LAUSR

Abstract In this study, the results relating to the thermodynamic properties of (NaBr + monosodium aspartate + water) system were studied using the potentiometric method at T = (298.2 and 310.2)K and P = 0.1 MP. The electromotive force (emf) measurements were performed on the galvanic cell of the type: Br-ISE |NaBr (m 1 ), monosodium aspartate (m 2 ), H 2 O |Na-ISE, over total ionic strengths from 0.01 to 3.0073 mol.kg −1 for different series of salt molal ratios r (r = m NaBr /m NaAsp  = 1.0,2.5, 5.0,7.5,10.0) and single salt NaBr in aqueous system at T = (298.2 and 310.2)K. The mean activity coefficients of NaBr in the NaBr + monosodium aspartate + water system were determined from emf measurements based on Nernst equation by using a galvanic cell containing a solvent polymeric (PVC) Na + and Br − ion selective electrodes which were prepared in our laboratory. The study of ternary system was made based on the Pitzer interaction model and Harned rule. The resulting values of the mean activity coefficients, the osmotic coefficients and the excess Gibbs free energy together with Pitzer mixing interaction parameters ( θ BrAsp and  ψ NaBrAsp ) for the series under investigated system were reported.