ENTHALPIES OF DISSOLUTION OF PROPYLENE CARBONATE, ACETONITRILE, AND 1,4-DIOXANE IN MIXTURES OF WATER WITH ACETONE OR DIMETHYL-SULFOXIDE

Enthalpies of dissolution of acetonitrile, propylene carbonate, and 1, 4-dioxane in mixtures of water with acetone or DMSO were measured in t he whole concentration range of the mixed solvents. Standard enthalpie s of dissolution and enthalpies of transfer of solutes from water to i ts mixtures with acetone or DMSO were determined. In the region of sma ll proportions of the nonaqueous component, the enthalpy of cavity for mation in the mixed solvent makes the main contribution to the variati on of the enthalpy of dissolution. An increase in the proportion of th e nonaqueous component leads to competition between the contributions of cavity formation and specific interaction between the solute and th e solvent during solvation.