SODIUM DITHIONITE, DECOMPOSITION IN AQUEOUS SOLUTION AND IN THE SOLID STATE

Abstract

The decomposition of sodium dithionite has been investigated in alkaline aqueous solution. Under these conditions it decomposes by a first order reaction with a rate constant of 4.5 × 10 −4 min −1 at 88.5 °C and an activation energy of 26.5 kcal/g-molecule. The ionic strength, and the concentration of the sodium hydroxide also present, affect the rate to some extent. A possible mechanism is suggested. The decomposition of solid sodium dithionite was also examined, and was found to give the best fit to the equations deduced assuming random nucleation, followed by linear growth of nuclei, with possible ingestion and interference of reacting zones. The activation energy of nucleus growth is 32 to 33 kcal/g-molecule, and that for nucleation probably between 40 and 45 kcal/g-molecule.