Calcium iodide

Calcium iodide (chemical formula CaI2) is the ionic compound of calcium and iodine. This colourless deliquescent solid is a salt that is highly soluble in water. Its properties are similar to those for related salts, such as calcium chloride. It is used in photography.[1] It is also used in cat food as a source of iodine.

Calcium iodide
IUPAC name
calcium iodide
3D model (JSmol)
ECHA InfoCard 100.030.238
EC Number
  • 233-276-8
RTECS number
  • EV1300000
  • InChI=1S/Ca.2HI/h;2*1H/q+2;;/p-2 Y
  • InChI=1/Ca.2HI/h;2*1H/q+2;;/p-2
  • I[Ca]I
  • [Ca+2].[I-].[I-]
Molar mass 293.887 g/mol (anhydrous)
365.95 g/mol (tetrahydrate)
Appearance white solid
Density 3.956 g/cm3 (anhydrous)[1]
Melting point 779 °C (1,434 °F; 1,052 K) (anhydrous) [2]
Boiling point 1,100 °C (2,010 °F; 1,370 K)[2]
64.6 g/100 mL (0 °C)
66 g/100 mL (20 °C)
81 g/100 mL (100 °C)
Solubility soluble in acetone and alcohols
-109.0·10−6 cm3/mol
Rhombohedral, hP3
P-3m1, No. 164
NFPA 704 (fire diamond)
Related compounds
Other anions
calcium fluoride
calcium chloride
calcium bromide
Other cations
beryllium iodide
magnesium iodide
strontium iodide
barium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references


Henri Moissan first isolated pure calcium in 1898 by reducing calcium iodide with pure sodium metal:[3]

CaI2 + 2 Na → 2 NaI + Ca

Calcium iodide can be formed by treating calcium carbonate, calcium oxide, or calcium hydroxide with hydroiodic acid:[4]

CaCO3 + 2 HI → CaI2 + H2O + CO2

Calcium iodide slowly reacts with oxygen and carbon dioxide in the air, liberating iodine, which is responsible for the faint yellow color of impure samples.[5]

2 CaI2 + 2 CO2 + O2 → 2 CaCO3 + 2 I2


  1. Turner, Jr., Francis M., ed. (1920), The Condensed Chemical Dictionary (1st ed.), New York: Chemical Catalog Co., p. 127, retrieved 2007-12-08
  2. R. J. Lewis (1993), Hawley's Condensed Chemical Dictionary 12th edition
  3. Mellor, Joseph William (1912), Modern Inorganic Chemistry, New York: Longmans, Green, and Co, p. 334, 6909989325689, retrieved 2007-12-08
  4. Gooch, Frank Austin; Walker, Claude Frederic (1905), Outlines of Inorganic Chemistry, New York: Macmillan, p. 340, retrieved 2007-12-08
  5. Jones, Harry Clary (1906), Principles of Inorganic Chemistry, New York: Macmillan, p. 365, retrieved 2007-12-08
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