Electrochemical measurements were made on (H2O + NaBr + K3PO4 + glycine) mixtures at T = 298.15 K by using ion selective electrodes. The mean ionic activity coefficients of NaBr at molality 0.1 were determined at five K3PO4 molalities (0.01, 0.03, 0.05, 0.07, and 0.1) mol center dot kg(-1). The activity coefficients of glycine were evaluated from mean ionic activity coefficients of NaBr. The modified Pitzer equation was used to model the experimental data. (c) 2005 Elsevier Ltd. All rights reserved.