Mercury compounds: mercury diiodide

mercury symbol icon

The mercury in mercury diiodide formally is in the oxidation state 2.

Crystal structure of mercury diiodide

Mercury diiodide

  • Formula as often written: HgI2
  • Hill system formula: Hg1I2
  • CAS registry number: [7774-29-0]
  • Formula weight: 454.399
  • Class: iodide


  • mercury diiodide
  • mercury(II) iodide
  • mercuric iodide
  • mercury iodide

Physical properties

  • Colour: red (α form); yellow (β form)
  • Appearance: crystalline solid
  • Melting point: 257°C (α form transforms to β at 127°C; β form melts at 257°C)
  • Boiling point: 351°C
  • Density: 6280 kg m-3 (α form); 6090 kg m-3 (β form)


Coming soon...

Element analysis

Element percentages for the elements in mercury diiodide
Element %
Hg 44.14
I 55.86


Not available

Solid state structure

  • Geometry of mercury:
  • Prototypical structure:

Crystal structure of mercury diiodide

Isotope pattern

What follows is the calculated isotope pattern for the HgI2 unit with the most intense ion set to 100%.

Formula: Hg1I2

mass  %
450   0.5 
451 0.0
452 33.4 _________________
453 56.5 ____________________________
454 77.4 _______________________________________
455 44.1 ______________________
456 100.0 __________________________________________________
457 0.0
458 23.0 ____________


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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mercury atomic number