Mean Activity Coefficients Measurements of KCl in “KCl + H2O + Serine” Electrolyte System and Thermodynamics Investigation

In this research, ternary electrolyte system “KCl + H2O + Serine” was investigated as thermodynamics aspect and based on Pitzer ion-interaction model. For this reason, determination of mean activity coefficients was performed by a potentiometric method and using galvanic cell without a liquid junction. The galvanic cell used was type as K+-ISE | KCl (m), Serine (%wt.), H2O (100-%wt.) | AgCl-Ag and the ion selective electrodes used were potassium ion selective electrode based on PVC and Ag-AgCl electrode that both of them were created in our laboratory. Measurements were carried out at T = 298 K and ionic strength range from 0.0017 to 2.5 molal for different percentage mass fraction of serine (%wt. = 0, 2, 4, 8 and 10) in solution. Thermodynamic investigations were performed by correlation of experimental potentiometric data with Pitzer ion-interaction model. In this work, by determination of mean activity coefficients of KCl electrolyte and comparison of them with the calculated amounts by Pitzer ion-interaction model, the application of the pair electrodes was investigated. Then, by correlation of mean activity coefficients determined with the mode, the adjustable Pitzer parameters (βo, β1, and CØ) were determined. In the long run, thermodynamic properties such as osmotic coefficient (Ø) and excess Gibbs free energy (GE) were calculated by using the adjustable parameters based on Pitzer ion-interaction model. The results showed that the Pitzer ion-interaction model was successfully for a description of the investigated system.