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Author: Subject: So it's hydrated silica gel and... what?
Eddygp
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[*] posted on 4-4-2012 at 03:18
So it's hydrated silica gel and... what?


I made this reaction with waterglass and acetic acid to form a gelatinous precipitate. However, I used an old sample of waterglass I had mixed with magnesium sulfate, but hadn't noted it on the label.
Will that affect the dehydration process to make the dry silica gel? Furthermore, how do I get out the sodium acetate?

Thanks!
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ManBearSwine
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[*] posted on 5-4-2012 at 06:49


Did you mix the sodium silicate and magnesium sulfate to precipitate magnesium silicate? If you did, and you filtered it out of the solution, then you should be fine. To remove the sodium acetate, you can simply wash the precipitate well with water. Impurities in the silicic acid will not generally affect its dehydration, but will decrease the purity of the final product.
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Nicodem
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[*] posted on 5-4-2012 at 07:04


I doubt there would be much magnesium whatever in such a basic solution. The solubility of Mg(OH)2 is very poor already in water, let alone in waterglass. Practically all of the MgSO4 would be converted to insoluble material and soluble sulfates.

I would expect that moist silicagel is not easy to wash (it is a gel) so you would need some pressure filtering to remove the sodium acetate solution. But guessing is pointless. I'm sure there are detailed procedures on how this can be done. Have you searched the literature at all?
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