> My question is would that be effective or is there a better way.
It can be reasonably effective - ways to improve it are to use metal (ie
copper) tubing in contact with the top of the tower (rather than plastic -
which has such a low ability to transfer heat well), and then to braize it
in place for even better contact. Obviously the more tube you have in
contact with the tower, the more heat you will transfer.
But this will only cool the vapour that is against the side of the column.
The hit more of it, you want the cooling coils to be inside the column.
You can do this easily by just putting in some "pass-through" tubes, or do
even better and make a wee coiled setup inside there.
Time to get on my hobby-horse again ... make sure that you do all this
reflux cooling at the TOP of the column, not the base, if you want to make
the most effective use of this refluxing liquid in stripping and purifying
the rising vapour.
To really help out as well, its nice to make sure that your refluxed liquid
is being distributed evenly over the packing. One trouble of just doing
the cooling around the outside is that the reflux starts off just running
down the sides as well, instead of over the packing. Commercial columns
(big ones) have redistributors every metre or so, to make sure that both
the vapour and liquid are going through the packing evenly. You can do
similar by having a perforated plate just below where the reflux is
generated, to encourage it over the full width of the column.
>The second thing I wanted to ask is how much of the
>column should be taken up with packing if I was to pot scrubbers.
The more the merrier ! The more height you have of them, the greater your
explaination of how this works.
Just two points - 1) don't jam them in too tight - keep them loose enough
to easily breath through, and 2) do have a bit of an airgap between them
and your thermometer, so that it is measuring the VAPOUR temperature just
prior to where it enters the final condensor, so that you get an accurate
idea of its true temperature (and hence purity).