Solid state vibrational spectroscopy. Part 7. A vibrational spectroscopic study of the thermal decompositions of sodium and potassium thiosulphate

Abstract

The thermal decompositions of Na₂[S₂O₃] and K₂[S₂O₃] have been studied using thermal gravimetric analysis, and by recording the i.r. and Raman spectra of the products formed when the two salts are heated to various temperatures in air and in nitrogen. The spectroscopic studies reveal the formation of polysulphides: Na₂S₂ and γ-Na₂S₅, in the case of Na₂[S₂O₃], and K₂S₃, K₂S₄, and K₂S₅, in the case of K₂[S₂O₃], which, in air, are subsequently oxidized to give the sulphate salt as the final product. Studies on the decomposition of solid mixtures of Na₂[S₂O₃] and Na₂[SO₃] show that all the Na₂[SO₃] is consumed, supporting the hypothesis that sulphite is an intermediate in the decomposition.