Mise en evidence electrochimique et preparation d'une nouvelle phase dans le systeme WSiO

High temperature e.m.f. studies of tungsten rich mixtures in the system WSiO show evidence of the existence of a new phase, stable up to 1000°C. Attempts to synthesize such a phase resulted in the obtention of a f.c.c. structure with a lattice parameter of 4.05 Å, which may well be the phase responsible for the e.m.f. results. Closeness of size between W and O²⁻ radius suggests that oxygen could replace tungsten to form tetrahedral groups surrounding silicon.     

Caractérisation de la solution solide In1−xLi3xVO4 (0 < x ≤ 0,4) dans le système InVO4Li3VO4 et examen des systèmes CrVO4Li3VO4 et InVO4CrVO4

In the InVO₄Li₃VO₄ system, a continuous solid solution In_1−xLi⁽⁶⁾_a□⁽⁶⁾_bLi⁽⁴⁾_c□⁽⁶⁾_dVO₄ exists between InVO₄ and In_0.6Li_1.2VO₄, with a + b = x, c + d = 1, and a + c = 3x. The solid solution is of two types: in the first, 0 < x ≤ 0.33, a = 0, interstitial Li⁺ ions are in the vacant tetrahedral sites of InVO₄; in the second, 0.33 < x ≤ 0.4, c = 1, Li⁺ ions are also in the octahedral sites vacated by In³⁺. The ionic conductivity measured for some compositions is weak, 10⁻⁷ (Ω cm)⁻¹ at 493 K. Solid solution has not been found between CrVO₄ and Li₃VO₄, although CrVO₄ is isostructural with InVO₄. Mutual solid solution between CrVO₄ and InVO₄ is extremely limited. Yellow and weakly hygroscopic monocrystals have been synthetized for R₂Li₃(VO₄)₃ compositions (R = In,Cr,Fe); their chemical formula can be symbolized by LiVO₃: R³⁺. The R³⁺ percentage was too low to be detected by analysis of electronic densities based on X-ray diffraction intensities.     

Etude vibrationnelle de la phase II des hydrogénodisulfates de triammonium, (NH4)3H(SO4)2 et (ND4)3D(SO4)2

The i.r. and Raman spectra of room temperature phase (phase II) of (NH₄)₃H(SO₄)₂ and (ND₄)₃D(SO₄)₂ as polycrystalline samples and single crystals have been investigated between 4000 and 30 cm⁻¹. An assignment of internal and external modes is given in terms of group frequencies and symmetry types. This crystal contains non-centrosymmetric dimers (SO₄HSO₄)³⁻ where sulphate ions are associated by strong asymmetric OH … O hydrogen bonds; they are characterized by two strong Raman bands at 1078 and 966 cm⁻¹, and a νOH frequency at about 1250 cm⁻¹. The acidic proton is statistically disordered around the crystallographic symmetry centre while all of the NH⁺₄ ions show an important dynamical orientational disorder.     

Phase equilibria in the ternary system: MgONa2OP2O5: Partial system: Mg3(PO4)2Mg4Na(PO4)3Na4P2O7Mg2P2O7

The partial system Mg₃(PO₄)₂Mg₄Na(PO₄)₃Na₄P₂O₇Mg₂P₂O₇ in the ternary system MgONa₂OP₂O₅ was investigated using thermal and X-ray diffraction analyses and microscopy, and its phase diagram has been determined. In this range of composition, two binary phosphates occur: Mg₄Na(PO₄)₃ and Mg₆Na₈(P₂O₇)₅. The former melts incongruently (at 1155°C) and the latter does congruently (at 808°C). In the partial system of interest, the two sections Mg₄Na(PO₄)₃Mg₂P₂O₇ and Mg₄Na(PO₄)₃Mg₆Na₈(P₂O₇)₅ are studied, and their phase diagrams are established. The partial system is divided into three partial ternary systems in which two ternary eutectics and one ternary peritectic occur.     

Decomposition thermique et etude vibrationnelle de NiNa4(P3O9)2·6H2O

We have studied the dehydration and the calcination under atmospheric pressure of cyclotriphosphate tetrahydrate of nickel and sodium, NiNa₄(P₃O₉)₂·6H₂O, between 25 and 700°C by thermal analyses (TG, DTA) infrared spectrometry and X-ray diffraction. This study allows us the identification and the crystallographic characterization of a new phase, NiNa₄(PO₃)6, obtained between 350 and 450°C. NiNa₄(PO₃)₆ crystallizes in the triclinic system, P_–1, with the following unit cell parameters a=6.157(3) Å, b=6.820(6) Å, c=10.918(6) Å, =80.21(5)°, =97.80(9)°, =113.49(3)°, V=409.8 ų, Z=1, M(19)=25 and F(19)=48 (0.0095; 42). The calcination of NiNa₄(PO₃)₆, between 500 and 600°C, leads to a mixture of long-chain polyphosphates NiNa(PO₃)₃ and NaPO₃. The kinetic characteristics of the dehydration of NiNa₄(P₃O₉)₂·6H₂O were determined and discussed. The vibrational spectrum of the title compound, NiNa₄(P₃O₉)2·6H₂O, was interpreted in the domain of the stretching vibrations of the P₃O₉ rings, on the basis of its crystalline structure and in the light of the calculation of the normal IR frequencies of the P₃O₉ ring with D_3h symmetry.

This revised version was published online in November 2005 with corrections to the Cover Date.     

Fe(III) extraction equilibria in the system: Fe2(SO4)3(NH4)2SO4 vs primene JM-T sulfate-toluene

Distribution coefficients for Fe(III) have been determined in the liquid-liquid extraction system Primene JM-T-toluene vs aqueous ammonium sulfate (and sodium sulfate) as a function of sulfate, acid, Fe(III) and amine sulfate concentrations. A study of loading equilibria as a function of time for this system indicates that equilibrium was largely achieved in 1 hr although some changes, possibly in the nature of the extracted species, occur up to approx. 20 hr. Extraction isotherms show a slope of 1 at low loadings, indicating the same degree of self association in both organic and aqueous phases, while the amine sulfate/iron ratio appears to approach 2.5 ± 0.25 at saturation loading. Results obtained by varying the sulfate concentration matrix indicates the formation of an aqueous complex of ferric ammonium sulfate which depresses iron distribution to the organic phase. The degree of aggregation of the amine sulfate, derived from iron distribution coefficient dependence on amine sulfate concentration data, is shown to be approx. 10.     

Li2SO4-MgSO4及LiNO3-Mg(NO3)2熔盐体系的研究

用目测变温法和差热分析法研究了Li₂SO₄-MgSO₄、LiNO₃-Mg(NO₃)₂熔盐体系。在前一体系中有固液异组成化合物Li₂SO₄·2MgSO₄生成,它在832°熔化分解。化合物与Li₂SO₄间形成低共熔点,温度为647℃,组成含MgSO₄23.6Wt%。Li₂SO₄多晶转变点575℃,在加入MgSO₄后形成类低共熔点,温度552℃,组成含MgSO₄4.2%。LiNO₃-Mg(NO₃)₂为一简单低共熔体系,共晶点含Mg(NO₃)₂47.3%,温度200℃。     

纳米晶MgSO4·5Mg(OH)2·3H2O合成与表征

纳米材料由于具有表面、体积和量子尺寸效应的特殊性而受到广泛重视[1～3]. 微米级硫氧镁晶须作为塑料添加增强和阻燃剂已有报道[4～7]. 纳米晶MgSO4*5Mg(OH)2*3H2O不仅对塑料起补强作用, 而且其粒度小, 使塑料变得更致密, 强度、韧性与防水性能大大提高. 目前纳米材料的合成方法多种多样[8～10], 本文采用水热法制得纳米硫氧镁晶粒, 产物纯度高、分散性好且粒度易控制.     

The system YPO4Ca3(PO4)2Ca2P2O7

The ternary system YPO₄Ca₃(PO₄)₂Ca₂P₂O₇ has been investigated by differential thermal analysis, powder X-ray diffraction, and microscopy in reflected light. Its phase diagram and isothermal section at room temperature have been determined. The system contains only one double phosphate which is formed at the 1:1 molar ratio YPO₄:Ca₃(PO₄)₂, i.e., Ca₃Y(PO₄)₃.     

Reactions de michael sur des amides α,β insatures activees par le systeme CsF/Si(OCH3)4

Michael additions of compounds having acidic hydrogen (ketones, nitro derivatives, ethyl cyanacetate and ethyl malonate) on α,β unsaturated amides are carried out in the presence of the system CsF/Si(OCH₃)₄. The reaction takes place in heterogeneous medium without solvent. Final products are obtained (in good yields) without hydrolysis. Normal 1–4 addition products are obtained with tertiary α,β ethylenic amides while primary α,β ethylenic amides lead to glutarimides or dihydropyridinones derived from the first-formed 1–4 addition products.     

Spectres de vibration des complexes PtII(CNCH3)4(PF6)2, PtI2(CNCH3)6(PF6)2 et PdIPtI(CNCH3)6(PF6)2; étude des liaisons métal-métal,PtPt et PdPt

Infrared and Raman spectra (4000-20 cm⁻¹) of Pt^II(CNCH₃)₄(PF₆)₂, Pt^I₂(CNCH₃)₆(PF₆)₂ and Pd^IPt^I(CNCH₃)₆(PF₆)₂ complexes, in the solid state and in solution have been investigated; assignments for most of the vibrational modes are proposed. Metal-ligand and metal-metal bonding forces in the dinuclear cations Pd₂L₆²⁺, Pt₂L₆²⁺ and PdPtL₆²⁺ (L= CNCH₃) are compared and the fluxional properties of these cations in solution are discussed. Also, from Raman intensities measurements, the bond polarizability derivative and the bond order of the Pt^IPt^I bond are estimated.     

Influence d'une reduction cathodique prealable sur le comportement electrochimique du titane et des alliages TiAu et TiPt en solution H2SO4 10N

The study of the behaviour of Titanium and its alloys containing “cathodic” elements shown that the electrolytically formed hydride film is unable to modify their corrosion resistance in a 10N H₂SO₄ solution.This fact disagrees with the generally accepted hypothesis that the corrosion inhibition of titanium and its alloys is exherted by a hydride film in a 10N H₂SO₄ solution; it stresses the rôle played by noble elements which enhance the trend toward passivation of titanium in acid media; it finally clarifies the influence of side reactions, which may sometimes occur at the counterelectrode and modify the behaviour of the working electrode.     

Etudes sur le système ternaire SnInS. Analyses thermique differentielle et radiocristallographique du pseudobinaire SnSIn2S3. Croissance en phase vapeur et caractérisation de composés a valences mixtes de l'étain

The SnInS ternary system has been studied using two different methods of crystal synthesis. By direct combination of the two sulfides (SnS and In₂S₃) various melts have been prepared, and the ternary phase diagram determined by differential thermal analysis. Three ternary phase are found: In₂Sn₂S₅, In₂SnS₄, and In₁₂Sn₅S₂₃. Chemical vapor transport (CVT), using iodine as transport gas, leads to different crystal morphologies (needles, sheets, and polyhedra) according the ratio of iodine to reagent. Several methods have been used to characterize the crystals, specifically X-ray diffraction, electronic microscopy, and Mössbauer spectrometry. The latter shows that both Sn(II) and Sn(IV) are present in all the crystals prepared by CVT.     

Mg(OH)2· 2MgSO4· 2H2O晶体的水热生长过程

对 MgSO4- NaOH- H2O四元交互体系在 160 ℃水热条件下 ,相同物料配比 ,不同反应时间的晶体生长过程进行了研究 ,得到 5Mg(OH)2@ MgSO4@ 2H2O(简称 MOS)晶须和 Mg(OH)2@ 2MgSO4@ 2H2O棒状晶体两种硫氧镁化合物 .通过化学分析、 X- ray粉末衍射、 FT- IR光谱和 SEM对反应产物进行了表征 .前者是该体系水热条件下介稳产物 ,而新的硫氧镁化合物 Mg(OH)2@ 2MgSO4@ 2H2O是该体系的稳定相.     

Synthesis and crystal structures of yttrium sulfates Y(OH)(SO4), Y(SO4)F,YNi(OH)3(SO4)-II and Y2Cu(OH)3(SO4)2F·H2O

Y(OH)(SO₄), Y(SO₄)F, YNi(OH)₃(SO₄)-II and Y₂Cu(OH)₃(SO₄)₂F·H₂O are obtained from hydrothermal reactions at 380°C under a pressure of 210 MPa. Their crystal structures were refined from single-crystal X-ray diffraction data. The four compounds have the following space groups and unit cells: Y(OH)(SO₄), P2₁/n, a=7.9498(6), b=10.9530(9), c=8.1447(6) Å, β=93.764(1)°; Y(SO₄)F, Pnma, a=8.3128(9), b=6.9255(7), c=6.3905(7) Å; YNi(OH)₃(SO₄)-II, Pnma, a=6.9695(8), b=7.2615(8), c=10.292(1) Å; Y₂Cu(OH)₃(SO₄)₂F·H₂O, P2₁/n, a=11.6889(7), b=6.8660(4), c=12.5280(8) Å, β=97.092(1)°. The coordination environments of the yttrium atoms in the four structures vary from highly irregular 6+2, 6+3, 7+1 coordination polyhedra to relatively regular dodecahedra.     

Reactivite des β-Cetophosphonates dans la Reaction de Gewald: Synthese de 2-Amino-5-phosphono et de 2-Amino-4-(phosphonomethyl)thiophenes

The reaction of β-ketophosphonates 1 with active methylenenitriles 2 and sulfur in basic conditions led to new 2-amino-5-phos-phonothiophenes 3 and 2-amino-4-(phosphonomethyl)thiophenes 3′. The structure of all obtained products was confirmed by NMR (¹H, ³¹P, ¹³C), IR spectroscopy and in some cases by mass spectrometry.     

La basicité de l'atome d'azote dans quelques iminophosphanes (PNR) et aminophosphanes (PNR2). Etude en spectrographie infrarouge

Using i.r. spectroscopy the lone pair basicity of a nitrogen atom on two iminophosphanes (PN-) and six aminophosphanes (PN-) has been estimated. This was done measuring the decreasing Δν_XH between ν_XH absorption of one XH vibrator (HO- or HN) bonded to a nitrogen atom by hydrogen bonding (PN … HX; PN … HX) and the free absorption ν_XH of the same vibrator. For identical substituents on the phosphorus atom, the basicity of nitrogen in iminophosphanes is more important than in aminophosphanes.