RADIOCHEMICAL MEASUREMENTS OF ACTIVITY COEFFICIENTS IN MIXED ELECTROLYTES

A method is described for the precise measurement of the activity coefficients of salts in mixed electrolytic solutions. It involves the use of synthetic ion exchange resins and radioactive tracers. The activity coefficients of the chlorides of sodium, potassium, rubidium, and cesium were measured at effectively zero concentration in hydrochloric acid solutions from 0.005 to 1.5 m. The activity coefficient of sodium chloride in solutions of lithium and potassium chlorides was also determined. The results are discussed in terms of both the Harned rule and the Stokes–Robinson theory of activity coefficients.