Sodium hexafluorosilicate

Crystal structure
__ Na + __ Si 4+ __ F -
Crystal system	trigonal
Space group	P 321 (No. 150)
Lattice parameters	a = 885.9 pm, c = 503.8 pm, Z = 3
Coordination numbers	[6] Si, [6] Na
General
Surname	Sodium hexafluorosilicate
other names	Sodium silicofluoride Silica fluorosodium Sodium hexafluorosilicate Sodium hexafluoridosilicate Sodium fluorosilicate
Ratio formula	Na 2 [SiF 6 ]
Brief description	colorless to white, odorless and tasteless solid
External identifiers / databases
CAS number 16893-85-9 EC number 240-934-8 ECHA InfoCard 100.037.198 PubChem 28127 Wikidata Q532908
properties
Molar mass	188.06 g mol −1
Physical state	firmly
density	2.68 g cm −3
Melting point	800 ° C (decomposition)
solubility	sparingly soluble in water (7.62 g l −1 at 20 ° C) insoluble in ethanol
Refractive index	1,312
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 331-311-301 P: 261-280-301 + 310-311
Toxicological data	125 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Sodium hexafluorosilicate is a chemical compound from the group of sodium compounds , hexafluorosilicates and fluorocomplexes .

Occurrence

Sodium hexafluorosilicate occurs naturally in the form of the mineral malladrite .

Extraction and presentation

Sodium hexafluorosilicate can be obtained by neutralizing hexafluoridosilicic acid with sodium hydroxide , sodium carbonate or sodium chloride .

${\displaystyle {\ce {H2[SiF6] + 2NaCl -> Na2[SiF6] + 2HCl}}}$

It is also a by-product of the manufacture of superphosphates using silicon fluoride .

properties

Sodium hexafluorosilicate is a colorless to white, odorless and tasteless solid that is sparingly soluble in water. When heated, it decomposes from around 800 ° C to silicon tetrafluoride and sodium fluoride .

Sodium hexafluorosilicate has a trigonal crystal structure with a = 885.9 pm, c = 503.8 pm, Z = 3 and the space group P 321 (space group no. 150) .

use

Sodium hexafluorosilicate is used as a gelling agent in foam rubber manufacture, as an opacifier in enamel and milk glass manufacture, as an insecticide and rodenticide, and in the manufacture of synthetic cryolite . It is also used in the production of beryllium : by roasting beryllium salts with sodium hexafluorosilicate, beryllium fluoride is formed , which is converted to beryllium by reacting with magnesium .

Admission

Sodium hexafluorosilicate is not approved as an active ingredient in plant protection products in the European Union. In Germany, Austria and Switzerland, no pesticides with this active ingredient are permitted.

Individual evidence

1. ↑ ^{a b} A. Zalkin, JD Forrester, DH Templeton: The crystal structure of sodium fluorosilicate , Acta Cryst. (1964) 17, pp. 1408-1412; doi : 10.1107 / S0365110X64003516 .
2. ↑ ^{a b c d e f g h i} Entry for CAS no. 16893-85-9 in the GESTIS substance database of the IFA , accessed on February 4, 2012(JavaScript required) .
3. ↑ ^{a b c d} Entry on Sodium silicofluoride in the Hazardous Substances Data Bank , accessed July 29, 2012.
4. ↑ Entry on Disodium hexafluorosilicate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
5. ↑ Mindat: Malladrite
6. ^ Uni-Regensburg: alkaline earth metals
7. ↑ Regulation (EC) No. 2076/2002 of the Commission of November 20, 2002 ... (PDF)
8. ^ Directorate-General for Health and Food Safety of the European Commission: EU pesticide database ; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on March 8, 2016.