in Wiley Online Library (wileyonlinelibrary.com).The Cubic-Plus-Association (CPA) equation of state is applied to a large variety of mixtures containing H 2 S, which are of interest in the oil and gas industry. Binary H 2 S mixtures with alkanes, CO 2 , water, methanol, and glycols are first considered. The interactions of H 2 S with polar compounds (water, methanol, and glycols) are modeled assuming presence or not of cross-association interactions. Such interactions are accounted for using either a combining rule or a cross-solvation energy obtained from spectroscopic data. Using the parameters obtained from the binary systems, one ternary and three quaternary mixtures are considered. It is shown that overall excellent correlation for binary mixtures and satisfactory prediction results for multicomponent systems are obtained. There are significant differences between the various modeling approaches and the best results are obtained when cross association is explicitly accounted for, especially using the cross-association energy from independent experimental studies rather than from combining rules. Figure 3. H 2 S-water liquid-liquid equilibria.Experimental data 37 (points) and CPA calculations assuming that H 2 S is self-associating fluid and using 3B associating scheme (solid lines) and that H 2 S in non-self-associating fluid, but has two proton donors able to cross associate with water (dotted lines). Calculations using first and second approach.Calculations using different association schemes for H 2 S and the zeroth approach (i.e. no solvation is included and only one interaction parameter is used) described in ''The CPA Equation of State'' section (experimental data [43][44][45][46] ). d, proton donor; a, proton acceptor, %AAD ¼ 1, where X stands for pressure, P, or mole fraction, y, and n is the number of experimental data points, DT ¼ 1, where T is the temperature and n is the number of experimental data points. 100, where X stands for mole fractions, x or y, and n is the number of experimental data points.