Dy; at. wt 162.500; at. no. 66; valences 2, 3, 4. A lanthanide; belongs to the yttrium group of rare earth metals. Naturally occurring isotopes (mass numbers): 156 (0.06%); 158 (0.10%); 160 (2.34%); 161 (18.9%); 162 (25.5%); 163 (24.9%); 164 (28.2%); known artificial radioactive isotopes: 145-155; 157; 159; 165-167. Abundance in earth's crust: ≈4.5 ppm. Occurs in gadolinite, xenotime, samarskite and other rare earth minerals. Discovered in 1886 by Lecoq de Boisbaudran. Sepn: Urbain, Compt. Rend. 139, 736 (1904); 141, 521 (1905); 142, 785 (1906); Spedding et al., J. Am. Chem. Soc. 69, 2812 (1947); 76, 2557 (1954). Prepn of salt: Engle, Balke, ibid. 39, 53 (1917); prepn of a Dy-Al alloy: Schumacher, Harris, ibid. 48, 3108 (1926). Toxicity studies: Bruce et al., Toxicol. Appl. Pharmacol. 5, 750 (1962); Haley et al., ibid. 8, 37 (1966). Reviews of prepn, properties and compds: The Rare Earths, F. H. Spedding, A. H. Daane, Eds. (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. (Univ. 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).