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Abstract
The experimental data of excess enthalpies for β-carotene/n-alkane+n-alkane/AOT/water systems at 298.15 K are reported. The H E dependence on AOT (sodium bis(2-ethylhexyl) sulfosuccinate) concentration and hydrocarbon chain length was investigated. The excess enthalpy was measured using the flow microcalorimeter UNIPAN type 600.
Abstract
Excess enthalpies of sixteen binary mixtures between one each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) and one of ketone {CH3CO(CH2)nCH3, n=0 to 6 and CH3COC6H5} have been determined at 298.15 K. All the mixtures showed positive excess enthalpies over the whole range of mole fractions. Excess enthalpies of ketone+MMTSO or DMSO increased with increasing the number of methylene radicals in the methyl alkyl ketone molecules. Excess enthalpies of MMTSO+ketone are smaller than those of DMSO+ketone for the same ketone mixtures. The limiting excess partial molar enthalpies of the ketone, H 1 E,∞, in all the mixtures with MMTSO were smaller than those of DMSO. Linear relationships were obtained between limiting excess partial molar enthalpies and the number of methylene groups except 2-propanone.
Excess enthalpies of mixtures of mono-carboxylic acid with dibutylether
Comparison with DISQUAC predictions
and excess enthalpies, H E . Experimental Materials All organic chemicals were high purity reagents purchased from Sigma-Aldrich and were used without further purification. Their properties and
Abstract
A new local composition model NRTLmKW has been used for correlation of 15 binary excess enthalpy data. The data, binary systems formed by hydrocarbons and alkanols, have been selected to give a wide representation of various kinds molecular interactions in solution. Further the model, basing on the results of the correlation, has been used for prediction of excess enthalpy and VLE (vapour-liquid equilibria) in these systems. The obtained results have been discussed from the point of view of intermolecular interactions and some recommendations have been made on the use of the NRTLmKW model for such calculation.
Abstract
A flow microcalorimeter has been used to determine excess enthalpies, H E, at 298.15 K, of binary mixtures of aromatic ether or aromatic ketone(1)+n-heptane(2). All systems investigated are characterized by positive values of H Es. These data along with the data available in the literature on H E, molar excess Gibbs energies, G E, and liquid-vapour equilibria (LVE) are treated in the framework of DISQUAC. Using a set of adjusted interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The occurrence of the ‘hetero-proximity effect’ between C6H5-and-CO-or-O-groups is suggested by the variation of the interchange parameters.
Abstract
The excess molar enthalpies of (1–x)water+x1,4-dioxane have been measured at four different temperatures. All the mixtures showed negative enthalpies in the range of low mole fraction but positive ones in the range of high mole fraction of 1,4-dioxane. Excess enthalpies were increased with increasing temperature except those of at 278.15 K. Partial molar enthalpies have maximum around x=0.13 and minimum around x=0.75. Three different behaviors for the concentration dependence of partial molar enthalpies were observed for all temperature. Theoretical calculations of molecular interactions of three characteristic concentrations were carried out using the molecular orbital method.
Abstract
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.
Abstract
Excess enthalpies of six binary mixtures of CH3 OD+CH3 OH, CH3 OD+CD3 OD, CD3 OD+CH3 OH, C2 D5 OD+C2 H5 OH, C2 D5 OD+C2 H5 OD, C2 H5 OD+C2 H5 OH have been determined over the whole range of mole fractions at 298.15 K in order to know the isotopic effect on hydrogen-bonding accurately, although there are many reports on the differences in the strength of hydrogen-bonding between OH and OD. All excess enthalpies measured are very small and endothermic. The mixtures of CH3 OD+ CH3 OH, and C2 D5 OD+C2 H5 OH showed the largest excess enthalpies among each methanol and ethanol mixtures. The difference of intermolecular interaction between OH and OD in methanol and ethanol was almost same value of (1.820.04) J mol-1 Excess enthalpies of 1,4-dimethylbenzene+1,3-dimethylbenzene and 1,4-dimethylbenzene+1,2-methylbenzene were measured by three different principle calorimeters at 298.15 K in order to know the precision of calorimetry for a small enthalpy change.
-tolunitrile ( A 9 ) and p -fluorobenzonitrile ( F 8 ) are solid at 298.15 K, the excess enthalpies change for ( o + p ) and ( m + p )- A 9 / F 8 cannot be measured directly by mixing the two pure liquids. For this reason, liquid solutions of binary
The excess enthalpy of mixing versus composition was studied at 293.15 K and 303.15 K for some binary mixtures of methanol with pyridine bases. The results are presented in Tables.