Heat Capacity of Gases in the Critical Region

A theory of the heat capacity of a one-component gas in the critical region is based on approximations similar to those previously applied to binary mixtures. The excess constant volume heat capacity per mole is found to be ΔM=(R/16πn0c)(6/l2)32(Tc/T−Tc)12 at the critical number density n0c. l is a short-range correlation length and R is the gas constant. A fit to CO2 data gave reasonable agreement with l=4.5 Å.