se-copper. A
shorter process (the so-called "direct process") converts the fine-metal
into refined copper directly. The "Welsh process" closely resembles the
English method; the main difference consists in the enrichment of the
matte by smelting with the rich copper-bearing slags obtained in
subsequent operations. The "German or Swedish process" is characterized
by the introduction of blast-furnaces. It is made up of the following
operations: (1) calcination, (2) smelting in blast-furnaces to form the
matte, (3) roasting the matte, (4) smelting in blast-furnaces with coke
and fluxes to "black-" or "coarse-metal," (5) refining the coarse-metal.
The "Anglo-German Process" is a combination of the two preceding, and
consists in smelting the calcined ores in shaft furnaces, concentrating
the matte in reverberatory furnaces, and smelting to coarse-metal in
either.

The impurities contained in coarse-copper are mainly iron, lead, zinc,
cobalt, nickel, bismuth, arsenic, antimony, sulphur, selenium and
tellurium. These can be eliminated by an oxidizing fusion, and slagging
or volatilizing the products resulting from this operation, or by
electrolysis (see below). In the process of oxidation, a certain amount
of cuprous oxide is always formed, which melts in with the copper and
diminishes its softness and tenacity. It is, therefore, necessary to
reconvert the oxide into the metal. This is effected by stirring the
molten metal with a pole of green wood ("poling"); the products which
arise from the combustion and distillation of the wood reduce the oxide
to metal, and if the operation be properly conducted "tough-pitch"
copper, soft, malleable and exhibiting a lustrous silky fracture, is
obtained. The surface of the molten metal is protected from oxidation by
a layer of anthracite or charcoal. "Bean-shot" copper is obtained by
throwing the molten metal into hot water; if cold water be used,
"feathered-shot" copper is formed. "Rosette" copper is obtained as thin
plates of a characteristic dark-red colour, by pouring water upon the
surface of the molten metal, and removing the crust formed. "Japan"
copper is purple-red in colour, and is formed by casting into ingots,
weighing from six ounces to a pound, and rapidly cooling by immersion in
water. The colour of these two varieties is due to a layer of oxide.
"Tile" copper is an impure copper, and is obtained by refining the first
tappings. "Best-selected" copper is a purer variety.