The electromotive force of the cell containing two ion-selective electrodes (ISE). K-ISE[KCl(m), PEG 4000(Y). H2O(100 - Y)]CI-ISE has been measured at temperatures of 288 15, 298.15. and 308 15K as a function of the weight percentage Y of PEG 4000 in a mixed solvent Y was varied between O and 25 wt.% in five-unit steps and the molality of the electrolyte (m) was between ca 0 05 mol kg(-1) and almost saturation. The values of the standard electromotive force were calculated using routine methods of extrapolation together with extended Debye-Huckel and Pitzer equations. The results obtained produced good internal consistency for all the temperatures studied Once the standard electromotive force was determined, mean ionic activity coefficients for KCl. Gibbs eneigy of transfer from the water to PEG 4000 + water mixtures. interaction parameters (g(EN,) h(EN), S-EN, c(p) (EN)), salting constants. and the KCl primary hydration number were estimated and comparatively discussed in terms of a model of structural and electrostatic interactions with those of the LICI and NaCl previously obtained in similar mixtures. (C) 2010 Elsevier B.V All rights reserved