Everything you’re saying here is accurate – when it comes to the case of a compound changing from liquid to solid (which is a phase transition). Like you observe, that is not a solubility issue. The reason why you can “freeze” liquid isolate without it crystallizing has to do with molecular mobility. This effect is often seen in polymers and is called a glass transition.
The issue is trying to apply that to the case of precipitating out of hexane. That is both a solubility and purity issue.
Let me a explain a little bit about glass transition and why cooling something excessively can actually stop it from crystallizing (in the case of a liquid – not a solution). It’s actually a very interesting topic.
There is a characteristic temperature, the freezing point, where crystallization takes place. However, that’s not the whole story. Crystallization doesn’t occur instantly. There is a characteristic time it takes to crystallize. This is the time it takes for molecules to maneuver themselves into the correct position to form a crystal.
For a small, symmetric, low viscosity molecule like water, this time is very short. But for a big awkward molecule like CBD (or even more dramatically, in polymers), it can take quite a long time for the molecules to line themselves up. So what happens if you just keep cooling it colder and colder, without giving it time to crystallize?
Well the colder you get it, the slower the molecules move. The time it’s going to take to crystallize gets longer and longer the more excessively you cool it below the freezing point. If you cool it far enough while it’s still a supercooled liquid, you encounter a 2nd-order phase transition called the glass transition. At this point, the translational speed of the molecules is basically nil. So, even though the molecules would “like” (thermodynamically) to crystallize, their motion is so restricted they can’t do so. It exists in a metastable state as an amorphous glass, not a proper solid state nor a liquid.
Hence, from this we can say crystallization of liquid CBD will occur fastest when it’s just below the freezing point. Getting it colder than that will only make it take longer. Get it cold enough fast enough and it will never crystallize, even though it’s below it’s freezing point. You’ll actually have to heat it up to freeze it (this is called annealing).
You can actually make glassy water! You just need to cool it extremely, extremely fast (you never see this in nature). And when you do, it never releases phase transition energy, but only undergoes a 2nd order transition, where the heat capacity changes but there is no free energy change.
To go further on this topic, have you ever seen such thing as in this video @Kingofthekush420 ?
https://youtu.be/_9N-Y2CyYhM
Crystalization it is generally exothermic, it produces energy, mainly as heat. Thus, in the right conditions, the process happens by itself because its always favorable to release energy. Still, you can produce a fluid which is at a metastable equilibrium under indefinite amount of time, and a small pinch of energy is necessary to initiate the crystalisation process. That pinch can be a small shock as in the video above, stirring, pourring, or a particle of dust, a defect on container’s surface, or a seeding crystal… you can produce this with water, by cooling ultrapure water in a perfectly clean container.
thank god we have @Kingofthekush420 here to explain the chemistry to the… chemists.
could you imagine telling someone whos an expert in a complex field theyre wrong when you havent studied it yourself? thats wild
Why don’t you try the experiment I stated above and see for yourself?
he didn’t decarb the biomass prior correct?
Challenging and questioning are parts of the learning process. It’s not (all) about being right or wrong, you won’t learn much if you never challenge or question. The smartest people always do this.
What is the moisture level of the biomass? I have experienced that higher moisture levels can prevent hexane from extracting as much as a biomass that is very dry. I’m sure its similar with heptane.
I don’t know what the moisture content of the biomass was but it felt pretty dry. I ended up extracting it with ethanol instead.
I was planning on trying more CBG with hexane instead of heptane but recently decided to give up hemp extraction so not sure how much better it would have worked unfortunately.
I can’t speak to the use of heptane, but CBG is almost completely insoluble in hexane. 1 g of CBD will go into 10 mL of hexane in almost no time but 1 g of CBG doesn’t dissolve in 10 mL of hexane with extended sonication and vortexing. I haven’t tried heating other than residual heat put off by sonication, but CBG definitely lacks solubility in alkanes.
In fact it depends on temperature, but yeah, its pretty low anyway…
Following the discussion above, I measured it at various temperature, starting from a CBG-heptane mix (18% CBG, melted) mixed at 60°C and then cooled down to various temperatures, in clean tubes…
The solubility of CBG in heptane is 17.9 mg/ml at room temperature, 6.6 mg/ml at 8°C, and 1.4 mg/ml at -30°C.
Dealing with crystalisation processes, the gain of cooling down to -30°C is thus 10g/L of heptane… it is not much.
Also messing up with concepts and theories, @Kingofthekush420 was in fact not that wrong neither. 
This is one of the posts I’m going to reference again and again and again - thank you @MagisterChemist
I’m curious why Hexane or Hepatane would have low yields. looking at CBG it has the same hydro carbon tale as CBD plus it has the carbon chain on the top left as well. I would have assumed that the efficiency would have been great. What am I missing?
Fair enough.
Its out
I have extracted it with butane.
It does not yield that well. It does taste pretty good though at least as an extract, it tastes good.
Figured I would come back here and give an update, I ran some CBG with 97% hexane and 3% methyl acetate with great yields. it was around 95% extracted.
Super interested because I’ve heard you mention it before but I’ve never heard anyone other than you talk about MeAOc with hexane. What’s the benefit? Seems like it would cause increased water solubility in the solvent but can’t figure out why you would use it otherwise. Does it behave similarly to EtOAc except more polar? Care to share?
When there is a higher moisture content (>10%) we have found it was needed as we were leaving a little more cbd behind in our spent biomass. I was also noticing when we moved into our new facility from our pilot lab and we were using 100% hexane (our last seasons biomass was very dry) so I didnt use the methyl acetate for extraction for the first few test runs and I found there wasn’t much CBG showing up in our crude. So we switched back to the 3-5% methyl acetate and were getting our CBG again 
I dont see many people on here using methyl acetate but we use it to help extract and also to do our final flush on our remediation columns.