Praseodymium - chemistry.

Praseodymium - chemistry. Praseodymium, symbol Pr, silvery metallic element with an atomic number of 59. Praseodymium is one of the rare earth elements in the lanthanide series of the periodic table (see Periodic Law). Praseodymium was discovered in 1885 by the German chemist Carl Auer von Welsbach, who separated it from neodymium. A mixture of the two elements had formerly been considered a single element, called didymium. Praseodymium forms green trivalent salts. Its salts and its similarity to neodymium inspired its name: the Greek words prasios didymos mean "green twin." Praseodymium is a paramagnetic (see Magnetism) metal that corrodes rapidly in moist air. Praseodymium is widely distributed in nature and ranks 37th in order of abundance of the elements in Earth's crust. It is found in cerite and other rare earth minerals such as monazite and bastnasite. It is used, with small amounts of other rare earth metals, in magnesium alloys and in misch metal, an alloy used for cigarette-lighter flints and as a deoxidizer in alloys and vacuum tubes. A mixture of praseodymium and neodymium is used to tint goggles for welders. Praseodymium melts at about 931°C (1708°F), boils at about 3520°C (about 6368°F), and has a specific gravity of 6.77. The atomic weight of praseodymium is 140.9. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.