Sodium. Natrium. Na; at. wt 22.98977; at. no. 11; valence 1. Alkali metal. Occurrence in earth's Crust: 2.83% by wt; principal cation in hydrosphere. Natural isotopes: 23 (100%); radioactive isotopes (mass number): 20-22; 24-26. Prepd by Davy in 1807 by electrolysis of fused sodium hydroxide. Found in form of its compds, halides, silicates, carbonates; does not occur free. Industrial prepns: primarily in Downs cells; also in Castner cells: Batsford, Chem. Met. Eng. 26, 888, 932 (1932); Regelsberger, Chemisehe Technologie der Leichtmetalle. Leipzig, 1926; Hardie, Ind. Chemist 30, 161 (1954). Reviews: M. Sittig, Sodium A.C.S. Monograph Series, no. 133 (Reinhold, New York, 1956); whaley, "Sodium, Potassium, Rubidium, Cesium and Francium" in Comprehensive Inorganic Chemistry, Vol. 1, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 369-529.

Light, silvery-white metal; body-centered cubic structure; lustrous when freshly cut; tarnishes on exposure to air, becoming dull and gray. Soft at ordinary temp, fairly hard at -20. mp 97.82; bp 88l.4; d20 0.968. Heat capacity of solid: 0.292 cal/g deg; heat capacity of liquid at mp: 0.331 cal/g deg. Heat of fusion: 27.05 cal/g; thermal conductivity (cal/sec C cm): 0.205 (97.82 0.170 (400). E (aqueous) Na/Na+ 2.714 V. Violently decomposes water. forming sodium hydroxide and hydrogen which may ignite spontaneously. Decomposes alc. Reacts vigorously with oxygen, burning with a yellow flame. Combines directly with the halogens, with phosphorus. Reduces most oxides to the elemental state, reduces metallic chlorides. Dissolves in liq ammonia to give a blue soln; when heated in ammonia gas yields sodamide. Dissolves in mercury, forming sodium amalgam. Keep under liquids contg no oxygen, such as kerosene, naphtha.

USE: Manuf of sodium compds, such as the cyanide, azide, peroxide, etc.; in manuf of tetraethyllead; in org syntheses; for photoelectric cells; in sodium lamps. Alloyed with potassium in heat transfer media. Human Toxicity: Extremely caustic to all tissue.
Ref.: 8512, 1355 pp.
The Merck Index - Eleventh Edition.
Copyright 1989 by Merck & Co., Inc.