Vanadium , reduction perchlorate ions

Strongly acidic vanadium(V) oxidises bromide in a sulphate ion medium . The reaction is first-order in both oxidant and sulphuric acid. The dependence of the rate on bromide ion concentration is complex and a maximum is exhibited at certain acidities. A more satisfactory examination is that of Julian and Waters who employed a perchlorate ion medium and controlled the ionic strength. They used several organic substrates which acted as captors for bromine radical species. The rate of reduction of V(V) is independent of the substrate employed and almost independent of substrate concentration. At a given acidity the kinetics are... 

DR. RICHARD THOMPSON (University of Missouri) I do not believe that experiment will work. In addition to the presumably slow reduction of the perchlorate ion by vanadium(II), the V(II)-V(IV) reaction would be rapid enough to preclude the... 

Effecting deposition-precipitation by decreasing the pH level is interesting with metal ions present in the stable state in aqueous solution as anions [35]. With silica no interaction is observed, which has led to the development of the electrochemical reduction procedure. To apply metal ions, such as, molybdenum or vanadium, on alumina, a homogeneous decrease in pH level is interesting. The pH level has been decreased by injection of nitric acid or perchloric acid and electro-chemically. However, the rate of crystallization of the hydrated oxides of vanadium(V) and molybdenum(VI) was observed to be fairly low. To prevent dissolution of the alumina supports the pH cannot be decreased to levels below about 3, at which the crystallization of the hydrated metal oxides does not proceed rapidly. 

A third-order rate-determining step involving iron(ii), ClOj, and a proton is suggested, and slight differences in rate have been noted using Li+ and Na+ as counter-ions in the perchlorate electrolyte. Chloride ion has been shown to inhibit the vanadium(iv)-chlorate redox reaction. When the VO + ion is present in excess, in the presence of initially added chloride ion, the stoicheio-metry is four, whereas in the absence of initial Cl, 5 moles of reductant are required. The rate law imder both conditions is of the form... 

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