The thermophysical properties of uranium hexafluoride: Properties in the region of dense gas and liquid

Updated results of experimental studies of the thermophysical properties of uranium hexafluoride $(\rm UF_6)$ were obtained by processing the author's data using the Origin-$8$ program. Updated $\rm UF_6$ state parameter values in the area of vapor–liquid equilibrium and updated data for the heat of vaporization were obtained. A physical and mathematical method for determining the critical temperature from experimental data on the boundary curve (binodal) has been developed, which made it possible to refine the critical parameters of $\rm UF_6: T_c = 504.6 \pm 0.5$ K, $\rho_c = 1.385 \pm 0.0015$ g/cm$^3{,}~P_c = 45.5 \pm 0.3$ bar. Using $P$–$V$–$T$ data two virial equations of state for a dense and highly compressed $\rm UF_6$ gas were constructed. One of them describes the experimental data for a dense gas in the entire studied range of state parameters with a standard deviation $MSD$ of $0.47$ bar and $0.56\%$. The second equation provides the definition of pressure for $\rm UF_6$ with $MSD = 0.16$ bar and $0.36\%$ in the entire subcritical region. The data for the second virial coefficient for $\rm UF_6$ in the temperature range $310$–$592$ K were updated. The equation of state for liquid $\rm UF_6$ is presented for the first time, which describes the experimental data with $MSD$ less than $7$ bar and $6\%$ in the temperature range $453$–$493$ K, density from $\rho_l$ at the phase boundary up to $2.9$–$3.1$ g/cm$^3$ and pressures up to $200$–$240$ bar. The description of the experimental high-pressure equipment and the methodology for conducting research and determining the parameters of the state of $\rm UF_6$ is given.