Thermodynamics of the NaCl–KCl system

•The complementary methods of DSC, DTA, DROP and XRD analyses were used.•The heat capacity of solid phase of the NaCl–KCl mixtures was measured.•The heat capacity of liquid phase of the 50NaCl–50KCl mixture was obtained.•The enthalpy of fusion and solid solution formation were determined.•The thermodynamic functions of the 50NaCl–50KCl mixture were calculated.

The heat capacity of the solid phase of the NaCl–KCl mixtures was measured by the differential scanning calorimetry. These results and X-ray diffraction data were used for the explanation of the solid solution formation. The heat capacity of the liquid phase of the eutectic 50NaCl–50KCl mixture has been obtained in a closed glass container. The enthalpy increment (H°T − H°298.15) and the fusion enthalpy of the 50NaCl–50KCl mixture have been measured by a drop calorimeter. The joint analysis of these values with the heat capacity data allowed the calculation of the enthalpy of the solid solution. As the final result, the thermodynamic functions of the eutectic 50NaCl–50KCl mixture have been obtained.