N2 and CO have similar molecular weights, the He2 is lighter so would elute out the top. I am assuming the design is to use the He2 as a mobile phase, and N2 as the non mobile blanket
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N2 also denser than CO2 or CO
Twenty plus years experience as an organic chemist. I worked in the Environmental Organic Analytical World until 2014. I have extensive GC experience as well as some of the better instruments, C13 and H1 NMR, FTIR, UV-VIS and a ton of extraction experience. Not sure why Helium other than it may be more inert than Nitrogen. Might be an issue of purity but we were able to obtain 5 9’s which is 99.999% pure.
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then why both? Cause N2 is cheaper? But is lacking what?
First place I go is high pressure. Which I just don’t buy. Their cartoon vessel is too big in relationship to the tanks to take much more than 200psi if my cartoon physics is any good.
I can fathom an inert blanket. I understand getting better terp retention at higher pressures. I could even get behind removing reaction products to improve kinetics if it seemed like it would help (not sure it does).
I just don’t understand a nitrogen blanket failing to mix with the He and entrained CO2 bubbling through it.
I might could be convinced though.
Interesting, so maybe they are actually sparging with hot He2 and using the nitrogen as a blanket to separate out the CO2 for reclamation from the top with the He2 while keeping the terps down.
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This idea is reasonable, but there are a few very important caveats and notes that you must know before doing it:
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Pressure does not significantly affect the decarboxylation reaction kinetics, so it should proceed at normal temperatures and times, even under pressure. With enough pressure, you may find you can get away with slightly lower temperatures, but there are severe limitations on that, as described below. Of course any pressure applied should be devoid of reactive compounds like oxygen, lest they react with your material, especially under pressure! Nitrogen (N2) is relatively inert and inexpensive, as it is very abundant in our atmosphere. Besides inert gases like argon, N2, (please don’t waste helium on this), the only other gases in the headspace above the reactants should be the vapors of the terpenes and other volatile compounds naturally present in the resin.
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Pressure DOES affect other reactions! Terpene decomposition and cannabinoid isomerization are the two most important for you to know about for this application. Decomposition and isomerization (and really all reactions) have a certain activation energy that must be reached above the steady state energy of the reactant materials, before they can react and come to rest at a state of energy lower than where they started.
For example, because Δ8-THC exists with lower potential energy than Δ9, the Δ8 is the naturally preferred conformation between the two. That said, Δ10, Δ10a, CBN, and many of the isomers & derivatives in between are lower energy than Δ9 or Δ8.
So, activation energy is an energy “hill” that reactants must climb before a reaction can proceed spontaneously, sliding down the hill, as it were. This energy can be provided in the form of heat (very commonly), pressure, light energy of effective interacting wavelengths and sufficient power (amplitude), stirring (mechanical energy), and other forms, depending on the type of reaction. -
A catalyst is a chemical that can reduce the activation energy for the desired end resulting rxn. To accomplish this, the catalyst may temporarily and reversibly interact or react with a reactant or even the solvent, thereby changing the starting conditions and thus activation energy of the reaction, but without permanently changing the catalyst, itself. Unless something “poisons” your catalyst, it will not be used up in the reaction, so very small quantities are needed. However, the rate of catalysis is usually proportional to the quantity of catalyst present… so more catalyst = more reacting happening at the same time.
One example is a Brönstead acid (H+ or proton donor) is a catalyst for isomerization of Δ9-THC to Δ8-THC. This is so common that many folks believe acid is required for isomerization to occur, but it most certainly is not!
Lest we forget, many reactions that are commonly done by catalysis can still be done without a catalyst, just by applying sufficient energy. Pressure can give the resin compounds that extra boost they need to isomerize or decompose. So be wary! -
Catalysts can be used to your advantage for the decarboxylation reactions of cannabinoid acids, without affecting (or even hopefully increasing) the activation energy of undesired rxns. As long as your crude or solution thereof is totally devoid of water (anhydrous), I usually recommend dry magnesium oxide (MgO) as a decarboxylation catalyst, though other alkaline earth metal oxides and some transition metal oxides will also work, to varying degrees. Since decarboxylation is a pseudo-first-order rxn, the catalyst lowers the required temperature to achieve a given rate of decarboxylation. For example, based on my observation, just a teaspoon or less of MgO per liter of crude resin appears to let the THCa and other cannabinoid acids decarboxylate at a rate typically seen at about 280-300°F, at only 180°F.
MgO has the ancillary benefit of neutralizing acids present, even under the requisite anhydrous conditions, thereby effectively eliminating some or all of the plant acids present that could otherwise catalyze isomerization. However, that benefit uses the MgO as a reactant, not a catalyst, so if there is too much heat-ionizable acid present in your crude, it will “poison” (use up) your MgO decarboxylation catalyst.
I think you will find decarboxylation catalysis “essential” (heh) to retaining your terpenes, with or without inert gas pressure.
In any case using MgO, you should be forewarned that adding too much MgO to your crude will cause it to coalesce, turning the MgO into a blob of concrete at the bottom of your decarboxylation flask or beaker, even with stirring. So err on the side of caution and only add that maximum of 1 teaspoon per liter of crude!
@McWest I am fairly certain that for a given temperature, CO2 is more dense than N2… though I may just assume that based on the fact that CO2 is heavier than air.
Ultimately, I think catalysis to lower your decarboxylation temperatures will be the most crucial implement toward terpene retention in the resin. Helium is very inert, but it is also a valuable resource that is ever-depleting from our planet until we perfect controlled nuclear fusion of hydrogen for energy production. N2 will work just as well for this purpose.
I think a sealed atmospheric pressure blanket of N2 devoid of oxygen should suffice, since I have heard that even 10 psi can jumpstart isomerization. Any additional pressure should be provided by the partial vapor pressures of the volatile compounds in the resin at decarboxylation temperature. If you do decide to use N2 pressure above atmospheric, please let me know if it caused any isomerization… this would be indicated using HPLC standardized with Δ8-THC as well as the usual Δ9-THC, but even a “before and after” test of just the Δ9 would tell you if the amount was diminished or not. Good luck! 
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agreed on the “wasting He”, at least until we can reliably make more, and using what we have to get high is stupid.
However, your reminders on reaction kinetics made me wonder if He was being used to lower the kinetic energy transferred in some portion of those collisions, so as to lower the side reactions. Not a valid reason to off-gas He imo, but made me wonder.
Thank you for that. Lots of very useful tips.
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http://www.harvestdirectenterprises.com These guys say they are the first and only that age able to retain all terpenes during decarb.
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Hmm… sounds like a fishy marketing scheme at first glance, as it really seems that terpene modulation of cannabinoid effects is only really notable (at least to me) when administered by inhalation (vaping or smoking), and not when ingested through the GI tract.
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You’re quite welcome @cyclopath ! That’s an interesting thought… less mass = less momentum = less force. I guess that might be a thing in the gas phase, where terpene vapors might be hanging out… but those vaporized terps would only go back down into the liquid if significantly chilled to condense them… and since the jacketed walls would do the chilling, the profile or aspect ratio of the vessel would have to be pretty wide and flat to reduce condensation on the walls, so the terps would actually reetner the liquid body.
yep. using Helium.
which why we were discussing how that might work. the pros of nuclear fusion, and the cons throwing away a non-renewable like Helium for the sake of getting high 
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Oh! @cyclopath I don’t think you were around when I said it today, but why not replace He with Ar (argon)? It makes up 0.7% of our atmosphere and it probably the cheapest inert (noble, in fact) gas to buy!
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Nope! Nitrogen is still the cheapest 
it may not have nobility, but is still the king in my book for price!
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Yes, N2 is the cheapest, being 78+% of our atmosphere. I am just saying if a Noble gas is needed, then Argon is the least expensive of them.
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Very true.
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I assume you would need to remove the MgO before smoking if desired?
How could one do that w/o a run of the spd??
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@lefties.cannabis Yes and no. Yes, MgO will leave a weird, water soluble residue in your dab rig… although most people decarbing like this are doing it for edibles (MgO is a nutrient supplement) or crude for distillate. Are you asking how to pre-decarb your dabs?
That was the “yes” answer. The no answer is simply no, it is not necessary to remove it. MgO is used to make high temperature crucibles for melting transition metals and such. It will not vaporize.
Mainly looking at this process for RSO carts. Would be nice to actually keep a strain profile instead of re-introducing terps
Hmm… Well, a water wash of RSO:alkane solution should do it… and you can add MgO to the extracted alkane solution to lower the decarboxylation temperature, but I don’t know how long it would take to decarboxylate in boiling alkane. Of course, you still have to recover the solvent, too. To preserve the full profile takes pressure and/or skill.
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Will the Mg0 effect the taste of the oil ? Could it be used on a honey oil that has to be acitivated for vape carts -
If it’s not activated it bubbles
I am using a short path right now to activate it under pressure but it alway seems to bubble
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