Sodium concentration profile, glass

Precipitated silicas are normally made from solutions of sodium silicate (water glass). The sodium silicate solution is usually made by digesting a massive form of silica, such as sand, with sodium hydroxide solution. Precipitation is carried out by adjusting the pH with acid (sulfuric is usually used). Like all precipitations, the process is complex and governed by many variables, including temperature, pH profile, electrolyte concentration, agitation and time. Useful information can be found in Her [38], in Watson [39] and in manufacturer s literature [40]. 

Fig. 1.32. Concentration profile of sodium ions expressed as relative values c/cb in a soda lime silicate glass of the following composition (mol%) 20 Na20—6 CaO—74 Si02 during exposure to O.IN HCl at 60°C [451]...

Berg K.-J., Berger A, Hoffmeister H. Small silverparticles in glass surface layers produced by sodium-silver ion exchange their concentration and size depth profile. Z. Phys. D—Atoms, Molecules Clusters 1991 20 309... 

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