Ultrasonic Study of Basic α‐Amino Acids in Different Acetate Salt Solutions at Different Temperatures

The ultrasonic velocity (U), has been measured for three α‐amino acids, namely L‐lysine monohydrochloride, L‐arginine and L‐histidine in solutions (1 mol/L aqueous) of sodium acetate (SA), potassium acetate (PA) and calcium acetate (CA) at different temperatures (303.15, 308.15, 313.15, 318.15 and 323.15 K). With the help of these results various ultrasonic derived parameters, viz. isentropic compressibility (κ_s), change in isentropic compressibility (Δκ_s), relative change in isentropic compressibility (Δκ_r), specific acoustic impedance (Z), relative association (RA), and apparent molal compressibility (?) have been estimated. The results have been interpreted in the light of intermolecular interactions between solute and solvent.     

Volumetric and Ultrasonic Investigation of Glycylglycine in Aqueous FeCl<Subscript>3</Subscript> Solutions

Viscosity, ultrasonic velocity and density measurements have been carried out for glycylglycine in aqueous FeCl₃ solution as a function of molality at T=288.15 K, 298.15 K and 308.15 K. The experimental data have been used to derive properties such as isentropic compressibility (κ _S ), change in isentropic compressibility (Δκ _S ), relative change in isentropic compressibility (Δκ _S /κ ₀), apparent molar compressibility, volume and their limiting apparent molar quantities along with the constants S _K , S _V and viscosity B-coefficient. The obtained thermodynamic properties have been discussed in terms of molecular interactions.     

Acoustical studies of some derivatives of 4-amino antipyrene in 1,4-dioxane and dimethylformamide at 318.15 K

For three derivatives of 4-amino antipyrene, density, viscosity and ultrasonic velocity are measured at 318.15 K in 1,4-dioxane (DO) and dimethylformamide (DMF). From these experimental data, various acoustical properties such as specific impedance (Z), isentropic compressibility (κ_s), Rao’s molar sound function (R_m), the van der Waals constant (b), molar compressibility (W), intermolecular free length (L_f), relaxation strength (r), relative association (R_A), free volume (V_f), etc. and apparent molar volume and apparent molar compressibility were calculated. The results are interpreted in terms of molecular interactions occurring in the solutions. It is observed that in 1,4-dioxane solutions, solute–solute interactions exist whereas solvent–solute interactions predominant in DMF system.     

Molecular Interactions in Binary Mixtures of Benzene with 1-Alkanols(C5,C7,C8) at 35℃:An Ultrasonic Study

Densities and ultrasonic speeds have been measured in binary mixtures of benzene with 1‐pentanol, 1‐heptanol and 1‐octanol, and in the pure components, as a function of composition at 35 °C. The isentropic compressibility, intermolecular free length, relative association, acoustic impedance, isothermal compressibility, thermal expansion coefficient, deviations in isentropic compressibility, excess free length, excess volume, deviations in ultrasonic speed, excess acoustic impedance, apparent molar compressibility, apparent molar volume, partial molar volume of 1‐alkanol in benzene have been calculated from the experimental data of densities and ultrasonic speeds. The variation of these parameters with composition indicates weak interaction between the component molecules and this interaction decreases in the order: 1‐pentanol > l‐heptanol> 1‐octanol. Further, theoretical values of ultrasonic speeds were evaluated using free length theory, collision factor theory, Nomoto's relation and Van Dæl‐Vangeel ideal mixing relation. The relative merits of these theories and relations were discussed for these systems.     

Volumetric and viscosity studies of interactions between sodium phosphate salts and poly(propylene glycol) 400 in aqueous solutions at different temperatures

Density and sound velocity at the 288.15–313.15 K and viscosity at the 298.15–313.15 K temperature range at 5 K intervals for polypropylene glycol (PPG) in aqueous solutions of sodium di-hydrogen phosphate, di-sodium hydrogen phosphate and tri-sodium phosphate with salt mass fractions 0.00, 0.010 and 0.020 are reported at atmospheric pressure. From the experimental density and sound velocity data, the apparent specific volume, excess specific volume, isentropic compressibility and isentropic compressibility deviation values have been determined. The infinite dilution apparent specific volume and isentropic compressibility values of PPG have been obtained and from which the infinite dilution apparent specific volumes of transfer of PPG from water to aqueous sodium phosphate solutions have been obtained for the investigated salt concentrations and temperatures. The excess specific volume, isentropic compressibility and viscosity deviation are negative and decrease in magnitude as temperature, concentration of sodium phosphate and charge on the anion of electrolyte increases.     

Effect of tri-potassium phosphate on volumetric,acoustic, and transport behaviour of aqueous solutions of 1-ethyl-3-methylimidazolium bromide at T = (298.15 to 318.15) K

Density, sound velocity, and viscosity of 1-ethyl-3-methylimidazolium bromide, [Emim][Br], in aqueous solutions of tri-potassium phosphate with salt weight fractions (w_s = 0.00, 0.10, 0.15, and 0.20) have been measured as a function of concentration of [Emim][Br] at atmospheric pressure and T = (298.15, 303.15, 308.15, 313.15, and 318.15) K. The apparent molar volume, isentropic compressibility, apparent isentropic compressibility, and relative viscosity values have been evaluated from the experimental data. The partial molar volume and isentropic compressibility at infinite dilution, and viscosity B-coefficient obtained from these data have been used to calculate the corresponding transfer parameters for the studied IL from water to the aqueous tri-potassium phosphate solutions. Also, an empirical equation was satisfactorily used to correlate the experimental viscosity data.     

Thermodynamic and optical studies of some ethylene glycol ethers in aqueous solutions at T = 298.15 K

Experimental results of density (ρ), speed of sound (u), and refractive index (n_D) have been obtained for aqueous solutions of ethylene glycol monomethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMME), and diethylene glycol monoethyl ether (DEGMEE) over the entire concentration range at T = 298.15 K. From these measurements, the derived parameters, apparent molar volume of solute (?_V), excess molar volume (V^E), isentropic compressibility of solution (β_S), apparent molar isentropic compressibility of solute (?_KS), deviation in isentropic compressibility (Δβ_S), molar refraction [R]_1,2 and deviation in refractive index of solution (Δn_D) have been calculated. The Redlich–Kister equation has been fitted to the calculated values of V^E, Δβ_S and Δn_D for the solution. The results obtained are interpreted in terms of hydrogen bonding and various interactions among solute and solvent molecules.     

Apparent Molar Volume, Isentropic Compressibility, Refractive Index, and Viscosity of DL-Alanine in Aqueous NaCl Solutions

New experimental data at 25^°C for the density, velocity of sound, refractive index, and viscosity of aqueous solutions of DL-alanine and NaCl are reported. The apparent molar volume and isentropic compressibility of DL-alanine in aqueous electrolyte solutions have been calculated from the measured properties. The results show that DL-alanine exhibits a positive volume transfer to solutions of a higher NaCl concentration and a negative apparent isentropic compressibility for DL-alanine in the presence of NaCl. These effects indicate that the apparent volume of DL-alanine is larger in solutions with higher electrolyte concentration and the water molecules surrounding the DL-alanine molecules are less compressible than the water molecules in the bulk solution. The results also show an increase in the viscosity of the solution with an increase in both DL-alanine and NaCl concentrations. These effects are attributed to the two charged groups of DL-alanine and the interactions between the charged groups and the hydrocarbon backbone of DL-alanine with the ions. A model, consisting of a short-range interaction term represented by a virial expansion and a Debye-Hückel term that considers long-range interactions, has been developed to correlate the measured experimental data.     

A Study on Hydration of Urea and Urotropin by Density and Speed of Sound Measurements in Aqueous Solutions

Experimental data on the speed of propagation of ultrasound waves, density, and isobaric heat capacity in aqueous solutions of urea and urotropin have been considered. The findings have been used for calculating the molar isentropic compressibilities of solutions of the investigated substances over the temperature range 278.15 to 308.15 K. Invoking a theoretical solvation model based on the isentropic compressibility, which takes into account compressibilities of the hydrated complexes, their structural characteristics have been determined in aqueous solutions of nonelectrolytes: hydration numbers h, molar isentropic compressibility of hydrated complexes ?? _h V _h , molar volumes of water in a hydration shell V _1h , molar volumes of the solute without its hydration environment V _2h , and many other properties. The possibility of hydrophobic solvation has been shown for urotropin solutions and hydrophilic solvation for urea solutions.     

Volumetric and compressibility studies for (L-arginine + D-maltose monohydrate + water) system in the temperature range of (298.15 to 308.15) K

The density and speed of sound of L-arginine (0.025–0.2 mol kg^?1) in aqueous + D-maltose (0–6 mass% of maltose in water) were obtained at temperatures of (298.15, 303.15 and 308.15) K. The apparent molar volume, limiting apparent molar volume, transfer volume, as well as apparent molar compressibility, limiting apparent molar compressibility, transfer compressibility, pair and triple interaction coefficients, partial molar expansibilities, coefficient of thermal expansion and also the hydration number, were calculated using the experimental density and speed of sound values. The results have been discussed in terms of solute–solute and solute–solvent interactions in these systems. Solute–solvent (hydrophilic–ionic group and hydrophilic–hydrophilic group) interactions were found to be dominating over solute–solute (hydrophobic–hydrophilic group) interactions in the solution, which increases with increase in maltose concentration.     

Thermo-physical properties of the binary mixture of benzaldehyde with bromobenzene at 303.15, 308.15, and 313.15?K

The values of density, viscosity, and ultrasonic velocity for the binary liquid mixture of benzaldehyde with bromobenzene have been measured over the entire range of composition at 303.15, 308.15, and 313.15?K. These values have been used to calculate the excess molar volume (V ^E), deviation in viscosity (????), deviation in velocity (?U), deviation in isentropic compressibility (??? _s), excess internal pressure (???), excess intermolecular free length (?L _f), and excess acoustic impedance (?Z). McAllister??s three-body-interaction model is used for correlating kinematic viscosity of binary mixtures. The excess values were correlated using the Redlich?CKister polynomial equation to obtain their coefficients and standard deviations. The thermo-physical properties (density, viscosity, and ultrasonic velocity) under the study were fitted to the Jouyban?CAcree model.     

Physico-chemical studies of a biologically active molecule (L-valine) predominant in aqueous alkali halide solutions with the manifestation of solvation consequences

The apparent molar volume (?_V), viscosity B-coefficient and molar refraction (R_M) have been determined of L-valine in aqueous solution of LiCl, NaCl and KCl at 298 K, 303 K and 308 K from density (ρ), viscosity (η) and refractive index (n_D) measurements, respectively. The limiting apparent molar volumes (?_V⁰) and experimental slopes (S_V*) derived from the Masson equation have been interpreted in terms of solute–solvent and solute–solute interactions, respectively. The viscosity data were analysed using the Jones–Dole equation and the derived parameter B has also been interpreted in terms of solute–solvent interactions in the solutions. Molar refraction (R_M) has been calculated using the Lorentz–Lorenz equation.     

Effect of KCl on the volumetric and transport properties of aqueous tri-potassium citrate solutions at different temperatures

Density, speed of sound and viscosity measurements of binary aqueous solutions of tri-potassium citrate were performed from dilute up to near saturated concentration range at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. Volumetric and transport properties of ternary aqueous solutions of (tri-potassium citrate + KCl) have also been measured within the molality range of KCl (0.05, 0.15, 0.25, 0.35, 0.45, and 0.55) at different temperatures. Apparent molar volume and apparent molar isentropic compressibility have been calculated from the density and speed of sound for binary and ternary aqueous solutions of tri-potassium citrate. Apparent molar volume and apparent molar isentropic compressibility of ternary aqueous solutions of (tri-potassium citrate + KCl) have been correlated with the Redlich–Mayer equation. Viscosity values of ternary aqueous solutions of (tri-potassium citrate + KCl) have been fitted with the Jones–Dole equation. The results obtained have been interpreted in elucidating the effect of tri-potassium citrate on the interaction of KCl–H₂O. Density and viscosity values of ternary aqueous solutions of (tri-potassium citrate + KCl) have been predicted successfully using the methods proposed by Laliberte (2007), Laliberte and Cooper (2004) [9], [10] and Zafarani-Moattar and Majdan-Cegincara (2009) [11].     

Physicochemical Properties of Amino Acids in AqueousCaffeine Solution at 25, 30, 35 and 40 ℃

Density, viscosity, and refractive index, for glycine, DL-alanine, L-serine and DL-valine have been determined in aqueous solution of 0.05 mol/kg caffeine as a function of amino acid （AA） concentration at 25, 30, 35, and 40 ℃ The density data have been used to compute apparent molar volume. The partial molar volume （limiting apparent molar volume） was obtained by applying the Masson＇s equation. The viscosity data have been analyzed by means of Jones-Dole equation. The values of Falkenhagen coefficient and Jones-Dole coefficient thus obtained are used to interpret the solute-solute and solute-solvent interactions, respectively. Hydration number was also computed. The transition-state theory was applied to obtain the activation parameters of viscous flow, i.e., free energy of activation per mole of solvent, and solute. The enthalpy and entropy of activation of viscous flow were computed for the system. Refractive index was used to calculate molar refractivity of the mixtures. The results have been interpreted in the light of various interactions occurring between the components of the mixtures under applied experimental conditions.     

Acoustical and excess thermodynamic studies of mixtures of 2-pyrrolidone with 1,3-propanediol and water as well as 1,3-propanediol with water at 308.15 K

The density (ρ), viscosity (η) and ultrasonic velocity (u) of three mixtures consisting of 2- pyrrolidone with 1,3-propanediol (PD) and water and also of PD and water have been measured as a function of mole fraction at 308.15 K. The experimentally collected data has been used to calculate the excess molar volume (V^E), deviation in viscosity (Δη), deviation in ultrasonic velocity (Δu), isentropic compressibility (κ_s), deviation in isentropic compressibility (Δκ_s) and excess Gibbs free energy of activation (ΔG*^E). The Redlich–Kister polynomial equation has been used to fit the derived parameters. The variation in excessive thermodynamic properties as a consequence of possible molecular interactions is discussed.     

Thermodynamic properties of ternary mixtures containing water, 2-ethoxyethanol,and <Emphasis Type="Italic">t</Emphasis>-butanol at 298.15 K

Ultrasonic speeds and isentropic compressibilities were measured at 298.15 K in the water-rich region of aqueous solutions of water + 2-ethoxyethanol (2EE) + t-butanol. The excess properties of ultrasonic speed and isentropic compressibility were also calculated and have been discussed in terms of molecular interactions. The concentrations of t-butanol at which ultrasonic speed becomes maximum and isentropic compressibility becomes minimum are found to decrease with increase in the concentration of 2EE in the cosolvent (aqueous 2EE). This behavior indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. This behavior is explained as due to a decrease in the ability of t-butanol to form clathrate hydrates owing to the presence of 2EE. When the concentration of 2EE in the cosolvent (x _2EE) > 0.14, ultrasonic speed decreases and isentropic compressibility increases with concentration of t-butanol indicating that the ternary solution behaves as normal solution wherein any further addition of 2EE or t-butanol leads to destabilization of the hydrogen bonded structure of water and t-butanol looses its ability to form clathrate hydrates in aqueous solutions.     

Dielectric relaxation studies of binary mixtures of N-methylacetamide and N-methylformamide in benzene solutions using microwave absorption data

Using standard microwave X-band technique and by following Gopala Krishna's single frequency (9.90?GHz) concentration variational method, the dielectric relaxation times (τ) and the dipole moments (μ) of dilute solution of N-methylacetamide (NMA), N-methylformamide (NMF) and NMA?+?NMF binary mixtures in benzene solutions have been calculated at different temperatures. The energy parameters for the dielectric relaxation process for NMA?+?NMF binary mixture containing 30?mol% NMF have been calculated at 25, 30, 35 and 40°C and compared with the corresponding viscosity parameters. A good agreement between the free energy of activation from these two sets of values shows that the dielectric relaxation process like the viscous flow process can be treated as the rate process. From relaxation time behavior of NMA and NMF binary mixture in benzene solution, solute–solute types of the molecular association has been proposed.     

Volumetric,Acoustic and Transport Properties of Metformin Hydrochloride Drug in Aqueous <Emphasis Type="SmallCaps">d</Emphasis>-Glucose Solutions at <Emphasis Type="Italic">T</Emphasis> = (298.15–318.15) K

Apparent molar volumes, apparent molar adiabatic compressibilities and viscosity B-coefficients for metformin hydrochloride in aqueous d-glucose solutions were determined from solution densities, sound velocities and viscosities measured at T = (298.15–318.15) K and at pressure p = 101 kPa as a function of the metformin hydrochloride concentrations. The standard partial molar volumes (\( \phi_{V}^{0} \)) and slopes (\( S_{V}^{*} \)) obtained from the Masson equation were interpreted in terms of solute–solvent and solute–solute interactions, respectively. Solution viscosities were analyzed using the Jones–Dole equation and the viscosity A and B coefficients discussed in terms of solute–solute and solute–solvent interactions, respectively. Adiabatic compressibility (\( \beta_{s} \)) and apparent molar adiabatic compressibility (\( \phi_{\kappa }^{{}} \)), limiting apparent molar adiabatic compressibility (\( \phi_{\kappa }^{0} \)) and experimental slopes (\( S_{\kappa }^{*} \)) were determined from sound velocity data. The standard volume of transfer (\( \Delta_{t} \phi_{V}^{0} \)), viscosity B-coefficients of transfer (\( \Delta_{t} B \)) and limiting apparent molar adiabatic compressibility of transfer (\( \Delta_{t} \phi_{\kappa }^{0} \)) of metformin hydrochloride from water to aqueous glucose solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were calculated using transition state theory. Hepler’s coefficient \( (d\phi /dT)_{p} \) indicated the structure making ability of metformin hydrochloride in the ternary solutions.     

Study of molecular interactions in solutions of azomethines of sulfamethoxazole in N,N-dymethylformamide and tetrahydrofuran

Density, ultrasonic velocity and viscosity of azomethines containing sulfamethoxazole nucleus have been measured in N,N-dimethylformamide and tetrahydrofuran solutions over a wide concentration range at temperature 308.15 K. From these experimental data, acoustical parameters such as intermolecular free path length, isentropic compressibility and relaxation strength have been evaluated, that help understanding the molecular interactions occurring in these solutions. Furthermore, compressibility solvation number, the apparent molar compressibility and apparent molar volume of the solutions have been determined and discussed.     

Volumetric and isentropic compressibility behaviour of aqueous solutions of (polyvinylpyrrolidone + sodium citrate) at T = (283.15 to 308.15) K

The apparent specific volumes and isentropic compressibilities have been determined for polyvinylpyrrolidone in aqueous solutions of sodium citrate by density and sound velocity measurements at T = (283.15 to 308.15) K at atmospheric pressure. The results show a positive transfer volume of PVP from an aqueous solution to an aqueous sodium citrate solution. For low concentrations of PVP, the apparent specific volumes of PVP in water increased along with an increase in the polymer mass fraction, while in aqueous sodium citrate solutions decreased along with an increase in the polymer mass fraction. For high concentrations of PVP, the apparent specific volumes of PVP in water and in aqueous sodium citrate solutions were independent of the polymer mass fraction. The apparent specific isentropic compressibility of PVP is negative at T = (283.15 and 288.15) K, which imply that the water molecules around the PVP molecules are less compressible than the water molecules in the bulk solutions. The positive values of apparent specific isentropic compressibility at T = (298.15, 303.15, and 308.15) K imply that the water molecules around the PVP molecules are more compressible than the water molecules in the bulk solutions. Finally, it was found that the apparent specific isentropic compressibility of PVP increases as the concentration of sodium citrate increases.