GLASS ELECTRODE It is a secondary reference electrode that produces a constant and reproducible electrode potential. It is an ion-selective electrode used with other reference electrodes to generate a potential difference. Construction It is made up of a special glass of relatively low melting point and high electrical conductivity, in the form of a sealed glass tube filled with 0.1M HCl, a platinum wire is inserted into it, to make electrical contact. The glass electrode is represented as Pt| 0.1M HCl | Glass | H+ The H+ ion concentration inside the electrode is constant. When the electrode is immersed into a solution of unknown H+, it becomes sensitive to the outside concentration in the solution. Such a sensitivity arises because of the difference between the H+ ion concentration inside and outside. The electrode potential of the glass rod is : EG = EG0 + 0.0591 log [ H+ ] EG = EG0 - 0.0591 pH The glass electrode is used as the internal reference electrode for th
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