Water solubility and diffusion in sodium silicate melts

Water diffusivities and solubilities at temperatures of 900 to 1200degreesC are reported for sodium silicate melts containing 18-40 mol% soda. Water diffusivities at 500degreesC are also reported for glasses containing 4-30 mol% soda. Water solubilities reported here are similar to those of earlier work, lying in the range 1200-1600 wt ppm/atm(1/2) where 1 atm = 101.3 kPa. Water diffusivities, which lie in the range 10(-6) to 2x10(-5) cm(2)/s in this temperature range, are consistently greater than those of the earlier work by a factor of 2 to 3. Changes in water concentration alter the glass transformation temperature of soda silicate glasses by 40-50 K. A direct correlation between water diffusivity and melt viscosity does not exist for sodium silicate melts.