Viscous Flow of Concentrated Aqueous Solutions of NiCl<Subscript>2</Subscript> + FeCl<Subscript>2</Subscript>

The dynamic viscosity, apparent molar volume, enthalpy, and Gibbs energy of activation of a viscous flow of concentrated aqueous solutions of NiCl₂ + FeCl₂ were calculated. The concentration dependences of these parameters were analyzed in terms of structural transformations. A polynomial approximation of the concentration dependences of the dynamic viscosity of the solutions under study was performed using MATLAB 6.1 software package.     

Electrodeposition of thin Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> films

The electrochemical behavior of copper(II), zinc(II), and thiosulfate (S₂O₃ ^2-) ions on the molybdenum electrode in individual 0.2 М sodium sulfate solutions (рН 6.7) and with addition of either 0.1 М tartaric acid (рН 4.6) or 0.1 М citric acid (рН 4.7) is studied. A one-step electrochemical method is developed for the deposition of thin Cu₂ZnSnS₄ films, which is carried out on the molybdenum electrode at a constant potential in sodium sulfate solutions containing tartaric acid. The effect of the concentration of electrolyte components on the chemical composition of Cu₂ZnSnS₄ films is determined. The phase composition is confirmed by the Raman spectroscopy data. The surface morphology of synthesized films is studied by means of scanning-electron and atomic-force microscopes. The photoelectrochemical characteristics of Cu₂ZnSnS₄ films are determined. Samples of these coatings on the Mo electrode are found to be highly photosensitive.     

Phase equilibria in the NaCl-NaBr-Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript> system

The binary systems NaBr-Na₂MoO₄ and NaBr-Na₃ClMoO₄ and the ternary system NaCl-NaBr-Na₂MoO₄ have been studied using physicochemical methods (DTA and powder X-ray diffraction). The compositions, melting points, and heats of phase transitions have been determined for three invariant points. The liquidus surface of the ternary system consists of the fields of sodium molybdate, Na₃ClMoO₄, and sodium chloride and bromide solid solutions. The eutectics melt at 531, 612, and 524°C; the respective heats of phase transitions are 149.27, 167.55, and 215.38 J/g.     

Calorimetric and volumetric data of nucleating bovine albumin solutions at various NaCl,Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and (NH4)<Subscript>2</Subscript>SO<Subscript>4</Subscript> concentrations

Summary Heat effects and densities of bovine albumin solutions in Na-acetate buffer pH 4.2 at various NaCl, Li₂SO₄ and (NH₄)₂SO₄ concentrations were determined by a LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter (25&deg;C). The density measurements were made after 1 and 48 h of the dissolution of bovine albumin in the buffer. The correlations between the changes of the enthalpy of salting and apparent molar volumes vs. concentrations of salts were determined.     

Interaction of components in the Tl<Subscript>2</Subscript>Se-Tl<Subscript>4</Subscript>SnSe<Subscript>4</Subscript>-Tl<Subscript>9</Subscript>SbSe<Subscript>6</Subscript> quasi-ternary system

The interaction in the Tl₂Se-Tl₄SnSe₄-Tl₉SbSe₆ quasi-ternary system was studied by differential thermal analysis, X-ray powder diffraction analysis, and mathematical modeling. The projection of the liquidus surface and a spatial phase diagram of the system were constructed. It was determined that this system is of the eutectic type with boundary solid solutions based on the initial components. No formation of new intermediate compounds in the quasi-ternary system was detected.     

Synthesis of complex sulfide phases BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript>-Tm<Subscript>2</Subscript>S<Subscript>3</Subscript> and studies of their electrolytic properties

The possibility of synthesizing complex sulfide phases in the BaSm₂S₄-Tm₂S₃ system has been studied. Tm₂S₃ solid solutions were obtained with BaSm₂S₄ (CaFe₂O₄ structural type). The samples were identified by X-ray diffraction analysis and electron microscopy. The range of the solid solutions was determined. The total conductance was studied, and the conductance activation energy was calculated for samples with different dopant contents. The electrolytic properties of basic ternary sulfide and complex sulfide phases in the BaSm₂S₄-x mol % Tm₂S₃ system were investigated. A possible mechanism of defect formation was proposed.     

Physicochemical properties of KOH-H<Subscript>2</Subscript>O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O solutions

Density, viscosity, and surface tension of KOH-H₂O₂-H₂O solutions used to synthesize potassium superoxide in sprayer apparatus were studied with various relative amounts of the components in the temperature range 0–30°C. Analytical dependences of the above-mentioned quantities on temperature and solvent (water) content of the system were found.     

Dielectric constant and dielectric relaxation in aqueous solutions of K<Subscript>2</Subscript>[PdCl<Subscript>4</Subscript>] and K<Subscript>2</Subscript>[PtCl<Subscript>4</Subscript>]

The MW-dielectric properties of aqueous solutions of K₂[PtCl₄] (I) and K₂[PdCl₄] (II) were studied at 298 and 313 K in the frequency range (12–25 GHz) corresponding to the maximum dielectric constant dispersion for water and aqueous solutions of these salts. The low-frequency conductivities were measured. The static dielectric constant, the dielectric relaxation time, and the enthalpy of activation of the dielectric relaxation of the solutions were determined. Compared to pure water, in solutions of salts I and II, the orientational mobility of water molecules is increased and the network of H-bonds is violated more strongly than that of most other ions with hydrophilic hydration. It was demonstrated for the first time that dielectric spectroscopy can be used for analyzing complexation processes in systems containing aqua and hydroxo chloride complexes of metals.     

Volumetric and Viscometric Studies on Sodium Nitrate and Potassium Nitrate in Aqueous and H<Subscript>2</Subscript>O-urea Solutions

Summary.  Density and viscosity of NaNO₃ and KNO₃ in aqueous and in H₂O-urea solutions were determined as a function of electrolyte concentrations at 308, 313, 318, 323, and 328 K, respectively. The apparent molal volume (φ _v ) of the electrolytes were found to be linear functions of the square root of the solute molality (b). The φ _v and data were fitted to the Masson equation [1] by the least square method to obtain the apparent molar volume at infinite dilution (φ _v ^{^}), which is practically equal to the partial molar volume . The viscosity coefficients A and B were calculated on the basis of the viscosity of the solutions and the solvent concerned using the Jones–Dole [2] equation. The activation parameters for viscous flow (ΔG ^≠, ΔS ^≠, and ΔH ^≠) were calculated according to Eyring [3]. The values of for the two systems were also calculated from B-coefficient data. The results were found to be of opposite nature in the two electrolyte systems. Where sodium nitrate showed structure making behaviour both in aqueous and in H₂O-urea solutions, KNO₃ showed structure breaking behaviour in aqueous solutions and structure making behaviour in 5 molal H₂O-urea solutions in the studied temperature range. The behaviour of these two electrolytes in aqueous binary and in aqueous-urea ternary systems are discussed in terms of charge, size, and hydrogen bonding effects. Corresponding author. E-mail: chemistry_ru@yahoo.com Received January 24, 2002; accepted (revised) April 5, 2002     

Enthalpies of dilution of aqueous mixed solutions of LiCl and Li<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript> at 298.15 K

The enthalpies of dilution, Δ_dil H _m, have been measured for LiCl+Li₂B₄O₇+H₂O system at T=298.15 K by using a RD496-III microcalorimeter. A suitable measurement method was used to obtain the better data of the enthalpies of dilution for the ternary mixing solutions to low concentrations. The relative apparent molar enthalpies, L _ϕ, have been determined and the relationships between L _ϕ and ionic strength I at different molal fractions of Li₂B₄O₇ were obtained. The effect of the borate Li₂B₄O₇ on the heat properties for the studied system was discussed.     

Viscosity and shrinkage of porous and quartzoid glasses of the Na<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

Shrinkage of porous glasses on heating from 20 to 800°C was studied and temperature dependences of the viscosity in the range of 10¹¹–10¹³ P were determined for quartzoid (sintered) glasses based on five glasses with different compositions in the Na₂O-B₂O₃-SiO₂ system. The shrinkage of porous glasses and the viscosity of quartzoid glasses were analyzed in relation to their composition and temperature of preliminary thermal treatment.     

Three-component systems LiBr-LiVO<Subscript>3</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript> and LiBr-Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>

Phase equilibria in the three-component systems LiBr-LiVO₃-Li₂MoO₄ and LiBr-Li₂SO₄-Li₂MoO₄ have been studied using differential thermal analysis (DTA). Eutectic compositions have been determined (mol %): in the system LiBr-LiVO₃-Li₂MoO₄, 56.0 LiBr, 22.0 LiVO₃, and 22.0 Li₂MoO₄ with a melting temperature of 413°C; and in the system LiBr-Li₂SO₄-Li₂MoO₄, 65.0 LiBr, 14.0 Li₂SO₄, and 21.0 Li₂MoO₄ with a melting temperature of 421°C. Phase fields have been demarcated.     

LiF-LiCl-LiVO<Subscript>3</Subscript>-Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript> system

Phase equilibria in the LiF-LiCl-LiVO₃-Li₂SO₄-Li₂MoO₄ system have been studied by differential thermal analysis. The eutectic composition has been determined as follows (mol %): LiF, 17.4; LiCl, 42.0; LiVO₃, 17.4; Li₂SO₄, 11.6; and Li₂MoO₄, 11.6, with the melting temperature equal to 363°C and the enthalpy of melting equal to (284 ± 7) kJ/kg.     

Phase formation in the InPO<Subscript>4</Subscript>-Na<Subscript>3</Subscript>PO<Subscript>4</Subscript>-Li<Subscript>3</Subscript>PO<Subscript>4</Subscript> ternary system

The 950°C isothermal section of the InPO₄-Na₃PO₄-Li₃PO₄ ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa₅(PO₄)₂ (olympite structure), the indium ion stabilized high-temperature Na₃PO₄ phase (Na_{3(1 − x)}In _x (PO₄); space group Fm [`3]\bar 3 m), the complex phosphate Na₃In₂(PO₄)₃, and the α and β phases of the compound Li₃In₂(PO₄)₃. A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na₃In₂(PO₄)₃ leads to a significant increase in the region of a NASICON-like solid solution.     

High-temperature heat capacity and thermodynamic properties of Pb<Subscript>4</Subscript>V<Subscript>2</Subscript>O<Subscript>9</Subscript> and Pb<Subscript>8</Subscript>V<Subscript>2</Subscript>O<Subscript>13</Subscript>

The molar heat capacity of Pb₄V₂O₉ and Pb₈V₂O₁₃ in the temperature range 350–1000 K was measured by differential scanning calorimetry. It was determined that the plot C_p = f(T) for Pb₈V₂O₁₃ has an extremum within the range 416–516 K, which is due to a phase transition. A correlation was found between the heat capacity and composition of oxides in the PbO–V₂O₅ system. The data obtained allowed one to predict the specific heat capacity value for Pb(VO₃)₂.     

Interactions in the Al<Subscript>2</Subscript>TiO<Subscript>5</Subscript>-Ti<Subscript>2</Subscript>O<Subscript>3</Subscript> System

Interactions in the Al₂TiO₅-Ti₂O₃ system were studied and the regions of existence of Al_2?2xTi _2x ³⁺ Ti⁴⁺O₅ solid solutions with a pseudobrookite structure were determined.     

NaBO<Subscript>2</Subscript>-Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>-Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-Na<Subscript>2</Subscript>WO<Subscript>4</Subscript> quaternary system

This is the first study of the NaBO₂-Na₂CO₃-Na₂MoO₄-Na₂WO₄ quaternary system by differential thermal analysis. Na₂[MoO_4(x)WO_{4(1 − x)}] solid solutions in the quaternary system are found to not decompose.     

Phase formation in the ZrO(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript>-CsF-H<Subscript>2</Subscript>O system at low concentration of the phosphorus-containing component

The ZrO(NO₃)₂-H₃PO₄-CsF-H₂O system was studied at 20°C along the section at a molar ratio of PO₄³⁻/Zr = 0.5 (which is of the greatest interest in the context of phase formation) at ZrO₂ concentrations in the initial solutions of 2–14 wt % and molar ratios of CsF: Zr = 1−6. The following compounds were isolated for the first time: crystalline fluorophosphates CsZrF₂PO₄ · H₂O, amorphous oxofluorophosphate Cs₂Zr₃O₂F₄(PO₄)₂ · 3H₂O, and amorphous oxofluorophosphate nitrate CsZr₃O_1.25F₄(PO₄)₂(NO₃)_0.5 · 4.5H₂O. The compound Cs₃Zr₃O_1.5F₆(PO₄)₂ · 3H₂O was also isolated, which forms in a crystalline or glassy form, depending on conditions. The formation of the following new compounds was established: Cs₂Zr₃O_1.5F₅(PO₄)₂ · 2H₂O, Cs₂Zr₃F₂(PO₄)₄ · 4.5H₂O, and Zr₃O₄(PO₄)_1.33 · 6H₂O, which crystallize only in a mixture with known phases. All the compounds were studied by X-ray powder diffraction, crystal-optical, thermal, and IR spectroscopic analyses.     

Sorption of phosphate and arsenate ions from solutions by sorbents of the system TiO<Subscript>2</Subscript>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-H<Subscript>2</Subscript>O

Hydrated nanosize oxides of the system TiO₂-Fe₂O₃-Al₂O₃-H₂O were tested as sorbents for recovery of phosphate and arsenate ions from aqueous solutions in a wide range of pH values. The optimal compositions of the sorbents were found, their ion-exchange functions were studied, and limiting sorption capacities were determined.     

Thermodynamic study of Ag<Subscript>8</Subscript>GeSe<Subscript>6</Subscript> by EMF with an Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> solid electrolyte

The Ag–Ge–Se system was studied in the range of compositions Ag₂Se–GeSe₂–Se by measuring the EMF of the concentration (relative to the silver electrode) circuits with a solid electrolyte Ag₄RbI₅ in the temperature range 290–430 K. The polymorphic transition temperature of Ag₈GeSe₆ (320 K) was determined and the partial molar functions of silver were calculated for both crystal modifications of this compound based on the EMF measurements. The thermodynamic functions of formation and entropy of both modifications of Ag₈GeSe₆ and the thermodynamic functions of its polymorphic transition were calculated.