3 Na2S2IVO5 + 6 CuIISVIO4*5H2O + 10 NaOH 2 Cu34/3(SIVO3)2*2H2O + 8 Na2SVIO4 + 31 H2O

This is an oxidation-reduction (redox) reaction:

6 CuII + 4 e- 6 Cu4/3 (reduction)

2 SIV - 4 e- 2 SVI (oxidation)

Change the oxidation states