Aggregation in Binary Solutions Containing Hexafluorobenzene

Abstract

Some information about the aggregation in aromatic fluorocarbon−aromatic hydrocarbon systems was obtained on the basis of the Kirkwood−Buff theory of solution. The Kirkwood−Buff integrals and the excess (or deficit) number of molecules aggregated around a central one were calculated for the following systems: hexafluorobenzene−benzene, hexafluorobenzene−toluene, hexafluorobenzene−cyclohexane, benzene−toluene, and benzene−cyclohexane. It was found that the composition dependence of the excess (or deficit) number of molecules aggregated around a central one for the systems hexafluorobenzene−benzene and hexafluorobenzene−toluene has a nontypical character since it changes sign for a mole fraction of about 0.4 for the former and 0.2 for the latter. It was found that such compositions correspond to extrema in the activity coefficients and inflection points in the excess Gibbs energy. The excess (or deficit) number of molecules aggregated around a central one in the systems investigated allowed us to conclude ...