An Equation of State for the Thermodynamic Properties of Fluid n-Butane in the Critical Region

An equation of state that predicts the critical thermodynamic behavior of n-butane is formulated. This equation takes into account the global behavior that includes the singular thermodynamic behavior asymptotically close to the critical point and the crossover to the regular thermodynamic behavior far away from the critical point. The formulated equation is based on the transformation of a truncated classical Landau expansion and represents the thermodynamic properties of n-butane in a wide range of temperatures and densities around the critical point. A comparison of the pressure P–ρ–T data measured by Beattie and co-workers and those calculated with the crossover EOS is made. Finally, the specific heat at constant volume, Cv, for n-butane along the critical density within a restricted temperature interval around the critical point is presented.