The Volatility of Soda–Lime–Silica Glasses

JSGT_1935_V19_T104_T117

A detailed account is given of the conditions which must be observed in studying the volatilisation from glasses at temperatures up to 1400°. These conditions include the shape of the containing vessel and the furnace conditions, as both influence the rate of diffusion of vapour from above the glass surface. The losses of platinum were determined at different temperatures. The presence of volatile constituents such as As₂O₃, SO₃ and traces of moisture increase the initial rate of volatilisation and must be guarded against. Under a fixed set of conditions it was shown that the rate of volatilisation was proportional to the area of the surface exposed. The volatilisation losses from the glass SiO₂ 73·35, Fe₂O₃+Al₂O₃ 0·40, CaO 9·90,Na2O 15·94%, prepared so as to be free from all but possible traces of the volatile constituents H₂O and CO₂ were studied and, for the first 20 hours in each case, were found to be 1·7 mg/cm² at 1400°; 0·69 at 1300°; 0·31 at 1200°, and 0·1 at 1100°. It was confirmed that up to 1400°, only Na₂O was volatilised.

H. W. Howes, H. Laithwaite, Eric Preston & W. E. S. Turner