Solubility isotherm for the Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system

Solubility in the Na₂MoO₄-Na₂SO₄-H₂O system was studied using isothermal saturation at 5–100°C. The boundaries of crystallization fields were determined for sodium sulfate and sodium molybdate. Solid solutions were not observed within the range of the temperatures studied. The density, refractive index, and dynamic viscosity of the saturated solutions of the system were determined, and these data were used to calculate the molar volume, kinematic viscosity, and apparent molar volume of the sum of salts in these solutions. All property isotherms of solutions are in a strict correlation with the solubility in the system; this correlation is represented as an isobaric-isothermal diagram.     

Velocity correlations in aqueous electrolyte solutions from diffusion,conductance and transference data: Application to concentrated solutions of nickel chloride and magnesium chloride

Velocity cross-correlation coefficients have been calculated for aqueous solutions of NiCl ₂ and MgCl ₂ up to concentrations of 4M. Examination of the concentration-dependence of these coefficients show that it is very similar for the two salts. There is no evidence for any special structural characteristics in NiCl ₂ solutions. The velocity correlation technique is apparently not sensitive enough to detect the small amount of complexation that is thought to be present in NiCl ₂ solutions.     

Effect of electrization on molecular mobility in gold nanocomposites based on arabinogalactan

A correlation is found between the proton spin-spin relaxation times in gold nanocomposites based on arabinogalactan in aqueous solutions and the maximum conducting layer thicknesses of films cast from solutions of composites. The obtained correlation is considered from the viewpoint of electrization’s effect on the mobility of macromolecules of the investigated polymer nanocomposites. The dependence of arabinogalactan mobility on the type of solvent (H₂O or D₂O) is established, and a conclusion is drawn as to the effect of the hydrogen bonds of arabinogalactan with solvent on polymer mobility in solutions.     

Raman study of molecular dynamics of inorganic fluoroxidizers in nonaqueous solutions—Part 1. Xenon difluoride in acetonitrile

The Raman spectra of the totally symmetric ν₁(Σ_g⁺) mode of XeF₂ molecules have been measured in CH₃CN solutions at various temperatures and concentrations. The vibrational and rotational correlation functions as well as the characteristics times have been calculated. It was concluded that the vibrational band width in these solutions is to be attributed to the vibrational dephasing, whereas the contribution from the rotational relaxation has been found to be of less importance.     

Hydrophobic nitroxide radicals as probes to investigate the hydrophobic interaction

The EPR spectrum of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) has been systematically investigated in several solvents and in aqueous solutions of glycerol,t-BuOH, Bu₄NBr,n-HexNH₃Br,n-OctNH₃Br, NaBPh₄, and Ph₄AsCl. Most of the results have been obtained at 25°C, though the temperature dependence of the linewidths has been examined in water and several organic solvents. Data on the spectrum of ditertiarybutylnitroxide in aqueous solutions of glycerol and Bu₄NBr are also presented. The spectrum was simulated to determine W_H, the linewidth after allowance for the unresolved proton hyperfine interaction, in each manifold of the triplet due to the nitrogen hyperfine interaction. The linewidth W_H is analyzed in terms of the reorientational correlation time Äθ and the angular velocity correlation time ÄJ. In most solutions Äθ is determined only by the bulk solution viscosity, except in situations where significant clustering of hydrophobic solute molecules occurs. In pure nonaqueous solvents the temperature dependence results are consistent with ÄJ being determined by the bulk viscosity, while in water or aqueous solutions, a very different behavior is found which is interpreted as a manifestation of clathrate-like hydration of the hydrophobic radical. This interpretation is incorporated in a two-state model developed to account for the W_H data of TEMPO in aqueous solutions of various hydrophobic solutes. The equilibrium parameters derived from the model, for the association of TEMPO with several hydrophobic solutes, support the concept of hydrophobic interactions as pictured from thermodynamic excess functions.     

Vapor pressure measurements on nonaqueous solutions. Part IV. HNC calculations using Friedman's cosphere overlap model

Vapor pressure data for solutions of various alkali metal and tetraalkylammonium salts in methanol at 25° and NaI solutions in ethanol, 2-propanol, and acetonitrile at 25° in the concentration range 0.04–1]<0.75 are used to show the applicability of the HNC integral equation method to nonaqueous electrolyte solutions. Friedman's model of overlapping cospheres is used to express the non-electrostatic part of the ion-interaction potential. Data analysis is based on the Rasaiah-Friedman algorithm for the calculation of g₊₊ and g_+– functions. After conversion from Lewis-Randall to the McMillan-Mayer system the measured osmotic coefficients of all electrolyte solutions can be reproduced with the help of the calculated correlation functions.     

High pressure raman study of isotropic lineshapes of aqueous sodium nitrate solutions

The isotropic lineshape of the v₁ (A₁) stretching mode of the nitrate ion in solutions of sodium nitrate has been studied at 25°C as a function of NaNO₃ concentration ranging from 0.1 to 6M. The pressure dependence has been determined for 1 and 6M solutions at pressures ranging from 1 bar to 3 kbar. The isotropic band becomes more asymmetric with increasing concentration, and its v₁ peak frequency undergoes a blue shift both with increased concentration and increased pressure. At low concentration the vibrational correlation function is well described by the Kubo formula, whereas at higher concentration it becomes more Gaussian. The experimental data indicate that the v₁ vibrational lineshape in aqueous solutions of NaNO₃ is dominated by strong intermolecular interactions which produce inhomogeneous broadening at higher concentration.     

Phase equilibriums,ion association,and mechanisms of solvation in the LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript>-(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO<Subscript>2</Subscript> system

The phase diagrams, isotherms of the electrical conductivity, Raman spectra, and time correlation functions of vibrational dephasing are studied for the LiN(CF₃SO₂)₂-(CH₃)₂SO₂ system, which is promising for use as an electrolyte in medium-temperature lithium-ion batteries. The phase diagram of this system contains a broad supercooled region. It is shown that the concentration dependences of the electrical conductivity are typical for solutions of strong electrolytes. The Raman spectra and the time correlation functions of vibrational dephasing for the anion and the solvent indicate that in the supercooling range, cations are weakly solvated by solvent molecules and form ion pairs.     

Nuclear relaxation and molecular motion of 1,3,5-trifluorobenzene-d3 in liquid solutions

The ²D and ¹⁹F spin-lattice relaxation times of 1,3,5-trifluorobenzene-d₃ in 0.15 mol fraction solutions in various solvents have been measured over the temperature range 270–400 K. The relationship between the reorientational correlation times, τ_θ, and the angular momentum correlation times, τ_J, obtained from the nuclear relaxation data has been compared with the theoretical relationships predicted by the J-diffusion limit of the extended diffusion (EDJ) model and the Fokker-Planck-Langevin (FPL) model for symmetric top molecules. It was found that the rotational motion of 1,3,5-trifluorobenzene-d₃ in most solutions was better described by the FPL model with frictional anisotropy τ₆/τ_· in the range 1–2. (τ₆ and τ_· are the correlation times for the angular velocity components along the axes parallel and perpendicular to the molecular symmetry axis.) The viscosity and temperature dependence of τ_θ has been analyzed in terms of a modified Debye equation and values for the anisotropic interaction parameter, κ, in each solvent are reported. The variation in κ with solvent is attributed mainly to the variation in the dipole moment of the solvent molecules. The frictional anisotropy (τ₆/τ_·) is found to decrease as κ increases. This is interpreted in terms of the effects of molecular shape and electrostatic interactions between CF bond dipole moment and solvent dipole moments.     

Correlation between thermodynamic properties and coordination states of aqueous bivalent transition metal sulfates

The osmotic coefficients for CoSO₄, NiSO₄, CuSO₄, MnSO₄, and ZnSO₄ have been found to be approximately the same up to very highest concentrations, while they are significantly higher for MgSO₄. Negligible changes in the visible spectra of CoSO₄ and NiSO₄ induced by increasing concentration indicate little, if any, coordination of the sulfate anion, while the UV spectral effects indicate outer-sphere association. More distinct spectral effects are observed for CuSO₄. However, the free sulfate anion concentration is found to be the same in equimolal solutions of CoSO₄, NiSO₄, and ZnSO₄, and probably also in CuSO₄, while it is higher in the solutions of MgSO₄. The conclusion is drawn that the four isopiestic transition metal sulfates at any given molality are in corresponding coordination states. The general problem of correlation between thermodynamic properties of solutions and the coordination states of the dissolved salts is discussed.     

Raman study of molecular dynamics of inorganic fluoroxidizers in nonaqueous solvents—Part 2. Xenon difluoride in hydrogen fluoride and bromine pentafluoride

The Raman spectra of the totally symmetric ν₁(Σ⁺_g) mode of xenon dilluoride molecules have been measured in HF and BrF₅ solutions at various concentrations. It is shown that the XeF₂ spectrum in HF has a complicated structure with three visible peaks. The complicated contour was resolved on elementary components which were identified. The vibrational and rotational correlation functions as well as the characteristics times have been calculated. It was concluded that the ν₁ vibrational band width of XeF₂ molecules in HF and BrF₅ solutions is to be attributed to the vibrational dephasing, whereas the contribution from the rotational relaxation has been found to be of less importance.     

Water structure and electron trapping in aqueous ionic solutions

The optical absorption spectra observed by pulse radiolysis of alkaline (NaOH, KOH, RbOH), chloride (LiCl, MgCl₂, CaCl₂, NaCl, KCl) and perchloride (NaClO₄) solutions at temperature 298 K are reported. Some measurements were performed at low temperature with aqueous ionic glasses. With increasing concentration of the above solutes a uniform blue-shift of the maximum of the solvated electron (e¯_sol) absorption band is observed. Near infrared (NIR) spectroscopy was so used to examine the properties of water in several concentrated electrolyte solutions. It is shown that some inorganic electrolytes (e.g. NaOH, NaClO₄) substantially change the water structure whereas some others (e.g. LiCl, CaCl₂) influence water structure insignificantly. The correlation between the ability of excess electron trapping in electrolyte solutions and water structure deduced from NIR spectroscopy is discussed.     

Effect of the solvent on the 13C NMR spectra of pyrimidine nucleosides

The ¹³C NMR spectra of uridine and cytidine in d₆-DMSO, d₇-DMF, d₉-trimethyl phosphate, d₄-methanol, d₅-pyridine, and D₂O were investigated. A linear correlation between the C₁' chemical shifts and the J₁' vicinal spin-spin coupling constants of the protons was established. From the experimental data it may be assumed that the chief reason for the effect of the solvent on the C₁'₂' chemical shift is the different contribution of the effect of the base as a consequence of a change in the conformational equilibrium of the ribose ring. Deviations from the correlation in aqueous solutions and solutions of cytidine in pyridine are observed as a result of a change in the electron density in the base. The effect of the nature of the solvent on the position of the conformational equilibrium of the base relative to the glycoside bond was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1550–1552, November, 1980.     

Bonding in C2 and Be2: Broken symmetry and correlation in DFT solutions

Summary The solution of both Hartree-Fock (HF) and Kohn-Sham (KS) equations is based on the variational principle. Exact wavefunctions would obey the same symmetry restrictions contained in the total hamiltonian. However, the variational principle does not guarantee these symmetry restrictions and the HF and KS solutions are not necessarily symmetric in spin and space. Spatial and spin symmetry broken solutions with lower energies than their restricted analogues are examined for C₂ and Be₂, in the context of the KS formalism. Comparison with UHF solutions shows that KS instabilities are far less pronounced. The main differences between HF and KS solutions are related to effects of electron correlation.     

Relative pKa of some anilinium derivatives in methanol,acetonitrile, and tetrahydrofurane solvents

In this study, the relative pK_a values of nine anilinium derivatives in methanol (MeOH), acetonitrile (AN), and tetrahydrofurane (THF) solutions were successfully calculated with mean absolute deviations of 0.63, 0.68, and 0.75 pK_a units, respectively. To this aim, their gas‐phase basicities were computed using the CBS‐QB3 composite method. Also, conductor‐like polarizable continuum model (CPCM) with UAHF, UAKS and UA0 cavities and SM8 solvation models at HF/6‐31+G(d) level of theory were applied for the calculation of the solvation Gibbs free energies. The obtained results indicate that there is reliable correlation between the experimental and computed pK_a values in the studied solutions. Therefore, to extend the pK_a database for anilines, correlation equations were used to predict the pK_a values in the investigated solvents.     

A nuclear magnetic resonance study of toluene-polyisobutylene solutions. 3. Spin-lattice relaxation: Rotational and segmental motion

The spin-lattice relaxation times are determined for the methylene carbon of polyisobutylene (PIB), as well as for the ortho carbon of toluene in toluene-polyisobutylene solutions. The Hall-Helfand correlation function combined with restricted anisotropic rotational diffusion was used to treat the T₁ data of the methylene carbon of PIB. A simple exponential correlation function was used to describe the local motion of toluene in the solutions which falls in the extreme narrowing limit for the solutions studied. Both models described satisfactorily the temperature and field dependence of the spin-lattice relation times. From the temperature dependence of the correlation times for the polymer segmental motion, the free volume of the solution at each concentration is extracted and compared with the values obtained from previous studies of the translational motion of the toluene penetrant. The free volume values extracted from the T₁ data for the methylene carbon of PIB and the self-diffusion data for the toluene were found to be in substantial agreement. The interrelationship of the timescale of segmental motion of the polymer and the translational diffusion of the toluene was also examined and it was found that the two types of motion seem to be correlated in high polymer concentrated solutions. The toluene reorientational motion was found to be much faster than both the polymer segmental motion and the toluene translational diffusion leading to the conclusion that the toluene reorientational motion is uncoupled from these two motions. ©1995 John Wiley & Sons, Inc.     

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals were calculated by using the INDO method and the molecular geometry adjusting method. Our previous calculations of o-benzosemiquinone anion radical in the lithium ion solution showed that the total energy of the minimal energy conformation in the case of the assignment |A₃| > |A₄| were lower by approximately 320 kcal/mol than that in the case of the assignment |A₃| > |A₄|. Therefore, the calculations of the minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions were carried out in the cases of the assignment |A₃| > |A₄|. The conformations in both assignments A₃ < A₄ < 0 and (A₃ < 0 < A₄ and |A₃| > |A₄|) were calculated. Although the metal ions were not explicitly contained in the molecular geometries, the minimal energy conformations are considered to be close to the real minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions. The C? O bond lengths has a good positive rank correlation with the stabilities of o-benzosemiquinone radicals in the divalent metal ion solutions and the bond angles ∠C₃C₄H₄ had a good negative rank correlation with those stabilities.     

Raman study of vibrational relaxation of cyclohexane in benzene solutions

The Raman profiles of the ν₅ mode (802 cm^?1) of cyclohexane, ν₅ (723 cm^?1) of cyclohexane-_d12 and ν₂ (992 cm^?1) of benzene and its deuterated analogs have been measured as a function of concentration in the benzene—cyclohexane liquid system. The vibrational time correlation functions of cyclohexane in benzene solutions have been calculated by Fourier inversion of isotropic band contours. The concentration dependence of the experimental vibrational correlation times computed from the correlation functions and from the half width at half height have been compared with that predicted theoretically for various mechanisms of band broadening. We have tested the Fischer—Laubereau dephasing model and the Knapp—Fischer concentration-fluctuation model. We have found that the latter model reproduces well experimental data only for the ν₂ mode of benzene in solution.     

Li2Mo4-(NH4)2MoO4-H2O system at 25°C

Solubility in the Li₂MoO₄-(NH₄)₂MoO₄-H₂O system at 25°C was studied. A congruently saturating double molybdate crystal hydrate LiNH₄MoO₄ · H₂O was found to form in the system. The density, refractive index, viscosity, surface tension, and specific electrical conductivity were measured for saturated aqueous solutions of the system. Molar volume, ionic strength, and equivalent conductivity isotherms were calculated. A correlation is observed between the variations of these properties of solutions and solubility in the system. The double salt was recovered and characterized by chemical analysis, IR spectroscopy, and dynamic and quasi-equilibrium thermogravimetry. A thermolysis scheme is suggested proceeding from the thermal curves and chemical analysis of intermediate phases.     

Enhancement of the Sorption Ability of Aluminum Oxide Desiccants by Alkaline Modification

The influence of impregnation of aluminum oxide desiccants prepared by centrifugal thermal activation of hydrargillite with alkali (KОН and NaOH) and carbonate (Na₂CO₃ and K₂СО₃) solutions on the physicochemical properties of the products was studied. Impregnation with alkali solutions increases the dynamic capacity of the desiccants by a factor of 2 and more, whereas impregnation with carbonate solutions decreases the sorption characteristics of the desiccants at similar texture characteristics. Introduction of alkaline modifiers leads to a considerable decrease in the concentration of Lewis acid sites on the surface and to an increase in the concentration of strong base sites. Linear correlation was revealed between the concentration of strong base sites on the surface of the desiccants and their dynamic capacity in drying of humid air. The desiccants modified by impregnation exhibit not only high static and dynamic capacity, allowing improvement of the drying efficiency, but also considerably enhanced mechanical strength.