Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Density and isobaric heat capacity per unit volume were determined for aqueous mixtures of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,2-hexanediol over the wholecomposition range in the temperature interval (283.15 313.15) K at atmospheric pressure. From these data, excess molar volumes and excess isobaric molar heat capacities were obtained. The comparison of experimental data with literature values shows quite good agreement, not only for absolute magnitudes, but also for excess quantities. Excess volumes are negative over the whole composition range andthey become more ideal (less negative) as temperature increases. Excess isobaric molar heat capacityis mostly positive, although it is negative for some mixtures at several compositions and temperatures.Moreover, it was found that it presents a maximum at low mole fraction of the alcohol for most systems,as it was previously found for alkanol + water mixtures. As for temperature dependence, excess isobaricmolar heat capacity increases with raising temperature in all cases. This increase is more pronouncedfor concentrated solutions of dialcohol, with the exception of the 1,2-hexanediol system. The obtained results are interpreted in terms of well-known arguments based on definition of excess magnitudes andchemical nature of the compounds.