Ora of .Lead.—The methods of reducing lead ores have been given under the article LEAD. See 111110 SEPARATION.
Ora of Bismuth.—Biemuth is accompanied by native silver, galena, some other metals, and earthy substances. In conducting the analysis, previous roasting is not requisite. The low degree of heat at which bismuth is fusible renders the reduction of the ores of this metal a very simple process. In the large way, the ores were formerly reduced merely by heating theni along with burning fuel ; sometimes a shallow hole was made in the ground, and filled loosely with pieces of wood and bushes, and after the fire was kindled, the ore, reduced to small pieces, was thrown in ; sometimes the stump of a hollow pine tree was filled with wood and ore alternately, and set on fire, the bismuth sepa rated from its matrix, and collected in a mass at the bottom ; the scarcity of wood has, however, put an end to these rude and extravagant methods, and the ores of- bismuth are now reduced in a common reverberatory furnace, the bed of which is lined with charcoal, whence the melted metal is removed in iron ladles, and cast into masses weighing twenty or thirty pounds, in which state it is brought to market.
Ores of Zinc.—The ores of zinc are the native carbonate, or common cala mine, the oxide of zinc and blende, or the eulphuret of zinc. In the process for reducing the ore of zinc, it is first to be broken into small pieces, and the different impurities being separated, it is next calcined in a reverberatory fur nace, at a moderate red heat ; and if the ore be calamine, the carbonic acid is driven off; and if blende, it is deprived of its sulphur. After this it is washed, and the metallic oxide being separated from the earthy parts, it is dried, and carefully mixed with about one eighth of its weight of charcoal, by grinding the ingredients together in a mill, and is now ready for the smelting process. •Thie is performed in a circular furnace, in which are fixed six large earthen pots, about four feet high, and nearly in the shape of oil jars. An iron tube is in serted into the bottom of each pot, and passing through the arched floor of the furnace, terminates in a vessel of water placed beneath, while the other end of the tube rises within the crucible to a few inches of the top. The crucibles are
then filled with the mixture of the ore and charcoal, to the level of the tube ; the cover of each is carefully luted on, and an intense heat is to be kept for several hours. The zinc, as the process of reduction goes on, rises, in the form of vapour, to the top of the pot, but as it cannot escape, it descends through the iron tube, passes into the water, and is condensed in small drops. The globules are afterwards fused, and cast into the form of ingots, when it is fit for the market; but as common zinc contains a little of other metals, as copper, dead, arsenic, iron, and manganese, which impair its quality, these impurities are partially separated by melting the zinc in a crucible, and stirring into it, with a stick or earthen rod, a mixture of sulphur and fat; by the latter, the zinc is preserved from oxidation, and the sulphur combines with the other metals, except the zinc, and, converting them into sulphurets, they rise to the top in the form of scoriae, which may be removed. This process is to be repeated as long as any scorke appear. See Zinc.
Ores of ifithinony.—The sulphuretted ore of antimony is the only one which is found in sufficient quantity to be employed in the process of reduction in the large way, and the process it undergoes is extremely simple. The ore, being sepa rated from the greater part of the stony matters which adhere to it, is placed on the bed of a reverberatory furnace, and covered with charcoal powder, and being brought to a low red heat, the aulphuret enters into fusion, and the earthy parts, floating on the surface, are removed with a rake. The melted part is cast into the form of large citkes, and is the crude antimony of the shops. The metal is obtained in a state of purity from the crude antimony or sulphuret, by different processes. After its reduction to a pure state, it has been long known by appellation of regulus of antimony. In the reformed chemical nomen e indeed, it is now called simply antimony, but the term regulus still con tinues to be used by the merchant or the artisan. (See ANTIMONY.) The ores of Cobalt, Nickel, Arsenic, Titanium, and Manganese, are noticed under their metallic heads.