Activity coefficients of sodium, potassium, and nitrate ions in aqueous solutions of NaNO3, KNO3, and NaNO3+KNO3 at 25 degrees C

Ion selective electrodes have been used to measure the activity coefficients at 25 degrees C of individual ions in aqueous solutions of NaNO3 up to 3.5 molal, KNO3 up to 3.5 molal and mixtures of NaNO3 and KNO3 up to 2.4 molal total nitrate ion concentration. The experimental results confirm that the activity coefficient of anion and cation in aqueous single electrolyte solutions of NaNO3 and KNO3 were different from each other over the whole range of concentrations studied. These effects are attributed to the ion-ion and ion-solvent interactions. The results also show that the activity coefficients of nitrate ions in the presence of sodium and potassium counterions do not depend significantly on the nature of the counterions present in the solution. The experimental data obtained in this study were correlated by a model proposed previously.((1))