8 FeIIICl3 + H2S-II + 4 H2O 8 FeIICl2 + H2SVIO4 + 8 HCl

This is an oxidation-reduction (redox) reaction:

S-II - 8 e- SVI (oxidation)

8 FeIII + 8 e- 8 FeII (reduction)

H2S is a reducing agent, FeCl3 is an oxidizing agent.