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Volumetric properties of several low acentric factor fluids (Ar, CH4, C2H6, Kr, N2, Ne, O2, Xe) as well as CO2 are modeled using the Bender equation of state. This equation is a linear function of 19 adjustable parameters, which are evaluated from properties data, using a linear numerical procedure. The validity of the EOS is tested by calculating the Joule–Thomson inversion curve. A simple model is in particular used to correlate the inversion properties predicted by the Bender equation, expressed in term of reduced pressure as a function of reduced temperatures ranging from 0.8 to 6. The simple correlation reproduces accurately the used data. We employ data on state behaviour ρ ( P , T ) of homogeneous fluid phases, vapour–liquid equilibrium, second virial coefficient and the coordinates of the critical point.

Two correlations for the saturated liquid and vapor densities of pure substances particularly those used as working fluids in refrigeration machines are proposed. They are shown to represent well the reduced density as a function of the reduced temperature ranging from 0.5 to 1. For about 30 pure substances with acentric factor and critical compressibility factor varying in a wide range, the correlations predict accurately the saturation densities.