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Old 10-02-2017, 10:50 PM #1
bunbun
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Rotovap questions

Hi all,
New to extracts and have questions about rotovapping. Using a 5L rotovap with 29mm Hg of vacuum, which I thought should be plenty capable to extract ethanol at lower temps, like 40C or less, but it doesn’t seem to pull off ethanol as expected, or takes hours for small batches. Experimenting with higher temps, like 55-65C, and mixture will boil, but still seems little ethanol condenses off, and don’t want to degrade product. It does thicken, but even when it appears finished and nothing else comes off, I swear it still has the smell of ethanol. Even after hours of leaving it. Can rotovaps make final product or does there need to be a final finishing step?
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Old 10-02-2017, 10:56 PM #2
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I believe most people just use the rotovap to recover the pricey ethanol then finish the purge in a vac oven...

fyi u will need to bump ur temps up a bit with ethanl vs butane when it comes to the finishing step...well at least imho.
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Old 10-03-2017, 12:56 AM #3
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Set the vac regulator to 60 Torr, temp on the bath to 113F, start rotation to 100rpm and let the bath warm the flask while the vac pulls down.

Onc vac is achieved open the injection port and inject approx. 500ml of solution into the load flask. Once it starts condensing open the injection valve just enough to match the condensation rate. let it run and it should recover at a decent rate.


When it comes to the speed, I tend to try and have it at a speed that's enough to keep the puddle "chasing" the bottom of the flask, so essentially is always running down but never makes it to the bottom.
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Old 10-03-2017, 11:40 AM #4
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Here is our test of the Heidolph, which shows parameters:

https://skunkpharmresearch.com/evalu...ecision-ml-g3/
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Old 10-03-2017, 11:58 AM #5
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How do you get the final product out of the flask? Is it runny enough to just pour. Do you heat? Do you scrape it out?

Just observing.
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Old 10-03-2017, 12:57 PM #6
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Quote:
Originally Posted by Phineas Freak View Post
How do you get the final product out of the flask? Is it runny enough to just pour. Do you heat? Do you scrape it out?

Just observing.
We either pour early and use the vacuum oven to finish it off, or chase it out of the boiling flask with a heat gun, leaving behind a thin film.

We use alcohol to remove that film and process that once we collect enough for a batch.
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Old 10-03-2017, 07:39 PM #7
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How are you guys dealing with pouring out of 20L and 50L flasks? Seems a little sketchy to pour from unless you have some kind of lab jack that grips the flask and has rotational degrees-of-freedom.

My plan for the 20L I'll be working on soon is to grab some PFA tubing, and literally suck the hot oil out of the flask and into the short path apparatus, using vacuum suction.

For our smaller 2L or 5L loads we are more able to just pour it out hot (100-120C) and dissolve that final film like GW mentioned above.
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Old 10-03-2017, 11:33 PM #8
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Originally Posted by Old Gold View Post
How are you guys dealing with pouring out of 20L and 50L flasks? Seems a little sketchy to pour from unless you have some kind of lab jack that grips the flask and has rotational degrees-of-freedom.

My plan for the 20L I'll be working on soon is to grab some PFA tubing, and literally suck the hot oil out of the flask and into the short path apparatus, using vacuum suction.

For our smaller 2L or 5L loads we are more able to just pour it out hot (100-120C) and dissolve that final film like GW mentioned above.
I built a flask handling cart for pouring out of our 50L evaporating flask. It works quite well and we typically pour off 15kg of crude from the flask into a bucket in one shot. There's a frame on wheels and a square flat surface on top with a hole cut out into which the flask sits. There is a channel cut out to the from the circle to the front so the neck of the flask can fit through when rotating the flask for pouring.
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Old 10-04-2017, 12:49 AM #9
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Quote:
Originally Posted by Gray Wolf View Post
Here is our test of the Heidolph, which shows parameters:

https://skunkpharmresearch.com/evalu...ecision-ml-g3/
Thank you for the link. For some reason the figures and images don't appear, but the write-up was nice.
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Old 10-04-2017, 12:51 AM #10
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Originally Posted by BigJohnny View Post
Set the vac regulator to 60 Torr, temp on the bath to 113F, start rotation to 100rpm and let the bath warm the flask while the vac pulls down.

Onc vac is achieved open the injection port and inject approx. 500ml of solution into the load flask. Once it starts condensing open the injection valve just enough to match the condensation rate. let it run and it should recover at a decent rate.
Will try, thank you. From other comments seems like there will still be residuals that need vac oven or other way to fully purge.
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