Investigation of Activity Coefficient of Ca2+ in CaCl2-CaSO4 Electrolyte Solution Using Ion Selective Electrode

Khoshkbarchi and Vera established an experimental method which further modified by Wilczek-Vera and Vera for measuring activity coefficient of individual ions in electrolyte solutions using ion selective electrode. This work is an attempt to go through a neglected point regarding measuring activity coefficient of individual ions of a sparingly soluble salt, CaSO4. Because of low solubility of CaSO4, it is not possible to implement this method. In order to increase ionic strength of solution while CaSO4 remaining soluble, we used CaCl2 to make CaCl2-CaSO4 electrolyte solution, in the light of knowledge about interaction of Ca2+ and Cl-. Activity coefficient of Ca2+ has been evaluated in CaCl2-CaSO4 electrolyte solution by measuring electrical potential through an ion selective electrode sensitive to Ca2+ against an Ag/AgCl reference electrode. Liquid junction potential arisen at the tip of reference electrode has been estimated by well-known Henderson's equation. In order to correlate activities, Khoshkbarchi and Vera's model has been employed that is resulted an excellent performance in prediction of the activity coefficients obtained by potentiometer

کلیدواژه ها:

electrolyte ، activity coefficient ، ion selective electrode ، electromotive potential ، calcium