278.15-313.15 K下糖-水二元体系的介电常数

测定了D-(-)-果糖、D-(+)-葡萄糖、D-(+)-半乳糖、D-(+)-木糖和D-(-)-核糖五种糖的水溶液在不同质量摩尔浓度和不同温度下的介电常数(D). 结果表明, 在一定温度下, 这些糖的水溶液介电常数对数值都随糖浓度的增大而减小; 在一定糖浓度时, 介电常数值随温度升高而减小. 果糖、葡萄糖、半乳糖和木糖水溶液的介电常数(D)随温度的变化均满足关系式: lgD=A1-B1(T-298.15), 而核糖水溶液则符合: lgD=A2-B2(T-298.15)+C2(T-298.15)2. 此外, 这五种糖的水溶液的介电常数与摩尔分数(x)满足关系式: lg(D/D0)=-B3x. 在相同温度和浓度时, 介电常数的大小顺序通常为: 水>半乳糖-水>果糖-水>葡萄糖-水≥木糖-水(而核糖较特殊).     

CaCl2在甘氨酸+水和丙氨酸+水混合溶剂中的活度系数

利用离子选择性电极(ISE)测定了298.15 K时CaCl2在甘氨酸+水和丙氨酸+水混合溶剂中的活度系数. CaCl2的质量摩尔浓度变化范围为0.01～0.20 mol/kg, 氨基酸的质量摩尔浓度变化范围为0.10～0.40 mol/kg. 用Debye-Hückel扩展方程和Pitzer方程进行理论计算得到的活度系数基本一致. 依据McMillan-Mayer理论, 计算了CaCl2从纯水到氨基酸水溶液的标准转移Gibbs自由能, 利用最小二乘法拟合求得了对相互作用参数(gEA)和盐效应常数(ks). 讨论了这两种氨基酸的加入对CaCl2的活度系数、热力学稳定性及盐效应常数的影响.     

混和溶几种氨基酸解离热力学 IV. 278.15-318.15 K下甘氨酸-20Mass%葡萄糖-水体系

EMF measurement of cell (A) and cell (B) Pt, H_2(g,101.325 kPa) |HCl(m_1),20 mass% Glucose, 80 mass% H_2O|AgCl-Ag (A) and Pt, H_2(g,101.325 kPa)|HGCl(m_1),G(m_2), 20 mass% Glucose, 80 mass% H_2O|AgCl-Ag (B) at 5 temperatures ranging from 278.15 to 318.15 K were used to derive (a) the standard emf of the cell with 20 msas% glucose-water. (b) the dissociation constant of glycine by two methods, that is, tradition Debye-Hückel extrapolation and polynomial approximation proposed by us in our former paper. The results obtained from both methods are in good agreement within experiment error.     

278.15～318.15 K下葡萄糖在盐酸中的体积性质

测定了278.15～318.15 K(间隔10 K)下葡萄糖＋HCl＋水三元体系的密度, 计算了葡萄糖在盐酸(浓度0.2～2.1 mol•kg^–1)中的表观摩尔体积V_Φ,G、标准偏摩尔体积V⁰_Φ,G、葡萄糖-HCl在水中的体积对相互作用参数V_EG和标准偏摩尔膨胀系数(∂V⁰_Φ,G/∂T)_p. 结果表明: (1)葡萄糖在盐酸中的表观摩尔体积随葡萄糖和HCl的浓度的增加而线性增大; (2) V⁰_Φ,G随HCl的质量摩尔浓度的增加而线性增大; (3)葡萄糖与HCl在水溶液中的体积相互作用参数V_EG＞0, 但数值对温度变化不甚敏感; (4)葡萄糖在水和盐酸中的V⁰_Φ,G值随实验温度的变化关系均可表示为: V⁰_Φ,G＝a₀＋a₁(T－273.15 K) ^2/3; (5) (∂V⁰_Φ,G/∂T)_p为正值且随温度的升高而减小; 在一定温度下, 其值随HCl浓度的增加而稍稍减小. 糖的水化程度随温度的升高和HCl的浓度的增加而减小. 用结构相互作用模型对葡萄糖与HCl之间的体积相互作用进行了解释.     

Volumetric properties and viscosities of the methyl butanoate + n-heptane + cyclo-octane ternary system at 283.15 and 313.15 K and its binary constituents in the temperature range from 283.15 to 313.15 K

The density and kinematic viscosity of the systems methyl butanoate+cyclo-octane and n-heptane+cyclo-octane were determined at four temperatures in the range 283.15–313.15 K over the whole concentration range. The densities and viscosities of the ternary system methyl butanoate+n-heptane+cyclo-octane were determined at 283.15 and 313.15 K. For the binary systems, the dependence of V^E on composition and temperature was obtained in order to calculate other mixture properties, such as the isobaric thermal expansion coefficients, the temperature coefficients of the molar excess volume and the pressure coefficients of the molar excess enthalpy. In the case of the system n-heptane+cyclo-octane the values of these properties and have been compared with those predicted using the group-contribution model by Nitta et al. in combination with a parameters set available in the literature. Experimental binary and ternary viscosities were correlated for comparison, by means of several empirical and semi-empirical models. Kinematic viscosities were also used to test the predictive capability of the group-contribution model UNIFAC-VISCO. In addition, several empirical equations for predicting ternary properties from only binary results have also been applied.     

Water Activity and Osmotic Coefficients in Solutions of Glycine,Glutamic Acid,Histidine and their Salts at 298.15 K and 310.15 K

From vapor pressure osmometry data, the activity of water, osmotic coefficients and mean ionic activity coefficients of glycine (m=0.006−3.2 mol⋅kg⁻¹), L-histidine (m=0.005−0.23 mol⋅kg⁻¹), L-histidine monohydrochloride (m=0.008−0.63 mol⋅kg⁻¹), glutamic acid (m=0.004−0.05 mol⋅kg⁻¹), sodium L-glutamate (m=0.007−0.6 mol⋅kg⁻¹), and calcium L-glutamate (m=0.008−0.6 mol⋅kg⁻¹) have been obtained in aqueous solutions at 298.15 and 310.15 K. The Pitzer equations and the mean spherical approximation (MSA) are used for theoretical modeling. The results are supplied as reference thermodynamic material for the characterization of more complex molecules such as proteins.     

Densities and Viscosities for the Binary Mixtures (2-Methyl-1-Chloropropane + Isomeric Butanol) at 298.15 and 313.15 K

Abstract

This paper reports excess volumes, V^E , and viscosity deviations, Δ\eta, for binary mixtures of 2-methyl-1-chloropropane with an isomer of butanol at the temperatures 298.15 K and 313.15 K. These properties were obtained from density and viscosity measurements. The results are correlated by means of a Redlich-Kister type equation, and interpreted in terms of molecular interactions. The systems show positive values of V^E except in a short range of compositions for mixtures containing primary butanols (1-butanol at both temperatures and 2-methyl-1-propanol at 298.15 K), whereas Δ\eta presents negative values at both temperatures over the whole composition range.     

Transfer Volumes of Glycine, L–Alanine, and L–Serine from Water to 1,2-Butanediol–Water Mixtures at 298.15 K

Densities of solutions of glycine, L–alanine, and L–serine have been measured by an oscillating-tube densimeter in 1,2-butanediol–water mixtures with 1,2-butanediol mass fractions ranging from 0 to 0.35 at 298.15 K. Apparent molar volumes and limiting partial molar volumes of each amino acid have been used to obtain the corresponding transfer volumes from water to different concentrations of 1,2-butanediol–water mixtures. The transfer volumes are positive for glycine and L–serine, and both positive and negative for L–alanine over the concentration range studied. The results are interpreted in terms of solute–solvent interactions. Substituent effects are also discussed.     

Studies of Activity Coefficients for Ternary Systems: Water + 18-Crown-6 + Alkali Chlorides at 298.15 K

Osmotic vapor pressure measurements have been carried out for three ternary systems, H₂O + 0.2 m 18-crown-6 + LiCl, H₂O + 0.2 m 18-crown-6 + NaCl and H₂O + 0.2 m 18-crown-6 + KCl at 298.15 K using vapor pressure osmometry. Water activities for each ternary system were measured and used to calculate the activity coefficients of 18-crown-6 (18C6) and its salts following the methodology developed by Robinson and Stokes for isopiestic measurements. In the concentration range studied, it was found that (in NaCl and KCl solutions) there is considerable lowering of activity coefficients of one component in the presence of other solutes that has been attributed to the formation of the complexed 18C6:Na⁺ (or 18C6:K⁺) species in solution. The Gibbs energies of transfer of alkali chlorides from water to aqueous 18C6 solutions and that of 18C6 from water to aqueous electrolyte solutions have been calculated. These were further used to evaluate the pair and triplet interaction parameters. The calculation of thermodynamic equilibrium constants using the pair interaction parameter, g _NE (i.e., the nonelectrolyte–electrolyte pair interaction) for the studied complexation of cations yields values which are in good agreement with those reported in literature obtained by using ion-selective potentiometry and calorimetry. The results are discussed in terms of water structural effects, complex formation, and hydrophobic interactions.     

Liquid Densities and Excess Molar Volumes for Binary Systems (Ionic Liquids + Methanol or Water) at 298.15, 303.15 and 313.15 K,and at Atmospheric Pressure

Binary excess molar volumes, V _m ^E, have been evaluated from density measurements, using a vibrating tube densimeter over the entire composition range for binary liquid mixtures of ionic liquids 1-ethyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-butyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [BMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-methyl-3-octyl-imidazolium diethyleneglycol monomethylethersulphate [MOIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+methanol and [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+water at 298.15, 303.15 and 313.15 K. The V _m ^E values were found to be negative for all systems studied. The V _m ^E results are explained in terms of intermolecular interactions and packing effects. The experimental data were fitted by the Redlich-Kister polynomial.     

Liquid-Liquid Equilibria for Water + Nitromethane + (1-Propanol,or + Acetone,or + p-Dioxane) Ternary Systems at 303.15 K

Abstract

Liquid-liquid equilibria, distribution coefficients, and selectivities of ternary systems of the type: (water + K + nitromethane), where Kis 1-propanol, acetone, or p-dioxane, have been determined at (303.15 ± 0.05) K, in order to evaluate the suitability of nitromethane for extracting preferentially the second components from their aqueous solutions. The line data were satisfactorily correlated by the Othmer and obias method, and the plait point coordinates for the three systems were estimated. The experimental data were compared with values calculated using the NRTL and UNIQUAC models, and with those predicted by the UNIFAC group contribution method. This last method predicts qualitative and quantitative behaviour which are in disagreement with experimental results, while the values calculated using the other two models are in agreement but only when the concentration of component K is low. The three ternary systems studied have distribution coefficients higher than unity, and high selectivities. Therefore, nitromethane could be considered as a potential solvent for the extraction of K from its aqueous solutions     

Experimental and predicted viscosities of the binary system (n-hexane + 1,3-dioxolane) and for the ternary system (n-hexane + 1,3-dioxolane + 1-butanol) at 298.15 and 313.15 K

Viscosities of the ternary system n-hexane+1,3-dioxolane+1-butanol and the binary system n-hexane+1,3-dioxolane have been measured at atmospheric pressure at 298.15 and 313.15 K. Viscosity deviations for the binary and ternary systems were calculated from experimental data and fitted to Redlich–Kister and Cibulka equations, respectively. The group contribution method proposed by Wu has been used to predict the viscosity of all mixtures.     

Excess Molar Volumes and Partial Molar Volumes for Binary Mixtures of Water With 1,2-Ethanediol, 1,2-Propanediol,and 1,2-Butanediol at 293.15, 303.15 and 313.15 K

Abstract

From dilatometric method at 293.15,303,15, and 313.15K for binary mixtures of water and 1,2-alkane diols, the excess molar volumes, V^E and the partial molar volumes, V _i of both components at 293.15 K have been obtained as a function of mixtures composition. Excess molar volumes were calculated and correlated by a Redlich-Kister type function in terms of mole fraction. The partial molar volumes have been extrapolated to zero concentration to obtain the limiting values at infinite dilution, V ⁰ _i . All mixtures showed negative values and decreases with the chain length of diols. The values become less negative with increasing temperature. The results are explained in terms of dissociation of the self-associated diol molecules and the formation of aggregates between unlike molecules.     

Heat Capacities and Thermodynamic Properties of a H2O + Li2B4O7 Solution in the Temperature Range from 80 to 356 K

The molar heat capacities of an aqueous Li₂B₄O₇ solution were measured with a precision automated adiabatic calorimeter in the temperature range from 80 to 356 K at a concentration of 0.3492 mol⋅kg⁻¹. The occurrence of a phase transition was determined based on the changes in the curve of the heat capacity with temperature. A phase transition was observed at 271.72 K corresponding to the solid-liquid phase transition; the enthalpy and entropy of the phase transition were evaluated to be Δ H _m = 4.110 kJ⋅mol⁻¹ and Δ S _m = 15.13 J⋅K⁻¹⋅mol⁻¹, respectively. Using polynomial equations and thermodynamic relationship, the thermodynamic functions [H _T −H _298.15] and [S _T −S _298.15] of the aqueous Li₂B₄O₇ solution relative to 298.15 K were calculated in temperature range 80 to 355 K at intervals of 5 K. Values of the relative apparent molar heat capacities of the aqueous Li₂B₄O₇ solution, C _p,φ, were calculated at every 5 K in temperature range from 80 to 355 K from the experimental heat capacities of the solution and the heat capacities of pure water.     

Isopiestic Study of Water + Mannitol(sat) + Sodium Chloride + Ammonium Chloride + Barium Chloride at <Emphasis Type="Italic">T</Emphasis> = 298.15 K and Comparison with the Ideal-Like Solution Model

Isopiestic measurements have been carried out at the temperature 298.15 K for the quinary system (water + mannitol(sat) + sodium chloride + ammonium chloride + barium chloride) saturated with mannitol and its ternary sub-systems (water + mannitol(sat) + sodium chloride), (water + mannitol(sat) + ammonium chloride) and (water + mannitol(sat) + barium chloride). Taking aqueous sodium chloride as reference solutions, osmotic coefficients of the other aqueous solutions were determined. The experimental results show that the isopiestic activities of the quinary system in relation to its ternary sub-systems are in excellent agreement with the ideal-like solution model.     

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.     

Vapour–liquid equilibrium data for the 1,1,1,2 tetrafluoroethane (R134a) + dimethyl ether (DME) system at temperatures from 293.18 to 358.15 K and pressures up to about 3 MPa

Isothermal vapour–liquid equilibrium data have been measured for the binary system R134a + DME at five temperatures between 293.18 and 358.15 K, and pressures between 0.4899 and 2.9442 MPa. The peculiarity of this system is the existence of an azeotrope with a minimum pressure, which disappears at 358.15 K. The experimental method used in this work is of the static-analytic type, taking advantage of two pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in the CENERG/TEP Laboratory. The data were obtained with uncertainties within ±0.02 K, ±0.0001 MPa and ±1% for molar compositions.

The isothermal P, x, y data are well represented with the Redlich and Kwong equation of state using the Mathias–Copeman alpha function and the Huron–Vidal mixing rules involving the NRTL model.     

New p–ρ–T measurements up to 70 MPa for the system CO2 + propane between 298 and 343 K at near critical compositions

The vibrating tube densimeter method along with the Forced Path Mechanical Calibration model, is used to measure the high pressure isothermal p–ρ behavior of the CO₂+propane system along 17 isotherms between 293 and 343 K, at pressures up to 70 MPa. The compositions cover the range of mole fractions from x_CO2=0.45 to 1.0. The uncertainty in temperatures is ±0.015 K. The uncertainties in pressures are ±0.0013 MPa from 0.1 to 15.0 MPa and ±0.010 MPa from 5.0 to 70.0 MPa. The precision of the density measurements is ±0.014 kg m⁻³. The minimum global uncertainty is ±0.204 kg m⁻³, based on the calibration of the densimeter with pure water. A generalized Helmholtz energy model for mixtures is used to check the consistency of the new data with respect to previous p–ρ–T studies of this mixture. The average absolute deviation of our data with respect to the model is 0.64% which is fully consistent with the assessed accuracy.