Speed Of Sound Data Research Articles

Hydration behavior of D-calcium pantothenate (vitamin B5) in the presence of sugar-based deep eutectic solvents at different temperatures: experimental and theoretical study

Considerable efforts have been devoted in recent years to enhancing the efficacy medicinal substance, leading to the discovery of innovative drug formulations and delivery techniques. The successful design of these processes necessitates a profound understanding at the molecular level of how these substances interact with biological membranes. Thorough thermodynamic investigations provide invaluable insights into these interactions and aid in selecting suitable compounds for pharmaceutical production. This study aims to determine the density and speed of sound for D-calcium pantothenate in mixtures of water and deep eutectic solvents (DESs), specifically choline chloride/sucrose, choline chloride/ glucose, and choline chloride/ fructose (with 2:1 molar ratio) over a temperature range of 288.15 K to 318.15 K under atmospheric pressure. In order to predict the behavior of molecules, COSMO model (the Conductor-Like Screening Model) offer complementary strengths in quantum chemistry. This approach allows for calculating solvation free energies, making it ideal for predicting properties like solubility, where understanding solvent-solute interactions is crucial. By correlating the measured parameters using standard relationships, important partial molar parameters such as apparent molar volumes and apparent molar isentropic compressibility are calculated. Additionally, apparent molar isobaric expansion, and Hepler’s constant are derived from the density and speed of sound data. The experimental apparent molar volumes, and apparent molar isentropic compressibility data is fitted to the Redlich-Meyer equation to obtain significant quantities such as standard partial molar volume, and partial molar isentropic compression. The comprehensive thermodynamic analysis of this studied system holds immense significance for advancements in the pharmaceutical industry.

Speed of Sound Measurements of Binary Mixtures of 1,1-Difluoroethylene (R-1132a) + Propane and Derived Speed of Sound of Pure R-1132a

Speed of sound data, measured using a dual-path pulse-echo instrument, are reported for three binary mixtures of 1,1-difluoroethylene (R-1132a) with propane at temperatures ranging from 230 to 345 K and pressures ranging from slightly above the bubble curve to a maximum pressure of 50 MPa. Significant attenuation of the pulse-echo signals was observed for measurements on pure R-1132a. Therefore, the R-1132a sample was doped with propane at mole fractions ranging from 0.0274 to 0.0887 and the propane + R-1132a mixture data was used to derive sound speeds for pure R-1132a. The data were compared to a preliminary equation of state for R-1132a, and deviations ranged from 2 % to 8 %. This demonstrates that the preliminary R-1132a EoS needs to be refit to better represent the speed of sound.

Speed of Sound Measurements of R-1130(E) and an Azeotropic Blend of R-1336mzz(Z)/1130(E)

Sound speed data measured using a dual-path pulse-echo instrument are reported for pure trans-1,2-dichloroethene (R-1130(E)) and an azeotropic blend of cis-1,1,1,4,4,4-hexafluorobutene (R-1336mzz(Z)) and R-1130(E) with a composition of 74.8 mass % R-1336mzz(Z) with the balance being R-1130(E). The azeotropic blend of R-1336mzz(Z)/1130(E) is classified as R-514A in ANSI/ASHRAE standard 34. Liquid phase speed of sound data are reported from just above the saturation pressure of pure R-1130(E) or the bubble point pressure of R-514A to a maximum pressure of 26.7 MPa. The relative combined expanded uncertainty in the speed of sound varies from 0.032 % to 0.148 % with the greatest deviations occurring at the lowest sound speeds. At present, no reference Helmholtz-energy-explicit equation of state (EOS) is available for R-1130(E). Therefore, the reported data for pure R-1130(E) are compared to an extended corresponding states (ECS) model. Deviations between the pure R-1130(E) sound speed data and the ECS model were found to be consistently negative ranging between − 4.1 % and − 3.5 %. The R-514A data are compared to a multifluid model inclusive of the established reference Helmholtz-energy-explicit EOS for R-1336mzz(Z) and ECS model for R-1130(E) with estimated binary interaction parameters. Deviations between the experimental speed of sound data and the multifluid model were also found to be consistently negative. However, deviations from the multifluid model were found to be as great as − 17.1 %. The large deviations from the ECS model and multifluid model underscore the need for a robust Helmholtz-energy-explicit EOS for R-1130(E).

Speed of sound measurements and derived third and fourth acoustic virial coefficients of supercritical neon

We report comprehensive and accurate measurements of the speed of sound in neon. These measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range between 200 K and 420 K with pressures up to 100 MPa. The standard uncertainties are 1.9 mK in temperature, 22 parts in 106 in pressure and 35 parts in 106 in speed of sound. The third and fourth acoustic virial coefficients of neon were derived from the speed of sound data in the temperature range of the measurements by fitting a fourth-order acoustic virial expansion in pressure with the second acoustic virial coefficient constrained from first-principles calculations. To support our claimed uncertainty, we determined the ratio M/γ0 between the molar mass M and the ideal-gas heat capacity ratio γ0 of the neon sample with a relative standard uncertainty of 7.7 parts in 106 by additional speed of sound measurements using a spherical resonator at 273.16 K.

Effect of Additive (1-Butyl-1-methyl Pyrrolidinium Tetrafluoroborate) on Volumetric, Acoustic and Conductance Properties of Binary Aqueous Solutions of Benzylamine at T = (288.15, 298.15, 308.15, 318.15) K

Effect of additive, 1-butyl-1-methyl pyrrolidinium tetrafluoroborate [BmPyrr+][BF4–] on the volumetric, acoustic and conductance properties of binary aqueous solution of benzylamine has been analyzed at equidistant temperature range using different techniques. Using density and speed of sound data, volumetric and acoustic parameters like apparent and partial molar volumes (Vφ and Vφ0), apparent and partial molar isentropic compressions (Kφ,S and K0φ,S), partial molar volume of transfer and partial molar isentropic compression of transfer (ΔVφ0 and ΔK0φ,S) have been calculated. Conductance parameters like molar conductance (Λm), limiting molar conductance (Λ°m) and activation energy are also calculated using conductance data. All these parameters were used to analyze various types of interactions present in the system. Furthermore, density functional theory (DFT) calculations were conducted for comprehensive understanding of structural variations of ion pairs affecting their physical properties. The hydrogen bond formation in the mixture components was examined by using IR spectrum. Both DFT and Hartee-Fock (HF) methods were used to analyze the results. In addition, the DFT/B3LYP-D3 calculations were also carried out to gather data on the molecular geometry, interactions and other molecular characteristics of the ionic liquid under study.

Volumetric, compressibility and viscometric studies on intermolecular interactions of NaC and NaDC with Emtricitabine and Lamivudine in aqueous medium at (298.15–313.15) K

Bile salts are bio-compatible natural amphiphiles having a significant role in pharmaceutical field as a solubility and permeability enhancer and possess a great biological importance for release and transport of nutrients due to dynamic micellization behavior. Hence, to unfold the interactional mystery of drug − bile salt system in the field of anti-retroviral drugs, we have aimed to investigate solute–solute and solute–solvent interactions of bile salts (NaC and NaDC) with anti-HIV drugs (Emtricitabine and Lamivudine) by using various techniques like volumetry, compressibility, and viscometry at temperature range (298.15 K-313.15 K) with a regular variation of 5 K. Experimental density and speed of sound data have been used to evaluate various physicochemical parameters such as apparent molar volume (φv), isentropic compressibility (κs), and apparent molar adiabatic compression (φκ). The CMC values of bile salts in pure water and aqueous solution of ECT and LMV at 298.15 K have also been evaluated from speed of sound data which corroborate well with our earlier conductivity study on these surfactants. The trends of φv, κs and φκ values for both NaC and NaDC with temperature and in presence of drugs (ECT/LMV) indicate strong solute–solvent interactions in studied system. The results are elucidated in terms of electrostatic and hydrophilic-hydrophobic interactions in bile salt-drug-water system which is confirmed by co-sphere overlap model. Comparatively, NaC offers strong interactions with both drugs due to more hydrophilic character than NaDC. Similarly, out of ECT and LMV, ECT shows strong solute–solvent interactions with both bile salts due to more hydrophilic character than LMV. Relative viscosity parameter (ηr) determined from viscosity measurements further supports above results. This interactional knowledge of bile salts with ECT and LMV would be beneficial to develop a better mechanism in pharmacy for enhancing efficacy and permeability of anti-HIV drugs by using bile salts as a drug delivery agent.

Deep ocean hydrographic variability estimated from distributed geodetic sensor arrays off northern Chile

Observations of spatio-temporal variability of the deep ocean are rare and little is known about occurrence of deep ocean mesoscale dynamics. Here, we make use of 2.5 years of time series data from three distributed sensor arrays, which acquired high-resolution temperature, pressure and sound speed data of the bottom layer offshore northern Chile. Estimating salinity and density from the direct observations enable access to the full spectrum of hydrographic variability from a multi-hourly to annual time scale and with average inter-station distances of less than 1 km. Analyses revealed interannual warming over the continental slope of 0.002 °C yr−1–0.003 °C yr−1, and could trace periodic hydrographic anomalies, likely related to coastal-trapped waves, as far as to the lower continental slope. A concurrent change in the shape of the warm anomalies and the rate of deep-sea warming that occurs with the crossing of the deep-sea trench suggests that the abyssal part of the eastern boundary current system off Chile does not extend past the deep sea trench. Furthermore, the comparison of anomaly timing and shape in between stations implies southwards flow over the mid to lower continental slope, centred closer to the trench.

Structural elucidation of ternary mixtures of L‐valine/glycyl‐L‐valine and water + 1‐decyl‐3‐methylimidazolium bromide: Apparent molar properties at infinite dilution and expansivities

AbstractThis work comprises ternary systems of water + SAIL,1‐decyl‐3‐methylimidazolium bromide, and (S)‐2‐Amino‐3‐methylbutanoic acid generally identified as L‐valine/ (S)‐2‐(2‐Aminoacetamido)‐3‐methylbutanoic acid usually described as glycyl‐L‐valine, densities, and sound speed data have been computed at four operating temperatures, i.e., 288.15 to 318.15 K. Calculated density data have utilized for calculation of various thermodynamic parameters like Vϕ (apparent molar volume), (apparent molar volumes at infinite dilution), and calculated speed of sound statistics used to determine Kϕ,s (apparent molar isentropic compression), Ks (partial molar isentropic compression at infinite dilution). In our systems, the hydrophilic‐ionic interactions that are produced by co‐sphere overlap models are predominant. The Hepler's constant is used to analyze the solute's capacity to create or destroy solvent structures. The interaction parameter is computed using the McMillan‐Mayer theory. Understanding structure‐making, solvation characteristics, and numerous modifications in the ternary system of L‐valine/Glycyl‐L‐valine, water, and [C10MIm] [Br] is aided by a variety of thermodynamic factors.

Compression AutoEncoder for High-Resolution Ocean Sound Speed Profile Data

High-resolution ocean sound speed profile (HROSSP) data is essential for ocean acoustic modeling and sonar performance evaluation. However, the large volume and storage requirements of this data severely restrict its practical application in ocean acoustics. In this paper, we propose a compression autoencoder specifically designed for managing HROSSP data (CAE-HROSSP) and investigate the optimal network structure. Experimental results demonstrate that by using the min-max normalization method for input data and the corresponding inverse normalization for output data, along with employing the LeakyReLU function as the final activation layer, the accuracy of decompressed data reconstruction can be significantly improved. To tackle the challenges of fitting the distribution of surface sound speed data caused by significant variations and noise, we propose two loss functions: slice mean square error and elemental mean square error. These loss functions are combined with mean squared error through weighted summation to enhance CAE-HROSSP’s ability to fit the distribution of surface sound speed values and minimize the reconstruction errors of compressed data. Performance evaluation experiments reveal that CAE-HROSSP outperforms two existing methods in compressing HROSSP data, achieving superior performance with smaller data reconstruction errors at higher compression ratios. Furthermore, transfer learning is utilized to enhance the training of CAE-HROSSP, employing HROSSP data from the area where the mesoscale eddy is situated, as well as at the convergence of cold and warm ocean currents. The compression performance of both the training set and the validation set is comparable in the sea, where the structure of the sound speed profile varies greatly. This indicates that CAE-HROSSP can compress highly variable sound speed profile data in more sea areas using transfer learning, and has the potential to be extended globally. The findings and insights obtained from this study provide guidance for future endeavors in utilizing autoencoders to compress HROSSP data.

Expendable Conductivity–Temperature–Depth-Assisted Fast Underwater Sound Speed Estimation by Convolutional Neural Network with Reduced Fully Connected Layers

Obtaining accurate sound speed profiles (SSPs) in near-real-time is of great significance for ocean exploration, underwater communication and improving the performance of sonar systems. In response to the problem that traditional sound speed estimation methods cannot obtain real-time sound speed distribution or rely too much on sonar observation data, we propose an SSP estimation method based on a convolutional neural network with reduced fully connected layers (RFC-CNN) in this paper. This method utilizes neural networks to extract the complex nonlinear features of various types of data. With the help of the historical SSPs and shallow seawater sound speed and temperature data obtained by expendable conductivity–temperature–depth probes (XCTDs), a more accurate estimation of the regional sound speed distribution can be realized quickly. This approach can save the observation cost and significantly improve the real-time performance of SSP estimation.

Physicochemical properties, theoretical modelling and molecular interaction analysis in ternary liquid mixtures containing 1-propanol, 1,3-diaminopropane and ethyl acetate at temperature 298.15–318.15 K

In the present report, density (ρ), viscosity (η), speed of sound (u) and refractive index (nD) of ternary liquid mixture containing 1-propanol (1P) (1) + 1,3-diaminopropane (1,3-DAP) (2) + ethyl acetate (EAc) (3) were measured at five different temperatures (T = 298.15 to 318.15 K) and at 0.1 MPa pressure. Data of ρ, η, u and nD were used to compute the excess molar volume, VmE, deviation in viscosity, Δη, deviation in ultrasonic speed, Δu, excess isentropic compressibility, ksE, excess free volume, VfE, excess intermolecular free length, LfE, excess available volume, VaE, and deviation in refractive index, ΔnD, and these computed physicochemical properties were fitted to Singh equation. The VmE data were fitted to the Nagata and Cibulka equations. Further, Kohler model, Tsao-Smith model, Radojkovic model, Jacob-Fitzner model and Rastogi model were used to calculate the VmE values. The speed of sound data was analyzed by various correlations such as Van Dael, Nomato, Impedance dependence, Schaaff’s collision factor theory (CFT) and Jacobson’s free length theory (JFLT). Various correlations like Heller, Arago-Biot, Lorentz-Lorenz, Erying, Newton, Gladstone-Dale, and Weiner were used to correlate nD data.

Highly Accurate Densities and Isobaric and Isochoric Heat Capacities of Compressed Liquid Water Derived from New Speed of Sound Measurements

Comprehensive and accurate measurements of the speed of sound in liquid water are reported. The measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range from 273.65 K to 368.15 K with pressures up to 100 MPa. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties are 2.1 mK in temperature, 45 parts-per-million (ppm) in pressure, and between 40 ppm and 70 ppm in speed of sound. Furthermore, values for the density and specific isobaric and isochoric heat capacities were derived from the speed of sound data in the measured temperature range up to 100 MPa by the method of thermodynamic integration. Very accurate values for the derived properties were obtained by using density data of Takenaka and Masui (Metrologia 27:165–171, 1990) and isobaric heat capacity data of Osborne et al. (J Res Natl Bur Stand 23:197, 1939) at ambient pressure as initial values in combination with an accurate correlation of our speed of sound. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties of the derived properties are 2 ppm in density, 0.11% in isobaric heat capacity, and 0.12% in isochoric heat capacity. The experimental speeds of sound and derived properties are compared with experimental data of other authors from the literature, the IAPWS-95 (International Association of the Properties of Water and Steam) formulation for the thermodynamic properties of water, and a recent equation of state for supercooled water.

Impact of internal waves on underwater acoustic propagation

The propagation of internal waves in the ocean can produce significant fluctuations in the local sound speed field. Understanding how these fluctuations affect acoustic propagation is an area of considerable interest in underwater acoustics. Previous studies have indicated that large fluctuations (of the order of 20 dB) in transmission loss (TL) of acoustic waves can occur due to focusing and defocusing effects as the acoustic waves propagate through an internal wave. This work looks to extend some of these studies by exploring the frequency and directional dependence of these fluctuations through the implementation of a 3D acoustic model (FOR3D) suitable for modelling low frequency (<1 kHz) acoustic propagation. The study utilises sound speed data produced using the non-hydrostatic model MITgcm, simulating a nonlinear three-dimensional internal wave field that was verified using in situ mooring observations. By also considering results from a study utilising an acoustic ray model (Bellhop3D) on the same data, this work gives a comprehensive picture of the internal wave induced TL fluctuations across a range of acoustic frequencies.

Elucidation of hydrogen bond strength of benzylalcohol with alkyl Acetoacetates: The confirmation study by excess thermodynamic Properties, FTIR and DFT analysis

In this study, density of pure liquids and their binary mixtures of benzylalcohol (BA) with methyl acetoacetate (MAA), ethyl acetoacetate (EAA) and allyl acetoacetate (AAA) were measured experimentally at T=(298.15–313.15) K and P = 0.1 MPa by using Rudolph Research Analytical digital densitometer. Experimental data was correlate by applying Jouyban–Acree theoretical equation. Furthermore, the speed of sound of all studied pure and their binary solutions were measured at T= (298.15 and 308.15) K at atmospheric pressure at 2 MHz. The experimental density and speed of sound data further were used to calculate the excess molar volume (VmE), isentropic compressibility (κs), excess isentropic compressibility (κsE) and excess speed of sound (uE) at all compositions and temperature ranges. The calculated VmE, κsE, uE and experimental speed of sound were compared with theoretical models such as Redlich-Kister, Hwang, CFT and FLT equations. The obtained data were analyzed in terms of intermolecular interactions such as hydrogen bond formation between two atoms of benzylalcohol and acetoacetates. Among all the three systems, BA + MAA showed highest negative excess molar volume magnitude due to the change of molecular geometry through the keto-enol tautomerism. The negative magnitude of VmE data confirms the formation of H-bond between the –OH---O- groups of component molecules. Similarly, BA + EAA system showed highest negative magnitude of κSE owing to the more compressible than resultant ideal solutions. The deviation in κSE magnitude in binary systems due to the geometrical fitting and specific interactions in atoms of the benzylalcohol and acetoacetates. Furthermore, the existence of hydrogen bond and its strength in binary mixtures were confirmed by experimental FTIR spectroscopy and theoretical density functional theory (DFT) calculations.

Data Assimilation of Range- and Depth-Averaged Sound Speed from Acoustic Tomography Measurements in Fram Strait

Abstract The 2010–12 Acoustic Technology for Observing the Interior of the Arctic Ocean (ACOBAR) experiment provided acoustic tomography data along three 167–301-km-long sections in Fram Strait between Greenland and Spitsbergen. Ocean sound speed data were assimilated into a regional numerical ocean model using the Massachusetts Institute of Technology General Circulation Model–Estimating the Circulation and Climate of the Ocean four-dimensional variational (MITgcm-ECCO 4DVAR) assimilation system. The resulting state estimate matched the assimilated sound speed time series; the root-mean-squared (RMS) error of the sound speed estimate (∼0.4 m s−1) is smaller than the uncertainty of the measurement (∼0.8 m s−1). Data assimilation improved modeled range- and depth-averaged ocean temperatures at the 78°50′N oceanographic mooring section in Fram Strait. The RMS error of the state estimate (0.21°C) is comparable to the uncertainty of the interpolated mooring section (0.23°C). Lack of depth information in the assimilated ocean sound speed measurements caused an increased temperature bias in the upper ocean (0–500 m). The correlations with the mooring section were not improved as short-term variations in the mooring measurements and the ocean state estimate do not always coincide in time. This is likely due to the small-scale eddying and nonlinearity of the ocean circulation in Fram Strait. Furthermore, the horizontal resolution of the state estimate (4.5 km) is eddy permitting, rather than eddy resolving. Thus, the state estimate cannot represent the full ocean dynamics of the region. This study is the first to demonstrate the usefulness of large-scale acoustic measurements for improving ocean state estimates at high latitudes. Significance Statement Acoustic tomography measurements allow one to observe ocean temperature in large ocean volumes under the Arctic sea ice by measuring sound speed, which is hard to synoptically observe by other methods. This study has established methods for assimilation of depth- and range-averaged ocean sound speed from an acoustic tomography experiment in Fram Strait. For the first time, a 2-yr time series of ocean sound from acoustic tomography has been assimilated into an ocean state estimate. The results highlight the use of ocean tomography in ice-covered regions to improve state estimates of ocean temperature.

Solute–solvent interactions of glycine, L–alanine, and L–valine in aqueous 1–butyl–3–methylimidazolium methylsulfate ionic liquid solutions at different temperatures

The intermolecular interactions of amino acids (glycine, L–alanine, and L–valine) in aqueous solutions of an ionic liquid, 1–butyl–3–methylimidazolium methylsulfate [Bmim][MeSO4] as a function of temperature have been investigated by combination of volumetric and acoustic methods. The density, ρ, and speed of sound, u, of glycine, L–alanine and L–valine in aqueous 1–buytl–3–methylimidazolium methylsulfate solutions have been measured in the temperature interval T = (288.15, 298.15, and 308.15) K and atmospheric pressure. These data have been used to calculate apparent molar volume (V∅), and apparent molar adiabatic compressibility (K∅,s) of these mixtures at different temperatures. Later, the standard partial molar volume (V∅0), standard partial molar volumes of transfer (ΔV∅0), standard partial molar adiabatic compressibility (K∅,s0), and standard partial molar adiabatic compressibility (ΔK∅,s0) of transfer have been determined for these amino acid solutions from density and speed of sound data. Also, hydration number (nH) and various group contribution have been calculated. Finally the results have been interpreted in terms of solute - solvent interactions that exist among the currently investigated systems.

Speeds of Sound in Binary Mixtures of Water and Carbon Dioxide at Temperatures from 273 K to 313 K and at Pressures up to 50 MPa

Knowledge of thermodynamic properties of aqueous solutions of CO2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO2. We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO2 for mole fractions of CO2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO2. Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO2 gas.

Insights into the physicochemical properties of newly synthesized benzyl triethylammonium chloride-based deep eutectic solvents

In order to utilize deep eutectic solvents (DESs) as a replacement for conventional organic solvents for different applications, a detailed understanding of their physicochemical properties is extremely important. In this study, several novel DESs based on benzyl-triethylammonium chloride (BTEA) as a hydrogen bond acceptor (HBA) and acids/or alcohols as hydrogen bond donors (HBDs) have been synthesized. DESs have been thoroughly characterized and investigated for their physicochemical properties viz. thermal stability, glass transition temperature, viscosity (η), surface tension (γ), refractive index (nD), density (ρ), speed of sound (u), and conductivity (κ) in a temperature range of 293.15–343.15 K. The effect of temperature, type of HBDs, and alkyl chain length of HBDs of the DESs on the physicochemical properties are critically examined and discussed. Viscosity data are fitted to Vogel-Fulcher-Tamman (VFT) and Arrhenius models. A linear model was used to fit surface tension (γ), density, refractive index, and speed of sound data whereas conductivity data were fitted to a nonlinear equation. Primary data on physicochemical properties have been used to estimate the viscous flow parameters (activation entropy, activation enthalpy, and free energy of activation) and other derived parameters such as lattice energy, standard entropy, molar volume, intermolecular free length, and isentropic compressibility. A relationship between molar conductivity and dynamic viscosity has been established to evaluate the ionicity of the synthesized DESs. Insights into the structure–property correlations are discussed in detail.

Ultrasonic investigation of L- leucine in aqueous electrolyte solutions

This paper reports the densities as well as thespeed of soundL-leucine (0.02 –0.20 mol /kg) in (0.1 mol /kg) aqueous medium of the electrolytes: KCl and NaClat various temperatures (283.15–293.15 K) under atmospheric pressure. Acoustic impedance (Z), free length, isobaric thermal expansion coefficient (α), adiabatic compressibility (β), isothermal compressibility (KT), and specific heat (ϒ), surface tension (σ) using experimental density and speed of sound data, hasbeen computed. The outcomes are illustrated in terms of several electrostatic and hydrophobic interactions associated withthe ternary system of electrolyte, water,and amino acid. A great number of interactions between the electrolyte and L-leucine have been confirmed by electrolyte and temperature. Positive transfer quantities indicate that ion-hydrophilic and hydrophilic-hydrophilic interactions between leucine, sodium chloride, as well as potassium chloride in anaqueous medium, predominate. Overall findings are now explained in terms of solute–solvent as well as solute–solute interactions.

Gaseous speed of sound and virial coefficients for 2,3,3,3-tetrafluoropropene (R1234yf) + 1,1,1,2-tetrafluoroethane (R134a) binary mixture

The binary mixture 2,3,3,3-tetrafluoropropene (R1234yf) + 1,1,1,2-tetrafluoroethane (R134a) is commercially interesting and is widely studied in thermodynamics properties, but except for gaseous speed of sound. In this work, we modified the experimental procedure of the cylindrical fixed-path acoustic resonance method for the sound speed measurement of mixtures. Then we obtained the first two sets of gaseous sound speed data at the molar fraction of about (0.207/0.793) and (0.580/0.420) with a combined relative expanded uncertainty (k = 2) of 0.03%. The accurate molar fractions along each isotherm line were determined by extrapolating the experimental data with the absolute expanded uncertainty (k = 2) of 0.003. The interaction virial coefficients were derived from the experimental sound speed data and were used to establish a hard-core square-well molecular potential model. A previous virial coefficient correlation was modified to predict the virial coefficients for mixtures. The experimental results and model calculations agree well with each other, confirming the correctness of the experimental method. The data could provide references to test and develop the mixing model.