We talk all the time about running solvents cold but never talk about why that helps

Short answer: it changes the polarity

it seems so obvious and yet its never put in those terms.

Dependence of Polarity on Temperature.pdf (443.2 KB)


What evidence is available to demonstrate that changing the polarity in one direction is more effective than the other?

For example, solubility is dependent upon polarity and the subsequent intermolecular interaction. However, solubility of most solvent-solute interactions increases with increasing temperature.

Therefore, it would seem that (with that logic, which is not complete, I’m sure) using warmer solvents would extract more components overall.

Is it the case that one selectively removes cannabinoids and other molecules of interest by running solvent cold? If so, what info is out there to support that?

alot to unpack there
both solvent and solute have a polarity and the first thing ull see when talking about extraction is like dissolves like
water gets less polar as it approaches its critical points so its not a linear thing were colder always equals same decrease in polarity and heat always does the opposite
there are other factors that make hot solvents extract more but that is exactly what happens
with cannabinoids there are both more and less polar compounds in the mixture but usually the less polar the more “selective” the extraction thats why hexane and naptha r often used

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I’m assuming for a chromatography column. Running colder nonpolar solvents make the nonpolar/slightly polar impurities harder to dissolve in the solvent while cannabinoids would easily dissolve in something nonpolar with a stronger preference in comparison to the impurities. The colder temperature widens the elution range of when certain impurities elute, ideally seperating after cannabinoids, whereas some of those impurities might elute the same time as cannabinoids if warmer.


What do you think of agitation of your material at -40°c, then throwing it in a salad spinner, filtering, dewaxing at -40c° for 12 hrs., filering, reducing in reactor aka " distilling off" to mother liquor charcoal filtering, distilling in reactor again to get crude,??? Hmmm am I doing it right???

what ru going for crude to feed a SPD?
if ur talking about an ethanol extraction then its sounds like a decent plan but dont use any plastic with any solvents used in extraction, if u extraction stays -40 the whole time u prob dont need the 12 hours dewax tho and i might hold off on the carbon wash unless the color isnt what u want cause it can absorb cannabinoids too and activated carbon needs heat to really absorb and work well.
so far what ive been saying is what i know for sure but im working on projects with co2 expanded ethanol that is also about decreasing the polarity of ethanol to make a more selective extraction solvent and in that context i would say u might wanna add some dry ice to ur ethanol a hour or two before u extract

I am sure you are getting good answers above, but here is an article I found a while ago that was really interesting. It has been stated in earlier posts that the sweet spot is -67C.


Youve mentioned this expanded ethanol extraction in multiple threads. Do you have an quantitative data that compares expanded vs. Normal chilled ethanol?

I use dry ice directly in my ethanol during extractions and it increases the volume and boils off CO2 for at least a day afterwards. Curious of this is helping/hurting.

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no i dont have any hard data right now but thats exactly what im trying to figure out. there studies that say when optimised CXE r better but if it helps much at atmospheric pressure is at some specific temp or co2 content is the key question

Propane vapor I believe hold more water warm and drop it as it super cools just like a cooling crystallization. I always thought of winterizing almost like a crystallization reaction of precipitated non polars(why its a polar solvent). It seems that starting at a warmer winterization and going colder each filtration left less THC than going straight for -80 lol.

Anyone have any experience taking out all the heat energy out of a propane pot opposite of crystallizing thca to filter out precipitants? Some is definately waxxy bits but why does propane with no heat energy cause fats that look non polar to precipitate out? I did it on a propane cls for crude so I may have maxed out its water capacity, and filled with some residual terps I guess to… There’s a couple polarity change situations that I havent fully grasped @Plant2pipe ?

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Intermolecular forces, so called cohesive energy, upon which the Hildebrand solvent parameter is based, is dependent upon the Temperature and pressure. For isobutane, and other refrigerants, the Hildebrand parameter increases with decreasing temperature, according to Equations of State.

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Just curious why no plastic any other reason then it turns brittle?

And why do they then sell etho in plastic containers? As above poster, is there something I’m missing?

It’s all about the type of plastic.
Ever see one of these?Chemical Resistance Chart | Plastics International
If not it should be the first page in your lab notebook

LDPE, HDPE, PE, & PP are all extremely brittle a -80.

put an empty 5gal HDPE Ethanol tote in your -80 freezer (or use dry-ice/alcohol) for a few hrs, take it out and drop it on the floor, or give it a decent kick. Now imagine it was full of -80 solvent.

There are plastics that are compatible with some of our extraction solvents, but most of them have issues with the temperatures at which we extract. PTFE (aka teflon) would be the exception. It is compatible with most of our solvents & can handle the majority of the temps.

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I use stainless steel pots which are made for home brewing.

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Empty metal drums for winterization:

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u ever notice how vodka in plastic bottles taste worse? That’s why lol

Yea fermenters are what I would go with if not dealing with pressure. I use to work at a winery and I would have to go inside those giant fucking stainless steel conical silo’s lol

Gotcha. I’m slowly and steadily learning the fundamentals of this. And everyday leads to different insights.