Temperature dependence of the redox State of iron and sulfur in amber glass melts

In industrially melted amber glass the logarithm [Fe²⁺]/[Fe³⁺] shows no linear dependence on the logarithm of oxygen partial pressure. This nonlinearity is due to the interaction between iron and sulfur which can be described by means of a simple oxygen balance model. The change of chemically dissolved oxygen as a function of the oxygen partial pressure depends on the redox State and has a minimum at intermediate oxygen partial pressures. In this region small variations of the reducing additions in the batch cause large variations of the oxygen partial pressure.