Excess Volume Of Mixing Research Articles

1H nuclear magnetic resonance study of solute–solvent interactions of 1-methyl-2-pyrrolidone and some substituted benzenes

Solute–solvent interactions in binary mixtures of 1-methyl-2-pyrrolidone (NMP) with some substituted benzenes have been monitored using 1H n.m.r. spectroscopy. Changes in the chemical shift (Δδ) of alkyl protons adjacent to the amide group have been determined and NMP found to be an electron-accepting molecule. The electron-donating ability of the aromatic ring varies with ring substitution. Satisfactory correlations are found between ΔδCH2N and ΔδArH and excess volume of mixing.

Excess volumes of mixing of binary systems of methanol with acetone and chloroform at 298.15 K

Excess volumes measurements, using a v-shaped dilatometer, are reported for the binary systems formed by mixing methanol with acetone and with chloroform at 298.15 K.

Excess Volume of Mixing of Quaternary Phosphonium Chlorides with Potassium Chloride in Water

Abstract Volume changes upon mixing aqueous solutions of potassium chloride and the quaternary phosphonium chloride, n·Bu4−nPhnPCl, (n=0–4), have been measured at various constant total ionic strengths (I=0.25, 0.5, 1.0) at 25 °C. Based on Friedman’s theory for a mixed electrolyte solution, volume-interaction parameters, υo, were determined at each ionic strength. The dependence of υo on I shows that contributions to the excess volume due to structural effects of a pairwise interaction between the cations and triplet interactions including a single anion are most significant for the Bu4P+ ion and decrease with increasing n. A comparison of the υo’s with the excess-volume properties of the salts in each pure solution shows that the interaction between the phosphonium cations and the potassium ion results in negative contributions to the excess volume of mixing, which also decreases as n increases.

Analysis of the concept of polymer quasi-solution using data on the volume of mixing of polyethylene oligomers

Concentration dependences of the excess volume of mixing have been derived for mixtures of liquid homologues belonging to the same polymer-homologous series and also for homolog mixtures containing members of homomorphous series. The obtained functions have been analysed quantitatively using experimental data on the volume of mixing of higher linear alkanes, alkanols, and 1-chloroalkanes. The theory agrees with experiment for sufficiently long molecules. The lowest chain length limiting the range of applicability of the quasi-solution concept depends on the character of end groups.

A systematic study on volumetric interactions of cyclohexanone with various aliphatic hydrocarbons

Excess volumes of mixing, VE, for binary mixtures of eyelohexanone with n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane, n-tetradecane, and n-hexadecane at 25 °C were determined from the precise and accurate experimental density data. The sign and magnitude of VE were discussed in terms of the strength of the unlike interactions present in the binary mixtures.Excess volumes of mixing of equimolar concentration [Formula: see text] were also obtained. Attempts were made to interpret [Formula: see text] in terms of the size and polarity of the constituent molecule. The two effects could not be separated, but a good linear relation between [Formula: see text] and the solubility parameter was found.

Chiral discrimination in the liquid state a hard-core model for the role of repulsive forces

We report a study of the rōle of repulsive intermolecular forces in chiral discrimination. A realistic model based on hard-core repulsive potentials, the RISM formalism, and a superposition approximation is used to compare the interaction between the same (dextro—dextro) and opposite (dextro—laevo) enantiomers of chlorofluoroacetonitrile in the liquid phase, at room temperature. Chiral discrimination arises through differences in pairwise packing in the two types of pair. Calculations are made also for the gas phase. The excess volume of mixing (−0.1 to −0.2 cm 3 mol 1̄), derived predominantly from nearest-neighbour contact distances, shows more efficent (d, l) contact packing. The excess enthalpy ( = 12 J mol −1, obtained by using an isotropic Lennard-Jones interaction, weights larger intermolecular distances and is endothermic. These results emphasize the need to consider the dependence of intermolecular orientational correlations on intermolecular separation in the interpretation of experimental data on chiral discrimination in liquids. Experimental results are not available for the system studied here, however the results are compatible with measured values for other systems.

Partial Volume of Copolymers in Mixed Solvents and Volume Contraction in Bulk-Copolymerization

On the basis of a simple and unified phenomenological method for treating the excess volume of mixing in multicomponent systems, formulas were developed for the partial molar volume of a copolymer (or a mixture of two polymers) in a mixture of two solvents and for the volume contraction factor in the bulk-copolymerization of two monomers. The possible dependence of the “net” volume of a copolymer on its primary structure was taken into account. The proposed formulas were partly checked against some experimental data, and found satisfactory. The previously proposed formulas for the copolymerization contraction factor seem to be less generally applicable.

USING EXCESS VOLUME OF MIXING TO CORRELATE DIFFUSIVITIES IN LIQUIDS

It has been postulated in the past that diffusivities in liquids can be correlated with the excess volume or mixing. A system has been examined in which the diffusivities and excess volumes of mixing vary in a nonlinear manner with changes in concentration; however, the diffusivity is always a linear function of the excess volume of mixing.

Thermodynamic and Electrical Properties of Expanded Liquid Dilute Amalgams

Simultaneous measurements of the density and electrical conductivity have been carried out for expanded liquid dilute amalgants containing Cd, Bi, Na, Pb etc. in the range of temperature and pressure up to 1550°C and 2200 bar. At high temperatures and pressures, substantial volume contraction and large increase in conductivity are brought about by the addition of a small amount of the elements with high-valency such as Bi and Pb into expanded liquid Hg. The observed large negative excess volume of mixing can be attributed to the loosely-packed structure of Hg solvent and to the change in the character of cohesion due to the injection of excess electrons.

Ultrasonic investigations of mixtures of n-octane with isomeric octanols. Isoentropic compressibility and excess volumes of mixing

Volumes of mixing, isoentropic compressibilities, acoustic attenuations and viscosities are reported on mixtures of various isomeric octanols and octane at 298.15 K. The data are interpreted in terms of competing effects of the alkane chain taking up the ‘free’ volume in the system and the disturbance of the distribution between cyclic and linear structures and monomer forms in the mixtures.

The partial molar volumes of anesthetics in lipid bilayers

The excess volumes of mixing of benzyl alcohol, halothane, and methoxyflurane in water and in suspensions of several lipid bilayers have been determined at 25°C using a novel excess volume dilatometer. The excess volumes of mixing in water were all found to be negative, whereas in lipid suspensions they were all more positive than those in water alone. From known partition coefficients the partial molar volumes of these three solutes in the lipid bilayers were calculated. These values were all close to the molar volumes of the pure anesthetics, as was a value determined for halothane in olive oil. Halothane was studied in dipalmitoylphosphatidylcholine below its phase transition, and was found to exhibit a much larger excess volume than in any other system we studied. The potency of these three anesthetics was determined in tadpoles. It was calculated that at equi-anesthetic doses these three agents caused an expansion in egg lecithin/cholesterol (2:1) bilayers of 0.21 ± 0.051%. This result is consistent with the hypothesis that general anesthetics act by expanding membranes.

Molar excess volumes of mixing of tetrahydrofuran with some aliphatic compounds having different functional groups

Molar excess volumes of mixing of tetrahydrofuran with some aliphatic compounds having different functional groups

Excess thermodynamic properties of binary liquid mixtures containing cyclohexylamine at 30�C

The excess volumes of mixing of cyclohexylamine with n-hexane, n-heptene, n-octane, n-nonane, benzene, toluene, nitrobenzene, chlorobenzene and bromobenzene have been measured at 30°C. For all systems except for n-hexane, V E is positive over the entire mole fraction range. For the n-hexane mixtures, a sigmoid curve is obtained with negative V E at high mole fraction of amine.

Hard spheres simulation of the size effect in liquid and amorphous metallic alloys

Large random packings of hard spheres of different sizes were built to simulate binary liquid metallic alloys. The packing fractions of those networks were measured for various concentrations and diameter ratios. A light increase in packing fraction was found only for large differences in diameter ( d/ D < 0.7). This result is explained by the sizes of the interstitial sites of the random network. Expressed in term of molar volume for metallic alloys, it can be used to precise the contribution of the size effect to the excess mixing volume of alloys.

Thermodynamic studies of some binary mixtures containing a self-associated component. II. Excess volumes of some mixtures of tetrahydrofuran with alcohols

Excess volumes of mixing, V E, for binary mixtures of tetrahydrofuran (THF) with methanol, ethanol, n-butanol, tert-butanol, 2-bromoethanol and ethylene glycol have been determined from the experimental density measurements at 298.15 K over the entire composition range. The V E data follow the order: ethylene glycol < 2-bromoethanol < methanol < ethanol < n-butanol < tert-butanol. The results have been explained in terms of self-association and the hydrogen bond-donating abilities of alcohols.

Theoretical consideration on the number of external degrees of freedom and its application to poly(dimethylsiloxane) solutions

The Flory theory of polymer solution was modified by assuming the non-additivity of the number of the degree of external freedom for a binary mixture and applied the modified Flory theory to poly (dimethylsiloxane)-solvent systems. This theory can reproduce the experimental results of the interaction parameter χ and the excess volume of mixing, which the Flory theory failed to reproduce.

Molar volumes of ammonium chloride—ammonium salt solutions

The apparent molar volume of ammonium bromide and ammonium nitrate has been determined in various solutions of ammonium chloride at 30°C from density measurements using an hydrostatic balance. The molar volumes show a linear function of concentration. The values of NH4Br, NH4NO3 are larger in NH4Cl solutions than in pure water and this has been attributed to the increase in the interactions of NH4Br and NH4NO3 with NH4Cl. The mean apparent molar volume of NH4Br−NH4Cl and NH4NO3−NH4Cl solutions have also been estimated directly from density measurements as well as from pure water data using Young's rule. The deviations are approximately studied as excess volume of mixing of NH4Br and NH4NO3 with NH4Cl.

Mechanical properties of polymer mixtures: Effect of compatibility

Abstract The effect of compatibility on the mechanical properties of polymer mixtures is discussed. From solution thermodynamics we conclude that for compatible mixtures of high molecular weight polymers the excess internal energy of mixing must be negative. For most polymer mixtures, this results in a negative excess volume of mixing. The excess entropy of mixing is therefore also negative. These general conclusions point to a stiffening of the solid lattice and a reduction in chain mobility. In dynamic mechanical behavior, the relaxation of molecular moieties responsible for the specific interaction should be shifted to intermediate temperatures, and the relaxation of other moieties should be shifted to higher temperatures if the potential well is inter-molecular. In finite deformation behavior craze initiation stress and shear yielding stress should both be higher than a linear combination of the properties of the pure components.

Thermodynamics of poly(dimethylsiloxane) solutions

Improved expressions for thermodynamic excess functions for mixtures of a non-polar polymer and a solvent are presented on the basis of modification of the combining rules of mixing which were assumed by Flory in the equation-of-state theory of pure fluids and their solutions. The modified theory assumes that the number of external degrees of freedom is non-additive with respect to the segment fraction and that the sizes of the core volumes of segments in pure liquids and solution are different. This theory can reproduce the experimental results of the interaction parameter χ and the excess volume of mixing, which the Flory theory failed to reproduce. Direct comparisons of the modified combining rules with experimental results is satisfactory.

Excess volumes of mixing of 1,2-dichloroethane and aromatic hydrocarbons

Excess volumes of mixing, V E, for binary mixtures of 1,2-dichloroethane with benzene, toluene, o −, m −, and p-xylenes have been determined at 308.15 K over the complete composition range. V E is positive for all these mixtures and varies in the order m-xylene > o-xylene > p-xylene > benzene > toluene. The experimental data have been analyzed in terms of the Prigogine's average potential cell model coupled with Balescu's theory. The calculated V E values do not agree with the corresponding experimental values.