Potassium compounds: potassium chloride

potassium symbol icon

The potassium in potassium chloride formally is in the oxidation state 1.

Crystal structure of potassium chloride

Potassium chloride

  • Formula as often written: KCl
  • Hill system formula: Cl1K1
  • CAS registry number: [7447-40-7]
  • Formula weight: 74.551
  • Class: chloride


  • potassium chloride
  • potassium(I) chloride
  • sylvite

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 771°C
  • Boiling point: 1500°C
  • Density: 1988 kg m-3


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Element analysis

Element percentages for the elements in potassium chloride
Element %
Cl 47.55
K 52.45


One way to make potassium chloride is to react the hydroxide with hydrochloric acid. The resulting salt can then be purified by recrystallization. In practice however, potassium chloride is available in massive amounts in nature and can simply be recrystallized to recover it.

KOH(aq) + HCl(aq) → KCl(aq) + H2O(l)

While not a normal route of preparation because of the expense, potassium metal reacts vigorously with all the halogens to form potassium halides. So, it burns with chlorine, Cl2, to form potassium(I) chloride, KCl.

2K(s) + Cl2(g) → 2KCl(s)

Solid state structure

  • Geometry of potassium: 6 coordinate: octahedral
  • Prototypical structure: NaCl (rock salt)

Crystal structure of potassium chloride

Isotope pattern

What follows is the calculated isotope pattern for the KCl unit with the most intense ion set to 100%.

Formula: K1Cl1

mass  %
74 100.0 __________________________________________________
75 0.0
76 39.2 ____________________
77 0.0
78 2.3 _


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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potassium atomic number