Hydrogen fluoride

  • Formula: HF
  • Hill system formula: F1H1
  • CAS registry number: [7664-39-3]
  • Formula weight: 20.006
  • Class: fluoride
  • Colour: colourless
  • Appearance: gas
  • Melting point: -83.5°C
  • Boiling point: 19.5°C
  • Density: 1000 kg m-3 (liquid at 0°C)

The following are some synonyms of hydrogen fluoride:

  • hydrogen fluoride
  • hydrogen(I) fluoride
  • hydrofluoric acid

The oxidation number of hydrogen in hydrogen fluoride is 1.


Dry hydrogen fluoride gas may be made in the laboratory by heating anhydrous potassium hydrogen fluoride and collecting the evolved hydrogen fluoride gas.

KHF2(s) (500°C) → HF(g) + KF(s)

Hydrogen fluoride gas may be made on very large scales (20000 tonnes par year) by the reaction of calcium(II) fluoirde, CaF2, with sulphuric acid.

CaF2(s) + H2SO4(l) (200°C) → 2HF(g) + CaSO4(s)

Solid state structure

  • Geometry of hydrogen: 1 coordinate: terminus
  • Prototypical structure:

Crystal structure of hydrogen fluoride

Element analysis

The table shows element percentages for HF (hydrogen fluoride).

Element %
F 94.96
H 5.04

Isotope pattern for HF

The chart below shows the calculated isotope pattern for the formula HF with the most intense ion set to 100%.


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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