Rubidium monoxide, Rb₂O

When rubidium is partially oxidized by diluted oxygen, and the excess of metal removed by distillation, the Rubidium monoxide, Rb₂O, is obtained in transparent, pale-yellow crystals which become deeper yellow at 250° C. Its density is 3.72. At 400° C. it is decomposed into the metal and dioxide; and at 250° C. it reacts with hydrogen, forming equimolecular proportions of the hydroxide and hydride. It also reacts with fluorine, chlorine, and iodine. Its heat of formation is 83.5 Cal.