Portugaliae
Electrochimica Acta

In the present study the voltammetric behaviours of some phenothiazines namely Promazine hydrochloride, Promethazine hydrochloride and Fluphenazine hydrochloride were investigated. And it was shown that the electro oxidation of the substances was dependent on the nature of the supporting electrolyte, pH, scan rate. The results of the statistical analysis revealed that the quantitative analysis of these substances could be made using glassy carbon electrode, activated by a simple electrochemical procedure, with good accuracy and precision.

Mercury film microelectrodes, prepared by potentiostatic electrodeposition of Hg(II) from an acidic solution onto a gold microdisk electrode, in combination with adsorptive stripping voltammetry in the presence of catechol were used to study the behavior of copper, iron and nickel in aqueous solutions. The voltammetric behavior of hydrogen ion was also investigated by performing cyclic voltammetry and stripping voltammetry with mercury microelectrodes.

The use of some p-substituted benzoic acid derivatives as low cost inhibitors for the corrosion of aluminium in 60% H3PO4 solution was explored by weight loss and galvanostatic polarization measurements. The inhibition efficiency of the compounds increases in the order: p-OH > P-NH2 > benzoic acid > p-Br > p-N02- This order is not affected by the variation in temperature in the range 30-60 °C. Rate of corrosion is affected by both concentration of inhibitors and the temperature of the medium. The reaction rate was found to be proportional to the absolute value of Hammett constant (a). Some thermodynamic functions were computed and are discussed. Key words: Corrosion, aluminium, polarization, weight-loss measurements.

Basic concepts of electrochemistry are not yet properly understood in areas related with technical aspects where this science is fundamental, such as corrosion. Examples of this are given here with the objective of alerting electrochemists for the need to give their collaboration in technical bodies (e.g. ISO, CEN, OIML [1]) where it is useful to complement the very important technical knowledge of applied experts on the relevant field (e.g. corrosion) with fundamental knowledge of electrochemistry.

The effect of some 4-amino-4' -nitroazobenzene derivatives as corrosion inhibitors for copper in nitric acid solution at 30 °C was investigated using thermometric and polarization techniques. The corrosion rate was found to be a function of the nature, of inhibitor and temperature of the medium. The calculated degree of concentration surface coverage was used to evaluate the free energy of adsorption (A G°a) of the process. All the inhibitors follow the Frunkin adsorption isotherm. The mechanism of inhibitor action has been discussed on the basis of adsorption and molecular polarizahility of the inhibitors. The observed experimental data indicate that these compounds act as mixed inhibitors. Some thermodynamic function was calculated and discussed. Key words: Corrosion, inhibitors, acid solution, copper, dyes.

A recent survey of secondary school pupils' attitudes to chemical formulae show interesting similarities with the attitudes of XIX century scientists to the formulae system developed by Berzelius (the basis of the present system). Dalton's opposition to this system, Children's alterations of a Berzelius original when translating it to English, a fact praised by contemporaries, and other objections of the time are compared with today's secondary school pupil’s comments collected in a recent study. These comparisons make it easier to understand the difficulties in teaching formulae at school.