The Effect of Lead Oxide Additions on the Viscosity of Sodium Borosilicate Slags

The viscosities of sodium borosilicate slags containing lead oxide were measured with a Brookfield Rotational Viscometer at temperatures in the range of 950–1000°C. Increasing additions oflead oxide produced a marked decrease in viscosity. Also, the viscosity decreased as the borax to silica ratio in the melt increased, at constant lead oxide contents. The role of lead oxide and sodium oxide in rupturing the rigid silica network and effectively depolymerizing the melt is discussed and a mechanism is proposed which explains the observed changes.