Measurement of Ionic Activity of Sodium and Potassium in Clay-Water Systems by Membrane Electrodes

Clay and resin membrane electrodes were used to determine the Na⁺ and K⁺ activities in clay-water systems of pure kaolinite, bentonite, and vermiculite samples. The mobility ratio decreased slightly with increase in ionic activity by clay membrane electrode while with resin membrane one a reverse trend was noted. The bonding energy (ΔF) for Na⁺ of different clay minerals followed the order: vermiculite > bentonite > kaolinite. For any specific mineral with the two ions the order way found to be K⁺ > Na⁺. A combination of clay and resin membrane electrodes, within specific limits of concentrations, could be effectively employed in estimating the cationic activity in clay-water systems.