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The density (d), ultrasonic velocity (U), and viscosity (η) have been measured for the electrolytes, i.e., potassium chromate, sodium chromate, and sodium thiosulphate in an aqueous solution of dimethyl sulphoxide (DMSO) solution at 293 K, 298 K, 303 K, 308 K, and 313 K. By using the measured data, the other parameters like adiabatic compressibility (β), relative change in adiabatic compressibility (Δβ/β),change in adiabatic compressibility (Δβ),apparent molal volume (Øv), apparent molal compressibility (Øk),intermolecular free length (Lr), specific acoustic impedance (Z), limiting apparent molal compressibility ( ∅ k 0 ), limiting apparent molkal volume (Øv0) and their constants (Sk, Sv) can be calculated. The results obtained from the above parameters are helpful to determine the solute–solute and solute–solvent interaction. [ABSTRACT FROM AUTHOR]

Nanoparticles suspended in conventional fluids also named as nanofluids are being researched due to its unique thermal behaviour and its employability as heat transfer fluids. This report details the preparation and stabilization of Al2O3/CuO nanofluids and was analyzed by X-Ray diffraction, SEM and IR respectively. Further the synthesized nanoparticles are dispersed in different volume fractions of ethylene glycol solvent (0.001, 0.003, and 0.005 mass fractions) to prepare nanofluids. The nanofluids were prepared via rigorous stirring and ultrasonic agitation to maintain the stability. Further these nanofluids were prepared without any stabilizer at 2.7 pH. Further the thermal properties were investigated using KD2 Probe analysing unit, which showed that the thermal conductivity increased with higher concentrations of nanofluids. Ultrasonic velocity, yet another property of nanofluids, represents the speed in which sound propagates in a material and depends on density and elasticity of the material. Ultrasonic velocity of nanofluids is important for non-radiative and non-destructive structural analysis and hence the same has been investigated. Results proved that the prepared nanocoolants are stable and hence could be utilized for coolant applications.

The thermo-physical parameters like density (ρ), ultrasonic velocity (u) and viscosity (η) have been experimentally measured for the ternary liquid mixture of para-anisaldehyde (4-methoxy benzaldehyde) in n-Hexane solution with dimethylamine at various temperatures such as 303 K, 308 K and 313 K and at fixed frequency of 2 MHz. The thermodynamic and acoustical parameters such as adiabatic compressibility (β), internal pressure (πi), cohesive energy (CE), free volume (Vf), free length (Lf), acoustic impedance (z), viscous relaxation time, Lennard Jones potential (LJP), and K value have been calculated from the experimental data. The various excess properties including excess acoustic impedance (ZE), excess free length (LEf, excess adiabatic compressibility (βE), excess free volume (VfE), excess ultrasonic velocity (UE) and excess internal pressure (πiE) have also been computed from the calculated values. The values of UE, ZE, and LEF for each mixture have been fitted to the Redlich - Kister polynomial equation. The variation of these parameters with respect to different concentration at different temperatures for the ternary system of para-anisaldehyde + dimethylamine + n-hexane has been studied in accordance with their strength of molecular interaction under the influence of ultrasonic wave of frequency 2 MHz. [ABSTRACT FROM AUTHOR]

Polyphenols from Slovenian hops (Humulus lupulus L.) of the Aurora variety were extracted by different methods and using classical solvents and several deep eutectic solvents (DES) based on choline chloride as the hydrogen bond acceptor component. The obtained extract solutions were analyzed by HPLC for the content of extracted α- and β-acids and extracted xanthohumol. It was found that choline chloride:phenol DES concentrated aqueous solution had an extraction efficiency close to that of diethyl ether, which is considered one of the best classical extraction solvents for polyphenols from hops. The comparison of the extraction efficiency with other choline chloride-based DESs showed that the chemical similarity of the phenol ring in the solvent DES with the polyphenols in hops may be crucial for a highly efficient extraction with choline chloride:phenol DES. On the other hand, the choice of extraction method and the viscosity of the solvents tested seem to play only a minor role in this respect. As far as we know, this is the first study to attempt to relate extraction efficiency in the extraction of hydrophobic solutes to the compressibility of the DES extractants, the latter of which may be correlated with the extent of hydrophobic hydration around the DES components. In addition, using the heating and stirring method for the preparation of choline chloride-based DES concentrated aqueous solutions we found no support for the occurrence of water in two different roles (in the structural and in the dilution role) in these solvents. [ABSTRACT FROM AUTHOR]

Adiabatic compressibility βS of the 4-methylpyridine + water solution is investigated in a wide concentration and temperature variation interval using Mandelstam–Brillouin scattering spectroscopy. The adiabatic compressibility minimum caused by the microinhomogeneous structure of the solution is experimentally established at the concentration of 0.06 M. The results of the investigations allow constructing a diagram of possible states caused by a continuous three-dimensional hydrogen bond network of water. [ABSTRACT FROM AUTHOR]

Benzene with Butyl/Pentyl Parabens is evaluated using the volumetric and acoustic study as a function of temperature. The properties such as partial and apparent molar volumeand partial and apparent molar compressibility of the mixtures were studied. The thermoacoustic properties of the mixture, such as acoustic impedanceand free lengthwere analyzed. These measurements were utilized to interpret the intermolecular interactions among the constituents. [ABSTRACT FROM AUTHOR]

It is well known that polar organic compounds, such as alcohols and polyols, exert an appreciable influence on water structure and thus have important effects on surfactant micellization. These substances are often used to modify the properties of surfactants in aqueous solutions, increasing the practical applications they have in diverse industries. In this work, the critical micelle concentration (CMC) of decyltrimethylammonium bromide (C10TAB) in water and in 1,2-propanediol aqueous solutions was determined from both sound velocity and surface tension measurements as a function of surfactant concentration in the temperature range of (293.15 to 308.15) K. The critical micelle concentration of the surfactant increases as the concentration of 1,2-propanediol becomes higher, while the effect on temperature does not show important changes within the range considered. At the selected temperatures, the standard thermodynamic parameters of micellization suggests that the addition of 1,2-propanediol makes the micellization process less favorable. Thermodynamic analysis suggests that the micelle formation of C10TAB is an entropy-driven process at the temperatures considered in this study. [ABSTRACT FROM AUTHOR]

Ultrasonic velocity measurements, density measurements, and viscometric studies were conducted for the ternary mixture of pyridine and toluene separately with N, Ndimethylformamide (DMF) in butanol, at different temperatures and for different concentrations of component liquids. Using these basic experimental data, various acoustic and thermodynamic parameters, such as adiabatic compressibility (β), free length (Lf,), free volume (Vf), etc. were calculated. Also, Excess thermo-acoustical parameters were calculated from the experimentally measured data. The outcomes were expressed in terms of the molecular interactions and the variations in parameters under varying solute concentrations. A comparative study is discussed. Variation in the above parameters for the different mixtures is indicative of the nature of the interactions between the components in the liquid mixture. Concluding remarks regarding intermolecular interactions are provided. [ABSTRACT FROM AUTHOR]

Streptomycin is an antibiotic medication used to treat a number of bacterial infections. In the present study ultrasonic velocity (U), density (ρ) and viscosity (η) have been measured at frequency 1 MHz in the binary mixtures. The binary mixtures of streptomycin with water in the concentration range (0.1 to 0.0125%) at 303 K, 308 K, and 313 K using a multifrequency ultrasonic interferometer. The measured value of ultrasonic velocity, density and viscosity have been used to estimate the acoustical parameters namely adiabatic compressibility (βa), relaxation time (τ), acoustic impedance (z), free length (Lf), free volume (Vf) and internal pressure (Pi), Wada’s constant(W), Rao’s constant (R) to investigate the nature and strength of molecular interaction in the binary mixture with water. The obtained results support the occurrence of complex formation, molecular association through intermolecular hydrogen bonding in the binary liquid mixtures. DOI: http://dx.doi.org/10.17807/orbital.v13i4.1465

Polyphenols from Slovenian hops (Humulus lupulus L.) of the Aurora variety were extracted by different methods and using classical solvents and several deep eutectic solvents (DES) based on choline chloride as the hydrogen bond acceptor component. The obtained extract solutions were analyzed by HPLC for the content of extracted α- and β-acids and extracted xanthohumol. It was found that choline chloride:phenol DES concentrated aqueous solution had an extraction efficiency close to that of diethyl ether, which is considered one of the best classical extraction solvents for polyphenols from hops. The comparison of the extraction efficiency with other choline chloride-based DESs showed that the chemical similarity of the phenol ring in the solvent DES with the polyphenols in hops may be crucial for a highly efficient extraction with choline chloride:phenol DES. On the other hand, the choice of extraction method and the viscosity of the solvents tested seem to play only a minor role in this respect. As far as we know, this is the first study to attempt to relate extraction efficiency in the extraction of hydrophobic solutes to the compressibility of the DES extractants, the latter of which may be correlated with the extent of hydrophobic hydration around the DES components. In addition, using the heating and stirring method for the preparation of choline chloride-based DES concentrated aqueous solutions we found no support for the occurrence of water in two different roles (in the structural and in the dilution role) in these solvents.

• This review paper focuses on the ultrasonic studies to investigate the molecular structure and interactions in various liquid mixtures, including binary, ternary, and organic solutions. • The ultrasonic study has gained popularity due to its non-destructive testing (NDT) nature and finds applications in medical and scientific fields, agriculture, industries, and more. • The primary objective of this review is to explore the interactions between different liquid mixtures, employing different evaluation criteria. • Thermo properties, excess functions, and acoustic parameters are essential components of the examined research papers. An understanding of the molecular process can be gained by analyzing the molecule interaction using the knowledge of how thermodynamic parameters vary with composition and temperature. Reliable information about the chemical and physical characteristics of a broad range of liquid mixes is required by industry. This review examines multiple research papers investigating molecular interactions, focusing on the acoustic/ultrasonic technique. This technique employs ultrasonic waves to probe molecular interactions. Researchers utilized an ultrasonic interferometer to measure ultrasonic wave velocity, liquid density can be determined by using a specific gravity bottle, and employed the Ostwald viscometer for viscosity measurements. The velocity of ultrasonic waves, the density of a particular liquid combination, and viscosity can all be measured to analyze various acoustic and thermodynamic properties. Understanding the molecular interactions in each sample is greatly aided by this study. A detailed explanation of the many measured parameters has been provided. [ABSTRACT FROM AUTHOR]

It is well known that polar organic compounds, such as alcohols and polyols, exert an appreciable influence on water structure and thus have important effects on surfactant micellization. These substances are often used to modify the properties of surfactants in aqueous solutions, increasing the practical applications they have in diverse industries. In this work, the critical micelle concentration (CMC) of decyltrimethylammonium bromide (C10TAB) in water and in 1,2-propanediol aqueous solutions was determined from both sound velocity and surface tension measurements as a function of surfactant concentration in the temperature range of (293.15 to 308.15) K. The critical micelle concentration of the surfactant increases as the concentration of 1,2-propanediol becomes higher, while the effect on temperature does not show important changes within the range considered. At the selected temperatures, the standard thermodynamic parameters of micellization suggests that the addition of 1,2-propanediol makes the micellization process less favorable. Thermodynamic analysis suggests that the micelle formation of C10TAB is an entropy-driven process at the temperatures considered in this study.

Ultrasonic Velocity, density, viscosity have been measured experimentally for the solution of leaf extract of Ricinus communis in 50% ethyl alcohol with various concentrations at 298.15 K, 303.15 K, 308.15 K keeping constant frequency of 4 mhz. As the acoustical parameters like adiabatic compressibility, intermolecular free length, relative association, relaxation time, specific acoustic impedence would prove to be more useful to predict and confirm the molecular interactions, these have been determined by measuring the Ultrasonic Velocity, density, viscosity of the prepared solution. A variation in these parameters will provide strong information regarding the molecular interactions taking place in the solution. The propagation of ultrasonic waves affects the physical properties of the medium and hence gives useful information about the molecular interactions such as ion-ion, ion-dipole, dipole-dipole interaction, hydrogen bonding in the solution. Here the study shows that the ultrasonic velocity increases here with increase in concentration this is due to the solvation process of solute by two different solvent molecules like water and ethanol, from this we can say that there is strong solute-solvent interaction in the root extract solution of Ricinus communis. [ABSTRACT FROM AUTHOR]

Ultrasonic velocity, density and viscosity have been measured using Anton Paar DSA 5000 M in the binary mixtures of nHexane with Ethanol at various mole fractions from 0.1 to 0.9 with temperature ranging from 288K to 318K. Various derived parameters like adiabatic compressibility, acoustic impedance, free length and relaxation time have been calculated using standard formulae. Non covalent interaction taking place in the liquid mixture has been discussed on the basis of the values obtained from experimental parameters and derived parameters. [ABSTRACT FROM AUTHOR]

Ultrasonic Velocity, density, viscosity have been measured experimentally for the solution of leaf extract of Ricinus communis in 50% ethyl alcohol with various concentrations at 298.15 K, 303.15 K, 308.15 K keeping constant frequency of 4 mhz. As the acoustical parameters like adiabatic compressibility, intermolecular free length, relative association, relaxation time, specific acoustic impedence would prove to be more useful to predict and confirm the molecular interactions, these have been determined by measuring the Ultrasonic Velocity, density, viscosity of the prepared solution. A variation in these parameters will provide strong information regarding the molecular interactions taking place in the solution. The propagation of ultrasonic waves affects the physical properties of the medium and hence gives useful information about the molecular interactions such as ion-ion, ion-dipole, dipole-dipole interaction, hydrogen bonding in the solution. Here the study shows that the ultrasonic velocity increases here with increase in concentration this is due to the solvation process of solute by two different solvent molecules like water and ethanol, from this we can say that there is strong solute-solvent interaction in the root extract solution of Ricinus communis. [ABSTRACT FROM AUTHOR]

The adiabatic compressibility along the two-phase saturation line was calculated for nine molten immiscible mixtures, namely, LiF + KBr, LiF + CsCl, LiF + RbBr, LiF + KI, LiF + CsBr, LiF + RbI, LiF + CsI, LiCl + AgBr, and NaCl + AgI, using experimental data on the sound velocity and density. It is shown that the ratio of compressibility of the equilibrium phases depends significantly on the sizes of the mixed ions. The dependence of the changes in compressibility in the distance and in the vicinity of the critical mixing point on the characteristics of the chemical bond between the ions is discussed. [ABSTRACT FROM AUTHOR]

Streptomycin is an antibiotic medication used to treat a number of bacterial infections. In the present study ultrasonic velocity (U), density (ρ) and viscosity (η) have been measured at frequency 1 MHz in the binary mixtures. The binary mixtures of streptomycin with water in the concentration range (0.1 to 0.0125%) at 303 K, 308 K, and 313 K using a multifrequency ultrasonic interferometer. The measured value of ultrasonic velocity, density and viscosity have been used to estimate the acoustical parameters namely adiabatic compressibility (βa), relaxation time (τ), acoustic impedance (z), free length (Lf), free volume (Vf) and internal pressure (Pi), Wada's constant(W), Rao's constant (R) to investigate the nature and strength of molecular interaction in the binary mixture with water. The obtained results support the occurrence of complex formation, molecular association through intermolecular hydrogen bonding in the binary liquid mixtures. [ABSTRACT FROM AUTHOR]

The acoustic studies of the interactions between alcohol molecules and water soluble polar solvent DMF are significant for understanding the relationships between structure and function of polar molecule like DMF, and for explaining the mechanisms of interaction of alcoholic OH group with an electronegative moiety. In this piece of work Ultrasonic velocity, density and viscosity have been measured at 298 K, 308 K, 318 K and 328 K for mixture of N,N-dimethylformamide (DMF) and n-butanol, the frequency being maintained at a constant value. The experimental data have been used to calculate the acoustical and thermodynamical parameters like adiabatic compressibility, free length, free volume, internal pressure, acoustic impedance, Gibbs free energy. [ABSTRACT FROM AUTHOR]

Considering the Panigrahi and Chatterjee model (2017) for variable generalised Chaplygin gas, in this paper we found for this kind of exotic matter an analytic expression for the adiabatic compressibility βs. It was analyzed the behaviour of the adiabatic compressibility in the limit of high and low pressure. The derived equation for βs was used to deduce the value of the heat capacity at constant pressure Cp for variable generalised Chaplygin gas.

Abstract—In accordance with the energy conservation law, at convection, the total heat released through adiabatic flow and the dissipative heat mutually exactly compensate as these are the internal processes. However, the allowance for these processes, compared to the Boussinesq approximation for incompressible mantle, changes the temperature gradient, with the temperature itself changing by up to 500 K, and almost halves the mantle heat flow. In this work, the effects of dissipation and adiabatic compressibility of the material on the mantle temperature and heat flow distributions are analyzed and the role of internal heat sources is examined. The effects of dissipation and adiabatic compression can be interpreted as the effective heat sources nonuniformly distributed in space. Negative homogeneous heat sources always increase the heat flow from the core. However, in reality, adiabatic compressibility integrally equivalent to a negative heat source reduces the heat flow from the core just as dissipation. [ABSTRACT FROM AUTHOR]

Molecular interactions and aggregation behavior of cloxacillin sodium (CloNa) in water and aqueous NaCl solutions was studied through volumetric and ultrasonic sound velocity method at 298.15 K and atmospheric pressure. Density, ρ, and ultrasonic sound velocity, u, of cloxacillin sodium in water and aqueous NaCl solutions were measured with a digital density and ultrasonic sound velocity analyzer (DSA 5000, Anton Paar, Austria). And from the investigational data, apparent molar volume, ϕv, adiabatic compressibility, ϕS, apparent molar adiabatic compressibility, ϕk, limiting apparent molar volume, ϕn0, limiting apparent molar adiabatic compressibility, ϕk0, and aggregation concentration, CMC of cloxacillin sodium was calculated. The outcomes indication exhibits very significant evidence about the interactions among solute-solvent-co-solute (solute-solute, solute-solvent) and aggregation behavior in the aqueous environment and this result would be useful for the drug action in human body with pharmacological applications. [ABSTRACT FROM AUTHOR]

We analyze numerical methods for the determination of the adiabatic compressibility of fluids in computer experiments. Some of them like the Monte-Carlo (MC) method in constant pressure ensembles can be applied for particles which interact through hard-core potentials. We calculate adiabatic compressibility and sound velocity at different pressures for the hard-sphere fluid using conventional MC method in two ensembles: isothermal and adiabatic (isothermal-isobaric and isobaric-isoenthalpic). We show that the accuracy of adiabatic compressibility of the hard-sphere fluid is the same both for the isobaric-isoenthalpic and isothermal-isobaric- ensembles. [ABSTRACT FROM AUTHOR]

Novel 2, 4-dinitrophenyl hydrazine based Schiff bases (L1-L3) has been successfully synthesized and characterized. The ultrasonic velocity (C) and density (?) has been measured for the synthesized Schiff bases with DMSO (Dimethyl sulfoxide) solvents at 300 K. Using these experimental data ultrasonic Velocity, adiabatic compressibility, intermolecular free length and specific acoustic impedance have been evaluated. From the experimental data, it has been found that L1 ascribed higher ultrasonic velocity as compared to other molecular probes L2 and L3. The strength and nature of interaction between the molecular probes and DMSO solvents has been discussed. Scanning electron microscope studies of molecular probes are performed to discuss the microstructure and surface functionalities. [ABSTRACT FROM AUTHOR]

In the present study, the molecular association between (metal ions) ZnCl2 and extracted form of drug Zingiber officinale is investigated by ultrasonic investigation. The density (ρ), ultrasonic velocity (U), and viscosity (η) of an ethanolic extract of drug with metal ions of different concentrations (number of moles of drug = 0.7009, 1.4018, 2.1027, 2.8036, and 3.5045) at 2 MHz are measured through ultrasonic interferometer. From experimental parameters, various acoustic parameters such as adiabatic compressibility (β), intermolecular free length (Lf), specific acoustic impedance (Z) are calculated. This study proves the molecular association is present in liquid mixture system and such study is helpful for pharmacological applications of drugs. [ABSTRACT FROM AUTHOR]

The study of molecular interactions in the solutions and liquids are of considerable importance and has been undertaken by many researches now-a-days. Many physical methods are employed to study the physical properties of liquids/solutions. They are ultrasonic, thermodynamic, thermochemical and spectroscopic methods. Ultrasonic velocity measurements are highly sensitive to molecular interactions and used to provide qualitative information about the nature and strength of the intermolecular / inter-ionic interactions. Diseases in human beings and animals may be caused by a variety of microorganisms. Antibiotics, antiseptic and disinfectants are prescribed as drugs. The drug-solvent interactions play an important role in the understanding of drug action. The term “Sulfanilamides” (Sulphanilamide) is also used to describe a family of molecules containing these functional groups. Sulphanilamide reduces vaginal burning, itching and discharge that may occur with this condition. Sulfamerazine is also a sulfonamide antibacterial agent. It is bacteriostatic in nature. Inhibition of dihydrofolic acid synthesis decreases the synthesis of bacterial nucleotides and DNA. In the present investigation, the solutions of different molalities were prepared with the samples in non-aqueous medium and the experiments were carried out from low concentration to higher concentration, at different temperatures. The measured values of density, viscosity and ultrasonic velocity were used to compute adiabatic compressibility and specific acoustic impedance. An attempt is made to identify the entry solvate into the samples and the entry of biological molecules into the solvate which supports to identify the molecular structure. From the experimental data of ultrasonic velocity, density and viscosity, calculated the acoustical parameters. [ABSTRACT FROM AUTHOR]

• Compressibility, density and sound velocity for two-phase LiF + CsCl melt are investigated. • Critical temperature of the liquid-liquid phase transition is 1257 K, the critical compressibility is 271.9 TPa−1, the critical sound velocity is 1257 m s−1, the critical density is 2030 kg m−3. The adiabatic compressibility, β , of the immiscible liquid mixture (LiF + CsCl) along the saturation line was experimentally investigated in the temperature range from the melting point to the critical mixing temperature using sound velocity values, u , measured by the pulse method, and density quantities, ρ , determined using the hydrostatic weight procedure based on the relationship β = u −2 ρ −1. The coefficients of the temperature dependencies for the compressibility, sound velocity and density of the upper and lower equilibrium phases have opposite signs because of the superposition of the thermal motion intensity of the ions and the change in the phase compositions. The differences Δ β , Δ u and Δ ρ for the equilibrium phases decrease with temperature elevation. The temperature dependencies of the compressibility, sound velocity and density difference are described using the empirical equations Δ β ≈ (T c − T) 1.004, Δ u ≈ (T c − T) 1.003 and Δ ρ ≈ (T c − T) 0.504. [ABSTRACT FROM AUTHOR]

In this paper, the variation of the ultrasonic velocity and density, to extract other physical properties such as Viscosity, Adiabatic compressibility, Relative association, Internal free length, Acoustic impedance for the dielectric constants of Dimethyl Sulfoxide, Ethanol water, and Acetone with respect to the variation in the concentration are analysed. The comparison with experimental data in the literature has been performed. The study on the effect of the variations on the acoustical parameters in the binary mixture of DMSO, ethanol water, and acetone is also presented here. [ABSTRACT FROM AUTHOR]

Ultrasonic studies of (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-4-methylpentanoic acid (NPTLU), 2-(2-(2-(4-chlorophenyl)-1H-benzo[d]imidazol-1-yl)-2-oxoethyl)isoindoline-1,3-dione (C‑BI-CL-L), 2-(4-methyl-1-(2-(4-nitrophenyl)-1H-benzo [d]imidazol-1-yl) -1-oxopentan-2-yl)isoindoline-1,3-dione (C-BI-NO2-L), 2-(1-(2-(4-nitrophenyl)-1H-benzo[d]imidazol-1-yl)-1-oxobutan-2-yl)-2,3-dihydroinden-1-one (C-BI-NO2-G), 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-(4-oxo-2-phenylquinazolin-3(4H)-yl) acetamide (C-QA-GL), and 1-(2-((4-oxo-2-phenylquinqxolin-3(4H)-yl)carbamoyl)benzoyl)pyrrolidine-2-carboxylic acid (C-QA-PR) in solution of polar and non-polar solvent of various concentrations at 303–318 K. Density and ultrasonic velocity measured and with the help of these data, different thermo-acoustical parameters viz. adiabatic compressibility, intermolecular free length, acoustic impedance, surface tension, Rao's constant, molar volume, Wada's constant calculated using standard formulas. The variation of these parameters with concentration and temperature studied using graphical representations of these parameters. Ethyl alcohol and DMSO were chosen as polar and non-polar solvents, respectively. The variation in different properties reveals the presence of specific molecular interactions in solute and solvent used, which will give information regarding drug transmission and absorption. [ABSTRACT FROM AUTHOR]

Using the phase-time approach, the dependences of the speed of sound on the temperature and composition are measured in CsCl–CsBr, CsCl–CsI, and CsBr–CsI molten binary mixtures. The adiabatic compressibility of these mixtures is calculated from the experimental values of speed and density. Negative deviations from the additive values of the speed of sound and positive deviations from the additive values of adiabatic compressibility are observed. The magnitude of deviation depends on the ratio of the sizes of anions in the mixtures. [ABSTRACT FROM AUTHOR]

Abstract Physical and chemical structure affect properties of dissolved organic matter (DOM). Recent observations revealed that heating and cooling cycles at higher temperature amplitude lead to a change in DOM physical conformation assumingly followed by a slow structural relaxation. In this study, changes at lower temperature amplitudes and their relation to DOM composition were investigated using simultaneous measurements of density and ultrasonic velocity in order to evaluate the adiabatic compressibility, which is sensitive indicator of DOM structural microelasticity. Six fulvic acids (FAs) having various origins were analyzed at concentrations of 0.12, 0.6 and 1.2 g L−1 and at different temperature amplitudes. First, we validated that the used technique is sensitive to distinguish conclusively the structural changes upon heating and cooling of DOM with heating/cooling amplitude of ± 3 °C and higher. This amplitude was then applied to observe the relationship between change in adiabatic compressibility and chemical composition of FA. No correlation was observed with elemental composition and aromatic structures. Positive correlations were observed with content of alkyl moieties, carboxylic and carbonyl carbons and biological activity. Based on literature data, it was concluded that alkyl moieties undergo (re)crystalization during thermal fluctuation and their structural relaxation back is very slow (if occurs). The polar moieties form a flexible hydrogel responding to thermal fluctuation by moderate dissolution and re-aggregation. Negative correlation was observed in relation to the amount of peptide and O-alkyl systems, which can be attributed to very fast structural relaxation of proteinaceous materials, i.e. their larger content leads to lower difference between original and heat-induced compressibility. Last, the increase of the heating/cooling amplitude from ± 3 to ± 15 °C resulted in an increase of the change of the adiabatic compressibility and in the extension of the relaxation time needed for DOM structure to return to the equilibrium. We conclude that this increase is caused by the increase in inner energy, and DOM conformation can reach a cascade of energy minima, which may influence DOM reactivity and biodegradability. Graphical abstract fx1 Highlights • The DOM structure relaxes upon heat-cool cycles. • Structural relaxation time correlates with heat-cool amplitude. • Chemical composition of DOM influences relaxation time. • Structural flexibility of DOM is linked to its biological activity. [ABSTRACT FROM AUTHOR]

Abstract: Ultrasonic studies of compounds of dihydropyridine series in polar and non-polar solvents at various concentrations and temperatures 303-318 K. Density and ultrasonic velocity and different thermo-acoustical parameters measured. Rao's constant, molar volume, Wada's constant, isothermal compressibility reported with the help of these data using standard formulae. Ethanol and DMF selected as polar and non-polar solvents respectively. The variation in thermoacoustical parameters with temperature and concentration shows that the solute-solute molecular interaction takes place in solution which is more in DMF. [ABSTRACT FROM AUTHOR]

The recent literature data of density (ρ) at different temperatures (293.15, 298.15 and 303.15 K) and sound velocity ( u ) at 298.15 K on aqueous solutions of tetraalkylammonium bromides (R 4 NBr) in limiting concentration range (0.01–0.15) mol kg −1 have been used to obtain coefficient of thermal expansion (α) and adiabatic compressibility (β s ) of solutions at 298.15 K. Using specific heat capacity ( C p ) data, the appropriate calculations of isothermal compressibility (β T ) and internal pressure ( P i ) in solutions have been accomplished. In solutions the P i and β s were found to increase and decrease with increase in concentration of salt. These have been interpreted in terms of hydrophobic hydration of R 4 N + cations in contrast to normal alkali cation hydration. The Tammann-Tait-Gibson (TTG) model was applied to derive the excess volume change for the electrolytes ( V ‾ 2 0 E = V ‾ 2 - V int . ) and intrinsic volume ( V int. ) of the studied salts at 298.15 K. The V int. values are further used to compute ionic radii for tetraalkylammonium cations (R 4 N + ) by subtracting the intrinsic volume of bromide ions. The calculated radii agree satisfactorily with those obtained from model and geometry consideration of cations. The magnitudes of excess volumes are found to be negative and which increase with the extent of methylene group substitution (tetramethyl to tetrabutyl cations) in the salt cations. This is generally known as water structural and caging effect. The analysis of the present work indicates that the thermal expansion coefficient property of the organic cations and water structural alterations (in the form of clathrate like structures), govern the parameters like excess volumes of the ions in contrast to normal electrostrictive alkali cations. The results are in conformity of the Frank and Wen’s model of hydration of cations mainly governed by cation-cation interaction presumably due to the overlapping of extensive hydration structures and not directly caused by columbic hydration. [ABSTRACT FROM AUTHOR]

L -carnitine plays physiologically important roles specifically to decrease triglycerides, very low density lipoprotein (VLDL) and cholesterol. Considering these facts, it is believed to be helpful in the reduction of cardiovascular diseases and diabetes. Physicochemical properties of L -carnitine in aqueous or mixed aqueous solutions are scarcely available in literature. Such properties will be useful in understanding the interactions of L -carnitine with other cellular components like trimethylamine-N-oxide (TMAO), dextrose ( D -glucose) and NaCl. The values of densities (ρ) and speeds of sound (u) of L -carnitine were measured over the molality range of m  = 0.05 mol·kg −1 to m  = 0.3 mol·kg −1 at temperature T  = 293.15 K to T  = 313.15 K in water and in aqueous solutions of TMAO, dextrose, and NaCl. Using these data, values of apparent molar volume ( V 2, m , φ ) and apparent molar adiabatic compressibility ( K s ,2, m , φ ) have been determined. The results obtained from these measurements have been used to derive the standard partial molar volume ( V 2 , m o ), standard partial molar adiabatic compressibility ( K s , 2 , m o ), standard partial molar volume of transfer ( Δ tr V 2 , m o ) and standard partial molar isentropic compressibilities of transfer ( Δ tr K S , 2 , m o ) from water to aqueous solutions of TMAO, dextrose, and NaCl. Through Isothermal Titration Calorimetry (ITC), the enthalpies of dilution ( Δ dil H m ) of L -carnitine in water (over a temperature range of T  = 293.15 K to T  = 313.15 K) and in aqueous solutions of TMAO, dextrose, and NaCl have been determined. The values of standard molar enthalpy of dilution ( Δ dil H m o ) and their transfer values ( Δ tr Δ dil H m o ) have been derived from these measurements. The results have been discussed in terms of possible intermolecular interactions. The data suggest that there is overall balancing of hydrophobic and hydrophilic interactions in system containing L -carnitine and TMAO in aqueous solution, but hydrophobic effect dominates when the co-solute is NaCl or dextrose. [ABSTRACT FROM AUTHOR]

Densities and speed of sound of dilute aqueous solutions of three sodium sulfonamides structurally-related, namely, sodium sulfadiazine (NaSD), sodium sulfamerazine (NaSMR) and sodium sulfamethazine (NaSMT) were measured as a function of molal concentration at various temperatures (278.15–308.15) K. Standard molar quantities and related properties were calculated and the results were interpreted in terms of structural effects, and solute-solvent interactions. Results suggest that these sulfonamides are acting as structure makers of the water-structure. [ABSTRACT FROM AUTHOR]

Densities, ρ and ultrasonic speeds, u of L-histidine (0.02–0.12 mol·kg−1) in water and 0.1 mol·kg−1 aqueous citric acid solutions were measured over the temperature range (298.15–313.15) K with interval of 5 K at atmospheric pressure. From these experimental data apparent molar volume ΦV, limiting apparent molar volume ΦVO and the slope SV, partial molar expansibilities ΦEO, Hepler’s constant, adiabatic compressibility β, transfer volume ΦV, trO, intermolecular free length (Lf), specific acoustic impedance (Z) and molar compressibility (W) were calculated. The results are interpreted in terms of solute–solute and solute–solvent interactions in these systems. It has also been observed that L-histidine act as structure maker in water and aqueous citric acid. [ABSTRACT FROM AUTHOR]

Densities, ultrasonic speeds and viscosities of l -alanine and l -phenylalanine in water and in 0.1 mol·kg − 1 aqueous citric acid solutions were measured over the temperature range (298.15 to 313.15) K with interval of 5 K at atmospheric pressure. From these experimental data apparent molar volume, limiting apparent molar volume and the slope, partial molar expansibilities, adiabatic compressibility, transfer volume, Falkenhagen coefficient, Jone-Dole's coefficient, the temperature derivative of Jone-Dole's c oefficient, intermolecular free length, specific acoustic impedance, and molar compressibility were calculated. The results are interpreted in terms of solute – solute and solute-solvent interactions in these systems. It has also been observed that l -alanine acts as a structure breaker whereas l -phenylalanine acts as a structure maker in aqueous citric acid. [ABSTRACT FROM AUTHOR]