according to solubility charts Ca(OH)2 should dissolve at 20-25 oC at about 1.6g per litre. I have tried 0.8, 0.4 and 0.2g in 500ml and even the 0.2 does not completely dissolve, even left overnight. (in fact I would say most of it is undissolved on the bottom of the flask). rm temp is around 19-20oC, using lab grade ca(OH)2 and distilled water Any thoughts/suggestions?

  • 5
    $\begingroup$ Could part of it be already CaCO3 ? How does the not dissolved part behave in an acid? Another alternative is Ca(OH)2 can be covered by CaCO3 that kinetically slows down the dissolution. $\endgroup$
    – Poutnik
    Nov 28, 2023 at 18:34
  • $\begingroup$ Well, you should heat it and mix instead of wasting time - some things won't just do by itself. $\endgroup$
    – Mithoron
    Nov 28, 2023 at 19:15
  • $\begingroup$ Check for calcium carbonate with a little vinegar reation. The water may also contain dissolved calcium salts or CO2 whhich converts the hydroxide to the carbonate. $\endgroup$ Nov 30, 2023 at 12:17


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