A Study of the Volatilisation of Sulphate from Soda–Lime–Silica Glasses

JSGT_1936_V20_T127_T138

Four soda–lime–silica glasses containing 16% Na₂O and 0·31-0·83% SO₃ were prepared and samples heated at temperatures from 1300° to 1450° in an oxidising atmosphere. The order of volatility was the order of the sulphate contents, and the loss of sulphate was approximately proportional to the initial sulphate concentration. After 100 hours heating at 1350°, 1400° and 1450° the sulphate contents were reduced respectively to about 2/3, ½ and 1/3 of their initial values. The variation of total volatilisation loss with temperature obeyed a vapour pressure law. Comparison of the total volatilisation losses with the sulphate losses determined analytically showed that the presence of SO₃ caused an increase in the loss of alkali, approximately to the extent of twice the alkali volatilisation experienced by a pure glass of the same composition containing no sulphate.

Eric Preston, W. E. S. Turner & Horace Laithwaite