Hexafluorosilicate ions fluoride

So far, there have been no studies to confirm or refute the suggestion that water supplies contain polymeric species, and there have been only very few studies on the relevant equilibria which are involved in liberating free fluoride ions from the hexafluorosilicate additives [123]. What data there are, though, suggest that equilibrium will have been reached by the time the water reaches the consumer, even though it may not have been achieved when the water left the waterworks. 

The behavior of SiF4 as a Lewis acid enables it to add two additional fluoride ions to form the hexafluorosilicate ion ... 

In chromium baths, ion chromatography allows the determination of the major and minor anionic components [165, 166]. Major components include chromic acid itself and sulfuric acid acting as an anionic catalyst minor components include fluoride or hexafluorosilicate, chloride, and organic acids such as methanesulfonic acid. Methanesulfonic acid is added to the bath to improve the deposition on nickel. Analytical monitoring of chromic acid plating baths is of... 

All of the SiX4 tetrahalides except the fluoride hydrolyze rapidly to give hydrated sihca the fluoride also undergoes partial hydrolysis but also forms the hexafluorosilicate ion (equation 19). 

The formed silicium fluoride is gaseous. In water, it decomposes with the precipitation of silice and with the formation of fluosilicic acid. Fluosilicic acid derives from the anion complex hexafluorosilicate(IV), [SiFe] (fluosilicic ion). In alkaline medium, silice, whose formula is then SiOs ", can be detected after precipitation with tetramminezinc(n) cation, [Zn(NH3)4] +, according to the reaction... 

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