Permittivite complexe de solutions electrolytiques non aqueuses

The complex permittivity * = ′ — j″ of ethanolic solutions of electrolytes has been measured between wavelengths 90 and 3·2 cm, at 25°C. Methods of measurement are briefly described. The results are interpreted by separating the conductivity and the dielectric losses. For solutions of LiClO₄, Mg(ClO₄) ₂, LiCl and LiI, a dielectric relaxation analogous to that of the solvent is observed, ie the dielectric loss factor passes through a maximum at a wavelength of about 30 cm. The ‘static’ permittivity, defined in terms of the relaxation spectrum, undergoes an important fall with increase of concentration. Solutions of (n-Bu)₄NI give more complicated behaviour, characterized by the probable existence of a new relaxation domain at longer wavelengths. The results are discussed in relation to data in the literature on the intermolecular structure of alcohols and the dielectric properties of electrolyte solutions in other types of solvent.

Zusammenfassung

Man ermittelte bei 25°C die komplexe Permittivität * = ′ — j″ verschiedener Elektrolytlösungen in Äthanol bei Wellenlängen zwischen 3,2 und 90 cm. Die Messmethoden werden kurz beschrieben. Die Ergebnisse werden interpretiert, indem die Leitfähigkeitsverluste von den dielektrischen Verlusten getrennt werden. Bei en Lösungen LiClO₄, Mg(ClO₄)₂, LiCl und LiI stellt man eine dem Lösungsmittel analoge dielektrische Relaxation fest, m.a.W.: der dilektrische Verlustfaktor geht bei Wellenlängen in der Nähe von 30 cm durch ein Maximum. Die “statische Permittivität”, welche aud dem Relaxationsspektrum definiert werden kann, nimmt mit zunehmender Konzentration stark ab. Lösungen von (n-Bu)₄NI zeigen ein komplizierteres Verhalten, welches möglicherweise durch das Auftreten eines neuen Relaxationsgebietes bei längeren Wellenlängen gekennzeichnet ist. Man diskutiert die Ergebnisse mit Bezug auf die Literaturdaten der intermolekularen Struktur von Alkoholen, und das dielektrische Verhalten von Elektrolylösungen in anderen Lösungsmitteln.     

Redox chemistry of H2S oxidation by the British gas Stretford process part V: Aspects of the process chemistry

Stretford processes use air to oxidize H₂S in process and natural gases to elemental sulphur, by absorption in aqueous solution at about pH 9 and reaction of the resulting HS^– ions with dissolved oxygen, in the presence of anthraquinone disulphonates (AQDS) and vanadium (v) species, which act as catalysts. Kinetic measurements of the reactions (AQ27DS + HS^– ions), (V(v) + HS^– ions) and (AQ27DSH^– + O₂), primarily used stopped flow spectrophotometry, as reported here, following papers on the electrochemical behaviour of the individual redox couples in Stretford Processes. The course of reaction (AQ27DS + HS^– ions) was also followed with a gold bead indicator electrode, the potential of which was determined essentially by the AQ27DS/AQ27DSH^– couple as the former species were reduced to the latter. Attempts to use⁵¹V NMR to characterize aqueous vanadium-sulphur complexes were inconclusive. A possible mechanism for Stretford Processes is postulated, involving polysulphide (S _n ^2–) ions as intermediates, which are oxidized to elemental sulphur by another intermediate, H₂O₂, formed by reaction of AQ27DSH^– ions and dissolved oxygen.     

Analysis of Alkylbenzenes by Capillary Gas Chromatography

Suitable operating conditions are shown for GC separation of linear alkylbenzene (AB) samples on capillary columns. Retention data on SE-30 of n-phenylalkanes C₉-C₁₆ were measured and separation factors for n-phenylalkanes isomers were calculated. For quantitative evaluation from peaks areas of n-phenylalkanes, correction coefficients were calculated. By statistical evaluation of errors, standard deviations and further statistical parameters were calculated, showing GC method as sufficiently accurate and reliable. From results of collaborative testing of the GC procedure for quantitative AB analysis, some recommendations followed, esp. for application of capillary columns with apolar thermostable stationary phase only, with advantage under temperature programming, applying reduced sample volume at limited FID attenuation. It must be pointed out, this method is strictly limited for linear AB.     

Azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component

A number of new azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component have been prepared. The influence of polyfluoroalkyl groups on the colour and properties of azo dyes has been studied. The replacement of hydrogen atoms of the methyl group of the coupling component by polyfluoroalkyl radicals causes a hypsochromic shift of absorption maximum in a neutral solution and deepening of the dye colour in an acid solution. All tested dyes showed a high lightfastness on acetate and polyamide fibres.     

The influence of Na2O on the structure and properties of 3CaO.Al2O3

Four crystal forms of solid solutions of Na₂O in 3CaO.Al₂O₃ have been synthesized. Chemical, crystal-optical, X-ray diffraction and IR-spectroscopic investigations have been made.The hydration activity at the early and later stages has been studied. It is shown that the hydration process can be divided into three stages. The analysis of the kinetic curves permitted the conclusion that the retardation of the hydration process is controlled by diffusion of the liquid phase through the product layer.     

Liquid-phase stereoselective thymol hydrogenation over supported nickel catalysts

The stereoselective hydrogenation of thymol was studied in liquid phase over several nickel catalysts, modified by coimpregnation of inorganic compounds containing chlorine. The total activity of all catalysts studied was decreased and was on the same order of magnitude, indicating that chlorine even after reduction remains on the surface and is responsible for the poisoning effects. Such blocking of accessible sites results in similar reaction rates for the catalysts studied. Selectivity and stereoselectivity to menthols and menthones changed significantly. The modifiers could influence the rate of keto-enol transformations, which is thought to be the key selectivity and stereoselectivity governing step.     

Effect of stabilizer type on the physicochemical properties of rigid PVC. III

The crystallinity of rigid PVC specimens, stabilized by a tin mercaptide or a lead stabilizer, has been studied. It is found that the crystallinity of rigid PVC is greatly influenced by the type of stabilizer added, and that the response of the PVC toward subsequent UV exposure was also different. The effects of unstable structures and crystallinity, after UV irradiation, on the mechanical properties of rigid PVC have been investigated.