Measured Enthalpy and Derived Thermodynamic Properties of Crystalline and Liquid Potassium Chloride, KCl, from 273 to 1174 K.

The enthalpy of KCl relative to that at 273.15 K was precisely measured by drop calorimetry from 273 to 1174 K, and smooth thermodynamic functions were derived for this temperature range. The heat capacities found for the crystalline phase join smoothly the most precise published data for lower temperatures; those for the liquid phase are temperature-independent within the precision of measurement over the 120° range covered. It is concluded that the broad exponential upturn of the heat-capacity curve below the melting point, if attributed to lattice vacancies, indicates a predominance of large vacancy clusters.