Samarium
Title: Samarium
CAS Registry Number: 7440-19-9
Literature References: Sm; at. wt 150.36; at. no. 62; valences 2, 3. A lanthanide belonging to the cerium group of rare earth metals; named for the mineral "samarskite" from which it was isolated. Naturally occurring isotopes (mass numbers): 144 (3.1%); 147 (15.0%), radioactive, T½ 1.06 ´ 1011 years, a-emitter; 148 (11.3%), radioactive, T½ 7 ´ 1015 years, a-emitter; 149 (13.8%); 150 (7.4%); 152 (26.7%); 154 (22.7%). Known artificial radioactive isotopes: 133-143; 145; 146; 151; 153; 155-158. Abundance in earth's crust: 6.47-7.0 ppm. Commercially important sources are the rare earth minerals monazite and bastnaesite; also occurs in samarskite, cerite, orthite, ytterbite, and fluorspar. Isoln: L. de Boisbaudran, Compt. Rend. 88, 322 (1879); 89, 212 (1880). Sepn by crystn of the nitrates: Demarcay, ibid. 122, 728 (1896); Feit, Przibylla, Z. Anorg. Chem. 43, 203 (1905). Sepn of metal: Schumacher, Harris, J. Am. Chem. Soc. 48, 3108 (1926); by reduction of salts: Marsh, J. Chem. Soc. 1942, 398, 523; 1943, 8; Daane et al., J. Am. Chem. Soc. 75, 2272 (1953); Onstott, ibid. 75, 5128 (1953); 77, 812 (1955). Toxicity study: Haley, J. Pharm. Sci. 54, 663 (1965). Reviews of prepn, properties and compds: Prandtl, Z. Anorg. Allg. Chem. 238, 321-334 (1938); The Rare Earths, F. H. Spedding, A. H. Daane (Krieger, Huntington, N.Y., 1971, reprint of 1961 ed) 641 pp; Hulet, Bode, "Separation Chemistry of the Lanthanides and Transplutonium Actinides" in MTP Int. Rev. Sci.: Inorg. Chem., Ser. One Vol. 7, K. W. Bagnall, Ed. (University Park Press, Baltimore, 1972) pp 1-45; Moeller, "The Lanthanides" in Comprehensive Inorganic Chemistry Vol. 4, J. C. Bailar Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1-101; F. H. Spedding in Kirk-Othmer Encyclopedia of Chemical Technology vol. 19, (John Wiley & Sons, New York, 3rd ed., 1982) pp 833-854; Chemistry of the Elements, N. N. Greenwood, A. Earnshaw, Eds. (Pergamon Press, New York, 1984) pp 1423-1449. Brief review of properties: G. T. Seaborg, Radiochim. Acta 61, 115-122 (1993).
Properties: Yellow metal; tarnishes on exposure to air. Hardest metal of the cerium group. Crystalline forms: rhombohedral a-form, d 7.536, transforms to b-form at 917°; body-centered cubic b-form exists at >917°. mp 1074°. bp 1794°. Heat of fusion: 8.623 kJ/mol. Heat of sublimation (25°): 206.7 kJ/mol. E°(aq) Sm3+/Sm -2.41 V (calc).
Melting point: mp 1074°
Boiling point: bp 1794°
Density: d 7.536
 
Derivative Type: Oxide
Molecular Formula: Sm2O3
Molecular Weight: 348.72
Percent Composition: Sm 86.24%, O 13.76%
Properties: Yellowish-white powder. d 8.347.
Density: d 8.347
 
Derivative Type: Hydroxide
Molecular Formula: Sm(OH)3
Molecular Weight: 201.38
Percent Composition: Sm 74.66%, O 23.83%, H 1.50%
Properties: Gelatinous precipitate.
 
Derivative Type: Trichloride
Molecular Formula: SmCl3
Molecular Weight: 256.72
Percent Composition: Sm 58.57%, Cl 41.43%
Properties: White-yellowish powder. d 4.465, mp 686°. Forms addition compds with ammonia. Forms a hexahydrate, SmCl3.6H2O, d 2.382, yellow crystalline plates. By reducing the anhydr trichloride at high temps with hydrogen, ammonia or aluminum powder, samarium dichloride is obtained. LD50 in mice (mg/kg): 585 i.p.; >2000 orally (Haley).
Melting point: mp 686°
Density: d 4.465; d 2.382
Toxicity data: LD50 in mice (mg/kg): 585 i.p.; >2000 orally (Haley)
 
Derivative Type: Dichloride
Molecular Formula: SmCl2
Molecular Weight: 221.27
Percent Composition: Sm 67.95%, Cl 32.05%
Properties: Dark brown crystalline mass. d22 3.687. Practically insol in alcohol. Dec by water.
Density: d22 3.687
 
Derivative Type: Sulfate
Molecular Formula: Sm2(SO4)3
Molecular Weight: 588.91
Percent Composition: Sm 51.06%, S 16.33%, O 32.60%
Properties: Octahydrate, light yellow crystals, d18 2.930. Sparingly sol in water.
Density: d18 2.930
 
Use: Oxide in control rods of some commercial nuclear power reactors. Alloys with cobalt to produce extremely stong permanent magnets.

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