Dysprosium
. Dysprosium, symbol Dy, metallic element with an atomic number of 66. Dysprosium is one of the rare earth elements in the lanthanide series of the periodic table . The element was discovered in 1886 by Paul Émile Lecoq de Boisbaudran, who separated one of its compounds from an oxide of holmium . Dysprosium is 42nd in abundance among the elements in the earth's crust. The compounds of dysprosium are found in gadolinite, xenotime, euxenite, and fergusonite in Norway, the United States, Brazil, India, and Australia. Its salts are either yellow or yellow-green in color, the most common being a chloride, a nitrate, and a sulfate. The salts of dysprosium have an extremely high magnetic susceptibility. Dysprosium usually occurs as the white oxide dysprosia, with erbium and holmium, two other rare earth elements. Dysprosia is sometimes used in the control rods of nuclear reactors (see Nuclear Energy ). Dysprosium melts at about 1412° C (about 2574° F), boils at about 2567° C (about 465