my pleasure
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thanks @YeahBet
there are of course web based calculators too.
Ideal Gas Law Calculator | Calistry
requires knowing how many moles you’re using, which requires the molecular weight of the substance in question.
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Extending for folks that came here for decarb.
1mol of THCA (~358g) will produce 1mol of CO2 upon decarb.
the math done by @YeahBet can be rearranged to show that 358g THCA in a 6liter container at 100c would produce 35bar x 1mol/6.8mol => 5.1bar => ~75psi
putting 358g THCA in a 1liter jar would give closer to 450PSI (if canning jars were up for that sort of nonsense).
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Howdy @cyclopath do you mind clarifying something for me?
If I was going to decarb a batch of 2,000 g of THCa (assuming 100% for math’s sake) in a 6L vessel at 100C
2000 g (THCa) = 5.59 mol THCa
P(6L) = 5.59 mol (8.31e-2Lbar/Kmol)(373K)
P=28.87 bar
would I then take 28.87 bar and then multiply this by 1mol/6.8 mols to determine expected pressure within my vessel? I do not quite follow why this was done on your behalf.
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No.
That was to take pressure calculated for 6.8mols of CO2 in a 6L container and trivially recalculate for 1mol(of thca)
Why?
Because I’m an idiot and thought it would help….
You should go look at another example actually tailored to the task at hand.
And don’t forget that 2kg of thca takes volume.
You’ve got 1.8-2less liters for the CO2 to be with that thc…
Iirc the math is here: A Theory on BHO/Rosin Decarboxylation with Natural Terpene Preservation
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yea 28.87 bar is like 420 psi lol
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They obviously had us in mind when making that unit of measurement!
Yep, but with only 4l of headspace…
300g = 6.817mol CO2
511.258677 PSI
So you could absolutely multiply it by 6/4 (volume) and 5.59/6.8 (mols) to come up with
35.2bar x 1.5 x 0.82 ==> 43bar.
(wrapping your head around why that works might help…but don’t sweat it. Just use the online calc)
Then double check that with one of the online calculator’s…
Thanks for the link @DrWHY420; here’s todays math…
If you’re actually decarbing 100% THCA, performing it under vac makes more sense.
If you’re decarbing 80-90% thca, and want to keep pressures down, to avoid venting of your prv, you need more headspace.
Ok let me try this again…
If I am going to decarb a batch of 2,000 g of THCa (assuming 100% for math’s sake) in a 6 L vessel at 100C
2000 g (THCa) x 12.3% = 246 g CO2
246 g (CO2) = 5.59 mol
Due to headspace although I am in a 6L vessel assume volume of 4L
P(4L) = 5.59 mol(8.31e-2Lbar/Kmol)373K
P= 43.31 bar or 628.15 psi
So if I am mathing correctly that is way to much material for a 6L vessel.
So in reality the equation I should be performing is finding for mol of CO2 not P
Target pressure 8 bar / 115 psi
If I change batch size to 500g opposed to 2,000 g
500g (THCa) x 12.3% = 61.5 g CO2
61.5 g (CO2) = 1.4 mol
P(5.5L)= 1.4mol(0.0831Lbar/Kmol)373K
P= 7.89 bar or 114 psi
This seems like a much safer volume of THCa to decarb in a closed vessel
[grammar]
Why would you want that though. Id assume the pressure of the byproduct /product will slow the reaction over time
reaching 115 psi would indicate full decarboxylation of THCa in this hypothetical scenario. In theory you could utilize the pressure gauge to determine % conversion of THCa to THC
decarb is pretty efficient, and even if one were to miss a few percents, if one is distilling afterward, even a 90-95% efficiency wouldn’t matter because the terp strip/distillation will certainly get the rest.
I decarboxylated under vacuum, as others have suggested, because pressure is not friendly, in my chemistry mind, you always want to remove reaction by-products as they are formed to influence the forward reaction (not sure if Le Chaltier’s applies here or not), and a stable surface interface of the crude oil is a pretty good indication that decarb has ended.
I wonder if a heat/mass test would be appropriate here. Something like:
Take vial, add 5 grams of material to vial and weigh on analytic scale. Do a mega decarb in a closed vessel that has enough headspace to not pop. Weigh container after cooling and venting (in that order to ensure terpene recondensing). Weight loss would indicate incomplete. No reason to bring anything to 115 psi to check completion
1mol thca gives 1mol co2
You want mols. You have temp. You have volume . That gives your pressure.
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In this particular scenario the product would not be distilled. The thought process here is to take something like sugar and load it into a closed vessel, pull vac, backfill with N2, decarb, chill to room temp and fill carts. 115 psi was just a random number I pulled out that felt “safe” without exceeding my prv so terps wouldn’t excrete
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Skip the back fill, or vac twice. Only gives you another 14psi or so, but it helps…
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