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.

     

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.     

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.     

Sur la thermogravimétrie des précipités analytiques: Dosage du platine

The authors have studied the thermogravimetric curves of precipitates proposed for the determination of platinum. This precipitated metal is, like gold, sometimes oxidisable, sometimes deposited at constant weight. Bivalent platinum thiophenolate, isolated by the authors, is excellently suitable for gravimetry, after which comes the weighing as platinum (II) chlorides.     

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.

     

Premières applications du thiocarbohydrazide en chimie minérale

Résumé Les auteurs proposent l'emploi du thiocarbohydrazide en chimie minérale. Ils donnent une première liste d'ions réagissants. Ce réactif apparaît déjà intéressant pour le dosage gravimétrique ou colorimétrique du molybdène en présence de tungstène et d'uranium.

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Summary The authors propose the use of thiocarbohydrazide in inorganic chemistry. They give a preliminary list of reacting ions. This reagent appears to have some interest for the gravimetric or colorimetric determination of molybdenum in the presence of tungsten and uranium.

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Zusammenfassung Die Anwendung von Thiocarbohydrazid in der anorganischen Chemie wird vorgeschlagen und eine Liste der mit dieser Verbindung reagierenden Ionen angeführt. Für die gravimetrische oder kolorimetrische Bestimmung von Molybdän in Gegenwart von Wolfram und Uran scheint das Reagens von Interesse zu sein.

     

Semi-micro dosages gravimétrique et volumétrique de la silice

The author furnishes results checked by three years of practice, concerning the measurment of traces of silica.This is transformed into a complex silicomolybdate by means of hexamethylenetetramine Treated with special in precautions the Precipitate yields a residue of SiO₂ + 12MoO₃ ,weighing about tlurty times more than the starting silica.Since the titration of the hexamethylenetetramine used can be done by means of iodine, we have here a means of titrating the silica used after destroying hydrolytically the preipitaite of silicomolybdateThese methods have so far been applied only to solutions containing free silica or alkilisilicates.     

Sur la thermogravimétrie des précipités analytiques : Dosage du zinc

With the help of the CHEVENARD thermobalance, the authors have traced the pyrolysis curves of the precipitates which serve for the gravimetric determination of zinc. In the table, the temperature limits and the forms in which the precipitates are weighed, are listed. Eight new reagents for the automatic determination of zinc are included in the table.