Browsing by Author "Freude, Eberhard"
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- ItemIron in glass melts - Α voltammetric investigation(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1990) Freude, Eberhard; Rüssel, ChristianBy the aid of square-wave voltammetry, a fast potentiostatic pulse method, iron oxide-doped soda-lime-silica glass melts were investigated. The iron concentration (0.1 to 2 mol% Fe2O3) and the temperature (400 to 1300 °C) were varied in a wide range. At low iron concentrations as well as at high temperatures the reduction of the Fe3+ to the Fe2+ ion is a one-step process, while at high iron concentrations and at relatively low temperatures a two-step process is observed. By comparison with thermodynamic data of solid state iron oxides, especially of Fe3O4, it is assumed that this is due to the formation of aggregated species containing Fe3+ as well as Fe2+ ions.
- ItemSquare-wave voltammetry as a method for the quantitative in-situ determination of polyvalent elements in molten glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Montel, Christian; Rüssel, Christian; Freude, EberhardMany properties of glasses, especially the color are strongly influenced by the concentration of multivalent elements. Up to now the concentration of multivalent elements can only be determined from the solid glass by chemical or physical methods. This paper introduces a method which makes possible to determine the total concentration of the multivalent ion in-situ in the glass melt by an electrochemical method. In this paper the square-wave voltammetry is used for the quantitative determination of iron in a soda-lime-shica glass melt. The area of the test electrode can be adjusted by conductivity measurements. The Fe2O3 concentration can be detected down to a lower limit of 0.015 mol%.
- ItemVoltammetric investigations in Na2SO4-refined soda-lime-silica glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1990) Kordon, Thomas; Rüssel, Christian; Freude, EberhardThe redox behavior of sulfate-refined soda-lime-silica glass melts was investigated by the aid of voltammetric methods. Here the possibilities for a quantitative in-situ determination of sulfur and iron are predominatly treated. Measurements in technical glass melts show that a determination of iron in melts with low sulfate and high iron concentration such as amber brown or green glass melts is easily possible. In contrast, there are problems at glass melts with low iron and high sulfate concentrations, because the current-potential curves are predominantly affected by sulfur compounds.
- ItemVoltammetric methods for determining polyvalent ions in glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1987) Freude, Eberhard; Rüssel, ChristianVoltammetry is an in situ technique to investigate redox equilibria in glass melts. Its sensitivity and resolution have been improved by introducing the square-wave voltammetry. The results reported in this paper clearly demonstrate the superiority of this method over the cyclic voltammetry, which had been used so far in glass melts.
- ItemVoltammetric studies in a soda-lime-silica glass melt containing two different polyvalent ions(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1990) Rüssel, Christian; Freude, EberhardBy the aid of electrochemical methods, a quantitative determination of polyvalent ions in glass melts is possible. This paper investigates the square-wave voltammetry in soda-lime-silica glass melts doped with iron and additionally with arsenic or antimony. In principle, a simultaneous, quantitative determination of these elements is possible, but the experimental parameters should be chosen with care and the recorded current-potential curves should be carefully analyzed.