Sciencemadness Discussion Board

Strange behavior (temp drop when more heat is added) during distillation

RogueRose - 22-7-2016 at 01:19

When I am running a distillation of ethanol and putting 1 kw through it, the temp during the end of the run may be 200F and if I use a 1500w heatgun to heat the outside of the container, the temp right before the condenser drops drops about .1-.2 degree every second and dropped 4-5 degrees after 20-30 seconds.

Is this normal? Why does this happen?

Marvin - 22-7-2016 at 01:46

You've not described your set-up, but if you are fractionating there can be a delay before the next fraction hits and it's the lack of vapour that can make it look like the temperature is dropping.

RogueRose - 22-7-2016 at 01:49

Quote: Originally posted by Marvin  
You've not described your set-up, but if you are fractionating there can be a delay before the next fraction hits and it's the lack of vapour that can make it look like the temperature is dropping.


Simple pot still with a 2' vertical to a T (that is where the temp is taken) a short 4" connector to a T to a long condenser going down. The column is copper.

Also in ethanol distillation what happens if "too much" heat is used (if the purpose is to just "strip" a mix that has a low alcohol % - so it is just a fast stripping run. can too much heat be used?

[Edited on 22-7-2016 by RogueRose]

Magpie - 22-7-2016 at 05:54

I agree with Marvin that you are not getting any vapor to the bulb. the pot residue is not sufficiently volatile for the heat delivered.