Magnesium. Mg; at. wt 24.305; at. no.12; valence 2. An alkaline earth metal. One of the most common elements in the earth's crust: 2.1% by weight. Isotopes: 24 (78.7%); 25 (10.13%); 26 (11.17%). Found naturally only in the form of its compounds in magnesite, camallite, dolomite [CaMg(CO3)2], epsomite, kieserite, and many other minerals; found in sea-water; in animal and vegetable kingdom. First obtained in metallic form by Davy in 1808 by electrolysis of a mixture of magnesia and mercuric oxide. Methods of prepn: Deville, Caron, etc, cited in Gmelin's, Magnesium (8th ed.) 27A, 121 (1937). Prepd industrially by reduction of MgO contg materials. Examples of large-scale processes: Weiss, U.S. pat. 3,264,097 (1966 to Ver. Aluminium Werke). Review of magnesium and its compounds: Goodenough, Stenger, "Magnesium, Calcium, Strontium, Barium and Radium" in Comprehensive Inorganic Chemistry, vol. 1, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 591-664; L. F. Lockwood et al., in Kirk-Othmer Encyclopedia of Chemical Technology vol. 14 (Wiley-Interscience, New York, 3rd ed., 1981) pp 570-615.

Silvery-white metal; hexagonal close-packed structure. Slowly oxidizes in moist air. Available as bars, ribbons, wire and powder. mp 651°. bp 1100°. d20 1.738. Sp heat (20­°) 0.245 cal/g. Heat of fusion 88 cal/g. Electrical resistivity 4.46 µohm-cm. E° (aq) Mg2+/Mg -2.37 V. Reacts very slowly with water at ordinary temp, less slowly at 100°. Reacts readily with dil acids with liberation of hydrogen; reatcs with aq solns of ammonium salts, forming a double salt. Reduces carbon monoxide, carbon dioxide, sulfur dioxide, nitric oxide, and nitrous oxide at a red heat. Burns in air, Continues to burn in a current of steam. Combines directly with nitrogen, sulfur, the halogens, phosphorus, and arsenic. Reacts with methyl alcohol at 200° giving magnesium methylate.

Human Toxicity: Particles embedded in skin can produce gaseous blebs with a protracted course. Inhalation of the dust is irritating; fumes can cause metal fume fever.

USE: As a constituent of light alloys; for manuf precision instruments, optical mirrors; in pyrotechnics; in metallurgy as deoxidizing and desulfurizing agent; instead of zinc in dry batteries; for flash bulbs and flares, alumino-thermics, ignition of thermite mixture, intense signal lights; for Grignard reagents; in the recovery of titanium.
Ref.: 5529, 891 pp.
The Merck Index - Eleventh Edition.
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