DOUBLE-JUNCTION REFERENCE ELECTRODE

"A reference-electrode assembly (for example a silver/silver-chloride electrode) that is encased into a secondary containment vessel (typically a glass tubing) filled with an electrolyte not containing chloride ions (often a high concentration potassium nitrate solution). This second ""internal electrolyte"" of the reference electrode assembly and the external electrolyte into which the whole assembly is immersed are in ionic contact through a second separator (e.g., a porous ceramic plug). The purpose of this arrangement is the avoidance of chloride ion contamination of the test solution (many electrode reactions are strongly catalyzed by chloride ions) at the price of increased liquid-junction potential. "