The electrochemical series of elements in the Na2O center dot 2SiO(2) glass melt

The thermodynamics of redox equilibria were studied by square-wave voltamme try in a glass melt with the basic composition of Na2O . 2SiO(2) in the tem perature range of 850-1600 degrees C. The melts were hoped with oxides of A s, Sb, Sn, Cu, V, Fe, Cr and Ti. While iron and titanium-doped glass melts exhibit only one reduction step, all other polyvalent compounds studied are reduced in two electron steps. In the case of As-, Sb-, Sn- and Cu-doped m elts, the metallic state is formed during the second reduction step. Standa rd potentials measured depend linearly upon the temperature. In all cases s tudied, the reduced states are favored at higher temperatures. The electroc hemical series of elements is nearly the same as those previously reported for soda-lime-silicate and borosilicate glass melts. However, in comparison to these glass melt compositions, the standard potentials in the Na2O . 2S iO(2) melt are shifted to lower potentials. This cathodic shift can be expl ained as an effect of the higher basicity of the Na2O . 2SiO(2) melt. (C) 1 999 Elsevier Science B.V. All rights reserved.