The potential developed when a bright platinum electrode is immersed in a solution containing an ionic species in two interconvertible oxidation (valency) states. The potential is dependent upon the ratio of the concentrations of the two oxidation states, e.g., iron II and iron III ions; 4-dihydroxybenzene (hydroquinone) and 1,4-benzoquinone (p-benzoquinone); vat dye and leuco vat dye.
Note: The standard redox potential, E, is that developed when the concentrations of the two oxidation states are equal to each other, and in vat dye systems indicates the difficulty with which the vat dye (the oxidized state) can be reduced.
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