Equation of State for Dense Gases

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Abstract
A simple quantitative equation of state of the van der Waals type is proposed for dense fluids. The equation yields compressibility factors with a precision comparable to those from the more complicated temperature perturbation theory when tested against ``computer experiments'', including isotherms as low as 0.8 liquid‐vapor critical temperature. The equation is capable of predicting compressibility factors for real gases as illustrated by calculations for argon and nitrogen at pressures up to 10 000 atm. The derivation of the equation is based on a rearrangement of the terms in the Ursell—Mayer density expansion of the configuration integral. The equation contains two temperature‐dependent parameters, to be determined from the dilute gas second virial coefficients. A principal feature of our approach is that it does not require explicit knowledge of the details of the pair interaction.