The method of determination of silica content by potassium fluosilicate titration

Silica titration analysis method is an indirect measurement method, and potassium fluosilicate capacity is the most widely used, and it is accurate to say that potassium fluosilicate precipitation separation - acid alkali - alkali titration.
The principle is a sample containing silicon, which is combined with caustic soda and sodium carbonate
The soluble silicates were generated and potassium potassium fluoride (K 2 sif 6) was quantitatively produced by the presence of potassium chloride and F -.
Potassium fluosilicate was dissolved in boiling water to dissolve hydrofluoric acid (HF)
The droplets.
The content of silicon dioxide is calculated indirectly.
Main reactions:
SiO 2+2NaOH = Na 2SiO 3 = +H 2O...
(1)
Na 2SiO 3 = +2HCl = H 2SiO 3 = + 2NaCl...
(2)
H 2SiO 3 = +3H 2F 2 = H2 sif 6 3H2O...
(3)
H 2SiF 62kcl = K 2SiF 6.
(4)
K 2SiF 6+3H 2O = 4HF+H 2SiO 3+ 2KF...
(5)
HF +NaOH = NaF+H 2O...
(6)
The above (1) is the decomposition of the silicon sample and the HF decomposition sample.
(2) the silicate in the sample after decomposition was converted into soluble H 2 sio 3 (3) (4) H 2 sio 3 in a large amount of potassium chloride in the presence of HCl
-f exists to generate K 2 sif 6 precipitation (5) K 2 sif 6 precipitation to generate HF (6) with sodium hydroxide standard solution
Titration HF, indirect determination of silicon content.
Although the surface appears to be a sample dissolving - generating K 2SiF 6 - to dissolve K 2 sif 6

Standard sodium hydroxide solution titration - calculate silicon content, not complicated, but must pay attention to some key links in the actual application, can get accurate measurement result.