Self-made reflux

Sometimes one needs to boil small quantitie of liquid for long time. This is not as easy as it may seem because of liquid losses by evaporation. Loss of liquid is not always a problem - for example one may compensate evaporation of water by adding some more but this is not of any help if substances that become lost are your desired reaction products.

These problems can be solved by using reflux condensers. Dedicated reflux condensers can be bought from glassware sellers but you can make your own especially if you prefer to experiment with small quantities.

Probably simplest reflux condenser would be if we place cold object over boiling liquid. Vapour condenses on cold surface and flows back into liquid. This would be rather good way if only our cold object would remain cold as long as we want.

This can be done by palcing stopperd test tube over boiling liquid and driving cold water through it. If vapour can not escape without contact with cold surface then we have quite useable reflux condenser.

Another way is to take class tube aproximately 25 cm long and to bend it from center part so that to get incredible narrow U tube. I used glass tube with 6mm outer diameter. Central bent was rather hard to make. I had to try it 4 times (and spent 4 tubes) before i got "U" that was thin enough to fit into test tube with 15mm inner diameter. Two or three additional bends will make it coil-like for increased efficiency. Cheap resin tubing can be used to supply such condenser with cold tapwater. Such condenser can be placed onto neck of suitable test tube. Small quantity of liquid can boiled then for many hours without noticeable loss. Of course you have to use boiling stones and water (or oil) bath is good to ensure quiet boiling.

If condenser is intended to use solely with organic solvents then it can be made from metal tube. More complex coil shapes can probably even be placed in neck of common boiling flasks.

Condensers of this kind are good for many organic experiments. Synthesisizing of esters is good example.

[Edited on 2-12-2005 by chromium]

Air cooled reflux condenser

I have the difficulty of lacking a water supply in my lab, therefor i tried something different.....air cooling.
My prototype consists of an ordinary CPU-cooler(copper-heat sink + silent fan copper silent) which is attached to an eloxated heat-sink with lamella pointing inside the flask.

I have tested such a setup for use with non-corrosive solvents such as toluene or acetone........it works!

You can calculate from the performance of these heat-sinks that it would be best to incorporate 2-3 coolers for a normal reflux operation.
Ok, this is somewhat crazy and many would prefer to use just a high copper tube for air cooling, but it is the small size of the whole setup that fascinates me...

[Edited on 5-12-2005 by BASF]