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Monomeric, dimeric, trimeric and tetrameric silicate species were found in alkali (Li, Na, K, Cs) hydroxide solubilized silicates by laser Raman spectroscopy. Alkali chlorides promote condensation of these silicate species in solution. A siliceous precipitate whose Raman spectrum resembled that of alkali disilicate glasses was formed upon addition of LiCl to 1 M silicate solutions. This precipitate could be redissolved and the Raman spectrum indicated that it did so by hydrolysis into smaller silicate species. This study shows that, besides hydroxide ion, alkali cations can be used to control the degree of polymerization of aqueous silicate solutions and that Raman spectroscopy provides a convenient probe to monitor such changes.
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