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Activity coefficients of NaCl in aqueous three component solutions were measured at 25°C at ionic strength 1-6 with cation sensitive glass electrodes vs silver-silver chloride electrodes. The second salts were MgCl2, CaCl2, SrCl2, BaCl2, NaC2H3O2, NaClO4, NaNO3, and Na2SO4. Agreement with available literature values was satisfactory. Except possibly at low NaCl contributions to total ionic strength, Harned's Rule appeared to apply.
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R. D. Lanier (1965) studied this question.
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