Nomenclature
CAS number: 7440-61-1
Description and 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,
T 4.47 × 109 years, rel. at. mass 238.0508
(99.275%); 235, T 7.04 × 108 years, rel. at.
mass 235.0439 (0.718%); 234, T 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
LakeBlind 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 α-form, d 19.07, transforms to β-form
at 667.8° ±1.3°; tetragonal, β-form, d 18.11, transforms to γ-form at 774.9° ±1.6°; body-centered
cubic γ-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.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 α-particle radiation and by α-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.