8 I2 + 5 P4O6 → 3 P4O10 + 4 P2I4
This is an oxidation-reduction (redox) reaction:
8 PIII + 8 e- → 8 PII (reduction)
12 PIII - 24 e- → 12 PV (oxidation)
16 I0 + 16 e- → 16 I-I (reduction)
P4O6 is an oxidizing agent, P4O6 is a reducing agent, I2 is an oxidizing agent.