Qualitative Analysis of Sulphite Ion

Take about 0.1 g salt in a test tube. Add 1 mL H2SO4. Punget smell due to the formation of SO2.

Na2SO3 + H2SO4 → Na2SO4 + SO2 + H2O

Take a small quantity of salt in a test tube. Add a little amount of K2Cr2O7 and dil H2SO4. Warm the test tube, green colour appeared in test tube SO32– ion is confirm.

Na2SO3 + H2SO4 → Na2SO4 + SO2 + H2O

SO2 + K2Cr2O7 + H+ → Cr2(SO4)3 + H2SO4 + H2O