SURFACE CONCENTRATIONS AND COMPOUND FORMATION IN AQUEOUS SULFURIC-ACID

The concentration of free water molecules at the surface of a strong s ulfuric acid solution is found to be very low, mainly as a consequence of the formation of acid hydrates. Values of equilibrium constants an d enthalpy changes for successive hydration reactions of H2SO4 have be en calculated from the variation of water vapour pressure with acid st rength and temperature. The results support the conclusion of Fried et al.(1) that the rate of reaction of a molecule such as N2O5 with a su lfuric acid aerosol is controlled by the rate at which the molecule ca n penetrate into the bulk of the liquid.