An improved method to predict second cross virial coefficients

Abstract

A previous method of the author to calculate the second cross virial coefficients is re-considered to improve the reliability of the predictions and to reduce the number of empirical rules. The method is based on the reduced second cross coefficient at the normal boiling temperature, B b * , whose value is always assumed equal to unity. This value is then extrapolated to the experimental temperatures using only two empirical constants: K 1, a corrective multiplying factor of B b * and K, in an exponential term as a multiplying factor of temperature. To improve the reliability of the method, literature experimental data are grouped in three binary classes: - non-polar or slightly polar fluids; - at least one strongly polar fluid; - strong interactions of the acid–base type. Only the critical constants and the normal boiling temperature are required as input parameters. Deviations of calculated results from experimental one are in the range 25–40 cm 3 mol −1 for the first and the second class and below 300 cm 3 mol −1 for the third class.