On the Theory of Glass Electrodes

A glass electrode is considered schematically to be a difficultly soluble electrolyte which absorbs water and further salts present in an adjacent solution. The potential is the distribution potential at the boundary surface between the glass and the solution. According to the theory presented this potential varies if certain reasonable assumptions are made concerning the value of the constants occurring (dissociation constants in the glass, distribution constants between glass and water) over a wide range of concentration in acid and neutral solutions in the same manner as that at an H2 electrode. The variation of the potential differs from the latter in a strongly alkaline solution, in the manner ascertained experimentally and predicted in previous communications. The extremely simplified model describes quantitatively with one empirical constant the potentials hitherto observed. It is shown that the systems are completely explicable on the basis of the usual thermodynamic picture of equilibrium. Attempts on the other hand to describe the phenomena on the basis of diffusion potentials have not led to satisfactory results.