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New λ3-7-phosphanorbornenes are prepared either through the nickelocene reduction-complexation of the corresponding P-sulfides ( structure) or through the direct [14 + 2] cycloaddition of tervalent phospholes with N-phenylmaleimide ( structure). 相似文献
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Résumé On a étudié les méthodes et les techniques d'analyse par activation de minerais pour la détermination d'éléments rarès d'après
leurs isotopes de longue période: on donne la précision évaluée, la sensibilité, le rendement pour la détermination de Ta,
Cs, Hf, Sc, Sb. On a montré la nécessité de combiner les méthodes d'analyse par activation aux neutrons et par fluorescence
X dans les études géochimiques. 相似文献
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G. Revel M. Da Cunha Belo J. P. Meriaux C. Schneider N. Hilleret R. Bourguillot 《Journal of Radioanalytical and Nuclear Chemistry》1973,17(1-2):101-111
Résumé Dans le but de préciser les phénomènes responsables de la corrosion fissurante de l'acier inoxydable, nous avons analysé les
films de passivation formés à la surface d'échantillons exposés au MgCl2 bouillant. Suivant la durée du traitement l'épaisseur de ces films varie entre quelques centaines et quelques milliers d'angstr?ms.
Les méthodes d'analyse utilisées sont l'activation aux neutrons et aux particules chargées, l'émission ionique secondaire
et la io noluminescence atomique. Les résultats obtenus sont décrits et comparés entre eux. Ces expériences mettent en évidence
l'intérêt qu'il y a à associer les méthodes qui apportent des renseignements complémentaires. 相似文献
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A. Ait-Kaci J. C. Merlin J. C. David 《Journal of Thermal Analysis and Calorimetry》1991,37(5):1025-1042
The simultaneous estimation of chemical potentials of mixing and the latent heat of fusion of the pure constituents from liquid-solid equilibrium data of binary mixing is rather difficult. Since the activity coefficients change before the considered molar fraction and the temperature. Moreover chemical reaction may occur in the binary mixing therefore the application of the Gibbs-Duhem relation becomes impossible.The activity, the latent heat of fusion in the pure state and the C
p of fusion of NaI from the experimental data of the diagram of fusion of NaI-NaIO3 were calculated. The application of the results obtained near the eutectic point allowed the determination of the latent heat of fusion of the pure NaIO3. When the expression of the activity becomes complicated, the experimental data of heat of mixing in addition to the data obtained from the equilibrium of fusion were applied.
Zusammenfassung Eine simultane SchÄtzung der chemischen Potentiale von MischvorgÄngen und der SchmelzwÄrme der reinen Komponenten aus Liquid-Solid-Gleichgewichtsdaten von binÄren MischvorgÄngen ist recht schwer, da sich eher die AktivitÄtskoeffizienten Ändern als die betrachteten Molenbrüche und die Temperatur. Au\erdem können sich bei den binÄren MischvorgÄngen chemische Reaktionen abspielen, wodurch die Anwendung der Gibbs-Duhemschen Gleichung unmöglich wird. Es wurde die AktivitÄt, die SchmelzwÄrme im reinen Zustand und aus den experimentellen Daten des Schmelzdiagrammes von NaI-NaIO3 C p für das Schmelzen von NaI berechnet. Die Anwendung der erhaltenen Ergebnisse in der NÄhe des Eutektikums ermöglichte die Bestimmung der SchmelzwÄrme von reinem NaIO3.Wird der Ausdruck für die AktivitÄt kompliziert, werden zusÄtzlich zu den aus dem Schmelzgleichgewicht ermittelten Daten die experimentellen Daten für die MischungswÄrme verwendet.相似文献
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Amelioration des separations chimiques sur resines echangeuses d'ions: Influence de la granulometrie
In order to reduce the time requirement for ion exchange separations the kinetics of the elution of different ions was studied
in the function of the grain size of the ion exchange resins. Using a counter current apparatus seven differents fractions
could be separated in the case of commercial resin Dowex 1×10 and 50 W×12. Grain size was found to have a great influence
on the shape of the elution curves. The finer and more homogenous the resins are the sharper are the peaks on the elution
curves. These consderations were utilized for the separation of rare earth, alkaline and alkaline earth metals, respectively.
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Impurities contained in nuclear graphites have been determined so far individually. A method of systematic analysis is described
which permits to determine about twenty impurities in one sample, such as the following elements: Ag, Se, Hg, Sb, Cu, Fe,
Ga, Co, Cd, Zn, In, Zr, Cr, Sc, Ba, Ca, Na, K, Rb, and Cs. Brief mention is made of methods used for the determination of
all rare earth metals, Si, S and P, as well as the elements which can be determined without chemical separation, such as Cl,
Mn, V.
Determination quantitative des impuretes des graphites nucleaires par les methodes de radioactivation analyse systematique相似文献
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Jaffrezic H. Joron J. L. Treuil M. 《Journal of Radioanalytical and Nuclear Chemistry》1982,69(1-2):235-238
Correspondence Factor Analysis is a multivariate technique that may be applied to any type of data. The principal advantage
of this method is related to its simultaneous representation of subjects and variables on the same factorial axis. Two dimensional
graphs may be drawn and offer a strong aid in the interpretation of the results. In our case subjects are “analytical methods
or laboratories” and variables are “determined elements”.
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The tautomeric equilibrium, configuration, bond order PCO and structure of the common anion of phenylhydrazopyazolones have been investigated by means of semi-empirical MO methods (Hückel-ω, Extended Hückel). The results have been compared with those in the literature. Experiments have been made in order to verify the theoretical predictions. 相似文献
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4-Hydroxy cinnamic esters, thiolesters, aldehydes and alcohols, or related compounds, implied in the biosynthesis of lignins are easily synthesized in good yields from iminium salts of coumaric , ferulic and sinapic acids. No prior protection of the phenol group is needed in this method. 相似文献