Lillica - 16-3-2017 at 07:31
I've seen a few air cooled condensers on the market ranging from $200-500 and noticed that they are either based on Vigreux columns or utilize some
other means of high surface area contact. With the claims being that they are good for medium amounts of liquid (150-250ml) when the oil bath is only
around ~20c greater than the BP of the solvent.
Is there any reason why I couldn't use two Vigreux columns stacked on top of each other, with maybe a fan blowing on them?
Here's an example of this concept using two stacked air condensers that are currently for sale on the market. https://www.youtube.com/watch?v=QjROAkbp1ik
Sulaiman - 16-3-2017 at 08:00
I have only a little experience with air condensers,
mine are like this http://www.sigmaaldrich.com/catalog/product/aldrich/z303119?...
I believe that the main use for air condensers is when the b.p. is too high to use water-cooling in a condenser,
so air condensers are high temperature condensers...
It seems to me that the performance limiting parameter is the EXTERNAL cooling area,
so I would expect a Vigreaux to have negligible advantage over a straight tube,
but a Vigreaux with a fan should be relatively efficient,
... two even better 
but may be more succeptible to thermal stresses due to the less uniform shape.
[Edited on 17-3-2017 by Sulaiman]
JJay - 16-3-2017 at 09:01
http://www.sigmaaldrich.com/catalog/product/aldrich/z410411?...
Dr.Bob - 16-3-2017 at 16:38
I use Vigreux columns as air condensers all of the time. If you are distilling something with a Bp greater than about 70 C, they can work OK, even
better for solvents over 100 C. The key is to set your oil bath to only a couple degrees above the BP, or set your heating mantle to just get a very
mild reflux, The temp of the liquid will stay at the Bp as long as any solvent is boiling, the solvent is just transferring excess heat from the
heat source to the condenser, so as long as you have any reflux, the temp will be right or within a degree of the BP. You can double them up if you
are concerned or have a lower BP. You can often get away with them for THF, for instance, if you are careful, but ether, DCM, and hexanes will boil
off too fast for most uses without cooling water, even then ether can be tough to avoid boiling off in overnight experiments.
You can buy fancy ones with fins, but if you keep the heat low enough, you don't really need them, or unless you are dealing with lower BP solvents.
Radleys makes the best one I have seen, I think Chemglass resells them. Their price is pretty high, however, and Fisher sells them also. You might
find one cheaper on Ebay, but they are pretty rare.
http://www.radleys.com/products/our-products/benchtop-and-ho...
https://www.fishersci.com/shop/products/heidolph-radleys-fin...
adk - 16-3-2017 at 17:29
Asynt in the UK make them - they are pretty nice but will not work for all applications.
http://www.asynt.com/product/asynt-condensyn-air-condenser/
A Vigreux column will work quite well, but not as good as a unit designed specifically for this purpose. I wouldn't try it with ether 