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  • catalytic activities and selectivities  (1)
  • lichens  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 139-149 
    ISSN: 1572-8943
    Schlagwort(e): catalytic activities and selectivities ; thermal decomposition ; transition metal acetates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal decomposition of acetates of the transition metals Fe, Co, Ni, Mn and Cu in molecular hydrogen has been investigated by means of combined thermogravimetry/mass spectrometry, X-ray diffraction, and transmission as well as scanning electron microscopy. In the context of the reproducible preparation of the parent phases, i.e. the hydrated or anhydrous metal(II) acetates, single crystalline Fe3(CH3COO)6(DMSO)2, a novel DMSO solvate of iron(II) acetate, has been isolated and its crystal structure has been determined by means of X-ray diffraction. For the series of metal(II) acetates it has been found that the course of the thermal degradation in molecular hydrogen, in particular the formation of the gaseous products, strongly depends on the transition metal ion present in the parent compound. The detailed characterisation of the solid products revealed, that phases exhibiting different catalytic activities and selectivities are formed as micro- or nanocrystalline metals and/or metal oxides.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1601-1607 
    ISSN: 1572-8943
    Schlagwort(e): algae ; copper ; fungi ; human artifacts ; lichens ; oxalate films
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Simultaneous thermogravimetry and thermomicroscopy were performed on Ca-oxalates which play an important role in the appearance of oxalate films connected with lichens superficially growing on human artefacts. Ca-oxalate exists in two well-described modifications: as the more stable monoclinic monohydrate whewellite and the less stable tetragonal dihydrate weddelite. Weddelite serves for lichens as a water absorbing and accumulating substrate which transforms to whewellite when humidity drops. To follow these morphological changes optically and the water loss gravimetrically at the same time, a combination of thermomicroscopy and thermogravimétric analysis was constructed, The reflection light microscope was connected to a video camera and computer so that the morphological changes and the thermogravimetric curves could be shown simultaneously on the screen as function of time and temperature. Lichens — double organisms composed of algae and fungi — form surface layers not only on natural organic and inorganic material but also on human artefacts. In calcareous artefacts such as the famous Chinese terracotta soldiers or Egyptian epigraphs they lead to a destruction of the surface by forming Ca-oxalate layers and thus to a deterioration of the historian work of art. But in places where the surface is covered by some blue colours (Egyptian and Chinese Blue, Chinese Purple) the growth of lichens is inhibited and the artefacts are well preserved. The copper ion contained in the pigments is responsible for this effect since copper is a strong poison for microorganism. As lichens exhibit an extremely slow growth under natural and laboratory conditions the two lichen components: algae and fungi were investigated separately. The three mentioned ancient pigments have very low solubility products and thus do not act on the quickly growing fungi. But under special experimental conditions Egyptian Blue formed clear halos on the growth plates of the algaeChlorella minutissima andTrebouxia glomerata. These halos were compared with those of the easily soluble copper sulphate as a standard.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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