Structural Formula Vector Image
Title: Uranium
CAS Registry Number: 7440-61-1
Literature References: U; at. wt 238.0289 (characteristic naturally occurring isotopic mixture); at. no. 92; valence 6, 5, 4, 3. No stable nuclides; three naturally occurring isotopes (mass numbers): 238, T½ 4.47 ´ 109 years, rel. at. mass 238.0508 (99.275%); 235, T½ 7.04 ´ 108 years, rel. at. mass 235.0439 (0.718%); 234, T½ 2.46 ´ 105 years, rel. at. mass 234.0409 (0.005%); twelve artificial isotopes: 226-233; 236; 237; 239; 240. Occurrence in the earth's crust 2.1 ppm. Mined as uranium ore; main ores of commercial interest are carnotite, pitchblende, tobernite and autunite. Commercially important mines located in Elliot Lake-Blind River area in Canada, Rand gold fields in South Africa, Colorado and Utah in U.S., in Australia and France. Discovery from pitchblende: M. H. Klaproth, Chem. Ann. II, 387 (1789). Prepn of metal: E. Péligot, C.R. Hebd. Seances Acad. Sci. 12, 735 (1841); idem, Ann. Chim. Phys. 5, 5 (1842). Flowsheet and details of prepn of pure uranium metal: Chem. Eng. 62, no. 10, 113 (1955); Spedding et al., US 2852364 (1958 to U.S.A. E.C.). Reviews: Mellor's vol. XII, 1-138 (1932); C. D. Harrington, A. R. Ruehle, Uranium Production Technology (Van Nostrand, Princeton, 1959); E. H. P. Cordfunke, The Chemistry of Uranium (Elsevier, New York, 1969) 250 pp; several authors in Handb. Exp. Pharmakol. 36, 3-306 (1973); "The Actinides," in Comprehensive Inorganic Chemistry vol. 5, J. C. Bailar, Jr., et al., Eds. (Pergamon Press, Oxford, 1973) passim; F. Weigel in Kirk-Othmer Encyclopedia of Chemical Technology vol. 23 (Wiley-Interscience, New York, 3rd ed., 1983) pp 502-547; idem in The Chemistry of the Actinide Elements vol. 1, J. J. Katz et al., Eds. (Chapman and Hall, New York, 1986) pp 169-442; J. C. Spirlet et al., Adv. Inorg. Chem. 31, 1-40 (1987). Review of toxicology and health effects: Toxicological Profile for Uranium (PB99-163362, 1999) 462 pp.
Properties: Silver-white, lustrous, radioactive metal; malleable and ductile. Tarnishes rapidly in air, forming a layer of dark-colored oxide. Three allotropic modifications: orthorhombic a-form, d 19.07, transforms to b-form at 667.8° ±1.3°; tetragonal, b-form, d 18.11, transforms to g-form at 774.9° ±1.6°; body-centered cubic g-form, d 18.06, transforms to liquid at mp. mp 1132.8 ±0.8°. Heat of vaporization 446.7 kJ/mol; heat of fusion 19.7 kJ/mol; heat of sublimation 487.9 kJ/mol. Finely divided U metal and some U compounds may ignite spontaneously in air or oxygen. Rapidly soluble in aqueous HCl. Non-oxidizing acids, such as sulfuric, phosphoric and hydrofluoric, react only very slowly with U; nitric acid dissolves massive U at a moderate rate. Dissolution of finely divided U in nitric acid may approach explosive violence. Uranium metal is inert to alkalies.
Melting point: mp 1132.8 ±0.8°
Density: d 19.07; d 18.11; d 18.06
CAUTION: Uranium is a chemical hazard as well as a radiological hazard. Potential symptoms of overexposure to U metal or insoluble U compds are dermatitis; kidney damage; blood changes. Potential symptoms of overexposure to soluble U compds are lacrimation, conjunctivitis; shortness of breath, cough, chest rales; nausea, vomiting, skin burns; red blood cells and casts in urine; albuminuria; high blood urea nitrogen. Radiation hazard is caused by the direct emission of a-particle radiation and by a-particles emitted from radon gas and its particulate daughters formed during the natural decay of U. U and U compds are potential occupational carcinogens. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 326; Patty's Industrial Hygiene and Toxicology vol. 2C, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 4th ed., 1994) pp 2297-2317.
Use: 235U in nuclear power reactors and nuclear weapons. Uranium depleted of 235U to manuf armor-piercing ammunition, in inertial guidance devices and gyro compasses, as a counterweight for missile reentry vehicles, as radiation shielding material, and x-ray targets.

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