Interactions in (l-phenylalanine/l-histidine + 0.01 mol · kg−1 aqueous β-cyclodextrin) systems at T = (293.15, 298.15, 303.15 and 308.15) K

Densities (ρ) and speeds of sound (u) have been measured for (l-phenylalanine + 0.01 mol · kg⁻¹ aqueous β-cyclodextrin) and (l-histidine + 0.01 mol · kg⁻¹ aqueous β-cyclodextrin) systems at T = (293.15, 298.15, 303.15 and 308.15) K using the density and sound velocity Meter DSA 5000 M. The ρ and u values have been utilized to evaluate values of the partial molar volume (${\varphi }_v^{\circ }$), transfer partial molar volume (${\mathrm{\Delta }}_{\text{tr}}{\varphi }_v^{\circ }$), partial molar isentropic compressibility (${\varphi }_k^{\circ }$), and transfer partial molar isentropic compressibility (${\mathrm{\Delta }}_{\text{tr}}{\varphi }_k^{\circ }$) of the systems studied. The experimentally measured and calculated parameters have been interpreted in terms of host-guest and ion-hydrophilic interactions operative in the systems.     

Excess molar volume along with viscosity,refractive index and relative permittivity for binary mixtures of exo-tetrahydrodicyclopentadiene with four octane isomers

The fundamental physical properties including density, viscosity, refractive index and relative permittivity, have been measured for binary mixtures of exo-tetrahydrodicyclopentadiene (JP-10) with four octane isomers (n-octane, 3-methylheptane, 2,4-dimethylhexane and 2,2,4-trimethylpentane) over the whole composition range at temperatures T = (293.15 to 313.15) K and pressure p = 0.1 MPa. The values of excess molar volume $\left(V_{\text{m}}^{\text{E}}\right)$, viscosity deviation (Δη), refractive index deviation (Δn_D) and relative permittivity deviation (Δε_r) are then calculated. All of the values of $V_{\text{m}}^{\text{E}}$ and Δη are observed to be negative, while those of Δn_D and Δε_r are close to zero. The effects of temperature and composition on the variation of $V_{\text{m}}^{\text{E}}$ values are discussed. The negative values of $V_{\text{m}}^{\text{E}}$ and Δη are conductive to high-density and low-resistance of fuels, which is favorable for the design and preparation of advanced hydrocarbon fuels.     

Standard state thermodynamic properties of aqueous sodium perrhenate using high dilution calorimetry up to 598.15 K

Standard state thermodynamic properties for aqueous sodium perrhenate at temperature in the range of (298.15 to 598.15) K and at p_sat were determined by high dilution solution calorimetry down to 10^?4 m. Standard state partial molar heat capacities, $C_{p\text{,}2}^{°}$, of aqueous sodium perrhenate calculated from present study are compared to literature values up to T = 398.15 K. The differences between $C_{p\text{,}2}^{°}$ of ${\text{ReO}}_4^{-}(\text{aq})$ and Cl^?(aq) at lower temperature is much greater than that due to their internal molecular motions. Consequently, the perrhenate ion appears to have an ionic incomplete primary hydration shell as compared to the chloride ion. The ${\text{ReO}}_4^{-}/{\text{Cl}}^{-}$ difference in thermodynamic functions has now been well defined up to T = 598.15 K for other important high temperature calculations.     

Thermodynamics of solvation of some small peptides in water at T = 298.15 K

The enthalpies of solution in water, Δ_solH_m, of some small peptides, namely the amides of five N-acetyl substituted amino acids of glycine, l-alanine, l-proline, l-valine, l-leucine and two cyclic anhydrides of glycine and l-sarcosine (diketopiperazines), were measured by isothermal calorimetry at T = (296.84, 306.89, and 316.95) K. The enthalpies of solution at infinite dilution at T = 298.15 K were derived and added to the enthalpies of sublimation, ${\mathrm{\Delta }}_{\mathrm{sub}}{H}_{\mathrm{m}}^{\circ }$, at the same temperature, to obtain the corresponding solvation enthalpies at infinite dilution, ${\mathrm{\Delta }}_{\mathrm{solv}}{H}_{\mathrm{m}}^{\infty }$. Moreover, the partial molar heat capacities at infinite dilution at T = 298.15 K, $C_{p\text{,}2}^{\infty }$, were calculated by adding molar heat capacities of solid small peptides, C_p,m(cr), to the ${\mathrm{\Delta }}_{\mathrm{sol}}{C}_{p\text{,}\mathrm{m}}^{\infty }$ values obtained from our experimental data. CH₂ group contributions, in terms of solvation enthalpy and partial molar heat capacity, were −3.2 kJ · mol⁻¹ and 89.3 J · K⁻¹ · mol⁻¹, respectively, in good agreement with the literature data. Simple additive methods were used to estimate the average molar enthalpy of solvation and partial molar heat capacity at infinite dilution for the 1/2CONH⋯CONH functional group in the small peptides. Values obtained were −46.7 kJ · mol⁻¹ for solvation enthalpy and −42.4 J · K⁻¹ · mol⁻¹ for partial molar heat capacity, significantly lower than values obtained for the CONH functional group in monofunctional model compounds.     

Volumetric properties of binary liquid mixtures: Application of the Prigogine–Flory–Patterson theory to excess molar volumes of dichloromethane with benzene or toluene

The values of the density were measured for binary liquid mixtures of benzene and toluene with dichloromethane over entire range of concentration using a vibrating-tube densimeter at T = (288.15, 293.15, 298.15, and 303.15) K and atmospheric pressure. The excess molar volumes, calculated from the density results, are positive for the systems of dichloromethane with benzene over the whole concentration range and present an approximate sigmoid curve for the dichloromethane with toluene. The $V_{\text{m}}^{\text{E}}$ values have been fitted to the Redlich–Kister polynomial equation, and other volumetric properties such as the partial molar volumes, $\overline{V_i}$, the apparent molar volume, V_?i, and the partial molar excess volumes at infinite dilution, $(\overline{V_i^{\text{E}}}{)}^{\infty }$, were calculated over the whole composition range. The Prigogine–Flory–Patterson (PFP) theory and its applicability in predicting $V_{\text{m}}^{\text{E}}$ at T = 298.15 K are tested. Good agreement was found for the mixtures dichloromethane with benzene. For the mixtures dichloromethane with toluene, which shows an approximate S-shaped $V_{\text{m}}^{\text{E}}$ behaviour, the correlation fails.