Measurements of the heat capacity of an azeotropic mixture of water, ethanol and toluene from 79 to 320 K

Abstract

The molar heat capacity of the azeotropic mixture composed of 0.329 water, 0.397 ethanol, and 0.274 toluene, was measured by adiabatic calorimetry in the temperature range 79–320 K. The glass transition and phase transitions of the mixture were determined from the curve of the heat capacity with respect to temperature. The glass transition occurred at (108.4 ± 0.2) K. The phase transitions took place in the temperature range of 129–155 K corresponding to the solid–solid and solid–liquid phase transitions of ethanol, water and toluene, respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to standard temperature 298.15 K were derived from the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.