Stannous‐Stannic Equilibrium in Molten Binary Alkali Silicate and Ternary Silicate Glasses

Abstract

The stannous‐stannic equilibrium in binary alkali silicate and ternary silicate glasses was studied by equilibrating glassmelts with air at 1400°C. The Sn2+‐Sn4+ equilibrium shifts more toward the oxidized state with increasing ionic radii of the alkali ions or with increasing concentration of the alkali ions in the same series of glasses. The slope of the straight lines obtained on plotting log (Sn4+)/(Sn2+)(pO2)n/2 vs mol% R2O increased in the order Li→Na→K. In ternary silicate glasses having the base glass composition 20Na2O·10RO·70SiO2, the Sn2+‐Sn4+ equilibrium shifts more toward the reduced state, with increasing bond strength between the divalent cations and the nonbridging oxygens. With increasing temperature, the equilibrium shifts more toward the reduced state. Copyright © 1982, Wiley Blackwell. All rights reserved