Silicic Acid in phosphoric acid solution

  • Thread starter JohnP
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  • #1
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Consider the following reaction:
3Si3N4 + 27H2O + 4H3PO4 --> 4(NH4)3PO4 + 9H2SiO3 --> ^4NH3(g) + 4H3PO4 + 9H2SiO3 --> 4H3PO4 + ??

The phosphoric acid solution is 85%wt.

In your fella's opinion, what happens to the Meta Silicic Acid (H2SiO3)? Is the solution to acidic to form a polysilicic acid?
Will this occur: H2SiO3 --> H2O + SiO2 and form a gelatinous poly silica? Something else?
I do know that at relatively low concentrations of this silicate based product (~100PPM @ 155C) the product will come out of solution.
Appreciate your thoughts, thanks guys.
 
Last edited:

Answers and Replies

  • #2
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I would expect a gelatinous amorphous hydrated silica. It would be a polymer composed of Si(OH) and SiO units, not the stoichiometric dissociation that your equation suggests
 

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