Flux

Flux is the term given to the substances employed in the arts to assist the reduction of a metallic ore and the fusion of the metal. White flux is an intimate mixture of ten parts of dry carbonate of soda and thirteen parts of dry carbonate of potash, and is mainly instrumental in removing siliceous impurities by combining with the silica to form a fusible glass; black flux is prepared by heating in close vessels ordinary cream of tartar (bitartrate of potash), when an intimate mixture of finely-divided charcoal and carbonate of potash is obtained. The latter flux, when mixed with finely-divided metallic ores, and the whole raised to a high temperature in a furnace, not only is useful in removing the silica by the action of the carbonate of potash as above described, but the charcoal withdraws the oxygen from the metallic oxide and causes the separation of the pure metal. Limestone is employed as the flux in the smelting of iron ores. Its action is similar to that of soda and potash, and it is used because it is so much cheaper. Fluor spar, borax, protoxide of lead, and other basic substances are also used for fluxing. See IRON, COPPER, &c.