Sodium fluorosilicate is a compound with the chemical formula Na2[SiF<sub>6</sub>]. Unlike other sodium salts, it has a low solubility in water.
Sodium hexafluorosilicate occurs naturally as the rare mineral malladrite found within some volcanic fumaroles.[1]
Sodium fluorosilicate is made by neutralizing fluorosilicic acid with sodium chloride or sodium sulfate.
H2[SiF<sub>6</sub>] + 2 NaCl → Na2[SiF<sub>6</sub>] + 2 HCl
It is used in some countries as additives for water fluoridation, opal glass raw material, ore refining, or other fluoride chemical (like sodium fluoride, magnesium silicofluoride, cryolite, aluminum fluoride) production.[2]