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The relationship between ionic strength and electrical conductance (EC) developed by Ponnamperuma et al. (1966) was corrected for ion-pair formation and extended to more saline aqueous extracts. The linear regression for the ionic strength and the EC of 27 soil extracts and 124 river waters was where ionic strength, I, is in moles/liter and EC is in millimhos/cm at 25°C. The relation differed from the findings of Ponnamperuma et al. The electrical conductivity was found to be a sufficiently accurate measure of ionic strength for the estimation of individual ion activity coefficients. The values of the activity coefficients were verified by total solution analysis and specific ion electrode measurements.
Griffin et al. (Sun,) studied this question.