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I need to distill some reagents, and the book Purification of laboratory chemicals suggests first refluxing over $\ce{P2O5}$ for several hours before distilling across.

The obvious choice is a solvent still head like the ones used to distill THF, but I don't need very much of this so it seems wasteful.

The way suggested that I do it is to set up a normal reflux, let it cool, and then quickly change the condenser for a side arm. This will obviously work but seems like a lot of effort. I think there should be some other piece of glassware to allow this process. Is this the case?

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  • $\begingroup$ A Perkin triangle springs to mind, though I don't think I've ever actually came across one in my lab $\endgroup$ – NotEvans. Jun 29 '17 at 19:04
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http://www.sigmaaldrich.com/catalog/product/aldrich/z516333?lang=en&region=US

This condenses, and depending on what you have the knob turned too will either send it back to it's origin or to a collector. (I think, I have something similar in my lab but the link doesnt have a great drawing)

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  • $\begingroup$ Never came across one of those before. Very nice! $\endgroup$ – NotEvans. Jun 29 '17 at 17:15
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  • There are distillation heads below the reflux condenser with a central bulb / reservoir of about $\pu{250 mL}$, obviously not filled this much during operation:

enter image description here

(source)

  • Alternatively, if you need not to be super dry, if you may distil under a blanket of Argon and perhaps a colleague lends you a hand (or two), you may mount an intentionally empty Soxhlet between still pot and reflux condenser instead. (The small ones at Aldrich claim an extractor capacity of $\pu{50 mL}$.)
    After $\pu{x h}$ of refluxing, lower the heating intensity so that the condensed liquid is siphoned less frequently. After some stabilisation, to harvest your solvent, let the level of the condensed liquid in the Soxhlet almost reach the level of the syphon. Then 1) dismount the ensemble of (Soxhlet and condenser) from the still pot and 2) mount instead a dry / Argon flushed two necked flask below the Soxhlet. 3) Now tilt the Soxhlet just enough to let the siphon transfer all the dried solvent in the lower dry receiver flask. After this rapid fill, 4) mount Soxlet and condenser on the distil pot, and 5) syringe your liquid from the two-necked flask refilled with Argon.

    Well, this second ballet-like version requests some choreography, and definitely is not something for volatile solvents you get from the normal solvent still / bulb (vide supra) or a Grubbs system. To render the performance save, smooth (elegant), and quick, rehearse once (or twice) so that every hand does know what to do when and where.
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