Low-temperature heat capacities and phase transitions of the ternary system of (0.195 ethandiol + 0.132 ethanol + 0.673 water)

Abstract

The heat capacities of the ternary system of 0.195 mole fraction of ethandiol (ethylene glycol), 0.132 mole fraction of ethanol (ethyl alcohol), and 0.673 mole fraction of water (i.e. 0.40, 0.20, and 0.40 mass fraction, respectively) have been measured with an adiabatic calorimeter in the temperature rangeT= 80 K to T= 350 K. This mixture exhibits complex phase transitions in the solid state. A very broad heat capacity anomaly from T= 130 K toT= 240 K was observed in the heat capacity curve, and three heat capacity peaks were found atT= (149, 170, 186) K, in addition to the melting peak atT= 217.5 K. The corresponding phase transition and fusion enthalpies were determined to be (228 ± 10)J · mol−1, (230 ± 8)J · mol−1, (136 ± 8)J · mol−1, and (260 ± 10)J · mol−1, respectively. Experiments have demonstrated that the cooling rate between 0.1 K ·min−1and 10 K ·min−1had no obvious influence on the heat capacity anomaly. The thermal conductivity of this ternary system was measured with an instantaneous heating wire conductometer in the temperature range from T= 233.15 K to T= 343.15 K. All of the heat capacity and thermal conductivity results in the temperature range betweenT= 221 K and T= 350 K were correlated with temperatures for practical applications.