A general method for synthesis of folic acid, its conjugates and analogues (author's transl)]

A general method for synthesis of folic acid, its conjugates and analogues . A new and general method for the synthesis of folic acid, folic acid conjugates and folic acid analogues is described. The key step, i.e. the condensation of N(2′)-acetyl-6-formyl-pterine (I: R¹ ? COCH₃) with aminoaryl derivatives II, is achieved by refluxing in absolute ethanol to afford the azomethines III. NaBH₄-reduction followed by basic hydrolysis gives pure V products in high yield, free from 7-isomers.     

Un analogue d'un théorème de Hardy pour la transformation de DunklAn analogue of Hardy's theorem for the Dunkl transform

In this Note we give a generalization of Hardy's theorem for the Dunkl transform $\text{F}{}_{\mathrm{D}}$ on $\text{R}{}^{\mathrm{d}}$. More precisely, for all a>0, b>0 and p,q∈[1,+∞], we determine the measurable functions f such that and , where $\text{L}{}_{\mathrm{k}}{}^{\mathrm{p}}\text{(}\text{R}{}^{\mathrm{d}}\text{)}$ are the L^p spaces associated with the Dunkl transform. To cite this article: L. Gallardo, K. Trimèche, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 849–854.     

A new potentiometric method for the estimation of vanadium

Summary A new potentiometric method is given for the accurate determination of small amounts of vanadium after reduction to the 4-valent state, involving back-titration of an added excess of EDTA by mercuric solution. The fact that 5-valent, but not 4-valent, vanadium has no influence on the course of the back-titration of excess EDTA with mercuric ions was used in the analysis of various binary, ternary and quaternary mixtures with requisite accuracy by two, three or four potentiometric titrations of identical mixtures at different pH-values. The method, slightly modified, may be applied to the analysis of cobalto-and nickelo-vanadium alloys.

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Zusammenfassung Zur genauen Bestimmung kleiner Mengen Vanadium nach, der Reduktion zur 4 wertigen Stufe wird ein potentiometrisches Verfahren beschrieben, bei dem ein zugesetzter überschu\ an ÄDTA mit Quecksilber(II)-Lösung zurücktitriert wird. Die Tatsache, da\ 5 wertiges (jedoch nicht 4wertiges) Vanadium die Rücktitration von ÄDTA mit Hg²⁺-Ionen nicht stört, wurde zur Analyse von binÄren, ternÄren und quaternÄren Gemischen ausgenutzt, wobei 2, 3 oder 4 potentiometrische Titrationen identischer Proben bei verschiedenen pH-Werten durchgeführt wurden. Kobalt- und Nickel-Vanadiumlegierungen können nach geringer Modifizierung des Verfahrens ebenfalls analysiert werden.

     

Oxidation with manganate solutions

Summary Manganate solutions prepared by the reduction of permanganate with formic acid in 1 M NaOH are fairly stable in a concentration of 0.015 M in presence of 1 M NaOH. They can be titrated successfuly with arsenite in the presence of telluric acid but not in its absence owing to the sluggishness of the reaction. Titration of arsenite with manganate yields always lower results deviating by 0.77% from the theoretical values in presence of telluric acid and 0.1–0.2 M NaOH. Much earlier end points with errors amounting to – 17 or – 38% are obtained in the absence of telluric acid.This work was started during 1957. Since that time the reactions of manganate with arsenite, tellurite, bivalent manganese and hydrogen peroxide were studied in our laboratory. While this work was prepared for publication den Boef et al. published their first investigation in the same line in 1959.     

Application of arsenite reduction to the potentiometric determination of gold and to the analysis of mixtures and alloys

The present work is an application of iodide to the reduction of gold(III), in an attempt to develop new method for gold(III) based on potentiometric back-titration of the excess of iodide with mercury(II). Although it was proved by calculation that the reduction of tetrachloroaurate to the metal should proceed quantitatively to completion, yet our experiments showed that the reduction under ordinary conditions, gave Au(I) in the form of a white precipitate of AuI. We succeeded to push the reduction with iodide to the metal by an excess of ethanol-ether catalyzed iodide at somewhat elevated temperature.With the experimental conditions established a reliable procedure have been developed involving a potentiometric finish which enabled accurate determination of gold(III), either alone or in some of its alloys.     

Rapid potentiometric methods for vanadium and for analysis of ferrovanadium and some vanadium steels

Rapid and reliable potentiometric methods are given for determination of vanadium based on titrating unreacted KBr or KI in H₂SO₄ acid medium with Hg(I) or Hg(II), using silver amalgam as the indicator electrode. The methods are successfully applied to the analysis of ferrovanadium, three varieties of vanadium steels and synthetic mixtures of about identical constitution. In all cases the potential breaks were sharp enough for the accurate determination of the end points.     

Fast grey as a new indicator in titrations with EDTA

An acqueous solution of the Solochromate Fast Grey RA dye has proved a suitable indicator for the direct determination of thorium, ferric iron, bismuth and zinc, or the analysis of binary mixtures, thorium-iron, zinc-calcium, zinc-magnesium or zinc-thorium, with EDTA. Thorium can be determined in present of U, Fe, Zn, Ba, Be, Mg, and comparatively large amounts of rare carths. Ferric iron and zinc can be estimated in presence of U, Mg, Ca, Ba and Be. Cations of the rare and the alkaline carths can do not interfere with the determination of bismuth.     

Study of thermal behaviour of some derivatives of triphenylamine,with a view to obtaining new stationary phases for gas chromatography

A study was carried out upon the thermal behaviour of eight derivatives of triphen-y l amine, i. e. trinitrotriphenylamine; triaminotriphenylamine; triaminotriphenylamine chlorhydrate, tetraphenylborate and picrate; and a trisazo derivative and its compound with Be(II) and U(VI). The aim of this study was to find compounds with satisfactory thermal stability for use as stationary phases in gas chromatography.

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Zusammenfassung Eine umfassende Untersuchung zum thermischen Verhalten von acht Triphenylaminderivaten, d. h. Trinitrotriphenylamin, Triaminotriphenylamin, Triaminotriphenylamin Chlorhydrat, Tetraphenylborat und Pikrat, sowie ein Trisazoderivat und seine Verbindungen mit Be(II) und U(VI) wurde durchgeführt. Der Zweck dieser Studie war Verbindungen befriedigender Thermostabilität zum Einsatz als stationäre Phasen in der Gaschromatographie zu finden.

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: , , -, , () U(VI). .

     

Temperature effects on the extraxtion of divalent cobalt,zinc, cadmium and mercury by salicylaldoxime in carbon tetrachloride

The effect of temperature on the extraction of Co²⁺, Zn²⁺, Cd¹⁺ and Hg²⁺ by salicylaldoxime diluted with carbon tetrachloride was investigated radiometrically. It is found that the extraction constants at 25°C increase linearly with l/r, where r is the effective coordination radius of the metal cation. The thermodynamic data calculated from the effect of temperature on the extraction showed that, 1) the extraction process is endothermic, 2) the dehydration of the metal cation in the extraction process is the predominating factor in determining the enthalpy variation and 3) the entropy variation is a contribution of the degree of order caused by the hydration of the proton and the highly ordered chelate structure of the extracted species.