Rotovap questions

Have you ran a rotovap before?

I throttle my vac so my vapor level doesn’t go past the last 2-3 condenser rings.

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About to run it for the first time and I don’t have a throttle yet.

How long does it take with the 5L re-501 to complete? Also should you clean the condenser after every use if you have to make multiple runs in a day? Should I clean the rotating flask as well every time if using same batch as before?

That’s a good idea with hooking up a keg and pulling a vacuum so there is no risk of overfilling the receiving flask. Also, like the heat tape idea. Do you use a controller for the heat tape temp?

You shouldn’t have to clean the condenser unless your switching solvents, because it will be clean solvent dripping off of it. No need to fully clean out the boiling flask if your running the same batch.

If you don’t have a vacuum valve yet you can adjust the water bath temp instead. If your seeing dripping on the condenser at the very top you need to turn temp down, because some of your solvent is being pulled out into the vac pump. Adjusting the vacuum is much better, because you can dial it down quick if need be, unlike the water bath that will take time to cool down.

I use the vacuum inlet valve to feed a small continuous stream of liquid into the flask rather than filling the flask up and shutting the inlet valve. I use a silicone tube hooked up to the valve to pull solvent to be distilled out of a container. If you match the amount dripping off your condenser, you will only have a couple hundred milliliters l in the flask and it will spread out on the rotating flask, giving you better rate of evaporation.

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I run mine balls to the walls

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I suggest wa5ching some of the rotovap videos posted on here and places like youtube. It can help tremendously.

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What vacuum valve do you recommend? Also, I don’t have the setup to run it continuously so am I still ok to not clean out the rotating flask completely every time I got to reload the 5L flask? I got to run about 40-60L total.

Heres my filtering and rotovap vac pump arsenal.

3x welch wob-l diaphram pumps.

What can i say, im a vac pump whore.

3x welch wobl
1x welch 1400b
1x welch 1402
1x edwards speedivac
1x leybold trivac
1x robinair 2 stage 5cfm (vac oven use only)

The Welch wobl have an adjustment knob for vac. I dial that in, then never touch it untill all done with the rotovap. Iirc, it sits at -26.5hg

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Those pumps are great. The gauges and valves are perfect for filtering and rotovap. The liquid trap is nice to in case you accidentally get liquid in the vac line.

@WIGG_da_TERROR You could probably use a regular barbed ball valve, but it’s best to use a gauge as well, otherwise it will be hard to adjust properly. If you don’t have a pump yet, I would get one of the Welch pumps posted above. There worth the price with the valves and gauges built in.

If your using the re-501 you should be able to run a continuous feed, they come with the feed port. You will just need to break vacuum once the receiving flask is full, unless you setup another container like thetetraguy posted.

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I have a water circulating pump from usa lab equipment. The blue one.

Trying to make it work with what I got right now

I’m not familiar with those, but it looks like they do have a vacuum gauge. I would think a valve like this would work with the rubber vac hose from usa lab. 8mm barbed valve for sale | eBay

Junk!

The main issue with that is you MUST keep the water cold, or you loose vac depth as well as cold h20 for the condenser

I understand the water issue with the pump. Just trying to get these first passes through so I can level up to a better one

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Like @tare said, grab one of these

Equal 8mm Barb Barbed Brass 3 Ways Type Y Gas Fitting Connector Valve | eBay

Cheapo way to break and throttle vac

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Thank you everyone with the quick responses and input. Very much appreciated. I’ll let ya know how it goes

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Didn’t want to make a new thread but I have a rotovap question so here goes:

The Alcatel 2021i is clearly way too fucking powerful for a single 20L rotovap- anyone wanna give me hints on what pump I should be using? Or if there is a cheap way to make it work with the 2021i? I have a bleed valve but it’s so incredibly touchy that if I so much as flick the valve the pressure goes haywire.

Find a good deal on an eBay used diaphragm pump

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How many cfm though?