Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The mutual replacement of SO₃^2- and SO₄^2- anions was studied in Na₂SO₃.7 H₂O crystals where sulphite is slowly oxidized to sulphate by air oxygen. In a series of Na₂(SO₃, SO₄).7 H₂O samples, the C₁ or C_s site symmetry appears for the SO₃^2- anion and the site symmetry of the SO₄^2- anion is lowered gradually from T_d through D_2d or C_3v to C₁. The replacement was also studied for anhydrous sodium sulphite obtained by dehydration or by evaporation from aqueous solution. Despite the different structures of Na₂SO₃ and Na₂SO₄ crystals (C_3i¹ and D_2h²⁴, respectively), the favourable dimensions of the sterically different anions allow the SO₄^2- ions, with their own symmetry T_d, to be located in the C₃ sites of the SO₃^2- ions in Na₂SO₃.