Natriumwasserglaslösungen : Aufbau, Eigenschaften und Probleme

Abstract

The paper gives a review of more modern results of the 29Si n.m.r., chromatographic methods, molybdate and dye adsorption methods regarding the structure and characterization of technically important sodium water glass-(sodium silicate-solutions) with molar ratio SiO2/Na2O = 3-3,5. There are described the influence of molar ratio, SiO2 concentration, condensation degree, impurities and thermal treatment on the structure and properties respectively of sodium water glass (NaWG) solutions. The results show that the complicate structure of NaWG solution and their influenceability by temperature, impurities, molar ratio and SiO2 concentration and furthermore the lack of suitable methods are reasons for the present insufficient characterization of NaWG solutions. It is shown that a more complete characterization especially regarding the thermal history of NaWG solutions is possible by combination of the molybdate method with the dye adsorption method. There is a hint of the existence of a thermal equilibrium state, which is influenced not only by the silicate anion distribution but the association equilibrium caused by concentration and state of distribution of impurities.