Nomenclature
CAS number: 7439-95-4
Description and references
Mg; at. wt 24.3050; at. no. 12; valence 2.
Group IIA (2). Alkaline earth metal. One of the most common elements
in the earth's crust: 27,640 ppm. Naturally occurring isotopes:
24 (78.99%); 25 (10.00%); 26 (11.01%). Known radioactive isotopes:
20-23, 27-34. Found naturally only in the form of its compounds
in magnesite, carnallite, dolomite [CaMg(CO3)2], epsomite, kieserite, and many other minerals; found in sea-water, underground
natural brines and salt deposits. Essential nutrient for most plant
and animal life. Commercial production by electrolytic reduction
of magnesium chloride or thermal reduction of magnesium oxide. First
obtained in metallic form by Davy in 1808 by electrolyte reduction
of magnesium oxide with mercury cathode. Prepn: Deville et
al. in Gmelins, Magnesium (8th ed.) 27A, 121 (1937). 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; Chemistry
of the Elements N. N. Greenwood, A. Earnshaw, Eds. (Pergamon
Press, New York, 1984) pp 117-154; C. B. Wilson et al. in Kirk-Othmer Encyclopedia of Chemical Technology vol. 15 (Wiley-Interscience, New York, 4th ed., 1995)
pp 622-674.
Properties
Silvery-white metal; hexagonal close-packed structure.
Slowly oxidizes in moist air. Available as bars, ribbons, wire,
castings, sheets and powder. mp 651°. bp 1100°. d20 1.738. Specific 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. Dangerous when wet; spontaneously combustible. Reacts very slowly with water at ordinary temp, less slowly at
100°. Reacts readily with dil acids with liberation of hydrogen;
reacts 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. Fine powder, thin sheets, chips and
turnings are easily ignited and burn with intense heat and brilliant
white flame. Combines directly with nitrogen, sulfur, the halogens,
phosphorus, and arsenic. Reacts vigorously with anhydrous methyl
alcohol.Caution
Direct contact may cause irritation
of skin, eyes, respiratory system. See: Fire Protection Guide to Hazardous Materials (National Fire Protection Assoc., Quincy, MA, 12th ed., 1997) Section
49, p 83.Use
In alloys to produce light weight structural metals.
In aluminum alloys to improve mechanical properties; in Grignard
reagents; in dry cell batteries; in pyrotechnics. For hot metal desulfurization,
esp. molten iron; prodn of ductile iron; metal reduction to produce
elemental boron, titanium, zirconium; corrosion protection of steel
structures; sacrificial anodes for corrosion protection.