A GENERAL-MODEL FROM THEORETICAL COSOLVENCY MODELS

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 con verted to a general single model, GSM, using some appropriate substitu tions and rearrangements. The general model was a power series equatio n 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 Hildebran d approach, EHA, as well as those methods using an empirical power ser ies equations for expressing the solubility. The accuracy of GSM was c ompared with that of the original EFE and CNIBS/R-K models and the res ults 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 Els evier Science B.V.