Bernard Gilbert

The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO₂ into epoxides under mild experimental conditions. The combination of online kinetic studies, NMR titrations and DFT calculations allows understanding this synergistic effect that provides an active organocatalyst for CO₂/epoxides coupling.

For the last 40 years, Raman spectroscopy has been very useful in investigating the structure of corrosive molten salts, such as the cryolite-based melts widely used as electrolyte in the Hall-Heroult process. Even if this process remains the most economically efficient for metallic aluminum electro-production, it suffers from a high energy loss, which is dependent on the melt composition. Therefore, controlling the chemical composition of the electrolyte is essential. The present paper proposes to apply Raman spectroscopy for the direct determination of the NaF-AlF3 molar ratio in NaF-AlF3-CaF2-based melts. Despite the experimental difficulties, a calibration curve based on equilibria taking place in the melt has been developed and the procedure has been successfully compared to industrial samples of known compositions. The possible exportation of the laboratory scale procedure to an industrial environment application for the control of the Hall-Heroult process is finally discussed.

A novel setup is described to monitor the kinetics of homogeneous and heterogeneous reactions online using Raman spectroscopy under high pressure. The arrangement is based on a high‐pressure reactor equipped with a sapphire window in combination with a mobile probe that allows the collection of the back‐scattered Raman signal at 360°.

Studies on mural paintings from the Tournai Cathedral (Belgium) were carried out by micro‐Raman spectroscopy. The analyses were performed on micro‐samples extracted from the remaining paintings and architectonic decorations, and concerned the pigments, the binders and, in some case, the stratigraphy. The palette was established and various pigments were identified, according to the Romanesque and Gothic periods. Red color was largely made of iron oxides. Lapis lazuli was also found in abundance, mainly on the areas that are assigned by historians to the Romanesque period. The green pigments revealed the use of atacamite and posnjakite. It was also found that some of the paint layers were applied using egg yolk as binding medium. These layers cover the stone above a very thin coating made of gypsum and chalk. The presence of oxalates was often noticed. This can be related to aging due to degradation of chalk by aggressive lichen, but also as result of a degradation of organic substances applied during past restorations. The gypsum is also altered by partial or complete dehydration, thereby damaging the artwork on which the painting is based. In humid conditions, iron oxide could be transformed in its hydrolyzed counterpart, whose Raman spectrum was often observed. Finally, a stratigraphic analysis was carried out on a multilayer fragment from the outside whitewash of the Cathedral, and despite a clear visual difference in morphology, each layer showed surprisingly the same chemical composition. Copyright © 2006 John Wiley & Sons, Ltd.