A l'aube de la micro-analyse

Résumé L'auteur rappelle un certain nombre de découvertes notamment des XVII^e et XVIII^e siècles ayant conduit à des tests microchimiques encore utilisés de nos jours. Les découvertes géniales d'Emich prennent ainsi, par contraste, plus de valeur; son euvre est véritablement celle d'un pionnier.

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Summary The author calls attention to a certain number of discoveries, notably of the 17th and 18th centuries, which have led to microchemical tests still in use today. The brilliant discoveries ofEmich therefore acquire more value by contrast. His work is really that of a pioneer.

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Zusammenfassung Eine Reihe von Entdeckungen, insbesondere des 17. und 18. Jahrhunderts, werden angeführt, die zu mikrochemischen Reaktionen geführt haben, die auch heute noch in Anwendung stehen. Die genialen EntdeckungenEmichs erwiesen sich als noch wertvoller; sein Werk ist in Wahrheit das eines Pioniers.

     

Sur la stabilité thermique des étalons analytiques. XI

Résumé Nous avons étudié par thermogravimétrie et par spectrophotométrie infrarouge, entre 6 et 15, douze substances nouvelles proposées pour étalons en chimie analytique. Le chlorure de magnésium et d'ammonium, l'hydrogénocarbonate d'ammonium et le fluorure d'ammonium paraissent d'emploi douteux pour préparer avec certitude une liqueur titrée.

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Summary Twelve new substances suggested as standards in analytical chemistry have been investigated by thermogravimetry and infrared spectrography, between 6 and 15. Magnesium ammonium chloride, ammonium bicarbonate and ammonium fluoride seem to be of doubtful value for the accurate preparation of a standard solution.

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Zusammenfassung Zwölf zur Herstellung von Urtiterlösungen neu vorgeschlagene Substanzen wurden thermogravimetrisch und infrarotspektrophotometrisch zwischen 6 und 15 geprüft. Magnesium-Ammoniumchlorid, Ammoniumhydrogencarbonat und Ammoniumfluorid scheinen für diesen Zweck von zweifelhaftem Wert zu sein.

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Pour le dixième mémoire de cette série, voir Mikrochim. Acta [Wien]1962, 268.     

Emploi des thiocarbohydrazones en analyse organique fonctionelle

Résumé Le thiocarbohydrazide est un réactif d'accès facile précipitant quantitativement les aldéhydes et quelques cétones. Les points de fusion sont nets. Les précipités formés se prêtent à la gravimétrie. Nous avons étudié avec la thermobalance leur domaine de stabilité et fourni la température à ne pas dépasser pour le séchage à poids constant.

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Summary Thiocarbohydrazide is a readily available reagent which quantitatively precipitates aldehydes and some ketones. The melting points are sharp. The resulting precipitates are suitable for gravimetry. Their regions of stability have been investigated with the thermobalance and the temperatures which should not be exceeded in drying to a constant weight have been found.

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Zusammenfassung Thiocarbohydrazid ist ein leicht zugängliches Reagens zur quantitativen Fällung der Aldehyde und mancher Ketone. Die Schmelzpunkte der Niederschläge sind scharf. Diese eignen sich zur gravimetrischen Auswertung. Ihre Stabilität wurde mit Hilfe der Thermowaage untersucht und die Höchsttemperaturen für ihre Trocknung bis zur Gewichtskonstanz bestimmt.

     

Electrochemical activity of various types of aqueous In(III) species at a mercury electrode

An interpretation framework is presented which provides a straightforward means to characterise the electrochemical reactivity of aqueous ions together with their various hydrolysed counterparts. Our novel approach bypasses the more laborious strategy of solving rigorously, for all relevant species, the complete set of Butler-Volmer equations coupled to diffusion differential equations. Specifically, we consider the spatial variable via a Koutecký-Koryta type of differentiation between nonlabile and labile zones adjacent to the electrode. The theory is illustrated by an assessment of the electrochemical reactivity of aqueous In(III) species based upon proper comparison between relevant time scales of the involved interfacial processes, i.e. diffusion, (de)protonation of inner-sphere water, dissociation/release of H₂O and OH⁻, and electron transfer. The analysis reveals that whilst all In(III) species are labile on the experimental timescale with respect to (de)protonation and (de)hydration, there are large differences in the rates of electron transfer between \( \mathrm{In}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6^{3+} \) and the various hydroxy species. Specifically, in the case of \( \mathrm{In}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6^{3+} \), the rate of electron transfer is so slow that it replaces the traditional Eigen rate-limiting water release step in the overall passage from hydrated In³⁺ to its reduced metallic form; in contrast, the In(III) hydroxy species display electrochemically reversible behaviour.

     

Excitation processes leading to ruby emission

We excited the ²T₁-levels in ruby by tunable laser light, pumped bya pulsed YAG:Nd³⁺ laser, and observed the low temperature emissions from the 2$\text{A}$ and $\text{E}$ sublevels of ²E in the mild bottlenecking regime. The R₂-line decay time was about five-fold longer and the ratio of intensities R₂/R₁ higher (by up to a factor 10) than after pumping into ⁴T₂. It is suggested that when ⁴T₂ is pumped the relaxation is nonadiabatic, so that transitions between the sublevels occur while the ²E state relaxes to its normal (trigonal) configuration. The time-development of the relaxing state is studied. It is shown that its coherence between the 2$\text{A}$ and $\text{E}$ sublevels leads to a narrowing of the spectral width in transition between the sublevels.     

The LPCTrap experiment: measurement of the β–ν angular correlation in 6He using a transparent Paul trap

We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller decay of ⁶He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The ⁶He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this experiment. Up to 10⁵ coincidences were recorded during a second run in 2006.     

Dispersion and localization of electronic states at a ferrocene/Cu(111) interface

Low-temperature scanning tunneling microscopy and spectroscopy combined with first-principles simulations reveal a nondissociative physisorption of ferrocene molecules on a Cu(111) surface, giving rise to ordered molecular layers. At the interface, a 2D-like electronic band is found, which shows an identical dispersion as the Cu(111) Shockley surface-state band. Subsequent deposition of Cu atoms forms charged organometallic compounds that localize interface-state electrons.     

Geant4 Monte Carlo simulations for the LPCTrap setup

The LPCTrap setup at GANIL is fully operational since 2006. The first breakthrough was the detection of 100000 coincidences between the $ \beta$ particles and the recoil ions from the decay of ⁶He⁺ produced by the SPIRAL source. After preparation, the decaying nuclei are confined in a transparent Paul trap which is surrounded by a $ \beta$ -telescope made of a double-sided silicon strip detector followed by a scintillator, and by a micro-channel plate position-sensitive detector to record in coincidence the $ \beta$ particles and the recoil ions. Simulations of this system are needed in order to study possible systematic effects and extract with high accuracy the $ \beta$ - $ \nu$ angular-correlation coefficient. A code based on Geant4 is well suited for this purpose. In this contribution the results from the simulations compared with those from the experiment will be presented and discussed.