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Title: Electrochemical and kinetic studies with silver halides
Author: Ibrahim, Olfat Dessouky El-Sebaie
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1969
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The electrochemical and catalytic effect of platinum on oxidation-reduction reactions was studied in Part I. Potentiometric titrations using rotating disk electrodes were performed for two slow redox systems to test whether platinum catalysis could be used as an analytical tool for such reactions. The results of the titratione were interpreted using the mixture potential principle. The electrochemical behaviour of silver halide electrodes has been studied in Part II. An extensive survey has been carried out for electrode reactions at known semiconductor electrodes, and the properties of silver halides in particular, are discussed. Neither molten silver halide electrodes, nor those prepared by electroplating, produced more than tiny currents, and an investigation involving capacitance, resistance, photochemical, and current-voltage measurements demonstrated that it is impossible to make pure silver halide electrodes by electrodeposition. These results explain why silver halides are catalytically inactive towards oxidation-reduction reactions. In Part III, the catalytic effect of silver iodide on the substitution reaction between silver nitrate and ethyl iodide was studied quantitatively. It was found that the homogeneous rate follows a second order rate equation, while the heterogeneous rate was surface controlled. The silver nitrate kinetics at the surface of silver iodide followed Freundlich's isotherm and those of ethyl iodide followed the Langmuir isotherm; the reaction as a whole fitted the Langmuir-Hinshelwood mechanism. The heat of activation of the heterogeneous reaction was found to be 9.2 ± 1.5 kcal. The effect of the auto-catalytically formed silver iodide was calculated from the kinetic curves, and compared with that of the added solid.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available