3 As2IIIS3-II + 28 HNVO3 + 4 H2O 6 H3AsVO4 + 9 H2SVIO4 + 28 NIIO

This is an oxidation-reduction (redox) reaction:

6 AsIII - 12 e- 6 AsV (oxidation)

9 S-II - 72 e- 9 SVI (oxidation)

28 NV + 84 e- 28 NII (reduction)

Change the oxidation states