Volume changes on mixing perfluoroalkanes with alkanes or ethers at 298.15 K

Abstract

Excess molar volumes V E at 298.15 K have been determined by means of a vibrating-tube densimeter for binary mixtures of n-hexane with a perfluoroalkane, C 5–C 8, and of perfluorohexane with a n-alkane, C 5–C 8, or an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether). The systems perfluoropentane+hexane, perfluorohexane+pentane or hexane or diethyl ether have been investigated in the entire mole fraction range, while the other mixtures only in the miscibility regions. The observed V E values are positive (up to 5.5 cm 3 mol −1) and among the largest known for non-electrolyte systems. Limiting partial molar volumes, V ̄ ° , have been evaluated for each component of the examined mixtures. The behaviour of V ̄ ° has been discussed in terms of the scaled particle theory (SPT) and of a simple group additivity scheme based on surface interactions. An estimate has been made of the average separation distance of solvent from solute molecules.