Redox Equilibria of Transition Metals in Silicate Melts

摘要

An investigation is carried out at present by ourselves to determine the redox equilibria of titanium, niobium and chromium in calcium-silicate melts at low contents of the transition metals. The results have been discussed in this lecture together with data on vanadium which have been published previously by one of the authors and together with literature data on iron. The slags were equilibrated with gases of controlled oxygen pressure at 1600 鳦, and wet chemical analysis was used, after quenching, to determine the different metal ions. The project is not finished yet and some of the obtained data have to be checked. Nevertheless, it can already be demonstrated that the ratios of the two differently charged species depend on oxygen pressure, within their scatter, with the power required by the oxidation reaction. Increasing CaO/SiO_2 ratio stabilizes the higher valent metalion. The redox equilibria for chromium and vanadium are particularly interesting because ions with three oxidation states (Cr~(2+), Cr~(3+) and Cr~(6+), or V~(3+), V~(4+) and V~(5+)) can coexist in intermediate ranges of oxygen pressure which is very much in contrast to the behavior of these metals in aqueous solutions.