In the scope of investigating new solvents as potential replacements for chlorocarbons or aromatic hydrocarbons for separation of carboxylic acids from dilute aqueous solution, we have focused on the dibasic esters, which have perfect properties for industrial applications. For this purpose, liquid-liquid equilibrium data for water + formic acid + solvent (diethyl carbonate or diethyl malonate or diethyl fumarate) ternary systems were investigated at 298.15 K and atmospheric pressure. The equilibrium results consisted of solubility data and tie-lines were presented in ternary phase diagrams. The reliability of the experimental tie-lines was confirmed by using Othmer-Tobias correlation. The experimental tie-line data were correlated by UNIQUAC model, which gave satisfactory representation for the systems. It is concluded that diethyl carbonate, diethyl malonate and diethyl fumarate may be adequate solvents to extract formic acid from its dilute aqueous solutions. (C) 2010 Elsevier B.V. All rights reserved.