Values Of Partial Molar Volumes Research Articles

Use of partial molar volume for determining conformations of macromolecules in a solution

A formula was derived for determining the partial molar volume (PMO) of solute at various concentrations and on this basis a method was developed for determining the PMO at infinite dilution. The partial molar volumes of the homologous series of poly(ethylene glycol) with molecular masses 400, 1000, 1500, 2000, 4000, 20000 in aqueous solutions at infinite dilution were determined. Analysis of the calculated and experimental PMO showed that poly(ethylene glycol) molecules exist in dilute solutions in the conformations of elongated helices. In addition, the high-molecular polyethylene glycol molecules include the areas of statistical chaos, which leads to sites unavailable for the solvent molecules. Based on literature data were revealed the values of PMO for highly concentrated solutions of poly(ethylene glycol) PEG 400, PEG 4000, and PEG 6000. Effect of concentration on the structure of PEG solutions was demonstrated. We found that in the temperature range 25–40°C the conformational transitions were not observed.

Volumetric, Acoustic, and Refractometric Study of Cyclic Alanylalanine in Aqueous Cobalt Chloride Solutions at Temperatures T = (293.15 to 313.15) K

Density, refractive index, and speed of sound values of cyclic alanylalanine + aqueous CoCl2 systems have been reported as a function of concentrations of cyclic alanylalanine and that of CoCl2 at temperatures T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. The values of partial molar volumes, isentropic compressibilities, and partial molar isentropic compressibilities of the cyclic alanylalanine + aqueous CoCl2 systems have been calculated from the speed of sound and density data obtained from the experiment at various temperatures. The decreasing value of isentropic compressibility with respect to the molal concentration of cyclic alanylalanine and temperature indicated the presence of strong solute–solvent interaction operative in the present system. The variations in partial molar volumes as well as partial molar isentropic compressibilities have been discussed in terms of ionic, hydrophilic, and hydrophobic interactions present in the system.

Volumetric studies of aqueous solutions of monosodium salts of some aliphatic dicarboxylic acids at 298.15 K. A new method of data analysis

The apparent molar volumes, Vϕ, of monosodium salts of aliphatic dicarboxylic acids of the HOOC(CH2)n(COOH)2 [n=0–5] types in dilute aqueous solution have been determined by precise density measurements, at T=298.15K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T=298.15K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050≤m/(mol·kg−1)≤0.3000. A new method for determining the values of partial molar volume of the electrolyte of NaHA type has been proposed. This method takes into account all equilibrium occurring in the solution. The variations of Vϕ0 values with aliphatic chain length of analyzed salts were determined.

Volumetric approach to the interaction of diglycine in aqueous solutions of sulpha drugs at T = 288.15–308.15 K

Densities, ρ, were measured for ternary mixture of diglycine in aqueous of (0.01, 0.02, 0.03, and 0.04)molkg−1 sulphanilamide (SAM), sulphanilic acid (SAN), and sulphosalicylic (SSAD) acid dihydrate at T=288.15–308.15K, using vibrating tube digital densimeter. Apparent molar volume, Vϕ, has been determined from the experimental densities and the least-square fitting was carried out for the calculation of limiting apparent molar volumes values Vϕ0, and the increase in the Vϕ0 values has the following order in the investigated system: SAN<SAM<SSAD. The calculated Vϕ0 values indicate that diglycine–SSAD interactions are stronger than the other two drugs. These data were used to calculate the transfer ΔtrVϕ0 values of partial molar volumes. Transfer parameters have been interpreted from the point of view of concentration dependence of solute–solute and solute–solvent interactions. The limiting apparent molar expansibility Eϕ0 values for diglycine in aqueous solution of drugs have positive value and decrease with rise of temperature. The calculated values of thermal expansion coefficient, α2, have small and positive values whereas the values of Hepler's constant, ∂2Vϕ0/∂T2, have positive value except with SSAD. Hydration numbers have also been determined. The variation of these parameters with concentration and temperature clearly suggests the roles of diglycine and sulpha drugs in solute–solvent interactions.

Anomalies in the Change of Volumetric Parameters of the Diels–Alder Reaction in Solution

In this article negative values of the activation volume in retro-Diels–Alder reactions are interpreted in terms of the different possibilities of penetration of the solvent molecules into the sterically branched structures of the adduct and activated complex. Empty spaces, inaccessible to penetration of solvent molecules, lead to increases of the molar volume of the screened adducts in solution and, consequently, to a less negative value of the Diels–Alder reaction volume. The values of partial molar volumes of anthracene, maleic anhydride and the adducts cyclopentadiene–maleic anhydride, anthracene–maleic anhydride and anthracene–tetracyanoethylene, in several solvents, were calculated from the solution density data.

Partial molar volumes of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate in n-donor solvents

The values of partial molar volume (PMV) of ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate were determined in twelve n-donor solvents and compared with the known values of PMVs of lithium and magnesium perchlorates in the same solvents. The proportionality in the change in the molar volumes of these salts and the predominant contribution of anion solvation were observed. The values of PMVs of the 1-butyl-3-methylimidazolium cation were calculated.

Thermodynamic (volume and compressibility) and spectral investigations of the glycine, diglycine and triglycine in aqueous α- and β-cyclodextrin solutions at T=298.15K

Abstract Apparent molar volumes and apparent molar adiabatic compressibilities have been determined for glycine, diglycine, and triglycine in aqueous α- and β-cyclodextrin (0.002–0.008 mol kg− 1) solutions by measurements of densities and speeds of sound at 298.15 K. The limiting apparent molar volume, limiting apparent molar adiabatic compressibilities, and their corresponding slopes were computed using the density and speed of sound data. These data were used to calculate the transfer values of partial molar volumes and partial molar adiabatic compressibilities at infinite dilution. Transfer parameters have been interpreted from the point of view of concentration dependence of solute–solute and solute–solvent interactions. These transfer parameters have further been used to calculate the group contribution of a peptide backbone (− CH2CONH−)n unit. The experimental results have also been discussed on the basis of 1H NMR measurements.

Parameters of viscous flow in dilute solutions of polyalkyl glycol ethers in secondary alcohols

Densities and viscosities were measured for the binary dilute mixtures of triethylene glycol monomethyl ether (TRIEGMME) in 2-alcohols (2-propanol (2-PR), 2-butanol (2-BU), and 2-pentanol (2-PE)) and tetraethylene glycol dimethyl ether (TEGDME) in 2-pentanol, at temperatures from 288.15 K to 318.15 K and in 0 ≤ x 2 ≤ 0.10 mol fraction range of the polyalkyl glycol ethers. The values of the dynamic viscosity in the TRIEGMME + 2-PR systems are more viscous than pure solvent at the work temperatures. The Jones–Dole B coefficients and β G interaction parameters for viscous flow values were calculated and explain the behavior observed. The partial molar volumes at infinite dilution of solute in 2-alkanols were calculated by the parameters of viscous flow obtained in dilute solutions polyalkyl glycol ethers in 2-alkanols. The values have been compared with the values of partial molar volume at infinite dilution obtained by density measurement for both solutes in the 2-propanol, 2-butanol, and 2-pentanol.

Density, Apparent and Partial Molar Volumes, and Viscosity of Aqueous Na2CO3Solutions at High Temperatures and High Pressures

Density of five (0.124, 0.334, 0.706, 1.055, and 1.123) mol kg-1and viscosity of seven (0.124, 0.2918, 0.334, 0.706, 0.8472, 1.055, and 1.123) mol kg-1binary aqueous Na2CO3solutions have been measured with a constant-volume piezometer and capillary flow techniques, respectively. Measurements were performed at pressures up to 52MPa for the density and 40MPa for the viscosity. The range of temperature was from 299 to 577K for density and from 293 to 478K for the viscosity. The total uncertainty of density, viscosity, pressure, temperature, and composition measurements was estimated to be less than 0.06%, 1.6%, 0.05%, 15mK, and 0.02%, respectively. Apparent molar volumes were derived using measured values of density for the solutions and for pure water calculated with IAPWS formulation. The effect of the thermodynamic variables (temperature, pressure, and concentration) on density, apparent and partial molar volumes, and viscosity of Na2CO3(aq) solutions was studied. The derived apparent molar volumes have been interpreted in terms of the Pitzer’s ion-interaction model of electrolyte solutions to accurate calculates the values of partial molar volumes at infinite dilutionV¯2∞and the second (BV) and third (CV) virial coefficients for the apparent molar volume as a function of temperature. The viscosity data have been analyzed and interpreted in terms of extended Jones–Dole equation for the relative viscosity (η/η0) of strong electrolyte solutions to accurate calculate the values of viscosityA- andB-coefficients as a function of temperature. The Arrhenius–Andrade parametersηAandb = Ea/R(whereEais the flow activation energy) were calculated using present experimental viscosity data. The effective pressuresPedue to the salt (Na2CO3) in water in the TTG (Timmann-Tait-Gibson) model were calculated from present viscosity measurements.

Part 2: Limiting apparent molar volume of organic and inorganic 1:1 electrolytes in (water + ethylammonium nitrate) mixtures at 298 K – Thermodynamic approach using Bahe–Varela pseudo-lattice theory

Values of partial molar volumes at infinite dilution of 9 inorganic and 4 organic 1:1 electrolytes have been determined in (water+ethylammonium nitrate) (EAN) binary at 298.15K throughout the composition scale. Our theoretical analysis shows that the values of partial molar volumes at infinite dilution of a solute in a binary are linked to those of the partial molar volumes of the components of mixed solvent. This applies to mixtures of molecular solvents as well as (water+ionic liquid) media. The use of the “pseudo-lattice theory” of Bahe recently supplemented Varela can be used for calculations and to obtain information about the interactions between 1:1 electrolytes as solutes at infinite dilution and their concentrated saline environment. We show that the “pseudo-lattice theory” allows accurate description of the behaviours of symmetrical tetraalkylammoniums bromide between the infinitely dilute state and concentrations higher than 2mol·L−1.

Densities, apparent and partial molar volumes of aqueous KBr solutions at high temperatures and high pressures

Density of four (0.2378, 0.4645, 0.9440, and 2.2310) mol kg −1 binary aqueous KBr solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made at pressures up to 30 MPa. The range of temperature was from 298 to 629 K. The total uncertainty of density, pressure, temperature, and composition measurements were estimated to be less than 0.06%, 0.05%, 15 mK, and 0.02%, respectively. Apparent molar volumes ϕ V were derived using measured values of density for the solutions and for pure water calculated with IAPWS formulation. The apparent molar volumes were analytically extrapolated to zero concentration to yield partial molar volumes at infinite dilution V ¯ 2 ∞ . The temperature, pressure, and concentration dependence of apparent and partial molar volumes were studied. The derived apparent molar volumes have been interpreted in terms of the Debye–Hückel theory (limiting law) of electrolyte solutions to accurate calculates the values of partial molar volume at infinite dilution V ¯ 2 ∞ and limiting slope A V as a function of temperature and pressure. All experimental and derived properties (apparent and partial molar volumes) are compared with the experimental values and correlations reported in the literature. The maximum of the apparent and partial molar volumes at temperature around 340–363 K depending on concentration and pressure was found.

Sorption and swelling of semicrystalline polymers in supercritical CO2

AbstractThe equilibrium sorption and swelling behavior of four different polymers—poly(methyl methacrylate), poly(tetrafluoroethylene), poly(vinylidene fluoride), and the random copolymer tetrafluoroethylene–perfluoromethylvinylether–in supercritical CO2—are studied at different temperatures (from 40 to 80 °C) and pressures (up to 200 bar). Swelling is measured by visualization, and sorption through a gravimetric technique. From these data, the behavior of amorphous and semicrystalline polymers can be compared, particularly in terms of partial molar volume of CO2 in the polymer matrix. Both poly(methyl methacrylate) and the copolymer of tetrafluoroethylene exhibit a behavior typical of rubbery systems. On the contrary, polymers with a considerable degree of crystallinity, such as poly(tetrafluoroethylene) and poly (vinylidene fluoride), show larger values of partial molar volume. These can be related to the limited mobility of the polymer chains in a semicrystalline matrix, which causes the structure to “freeze” during the sorption process into a nonequilibrium state that can differ significantly from the actual thermodynamic equilibrium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1531–1546, 2006

Group Contributions for an Estimation of Partial Molar Volumes at Infinite Dilution for Aqueous Organic Solutes at Extended Ranges of Temperature and Pressure

Experimental data on the partial molar volume at infinite dilution in water for two groups of organic solutes (derivatives of benzene and aliphatic hydroxyl derivatives) measured using a vibrating-tube densimeter in the temperature and pressure ranges 298 to 573 K and 0.1 to 30 MPa are summarized. Smoothed values of partial molar volume as a function of temperature and pressure are employed for the evaluation of group and structural contributions. The contributions are used to estimate the partial molar volumes at infinite dilution in water for various solutes. The average deviation between partial molar volumes calculated from the contributions and the experimental data employed for the evaluation of the contributions is less than 1 cm3ċmol−1 in most cases. Predictions of partial molar volumes of solutes not included in the evaluation of the contributions are performed and results are compared with experimental data.

Influence of van der Waals interactions on volumetric properties of cholesterol in solvents of linear structure

The densities of solutions of cholesterol in several primary amines and 1-chloroalkanes have been measured at T=298.15 K. The values of partial molar volumes of cholesterol have been calculated and the effect of solute–solvent and solvent–solvent interactions on the partial molar volume of cholesterol have been discussed. For the solvents studied the increase of alkyl chain length enhances the dispersion solvent–solvent interactions and weakens (per one cholesterol molecule) the contribution of dispersion forces in the solute–solvent interactions. Both effects bring about an increase in the partial molar volume of cholesterol with increasing the alkyl chain length. The relation between interaction volume of cholesterol (s.p.t. calculation) and the alkyl chain length have been also discussed.

Volumetric properties of (4-methylphenol + NaOH) at high temperatures

The densities of aqueous solutions of 4-methylphenol and its mixtures with sodium hydroxide were measured as a function of concentration at T=298 K at atmospheric pressure, and between the temperatures 373 K and 463 K at a pressure of 2 MPa. The partial molar volume at infinite dilution of 4-methylphenol (HCRES) and its sodium salt (NaCRES) were determined by the application of the Pitzer ion-interaction treatment to the solutions neglecting high order terms. The reported values of partial molar volume of 4-methylphenol are in good agreement with literature data.

Temperature dependence of thermodynamic properties of leucyl–glycine aqueous solutions from 15 to 45 °C

Densities, ultrasonic speeds and refractive index of leucyl–glycine aqueous solutions were determined from 15 to 45 °C, at 5 °C intervals, for the molality range 0–0.3. Apparent molar volumes, V ϕ ,2, and apparent molar isentropic compressions, K S , ϕ,2 , of the solute have been derived from density and ultrasonic speed data. Limiting values of partial molar volumes, V 2 ∞, partial molar isentropic compressions, K S,2 ∞, and partial molar isobaric expansions, E P,2 ∞, have been obtained. Molar refractivities, R m, have been derived from the refractive index using the Lorentz–Lorenz equation. The molar refractivities of the solute, R m,2 ∗ , were calculated by a least squares fitting method. Interesting correlations between the temperature dependence of the different thermodynamic properties studied were found and interpreted in terms of molecular interactions in solution and configurations of the dipeptide skeleton.

PVTx measurements for H 2O+D 2O mixtures in the near-critical and supercritical regions

The PVTx relationships of H 2O+D 2O mixtures were measured in the near-critical and supercritical regions. Measurements were made using a constant-volume piezometer immersed in a precision thermostat. The volume of the piezometer V PT was corrected for both temperature and pressure expansions. The uncertainty of the density measurements was estimated to be 0.05–0.10%, depending on the experimental pressure and temperature. The uncertainty of the temperature, pressure, and composition measurements were respectively 10 mK, 0.05%, and 0.001 mol fraction. Measurements were made along various near-critical and supercritical isotherms between 517 and 680 K at pressures from 3 to 38 MPa and densities from 97 to 466 kg m −3 for two compositions, namely 0.5 and 0.6 mol fraction of H 2O. The measured PVTx data for H 2O+D 2O mixtures were compared with values calculated from a six-term Landau expansion and from parametric crossover equations of state. The accuracy of the method was confirmed by PVT measurements for pure water in the critical and supercritical regions. The values of partial molar volumes for dilute H 2O+D 2O mixtures near the critical point of pure H 2O and the Krichevskii parameter were calculated using a parametric crossover equation of state and the critical locus data. Using measured values of molar volumes and corresponding values for pure components, we derived the values of excess molar volumes as a function of pressure for the supercritical isotherms.

Infinite-Dilution Partial Molar Properties of Azulene and Acenaphthylene in Supercritical Carbon Dioxide

The effects of temperature and pressure on retention of azulene and acenaphthylene in supercritical fluid chromatography are investigated within 33−58 °C and 74−150 bar. The retention factors are used to derive the infinite-dilution partial molar volumes of the two solutes in supercritical carbon dioxide and infinite-dilution molar enthalpies of the transfer of azulene from the stationary phase to supercritical CO2. The partial molar volumes are converted to quantities characterizing short-range interactions between CO2 and the aromatic hydrocarbon. The results obtained by analyzing the retention data in the usual way are compared with a more refined treatment that takes account of the pressure- and temperature-dependent dissolution of CO2 in the stationary polymer (poly(dimethylsiloxane)) within the column. The corrections for composition changes in the stationary phase employ a combination of the Flory−Huggins theory, the regular solution theory, and the Panayiotou−Vera lattice-fluid model. Application of the composition correction makes the partial molar volumes and the transfer enthalpies more negative. It has recently been noted [Liu, H.; O'Connell, J. P. Ind. Eng. Chem. Res. 1998, 37, 3323] that the chromatographic values of partial molar volumes appear to be systematically less negative than those derived from solubility data. Therefore, the composition correction may help to reconcile the disparity between the chromatographic and the solubility values of partial molar volumes.

PVTx measurements and partial molar volumes for water–hydrocarbon mixtures in the near-critical and supercritical conditions

By means of a constant-volume piezometer, measurements have been made of the PVTx properties of water+hydrocarbon ( n-heptane, n-octane, and benzene) mixtures at near-critical and supercritical conditions. The measurements cover the pressure range from 5 to 40 MPa and densities between 20 and 450 kg m −3 for six compositions from 0 to 0.614 mole fraction of hydrocarbon. Tests on the piezometer and consistency tests on the measurements suggest that the results are free from significant `dead volume' error. The experimental errors of the present PVTx measurements are estimated to be within ±0.01 K in temperature, ±0.15% in density, ±2 kPa in pressure, and ±0.002 mole fraction in composition. Good agreement was obtained with values reported in the literature for pure components (water, n-heptane, n-octane, and benzene), measured using other techniques. Values of partial molar volumes and the Krichevskii parameter have been obtained from these measurements. Analysis of the results for dilute water–hydrocarbon mixtures shows that partial molar volumes of the hydrocarbon (solute) near the critical point of pure water (solvent) exhibit remarkable anomalies. The experimental results have been interpreted in terms of modern molecular thermodynamic models for the partial molar volumes of the solute near the solvent critical point and Kirkwood–Buff fluctuation theory of solutions in terms of direct correlation function integral.

Experimental Technique for a Study of Volumetric Properties of Dilute Aqueous Solutions at Superambient Conditions.

A new vibrating-tube densitometer for measuring densities of fluids in the temperature range from ambient to 580 K and the pressure range up to 35 MPa is described. A novel design of driving and pick-up systems of a metal vibrating tube was employed. The driving system is based on passing the driving electrical signal directly to the electrically insulated vibrating tube, the photo-electric pick-up system employs glass-fibre optics with light source and sensor. New values of partial molar volumes at infinite dilution in water for several derivatives of benzene obtained by means of the densitometer are presented.