Ethanol Azeotropes - Attn: EtOH cannabis extractors!


I see you must know well the chonk phenomenon, sadly. Strangely, I very rarely see people speaking of them in places like this, where it would be most beneficial to do so.

It isn’t exactly on topic for this thread, except in the hypothesis that they are a function of solvent type. So I will just say that, so far in the experiments with 190 proof potable and with 190 and even 200 proof heptane denatured (i.e. with and without water), the chonks seem to be herb batch dependent, rather than solvent dependent. Like you, I had guessed they were composed of some greasy lecithin-like material that has a higher affinity for water, and that may still be true. So far, I have determined that chonks mainly occur, at least with a CTS KDT-6 rolled film system, when using high-CBD / low-THC herb… no matter the solvent and pre-treatment of the crude (like AC filtering or not). The confounding variable not yet addressed has been the seed content of the flowers. The approximately 1:1 CBD:THC herb crude does not yield chonks. The 10:1 CBD:THC herb did yield chonks… but it also had seeds where the 1:1 did not. Chonk appearance is minimized by slowing down the wiper (roller) and feed rate on the CTS. So the chonks could be the result of splattering, due to the much lower viscosity of high-CBD crude at temperature, or they could just be the result of some material that is extracted from very seedy flowers… or a combination of both.



I like that people are using the phrase Chonk.

So can we all go back to using a real solvent like butane and propane and leave the ethanol to what it’s best used for… Cleaning out bullet wounds and stainless?

All joking aside, thank you so much for all the amazing information. You are a gentleman and a scholar.



@Photon_noir thanks for the information, we recently got heptane denatured ethanol (due to low cost) for winterizing bho crude, do the same problems arise even from using it to winterize bho vs. Extracting plant material?



@Photon_noir thank you for that; we always get it in our devolitizing pots prior to SPD and its a pain to SS brush clean all our pots at the end of the week. Interesting well I think it may have to do with seeds then, because we run mostly THC material as of now and get chonk all day long and there’s 110% seeds and micro seeds.



Good to note! Thank you! I’d like to hear everyone’s chonk parameters, so we can coalesce a working hypothesis!

You know it, @Thejamhole ! Chonk’s the word!

That is a good question, @Cryo13. My guess is no, but I’d like to hear your experience with BHO Winterizations using heptane-denatured ethanol. Characteristics of herb extracted, ratio and method of mixing denatured ethanol with resin, observations at temperatures and filter steps?

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10/1 mix ratio into mason jars then warmed to 85-90f to dissolve the oil, then let set capped at room temp and filtered through a buchner with coffee filter, next placed in a regular freezer which was measured at -4f for 24-48 hours filtered again using buchner and coffee filter, then usually one more round in the freezer for another 24 hours and a last filtration same as above, rotovap to recover at 80c
We just started using it, i cant say ive noticed anything different from it vs regular everclear, other than the smell…
I guess my concern is if we can continue to reuse it with no issues, the crude is for SPD runs.



I would assume that the main issue is with the initial extraction using the heptane and ethanol or temperatures that are not cold enough. But if the initial extraction was done with butane or propane you would not have pulled those sugars and chlorophylls out in the first place so one would assume winterization with the cheap denatured shit should be fine.

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That is the hope @Thejamhole… that the heptane (being an alkane, like butane, but more aggressively non-polar… e.g. heptane can dissolve paraffin wax!) does not keep veg oil and wax dissolved in the denatured ethanol. That would be an important time to pre-treat with a bit of water, or at least let it absorb some from the air!

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Ahh, so it has potential to not work as well for winterizing, and water may help it work better?
From my experience it does appear to drop out fats in the same manner as regular everclear, its taken the same amount of filtration and i see similar amounts after pulling from the freezer, i havent done a side by side to compare though.

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Correct, hypothetically… just as 200 proof ethanol is not as effective as 190 proof. 200 proof with heptane has inefficacy equal to or greater than that of pure 200 proof (fresh from new vessel, kept in closed vessels, and/or otherwise unable to absorb water from air). This inefficacy is mostly specific to what I call the “water wax”… that is the flocculant material that precipitates at room temperature when BHO is dissolved in 190 proof ethanol, which does not immediately precipitate when using 200 proof (at least not until it absorbs sufficient water from air).



And heptane-denatured ethanol, after absorbing water, begins to separate into 2 layers, as I described above. This may not happen if it only absorbs whatever small amount of water with which it naturally equilibrates by hygroscopy, but I cannot confirm that. All experiments with water thus far appear to result in a biphasic partition… although it is practically invisible until the whole biphasic solution is chilled, considerably, making one of the phases cloudy while the other remains transparent.



Thanks for the thorough answers!
I do remember a brief discussion about that in another thread.
Ill keep using it, and try chilling it after a few uses to see if i can see a seperation indication.

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Heptane is more toxic than hexane.

The headers for the chart are not displaying for me, but you can remove the azeotrope heptane-alcohol by distillation at 72 C (if I’m reading the chart right) and it will be slightly more than half heptane so you will loose 10% and have dryish ethanol.

Ethanol hexane will be mostly hexane and boil at 58 and you will loose at least 6% of the volume.

If someone who can see the header on the chart could double check me, I’m right in theory but I’m guessing a little what it says.

You can absolutely 100% remove the azeotrope by simple distillation it will be the head and boiler lower than either solvent



In what way? The reading I have done left the impression that hexane fumes were far more harmful than heptane fumes.

A google search yielded this from

It should be stated that both hexane and heptane are toxic . However, hexane is more volatile, can cause peripheral neuropathy and is more neurotoxic than heptane



Honestly, looking at the literature, your claim is justified. It may be old “wisdom” I am judging by. I was taught that odd numbered alkanes were more toxic than even numbered alkanes, but pentane is seemingly less toxic than hexane or heptane so I’m not sure now if that really works. I was taught that hexane was used as an extraction solvent more than heptane industrially not only bc of the lower bp but also bc odd numbered alkanes were very toxic by inhalation by the liver. Reading now for a minute makes me question that as well as oral ingestion should be worse for the liver and inhalation more neurotoxic.



Interesting to hear that, perhaps it’s a sort of “old wife’s tale” amongst chemists of the past.

If I remember correctly, heptane is considered a “green solvent” in the sense that it’s impact on the environment is less significant than many other solvents as well.

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Yeah “old wives tale” probably; I’m sorry to (almost) pass it on… I saw a paper from a European pentane lobby which (not surprisingly) shows pentane as being really safe to use.



@Photon_noir @Cryo13 definitely seen this cloudyness when cleaning glassware with heptane denatured ethanol. And as well with boiling points (temp vs vacuum depth) in our rotos.
We split 55gal drums between smaller runs and ive noticed the last 15gals if split into its own material; that said drum/keg will evap at way lower temps and not as deep of a vac. And the top layers of the drums need more heat and deeper vac depth



Well, I cannot go back and edit the original post now, but I meant to explain WHY ethanol becomes more selective as temperatures decrease! Although it is still a hypothesis because I cannot easily obtain direct evidence of the facts, according to my observations, I sincerely believe ethanol selectivity at low temperatures is more physical/mechanical than chemical:

In order to make sense of both of the following systems, one must understand a bit of cellular biology and think microscopically.

  1. At higher low temperatures, selectivity has to do with decreased solubility of undesirables in the plant; namely epicuticular wax (water-resistant protective layer on outer surfaces of leaves and plant parts, which inhibits passive evaporation of water in warm growing conditions) and the vegetable oil (e.g. food grade hemp oil and any other large-molecule fatty acid triglyceride compounds… similar to coconut LCT and MCT oils… which often coexist with free fatty acids, phosphatides, and other lipid components).
    Other undesirable compounds with decreased solubility in ethanol at lower temperatures include sugars and more complex carbohydrates (sugar polymers), free amino acids and proteins (amino acid polymers), and other intracellular materials, which brings us to the concepts of the secondary effects of decreasing temperature…

  2. At lower low temperatures, decreased uptake of undesirables by solvent has to do with the density & viscosity of the solvent, and the permeability & cellular mechanics of the plant material.
    This is similar to the conceptual difference between chopping/cutting/grinding the biomass, which breaks and opens many individual cells, and shredding/hand-breaking biomass, which mostly splits it up along the cell walls, leaving cells mostly closed and intact. In the case of cannabis, the latter (unopened cells) improves selectivity in the same way super low temperatures improve selectivity, if that makes sense.

*1. Ethanol at -40°C/F:
Temperatures at or below this point render the epicuticular wax on the plant material relatively insoluble, most especially in 190 proof potable ethanol (aka ethanol:water azeotrope)… and although the wax is less soluble at this temperature, it is still much more soluble in 200 proof pure or denatured ethanol. The same rule applies to vegetable oil and other non-polar intracellular compounds that are accessible to the ethanol due to open cells. This also applies to more polar compounds like sugars, but the prevailing belief is that said intracellular sugars are slightly more soluble in 190 proof than in 200 proof and denatured… the key words here are “intracellular” and “slightly”, though. Ultimately, proper shredding minimizes access to these compounds… as does lower temperature, described in *2.

*2. Ethanol at -70°C:
Temperatures at or below this point render most undesirables almost completely insoluble AND cause the ethanol to become so dense & viscous that it is less able to penetrate stomata, other pores, and even torn openings in the cells, which are surrounded by insoluble waxy cell walls and which are now minimized in size due to thermal shrinking! In other words (as usual, most especially 190 proof) ethanol is physically less able and less likely to penetrate into (and therefore less likely to wash back out of) cell interiors, where almost all of the undesirable compounds reside!

How resin extraction occurs:
Thinking this way, it is vital to also comprehend the nature of the glandular trichome membrane and the state of the material inside those trichome “heads” when starting the extraction process. Along with an understanding of the low heat capacity of very dry biomass, this should also help explain why it is better to leave dry plant matter at room temperature and hit it with cold solvent than it is to freeze said dry plant matter…
Only a thin part of the combined outermost cell membrane (cuticle) of the secretory disc cells expands like a balloon as it fills with cannabinoid acid rich terpene resin. These disc cells are specialized to create this elastic membrane, which becomes thinner and more (molecularly) porous as it expands, just like any elastic material. When this “stretched skin” (membrane) is exposed to alcohol or other solvents, the solvent can rapidly diffuse into the resin through the pores in the membrane, causing the gland to rapidly swell and rupture, releasing the already-partially-dissolved liquid resin into the wash of bulk solvent.
Naturally, small particles and even molecules of the exploded membrane can enter the solvent when this occurs, which is one reason there is always some phosphatide and other impurities in the resin.
Also, the disc cell plasma membranes (which keep their disc cell contents from spilling out into the resin) are more vulnerable to solvent attack than the wax-covered hard cell walls on the rest of the plant, which is one reason why relatively brief solvent/plant contact time is always preferred over extended solvent residence time in cannabis extractions.



So say I use methanol. And distill is down to oil then add ethanol and then purge again? How much ethanol do I add per oz of oil?

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