Journal of Solution Chemistry

Viscosities and densities have been measured for 1-propanol + n-heptane at 20, 25, 30, and 35°C and atmospheric pressure. Kinematic viscosities were determined using a capillary viscosimeter; densities were measured using vibrating-tube densimetry. The viscosity deviations were evaluated. Viscosity results were fitted to the equations of Grunberg–Nissan, McAllister, Auslander, and Teja. The experimental excess molar volumes were compared with the results obtained with the Nitta–Chao model.

An improved bubble column evaporator (BCE) system was used to determine accurate and precise enthalpy of vaporization (ΔH vap) values for concentrated salt solutions. The method is based on the steady state volumetric energy balance developed in a BCE. The BCE system offers a novel and simple approach for ΔH vap measurements because it only requires measurement of the hydrostatic differential pressure across the column and the temperatures of the steady state column and the inlet gas. In this work an automatic acquisition system was developed in order to study the frequency distribution of ΔH vap values. It was established that vacuum insulation of the bubble column and a data acquisition system enhanced both the accuracy and precision of ΔH vap measurements. In addition, a hygrometer was used to measure vapor pressures of concentrated Li2SO4 and ZnSO4 solutions to determine new ΔH vap values. The results obtained are in better agreement with expected values and indicate the conditions required to enhance evaporative cooling systems and improve thermal desalination. An analysis was also carried out on the effect of salt concentration on ΔH vap and on calculated values of the partial molar enthalpy of dilution (ΔH dil).

Excess volume, partial molar volumes, viscosity, and ultrasound velocity in H2O and D2O solutions of formamide (FM), acetamide (AM), dimethylformamide (DMF), and dimethylacetamide (DMA) were studied at 20°C. The change in the excess volume of the various amide solutions on substitution of D2O for H2O varies both in magnitude and direction. On the other hand, the isotope effect on the ultrasound velocity behaves similarly in all cases. Its magnitude is greatest for pure water and then decreases monotonically with increasing amide concentration. Although the behavior of the concentration dependence of viscosity is similar to that for ultrasound velocity, the isotope effect on the viscosity behaves in a different way. For methyl-substitued amides, a maximum isotope effect is observed at amide mole fraction 0.2, but the isotope effect for FM and AM increases monotonically with increasing amide concentration. The differences in the behavior of amides in aqueous solution are discussed in terms of their interactions with water.

Chromic acid oxidation of malonic acid in aqueous media has been investigated spectrophotometrically at 303 K. The product glyoxylic acid has been characterized by 13C-NMR and FTIR spectroscopy. Three representative N-heteroaromatic nitrogen base promoters, 2-picolinic acid, 2,2′-bipyridine (bpy) and 1,10-phenanthroline, in combination with the anionic surfactant sodium dodecylsulfate (SDS) enhanced the rate of the oxidation reaction compared to the unpromoted reaction. 2,2′-Bipyridine produced the maximum rate enhancement of the three promoters used. The mechanism of the reaction has been proposed with the help of kinetic results and spectroscopic studies. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. The SDS and bpy combination is suitable for malonic acid oxidation.

The equation of Reilly, Wood, and Robinson was used to predict the osmotic coefficient of seawater and of its concentrates at molal ionic strengths of 0.5 to 6.0 at 25°C. The results agree closely with experimental data at ionic strengths below 5. The average difference in osmotic coefficients over the entire concentration range is 0.0014. The only serious discrepancy is at an ionic strength of 6, where a difference of 0.0068 is found. The accuracy of the predictions of osmotic coefficients prompted the calculation of the activity coefficients of NaCl, Na2SO4, MgCl2, MgSO4, KCl, and K2SO4 in the mixture. The calculated activity coefficients of NaCl and Na2SO4 agree within experimental error with previous measurements. This agreement demonstrates the prediction of activity and osmotic coefficients for complex mixtures.

The micro amounts of ruthenium(III) catalyzed oxidation of chloramphenicol by cerium(IV) in an aqueous sulphuric acid medium has been studied spectrophotometrically at 25 °C and at I = 1.60 mol·dm−3. The order with respect to [Ce(IV)] and [Ru(III)] was found to be unity. Increasing [H+] accelerates the rate with less than unit order in [H+]. The reaction rate decreases with increasing ionic strength and increases with decreasing dielectric constant of the medium. The experimental results suggest that the active species of cerium(IV) and ruthenium(III) were CeSO4 2+ and [Ru(H2O)6]3+, respectively. Based on the experimental results a suitable mechanism was proposed and the rate law was derived. The activation parameters were calculated with respect to the slow step of the proposed mechanism and thermodynamic quantities were also determined. The reaction constants involved in the mechanism have been computed. There is a good agreement between the experimental and calculated rate constants under different experimental conditions.

The current research focuses on the adsorption of Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria on magnetic coated chitosan (MCC) adsorbent. The results showed that MCC was found to be an excellent adsorbent for bacteria removal. The structural elucidation of the adsorbent was made by PZC, SEM, TGA, XRD and FT-IR. It was observed that bacteria adsorption was enhanced with increasing concentration of bacteria and dosage of the magnetized chitosan adsorbent. The maximum adsorption capacity (Xm) of bacteria was observed 1 × 1010 CFU·g−1 with 99.5% removal efficiency at 303 K and pH = 7.4. The Langmuir adsorption isotherm was found to be applicable to the equilibrium data and a pseudo-second-order kinetic model described the kinetic data. Thermodynamic studies showed that the adsorption process is endothermic in nature.

Temperature dependent dielectric studies were carried out from 303 to 323 K for mixtures of anisole with acetic acid and with propionic acid, in order to investigate the molecular dynamics of these molecules. The low-frequency molecular dynamics of these molecules have been studied by computing some dielectric parameters such as the Kirkwood correlation factor, Bruggeman parameter, excess permittivity and excess Helmholtz energy. The observed Kirkwood effective correlation factor for both binary mixtures at all concentrations and temperatures were found to be less than unity. Negative values of the Bruggeman parameter were obtained for mixtures of anisole with acetic acid whereas positive values were obtained for the mixtures of anisole with propionic acid. The formation of β-multimers, with anti-parallel dipolar orientations, was identified in the above binary mixtures. This investigation showed that changes of temperature did not produce any significant structural changes over the studied temperature interval.

Densities and sound velocities in dilute aqueous solutions ofN-acetyl-DL-serinamide andN-acetyl-L-threoninamide were measured at 5, 15, 25, 35, and 45°C. Partial molar volumes and partial molar adiabatic compressibilities of these amino acid derivatives at infinite dilution were determined. The partial molar quantities for the parent amino acids, serine and threonine, were also determined and compared with the acetyl amide derivatives. The contribution of the side chain of theN-acetyl amino acid amide or amino acid to the partial molar quantities were estimated from the difference between the partial molar quantities for the solute studied and those for the corresponding species,N-acetyl-glycinamide or glycine, without the side chain.