Abstract In this work, the results relating to the mean activity coefficient measurements for KCl in the (1-PrOH+water) mixed solvent system using the potentiometric method were reported. The electromotive force measurements were performed on the cell of the type: Ag | AgCl | KCl (m), 1-PrOH (wt.%), H2O (1-wt) % | K -ISE, in various mixed solvent system containing 0, 10, 20, 30, and 40% mass fraction of 1-PrOH over ionic strength ranging from 0.0002 to 2.9644molkg−1 at T=298.2K. The PVC based potassium ion selective electrode and Ag–AgCl electrode used in this work were prepared in our laboratory and had a reasonably Nernstian response. The Pitzer and Pitzer – Simonson – Clegg models were used for the experimental data correlation and calculation of thermodynamic properties. The unknown parameters were determined for each model. Then, the obtained parameters were used to calculate the values of thermodynamic properties for under investigated system.