praseodymium

A soft, silvery, malleable, ductile rare-earth element that develops a characteristic green tarnish in air. It occurs naturally with other rare earths in monazite and bastnaesite and is used to color glass and ceramics yellow, as a core material for carbon arcs, and in metallic alloys. Atomic number 59; atomic weight 140.908; melting point 931°C; boiling point 3,520°C; specific gravity 6.773; valence 3, 4. cross-reference: Periodic Table.

One of the two elements into which, in 1885, Auer von Welsbach succeeded in resolving what had previously been known as didymium. See neodymium.

An elementary substance, one of the constituents of didymium; — so called from the green color of its salts. Symbol Ps. Atomic weight 143.6.

A metallic chemical element (symbol Pr) with an atomic number of 59.

a soft yellowish-white trivalent metallic element of the rare earth group; can be recovered from bastnasite or monazite by an ion-exchange process