Thermodynamic investigation on the azeotropic mixture composed of water + n-propanol + benzene

Molar heat capacity of the azeotropic mixture composed of water, n-propanol, and benzene was measured by an adiabatic calorimeter from 79 to 320 K. The glass transition and melting processes of the mixture were determined based on the curve of the heat capacity with respect to temperature. The glass transition occurred at 101.920 K. The melting processes took place in temperature ranges 258–268 and 268–279 K. The corresponding melting enthalpies and entropies were calculated to be 1.474 kJ mol−1, 5.508 J K−1 mol−1; 6.144 kJ mol−1, 22.28 J K−1 mol−1, respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to temperature 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.