Lemmon–Jacobsen reference equation

This is an empirical high-precision reference EOS, or rather an EOS template, for pure substances that covers the whole fluid range. The equation is a sum over products of powers of reduced density, reduced inverse temperature, and exponential terms; non-integer exponents are permitted [1].

The EOS is an extension of the Jacobsen–Stewart (JS) equation. Its new feature — terms containing exponentials of the reduced temperature — leads to a dampening of the oscillations of isotherms in the unstable region, a phenomenon often observed for the JS equation. Consequently, the LJ EOS exhibits a single van der Waals loop for most subcritical temperatures, and at most two pairs of extrema at very low temperatures.

The number of terms and the values of the (usually more than 40) coefficients and exponents depend on the substance. They were determined by careful data regression. The EOS can only be used for the substance for which this regression had been made.

adjustable parameters: 0

This *ThermoC* version contains an LJ equation of state for
R125 (pentafluoroethane) [1].

[1] E. W. Lemmon, R. T. Jacobsen, *J. Phys. Chem. Ref. Data* 34 (2005) 69–108.

[2] R. T. Jacobsen, R. B. Stewart, *J. Phys. Chem. Ref. Data* 2 (1973)
757–922.

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