Enthalpies and susceptibilities of coexisting vapor and liquid sodium at high temperatures

Most experimental data on fluid sodium are restricted to temperatures below 1800K. The liquid range extends, however, to ca. 2500K (its critical temperature). The extrapolation of the measured values to high temperature requires the guidance of the theory of critical phenomena. Here we reanalyze the enthalpy, and the thermal (CV, Cp) and mechanical (βS, βT) susceptibilities of coexisting liquid and gaseous sodium up to the critical point. •Theory-guided extrapolation of sodium properties to the critical point.•Enthalpies and susceptibilities were calculated in the complete vapor-liquid range.•Smooth dependence of enthalpies with the density, even at the critical point.•Corresponding State Principle and rubidium data give qualitatively similar results.