Liquid‐liquid equilibrium studies have been carried out on 11 solvents using two binary hydrocarbon mixtures for selective extraction of aromatics. The solvents used have been compared on the basis of selectivity, solvent capacity and tie line correlation curves. Tie line data have been determined for 18 systems. The selectivity and solvent power of solvents as obtained from limiting activity coefficient and tie line data have been compared. The selectivity and capacity of solvents have been related to their structure through an empirical parameter.

Nineteen organosulphur solvents have been studied by gas chromatography as potential solvents for the extraction of aromatics. The activity coefficients of nine typical hydrocarbon solutes have been determined in these solvents at three temperatures. From the activity coefficient data, the selectivities of all the solvents have been calculated for benzene with respect to each of the other hydrocarbons in order to screen them for extraction studies. Solvent losses in the g.c. column were also studied.

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Liquid-liquid equilibria for the systems: toluene-heptane-sulpholane, tolueneheptane-sulpholane plus thiodiglycol at 40°C, and benzene-heptane-sulpholane plus thiodiglycol and benzene-heptane-sulpholane plus 9 % water at 1 10°C have been studied. The results of the combined solvents have been compared with those obtained with sulpholane containing up to 9 % water. Several advantages of combined solvents are discussed. The selectivities of the mixed solvents for different hydrocarbon types have been calculated from the limiting activity coefficients determined by gas chromatography.