Volume 9, Issue 4, 1991
15th January, 2023
From Luigi Galvani up to now: Bioeletrochemistry two Centuries Later
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by Giulio Milazzo
473-485
DOI: DOI: 10.4152/pea.199104473
Linear Energy Relationships and Solvent Effects for the Solution of Tert — Buthyl Chloride and Bromide in Water and Alcohols
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by R. M. C. Gonçalves, L. M. P. C. Albuquerque, A. M. N. Simões
487-499
DOI: DOI: 10.4152/pea.199104487
Solvent effects on the enthalpies of solution of t-BuCl and t-BuBr in water and 13 monoalcohols, from 1 to 5 carbon atoms, are analysed in terms of linear solvation energy relationships. The experimental data, at 25°C and infinite dilution, are well correlated through equations of the type, isH° = aQ + a1 f(c) + a2 E^ + a3 C where f(e) is the Kirkwood function of the dielectric N constant, E^, is the normalized Dimroth and Reichardt parameter and C is the solvent cohesive energy. Pertinent information on the dominant solvent-solvent-solute interactions is obtained.
The Use of Non-Linear Techniques for the Assessment of Corrosion Rates
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by Alda M. P. Simões, Mário G. S. Ferreira
501-506
DOI: DOI: 10.4152/pea.199104501
The paper involves corrosion on mild steel in 0.1M HC1 solution, using harmonic analysis and faradaic rectification techniques. In the harmonic analysis a sweep of the three first harmonics of a Taylors Series expansion is carried out. The measurement of the sinusoidal currents produced allow the determination of the corrosion rate and the Tafel coefficients. In the faradaic rectification method, the corrosion rate is determined by measuring the d.c. current at the potential for which the second harmonic of a sinusoidal perturbation shows a minimum. This current is related to the corrosion rate by the equation icorr =0.6 i^.c. Values of the corrosion rate obtained for the system under study by both methods are presented which agree with the value obtained by electrochemical impedance.
Oxygen Reduction on Platinum Electrodes Coated with Nafion
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by C. Paliteiro, M. L. Pereira, A. M. Jorge
507-523
DOI: DOI: 10.4152/pea.199104507
The electroreduction of 02 in 0.5 M H^SO^ on platinum finely dispersed on pyrolytic graphite and coated with Nafion films ranging in thickness from 0.5 to 18 u was studied. It was found that i) the film does not alter the mechanism of the reduction reaction; ii) the film does not prevent sintering of the catalyst; HI) the film concentrates O? from the solution but, nevertheless, the current measured for the filmed electrodes only increases relatively to the uncoated electrodes near the onset of the reduction when electron transfer controls; once diffusion becomes important the current decreases because, whatever the thickness, the transport of 02 inside the film is slowed down; Iv) thick films behave like recast films whereas thin films behave like membranes.
by J. E. Simão
525-542
DOI: DOI: 10.4152/pea.199104525
