Sodium aluminum hexafluoride
| Chemical formula | Na3AlF6 |
|---|---|
| OTP appearance | white crystal |
| Molar Mass(g/mol) | 209.94 |
| Density(g/cc) | 2.9 |
| Melting Point(°C) | 950 |
| Boiling Point(°C) | decomp |
| Solubility in water(g/L) | 0.4 |
| NFPA 704 |  0
0
0
|
Uses
Primary
- Essential solvent for production of aluminum
Natural occurrence
- Cryolite does occur naturally, but is extremely rare
Hazards
- Toxic if ingested @ 200mg/kg
Production
Synthesis
Now that natural supplies of cryolite are both rare and uneconomic, synthesis of this compound is essential to aluminum production.[1]
Fluorite
- CaF2 + H2SO4 → CaSO4 + 2 HF
- Al2O3 + 6 NaOH + 12 HF → 2 Na3AlF6 + 9 H2O
Silicofluoride
Sodium silicofluoride is a byproduct of the production of hydrofluoric acid by way of silicon impurities in the raw materials. This is combined with aluminum hydroxide and sodium carbonate producing sodium aluminum hexafluoride.
- 2 Na2SiF6 + 2 Al(OH)3 + Na2CO3 → 2 Na3AlF6 + CO2 + 2 SiO2 + 3 H2O
Industrial
Fluorsid produces granular cryolite by reacting diluted hydrofluoric acid (HF) and aluminium hydrate (Al(OH)3). The H3AlF6 acid is then converted into sodium salt by ion exchange reaction with a sodium chloride solution. After a solid-liquid separation, the slurry of cryolite is calcined in an internally heated rotary kiln. The final product is in the form of pale pink granules. Milled cryolite is obtained from the granular quality after rotary milling.
See Also
References
- ↑ Finger, G. C.; Reed, Frank H. (1938) "Synthetic Cryolite" (local copy)
Transactions of the Illinois State Academy of Science; pp180-182.
link courtesy archive.org.