I was trying to make sodium silicate according to the following reaction:
$\ce{SiO2 + 2NaOH -> Na2SiO3 + H2O}$
I used colloidal silica available as an intestinal adsorbent since reaction with crystalline SiO2 would require a lot of heat. I mixed a solution containing 20 g of NaOH with a suspension of 15 g of SiO2, however, nothing seemed to happen. I checked the pH and it was still highly basic. Is there any way I could get the chemicals to react? Should I try bringing them to a boil?

  • $\begingroup$ I would use silica powder from a reputable source, if the silica from the intestinal adsorbent has had surface treatment (which it might) that would clobber things up. Always use laboratory chemicals. $\endgroup$ Sep 1 at 7:41
  • $\begingroup$ $\ce{SiO2}$ reacts with $\ce{NaOH}$ only at temperatures higher than 350°C. And then the obtained silicate is hard to dissolve in water. It lasts hours of dealing it with hot water under pressure. $\endgroup$
    – Maurice
    Sep 1 at 7:54
  • $\begingroup$ @StianYttervik Should I look at silica cat litter? $\endgroup$ Sep 1 at 9:31
  • $\begingroup$ @kwangmyonguser No, you should not. $\endgroup$ Sep 1 at 10:43
  • $\begingroup$ UPD: The next day the solution turned perfectly clear, and I could see no traces of silicon dioxide in it. I decided to boil the water off, and at the point when there was little to no water, the solution looked rather gooey and glue-like. In an aqueous solution it releases white precipitate upon acidifying, thus I think that I succeeded and that the product definitely contains some sodium silicate. $\endgroup$ Sep 5 at 9:48

Definitely, you should boil the solution of silica and sodium hydroxide few hours. I did this experiment many years ago. And, as I remember this, it is extremely dangerous and very boring experiment. So boring that I still remember it approximately after 40 years.


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