Uranium Pentoxide, U₂O₅

The existence of Uranium Pentoxide, U₂O₅, is not definitely established. It has been described as the black product obtained when a uranium salt of a volatile acid is strongly ignited in air; 7 when uranyl sulphate, (UO₂)SO₄.3H₂O, is rapidly heated; when ammonium diuranate, (NH₄)₂U₂O₇.6H₂O, is heated in a carbon crucible; and when a solution of uranyl nitrate is electrolysed. Many observers regard the substance as a mixture of uranous oxide and urano-uranic oxide, but from a study of the dissociation tension of the latter oxide Schwarz gained evidence of the existence of an intermediate oxide, and by heating the higher oxide in a stream of carbon dioxide in an electric furnace at 1122° C. he obtained a black product of the approximate composition U₂O₅. The substance is reduced to uranous oxide by strongly heating in hydrogen. It dissolves in acids to form uranous and uranyl salts.