Dipotassium tetraborate, K₂B₄O₇

Dipotassium tetraborate, K₂B₄O₇, of specific heat 0.2198 between 18° and 99° C., has been isolated in the form of hydrates, and a pentaborate, KB₅O₈,4H₂O, has also been prepared. This pentaborate separates from solutions in which the ratio

B₂O₃: KOH = 3: 1

or higher. Its solubility is only slightly greater than that of potassium perchlorate.