Ruisen Lin

Enthalpic interaction of glycine in aqueous glucose and sucrose solutions at 298.15 K

Abstract The dilution enthalpies of glycine in aqueous glucose and sucrose solutions (0–50xa0wt%) at 298.15xa0K were measured calorimetrically. The data were fitted to virial polynomials from which the enthalpic pair interaction coefficients of glycine ( h AA ) were evaluated. The values of h AA in the two aqueous saccharide solutions are all negative and become less negative with increasing saccharide concentrations. The results are discussed in terms of solute–solute and solute–solvent interactions.

Enthalpic interactions of L-alanine and L-serine in aqueous urea solutions

The enthalpies of dilution of L-alanine and L-serine in various aqueous urea solutions have been determined by flow microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients over the whole range of aqueous urea solutions have been calculated according to the excess enthalpy concept. The results were interpreted from the point of view of solute‐solute interactions moderated by solvent effects. # 2000 Elsevier Science B.V. All rights reserved.

Enthalpies of dilution of glycine, l-serine and l-valine in mixtures of water and N,N-dimethylformamide at 298.15 K

Abstract Enthalpies of dilution of glycine, l-serine and l-valine dissolved in mixtures of water and N,N-dimethylformamide (DMF) with mass percent of DMF 0, 5, 15, 25, 35 and 45, respectively, have been measured with an LKB 2277 Bio Activity Monitor at 298. 15xa0K. It was found that pairwise enthalpic interaction coefficients h2 of glycine and l-serine decrease with increasing DMF content in mixed solvents, while the influence of DMF on h2 values of l-valine is not obvious.

Enthalpies of vaporization of petroleum fractions from vapor pressure measurements and their correlation along with pure hydrocarbons

Abstract Enthalpies of vaporization for 58 petroleum fractions were obtained from the measurement of vapor pressures at various temperatures by using an inclined ebulliometer with a pump-like stirrer on the basis of the principle of the quasi-static method. Some existing methods for predicting the enthalpies of vaporization of pure hydrocarbons at the normal boiling temperature were tested to calculate those of the petroleum fractions. It was observed that these methods gave reasonable results only for the lower and middle petroleum fractions and had relatively large deviation for the heavier fractions. A new equation based on the normal boiling temperature, the molecular weight and specific gravity as input parameters has been developed, which is particularly suited for calculation of the enthalpy of vaporization of hydrocarbons (C3–C30) and petroleum fractions in a wide boiling point range from 231.1 to 722.8xa0K.

Homogeneous enthalpic interaction of amino acids in DMF–H2O mixed solvents

Abstract The dilution enthalpies of glycine, l -valine and l -serine in various DMF–H 2 O mixtures have been determined using LKB-2277 flow microcalorimetry at 298.15xa0K. The homogeneous enthalpic interaction coefficients over the whole range have been calculated according to the excess enthalpy concept. The results have been interpreted with the points of view of the structure alteration of the mixed solvents and the association interactions between solvated zwitterionic molecules of different side-chain natures.

Enthalpic interactions of amino acids in aqueous glucose solutions at 298.15 K

Abstract The dilution enthalpies of l -alanine and l -serine in various aqueous glucose solutions have been determined using LKB-2277 flow microcalorimetry at 298.15xa0K. The homogeneous enthalpic interaction coefficients over the whole range of aqueous glucose solutions have been calculated according to the excess enthalpy concept. The results were interpreted from the point of view of solute–solute interactions involved by solvent effects.

A new flow calorimeter for the determination of the isobaric heat capacity of vapors

Abstract A new flow calorimeter has been constructed to determine the isobaric heat capacity of vapors, especially multicomponent vapors. The calorimeter is capable of operation up to 673 K and 20 MPa. A novel design encloses the innermost part of the calorimeter within a double set of thick-wall, aluminum shields, replacing the traditional constant temperature bath, to minimize heat loss and precisely control the calorimeter temperature. An upper copper block within the outer shield is used to preheat the fluid while a lower copper block within the inner shield further heats the fluid to the operating temperature. Such a structure and temperature-controlling arrangement allow easy component replacement and operation. The apparatus was tested by determining the heat capacity of benzene and the benzene-carbon tetrachloride binary system at atmospheric pressure with an experimental error of less than 0.7%. Results for the two binary systems benzene-chloroform and benzene-acetone at 101.3 kPa and about 515.0 K are also given.

Excess enthalpies of seven binary liquid systems

Abstract A Martin-type isothermal displacement calorimeter was constructed for the determination of excess enthalpies of binary mixtures. Seven binary liquid systems of cyclohexane + benzene, + n -hexane, ethanol + benzene, n -butanol + methyl acetate, + ethyl acetate, + n -propyl acetate and + n -butyl acetate were investigated.

Thermodynamics of dissociation of glycine in aqueous ethanol and urea solutions

The dissociation enthalpies of glycine in aqueous ethanol and urea solutions have been determined at 298.15 K by LKB-2277 BioActivity Monitor. Combined with the corresponding Gibbs free energies, the dissociation entropies have been calculated. The results have been interpreted with the point of view of structure alteration of the two solvents.

The vapor heat capacities of acetone-chloroform, benzene-carbon tetrachloride and benzene-ethanol binary mixtures

The vapor heat capacities of acetone-chloroform, benzene-carbon tetrachloride and benzene-ethanol binary mixtures as a function of temperature and composition have been measured under atmospheric pressure in a multicomponent vapor flow calorimeter. It was found that the heat capacities of benzene-carbon tetrachloride vapors display ideal behavior, while those of acetone-chloroform vapors demonstrate positive deviation and those of benzene-ethanol vapors, negative deviation from the ideal linear additive values. These phenomena are explained and discussed.