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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 14 (1993), S. 1187-1200 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical phenomena ; equation of state ; ethane ; methane ; plait point ; specific heat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An isomorphic equation of state for near-critical binary mixtures is used to represent equation of state and specific heat data for mixtures of methane and ethane in a substantial range of densities and temperatures around the critical line.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 15 (1994), S. 283-308 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical phenomena ; ethane: methane ; thermal conductivity ; transport coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The behavior of the transport coefficients related to diffusion, heat conduction, and their cross-processes in fluid mixtures near the consolute point and the liquid-vapor critical line is investigated. Simple crossover equations for the critical enhancement of those coefficients are developed by incorporating a finite cutoff and time-dependent correlation functions of the order parameter and of the entropy into decoupled-mode theory integrals. It is shown that the thermal conductivity of a binary mixture is nondivergent and the crossover from the critical background in the critical point to the regular background far from the critical point is elucidated. The crossover to the behavior of the thermal conductivity in the one-component limit is also discussed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 20 (1999), S. 563-588 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical region ; D2O ; equation of state ; H2O ; phase behavior ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A parametric crossover model is adapted to represent the thermodynamic properties of pure D2O in the extended critical region. The crossover equation of state for D2O incorporates scaling laws asymptotically close to the critical point and is transformed into a regular classical expansion far from the critical point. An isomorphic generalization of the law of corresponding states is applied to the prediction of thermodynamic properties and the phase behavior of D2O + H2O mixtures over a wide region around the locus of vapor-liquid critical points. A comparison is made with experimental data for pure D2O and for the D2O + H2O mixture. The equation of state yields a good representation of thermodynamic property data in the range of temperatures 0.8T c(x)≤T≤1.5T c(x) and densities 0.35ρc(x)≤ρ≤1.65ρc(x).
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 14 (1993), S. 1187-1200 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical phenomena ; equation of state ; ethane ; methane ; plait point ; specific heat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An isomorphic equation of state for near-critical binary mixtures is used to represent equation of state and specific heat data for mixtures of methane and ethane in a substantial range of densities and temperatures around the critical line.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 143-148 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Intermolecular interactions ; Adsorption from solutions ; Chemically modified layers in LC ; Conformation of bonded chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the investigation of intermolecular interactions in adsorption from solution, which are the basis of selectivity in molecular liquid chromatography (LC), it is convenient to use the LC method itself. Using this method the Henry's constants, K1, and other thermodynamic adsorption characteristics of hydrocarbons and of a series of polar substances on hydroxylated silica surface were determined from aqueous solutions. On the basis of the adsorption of hydrocarbons from water solutions the structure of the chemically modifying layers formed by different hydrocarbon groups on the silica surface is considered. The role of conformation ability of straight-chain bonded phases is demonstrated. Hydrocarbons are adsorbed on the hydroxylated silica surface more strongly from aqueous solutions than from solutions in saturated hydrocarbons and their retention increases with the increase in the number of carbon atoms in the molecule. The retention in LC is determined by the intermolecular interaction of the solute and solvent molecules with the adsorbent, as well by the contribution of the intermolecular interaction, between the solute and the solvent. The thermodynamic characteristics of adsorption of cymarin from water-ethanol solutions on hydroxylated silica gel and on silica gel surface modified by diphenylsilyl groups is compared. The solubility of silica gel modified by diphenylsilyl groups at different composition of water-ethanol eluent at different temperatures is investigated.
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  • 6
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Polyaromatic hydrocarbons ; Polar stationary phase ; Relationship between retention and molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of polynuclear aromatic hydrocarbons (PAH) is studied in liquid chromatography, using columns packed with silica gel with a hydroxylated surface and the same silica gel with surface-bonded amine and nitrile groups. A linear relationship was found between retention and the number of π-electrons in the molecule, the size of the molecule and the different types of carbon atoms in the molecule. The different carbon atoms in a PAH molecule contribute differently to the retention and this contribution depends on the nature of the polar functional groups on the adsorbent's surface and on the nature and concentration of a polar modifier present in a non-polar eluent.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 245-248 
    ISSN: 1612-1112
    Keywords: Chromatoscopy ; Gas chromatography ; Graphitized carbon black ; Molecular structure and retention ; Aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A molecular-statistical calculation of the retention volumes at zero sample size on graphitized thermal carbon black is carried out for quasi-rigid molecules of fluorene, indene, 1-methylindene, 2-methylindene and three dimethylindenes. A reasonable agreement is observed between the calculated and the available experimental gas chromatographic data. The potential barrier to internal rotation and the torsional angle in styrene molecules are estimated by comparing theoretically calculated and measured retention volumes.
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  • 8
    ISSN: 1612-1112
    Keywords: Adsorption from solutions ; Liquid chromatography ; Cardiac glycosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the cardiac glycoside cymarin as the example the application of liquid chromatography for the study of adsorption from solutions and the determination of the corresponding thermodynamic characteristics was investigated. The adsorption isotherm of cymarin at small concentrations from a water-ethanol solvent on silica gel modified by dimethyldichlorosilane was measured under static conditions using analytical LC to determine the concentrations of solutions after adsorption. The values of the Henry constants were obtained by extrapolating the slope of the adsorption isotherm down to zero concentration. The specific retention volumes for different but small sample sizes of cymarin in the chromatographic column were measured, the adsorbent and the water-ethanol eluent being the same as in the static conditions. The specific retention volume for a small (zero) sample size determined by liquid chromatography experiment coincides with the Henry constant of cymarin adsorption determined in static conditions. In favourable cases liquid chromatography can be used to determine the equilibrium constants for adsorption from solution. The dependence of the Henry constants on temperature was investigated for several cardiac glycosides. The influence of the modification of the adsorbent surface on the separation of the cardiac glycosides was also studied.
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  • 9
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Graphitized carbon black ; Aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper defines values of retention volumes for zero surface coverage (Henry's constant) at different temperatures, retention indices and variations of the internal energy (differential heats of adsorption) of diphenyl and its alkyl derivatives, terphenyls, diphenylmethane, triphenylmethane, diphenylethanes and fluorene on graphitized thermal carbon black (GTCB). Adsorption on GTCB takes place in accordance with the geometry of these molecules, the strongest adsorption being observed for para-terphenyl with least inhibited internal rotation of the molecule, while the weakest adsorption occurs for 2,6,2′,6′-tetramethyldiphenyl with the most inhibited internal rotation of the molecules. The flat molecules of fluorene are adsorbed on GTCB more readily than the nonflat molecules of diphenylmethane.
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  • 10
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Porous copolymer containing epoxy groups ; Retention of nonpolar and polar benzene derivatives ; Dipole moment and liquid chromatography retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of benzene derivatives with nonpolar and polar substituents on a porous methacrylate copolymer containing epoxy groups using both nonpolar and polar eluents was investigated. When n-hexane is used as the eluent, the retention of n-alkylbenzenes and polymethylbenzenes is weaker than that of benzene. In the case of benzene derivatives containing polar functional groups their capacity ratios (k) on this porous polymer increases approximately linearly with the increase of the adsorbate molecules dipole moment. The retention characteristics of the methacrylate copolymer were compared with that of a styrene-divinylbenzene copolymer and silica gels with a hydroxylated surface and with a surface modified by chemically bonded alkylsilyl groups.
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