A miniaturized reference electrode called a polymer membrane reference electrode (PMRE) was designed and constructed according to the constitution of a second kind silver-sirver chloride electrode. The stickshaped electrode having about 2 mm outer diameter consists of a silver paste coated-copper wire as a conductive substrate and three coating layers of silver chloride (AgCl), polyvinyl chloride (PVC) incorporating potassium chloride (KCl) fine powder and epoxy resin. These layers were formed on the substrate according to the order above. The appropriate thicknesses of these layers were 0.3 mm, 0.4 mm and 0.1 mm, respectively. The optimum mixing weight ratio of the PVC to KCl powder was 1/3. Advantages of PMRE are easy and inexpensive fabrication, strong mechanical stregth, dry storage and long life time (most of the electrodes are still functioning after 4 months' use). The response potential stability as a reference electrode and potential changes of PMRE on pH and temperature were almost the same as those obtained by using a commercial silver-silver chloride reference electrode.
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