INVESTIGATIONS OF THE FEASIBILITY OF CONSTRUCTING A POLYPYRROLE-MERCURY MERCURY-CHLORIDE REFERENCE ELECTRODE

A polypyrrole-mercury/mercury chloride reference electrode was initial ly constructed by in situ electropolymerization of pyrrole on a mercur y pool anode in a 0.5 M sodium para-toluene sulfonate and 1.0 M sodium chloride mixture solution. However, in this procedure, insufficient a mount of mercury was incorporated in the polypyrrole film for reaction with chloride ions to yield a mercury/mercury chloride half cell. Alt ernatively, a polypyrrole film was galvanostatically deposited on a gr assy carbon electrode in the presence of sodium para-toluene sulfonate . Mercury was electrochemically deposited from mercury(I) nitrate at t he polypyrrole-coated electrode. The resulting film was deprotonated i n 5 M NaOH. Cyclic voltammetry was then carried out in 10 M HCl in ord er to exchange the para-toluene sulfonate ions with chloride ions and to oxidize mercury for the formation of mercury chloride within the fi lm. A reproducible null potential difference was obtained when the pol ypyrrole-mercury/mercury chloride electrode was employed as an indicat or electrode against a saturated calomel reference electrode in satura ted potassium chloride solution. (C) 1997 Elsevier Science Ltd.