Potassium monoxide, K₂O

The Potassium monoxide, K₂O, is formed by incomplete oxidation of potassium by dry oxygen at reduced pressure, and removal of the excess of metal by distillation in vacuum. The product forms microscopic octahedra, which become pale-yellow at 200° C., and have a density of 2.32 at 0° C. Above 400° C. in vacuum it is decomposed into the metal and the peroxide. The heat of formation of the monoxide from its elements is 86.80 Cal. It is reduced by hydrogen to the hydride and hydroxide. With water it reacts energetically to form the hydroxide, the heat of solution being 75.0 Cal. It also combines with fluorine, chlorine, and iodine. The heat of formation from the elements is 86.8 Cal.