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Study of Oxidation‐Reduction Systems II. The reversible systems Ce +4 Ce +3 AND Co +3 Co +2

1958; Wiley; Volume: 67; Issue: 5-6 Linguagem: Inglês

10.1002/bscb.19580670506

0037-9646

F. Verbeek, Z. Eeckhaut,

Oxidative Organic Chemistry Reactions

Abstract The validity of Nernst's law (equation 1), was studied for some reversible oxidation‐reduction systems, with oxidation potentials situated at the limit of, or outside the stability range of water. The Ce +4 ‐Ce +3 system in H 2 S0 4 0,5 N (E 0 = 1,444 V) and in HClO 4 1 N (E 0 = 1,694 V) was studied and also the Co +3 ‐Co +2 system in H 2 SO 4 1 N (E 0 = 1,81 V). It was shown that Nernst's law is valid, but that in some cases there occurs a decreasing of the experimentally measured potentials in regard to the reversible oxidation‐reduction potentials (E Nernst > E measured ). These deviations are due to an anodic oxidation current of the solvent, which is added to the anodic oxidation current of the reductant (Ce +3 or Co +2 ). The reductions of the potential are the larger as the total concentration of oxidant and reductant becomes smaller and as the potential itself becomes higher. Under influence of the solvent, there occurs, as function of time and dilution, a reduction of the oxidant (Ce +4 or Co +3 ) at the same time as a decreasing of the potential. This reduction continues until an equilibrium is reached with the solvent.