Volume 16, Issue 3, 1998
17th October, 2022
by Armando J. L. Pombeiro
121-132
DOI: doi:10.4152/pea.199803121
A Pitzer Theory Approach to Assignment of pH to Standard Buffer Solutions
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by M.I.A. Ferra
133-142
DOI: doi:10.4152/pea.199803133
The quantity pH=lg aH is immeasurable, as it involves a single ion activity. The IUPAC recommendations for the pH scale for aqueous solutions are based on the Bates-Guggenheim convention for the calculation of the chloride ion activity coefficient. The idea of this convention, intended to be applied to ionic strength not higher than 0.1 mol kg"1, was to impart pH with as much fundamental meaning as possible while recognising that it is conventionally based.
The Pitzer theory, involving ionic specific interactions, may be applied in the calculation of single ion activity coefficients at ionic strengths higher than 0.1 mol kg"1. This approach has the merit that all possible known buffers, with or without background electrolyte, and those yet to be developed, can be assigned pH values.
The Inhibition Effect of 4(2-Pyridyl)-l-Benzaldehyde-3-TWosemicarbazone Derivatives Towards the Iron Corrosion
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by S.A. Abd El-Maksoud
143-153
DOI: doi:10.4152/pea.199803143
The effect of 4(2-pyridyl)-l-benzaldehyde-3-thiosemicarbazone derivatives towards the corrosion of iron in 1M HC1 solution at 303K was investigated. Potentiodynamic and weight loss measurements show that compounds under investigation act as effective inhibitors for the corrosion of iron in 1 M HC1. The results show that these compounds behave as mixed type inhibitors. The corrosion rate was found to be a function of the nature and concentration of the inhibitors. The adsorption of the compounds on the iron surface is found to obey Temkin's adsorption isotherm.
Electrokinetic Study on Clays of Different Mineralogical Composition by Microelectrophoresis and Electroosmosis
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by J. M. Caridade Costa, M. Maribel M. Dias, J. Simões Redinha
155-163
DOI: doi: 10.4152/pea.199803155
The electrokinetic behaviour of aqueous suspensions of naturally occurring clays with different mineralogical composition is reported as a function of pH and electrolyte concentration. The results indicate that the clay particles carry a net negative charge in the examined pH range. The estimated zeta (Q potential values have been interpreted in terms of the composition and structural characteristics of the clay minerals, nature and charge of the particle surfaces and properties of the electric double layers developed at the clay/electrolyte solution interface. The potential values of the clays obtained using microelectrophoresis and electroosmosis techniques have also been compared.
Necessidade de Conhecimentos de Electroquímica no Âmbito da Corrosão
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by Victor M. M. Lobo
165-170
DOI: doi:10.4152/pea.199803165
Justifica-se a necessidade de compreender bem os fundamentos da electroquímica para entender e consequentemente resolver adequadamente os problemas da protecção contra a corrosão.
