Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Limiting activity coefficients ( A 1 ) of seven selected ethers (diethyl ether, tetrahydrofuran, tetrahydropyran, dimethoxymethane, 1,2- dimethoxyethane, 1,3-dioxolane, and 1,4-dioxane) in water were measured at several temperatures in the range from 273 to 373 K. Six experimental techniques were employed for the purpose. A comprehensive review is presented of experimental data on the limiting activity coefficients, infinite dilution partial molar excess enthalpies and heat capacities of these aqueous solutes. For each ether, the compiled data were critically evaluated and together with the data measured in this work correlated with a suitable model equation providing adequate simultaneous description of the equilibrium measurements and the calorimetric information. As a result, a recommended thermodynamically consistent temperature dependence of A 1 of superior accuracy was established in the range from the melting point to the normal boiling point of water. Analogous recommendations were derived also for the temperature dependence of their Henry fs law constants (KH). Variations of the infinite dilution thermodynamic properties of aqueous ethers with temperature and ether molecular structure are subsequently discussed. The performance of three group contribution approaches, namely the modified UNIFAC, and the methods of Cabani et al. and Plyasunov et al., to predict A 1 for the aqueous ethers was tested and found quite unsatisfactory.