Biological ion exchanger resins. VI. Determination of the donnan potentials of single ion-exchange beads with microelectrodes

Donnan potentials of Dowex 50W X 2 ion-exchange beads were determined by direct puncture of the single beads with microelectrodes. The voltages were found to be independent of the size of the bead and to vary in a nernstian manner with external salt activities below approximately 80 mm. Counterion activity coefficients inside the bead were calculated from the voltage, and the chemical determination of the internal molality. The single-ion activity coefficient for potassium was found to be approximately constant (at 0.27) below an external KC1 activity of 0.08 m.