CAS Registry Number: 7439-96-5
Literature References: Mn; at. wt 54.938045; at. no. 25; valences 2, 4, 7; 1, 3, 5, 6 rare. Group VIIB (7). One stable isotope: 55; artificial radioactive isotopes 49-54; 56-58. Widely-distributed, abundant element; constitutes 0.085% of earth's crust. Occurs in the minerals pyrolusite, hausmannite, manganite, braunite (3Mn2O3.MnSiO3), manganosite (MnO), and in several others; occurs in minute quantities in water, plants and animals. Essential dietary nutrient. First isolated by Gahn in 1774. Prepn of the metal: John et al., cited by Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry 12, 163 (1932); A. H. Sully, Manganese (Academic Press, New York, 1955) 305 pp. Review of physical properties: Meaden, Met. Rev. 13, 97-114 (1968). Review of manganese and its compds: Kemmitt in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 771-876; L. R. Matricardi, J. H. Downing in Kirk-Othmer Encyclopedia of Chemical Technology vol. 14, (Wiley-Interscience, New York, 3rd ed., 1981) pp 824-843. Review of toxicology and human exposure: Toxicological Profile for Manganese (PB2000-108025, 2000) 504 pp.
Properties: Steel gray, lustrous, hard, brittle metal. Exists in four allotropic forms: a-form, body-centered cubic, stable below 710° (approx), d20 7.47; b-form, cubic, stable in the range 710-1079°, d20 7.26; g-form or electrolytic Mn, face-centered cubic, stable in the range 1079-1143°C, d1100 6.37; d-form, body-centered cubic, stable from 1143° to mp, d1143 6.28. g-Mn when stabilized at room temp is face-centered tetragonal, d20 7.21. mp 1244°. bp 2095°. Sp heat 0.115 cal/g/°C; latent heat of fusion: 3.5 kcal/g-atom. Mohs' hardness 5.0. Superficially oxidized on exposure to air. Burns with an intense white light when heated in air. Dec water slowly in the cold, rapidly on heating; pure electrolytic manganese is not attacked by water at ordinary temp; slightly attacked by steam. Reacts with dil mineral acids with evolution of hydrogen and formation of divalent manganous salts. Reacts with aq solns of sodium or potassium bicarbonate. When heated in nitrogen above 2000° burns to form a nitride. Converted by fluorine into the di- and trifluoride, by chlorine into the dichloride. In form of powder reduces most metallic oxides on heating. On heating, reacts directly with carbon, phosphorus, antimony or arsenic.
Melting point: mp 1244°
Boiling point: bp 2095°
Density: d20 7.47; d20 7.26; d1100 6.37; d1143 6.28; d20 7.21
CAUTION: Potential symptoms of overexposure are parkinsonism; asthenia, insomnia and mental confusion; metal fume fever (dry throat, coughing, tight chest, dyspnea, rales and flu-like fever); lower back pain; vomiting; malaise; fatigue; kidney damage. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 190.
Use: In manuf of steel; for rock crushers, railway points and crossings, wagon buffers; as a constituent of several alloys, e.g., ferromanganese, copper manganese, Manganin.