The solubilities of three dibasic carboxylic acids (adipic acid, glutaric acid, and succinic acid) in water, in the ionic liquid of 1-butyl-3-methylimidazolim tetrafluoroborate ([Bmim][BF4]), and in the aqueous [Bmim][BF4] solutions have been measured by a solid-disapperance method. The binodal curve of water + [Bmim][BF4] was also determined experimentally from solid-liquid-liquid coexistence temperature up to near the upper critical solution temperature. Experimental results showed that each acid-containing binary behaved as a simple eutectic system. The solid-liquid equilibrium (SLE) data were correlated with the NRTL model for each binary system. The NRTL model with these determined binary parameters predicted the solid-disappearance temperatures of the aqueous ternary mixtures containing [Bmim] [BF4] and the dibasic acids to within an average absolute deviation of 2.0%. (C) 2007 Elsevier B.V All rights reserved.