rare metallic element, 1885, coined in Modern Latin by discoverer Carl Auer von Welsbach (1858-1929) from Greek prasios "leek-green" (from prason "leek") + didymos "double," the name given to an earth in 1840, so called because it was a "twin" to lanthana. When didymia was further analyzed in the 1880s, it was found to have several components, one of which was characterized by green salts and named accordingly, with the elemental suffix -ium.
praseodymium pra·se·o·dym·i·um (prā'zē-ō-dĭm'ē-əm, prā'sē-)
n.
Symbol Pr
A soft malleable ductile rare-earth element that develops a characteristic green tarnish in air and is used to color glass and ceramics yellow and in metallic alloy. Atomic number 59; atomic weight 140.908; melting point 931°C; boiling point 3,510°C; specific gravity 6.8; valence 3.
| praseodymium (prā'zē-ō-dĭm'ē-əm) Symbol Pr A soft, malleable, silvery metallic element of the lanthanide series that develops a green tarnish in air. It is used to add a yellow tint to glass and ceramics and to make the glass used in welding goggles. Atomic number 59; atomic weight 140.908; melting point 935°C; boiling point 3,127°C; specific gravity 6.8; valence 3, 4. See Periodic Table. |
((Pr), chemical element, rare-earth metal of transition Group IIIb of the periodic table, used as the element in special alloys and, as its oxide, in glasses. Moderately soft, ductile, and malleable, this silvery metal rapidly displaces hydrogen from water and slowly reacts in air, developing a green oxide coating, which chips. For preservation, the metal must be sealed in a plastic covering or kept in mineral oil. Praseodymium was discovered in didymia, a mixture of several rare-earth oxides. From it, by repeated fractional crystallization of ammonium didymium nitrate, Carl Auer von Welsbach separated (1885) salts of the elements praseodymium (the green fraction) and neodymium. Praseodymium occurs in minerals such as monazite and bastnaesite and as one of the products of nuclear fission. Natural praseodymium is all stable isotope praseodymium-141. This element is commercially separated and purified by ion-exchange techniques; the reduction of the fluoride or chloride with calcium is one way in which the metal itself is prepared