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vacuum distilling without a rotovap?

Christian_Hall_13

Hello all - first post, please be gentle..

I've been doing vacuum reductions using an aspirator pump and a stirrer (as described here: http://modernistcuisine.com/2011/11/vacuum-concentrating-part-2/) for a few weeks now, and have been wondering if there's a way to preserve at least some of the evaporating volatiles that at the moment are getting sucked into the aspirator, without having to invest in a full rotovap setup. Does anyone know whether it would make sense to try and add, say, a condenser and a recieving flask or some sort of cold trap between the boiling flask and the aspirator, to collect some of the distillate, and what kind of yield I could expect to pull? I'm assuming way less than with a proper rotovap, since that's what everyone seems to prefer for vacuum distillations.

Thanks!

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Chris_Young_80640

If you can add a cold trap to the vacuum line you wil be able to recover some of the volatiles. One way to do this is with a small side-armed flask that is set in a bath of liquid nitrogen (if available) or rubbing alcohol and dry ice (easier to find usually), vacuum line comes into a stopper with adaptor in the top and then goes out the side arm to the pump.

Christian_Hall_13

cheers Chris, and thanks for a great site btw - keep up the good work! Do you think a cold trap would provide a better yield than, say, a coil condenser? I've been reducing from about 3 litres at a time, and I'd really be tearing through our ln supply to keep a cold trap running for that long, and dry ice is extremely expensive around here. I guess I could test it out with an ice and salt bath as well.

Chris_Young_80640

A long condensing coil in an ice water bath will work too. It'll just be a bit more work to collect the condensate and you may not condense the most volatile compounds.