Manganese - Mn, 25

Manganese has a melting point of 1244+/-3°C, boiling point of 1962°C, specific gravity of 7.21 to 7.44 (depending on allotropic form), and valence of 1, 2, 3, 4, 6, or 7. Ordinary manganese is a hard and brittle gray-white metal. It is chemically reactive and slowly decomposes cold water. Manganese metal is ferromagnetic (only) after special treatment. There are four allotropic forms of manganese. The alpha form is stable at normal temperatures. The gamma form changes to the alpha form at ordinary temperature. In contrast to the alpha form, the gamma form is soft, flexible, and easily cut.

Manganese is an important alloying agent. It is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels. Together with aluminum and antimony, especially in the presence of copper, it forms highly ferromagnetic alloys. Manganese dioxide is used as a depolarizer in dry cells and as a decolorizing agent for glass that has been colored green due to iron impurities. The dioxide is also used in drying black paints and in the preparation of oxygen and chlorine. Manganese colors glass an amethyst color and is the coloring agent in natural amethyst. The permanganate is used as an oxidizing agent and is useful for qualitatitive analysis and in medicine. Manganese is an important trace element in nutrition, although exposure to the element is toxic in higher quantities.