In this work the results concerning the determination of the activity coefficients for NH4Cl in 2-PrOH/water mixed solvents, along with some thermodynamic correlations concerning the resulting osmotic coefficients and excess Gibbs free energies for this electrolyte in different ROH/water mixed solvent systems (where R = Me, Et, 1-Pr and 2-Pr) are presented. These electrolytic systems were modeled using the Pitzer ion-interaction model and based on the experimental electromotive. force (emf) data, of the following galvanic cell: Ag vertical bar AgCl vertical bar Nh(4)Cl(m), H2O(100 - w%), ROH(w%)vertical bar NH4+vertical bar SE, at 298.15 K. The results concern the previous and new collected experimental data using NH4+ ion-selective PVC membrane and Ag/AgCl electrodes for different mass fraction percents (w) of alcohol in water (with w = 0, 10, 20, and 30%, and R=Me, Et, 1-Pr, and R = 2-Pr, respectively). The thermodynamic behavior of these electrolyte systems were determined over the molality ranging from dilute solution to near salt saturation, or to phase separation (e.g. R = 2-Pr) in these mixed solvent systems. The nonideal behavior of these electrolyte systems were satisfactorily correlated in term of the linear dependence of the Pitzer ion-interaction parameters on the dielectric constant of the solvents, and also in term of the ion association phenomenon related to the Pitzer electrostatic interaction terms in the second virial coefficient for the used electrolytic systems. (c) 2006 Elsevier B.V. All rights reserved.