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Potassium iodide

  • Formula: KI
  • Hill system formula: I1K1
  • CAS registry number: [7681-11-0]
  • Formula weight: 166.003
  • Class: iodide
  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 681°C
  • Boiling point: 1323°C
  • Density: 3120 kg m-3

The following are some synonyms of potassium iodide:

  • potassium iodide
  • potassium(I) iodide

The oxidation number of potassium in potassium iodide is 1.

Synthesis

One way to make potassium iodide is to react the hydroxide with hydroiodic acid. The resulting salt can then be purified by recrystallization.

KOH(aq) + HI(aq) → KI(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 iodine, I2, to form potassium(I) iodide, KI.

2K(s) + I2(s) → 2KI(s)

Solid state structure

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

Crystal structure of potassium iodide

Element analysis

The table shows element percentages for KI (potassium iodide).

Element %
I 76.45
K 23.55

Isotope pattern for KI

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

References

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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