Ethanol Under Vacuum........
- Thread starter Chase4969
- Start date
Monsoon
Well-Known Member
What are you trying to accomplish or is it just a random question? Anyway a quick check shows the boiling point of ethanol at sea level is 79C and drops to around 34C under full vacuum, results will vary at different altitudes so you may need to do a little research. Determining an evaporation point is apparently much harder since there are more variables involved, doesn't really matter though since even under pressure you want to boil it or it will take forever.
I finally got a working model of the ExtractCraft Source (they're new so they're forgiven) that uses vacuum distillation, not sure if it reaches a full -29 but at 105F and a rolling boil it still takes 4 hours to evaporate and condense ~300ml of ethanol. They have another mode that does it faster but it's noisy as fuck. So if you end up going the DIY route I would aim for 34C (94F) at sea level which should make it steamy and still preserve your terps. You can go higher but you risk turning shatter into oily instead if you go too high and you lose different terps and cannbinoids at different temps. I don't completely grasp it all myself so I just try to aim for as low as possible when extracting which is usually 95-105F throughout the process.
Man I hope this isn't just to solve "9 across" on a crossword puzzle, but whatever I like dropping knowledge
Also welcome to FC!
Chase4969
NYC Space Cadet
Thank you very much, i wanted to know. im in nyc, what's the sea level here ? lol. i have seen the source but i think i can make a better machine on my own. i already have access to vacuum pumps and will get the glass i need here and there, way under the 500 for the price of that machine. Plus i like using scientific equipment that are precisely calibrated. and i read the posts you put up on how the temps are off and that would drive me insane.
t-dub
Vapor Sloth
With all due respect . . . If you can't find out what sea level is in your area, maybe extracting and purging with flammable solvents might require a bit of study before you begin eh?
Safety first . . .
Chase4969
NYC Space Cadet
It was a joke, chill out
What are you trying to accomplish or is it just a random question? Anyway a quick check shows the boiling point of ethanol at sea level is 79C and drops to around 34C under full vacuum, results will vary at different altitudes so you may need to do a little research. Determining an evaporation point is apparently much harder since there are more variables involved, doesn't really matter though since even under pressure you want to boil it or it will take forever.
I finally got a working model of the ExtractCraft Source (they're new so they're forgiven) that uses vacuum distillation, not sure if it reaches a full -29 but at 105F and a rolling boil it still takes 4 hours to evaporate and condense ~300ml of ethanol. They have another mode that does it faster but it's noisy as fuck. So if you end up going the DIY route I would aim for 34C (94F) at sea level which should make it steamy and still preserve your terps. You can go higher but you risk turning shatter into oily instead if you go too high and you lose different terps and cannbinoids at different temps. I don't completely grasp it all myself so I just try to aim for as low as possible when extracting which is usually 95-105F throughout the process.
Man I hope this isn't just to solve "9 across" on a crossword puzzle, but whatever I like dropping knowledge
I'm 88 feet above sea level, does that affect the boiling point under vacuum much +/- ?
Mod note: posts merged
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herbivore21
Well-Known Member
Greetings @Chase4969 I can assist here.
You have a chamber with a gauge pressure reading of -29inhg from the look of your original post.
You need to understand the local barometric (atmospheric) pressure in order to calculate the absolute pressure you are working with - which is essential to determine the relative boiling point of your solvent under vacuum. I will return to check my work later (this is very quick, rough working as it is an inopportune time for me to assist just now), however, the average current barometric pressure in New York State is 30.16inhg so we'll work with this.
If your gauge reads -29inhg, then you have an absolute pressure of 1.16inhg (Absolute Pressure = Atmospheric Pressure + Gauge Pressure) in your chamber. Looking at my vapor pressure charts for ethanol, the boiling point of ethanol at the absolute pressure in your chamber will be 86f
I should have shared this particular bit of information a long time ago lol, I'm sure it'll help a lot of folks figure out how to properly use their vacuum chambers! @Chase4969 I hope this helps! If you have any more questions, drop me a PM.
As an aside, please be sure that your vacuum pump is rated for the effluent being purged out of the chamber (ethanol + perhaps some lower boiling cannabis hydrocarbons aka terpenes). This typically means you are looking for an oil-less (no lubricant required) pump with PTFE internals.
@t-dub we need to be fair here man, most folks around these parts who purge solvents haven't got a clue how to properly calculate the correct boiling point of their chosen solvent under vacuum (many posts I've seen on this topic seem to ignore this factor altogether). Most folks seem to just pull the vac down to whatever arbitrary gauge pressure their buddy told them worked and apply some heat.
The OP is actually being reasonably diligent here. They knew well enough to understand that there is a different boiling point to be calculated under vacuum and that a formula must be required to determine this! We should give some credit where it is due here IMO.
T-dub is right to highlight that one should do one's homework when purging solvents though - I am glad that the OP posted this question so that we could clarify this for anybody who didn't know. 
You have a chamber with a gauge pressure reading of -29inhg from the look of your original post.
You need to understand the local barometric (atmospheric) pressure in order to calculate the absolute pressure you are working with - which is essential to determine the relative boiling point of your solvent under vacuum. I will return to check my work later (this is very quick, rough working as it is an inopportune time for me to assist just now), however, the average current barometric pressure in New York State is 30.16inhg so we'll work with this.
If your gauge reads -29inhg, then you have an absolute pressure of 1.16inhg (Absolute Pressure = Atmospheric Pressure + Gauge Pressure) in your chamber. Looking at my vapor pressure charts for ethanol, the boiling point of ethanol at the absolute pressure in your chamber will be 86f
I should have shared this particular bit of information a long time ago lol, I'm sure it'll help a lot of folks figure out how to properly use their vacuum chambers! @Chase4969 I hope this helps! If you have any more questions, drop me a PM.
As an aside, please be sure that your vacuum pump is rated for the effluent being purged out of the chamber (ethanol + perhaps some lower boiling cannabis hydrocarbons aka terpenes). This typically means you are looking for an oil-less (no lubricant required) pump with PTFE internals.
@t-dub we need to be fair here man, most folks around these parts who purge solvents haven't got a clue how to properly calculate the correct boiling point of their chosen solvent under vacuum (many posts I've seen on this topic seem to ignore this factor altogether). Most folks seem to just pull the vac down to whatever arbitrary gauge pressure their buddy told them worked and apply some heat.
The OP is actually being reasonably diligent here. They knew well enough to understand that there is a different boiling point to be calculated under vacuum and that a formula must be required to determine this! We should give some credit where it is due here IMO.
T-dub is right to highlight that one should do one's homework when purging solvents though - I am glad that the OP posted this question so that we could clarify this for anybody who didn't know.
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Chase4969
NYC Space Cadet
Greetings @Chase4969 I can assist here.
You have a chamber with a gauge pressure reading of -29inhg from the look of your original post.
You need to understand the local barometric (atmospheric) pressure in order to calculate the absolute pressure you are working with - which is essential to determine the relative boiling point of your solvent under vacuum. I will return to check my work later (this is very quick, rough working as it is an inopportune time for me to assist just now), however, the average current barometric pressure in New York State is 30.16inhg so we'll work with this.
If your gauge reads -29inhg, then you have an absolute pressure of 1.16inhg (Absolute Pressure = Atmospheric Pressure + Gauge Pressure) in your chamber. Looking at my vapor pressure charts for ethanol, the boiling point of ethanol at the absolute pressure in your chamber will be 86f
I should have shared this particular bit of information a long time ago lol, I'm sure it'll help a lot of folks figure out how to properly use their vacuum chambers! @Chase4969 I hope this helps! If you have any more questions, drop me a PM.
As an aside, please be sure that your vacuum pump is rated for the effluent being purged out of the chamber (ethanol + perhaps some lower boiling cannabis hydrocarbons aka terpenes). This typically means you are looking for an oil-less (no lubricant required) pump with PTFE internals.
@t-dub we need to be fair here man, most folks around these parts who purge solvents haven't got a clue how to properly calculate the correct boiling point of their chosen solvent under vacuum (many posts I've seen on this topic seem to ignore this factor altogether). Most folks seem to just pull the vac down to whatever arbitrary gauge pressure their buddy told them worked and apply some heat.
The OP is actually being reasonably diligent here. They knew well enough to understand that there is a different boiling point to be calculated under vacuum and that a formula must be required to determine this! We should give some credit where it is due here IMO.
T-dub is right to highlight that one should do one's homework when purging solvents though - I am glad that the OP posted this question so that we could clarify this for anybody who didn't know.
You are the man sir, Thank you for taking the time and answering my question. i do not have a oil less vac, but i do plan on using a cold trap to collect the Ethanol. would this work ? i have used the same pump in the past for purge and it worked fine
herbivore21
Well-Known Member
Glad to have helped, my friend! Cold traps are useful for condensing and collecting the majority of the stuff we want to keep away from pumps not designed to deal with ethanol coming through the works.
It depends on the design of the cold trap you are using (your choice of coolant will also be a variable) as to the extent to which a cold trap will keep unwanted solvents out of your pump. Briefly regarding choice of coolants; if you are using liquid nitrogen, please make sure that you observe proper cold trap/vacuum safety to avoid hazards such as liquid oxygen (google it if necessary). Also be sure to use appropriate safety equipment for storage, transport and handling of the liquid nitrogen, that shit has some hazards of its own!
In the more common, less efficient run-of-the-mill cold traps, there is still a likelihood that some of the effluent can get through your cold trap and into the pump. The cold trap would of course be expected to reduce what gets through into the pump from what you'd see without the cold trap. Still, I would recommend that you get your hands on a suitable pump as described above as soon as possible and avoid using the setup you describe on an ongoing basis.
thisperson
Ruler of all things person
I've read that you can leave an ethanol extract in the sun and it will all evaporate. Is this true? I ask because I don't have a purging chamber or pump but want to try making QWET.
I'm in sunny So Cal, roughly 1600 ft above sea level. It gets hotter than the target of 86 degrees the dude from New York was told to reach, but as I understand he's dealing with a lower pressure thus lower boiling point. So does this mean it's not safe? I can resort to good ole bubble hash, but really wanted to try ethanol extracts.
I do have a hot plate and can make a marie bain outside if need be, but wanted to try it with just sunlight.
I'm in sunny So Cal, roughly 1600 ft above sea level. It gets hotter than the target of 86 degrees the dude from New York was told to reach, but as I understand he's dealing with a lower pressure thus lower boiling point. So does this mean it's not safe? I can resort to good ole bubble hash, but really wanted to try ethanol extracts.
I do have a hot plate and can make a marie bain outside if need be, but wanted to try it with just sunlight.
Baron23
Well-Known Member
Assuming a standard atmosphere....then no.
Chase4969
NYC Space Cadet
yes 86f but under vacuum 0f -29, but i have done what you are saying, i used a pyrex bowl and put a big coffee paper filter over it to prevent dust from getting in and held it with a rubber band , it took about a week for it to evap with the occasional agitation of the slur to make things move along
thisperson
Ruler of all things person
Thank you for your reply. That's a really long time. Kinda sours me to the idea. Hot plate and marie bain it is.