Glass Electrode. It was found that the potential between a glass surface and a solution varied regularly with the pH and thus could be used as the basis for pH measurement. The electrode consists of a small, very thin walled doped glass sphere containing a buffer solution into which is dipped a platinum electrode. The glass sphere is immersed in the solution of which the pH is to be measured. The glass can be doped with alkali metal oxides (silicate based glass) or arsenic sulfide, selenide or telluride (the chalcogenide matrixes). The silicate based glass respond to single charged ions such as H⁺, Na⁺, Ag⁺ etc. whereas a few chalcogenide matrixes are sensitive to double-charges ions such as Pb⁺⁺ and Cd⁺⁺.

Further Information on this Topic can be found in the books of R.P.W. Scott by following the listed links