingeniously, well-known reactions to the refining of copper, raised to
the grade of white metal. This process is practised by the Cape Copper
and Elliot Metal Company. A portion of the white metal is calcined to
such a degree of oxidation that when fused with the unroasted portion,
the reaction between the oxygen in the roasted matte and the sulphur in
the raw material liberates the metallic copper. The metal is so pure
that it can be refined by a continuous operation in the same furnace.

_Wet Methods for Copper Extraction