Title: Lead
CAS Registry Number: 7439-92-1
Literature References: Pb; at. wt 207.2; at. no. 82; valence 2, 4. Group IVA (14). Four naturally occurring isotopes: 204 (1.40%); 206 (25.2%); 207 (21.7%); 208 (51.7%); artificial, radioactive isotopes: 195-203; 205; 209-214. One of the metals known to the ancient world. Extent of occurrence in earth's crust about 15 g/ton, also expressed as 0.002% (depth of crust: 16 km). Occurs chiefly as sulfide in galena, other minerals include anglesite (PbSO4), cerussite (PbCO3), mimetite [PbCl2.3Pb3(AsO4)2] and pyromorphite [PbCl2.3Pb3(PO4)2]. Recovery from ore and purification: Heuser, Metall. 9, 675 (1955), C.A. 49, 14609 (1955); Ziegfeld, Eng. Min. J. 153, 82 (1952), C.A. 46, 2975 (1952). Prepn of high purity lead: Piontelli, Fagnani, Chim. Ind. (Milan) 34, 629 (1952), C.A. 47, 12062 (1953); Giesen, Technik 2, 393 (1947), C.A. 42, 852 (1948); Hughes J. Electrochem. Soc. 101, 267 (1954); Baralis, Marone, Met. Ital. 59, 494 (1967), C.A. 67, 119613a (1967). Review of uses, corrosion metallurgy: Mullarkey, Ind. Eng. Chem. 49, 1607 (1957). Reviews of lead, its alloys and compds: W. Hofmann, Lead and Lead Alloys, Properties and Technology (Springer, New York, Eng. Ed., 1970) 551 pp; Abel in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 105-146; H. E. Howe in Kirk-Othmer Encyclopedia of Chemical Technology vol. 14 (Wiley-Interscience, New York, 3rd ed., 1981) pp 98-139. Review of carcinogenic risk: IARC Monographs 23, 325-415 (1980); of toxicology and human exposure: Toxicological Profile for Lead (PB99-166704, 1999) 640 pp.
Properties: Bluish-white, silvery, gray metal. Highly lustrous when freshly cut, tarnishes upon exposure to air. Very soft and malleable, easily melted, cast, rolled, and extruded. Cubic crystal structure. mp 327.4°; bp 1740°. d420 11.34; d (at mp) 10.65: Schneider et al., Naturwissenschaften 41, 326 (1954). Heat of vaporization (1740°) 206 cal/g. Heat capacity (20°): 0.031 cal/g/°C. Resistivity (m-ohm-cm) at 20°: 20.65; at 100°: 27.02; at 320°: 54.76; at 330°: 96.74. Vapor pressure at 1000°: 1.77 mm Hg. E° (aq) Pb/Pb2+ +0.126 v. Coefficient of linear expansion (0-100°) 29´10-6, (20-300°) 31.3´10-6, (-183° to +14°) 27´10-6; thermal conductivity varies from 0.083 at 50° to 0.077 at 225°: Francl, Kingery, J. Am. Ceram. Soc. 37, 80 (1954). Viscosity of molten lead (cP): 3.2 (327.4°); 2.32 (400°); 1.54 (600°); 1.23 (800°). Heat capacity and heat of fusion study: Douglas, Dever, J. Am. Chem. Soc. 76, 4824 (1954); hardness 1 on Mohs' scale; Brinell hardness (high purity Pb) 4.0: McLellan, Am. Mineral. 30, 635 (1945). Reacts with hot concd nitric acid, with boiling concd hydrochloric or sulfuric acid. Attacked by pure water, weak organic acids in the presence of oxygen. Resistant to tap water, hydrofluoric acid, brine, solvents.
Melting point: mp 327.4°
Boiling point: bp 1740°
Density: d420 11.34; d (at mp) 10.65: Schneider et al., Naturwissenschaften 41, 326 (1954)
CAUTION: Potential symptoms of overexposure are lassitude, insomnia; facial pallor; anorexia, weight loss, malnutrition; constipation, abdominal pain, colic; anemia; gingival lead line; tremor; paralysis of wrists or ankles; kidney disease; hypotension. Symptoms in children include encephalopathy, behavioral and learning deficits; in adults, peripheral motor neuropathy. See NIOSH Pocket Guide to Chemical Hazards (PB2003-100121, 2003) p 184; Patty's Industrial Hygiene and Toxicology vol 2C, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 4th ed., 1994) pp 2065-2087.
Use: Construction material for tank linings, piping, and other equipment handling corrosive gases and liqs used in the manuf of sulfuric acid, petr refining, halogenation, sulfonation, extraction, condensation; for x-ray and atomic radiation protection; manuf of tetraethyllead, pigments for paints, and other organic and inorganic lead compds; bearing metal and alloys; storage batteries; in ceramics, plastics, and electronic devices; in building construction; in solder and other lead alloys; in the metallurgy of steel and other metals. |