Liquid-liquid equilibrium data of water + acetic acid + propionic acid + solvent (amyl alcohol, cyclohexyl acetate, and toluene) quaternary systems were determined. Solubility curves and tie lines were measured at 298.15 K. A comparison of the extracting capabilities of the solvents was made with respect to distribution coefficients, separation factors, and solvent-free selectivity bases. The reliability of the data was ascertained from Othmer-Tobias plots. We conclude that all solvents are suitable separating agents for dilute aqueous acetic and propionic acid mixtures.