The solvent eluotropic strength on carbon adsorbents

Summary Two theoretical approaches are discussed to calculate the solvent strength () on carbon materials. One is based on the adsorbate-adsorbent interfacial tension and the other uses the theory of solubility parameters. It is shown that there is good agreement between these approaches. Experimental values are compared with theoretical ones and there is again a good agreement. Solvents having small and highly polar molecules have small values. Solvents having large and aromatic molecules have high values. Binary solvent mixtures can be classified in two groups depending on the rate of change of with the mole fraction of the strongest solvent in the mixture.Dedicated to Professor Dr. István Halász for his 60th birthday.     

Thermodynamics of 2,2′,2′'-terpyridinecopper(II) complexes in aqueous solution

Summary The thermodynamic quantities relative to the protonation and the complexation of 2,2,2'-terpyridine with copper(II) ion have been determined at 25° and I=0.1 mol dm^–3 (NaNO₃). The G data was obtained by potentiometric measurements; a copper selective electrode was employed for the study of the complexation equilibria. The H values have been determined by direct calorimetry.The hydrolytic species, existing at pH>6 and their relative G and H values have also been obtained.From the thermodynamic data the importance of enthalpy and entropy terms in stabilizing the complexes is assessed.Moreover some considerations on the chelating effect are reported.Presented in part at 2 Congresso Nazionale di Chimica Analitica, Catania (1977).     

The Properties of Mixtures of Sodium Dodecylsulfate and Diethylsulfoxide in Water

The aqueous mixtures of sodium dodecylsulfate (SDS) and diethylsulfoxide (DESO) have been studied using conductivity, viscosity and surface tension techniques. The critical micellar concentration (cmc) was determined in the presence of DESO at 30, 40, and 50 C from conductance and surface tension measurements. The enthalpy ( G_m), entropy ( S_m) and Gibbs energy ( G_m) of micellization were determined from the temperature dependence of the cmc. The results obtained were compared with published results for aqueous solutions of SDS and dimethylsulfoxide (DMSO). The data demonstrate a more pronounced inhibitory effect of DESO on the micellization of SDS, in comparison with the effect of DMSO. On the basis of the dependences of the relative viscosities on concentration, as given by the Jones–Dole semi-empirical equation, the B-coefficients have been calculated for the post-micelle composition region.     

Conductance of iron(III) laurate solutions in binary liquid mixtures

Summary The specific conductivity of iron(III) laurate solutions in binary liquid mixtures shows that the soap aggregates into micelles and CMC is found to be independent of temperature and concentration of benzene, acetone and tetrachloromethane in 1-butanol. The variation of molecular conductance,, with soap concentration, C, is expressed by the equation: = 10^AC^B. Both constants A and B vary with solvent composition but B remains constant with increase in temperature. Several parameters such as molecular conductance at infinite dilution, , dissociation constant, K, heat of dissociation, H, entropy, S and free energy, G of dissociation of soap have been evaluated and the effect of the nature of solvents has been discussed.     

Oxidation Behavior of Si–Nb–C–O Ceramics Prepared by the Pyrolysis of Methyltriethoxysilane Based Organic-Inorganic Hybrid Gel

The oxidative structural characterization of Si–Nb–C–O ceramic prepared by the heat-treatment of transition metal containing polymethylsilsesquioxane hybrid was investigated. The heating temperature for the pyrolysis of precursor hybrid gels strongly affected the oxidation behavior of the resultant ceramics. The hybrid gel pyrolyzed at 600C was rapidly oxidized, while the hybrid gel pyrolyzed at 1000C showed the higher resistance to oxidation. In the hybrid pyrolyzed at 600C, new Si–O–Nb oxygen-bridged heterometal bonds were formed after oxidation, which was confirmed by FT-IR spectra. On the other hand, silica and oxycarbide protective layer was formed on the oxidized surface of the hybrid heated at 1000C, as suggested by X-ray photoelectron spectroscopy (XPS). Raman spectra showed a large luminescence background, G and D bands before oxidation. After oxidation, however, the luminescence background disappeared and G band was more symmetric than that of non-oxidative product. This strongly suggested the predominant oxidation of radical and related unstable carbon species in the ceramics.     

Volumetric Parameters of Interaction of Monosaccharides (D-xylose,D-arabinose,D-glucose,D-galactose) with NaI in Water at 298.15 K

Densities for monosaccharide (D-xylose, D-arabinose, D-glucose, D-galactose)–NaI–water solutions were measured at 298.15 K and were used to calculate the apparent molar volumes of these saccharides and NaI. Infinite dilution apparent molar volumes for the saccharides (V_,S) in aqueous NaI and those for NaI (V_,E) in aqueous saccharide solutions and partial molar volumes of the saccharides (V_S) and NaI (V_E) at each composition have been evaluated, together with the standard transfer volumes of the saccharides (_tr V_S) from water to aqueous NaI and those of NaI (_trV_E) from water to aqueous saccharide solutions. It was shown that the _tr V_S and _trV_E values are positive and increase with increasing co-solute molalities. Volumetric parameters indicating the interactions of NaI with saccharides in water were also obtained and applied to explore the interactions between saccharides and NaI in water. A comparison of the _ES value for NaI with those for NaCl and NaBr showed that for a given saccharide, except for glucose, the _ES value for NaBr is the largest of three sodium halides (NaCl, NaBr and NaI). These were interpreted in terms of the apparent molar electrostriction volumes ( V_e) and the structure interaction model.     

Structural and Microstructural Evolution During Pyrolysis of Hybrid Polydimethylsiloxane-Titania Nanocomposites

The evolution during pyrolysis of hybrid polydimethylsiloxane-titania nanocomposites has been studied as a function of the ratio between polysiloxane and titania phases. The xerogels, prepared by the sol–gel process starting from diethoxydimethylsilane and titanium isopropoxide, have been heated under argon atmosphere and the evolution with temperature has been followed by infrared and ²⁹Si solid state nuclear magnetic resonance spectroscopies, thermal analyses, X-ray diffraction, N₂ sorption measurements and scanning electron microscopy. Below 800C, the polymer-to-ceramic conversion takes place at different temperatures with changing the titania content. The stability of Si–C bonds in polydimethylsiloxane networks depends on the metal oxide amount. The high reactivity of titanium atoms towards the Si–C bonds produces Si–C bond cleavage with mild thermal treatments and in the case of 30 mol% TiO₂, leads to the ceramization of the hybrid nanocomposite at 500C. Decreasing the titania load, a shift towards higher temperatures to complete the polymer-to-ceramic conversion is observed. The structural rearrangement of the siloxane moiety produces mesoporous and microporous materials, depending on the composition; in the case of 10 and 20 mol% TiO₂ content, the samples present high specific surface area up to 1200C.The crystallization process begins at 1000C and the phase evolution depends on the composition. The phase analysis obtained from XRD spectra shows that different crystalline oxide and oxycarbide phases develop during the thermal process, as a function of the amount of available carbon, ultimately leading to the preferential crystallization of titanium carbide. Between 1000 and 1600C the amorphous silicon oxycarbide phase undergoes a continuous structural evolution caused by the decrease of carbon content in the phase, leading to almost pure silica at 1600C.     

Physicochemical Properties of Ampicillin and Amoxicillin as Biologically Active Ligands with Some Alkali Earth,Transition Metal,and Lanthanide Ions in Aqueous and Mixed Solvents at 20, 30, and 40<Superscript>∘</Superscript>C

The acid-base equilibria of ampicillin and amoxicillin were investigated in pure water and different solvent + water mixtures (solvent = methanol, ethanol, acetone, dimethylformamide, and dimethyl sulfoxide) at a constant ionic strength (I = 0.1 mol-dm^–3 KNO₃) and organic solvent volume fractions of 10, 20, and 30%. The effect of temperature on these equilibria was studied at 20, 30, and 40C. Thermodynamic functions of these ligands were calculated and discussed in terms of G, H, and S. The number of ionizable protons was determined using conductometric titrations. The formation constant of the complexes, which form by reaction of the ligands with Mg(II), Ca(II), Zn(II), Cu(II), Ni(II), Co(II), Ce(III), Pr(III), Eu(III), Gd(III), Ho(III), Er(III), and Yb(III), are determined. The relative stability of the alkali earth, transition, and lanthanide elements are compared with each other and discussed in terms of the ionic radius and the electronic structure of the outer shell of that ion. The results obtained are discussed in terms of macroscopic properties of the mixed solvents and the possible variation in microheterogenity of the solvation shells around the solute.     

Donor-acceptor complex chromatography preparation of a chemically bonded acceptor-ligand and its chromatographic investigation

Summary The preparation of a TNF-phase for HPLC is described. From chemical and chromatographic evaluation it is concluded that chromatographic separation is the result of donor-acceptor complex formation. These findings are supported by the results of an investigation of solvent and temperature effect on retention. For solvent effects two models are discussed. According to the first model based on Fialkov and Borovikov a linear plot is obtained for log k against 1/ for 1/<0.4. In the second model it is shown that the Mass Law is appropriate to describe the solvent effect of binary mixtures of n-hexane and some polar component. Plots of k against 1/[S]^0.5 yield straight lines in all cases and the stoichiometry of complex formation is discussed. The slopes of the lines could be shown to be a measure of solvent strength and are found to parallel Snyder's parameters. From the temperature dependence of log k using the van't Hoff relationship changes in H for complex formation are obtained.     

Synthese des α,γ- und β,γ-Bipyridyls

Zusammenfassung P. Krumholz ¹⁵ hat kürzlich beim Vergleich physikochemischer Meßwerte erkannt, daß der als ,-Bipyridyl aufgefaßten Base die Formel des ,-Bipyridyls zuzuschreiben ist. Zur Prüfung dieser Frage und zur Kenntnis des wahren ,-Bipyridyls wurden die beiden Verbindungen auf eindeutigem Wege synthetisiert und ihre Konstanten mit denen der altbekannten Isomeren verglichen.Herrn Prof. Dr.F. Wessely zum 60. Geburtstag in alter Verbundenheit gewidmet.