33—THE UPTAKE OF SULPHURIC ACID VAPOUR BY WOOL

Wool has been shown to absorb sulphuric acid from the vapour phase. The rate of absorption increases with acid concentrations of up to 99·5% by weight and decreases with the pressure of inert molecules present in the system. Uptakes in excess of 200% on the original weight of wool have been observed at temperatures close to ambient. The observed weight increase due to absorbed acid is dependent on exposure time because degradation of the wool results in loss of material. A proposed mechanism for the absorption of H2SO4, molecules includes steps involving the effect of inert-gas molecules adsorbed onto the fibre surface, immobilization of absorbed acid by chemicai reaction with the wool, and barrier effects due to packing densities and the formation of a boundary layer in the presence of appreciable pressures of inert-gas molecules. The presence of absorbed H2SO4 has been shown to modify the subsequent water-sorption properties of the wool owing to reaction of acid with hydrophilic groups and also because ...