Voltammetric studies on redox equilibria of various polyvalent elements inCaO/BaO/Al2O3/SiO2-melts

The thermodynamics of redox equilibria of various polyvalent elements were studied by square-wave voltammetry in glass melts with the basic molar comp ositions of 10CaO . 10BaO . 15Al(2)O3 . 65SiO(2) and 10CaO . 10BaO . 10Al(2 )O(3) . 70SiO(2) doped with 0.5 mol% Na2O and oxides of As, Sb, Sn, Ti, V, Cr, Fe and Cu. Besides Fe and Ti, all elements may occur in these melts in three different oxidation states. Standard potentials measured increased li nearly with temperature, the redox equilibria were shifted to the reduced s tate. Most standard potentials were more negative in the melt with 15 mol% Al2O3. The electrochemical series of elements were almost the same as those previously observed in silicate melts possessing alkali contents in the ra nge 15-33 mol%. (C) 2001 Elsevier Science B.V. All rights reserved.