Oligomerization, aqueous monomeric silicic acid

Figure 1 gives results obtained by Alexander et al. (I) and Baumann (2) by dissolving fine particles of commercially available vitreous silica powders in aqueous solutions. Similar data obtained in polymerization and depolymerization experiments by Scheel et al. (15) and Friedberg (10) indicate that the curve shown in Figure 1 represents an equilibrium concentration for oligomeric acid. It can be approached from the supersaturated state of monomeric silicic acid as well as from a solution of pure polymeric silicic acid. 

Because polymerization of the water-glass solution gives rise to a broad distribution of silicate anions and thus results in poorly resolved Si NMR fines, the application of Si NMR spectroscopy in this type of reaction provides minor information about the different oligomerization steps and the reaction mechanism of monomeric silicic acid. Therefore a different approach to the study of aqueous silicate solutions was apphed. Because of the... 

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