A comprehensive thermodynamic investigation of water-ethylene glycol mixtures at 5, 25, and 45�C

Abstract

A detailed thermodynamic study of water (W)-ethylene glycol (EG) mixtures has been carried out as function of temperature (5, 25 and 45°C) and over the entire composition range. The data comprise heats of mixing, densities, heat capacities and compression coefficients. Using excess free energy data from earlier work, molar excess functions were calculated for free energies GE, enthalpies HE and entropies TSE, volumes VE, isobaric and isochoric heat capacities CPE, CVE, adiabatic and isothermal compression KE, KTE and thermal expansion EE, as well as the temperature derivatives of K, C and E functions. The corresponding partial molar quantities were also calculated except for G, H and S and are reported for both EG and W. Also calculated were cohesive energy density, internal pressure and Kirkwood-Buff integrals. The data reported here for EG-W mixtures are compared with similar data for other mixtures as available in order to gain insight into: 1) the relative discriminating ability of various thermodynamic coefficients towards weak cooperative intermolecular interactions in liquids; 2) the quantitative similarities and differences between liquid water and ethylene glycol; 3) the intermolecular phenomena which dominate the properties of EG-W mixtures of varying composition; 4) the usefulness of a qualtitative description of liquid water proposed by Lumry et al. which involves hydrogen-bonding interactions, hydrogen-bonding connectivity and small cooperative fluctuation units.