A general model from theoretical cosolvency models

Abstract

It has been shown that the two theoretical cosolvency models, i.e. the excess free energy, EFE, and the combined nearly ideal binary solvent/Redlich-Kister, CNIBS/R-K, despite different appearances could be converted to a general single model, GSM, using some appropriate substitutions and rearrangements. The general model was a power series equation with respect to the concentration of one of the solvents in a binary solvent system. From the obtained GSM a theoretical justification was provided to the cosolvency equations employing the extended Hildebrand approach, EHA, as well as those methods using an empirical power series equations for expressing the solubility. The accuracy of GSM was compared with that of the original EFE and CNIBS/R-K models and the results suggested differences in the accuracy between the original models and the corresponding GSM, which was attributed to differences in the arrangements of the independent variables in the models. (C) 1997 Elsevier Science B.V.