par Gierst, Lucien ;Vandenberghen, Lucienne ;E. Nicolas, E.T.
Référence Journal of electroanalytical chemistry and interfacial electrochemistry, 12, 5-6, page (462-476)
Publication Publié, 1966-11
Article révisé par les pairs
Résumé : It is known that the polarographic behaviour of the chlorite ion in alkaline media is characterized by a kinetic pre-wave, followed by a dip, which has been assumed to reflect a desorption process. The present work shows that this pre-wave is related to traces of ferrate ions, which are almost always present in unpurified hydroxide solutions. At potentials of the order of -1.0 V/S.C.E., ferrite ions are produced; these are catalytically reoxidised by the chlorite ions. The dip is explained by the direct reduction to metallic iron. The kinetic characteristics of the reactions: Fe(+III) + e ⇌ Fe(+II) Fe(+II) + 2e ⇌ Fe(O) and 4Fe(+II) + Cl(+IV) → 4 Fe(III) + Cl(-I) have been elucidated, taking into account the effects of concentration, cation composition and pH. The rate-determining step FeO2H- + ClO2- → proceeds with a rate constant of the order of 1.7·108 M-1 1 sec-1. The main wave, which follows the dip, corresponds to the direct irreversible discharge of ClO2-, the rate constant of which satisfactorily obeys the Frumkin theory, with αnα {reversed tilde equals} 0.37. © 1966.