Analysis of the saturation line on the basis of Clapeyron-Clausius and Gibbs-Duhem equations

• Published in: Journal of physics. Conference series 2019-01, Vol.1147 (1), p.12017
• Main Authors: Rykov, S V, Kudryavtseva, I V, Rykov, V A, Ustyuzhanin, E E, Ochkov, V F
• Format: Article
• Language: English
• Subjects: Arrays; Critical phenomena; Critical point; Equations of state; Mathematical models; Modernization; Saturation
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/1147/1/012017

We have considered some modernization of the equation of state for matter (EOS). This modernization is connected with increasing the accuracy of EOS that has a wide area of applicability including the critical region. Our analysis has shown that it is possible to increase the accuracy of such EOS if we prepare a special input array. It has to include heterogeneous reliable data including the isochore heat capacity, gas and liquid densities ρ−, ρ+ and the saturation line pressure p. The array has to be used as an input array in a statistical processing that allows calculating adjustable coefficients of the EOS. We have set the task to develop models ρ−(T) and ρ+(T) which describe densities ρ−, ρ+ and ps(T) model related to the saturation pressure. In our methodical approach, the Clapeyron-Clausius equation and the Gibbs-Duhem equation participate. We have elaborated structure that is related to these models and meets some requirements of the scaling theory of critical phenomena. Experimental data ρ+, ρ−, ps, T for SF6 are selected to calculate adjustable coefficients of these models. Comparison of models allows us to estimate that models ρ− (T), ρ+(T), ps(T) satisfactorily describe (within the limits of experimental errors) the experimental data obtained in the temperature range from triple point to critical point.