DEVELOPMENT AND APPLICATION OF A DOUBLE-JUNCTION REFERENCE ELECTRODE FOR PROCESS pH MEASUREMENTS

摘要

In the evolution of on-line pH measurements, the reference electrode has been a major source of difficulty. Early designs employed a flowing junction. Electrolyte was forced outward through the junction to prevent the sample stream from contaminating the electrolyte within the electrode. More recent designs incorporate a non-flowing junction. Electrolyte diffuses outward through the junction area while liquid from the stream diffuses inward (both at extremely slow rates). The two mingle in the junction area and provide electrical continuity. If the liquid from the stream and electrolyte from the electrode react to form a solid product, the junction area becomes impenetrable and the electrode is unusable. Streams which contain silver, lead, mercury or sulfide ion are particularly troublesome. The most recent designs involve a "double junction". A conventional non-flowing-junction electrode is contained within an outer body (also non-flowing junction) and an inert electrolyte is used within the outer body to maintain electrical continuity between the stream and the conventional electrode.rnThis paper presents our experiences with such an electrode. Particular emphasis is placed on field applications involving common, troublesome streams.