Barium compounds: barium diiodide dihydrate

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The barium in barium diiodide dihydrate formally is in the oxidation state 2.

Barium diiodide dihydrate

  • Formula as often written: BaI2.2H2O
  • Hill system formula: Ba1H4I2O2
  • CAS registry number: [7787-33-9]
  • Formula weight: 427.166
  • Class: iodide


  • barium diiodide dihydrate
  • barium(II) iodide 2-water
  • barium diiodide 2-water

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 740°C; 539°C (dehydrates to form BaI2)
  • Boiling point:
  • Density: 5000 kg m-3


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Element analysis

Element percentages for the elements in barium diiodide dihydrate
Element %
Ba 32.15
H 0.94
I 59.42
O 7.49


Barium iodide dihydrate is made by the neutralization of barium carbonate with HI in water. The product crystallizes as the hydrate BaI2.2H2O. If this heated, dehydration to anhydrous BaI2 occurs.

BaCO3 + 2HI(aq) → BaI2(aq)

Isotope pattern

What follows is the calculated isotope pattern for the BaI2.2H2O unit with the most intense ion set to 100%.

Formula: Ba1I2H4O2

mass  %
420   0.2 
421 0.0
422 0.1
423 0.0
424 3.4 __
425 9.2 _____
426 11.0 ______
427 15.7 ________
428 100.0 __________________________________________________
429 0.2
430 0.4


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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barium atomic number