Activity of the electrolyte and the amino acid in the systems water + dl,α-aminobutyric acid + NaCl, +NaBr, +KCl, and +KBr at 298.2 K

The activity coefficients of dl,α-aminobutyric acid in four aqueous single-electrolyte solutions (NaCl, NaBr, KCl and KBr) were obtained at 298.2 K. Electrochemical cells with two ion-selective electrodes, a cation and an anion ion-selective electrode and a double junction reference electrode were used to measure the activity coefficients of the electrolyte. The activities of dl,α-aminobutyric acid in each electrolyte solution were calculated using a cross-differential thermodynamic relation. The results show that the nature of the ions in solution has significant effect on the value of activity coefficient of dl,α-aminobutyric acid. Comparison with literature data for dl,α-aminobutyric acid in NaCl aqueous solutions, shows a strong effect of the chemical structure of the amino acid. In the presence of dl,α-aminobutyric acid, the behavior of the activity coefficients of the electrolytes is distinctively different in the dilute and in the concentrated electrolyte regions.