The study covers the liquid-liquid equilibrium (LLE) of the type 2 ternary systems (water + valeric acid + aromatic solvent) measured at T = (298.2 +/- 0.1) K and P = (101.3 +/- 0.7) kPa. The extraction efficiency of valeric acid by the aromatic solvents is better for xylene and chlorobenzene as compared to benzyl ether and 1-phenyl ethanol. An optimization algorithm utilizing the derivative variation method has been applied to the prediction of the optimization range of a type 2 LLE system. The capability of the proposed six optimization factors and two six-parameter models to represent conformably the,optimum extraction field has been rigorously tested regarding the variation profile of the derivatives of the optimized quantity. A solvation energy relation SERLAS involving six physical descriptors has been implemented on the relevant systems,, and checked for consistency in reproducing the observed performance. The deviation statistics obtained for SERLAS testify its ability to simulate accurately the observed performance with a mean error of 5.1%. The predictive capability of the UNIFAC-original model has been also studied. (C) 2016 Elsevier B.V. All rights reserved.