A substance on treatment with dil. H2SO4 librates a colourless gas whichI. turns acidified dichromate solution green.II. produces turbidity with baryta water.   These reactions indicate the presence of

Baryta water is a solution of Ba(OH)2 in water. SO2 gives white precipitate (or turbidity) with Ba(OH)2 solution. It is due to the formation of insoluble BaSO3.SO2+Ba(OH)2⟶BaSO3↓+H2OSO2 also turns acidified K2Cr2O7 solution green due to the formation of green coloured Cr2 (SO4)3. K2Cr2O7+3SO2+H2SO4⟶K2SO4+Cr2SO43+H2OSO2 is obtained by the action of dil. H2SO4 on a sulphite, SO32- (or thiosulphate).