On the thermodynamics of partially miscible liquid binary systems

摘要

Isobaric coexistence curves of two liquid phases are predicted from the temperature and composition at the consolute point of binary solutions consisting of a hydrocarbon and the corresponding perfluorocarbon. Excess enthalpies obtained from the free volume theory ofFloryas well as from calorimetric measurements are used to account for the temperature dependence of theGibbsenergy of mixing. The treatment is based on the extension of theFlory-Hugginsmodel to nonathermal polymer solutions. Formal applicability to mixtures of molecules not largely differing in size is achieved by introducing generalized variables characterizing composition in place of volume fractions. Phase diagrams of following systems are predicted and compared with experimental results: methane+carbontetrafluoride,n-hexane+perfluoro-n-hexane,n-heptane+perfluoro-n-heptane, methylcyclohexane+perfluoromethyl-cyclohexane.