Aluminum. Aluminium. Al; at. wt 26.98154; at. no.13; valence 3. One naturally occurring isotope: 27Al. In addition, six radioactive isotopes and one isomer are known; the most important, 26Al (found in meteors), decays with emission of b+ and g-radlation, T½ 7.4 x 105 years. One of the most abundant metals in earth's crust: 8.8 % by wt; occurs in nature primarily in combination with silica, also as oxide (See Aluminum Silicate; Aluminum Oxide). First obtained in impure form by Oersted in 1825; prepd as metal powder by Wöhler in 1827. Reviews of aluminum, its alloys and compds: Brandt, "Aluminum and Aluminum Alloys" in Proc. Met. Soc. Conf. Vol. 40, E. D. Verink, Ed. (Gordon & Breach, New York, 1966); Aluminum, 3 Vols. K. R. Van Horn, Ed. (American Society for Metals, Metal Park, Ohio, 1967); Wade, Bannister, "Aluminum, Gallium, Indium and Thallium" in Comprehensive Inorganic Chemistry, Vol. 1, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 993-1064.

Tin-white, malleable, ductile metal, with somewhat bluish tint; Capable of taking brilliant polish which is retained in dry air. In moist air, oxide film forms which protects metal from corrosion. Available in bars, leaf, powder, sheets, or wire. d 2.70. mp 660°. bp 2327°. Does not vaporize even at high temps, but finely divided aluminum dust is easily ignited, and may cause explosions. Reacts with dil HCl, H2SO4, KOH and NaOH with evolution or hydrogen. Reduces the cations of many heavy metals to the metallic state E°(aq) Al3+/Al -1.66 V. Solns of Al3+ in dil HCI or neutral or slightly acid solns of most aluminum salts, yield with Na2S a white ppt soluble in excess of Na2S. Dil neutral soln of aluminum salts yields white gelatinous ppt on boiling with sodium acetate.

USE: As the pure metal or as alloys (magnalium, aluminum bronze, etc.) for aircraft, ustensils, apparatus, electrical conductors; instead of copper in dental alloys. The coarse powder is used in aluminothermics (thermite process); the fine powder as flashlight in photography; in explosives, fireworks and in aluminum paints; for absorbing occluded gases in manuf of steel. In testing for Au, As, Hg; coagulating colloidal solns of As or Sb; pptg Cu; reducer for determining nitrates and nitrites; instead of Zn for generating hydrogen in testing for As. Forms complex hydrides with lithium and boron, such as LiAlH4, which are very useful in preparative organic chemistry.

Human Toxicity: Evidence that dust may cause "aluminosis" or aluminum pneumoconiosis not definitive: E. Browning, Toxicity of Industrial Metals (Appleton-Century-Crofts, New York, 2nd ed., 1969) pp 3-22.
Ref.: 321, 54 pp.
The Merck Index - Eleventh Edition.
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