Excess heat capacities and excess volumes of binary liquid mixtures of chloroform with cyclic ethers at 298.15 K

Molar excess heat capacities at constant pressure, C^E_p, of binary liquid mixtures chloroform + oxolane, chloroform + 1,3-dioxolane, chloroform + oxane, and chloroform + 1,4-dioxane have been determined at 298.15 K from measurements of volumetric heat capacities in a Picker flow microcalorimeter. A precision of ±0.04 J K^?1 mole^? was achieved by using the stepwise procedure. Experimental molar excess heat capacities are compared with values derived from H^E results at different temperatures. Excess molar volumes, V^E, for the same systems at 298.15 K have been determined by measuring the density of the pure liquids and solutions with a high-precision digital flow densimeter.     

Calorimetric effects of short-range orientational order in solutions of benzene or n-alkylbenzenes in n-alkanes

A Picker flow microcalorimeter was used to determine molar excess heat capacities, C^E_p, at 298.15 K, as function of concentration, for the eleven liquid mixtures: benzene+n-tetradecane; toluene+n-heptane, and +n-tetradecane; ethylbenzene+n-heptane, +n-decane, +n-dodecane; and +n-tetradecane; n-propylbenzene +n-heptane, and +n-tetradecane; n-butylbenzene+n-heptane, and +n-tetradecane. In addition, molar excess volumes, V^E, at 298.15 K, were obtained for each of these systems (except benzene+n-tetradecane) and for toluene+n-hexane. The excess volumes which are generally negative with a short alkane, increase and become positive with increasing chain length of the alkane. The excess heat capacities are negative in all cases. The absolute ¦C^E_p¦ increased with increasing chain length of the n-alkane. A formal interchange parameter, C_p12, is calculated and its dependence on n-alkane chain length is discussed in terms of molecular orientations.     

Excess heat capacities and excess volumes of binary liquid mixtures of 1,1,1,-trichloroethane with cyclic ethers at 298.15 K

Measurements of volumetric heat capacities at constant pressure, C_p/V (V being the molar volume), at 298.15 K, of the binary liquid mixtures 1,1,1-trichloroethane + oxolane, +1,3-dioxolane, +oxane, +1,3-dioxane, and +1,4-dioxane were carried out in a Picker-type flow microcalorimeter. Molar heat capacities at constant pressure. C_p, and molar excess heat capacities, C^E_p, were calculated from these results as a function of the mole fraction. C^E_p values for these systems are positive and the magnitude depends on the size of the cycle and on the relative position of the oxygen atoms in the cyclic diethers. The precision and accuracy for C^E_p are estimated as better than 2%. Molar excess volumes, V^E, for the same systems, at 298.15 K, have been determined from density measurements with a high-precision digital flow densimeter. The experimental results of V^E and C^E_p, are interpreted in terms of molecular interactions.     

Excess heat capacities of binary mixtures of carbon tetrachloride with n-alkanes at 298.15 K

A Picker flow microcalorimeter was used to determine molar excess heat capacities C_P^E at 298.15 K for mixtures of carbon tetrachloride + n-heptane, n-nonane, and n-decane. The excess heat capacities are negative in all cases. The absolute value |C_P^E| increases with increasing chain length of the alkane. A formal interchange parameter, c_P12, is calculated and its dependence on n-alkane chain length is discussed briefly in terms of molecular orientations.     

Excess volumes for trichloroethene + benzene, + toluene, + p-xylene, + tetrachloromethane,and + trichloromethane at 303.15 K

Excess volumes V^E for trichloroethene (CCl₂CHCl) + benzene, + toluene, + p-xylene, + tetrachloromethane, and + trichloromethane have been measured at 303.15 K, by direct dilatometry. V^E has been found to be positive for trichloroethene + benzene, and + trichloromethane, and negative for trichloroethene + toluene, and + p-xylene. For trichloroethene + tetrachloromethane V^E is positive at low mole fractions of C₂HCl₃ and negative at high mole fractions.     

Ultrasonic behaviour of methyl methacrylate+hydrocarbon mixtures at 298.15 and 308.15 K

The excess isentropic compressibilities, K_s^E for seven binary mixtures of methyl methacrylate+benzene, +o-xylene, +m-xylene, +p-xylene, +toluene, +ethylbenzene and +cyclohexane were estimated from the measured densities and speeds of sound at 298.15 and 308.15 K. The K_s^E values were large and positive for MMA+cyclohexane and +m-xylene, while they were negative for other mixtures. A qualitative analysis of K_s^E values was made in terms of molecular interactions. The speeds of sound of all the mixtures were also predicted from the free length theory (FLT) and collision factor theory (CFT).     

Mesure des chaleurs de Mélange de duex liquides,sans programmation des débits,avec le microcalorimètre picker à écoulement

A method is proposed for using the Picker microcalorimeter without programmation of the flow rates of the reactant liquids. From the measurements of the three systems (carbon tetrachloride+benzene, +n-heptane and +cyclopentane) it is shown that the excess enthalphy curves obtained point by point are better defined than those obtained directly in the scanning mode, especially in the dilute regions.     

Excess molar enthalpies of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene,and + isobutylbenzene at 303.15 K

Excess molar enthalpies H_m^E of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene, and + isobutylbenzene were measured over the entire composition range at 303.15 K with an LKB flow microcalorimeter. H_m^E values are positive and decrease with increasing chain length of the alkylbenzene.     

Molar heat capacity of binary liquid mixtures: 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane

The molar heat capacity at constant pressure, C_P, of the two binary liquid mixtures 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane were determined at 298.15 K from measurements of the volumetric heat capacity, C_P/V, in a Picker flow microcalorimeter (V is the molar volume). For the molar excess heat capacity, C_P^E, the imprecision of the adopted stepwise procedure is characterized by a standard deviation of about ± 0.05 J K^?1 mole^?1, which amounts to ca. 3% of C_P^E. Literature data on ultrasonic velocities, on molar volumes, and on coefficients of thermal expansion were used to calculate the molar heat capacity at constant volume, C_v, and the isothermal compressibility, β_T, of the pure substances, as well as the corresponding excess quantities C_V^E and (Vβ_T)^E of the binary mixture 1,2-dichloroethane + cyclohexane. A preliminary discussion of our results in terms of external and internal rotational behavior (trans-gauche equilibrium of 1,2-dichloroethane) is presented.     

Excess enthalpies of the liquid systems: 1,2-dichloroethane + n-alkanes or +2,2,4-trimethylpentane

Hahn, G. Svejda, P. and Kehiaian, H.V., 1986. Excess enthalpies of the liquid systems: 1,2-dichloroethane + n-alkanes or +2,2,4-trimethylpentane. Fluid Phase Equilibria, 28: 309-323.Molar excess enthalpies, h^E, at 293.15 K and atmospheric pressure are reported for the binary liquid mixtures of 1,2-dichloroethane + haptane, + decane, + dodecane, + tetradecane, + hexadecane or + 2,2,4-trimethylpentane, all determined by means of a flow microcalorimeter of the Picker-type. These measurements could be reproduced within the experimental limits by calculations according to a quasi-chemical group contribution theory, using constant values for two interchange energy coefficients, C_1,ad (Gibbs energy) and C_2,ad (enthalpy). Fair agreement between the calculated excess heat capacities, e^E_p, and the experimental literature values could be obtained by adjusting a third coefficient, C_3,ad (heat capacity). However, C_3,ad decreases with increasing chain length of the n-alkane. Even with three C_1,ad coefficients the model cannot reproduce the exact shape of the c^E_p versus composition curves. Apparently, not only the terms of an interchange of group surface contacts, but also conformational changes occurring in n-alkanes on mixing, contribute to the excess functions. The set of C_1,ad coefficients reported in this paper should prove useful in predicting phase equilibria in liquid 1,2-dichloroethane + n-alkane mixtures.     

Determination of excess molar enthalpies for the ternary system <Emphasis Type="Italic">p</Emphasis>-xylene+octane+diethyl carbonate

Excess molar enthalpies, H ^E, for the binary mixtures {p-xylene+(1–x) octane}, {x p-xylene+(1–x) diethyl carbonate}, {x octane+(1–x) diethyl carbonate} and the corresponding ternary system {x ₁ p-xylene+x ₂ octane+(1–x ₁–x ₂) diethyl carbonate} have been measured by using a Calvet microcalorimeter at 298.15 K under atmospheric pressure. The experimental H ^E values are all positive for the binary and ternary mixtures over the entire composition range.     

Molar excess enthalpies of cis-decalin + benzene, + toluene, +isooctane and +heptane at 298.15 K

Molar excess enthalpies H^E of cis-decalin + benzene, +toluene, +isooctane and +heptane mixtures have been measured by an LKB flow microcalorimeter at 298.15 K. The experimental results are analyzed using the Flory-Patterson-Prigogine theory. The isomer effect of decalin molecule and the effect of the molecular size and shape of the component molecules are discussed.     

Enthalphy of mixing of bromobenzene with n-alkanes,with cyclohexane,and with benzene

A dynamic flow microcalorimeter of the Picker design was used to measure enthalpies of mixing at 298.15 K and atmospheric pressure of the six binary systems bromobenzene + n-hexane, + n-heptane, + n-nonane, + n-tetradecane, + cyclohexane, and + benzene. Within the homologous series of n-alkane systems, the interaction parameter, h₁₂, calculated from rigid-lattice group contribution theory, decreases weakly with increasing chain length of the alkane. This behavior is quite analogous to that observed with chloro-derivatives of benzene + n-alkane.     

Excess heat capacities and orientational order in systems containing hexadecane isomers of different molecular structure

Using the Picker flow microcalorimeter, excess heat capacities have been obtained at 25°C throughout the concentration range for 2,2-dimethylbutane,n-hexane, and cyclohexane each mixed with a series of hexadecane isomers of increasing degrees of orientational order, as determined by depolarized Rayleigh scattering. The isomers are 2,2,4,4,6,8,8-heptamethylnonane, 6-, 4-, and 2-methylpentadecane, andn-hexadecane. Thec _p ^E values are negative, increasing rapidly in magnitude with increase of orientational order, and are not predicted by the Prigogine—Flory theory which neglects order. Values ofc _p ^E are obtained at 10, 25, and 55°C for cyclohexane +6-, 4-, and 2-methylpentadecane which with other literature data lead to the temperature dependence of the thermodynamic excess functions for cyclohexane solutions of the five C₁₆ isomers. The excess enthalpy and entropy vary with the C₁₆ isomer and with temperature, but the corresponding variation of the excess free energy is small, indicating a high degree of enthalpy-entropy compensation. This is consistent with a rapid decrease with temperature of orientational order in the C₁₆ isomers.     

Excess molar enthalpy of binary mixtures of hexane+ethyl benzene, <Emphasis Type="Italic">o</Emphasis>-xylene, <Emphasis Type="Italic">m</Emphasis>-xylene and <Emphasis Type="Italic">p</Emphasis>-xylene at 298.15 K

Summary This paper reports excess molar enthalpies of the binary systems hexane+ethyl benzene, hexane+o-xylene, hexane+m-xylene and hexane+p-xylene at 298.15 K and atmospheric pressure, over the whole composition range. The data was measured directly using a Calvet microcalorimeter. The excess magnitude was correlated to a Redlich-Kister type equation for each mixture. Also, we will discuss the results for the four mixtures studied here and by comparison with the same binary systems but containing propyl propanoate as first component. Finally, we will correlate our results with the Nitta-Chao and the three UNIFAC theoretical approximations.     

Thermodynamics of molecular interactions in binary mixtures of non-electrolytes. Molar excess volumes

Molar excess volumes, V^E, for pyridine (A) + α-picoline (B), + β-picoline (B) and + γ-picoline (B) and benzene (A) + toluene (B), + o-xylene (B) and + p-xylene (B) and carbon tetrachloride (A) + n-heptane (B) have been measured dilatometrically as a function of temperature and composition and have been utilized to study B—B and B—B—B interactions in the presence of A via the Mayer—McMillan approach. A model has also been presented to account for these B—B and B—B—B interactions. The V^E data at 308.15 K have also been analysed in terms of the “graph theoretical” approach which describes the V^E data well for all these mixtures at 308.15 K. The “graph theoretical” approach has further been extended to successfully evaluate V^E data for a mixture at any temperature, T₂, when the V^E data at T₁ are known.     

Thermodynamics of binary mixtures containing alkynes

Molar excess enthalpiesH ^E of 1-hexyne +n-heptane, +n-decane, +cyclohexane, and +benzene, and of 3-hexyne +n-heptane, +n-decane, +cyclohexane, and +benzene, at 298.15 K and atmospheric pressure were measured with a Picker type flow microcalorimeter. Generally, the 1-hexyne systems are more endothermic than the corresponding 3-hexyne systems, the increment ofH _mas ^E being of the order of 170 to 260 J/mol, which is clearly too large to be accounted for by orientational contributions toH ^E due to the permanent dipole moment of 1-hexyne. It is suggested that other contributions, for example contributions resulting from different conformational behavior of the hexynes, have to be considered.With 2 FiguresDidicated to Prof.H. Nowotny on the occasion of his 65th birthday. Communicated in part at the 2. Ulmer Kalorimetrietage, March 24–25, 1977, Ulm, Germany.     

Excess volumes of mixing of 1,2-dichloroethane and aromatic hydrocarbons

Excess volumes of mixing, V^E, for binary mixtures of 1,2-dichloroethane with benzene, toluene, o^?, m^?, and p-xylenes have been determined at 308.15 K over the complete composition range. V^E is positive for all these mixtures and varies in the order m-xylene >o-xylene >p-xylene > benzene > toluene. The experimental data have been analyzed in terms of the Prigogine's average potential cell model coupled with Balescu's theory. The calculated V^E values do not agree with the corresponding experimental values.     

Intermolecular Interactions in Binary Liquid Mixtures of Styrene with m-, o-, or p-xylene

The densities (ρ), ultrasonic speeds (ν), and refractive indices (n) of binary mixtures of styrene (STY) with m-, o-, or p-xylene, including those of their pure liquids, were measured over the entire composition range at the temperatures 298.15, 303.15, 308.15, and 313.15 K. The excess volumes (V^E), deviations in isentropic compressibilities (Δks), acoustic impedances (ΔZ), and refractive indices (Δn) were calculated from the experimental data. Partial molar volumes (V⁰_?,2) and partial molar isentropic compressibilities (K⁰_?,2) of xylenes in styrene have also been calculated. The derived functions, namely, V^E, Δk_s, ΔZ, Δn, V⁰_?,2, and K⁰_?,2 were used to have a better understanding of the intermolecular interactions occurring between the component molecules of the present liquid mixtures. The variations of these parameters suggest that the interactions between styrene and o-, m-, or p-xylene molecules follow the sequences: p-xylene>o-xylene>m-xylene. Apart from using density data for the calculation of VE, excess molar volumes were also estimated using refractive index data. Furthermore, several refractive index mixing rules have been used to estimate the refractive indices of the studied liquid mixtures theoretically. Overall, the computed and measured data were interpreted in terms of interactions between the mixing components.     

Excess molar enthalpies of the ternary system <Emphasis Type="Italic">p</Emphasis>-xylene+decane+diethyl carbonate

Excess molar enthalpies of the ternary system {x ₁ p-xylene+x ₂decane+(1–x ₁–x ₂)diethyl carbonate} and the involved binary mixtures {p-xylene+(1–x)decane}, {xp-xylene+(1–x)diethyl carbonate} and {xdecane+(1–x)diethyl carbonate} have been determined at the temperature of 298.15 K and atmospheric pressure, over the whole composition range, using a Calvet microcalorimeter. The experimental excess molar enthalpies H _m ^E are positive for all the binary systems studied over the whole composition range. Excess molar enthalpy for the ternary system is positive as well, showing maximum values at x ₁=0, x ₂=0.4920, x ₃=0.5080, H _m,123 ^E=1524 J mol^–1.