noun
: any of a series of oxides of uranium that are usually regarded as definite compounds but are better considered phases with a range of compositions: as
a. : the dioxide UO 2 or approximately UO 2.0-2.6(?) obtained as a brown to black crystalline powder by heating uranium trioxide or tri-uranium oct-oxide in hydrogen or carbon monoxide and formerly used in gas mantles and in ceramic glazes — compare uraninite
b. : the most stable of the oxides U 3 O 8 that occurs in pitchblende, that is obtained as a green to black crystalline compound by treating pitchblende successively with acids, bases, and dilute acids or by igniting other uranium oxides or most other uranium compounds in air, that is reduced to metallic uranium by heating with carbon or aluminum, and that is a primary source of uranium for atomic energy work : tri-uranium oct-oxide
c. : the trioxide UO 3 that is obtained as a light yellow to orange to brick-red amorphous or crystalline substance usually by heating uranyl nitrate or ammonium di-uranate, that loses oxygen on heating to form tri-uranium oct-oxide, and that is sometimes used as a pigment for green-yellow colors in glass