Ceramics-Silikáty 29, (1) 1 - 11 (1985)

Glass melt of the type SiO₂-Al₂O₃-CaO-Ba0-Na₂O-K₂O-F, is regarded as a binary system composed of alkali fluorides and non-volatile mother glass melt. At fluorine concentrations lower than 1.6 wt. % , diffusion in the melt is the controlling process of the vaporization of alkali fluorides. Convection increases at a higher fluorine concentration, and transport of these fluorides between the boundary layer of the flowing dry gaseous phase becomes the controlling process, where the diffusion in the glass melt at a content of 4.0 wt. % F upwards is negligible. The resistance of the phase boundary is insignificant owing to the high volatility of alkali fluorides. The calculated time dependence of the volatilization losses of both fluorine and alkali fluoride are in agreement with the experimental values.