The excess enthalpy of (tetrachloromethane + carbon disulphide) and (tetrachloromethane + dichloromethane) over a range of temperatures and pressures

Measurements of the excess molar enthalpy of (tetrachloromethane + carbon disulphide) and (tetrachloromethane + dichloromethane) have been made using an isothermal high-pressure flow calorimeter. The measurements for (tetrachloromethane + carbon disulphide) cover the range 283.15 to 323.15 K at pressures between 0.1 and 30 MPa. The excess molar enthalpies for (tetrachloromethane + dichloromethane) are reported at 298.15 K at 0.1, 15, and 30 MPa, and at 323.15 K at 0.2 MPa. The thermodynamic consistency of the results is shown by deriving the temperature dependence of the excess molar Gibbs free energy from them and comparing with published experimental values.     

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.     

Thermodynamics of liquid mixtures of krypton+ethane

The total vapour pressure, the excess Gibbs energy Q^E (at 115.77 K), the excess enthalpy H^E (at 117.0 K) and the excess molar volume V^E (at 115.77 K) are reported for liquid mixtures of krypton and ethane. The results are interpreted in the light of some recent statistical theories of liquid mixtures.     

DSC Studies of the Effects of Cisplatin and Transplatin on G-Actin

The effects of cisplatin and its trans isomer transplatin on the thermal denaturation of G-actin were studied with a Micro DSC-III differential scanning calorimeter. The denaturation enthalpy of G-actin was found to be 12 J g^–1, and the denaturation temperature was 328 K. The thermal denaturation curve showed that increasing cisplatin concentration decreased the enthalpy change. However, after the ratio of cisplatin to G-actin attained 8:1 (mol:mol), the denaturation enthalpy no longer decreased. Transplatin decreased the enthalpy change more rapidly. In contrast with cisplatin, the denaturation peak at 328 K disappeared, and a strong exothermic peak appeared at 341 K when the ratio of transplatin to G-actin was 8:1 (mol:mol). The enthalpy change was 75 J g^–1, which is far in excess of the range of weak interactions. This strong exothermic phenomenon probably reflects the agglutination of protein. The effects of cisplatin and transplatin on the number of the free thiol groups of G-actin are discussed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of NaCl on the excess enthalpies of binary liquid systems

The excess molar enthalpies h^E₁₊₂₃ of ethanol+(water+NaCl), benzylalcohol+(water+NaCl), and cyclohexane+(methanol+NaCl) were measured at 298.15 K, those of methanol+(water+NaCl) at 298.15 and 323.15 K. An LKB flow microcalorimeter was used and a special flow-mix cell was developed with regard to the corrosive electrolyte solutions. Knowing the integral enthalpy of solution and the solution enthalpy at infinite dilution for a salt (3) in a solvent (2), the molar excess enthalpy h^E₁₂₃ can be calculated.     

Influence of pressure and temperature on mixing properties of Ar-Kr mixtures

The mixing properties or equimolar Ar-Kr mixtures are studied by Monte Carlo calculations in the isobaric-isothermal ensemble and by the van der Waals one-Fluid model. Results of excess volume and enthalpy at T = 300 K calculated by both methods are compared: these are in close agreement for excess volume while the conclusion appears less clear in the case of excess enthalpy.     

Excess enthalpy of ternary mixture for diamine+heptane+cyclohexan

The excess molar enthalpy of ternary mixture for 3-diethylaminopropylamine+heptane+cyclohexane were measured using a Calvet microcalorimeter at 303.15 K. Empirical equations, Redlich-Kister, Tsao-Smith, and Kohler and group contribution models, UNIFAC (modified version) and DISQUAC have been applied. A reasonable representation of ternary data is obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

等温稀释型量热计的建立和过量焓的测定

本文建立了一套等温稀释型量热计, 该量热计可用于吸热型体系过量焓的测定,量热计灵敏度为2μV.J^-^1, 恒温精度为±8*10^-^3K。经环己烷-苯体系和环己烷-正己烷体系在298.15K时标定, 精确度在15%以内, 测定了缔合体系在乙醇 -苯体系303.15K时溶液的过量焓。     

Excess enthalpy of the system chloroform + carbon tetrachloride and a thermodynamic evaluation of its state dependence

Siddiq, M.A. and Lucas, K., 1984. Excess enthalpy of the system chloroform + carbon tetrachloride and a thermodynamic evaluation of its state dependence. Fluid Phase Equilibria, 16: 87–98.Excess molar enthalpies of the system chloroform + carbon tetrachloride have been measured over the entire concentration range at 283.15, 293.15, 303.15, 313.15 and 323.15 K using an isothermal high-pressure flow calorimeter. The effect of pressure was also studied by measuring excess enthalpies at 15 and 30 MPa along the 293.15, 313.15 and 323.15 K isotherms. The temperature dependence of the excess enthalpies was used to calculate vapour-liquid equilibria as a function of temperature. The results are excellent. Further evaluation of the temperature and pressure dependences of the excess enthalpy is discussed.     

Measurement and correlation of excess molar enthalpy at various temperatures acetonitrile + diethylamine or <Emphasis Type="Italic">s</Emphasis>-butylamine mixtures

Summary As a continuation of our studies on excess functions of binary systems containing acetonitrile-amines mixtures, in this work excess molar enthalpy (H_m^E) of acetonitrile+diethylamine or s-butylamine mixtures have been determined as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure using a modified 1455 Parr adiabatic calorimeter. The excess enthalpy data are positive for both systems over the whole composition range. ERAS-Model calculations allowing for self-association and cross-association of the components were performed. The results of the calculations and the influence of temperature and isomers chains on the excess enthalpy behavior are discussed.     

Excess Enthalpies of Binary Mixtures of Propanediamine+Propanediol at 298.15 K

The molar excess enthalpies of 1,2- and 1,3-propanediamine+1,2- and 1,3-propanediol have been determined at 298.15 K by using a twin-microcalorimeter which requires each component liquid 1 to 1.5 cm³ for a series of runs over the whole range of mole fraction. All excess enthalpies are exothermic and large. An equilibrium constant K₁ expressed in terms of mole fractions and standard enthalpy of formation of 1:1 complex have been evaluated by ideal mixtures of momomeric molecules and their associated complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

H2O-NH4Cl system: Thermodynamics and structure of supersaturated (8÷28m) solutions at 298.15 K

Thermodynamic characteristics are determined for supersaturated (8÷28m) aqueous ammonium chloride solutions at 298.15 K: activity as well as partial molar enthalpy, volume, and excess entropy of water, osmotic coefficients, density, and salt hydration numbers. The relative humidity above the solution decreases from 75.6% (8m solution) to 44.7% (28m solution). A directly proportional dependence is found between the enthalpy and entropy characteristics. The negative values of the nonideal portion of the Gibbs energy are due to structural effects (excess entropy). The excess entropy of water has the same value 1.8 J/(mol·K) in supersaturated 12m NaCl and 28m NH₄Cl. The ratio 12/28 = 3/7 is also valid for other “isoentropic” molalities of the said salts.     

Partial molar enthalpy properties and correlation of excess molar enthalpy data of acetonitrile + diethylamine or S-butylamine mixtures at various temperatures and atmospheric pressure

Experimental data of excess molar enthalpy of binary mixtures of acetonitrile + diethylamine or S-butylamine mixtures as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure have been used to calculate excess partial molar enthalpy and partial molar enthalpy of each component as a function of composition as well as partial molar enthalpy properties at infinite dilution. The Flory and Prigogine–Flory–Patterson (PFP) theories were applied to correlate the data. The results of the calculations as well as the influence of temperature and isomers chain on the partial molar enthalpy properties are discussed.     

Excess molar enthalpies of the ternary mixtures: (diisopropyl ether or 2-methyltetrahydrofuran) + cyclohexane + n-heptane at 298.15 K

Microcalorimetric measurements of excess molar enthalpies, at 298.15 K, are reported for the two ternary systems formed by mixing either diisopropyl ether or 2-methyltetrahydrofuran with binary mixtures of cyclohexane and n-heptane. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann and Fried model, using only the physical properties of the components and their binary mixtures.     

Excess molar enthalpies of the ternary mixtures: (diisopropyl ether or tetrahydrofuran)+3-methylpentane+n-dodecane at 298.15 K

Microcalorimetric measurements of excess molar enthalpies, at 298.15 K, are reported for the two ternary systems formed by mixing either diisopropyl ether or tetrahydrofuran with binary mixtures of 3-methylpentane and n-dodecane. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann and Fried model, using only the physical properties of the components and their binary mixtures.     

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.     

Measurements of excess molar enthalpy and excess molar heat capacity of (1-heptanol or 1-octanol)+(diethylamine or <Emphasis Type="Italic">s</Emphasis>-butylamine) mixtures at 298.15 K and 0.1 MPa

Experimental data of excess molar enthalpy (H _m^E) and excess molar heat capacity (C _pm^E) of binary mixtures containing (1-heptanol or 1-octanol)+(diethylamine or s-butylamine) have been determined as a function of composition at 298.15 K and at 0.1 MPa using a modified 1455 Parr solution calorimeter. The excess molar enthalpy data are negative and show parabolic format over the whole composition range; however, the excess molar heat capacity values, whose curves show a S-shape, are positive in the 0.0 to 0.7 molar fraction range and negative between the molar fraction values 0.7 to 1.0. The applicability of the ERAS-model to correlate the excess molar enthalpy data was tested. The calculated data values are in good agreement with the experimental ones. The experimental behavior of H _m^E is interpreted in terms of specific interactions between 1-alkanol and amine molecules.     

Vapour-liquid equilibria in nonpolar mixtures : II. Carbon tetrachloride with alkylbenzenes and n-alkanes at 313.15 K

Góral, M. and Zawadzki, S., 1993. Vapour-liquid equilibria in nonpolar mixtures. II. Carbon tetrachloride with alkylbenzenes and n-alkanes at 313.15 K. Fluid Phase Equilibria, 90: 355-364.

Total vapour pressure measurements using a modified static method at 313.15 K are reported for binary mixtures of CCl₄ with benzene, toluene, o-xylene, p-xylene, hexane, heptane, octane, nonane and decane. The results were correlated with the generalized Redlich-Kister equation for excess Gibbs energy. A comparison with literature vapour-liquid equilibrium data and excess enthalpy was made. Consistency within homologous series was checked. Predictions made using the UNIFAC method and the Hildebrand-Scatchard equation were compared.     

Excess enthalpy in the methanol-water system at 278.15, 298.15 and 323.15 k under pressures of 0.1, 20 and 39 mpa: II. Experimental results and their analytical presentation

Results are presented of flow-calorimetric measurements of excess enthalpy in the methanol-water system at temperatures 278.15, 298.15 and 323.15 K under pressures of 0.1, 20 and 39 MPa. The experimental results are correlated with the use of Redlich-Kister, NRTL and UNIQUAC formulas.     

The thermochemical characteristics of cellulose and its mixtures with water

The heat capacity of cotton microcrystalline cellulose was measured on an adiabatic vacuum calorimeter over the temperature range 80–330 K, and the differential thermal analysis data on the substance were obtained from 80 to 550 K. The enthalpy of cellulose interaction with water was measured at 303 K using a differential microcalorimeter. The standard enthalpies of combustion and formation of microcrystalline cellulose and wood celluloses with different crystallinity indices were determined. The concentration of saturated water solution in microcrystalline cellulose at 273 K was determined calorimetrically from the enthalpy of fusion of the excess water phase.