1. An external electrode system which comprises an inner element, usually mercury–mercury(I) chloride (calomel), silver–silver chloride or thallium amalgam–thallium(I) chloride, a chamber containing the appropriate filling solution and a device for forming a @L03584@, e.g. capillary, @CT07540@ plug, fritted disc or ground glass sleeve.
    Orange Book, 2nd ed., p. 27 [Terms] [Book]
  2. An electrode that maintains a virtually invariant potential under the conditions prevailing in an electrochemical measurement, and that serves to permit the observation, measurement, or control of the potential of the indicator (or test) or @W06686@.
    Orange Book, 2nd ed., p. 60 [Terms] [Book]
See also:
Orange Book, 2nd ed., p. 65 [Terms] [Book]
PAC, 1994, 66, 2527. (Recommendations for nomenclature of ionselective electrodes (IUPAC Recommendations 1994)) on page 2533 [Terms] [Paper]