Thermodynamics of transfer of sorbitol and mannitol from water to aqueous solutions of urea, guanidine hydrochloride and sodium chloride

Abstract

Integral enthalpies of solution at 298.15 and 308.15 K and densities at 298.15 K for sorbitol and mannitol in aqueous solutions of urea (2, 4 and 6 mol kg^–1), guanidine hydrochloride (2 and 4 mol kg^–1) and sodium chloride (2 and 4 mol kg^–1) have been determined. These data have been used to derive thermodynamic functions (viz. enthalpy, heat capacity and partial molal volumes) for transfer from water to aqueous solutions of urea, guanidine hydrochloride and sodium chloride. The thermodynamic data have been rationalized in terms of polyol–cosolute interactions. The difference in the behaviour of sorbitol and mannitol has been explained in terms of a specific hydration model.