Thermodynamics of sorption of 1,3,4-oxadiazoles and 1,2,4,5-tetrazines according to reversed phase high-performance liquid chromatography

The thermodynamics of sorption of several 1,3,4-oxadiazoles and 1,2,4,5-tetrazines on octadecyl silica gel from aqueous acetonitrile solutions of different compositions has been studied. The thermodynamic characteristics of the chromatographic systems under study were calculated. The dependences of the standard molar change in the entropy term of the dependence lnk-1/T and the enthalpy after the transfer of the sorbate from bulk solution to the surface layer on the content of the organic component in the eluent were analyzed for the compounds. It was shown that the structure of sorbate molecules affected the thermodynamic characteristics of their quasichemical sorption and solvation. Tendencies of compensation were found for sorption and solvation of the heterocyclic compounds under study.     

Effect of the nature of binary water-organic solvents on the thermodynamic characteristics of adsorption of certain 1,3,4-oxadiazoles and 1,2,4,5-tetrazines on phenyl-bonded silica gel

The thermodynamics of adsorption in the Henry region for certain 1,3,4-oxadiazoles and 1,2,4,5-tetrazines from water-acetonitrile, water-methanol, and water-isopropyl alcohol solutions on silica gel with grafted phenyl groups is studied according to the dynamic method under conditions close to equilibrium. The effect of the nature of the organic component of a solvent on the values of standard differential molar changes in Gibbs energy, enthalpy, and entropy is shown upon adsorption of the investigated substances from solutions. The role of intermolecular interactions occurring in bulk solutions and at the interface during the adsorption of heterocycles from diluted water-organic solutions is discussed. The compensation effect and linear Gibbs energy relationship upon the adsorption of 1,3,4-oxadiazoles and 1,2,4,5-tetrazines from the investigated water-organic solutions on silica gel with grafted phenyl groups is determined.     

Supermolecular structure of cotton cellulose isolated by the soda-oxygen method

The supermolecular and fine structures of celluloses obtained on the soda-oxygen digestion of cotton lint under various conditions have been investigated by electron microscopy, IR spectroscopy, and x-radiography. It has been shown that under these conditions there is a weakening of intermolecular hydrogen bonds between the cellulose microfibrils and a loosening of their packing.Tashkent Institute of Chemical Technology. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–374, May–June, 1998.     

Modification of Epoxy Binders for Glass- and Basalt-Reinforced Plastics

The process parameters of production of epoxy binders modified with glycidyl esters of phosphorus acids were studied, and the performance characteristics of glass- and basalt-reinforced plastics on their basis were determined.     

Effect of Praestol Cationic and Anionic Flocculants on the Efficiency of Water Pretreatment at Heat and Electric Power Plants

The efficiency of water purification at simultaneous use of Praestol macromolecular flocculants, iron(II) sulfate coagulant, and calcium hydroxide alkalizing agent was studied as influenced by the nature (cationic and anionic), chemical composition, and conformational state of the flocculant macromolecules in solution and by the concentrations of the flocculant and coagulant.     

Features of the adsorption of aryl- and hetaryl-substituted 1,3,4-oxadiazoles from solutions on the surface of porous graphitic carbon in Henry’s range

Adsorption in Henry’s range of structurally related aryl- and hetaryl-substituted 1,3,4-oxadiazoles from n-hexane-dichloromethane and water-acetonitrile solutions on the surface of porous graphitic carbon (PGC) under the conditions close to equilibrium is studied by high-performance liquid chromatography. The characteristics of sorption of 1,3,4-oxadiazoles from solutions on the surface of this adsorbent, octadecyl silica gel, and on hypercrosslinked polystyrene are compared. It is shown that the structure of the molecules and their Van der Waals surface area and polarity affect adsorption on a PGC surface. A variant of the mechanism of adsorption of the polar molecules on the PGC surface, explaining the anomalously high values of their Henry constants of adsorption and based on the planar location of the 1,3,4-oxadiazoles molecules with respect to the adsorbent surface and the specific adsorbate-adsorbent intermolecular interaction in addition to the background dispersion interactions, is proposed. It is established that the linear the Gibbs energy relationship upon the adsorption of the studied compounds from n-hexane-dichloromethane and water-acetonitrile solutions on the PGC surface holds.     

Plasma-Chemical Decomposition of Hydrocarbons on the Basis of the Micro-Arc Discharge with Disc Electrodes Rotating in the Bulk of Raw Materials

Russian Physics Journal - An innovative plasma-chemical hydrocarbon processing reactor has been developed. It is based on the interaction of nonequilibrium gas-discharge plasma with hydrocarbons in...     

Numerical Investigation of a Surface Barrier Discharge in Air at Atmospheric Pressure

Russian Physics Journal - An extended hydrodynamic model describing the surface dielectric discharge in air is formulated in the paper. Preliminary numerical calculations have been performed...     

Physical Methods for Determining the Phase Composition of Gallstones

Crystallography Reports - Gallstones with a zonal morphological structure have been studied using X-ray microtomography, X-ray diffraction analysis, Raman spectroscopy, and elemental analysis....