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Related article sulphur dioxide

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It is prepared by boiling sulphur with an aqueous solution of sodium sulphate Na2SO3 + 1/8 S8 ------> Na2S2O3 Properties Sodium thiosulphate is a water soluble crystalline substance. a) Reaction with iodine Sodium thiosulphate is oxidised by iodine to form sodium tetra thionate. This reaction is the basis of iodometric titrations. 2Na2S2O3 + I2 ---------> Na2S4O6 + 2NaI b) Reaction with chlorine Sodium thiosulphate can remove excess chlorine by forming HCl. Hence it is used as an antichlor. Na2S2O3 + Cl2 + H2O -----------> Na2SO4 + 2HCl + S c) Reaction with silver halides Silver halides dissolve in sodium thiosulphate solution due to formation of a complex sodium argento thiosulphate. This reaction is the basis of its use in photography as fixer. AgCl + Na2S2O3 -------------> NaAgS2O3 + NaCl

The stable oxides of sulphur are sulphur dioxide (SO2) and sulphur trioxide (SO3) Sulphur when burnt in air form sulphur dioxide. S8 + 8O2 -------------> 8SO2 SO2 is a gas at room temperature. It exists as descrete SO2 molecule with angular structure. SO3 is an acidic oxide and exist as planar triangular molecule in gas phase. In solid state, SO3 exist either as cyclic trimer or linear chain polymer.