Thanks il try that. I cant get dry ice for my cold trap all the time. Do you guys recommend any substitute? I just have about 3 gallons of etoh crude i need to do
Aspirator…
Condenser on rotovap is too restrictive to get decent flow through that AND the aspirator.
Was hoping for an AC hack that sucked…
1 Like
Anyone else using a bump trap?
Not sure if it’s helping…makes spraying into an almost empty evaporator pretty much impossible…
2 Likes
i ran my roto vap 4 times before this a no problems. but i was using a thinner hose that used to collapse basically as i turned my vac on and it didnt pull ethanol and it didnt bump. but i switched to a non collapsible hose and then the problems happened.
Co2 tank with syphon tube. Put a sock over the end of the bottle valve opening and fill with dry ice.
1 Like
Remember the four variables you control are pressure/temperature and flow/level.
Pressure increases so does temperature and vice versus. The same thing applies to flow/level.
The best thing for this process is manipulating Pressure. As stated above a needle valve is best Bc this type of valve is made for precision vapor/air flow. If you are not able to acquire this than you will need to adjust your temperature.
When i run the roto i bring up the speed to max (sometimes not applicable due to the viscosity of the mixture) and bring my temperature up to designated temp. I wait a bit till my water temps are steady go know my sloution is the same temp as my water bath. I’ll start introducing vacuum. Once i see the bubbles starting to come out i will continue vacuum for another second and wait a bit. Than keep adding vacuum once the bubbles die down
My suggestion. vacuum down and max out your rotater. Slowly work your temperatures up. Try to avoid introducing outside air in the process but def relive the vacuum if you’re over bubbling. you can bring down the speed of the rotation to slow slow down the reaction.
Second problem. Your solution is instantly bubbling Bc your introducing a liquid that isn’t close to the same temperature of what’s in your flask. Preheat the liquid for batch.
I use to run a a Buchi-220 pro
3 Likes
Semi found the solution and fixed my problem
i swapped out my hose for a much lighter hose (10 ft in length)
As soon i turned my vacuum on the hose collapsed making the pull much more weaker and im pretty sure it made it much harder for the ethanol to reach my pump. I turned on my pump for about 15 seconds then turned it off when i saw my etoh bubbling … it maintained a vacuum and all of my ethanol was captured into my collection flask
i didnt use a cold trap, my pump ran for maybe 3-4 times at 15second intervals through the entire process. The oil doesn’t look contaminated in my pump and it didnt run long enough to even get warm.
2 Likes
Hey if it works… it works… even if it’s a bunch of things that don’t work… this is like adding a whole bunch of negative numbers together and then getting a positive result- abstract to most but to the scientist 
it’s all about the results- which will be very inconsistent if you keep this up.
still makes every part of my ass itch please just get an $8 vacuum relief valve off of amazon and some proper hosing.
6 Likes
Haha yeah man… it wasnt a permanent solution just so i could finish the crude i had .
1 Like
i will be! Thanks!
Use the continuous feed line like Plague says, If you add a bunch of new ethanol to a hot solute that’s in the boiling flask it will boil over every time. Let it drip in at the same rate that your are precipitating ethanol from the column. I like my solute feed to not shoot into the middle of the boiling flask, but hit the neck and run down the side of the glass into the sample thats in the boiling flask. There should be no sudden changes when running your roto, do everything in small increments, keep everything smooth, so you don’t boil over, or crack any glass, or get ethanol in your vac pump. Cold trap (or even two) is a must.
1 Like
And the pharmacy guys looking to take over this field are laughing like hell at you. if you are looking to have others consume and you don’t control all the controllable inputs you are going to be inconsistent in the outputs. I would recommmend a real vacuum hose, needle valve vacuum vent then as soon as you can a water aspiration vacuum. No oil, very rugged, forgiving, and consistent. I believe greenbuggy on here has some for sale around $300. Then you can start the long fun journey learning how to process your product. Rotavac alone may take a year or more to master. But man you are a chemist.
2 Likes
Agreed. I always say it takes a few days to learn HOW to do it, and a couple years to MASTER it. That’s hard for people to understand. They think if they see it once they know HOW, but they don’t realize the guy they watched has been doing it for years, thats WHY he makes it look easy.
1 Like
I like this one, it’s not strong enough to surprise bump on you and no oil changing. I don’t use a needle valve. But do get a cutoff valve or water from the pump goes up the vac tube into the condenser.
If the solution is bumping into your recovery flask right as youre feeding, I likely know why. I have 2 of these at work. When I feed more solution i have to pull the flask out of the heating bath, feed, then lower again. On mine the vapor stream going from the flask to the condenser is enough to blow my fed solution back into recovery. Maybe get a ptfe tube to extend your feed tube further into the evap flask.
BVV use to have them. Amazon has a bit cheaper one and I’ve used the roto and buchi with it. Just watch the. Vacuum back pressure when you shut them down
They have surgical tubing that doesn’t bend like that. Those type of lines tend deform with consistent vacuum
It took me 1 try after watching a video. And now 30 mins into a run, shes dialed in and no more babysitting.
1 Like