Enthalpie de dissolution a 298 K des fluorures de potassium et de cesium dans l'acide fluorhydrique et le fluorure d'hydrogene

A calorimetric cell designed for studies of reaction in anhydrous hydrogen fluoride has been constructed. Enthalpies of solution of KF and CsF in aqueous solution of HF (from 0 to 100 % HF) have been measured.     

Les systemes binaires fluorure de lithium-fluorure d'hydrogene et fluorure de sodium-fluorure d'hydrogene

Liquid-solid equilibria in the binary systems LiF-HF and NaF-HF were studied up to 400° by thermal analysis. On account of the properties of hydrogen fluoride, a special apparatus was built. Several compounds were observed: LiF · HF-NaF · HF; NaF · 2HF; NaF · 3HF and NaF · 4HF. The characteristic temperatures of the systems, and especially the peritectic decompositions of LiF · HF and NaF · HF were determined, and the bibliographic data were corrected.     

Mise au point d'un appareillage de preparation et de manipulation de melanges anhydres HFNH3MF (M alcalin) — tension de vapeur totale au-dessus de solutions HFNH3 riches en HF

An apparatus for preparing and handling HFNH₃MF mixtures (M alkali metal) has been designed and constructed. The vacuum line made of plastic materials (PVF₂, PTFCE, PTFE) allows the purification of anhydrous hydrogen fluoride, preparation and analysis of HFNH₃ or HFNH₃MF mixtures and their handling for further study or destruction.Total vapour pressures above HFNH₃ binary mixtures rich in HF have been measured and are described as a function of ammonia concentration and temperature (?10 to +20°C).     

Analyse systematique des elements traces dans l'eau de mer par activation neutronique

The trace elements in sea water, particularly the pollutant elements (Cu, Cd, As, Zn, Hg and Cr) are present in very low concentrations (in the order of 10^?9 g/ml). For the determination of the concentration of these elements the neutron activation analysis has been used successfully. The separation of the impurities has been studied using radioactive tracers by coprecipitation with carriers and on ion exchange resins. The preconcentration technics applied before the irradiation introduces too large “blank” values, which can be reduced by etching the containers with HF—EDTA. In order to have representative samples, the water must be quickly frozen after taking out from the sea. With these precautions, the method developed allows to analyse samples of 3 ml volumes. The results of sea water sample analyses from different areas are presented.     

Mise au point d'un calorimetre de reaction en milieu fluorhydrique - enthalpies de dissolution de kf dans les solutions aqueuses de HF

A calorimeter designed for studies of reactions in hydrofluoric acid has been constructed. Enthalpies of dissolution of KF in aqueous solutions of HF (from 1,05 N to 28,3 N) have been measured.     

Enthalpies de formation de l'acide fluorhydrique dan les solutions ternaires HF/HX/H2O (HX  HCl ou H2SO4) II—enthalpies de dilution de l'acide chlorhydrique dans les solutions ternaires HF/HCl/H2O a concentration constante EN HF

The enthalpies of formation of HF in the ternary solutions HF/HCl/H₂O have been determined by measurement of the heats of dilution of HCl in the ternary solutions at a constant concentration of HF.     

Enthalpies de formation de l'acide fluorhydrique dans les solutions ternaires HF/HX/H2O (HX = HCl, H2SO4) IV — Enthalpies de formation de l'acide fluorhydrique dans les solutions ternaires H2SO4/HF/H2O

The enthalpies of mixing of aqueous hydrofluoric and sulfuric acids and the enthalpies of dilution of the ternary solutions HF/H₂SO₄/H₂O at fixed concentration of HF or H₂SO₄ have been measured. The standard enthalpies of formation of HF in these solutions have been derived.     

Enthalpies de formation de l'acide flourhydrique dans les solutions ternaires HF/HX/H2O (HX  HCl ou H2SO4) III—enthalpies de formation de l'acide fluorhydrique dans les solutions ternaires HF/HCl/H2O

The enthalpies of mixing of aqueous hydrofluoric and hydrochloric acids and the enthalpies of dilution of the ternary solutions HF/HCl/H₂O at fixed concentration of HCl have been measured. The standard enthalpies of formation of HF in these solutions have been derived.     

Nouvelle synthèse des composés polysubstitués d'esters de l'acide pyrrolecarboxylique-3 par réarrangement d'époxy-1,2 pyrrolidines

In presence of acides (HF/pyridine) substitutes 3-ethoxycarbonyl-6-oxal-azabicyclo[3.1.0[hexanes 1 afforded subtituted 3-ethoxycarbonyl-pyrroles 3 in stereospecific manner. Spiro substrates gave polycyclic product under the conditions used.     

Enthalpies de formation de l'acide fluorhydrique dans les solutions ternaires HF/HX/H2O (HX  HCl ou H2SO4) I—technique experimentale,methodes de calcul

The apparatus used for the determination of the enthalpies of formation of HF in the ternary solutions HF/HX/H₂O (HX  HCl or H₂SO₄) and the methods of calculation are described.     

Fluoration anodique dans le chlorure de methylene (polymethyl- et vinylbenzenes)

The anodic oxidation of polymethyl and of ethylenic derivatives of benzene in CH₂Cl₂/Et₄NF, 3HF or Et₃N, 3HF has been studied. The fluoro compounds are obtained in good yields. With the ethylenic compounds cis-addition products predominate.     

Synthese de polymeres fonctionnels modelisant des sites recepteurs de proteines. Etude de leur interaction avec des anti-coagulants de la famille des phenylindanedione

Modelling of biological receptors of proteins by the synthesis of polymers with side-groups resembling proteins is one way of studying the interaction between drug and protein. For this purpose, various methacrylic monomers with amine para(2-hydroxyethyl) aniline as its acetanilide derivatives onto methacrylic chloride or onto 2-chlorocarbonyloxy-ethyl methacrylate. The corresponding polymers are used as protein models, particularly those having a free amine function. A comparative study by differential spectroscopy of drug-albumin and polymer-drug model interaction for the anticoagulant as phenylindanedione) has made it possible to obtain information on the nature of the albumin receptors.     

Evolution des rejets saumatres des stations de dessalement de l'eau de mer au cours de leur evaporation isotherme

Desalination of sea-water was investigated. Effluent of desalination plant was evaporated in isotherm and isobar condition. Density, electric conductivity measurements and chemical analysis were carried out during the process. The results characterising the crystalline phase provide the fields and limits of the precipitation and separation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enthalpies de formation des hydroxynitrates de zinc

The standard enthalpies of reaction of four zinc hydroxide nitrates Zn(OH)(NO₃)-H₂O, Zn₃(OH)₄(NO₃)₂, Zn₅(OH)₈(NO₃)₂·2H₂O et Zn₅(OH)₈(NO₃)₂ and zinc oxide with a solution of nitric acid (2N) were measured in a solution calorimeter. These results, combined with auxiliary thermochemical values from the literature, yielded values of ?429.34, ?442.41, ?897.41 and ?750.70 kcal mol^?1 respectively, for the molar enthalpies of formation of these zinc hydroxide nitrates.     

Methode calorimetrique de mesure des enthalpies de formation des alliages liquides a forte tension de vapeur

The heat effects corresponding to the dissolution of solid PbSe in liquid Pb-Se alloys starting from pure Pb were measured with a direct reaction calorimeter. The partial enthalpy of formation of PbSe in the melt and the integral enthalpy of formation of the Pb-PbSe system in the liquid state referred the liquid Pb and PbSe were deduced. Then, from a very simple change of reference state, and in the knowledge of the enthalpy of PbSe, the integral enthalpy of formation of Pb-Se liquid alloys with reference to pure liquid components could be derived. The results agreed very well with those obtained previously on the dissolution of Se in Pb. The method used can be applied whenever the component to be added to the bath has a high vapor pressure.

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Zusammenfassung Die bei der Überführung von festem PbSe in flüssige Pb-Se-Legierungen auftretenden Wärmeeffekte wurden mittels direkter Reaktionskalorimetrie bestimmt. Die auf flüssiges Pb und PbSe bezogene partielle Bildungsenthalpie des Pb-PbSe-Systems im flüssigen Zustand wurde ermittelt. Durch eine geringfügige Veränderung des Referenzzustandes konnte bei Kenntnis der Enthalpie von PbSe die integrale Bildungsenthalpie von flüssigen Pb-Se-Legierungen in Bezug auf die reinen Komponenten abgeleitet werden. Die Ergebnisse stimmen gut mit denen überein, die früher für die Auflösung von Se in Pb erhalten wurden. Die Methode ist anwendbar, wenn dem Bade zuzugebende Komponenten einen hohen Dampfdruck haben.

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Pb-Se Pb-Se, . Pb-Se Pb-PbSe Pb Pb-Se. PbSe, Pb-Se . , . , .

     

Analytische Redoxreaktionen und Redoxpotentiale des Wolframs und seiner Begleiter

Zusammenfassung Es wird gezeigt, daß Wolfram durch Redoxtitrationen besser als durch Gravimetrie bestimmbar ist. Der Vorteil besteht nicht nur in geringerem Aufwand, sondern auch in der Möglichkeit, aus einer einzigen Titration mehrere Bestandteile einer wolframhaltigen Probe zu bestimmen. Hierzu wurden die effektiven Redoxpotentiale von W, Mo, Fe, V, Ti, Sn, Cu, Cr in HCl, HCl + HF und HCl + H₃PO₄ gemessen. HF und/oder H₃PO₄ erlauben Probenvorbereitungen, bei denen keine Wolframsäure ausfällt. Der Einfluß dieser Hilfskomplexbildner auf den Ablauf der Redoxreaktionen wird angegeben und eine Deutung der Ligandeneinflüsse versucht. Die Titrationen können reduzierend oder bequemer oxidierend unter potentiometrischer oder amperometrischer Anzeige erfolgen. Nur für Schiedsanalysen ist die Gravimetrie noch überlegen.

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Analytical redox reactions and redox potentials of tungsten and its concomitants

Summary It is demonstrated that tungsten can be more effectively determined by redox titrimetry than by gravimetry. In addition to its inherent greater simplicity the volumetric approach offers to determine several components of the sample from consecutive redox titrations. To provide the necessary information the conditional redox potentials of W, Mo, Fe, V, Ti, Sn, Cu, Cr in HCl, HCl + HF and HCl + H₃PO₄ have been determined. Use of HF and/or H₃PO₄ allows sample preparations without any precipitation of tungstic acid. The influcence of these auxiliary complexing agents on the potentials and kinetics is discussed. The titrations can be performed reductimetrically or more conveniently oxidimetrically using potentiometric or amperometric indication. The use of strongly reducing agents restricts the tolerance interval to ±0.6%, so that the gravimetric determination of tungsten remains superior for high precision analyses.

     

Analyse des composes fluores corrosifs par chromatographie gazeuse : Controle du fluor libre

A purely chromatographie and sufficiently general method is described for the analysis of molecular fluorine in permanent inert gases or in other corrosive fluorine compounds (UF₆, HF). The method is also applied to the analysis of permanent inert gases (even in trace quantities) in the same fluorine compounds. In this method, one or several chemical “precolumns” are placed in series with a gas-liquid chromatography column. The “precolumn” system retains or destroys the corrosive compounds (UF₆, HF, F₂) and the chromatography column separates the components formed.     

Neusynthese des rinderinsulin-b-ketten-s-sulfonates

A novel synthesis of the bovine insulin B chain in the blocked form (7) applying N^im-Trt-, Cys-SEt-, N^G-H⊕- and Benzyl-protection in the residual positions is described starting from the partial fragments 1–4. By choice the deprotection is possible by HF, HBr/TFE with C₂H₅SH addition and also under special conditions by catalytic hydrogenolysis. HBr/TFE acidolysis and hydrogenolysis lead to the best resultates in respect to yield and homogeneity of the final product. Thus Bunte salts are received in good yield related to the protected B chain and with the same insulin forming potency as such of native provenience.