Thermodynamic stability of solid phases in the system Cu–O–Al2O3 by means of the EMF and DSC-TGA techniques

Journal of Solid State Electrochemistry - Thermodynamic properties of solid phases in the Cu–O–Al2O3 system were measured by means of the EMF method with oxygen concentration galvanic...     

Kinetics of decomposition of the liquid phase of the ternary system LiOH-H2O2-H2O in the presence of the solid phase of Li2O2 · H2O

The kinetics of decomposition of hydrogen peroxide in the liquid phase of the ternary system LiOH-H₂O₂-H₂O was studied in the presence the solid phase of Li₂O₂·H₂O and without it. The main kinetic parameters of the processes studied were determined.     

Comparative analysis of the solubility in the systems CuBr2-NR4Br-H2O at 25°C

The solubility in the CuBr₂-NR₄Br-H₂O (R = Me, Et, n-Bu) ternary systems at 25°C was determined by the isothermal saturation method. Comparative analysis of the phase equilibria diagrams was done. The results obtained were interpreted in terms of the competition of two processes, association of tetraalkylammonium salts and copper(II) complex formation in water-salt systems.     

Determination of apparent binding constants by NSAIDs-βcyclodextrin complexes: HPLC, phase solubility diagrams and theoretical studies

The complexation of NSAIDs (nonsteroidal antiinflamatory drugs): Ibuprofen (Ibu), Ketoprofen (Ket) and Naproxen (Nap) with βcyclodextrin (βCD) has been studied from structural and thermodynamic points of view. The binding constants of NSAIDs-βCD complexes were determined by reversed phase liquid chromatography (RP-HPLC) and phase solubility diagrams using a UV–Vis spectrophotometric method varying the working temperature. The complexation efficiency (CE) values were determined: CE_Ibu ≈ CE_Nap < CE_Ket. Experimental measurements indicated that K_Nap-βCD > K_Ibu-βCD > K_Ket-βCD, and that the apparent stability constants decrease as the polarity of the solvent decreases. The changes of ?Hº (enthalpy), ?Sº (entropy) and ?Gº (Gibbs free energy) for the inclusion process were obtained by means of the van’t Hoff equation. In addition, semiempirical quantum mechanics calculations using the PM6 method were performed. The energetically favorable structures of the inclusion complexes were identified: the most favorable orientation was found to be the head down for all the complexes. Enthalpy for complexation processes was found to be favorable (?Hº < 0), entropy was found unfavorable (?Sº < 0) and Gibbs free energy was favorable (?Gº < 0). The theoretical results are in agreement with the experimental parameters associated with the encapsulation process.     

A thermodynamic model for calculating nitrogen solubility,gas phase composition and density of the N2–H2O–NaCl system

A thermodynamic model is presented to calculate N₂ solubility in pure water (273–590 K and 1–600 bar) and aqueous NaCl solutions (273–400 K, 1–600 bar and 0–6 mol kg⁻¹) with or close to experimental accuracy. This model is based on a semi-empirical equation used to calculate gas phase composition of the H₂O–N₂ system and a specific particle interaction theory for liquid phase. With the parameters evaluated from N₂–H₂O–NaCl system and using a simple approach, the model is extended to predict the N₂ solubility in seawater accurately. Liquid phase density of N₂–H₂O–NaCl system at phase equilibrium and the homogenization pressure of fluid inclusions containing N₂–H₂O–NaCl can be calculated from this model. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.     

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.     

Phase equilibria of the Na,K,Mg,Ca//SO4,Cl-H2O system at 50°C in the crystallization range of glaserite 3K2SO4·Na2SO4

Phase equilibria of the Na,K,Mg,Na,K,Mg,Ca//SO₄,Cl-H₂O system are studied at 50°C via translation in the crystallization range of glaserite (3K₂SO₄ · Na₂SO₄). It is found that glaserite as the equilibrium phase of the investigated system at 50°C participates in the formation of 21 invariant points, 21 monovariant curves, and 34 divariant fields. A fragment of the phase equilibria diagram of the investigated system is constructed in the crystallization range of glaserite.     

Investigation of the Crystallization Kinetics of Zn(Leu)SO _4·0.5H_2O in Mixing Solvent by

IntroductionZincisanessentialtraceelementtoorganism .α Aminoacidisthebasicunitofproteinrelatedwithlife .L α Leu(leucine)isoneofeightsortsofaminoacidsindispensabletolifewhichareabsorbedfromfoodbecauseitcannotbesyn thesizedinhumanbody .Thecomplexesofzincsaltswithα aminoacidasadditivehaveawideapplicationinmedicine ,foodstuffandcosmetics.1 3Thesyntheticmethodsofthecom plexesofzincsaltswithα aminoacidhavebeenreviewed .4 ,5ThesolubilityofZnSO4 Leu H2 Osystemat 2 98 15Khasbeeninvestigatedbys…     

Investigation of phase equilibria in the Er2O3–Na2O–P2O5 system: the partial system ErPO4–NaPO3–Er(PO3)3

The partial system ErPO₄–NaPO₃–Er(PO₃)₃ of the Er₂O₃–Na₂O–P₂O₅ oxide system has been investigated by thermoanalytical methods and X-ray powder diffraction. On the basis of the obtained results the phase diagram of the partial system is proposed. The system is bounded by three subsystems: (i) ErPO₄–Er(PO₃)₃, (ii) Er(PO₃)₃–NaPO₃ and (iii) ErPO₄–NaPO₃. Their phase diagrams are proposed. In the Er(PO₃)₃–NaPO₃ subsystem an intermediate compound NaEr(PO₃)₄ occurs; it melts incongruently at 655 °C. It was found that ErPO₄ and NaEr(PO₃)₄ form a section which is a real system only in the subsolidus region (below 646 °C). Two ternary invariant points (one ternary peritectic and one ternary eutectic) occur in the investigated partial system ErPO₄–NaPO₃–Er(PO₃)₃.     

Temperature dependence of the substrate selectivity in the hydroxylation of alkylbenzenes in the H2O2−H2SO4 system

The substrate selectivity in the hydroxylation of methylbenzenes in the H₂O₂−H₂SO₄ (70 wt.%) system was studied at 15–55 °C. The activation entropy correlates with the basicity of the arenes, while the substrate selectivity and activation enthalpy correspond both with the basicity and ionization potentials of ArH. We concluded that the structure of the reaction transition state is intermediate between a charge transfer complex and σ-complex. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 39–43, January–February, 1999.     

Phase equilibria in the solid state and colour properties of the CuO–In2O3 system

Phase equilibria up to solidus line in CuO?CIn₂O₃ system have been investigated using XRD and DTA/TG methods. According to the results, only one compound of the formula Cu₂In₂O₅ formed in the system studied. Its thermal stability was determined in the air and argon proving that the compound did not melt but underwent decomposition. The decomposition of Cu₂In₂O₅ in the air atmosphere began at 1080?°C, while in argon at 835?°C. Additional studies were undertaken to determine the hitherto unknown colour properties of samples representing the CuO?CIn₂O₃ system in the equilibrium state.     

Prediction of phase equilibrium for the aqueous systems Rb+, Cs+/Cl−, SO 4 – -H2O and K+, Cs+/Cl−, SO 4 2− -H2O at 25°C

The Pitzer ion-interaction extended by Harvic and Weare was applied to predict the solubility isotherms of reciprocal quaternary systems in which mixed crystals are formed. On the basis of data concerning the binary and ternary subsystems, the four components systems Rb⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O, and K⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O were investigated at 25°C.The results of calculation can be used to model salt crystallization during the concentration of brines.     

Formation of SO−2, SO2·O− and SO2·SO− by electron attachment to van der waals SO2 clusters

SO⁻₂, SO₂·O⁻ and SO₂·SO⁻ are produced by electron attachment to SO₂ clusters under single collision conditions. SO⁻₂, which is not produced at all in low-pressure ion sources, is more abundant than SO₂·O⁻ and SO₂ ·SO⁻. Measured relative attachment cross sections for these ions show significant differences when compared to O⁻ and SO⁻ produced by attachment to SO₂, i.e. the first resonance is very efficiently quenched in favor of SO⁻₂ production. This is in contrast to previous findings in O₂, CO₂ and N₂O.     

Solubilities in the Na,Ca‖SO4,F-H2O system at 0°C

Solubilities at invariant points of the Na,Ca‖SO₄,F-H₂O system at 0°C was studied, and a phase diagram of this system at 0°C was constructed.     

A thermodynamic study of Cu—Tl—S system by EMF method with Cu4RbCl3I2 solid electrolyte

The Cu—Tl—S system was studied by the EMF method with Cu₄RbCl₃I₂ solid Cu⁺-conducting electrolyte within the temperature range from 300 to 390 K. The earlier plotted solid-phase equilibrium diagram of this system was confirmed, the partial copper molar functions $ (\Delta \bar G,\Delta \bar H,\Delta \bar S) $ ) in alloys and standard thermodynamic formation functions and standard entropies of CuTlS₂, CuTlS, Cu₃TlS₂, and Cu₉TlS₅ ternary compounds were calculated. The derived results demonstrated an opportunity of thermodynamic studies of copper-containing ternary systems of this modification by EMF method even if they contain a less noble component than copper.