Universal equations of state for hexafluorides and thermodynamic similarity

Curves have been fitted to the measured values for the thermodynamic parameters of the hexafluorides of sulfur, molybdenum, tungsten, and uranium in the van der Waals region. The similarity criteria have been tested by graphical construction in terms of reduced parameters and by analytical determination of the coefficients in the corresponding universal equations of state. Seven criteria for thermodynamic similarity are found to be obeyed. Universal equations of state have been derived for the hexafluorides in the low-density and dense-gas regions.