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Densities, ρ and speeds of sound, u of four benzylalkylammonium ionic liquids (ILs), namely, benzylmethylammonium propionate (BMAP), benzylmethylammonium hexanoate (BMAH), benzyldimethylammonium propionate (BDMAP) and benzyldimethylammonium hexanoate (BDMAH) with dimethylsulfoxide (DMSO) have been determined as a function of ILs concentration, ranging from (0.1 to 0.8) mol kg−1, at temperatures from 293.15 K to 328.15 K with 5 K interval and at atmospheric pressure. The apparent molar volumes, Vm, apparent molar isentropic compression, Ks,m and limiting apparent molar expansion, Em∞ of the ILs have been calculated from the experimental density and speed of sound data. The Redlich–Mayer type of equation was fitted to the apparent molar volume and apparent molar isentropic compression data, to evaluate apparent molar volume at infinite dilution Vm∞ and apparent molar isentropic compression, Km∞ at infinite dilution.

Apparent molar volume, ultrasonic velocity and absorption studies have been carried out in aqueous solutions of some bile salts namely sodium cholate and sodium deoxycholate containing 10% (v/v) of dioxane, dimethyl sulphoxide, dimethyl formamide, tetrahydrofuran and acetonitrile. These studies are carried out in the bile salt concentration of 1–15 mM at a fixed frequency of 2 MHz and at a fixed temperature of 303.15 K. The variation of apparent molar volume and ultrasonic velocity in aqueous solutions of bile salts containing 10% (v/v) of dioxane, dimethyl sulphoxide, dimethyl formamide, tetrahydrofuran and acetonitrile with bile salt concentration exhibiting break at critical micelle concentration (CMC). The observed absorption increases with increasing bile salt concentration and also exhibiting a break at CMC similar to velocity curve. The results are discussed in terms of formation of bile salt micelles through hydrophobic interaction and hydrogen bonding. The results obtained from apparent molar volume, ultrasonic velocity and apparent molar compressibility studies are confirmed by the equivalent conductance measurements carried out in the solutions of bile salts.

The apparent molar volume (ϕV), viscosity B-coefficient, molal refraction (R) and adiabatic compressibility (ϕK) of glycine, l -alanine, and l -valine have been studied in 0.001, 0.003, 0.005 mol dm−3 aqueous tetrabutylphosphonium Tetrafluoroborate (Bu4PBF4) solutions at 298.15 K from the values of density (ρ), viscosity (η), refractive index (nD) and speed of sound (u) respectively. The limiting apparent molar volumes ( ϕ V 0 ), experimental slopes ( S V * ) are obtained from the Masson equation and have been interpreted in terms of solute–solvent and solute–solute interactions respectively. Jones–Dole equation were employed to analyze the viscosity data and the interpretation of the derived parameters A and B have also been carried out in terms of solute-solute and solute–solvent interactions in the solutions respectively. Molal refractions (R) have been determined with the help of Lorentz–Lorenz equation. Limiting apparent molar adiabatic compressibilities ( ϕ K 0 ) of three amino acids at infinite dilution were evaluated and discussed.

Density, isobaric molar heat capacity and excess molar enthalpy were experimentally determined at atmospheric pressure for a set of binary systems of ionic liquids and ethanol. Density and heat capacity were obtained within the temperature range (293.15–318.15 K) whereas excess molar enthalpy was measured at 303.15 K; excess molar volume and excess molar isobaric heat capacity were calculated from experimental data. The Extended Real Associated Solution (ERAS) model is applied to extract information about the association capability of each ionic liquid with ethanol molecules through hydrogen bonds. The chemical nature of the anion is revealed as the main factor that determines the thermodynamic behavior of the studied systems.

Density, sound velocity and electrical conductivity of solutions of tri-sodium phosphate (Na3PO4) in 1-propanol + water mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported in the 283.15–303.15 K temperature range at 5 K intervals. From the experimental density and sound velocity data, the apparent molar volume and isentropic compressibility values of tri-sodium phosphate are evaluated and fitted to a Redlich + Meyer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution are calculated at working temperature. The results show a positive transfer volume of Na3PO4 from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of Na3PO4 in aqueous 1-propanol solutions is negative and it increases with increasing concentration of Na3PO4, 1-propanol and temperature. The effects of the electrolyte concentration, temperature and relative permittivity of the medium on the molar conductivity are also investigated. Comparisons between the results obtained in this work are made with those for Na2HPO4 and NaH2PO4 obtained in our previous works.

Density of four (0.2378, 0.4645, 0.9440, and 2.2310) mol kg−1 binary aqueous KBr solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made at pressures up to 30 MPa. The range of temperature was from 298 to 629 K. The total uncertainty of density, pressure, temperature, and composition measurements were estimated to be less than 0.06%, 0.05%, 15 mK, and 0.02%, respectively. Apparent molar volumes ϕV were derived using measured values of density for the solutions and for pure water calculated with IAPWS formulation. The apparent molar volumes were analytically extrapolated to zero concentration to yield partial molar volumes at infinite dilution V ¯ 2 ∞ . The temperature, pressure, and concentration dependence of apparent and partial molar volumes were studied. The derived apparent molar volumes have been interpreted in terms of the Debye–Huckel theory (limiting law) of electrolyte solutions to accurate calculates the values of partial molar volume at infinite dilution V ¯ 2 ∞ and limiting slope AV as a function of temperature and pressure. All experimental and derived properties (apparent and partial molar volumes) are compared with the experimental values and correlations reported in the literature. The maximum of the apparent and partial molar volumes at temperature around 340–363 K depending on concentration and pressure was found.

Densities, ultrasonic speeds and refractive index of leucyl–glycine aqueous solutions were determined from 15 to 45 °C, at 5 °C intervals, for the molality range 0–0.3. Apparent molar volumes, V ϕ ,2 , and apparent molar isentropic compressions, K S , ϕ ,2 , of the solute have been derived from density and ultrasonic speed data. Limiting values of partial molar volumes, V 2 ∞ , partial molar isentropic compressions, K S ,2 ∞ , and partial molar isobaric expansions, E P ,2 ∞ , have been obtained. Molar refractivities, R m , have been derived from the refractive index using the Lorentz–Lorenz equation. The molar refractivities of the solute, R m ,2 ∗ , were calculated by a least squares fitting method. Interesting correlations between the temperature dependence of the different thermodynamic properties studied were found and interpreted in terms of molecular interactions in solution and configurations of the dipeptide skeleton.

Excess molar volumes at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of triethylamine (TEA) or tributylamine (TBA) with n -hexane, n -octane, n -decane, n -decane, n -tetradecane, or n -hexadecane, or of TBA with n -dodecane are reported from densities measured with a vibrating-tube densimeter. At equimolar composition, the excess molar volume for TEA+ n -alkane systems increases up to heptane and then decreases, being negative for the larger alkanes. In the case of TBA mixtures, the excess molar volume increases regularly with the chain length of the alkane, and is negative when a shorter alkane is the second component. The negative values of the excess molar volumes indicate that the contribution from free volume effects to excess volume is predominant over the interactional contribution. For the investigated solutions, the Flory theory represents the dependence of the excess molar enthalpy and of the excess molar volume with the size of the n -alkane.

Densities of 1-propanol+water+lithium chloride mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of the salt and 1-propanol at 288.15, 298.15, 308.15, and 318.15 K. From these densities, apparent molar volumes of lithium chloride in 1-propanol+water mixtures have been calculated for each temperature, and apparent molar volumes at infinite dilution have been evaluated. An empirical correlation for partial molar volumes of lithium chloride in 1-propanol+water mixtures with solvent composition and temperature has been derived.

The densities of aqueous solutions of some poly(ethylene glycol)s with nominal molecular weights ranging from 300 to 35 000 g mol −1 have been determined up to a weight molality of 0.7960 at 298.15 K. From these data, the apparent specific volume of the solute and the partial specific volume of the solute and solvent were calculated. The specific excess volume of the solutions and the coefficients of the virial expansion of the excess property were evaluated and interpreted in terms of solute–solute and solute–solvent interactions. From the partial specific volume of the solute at infinite dilution and the value of the average degree of polymerization, the partial molar volume of the repeating unit was evaluated, as well as the excluded volume between the solvent molecules and repeating unit, and the excess excluded volume representing the end-group effects.

Molar volume data are analyzed for n-alkanes and their mixtures over the range 10 to 126°C and n = 6 to n = 62. At a given temperature the logarithm of the molar volume of pure n-alkane liquids divided by the carbon number is equal to a constant plus a term proportional to the reciprocal of the carbon number. For solutions, deviations from the Bronsted principle of congruence are small, and for any given solution the deviations are proprotional to the product of the volume fractions of the individual components.