Prediction of vapor-liquid equilibrium from excess enthalpy data for binary ether +n-alkane or cyclohexane mixtures

Vapor liquid equilibrium (VLE) is successfully predicted from excess enthalpy H^E data for binary ether + n-alkane or cyclohexane mixtures. Parameters for the continuous linear association model (CLAM) and for the UNIQUAC Model for the excess Gibbs energy G^E were determined from H^E data measured at a low temperature (ambient temperature). These parameters are used to predict VLE data at low and high temperatures. The dependence of the accuracy of predictions on the set of H^E data chosen to evaluate the parameters and on the model for G^E are discussed.     

Correlation of the prigogine-flory theory with isothermal compressibility and excess enthalpy data for benzene +n-alkane mixtures

Isothermal compressibilitiesκ _T for benzene + n-alkane systems at 25, 35, 45, and 60°C have been used to check the Prigogine-Flory theory using the van der Waals and Lennard-Jones potentials in order to study the energy-volume dependence. The Flory interaction parameter χ₁₂ has also been calculated for those set of systems at four temperatures. The variation of χ₁₂ with the number of carbon atoms in the n-alkane was studied. Three excess functions have been obtained from χ₁₂ for the equimolecular mixture: (?V ^E/?p)_T which is related toκ _T ^E , the excess enthalpy H ^E , and the excess volume V ^E . Except for H ^E theoretical predictions using a Lennard-Jones potential are in good agreement with the experimental data. A similar treatment has been performed for the same set of systems but using H ^E data at 25°C. The theory, using a van der Waals potential, predicts correctly the variation of the three excess functions with the chain length of the n-alkane but using a Lennard-Jones potential results in better agreement for the order in the magnitude of these excess functions.     

Solubilities of 1,2,3-trimethylbenzene and 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene in t-butyl alcohol+water mixtures and hydrophobic interaction

The solubilities of 1,2,3- trimethylbenzene, 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene in mixed solvents of t-butyl alcohol (TBA) and water at 283.15, 288.15, 293.15 and 298.15 K have been determined by spectrophotometry. The mole fractions of TBA [x(TBA)] in the mixed solvent are 0.000, 0.010, 0.020, 0.030, 0.040, 0.045, 0.050, 0.060, 0.080 and 0. 1000. The Gibbs energies of hydrophobie interaction (HI) for the aggregating process of three methane molecules with one benene molecule in the mixed solvent are studied, and the effect of solvent structure and solute aggregating state on the strength of HI is discussed.     

Excess enthalpy,density, and heat capacity for binary systems of alkylimidazolium-based ionic liquids + water

Experimental measurements of excess molar enthalpy, density, and isobaric molar heat capacity are presented for a set of binary systems ionic liquid + water as a function of temperature at atmospheric pressure. The studied ionic liquids are 1-butyl-3-methylpyridinium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Excess molar enthalpy was measured at 303.15 K whereas density and heat capacity were determined within the temperature range (293.15 to 318.15) K. From experimental data, excess molar volume and excess molar isobaric heat capacity were calculated. The analysis of the excess properties reveals important differences between the studied ionic liquids which can be ascribed to their capability to form hydrogen bonds with water molecules.     

Excess enthalpies and excess volumes of 1-nitropropane +, and 2-nitro-propane +, each of several non-polar liquids

Excess molar enthalpies H_m^E and excess molar volumes V_m^E have been measured for xC₃H₇NO₂ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 and 318.15 K; +(1 ? x)C₆H₁₄ (V_m^E only) at 298.15 K; +(1 ? x)p-C₆H₄(CH₃)₂ at 298.15 K; and for xCH₃CH(NO₂)CH₃ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 K; +(1 ? x)C₆H₁₄ at 298.15 K; +(1 ? x)(CH₃)₂CHCH(CH₃)₂ for H_m^E at 318.15 K and for V_m^E at 298.15 K; and +(1 ? x)C₁₆H₃₄ at 298.15 K. The H_m^E′s were determined with an isothermal dilution calorimeter and the V_m^E′s with a continuous-dilution dilatometer. Particular attention was paid to the region dilute in nitroalkane. In general H_m^E is large and positive for (a nitropropane + an alkane), less positive for (a nitropropane + tetrachloromethane), and small for (a nitropropane + benzene) and for (a nitropropane + 1,4-dimethylbenzene). The mixture with hexadecane shows phase separation. V_m^E is large and positive for (1-nitropropane + cyclohexane), less positive for (1-nitropropane + hexane), and S-shaped for (1-nitropropane + tetrachloromethane) with negative values in the 1-nitropropane-rich region. For (1-nitropropane + benzene) and for (1-nitropropane + 1,4-dimethylbenzene) V_m^E is negative. For mixtures with 2-nitropropane the results are similar except that for benzene V_m^E is S-shaped with positive values in the 2-nitropropane-rich region.     

Application of the flory and sanchez-lacombe theories to the excess enthalpy and excess volume of ether + hydrocarbon systems

Excess volume measurements for 2,5-dioxahexane + heptane and + octane, for 3,5-dioxaheptane + heptane and for isopropyl ether + heptane at 298.15 K are reported. The changes in excess volume observed in this work and described in the literature, as well as the reported excess enthalpy data for chain aliphatic ether+alkane systems as a function of composition are discussed in terms of the new Flory and the Sanchez-Lacombe theories. The interaction parameters for this class of mixtures have been correlated with the oxygen-atom surface fraction in the ether molecule.     

Excess molar quantities of (a halogenated n-alkane + an n-alkane) A comparative study of mixtures containing either 1-chlorobutane or 1,4-dichlorobutane

Excess molar volumes V_m^E at 298.15 K were obtained, as a function of mole fraction x, for series I: {x1-C₄H₉Cl + (1 ? x)n-C_lH_{2l + 2}}, and II: {x1,4-C₄H₈Cl₂ + (1 ? x)n-C_lH_{2l + 2}}, for l = 7, 10, and 14. 10, and 14. The instrument used was a vibrating-tube densimeter. For the same mixtures at the same temperature, a Picker flow calorimeter was used to measure excess molar heat capacities C_{p, m}^E at constant pressure. V_m^E is positive for all mixtures in series I: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.277 for l = 7, 0.388 for l = 10, and 0.411 for l = 14. For series II, V_m^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆} is small and S-shaped, the maximum being situated at x_max = 0.178 with V_m^E(x_max)/(cm³ · mvl^?1) = 0.095, and the minimum is at x_min = 0.772 with V_m^E(x_min)/(cm³ · mol^?1) = ?0.087. The excess volumes of the other mixtures are all positive and fairly large: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.458 for l = 10, and 0.771 for l = 14. The C_{p, m}^Es of series I are all negative and |C_{p, m}^E| increases with increasing l: at x = 0.5, C_{p, m}^E/(J · K^?1 · mol^?1) is ?0.56 for l = 7, ?1.39 for l = 10, and ?3.12 for l = 14. Two minima are observed for C_{p, m}^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆}. The more prominent minimum is situated at x′_min = 0.184 with C_{p, m}^E(x′_min)/(J · K^?1 · mol^?1) = ?0.62, and the less prominent at x″_min = 0.703 with C_{p, m}^E(x″_min)/(J · K^?1 · mol^?1) = ?0.29. Each of the remaining two mixtures (l = 10 and 14) has a pronounced minimum at low mole fraction (x_min = 0.222 and 0.312, respectively) and a broad shoulder around x = 0.7.     

High temperature enthalpy and heat capacity of GaN

The heat capacity and the heat content of gallium nitride were measured by calvet calorimetry (320-570 K) and by drop calorimetry (670-1270 K), respectively. The temperature dependence of the heat capacity in the form C_pm=49.552+5.440×10⁻³T−2.190×10⁶T⁻²+2.460×10⁸T⁻³ was derived by the least squares method. Furthermore, thermodynamic functions calculated on the basis of our experimental results and literature data on the molar entropy and the heat of formation of GaN are given.     

Excess enthalpies,heat capacities,and excess heat capacities as a function of temperature in liquid mixtures of ethanol + toluene,ethanol + hexamethyldisiloxane,and hexamethyldisiloxane + toluene

The heat capacities of liquid ethanol, toluene, and hexamethyldisiloxane, and of 14 binary mixtures of these were measured at atmospheric pressure at a series of temperatures between 298 and 348 K. In addition, the excess enthalpy was measured for each of the 14 mixtures at room temperature and corrected with the aid of the heat capacities to 298.15 K. The results were represented by empirical equations of a polynomial form. From these equations, the excess heat capacity was derived and the excess enthalpy was calculated, and fitted to equations, as a function of composition at temperatures between 298 and 348 K. All the mixtures are non-ideal as evidenced by the substantial excess enthalpy. The excess enthalpy for the mixtures containing ethanol showed a strong positive temperature dependence, while the variation of temperature between 298 and 348 K had little effect on the excess enthalpy of toluene + hexamethyldisiloxane.     

Standard enthalpy and heat capacity of solid tin telluride

The published data on the heat capacity of tin telluride were analyzed. The C _p values were demonstrated to be consistent only at temperatures below 56 K. Some data on the heat capacity of SnTe within 80–453 K were found to differ significantly. The heat capacity C _p was measured on a DSM-2M calorimeter within a temperature range of 350–600 K and other thermodynamic functions of tin telluride were calculated.     

The enthalpy and heat capacity characteristics of the water-N,N-dimethylpropyleneurea system

A variable-temperature isothermic-shell calorimeter was used to measure the heat effects of dissolution of N,N-dimethylpropyleneurea (DMPU) in the water-N,N-dimethylpropyleneurea system at 298 and 313 K over the interval of compositions x ₂ = 0−0.1 mole fractions. The partial molar enthalpies of mixture components and the enthalpies and heat capacities of mixing were calculated. The results were compared with the data on water-amide systems. The exothermic effect of mixing of nonelectrolytes with water was found to increase in the series dimethylformamide < dimethylacetamide ∼ DMPU < hexamethylphosphorotriamide (HMPT). The McMillan-Mayer formalism was used to determine the enthalpy and heat capacity parameters of pair and three-particle interactions between DMPU molecules in water. The behavior of DMPU in water was to a substantial extent determined by hydrophobic interactions between nonpolar molecule moieties. This interaction was, however, noticeably weaker than in solutions of HMPT.     

Excess volume of mixing of some electron-donating hydrocarbons with an electron-accepting liquid 1,2,4-trichlorobenzene

The excess volume of mixing of some electron-donating aromatic hydrocarbons like benzene, toluene,p-xylene, and mesitylene with an electronaccepting liquid 1,2,4-trichlorobenzene have been measured at 30°C. The results indicate that the interaction between the components increases as the electron-donating power of the hydrocarbons increases. The V _m ^e values are related to the ionization potentials of the hydrocarbons.     

Excess volumes and excess heat capacities of nitromethane+(1-propanol or 2-propanol)

Densities and heat capacities of binary mixtures containing nitromethane+(1-propanol or 2-propanol) were determined at the temperatures (288.15, 293.15, 298.15, and 308.15) K and atmospheric pressure, over the whole composition range. Excess molar volumes and excess molar isobaric heat capacities were calculated from the results thus obtained. The effect of specific interactions on the excess properties, and the dependence on the position of the OH group in the alkanol, are analysed.     

Predictions of solvation and vaporization enthalpies. 1.n-alkane +n-alkane solutions

A simple method for the calculation of the enthalpy of solvation is presented and demonstrated for 35 n-alkane + n-alkane solutions at 25°C. There is a good agreement between the predicted and experimental values. The calculation was based on the separation of the solvation enthalpy into the cavity formation and solute-solvent interaction contributions. The former term was determined from the activation enthalpy of the solvent viscous flow and solute molar volume while the latter on the basis of the dispersion energy using van der Waals diameters for n-propyl group. The procedure was also successful in prediction of the vaporization enthalpy of C₅–C₁₇ n-alkanes.     

Excess volume of mixing and excess enthalpies of mixing of ethyl iodide + aromatic hydrocarbons at 25°C

The excess volumes and enthalpies of mixing of binary mixtures of ethyl iodide with benzene, toluene, o-xylene, m-xylene and p-xylene have been measured experimentally over the whole composition range at 25°C. Qualitatively the data have been explained on the basis of electron donoracceptor interactions between the ethyl iodide and aromatic hydrocarbons and also on the loss of favorable orientational order of the pure components. Flory's theory correctly predicts the sign and to some extent magnitude of the V _E and H ^E values.     

New experimental heat capacity and enthalpy of formation of lithium cobalt oxide

The heat capacity of LiCoO₂ (O3-phase), constituent material in cathodes for lithium-ion batteries, was measured using two differential scanning calorimeters over the temperature range from (160 to 953) K (continuous method). As an alternative, the discontinuous method was employed over the temperature range from (493 to 693) K using a third calorimeter. Based on the results obtained, the enthalpy increment of LiCoO₂ was derived from T = 298.15 K up to 974.15 K. Very good agreement was obtained between the derived enthalpy increment and our independent measurements of enthalpy increment using transposed temperature drop calorimetry at 974.15 K. In addition, values of the enthalpy of formation of LiCoO₂ from the constituent oxides and elements were assessed based on measurements of enthalpy of dissolution using high temperature oxide melt drop solution calorimetry. The high temperature values obtained by these measurements are key input data in safety analysis and optimisation of the battery management systems which accounts for possible thermal runaway events.     

Excess heat capacities and excess molar enthalpies of the mixtures containing tetrahydropyran,piperidine and cyclic alkanones

Journal of Thermal Analysis and Calorimetry - In the present study, molar heat capacities, $$\left( {C_{\text{P}}^{{}} } \right)_{123}$$ , at T/K&nbsp;=&nbsp;293.15–308.15&nbsp;K...