Element Praseodymium, Pr, Lanthanide

Praseodymium is one of the most abundant of the rare earth elements, but it is decidedly less plentiful than lanthanum or neodymium. The relative proportions of praseodymium and neodymium in different minerals do not vary very much, the ratio praseodymium to neodymium being approximately 1 to 2.

Praseodymium is a yellow metal of density 6.475. It melts at 940° and is strongly paramagnetic, the magnetic susceptibility at 18° being about 25×10^-6 c.g.s. units per gram. Very little else is known of the properties of the metal.

Praseodymium was discovered in a close conjunction with neodymium recovery. In 1841 Mosander divided the lanthanum in two: lantana and didimia, from the Greek διδνμος (didymos) = twins). For several years after that didymium was included to elements tables as the name of the new element. In 1879 Francois Lecoq de Boisbaudran showed that it contained samarium. In 1885 the Austrian chemist Carl Auer von Welsbach (1858-1929) separated the residual didymium after removal of Samarium, into two groups of compounds. One of them included green salts and oxides; in the other one the salts and oxides were of various colors, from pink to purple and grayish-blue. The discovered elements were named as neodymium (new twin) and praseodymium (green twin), so retaining a part of the original names, with new suffices.

Lanthanide Praseodymium is available in small quantities in Earth's crust 7x10^-4 mass %; in seawater its abundance is 2.6x10^-6 mg/L. With other rare earth elements of the cerium subgroup it is found in minerals monazite and bastnasite (up to 8%) as well as in loparite, samarskite, and apatite.