Browsing by Author "Sing, Kenneth S. W."

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    Magnetic and Optical Studies of Chromium Oxides Part 2. Calcination of Chromic Chloride Supported on Alumina
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (08), 1978) Ellison, Alan; Sing, Kenneth S. W.
    Magnetic and optical studies were made on chromium (III) chloride supported at various concentrations on a porous alumina, the impregnated samples having been calcined at different temperatures between 50–1150°C. The measurement of magnetic susceptibility and electron paramagnetic resonance spectra was carried out at controlled temperatures from –196 to 300°C. Optical reflectance spectra were obtained at room temperature on selected samples. The results suggest that clustering of the chromium chloride occurs, even in the lowest concentration studies (1.5 wt.% Cr); heat treatment in air leads to the formation of a mixed oxide phase containing CrVI, the stability of which is discussed in terms of electron transfer between the support and the chromium species.
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    Magnetic and Optical Studies of Chromium Oxides Part 3.—Calcination of Coprecipitated Chromium and Aluminium Hydroxide Gels
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Ellison, Alan; Sing, Kenneth S. W.
    Magnetic and optical studies were performed on coprecipitated chromium and aluminium hydroxide gels after calcination in air at temperatures between 50 and 1150°C. The results show that magnetic dilution was not achieved and that surface clusters of chromium oxide were formed. The magnetism, e.s.r. and optical spectra of oxidised samples are discussed in terms of a mixed-valency phase of partially-oxidised chromium containing Cr3+ and Cr6+ species. This new model of γ-phase chromium is shown to be consistent and an acceptable part of the extensive mixed-valency chemistry of chromium.