Collect. Czech. Chem. Commun. 2000, 65, 326-342

Analysis of the Electrode Kinetics of Ni(II) Reduction in Thiocyanate Media on the Dropping Mercury Electrode

María S. Crespo-Pinilla, Fernando Mata-Pérez* and Rosa M. Villamañán

Departamento de Química Física, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain


A study of two prewaves of the Ni(II)-SCN- system was carried out under the experimental conditions when the influence of electroreduction of SCN- is negligible. Kinetics of Ni(II) reduction in thiocyanate media on the dropping mercury electrode was studied by DC Tast Polarography (DCTP) via determination of Koutecký's parameter χ; the influence of different variables was analyzed. The study of prewaves was performed using various polarographic techniques. Values of χ depend on the SCN- concentration, pH, ionic strength (Ψ-effect) and on the nature of the supporting electrolyte. The number of electrons n, the transfer coefficient α, the stoichiometric number ν, ∆H, and ∆S were determined (compensation effect). The first prewave has character of a reaction in the solution, the second prewave is a surface process. Main features of both mechanisms are common: catalytic nature, one-electron step discharge and the rate-determining process between species of opposite charges.

Keywords: Catalytic prewaves; Polarography; Kinetics; Nickel(II) thiocyanate; Electroreduction; Electrochemistry.

References: 38 live references.