Potassium hydrogen fluoride, KHF₂

Potassium fluoride combines with hydrofluoric acid to form a primary fluoride, KF,HF or KHF₂, crystallizing in tetragonal plates, and decomposed at red heat with evolution of hydrofluoric acid. Its heat of formation from the fluoride and hydrogen fluoride is 21.1 Cal., and its heat of solution is -6.0 Cal. Other unstable compounds of potassium fluoride with 2 and with 3 molecules of hydrogen fluoride have been prepared.

Precipitation with alcohol of a solution of potassium fluoride and hydrogen peroxide yields an unstable compound of the formula KF,H₂O₂.