Bifluoride
The bifluoride ion is an inorganic anion with the chemical formula. The anion is colorless. Salts of bifluoride are commonly encountered in the reactions of fluoride salts with hydrofluoric acid. The commercial production of fluorine involves electrolysis of bifluoride salts.
Structure and bonding
The bifluoride ion has a linear, centrosymmetric structure, in a sort of hybrid between a hydrogen bond and a covalent bond.Reactions
Salts, such as potassium bifluoride and ammonium bifluoride are produced by treating fluoride salts with hydrofluoric acid:Potassium bifluoride binds a second equivalent of HF:
Heating these salts releases anhydrous HF.
The bifluoride anion is present in solutions of HF and buffered oxide etch, used in microfabrication etching. In these processes, bifluoride breaks down silicon oxides, doing more effectively than HF.