Oxygen balance in sulfur-containing glass melts

Abstract

In sulfur-containing glasses the Fe²⁺/Fe³⁺ ratio at a given oxygen partial pressure shows a considerable shift compared to glasses without sulfur. This effect is caused by an electron exchange and governs the redox behavior of industrial glass melts at fming temperature. The electron exchange is formulated by a thermodynamic approach which can quantitatively describe the redox reactions between melting temperature and room temperature in flint glasses. In amber and green glasses this dependence is superimposed by the dissolution of SO₂-containing bubbles, which results in an additional shift of the oxygen partial pressure in the direction of the sulfur solubility minimum during cooling. From this shift the maximum solubility of sulfite in soda-lime-sihca glass melts can be estimated to be about 0.025 wt% SO₃. Resorption curves of sulfite sulfur in the melt describe the refining quahty. They can serve as a tool for improving the secondary refining in sulfur-containing industrial glass melts.