AbstractThe effect of‐surface‐active agents on the rate of solution of sulphur in sodium and ammonium sulphite slurries has been studied. Cationic surface‐active agents greatly increase the rate of solution. Anionic agents produce some acceleration in the bulk reaction by improving the dispersal of the powder, but retard the specific reaction rate per unit surface area of the sulphur. The Catalytic effectiveness of a homologous series ofn‐alkylpyridinium bromides increases up to the dodecyl member, then decreases with further increase in chain length. The catalytic behaviour of the cationic accelerators is thought to be due partly to a surface‐charge effect and partly to a local generation of pol