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.     

Study of the behavior of chromium(III) in potassium nitrate solutions at 25°C

Solubility in the KNO₃-Cr(NO₃)₃-H₂O system at 25°C was studied by an isothermal method. The existence of solid phases of potassium nitrate and chromium(III) nitrate nonahydrate was confirmed by constructing a phase diagram, chemical analysis, and IR spectroscopy. Crystallization of potassium nitrate from aqueous solutions was studied. Potassium nitrate does not interact with chromium(III) nitrate within the range of micro and macro concentrations. The capture of chromium(III) by KNO₃ crystals is due to adsorption and occlusion of a mother solution.     

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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Aluminum electrode for electrochemical studies in cryolite-alumina melts at 700–960°C

The paper presents the results of tests of different aluminum electrode designs for electrochemical studies in cryolite-alumina melts in the temperature range of 700?C960°C. Their operation as regards stability and reproducibility of the potential and the highest activity of metallic aluminum is analyzed. The new design of the aluminum electrode is suggested that is characterized by a more stable and reproducible potential, as compared to the designs earlier suggested. Herewith, the activity of metallic aluminum is higher. It is shown that the suggested electrode is suitable for operation in cryolite-alumina melts in the temperature range from 700°C. The electrode can be used for a prolonged time. Herewith, its potential remains stable and reproducible.     

Carbon electrode for electrochemical studies in cryolite-alumina melts at 700–960°C

The paper presents the results of tests of different carbon electrode designs for electrochemical studies in cryolite-alumina melts in the temperature range of 700?C960°C. Operation of the electrode and its applicability as the reference electrode is analyzed. The theoretical value of the maximum possible instability of its potential related to instability of the gas composition is calculated. A new design of the carbon electrode is suggested in which the gas composition is much more stable. It is shown that the suggested electrode is suitable for application as the reference electrode in cryolite-alumina melts in the temperature range of 750°C and above. The electrode can be used for a prolonged time. Herewith, its potential remains stable and reproducible.     

Thermodynamic properties of binary mixtures: Hexamethylphosphoric triamide + a polar liquid at 25°C

Excess enthalpies H _m ^E excess isobaric heat capacities C _p,m ^E , densities, and speeds of sound of hexamethylphosphoric triamide (HMPA)+acetonitrile (AN), + N,N-dimethylformamide (DMF), and + dimethylsulfoxide (DMSO) were measured at 25degrC. H _m ^E =–1200 J-mol^–1 for HMPA + AN, –180 J-mol^–1 for HMPA + DMF, and 75 J-mol^–1 for HMPA + DMSO C _p,m ^E is positive and considerably larger than C _v,m ^E . V _m ^E for HMPA + DMSO was small and changed sign from negative to positive around HMPA mole fraction x=0.6. V _m ^E for the other two mixtures were negative. The excess compressibilities, K _m ^E for the other two mixtures were negative. The excess compressibilities, K _S ^E and K _T ^E were similar to V _m ^E Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30-June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Viscosity of Hg5Tl2 at 14.5°C

Abstract

By means of a toroidal oscillating viscometer, the shear viscosity of some mercury-thallium alloys has been measured in the composition range 28.5–29.5 atomic percent thallium and over the temperature range from 12.5–15.5°C. Some discussion of the experimental results is given in terms of liquid coordination number.     

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...     

Thermodynamic properties and amorphization of Zr–Si melts

The relationship between the thermodynamic properties of Zr–Si liquid alloys and their propensity to amorphization is studied. The temperature–concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr₃Si associative groups with low formation entropy.     

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.     

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 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.     

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.     

The Solubility of Hydrogen Sulfide in Acetonitrile at 25°C

Abstract

The solubility of hydrogen sulfide in acetonitrile at 25°C has been determined both gravimetrically and titrimetrically to be 0. 528 M. The effects of the presence of water and an electrolyte (LiClO₄) on this parameter are reported.     

Thermodynamic properties of o-phthalic acid and its products of dissociation at 0–200°C and 1–5000 bar

Values of the pH for four solutions in a KHPh-HCl-KOH system, where Ph denoting C₈O₄H₄, are measured at 25–70°C depending on pressure (1–1000 bar). The experimental results and the available literature data are processed on the base of Helgeson-Kirkham-Flowers (HKF) equation of state [1] and the GIBBS, OptimA, and OptimB programs from the HCh software package [2]. The obtained standard thermodynamic properties and HKF parameters of H₂Ph_aq, HPh^?, and Ph^2? aqueous species, provides calculation of the pH of phthalate buffers in a wide range of temperatures (up to 200°C) and pressures (up to 5 kbar). The calculated values for the biphthalate buffer (0.05m KHPh) correspond to the IUPAC recommendations (at 0–50°C and 1 bar) with an accuracy of 0.005 pH units, and to the values of pH measured in this study at elevated Tp parameters (25–70°C and pressures of up to 1 kbar) within the limits of ±0.02 pH units.