In our previous paper, we extended the Tao and Mason equation of state (TM EOS) to pure ionic liquids. Here we apply TM EOS based on statistical–mechanical perturbation theory to binary mixtures of ionic liquids. Three temperature-dependent quantities are needed to use the equation of state: the second virial coefficient, B2, effective van der Waals co-volume, b, and a scaling factor, α. The second virial coefficients are calculated from a correlation that uses the normal boiling temperature and normal boiling density. α and b can also be calculated from the second virial coefficient by scaling. In this procedure, the number of input parameters, for calculation of B2, α, and b reduced from 5 (i.e., critical temperature, critical pressure, acetric factor, Boyle temperature TB, and the Boyle volume υB) to 2 (i.e., Tbp and ρbp). At close inspection of the deviations given in this work, the TM EOS predicts the densities with a mean AAD of 1.69%. The density of selected system obtained from the TM EOS has been compared with those calculated from perturbed-hard-sphere equation of state. Our results are in favor of the preference of the TM EOS over another equation of state. The overall average absolute deviation for 428 data points that calculated by perturbed-hard-sphere equation of state is 2.60%.
