Simplified Gas State Equations at Saturation and Isotherm

This paper further simplifies the gas state equation (EOS) by introducing a thermodynamic constant, <i>P</i> _c ^*, into the equation, a theoretical pressure that all gas converts into liquid. In the gas-liquid saturation system, linear regressions of ln <i>P</i>-ln <i>x</i> ₂ from M.P. to <i>T</i> _c give <i>P</i> = <i>P</i> _c ^* <i>x</i> ₂. It verifies Henry's law of gas solubility. Meanwhile, <i>P</i> _c ^*s for most substances are found in the range of 15-16, i.e., 3.269-8.886 MPa. Hence, EOS deforms into . Isotherm is a forced equilibrium system sustained by an outer force. Isothermal EOS is derived by differentiating heat over <i>V</i> _G. , where or . Empolying Ar as an example, EOS are demonstrated over the whole pressure range, 0-1000 MPa, including the supercritical state. Applausive results are obtained in the pressure range before the gas-liquid transition and high temperatures (1000-2000 K), respectively. The supercritical state of intermediate temperatures (160-800 K) is likely liquid-like. Hence, EOS is not fittable.