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The aim of this work is to determine the Tafel parameters with and without ultrasound. The total overvoltage has been corrected for diffusion by using rotating disk technique and potentiostatic extrapolation to infinite rotating speed. Three well known redox systems have been selected regardless to their different electrochemical behaviour: the quinone-hydroquinone, the Fe(II)Fe(III) chlorides and Fe(II)-Fe(III) cyanide systems. This work shows that the reversibility is higher with ultrasound only in the case of the quinone-hydroquinone system.

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Solvated electrons, es-, have been generated in hexamethylphosphoric triamide (HMPA) by chemical and electrochemical means. W h e n Na metal was used to release es-, two distinct bands, already reported in the literature, appeared in t h e absorption spectrum of t h e solution, which rapidly turned red-brown and decomposed according to irreproducible complex kinetics which could not be analysed. When Li was used instead of sodium, a single broad band extending into t h e IR region developed and later decayed obeying consistently first-order kinetics in absorbance. Kinetic rate constants are reported and half-lives at ambient temperature were about 1 h duration. A systematic study of the disappearance of solvated electrons in HMPA was carried out at several temperatures (from 7 to 27°C) and an activation energy ( 8 H 9 kJ mol-') is estimated both in t h e absence and in the presence of lithium perchlorate. However, t h e overall reaction rate is markedly increased in the presence of Li' ; a mechanism is proposed to account for this lithium salt effect.

The issue of domestic energy is still a major concern in developing countries. A sound knowledge of fuel characteristics is a major asset for their acceptability and their distribution. Samples of briquettes made partially with Municipal Solid Waste (MSW) were collected in several companies with unknown characterization. This study intended first to characterize them for physical and chemical properties. Subsequently, energy content of the briquettes and the energy price are presented and compared to those of charcoal and peat, which is typically used by the local population as fuel. To classify the different briquettes according to their quality in terms of rate as well as their level in fire resistance, cooking tests and heating curves have been made. The calorific value of the studied briquettes varied from 12.3 to 18.6 MJ/kg compared to 32.5 MJ/kg for charcoal and 14.7 MJ/kg for peat. Consequently, their value as viable substitutes for charcoal or peat is apparent. However, some samples burn very quickly and do not provide prolonged heating while other samples have a slow rate of combustion and release little energy. Finally, the briquettes using MSW have a low price between $0.16 and $0.19/kg compared to the price of $0.53/kg for charcoal and $0.20/kg for peat. The promotion of these briquettes as a valuable substitution fuel is proved and contribute to sustainable development by reusing MSW and avoiding deforestation.

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