Monofunctional electrodes

Monofunctional and Polyfunctional Electrodes At monofunctional electrodes, one sole electrode reaction occurs under the conditions specified when current flows. At polyfunctional electrodes, two or more reactions occur simultaneously an example is the zinc electrode in acidic zinc sulfate solution. When the current is cathodic, metallic zinc is deposited at the electrode [reaction (1.21)] and at the same time, hydrogen is evolved [reaction (1.27)]. The relative strengths of the partial currents corresponding to these two reactions depend on the conditions (e.g., the temperature, pH, solution purity). Conditions may change so that a monofunctional electrode becomes polyfunctional, and vice versa. In the case of polyfunctional electrodes secondary (or side) reactions are distinguished from the principal (for the given purpose) reaction (e.g., zinc deposition). In the electrolytic production of substances and in other practical applications, one usually tries to suppress all side reactions so that the principal (desired) reaction will occur with the highest possible efficiency. 

Schill G and Gustavii K, Acid dissociation constants of morphine, Acta Pharm. Suec., 1, 24-35 (1964). Cited in Perrin Bases Suppl no. 7484. NB Glass electrode was only calibrated at pH = 9.20 at 20 ° C. The values were validated by comparisons with pJCa values for monofunctional morphine derivatives and checked by potentiometric and partitioning (against dichloromethane) experiments. Reported also codeine (8.26) ethylmorphine (8.33) morphine N-methyl bromide (8.83). 

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