Interaction of selenous acid with thiosulphate in the presence of ascorbic acid
The reaction between selenous acid, H2SeO3, sodium thiosulphate, Na2S2O3, and ascorbic acid, C6H8O6, in the solution of hydrogen chloride proceeds with the formation of monoselenane-dithiosulphate – monoselenopentathionate, Se(S2O3)2- – SeS4O6 2-, which in certain conditions are isolated from the reaction mixture as the crystalline salt trans-dianilinebis(dimethylglyoximato)cobalt(III) monoselenopentathionate tetrahydrate, [Co(DH)2A2]2SeS4O6·4H2O. The isolated compound is characterized by the chemical analysis, thermogravimetric and differential thermal anlysis methods, and IR spectra. The dehydratation of isolated compound proceeds at a temperature of ~45–140 °C, and its decomposition begins at 140–145 °C. The final product of [Co(DH)2A2]2SeS4O6·4H2O decomposition at a high temperature is cobalt oxide Co3O4. The IR spectra of the isolated compound showed the maxima of absorption bands characteristic of the monoselenopentathionate anion at 249.5, 265.9, 323.8, 390.6, 445.5, 511.6, 566, 581 and 605.4, 979, 1017.7, 1073 and 1094, 1219.7 and 1236 cm-1; they are assigned to δ(S–Se–S), ν(Se–S), γr(SO3), ν(S–S), δas(S–O), δs(S–O), νs(S–O), νas(S–O), respectively.