Thermodynamic study of perfluorohexane + ether mixtures: VLE, LLE, and HE

Vapour–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and excess enthalpies (HE) of binary mixtures of perfluoro-n-hexane plus an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether), have been determined using a head-space gas-chromatographic technique, a turbidimetric apparatus, and a heat-flow calorimeter, respectively. A recently designed titration technique and calculation procedure have been used to obtain HE from heats of solution. The observed liquid–liquid coexistence curves have been compared with those predicted by the activity coefficients γi and their temperature dependence. All mixtures are strongly endothermic (HE > 0) and show large positive deviations from ideality (GE > 0), which increase with the size of the ether. Molecular interactions have been examined by calculating and discussing solvation functions and Kirkwood–Buff (KB) integrals. Perfluorohexane proved to be an inert molecule that interacts with ethers more weakly than hexane.