Equation of state and thermodynamic parameters of NaCl to 300 kbar in the high‐temperature domain

Data of several kinds (ultrasonic, volumetric, shock compression) are combined to produce a set of isotherms for NaCl in the temperature‐pressure region between 25° and 500°C and 0–300 kbar. A preliminary examination of the Boehler‐Kennedy measurements of linear compression to 30 kbar and 500°C supports the provisional assumption that (∂ P /∂ T ) v is independent of P and possibly also of T in the “high‐temperature” domain. The equation of state may consequently take the form P ( V , t ) = P 25 ( V ) + ( t ‐ 25)(∂ P /∂ T ) v , where t is Celsius temperature. P 25 ( V ) is the 25°C isotherm of an earlier paper, with small adjustments; this equation was controlled at 300 kbar by the shock measurements and at zero pressure by ultrasonic measurements. Isotherms of the BE 2 form are constructed for the five additional temperatures of the Boehler‐Kennedy data with (∂ P /∂ T ) v = 0.0286 kbar/deg. These are in nearly as good agreement with the volumetric data as were the curves fitted to these measurements alone. At the same time, the parameters of these isotherms show a regular dependence upon temperature. Various thermo dynamic parameters are tabulated, with the aid of handbook values of C P and zero‐pressure thermal expansion coefficients. In particular, Grüneisen's ratio γ is found to be nearly independent of temperature, while γ/ V is nearly independent of pressure.