Thermodynamic Properties of Aqueous Solution of 2-Isopropoxyethanol at 25°C

Excess enthalpy, excess isobaric heat capacity, density, and speed of sound for aqueous 2-isopropoxyethanol solutions were measured at 25°C. The density was also measured at 20°C. The excess enthalpy was –800 J-mol^–1 at the minimum (mole fraction alcohol, x = 0.2), showing that the hydrogen bonds formed between unlike molecules are stronger than those in both pure liquid states. The excess volume also was large and negative, more than –1.2 cm³-mol^–1 at the minimum (x = 0.35). Excess isentropic and isothermal compressibilities are extremely negative. These results suggest that breaking the hydrogen bond network in water and forming the stronger hydrogen bonds between unlike molecules reduces the volume of the solution and makes the solution less compressible. The excess isobaric heat capacity is positive and large, up to 10 J-K^–1-mol^–1 and shows anomalous behavior in the neighborhood of x = 0.15.     

Prediction of the solubility of HCl-MgCl2-H2O system at −5°C using the ion-interaction model

The component solubilities of the HCl-MgCl₂-H₂O system at −5°C were predicted by using the Pitzer ion interaction model and its extended Harvie and Weare model. The results indicated that the model supplies a good prediction of the above-mentioned system. The values of parameters of β⁽⁰⁾, β⁽¹⁾, and C ^φ of HCl and MgCl₂ were obtained by using the same optimization methods as in the literature, while those of θ_MgH and Ψ_MgHCl were derived by extrapolating the published data of 5, 15, 25, 35, and 45°C, as well as coupling the activity coefficients with the solubility data. The comparison between the calculated results and the experimental data indicated that the Pitzer ion interaction model and its extended Harvie and Weare model are quite reliable in the solubility prediction. The text was submitted by the authors in English     

Solubility Diagram of a Fullerenol-d-NaCl-H2O System at 25°C

Solubility in a ternary fullerenol-d-NaCl-H₂O system is studied at 25°C with the use of isothermal saturation. It is established that the solubility diagram is composed of two branches that are responsible for the crystallization of fullerenol-d crystallohydrate and anhydrous sodium chloride, and it contains one invariant eutonic-type point that corresponds to cosaturation by the above two solid phases. The so-called salting-out effect was observed on the branch of the crystallization of fullerenol-d, while salting in was observed on the branch of the crystallization of sodium chloride.     

Acid properties of ZSM-5 zeolites after hydrothermal treatment at 540°C

Acid properties of ZSM zeolites have been studied under various conditions of hydrothermal treatment. It is shown that with increasing , the concentration of proton centers monotonically decreases and variations in the concentration of Lewis acid centers is of extremal character.

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ZSM . , , .

     

Synthesis of potassium fluorophosphate hafnates at 20°C

Potassium fluorophosphate hafnates (PFPH) K₃H₃Hf₃F₃(PO₄)₅ and KHf₂F₃(PO₄)₂ · 2H₂O were synthesized for the first time, and a KZr₂F₃(PO₄)₂ · 2H₂O phase was found to exist. The compounds were studied by crystal-optical, elemental, X-ray powder diffraction, thermogravimetric, IR spectroscopic, and electron microscopic analyses. It was found that PFPH crystallize as one-dimensional nanoparticles. The IR spectra showed that PFPH K₃H₃M₃F₃(PO₄)₅ (M = Zr, Hf) are crystal solvate K₃M₃(PO₄)₅ · 3HF. Annealing of K₃H₃Hf₃F₃(PO₄)₅ and KHf₂F₃(PO₄)₂ · 2H₂O at 1000°C gives rise to mixtures that mostly contain various phosphate hafnates.     

Volumetric Properties of Acetonitrile with 1,2-Alkanediols (C2–C6) at 20°C

Dilatometric measurements of excess molar volumes, V^E and excess partial molar volumes, [`(V)] <sub>\texti</sub><sup>\textE</sup>\overline V _{\text{i}}^{\text{E}} have been made for binary mixtures of acetonitrile with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20°C over the entire composition range. V<sup>E</sup> for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through O—H...N=C hydrogen bonding. From the experimental results, V<sup>E</sup> were calculated and correlated by Redlich–Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, [`(V)] _\texti^\textE,o\overline V _{\text{i}}^{{\text{E,o}}} .     

Oxoacidic properties of potassium halide melts at 800°C

The equilibrium CO₃²⁻ = CO₂+O²⁻ (pK) in molten potassium halides (KCl, KBr and KI) and KCl-NaCl eutectic at 800°C was investigated to compare the oxoacidic properties of the melts. A potentiometric cell involving Pt(O₂)|ZrO₂(Y₂O₃) membrane oxygen electrode was used to detect the equilibrium O²⁻ molalities. The obtained pK values were 3.2±0.2 (KCl), 2.4±0.2 (KBr), 4.4±0.2 (KI) and 3.6±0.2 (KCl-NaCl) allowing arrangement of the melts studied in the following sequence: KI–KCl-NaCl–KCl–KBr with the melt acidities increasing within 2 pI units. The oxides solubilities were found to decrease sequentially from the chloride to the iodide melt.     

Heat capacities and volumes of methanol+acetonitrile mixtures at 5 and 25°C

Densities and heat capacities of methanol + acetonitrile mixtures were determined over the whole composition range at 5 and 25°C. Apparent and partial molar volumes and heat capacities for both components of the mixture were calculated from these data. These functions for acetonitrile run monotonously over the whole composition range of the mixture at both temperatures, while those for methanol exhibit extrema (volumes-minimum and heat capacities-maximum) at high acetonitrile content. The reasons of the observed behavior of the system are discussed.     

A new determination of the structure of water at 25°C

The results of a new neutron diffraction experiment to measure the structure of water are presented. The data, measured at the McMaster Nuclear Reactor, are of a high quality and are analysed to yield the hydrogen-hydrogen pair correlation function using a subtraction procedure which has been used in previous experiments of this kind. This procedure circumvents the necessity of applying inelasticity corrections. The results are in good agreement with earlier work and serve to establish the general correctness of the subtraction procedure when used to determine hydrogen correlations. The data are further analysed to yield separate oxygen-hydrogen and oxygen-oxygen partial structure factors for liquid water. For the second part of the analysis an effective mass model of the dynamic scattering law is used, with the model parameter, the effective mass of the scattering particle, chosen by a least-squares fit to the measured differential cross sections. The final pair correlation functions are obtained using a maximum entropy analysis of the structure functions.     

Excess Molar Enthalpies of Binary Mixtures of Trichloroethylene with Six 2-Alkanols at 25°C

Excess molar enthalpies H^E have been measured for the binary mixtures trichloroethylene + 2-propanol, + 2-butanol, + 2-pentanol, + 2-hexanol, + 2-heptanol, and + 2-octanol using an isothermal microcalorimeter at 25°C. All the mixtures present exothermic events and showed minimum negative H^E values around 0.50–0.60 mole fraction of trichloroethylene. Minimum values of H^E vary from 450 J-mol^-1 up to 530 J-mol^-1 depending on the molecular weight of alkanol. The results are explained in terms of the strong self-association exhibited by the 2-alkanols and the formation of aggregates between unlike molecules through O···HO hydrogen bonding. The experimental results for mixtures are well represented by the Redlich–Kister, NRTL, and Wilson equations, respectively.     

Electrochemical Deposition of NiFe Alloy at a Temperature of 70°C

Russian Journal of Electrochemistry - The heating of chloride electrolyte to a temperature of 70°C excludes anomalous codeposition of NiFe alloy components as a result of a change of the...     

Excess enthalpies of aqueous solutions of small peptides at 25°C

Heats of dilution of aqueous solutions of the following di-and tripeptides were determined at 25°C over a wide concentration range: -alanyl-glycine, -alanyl--alanine, DL--alanyl-glycine, glycyl-DL--alanine, L--alanyl-L-alanine, DL--alanyl-DL--alanine, DL--alanyl-DL-valine, DL--alanyl--alanine, glycyl--aminobutyric acid, glycyl-L-leucine and DL--alanyl-glycylglycine. The excess enthalpies H^ex and partial molar relative enthalpies L₂ were calculated and enthalpy coefficients of intermolecular interaction were analysed using the additivity principle of Savage and Wood. The concentration dependence of the enthalpic characteristics of peptide-peptide interactions is discussed based on of their hydrophobicity and hydrophilicity. The three-stage model of peptide association is described using enthalpic coefficients of intermolecular interactions.     

Viscosity B Coefficients for Alkali–Metal Bromides in 3-Hydroxypropionitrile–Acetonitrile Mixtures at 25°C

The viscosity B coefficients were measured for LiBr, NaBr, KBr, RbBr, CsBr, Bu₄NBPh₄ and Bu₄NBr in 3-hydroxypropionitrile–acetonitrile mixtures over the entire composition range at 25°C. The B coefficients of these electrolytes were large and positive and were split into their respective ionic values using the method of Gill and Sharma. The ionic B coefficients were positive for all the electrolytes.     

Isothermal sections of Au-Pd-Sn system at 500 and 800°C

Alloys of a Au-Pd-Sn system containing up to 35 at % Sn were investigated using a complex of physico-chemical methods of analysis. Partial isothermal sections were drawn at 500 and 800°C. The ternary phase having a tetragonal structure has been established. The solid solubility of gold in Pd-Sn phases goes up with the temperature increase. In all these phases gold seems to replace not only palladium, but also tin.     

Diffusion coefficients of the system α-cyclodextrin-n-butylurea-water at 25°C

Diffusion coefficients were measured for the ternary system -cyclodextrin(I)-n-butylurea(2)-water at three average concentrations. The cross coefficient D₁₂ was found to be almost zero and D₂₁ large and negative. These results are in agreement with the presence of an inclusion complex whose mobility is close to that of the host cyclodextrin molecules. The values of the four experimental diffusion coefficients are used to compute a value of the inclusion constant which is in reasonably good agreement with the calorimetric value.     

Solution behavior of metoclopramide in aqueous-alcoholic solutions at 30°C

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.     

Phase diagram of an iodine-potassium iodide-water-ethanol system at 25°C

Phase equilibriums are studied in the isothermal-isobaric sections of the phase diagram of a fourcomponent iodine-potassium iodide-water-ethanol system at 25°C and atmospheric pressure. The compositions of the solvent at which it exhibits the greatest ability to dissolve iodine are established. It is shown that in all the investigated sections, there is three-phase eutonic equilibrium with potassium iodide and crystalline iodine as the solid phases. It is revealed that in the sections containing 30 and 50% of ethanol, potassium iodide serves as the salting in agent for crystalline iodine, due to the formation of polyiodide complexes of various composition in the studied system.     

Copper nitrate-formamide-water system at 25°C

The solubility and solid phases in the Cu(NO₃)₂-HCONH₂-H₂O system at 25°C were studied. The formation region of the congruently soluble compound Cu(NO₃)₂ · 2HCONH₂ · 2H₂O was determined. Thysicochemical properties of this complex were investigated by X-ray powder diffraction, differential thermal, crystal-optical, and IR spectroscopic analyses.     

Volumetric properties of cyclic hydrocarbons in tetrachloromethane at 25°C

By means of a vibrating-tube densimeter, the densities at 25°C have been determined for binary mixtures of tetrachloromethane with a liquid (cyclodecane, cis-decahydronaphthalene, trans-decahydronaphthalene, bicyclohexyl, pentane) or a solid hydrocarbon (cyclododecane, cyclopentadecane, norbornane, adamantane, octahydro-4,7-methano-1H-indene). Excess molar volumes have been obtained in the whole mole fraction range for mixtures containing a liquid hydrocarbon. For solid cycloalkanes, apparent molar volumes have been evaluated in the whole range of miscibility. The partial molar volumes at infinite dilution have been calculated for all examined cycloalkanes and compared with those of n-alkanes. The dependence of upon the size and shape of the ring or cage structure of the solute is discussed. The capability of the Flory theory to reproduce V^E for these mixtures is also tested.