This is an empirical EOS, or rather a group of EOS, that can be regarded as a simplified Wagner-Setzmann equation. It is shorter and of lesser precision than, e.g., the Wagner type EOS for argon or water, but can be applied to several substances.
It turns out that, of the many powers of density and temperature used in the Wagner type equations, some are more important than others, and the exponents of the most significant terms are the same for many substances. By keeping these terms only, Wagner and Span created an EOS that covers the whole fluid range almost within the experimental error, but has 12 substance-specific parameters only. The EOS comes in two variants—one for nonpolar and one for polar substances.
Here the EOS has been implemented as a special case of the Wagner–Setzmann EOS.
Parameters have been determined by the authors for several nonpolar and weakly polar substances. The EOS should be applied to these substances only.
The EOS is valid over the whole stable fluid range. Care is advised in the metastable and unstable ranges: the EOS can exhibit multiple van der Waals loops. Critical volumes calculated from the EOS can deviate 1–4% from the experimental value.
Note: The critical data given in the parameter files are not the results from the EOS, but the values used for the correlation, i.e., the recommended experimental data.
adjustable parameters: 0
 R. Span and W. Wagner, Int. J. Thermophys. 24 (2003) 1–39, 41–109, 111–162.
 E. W. Lemmon and R. Span, J. Chem. Eng. Data 51 (2006) 785–850.
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