Potassium borates

Fusion of boron trioxide with the equivalent proportion of potassium carbonate yields the metaborate, KBO₂, white, monoclinic crystals melting at 947° C., and of specific heat 0.2248 between 16° and 98° C. It dissolves in water, forming a strongly alkaline solution, from which a 1.5-hydrate and a 1.25-hydrate are said to crystallize. At 0° C. Rosenheim and Leyser observed the formation of crystals with 4H₂O, and at 30° C. that of crystals with 1.25H₂O. The salt is gradually transformed by atmospheric carbon dioxide into the tetraborate and carbonate.