The properties of glasses containing small quantities of Na2O were determined. It was found that the Na diffusivity could be described by:

D (cm2/s) = 2.5 x 10-3 exp[-20(kcal/mol)/RT]

For 52ppm of Na2O, and by:

D (cm2/s) = 4.2 x 10-3 exp[-21(kcal/mol)/RT[

For 47ppm of Na2O.

J.F.Cordaro, J.E.Kelly, M.Tomozawa: Physics and Chemistry of Glasses, 1981, 22[4], 90-3