Ethanol extraction question for chemists

[Mitakuye Oyasin]

I have a question about using high proof ethanol as a solvent and would love some feedback from those well versed in chemistry. Let's say someone uses high proof ethanol as a solvent for cannabis. Then sets up a simple heat distiller to reclaim most of the ethanol on one side and concentrate the cannabis extract goodies on the other side. Would the reclaimed ethanol still be OK to be used as a cannabis solvent on future extractions? As long as the proof of the reclaim remains high and not diluted with water will it still have the same power and strength as it did the first time with being able to dissolve and hold active cannabinoids? Can one keep using the same reclaimed ethanol time after time to extract cannabis goodies or will there be a point where it looses its strength? Besides water lowering the proof, are there any other factors that would weaken the ability for the reclaimed ethanol to extract cannabis actives?

An example scenario: 1000 ml of 195 proof ethanol is used to extract 2 ounces of cannabis. An ethanol reclaim distiller is set up and it is able to reclaim 920ml of 190 proof ethanol. Would this reclaimed ethanol still have all the solvent power as a fresh batch of ethanol with the same 190 proof or would there be falloff after multiple uses?

Thanks for any suggestions or guidance.

 

[Hailstorm]

If you distill it out, and the boiling point is close to 78.2 °C, you can be fairly confident you have ~190 proof ethanol, which you can measure with a hydrometer. It will be as good as it gets, and you can always dry it (up to 200 proof) by letting it stand over 3Å molecular sieves.

 

[downwardsfromzero]

Basically yes to all of that, although I'd advise using some kind of steam bath for heating so you don't scorch your extract by mistake. The ethanol will largely retain its proof strength - except anything over 96% ABV/192° proof will absorb moisture from the air to bring it down to that concentration fairly promptly anyhow. This partly depends on how dry the material is from which you'll be extracting - extract too many batches of damp weed and you'll see a drop in the ABV of your ethanol.

It's quite easy to dry ethanol though, but if you want to separate ethanol from excess water by distillation you'll need to have a reasonably good fractionation column such as a Vigreux or be prepared to do it incredibly slowly.

Ethanol pulls a lot of chlorophyll though, which will have a tendency to produce fusty gunk - this is more of a problem in a hot extraction. Presumably you're largely interested in the resinous trichomes, which you could just rinse off with acetone and thereby pull a little less chlorophyll. Acetone has the advantage of evaporating very easily along with correspondingly more of a flammability hazard.

The main question is, perhaps, what distillation equipment, and what experience, do you actually have?

 

[Mitakuye Oyasin]

Thanks for the replies.

 

[Mitakuye Oyasin]

My buddy informs me that using a simple glass distillation rig with a double boiler they were able to get back approx 94% of the 196 proof ethanol they used to extract goodies from Cannabis. They think they got around 190-195 proof reclaimed ethanol back using a Hydrometer. They only tested 2 bottles out of about 20 bottles, but on average they don't think any are less than 190 proof. A total of 20 x 750 ml bottles of 196 proof ethanol was used and 19 and roughly 2/3 bottles was reclaimed. If this reclaimed ethanol has the same extracting power as it did before, that is a huge win-win for Cannabis extraction. Ethanol ain't cheap. The reclaim smells the same, but does have a significant planty taste to it as most likely lots of Chlorophyll carried over. No longer good for making cocktails, but good for future Cannabis extractions. Not sure how much Cannabis goodies they got yet, but looks promising. :thumb_up:

 

[downwardsfromzero]

Careful distillation with good equipment should produce satisfactory results, indeed. There will always be some scented volatiles among the extractables so at some point in the continuation of solvent recovery cycles it becomes necessary to run it through a carbon filter.

If this is something that you're (or your friend is) doing in bulk on an ongoing basis you might want to consider ozonation: Purification and Quality Enhancement of Fuel Ethanol to Produce Industrial Alcohols with Ozonation and Activated Carbon
although this is of course a technical solution which presents significant hazards and requires an appropriate level of competence, expertise and understanding.

Footnote: chlorophyll itself won't distil over because it's too large a molecule to be volatile, but various of its decomposition products are destillable.

 

[Mitakuye Oyasin]

Thanks for that info. I'll pass it along.