Title: Gadolinium
CAS Registry Number: 7440-54-2
Literature References: Gd; at. wt 157.25; at. no. 64; valence 3. A lanthanide; belongs to yttrium group of rare earth metals. Naturally occurring isotopes (mass numbers): 152 (0.20%), radioactive, T½ 1.08 ´ 1014 years, a-emitter; 154 (2.18%); 155 (14.80%); 156 (20.47%); 157 (15.65%); 158 (24.84%); 160 (21.86%); known artificial radioactive isotopes: 137, 139, 142-151, 153, 159, 161, 162. Abundance in earth's crust: 6.1-6.36 ppm. Sources: samarskite, gadolinite (ytterbite), xenotime, and other rare earth minerals. Discovered by J. C. G. de Marignac in 1880. Prepn of metal: Trombe, Compt. Rend. 200, 459 (1935); idem, Bull. Soc. Chim. Fr. 2, 660 (1935); Klemm, Bommer, Z. Anorg. Chem. 231, 138 (1937). Sepn from other rare earths: F. H. Spedding et al., J. Am. Chem. Soc. 69, 2812 (1947); 76, 2557 (1954). Spectrum: Albertson, Phys. Rev. 47, 370 (1935); Spedding et al., J. Chem. Phys. 5, 33 (1937). Toxicity study: Haley, J. Pharm. Sci. 54, 663 (1965). Reviews of prepn, properties and compds: 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, l971) pp 1-45; T. 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: Colorless or faintly yellowish metal; tarnishes in moist air. Crystalline forms: hexagonal close-packed a-form, d 7.886, transforms to b-form at 1262°; body-centered cubic b-form exists at >1262°. mp 1312°. bp 3273°. Heat of fusion: 10.05 kJ/mol. Heat of sublimation (25°): 397.5 kJ/mol. E°(aq) Gd3+/Gd -2.4 V (calc). Experimental reduction potentials (referred to a normal calomel electrode): -1.810, -1.955 V: Noddack, Brukl, Angew. Chem. 50, 362 (1937).
Melting point: mp 1312°
Boiling point: bp 3273°
Density: d 7.886
Derivative Type: Oxide
Additional Names: Gadolinia
Molecular Formula: Gd2O3
Molecular Weight: 362.50
Percent Composition: Gd 86.76%, O 13.24%
Properties: Colorless, hygroscopic powder; prepd by igniting the hydroxide, nitrate, carbonate or oxalate, d15 7.407, absorbs CO2 from the air.
Density: d15 7.407
Derivative Type: Hydroxide
Molecular Formula: Gd(OH)3
Molecular Weight: 208.27
Percent Composition: Gd 75.50%, O 23.05%, H 1.45%
Properties: Gelatinous precipitate, prepd by the action of alkali or ammonium hydroxide on a soln of a gadolinium salt. Absorbs CO2 from the air.
Derivative Type: Chloride
Molecular Formula: GdCl3
Molecular Weight: 263.61
Percent Composition: Gd 59.65%, Cl 40.35%
Properties: White monoclinic crystals, prepd by heating the oxide with excess of ammonium chloride above 200°. d0 4.52. mp ~609°. Sol in water; forms double salts with platinic and auric chlorides. A hexahydrate, GdCl3.6H2O, deliquesc crystals, d 2.424, is obtained from the aq soln. LD50 in mice (mg/kg): 550 i.p.; >2000 orally (Haley).
Melting point: mp ~609°
Density: d0 4.52; d 2.424
Toxicity data: LD50 in mice (mg/kg): 550 i.p.; >2000 orally (Haley)
Derivative Type: Sulfate
Molecular Formula: Gd2(SO4)3
Molecular Weight: 602.69
Percent Composition: Gd 52.18%, S 15.96%, O 31.86%
Properties: Octahydrate, colorless monoclinic crystals. Soly in water decreases with rise in temp. On heating at 400° yields the anhydr sulfate, d 4.139; begins to dec at 500°.
Density: d 4.139
Derivative Type: Nitrate
Molecular Formula: Gd(NO3)3
Molecular Weight: 343.26
Percent Composition: Gd 45.81%, N 12.24%, O 41.95%
Properties: Hexahydrate, deliquesc triclinic crystals. d 2.332. mp 91°. Sol in water, in alcohol. A pentahydrate, prismatic crystals, mp 92°, d 2.406, very insol, has been prepd. LD50 (hexahydrate) in rats (mg/kg): 230 i.p.; >5000 orally (Haley).
Melting point: mp 91°; mp 92°
Density: d 2.332; d 2.406
Toxicity data: LD50 (hexahydrate) in rats (mg/kg): 230 i.p.; >5000 orally (Haley)
Use: Oxide in control rods of some nuclear power reactors.

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