Oxidation-reduction electrodes range

When ja is very small, i.e. in the electroreduction of molecular oxygen, the linear polarization region may not be accessible in a large potential range due to oxidation—reduction of impurities at the electrode surface. 

A very useful extension of the voltammetric technique is cyclic voltammetry (Adams, 1969 Cauquis and Parker, 1973) in which one scans the potential of the working electrode in an unstirred electrolyte solution in the anodic (cathodic) direction and records one or several peaks due to oxidation (reduction) of the substrate. At some suitable potential, the direction of the scan is reversed and peaks due to reduction (oxidation) of intermediates and/or products formed during the forward scan are observed. In the simplest case a linear increase (decrease) of the potential with time is employed (triangular cyclic voltammetry) with scan rates in the range 0 01-1000 V s 1. It should be noted that cyclic voltammetry at scan rates above 1 Vs"1 requires the use of a differential cell to reduce the residual current due to charging of the electrified interface (see, for example, Peover and White, 1967). The theory of cyclic voltammetry has been... 

Cyclic-voltammetric curves (360, 362-367) in the potential range 1.2 to 0.4 V in acid and alkaline solutions show (Fig. 41) that although the volt-ammagram in acid media is featureless, a well-developed reversible peak is noticed in alkaline solutions just prior to oxygen evolution (360, 364). The voltammetric behavior of RuOj electrodes has been attributed (360, 368) to reversible oxidation-reduction through a mechanism involving proton exchange with the solution ... 

Redox potential (Eh) characterises the oxidation-reduction condition of a soil. This in turn provides a means to assess soil genesis, soil fertility and status of soil contaminants (Liu Yu 1984). Redox potential is well known to be difficult to measure precisely with conventional methods, for reasons ranging from slow electrode response to soil condition, especially for poorly poised (redox capacity) soils (Bohn 1971 Ponnamperuma 1972). Usually measurements are made under specified conditions, with values being dependent on the experimental conditions. As the measured value is conditional, it may not be sufficiently precise for some physicochemical studies. Nevertheless, there is unique information about soil condition that can be derived by measuring the redox potential. 

Iron-containing proteins are those in which iron atoms are bound with sulfur-containing ligands. The number of labile sulfur atoms is usually equal to that of iron atoms which varies between 1 and 18. The molecular mass of these proteins is in the range of 6000 to 750,000 units. Such proteins effect electron transfer in photosynthesis, nitrogen fixation, and respiration in mitochondria. They are capable of transferring electrons under a potential close to that of a reversible hydrogen electrode. Their oxidation-reduction potential is between +0.35 and -0.49 V. 

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