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What's the best way to separate a dissolved mixture

  1. Jun 15, 2011 #1
    Hi folks,

    I like to recreate medival medicines from old manuscripts but I have come to a slight problem when it comes to the prepairation...

    I'm trying to separate sodium bicarbonate which is dissolved in water. What I usually do is have a baking dish like the one below filled with the solution of water and sodium bicarbonate...I then put it in the oven on a low heat. After a while the water evaporates leaving mostly the sodium bicarbonate in the dish...


    The problems is that I can't get it very dry. I would like to evaporate all the water so I get a 100% powdered solution. If I carry on heating the solution, eventually the sodium bicarbonate crystalises which traps some water underneath and the crystals heat up and the whole thing starts spitting and then I get sodium bicarbonate all over my oven...

    I was wondering if anyone knew a better way to separate the two and get a nice dry powder without too much work or expensive equipment?


  2. jcsd
  3. Jun 15, 2011 #2


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    Gold Member

    Seems to me your solution should work OK if you just keep the temp below boiling and let it simmer long enough.

    Or you could just put a lid on the pan. Does it matter whether your precipitate is collected in the pan or on the underside of a lid?
  4. Jun 15, 2011 #3


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    @OP, do you have access to a dehydrator (usually used to dry fruits and vegetables)? Very little monitoring is necessary, and you can use the various trays to dry several solutions at once, if you like.
  5. Jun 15, 2011 #4


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    Staff: Mentor

    Many hours at temp below boiling, that's more or less the standard procedure.

    Some mixing/crushing during drying won't hurt - you will break the surface and allow water to escape.

    Lid will slow the process, you want the vapor to be able to leave the volume above the salt, as salt will be not drying under saturated atmosphere.
  6. Jun 15, 2011 #5


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    Gold Member

    Right. A screen then.
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