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elements earth rare called

Praseodymium, chemical element, symbol Pr; for physical constants see Periodic Table. Praseodymium was discovered by C.A. von Welsbach in 1885 after he separated didymia into earths (oxides) called praseodymia and neodymia. The element occurs in the minerals monazite and bastnasite, the two principal sources of the rare-earth elements. It is prepared by reducing the anhydrous chloride with calcium. Praseodymium is a silvery, soft, reactive metal, belonging to the series of elements known as the rare-earth metals. Ion-exchange and solvent extraction techniques have led to much easier isolation of the so-called rare-earth elements. Praseodymium and its compounds are used in carbon lighting applications, special glasses and enamels, and refractory materials.

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