EQUILIBRIA IN SULPHUR DIOXIDE SOLUTIONS

Abstract

The investigation described deals with the equilibria existing in a water solution of sulphur dioxide. The vapor pressures and conductivities of solutions of sulphur dioxide were measured over the temperature range 23° to 135 °C. at various concentrations up to 8%. The densities of the aqueous solutions up to 15% were also measured. A discussion of the various equilibria in the light of these data leads to the conclusion that sulphurous acid is one of considerable strength, its apparent weakness being due to the small amount of H2SO3 actually present. With rise in temperature the free sulphur dioxide increases and the hydrogen-ion concentration of the sulphite liquor used in current practice is so low that it seems highly improbable that the cooking reaction is due essentially to this factor. Apart from the bearing this work may have on the theory of sulphite cooking and the theory of the equilibria existing in the SO2−H2O system, it fills a considerable gap in the data regarding sulphur dioxide.