Slag

Slag. In the smelting of a metal a flux (q.v.) is usually added to the ores, which combines with the siliceous and earthy impurities of the ores to form a fusible substance, which floats above the metal and can be tapped off or withdrawn, and wbich is known as slag. The slags vary in composition, according to the nature of the ores and flux. They are usually mixtures of silicates of lime, soda, potash, iron, etc., and are generally vitreous compounds, closely resembling many of the lavas and volcanic rocks.