Influence de la nature de l'electrolyte sur la reactivite electrochimique du chromate de baryum incorpore dans une electrode a pate de carbone

Abstract

The electrochemical behaviour of baryum chromate is investigated by means of a carbon paste electrode with conducting binder. Current potential curves recorded, when electrolyte and binder are 1 M aqueous solutions of strong mineral acids, evidence only the reduction of chromium (VI) ions resulting from the more or less complete dissolution of the sample at the beginning of the experiment. The behaviour is different in the acids CH 3COOH and HCOOH. The curves then exhibit two peaks corresponding to the electrochemical transformations of chromium: the first is due, as in strong mineral acids, to the reduction of chromium (VI) ions, coming from the dissolution of the finest particles at the beginning of the experiment, into Cr 3+ ions; the second one is characteristic of the progressive electrodissolution of the solid, via a chemical-electrochemical mechanism, during the potential sweep; its shape and position are greatly influenced by the morphology of the sample.