Search

• 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]

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]

The adiabatic compressibilities κ S of 64 liquid metallic elements at their melting points were obtained from the densities ρ and speeds of sound u reported in the literature. The isothermal compressibilities were obtained from the κ S values by means of the molar volumes V , isobaric expansibilities α P , and isobaric molar heat capacities C P from the literature. The ratios γ = κ T / κ S = C P / C V yielded the isochoric molar heat capacities C V . The products κ T σ , using surface tension data from the literature, were calculated and shown to diminish linearly with increasing cohesive energy densities. [ABSTRACT FROM AUTHOR]

Abstract: Values of the adiabatic and isothermal compressibility, κ S and κ T, of some 80 molten salts at the corresponding temperature of T =1.1T m (T m is the melting point) are obtained from literature data either directly or re-calculated here. For some of the series of salts: alkali metal halides and nitrates, divalent metal halides, and alkali metal sulfates and carbonates the κ T values are inversely proportional to the corresponding cohesive energy densities ced (internal energies per unit volume, separately for each class of compounds). The ced values for 1:2 and 2:1 salts not previously evaluated are presented here too. [Copyright &y& Elsevier]

Abstract: The interactions of alkoxyalkanols with the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim][Br] as a function of temperature were investigated by combination of volumetric and acoustic methods. The density, ρ, and speed of sound, u, of ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and triethylene glycol monomethyl ether (0.00–1.01mol·kg−1) in aqueous 1-butyl-3-methylimidazolium bromide solutions ranging from pure water to 0.29mass% of ionic liquid have been measured at T =(288.15, 298.15 and 308.15)K and atmospheric pressure. The apparent molar volume (Vϕ ) and adiabatic compressibility (Kϕ , S ) of alkoxyalkanols in aqueous ionic liquid solution were determined at the measured temperatures. The partial molar volume and partial molar adiabatic compressibility of alkoxyalkanols at infinite dilution were evaluated. Transfer volumes and transfer adiabatic compressibility () at infinite dilution from water to aqueous ionic liquid solution were also calculated. The temperature dependence of the apparent molar volume was used to calculate apparent molar expansivity () and the Hepler’s constant values, . The results were explained on the basis of competing patterns of interactions of co-solvent and the solute. [Copyright &y& Elsevier]

Abstract: The densities and speeds of sound of (ethanol+isooctane), (ethanol+toluene), and (ethanol+isooctane+toluene) were measured at four temperatures over the range (298.15 to 328.15)K, and the respective values of excess volumes and adiabatic compressibility κS were calculated. The and κS values for the binary systems were fitted to the Redlich–Kister equation. The respective ternary data together with corresponding binary data were then fitted to the modified Redlich–Kister equation considering various numbers of ternary constants. It was found that even for the systems containing self-associating alcohol, only one ternary parameter is sufficient to describe well the ternary system. [Copyright &y& Elsevier]

Abstract: The densities and speeds of sound of (methyl tert-butyl ether {MTBE}+toluene+isooctane) were measured at four temperatures over the range (298.15 to 328.15)K and the respective values of excess volumes and adiabatic compressibility κS were calculated. The and κS values for the ternary and corresponding binaries were fitted to the Redlich–Kister equation considering various numbers of ternary constants. The necessary number of ternary constants needed to describe the system is discussed. [Copyright &y& Elsevier]

Abstract: The density and speed of sound of hexadecane have been measured with two instruments. Both instruments use the vibrating-tube method for measuring density. Ambient pressure (83kPa) density and speed of sound were measured with a commercial instrument from T =(290.65 to 343.15)K. Adiabatic compressibilities are derived from the density and speed of sound data at ambient pressure. Compressed liquid density was measured in a second instrument and ranged from T =(310 to 470)K with pressures from (1 to 50)MPa. The overall relative expanded uncertainty of the compressed liquid density measurements is 0.10–0.13% (k =2). The overall relative expanded uncertainty (k =2.3) of the speed of sound measurements is 0.2% and that of the ambient pressure density measurements is approximately 0.04% (k =2.3). The ambient pressure and compressed liquid density measurements are correlated within 0.1% with a modified Tait equation. [Copyright &y& Elsevier]

Abstract: The densities and speeds of sound of (toluene+isooctane), (MTBE+toluene), and (MTBE + isooctane) were measured at four temperatures from (298.15 to 328.15)K, and the respective values of excess volumes and adiabatic compressibility κ S were calculated. The and κ S values were fitted to the fourth-order Redlich–Kister equation. The values for (MTBE+toluene) are negative and decreasing with increasing temperature. The other systems show positive with comparatively small temperature dependence. [Copyright &y& Elsevier]