Space Predictor for Infinite Dilution Activity Coefficients

A new formulation (SPACE) is presented for the prediction of infinite dilution activity coefficients in nonionic solutions. Statistical methods have been used to develop a critically evaluated γ^∞ database at 25 °C and to determine optimum mathematical expressions. The predictive method stems from earlier work using additive contributions to the cohesive energy density, but all compound-specific adjustable parameters have been avoided by using known molecular properties, especially the solvatochromic parameters for dipolarity/polarizability and for hydrogen bonding. This method has the advantages of including explicitly “chemical” interactions and of being uncoupled from any specific g^E(x) expression. For the present, it is limited to monofunctional molecules at 25 °C, and it has not yet been applied to water. Although it appears somewhat more accurate for this database than the UNIFAC method, it should be viewed as a complementary technique—an additional tool for solvent selection by the design engineer.