FLUORO COMPLEXES IN AQUEOUS SOLUTION .2. FORMATION AND PROPERTIES OF TETRAFLUOROSILICIC ACID

The SiF4 partial pressures of strongly acidified fluorosilicate solutions has been measured as a function of various parameters (Si:F ratio, total concentration of fluorine, water activity, acidity, temperature). The experimental data provide information on formation and properties of the silicon tetrafluoro complexes. Tetrafluorosilicon complexes are formed in high yield when hexafluorosilicate solutions are saturated with silica at high acid concentrations. They contain 2 moles H2O per mole SiF4; their formula can be written as SiF4·2 H2O. Silicon tetrafluoride dihydrate behaves like a strong acid. As to be expected, it is less stable than the corresponding ammonia adduct. © 1969 Springer-Verlag.