A paper has recently been published by G. Wilczek-Vera and J.H. Vera [G. Wilczek-Vera, J.H. Vera, Fluid Phase Equilbr. 236 (2005) 96-110], to corroborate their belief that ion activity coefficients can be measured, and to rebut opposing arguments. The present analysis, which deduces exact equations valid for any kind of cell in terms of electrolytes instead of constituent ions, reverses their conclusions and confirms that Vera and collaborators have for many years published, as experimental values of ionic activity coefficients, other no-better-identified quantities with no relationship to the unknown values of the real ionic activity coefficients. (c) 2005 Elsevier B.V. All rights reserved.