Determination and Modeling of Activity Coefficients of Sodium Chloride in (Glycerol + Water) Mixtures Based on Potentiometric Measurements

In this work, the results concerning to the mean activity coefficient measurements for NaCl in the (glycerol + water) system using the potentiometric method are reported. The potentiometric measurements were performed on the galvanic cells without liquid junction of the type: Ag|AgCl|NaCl (m), glycerol (wt%), H2O (1 - wt)%|Na-ISE, in various mixed solvent systems containing 0, 5, 10, 20 and 30 mass fraction percents of glycerol over ionic strength ranging from 0.0020-3 mol kg-1 at T = 298.2 K. The sodium ion selective electrode and Ag-AgCl electrode as self-made electrodes had a reasonably Nernst response. The modified zeolite was used to fabricate the sodium ion selective electrode as electrochemical sensor.  The modeling of the investigated system was made based on an extended Debye-Hückel equation, the Pitzer and Pitzer-Simonson-Clegg models. The unknown parameters were determined for each model. The resulting values of the mean activity coefficients, osmotic coefficients and excess Gibbs energy are reported for the studied system.