I just sent some emails out for a sample.
@Qtp The extraction efficiency of the EtOH:H2O azeotrope is just about the same as pure EtOH at most temperaturesā¦ that is, over 99% if you collect all of the ethanol from the marc (wetted biomass), and it can do it in just a few minutes, regardless of temp, as long as it is liquid, it seemsā¦ though I have only tested it down to -85Ā°C, as it gets very syrupy below about -60Ā°C. I will say that the azeotrope is technically more efficient for resin, since it does not grab much if any epicuticular wax or vegetable oil. It is only when you add water more than the azeotrope that efficiency lowers, and it goes down very rapidly. At just 5% excess water, nearly all of the cannabinoids precipitate as a microemulsion (louche) even with terpenes, terpenols, and other resin compounds present as cosolvents.
I would use silica gel or drying salts to dehydrate ethanol, since mol-sieve has a very low water capacity, and since mol-sieve can supposedly break the azeotrope, which I never desire to do. However, if you donāt care about that and still want at least 1:1 molar water capacity, you can use calcium oxide (quicklime or slaked lime) to completely dry ethanol. Just tell the vendor you need to dissolve a body. Theyāll understand. 
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Sweet! Thanks! Geez, how many subscriptions do you have? I am an ACS member and have a hard time finding some of these!
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Doesnāt always work, but Iāve peeled off many papers from behind payways using this site
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Agreed. SciHub rocks. Were you saying that breaking the azeotrope doesnāt always work, or scihub doesnāt?
Scihub does not always retrieve the paper you need. Sometimes itās hit or miss.
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Has anyone seen 710spirits? They have 200 proof ethanol with n-heptane as cosolvent, effectively denaturing it. We are thinking about testing it, but i donāt know if having heptane in the extraction would alter things more than having to increase the temp when roto vaping. Iām thinking it might get better clarity from using it due to there being very little water in there, pulling less unwanted compounds. I might be wrong. What do you guys think? I thought one would want to stay away from dentured products, but since heptane is used with brine washes Iām curious about their product. Donāt know the difference between n-heptane and heptane though.
Also the specs say there are trace amounts of impurities in it. Specs are at the bottom of their tell me more page.
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Whatever solvent you choose I would distill before useing.
Distill it through the roto before first use?
You can use a roto, I prefer a fractional distillation. Your can add mol seives to the flask to scavenge h20.
Thatās why this seems interesting, due to the n-heptane pretty much removing any water. But i really donāt know enough about heptane, havenāt used it. Thereās isnāt enough info on their site for me to adequately decide. Iām waiting to hear back from scientific solutions about this before making up my mind. I was hoping people here might have an idea about cosolvents in extraction and recovery.
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We sell the same formula. Heptane is an awesome non-polar extraction solvent by itself. We have had nothing but great reviews, from both the cannabis and hemp industries, regarding its use as a drop in replacement for tax paid ethanol.
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Doesnāt running heptane denatured alcohol through a decent reflux still (and thus removing the majority of the heptane) violate the spirit of the law?
You can actually request all but $1 of the excise tax on your ethanol back if youāve got the balls to tell the feds what youāre using it for. Not sure if our accountant was up for that or not.
https://www.ttb.gov/applications/manufacturer_nonbeverage_products_packet.shtml
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Yeah, you could separate the heptane through distillation. I distill solvents before use in order to insure putity. After the solvent comes off the rotos it goes back into a refinement still. Heptane has a specific gravity of .68, etoh is .791. Heptane is nonpolar, it should be floating on top of the etoh correct? Separation could be achieved with a sep funnel.
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if they are immiscible in each other, how can folks be selling heptane denatured ethanol?
Adding a refining step before reuse of the ethanol Iām pulling via rotovap sounds like something I ought should implement. Especially as I scale up.
Iām still doing the majority of our ethanol recovery in a home built still. I seem to get 190proof back every time, and have not seen accumulation of anything odd in my residual solvent or pesticide tests.
I may have a little ethyl acetate in there that Iāve picked up from the plant material, but the residual seems to be steady over time. I really should send it out to check the terpene profile 
Edit: Solubility: http://www.sciencelab.com/msds.php?msdsId=9924237
Soluble in diethyl ether, acetone. Insoluble in cold water. Soluble in alcohol. Solubility in Chloroform, Petroleum Ether, Ether,
Acetone: >10% Floats on water
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Nice, so question. Are they miscible or not? I was under the assumption they were and mixed 95.4% etho to 4.6% n-heptane, according to the specs i got. Was told to just increase temps in roto when getting the heptane out. Also seems Polycarbonate withstands pure heptane. Donāt know corrosiveness mixed with etho. Do you have any experience running the mix through a normal washer/dry spinner? And would a standard viton seal be fine with heptane? Iāve been told to be careful with silicone. Excuse all the questions, but the other seller had zero actual experience with the product, so getting any real info was somewhat hard.
Heptane and 200proof ethanol are miscible up to a high ratio. The special heptane denatured formula is roughly 95%etoh, 5% n-heptane as you mentioned. The ethanol portion will form an azeotrop with water separate from heptane so you can partition the heptane if you absolutely have to.
If you look up the compatibility chart for heptane you will see that nitrile, polyacrylate, viton, and polyurethane are acceptable materials. Silicone is a definite NO, as is EPDM.
Iām recovering my ethanol in fairly primitive stripping still, I then finish in a rotovap. The only time Iāve used 200 proof, I got back 190, which was absolutely expected.
Given hepaneās higher boiling point (higher than I can drive my still with a hot water heater), I would expect my (bulk) recovered solvent to have very little heptane in it. certainly less than the 5% starting concentration. although Iām guessing here.
I would also expect my rotovap recovered solvent to contain most of the heptane.
If I adopt @Soxhletās practice of distilling the solvent recovered from my rotovap through a more sophisticated still (8āx 2" copper reflux column), Iām going to end up with 190 and heptane.
If the SOP calls for heptane denatured ethanol, Iām going to have to add the heptane back. Or lie and say I thought it was in there. Or?!?
How are others dealing with this?
certainly $800 for 55gal beats the hell out of the $3300 weāre paying for āorganicā 190.
It doesnāt have the same āhippie appealā thoughā¦
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