labwarenotes_v1_7 (1).pdf (428.6 KB)
3 Likes
5 Likes
I love the assumption that everyone has a decent vacuum controller on their benchtop rotovaps and therefore has fine control of vacuum. I reckon 95% or more of rotovap users are adjusting vacuum depth/bleed with either a stopcock valve or a needle valve, and not a digital buchi vac controller.
7 Likes
Dude this is cannabis…folks are out of control…
I’m more surprised by the number of folks who don’t have even a rudimentary “controlled leak”.
2 Likes
my benchtop rotovap doesnt even need one - it barely holds vacuum as is haha just TRY and bump on my 1980 academic buchi we found in a heap of garbage lab equipment.
3 Likes
I’ll be honest. I just wanted a reason to post
BĂĽchake: too much suck on your Rotovap!
5 Likes
Hell, I bought one and used it like once. I’ve found that the stopcock method worked just fine. We put the bath on 90C, adjust the stop cock, and let 'er suck!
I do think the 20/40/60 rule is neat, but I thought the whole point was to get it hot as fuck and meter the solvent recovery speed by the vacuum. Maybe I’m just stupid 
They sure are nice though. And you can get one to control like a dozen rotos if you’re smart.
4 Likes
All with the same vacuum depth I assume
Or am I missing something
I have two vacuubramd controllers on one roto to avoid drowning of the condensor s when ripping treu low bp
Solvents like pentane and dcm
But in my opinion the best way to Handel these solvents is by using a knf
Gas/vacuum pump on the system where the discharge of the pump is in a oversized jacketed and cooled receiver tank making vapor losses nihil and cutting the cost of solvent losses and
Condensing cooling
1 Like
I have a digivac and while it sets a nice point for vac you still need to throttle the stop cock as the tincture warms up and likes to bump. You can either let it sit with no vac or ramp up the vac with the temp but I feel it’s easier to just throttle the stopcock
Should note that this rule is only a particularly good guideline for benchtop scales. Doesn’t hold nearly as well for larger-scale systems.
To follow that - With larger scale systems, it’s been my experience that it’s generally preferred to lead with vacuum, not heat.
Take it down to vacuum leaving like 10-20% wiggle room on your vac, and add heat as needed. If you’re getting flashing (lookin’ at you Ecodyst), increase your agitation. Back off or tighten up your vacuum to match your condensing capacity.
The more heat you add to the system, the harder your condensers have to work.