Adsorption of bromocadmium (II) complexes at mercury/aqueous melt interfaces

Abstract

Maxima observed on cathodic D.C. polarograms for the system Cd²⁺+ Br^– in the molten solvent Ca(NO₃)₂·4H₂O at 50°C have been investigated further by electrochemical relaxation techniques. Linear sweep polarograms, instantaneous (current, time) curves and chronopotentiograms all exhibit two-part waveforms. Deposition of cadmium occurs via reduction of a solution species in series with an adsorbed species. The apparent correlation between the surface excesses of the adsorbed species and the concentration of the CdBr^–₃ complexes in the solution has been interpreted in terms of an interaction between the latter and adsorbed Br^– ions to give adsorbed CdBr^2-₄ complexes.