Sciencemadness Discussion Board

Rotary Evaporator vs Magnetic Stirrer for Distillations - which is superior?

beerwiz - 1-12-2016 at 14:43

I've tried doing simple distillations with a rotary evaporator and a magnetic stirrer, and to me it looks like the magnetic stirrer does a better job. Am I wrong or are the two really the same? Both move the solvent around increasing the surface area.

And frankly based on my experience the rotavap takes longer to distill than the mag stirrer, but maybe my rotavap technique is flawed?

[Edited on 1-12-2016 by beerwiz]

DDTea - 1-12-2016 at 17:00

Rotovap is not for distillation per se. Rotovap is to remove solvent from a non-volatile component.

If you're trying to separate a mixture on the basis of the boiling points of its components, use a still with a stir bar/boiling chips.

Dr.Bob - 1-12-2016 at 18:15

Using a rotovap allows lower BP temps, less likely to burn the residue. But if you are careful a stirred flask can boil solvent just fine. I use simple distillations in some cases where I want more control or to keep a reaction warm or if the volumes are smaller. But if you need to concentrate 12+ L of column fractions (Sadly that was my week), a good rotovap is great. The trick is to find the sweet spot of bath temp, vacuum pressure, and rotation to get a nice constant evaporation without bumping.