Limiting Partial Molar Volumes of Water in 1-Hexanol, 1-Octanol, 1-Decanol, and Cyclohexanol at 298.15?K

From the density of solutions of water in 1-hexanol, 1-octanol, 1-decanol, and cyclohexanol, measured at 298.15K, the limiting partial molar volume and the excess limiting partial molar volume of water was estimated. The limiting partial molar volume of water in alcohols was discussed in terms of the void space created by the addition of water to alcohol and by the packing density of water. On the basis of the Kirkwood-Buff theory and the activity of water in alcohols an average aggregation number of water molecules, as well as the number of the excess alcohol molecules in the surroundings of the water molecule was calculated. The solvation ability of the investigated alcohols was estimated as the difference in the solvation Gibbs energy of an alcohol molecule in solution relative to the pure alcohol. The observed difference was mainly ascribed to an indirect effect caused by water molecules on the alcohol structure and to a lesser extent to the hydrogen bonding of water to alcohol molecules. The limiting partial molar volume of water was also interpreted in terms of scaled particle theory and the various volume contributions arising from dispersion, dipole–dipole, and inductive interactions between water and an alcohol molecule were calculated.     

Limiting Partial Molar Excess Heat Capacities and Volumes of Selected Organic Compounds in Water at 25°C

Well-known Picker flow microcalorimeters for the differential measurements of volumetric heat capacities have been employed in conjunction with vibrating tube densimeters to determine the molar heat capacity, volume, and the apparent properties in dilute aqueous solutions for 17 organic solutes of moderate hydrophobicity. The dependence on concentration of the apparent properties allowed the limiting partial molar quantities at infinite dilution to be extrapolated and the limiting partial molar excess quantities to be evaluated. Comparison with available literature data shows good agreement. The application of group contribution rules to the limiting partial properties has been tested using the original method and parameters proposed by Cabani et al. The predicted values of the partial molar volumes are in fair agreement with the present data except for some less common solutes. With partial molar heat capacities, the agreement is less satisfactory. To improve the performance of the method, missing parameters for some types of monofunctional and bifunctional molecules have been evaluated.     

Partial Molar Volumes of Glycine and dl-Alanine in Aqueous Ammonium Sulfate Solutions at 278.15, 288.15, 298.15 and 308.15 K

In this work, the partial molar volumes of glycine and dl-alanine in aqueous solutions of ammonium sulfate at 0.0, 0.1, 0.3, 0.7, and 1.0 mol·kg^?1 are determined between 278.15 and 308.15 K. Transfer volumes were obtained, which are larger for glycine than dl-alanine. On the contrary, the hydration numbers are higher for dl-alanine than glycine, and dehydration of the amino acids is observed with increasing temperature or salt molality. The data suggest that interactions between ion and charged/hydrophilic groups are predominant and, by applying the methodology proposed by Friedman and Krishnan, it was concluded that they are mainly pairwise. A group-contribution scheme has been successfully applied to the pairwise volumetric interaction coefficient. Finally, the dehydration effect on glycine, alanine and serine in the presence of different electrolytes has been rationalized in terms of the charge density and a parameter accounting for the cation’s hydration.     

Partial Molar Volumes of Uracil,Thymine, Adenine in Water and of Adenine in Aqueous Solutions of Uracil and Thymine

The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine, at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil and thymine are less than in pure water.     

Excess Molar Volumes and Partial Molar Volumes of Dipropylene Glycol Monomethyl Ether + n-Alkanol Mixtures at 25°C

The excess molar volumes V^E for binary liquid mixtures containing dipropylene glycol monomethyl ether and methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-heptanol have been measured using a continuous dilution dilatometer over the whole mole fraction range at 25°C at atmospheric pressure. V^E are negative over the whole composition range except for the systems containing 1-pentanol, 1-hexanol, or 1-heptanol which are positve at every composition. V^E increases in a positive direction with increase in chain length of the n-alcohol. The results have been used to estimate the excess partial molar volumes V_i^E of the components. The change of V^E and V_i^E with composition and the number of carbon atoms in the alcohol molecule are discussed as a basis to understand some of the molecular interactions present in the mixtures:     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monoethyl Ether–n-Alcohol Mixtures at 25°C

We have measured excess molar volumes V^E _m of binary mixtures of triethylene glycol monoethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol over the full range of compositions at 25°C. The measurements were carried out with a continuous-dilution dilatometer. The excess molar volumes V^E _m are negative over the entire range of composition for the systems triethylene glycol monoethyl ether + methanol, + ethanol, and + 1-propanol and positive for the remaining systems, triethylene glycol monoethyl ether + 1-pentanol, and + 1-hexanol. The excess V^E _m increases in the positive direction with increasing chain length of the n-alcohol. The measured excess volumes have been compared to our previous published data with an effort to assess the effects of replacing methyl by ethyl groups and of inserting oxyethylene groups. The results have been used to estimate the excess partial molar volumes V^E _m,i of the components. The behavior of V^E _m and V^E _m,i with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Viscosities for Binary Mixtures of 1-Alkoxypropan-2-ols with 1-Butanol, and 2-Butanol at 298.15 K and Atmospheric Pressure

Excess molar volumes Vm^E and kinematic viscosities v have been measured as a function of composition for binary mixtures of propylene glycol monomethyl ether （1-methoxy-2-propanol）, MeOCH2CH（OH）Me, propylene glycol monoethyl ether （1-ethoxy-2-propanol）, EtOCH2CH（OH）Me, propylene glycol monopropyl ether （1-propoxy-2-propanol）, PrOCH2CH（OH）Me, propylene glycol monobutyl ether （1-butoxy-2-propanol）, BuOCH2CH（OH）Me, and propylene glycol tert-butyl ether （1-tert-butoxy-2-propanol）, t-BuOCH2CH（OH）Me with 1-butanol, and 2-butanol, at 298.15 K and atmospheric pressure. The excess molar volumes are negative across the entire range of composition for all the systems with 1-butanol, and positive for the systems 2-butanol＋ 1-methoxy-2-propanol, and ＋1-propoxy-2-propanol, negative for the systems 2-butanol＋1-butoxy-2-propanol, and change sign for the systems 2-butanol＋ 1-ethoxy-2-propanol, and ＋ 1-tert-butoxy-2-propanol. From the experimental data, the deviation in dynamic viscosity η from ∑χiηi has been calculated. Both excess molar volumes and viscosity deviations have been correlated using a Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors.     

Partial Molar Volumes and Isentropic Compressions of Cyclic Ethers in Aqueous Solutions from 288.15 to 313.15 K at Atmospheric Pressure

The partial molar volumes and isentropic compressions of aqueous solutions of tetrahydrofuran, tetrahydropyran, 1,4-dioxane, tetrahydropyran-2-methanol, 3-hydroxytetrahydrofuran, and tetrahydrofurfuryl alcohol were measured at 288.15, 298.15, and 313.15 K. Results are analyzed in terms of the effects of group addition to the molar volumes and isentropic compressions. The temperature dependence of the molar volumes and compressions, and their group contributions, are used to characterize changes in hydration.     

Deptermination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical-fluid shromatogrphy for determining partial molar volumes of ethyl esters of cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and cis-4,7,10,13,16,19-docosa-hexaenoic acid(DHA) in supercritical carbon dioxide is presented and discussed. Partial molar volumes of EPA and DHA esters are obtained from the variation of the retention properties with the density of mobile phase at 313.15K,323.15K,333.15K and in the pressure range from 9 MPa to 21 MPa.     

Transfer Volumes of Small Peptides from Water to Aqueous Xylitol Solutions at 298.15 K

Densities have been measured by an oscillating-tube densimeter for aqueous solutions of glycylglycine and glycylglycylglycine in aqueous xylitol solutions with xylitol mass fractions ranging from 0 to 0.15 at 298.15 K. Apparent molar volumes and limiting partial molar volumes have been used to calculate the corresponding transfer volumes from water to different concentrations of xylitol + water mixtures. The results are interpreted in terms of the cosphere overlap model.     

Densities and Partial Molar Volumes of Some Amino Acids and Diglycine in Aqueous n-Propanol Solutions at 25°C

Apparent molar volumes, V , of glycine, DL--alanine, DL--amino-n-butyric acid, L-valine, L-leucine, and diglycine in water and in 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m _B [molality of n-propanol in water (mol-kg^–1)] aqueous solutions of n-propanol have been obtained from densities of their solutions at 25 °C measured by using a precise vibrating-tube digital densimeter. The calculated partial molar volumes of amino acids and diglycine at infinite dilution, V _2,m ^o , have been used to obtain the corresponding transfer volumes, _tr V _2,m ^o , from water to different n-propanol–water mixtures. _tr V _2,m ^o values are positive for glycine, DL-- alanine, and diglycine (except at lower concentration 1.0 m _B ), negative for L-valine, and both positive and negative for the remaining amino acids over the concentration range studied. The side-chain contributions and hydration numbers have been calculated from V _2,m ^o data. Interaction coefficients have also been obtained from the McMillan–Mayer approach and the data have been interpreted in terms of various interactions.     

Partial Molar Volumes of Transfer of Some Amino Acids from Water to Aqueous Glycerol Solutions at 25°C

Apparent molar volumes of glycine, DL--alanine, L-valine, L-leucine, and L-phenylalanine in 0.5, 1.0, 2.0, 3.5, and 5.0 m _B (mol-kg^–1) aqueous solutions of glycerol have been obtained from solution densities at 25°C using precise vibrating-tube digital densimeter. The estimated partial molar volumes at infinite dilution V ^o ₂ have been used to obtain the corresponding transfer volumes _tr V ₂ ^o from water to different glycerol–water mixtures. The transfer volumes are positive for glycine and DL--alanine, and both positive and negative for the other amino acids over the concentration range studied. Interaction coefficients have been obtained from McMillan–Mayer approach and the data have been interpreted in terms of solute–cosolute interactions.     

Determination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical fluids (SCFs) as solvents has been attracting widespread interest in the research and commercial applications. The study of partial molar volumes of solutes at infinite dilution in the near-critical region is of considerable fundamental importance, as these data reflects the interactions occurring between the solute and the solvent. Experimental measurements of partial molar volumes may be divided into two categories: direct and indirect methods. The direct methods…     

The Partial Molar Heat Capacities and Expansions of Inosine, 2′-Deoxyinosine and 2′-Deoxyguanosine in Aqueous Solution at 298.15 K

Solution densities over the temperature range 288.15 to 313.15 K have been measured for aqueous solutions of the nucleosides inosine, 2′-deoxyinosine, and 2′-deoxyguanosine, from which the partial molar volumes of the solutes at infinite dilution, V ₂^o, were obtained. The partial molar expansions for the nucleosides at infinite dilution and 298.15 K, E ₂^o {E ₂^o=(∂ V ₂^o/∂ T) _p }, were derived from the V ₂^o results. The V ₂^o values at 298.15 K for the two sugars D-ribose and 2-deoxyribose also have been determined. The partial molar heat capacities at infinite dilution for all the solutes, C _p,2^o, have been determined at 298.15 K. These V ₂^o,E ₂^o, and C _p,2^o results are critically compared with all of the results available from the literature, and the use of group additivity to evaluate these solution thermodynamic properties for the sparingly soluble nucleoside guanosine is explored.     

Limiting partial molar volumes at 298.15 K of some open chain and cyclic organic compounds in 1—octanol

Partial molar volumes at 298.15 K in 1—octanol have been determined for some hydrocarbons, ethers, ketones, and water from density measurements carried out with a vibrating-tube density meter.In the transfer process from the pure liquid state to the infinitely dilute solution in 1—octanol, a slight shrinkage is generally observed for solutes showing density values lower than that of the solvent. On the contrary, for solutes with higher density values, a weak expansion is produced.Comparisons are made among the partial molar volumes of organic solutes in 1—octanol, in water, and in other organic solvents. The case of water as a solute in 1—octanol and in many other organic liquids is carefully considered. In non-polar solvents the value of the limiting partial molar volume of water is always larger in respect to the value of the molar volume of pure water, but in polar solvents the contrary occurs. An explanation of this phenomenon is provided and a rationale is given to the value of the limiting partial molar volume of water in 1—octanol and to the trend exhibited by the partial molar volume of water in the 1—octanol/water mixture as water concentration is increased.     

A Study of Excess Molar Enthalpies and Excess Molar Volumes of Binary Mixtures of 1-Chloropentane + 1-Alkanol (from 1-Butanol to 1-Octanol) at 25°C.

Excess molar enthalpies H ^E _mand excess molar volumes V ^E _m at 25°Cand normal atmospheric pressure for the binary mixtures 1-chloropentane + 1-alkanol(from 1-butanol to 1-octanol) have been determined using a Calvet microcalorimeterand from density measurements using a vibrating tube densimeter. The H ^E _m valuesfor all the mixtures are positive and V ^E _m values are positive or negative dependingon the mole fraction of the chloroalkane. Experimental H ^E _m results are comparedwith the predictions of UNIFAC group-contribution models proposed by Dang andTassios and by Larsen et al., and are discussed in terms of molecular interactions.     

Apparent and Transfer Molar Volumes for Aqueous Solution Containing Polyethylene Glycols and Amino Acid Ionic Liquids at 298.15 K

The densities of 1-n-butyl-3-methylimidazolium ([Bmim]) based amino acid ionic liquids (AAILs) prepared from glycine [Gly], alanine [Ala], and valine [Val], namely [Bmim][Gly], [Bmim][Ala] and [Bmim][Val], in aqueous?~?0.2 mol·kg^?1 polyethylene glycol (PEG400, PEG600 or PEG1000) and PEG400 solutions containing?~?(0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly], have been determined at 298.15 K. The experimental densities were used to evaluate the apparent molar volumes in the mixed solvent system and further used to obtain transfer molar volumes of AAILs for their transfer from water to aqueous PEG solutions and of PEG400 for its transfer from water to aqueous solutions containing (0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly]. The transfer molar volumes of AAILs and of PEG400 are found to be negative. The effects of alkyl chain-length variation on the anion of AAILs as well as the chain-length of PEG on transfer molar volumes are investigated and discussed in terms of hydrophobic–hydrophilic, hydrophobic–hydrophobic, and ion–hydrophobic interactions.     

Excess Molar Volumes for Binary Mixtures of 1-Alkanol and 1-Alkene. III. The System 1-Hexanol + 1-Alkene at 25°C

Excess molar volumes, V ^E, are reported for binary mixtures of 1-hexanol with the homologous C₆, C₇, C₈, and C₁₀ 1-alkenes at 25°C. In this series of mixtures, the V ^E values vary as a function of mole fraction from positive–negative sigmoid shaped curves exhibiting a very small positive lobe in the dilute alkanol region for the shortest chain 1-alkene to positive values over the whole concentration range for the longer chain 1-alkene. The partial molar excess volumes, V _i ^E, were calculated for the components over the whole concentration range. The partial molar volume of 1-hexanol in the 1-hexene system shows a large and sharp minimum and in the 1-decene system is positive over the whole concentration range. The modified model [Treszczanowicz et al., J. Solution Chem. 31, 455 (2002) originally proposed by Treszczanowicz and Benson Fluid Phase Equilibr. 23, 117 (1985)] was used for the interpretation and prediction of the reported data. The model describes qualitatively the variation of V ^E with the length of the molecule and concentration as a result of superposition of the contributions of association, free volume, and nonspecific interactions.     

Apparent Molar Volume and Apparent Molar Refraction of Mono-, Di-, Tri-, and Tetra(oxyethylene) Glycol in Aqueous, 1,4-Dioxane,and Benzene Solutions at 298.15 K

Summary. The density and refractive index of aqueous, 1,4-dioxane, and benzene solutions of poly (oxyethylene) glycols of the type HO–(CH₂CH₂O) _n –H (n varying from 1 to 4) were measured at 298.15K. From these experimental data the apparent molar volume and the apparent molar refraction at infinite dilution were calculated. The limiting apparent molar volume of the investigated compounds in a definite solvent depends linearly on the number of oxyethylene groups. From these data, the volume of the monomeric unit was evaluated and found to be greater in non-aqueous solvents than in water. The limiting apparent molar refraction of the solute for the investigated systems, within the experimental uncertainties, is equal to the molar refraction of the pure solute. The electronic polarizability of the solute molecule depends linearly on the number of monomeric units and the ratio of the electronic polarizability to the molecular van der Waals volume is constant and independent of the number of oxyethylene groups.Received February 24, 2003; accepted (revised) April 10, 2003 Published online August 18, 2003