The activity coefficients of NaBr in the system NaBr - NaAc - H_2O at 298. 15K were determined from EMF measurements at constant total ionic strengths of 0. 1
0. 5
1. 0
1. 5
2. 0
2. 5 and 3. 0 mol/kg. At each total ionic strength studied the measurements were carried out at different ratios of the NaAc to NaBr ionic strengths. The experimental activity coefficients were fitted by using the Harned equation
Scatchard equation and Pitzer equation. Although all these models can be successfully applied to the analysis of this system
the Pitzer equation leads to better fitting than the others. Finally
the excess Gibbs free energy of these mixtures was also calculated.