[Cr(CN)6]2 + 19 K2Cr2O7 + 73 H2SO4 → 20 Cr2(SO4)3 + 12 KNO3 + 13 K2SO4 + 12 CO2 + 73 H2O
This is an oxidation-reduction (redox) reaction:
12 CII - 24 e- → 12 CIV (oxidation)
12 N-III - 96 e- → 12 NV (oxidation)
40 CrVI + 120 e- → 40 CrIII (reduction)