Background. The present study investigated the hydrolytic instability of ammonium, 2-, 3-, 4-carboxypyridinium, 2,2′-, 4,4′-dipyridinium hexafluorosilicates in 1×10-4 M aqueous solutions of salts.
Methods. The soluble form of silica in the hydrolysis products of hexafluorosilicates were determined by the photocolorimetric method. The measurements were performed at a wavelength of 380 nm using a spectrophotometer KFK-3.
Results. The degree of hydrolysis a is within 89.0–99.8%, approaching to quantitative values in some cases. The closeness of the values a agrees with the determination of the pH of aqueous solutions of salts which were in a narrow range of 2.95–3.15. The high degree of conversion of SiF62- ions in silica in dilute aqueous solutions involves the efficient release of fluoride ions, which, along with the formation of silica, provides the caries-preventive effect of the studied compounds.
Conclusions. Following the results of this study, caries-preventive agents based on hexafluorosilicates with heterocyclic onium cations are as effective as those based on ammonium salts and manifest various kinds of biological activity that enhance caries-preventive action.