29Si-NMR-Spektroskopie an Silicatlösungen. II. Zur Abhängigkeit der Struktur der Silicatanionen in wäßrigen Natriumsilicatlösungen vom Na : Si-Verhältnis

²⁹Si-NMR Spectroscopy of Silicate Solutions. II. On the Dependence of the Structure of Silicate Anions in Water Solutions from the Na : Si Ratio The ²⁹Si-FT-NMR spectra of 13 sodiumsilicate solutions with different Na:Si ratios are investigated with regard to the structure of the silicate anions in the solutions. The 5 typical building units (Monosilicate, end-, middle-, branching and crosslinking groups) show characteristic and non overlapping ranges of the ²⁹Si chemical shift with many signals splittings caused by different neighbouring group effects. The relative intensities of the signals give informations on the concentrations and the equilibrium of condensation of the silicate anions in dependence of the Na:Si ratio. It is shown, that many types of anions with different degree of condensation coexist in an equilibrium, which is shiftet to the polymer silicate anions with high content of branching and crosslinking groups on the decrease of the Na:Si ratio.