An analytical study of pressure effect on the inversion temperature of gases and a comparison of equations of state on the basis of this study

In this study the pressure effect on the inversion temperature of gases was determined. The gases selected for this study were two of the more common ones, namely, air and nitrogen. An equation of state is a means for analytically determining the values of inversion temperature for gases at various pressures. Thus, ten of the best known equations of state were selected. The values of the inversion temperature at different pressures were calculated separately with the assistance of each of these equations of state. A numerical technique was applied for this purpose. The values of the inversion temperature obtained theoretically, in the case of each of the equations of state, were compared with the experimental data available. By comparing the inversion temperature-pressure relations found using the different equations of state, the accuracy and reliability of these equations were compared. Agreement was found to exist between experiment and theory in the case of all equations of state for a certain pressure range. On the basis of general agreement in a wide range of pressure, the Redlich-Kwong equation of state was found to be the most accurate and reliable. The equation of state [p + (a/T(V+b)²](V-b) = RT was also found reliable to a certain extent