New type of blue ternary complex of arsenazo I with plutonium (IV) in the presence of hydrogen peroxide: preliminary investigations

The preparation and spectrophotometric properties of a new type of complex compound of arsenazo I with Pu(IV) in the presence of H₂O₂ are described. The new compound has a blue colour, derived from a wide absorption band with a maximum at 610 nm. and a corresponding molar absorptivity of 4 × 10⁴ l. mole⁻¹.cm⁻¹. From 2 hr after its preparation this curious new compound undergoes for several days a steady decomposition accompanied by decolorization. The formation of similar peroxy Pu(IV) complexes has not so far been shown to take place with arsenazo III or with any other “arsenazo-type” reagent.     

Kinetics and mechanism of substitution reactions of complexes,XX

Thermal decomposition of 21 complexes of the type [Co(DH)₂(amine)₂]NCS has been studied under the conditions of thermogravimetric analysis, by using different heating rates. From the thermogravimetric curves apparent kinetic parameters of the pyrolysis reaction have been derived by means of the modified Doyle method. Apparent reaction order increases and apparent activation energy decreases with increasing heating rate. Thus, the obtained kinetic parameters do not characterize the purely chemical reaction, but the complex heterogeneous process as a whole. The explanation of the observed effect is discussed. Results are compared with those obtained with other analogous complexes.

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Zusammenfassung Die thermische Zersetzung von 21 Komplexen des Typs [Co(DH)₂(Amin)₂]NCS wurde thermogravimetrisch bei verschiedenen Aufheizungsgeschwindigkeiten untersucht. Aus den TG-Kurven wurden die scheinbaren kinetischen Parameter der Reaktion mit Hilfe der Doyleschen Methode ermittelt. Bei zunehmender Aufheizungsgeschwindigkeit wächst die scheinbare Reaktionsordnung während die scheinbare Aktivierungsenergie abnimmt. Die erhaltenen chemischen Parameter kennzeichnen nicht die eigentliche chemische Reaktion, sondern den ganzen komplexen heterogenen Vorgang. Die beobachteten Effekte wurden diskutiert und die Ergebnisse verglichen mit Resultaten von Untersuchungen anderer analoger Komplexe.

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Résumé On a étudié par thermogravimétrie, avec différentes vitesses d'échauffement, la décomposition thermique de 21 complexes du type [Co(DH)₂(amine)₂SCN. On a calculé suivant la méthode deDoyle les paramètres cinétiques apparents déduits des courbes d'ATG. L'ordre apparent de la réaction augmente si la vitesse d'échauffement croît, alors que l'énergie d'activation apparente décroît. Les paramètres cinétiques obtenus ne caractérisent que le processus hétérogène complexe et non la réaction chimique proprement dite. Les effets observés ont été discutés et comparés avec les résultats obtenus avec d'autres complexes analogues.

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21 [(D)₂()₂]NS , . . . , , . . , .

     

Effective interactions in the colloidal suspensions from hypernetted-chain theory

The hypernetted-chain (HNC) Ornstein-Zernike integral equations are used to determine the properties of simple models of colloidal solutions where the colloids and ions are immersed in a solvent considered as a dielectric continuum and have a size ratio equal to 80 and a charge ratio varying between 1 and 4000. At an infinite dilution of colloids, the effective interactions between colloids and ions are determined for ionic concentrations ranging from 0.001 to 0.1 mol/l and compared to those derived from the Poisson-Boltzmann theory. At finite concentrations, we discuss on the basis of the HNC results the possibility of an unambiguous definition of the effective interactions between the colloidal molecules.     

Etude de la séparation du thorium d'avec les terres cériques

Résumé Nous avons étudié les complexes que forment les acides éthylèneglycolbis-(-aminoéthyléther)] Sr,N-tétracétique et ,-diaminodiéthylétherN,N-tétracétique, soit avec le thorium, soit avec les terres cériques et, à la suite de cette étude, nous avons pu établir une méthode d'analyse et une séparation du thorium d'avec les terres cériques qui nous a donné satisfaction.

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Summary A study has been conducted of the complexes formed by the ethyleneglycol-bis (-amino-ethylether)-N,N-tetraacetic acid and,-diaminodiethylether-N,N-tetraacetic acid with either thorium or the ceric earths. As a result of this investigation, it was possible to set up a method of analysis and a separation of thorium from the cerium earths. These procedures have proved satisfactory.

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Zusammenfassung Die von Äthylenglykol-bis-(-aminoäthyläther)-N,N-tetraessigsäure bzw.von ,-Diaminodiäthyläther-N,N-tetraessigsäure mit Thorium bzw. mit den Cer-Erden gebildeten Komplexe wurden untersucht. Auf Grund der Ergebnisse konnte ein Analysenverfahren und eine Trennungsmethode für Thorium und Cer-Erden entwickelt werden.

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Une communication de ce travail a été faite à Graz, lors de la commémoration du centenaire de la naissance deF. Emich.     

Planar defects in β-alumina

Sodium β-alumina crystals were elaborated by melting of a mixture of Na₂CO₃ and Al₂O₃ or by PbO flux evaporation and were studied by transmission electron microscopy. They exhibit regular planar defects lying in the {11.0} prismatic planes. These defects are described as antiphase boundaries for the cationic sublattice with fault vectors $\text{1}\text{2}\text{〈10.0〉}$ (such faults do not affect the anionic sublattice). As a consequence it would be interesting to study precisely the structure of the sodium β cationic lattice in the vicinity of the melting point.     

Trace crossings in cyclic voltammetry and electrochemic electrochemical inducement of chemical reactions: Aromatic nucleophilic substitution

Crossing of anodic and cathodic traces is frequently observed on cyclic voltammograms featuring the electrochemical induction of a chemical reaction in the case where the product standard potential is positive to the reactant reduction potential. The theory of this phenomenon has been established in the contaxt of aromatic nucleophilic substitution. The reaction of potassium diethyl phosphite on 4-chlorobenzonitrile in liquid ammonia was investigated as an example illustrating this type of phenomenon and its interpretation. The simulation of the experimental voltammograms demonstrates the proposed mechanistic and kinetic model and allows the rate constants of the various steps to be determined. Much higher rate constants can thus been attained than by the standard application of electrochemical techniques (the gain may reach five or six orders of magnitude). A procedure is derived from these observations and then a rationalization for inducing chemical reactions with a very low electricity consumption as opposed to that which occurs when the electrode potential is settled at the level of the reactant wave.     

Exploiting C3-symmetry in the dynamic coordination of a chiral trisoxazoline to copper(II): improved enantioselectivity, and catalyst stability in asymmetric lewis acid catalysis

Chiral C3-symmetric trisoxazolines are highly efficient stereodirecting ligands in enantioselective Cu(II) Lewis acid catalysis which is based on the concept of a stereoelectronic hemilability of the divalent copper; in direct comparison with the analogous bisoxazoline systems they are more efficient in the enantioselective alpha-amination as well as the enantioselective Mannich reaction of prochiral beta-ketoesters.     

Sorption of binary liquid mixtures on polymer networks Part I. Determination of surface excess isotherms and free energy functions

Two groups of polymer networks (polymer resins) are investigated by selective liquid sorption fromn-propanol-water mixtures. Group 1 consists of gel polymerized polar (hydrophilic) ion exchangers which swell in the binary liquid mixture. Group 2 consists of non-polar, non-swelling, macroporous resins. The free energy isotherms accompanying the sorption processes are calculated from the excess isotherms and the bulk activities. The adsorption excess free energies reveal the differences in polarity of the polymer network.     

Tüpfelnachweis von Magnesium

Zusammenfassung Diazotiertes p-Nitroanilin gibt mit Ammoniumhydroxid einen gelben Niederschlag, der sich in alkalischem Medium rot färbt. Dieses Reagens kann in alkalischem Milieu zum Tüpfelnachweis von Magnesium angewendet werden. Auch Nickel gibt die Reaktion, aber nur in geringerem Maß. Die mit Alkali fällbaren Metalle müssen vorher entfernt werden. Alkaliund Erdalkalimetalle stören den Nachweis nicht. Der Nachweis der Struktur des Reagens wird eingehend beschrieben.

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Spot test detection of magnesium

Summary Diazotizedp-nitroaniline yields a yellow precipitate with ammonium hydroxide and this product turns red in alkaline medium. This reagent in an alkaline milieu may be employed for the spot test detection of magnesium. Nickel likewise gives this reaction, but only to a slight extent. The metals that can be thrown down with alkali must be removed beforehand. Alkali and alkaline earth metals do not interfere with the test. The question as to the structure of the reagent was been studied in detail.

     

A schematic overview of the historical evolution of Analytical Chemistry

The historical evolution of Analytical Chemistry is briefly discussed as related to the progress of Chemistry within the 16–19th centuries under the leadership of Paracelsus, Boyle, Lavoisier and Dalton. A clear distinction is made between chemical analysis (up to the end of the 19th c.) and today’s Analytical Chemistry, paying close attention to a number of aspects and consequences related to the chemical revolution which took place at the overlap of the 18–19th c. which resulted in the quantification of Chemistry, causing increasing development and improvement of the chemical metrology which was an essential factor for Chemistry to acquire a scientific dimension and to become more specialised during the 19th century. A panoramic view of the whole development is presented by resorting to the inclusion of a number of synoptical tables outlining the stepwise progress of Chemistry, chemical analysis and Analytical Chemistry within the five last centuries taking into consideration the main protagonists involved as well as the experimental means, techniques and methodologies used and/or developed. Received: 20 February 1996 / Accepted: 21 May 1996