Measurement of dilute mixture vapor–liquid equilibrium data for aqueous solutions of methanol and ethanol with a recirculating still

A Gillespie-type still which recirculates vapor and liquid phases was used in the measurement of pressure and phase compositions for dilute aqueous solutions of methanol and ethanol at vapor–liquid equilibrium at temperatures between 50 and 100°C. Liquid and condensed vapor samples from each run were analyzed for alcohol concentration by gas chromatography. Liquid activity coefficients calculated with the experimental data are compared with infinite dilution activity coefficients reported in the literature. The calculated infinite dilution activity coefficients agree within 5% with several independent results and are well represented by curves with slopes regressed from experimental enthalpy of mixing data. The curves, when extrapolated to 25°C, agree within 8.5 and 5.5%, respectively, of the mean values of numerous results for aqueous solutions of methanol and ethanol.