The binary interaction parameters, k(ij), of 119 mixtures were determined by fitting the second cross-virial coefficients of mixtures with correlations for pure compounds [L. Meng, Y.Y. Duan, L. Li, Fluid Phase Equilib. 226 (2004) 109-120; L. Meng, Y.Y. Duan, Fluid Phase Equilib., 258 (2007) 29-33] and classical mixing rules. The mixtures included nonpolar/polar (associated), polar/polar, quantum/nonpolar (quantum) binaries. Very simple correlations for k(ij) of H2O/n-alkane, CO/nonpolar and quantum/nonpolar (quantum) binaries were successfully developed. The results show that the present correlations can accurately predict the second cross-virial coefficients. (C) 2007 Elsevier B.V. All rights reserved.