Construction of low-cost s-silver chloride and carbon paste electrodes for potentiometry practicals and pH measurements

Abstract

Reference and inert electrodes are frequently used in physical chemistry practicals like potentiometric and voltammetry, but they are commercially expensive. However, these electrodes can be made at low cost within the laboratories. Therefore, the main objective of this research was to construct more affordable, low-cost silver-silver chloride and carbon paste electrodes for laboratory experiments. Also, using these electrodes we intend to construct a potentiometric device to measure the pH of a solution with reasonable accuracy. A low-cost silver-silver chloride electrode was prepared by filling a syringe with a hot agar solution, and partially immersing AgCl- coated silver wire in a saturated 3 M KCl solution. The carbon paste electrode was prepared using graphite powder and paraffin oil. These electrodes were applied for strong acid-base potentiometric titrations and endpoints were obtained using three different concentrations of NaOH (0.10 M,0.20 M, 0.30 M) and 0.10 M HCl, and these values were compared with standard pH titration and a potentiometric titration with the commercial standard electrodes. Then the pH was determined by substituting the Ecell values to the Nernst equation and that pH was compared with the direct pH readings. According to the titration results, the same endpoints were obtained from four different methods. Statistical analysis revealed there is no significant difference between the measured and the calculated pH of constructed electrodes. The accuracy of the calculated pH was further improved by applying mathematical modeling. The study suggests that constructed low-cost electrodes can be effectively and economically cost-effectively utilized for measuring pH in laboratories.