Activity measurements at high ionic strengths using halide-selective membrane electrodes

The nature of single-ion activity coefficients calculated from potentiometric measurements on cells with liquid junctions

“…The activity coefficients reported by Hurlen almost coincide with those by Bagg and Rechnitz [63]. To be precise, the latter workers did not calculate activity coefficients from EMF measurements but checked if the convention for single-ion activity coefficients based on the hydration theory [64] fitted their EMF measurements with halide-selective membrane electrodes, provided that the liquid junction potentials were estimated by the Henderson equation.…”

“…Inspection of the remaining eight reveals that all deviate likewise from the Debye-Hückel equation in the calibration range, some even more spectacularly than shown in figure 4. No comment is given in either [23] or [60] on this discrepancy or on the earlier data of Bagg and Rechnitz [63] or Hurlen [49]. It appears therefore that their data for KCl solutions are biased and cannot serve the purpose of testing.…”

“…Still, depending on the mechanism of their functioning, they may be equivalent to ideal membrane electrodes as regards following Eqs. (60) and (63). The possibility of this is a problem for a separate investigation and cannot be discussed here in full detail.…”

“…In addition, with this liquid-junction system, there happen to be opportunities to test equation (63) which is presumed to be applicable to measurements with the Na + ion-selective glass electrodes, since a number of papers report on c Na values calculated from such measurements. To use them, the computational equation (76) is modified as appropriate to equation (63).…”

“…To use them, the computational equation (76) is modified as appropriate to equation (63). Use is made of two datasets.…”