Measurement of Activity Coefficients of Amino Acids in Aqueous Electrolyte Solutions: Experimental Data for the Systems H2O + NaCl + Glycine and H2O + NaCl + dl -Alanine at 25 °C

Electrochemical cells with two ion-selective electrodes, a cation and an anion ion-selective electrode, vs a double-junction reference electrode were used to measure the activity coefficients of amino acids in aqueous electrolyte solutions. Activity coefficient data were measured for the H 2 O−NaCl−glycine and H 2 O−NaCl− dl -alanine systems at 25 °C. The results of the activity coefficients of glycine were compared with values reported in the literature which were obtained by the isopiestic method and by electrochemical cells with one single sodium ion-selective electrode vs a reference electrode. It was found that the method proposed in this study provides more accurate activity coefficient data. From a theoretical point of view, it is shown that the present method is exact and it should be employed for future measurements.