527. Ammonium Hexafluorosilicate

Nomenclature

CAS number: 16919-19-0
Hexafluorosilicate(2) ammonium (1:2); ammonium fluosilicate; ammonium silicofluoride.
F6H8N2Si; mol wt 178.15.
F 63.99%, H 4.53%, N 15.72%, Si 15.77%.
(NH4)2SiF6.

Description and references

Occurs in nature as the mineral cryptohalite. Prepn: Gmelins, Ammonium (8th ed.) 23, pp 414-415 (1936). Crystal structure: Schlemper et al., J. Chem. Phys. 44, 2499 (1966); 45, 408 (1966). Toxicity study: Simonin, Pierron, C. R. Seances Soc. Biol. Ses Fil. 124, 133 (1937).

Properties

Odorless crystalline powder. Two modifications at room temp: stable, cubic phase; metastable, trigonal phase. Freely sol in water. Practically insol in alcohol, acetone. LD orally in guinea pigs: 150 mg/kg (Simonin, Pierron).

Caution

Toxic symptoms similar to sodium fluoride.

Use

In pesticides; in soldering flux; etching glass.