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CAS NO 16893-85-9 Sodium Fluorosilicate powder use for building industry and glass making
Sodium fluorosilicate appears as white crystal, crystalline powder or colorless
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.
►Reference quality standards
105 ℃ Loss of weight upon drying% 0.17%
Sodium fluorosilicate (based on dry mass) 99.50
Free acid (calculated based on HCL) 0.0075
Water insoluble matter 0.12%
Heavy metals (Pb) content% <0.02
% Fineness (through 250um sieve) 98.00
Appearance white powder
|Loss of Weight on drying at 105°C||≤0.40%|
|Insoluble in Water||≤0.50%|
This product is toxic with stimulation effect on the respiratory organ. People of
mistakenly oral poisoning will get severe symptoms of damage to the
gastrointestinal tract with the lethal dose being 0.4~4g. During the working of the
operator, they should wear the necessary protective equipment to prevent
poisoning. Production equipment should be sealed and the workshop should be
Calcium superphosphate byproduct method: use sulfuric acid and ground
phosphate rock for production of superphosphate or fluorine-containing waste gas
during extraction of phosphate with water absorbing silicon tetrafluoride to make it
into fluorosilicate. When the concentration of fluorine acid solution reaches 8% to
10%, stand static for clarification and remove the impurities with the clarified
fluorine silicate solution being added of sodium chloride (being excess of about
25%) for reaction of sodium fluorosilicate. Further go through centrifugation
isolation, washing, air drying at a temperature below 300 ℃ and then pulverize to
obtain the finished product of sodium fluorosilicate.
H2SiF6 + 2NaCl → Na2SiF6 + 2HCl
Treasury: ventilation, low-temperature and drying; store it separately from food and
Sodium fluorosilicate can be used as:
1. The insecticide in agriculture.
2. Milky agent of enamel.
3 the corrosion production agent of opal glass
4. Wood preservatives and the raw material for the production of other kinds of
fluoride as well as being applied to the smelting of beryllium and aluminum and
pharmaceuticals, leather and rubber industry.
5. the refractory material, it can be used as the coagulant as the water glass binding
agent. Since sodium fluorosilicate has a low water solubility, it reaction with the
water glass is slow and gradual. This can not only boost the construction but also
has a high density and strength of the cured products.
6. It is most commonly used in the inorganic material binding with the water glass.
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