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Environmental fate & pathways

Hydrolysis

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Description of key information

Thiosulfates are known to be  stable under alkaline conditions, but not in acidic media. In aqueous media, thiosulfates irreversibly disproportionate to sulfite and sulfate anions.

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Additional information

Thiosulfates are known to be stable under alkaline conditions, but not in acidic media. Thiosulfates disproportionate in aqueous solution to form polythionic acids and SO2(HSO3-), this requires somewhat different, more acidic conditions. [1]

         HS2O3-+ H2S2O3HS3O3- + SO2+ H2O

Nevertheless, one key study (Lange, 2011) demonstrated that sodium thiosulfate is stable at pH 4, 7 and 9 with an estimated half-life of >1 year at room temperature.

[1]Hollemann Wiberg, Lehrbuch der Anorganischen Chemie, 101. Auflage