I20 + 11 Cl20 + 12 H2O 2 HIXIO3O3 + 22 HCl-I

This is an oxidation-reduction (redox) reaction:

2 I0 - 22 e- 2 IXI (oxidation)

22 Cl0 + 22 e- 22 Cl-I (reduction)

I2 is a reducing agent, Cl2 is an oxidizing agent.