Phase equilibria in the system YPO4−KMgPO4−Mg3(PO4)2

The phase equilibria in that part of the ternary system YPO₄?K₃PO₄?Mg₃(PO₄)₂ which contains the composition range YPO₄?KMgPO₄?Mg₃(PO₄)₂ were examined and determined by differential thermal analysis, X-ray powder diffraction and microscopic analysis in reflected light.     

Syntheses and crystal structures of NH4Ag2(AsS2)3 and (NH4)5Ag16(AsS4)7 with a discussion of (NH4)Sx polyhedra

Summary The atomic arrangements within the structures of NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; space group P2₁/n;R(F)=0.042] and (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; space group Cc;R(F)=0.073] were determined from single crystal X-ray data. In these two compounds the coordination spheres of the Ag atoms are quite different. In NH₄Ag₂(AsS₂)₃, the Ag atoms exhibit a [2+2]- and a [3+1]-coordination to S atoms up to 3.3 Å and with Ag atom neighbours at 2.93 Å and 3.05 Å respectively. In (NH₄)₅Ag₁₆(AsS₄)₇, the Ag atoms are — with one exception- [4] coordinated (Ag-S<3.3 Å) and the distances to further Ag atom neighbours are greater than 3.1 Å. NH₄Ag₂(AsS₂)₃ represents an ordered cyclo-thioarsenate(III) with three-membered As₃S₆ rings, (NH₄)₅Ag₁₆(AsS₄)₇ a neso-thioarsenate(V) with two split Ag atom positions. Both compounds were synthesized under moderate hydrothermal conditions.

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Synthesen und Kristallstrukturen von NH₄Ag₂(AsS₂)₃ und (NH₄)₅Ag₁₆(AsS₄)₇ mit einer Diskussion über (NH₄)S_x Polyeder

Zusammenfassung Die Atomanordnungen in den Strukturen von NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; Raumgruppe P2₁/n;R(F)=0.042] und (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; Raumgruppe Cc;R(F)=0.073] wurden anhand von röntgenographischen Einkristalldaten bestimmt. In diesen beiden Verbindungen sind die Koordinationsverhältnisse um die Ag-Atome sehr unterschiedlich. In NH₄Ag₂(AsS₂)₃ besitzen die Ag-Atome bis 3.3 Å eine [2+2]- und [3+1]-Koordination durch S-Atome mit weiteren Ag-Atomen bei 2.93 Å und 3.05 Å. In (NH₄)₅Ag₁₆(AsS₄)₇ sind die Ag-Atome mit einer Ausnahme [4]-koordiniert (Ag-S < 3.3 Å), und die Abstände zu weiteren Ag-Atomen sind größer als 3.1 Å. NH₄Ag₂(AsS₂)₃ stellt ein geordnetes Cyclothioarsenat(III) mit dreigliedrigen As₃S₆-Ringen dar, (NH₄)₅Ag₁₆(AsS₄)₇ ein Nesothioarsenat (V) mit zwei aufgespaltenen Ag-Positionen. Beide Verbindungen wurden unter mäßigen Hydrothermalbedingungen synthetisiert.

     

Phase equilibria up to the solidus line in the V2O5−Cr2(MoO4)3 system

Phase equilibria being established in the subsolidus area of the V₂O₅?Cr₂(MoO₄)₃ system at the whole component concentration range have been studied basing on DTA and X-ray phase powder diffraction. It has been established that the system is not a real two-component system in the subsolidus area. The fact has been proved by the presence of fields in that area, where three solid phases remain in mutual equilibrium.     

(Liquid + liquid) equilibria of ternary and quaternary systems with two hydrocarbons, an alcohol, and water at 303.15 K. Systems containing cyclohexane, benzene, ethanol, and water

Tie-line data for the water, ethanol, and cyclohexane [{w₁H₂O + w₂C₂H₅OH + (1−w₁−w₂)C₆H₁₂}] ternary system, where w is the mass fraction, was investigated at T=303.15 K. A quaternary system containing these three compounds and benzene {w₁C₂H₅OH + w₂C₆H₆ + w₃C₆H₁₂ + (1−w₁−w₂−w₃)H₂O} was also studied at the same temperature, while data on its other two partially miscible ternary systems were taken from the literature [the fourth {w₁C₂H₅OH + w₂C₆H₆ + (1−w₁−w₂)C₆H₁₂} is not partially miscible]. From our experimental results we conclude that this quaternary system presents a very small water tolerance and that phase separation could produce a considerable loss of C₂H₅OH drawn into the aqueous phase. On the other hand, the results also show that the aqueous phase generally contains a higher concentration of C₆H₆ than of C₆H₁₂. A comparison with other similar quaternary systems investigated in our laboratory was also made. The ternary experimental results were correlated with the UNIQUAC equation, and predicted with the UNIFAC group contribution method. As previously, the equilibrium data of the three ternary systems (including those taken from the literature) were used to determine interaction parameters for the UNIQUAC equation. These parameters were then averaged in order to predict equilibrium data of this quaternary system. The UNIFAC method was also used with the same purpose. The UNIQUAC equation appears to be more accurate than the UNIFAC method for this ternary system. However, this last model is slightly better for the quaternary system, as can be seen from the values of both residuals.     

Stabilization of the (C2H5)4NHSO4 High-Temperature Phase in New Silica-Based Nanocomposite Systems

In this study, the electrotransport, thermal and structural properties of composite solid electrolytes based on (C₂H₅)₄NHSO₄ plastic phase and silica (1 − x)Et₄NHSO₄₋xSiO₂, where x = 0.3–0.9) were investigated for the first time. The composites were prepared by mechanical mixing of silica (300 m²/g, R_pore = 70Å) and salt with subsequent heating at temperatures near the Et₄NHSO₄ melting point. Heterogeneous doping is shown to change markedly the thermodynamic and structural parameters of the salt. It is important that, with an increase in the proportion of silica in the composites, the high-temperature disordered I4₁/acd phase is stabilized at room temperature, as this determines the properties of the system. Et₄NHSO₄ amorphization was also observed in the nanocomposites, with an increase in the matrix contents. The enthalpies of the endoeffects of salt melting and phase transitions (160 °C) changed more significantly than the Et₄NHSO₄ contents in the composites and completely disappeared at x = 0.9. The dependence of proton conductivity on the mole fraction reached a maximum at x = 0.8, which was three or four orders of magnitude higher than the value for pure Et₄NHSO₄, depending on the composition and the temperature. The maximum conductivity values were close to those for complete pore filling. The conductivity of the 0.2Et₄NHSO₄-0.8SiO₂ composite reached 7 ∗ 10⁻³ S/cm at 220 °C and 10⁻⁴ S/cm at 110 °C.     

(Liquid + liquid), (solid + liquid), and (solid + liquid + liquid) equilibria of systems containing cyclic ether (tetrahydrofuran or 1,3-dioxolane), water,and a biological buffer MOPS

Two liquid phases were formed as the addition of a certain amount of biological buffer 3-(N-morpholino)propane sulfonic acid (MOPS) in the aqueous solutions of tetrahydrofuran (THF) or 1,3-dioxolane. To evaluate the feasibility of recovering the cyclic ethers from their aqueous solutions with the aid of MOPS, we determined experimentally the phase diagrams of the ternary systems of {cyclic ether (THF or 1,3-dioxolane) + water + MOPS} at T = 298.15 K under atmospheric pressure. In this study, the solubility data of MOPS in water and in the mixed solvents of water/cyclic ethers were obtained from the results of a series of density measurements, while the (liquid + liquid) and the (solid + liquid + liquid) phase boundaries were determined by visually inspection. Additionally, the tie-line results for (liquid + liquid) equilibrium (LLE) and for (solid + liquid + liquid) equilibrium (SLLE) were measured using an analytical method. The reliability of the experimental LLE tie-line results data was validated by using the Othmer–Tobias correlation. These LLE tie-line values were correlated well with the NRTL model. The phase diagrams obtained from this study reveal that MOPS is a feasible green auxiliary agent to recover the cyclic ethers from their aqueous solutions, especially for 1,3-dioxolane.     

An isothermal (30 °C) study of heterogeneous equilibria in the sucrose (C12H22O11)-calcium hydroxide (Ca(OH)2)-water system

Solid-liquid equilibria in the C₁₂H₂₂O₁₁-Ca(OH)₂-H₂O system have been determined at 30 °C. Two phases C₁₂H₂₂O₁₁·3Ca(OH)₂ and C₁₂H₂₂O₁₁·2Ca (OH)₂ have been evidenced, and solubility (liquidus) curves have been determined. It is thus shown that these ternary phases exhibit incongruent solubilities at 30 °C. These solid phases were characterized using Infrared Spectroscopy (IR), Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).     

The La0.95Ni0.6Fe0.4O3-CeO2 system: Phase equilibria, crystal structure of components and transport properties

Phase equilibria, crystal structure, and transport properties in the (100−x) La_0.95Ni_0.6Fe_0.4O₃-xCeO₂ (LNFCx) system (x=2-75 mol%) were studied in air. Evolution of phase compositions and crystal structure of components was observed. The LNFCx (2≤x≤10) are three-phase and comprise the perovskite phase with rhombohedral symmetry (R3?c), the modified ceria with fluorite structure (Fm3?m), and NiO as a secondary phase. These multiphase compositions exhibit metallic-like conductivity above 300 °C. Their conductivity gradually decreases from 395.6 to 260.6 S/cm, whereas the activation energy remains the same (E_a=0.04-0.05 eV), implying the decrease in the concentration of charge carriers. Phase compositions in the LNFCx (25≤x≤75) are more complicated. A change from semiconducting to metallic-like conductivity behavior was observed in LNFC25 at about 550 °C. The conductivity of LNFCx (25≤x≤75) could be explained in terms of a modified simple mixture model.     

Thermodynamic analysis of equilibria between binary liquid and solid solutions in ternary systems. Application to systems in which two guests compete for sites in the same host,tetrakis(4-methylpyridine)nickel(II) isothiocyanate

A thermodynamic analysis is presented of the equilibria between liquid solutions of guest A in guest B and solid solutions of HA in HB, where HA and HB are isomorphous 1:1 compounds of these guests with the host H. (The treatment is applicable whether or not HA and HB are inclusion compounds.) The mole ratio of A to B in the liquid,R ₁, is generally different from the same ratio in the solid,R _s. Data on many systems have indicated a linear relation between InR ₁, and InR _s, but to date no theoretical basis has been forthcoming. The present analysis shows that this relation is usually sigmoidal in shape but, with certain restrictions, is nearly linear. The slope and intercept are interpreted in terms of the equilibrium constant for the displacement of A from HA by B and the deviations from ideality in the liquid and solid phases. If the deviations from ideality in the liquid phase are known or can be estimated, those for the solid phase can be determined, and thermodynamic equilibrium constants and standard free energy changes for the displacement of A by B calculated. These methods were applied to available data for the following pairs of guests with the host Ni(4-mepy)₄(NCS)₂:p-xylene with each ofp-dibromobenzenp-xylene-d₆,p-xylene-d ₁₀,p-bromotoluene,p-chlorotoluene,p-dichlorobenzene,p-fluorotoluene, ethylbenzene, toluene, and benzene, and the pairsp-dichlorobenzene/p-chlorotoluene and ethylbenzene/ toluene.     

Cu2O(SO4), dolerophanite: Refinement of the crystal structure,with a comparison of [O Cu(II)4] tetrahedra in inorganic compounds

The refinement of the crystal structure of Cu₂O(SO₄), dolerophanite, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; space group C 2/m;Z=4;R=0.035] confirmed the trigonal dipyramidal coordination of one Cu(II) atom (mean distance Cu-O=2.025 Å). One O atom is tetrahedrally surrounded by four Cu(II) atoms; the mean Cu(II)-O distance of 1.918 Å compares well to [O Cu(II)₄] tetrahedra found in inorganic crystal structures.de|Die Verfeinerung der Kristallstruktur von Cu₂O(SO₄), Dolerophanit, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; Raumgruppe C 2/m;Z=4;R=0.035] bestätigte die trigonal dipyramidale Koordination des einen Cu(II)-Atoms (mittlerer Cu-O-Abstand=2.025 Å). Ein O-Atom ist tetraedrisch von vier Cu(II)-Atomen umgeben; der mittlere Cu(II)-O-Abstand von 1.918 Å entspricht den in ähnlichen [O Cu(II)₄]-Tetraedern von anorganischen Kristallstrukturen gefundenen Werten.

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Cu₂O(SO₄), Dolerophanit: Verfeinerung der Kristallstruktur mit einem Vergleich von [O Cu(II)₄]-Tetraedern in anorganischen Verbindungen

     

Phase equilibria and crystal structure of the complex oxides in the Ln-Ba-Co-O (Ln=Nd, Sm) systems

The phase equilibria in the Ln-Ba-Co-O (Ln=Nd, Sm) systems were systematically studied at 1100 °C in air. The homogeneity ranges and crystal structure of the solid solutions: Ln_2−xBa_xO_3−δ (0<x≤0.1 for Ln=Nd and 0<x≤0.3 for Ln=Sm), Nd_3−yBa_yCo₂O₇ (0.70≤y≤0.80), BaCo_1−zSm_zO_3−δ (0.1≤z≤0.2) were determined by X-ray diffraction of quenched samples. The values of oxygen content (5+δ) for slowly cooled LnBaCo₂O_5+δ (Ln=Nd, Sm) samples were estimated as 5.73 for Ln=Nd, and 5.60 for Ln=Sm. The unit cell parameters were refined using Rietveld full-profile analysis. It was shown that NdBaCo₂O_5.73 possesses tetragonal structure and SmBaCo₂O_5.60 - orthorhombic structure. The projections of isothermal-isobaric phase diagrams for the Ln-Ba-Co-O (Ln=Nd, Sm) systems to the compositional triangle of metallic components were presented.     

Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Ce(SO4)2-SiO2 as a Heterogeneous and Recyclable Catalyst

A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported ceric sulfate [Ce(SO₄)₂-SiO₂] as a heterogeneous catalyst from an aldehyde, 1,3-dicarbonyl compound, and urea or thiourea at 110 °C under solvent-free conditions. Compared with the classical Biginelli reaction, this new method consistently has better yields, short reaction time, easy separation, and tolerance toward various functional groups.     

Phase equilibria and crystal chemistry of the R-Cu-Ti-O systems (R=lanthanides and Y)

As part of the study of interaction of the Ba₂RCu₃O_6+z (R=lanthanides and Y) superconductor with SrTiO₃ buffer, phase equilibria of the subsystem, R₂O₃-TiO₂-CuO (R=Nd, Y, and Yb), have been investigated in air at 960 °C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd₂O₃-TiO₂-CuO system, partly due to different phase formation in the binary R₂O₃-TiO₂ and R₂O₃-CuO systems. R₂CuTiO₆ and R₂Cu₉Ti₁₂O₃₆ were the only ternary phases established in all the three diagrams. R₂Cu₉Ti₁₂O₃₆ belongs to the perovskite-related [AC₃](B₄)O₁₂ family which is cubic Im3. Depending on the size of R³⁺, R₂CuTiO₆ crystallizes in two crystal systems: Pnma (R=La-Gd), and P6₃cm (R=Dy-Lu). The structure and crystal chemistry of the Pnma series of R₂CuTiO₆ (R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R₂CuTiO₆ have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF).     

Ce(SO4)2‐Mediated Nitration of N,N‐Dialkylanilines with NaNO2 in Water

Ce(SO₄)₂‐mediated nitration of N,N‐dialkylanilines with NaNO₂ using water as the solvent has been achieved in good to excellent yields. The nitrating reaction proceeded smoothly at ambient temperature.     

Investigation of radical reactions in C2Cl4 and C2Cl4/O2 discharges by EPR,mass, and emission spectroscopy

The reaction of tetrachloroethylene, C₂Cl₄, with O(³P) atoms as well as the plasma decomposition of C₂Cl₄ and C₂Cl₄/O₂ mixtures have been investigated by combined application of electron paramagnetic resonance (EPR) and emission and mass spectroscopies. C₂Cl₄ plasma decomposition is shown to proceed primarily to the formation of CCl₃ radicals and chlorine-deficient products, which are ultimately involved in the formation of carbonaceous layers. A simple reaction model accounts for all the detected stable and radical species, encountered during the plasma decomposition. The model also enables order-of-magnitude estimates of decomposition rate constants to be made. The suppression of the formation of both carbonaceous layers and products C_mCl_n (m3) in C₂Cl₄/O₂ discharges is explained using results of an investigation of elementary reactions in the system C₂Cl₄/O(³P)/O₂. The stable products of C₂Cl₄/O₂ discharges, i.e., COCl₂, CCl₄, and C₂Cl₆, respectively, are shown to originate from recombination of the peroxy radicals CCl₃OO and C₂Cl₅OO.     

Supramolecular architecture built of Co(II) and a tripodal ligand containing 1-D water tapes with (H2O)16 cluster units

The reaction of Co(NO₃)₂?·?6H₂O with a tripodal ligand leads to a new complex {[Co(L)]?·?2NO₃?·?8H₂O} (1) confirmed by single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. The particular interest of 1 is in the formation of a 1-D water tape consisting of (H₂O)₁₆ cluster units, the neighboring water tapes are connected by free nitrate anions via hydrogen bonds into a 2-D guest layer. These guest layers are alternately packed face-to-face with the 2-D host layers along the a-axis to form a 3-D supramolecular architecture. There exist C–H?···?N and C–H?···?O weak hydrogen bonds between the guest layer and host layer. These weak hydrogen bonds and water–nitrate, water–water hydrogen bonds are important for the stability of the overall structure.     

The effect of experimental methods and measurement conditions on values of the kinetic parameters of [Co(NH3)6]2(C2O4)3·4H2O

Using the thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O as a basis, the paper presents results which show how computed values of kinetic parameters are influenced by experimental conditions (ambient atmosphere, sample mass, linear heating rate) when using the non-isothermal methods and the Coats-Redfern (CR) modified equation. It also illustrates the influence of the experimental methods i.e. non-isothermal and isothermal (conventional) methods and also a quasiisothermal-isobaric one which can be recognised as equivalent to Constant Rate Thermal Analysis (CRTA). The results obtained have confirmed the significant influence of the experimental parameters as well as that of the experimental method used on the estimated values of kinetic parameters. The correlation between activation energy (E) and sample mass (m) or heating rate (β) is generally of a linear nature:E=a+bx     

LnSrScO4 (Ln=La, Ce, Pr, Nd and Sm) systems and structure correlations for A2BO4 (K2NiF4) structure types

The compounds LnSrScO₄, where Ln=La, Ce, Pr, Nd and Sm, have been synthesized. Rietveld profile analysis of powder X-ray diffraction data collected at room temperature reveal that the compounds possess a modified K₂NiF₄-type structure with orthorhombic cell symmetry formed by tilting of the ScO₆ octahedra. Variable temperature (25-1200 °C) powder X-ray diffraction data show that at the highest temperatures the structures of LaSrScO₄ and PrSrScO₄ transform to the regular tetragonal K₂NiF₄-structure type but the degree of orthorhombicity (c/a) in the unit cells initially increases on heating for all materials, reaching a maximum near 300 °C. This structural behavior is analyzed in terms of relative ionic radii of the various lanthanides and scandium. A general structural model based on tolerance factors has been developed for the family of materials A₂BO₄ with various A and B cation sizes.     

Liquid–liquid equilibria for binary systems of tert-amyl ethyl ether (TAEE), isopropyl tert-butyl ether (IPTBE) and di-sec-butyl ether (DSBE) with water and for ternary systems with methanol or ethanol

The liquid–liquid equilibria for binary systems of tert-amyl ethyl ether (TAEE) + water, isopropyl tert-butyl ether (IPTBE) + water and di-sec-butyl ether (DSBE) + water are analytically determined in the temperature range 278.65–358 K. Additionally, tie-lines for six ternary systems of TAEE, IPTBE and DSBE with methanol and water or with ethanol and water are also measured at 298.15 K. All the measured binary and ternary data were correlated with the NRTL and UNIQUAC model. The reliability of the experimental tie-line data for ternary systems was ascertained by using the Othmer–Tobias correlation.     

On phase equilibria and crystal structures in the systems Ce-Pd-B and Yb-Pd-B. Physical properties of R2Pd13.6B5 (R=Yb, Lu)

Phase equilibria and crystal structures of ternary compounds were determined in the systems Ce-Pd-B and Yb-Pd-B at 850 °C in the concentration ranges up to 45 and 33 at% of Ce and Yb, respectively, employing X-ray single crystal and powder diffraction. Phase relations in the Ce-Pd-B system at 850 °C are governed by formation of extended homogeneity fields, τ₂-CePd₈B_2−x (0.10<x<0.48); τ₃-Ce₃Pd_25−xB_8−y (1.06<x<1.87; 2.20<y<0.05), and CePd₃B_x (0<x<0.65) the latter arising from binary CePd₃. Crystallographic parameters for the new structure type τ₂-CePd₈B_2−x (space group C2/c, a=1.78104(4) nm, b=1.03723(3) nm, c=1.16314(3), β=118.515(1)° for x=0.46) were established from X-ray single crystal diffraction. The crystal structures of τ₂-CePd₈B_2−x and τ₃-Ce₃Pd_25−xB_3−y are connected in a crystallographic group-subgroup relationship. Due to the lack of suitable single crystals, the novel structure of τ₁-Ce₆Pd_47−xB₆ (x=0.2, C2/m space group, a=1.03594(2) nm, b=1.80782(3) nm, c=1.01997(2) nm, β=108.321(1)°) was determined from Rietveld refinement of X-ray powder diffraction data applying the structural model obtained from single crystals of homologous La₆Pd_47−xB₆ (x=0.19) (X-ray single crystal diffraction, new structure type, space group C2/m, a=1.03988(2) nm, b=1.81941(5) nm, c=1.02418(2) nm, β=108.168(1)°).The Yb-Pd-B system is characterized by one ternary compound, τ₁-Yb₂Pd₁₄B₅, forming equilibria with extended solution YbPd₃B_x, YbB₆, Pd₅B₂ and Pd₃B. The crystal structures of both Yb₂Pd₁₄B₅ and isotypic Lu₂Pd₁₄B₅ were determined from X-ray Rietveld refinements and found to be closely related to the Y₂Pd₁₄B₅-type (I4₁/amd). The crystal structure of binary Yb₅Pd_2−x (Mn₅C₂-type) was confirmed from X-ray single crystal data and a slight defect on the Pd site (x=0.06) was established.The three structures τ₁-Ce₆Pd_47−xB₆, τ₂-CePd₈B_2−x and τ₃-Ce₃Pd_25−xB_8−y are related and can be considered as the packings of fragments observed in Nd₂Fe₁₄B structure with different stacking of common structural blocks.Physical properties for Yb₂Pd_13.6B₅ (temperature dependent specific heat, electrical resistivity and magnetization) yielded a predominantly Yb-4f¹³ electronic configuration, presumably related with a magnetic instability below 2 K. Kondo interaction and crystalline electric field effects control the paramagnetic temperature domain.