J. Carre

Synthèse du pentafluorotellurate IV de sodium NaTeF5 en milieu fluorure d'hydrogène anhydre. Préparation du tétrafluorure de tellure TeF4

Abstract A new synthesis of sodium pentafluorotellurate IV has been performed in liquid hydrogen fluoride. Tellurium tetrafluoride is prepared by thermal decomposition of NaTeF 5 under vacuum : NaTeF 5 → NaF + TeF 4

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie I. Etude du pentafluorotellurate IV de lithium LiTeF5

Abstract Lithium pentafluorotellurate (IV) LiTeF5 has been prepared by different methods: • slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride, • heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF5 is orthorhombic (a = 9,52 A b = 9,12 A c = 11, 60 A)

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie II: Etude des fluorotellurates d'ammonium NH4TeF5 et (NH4)2TeF6

Abstract New methods of synthesis: • reaction of aqueous or anhydrous HF with TeO 2 and NH 4 F or NH 4 HF 2 , with (NH 4 ) 2 TeCl 6 • reaction of TeF 4 with NH 4 F or NH 4 HF 2 • reaction of NH 4 HF 2 with TeO 2 have been investigated for NH 4 TeF 5 and a new compound (NH 4 ) 2 TeF 6 . The resulting compounds have been analysed and characterized.

Crystal structure of PbTeF6

Abstract PbTeF6 crystallizes with monoclinic symmetry (space group P2 1 c ) and the unit cell parameters a = 462.5(1) pm, b = 1281.2(2) pm, c = 851.9(1) pm, β = 102.36(1)°, Z = 4. Its crystal structure has been solved by a Rietveld analysis of its X-ray powder pattern and refined to the final agreement factors Rb = 0.059 and Rp = 0.073. The PbII and TeIV atoms are respectively seven- and five-fold coordinated and their lone pair E is stereochemically active. By sharing edges, the PbF7E polyhedra constitute infinite zig-zag chains parallel to Ox. These chains are connected to each other by sharing their free corners with the TeF5E polyhedra, one of the corners being non-bridging. Structural relationships with ReO3-type materials are described and analyzed.

Etude du comportement thermique des hexitols: Partie 2. Polymorphisme du dulcitol

Dulcitol, known in a single crystalline form (hereafter called I), in fact exhibits complex thermal behaviour. A second polymorph II appears when the glassy material is allowed to crystallize at room temperature. This form always coexists with I and cannot be well characterized. The mixture I + II transforms very slowly to pure I when annealed at room temperature for a week. When a melt of dulcitol is cooled very slowly vitrification does not occur and a new pure crystalline form III is obtained. Analysis of X-ray powder data leads to a possible monoclinic cell with a = 8.82 A, b = 11.41 A, c = 8.61 A, β = 110.55°, Dx = 1.49, Z = 4. These parameters are very close to those of I but the slightly smaller values for a and b could indicate a shrinking of some bonds in the molecular packing. Each of the two forms II (mixed with I) and pure III are thermodynamically unstable. The “normal” form I is always obtained by evaporation from methanol/water solutions.

Préparation, caractérisation et analyses du pentafluorotellurate(IV) de triéthylammonium, essais d'utilisation des pentafluorotellurates(IV) de triéthylammonium et de pyridinium comme agents fluorants

Abstract Triethylammonium pentafluorotellurate(IV) has been prepared by the reaction of (C 2 H 5 ) 3 N·3HF with TeO 2 in aqueous HF. The resulting compound has been analyzed and characterized using Raman spectrometry, chemical determinations and thermal analysis. Triethylammonium and pyridinium pentafluorotellurates(IV) do not act as organic fluorinating agents.

Mesure des densites des solutions binaires HF-pyridine exploitation des resultats obtenus

Abstract Densities of HF-pyridine solutions have been studied. The data show the existence of pyridine and py.2 HF (for the mole fraction x HF HF HF HF > 0,80).

Mesure des densites et des conductivites des solutions binaires HFNH3 dans le domaine pauvre en ammoniac (xNH3 < 0,15). Exploitation des resultats obtenus

Abstract The densities and conductivities of HFNH3 solutions have been studied in the low concentration region of ammonia (xNH3 6 %) and NH4HF2 species (for x

Mise au point d'un appareillage de preparation et de manipulation de melanges anhydres HFNH3MF (M alcalin) — tension de vapeur totale au-dessus de solutions HFNH3 riches en HF

Abstract An apparatus for preparing and handling HFNH 3 MF mixtures (M alkali metal) has been designed and constructed. The vacuum line made of plastic materials (PVF 2 , PTFCE, PTFE) allows the purification of anhydrous hydrogen fluoride, preparation and analysis of HFNH 3 or HFNH 3 MF mixtures and their handling for further study or destruction. Total vapour pressures above HFNH 3 binary mixtures rich in HF have been measured and are described as a function of ammonia concentration and temperature (−10 to +20°C).

Etude calorimetrique des enthalpies de dilution de NH3 dans le systeme binaire HF-NH3

Abstract Enthalpies of dilution of NH3 in the binary system HF-NH3 have been determined using a suitable home-made calorimeter. Compilation of the results gives the enthalpy of reaction of gaseous NH3 with a HF-NH3 solution, in the NH3 low concentration region (xNH3