Vol 90, No 7 (2016)

The phase equilibria of the Ag–Bi–Te–I system in the part AgI–Bi–Bi₂Te₃–BiTeI is studied in the interval of 500–540 K by means of physicochemical analysis. Thermodynamic properties of phases are determined via EMF. Potential-forming processes occur in electrochemical cells (ECCs) of the C|Ag|glass Ag₃GeS₃I|D|C structure (where C denotes inert (graphite) electrodes; Ag, D denotes ECC electrodes; D denotes four-phase alloys of the AgI–Bi–Bi₂Te₃–BiTeI system; and Ag₃GeS₃I glass is the selective Ag⁺ conducting membrane). Linear dependences of the EMFs of cells Е(Т) in the interval of 505–535 K are used to calculate the values of the thermodynamic functions of BiTeI, Bi₂TeI, and Bi₄TeI_1.25 phases saturated over silver.

The formation of nonvolatile products of the oxidation of a bromide ion during the interaction between gaseous ozone and powdered crystalline KBr is studied. It is found that potassium bromate KBrO₃ is the main product of the reaction. The influence of major experimental factors (the duration of ozonation, the concentration of ozone, the humidity of the initial gas, and the temperature) on the rate of formation of bromate is studied. The effective constants of the formation of bromate during the interaction between O₃ and Br^– in a heterogeneous gas–solid body system and in a homogeneous aqueous solution are compared.

In this study, MeAPO-25 (Me = Fe, Cu, Mn) molecular sieves were first synthesized by a vapor phase transport method using tetramethyl guanidine as the template and applied to hydroxylation of phenol. The zeolites were characterized by XRD, SEM, FT-IR, and DR UV–Vis. As a result, MeAPO-21 and MeAPO-15 were synthesized by changing the Me/Al ratio. UV–Visible diffuse reflectance study suggested incorporation of heteroatoms into the framework and FT-IR study also supported these data. Effects of heteroatoms, contents of Me in MeAPO-25, reaction temperature, phenol/H₂O₂ mole ratios, reaction time and concentration of catalyst on the conversion of phenol, as well as on the selectivity were studied. FeAPO-25 exhibited a high catalytic activity at the mole ratio of FeO and Al₂O₃ equal to 0.1 in the synthesis gel, giving the phenol conversion of 88.75% and diphenols selectivity of 66.23% at 60°C within 3 h [n(phenol)/n(H₂O₂) = 0.75, m(FeAPO-25)/m(phenol) = 7.5%]. Experimental results indicated that the FeAPO-25 molecular sieve was a fairly promising candidate for the application in hydroxylation of phenol.

It is assumed that critical phenomena are generated by density wave fluctuations carrying a certain kinetic energy. It is noted that all coupling equations for critical indices are obtained within the context of this hypothesis. Critical indices are evaluated for 15 liquids more accurately than when using the current theory of critical phenomena.

Densities (ρ) and refractive indices (n_D) of solutions of antiemetic drug metoclopramide (4-amino-5-chloro-N-(2-(diethylamino)ethyl)-2-methoxybenzamide hydrochloride hydrate) in methanolwater and ethanol-water mixtures of different compositions were measured at 30°C. Apparent molar volume (φ_v) of the drug was calculated from density data and partial molar volumes (φ_v⁰) were determined from Massons relation. Concentration dependence of nD has been studied to determine refractive indices of solution at infinite dilution (n_D⁰). Results have been interpreted in terms of solute-solvent interactions.

The effect the number of chitosan monomer units CTS_n (n = 1–5), the protonation of chitosan dimers, and the interaction between CTS_n (n = 1–3) and acetate ions have on the energy of intramolecular hydrogen bonds is investigated by means of QTAIM analysis and solving the vibrational problem within the cluster-continuum model. It is established that the number of H-bonds in CTS_n is 2n − 1 and the total energy of H-bonds grows by ~20 kJ/mol. It is concluded that the hydrogen bonds between CTS and acetate ions play a major role in the stabilization of polyelectrolyte complexes in dilute acetic acid solutions of CTS.

Hydrogen-bonded complexes of acetylsalicylic acid with polar co-solvents in supercritical carbon dioxide, modified by methanol, ethanol, and acetone of 0.03 mole fraction concentration, are studied by numerical methods of classical molecular dynamics simulation and quantum chemical calculations. The structure, energy of formation, and lifetime of hydrogen-bonded complexes are determined, along with their temperature dependences (from 318 to 388 K at constant density of 0.7 g cm⁻³). It is shown that the hydrogen bonds between acetylsalicylic acid and methanol are most stable at 318 K and are characterized by the highest value of absolute energy. At higher supercritical temperatures, however, the longest lifetime is observed for acetylsalicylic acid–ethanol complexes. These results correlate with the known literature experimental data showing that the maximum solubility of acetylsalicylic acid at density values close to those considered in this work and at temperatures of 318 and 328 K is achieved when using methanol and ethanol as co-solvents, respectively.

The optimized geometry, vibrational wavenumbers, ¹H and ¹³C chemical shift values of 1,3-bis(4-benzamido)triazene, BBT, in the ground state were computed with the Hartree-Fock (HF) and density functional theory method (PBE1PBE) with 6-311+G(2d,p) basis set. The harmonic vibrational wavenumbers of BBT were calculated and the scaled values were compared with the experimental FT-IR spectra. A detailed interpretation of the NMR spectra of BBT was reported. The calculated data are in reasonably good agreement with experimental measurements. Moreover, the log P value was estimated with ChemBioOffice Ultra 11.0, ACD/LogP, and ALOGPS programs.

A method for obtaining Gd nanoparticles with diameters of 89 to 18 nm upon metal evaporation both in a flow of pure helium and with the addition of 0.5% of oxygen is described. It is found that the addition of O₂ does not affect the size of the particles, their structure, or the Curie temperature, though the magnetization is reduced. Particles with sizes of 18 nm have cubic lattice symmetry (fcc) and remain paramagnetic below T_c; with an increase in the size of nanoparticles, the proportion of the hexagonal (hcp) phase, which coincides with the gadolinium structure, also grows, and below T_c such particles become ferromagnetic. Oxygen impurities seem to have no effect on magnetic and structural transitions in nanoparticles.

The adsorption properties of nanocomposites based on γ-Al₂O₃ modified with CeO_x, Au/CeO_x, and Pd/CeO_x nanoparticles with contents of deposited metals ranging from 0.07 to 1.71 wt % are investigated by means of dynamic sorption method. n-Alkanes (C₆–C₈), acetonitrile, diethyl ether, tetrahydrofuran, and dioxane are used as test adsorbates. Adsorption isotherms are measured, and the isosteric heats of adsorption of a number of test adsorbates are calculated. Electron-donor and electron-acceptor characteristics of the surfaces of γ-Al₂O₃-based nanocomposites are estimated. It is shown that Au(0.1%)/CeO_x(0.07%)/γ-Al₂O₃ nanocomposite, which has the lowest content of nanoparticles of the deposited metals, has the highest adsorption activity.

The structure formed in a sorbent during the super-equivalent sorption of glycine by cation exchanger KU-2-8 is optimized via quantum chemical simulation. The differential thermodynamic characteristics of ion exchange and super-equivalent sorption in the studied system are calculated using a thermodynamic approach that allows us to describe the simultaneous exchange and super-equivalent sorption of compounds by ion-exchangers.

Polysiloxane functionalized with aminoacetic acid groups was synthesized using sol–gel technology. Elemental analysis and FTIR spectroscopy were used to determine the composition of the polysiloxane show that it is a mesoporous material with a developed surface (109.4 m2/g). It was found that the selective properties of carboxymethylated polysiloxane towards transition metal ions simultaneously present in an ammonium acetate solution change in the order Zn < Cu > Ni > Co > Pb > Cd. It was shown that the sorption of copper(II) ions by carboxymethylated aminopropylpolysiloxane with particle sizes of 50–71 μm reaches its maximum level within 2 h; the rate-limiting step of the process is the chemical reaction between the ions and the polysiloxane functional groups; and the pseudo-second-order model is the best way of describing sorption.

Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

The molecular weights of poly(N-isopropylacrylamide) (PNIPA), calculated according to polystyrene calibration standards upon the elution of THF on styragel columns, appear to be much lower than their actual values determined using independent approaches. This is likely due to interactions between the nitrogen-containing units of PNIPA polymer chains and the sorbent, so the polymer is eluted in the mode intermediate between exclusion and critical. An effective exclusion mode during the elution of PNIPA on a styragel column can be achieved by using an eluent more polar than tetrahydrofuran (particularly, 1-methylpyrrolidone).

The polarized and nonpolarized fluorescence of bovine serum albumin and human serum albumin in Triton X-100 solutions is studied at different pH values. Analysis of the constants of fluorescence quenching for BSA and HSA after adding Triton X-100 and the hydrodynamic radii of BSA/HSA–detergent complexes show that the most effective complexation between both serum albumins and Triton X-100 occurs at pH 5.0, which lies near the isoelectric points of the proteins. Complexation between albumin and Triton X-100 affects the fluorescence of the Trp-214 residing in the hydrophobic pockets of both BSA and HSA.

The distribution of NO molecules desorbed from a Pt(111) surface due to valence electron excitation over rotational energy levels N(J) is analyzed using a simple impulse-induced model. A linear dependence is found between lnN(J) and (E_r)^1/2, where E_r is the rotational energy of the desorbed molecules. The lifetime of the excited state and the critical time of residence in the excited state estimated using this dependence are found to be close to one another (~10⁻¹⁵ s). The frequency and amplitude of the tilting vibrations of the adsorbed molecules in the excited state are estimated.

A new nonparametric scaling equation with density and temperature as variables is proposed using the phenomenological theory of critical phenomena and the experimentally confirmed Benedek’s hypothesis, on the basis of which we assume that the behavior of a number of thermodynamic functions for the critical and near-critical isochores in the neighborhood of an asymptotic critical point is similar. In comparison to Scofield’s linear model (LM), the proposed scale equation is not inferior to known nonparametric equations of the same type; in contrast to the latter, however, its physical grounds are just as valid as the LM equation.

Phase equilibria in the system n-docosane–cyclododecane–n-decane are studied by means of differential thermal analysis. It is found that the system is of the eutectic type. The temperature of eutectic melting is found to be–34.9°C, the n-docosane content is 3.5 wt %, the n-decane content is 86.5 wt %, and the cyclododecane content is 10.0 wt %. It is concluded that the results can be used to create new optimal heatstorage materials.

The characterization of the boron carbide investigated in the above-mentioned paper and some of the conclusions made on it by the authors are critically appraised with regard to reliable results obtained earlier by other scientists.