U*ra"ni*um (?), n. [NL., from Uranus the planet. See Uranus.] Chem.

An element of the chromium group, found in certain rare minerals, as pitchblende, uranite, etc., and reduced as a heavy, hard, nickel-white metal which is quite permanent. Its yellow oxide is used to impart to glass a delicate greenish-yellow tint which is accompanied by a strong fluorescence, and its black oxide is used as a pigment in porcelain painting. Symbol U. Atomic weight 239. �x3c;--radioactive, U-235 isotope is used in atomic fission, in bombs or power plants --�x3e;

⇒ Uranium was discovered in the state of an oxide by Klaproth in 1789, and so named in honor of Herschel's discovery of the planet Uranus in 1781.


© Webster 1913.