Oxidizing agents, oxidation-reduction potentials

The peroxodisulfate ion in aqueous solution is one of the strongest oxidising agents known. The standard oxidation—reduction potential for the following reaction is 2.08 V (77,78). 

Red lead (Pb304) is manufactured on the 20000-tonne scale annually and is used primarily as a surface coating to prevent corrosion of iron and steel (check oxidation-reduction potentials). It is also used in the production of leaded glasses and ceramic glazes and. very substantially, as an activator, vulcanizing agent and pigment in natural and artificial rubbers and plastics. 

Several workers have shown that a high concentration of ascorbic acid added to liquid milk inhibits oxidation. Chilson (1935) suggested that added ascorbic acid acts as a reducing agent, which is oxidized more readily than milk fat. Bell et al. (1962) suggested that addition of L-ascorbic acid to cream produced a medium less conducive to oxidation by lowering the oxidation-reduction potential. Addition of an adequate level of surface-active ascorbyl palmitate to milk products may retard lipid oxidation by orientation at the lipid-aqueous interface where it intercepts free radicals (Badings and Neeter, 1980). 

By the loss of 4f electrons, La attains a stable electronic configuration giving rise to a trivalent oxidation state. Other oxidation states, such as two and four in some lanthanides, are possible when electronic configurations 4/°, 4 f1 and 4/14 are attained. The oxidation states and the oxidation-reduction potentials of some couples are given in Table 6.1. The lanthanides in 4+ oxidation state are strong oxidizing agents and an example is Ce4+. 

Arsenic(III), antimony(III), and tin(II) ions can be oxidized to arsenic(V), antimony(V), and tin(IV) ions respectively. On the other hand, the latter three can be reduced by proper reducing agents. The oxidation-reduction potentials of the arsenic(V)-arsenic(III) and antimony(V)-antimony(III) systems vary with pH, therefore the oxidation or reduction of the relevant ions can be assisted by choosing an appropriate pH for the reaction. 

Flor yeast may be able to use amino acids not only as nitrogen source but also as redox agent to balance the oxidation-reduction potential under conditions of restricted oxygen. Thus, amino acids as threonine, methionine, cysteine, tryptophan, and proline can be released to the wine to restore the intracellular redox balance by means of the oxidation of NADH in excess (Berlanga et al. 2006 Mauricio et al. 2001 Moreno-Arribas and Polo 2005 Valero et al. 2003). 

The potential thus depends on the volume of the solution, and hence the position of the curve showing the variation of the oxidation-reduction potential during the course of the titration of H2Q by a strong oxidizing agent varies with the concentration of the solution. At constant volume equation (32) becomes... 

The Co(bipy)3+ ion is a useful catalyst for a number of borohydride reductions, e.g., organic nitro compounds are reduced smoothly to amines at pH 6.5-7 the true reducing agent is Co(bipy)3+. The oxidation-reduction potential for Co(I)/Co(II) is 0.91 volt (vs. standard calomel electrode in 50% aqueous ethanol) and this should fall between the potentials of the other reactants (709). Catalytic reductions of organic halogen compounds may be achieved (436), and the system is reactive to small molecules such as NgO (38). 

The exact mechanism of toxicity has not been elucidated, although there is a lot of information on how sulfur-based compounds are detoxified by the liver. Sodium sulfite is a mild reducing agent that would most likely cause burning or irritation at the site of exposure or application by altering oxidation-reduction potential and pH. 

Pentaralent neptunium is the most stable state in solution. It hydrolyzes only in basic solutions, disproportionates only at high acidity, and forms no polynuclear complexes. As shown by the oxidation-reduction potentials of Table 9.6, hexavalent neptunium is much less stable in solution than is hexavalent plutonium in fact, hexavalent neptunium is a strong oxidizing agent and is easily reduced in the presence of oxidizable substances, such as those present in ion-exchange and solvent extraction separations [K2]. 

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