Browsing by Author "Masabo, Mathias Karemera Juvenal"

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    Preparation and physicochemical studies of selected rare earth oxalato halide complexes
    (University of Dar es Salaam, 1990) Masabo, Mathias Karemera Juvenal
    The activation energies for thermal decomposition of crystalline preparations of rare earth metal oxalato halide tri hydrates, were determined according to the method by Ozawa. The activation energy Ea of oxalate thermal decomposition was found to increase as the ionic size of the cation decreased. The effect of the atmosphere on activation energy was investigated. The probable explanation for higher value of Ea in static air than in the dynamic inert atmosphere is given. The structures of the rare earth metal oxalato halides and their parent oxalates were established by conducting X—ray diffraction and infrared spectroscopic studies. The structural changes that occur as the complexes undergo dehydration are described. The infrared findings reveal that oxalate in the hydrates is tetra dentate and predominantly bidentate in the anhydrous compounds. The activation energy is high, apparently because of an interaction between the metal and oxalate ions. Thus, the mechanism of oxalate thermal decomposition is determined by the presence of bidentate oxalate. The decomposition scheme of the oxalate is elucidated. The products formed at about 600 C are revealed by interpreting the respective DTG curves.