Showing papers on "Binary system published in 1986"

Vapor-liquid critical curve of the system ethane + 2-methylpropane

Abstract: The vapor-liquid critical curve of the binary system ethane + 2-methylpropane was determined from the critical temperature of ethane up to the critical temperature of 2-methylpropane. The results are compared with vapor-liquid equilibrium data reported earlier on this system and with the critical curve that is predicted for this system from the Peng-Robinson equation of state.

An Equation of State for Binary Fluid Mixtures to High Temperatures and High Pressures

Abstract: An equation of state has been constructed which can describe and predict phase equilibria and critical curves of fluid binary systems. The equation is particularly suitable for regions of elevated temperatures and pressures and for systems with molecules of high polarity, for example for aqueous systems. The computer simulation based Carnahan-Starling term with temperature dependent particle diameter describes the repulsion. The attraction term uses a square well potential. The values of the parameters in the equation are derived from critical data of the pure mixture partners or have a defined relation to the chosen model of molecular interaction. Thus predictions are possible. The experimental critical curve of the H2O-N2 system to 250 MPa could be well represented with two adjusted parameters. With the same set of adjusted parameter values critical curves of the systems H2O-CH4 and H2O-Xe have been calculated to 220 MPa. Critical curve and the binodal (phase-equilibrium) surface in the pressure-temperature-composition diagram could be calculated for H2O-CO2 above about 500 K to 200 MPa with a different pair of mixture parameters. A comparison with other equations is made. The possibility to predict excess molar volumes of supercritical dense H2O-CH4-mixtures to 400°C and 150 MPa is demonstrated.

A Neutron and X‐Ray Diffraction Study of the Binary Liquid Aromatic System Benzene‐Hexafluorobenzene II. The Mixtures

Abstract: A series of X-ray and neutron diffraction experiments has been performed on liquid benzene, hexafluorobenzene and their liquid mixtures in order to find out whether packing effects or electrostatic interactions are the structure determining factors The results for the mixtures are reported together with a qualitative interpretation of the experimental data By combined analysis of the X-ray and neutron diffraction experiments it could be proved that a reorientation takes place from a L-type pair geometry in the pure components to a nearly parallel alignment of the molecules in a 1:1 complex In a second approach a new quantity - a so-called excess structure factor - was defined, the analysis of which confirmed the deduced change of orientation With a stacking distance of 37 A and a separation of 76 A between two consecutive hexafluorobenzene molecules the structure of the equimolar mixture in the liquid phase very closely ressembles the one obtained for the solid phase It can be concluded that the quadrupolar interaction is the structure determining factor in the investigated liquid aromatic systems

Infinite dilution fugacity coefficients and the general behavior of dilute binary systems

Abstract: A universally valid formal expression for the composition dependence of solute and solvent fugacity coefficients in any dilute binary system far from criticality is derived in this paper. In the present context, dilution denotes the y1 → O limit, regardless of the mixture's molar density. The results are independent of the system under study and of the choice of equation of state. The solute fugacity coefficient is simply the product of a composition-independent term (the infinite dilution fugacity coefficient) and an exponential decay composition correction. These two parameters have important thermodynamic implications: their temperature and pressure derivatives are related to the solute's partial molar enthalpy and volume, respectively. When applied to activity coefficients, the same theoretical analysis yields universal relationships for the composition dependence of activity coefficients which can be used as consistency checks for empirical correlations. The relationship between infinite dilution activity and fugacity coefficients can be used to estimate relative solubilities of a given solute in different solvents. Excellent agreement is found when the theoretical expressions are tested with three different binary systems involving a nonvolatile solid solute and a supercritical fluid.

Study of the enthalpies of formation in the Gd-Ni system

Abstract: The enthalpies of formation of seven intermetallic phases of the Gd-Ni binary system were measured by a calorimetric method involving dissolution of the compounds in molten Al. These experimental values are compared with model predictions obtained from a tight-binding approach. It is shown that the relatively large difference between the energy levels of the two elements is a dominant factor in the determination of the formation energy. The highly asymmetric shape of the formation energy as a function of composition is discussed considering the particular shape of the density of states of these compounds.

On the modern algebraic representation of general thermodynamic excess properties

Abstract: Strict algebraic evaluation of experimental thermodynamic excess data yields necessarily consistant values of the excess functions H E , S E , and G E . The thermodynamically adapted power (T.A.P)-series may be the most profitable expansion to represent the molar partial and integral excess functions of binary and ternary systems. Detailed expressions of the corresponding approximation formulas are enclosed.

A nematic gap in mixtures of smectics A1 and Ad

Abstract: The effect is tested of the smectic layer spacing ratio, r, on the phase diagram for the binary systems consisting of 80CB (smectic A d ) and one of the twelve compounds of the 5-n-alkyl-2-(4'-isothiocyanatophenyl) dioxane-1,3 homologous series (DBT compounds-smectics A 1 ) has been studied. The stability of the smectic phase in the mixture decreases with increasing r, and for r≥1.4 a nematic gap separating the smectics A 1 and A d is observed. The density, viscosity and scattering of X-rays as a function of temperature are measured and the enthalpy of the phase transitions is determined for the binary system 80CB-4DBT. The nematic phase reveals in the nematic gap a viscosity and structure characteristic for typical nematics. The binary system increases its molar volume as a result of mixing and assumes a maximum in the concentration range x 80CB Influence du rapport r des epaisseurs des couches smectiques des composants d'un melange binaire sur l'allure du diagramme de phases. Les melanges de 80CB et d'un des composes de la serie 5-n-alkyl-2-(4-isothiocyanatophenyl) dioxanne-1,3 sont pris comme exemples

The alloy systems Ln-Sb

Abstract: The phase diagram of Gd-Sb has been constructed using thermal, microstructural and X-ray methods of analysis. In this binary system four compounds are formed: Gd5Sb3, Gd4Sb3 and GdSb2, formation takes place according to peritectic reactions at 1640, 1770 and 780 °C, respectively, GdSb melts congruently at 2130 °C.

The Effect of Molecular Structure on the Formation of Induced Nematic Phases in Binary Mixtures

Abstract: A variety of 4-halophenyl-4′-alkoxybenzoates and 4-alkoxyphenyl-4′-halobenzoates were synthesized, their mesomorphic properties determined and compared with those of the analogous halo anils. The ability of these esters to form induced nematic phases (INPs) in binary mixtures was studied along with a variety of other mesogenic type compounds not having a nematic phase. The contact method was used to screen 258 mixtures for INPs in an attempt to determine which molecular structural features favored formation of this phase in binary mixtures. INPs were observed in many of these mixtures and with a wide variety of structures. Phase diagrams of some of these mixtures were obtained in order to compare the abilities of certain structural features to form INPs. Two types of diagrams were observed. Type I showed a narrow INP range ocurring over most of the composition range between two nearly linear SN and MI curves and was observed only when the two components had similar molecular lengths either short ...

Kerr effect in binary liquid mixtures

Abstract: Measurements of the Kerr constant of several binary liquid mixtures are reported. Most of the cases do not show any additivity of the Kerr effect. The results are in qualitative agreement with a mean-field theory that takes into account the local-field corrections, with the only exception the water–lutidine mixture, which presents a consolution point near room temperature. The long-range concentration fluctuations due to the proximity of the critical point strongly influence the electric birefringence of the mixture.

Binary vapour—liquid equilibria of methanol with sulfolane. Tetraethylene glycol dimethyl ether and 18-crown-6 = Phasengleichgewichte in binären systemen von Methanol mit Sulfolan, Tetraethylenglycoldimethylether und 18-krone-6 Kronenether

Abstract: The activity coefficients of methanol in sulfolane, tetraethylene glycol dimethyl ether (TEGDME) and 18-crown-6 under conditions of equilibrium have been determined in the temperature range 423–503 K and in the pressure range 0.28–3.5 MPa. A minimum in the activity coefficient was found for the methanol—TEGDME and methanol—18-crown-6 solutions.

Vapor‐Liquid Equilibria for Binary and Ternary Mixtures of Benzene, Toluene and n‐Butyraldehyde

Abstract: Isothermal vapor-liquid equilibria were investigated in a pressure controlled, dynamic still with vapor and liquid recirculation. The temperature, the pressure and the compositions of the vapor and the liquid phase were determined for benzene/toluene at 313.15 K and 334.15 K, n-butyraldehyde/benzene at 313.15 K and 343.15 K, n-butyraldehyde/toluene at 313.15 K and 333.15 K and for the ternary mixture at 313.15 K.—The experimental binary VLE-data were reduced: a point-to-point consistency test was performed, with a maximum likelihood method binary parameters were fitted for five popular activity coefficient models. The experimental ternary VLE-data could be used to check the adequacy of gE-models.

Deuteron nuclear magnetic resonance and orientational order in binary mixtures of liquid crystals

Abstract: We have observed deuteron quadrupolar splittings as a function of temperature in a series of binary mixtures of the liquid crystals 4-n-pentyl-4′-cyanobiphenyl (5CB) and 4-n-pentyl-phenylthio-4′-octyloxybenzoate (S5). The 5CB molecule is deuterated at the β-position of the alkyl chain and the S5 in the phenylthiol ring positions. The results have been interpreted in terms of a mean field theory of orientational order in binary mixtures of liquid crystals. Experimental results are in good qualitative agreement with predictions of the theory. The problems of relating order parameters for specific sites in flexible molecules as determined by deuteron nuclear magnetic resonance to the order parameters which enter mean field theories for cylindrically symmetric molecules are discussed.