Oxygen-containing solutions

In accounting for the yield of carbon dioxide,which is equivalent to about 20% of the yield of hydroxyl radicals, it would be reasonable to suppose that the carboxyl group of the glucuronic-acid subunit is involved. If this is the case, some release of condensed counter ions might be expected following decarboxylation. Such a process would be expected to contribute to the conductivity changes observed in the pulse-radiolysis experiments described later. 

The yield of superoxide radicals given in Table 1 amounts to some 60% of the hydroxyl-radical yield and most likely arises from the elimination of superoxide from peroxy radicals, the latter being formed in Reaction (15). From the careful design of these experiments, the yield of superoxide also represented the maximum yield of those hyaluronic-acid peroxy free radicals 

Radiolytic yields expressed in terms of 10 7 mol J l for oxygen consumption and the formation of superoxide radical anions, peroxides and carbon dioxide in the steady-state g-radiolysis of N2O/O2 (4/1) saturated solutions of hyaluronic acid (1 x 10-3 mol dm-3). Hyaluronic acid concentrations are in terms of dimeric subunits 

In further experiments in oxygenated solutions using pulse radiolysis techniques with low-angle laser-light scattering detection, the yields of strand breakage were measured at pH values of 7, 9.7 and 10.4. Table 2 summarises these data. 

The kinetic behaviour of strand-break formation in oxygen-containing solutions is quite different to that observed in oxygen-free solutions where 

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Figure 6. Electrode polarization curves for oxygen-containing solutions in otherwise-pure water. Curves are schematic but in accord with available data at significant points...

Figure 8.28. Electnxie polarization curves for oxygen-containing solutions (a) in otherwise pure water and (b) in the presence (nonequilibrium) of some Fe. Curves are schematic but in accord with available data at significant points. Because the net current (a) is virtually zero over a considerable span of the electrode potentials, the exact location of the redox potential becomes difficult to determine or is determined by insidious redox impurities. A mixed potential (b) may be observed at the point where the anodic and cathodic currents are balanced but because the various redox partners are not in equilibrium with each other, it is not amenable to quantitative interpretation.

A mechanism has been proposed to explain the heterogeneous photocatalytic oxidation of hydrocarbons in oxygen-containing solutions at platinized Ti02. This is based on the photogeneration of hydroxyl radicals at the Ti02 surface [equations (2)—(4), where h" = hole]. However, another paper suggests that the... 

In oxygen-containing solutions, the cathodic reaction is oxygen reduction. 

To achieve inhibition, it is necessary that the reaction affected by the inhibitor actually determines the corrosion rate. This point is illustrated by the important case that the cathodic reaction is limited by the diffusion of the reacting species (Fig. lb), a common situation for corrosion in neutral, oxygen-containing solutions. Obviously,... 

HEDP acts as an anodic inhibitor of medium efficiency for carbon steel corrosion in a neutral, oxygen-containing solution (Kalman et al., 1994). It was found that inhibition may be enhanced by various chemical additives. The salts of bivalent cations (such as Zn " and Ca ) are often applied as additives (Kuznetsov, 1996 Kdlman, 1994 ... 

The irradiation with visible light of an oxygen-containing solution with hydrochloric acid containing [Ru(bipy)3] and antimony (III) gives hydrogen peroxide and Sb(V). It is suggested that the Sb(III) is converted to Sb(IV), which then disproportionates to Sb(III) and Sb(V). ... 

Alloys, such as 316 stainless steel, monel, or Hastelloy, did not cause significant PAA degradation in oxygen-containing solutions stored at 115 F(46 C) for 2months. 

When a metal is exposed to oxygen containing solution (electrolyte or pure water) so that the whole area is uniformly accessible, without the conditions for the formation of differential areation cells, the whole area may be covered with a corrosion resistant film of oxide, thus retarding the rate of the anodic reaction. This situation can also be obtained by treating the metal with oxidizing agents, such as concentrated nitric acid. The phenomenon, called passivity , will be discussed in greater detail after the description of corrosion by electric current. 

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