Behavior of the Principal Elastic Moduli and Specific Heat at Constant Volume of KCl at Elevated Temperatures

Measurements of the adiabatic elastic constants of potassium chloride (KCl) have been made in the region 300°K to the melting point (1043°K) by a dynamical method developed by Balamuth. Recently determined values of the specific heat at constant pressure ($C_p$) have been used to calculate the isothermal values of the compressibility. Values of the specific heat at constant volume ($C_v$) have been obtained, using recent values of the coefficient of thermal linear expansion ($\alpha$), the above mentioned values of $C_p$, and the isothermal compressibilities. The results indicate that there is a slight rise in $C_v$ above the Dulong-Petit value above 725°K. This rise is not significant, since the estimated error interval incloses the Dulong-Petit value, and consequently the D-P law is most likely valid up to the melting point.