Hexafluorosilicic acid

Hexafluorosilicic acid is a chemical compound that is an acid. It has the simplified chemical formula , but has a complicated chemistry that means no compound with this formula truly exists. A better formula is , indicating a hydrated hydronium salt.

It can be reacted with bases such as sodium hydroxide to produce a fluorosilicate salt such as sodium fluorosilicate. It is used to make artificial cryolite. It releases hydrogen fluoride when it is heated, so it is toxic like hydrofluoric acid. It is used in fluoridation of water. 

 Production 
Most hexafluorosilicic acid is a byproduct from refining minerals that contain fluoride.

For example, pure fluorite has the formula , and makes hydrofluoric acid in a chemical reaction with sulfuric acid:

Silica, , is a common impurity in fluorite. If silica is present during the above reaction, it will react with the  product. This equation can be written as

Related pages
Silicate
Silicon
Fluoride

 References 

Category:Solvated proton acids
Category:Silicon compounds
Category:Fluorine compounds