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  • 1
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Graphitized thermal carbon black ; Cyclic ethers and ketones ; Atom-atom oxygen … carbon potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper is concerned with molecular-statistical determination of retention volumes of oxygen-containing organic substances such as cyclic ethers and ketones by presenting the potential energy of intermolecular interaction of the molecules with a monoatomic adsorbent having homogeneous flat surface (graphitized thermal carbon black) as a sum of atom-atom potentials. In order to eliminate the specific interactions of ethers and ketones with the traces of surface oxygen compounds on graphitized thermal carbon black, the latter was treated additionally with hydrogen. Comparison is made between the experimentally measured retention volumes and the Henry constants calculated for reference molecules of ethers (dioxane) and ketones (cyclohexanone) to correct the atom-atom potentials. It is shown that the atom-atom potentials obtained for the reference molecules can be used for other ethers and ketones of known structure with the subsequent calculation of the corresponding values of the retention volumes in terms of molecular statistics. When the structure is not known its parameters are optimized using the chromatostructural method (chromatoscopy). The calculated heat of adsorption values agree well with those determined from the chromatographic measurements. Chromatograms showing the full separation of mixtures of the ethers and ketones studied were obtained.
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  • 2
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Graphitized thermal carbon black ; Indan ; Indan-type hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden die Werte der Retentionsvolumina, der Retentionsindices und andere thermodynamische Adsorptionscharakteristiken von zehn Indan- und Inden-Kohlenwasserstoffen mit 9–11 Kohlenstoffatomen auf graphitiertem thermischem Ruß (GTR) bestimmt. Es wurde festgestellt, daß auf GTR die Kohlenwasserstoffe der Inden-Reihe am stärksten adsorbiert werden und am schwächsten cis-Hydrandan, was mit den Besonderheiten der geometrischen Struktur dieser Verbindungen zusammenhängt. Es wird die Möglichkeit der Anwendung von GTR für die vollständige Trennung der cis- und trans-Isomeren von Hydrindan gezeigt.
    Notes: Summary The retention volumes, retention indices and other thermodynamic values characteristic of the adsorption of ten indan-hydrocarbons having 9–11 carbon atoms were determined on graphitized thermal carbon black (GTCB). It is shown that GTCB adsorbs strongest the hydrocarbons of the indan series and weakest cis hydrindan. This is related to the peculiarities of the geometric structure of the compounds. The possibility of the application of GTCB for the complete separation of cis and trans hydrindan is shown.
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  • 3
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Packed capillary columns ; Modification of BaSO4 ; Separation of isomeric unsaturated and aromatic hydrocarbons ; Selectivity and dipole moment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isomeric hydrocarbons with molecules having similar geometry but differing in the electron density distribution were separated on capillary columns packed with barium sulphate, a non-porous ionic adsorbent. Samples of BaSO4 were washed free of foreign ions and modified by solutions of alkaline metal halides. The selectivity of the separation of unsaturated and aromatic hydrocarbons can be controlled by varying the conditions of the BaSO4 treatment. Capillary columns packed with the ionic adsorbent were successfully used to separate all xylene and butene isomers, as well as isomers of cis and trans octene-2.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Molecular structure and adsorption ; Graphitized carbon black ; Capillary packed adsorption columns ; Tricyclic hydrocarbon separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Due to their high efficiency capillary columns packed with graphitized thermal carbon black (GTCB) permit to realize high selectivity in the chromatographic separation of isomers on the flat surface of this adsorbent. However, the increase in the efficiency is connected to a considerable increase of the pressure drop across the column which hinders the determination of the thermo-dynamic adsorption characteristics. The optimum conditions for the preparation of such columns designed both for analytical purposes and for thermodynamic measurements of the individual isomers have been established. The retention volumes for small (zero) sample size (Henry constants for adsorption on GTCB) of six isomers of tricyclo(8,4,0,02,7)tetradecane (perhydrophenanthrene), seven isomers of tricyclo-(7,4,0,02,6)tridecane (1,2-cyclopentanodecalin) and six isomers of tricyclo(7,3,0,02,6)dodecane have been determined. The Henry constants increase with the flattening of the isomeric molecules in these hydrocarbon series. A qualitative procedure of identification of the isomers on the basis of optimum orientation of their molecules on a flat surface has been considered.
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 81-84 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new approach to the quantitative evaluation of the thickness hi and the volume fraction Vi of the interfacial layer in polyimide coatings has been developed using the model of a one-sided polymer coating as a three-phase system (a substrate, an interfacial layer and a polymer matrix) and the method of differential scanning calorimetry. The new approach is characterized by the fact that a “pure” polymer matrix is modeled with the help of free films obtained on mercury. The formulas for the calculation of the thickness and volume fraction of the interfacial layer have been proposed. The value hi has been determined in polymer coatings of different thicknesses on aluminium foil. This parameter has been shown to be independent of the film thickness if the latter is not larger than the length of the interfacial layer. An assumption has been made about the “mechanical” origin of thick (〉 1-5 μm) interfacial layers, and their relaxation character has been revealed.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A tool was developed for enhancement of plasmid penetration into an intact cell, based on increasing DNA hydrophobicity via inclusion into a soluble interpolyelectrolyte complex (IPC) with polycations. The characteristics of formation of DNA IPC with synthetic polycations [poly(N-ethyl-4-vinylpyridinium)bromide (PVP) and PVP modified with 3% of N-cetyl-4-vinylpyridinium units (PVP-C)] were studied using ultracentrifugation and polyacrylamide gel electrophoresis methods. The conditions were established under which the mixing of DNA and polycation aqueous solutions results in the selfassembly of soluble IPC species. Incorporation of DNA into IPC results in the enhancement of DNA binding with isolated Bacillus subtilis membranes. A considerable increase in the efficiency of transformation of B. subtilis cells with pBC16 plasmid resulted from incorporation of the plasmid into the IPC with PVP and CVP.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die Säure-Base-Eigenschaften des Di- und Tetrafluorxenons in Reaktionen bei erhöhten TemperaturenEs wurde die Reaktion von Xenondifluorid und Xenontetrafluorid mit Fluorkomplex-Verbindungen verschiedener Übergangsmetalle bei erhöhter Temperatur untersucht. Unter diesen Bedingungen wurde die Bildung von Anionenkomplexen M2XeIVF6 festgestellt. Es wurde gezeigt, daß XeF4 unabhängig davon, ob es direkt in die Reaktion eingeführt wird oder dort aus XeF2 entsteht, zwei typische Eigenschaften aufweist: die eines Oxydationsmittels (〉 300°C) und einer Säure (zwischen 150°C und 300°C). Das Reaktionsverhalten des XeF4 hängt ferner von den Eigenschaften des Reaktionspartners ab. Die Eigenschaften der Xenonfluoride als Lewis-Säuren folgen der Reihe: XeF6 ≈ XeF4 ≫ XeF2.
    Notes: Reaction of xenon di- and tetrafluoride with different transition element fluorocomplexes at high temperatures has been studied. The formation of XeIV anionic complexes M2XeF6 has been found. XeF4 is shown to reveal two kinds of properties: oxidative (higher than 300°C) and acidic (between 150-300°C), independently whether it was initially introduced into the system or arised in it from XeF2. The reaction path of xenon tetrafluoride is shown to depend upon the other reagent properties. The conclusion is made that Lewis acidic properties of xenon fluorides decrease as follows: XeF6 ≈ XeF4 ≫ XeF2.
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die Umsetzung der Di- und Tetrafluoride des Xenons mit Fluoriden der AlkalimetalleDie Umsetzung von XeF2 und XeF4 mit Verbindungen des Typs MF (M = Na, K, Rb, Cs) wird untersucht. Es bilden sich dabei Hexafluoroxenate(IV) mit der Summenformel M2XeF6, die das oktaedrische Anion XeF62- enthalten. Cs2XeF6 und Rb2XeF6 bilden monokline Kristalle (a0 = 853,7(5); b0 = 669,6(2); c0 = 843,6(5) pm; β = 121,7(1)° für Cs2XeF6 und a0 = 812,6(4); b0 = 631,9(2); c0 = 795,6(4) pm; β = 121,5(1)° für Rb2XeF6). K2XeF6: tetragonal mit a0 = 868,8(2); c0 = 747,8(2) pm; Na2XeF6: hexagonal mit a0 = 642,1(3); c0 = 844,8(5) pm. Es wird gezeigt, daß sich die Verbindungen M2XeF6 inkongruent in wasserfreiem HF lösen, wobei sich unter anderem das Solvolyseprodukt XeF4 bildet. Es wird nachgewiesen, daß die Thermolyse von M2XeIVF6 und M2XeVIF8 unter ähnlichen Bedingungen abläuft.
    Notes: Interaction of XeF2 or XeF4 with MF (M = Na, K, Rb, Cs) has been studied. Hexafluoroxenates(IV) M2XeF6 containing the octahedral XeF62- anion (in accordance with spectroscopy data) were formed in the reaction. Cs2XeF6 and Rb2XeF6 form monoclynic crystals (a0 = 853.7(5); b0 = 669.6(2); c0 = 843.6(5) pm; β = 121.7(1)° and a0 = 812.6(4); b0 = 631.9(2); c0 = 795.6(4) pm; β = 121.5(1)°, respectively). K2XeF6 has a tetragonal lattice (a0 = 868.8(2); c0 = 747.8(2) pm), while Na2XeF6 has a hexagonal one (a0 = 642.1(3); c0 = 844.8(5) pm). M2XeF6 is shown to dissolve in unhydrous HF incongruently, one of the solvolitic products being XeF4. Thermolysis of M2XeIVF6 and M2XeVIF8 were shown to proceed under similar temperatures.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Schwingungsspektren kristalliner Hexachlorocerate(IV), R2CeCl6Eine vollständige Zuordnung aller Fundamentalbanden in den Spektren kristalliner R2CeCl6, die zu den Ce—Cl-Schwingungen gehören, wurde unter Benutzung von Daten über Kombinationsschwingungen und im Raman-Spektrum aktiver Oberschwingungen vorgenommen. Die Vermutung über die Existenz einer isolierten [CeCl62-]-Gruppe, die in Kristallen mit einer genügend hohen Gitterpunktsymmetrie eine oktaedrische Struktur aufweist, konnte bestätigt werden. Auf der Grundlage des experimentellen Materials und seiner Deutung wird die Vermutung über das Auftreten eines Pseudo-Jahn-Teller-Effektes in der Hexachloroceraten(IV) geäußert.
    Notes: A complete assignment of all fundamentals in the spectra of crystalline R2CeCl6 belonging to the Ce—Cl vibrations was undertaken using data about combination bands and active in the Raman spectrum overtones. The assumption of the presence of a separate [CeCl62-] group possessing an octahedral structure in crystals with a sufficient high site symmetry has been confirmed. Based on the experimental material and its interpretation a presumption concerning the appearence of a pseudo-Jahn-Teller effect in the hexachlorocerates(IV) was supposed.
    Additional Material: 2 Ill.
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  • 10
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Aminolyse von makroporösen Copolymeren aus Glycidylmethacrylat und Ethylendimethacrylat führte zu Sorbentien mit einem unterschiedlichen Gehalt an Amino-und Hydroxygruppen. Es wurde die Abhängigkeit zwischen strukturellen Parametern und der Schwefeldioxidsorption auf der einen und der Konzentration des Vernetzungsmittels und der porogenen Lösungsmittel in der Polymerisationsmischung auf der anderen Seite untersucht. Die Schwefeldioxidsorption hängt von der geometrischen Struktur des Sorbens, der Konzentration, der chemischen Struktur und der Erreichbarkeit der funktionellen Gruppen ab.
    Notes: Macroporous copolymers of 2,3-epoxypropyl methacrylate and ethylenedimethacrylate modified by aminolysis yielded sorbents with various contents of amino and hydroxy groups. The dependences of structural characteristics of these sorbents and of the sorption of sulphur dioxide on the content of crosslinking agent and on the cyclohexanol/dodecanol ratio used as the porogenic medium in the preparation of copolymers were investigated. The sorption of sulphur dioxide depends on the geometrical structure of the sorbent, concentration, chemical structure and accessibility of functional groups.
    Additional Material: 7 Ill.
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