Oxidation-reduction equilibrium experiments were conducted with oxide melts containing CaO, Li_2O, A1_2O_3, ZnO, B_2O_3, SiO_2 and small concentrations of iron oxide. The results indicated that for compositions within the acidic regime, the ratio {(Fe~(3+))/(Fe~(2+)) P_(O_2)~(1/4)} decreased with an increase in basicity while for relatively basic melts, the ratio increased with an increase in basicity. This variation of {(Fe~(3+))/(Fe~(2+)) P_(O_2)~(1/4)} could be interpreted in terms of the optical basicity of the glass melts and is consistent with the following expressions for the red-ox equilibria within acidic and relatively basic melts, respectively:Fe~(2+) + (1/4)O_2 = Fe~(3+) + (1/2)O_2Fe~(2+) + (1/4)O_2 +(3/2)O~(2-) = FeO_2~- In an acidic melt, the temperature dependence of the reaction yielded an enthalpy value which was in excellent agreement with the enthalpy change for the reaction:FeO(s)+ (1/4)O_2(g)= (1/2) Fe_2o_3(s).
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