Liquid-liquid equilibria (LLE) for the aqueous 1-butyl-3-methylimidazolium bromide, [C(4)mim]Br, + potassium phosphate and [C(4)mim]Br + dipotassium hydrogen phosphate systems have been determined experimentally at 298.15 K. The effect of the type of salt on the binodal and tie-lines has been studied on the basis of effective excluded volume values of the salt obtained from fitting the binodal data to the binodal model and Gibbs free energy of hydration of the constituent ions. Furthermore, the extended NRTL model has been used for the correlation of the obtained tie-line data. The six binary adjustable model parameters for this local composition model have been estimated either simultaneously from correlation of the experimental tie-line data or in the calculation; the model parameters between ionic liquid and water or between salt and water have been initially correlated with the vapor-liquid equilibrium (VLE) of the corresponding binary systems, and then those between ionic liquid and salt have been correlated with the tie-line data. The results show that good agreement was obtained with the experimental data.