Ammonium Bifluoride

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Production and applications

  • Ammonium bifluoride is a component of some etchants. It attacks silica component of glass:
SiO2 + 4 [NH4][HF2] → SiF4 + 4 [NH4]F + 2 H2O
  • Potassium bifluoride is a related more commonly used etchant.
  • Ammonium bifluoride has been considered as an intermediate in the production of hydrofluoric acid from hexafluorosilicic acid. Thus, hexafluorosilicic acid is hydrolyzed to give ammonium fluoride, which thermally decomposes to give the bifluoride:
H2SiF6 + 6 NH3 + 2 H2O → SiO2 + 6 NH4F
2 NH4F → NH3 + [NH4]HF2
  • The resulting ammonium bifluoride is converted to the sodium bifluoride, which thermally decomposes to release HF