REEXAMINATION OF COLLINEARITY TESTS FOR DENSITY-DEPENDENT MIXING RULE

This article corrects a mistaken conclusion reached by one of us (PTE) in an earlier article in this journal [Fluid Phase Equilibria 48 (198 9) 209-222]. We had found that density dependent mixing rules, when us ed with the Redlich-Kwong equation of state (RK/EoS), violated the iso choric collinearity constraint at the cricondentherm (CT), while use o f the more familiar van der Waals one-fluid mixing rules do not. Here we repeat the collinearity tests but with the simpler equation of stat e of van der Waals. Collinearity at the CT is found for both density d ependent and quadratic mixing rules. Because the exact form of the cub ic EoS should not affect collinearity, we conclude that numerical erro rs in our earlier RK/EoS calculations are the culprit for the mistaken conclusion involving density dependent mixing rules. All terms but on e can be found analytically with the vdW/EoS, increasing the accuracy of the test by more than one order-of-magnitude.