10 H+ + SVIO42- + 8 (I-I)- H2S-II + 4 I20 + 4 H2O

This is an oxidation-reduction (redox) reaction:

SVI + 8 e- S-II (reduction)

8 I-I - 8 e- 8 I0 (oxidation)

SO42- is an oxidizing agent, I- is a reducing agent.