Solubility of benzil in binary alkane + dibutyl ether solvent mixtures. Comparison of predictive expressions derived from the nearly ideal binary solvent model

Experimental solubilities are reported for benzil dissolved in six binary mixtures containing dibutyl ether with hexane, heptane, octane, cyclohexane, methylcyclohexane, and 2,2,4-trimethylpentane at 25°C. Results of these measurements are compared to the predictions of equations developed previously for solubility in systems of nonspecific interactions. The most successful equation in terms of goodness of fit involved a volume fraction average of the excess Gibbs energies relative to the Flory-Huggins model, and predicted the experimental solubilities in the six systems studied to within an overall average absolute deviation of 3.4% and with a maximum deviation of 6.0%.     

Evaluation of excess molar polarization in binary mixtures of Polar–Nonpolar liquids

Excess molar polarization in the binary mixture of polar solutes (acetic acid, n-tributyl phosphate) in nonpolar solvents (benzene, tetrachloromethane, p-xylene) is evaluated with the help of our proposed equation. The results have been compared with those obtained from a previously proposed equation. It is observed that our proposed equation is more accurate to interpret the liquid structure and molecular association in the binary liquid mixtures.     

Micellization of Sodium Dodecyl Sulfate in Glycerol Aqueous Mixtures

The effect of glycerol on both micellar formation and the structural evolution of the sodium dodecyl sulfate (SDS) aggregates in the context of the action mechanism of the cosolvent has been studied. The critical micelle concentration and the degree of counterion dissociation of the surfactant over a temperature range from 20°C to 40°C were obtained by the conductance method. The thermodynamic parameters of micellization were estimated by using the equilibrium model of micelle formation. The analysis of these parameters indicated that the lower aggregation of the surfactant is mainly due to a minor cohesive energy of the mixed solvent system in relation to the pure water. The effect of glycerol on the mean aggregation number of the micelles of SDS was analyzed by the static quenching method. It was found that the aggregation number decreased with the glycerol content. This reduction in the micellar size seems to be controlled by an increase in the surface area per headgroup, which was ascribed to a participation of glycerol in the micellar solvation layer. Studies on the micropolarity of the aggregates, as sensed by the probe pyrene, indicated that this microenvironmental parameter is almost unaffected by the presence of glycerol in the mixture. However, an increase in the micellar microviscosity at the surface region was observed from the photophysical behavior of two different probes, rhodamine B and auramine O. These results suggest a certain interaction of the cosolvent in the micellar solvation of SDS micelles.     

Characterization of the solid phases of paracetamol and fenamates at equilibrium in saturated solutions

Differential scanning calorimetry (DSC), supported by hot stage microscopy, IR spectroscopy and X-ray powder diffractometry, was used to investigate the characteristics of the solid phases of mefenamic, niflumic, and flufenamic acids and of paracetamol, before and after equilibration with saturated solutions in different solvents. Mixtures of Lewis base (dioxane and ethyl acetate) and amphiprotic solvents (ethanol and water) were prepared for evaluating the influence of both nature and polarity of the solvents. Solid-state analysis performed on the original samples (commercial products) made it possible to establish that paracetamol, mefenamic acid and flufenamic acid were in their respective Form I. No polymorphic modifications are known for niflumic acid. Paracetamol, niflumic and mefenamic acids did not show any change after equilibration with the various solvents or solvent mixtures, regardless of their different chemical nature. In contrast, DSC, IR and X-ray analyses revealed the partial recrystallization of flufenamic acid into its polymorphic Form III in solid phases at equilibrium with ethanol, ethyl acetate and their blends, as well as in dioxane-water mixtures containing 30 to 100% dioxane and in ethanol-water mixtures with a water content less than 50%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of the Temperature and Composition Dependence of Viscosimetric Properties of 2-Butanone <Emphasis Type="Bold">+</Emphasis> 2-Butanol Solvent Mixtures

Kinematic viscosities were measured for 2-butanone + 2-butanol binary liquid mixtures with a capillary Ubbelohde routine viscometer in the temperature range from 273.15 to 353.15 K at atmospheric pressure, and covering the whole miscibility field (0x_i1). Experimental data have been correlated by means of different empirical or semiempirical relationships, such as =(T), =(x_i), and =(T, x_i). Viscosity deviations, , from ideal behavior are negative at all experimental conditions, confirming that structure breaking effects prevail in the liquids. Furthermore, the thermodynamics of viscous flow and excess Gibbs energy of activation of viscous flow, G*^E, have been calculated. As an alternative and complementary approach to such investigations, the fluidity () of this binary system has been analyzed by the modified—Batschinski theory. The results are discussed in terms of the specific molecular interactions between the mixture components.     

Crystal Structure of Ternary Molybdate Rb5FeHf(MoO4)6 — a New Phase in the Rb2MoO4-Fe2(MoO4)3-Hf(MoO4)2 System

Physicochemical analysis (XRPA, DTA) was used to study phase equilibria in a ternary salt system Rb₂MoO₄-Fe₂(MoO₄)₃-Hf(MoO₄)₂ in the subsolidus region. Ternary molybdates with compositions 5:1:3, 5:1:2, and 1:1:1 have been found and synthesized. Crystal and thermal characteristics have been determined. Single crystals of the ternary molybdate Rb₅FeHf(MoO₄)₆ with a composition of 5:1:2 were grown. The crystal structure of the compound was solved using X-ray diffractometry (CAD-4 automatic diffractometer, MoK _α radiation, 1766 F(hkl), R = 0.0298). Hexagonal crystals with unit cell dimensions: a = b = 10.124(1) Å, c =15.135(3) Å, V = 1343.4(4) ų, Z = 2, ρ_calc = 4.008 g/cm³, space group P6₃. The mixed three-dimensional framework of the structure is formed from two sorts of MoO₄ tetrahedra and Fe and Hf octahedra linked through their common O-vertices. Rubidium atoms of three varieties occupy the large voids of the framework.Original Russian Text Copyright © 2004 by B. G. Bazarov, R. F. Klevtsova, A. D. Tsyrendorzhieva, L. A. Glinaskaya, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1038–1043, November–December, 2004.     

Limiting Partial Molar Volumes of Electrolytes in 2-Methyl-2-Butanol <Emphasis Type="Bold">+</Emphasis> Water Mixtures at 298.15 K

Partial molar volumes at infinite dilution, V⁰₂, of alkali–metal halides (LiCl, NaCl KCl RbCl CsCl, NaBr, KBr, KI), tetra-n-alkylammonium bromides, R₄NBr (R=Me, Et, n-Pr, n-Bu, n-Pen), NaBPh₄, and Ph₄PCl have been determined in binary solvent mixtures of water with 2-methyl-2-butanol covering the water-rich region and the alcohol-rich region at 298.15 K. V⁰₂ for alkali–metal halides show relatively little dependence on the solvent composition. However, in the case of hydrophobic electrolytes the observed effects are more pronounced. A good linear dependence between V⁰₂(R₄NBr) and the molecular weight of the tetra-n-alkylammonium cation is found. Limiting single-ion volumes have been obtained using the assumption that V⁰(Ph₄P⁺)–V⁰(BPh^–₄)=2.0 cm³-mol^–1. The trends in the single-ion volumes are discussed in both solvent regions.     

Equilibrium Studies of Binary and Ternary Complexes Involving Tricine and Some Selected α-Amino Acids

Summary. The formation equilibria for the binary complexes of Co^II, Ni^II, Cu^II, Zn^II, Cd^II, Mn^II, Pb^II, Th^IV, UO₂^II, and Ce^III with tricine and for the ternary complexes involving some -amino acids (glycine, -alanine, proline, serine, asparagine, and aspartic acid) were investigated using pH-metric technique. The formation of binary and ternary complexes was inferred from the pH-metric titration curves. It was deduced that tricine acts as a primary ligand in the ternary complexes involving the monocarboxylic amino acids (glycine, -alanine, proline, serine, and asparagine), whereas it behaves as a secondary ligand in the ternary systems containing the dicarboxylic aspartic acid. The ternary complex formation was found to take place in a stepwise manner. The stability constants of the complexes formed in aqueous solutions were determined potentiometrically under the experimental conditions (t=25°C, I=0.1moldm^–3 NaNO₃). The order of stability of the ternary complexes in terms of the nature of the amino acids is investigated and discussed. The values of log K for the ternary complexes have been evaluated and discussed. Evaluation of the effects of ionic strength and temperature of the medium on the stability of the ternary system M^II-tricine--alanine (M^II=Co^II, Ni^II, and Cu^II) has been studied. The thermodynamic parameters were calculated and discussed.     

Possibilities of Production of New Reference Material – Preparation of Gaseous Standard Mixtures Using Thermal Decomposition of Immobilized Compounds – the Effect of Selected Parameters on the Amount of Released Analyte

The paper presents the results of research on a novel type of matrix-free reference materials for volatile organic compounds based upon thermal decomposition of appropriate immobilized compounds. The effect of parameters such as the kind of support (silica gel, porous glass, glass fiber) and the method of chemical modification of the support surface on the amount of chloromethane released as the analyte has been investigated. It was demonstrated that the amount of chloromethane released during thermal decomposition of immobilized compounds formed on the surface of silica gel and porous glass was larger when trimethylamine rather than N-morpholine was used for the preparation of immobilized compound. Reproducibility of the chemical modification procedure using silica gel and the stability of support with the immobilized compound were also examined. The full uncertainty budget of determination of liberated amount of chloromethane has been calculated.