Isentropic Compressibility Changes Research Articles

Refractive Indices and Speeds of Sound of Binary Mixtures of N-Octane with 1-Alkanol at the Temperature 298.15 K

This paper reports experimental values for the refractive index, speed of sound, and isentropic compressibility of binary mixtures of n-octane with (1-butanol, 1-hexanol and 1-octanol) at the temperature of 298.15 K and atmospheric pressure, as a function of mole fraction. From the experimental values, the corresponding derived values were computed (changes of refractive index, changes of speed of sound and changes of isentropic compressibilities) using variable-degree polynomials to fit the data. Also, an attempt was made to correlate the behaviour of these magnitudes to the number of carbon atoms in the 1-alkanol chain.

Thermodynamic properties of the mixture benzene+cyclohexane+2-methyl-2-butanol at the temperature 298.15 K: excess molar volumes prediction by application of cubic equations of state

Excess molar volumes, changes of refractive indices, and changes of isentropic compressibilities of the ternary mixture benzene (1)+cyclohexane (2)+2-methyl-2-butanol (3), and the corresponding binary mixtures benzene (1)+2-methyl-2-butanol (3), and cyclohexane (2)+2-methyl-2-butanol (3) have been evaluated from density, refractive index, and speed of sound measurements at 298.15 K, and atmosphere. These derived properties of binary, and ternary mixtures were fitted to Redlich–Kister, and Nagata equations, respectively, the correlation parameters being gathered. In spite of the high non-ideality observed, the excess molar volumes were satisfactorily predicted by means of cubic equations of state with simple mixing rules.

Refractive indices and speeds of sound of binary mixtures ofn-hexane with 1-alkanol at the temperature 298.15 K

In this work experimental values for the refractive indexnD, speed of soundu, and isentropic compressibilitykSof binary mixtures ofn-hexane with (1-butanol, 1-hexanol, and 1-octanol) atT=298.15 K and atmospheric pressure are presented. From the experimental values, the corresponding excess and deviation values were computed (changes of refractive index, changes of speed of sound, and changes of isentropic compressibilities) using variable-degree polynomials to fit the data.

Thermodynamic Properties of Alkanediols+Acetates at 298.15 K

In this work we present experimental values of the density, refractive index, speed of sound, isentropic compressibility and liquid-liquid equilibria of the binary mixtures (methyl acetate, ethyl acetate, propyl acetate, and butyl acetate) with (1,2-ethanediol, 1,2-propanediol, or 1,3-propanediol) at 298.15 K and atmospheric pressure, as a function of mole fraction. From the experimental values, the corresponding excess and deviation values were computed (excess molar volumes, changes of refractive index on mixing, and changes of isentropic compressibility), variable-degree polynomials being fitted to the results. The validity of different estimation methods for predicting the experimental values of physical properties was tested. The limiting partial excess molar volume of the components in each binary mixture was determined by means of predetermined Redlich-Kister parameters. Group contribution method (UNIFAC-Dortmund) was applied in order to compare their capability in predicting the experimental equilibria values.

Molar Volume, Molar Refraction, and Isentropic Compressibility Changes of Mixing at 25°C for the System Ethanol + Methanol + Dibutyl Ether

The densities, refractive indexes, and sound velocities for mixtures of ethanol + methanol + dibutyl ether at 25°C and atmospheric pressure, were determined and used to calculate molar volumes, molar refractions, and isentropic compressibilities. The excess molar volumes and the deviations of molar refractions and isentropic compressibilities from mole fraction and volume fraction averages, respectively, of these properties of the pure components were satisfactorily correlated with the composition data by means of the Redlich–Kister polynomial.

Mixing properties of (methanol, ethanol, or 1-propanol) with (n-pentane, n-hexane, n-heptane and n-octane) at 298.15 K

In this work, we present experimental values of the density, refractive index, speed of sound, and dynamic viscosity of the binary mixtures (methanol, ethanol or 1-propanol) with (n-pentane, n-hexane, n-heptane, and n-octane) at 298.15 K and atmospheric pressure, as a function of the molar fraction. From the experimental values, the corresponding excess and deviation values were computed (excess molar volumes, changes of refractive index on mixing, changes of isentropic compressibility and dynamic viscosity deviations), variable-degree polynomials being fitted to the results. Different methods were applied in order to estimate values of these physical properties, in good agreement with experiment. The binodal tie lines for each methanol + alkane binary mixture at different temperatures were determined by the measurement of physical properties and application of the corresponding fitting polynomials. UNIFAC-Dortmund group contribution method was applied to predict these liquid-liquid equilibria.

Tastes, structure and solution properties of D-glucono-1,5-lactone.

D-glucono-1,5-lactone differs from D-glucopyranose only in that it has a C = O group instead of CHOH group at carbon atom number one. The molecule therefore possesses an intact 3,4 alpha-glycol group and is sweet. However, it autohydrolyses in water solution at room temperature, forming D-gluconic acid and D-glucono-1,4-lactone. As the solution pH falls it becomes sweet-sour and eventually almost completely sour as the generated hydronium ions dominate both the solution properties and the taste perceptions elicited. It is shown that the ratio of generated hydronium ions to unchanged lactone accords with anticipated taste quality during the first 28 min of autohydrolysis. Changes in both apparent specific volume and apparent isentropic compressibility illustrate increasing solute-solvent interaction and increasing disturbance of water structure during the course of autohydrolysis. These changes are consistent with the concurrent sweet to sour change, but do not explain the weak bitterness which also accompanies them.

Densities, Refractive Indices, Speeds of Sound and Shear Viscosities of Diethylene Glycol Dimethyl Ether Methyl Salicylate at Temperatures from 298.15 to 318.15 K

Densities, refractive indices, speeds of sound and viscosities of the diethylene glycol dimethyl ether - methyl salicylate system were measured as a function of mole fraction at 298.15, 303.15, 308.15, 313.15 and 318.15 K. The results are fitted by a power series equation involving both the temperature and mole fraction variables. The basic physical data of the mixtures are further used to calculate the excess molar volume VE, changes in isentropic compressibility ∆β, changes in refractivity ∆R and changes in viscosity ∆η. The results are fitted by the Redlich-Kister polynomial relation. The isobaric thermal expansion coefficients of the mixtures are also determined from density measurements. The data are compared with those obtained from equations derived by differentiation of the Lorentz-Lorenz and Eykman relations. Refractive indices of the mixture are used to test the validity of mixing relations. The changes in isobaric thermal expansion coefficients ∆α of the mixtures were examined. Viscosity data were tested in terms of the McAllister, Heric and Auslaender relations.

Volumetric, acoustic, optical, and viscometric properties of binary mixtures of 2-methoxyethanol with aliphatic alcohols (C1-C8)

Densities, refractive indexes, speed of sound data, and viscosities of 2-methoxyethanol/alcohol mixtures are determined at 298.15, 303.15, and 308.15 K. Density results are used to calculate excess molar volume. The results of speed of sound data, refractive index, and viscosity are used to calculate the changes in isentropic compressibility, molar refractivity, and viscosity. These properties are fitted to the Redlich-Kister type equation. Intermolecular interactions in mixtures of 2-methoxyethanol with alcohols have led to rather widely varying excess molar volumes from negative to large positive values, depending on the size of the alcohols. McAllister's three-body-interaction model is used to correlate the binary kinematic viscosities, and results are compared with those from Lobe's relation. Furthermore, speed of sound data for mixtures are calculated from the theoretical relation of Auerbach

Excess thermodynamic properties of ( cis-decalin or trans-decalin + cyclohexane or methylcyclohexane or cyclooctane) at 298.15 K

Excess molar enthalpies, excess molar isobaric heat capacities, excess molar volumes, and changes of isentropic compressibility of ( cis-decalin or trans-decalin + cyclohexane or methylcyclohexane or cyclooctane) were measured at 298.15 K. They were not very large in magnitude but showed interesting composition dependences.

ChemInform Abstract: Structural Effects in the Partial Molar Volumes and Isentropic Compressibilities of Organic Bases and Their Conjugate Ions

Abstract Partial-molar-volume and isentropic-compressibility measurements in water are reported for a systematically chosen series of organic N-bases and their conjugate Bronsted-acid ions so as to investigate the role of the structures of these molecules in their interactions with the water solvent in the ionized and un-ionized states. The results also give the changes of volume and isentropic compressibility upon ionization, hence information on solvent electrostriction due to ionization. The electrostriction effect is related to the entropy of ionization in cases where suitable reliable information exists. The molecular structures are mainly aromatic and saturated heterocycles with one or two N atoms in the ring, or rings with an N and an O atom. Comparisons are also made with a “linear” N-base, ethylenediamine. The results for these various molecules enable the volumetric effects of the following molecular structure changes to be accurately evaluated: effect of one or two N atoms in a ring; effect of CH 2 ·CH 2  bridging with respect to hydrophobicity; effect of replacement of O by N and by CH 2  and of N by CH, or NH by CH 2  in a ring; introduction of aromaticity; position of N atoms in isomeric heterocyclic structures; and number of CH 2  groups in a ring. The results from this series of comparisons enable some conclusions to be reached regarding additivity of “group contributions” and the role of structural specificity in the volumetric properties of organic bases and their cations in aqueous solution.

Structural effects in the partial molar volumes and isentropic compressibilities of organic bases and their conjugate ions

Partial-molar-volume and isentropic-compressibility measurements in water are reported for a systematically chosen series of organic N-bases and their conjugate Brønsted-acid ions so as to investigate the role of the structures of these molecules in their interactions with the water solvent in the ionized and un-ionized states. The results also give the changes of volume and isentropic compressibility upon ionization, hence information on solvent electrostriction due to ionization. The electrostriction effect is related to the entropy of ionization in cases where suitable reliable information exists. The molecular structures are mainly aromatic and saturated heterocycles with one or two N atoms in the ring, or rings with an N and an O atom. Comparisons are also made with a “linear” N-base, ethylenediamine. The results for these various molecules enable the volumetric effects of the following molecular structure changes to be accurately evaluated: effect of one or two N atoms in a ring; effect of CH 2·CH 2 bridging with respect to hydrophobicity; effect of replacement of O by N and by CH 2 and of N by CH, or NH by CH 2 in a ring; introduction of aromaticity; position of N atoms in isomeric heterocyclic structures; and number of CH 2 groups in a ring. The results from this series of comparisons enable some conclusions to be reached regarding additivity of “group contributions” and the role of structural specificity in the volumetric properties of organic bases and their cations in aqueous solution.

Changes in partial molar volume and isentropic partial molar compressibility of self-association of purine and caffeine in aqueous solution at 1?1600 bar

Ultrasound measurements of purine and caffeine in aqueous solution as function of pressure are reported at 25°C and used to calculate the changes in their partial molar volumes and partial molar compressibilities due to self-association. The effect of pressure is to increase the association. The volume changes are negative for the self-association process, becoming less negative with increasing pressure. This is caused by the monomer in the associated state. The partial molar volume of the monomer in the associated state increases with pressure, contrary to what is expected for nonelectrolytes in water. Hydration of the associated monomer must be a key to this increase. The result suggest that dipole-induced dipole interactions is a possible mechanism for the association process and not hydrophobic interactions. The change in the partial molar compressibility of the association is positive, decreasing with increasing pressure.