Phase behavior of the quasiternary system N-methylmorpholine-N-oxide,water, and cellulose

The crystallization and melting behavior of the system N-methylmorpholine-N-oxide (MMNO)–H₂O–cellulose has been studied by differential scanning calorimetry, optical and electron microscopy, and x-ray scattering. The phase diagram of the MMNO–H₂O solvent system is reported up to a water content of 28% w/w. MMNO forms two crystalline hydrates, namely a monohydrate (13,3% w/w H₂O) and a hydrate comprising five molecules of crystal water per two MMNO molecules (28% w/w H₂O), which melts at 78°C and 39°C, respectively. The melting points of the various diluent crystals are strongly depressed in the presence of cellulose. For example, the solvent liquidus curve in the quasibinary system MMNO.1H₂O–cellulose can be described very well using the simple Flory–Huggins expression with an interaction parameter χ = ?3. Finally, the MMNO-rich part of the melting point/composition diagram of the quasiternary MMNO–H₂O–cellulose system is constructed and discussed.     

Phase equilibria in the aluminium-rich side of the Al–Zr system

The Al-rich phase equilibria in the Al–Zr binary system were investigated experimentally. The phase diagram for compositions up to 40 at.% Zr was determined experimentally by differential thermal analysis and metallography. Three stable intermetallic compounds exist in this region of the diagram: Al₃Zr₂, Al₂Zr, and Al₃Zr. The peritectic melting of Al₃Zr₂ and the congruent melting of Al₂Zr were confirmed. Al₃Zr, the most Al-rich intermetallic compound, melts peritectically, which contradicts information available in the literature. In addition, the reaction between Al₃Zr and the (Al) solid solution seems to be of eutectic nature, in contradiction with previous results found in the literature. Based on these new experimental evidence, a revised phase diagram is drawn.     

Phase Diagram of the NaNO<Subscript>2</Subscript>—KNO<Subscript>3</Subscript> System in the 0 to 1 Molar Fraction Range of Concentrations of KNO<Subscript>3</Subscript>

The temperature dependence of the phase composition of KNO₃—NaNO₂ mixtures in the 0 to 1 molar fraction range of concentrations of KNO₃ is investigated. A phase diagram of the KNO₃—NaNO₂ binary system in the range of concentrations from 0 to 1 molar fractions of KNO₃ is drawn on the basis of DTA results. The composition of the eutectic mixture and its melting temperature is determined experimentally.     

Mass spectrometric studies of the vapour phase in the (Pu + O) system

Vapour pressure measurements at high temperatures have been performed on plutonium oxide samples using a Knudsen cell coupled with a mass spectrometer. Different experimental conditions were applied for the derivation of the solid–gas phase relations for three composition in the Pu–O phase diagram: the (Pu₂O₃–PuO_2?x) two-phase domain, the congruent vapourisation composition and near stoichiometric PuO_2.00. The partial pressures of the gaseous species PuO₂, PuO, and Pu were assessed from ionisation efficiency curves recorded at constant temperature. The vapour pressure results for different phase fields were discussed together with all the available literature data.     

Thermodynamic properties of citric acid and the system citric acid-water

The binary system citric acid-water has been investigated with static vapour pressure measurements, adiabatic calorimetry, solution calorimetry, solubility measurements and powder X-ray measurements. The data are correlated by thermodynamics and a large part of the phase diagram is given. Molar heat capacities of citric acid are given from 90 to 330 K and for citric acid monohydrate from 120 to 300 K. The enthalpy of compound formation Δ_comH (298.15 K)=(?11.8±1) kJ mole^?1.     

Phase behaviour of tri-n-butylmethylammonium chloride hydrates in the presence of carbon dioxide

The phase behaviour of the system water?Ctri-n-butylmethylammonium chloride (TBMAC)?CCO₂ was investigated by pressure-controlled differential scanning calorimetry in the range 0?C10?mol% TBMAC in water and at CO₂ pressures ranging from 0 to 1.5?MPa. In the absence of CO₂, an incongruent melting hydrate, which estimated composition corresponds to TBMAC·30H₂O, crystallizes at temperatures below ?13.6?°C and forms with ice a peritectic phase at approximately 3.9?mol% TBMAC. In the presence of CO₂ at pressures as low as 0.5?MPa, curves evidenced the presence of an additional phase exhibiting congruent melting at temperatures that are strongly pressure dependent and significantly higher than those of hydrates obtained without CO₂. This new phase, whose enthalpy of dissociation and CO₂ content increase slightly with CO₂ pressure, was identified as a mixed semi-clathrate hydrate of TBMAC and CO₂ of general formula: (TBMAC?+?xCO₂)·30H₂O.     

Sm<Subscript>2</Subscript>S<Subscript>3</Subscript>-Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> phase diagram

The Sm₂S₃-Sm₂O₃ phase diagram was studied by physicochemical methods of analysis from 800 K up to melting. Two oxysulfides are formed in the system: Sm₁₀S₁₄O with tetragonal crystal structure (space group I41/acd; unit cell parameters: a = 1.4860 nm, c = 1.9740 nm; microhardness: H = 4700 MPa; solid decomposition temperature: 1500 K) and Sm₂O₂S with hexagonal structure (space group P-3m1; a = 0.3893 nm, c = 0.6717 nm; H = 4500 MPa; congruent melting temperature: 2370 K). Within the extent of the Sm₂O₂S-based solid solution (61–70 mol % Sm₂O₃) at 1070 K, a singular point appears at the compound composition on property-composition curves. The eutectic coordinates: 23 mol % Sm₂O₃ and 1850 K; 80 mol % Sm₂O₃ and 2290 K.     

Tude par ACD du domaine hors d'equilibre du systemexLiCl-(1−x)H2O (0<x<0.18)

The non-equilibrium region of the phase diagramxLiCl-(1?x)H₂O (0<x< 0.18) has been studied by means of a Mettler TA 2000 B heat flow differential scanning calorimeter. The metastable lines of the diagram have been established and the different phases obtained explained. A region has been found where the glass formed cannot recrystallize, the eutectic line being below the temperature of the transition glass.     

Thermal and conductometric studies of NdBr3 and NdBr3-LiBr binary system

The heat capacity of solid NdBr₃ was measured by Differential Scanning Calorimetry in the temperature range from 300 K up to the melting temperature. The heat capacity of liquid NdBr₃ was also determined. These results were least-squares fitted to a temperature polynome. The melting enthalpy of NdBr₃ was measured separately. DSC was used also to study phase equilibrium in the NdBr₃-LiBr system. The results obtained provided a basis for constructing the phase diagram of the system under investigation. It represents a typical example of simple eutectic system. The eutectic composition, x(NdBr₃)=0.278, was obtained from the Tamman construction. This eutectic mixture melts at 678 K. The electrical conductivity of NdBr₃-LiBr liquid mixtures and of pure components was measured down to temperatures below solidification. Reflectance spectra of the pure components and their solid mixtures (after homogenisation in the liquid state) with different composition were recorded in order to confirm the reliability of the constructed phase diagram. This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of mineral solubilities in the ternary systems NaCl−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O and MgCl<Subscript>2</Subscript>−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O at 373 K

In this work, the solubilities of the salt minerals and the densities of solution in two ternary systems sodium chloride–zinc chloride–water and magnesium chloride–zinc chloride–water were measured at 373 K using an isothermal solution saturation method. Based on the determined equilibrium solubility data and the corresponding equilibrium solid phase, the phase diagrams and density diagrams of the two systems were plotted. The results show that the two ternary systems are complex and the eutectic points, the univariant solubility curves and the solid crystalline phase regions are shown and discussed. The phase diagram of the ternary system NaCl?ZnCl₂?H₂O at 373 K is constituted of two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to NaCl, ZnCl₂ and 2NaCl · ZnCl₂. And the phase diagram of the ternary system MgCl₂?ZnCl₂?H₂O at 373 K includes two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to MgCl₂ · 6H₂O, MgCl₂ · ZnCl₂ · 5H₂O and ZnCl₂. The experimental results were simply discussed.     

The dissolution of microcrystalline cellulose in sodium hydroxide-urea aqueous solutions

It has been reported that cellulose is better dissolved in NaOH-water when a certain amount of urea is added. In order to understand the mechanisms of this dissolution and the interactions between the components, the binary phase diagram of urea/water, the ternary urea/NaOH/water phase diagram and the influence of the addition of microcrystalline cellulose in urea/NaOH/water solutions were studied by DSC. Urea/water solutions have a simple eutectic behaviour with a eutectic compound formed by pure urea and ice (one urea per eight water moles), melting at −12.5 °C. In the urea/NaOH/water solutions, urea and NaOH do not interact, each forming their own eutectic mixtures, (NaOH + 5H₂O, 4H₂O) and (urea, 8H₂O), as found in their binary mixtures. When the amount of water is too low to form the two eutectic mixtures, NaOH is attracting water at the expense of urea. In the presence of microcrystalline cellulose, the interactions between cellulose and NaOH/water are exactly the same as without urea, and urea is not interacting with cellulose. A tentative explanation of the role of urea is to bind water, making cellulose-NaOH links more stable. Member of the European Polysaccharide Network of Excellence (EPNOE),     

Diagramme De Phases Du Systeme Binaire CsNO3—LiNO3. Activité des constituants du liquide

Phase diagram of the binary system CsNO₃–LiNO₃ has been drawn by using simultaneously direct and differential thermal analysis between 323 and 723 K. This system is characterized by a congruent intermediate equimolar compound with melting point at 463 K, two eutectic reactions at 447 and 433 K; the eutectic points are respectively at 0,47 and 0,63 mol fraction of LiNO₃; a plateau due to the phase transition of CsNO₃ at 428 K and an other one at 333 K due to the formation of CsLi(NO₃)₂. The miscibility in solid state seems to be nil or negligible. These results associated with some other thermodynamic data have been used to calculate the activities of the constituents along the liquidus curve and the activities of the liquid constituents at 723 K. The binary liquid (Cs–Li)NO₃ exhibits a negative deviation from the ideal behaviour.This revised version was published online in November 2005 with corrections to the Cover Date.     

Phase behavior of dodecane–tridecane mixtures confined in SBA-15

Phase behavior of dodecane–tridecane (n-C₁₂H₂₆–C₁₃H₂₈, C₁₂–C₁₃) mixtures in bulk and confined in SBA-15 have been investigated using differential scanning calorimetry. Bulk C₁₂–C₁₃ system has a complicated behavior due to special rotator phase. It has been found that phase diagram of C₁₂–C₁₃/SBA-15 (3.8 nm) system is a straight line, C₁₂–C₁₃/SBA-15 (7.8 nm) a curve, and C₁₂–C₁₃/SBA-15 (8.9, and 17.2 nm) a loop line. The growth of the phase diagram shows size effect on phase behavior of C₁₂–C₁₃ mixtures. Moreover, in the range of 3.8–17.2 nm melting temperatures of pure C₁₂ and mixtures at mole fractions x _C13 = 0.1–0.5 have linear relation with inverse pore diameter, while C₁₃ and mixtures at x _C13 = 0.6–0.9 present curved lines. The confined mixtures show a similar melting behavior with pure C₁₂, C₁₃.     

Reinvestigation of phase equilibria in TbCl<Subscript>3</Subscript>–LiCl binary system

The phase equilibria in the terbium(III) chloride–lithium chloride pseudobinary system were established by means of differential scanning calorimetry. It was established that the pure terbium(III) chloride undergoes solid–solid phase transition at 790 K and melts at 859 K. The TbCl₃–LiCl pseudobinary system is characterized by the existence of two compounds. First one, namely Li₃TbCl₆, forms at 553 K and melts incongruently at 727 K. Second compound, LiTbCl₄, decomposes in the solid state at 609 K. The composition of Li₃TbCl₆–TbCl₃ eutectic corresponding to terbium(III) chloride mole fraction x = 0.521 (T = 665 K) was found from Tammann plot, which predict, through application of the lever rule, the variation of the enthalpy associated with eutectic melting as a function of composition. The obtained results have been compared with the literature data concerning for the TbCl₃–LiCl pseudobinary system. The phase diagram of the TbCl₃–LiCl pseudobinary system was also optimized by CALPHAD method.     

Phase Diagram for the RbBr–CuBr System

The phase diagram for the RbBr–CuBr system has been determined. In the system two intermediate compounds are formed: RbCu₂Br₃, melting congruently at 537 K and Rb₃CuBr₄, melting incongruently at 544 K. The coordinates of the two eutectic points are: 501 K, 54 mole% CuBr and 522 K, 74 mole% CuBr. This revised version was published online in July 2006 with corrections to the Cover Date.     

The phase diagrams and Pitzer model representations for the system KCl + MgCl2 + H2O at 50 and 75°C

The solubilities in the KCl-MgCl₂-H₂O system were determined at 50 and 75°C and the phase diagrams and the diagram of refractive index vs composition were plotted. Two invariant point, three univariant curves, and three crystallization zones, corresponding to potassium chloride, hexahydrate (MgCl₂ · 6H₂O) and double salt (KCl · MgCl₂ · 6H₂O) showed up in the phase diagrams of the ternary system, The mixing parameters ??_{K, Ca} and ??_{K, Ca, Cl} and equilibrium constant K _sp were evaluated in KCl-MgCl₂-H₂O system by least-squares optimization procedure, in which the single-salt Pitzer parameters of KCl and MgCl₂ ??⁽⁰⁾, ??⁽¹⁾, ??⁽²⁾, and C ^? were directly calculated from the literature. The results obtained were in good agreement with the experimental data.     

Synthesis and crystal structure of the lithium perrhenate monohydrate LiReO4·H2O

A new monohydrate of lithium perrhenate LiReO₄·H₂O was prepared by dehydration of LiReO₄·1.5H₂O at room temperature. The single crystals of LiReO₄·H₂O were obtained by crystallisation from the isoamyl acetate solution of LiReO₄·1.5H₂O. The structure of monohydrate (a=5.6674(4), b=10.771(1), c=7.4738(7) Å, β=102.422(7)°, R₁=0.0414, space group P2₁/a, Z=4) is built up from LiO₃(H₂O)₂ trigonal bipyramids and ReO₄ tetrahedra sharing common edges and corners inside the layers. The layers are connected together by hydrogen bonds. The relationships between the structures of sesquihydrate, monohydrate and anhydrous LiReO₄ are discussed.     

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.     

An investigation of the polythermal diagram of the H2ONa2HPO4Na2SO4 system

The polythermal diagram of the ternary system H₂ONa₂HPO₄Na₂SO₄ has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow.     

(Solid + liquid) isothermal evaporation phase equilibria in the aqueous ternary system (Li2SO4 + MgSO4 + H2O) at T = 308.15 K

The solubility and the density in the aqueous ternary system (Li₂SO₄ + MgSO₄ + H₂O) at T = 308.15 K were determined by the isothermal evaporation. Our experimental results permitted the construction of the phase diagram and the plot of density against composition. It was found that there is one eutectic point for (Li₂SO₄ · H₂O + MgSO₄ · 7H₂O), two univariant curves, and two crystallization regions corresponding to lithium sulphate monohydrate (Li₂SO₄ · H₂O) and epsomite (MgSO₄ · 7H₂O). The system belongs to a simple co-saturated type, and neither double salts nor solid solution was found. Based on the Pitzer ion-interaction model and its extended HW models of aqueous electrolyte solution, the solubility of the ternary system at T = 308.15 K has been calculated. The predicted solubility agrees well with the experimental values.