Measurement of activity coefficients in highly dilute solutions. Part II

Abstract Wobst, M., Hradetzky, G. and Bittrich, H.-J., 1992. Measurement of activity coefficients in highly dilute solutions. Fluid Phase Equilibria , 77: 297-312 The measurement of the concentration dependence of the activity coefficients in highly dilute solutions of non-electrolytes by the entrainment method is presented as a new field of application. The method is based on the entrainment principle for measuring the limiting activity coefficients (“exponential dilutor method”) developed by Leroi et al. (1977) (Ind. Eng. Chem. Process Des. Dev., 16: 139-144) and modified by Hradetzky et al. (1990) (Fluid Phase Equilibria, 27: 81). The new measuring method is rapid and exact, particularly in the case of highly dilute volatile substances in a mixture exhibiting strong positive deviations from Raoult's law (e.g. for systems involving miscibility gaps). One run of measurements can cover a range of concentration of about 2.5 mol% down to less than 0.01 mol%. This work presents experimental results for activity coefficients of methanol in saturated hydrocarbons and ethanol in cyclohexane.