The Chemical Behavior of Low Valence Sulfur Compounds. X. Disproportionation of Thiosulfate, Trithionate, Tetra-thionate and Sulfite under Acidic Conditions

The disproportionation of thiosulfate, trithionate, tetrathionate and sulfite in acidic solutions has been studied at relatively high temperatures. Thiosulfate hardly decomposes in the absence of sulfuric acid, even at 150 °C, but decomposes very easily in the presence of sulfuric acid at 70 °C, forming elemental sulfur, tetrathionate and sulfite. Trithionate decomposes to thiosulfate and sulfate at 70 °C, while tetrathionate decomposes only at temperatures above 130 °C after an induction period forming thiosulfate as an intermediate. Sulfite undergoes disproportionation, giving thiosulfate and sulfate at 150 °C, and then elemental sulfur and sulfate accompanied by intermediate formation of tetrathionate. A disproportionation pathway of low valence sulfur oxyacids including thiosulfate, trithionate, tetrathionate and sulfite has been proposed.