In this work, solid-liquid equilibria (SLE) data for ternary 3-nitrophthalic acid + 4-nitrophthalic acid + 1,4-dioxane system was determined at (283.15, 293.15, 303.15, 313.15 and 323.15) K, respectively. The solid-liquid phase diagrams of the ternary system were constructed based on the measured solubility data. The solid phases formed in the studied system were determined by Schreinemaker's wet residue method. In addition, the density of equilibrium liquid phase was obtained. At each temperature, there are two pure solids formed which correspond to 3-nitrophthalic acid and adduct of 4-nitrophthalic acid with 1,4-dioxane, in which the mole ratio of the two components is 2:3, in the ternary 3-nitrophthalic acid + 4-nitrophthalic acid + 1,4-dioxane system. The solubility data for the ternary system were regressed and calculated using the NRTL model which gives acceptable results for the investigated systems. (C) 2013 Elsevier B.V. All rights reserved.