Sciencemadness Discussion Board

Basic vacuum distillation question

SuperOxide - 8-1-2023 at 22:59

I've done a decent amount of vacuum distillations over the past ~4ish years of amateur chemistry, and there's one question I've wondered that I keep forgetting to ask/research.

Whenever I do a vacuum distillation, I will leave the vacuum running the entire time, which is pretty hard on my pumps. In theory, shouldn't one be able to run the vacuum til a certain point then turn it off after sealing the system? Since you're condensing some of the vapour as more vapour is being made, I would think that as long as you keep the condenser coolant cold enough (and maybe keep the receiving flask cool as well), that you should be able to seal the system at some point, maybe prolonging the life of your vacuum pump.

Sorry if this is a silly question. Just trying to look out for my KNF pumps :-D

Deathunter88 - 9-1-2023 at 00:15

Ground glass joints aren't really vacuum tight so you need the pump to keep the vacuum low enough.

XeonTheMGPony - 9-1-2023 at 03:13

As above but all so no system is truly sealed no matter how hard one tries short of fusing the glass wear into one solid piece. and as one can imagine it makes it rather inconvenient to get your reactants back after!

Rainwater - 9-1-2023 at 18:20

Ummm. I use high vacuum grease and can leave a vacuum on my setup for days at a time without the pump running. I distill water at 40c using this method to.

Grizli7 - 18-12-2023 at 10:03

You can use an electrocontact vacuummeter -if you do not need a deep vacuum, but it arranges a certain value from and to, it is also advisable to use the receiver in the system system will not prevent sharp pressure surges. But there is an important nuance when the pump is turned on under the vacuum increases the starting load - this can lead to a breakdown. Look at the instructions for the pump or information on the official website whether the launch is allowed at the load. Well, the last one - it may make sense to look towards the waterfront pumps.