The solubility values of potassium dihydrogen phosphate in binary mixtures of acetone + water, ethyl acetate + water, and thiourea + water were measured using a gravimetric method in a temperature range of (298.15-313.15) K. All results from these measurements were correlated using a simplified Pitzer approach. The relationship obtained between the Pitzer parameter concerning the interactions of ions and non-electrolyte molecules (=lambda) and temperature applies well to the solubility data in the ternary systems tested. The values of lambda parameter were also compared to those obtained in the literature (Y. Enqvist, J. Partanen, M. Louhi-Kultanen, J. Kallas, Trans IChemE A, 81 (2003) 1355-1362) for systems urea + water, ethanol + water, and 1-propanol + water. (c) 2012 Elsevier B.V. All rights reserved.