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Can I get rid of the alcohol in a tincture?
July 13, 2006 6:56 PM   Subscribe

Here's one for all the chemistry majors out there. I'm going to be making an herbal tincture using Everclear as the solvent. After the tincture has been made, is it possible to get rid of the alcohol by heating the solution gently in a double boiler without affecting the potency of the tincture?

I was hoping to store the tincture as is, then try to get rid of the alcohol on a dose by dose basis. I'm afaid that by evaporating the solvent, I'll be reducing the herbal potency of the elixir.
posted by TorontoSandy to Science & Nature (13 answers total) 1 user marked this as a favorite
 
If the herbs in question are thermally stable, I would expect this to be fine.

Everything has a vapor pressure which varies (exponentially) with temperature; alcohols such as ethanol tend to have high vapor pressures and therefore evaporate relatively quickly, especially at slightly elevated temperatures. For the most rapid results at a moderate temperature, increase the surface area of the tincture (wide-mouthed container).
posted by JMOZ at 7:04 PM on July 13, 2006


I'm thinking yes.
The heat would destroy many of the compounds you have extracted from the plant -- if the alcohol has not done so already. Also, you want to store it in the fridge.
posted by Methylviolet at 7:08 PM on July 13, 2006


There's also a good chance that the medicinal effects of the tincture are due solely to the alcohol content anyway.
posted by TheOnlyCoolTim at 7:12 PM on July 13, 2006


I doubt it, even if it means bucking the trend of the above answers. Water and many aromatics and aliphatics make azeotropes with ethanol. This means you can't boil off the ethanol without boiling off the other compounds in proportion.

Many of the pleasant-smelling or medicinally-active things you extract from plants with ethanol are not very thermo-stable, either. Boiling them might well alter or destroy them.
posted by ikkyu2 at 7:19 PM on July 13, 2006


Isn't methylene chloride sometimes used as a solvent because it evaporates rapidly at room temperature?
posted by StickyCarpet at 7:33 PM on July 13, 2006


Sticky -- Sandy's going to drink this!
posted by Methylviolet at 7:37 PM on July 13, 2006


The alcohol should be more volatile that the extracted compound. You can evaporate the alcohol with gentle heat, or if you are concerned with the thermal stability of your extracted compounds you can try to be patient and allow the alcohol to evaporate at room temperature leaving behind a more concentrated solution of the extracted compound. Like JMOZ says, use a container that maximizes the exposed surface area of the solution that you would like to evaporate.

Also, StickyCarpet: Yes, because CH2Cl2 evaporates easily and also it dissolves some compounds quite readily. But like MethylViolet says, methylene chloride isn't something that one should consume regularly.

Finally, to TorontoSandy: can you tell us what you are trying to extract? There may be better solvents than Everclear available to even those without a home chemistry lab.
posted by peeedro at 8:21 PM on July 13, 2006


If you are trying to do what I think you're trying to do (and even if it's some OTHER herbal material *cough*), check out Erowid. They have some pretty thorough documentation on using household solvents to extract various plant materials.
posted by muddgirl at 8:56 PM on July 13, 2006


If you're talking about green dragon like muddgirl is suggesting, erowid is the place to look. I was there recently looking for info on it. Of course, all the green dragon recipes I've seen don't mention getting rid of the alcohol.
posted by bob sarabia at 9:01 PM on July 13, 2006


I just put this to my chemist husband...

Answer: Maybe

If the "herbal potency" is more volatile than ethanol then you'll throw out the baby with the bathwater, otherwise you're probably fine.

If, as someone suggest, the poster is attempting to isolate some THC, gently evaporating the ethanol should work just fine. The boiling point of THC is quite high. The thing is that by removing the alcohol you'll end up with more and more water (proportionally) in the solution, and the solubility of
the THC will decrease. At some point, you'll have mostly water and the THC will start to crystalize out. In fact, one way to isolate the THC would be to add a bunch of ice-cold water to the tincture, causing precipitation, and then filter. The main consideration when evaporating things like this is to remove it from the heat when there is still some liquid and leave the rest to evaporate naturally. That way you avoid scorching the product.

Of course, if the guy is trying to isolate lavender oil or something then this is all out the window.
posted by web-goddess at 10:41 PM on July 13, 2006


Use ether, it evaporates very quickly at room temp, but, notoriously volatile, so be careful.
posted by hortense at 12:16 AM on July 14, 2006


I'm not so sure about the ether idea; it is flammable to the point of explosiveness; I learned this the hard way in organic chemistry lab in college. If you do try ether as a solvent, do it away from any potential sources of ignition, keep a fire extinguisher handy, and definitely do not try to heat it directly, even if you are gentle. (The last bit is what blew up my beaker in chemistry lab.)
posted by TedW at 5:16 AM on July 14, 2006


Another way to extract essential oils from plant material that doesn't involve the use of potentialy flammable and/or toxic solvents is steam distillation.
posted by TedW at 5:22 AM on July 14, 2006


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