Iodine trichloride

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Iodine trichloride
Iodine trichloride ampoule sample by ChemicalForce.jpg
Ampoule containing ICl3 and its dimer formula
IUPAC name
Iodine trichloride
Other names
Diiodine hexachloride (dimer)
iodine(III) chloride
ICl3 (monomer)
I2Cl6 (dimer)
Molar mass 233.264 g/mol (monomer)
466.5281 g/mol (dimer)
Appearance Yellow or red solid
Odor Pungent
Density 3.203 g/cm3 (-40 °C)
3.11 g/cm3 (15 °C)
Melting point 63 °C (145 °F; 336 K)
Boiling point Decomposes
Solubility Reacts with alcohols
Soluble in acetic acid, acetone, arsenic trichloride, bromine, dichloroacetic acid, methyl ethyl ketone, phosgene, phosphoryl chloride, sulfuryl chloride
Slightly soluble in liq. SO2[1][2]
899.5 kJ/mol
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Related compounds
Related compounds
Iodine monochloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Iodine trichloride is an interhalogen compound of iodine and chlorine. In the solid state is present as a planar dimer I2Cl6, better represented as Cl2I(μ-Cl)2ICl2, with two bridging Cl atoms.



Iodine trichloride slowly fumes in open air, more vigorously in liquid form. It reacts with water, slowly with cold water and rapidly with warm/hot water. It also reacts vigorously with alkalis.

2 ICl3 + 3 H2O → 5 HCl + HIO3 + ICl (cold water)
5 ICl3 + 9 H2O → 15 HCl + 3 HIO3 + I2 (hot water)

Iodine trichloride decomposes above its boiling point to iodine monochloride and chlorine gas.

ICl3 → ICl + Cl2

Addition of tin(II) chloride to ICl3 gives tin(IV)chloro-iodide (SnCl2I2). This in turn evolves into tin(IV) chloride, releasing purple iodine vapors.

Red phosphorus and lithium borohydride ignite on contact with ICl3.[3]


Iodine trichloride is a bright yellow solid which upon exposure to light turns red due to the presence of elemental iodine.


Iodine trichloride is sold by chemical suppliers, but it's not easy to acquire.


Can be prepared by reacting iodine with an excess of liquid chlorine at −70 °C.


  • Compound collecting
  • Pyrotechnic demonstrations



Iodine trichloride is highly corrosive and toxic. Wear proper protection when handling it.


The only safe way to store this compound is in glass ampoules.


Iodine trichloride can be safely neutralized by adding it in very cold water containing very diluted solution of sodium hydroxide and sodium thiosulfate.



  1. Finkelstein, W.; Zh. Russ. Fiz. - Khim. O - va., Chast Khim.; vol. 58; (1926); p. 565
  2. Beckmann, E.; Junker, F.; Z. Anorg. Chem.; vol. 55; (1907); p. 375 - 375

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