Potentiometric determination of activity coefficients for NH4Cl in the ternary NH4Cl/LiCl/H2O mixed electrolyte system

This work reports the results of the determination of mean activity coefficients for NH4Cl in ternary (NH4Cl(m(1)) + LiCl(m(2)) + H2O) electrolyte system by potentiometric method at 25 degrees C. The experimental potentiometric data were obtained by combining a solvent polymeric (PVC) ammonium-selective membrane electrode (NH4+ ISE), containing a mixture of nonactin/monactin as ionophore, and an Ag vertical bar AgCl electrode. The measurements were performed, at constant ionic strength, in different series of mixed salt solutions characterized by a fixed salt mole ratio r (where r = m(1)/m(2), = 25, 50, 75, 100). The non-ideal behavior of the system was described on the base of the Pitzer ion-interaction model for mixed salts, over the molality ranging from 0.01 to 3 mol/kg. (c) 2005 Elsevier B.V. All rights reserved.