Sodium diuranate, Na2U2O7·6H2O, is a uranium salt also known as the yellow oxide of uranium. Along with ammonium diuranate it was a component in early yellowcakes, the ratio of the two species determined by process conditions; yellowcake is now largely a mix of uranium oxides. It is commonly referred to by the initials SDU.
In the classical procedure for extracting uranium, pitchblende is broken up and mixed with sulfuric and nitric acids. The uranium dissolves to form uranyl sulfate, and sodium hydroxide is added to make the uranium precipitate as sodium diuranate. This older method of extracting uranium from its uraninite ores has been replaced in current practice by such procedures as solvent extraction, ion exchange, and volatility methods.
In the past it was widely used to produce vaseline glass, the sodium salt dissolving easily into the silica matrix during the firing of the initial melt.