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-)
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.
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.