Showing papers by "Jose A. Garrido published in 1987"

A cyclic voltammetry experiment using a mercury electrode

Abstract: An easy and inexpensive experiment designed to illustrate cyclic voltammetry in the study of a simple reversible reaction.

Medium effect on the electrochemical behaviour of the CdII/Cd (Hg) system in propane-1,2-diol–water mixtures

Abstract: The electrochemical behaviour of the CdII/Cd(Hg) system in propane-1,2-diol (PD)–water mixtures containing 5.0 × 10–2 mol dm–3 LiClO4 has been studied by polarography and cyclic voltammetry. The reversible half-wave potentials, the diffusion coefficients and the Walden products for CdII have been determined polarographically. From the half-wave potentials vs. the ferrocene electrode scale, the standard free energies of transfer of 1 mol of CdII ions from water to PD–water mixtures, ΔG°t, have been obtained. These values are always negative, indicating a greater stability of CdII in PD-water mixtures than in pure water. The splitting of the ΔG°t values into electrostatic and chemical contributions shows that the mixtures are more basic than water, increasing the CdII solvation when the PD mole fraction rises. The analysis of the variation of the Walden product with solvent composition indicates an enhancement of the solvent structure in the water-rich region. The diffusion coefficient for Cd in mercury, the transfer coefficients for CdII electroreduction and the apparent standard rate constants of the CdII/Cd(Hg) system have been determined by cyclic voltammetry. The change in the kinetics with solvent composition is discussed in terms of existing models. The results obtained are compared with those previously reported in ethylene glycol–water mixtures.