SO32− and SO42− when treated with BaCl2, give white ppt of BaSO3 and BaSO4 respectively. BaCl2+SO32−⟶sulphideBariumBaSO3+2Cl− BaCl2+SO42−⟶Barium sulphateBaSO4+2Cl−
Barium sulphate Out of these two, SO32− is soluble in HCl but SO42− does not.