Hydrogen peroxide decomposition inhibition

With these processes a similar reaction mechanism as with sulphate oxidation is assumed. This opinion is verified also by the observation that the presence of substances catalysing the hydrogen peroxide decomposition (iron, copper and manganese salts and finely dispersed platinum) inhibit almost entirely the proceeding of the oxidation in the required direction. 

The peroxomonosulphuric acid so formed is supposed to decompose rapidly to form oxygen at acid concentrations less than or equal to 0.5 M under the experimental conditions used. The result of the oxygen-tracer experiment (O2 from S20 ) resembles observations of hydrogen peroxide decompositions. The reaction does not show inhibition related to the concentration product [H ]... 

By the presence of either HRP or apFe, the Bray-Liebhafsky reaction is changed in a similar manner. Some amounts of the mentioned catalysts influence decrease, whereas the other amounts influence increase of the characteristic periods Ti and Tend - In other words, some amounts of mentioned catalysts cause the acceleration of the reactions (R), (O), and (D), whereas the other amounts cause their inhibition. Anyhow, by the presence of either HRP or apFe in the BL reaction, the new reaction system for hydrogen peroxide decomposition is formed. 

Although red mercuric oxide usually vigorously decomposes hydrogen peroxide, the presence of traces of nitric acid inhibits decomposition and promotes formation of red mercury(II) peroxide. This explodes on impact or friction, even when wet, if the mercury oxide was finely divided. 

The effect of jumping of the maximal hydroperoxide concentration after the introduction of hydrogen peroxide is caused by the following processes. The cumyl hydroperoxide formed during the cumene oxidation is hydrolyzed slowly to produce phenol. The concentration of phenol increases in time and phenol retards the oxidation. The concentration of hydroperoxide achieves its maximum when the rate of cumene oxidation inhibited by phenol becomes equal to the rate of hydroperoxide decomposition. The lower the rate of oxidation the higher the phenol concentration. Hydrogen peroxide efficiently oxidizes phenol, which was shown in special experiments [8]. Therefore, the introduction of hydrogen peroxide accelerates cumene oxidation and increases the yield of hydroperoxide. 

Abstract In this chapter, the depression mechanism of five kinds of depressants is introduced respectively. The principle of depression by hydroxyl ion and hydrosulphide is explained which regulates the pH to make the given mineral float or not. And so the critical pH for certain minerals is determined. Thereafter, the depression by cyanide and hydrogen peroxide is narrated respectively which are that for cyanide the formation of metal cyanide complex results in depression of minerals while for hydrogen peroxide the decomposition of xanthate salts gives rise to the inhibitation of flotation. Lastly, the depression by the thio-organic such as polyhydroxyl and poly carboxylic xanthate is accounted for in detail including die flotation behavior, effect of pulp potential, adsorption mechanism and structure-property relation. 

The double role as scavenger and initiator, observed for hydrogen peroxide in the 03/H202 system, has also been reported in the UV/H202 system. It should be noted that hydrogen peroxide does not inhibit the ozone decomposition and Eq. (75) is valid only in the cases that ozone is present in the reaction mixture and the process is chemically controlled (low concentrations of hydrogen peroxide). This is because reactions of hydrogen peroxide with the hydroxyl radical release the superoxide ion radical that... 

Peroxidase, in combination with phenolic compounds, utilizes hydrogen peroxide to bring about oxidation. The enzymes do not act in intact fruits because of the physical separation of enzyme and substrate. Mechanical damage, rot, or senescence lead to cellular disorganization and initiate decomposition. Inhibition of the enzymes in vegetables is achieved by blanching with steam or by... 

One of the best known catalytic reactions of carbon, the decomposition of hydrogen peroxide, appears to be very dependent upon the nature of the surface complexes present. Decomposition is inhibited by the presence of acidic surface complexes and accelerated by bases. As a result, the decomposition has been suggested to proceed through the dissociation of the weak acid, ... 

Apart from poisoning by adsorbing impurities, the working electrode potential can also contribute to suppress electrocatalytic activity. Platinum metals, for instance, passivate or form surface oxygen and oxide layers above 1 V (Section IV,D), which inhibit Oj reduction (779,257,252) and oxidation of carbonaceous reactants (7, 78, 253, 254) however, decomposition of hydrogen peroxide on platinum is accelerated by oxygen layers (255). Some electrocatalysts may corrode or dissolve, especially in acidic electrolytes, while reactants may contribute to dissolution. Thus, ethylene oxidation on palladium to acetaldehyde proceeds via a Pd-ethylene complex, which releases colloidal palladium in solution (28, 29). Equivalent to this is the surface roughening and the loss of Pt in gas phase ammonia oxidation (256, 257). 

As in the case of catalytic decomposition of hydrogen peroxide the peroxidatic activity of the enzyme shows no inhibition by carbon monoxide. Chance investigated this in the system primary methyl hydroperoxide complex reacting with ethyl alcohol. Instead of inhibition a slight increase in the rate of disappearance of the complex was noted which could be attributed to formate being produced by the hydration of the carbon monoxide and acting as an additional substrate (71). 

The noncompetitive inhibition of the decomposition of hydrogen peroxide by cyanide is not immediately obvious from the above reaction mechanism for if cyanide can compete in the formation of the peroxide complex which is responsible for the oxygen evolution in step IV, competitive inhibition might be expected. However, under the experimental conditions necessary to observe peroxide decomposition, an excess of peroxide is required and this is sufficient to give the maximal concentration of the peroxide complex, 1.2 or 1.6 moles of bound peroxide for each erythrocyte or bacterial catalase molecule respectively, i.e., the peroxide complex concentration is independent of the peroxide concentration. Analysis of the system under these conditions shows noncompetitive inhibition to hold. 

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