Ultrasound speeds and molar isentropic compressions of (3-ethoxypropane-1-amine + water) mixtures from T = (283.15 to 303.15) K

Alkoxyamines containing two hydrophilic groups with great affinity to water are multipurpose compounds with important applications, either on theoretical or practical grounds. The thermodynamic characterization of aqueous mixtures of these compounds is scant. Ultrasound speed measurements have been made in 53 mixtures of the aqueous ethoxypropane-1-amine binary system, across the entire composition range and temperatures between T = (283.15 and 303.15) K, at atmospheric pressure. By combining ultrasound speed and density data, values of the isentropic compressibility were derived. Excess molar isentropic compressions were estimated and analytically fitted to Redlich–Kister polynomial equations. Excess partial molar quantities were then calculated including their limiting values, which were obtained from the Redlich–Kister fitting coefficients. The temperature dependences of limiting partial molar isentropic compressions and isobaric expansions were also scrutinized. Compressibility changes associated with different patterns of aggregation and hydration over the whole composition range are identified.     

Partition behaviour of benzoic acid in (water + n-dodecane) solutions at T = (293.15 and 298.15) K

The partition coefficients of benzoic acid in solutions of two immiscible solvents, water and n-dodecane, were measured at temperatures of (293.15 and 298.15) K. The experimental results indicated that at both temperatures the partition coefficients were not constant, but showed linear dependences on the concentration of benzoic acid in water. Dimerization of benzoic acid in n-dodecane and ionization in water were assumed based on the chemical theory and the experimental results verified this assumption quite well. Accordingly the association equilibrium constants of benzoic acid in n-dodecane were obtained by a linear regression. The regression results also showed that there was a very strong dimerization of benzoic acid in n-dodecane over the temperatures and concentration range investigated.     

Activity coefficients of electrolyte and amino acid in the systems (water + potassium chloride + dl -valine) at T = 298.15 K and (water + sodium chloride + l -valine) at T = 308.15 K

The activity coefficient data were reported for (water  +  potassium chloride  + dl -valine) at T =  298.15 K and (water  +  sodium chloride  + l -valine) at T =  308.15 K. The measurements were performed in an electrochemical cell using ion-selective electrodes. The maximum concentrations of the electrolytes and the amino acids studied were 1.0 molality and 0.4 molality, respectively. The results of the activity coefficients of dl -valine are compared with the activity coefficients of dl -valine in (water  +  sodium chloride  + dl -valine) system obtained from the previous study. The results show that the presence of an electrolyte and the nature of its cation have a significant effect on the activity coefficient of dl -valine in aqueous electrolyte solutions.     

(Liquid + liquid) equilibria of (water + linalool + limonene) ternary system at T = (298.15, 308.15, and 318.15) K

(Liquid + liquid) equilibrium (LLE) data for {water (1) + linalool (2) + limonene (3)} ternary system at T = (298.15, 308.15, and 318.15 ± 0.05) K are reported. The organic chemicals were quantified by gas chromatography using a flame ionisation detector while water was quantified using a thermal conductivity detector. The effect of the temperature on (liquid + liquid) equilibrium is determined and discussed. Experimental data for the ternary mixture are compared with values calculated by the NRTL and UNIQUAC equations, and predicted by means of the UNIFAC group contribution method. It is found that the UNIQUAC and NRTL models provide a good correlation of the solubility curve at these three temperatures, while comparing the calculated values with the experimental ones, the best fit is obtained with the NRTL model. Finally, the UNIFAC model provides poor results, since it predicts a greater heterogeneous region than experimentally observed.     

Diffusion of sodium alginate in aqueous solutions at T = 298.15 K

Taylor dispersion technique was used for measuring mutual diffusion coefficients of sodium alginate aqueous solutions at T = 298.15 K, by using as carrier stream solution both pure water and solutions of this polyelectrolyte at a slightly different concentration. The limiting values found at infinitesimal ionic strength, D⁰, were determined by extrapolating to c → 0. These studies were complemented by molecular mechanics calculations. From the experimental data, it was possible to estimate both the limiting conductivity and the tracer diffusion coefficient values for the alginate anion, and the hydrodynamic radius of the sodium alginate (NaC₆H₇O₆), as well as to discuss the influence of the kinetic, thermodynamic and viscosity factors on the diffusion of sodium alginate in aqueous solutions at finite concentrations. Thus, the aim of our innovative research is to contribute to a better understanding of the structure and the thermodynamic behavior of these polymeric systems in solution and supplying the scientific and technological communities with data on these important parameters in solution transport processes.     

Speeds of sound and isentropic compressibilities of (n-alkoxyethanols + toluene) at T = 298.15 K

Speeds of sound u at the temperature 298.15 K for six ( n -alkoxyethanol  +  toluene) were measured over the whole composition range. The n -alkoxyethanols were 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol. Excess molar volumes V_m^E atT =  298.15 K were also measured for the mixtures of toluene and 2-methoxyethanol, 2-ethoxyethanol, or 2-butoxyethanol over the whole composition range. The speed of sound values were combined with excess molar volumes to obtain values for the product K_{S, m} of the molar volume and the isentropic compressibilityκ_S , and the corresponding excess quantities K_S,m^E were also calculated. The K_S,m^E curves are sigmoid for all mixtures. The deviations of the speeds of soundu^D from their values u^id in an ideal mixture were obtained for all measured mole fractions. These values are compared with the mixing function δu calculated in the paper. The behaviour ofu , u^D, δu, and K_S,m^E as a function of composition and number of carbon atoms in the aliphatic chain of the alkoxyethanol is discussed. Also, theoretical values of the molar isentropic compressibility K_S,m and speed of sound u were calculated using the Prigogine-Flory-Patterson theory with a van der Waals potential energy model and the results compared with experimental data.     

Excess properties of the binary mixtures of methylcyclohexane + alkanes (C6 to C12) at T = 298.15 K to T = 308.15 K

Experimental values of density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K while the speed of sound at T = 298.15 K in the binary mixtures of methylcyclohexane with n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane, and iso-octane are presented over the entire mole fraction range of the binary mixtures. Using these data, excess molar volume, deviations in viscosity, molar refraction, speed of sound, and isentropic compressibility are calculated. All the computed quantities are fitted to Redlich and Kister equation to derive the coefficients and estimate the standard error values. Such a study on model calculations in addition to presentation of experimental data on binary mixtures are useful to understand the mixing behaviour of liquids in terms of molecular interactions and orientational order–disorder effects.     

Viscometric studies on saccharides in aqueous magnesium chloride solutions at T = (288.15 to 318.15) K

The viscosity B-coefficients of mono-, di-, tri-saccharides and the derivatives (methyl glycosides) in m_B = (0.5, 1.0, 2.0, and 3.0) mol · kg⁻¹ aqueous solutions of magnesium chloride have been determined from viscosity data using the Jones–Dole equation at T = (288.15, 298.15, 308.15, and 318.15) K. The viscosity B-coefficients of transfer (Δ_tB), the temperature derivatives of B-coefficients (dB/dT), pair and triplet viscometric interaction coefficients (η_AB, η_ABB) have been determined. The viscosity B-coefficients data of systems studied in water have been reported earlier. The results have been interpreted in light of the solute–solute and solute–solvent interactions occurring in these systems. The comparison of results has been made with those reported in the presence of potassium chloride, ammonium sulphate, and sodium sulphate.     

Excess molar enthalpies of the binary systems: (Dibutyl ether + isomers of pentanol) at T = (298.15 and 308.15) K

In this work, we present the experimental measurements of excess molar enthalpies for the binary systems of dibutyl ether with different isomers of pentanol: 1-pentanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-methyl-2-butanol; all of them at T = (298.15 and 308.15) K and atmospheric pressure. Our goal was to determine the influence of the OH-group position on the different isomers of pentanol in the excess molar enthalpies of the binary systems studied. For this purpose we have analysed their experimental effective-reduced dipole moments. All values of excess molar enthalpies for the mixtures studied are positive whereas the results obtained for the effective-reduced dipole moments of the isomers of pentanol are similar.     

Mean activity coefficients of NaCl in (sodium chloride + sodium bicarbonate + water) fromT = (293.15 to 308.15) K

The mean activity coefficients of NaCl in (sodium chloride  +  sodium bicarbonate  +  water) were determined experimentally in the temperature range 293.15 K to 308.15 K at four NaHCO₃molality fractions (0.1, 0.3, 0.5, and 0.7). The measurements were made with an electrochemical cell, using a Na ⁺ glass ion-selective electrode and a Cl ⁻ solid-state ion-selective electrode. The experimental values reported by Butler and Huston are found to be higher than those calculated from the Pitzer equation using the existing parameters while the experimental results of this work are close to the calculated values, up to an NaHCO₃molality fraction of 0.5. At the NaHCO₃molality fraction of 0.7, the experimental data are much lower than the calculated values, implying that the interference of HCO₃ ⁻ on the Na ⁺ glass ion-selective electrode can only be neglected up to a molality fraction of NaHCO₃of 0.5, an observation which is consistent with that of Butler and Huston.     

(Liquid + liquid) equilibrium data of (water + phosphoric acid + solvents) systems at T = (308.2 and 318.2) K

Ternary equilibrium data for the mixtures of {water + phosphoric acid + organic solvent (cyclohexane, methylcyclohexane, and toluene)} were determined at T = (308.2 and 318.2) K and atmospheric pressure. Solubility data were determined by the cloud-point titration method. In order to obtain the tie-line data, the concentration of each phase was determined by acidimetric titration, the Karl–Fischer technique, and refractive index measurements. The experimental tie-line data were correlated using the UNIQUAC and NRTL models. The reliability of the experimental data was determined through the Othmer–Tobias and Hand plots. Distribution coefficients and separation factors were evaluated over the immiscibility regions. The Katritzky LSER model was applied to correlate distribution coefficients and separation factors in these ternary systems.