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Solvent washing

  1. Jul 8, 2007 #1
    I was reading about washing non polar soluble chemicals with a polar solvent like water. How exactly is that done? If you add water to the non polar solvent containing the chemical to wash away all the water soluble chemicals how would you separate the water from the non polar? Would you have to evaporate the non polar solvent before adding the water?

    For example say I have a mixture of chemicals. Only one chemical is soluble in a non-polar solvent like acetone and thats the one I want to isolate. Would I have to evaporate the acetone and wait until the solid chemicals are completely dry before washing with water?
  2. jcsd
  3. Jul 8, 2007 #2
    Separatory funnel. If you have your stuff dissolved in a non polar organic solvent and wash with water you will have two layers (like salad dressing). Just separate off the water layer and then obtain the organic layer. Once you have the organic layer just evaporate off the organic solvent and your desired compound should be left behind.
  4. Jul 8, 2007 #3
    What if your organic layer is something like acetone though? Acetone is miscible with water so there won't be any layers. I know diethyl ether is insoluble in water but I think ether is illegal to carry without a license so I'll have to use other solvents for my experiments.
  5. Jul 9, 2007 #4
    technically, if you know your compound isn't soluble in water and is stable I guess you could really just throw it in water and filter it out. The impurities that are water soluble should then dissolve in the water. Just make sure you wash what you filter off thoroughly with water. I have done stuff like this plenty of times before and it has worked beautifully at getting some impurities out.

    If you don't want to do that you will just have to try to find a different solvent that your compound will dissolve in that isn't miscible in water. Other good ones to try are ethyl acetate and DCM. What kind of access to chemicals do you actually have? Are you doing this at home or in an actual lab.
  6. Jul 9, 2007 #5
    I'm planning on studying chemistry in university in September so I'll have access to a proper lab then but in the meantime to prepare myself I'm practicing at home. I have access to all chemicals as long as they aren't watched or illegal or anything like that.
  7. Jul 9, 2007 #6
    how about kerosene, perfectly legal, cheap, readily avaliable
  8. Jul 10, 2007 #7
    Could also try gasoline. I'm not 100% of everything that is in gasoline, but I believe most or it should evaporate off easily. Just be careful (obviously) with the whole flammability issue as well as trying not to breathe in the vapors.
  9. Jul 10, 2007 #8
    Try solvents like toluene or VM&P naptha. They are excellent non-polar solvents and separate out of water completely. And are available at your local hardware store. Only thing is it doesn't evaporate quickly, so if your in a hurry you're SOL.
    Only thing I don't like about (diethyl)ether is its soulubility in water. (nearly 10%) And it is extremely dangerous in terms of flammability.

    What kind of compounds were you thinking of experimenting with or extracting ??

  10. Jul 11, 2007 #9
    Well I started reading Organic Chemistry by Clayden a while ago and it has to be the most informative and interesting chemistry books I've ever came across. I thought I might give extracting methol from spearmint oil a shot and if I can do that I'll try extracting cis-jasmone from jasmine plants.

    I thought it would be fairly cool having crystallized menthol or jasmone. Menthol is highly soluble in hexane and diethyl ether so I figure it will be soluble in other non-polar solvents like them.

    It's only slightly soluble in water so I could give it a cold water wash I have it dissolved.

    I noticed on the property list on wikipedia it says it has a flash point of 93 degrees. What exactly is a flash point? I thought it was auto-ignition but how the hell could the auto-ignition temperature be lower than the boiling point?
  11. Jul 11, 2007 #10
    The flash point is the lowest temperature where a flammable liquid will form an ignitable mixture in air.

    Usually flash point is lower than boiling if the liquid is very flammable, like diethyl ether.

    Anyway I tried once to extract eucalyptol from a bunch of leaves that I had and ended up with a bunch of junk.

    I found that the plant resins which were extracted along with the oils were not soluble in water.

    I needed more sophisticated equipment than I had.

    How about steam distillation? I have a Graham condenser, but haven't tried it yet.

    Anyway Mr. B good luck in your research.

  12. Jul 11, 2007 #11


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    Out of curiosity, what is your source for all these chemicals you have access to?

    And, of course, it would not hurt any to do these experiments in a well ventilated area (outside), especially for the more volatile ones.
  13. Jul 14, 2007 #12
  14. Jul 14, 2007 #13
    Ah so the flash point is the temperature where the substance starts to evaporate. That makes sense. I noticed acetone is highly volatile and evaporates at room temperature. Is that due to the low density of acetone or are there other factors involved?

    A steam distillation is way too complicated for me at the moment. I haven't got a distillation setup but even if I did I only understand simple and vacuum distillations and I have a basic understanding of fractional distillation.

    From what I've read though most of these essential oils are extracted with steam distillations so maybe I'd be better off starting with the essential oil rather than the actual plant material.

    jeff I'm sure I can go to the local chemical supply house for solvents but seeing as I can get some relatively pure solvents in the hardware store I don't see why not. I may just wait until I'm in college before experimenting any further since I will have access to a proper lab to work in and all sorts of different solvents. I can get a head start by practicing at home but then again chemistry is dangerous so it might not be the best idea.
    Last edited: Jul 14, 2007
  15. Jul 20, 2007 #14


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    If you do not even know the definition of flash point, you have no business attempting any chemistry experiment at home. This is extremely unsafe in an uncontrolled environment. Wait until you are in a classroom with proper safety equipment and procedures and supervision in place.

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