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Man-made cryolite powder sodium hexafluorosilicate UN number 2674 can use for wood preservation and insecticide
►Description
Sodium fluorosilicate appears as white crystal, crystalline powder or colorless
hexagonal crystals.It has many features . It is odorless and tasteless. Its relative
density is 2.68; it has moisture absorption capability. It can be dissolved in a solvent
such as ethyl ether but insoluble in alcohol. The solubility in acid is greater than that
in water. It can be decomposed in alkaline solution, generating sodium fluoride and
silica. After searing (300 ℃), it is decomposed into sodium fluoride and silicon
tetrafluoride. It is poisonous!In 25 degrees, the sodium fluorosilicate has its water
solubility being 0.78%. Upon production, addition of an excess amount of sodium
sulfate or sodium chloride can increase the concentration of sodium ions in the
system, thereby increasing the solubility product of fluorine silicate and sodium
ions, so that sodium fluoride can be subject to more complete precipitation. Sodium
fluorosilicate is the byproduct in the production of calcium phosphate or the
production of fluoride salt in aluminum factory. It generally appears as a white
crystalline powder with low solubility in water (being 1% or less at room
temperature), and the water solubility increases slightly with increasing
temperature. The aqueous solution of sodium fluorosilicate is acidic (pH3). This is
due to that its hydrolysis product contains hydrofluoric acid. Reduction of the
acidicity of the solution facilitates the hydrolysis of sodium fluorosilicate. When pH
is lower than 3.5-3.55, the hydrolysis reaction is stabilized. When the pH is equal to
4, the hydrolysis reaction rate is significant. When the pH value is equal to 8-8.5,
the sodium fluorosilicate can be completely hydrolyzed to exhibit as silica gel and
precipitated out. Therefore, when sodium fluorosilicate is added to the water glass,
in addition to hardening effect of precipitation of silicon dioxide gel caused by the
neutralization of the sodium hydroxide in the solution of water glass, the sodium
fluorosilicate itself is also a source of silica gel.
| Na2Si6 | Item | Specification |
| Na2SiF6 | ≥99% | |
| Fe | ≤0.02% | |
| Loss of Weight on drying at 105°C | ≤0.40% | |
| Insoluble in Water | ≤0.50% | |
| Free Acid(HCL) | ≤0.15% | |
| Heavy Metal(Pb) | ≤0.05% |
►Reactivity Profile
Sodium fluorosilicate has weak oxidizing or reducing powers. Redox reactions
can however still occur. The majority of compounds in this class are slightly soluble
or insoluble in water. If soluble in water, then the solutions are usually neither
strongly acidic nor strongly basic. These compounds are not water-reactive.
►Health Hazard
Inhalation of dust may irritate nose and throat. Ingestion causes symptoms
similar to fluoride poisoning; compound is highly toxic; initial symptoms include
nausea, cramps, vomiting, diarrhea, and dehydration; in severe cases, convulsions,
shock, and cyanosis are followed by death in 2-4 hr. Contact with eyes causes
irritation. Contact with skin causes rash, redness, and burning, sometimes followed
by ulcer formation.
►Storage characteristics
Treasury: ventilation, low-temperature and drying; store it separately from food and
acid.
►Application
1. The insecticide in agriculture.
2. Wood preservatives
3. Man-made cryolite
