Study of the Disproportionation of Sodium Thiosulfate by X-Ray Photoelectron Spectroscopy

The disproportionation of sodium thiosulfate to form sodium sulfite and elemental sulfur has been studied in the temperature range 495–548°K by means of X-ray photoelectron spectroscopy (XPS). The disproportionation started with an induction period, followed by a steady-state disproportionation rate regime, and ended up with a diffusion rate-controlling process. The duration of the induction period was inversely proportional to the temperature of heating. The disproportionation in the steady-state regime followed a first-order reaction rate law with the enthalpy and entropy of activation H* = 26.0 kcal/ mol and S* = -14.9 eu.