Virial: Virial equations evaluated for pure components are used. The interaction virial coefficient is evaluated if data are available for the mixture; otherwise it is assumed to be B12= (B1 + B2)/2. Third interaction virial coefficients are estimated as follows:
C112 = (2×C1 + C2)/3 and C122 = (C1 + 2×C2)/3.
Peng -Robinson: The Peng-Robinson equation in its original form is used with critical parameters evaluated for the pure components. Interaction parameters kij are assumed to be 0. Reference: D.-Y. Peng, D.B.Robinson, Ind. Eng. Chem., Fundam. 1976, 15, 59-64.
Redlich-Kwong: The Redlich-Kwong equation with critical parameters evaluated for the pure components components is used. Reference: O. Redlich and J.N.S Kwong, Chem. Rev., 1949, 44, 233-244.
Hayden-O'Connell: J.G. Hayden and J.P. O'Connell, "A Generalized Method for Predicting Second Virial Coefficients," Ind. Eng. Chem. Proc. Des. Dev. 1975, 14, 209-216.