[chimhead]

Hi There

Bit of a Noob question, I was just wondering what is the difference in length of glassware? for example 24/40 200mm distillation column and a 600mm distillation column, what are the differences, i am using them to distill essential oils and fractionally distill oils. Most of my glassware is 24/40 fittings with 2l flat bottoms and my distillation colmn is 34 cm long 

[Altered State]

When it comes to a distillation column, which is also, in effect, a reflux condenser, increasing the length of the column increases the efficiency of the recondensation that takes place inside it.
As you probably know, the function of this glassware is to lower the temperature of the gas that reaches the water zone, so it condenses and returns to the flask in case of a reflux purpose or goes to the collector flask as a liquid in case of a destillation.

Regarding the size, well, most of the times, in the moment the vapour reacheas the water-zone of the condenser, it will inmediately condense, so a short piece will do the work. But in cases where, for example, you are working with very volatile compounds, or if the mixture is boiling vigorouslly, the gas might not have time to recondense before it reaches the end of the column, so it leaks from the system. In those cases, you obviously need a larger column.

Also there are many kinds of condensers that can increase that efficiency without the need of increasing its lenght, like this guy over here:
http://i01.i.aliimg.com/wsphoto/v2/605742509_1/Coil-Reflux-font-b-glass-b-font-condenser-200mm-24-29-Chemistry-Laboratory-Glassware.jpg
Superfice of contact between water-cooled glass and vapour is increased, and so will be the condensation efficiency.