Le comportement polarographique de l'ion chromate

Tondeur, J. J.; Dombert, A.; Gierst, Lucien

doi:10.1016/0022-0728(62)80001-1

Cited by 20 publications

(8 citation statements)

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“…[30Ϫ35] More specifically, the anion effect in the reduction of chromate ions has been described in detail by Gierst and co-workers. [36,37] However, examination of Figure 8A. and Figure 9A, indicates that α 2 P 2 W 15 Mo 2 and its reduced species should fix protons irreversibly, thus raising the pH value in the reaction layer.…”

Section: Discussionmentioning

confidence: 99%

Influence of Charge Distribution on the Properties of Keggin- and Dawson-Type Heteropolyanions

Keita

Nadjo

et al. 2000

Eur. J. Inorg. Chem.

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The cyclic voltammetric behavior of selected Keggin‐ and Dawson‐type heteropolyanions has been studied as a function of electrolyte composition. The buffer capacity of the electrolyte is shown to be an important parameter that can be used to reveal the symmetry or dissymetry in charge distribution within each oxometalate. A fully symmetrical heteropolyanion like [P2W18O62]6− exhibits a uniform protonability, while its α1 and α2 lacunary derivatives present a donor set of hard oxide ions with stepwise acid‐base equilibria. The behavior of these sites is revealed readily in unbuffered or poorly buffered media at pH = 3, and is ascribed to the change in symmetry of charge distribution in the molecules. It is shown that cations other than the proton, even in very high excess, fail to give rise to the classical voltammograms of lacunary heteropolyanions. The same behavior also appears in α2[Mo2P2W15O61]10−, α[PW11O39]7−, α[SiW11O39]8−, [H2P2W12O48]12−, and, to a lesser extent, in α2[Ni(H2O)P2W17O61]8− and α2[Zn(H2O)P2W17O61]8−. The analogy in the cyclic voltammograms of most dication‐substituted heteropolyanions with those of the precursor lacunary species could thus be explained.

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Section: Discussionmentioning

confidence: 99%

Influence of Charge Distribution on the Properties of Keggin- and Dawson-Type Heteropolyanions

Keita

Nadjo

et al. 2000

Eur. J. Inorg. Chem.

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“…This effect becomes more apparent if the surface activity of added anions increases. Thiocyanate and bromide ions had the largest effect [634]. Addition of cesium ions to the solution in-creases the height of the positive wave.…”

Section: G the Effect Of The Nature Of Supporting Electrolytesmentioning

confidence: 95%

“…Gierst and co-workers [624,634] described certain interesting phenomena, caused by the effect of surface-active cations and anions on the first positive waves of chromate ion reduction. This peaklike positive wave has a kinetic character and its height is limited by the rate of surface protonation of chromate dianions to form monoanions [634] Crü!-+ AR <=!…”

Section: G the Effect Of The Nature Of Supporting Electrolytesmentioning

confidence: 99%

“…This peaklike positive wave has a kinetic character and its height is limited by the rate of surface protonation of chromate dianions to form monoanions [634] Crü!-+ AR <=! RCrü~ + A-.…”

Section: G the Effect Of The Nature Of Supporting Electrolytesmentioning

confidence: 99%

“…In this case the change of I/Jl potential caused by the change of concentration of salts and nature of anions and cations of these salts affects not only the concentration of chromate anions at the electrode, but also the concentration of proton donors. In the presence of uncharged (H20) and negatively charged (HC03") proton donors and also in the presence of added salts whose ions do not have a significant surface activity, the height of the positive wave increases with the ionic strength of the solution [634]. An addition of surface-active anions to the solution results in a decrease of the positive wave due to increasingly negative ~1 potentials (the positive wave is close to the potential of the electrocapillary maximum).…”

Section: G the Effect Of The Nature Of Supporting Electrolytesmentioning

confidence: 99%

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