Excess volumes and excess enthalpies of cyclohexanone with alkanes,benzene, toluene and tetrachloromethane at 298.15 K

Excess volumes and excess enthalpies have been measured for binary liquid mixtures of cyclohexanone with n-hexane, n-heptane, 2,2,4-trimethylpentane, benzene toluene and tetrachloromethane at 298.15 K. The results have been discussed in terms of the difference in molecular shape and specific interactions between unlike molecules. The Prigogine—Patterson—Flory equation of state theory has been used to evaluate the free volume and interactional contributions of the excess properties, and to predict excess volumes and excess enthalpies. The calculated values of V^E and H^E are in qualitative agreement with the experimental data in all the systems.     

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.     

Excess molar enthalpies at 298.15 k of the binary mixtures

We have determined the excess molar enthalpies H _m ^E at 298.15 K and normal atmospheric pressure for the binary mixtures containing tert-butyl methyl ether (MTBE)+(methanol, ethanol, 1-propanol, 1-pentanol) using a Calvet microcalorimeter. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isobaric vapor–liquid equilibria for mixtures of acetone,ethanol, and 2,2,4-trimethylpentane at 101.3 kPa

Isobaric vapor–liquid equilibrium (VLE) data were determined at the pressure of 101.3 kPa for binary and ternary systems composed of acetone, ethanol, and 2,2,4-trimethylpentane (isooctane). Minimum boiling azeotropes were found in the acetone + 2,2,4-trimethylpentane and ethanol + 2,2,4-trimethylpentane systems. Azeotropic behavior was not found for the ternary system. Thermodynamic consistency tests were performed for all VLE data. The activity coefficients of the binary mixtures were satisfactorily correlated as function of the mole fraction using the Wilson, NRTL, and UNIQUAC models. The models with their best-fitted parameters were used to predict the ternary vapor–liquid equilibrium. The Wilson model appears to yield the best prediction in boiling temperatures.     

Excess enthalpies and excess heat capacities of the binary mixtures of acetonitrile,dimethylformamide, and benzene at 298.15 K

Excess enthalpies and excess isobaric heat capacities of binary mixtures consisting of acetonitrile, dimethylformamide and benzene were measured at 298.15 K. Excess enthalpy of acetonitrile + benzene is positive and that of acetonitrile + dimethylformamide is negative. That of dimethylformamide + benzene is positive and nearly equals to zero as shown in the previous report [1]. Excess heat capacities of acetonitrile + benzene and benzene + dimethylformamide change sign from negative to positive with increase of benzene. That of acetonitrile + dimethylformamide is not simple. It is slightly positive near both ends of mole fraction and not so large negative in the middle of mole fraction. The curve tends to flatten in that region.

---

Zusammenfassung An binären Gemischen aus Acetonitril, Dimethylformamid und Benzol wurden bei 298.15 K die Überschußenthalpien und die isobaren Überschußwärmekapazitäten gemessen. Die Überschußenthalpie von Acetonitril + Benzol ist positiv, die von Acetonitril + Dimethylformamid ist negativ. Die Überschußenthalpie ist bei Dimethylformamid positiv und wie bereits berichtet [1] annähernd Null. Die Überschußwärmekapazität von Acetonitril + Benzol und Benzol + Dimethylformamid wechselt bei Zunahme von Benzol das Vorzeichen von negativ zu positiv. Die von Acetonitril + Dimethylformamid ist nicht einfach. An beiden Enden der Molenbruchskaie ist sie leicht positiv und nicht allzu negativ in der Mitte der Molenbruchskale. Die Kurve flacht in dieser Region ab.

     

The enthalpies of solution and solvation of glycine in mixed water-formamide solvents at 298.15 K

The enthalpies of solution (ΔH _sol ^o ) of glycine in aqueous formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were determined by calorimetry at 298.15 K over the concentration range x ₂=0–0.3 mole fractions. The enthalpies of glycine solvation (ΔH _solv ^o ) and transfer from water to mixed solvents (ΔH _tr ^o ) were calculated. The ΔH _sol ^o =f(x ₂) dependences for glycine in water-N-and water-N,N-substituted amide mixtures had extrema and, in water-formamide mixtures, this dependence was a smooth function, whose values changed in the opposite direction. The enthalpy coefficients of pair glycine-amide interactions were calculated. The interrelation between the enthalpy characteristics of solution, transfer, and solvation of glycine and the structure and physicochemical characteristics of solvents, on the one hand, and the composition of mixtures, on the other, was revealed.     

The enthalpies of solution of DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (298.15 K) of DL-α-alanine in water-organic solvent mixtures were measured at organic component concentrations x ₂ = 0–0.4 mole fractions. The organic solvents used were acetonitrile (ACN), formamide (FA), N,N-dimethylformamide (DMFA), and N,N-dimethylsulfoxide (DMSO). The standard enthalpies of solution Δ_sol H ^o, solvation Δ_solv H ^o, and transfer (Δ_tr H ^o) of DL-α-alanine from water to mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics was considered. The solution of DL-α-alanine in the mixtures studied was endothermic over the whole range of organic component concentrations. The Δ_sol H ^o, Δ_tr H ^o, and Δ_solv H ^o values as functions of x ₂ can pass extrema (DMSO and DMFA), be almost independent of mixed solvent composition (FA), or be exothermic and monotonic functions (ACN). The enthalpy coefficients of pair interactions (h _xy ) between DL-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft equation was used to correlate the h _xy values with the properties of organic solvents.     

Excess heat capacities at T=298.15 K and excess enthalpies at T=293.15 and 298.15 K of aqueous solution of 2-methoxyethanol

Excess isobaric heat capacities of mixture (2-methoxyethanol+water) were measured at T=298.15 K and excess enthalpies at T=293.15 and 298.15 K. Excess enthalpies were extremely exothermic, up to -1290 J mol^-1 atT=293.15 K and -1240 J mol^-1 at T=298.15 K. Excess isobaric heat capacities were positive and very large, approximately 9 J K^-1 mol^-1 at the maximum. In contrast to the data reported by Page and coworkers, the excess heat capacity data were positive in the entire composition range and there was no change in their signs. Consistently, no crossing was found between the curves of excess enthalpies at T=298.15 and 293.15 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

Excess enthalpies of 2-propanol + cyclohexane and 2-propanol + benzene + cyclohexane at 298.15 K

With an isothermal dilution calorimeter excess enthalpies have been determined at 298.15 K for 2-propanol + cyclohexane and 2-propanol + benzene + cyclohexane mixtures. The results are fitted with an associated-solution model. Predicted excess enthalpies for the ternary mixture agree well with the experimental results.     

Vapor–liquid equilibria for binary and ternary mixtures of ethanol, 2-butanone,and 2,2,4-trimethylpentane at 101.3 kPa

Vapor–liquid equilibrium (VLE) at 101.3 kPa have been determined for the ternary system ethanol + 2-butanone + 2,2,4-trimethylpentane (isooctane) and its constituent binary systems: ethanol + 2,2,4-trimethylpentane, ethanol + 2-butanone, and 2-butanone + 2,2,4-trimethylpentane. Minimum boiling azeotropes were observed for all these binary systems. No azeotropic behavior was found for the ternary system. Thermodynamic consistency tests were performed for all VLE data. The activity coefficients of the binary mixtures were satisfactorily correlated with the Wilson, NRTL, and UNIQUAC models. The models with their best-fitted binary parameters were used to predict the ternary vapor–liquid equilibrium.     

Excess enthalpies for the systems acetonitrile-benzene-tetrachloromethane and acetonitrile-dichloromethane-tetrachloromethane at 298.15 K

Nagata, I., Tamura, K. and Tokuriki, S., 1982. Excess enthalpies for the systems acetonitrile-benzene-tetrachloromethane and acetonitrile-dichloromethane-tetrachloromethane at 298.15 K. Fluid Phase Equilibria, 8: 75-86Excess enthalpies at 298.15 K are reported for the binary mixtures acetonitrile-benzene, acetonitrile-tetrachloromethane, benzene-tetrachloromethane, acetonitrile-dichloromethane and dichloromethane-tetrachloromethane, and for the ternary mixtures acetonitrile-benzene-tetrachloromethane and acetonitrile-dichloromethane-tetrachloromethane. The results are analysed by means of an associated-solution theory which includes two types of self-association for acetonitrile, the formation of binary complexes CH₃CN·C₆H₆, CH₃CN·CH₂Cl₂ and C₆H₆·CCl₄, and a physical-contribution term expressed by the NRTL equation.     

Microcalorimetric determination of enthalpies of solution of methyl alkanes in glacial acetic acid

An empirical equation H _{s, m}=0.84n gives the enthalpy of solution of 30 branched, linear and cyclic alkanes in glacial acetic acid. The parametern is an effective carbon number which expresses the number of carbon atoms in the longest chain plus one half of the pendant methyl groups.     

The enthalpies of dilution of pyridine and methylpyridine at 298.15 K

The enthalpies of dilution of aqueous solutions for pyridine and methylpyridine isomers have been determined with a 2277-Thermal Activity Monitor at 298.15 K. The results have been treated using the excess function concept and homotactic interaction coefficients have been obtained. The homotactic enthalpic pairwise interaction coefficients are discussed qualitatively in terms of substitution effects of methyl group introduced into the pyridine ring.     

Excess molar volume of dimethyl carbonate +p-xylene + n-decane at 288.15 and 298.15 k

Densities for dimethyl carbonate + p-xylene + n-decane ternary system, at 288.15 and 298.15 K and at atmospheric pressure, were measured. The corresponding excess molar volumes were calculated from the experimental data and were fitted by means of Cibulka equation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase equilibrium for the systems diisopropyl ether,isopropyl alcohol + 2,2,4-trimethylpentane and +n-heptane at 101.3 kPa

Consistent vapour–liquid equilibrium data for the ternary systems diisopropyl ether + isopropyl alcohol + 2,2,4-trimethylpentane and diisopropyl ether + isopropyl alcohol + n-heptane are reported at 101.3 kPa. The vapour–liquid equilibrium data have been correlated by Wilson, NRTL and UNIQUAC equations. The ternary systems do not present ternary azeotropes.     

Adsorption of benzene,toluene, ethylbenzene and p-xylene by NaOCl-oxidized carbon nanotubes

Multiwalled carbon nanotubes (CNTs) were oxidized by sodium hypochlorite (NaOCl) solution and were employed as adsorbents to study their characterizations and adsorption performance of benzene, toluene, ethylbenzene and p-xylene (abbreviated as BTEX) in an aqueous solution. The physicochemical properties of CNTs such as purity, structure and surface nature were greatly improved after oxidation, which significantly enhanced BTEX adsorption capacity. The adsorption capacity of CNT(NaOCl) increased with contact time and initial adsorbate concentration, but changed insignificantly with solution ionic strength and pH. A comparative study on the BTEX adsorption revealed that the CNT(NaOCl) had better BTEX adsorption as compared to CNTs and granular activated carbon. This suggests that the CNT(NaOCl) are efficient BTEX adsorbents and that they possess good potential for BTEX removal in wastewater treatment.     

Microcalorimetric determination of displacement adsorption enthalpies of protein refolding on a moderately hydrophobic surface at 308 K

Both microcalorimetric determination of displacement adsorption enthalpies ΔH and measurement of adsorbed amounts of guanidine – denatured lysozyme (Lys) refolding on the surface of hydrophobic interaction chromatography (HIC) packings at 308 K were carried out and compared with that at 298 K. Study shows that both temperature and concentration of guanidine hydrochloride (GuHCl) affect the molecular mechanism of hydrophobic interaction of protein with adsorbent based on the analysis of dividing ΔH values into three kinds of enthalpy fractions. The adsorption in higher concentrations of GuHCl (>1.3 mol L^–1) at 308 K is an enthalpy-driving process, and the adsorption under other GuHCl concentrations is an entropy-driving process. The fact that the Lys denatured by 1.8 mol L^–1 GuHCl forms a relatively stable intermediate state under the studied conditions will not be changed by temperature.     

Dissolution enthalpies of L-proline and its interactions with methanol, 2-propanol,ethylene glycol,and glycerin in aqueous solution at 298.15 K

The dissolution enthalpies of L-proline in mixtures of water with methanol, 2-propanol, ethylene glycol, and glycerin were measured calorimetrically at 298.15 K. The enthalpy coefficients of the interaction of proline with alcohols in aqueous solutions were determined. The enthalpy coefficients of the pair interaction of proline and glycine with alcohols were shown to be directly proportional.