III.

Uses

Manganese is used principally in the form of alloys with iron, obtained by treating pyrolusite in a blast furnace with iron ore and carbon. The most important of these alloys, which are used in steelmaking, are ferromanganese, containing about 78 percent manganese, and spiegeleisen, containing from 12 to 33 percent manganese. Small amounts of manganese are added to steel as a deoxidizer; large amounts are used to produce a very tough alloy, resistant to wear. Safes, for example, are made of manganese steel containing about 12 percent manganese. Nonferrous manganese alloys include manganese bronze (composed of manganese, copper, tin, and zinc), which resists corrosion from seawater and is used for propeller blades on boats and torpedoes, and manganin (containing manganese, copper, and nickel), used in the form of wire for accurate electrical measurements because its electrical conductivity does not vary appreciably with temperature. See also Iron and Steel Manufacture.

Manganese commonly forms compounds in which its valence is 2, 3, 4, 6, or 7. Manganese dioxide (MnO₂) occurs natively as pyrolusite and is prepared artificially by heating manganese nitrate; it is used in dry-cell batteries as a depolarizer, in paint and varnish oils, for coloring glass and ceramics, and in preparing chlorine and iodine. Manganese sulfate (MnSO₄), a pink crystalline solid, is prepared by the action of sulfuric acid on manganese dioxide and is used in dyeing cotton. Sodium and potassium permanganate (NaMnO₄ and KMnO₄) are dark purple crystals, formed by the oxidation of acidified manganese salts, which are used as oxidizers and disinfectants.