Hydrofluoric acid is considered to react with silica or silicate to form gaseous material, silicon tetrafluoride (SiF4), which reacts with silica or silicate to form gaseous material. The reaction of the chemical equation is:

SiO2 + 4HF = SiF4 + 2H2O,

CaSiO3 + 6HF = CaF2 + SiF4+ 3H2O.

Hydrofluoric acid added to the glass, the solution turbidity and a flocculent precipitate generated, while a small amount of white mist in the solution produced.

A small amount of white mist is hydrofluoric acid dissolved in water vapor generated acid mist. The main basis is as follows:

Inorganic hydrolysis is mainly affected by the following three factors: ion (atomic) radius and the number of charged charge; For SiF4, although the Si-F bond energy (565 kJ /mol) is larger than the bond energy of the C-F bond (485 kJ /mol), Si-F4 does not decompose at 1273 K, but Si-F4 is readily hydrolysable. The reason is that the radius of silicon atoms is larger, both 3s and 3p orbitals can form covalent bonds, and 3d empty orbitals can accept water molecules in the lone pair of electrons to form coordination bonds, thereby weakening the role of silicon and fluorine force, so that Si-F bond fracture. Therefore, Si-F4 is easily hydrolyzed and can not be present in water.