A23 Reactions of Hydrogen Iodide and Chlorine

Description
A bottle of hydrogen iodide mixes with a bottle of chlorine gas. Three different products are observed at different reactant concentrations. Yellow crystals form in the chlorine bottle where little HI has diffused. Violet iodine and even some reddish brown iodine monochloride are observed.

Equation
Cl₂ + 2HI --> 2 HCl + I₂(violet crystals)

Cl₂ + HI --> HCl +ICl (brown liquid)

4 Cl₂ + 2 HI --> 2 HCl + I₂Cl₆(yellow crystals)

Reference
H. N. Alyea and F. B. Dutton, Eds.,"Tested Demonstrations in Chemistry", 6th ed., Journal of Chemical Education, Easton, Pennsylvania (1965) p..

and B. Z. Shakhashiri, "Chemical Demonstrations", Vol. 2, The University of Wisconsin Press, Madison ,Wisconsin, (1985) p.224.