Diagramme de phase du systéme Hg-Cu-S: Étude du triangle HgS-Cu2S-S

The phase diagrams of the quasi-binary HgS-Cu₂S system and of the HgS-CuS and “HgS₂”-“CuS₂” sections were determined using differential thermal analysis, high temperature X-ray diffraction and metallography. A ternary homogeneous phase range (cubic with the digenite structure) is formed from the binary homogeneous phase range of the Cu-S system. In the ternary system it extends along the HgS-Cu₂S system, with a limiting composition M of Hg_0.18Cu_0.42S_0.39. This solid solution is only stable at high temperatures and is not quenchable. It has a eutectoid point in the HgS-Cu₂S system at 415°C for the composition M. Over most of the HgS-Cu₂S-S system there are two immiscible liquids; the monotectic invariant equilibrium L₁⇌ L₂ + HgS + M is at 635°C with L₁ ≡; Hg_0.31Cu_0.22S_0.47; L₂ has a composition around the sulphur apex.     

Congruent melting of binary compounds with non-negligible vapour pressure

The sulfaguanidine—water (SG-H₂O) system is a binary system with non-negligible vapour pressure which presents a monohydrate. The phase diagram of this system is drawn from DTA experimental results, using the temperature-specific volume-molar fraction (T-v-x) model which was described in part I of this work. The melting of the monohydrate (SG, H₂O) is found to be congruent. Isochoric sections are drawn; they make it possible to determine the limits of the two eutectic invariant planes. The composition and specific volume of the vapour phase at the eutectic equilibrium of theSG-SG, H₂O subsystem are given. The triple line solid-liquid-vapour of the one-component phase diagram of the monohydrate is drawn. The experimental results are consistent with the congruent melting of the monohydrate. These results also show that the solid, liquid and vapour phase at the triple line have not the same composition.     

Representation T-V-x des systemes binaires a tension de vapeur non negligeable

The effect of the variableV/m on the appearance of DTA endotherms has been used to obtain quantitative data on theT-V-x representation of the NdAs-As system. The peritectic reaction is NdAs₂ (solid)+vapour ? NdAs (solid)+liquid at 1185 K. At this temperature, the four phases set up a quadrangle in theV/m-x plane. The sides of this quadrangle have been defined by experiment: the vapour phase is composed of 87 mol% As and itsV/m value is 12.2 mm³ mg^?1. The peritectic liquid is composed of 87 mol% As. The eutectic equilibrium at 1080 K appears to be NdAs (solid)+As (solid)+vapour ← liquid It sets up a triangle, inside which the liquid phase is placed. The vapour phase is composed of 100 mol% As, and itsV/m value is 10 mm³ mg^?1. The eutectic liquid is composed of 90 mol% As. Three polythermal sections of the NdAs-As binary system are described for a constant volume.     

Solid–liquid equilibria, thermochemical and microstructural studies of binary organic monotectic and eutectic alloy

The phase diagram of 1,4-dibromobenzene (DBB) with pyrogallol (PG) shows the formation of a monotectic and a eutectic alloys at 0.12 and 0.99?mol fractions of DBB, respectively. The phase equilibrium shows the large miscibility gap region with the upper consolute temperature 159.0?°C at 0.55?mol fraction of DBB. Growth kinetics of pure compounds and their monotectic and eutectic at different undercooling (??T) obey Hillig?CTurnbull??s equation: v?=?u (??T) ⁿ . Thermodynamic parameters such as enthalpy of mixing, entropy of fusion, interfacial energy, roughness parameters and excess thermodynamic functions were computed based on enthalpy of fusion values obtained from DSC studies. The Cahn wetting condition is applicable for monotectic alloy. The optical microphotographs of binary alloys show lamellar and dendritic features.     

A simple, universal theory and method for computer plotting of stable equilibrium phase diagrams of a multisystem—SFM method

A new easy method has been presented to calculate the variable intervals corresponding to the stable univariant curves and to discriminate the stabilities of invariant points. This method and the one reported previously constitute a simple and universal theory for the computer-plotting of the equilibrium phase diagrams of a multisystem—sign function matrix (SFM) discrimination method. Its main steps are: determining the stable univariant scheme according to the derivative (or difference) of A_IG _m ; grouping the univariant curves by comparisons of the mutual relations among them; determining the existing intervals of the variables for the stable curves by comparisons of coordinate values of the curves about the invariant point; determining the stabilities of invariant points by comparisons of relations between the common curves and the invariant points. This method is suitable for any kind of phase diagram of closed or open systems in a phase diagram “space” with either 2 or more than 2 dimensions.     

Liquid–liquid equilibria for the ternary system water+n-dodecane+2-(2-n-hexyloxyethoxy)ethanol

Experiments of the fish-shaped phase diagram for the ternary system water+n-dodecane+2-(2-n-hexyloxyethoxy)ethanol (abbreviated by C₆E₂ hereafter) under atmospheric pressure were performed at constant water/n-dodecane weight ratio (1/1) to locate the critical end points. The upper and lower critical consolute temperatures for the system of interest are 307.80 K and 282.30 K, respectively. Compositions of two- and three-phase liquid–liquid equilibrium for the ternary system water+n-dodecane+C₆E₂ at 293.15 K and 303.15 K under atmospheric pressure are presented in this paper.     

Computer model of a T-x-y diagram for a ternary system with monotectic monovariant equilibrium

Computer design with the kinematic specification of nonlinear and ruled surfaces is proposed for a T-x-y diagram of a ternary system with monotectic monovariant equilibrium. The three-dimensional model makes it possible not only to design any iso-or polythermal section but also to solve mass-balance problems associated with computer design of heterogeneous materials.     

Strongly Basic Anion Exchange Resin Based on a Cross-Linked Polyacrylate for Simultaneous C.I. Acid Green 16, Zn(II), Cu(II), Ni(II) and Phenol Removal

The adsorption ability of Lewatit S5528 (S5528) resin for C.I. Acid Green 16 (AG16), heavy metals (Zn(II), Cu(II) and Ni(II)) and phenol removal from single-component aqueous solutions is presented in this study to assess its suitability for wastewater treatment. Kinetic and equilibrium studies were carried out in order to determine adsorption capacities, taking into account phase contact time, adsorbates’ initial concentration, and auxiliary presence (NaCl, Na₂SO₄, anionic (SDS) and non-ionic (Triton X100) surfactants). The pseudo-second-order kinetic model described experimental data better than pseudo-first-order or intraparticle diffusion models. The adsorption of AG16 (538 mg/g), phenol (14.5 mg/g) and Cu(II) (5.8 mg/g) followed the Langmuir isotherm equation, while the uptake of Zn(II) (0.179 mg^1−1/nL^1/n/g) and Ni(II) (0.048 mg^1−1/nL^1/n/g) was better described by the Freundlich model. The auxiliary’s presence significantly reduced AG16 removal efficiency, whereas in the case of heavy metals the changes were negligible. The column studies proved the good adsorption ability of Lewatit S5528 towards AG16 and Zn(II). The desorption was the most effective for AG16 (>90% of dye was eluted using 1 mol/L HCl + 50% v/v MeOH and 1 mol/L NaCl + 50% v/v MeOH solutions).     

Models of p-T diagrams for a ternary system with invariant equilibrium of three solid phases, liquid, and vapor

A version of a model of the p-T diagram for a ternary system in which three solid phases, liquid, and vapor are in invariant five-phase equilibrium is developed. The phase equilibria and phase transitions in the isobaric T-x-y diagram are analyzed, and isothermal and polythermal sections are presented.     

Metastable phase equilibria for the ternary aqueous system of lithium sulfate and potassium sulfate at <Emphasis Type="Italic">T</Emphasis> = 308.15 K: Experimental data and prediction using Pitzer model

The metastable solubilities and the physicochemical properties including density, refractive index, pH and conductivity in the ternary system (Li₂SO₄ + K₂SO₄ + H₂O) at T = 308.15 K were determined experimentally using the isothermal evaporation method, and the metastable phase diagram and the physicochemical properties versus composition diagram were plotted. In the metastable phase diagram, there are two invariant points, three univariant curves and three crystallization regions corresponding to lithium sulfate monohydrate (Li₂SO₄ · H₂O), double salt (K₂SO₄ · Li₂SO₄) and arcanite (K₂SO₄). It was found that the double salt of K₂SO₄·Li₂SO₄ belongs to the incongruent double salt, and the hydrate of Li₂SO₄ · H₂O belongs to hydrate type I. On the basis of Pitzer model of the electrolyte solution theory, the mixing-ion parameter of θ_Li,K, \({\Psi _{Li,K,S{O_4}}}\) and the metastable equilibrium constants of the solid phases K₂SO₄, Li₂SO₄ · K2SO4 and Li₂-SO₄ · H₂O at 308.15 K were obtained for the first time. The calculated metastable solubility data for this ternary system at 308.15 K agree well with the experimental values, and this result indicates that the mixing-ion parameters and the metastable equilibrium constants obtained in this work are reliable.     

The phase diagram of fullerene C60 at high temperatures and pressures

Experimental and literature data were used to calculate the Gibbs energies of polymerized C₆₀ phases and construct the equilibrium T-p phase diagram of fullerene C₆₀ at temperatures from 0 to 1000 K and pressures from 0 to 8 GPa. The diagram contains stability regions of the orthorhombic, tetragonal, and rhombohedral polymerized C₆₀ phases and primitive cubic (PC) and face-centered cubic (FCC) nonpolymerized C₆₀ phases. The orthorhombic phase (linear polymer) is an equilibrium phase at 298 K and 1 bar and in the adjacent region. The equilibrium line observed experimentally (FCC C₆₀—orthorhombic phase) is well described by the phase diagram. The optimum temperatures and pressures of the synthesis of polymerized phases are determined by kinetic rather than thermodynamic parameters.     

Solvent effect on u.-vis and EPR spectra and on the relative stability of mononuelear and binuclear complexes of Cu(II) acetate with pyridine derivatives

Electronic (298.2 K) and ESR (298 and 77 K) spectra have been measured for Cu(O₂CMe)₂ solutions in pyridine derivative (L)-solvent (S) binary mixtures (L = pyridine, 3-chloropyridine, 2-chloropyridine; S = n-hexane, n-heptane, cyclohexane, benzene, chlorobenzene, carbon tetrachloride, propylene carbonate). The results are interpreted in terms of the equilibrium between mononuclear and binuclear complexes: 2Cu(O₂CMe)₂ ⇌ Cu₂(O₂CMe)₄L₂ + 2L.The calculated quotient ofthe activity coefficients ofthe two forms strongly depends on the L-ligand activity in the solutions (preferential salvation by L) and on the solvent properties. Chlorobenzene, benzene and carbon tetrachloride compete with pyridine for solvation. The ln of the activity coefficient quotient varies linearly with the solubility parameter of the solvent, δ, while no satisfactory correlation with the polarity parameter (ε − 1)/(2ε + 1) has been found. The solvent effect on electronic spectra (λ_max, g3_max) is stronger for mononuclear, more flexible, complexes than for binuclear ones.     

Solid–liquid equilibria in the NaCl–SrCl2–H2O system at 288.15 K

The phase equilibria in the ternary system NaCl–SrCl₂–H₂O at 288.15 K were studied with the isothermal equilibrium solution method. The phase diagram and refractive index diagram were plotted for this system at 288.15 K. The phase diagram contains one invariant solubility point, two univariant solubility curves, and two crystallization fields of NaCl and SrCl₂ · 6H₂O. The refractive indices of the equilibrium solution change regularly with w(NaCl) increase. The calculated refractive index data are in good agreement with the experimental data. Combining the experimental solubility data of the ternary system, the Pitzer binary parameters for NaCl at 288.15 K and SrCl₂ at 298.15 K, the Pitzer mixing parameters θ_{Na, Sr}, Ψ_{Na, Sr, Cl} and the solubility equilibrium constants Ksp of solid phases existing in the ternary system at 288.15 K were fitted using the Pitzer and Harvie-Weare (HW) models. The mean activity coefficients of sodium chloride and strontium chloride, and the solubilities for the ternary system at 288.15 K were presented. A comparison between the calculated and measured solubilities shows that the predicted data agree well with the experimental results.     

Rigid ferrocenophane and its metal complexes with transition and alkaline-earth metal ions

The rigid [6]ferrocenophane, L¹, was synthesised by condensation of 1,1′-ferrocene dicarbaldehyde with trans-1,2-diaminocyclohexane in high dilution at r.t. followed by reduction. When other experimental conditions were employed, the [6,6,6]ferrocenephane (L²) was also obtained. Both compounds were characterised by single crystal X-ray crystallography. The protonation of L¹ and its metal complexation were evaluated by the effect on the electron-transfer process of the ferrocene (fc) unit of L¹ using cyclic voltammetry (CV) and square wave voltammetry (SWV) in anhydrous CH₃CN solution and in 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte. The electrochemical process of L¹ between −300 and 900 mV is complicated by amine oxidation. On the other hand, an anodic shift from the fc/fc⁺ wave of L¹ of 249, 225, 81 and 61 mV was observed by formation of Zn²⁺, Ni²⁺, Pd²⁺ and Cu²⁺ complexes, respectively. Whereas Mg²⁺ and Ca²⁺ only have with L¹ weak interactions and they promote the acid-base equilibrium of L¹. This reveals that L¹ is an interesting molecular redox sensor for detection of Zn²⁺ and Ni²⁺, although the kinetics of the Zn²⁺ complex formation is much faster than that of the Ni²⁺ one. The X-ray crystal structure of [PdL¹Cl₂] was determined and showed a square–planar environment with Pd(II) and Fe(II) centres separated by 3.781(1) Å. The experimental anodic shifts were elucidated by DFT calculations on the [ML¹Cl₂] series and they are related to the nature of the HOMO of these complexes and a four-electron, two-orbital interaction.     

The Template Synthesis of the New Macrocyclic and Acyclic Metal Ion Complexes Derived from Putrescine

The template reaction of 2,6-diacetylpyridine with biogenic diamine–putrescine in the presence of cadmium(II), mercury(II) or lead(II) ions produces the complexes of 22-membered macrocyclic ligand L¹ with an N₆ set of donor atoms as a result of [2 + 2] Schiff base cyclocondensation. The lead(II) complex containing Schiff base acyclic ligand L² terminated by one carbonyl and one amine group as product of the partial [2 + 2] condensation has been also isolated and might be regarded as possible intermediate in the formation of the macrocyclic L¹ complex. Analogous reaction involving the uranyl nitrate generates the complex containing the same Schiff base acyclic ligand L² as a final product of template reaction. The complexes were characterized by spectral data (IR, ¹H NMR, FAB-MS), thermogravimetric and elemental analyses. A notable feature of the FAB mass spectrum of the uranyl complex is the appearance of the clusters of the form [(UO₂) _n O]⁺(n= 1–7) along with the peak corresponding to molecular ion.     

Conformational fluxionality in a palladium(II) complex of flexible click chelator 4-phenyl-1-(2-picolyl)-1,2,3-triazole: A dynamic NMR and DFT study

An experimental and theoretical DFT study was carried out on the solution behavior in [D₇]DMF for bis-chelate complex [Pd(L)₂](BF₄)₂·2CH₃CN (L = 4-phenyl-1-(2-picolyl)-1,2,3-triazole). In structure of [Pd(L)₂]²⁺, the central square-planar palladium(II) cation is trans-chelated by two L substrates, each through the pyridine and the triazole N2 nitrogen atoms, forming two six-membered metallacycles. These can adopt boat-like conformations anti-trans-[Pd(L)₂]²⁺ and syn-trans-[Pd(L)₂]²⁺ in which the picolyl methylene carbons are anti or syn, respectively, relative to the palladium coordination plane. In solution, the boat-to-boat inversion at both metallacycles takes place. The conformers are in a dynamic equilibrium, which was monitored by variable-temperature (VT) ¹H NMR spectroscopy in the temperature range of 223-353 K. The equilibrium lies on the side of the anti-trans-[Pd(L)₂]²⁺ conformer and the corresponding reaction enthalpy and entropy is estimated to be 0.6 ± 0.5 kcal mol⁻¹ and 0.8 ± 1 cal mol⁻¹ K⁻¹, respectively. From the full-line-shape analysis of resonances in the VT ¹H NMR spectra, the activation enthalpy and activation entropy was determined to be 13.0 ± 0.4 kcal mol⁻¹ and 2.7 ± 1.6 cal mol⁻¹ K⁻¹, respectively. The activation entropy close to zero suggests a nondissociative mechanism for the isomerisation. DFT investigation revealed that the isomerisation proceeds through a one step mechanism with a barrier of 11.40 kcal mol⁻¹. The structures of the syn and anti conformers as well as that of the transition state were characterized. Energy decomposition analysis was carried out in order to explore the origins of the stability difference between the syn and anti isomers.     

Vanadyl complexes with ethylenedithiodiacetic acid

The complex formation between vanadyl ions and ethylenedithiodiacetic acid (H₂ L) has been studied at 25 °C in 0.5M-NaClO₄ as inert medium, by measuring the hydrogen ion concentration with a glass electrode. In acidic medium and in the investigated concentration ranges (2.07mM≤C _M≤7.50mM, C _L up to 12.5mM) the emf data can be explained assuming the equilibrium: $$VO^{2 + } + L^{2 - } \rightleftharpoons VOL log\beta _{101} = 2.68 \pm 0.03$$      

Systems of fluorides and bromides of lithium, sodium, and cesium with mono- and invariant monotectic equilibria

Phase diagram with mono- and invariant equilibrium were studied by differential thermal analysis by the example of a system of fluorides and bromides of group 1 s-block elements (lithium, sodium, and cesium). Bordering elements were studied, the quaternary reciprocal system Li,Na,Cs∥F,Br was partitioned into simplexes, and a tree of phases was constructed. The liquidi of the systems LiF-NaBr-CsBr and LiF-NaF-CsBr were constructed, the T-x diagrams of polythermal sections passing through phase separation regions were built, and phases being in equilibrium under specific thermodynamic conditions were described.