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Silicic Acid in phosphoric acid solution

  1. May 15, 2015 #1
    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: May 15, 2015
  2. jcsd
  3. May 16, 2015 #2
    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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