Excess Ultrasonic Speed Research Articles

Thermophysical properties of binary mixtures of pentyl acetate with butanol at 298.15 K to 318.15 K: PFP theory, FTB model, and Graph theoretical approach

The measured density (ρ) and refractive index (nD) of binary pentyl acetate (1) + isomers of butanol (2) mixtures were reported at T = 298.15 K to 318.15 K and at 0.1 MPa pressure. Using the experimental ρ, u and nD data, excess molar volume (VmE), excess ultrasonic speed (uE), excess isentropic compressibility (κSE), and excess refractive index (nDE) were calculated and correlated with the Redlich–Kister (RK) equation. The findings suggest that the behavior of a mixture is affected by intermolecular interactions (cohesive forces such as dipole–dipole, H–bonding, dispersive force) and structural aspects of the molecules. The Prigogine–Flory–Patterson (PFP) theory, Flory–Treszczanowicz–Benson (FTB) model, and Graph theoretical approach (GTA) accurately analyzed the VmE values. Both the FTB model and PFP theory predicted the VmE curves not only successfully but also accurately represented their shape and magnitude except GTA at a lower mole fraction of pentyl acetate (xA<0.2). The positive values of VmE values were observed for binary mixtures across all temperatures. The intermolecular interactions were also corroborated by uE, κSE and nDE.

Experimental analysis of volumetric, acoustic, viscometric and optical properties of water with 1-amino-2-propanol, 1,2-diaminopropane and 1,3-diaminopropane at T=298.15 -318.15 K: Molecular Modelling by Graph, PFP and IR spectroscopy investigations

BackgroundLiquid mixtures are used as a solvent in most of the natural systems and chemical processes. Therefore, the physicochemical properties of liquid mixtures at different compositions and at different temperatures have a significant role in the optimization of chemical processes. The present report involves the analysis of the thermophysical properties of water (1) and amines (2). MethodsDensity, ρ, dynamic viscosity, η, refractive index, nD, and speed of sound, u, data were measured for binary mixtures of water (1) and amines (1A2P (1-amino-2-propanol), 1,2-DAP (1,2-diaminopropane) and 1,3-DAP (1,3-diaminopropane) (2) at five different temperatures (T = 298.15 to 318.15 K) and at 0.1 MPa pressure. Based on experimental data, the excess molar volume, VmE, deviation in dynamic viscosity, Δη, excess Gibbs free energy of activation, G*E, deviation in refractive index, ΔnD, excess ultrasonic speed, uE, excess isentropic compressibility, KsE, deviation in free volume, ΔVf, excess available volume, VaE, and excess intermolecular free length, LfE, were calculated and these evaluated properties were fitted to Redlich-Kister polynomial (R.K.). The VmE data was analyzed by Prigogine-Flory-Patterson (PFP) theory. The dynamic viscosity, η, values were studied by different correlations. The VmE and Δη data were also analyzed by Graph theoretical approach (GTA). Raman and FT-IR spectroscopic studies give important information about the intermolecular interactions present between unlike molecules water (1) and amines (2) which is also recognized by GTA. Significant findingsThe value of VmE and KsE values were found negative over the whole composition range, and it follow the sequence as: 1,2-DAP > 1,3-DAP > 1A2P with water at equimolar composition. GTA and PFP well supported the VmE data. GTA studies help in investigating the specific intermolecular interactions between unlike components. Further, Graph theory studies predicted OH—–NH interaction is dominant interaction among all interactions which were also supported by Raman and FTIR spectroscopic studies.

Experimental, theoretical, computational and spectroscopic analysis in binary liquid mixtures containing 1-propanol and C-1 to C-4 alkyl acetates (T = 298.15–318.15 K): Physicochemical properties and molecular interaction studies

The molecular interactions between 1-propanol (1P) (1) and alkyl acetates (AAc) (C1-C4) (2) were examined by understanding of thermophysical properties of given binary liquid mixtures. Density (ρ), viscosity (η) and speed of sound (u) were measured for 1P, AAc and their binary mixture at T = 298.15–318.15 K with interval of 5 K at 0.1 MPa. Experimental data of ρ, η and u were used to evaluate VmE (excess molar volume), uE (excess ultrasonic speed), Δη (deviation in viscosity), ksE (excess molar isentropic compressibility), G∗E (excess Gibbs free energy of activation of viscous flow), VfE (excess free volume), LfE (excess intermolecular free length) and VaE (excess available volume) and correlated with R.K. (Redlich-Kister polynomial) equation. VmE data was also examined in term of Graph theoretical approach (GTA) and Prigogine-Flory-Patterson (PFP) theory. Δη were analyzed by Bloomfield and Dewan model (BFD) and also examined in terms of Graph theoretical approach (GTA). The u data was examined by different correlations like Van Dael, Nomoto, JFLT (Jacobson’s free length theory), Impedance dependence and CFT (Schaaff’s collision factor theory). FT-IR spectroscopic studies provide important information for understanding the intermolecular interactions between 1P (1) and AAc (2) components in the binary mixture which is also recognized by GTA. Further, DFT studies indicated the strength of molecular interactions and supported the graph theory in predicting probable associative molecular species in the liquid mixtures.

Analysis of thermo-physical properties and qualitative investigation of molecular interactions in terms of Graph Theoretical Approach in binary liquid mixtures containing 1-propanol + Amines (1,3-diaminopropane or 1,2-diaminopropane or 1-amino-2-propanol) at T = 298.15–318.15 K

In the present report, the molecular interactions between 1P (1-propanol) and Amines (1,3-DAP (1,3-diaminopropane) or 1,2-DAP (1,2-diaminopropane) or 1A2P (1-amino-2-propanol)) are examined by insight of thermo-physical properties of binary liquid mixtures. Density (ρ) and speed of sound (u) were measured for 1P, Amines and their binary mixture at T = 298.15–318.15 K at 0.1 MPa. Experimental data of ρ and u were used to evaluate VmE (excess molar volume), ksE (excess molar isentropic compressibility), VfE (excess free volume), uE (excess ultrasonic speed), LfE (excess intermolecular free length) and VaE (excess available volume). Further, these calculated properties were correlated with Redlich-Kister polynomial (R.K.). VmE data is also examined in term of GTA (Graph theoretical approach) and PFP (Prigogine-Flory-Patterson) theory. FT-IR spectroscopic studies supported the results and clearly indicated that a strong intermolecular interactions exist between 1P and Amines components in the binary mixture which is also recognized by GTA. The u data were examined by different correlations like Nomoto, Impedance dependence, Van Dael, JFLT (Jacobson’s free length theory) and CFT (Schaaff’s collision factor theory).

Molecular interaction analysis of 1-amino-2-propanol with alkyl acetate (C1-C4): Volumetric, acoustic, isentropic compressibility (T = 298.15–318.15 K) and IR spectroscopic investigations

In the present report, density (ρ) and speed of sound (u) of binary mixtures 1A2P (1-amino-2-propanol) (1) + AAc (2) (MAc (methyl acetate), EAc (ethyl acetate), PAc (propyl acetate) and BAc (butyl acetate)) mixture were calculated at T = 298.15–318.15 K at 0.1 MPa. Based on experimental data different thermo-physical properties like excess molar volume (VmE), excess molar isentropic compressibility (ksE), excess free volume (VfE), excess ultrasonic speed (uE), excess intermolecular free length (LfE) and excess available volume (VaE) were evaluated and also correlated with Redlich-Kister polynomial (R.K.) equation. The obtained result were interpreted in terms of structural and molecular interactions between the mixing components. The effects of steric hindrance and temperature on the excess properties are discussed. In addition, the various correlations like Nomoto, Impedance dependence, Van Dael, Jacobson’s free length theory (JFLT) and Schaaff’s collision factor theory (CFT) were employed to analyze the u data. Further, FT-IR spectroscopy studies clearly indicate that a strong intermolecular hydrogen bonding exist between 1A2P and alkyl acetates components in the binary mixture.

Study of intermolecular interactions in binary mixtures of methyl acrylate with benzene and methyl substituted benzenes at different temperatures: An experimental and theoretical approach

• Reports new u and η data of methyl acrylate + aromatic hydrocarbons mixtures. • The study provides estimation of excess properties of these mixtures. • Provides information on nature and relative strength of interactions in these media. • Various empirical and semi-empirical models are used to correlate viscosity data. • The scaled particle theory (SPT) is used to predict ultrasonic speed theoretically. The ultrasonic speeds, u and viscosities, η of the binary mixtures of methyl acrylate with benzene, toluene, o -xylene, m -xylene, p -xylene, and mesitylene over the whole mole fraction range were measured at six different temperatures and at atmospheric pressure. From the experimental data, the excess isentropic compressibility, κ s E , excess ultrasonic speed, u E , excess molar isentropic compressibility, K s,m E , excess specific impedance, Z E and deviations in viscosity, Δ η have been calculated. The partial molar isentropic compressions, K ¯ s,m,1 and K ¯ s,m,2 , and excess partial molar isentropic compressions, K ¯ s,m,1 E and K ¯ s,m,2 E over the whole composition range, partial molar isentropic compressions, K ¯ s,m,1 ̂ and K ¯ s,m,2 ̂ , and excess partial molar isentropic compressions, K ¯ s,m,1 ̂ E and K ¯ s,m,2 ̂ E of the components at infinite dilution have also been calculated. The results specified the existence of weak interactions between unlike molecules, and these interactions follow the order: benzene > toluene > p -xylene > m -xylene > o -xylene > mesitylene. The magnitude of interactions was found to be dependent on the number and position of the methyl groups in these aromatic hydrocarbons.

Thermo-physical properties of 1,3-Diaminopropane + alkyl acetate (C1-C4) liquid mixtures: Investigation of molecular interactions by insight of IR spectroscopy and DFT studies

The density (ρ) and speed of sound (u) data of 1,3-Diaminopropane (1,3-DAP) (1) + alkyl acetate (AAc) (C1-C4) (2) mixtures at the temperatures (298.15, 303.15, 308.15, 313.15, and 318.15) K and pressure 0.1 MPa were measured. ρ and u data have been used to calculate excess molar volume (VmE), excess molar isentropic compressibility (ksE), excess ultrasonic speed (uE), excess free volume (VfE), excess available volume (VaE) and excess intermolecular free length (LfE). The result of speed of sound have been analyzed in term of various correlations like Nomoto, Van Dael, Impedance dependence and Schaaff's collision factor theory at temperature 298.15 K. The calculated deviation and excess properties are well fitted with Redlich-Kister polynomial equation and further results were analyzed with the help of the structural, inter and intramolecular interaction aspects. IR spectra of the liquid mixture supported the intermolecular interaction between the 1,3-DAP and AAc molecules through shifting of the position of the stretching frequency of some specific functional groups. The results obtained from DFT studies clearly indicates the formation of strong intermolecular interaction between 1,3-DAP and AAc.

Volumetric, acoustic and IR spectroscopic properties of binary mixtures (1,2-diaminopropane + methyl-, ethyl-, n-propyl- and n-butyl acetates: A combined experimental and first-principles investigation

Studies of density and speed of sound are commonly used tools to ascertain the properties of pure liquids and the nature of interactions between component molecules of a binary mixture. Herein, the density (ρ) and speed of sound (u) of methyl acetate (MAc), ethyl acetate (EAc), n-propyl acetate (n-PAc) and n-butyl acetate (n-BAc) and their binary mixture with 1,2-diaminopropane (1,2-DAP) were measured over the entire composition range at atmospheric pressure 0.1 MPa and in the temperature range of 298.15–318.15 K with a step of 5 K. Different excess thermo-physical properties including the excess molar volume (VmE), excess ultrasonic speed (uE), excess free volume (VfE), excess intermolecular free length (LfE), and excess molar isentropic compressibility were evaluated from the measured results of ρ and u. The evaluated properties were also analysed in terms of the extent and nature of interactions. The Redlich-Kister polynomial equation was used to correlate the various excess properties to the composition. Further, the u data is analysed by various correlations, Schaaff’s collision factor theory (CFT) and Jacobson’s free length theory (JFLT). The effect of chain length, branching and temperature on the intermolecular interactions and the magnitude of the measured properties have also been systematically analysed. Furthermore, excess molar properties and the intermolecular interactions have been interpreted in the light of Fourier transform infrared spectroscopy (FT-IR) and density functional theory (DFT) studies. Hydrogen-bonded interactions are predicted to play important role in stabilising the binary mixtures.

Ultrasonic Speeds, Molar Isentropic Compressions and FTIR analysis of aqueous solutions of 2-dialkylaminoethanols from 293.15 to 313.15 K

ABSTRACT The present work reports the experimental densities ρ and ultrasonic speeds u of binary mixtures of 2-dimethylaminoethanol (2-DMAE) and 2-diethylaminoethanol (2-DEAE) with water at temperatures 293.15, 303.15 and 313.15 K over the entire composition range. Excess molar volume , excess ultrasonic speed uE , excess isentropic compressibility , excess intermolecular free-length and excess molar isentropic compression were calculated using the experimental data. The variations of excess parameters are modelled by the Redlich-Kister polynomial equation rendering strong deviations from ideality. The excess partial molar compressions and , excess partial molar compressions at infinite dilution and expose about the structural configuration and molecular bonding in the aqueous binary system. The consequences of aqueous 2-DMAE/2-DEAE system may become a driving force for hydrophobic hydration to support solute-solvent hydrophilic interaction. The pattern and position of FT-IR spectra (recorded at room temperature 293.15 K) was consistent with the variations of excess parameters.

Insight into intermolecular interactions in benzonitrile + methyl acrylate/ethyl acrylate/n-butyl acrylate/t-butyl acrylate binary mixtures at temperatures from 293.15 to 318.15 K: Ultrasonic and viscometric study

The ultrasonic speeds, u and viscosities, η of binary mixtures of benzonitrile with alkyl acrylate (methyl acrylate, ethyl acrylate, n-butyl acrylate and t-butyl acrylate) over the entire composition range, including the pure liquids, were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and at pressure, p = 101 kPa. From the experimental data, the excess isentropic compression, κsE, excess ultrasonic speed, uE, excess molar isentropic compression, Ks, mE and deviations in viscosity, Δη have been calculated. The excess properties were correlated by the Redlich-Kister polynomial equation. The partial molar isentropic compressions and excess partial molar isentropic compressions over the whole composition range; and partial molar isentropic compressions and excess partial molar isentropic compressions of the components at infinite dilution have also been calculated. The variations of these parameters with composition and temperature have been discussed in terms of intermolecular interaction prevailing in these mixtures. Further, the η data of these mixtures were theoretically correlated with various empirical and semi-empirical models and the results were compared with the experimental data.

Physicochemical study of intermolecular interactions in binary mixtures of acetonitrile with alkyl acrylate monomers at temperatures from 293.15 K to 318.15 K by using ultrasonic speed and viscosity data

The ultrasonic speeds, u and viscosities, η of binary mixtures of acetonitrile with alkyl acrylate (methyl acrylate, ethyl acrylate, n-butyl acrylate and t-butyl acrylate) over the entire composition range were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and at atmospheric pressure. From the experimental data, the excess isentropic compressibility, κsE, excess ultrasonic speed, uE, excess molar isentropic compressibility, Ks,mE and deviations in viscosity, Δη have been calculated. The partial molar isentropic compressibilities and excess partial molar isentropic compressibilities over whole composition range, partial molar isentropic compressibilities and excess partial molar isentropic compressibilities of the components at infinite dilution are calculated. The variation of these parameters is discussed in terms of molecular interactions in these mixtures. The viscosities of these mixtures were correlated using various models and the ultrasonic speeds of these mixtures were theoretically calculated using scaled particle theory and the results are compared with experimental values.

Thermodynamics of haloarenes with n-hexane at 298.15–318.15 K: Density, ultrasonic speed and viscosity

Densities (ρ), ultrasonic speeds (u) and dynamic viscosity (η) of the binary 2-chlorotoluene or 4-chlorotoluene or 1,3-dichlorobenzene (1) + n-hexane (2) mixtures were measured at (T = 298.15–318.15) K and atmospheric pressure. Using these measurements, excess volume (VmE), excess ultrasonic speed (uE) and deviation in dynamic viscosity (Δη) were calculated. Excess isentropic compressibility (κsE) was calculated using ρ and u values. The VmE values have been interpreted by Prigogine-Flory-Patterson (PFP) theory. The VmEobtained using PFP theory agree well with experimental values. The u values were also calculated using various empirical relations. The available volume (Va) and intermolecular free length (Lf) were calculated using experimental u values employing Jacobson free length theory. The Δη values were coupled with VmE values to understand intermolecular interaction. Further, Bloomfield and Dewan model was applied to calculate η and Δη values of the studied binary mixture and calculated values agree well with experimental values.

Physicochemical investigations of polyethylene glycols with N, N dimethylacetamide

The densitiesρ and ultrasonic speeds u for the binary mixture of polyethylene glycol (PEG 200) and poly ethylene glycol 400 (PEG 400) with N, N dimethylacetamide (DMA) are measured over the entire mole fraction range and at temperatures 303.15, 313.15, and 323.15 K. From the experimental data, and excess molar volume, VmE, excess ultrasonic speed uE, excess isentropic compressibility κsE, Excess intermolecular free length LfE, excess acoustic impedance ZE and excess molar isentropic compressibility Ks,mE are evaluated. The partial molar properties and their excess properties are also determined. The solute-solvent interactions are also analyzed using FTIR spectra, recorded at the room temperature.

Densities, speeds of sound and excess properties of (benzonitrile + methyl methacrylate, or + ethyl methacrylate, or + n-butyl methacrylate) binary mixtures at temperatures from 293.15 K to 318.15 K

Experimental measurements of densities and ultrasonic speeds for the binary mixtures of benzonitrile with methyl/ethyl/n-butyl methacrylates over the entire composition range were carried out in the temperature range 293.15 K–318.15 K and atmospheric pressure of 0.1 MPa. Using the experimental data, the excess molar volume, excess ultrasonic speed, excess isentropic compressibility, and excess molar isentropic compressibility have been calculated and correlated by Redlich-Kister equation. The partial molar and excess partial counterparts of molar volumes and molar compressibilities over the whole composition range; and at infinite dilution have also been calculated. The dependence of these parameters on composition and temperature has been interpreted in terms of intermolecular interactions prevailing in these mixtures. The order of interactions suggested by the excess functions is found to be MMA > EMA > BMA. The major cause of the order is the steric hindrance caused by alkyl group. The results showed the effect of varying chain length on excess functions and interactions of the system.

Experimental and theoretical studies of acoustic and viscometric properties of binary mixtures of tetrahydrofuran with some alkyl acrylates at temperatures from 293.15 to 318.15 K

The ultrasonic speeds, u and viscosities, η of binary mixtures of tetrahydrofuran (THF) with methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (n-BA) and tert-butyl acrylate (t-BA) over the entire composition range expressed by mole fraction, x1 of THF, including those of pure liquids, were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and at atmospheric pressure. From the experimental data, the excess isentropic compressibility, κsE, excess ultrasonic speed, uE, excess molar isentropic compressibility, Ks,mE and deviations in viscosity, Δη have been calculated. The partial molar isentropic compressibilities, K¯s,m,1 and K¯s,m,2, and excess partial molar isentropic compressibilities, K¯s,m,1E and K¯s,m,2E over the whole composition range, partial molar isentropic compressibilities, K¯s,m,1° and K¯s,m,2°, and excess partial molar isentropic compressibilities, K¯s,m,1°E and K¯s,m,2°E of the components at infinite dilution have also been calculated. The variation of these parameters is discussed in terms of molecular interactions in the solution. Also, the viscosities of these binary mixtures were correlated with various empirical and semi-empirical models and the theoretical results were compared with the experimental findings. Furthermore, the ultrasonic speeds of these mixtures have been theoretically calculated by using scaled particle theory and the results are compared with experimental values.

Thermophysical and Spectroscopic Studies of Pure 1-Butyl-3-methylimidazolium Tetrafluoroborate and Its Aqueous Mixtures

Intermolecular interactions in the aqueous mixtures of the room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), have been studied. The thermophysical properties: density ρ, speed of sound u, specific conductivity κ and refractive index nD have been measured over the whole composition range at different temperatures (293.15–323.15 K) and are discussed. The results from thermophysical measurements are explained with the help of spectroscopy. In order to interpret the nature of molecular interactions occurring between [BMIM][BF4] and water molecules, as well as to identify the moieties in which interactions are taking place, 1H, 13C NMR and FT-IR spectra of the solutions have been studied. Excess molar volume VE, excess molar isentropic compressibility \( K_{S}^{\text{E}} \), partial molar excess volume \( V_{i}^{\text{E}} \), partial molar excess isentropic compressibility \( K_{S,i}^{\text{E}} \), deviation in specific conductivity ∆κ, and deviation in refractive index ∆R have also been determined and analyzed to have a better understanding of the interactions taking place between the different components. Additionally, the excess ultrasonic speed uE and excess isentropic compressibility \( k_{S}^{\text{E}} \), in terms of volume fractions, have been calculated and analyzed. It has been observed that temperature has a significant effect on the thermophysical properties of the studied system. Spectroscopic measurements confirm the disruption of ion-pair interactions of [BMIM][BF4] and hydrogen-bonded network of water in the aqueous mixture of [BMIM][BF4].

Measurements of some physical properties of binary liquid mixtures (N-methyl-2-pyrrolidone + an aliphatic ester) at several temperatures and data processing of viscosity and ultrasonic speed

The ultrasonic speed (U) studies are carried out using single crystal variable path fixed frequency (2MHz) ultrasonic interferometer on some aliphatic esters in N-methyl-2-pyrrolidone (NMP) at temperatures of 303.15, 308.15, 313.15 and 318.15K. Excess molar volume, excess isobaric thermal expansion coefficient, excess isentropic compressibility and excess ultrasonic speed are computed from the experimentally measured ultrasonic speeds and densities of pure liquids NMP, methyl acetate (MA), ethyl acetate (EA), butyl acetate (BA) and their binary mixtures over the entire range of composition of NMP. The variation of these properties with composition and temperature of the binary mixtures is discussed in terms of molecular interactions of component molecules. The excess parameters are fitted to a Redlich–Kister type polynomial and the corresponding standard deviations are calculated. Thermodynamic parameters under study suggest the existence of strong interactions between NMP and aliphatic esters. The experimental data of viscosity is used to test the applicability of empirical relations of Grunberg–Nissan, Katti–Chaudhri, Heric–Brewer and McAllister for the systems studied. Also, ultrasonic speeds are theoretically evaluated based on scaled particle theory and compared with the experimentally measured values. The study reveals a close agreement between experimental and theoretical values of ultrasonic speed of these mixtures at all the temperatures under study. An attempt is made to study the temperature effect on the shapes of the interacting molecules in the binary liquid mixture using scaled particle theory in the temperature range 303.15–318.15K.

Density, ultrasonic velocity, viscosity and their excess parameters of the binary mixtures of N,N-dimethylaniline+1-alkanols (C3-C5), +2-alkanols (C3-C4), +2-methyl-1-propanol, +2-methyl-2-propanol at 303.15K

The density, ultrasonic velocity of sound and viscosity of binary mixtures of N,N-dimethyl aniline (N,NDMA) with 1-propanol, +2-propanol, +1-butanol, +2-butanol, +1-pentanol, +2-methyl-1-propanol, +2-methyl-2-propanol were measured at 303.15 K. These experimental data have been used to calculate excess volume V E , excess ultrasonic speeds u E , excess intermolecular free length L , excess acoustic impedance Z E , excess isentropic compressibility κ , deviation in viscosity Δη and excess Gibbs free energy of activation of viscous flow (G* E ). The values of L and κ are negative over the wide range of composition for all the binary mixtures, while the values of Z E are positive. These results have been used to discuss the nature of interaction between unlike molecules in terms of hydrogen bonding, dipole-dipole interaction, proton-acceptor interaction and dispersive forces. The viscosity data have been correlated using three equations: Grunberg and Nissan, Katti & Chaudhri and Hind et al. The excess/deviations were fitted by a Redlich-Kister equation and the results were analyzed in terms of specific interactions present in these mixtures.

Ultrasonic speeds and isentropic compressibilities of {difurylmethane + (C 1–C 6) n-alkanol} binary mixtures at T = 298.15 K

Densities ( ρ), and ultrasonic speeds ( u) of {difurylmethane + (methanol or ethanol or propan-1-ol or butan-1-ol or pentan-1-ol or hexan-1-ol)} binary mixtures have been measured over the entire composition range at T = 298.15 K and atmospheric pressure. Excess isentropic compressibility coefficient, κ s E , excess ultrasonic speeds, u E and excess intermolecular free length, L f E , of each binary system were calculated and correlated by the Redlich–Kister equation. The results are discussed in terms of possible intermolecular interactions and structural effects.

Ultrasonic Investigations in Ternary Mixtures Containing Water, 2-Butoxyethanol and t-Butanol at 298.15 K

Ultrasonic speeds in, and isentropic compressibilities of, aqueous solutions of water + 2-butoxyethanol (2BE)+t-butanol have been determined at 298.15 K. The concentrations of t-butanol at which the ultrasonic speed becomes maximum and isentropic compressibility becomes minimum are found to decrease with increases in the concentration of 2BE, x2BE, in the cosolvent (aqueous 2BE). This behavior indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. In the presence of 2-butoxyethanol, enhancement in the hydrogen bonded structure of water due to hydrophobic hydration between t-butanol and water molecules decreases as the concentration of x2BE in the cosolvent increases. When x2BE>0.2, the ternary solution behaves like a normal liquid. This behavior is also very well reflected in the concentration dependence of the excess ultrasonic speed and excess isentropic compressibility. The optimum concentrations of t-butanol, (\(x_{\mathrm{t}\mbox{-}\mathrm{B}}\))opt, at which extrema in ultrasonic speed, isentropic compressibility, excess ultrasonic speed and excess isentropic compressibility are observed decrease with increase in x2BE in the cosolvent. The results are explained as being due to a reduction in the strength of hydrophobic interactions responsible for enhancement in the structure of water in aqueous t-butanol in the presence 2BE. Beyond (\(x_{\mathrm{t}\mbox{-}\mathrm{B}}\))opt, the hydrogen bonded network of water collapses and water, 2-butoxyethanol and t-butanol molecules interact with each other as normal liquid molecules.