Liquid-liquid equilibria (LLE) for the aqueous poly(propylene glycol) (PPG) + tripotassium citrate system have been determined experimentally at T = (293.15, 298.15, 308.15, and 318.15) K. An empirical nonlinear three-parameter expression developed by Merchuk was used for reproducing the experimental binodal data, and the fitting parameters were obtained for the corresponding temperatures. The effect of temperature on the phase-forming ability in the investigated system has been studied based on a salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation for each temperature. The values of the salting-out coefficients reflect the extent of preferential hydration of the propylene oxide units in the polymer chain.