ABSTRACT
Abstract: As is well known, the methods of classical thermodynamics (activity coefcient or equation of state approaches) have frequently failed to correctly predict the solubilities of various solutes in pure or multiple solvents. This is true for the solubility of gases, large molecules (drugs, biomolecules), and very large molecules (polymers and proteins) in water and aqueous solutions. The main reason for this difculty is that these systems are highly nonideal and the activity coefcients cannot be predicted using the traditional thermodynamic methods. Fortunately, the uctuation theory of solutions (or the Kirkwood-Buff [KB] theory of solutions) has proven to be a very effective tool for predicting the solubility of various solutes, especially in mixed solvents. During the last decade, the KB theory was successfully applied to the solubility of solid solutes in supercritical solvents, to the solubility of gases in multiple solvents and polymer solutions, to the solubility of drugs and pollutants in aqueous mixtures and to the solubility of proteins in mixed solvents.
