Nomenclature
CAS number: 7440-54-2
Description and 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, T 1.08 × 1014 years, α-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 α-form, d 7.886, transforms to β-form
at 1262°; body-centered cubic β-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).Derivative
Oxide.
Nomenclature
Gadolinia. Gd
2O
3; mol wt 362.50.
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.Derivative
Hydroxide.
Gd(OH)
3; mol wt 208.27.
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
Chloride.
GdCl
3; mol wt 263.61.
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).Derivative
Sulfate.
Gd
2(SO
4)
3; mol wt 602.69.
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°.Derivative
Nitrate.
Gd(NO
3)
3; mol wt 343.26.
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).Use
Oxide in control rods of some nuclear power reactors.