110th Anniversary: From Solubility Parameters to Predictive Equation-of-State Modeling

A simple predictive molecular thermodynamic model for bulk phases and interfaces is presented. The model combines features of the quantitative structure-property relationships (QSPR) approach, the equation-of-state approach, and quantum-chemical calculations. Simple formalisms on a sound thermodynamic basis have been developed for the main thermodynamic quantities of pure components and mixtures while the required parameters for the calculations are rather easily obtained from common databases in the public domain. The widely available solubility parameters or the linear solvation energy relationships (LSER) molecular descriptors are exploited for the extraction of the required information. The predictive capacity of the model with a variety of properties and types of systems including highly nonideal hydrogen-bonded mixtures is reviewed. Emphasis is given in this work on predictions of solvation free energies and the results are rather satisfactory. The strength and weakness of the model and its perspectives are also critically discussed.