Smelting
the act or process of action of heat, air, and fluxes. The oper- ation varies according to the different obtaining metal from ore by the combined ation varies according to the different metallic ores to be operated on. In smeltin order to drive off the water, sulphur, in order to drive off the water, sulphur, and arsenic with which it is more or less combined in its native state, and is then subjected to the heat of a blast-furnace along with certain proportions of coke or coal and limestone, varying according to the quality and composition of the ore to be heated. The smelting of copper consists in alternate roastings and fusions. The first of these operations is calcining the ore in furnaces in which the heat is applied and increased gradually till the temperature is as high as the ore can support without melting or agglutinating, when the ore is thrown into an arch formed under the sole of the furnace.
The second operation, or fusion of the nace, the ore having been spread uniformly over the hearth, and fluxes, such as lime, sand, or fluorspar, being added when required, though the necessity for 1 SMELTING FURNACE a careful admixture of ores of different qualities, the several earthy components of which serve as fluxes in the fusion of the mass. These two processes of calcination and fusion are repeated alternately till the ore is completely freed from all the earthy materials, and pure metal is obtained. In smelting lead, the ores, after being sorted, cleansed, ground, and washed, are roasted in furnaces which are without any blast or blowing apparatus, the ores being separable from the metal by its great fusibility. The smelting of tin consists of the calcining or roasting of the ores after they have been cleaned, sorted, stamped, and washed.
See BLAST FURNACE; IRON AND STEEL.