The viscosity of triethylamine vapor at low densities and in the saturated vapor phase

For the first time, results of high-precision measurements of the viscosity coefficient of triethylamine vapor at low densities are reported. The relative measurements with an all-quartz oscillating-disk viscometer were carried out along seven isochores at densities from 0.002 to 0.009 mol m⁻³ in the temperature range between 298 and 498 K. The uncertainty is estimated to be ±$\pm$0.2% at ambient temperature, increasing up to ±$\pm$0.3% at higher temperatures. First isothermal values were recalculated from the original experimental data and then evaluated with a first-order expansion for the viscosity, in terms of density. In addition, viscosity values of the saturated vapor were determined at low temperatures. The results are utilized to model the viscosity coefficient of triethylamine vapor at moderately low densities. A so-called individual correlation on the basis of the extended theorem of corresponding states was employed to describe the zero-density viscosity coefficient, whereas the Rainwater–Friend theory was used to represent the initial density dependence expressed as second viscosity virial coefficient.     

Density,viscosity, and saturated vapor pressure of ethyl trifluoroacetate

The properties of ethyl trifluoroacetate (CF₃COOCH₂CH₃) were measured as a function of temperature: density (278.08 to 322.50) K, viscosity (293.45 to 334.32) K, saturated vapor pressure (293.35 to 335.65) K. The density data were fitted to a quadratic polynomial equation, and the viscosity data were regressed to the Andrade equation. The correlation coefficient (R²) of equations for density and viscosity are 0.9997 and 0.9999, respectively. The correlation between saturated vapor pressures and temperatures was achieved with a maximum absolute relative deviation of 0.142%. In addition, the molar evaporation enthalpy in the range of T = (293.35 to 335.65) K was estimated by the Clausius–Clapeyron equation.     

Self-diffusion,mass transfer,and viscosity coefficients for a binary mixture in narrow slit-like pores

The concentration dependences of the dynamic characteristics of a binary mixture in narrow slit-shaped pores of different widths are considered. The local and mean partial self-diffusion, label transfer, mass transfer (mutual diffusion), and shear viscosity coefficients for binary mixtures of various compositions were calculated. The calculation was based on the lattice-gas model in the quasichemical approximation for spherical components with approximately the same size. The calculation of dynamic characteristics took into account collisions between the molecules that determine the direction of their motion. All the kinetic coefficients depend substantially on the mixture density, the direction of motion, and the distance to the pore wall. The effect of the pore width on the calculated dynamic characteristics is considered. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1726—1735, August, 2005.     

Excess properties and vapor-liquid equilibrium data for the chloroform + tetrahydrofuran binary system at 30°C

Excess molar volume, excess viscosity, excess molar enthalpy, and excess molar Gibbs free energy were calculated from the experimental density, viscosity, heat of mixing and vapor-liquid equilbrium data, respectively, for the chloroform + tetrahydrofuran system at 30°C over the complete molar fraction range. The results have been satisfactorily interpreted by assuming the existence of three species A, AB, and B in mutual equilibrium and that these species mix ideally. Values are given for the equilibrium constant and heat of formation of AB.     

The viscosity anomaly of polymer mixture solution in extremely dilute concentration region

The measured reduced viscosity-concentration (η_sp/C-C) curves of compatible PPO/PS incompatible PMMA/PS mixtures with different composition in toluene all deviate linear and reveal downward turn in extremely dilute concentration region. Moreover, with the variation of composition, the η_sp/C-C curve of PS/PMMA/m-xylene solution bends downwards sometimes and bends upwards sometimes in the extremely dilute concentration region. It indicates that such viscosity anomaly should not be attributed simply to incompatibility, but be related to solvent, composition and so on. It is further suggested that, like the single polymer solution, the viscosity anomaly of polymer mixture solution be resulted mainly from the interference of wall effects on viscosity measurement, which could be eliminated quantitatively with a proposed theoretical formula.     

A new continuous dilution vapor liquid equilibrium apparatus: The activity coefficients of benzene and water in cyclohexane at 50°C

A semi-automated apparatus to measure vapor pressure differences between a reference solvent and dilute solutions as a function of concentration at constant temperature is described. Application to the benzene-cyclohexane and benzene-cyclohexane-water systems at high cyclohexane concentrations and low water concentrations is reported. At 50°C in the two component mixture we find ln_B=ln(f _B/X _B f _B ⁰ )=0.408–0.89X_B for 10^–3 B <3×10^–2 and in the three component system, ln_W=6.79±0.04 for 10^–6 W <2×10^–5 and 10^–3 B <3×10^–2.Taken in part from a PhD. thesis, University of Tennessee, 1983.     

Viscosities and densities of tetraalkylammonium bromides in dimethylformamide-water mixtures at 25 and 35°C

Viscosity and desity data for KCl, KBr, Me₄NBr, Et₄NBr, Pr₄NBr, and Bu₄NBr from 0.005 to 3M in aqueous dimethylformamide solutions at 25°C and 35°C are presented. The data for dilute solutions were analyzed by means of the Jones-Dole equation and the ionic B coefficients evaluated. The data for concentrated solutions were analyzed by the Breslau and Miller equation and the effective flow volume, V₃ of the electrolytes obtained as a function of concentration. The limiting effective flow volume, V _e ^o was obtained from the Vand equation in the form used by Eagland and Pilling and it is shown that B=2.5 V _e ^o . With increasing DMF concentration V _e ^o increases for Me₄NBr but decreases for Pr₄NBr and Bu₄NBr. The same effect was observed by increasing temperature. This behavior is explained in terms of the structuring effect of the constituent ions and the effect of DMF on the overall structure of the binary solvent.     

Measurement of splay elastic constant and rotational viscosity of an induced nematic binary system

We investigated the temperature dependence of the splay elastic constant (K₁₁) and rotational viscosity (γ₁) of a binary liquid crystal system comprising 5-trans-n-butyl-2-(4-isothiocyanatophenyl)-1,3-dioxane (4DBT) and 4-cyano-4′-n-undecyloxy-biphenyl (11OCB), exhibiting induced nematic phase. Both the splay elastic constant and rotational viscosity increased following lowering of the temperature. In the vicinity of smectic A-nematic (SmA-N) transition, both the relaxation time and rotational viscosity exhibited a strong pretransitional behaviour. The critical exponent (ν) presented here led to valuable qualitative information about the pre-transitional behaviour of the rotational viscosity data near the SmA-N phase transition. The extracted ν values ranging between 0.336 and 0.352 are in fair agreement with those predicted in the de Gennes model as compared to that by the mean-field model.     

An analysis of the swelling equilibrium of an ionic polymer network in a binary liquid mixture

An equation which represents the swelling equilibrium of an ionic polymer network in a binary liquid mixture is introduced and evaluated numerically. Discontinuous volume changes are obtained with pertinent values of the parameters. From two types of dependence of the degree of ionic dissociation on the composition of a liquid mixture, two types of volume transitions of an ionic gel are illustrated. One is the transition typically seen in acrylamide gels, and the other is a re-entrant transition typical of isopropylacrylamide gels. The selective dissolution factor of two liquids into a swollen polymer network also becomes discontinuous in accordance with the discontinuous volume change. Transition points and the spinodal line are calculated from a generalized form of the free energy change of the swollen gel system. © 1994 John Wiley & Sons, Inc.     

Studies on the viscosity behavior of polymer solutions at low concentrations

Viscosity measurements had been made on poly(vinyl alcohol) (PVA), poly(N-vinyl-2-pyrrolidone) (PVP) and poly(ethylene oxide) (PEO) solutions down to low concentrations. It was found that defined as the flow time of the pure solvent in ideal conditions and obtained practically by extrapolating the flow time of polymer solution t to zero concentration, was not equal to the flow time of the pure solvent t₀ measured. The reduced viscosity η_sp/C determined by (t/t₀-1)/C exhibited either a drastic increase or a significant decrease with dilution, depending upon the polymer solution investigated. On the other hand, η_sp/C determined by was proportional to C even at low concentrations. The anomalous viscosity behavior of neutral polymer solutions at low concentrations, therefore, was due to the incorrect method by which η_sp/C was determined. The detailed experiments indicated that the effective diameter of the viscometer capillary, the surface property of the capillary wall and the additional pressure corresponding to the measurement of t and t₀ for PVA, PVP and PEO solutions were not the same. Taking into account the contact anger and the surface tension of the liquid, together with the geometric parameter of the viscometer, the influence of the additional pressure upon the flow time measurement could be studied quantitatively. The calculation was in a good agreement with the experimental result. According to the method presented in this paper, the thickness of the adsorbed polymer layers on the capillary walls could be determined. It was noted that the thickness of the adsorbed polymer layers on the capillary walls was closely related to the solvent in which the polymer molecules were dissolved. The polymer molecular weight, however, had little or no effect on the thickness of the adsorbed polymer layers on the walls of the viscometer capillary.     

On the analyses of mixture vapor pressure data: the hydrogen peroxide/water system and its excess thermodynamic functions

Reported here are some aspects of the analysis of mixture vapor pressure data using the model-free Redlich-Kister approach that have heretofore not been recognized. These are that the pure vapor pressure of one or more components and the average temperature of the complex apparatuses used in such studies can be obtained from the mixture vapor pressures. The findings reported here raise questions regarding current and past approaches for analyses of mixture vapor pressure data. As a test case for this analysis approach the H2O2-H2O mixture vapor pressure measurements reported by Scatchard, Kavanagh, and Tickner (G. Scatchard, G. M. Kavanagh, L. B. Ticknor, J. Am. Chem. Soc. 1952, 74, 3715-3720; G. M. Kavanagh, PhD. Thesis, Massachusetts Institute of Technology (USA), 1949) have been used; there is significant recent interest in this system. It was found that the original data is fit far better with a four-parameter Redlich-Kister excess energy expansion with inclusion of the pure hydrogen peroxide vapor pressure and the temperature as parameters. Comparisons of the present results with the previous analyses of this suite of data exhibit significant deviations. A precedent for consideration of iteration of temperature exists from the little-known work of Uchida, Ogawa, and Yamaguchi (S. Uchida, S. Ogawa, M. Yamaguchi, Japan Sci. Eng. Sci. 1950, 1, 41-49) who observed significant variations of temperature from place to place within a carefully insulated apparatus of the type traditionally used in mixture vapor pressure measurements. For hydrogen peroxide, new critical constants and vapor pressure-temperature equations needed in the analysis approach described above have been derived. Also temperature functions for the four Redlich-Kister parameters were derived, that allowed calculations of the excess Gibbs energy, excess entropy, and excess enthalpy whose values at various temperatures indicate the complexity of H2O2-H2O mixtures not evident in the original analyses of this suite of experimental results.     

A partial derivatives approach for estimation of the viscosity Arrhenius temperature in N,N-dimethylformamide + 1,4-dioxane binary fluid mixtures at temperatures from 298.15 K to 318.15 K

Excess properties calculated from the literature values of experimental density and viscosity in N,N-dimethylformamide (DMF) + 1,4-dioxane (DO) fluid binary mixtures (from 303.15 to 318.15) K can lead us to test the different correlation equations as well as their corresponding relative functions. Inspection of the Arrhenius activation energy Ea and the enthalpy of activation of viscous flow ?H* shows very close values; here we can define partial molar activation energy Ea₁ and Ea₂ for DMF and DO, respectively, along with their individual contribution separately. Correlation between the two Arrhenius parameters of viscosity in all compositions shows the existence of the primary distinct behaviours separated by particular mole fractions in DMF. In addition, we add that the correlation between Arrhenius parameters reveals interesting Arrhenius temperature (T_A), which is closely related to the vaporisation temperature in the liquid–vapour equilibrium; moreover, the limiting corresponding partial molar properties allow us to estimate the boiling points of the pure components.     

On the visco-elastic and dielectric behaviour of two alcohols and their binary mixture

Inter-molecular and intra-molecular interactions in liquids determine the physical properties of the systems. These interactions are understood through the measurement of these physical properties. These become especially important in the case of alcohols in view of the specific type of interactions involved. Study of the variation of dielectric relaxation time with the viscosity of the medium is relevant in drawing certain quantitative conclusions regarding molecular motion and the inter-molecular forces in liquids, liquid mixtures, dilute solutions and multi-component polar solutes in dilute solution. In the absence of a perfect empirical or theoretical equation for the variation of dielectric relaxation time with viscosity, the experimental investigations on different systems can only give an insight. In the present study, the results of dielectric measurements carried out on pure samples of methyl alcohol and propyl alcohol in dilute solutions in different mixed solvents (benzene?+?paraffin) and on binary mixture (1?:?1) of methyl alcohol?+?propyl alcohol are reported. Different parameters determined are presented and these studies indicate that the dielectric behaviour at microwave frequencies favour the concept of dynamic viscosity and a single visco-elastic relaxation time for the systems under study.     

Surface tension of equilibrium spherical drops in the vapor phase

The properties of metastable and equilibrium drops that occur in the vapor phase and differ in the size and position of the dividing surface are compared. Using an equimolecular dividing surface, it was found that the total free energy and the total mass of the substance in drops of the same size over a broad temperature range differ by not more than 0.3%. A similar comparison for a dividing surface chosen from the equality condition of the moments of forces gives rather similar results. Using the surface where the maximum surface tension is attained as the dividing surface is impossible at low temperatures, because under these conditions, the notion of surface tension has no physical meaning. At high temperatures, the difference between the total mass of the substance for metastable and equilibrium drops does not exceed 0.6%. The calculations were carried out over a broad temperature range on the basis of the lattice-gas model in the quasichemical approximation.     

LiCl-Urea两元体系离子液体的研究

自从1914年第一种离子液体[EtNH3]NO3问世以来,室温离子液体的研究与应用取得了飞速的发展,离子液体以其诸多的优良性能,在催化、有机反应、萃取、以及气相色谱、电化学中得到了广泛地应用。近几年来,多元离子液体体系的研究受到关注。本文报导了由LiCl简单盐和Urea形成的二元体系离子液体,最低共熔点为55℃(LiCl的熔点是608℃,尿素本身的熔点是132℃)。     

Excess molar volumes and isothermal vapor-liquid equilibrium in the binary system 1,1,1-trichloroethane with 1-chlorobutane and with pyridine at 25°C

Densities and vapor-liquid equilibrium were determined for 1-chlorobutane and pyridine with 1,1,1-trichloroethane at 25°C. From the experimental results, excess molal volumes and excess molar Gibbs energies were calculated. Information could be obtained about the possible interactions between the components of both binary systems. The Prigogine-Flory-Patterson theory was applied to calculate excess molar volumes. Liquid activity coefficients were calculated and correlated with different expressions existing in the literature.     

Application of a generalized multiproperty apparatus to measure phase equilibrium and vapor phase densities of supercritical carbon dioxide in n-hexadecane systems up to 26 MPa

A high pressure multi-property apparatus has been developed to measure several thermodynamic and transport properties. In this study the apparatus has been applied to measure phase and volumetric properties of supercritical carbon dioxide in hexadecane from low pressures to the very vicinity of the critical pressure. The experimental data have been successfully fitted over the entire range of the experiment using the Wilson—Wegner expansion including the use of the latter to obtain an improved estimate of the critical pressure and composition.The relation between the occurrence of multiple condensed phases (at some lower temperature) and supercritical extraction is discussed.     

Solubility of carbon dioxide,methane, and ethane in 1-butanol and saturated liquid densities and viscosities

A designed pressure–volume–temperature (PVT) apparatus has been used to measure the (vapor + liquid) equilibrium properties of three binary mixtures (methane +, ethane +, and carbon dioxide + 1-butanol) at two temperatures (303 and 323) K and at the pressures up to 6 MPa. The solubility of the compressed gases in 1-butanol and the saturated liquid densities and viscosities were measured. In addition, the density and viscosity of pure 1-butanol were measured at two temperatures (303 and 323) K and at the pressures up to 10 MPa. The experimental results show that the solubility of the gases in 1-butanol increases with pressure and decreases with temperature. The dissolution of gases in 1-butanol causes a decline in the viscosity of liquid phase. The saturated liquid density follows a decreasing trend with the solubility of methane and ethane. However, the dissolution of carbon dioxide in 1-butanol leads to an increase in the density of liquid phase. The experimental data are well correlated with Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) equations of state (EOSs). SRK EOS was slightly superior for correlating the saturated liquid densities.