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(L. magnes, magnet, from magnetic properties of pyrolusite; It. manganese, corrupt form
Recognized by Scheele, Bergman, and others as an element and isolated by Gahn in 1774
by reduction of the dioxide with carbon.
Manganese minerals are widely distributed; oxides, silicates, and carbonates are the
most common. The discovery of large quantities of manganese nodules on the floor of the
oceans may become a source of manganese. These nodules contain about 24% manganese
together with many other elements in lesser abundance.
Most manganese today is obtained from ores found in Russia, Brazil, Australia, Republic
of S. Africa, Gabon, and India. Pyrolusite and rhodochrosite are among the most common
manganese minerals. The metal is obtained by reduction of the oxide with sodium, magnesium,
aluminum, or by elctrolysis.
It is gray-white, resembling iron, but is
harder and very brittle. The metal is reactive chemically, and decomposes cold water
slowly. Manganese is used to form many important alloys. In steel, manganese improves the
rolling and forging qualities, strength, toughness, stiffness, wear resistance, hardness,
With aluminum and antimony, especially with small amounts of
copper, it forms highly ferromagnetic alloys.
Manganese metal is ferromagnetic only after special treatment. The pure metal exists in
four allotropic forms. The alpha form is stable at ordinary temperature; gamma manganese,
which changes to alpha at ordinary temperatures, is said to be flexible, soft, easily cut,
and capable of being bent.
The dioxide (pyrolusite) is used as a depolarizer in dry cells, and is used to
"decolorize" glass that is colored green by impurities of iron. Manganese by
itself colors glass an amethyst color, and is responsible for the color of true amethyst.
The dioxide is also used in the preparation of oxygen and chlorine, and in drying black
paints. The permanganate is a powerful oxidizing agent and is used in quantitative
analysis and in medicine.
Manganese is widely distributed throughout the animal kingdom. It is an important trace
element and may be essential for utilization of vitamin B1.
Exposure to manganese dusts, fume, and compounds should not exceed the ceiling value of
5 mg/m3 for even short
periods because of the element's toxicity level.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.
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