PDA

View Full Version : How to set up a vacuum distillation set up.



elixirmixer
10-12-2016, 11:50 PM
This thread is to help people who want to set up a vacuum distillation apparatus...

But since i have no idea how to set up a vacuum distillation, i will invite any learned man to come and share some DO's and DONT'S on how to get that sweet low temp boil (without wrecking $1500 worth of glassware)

Axismundi000
10-13-2016, 10:06 PM
Here is my current set up for vacuum distillation I put it on this thread.

http://forum.alchemyforums.com/showthread.php?4854-Vacuum-is-a-Key/page2

Post 15 I think.

I think the best instruction stuff is this video from MIT although cow and pig adapter is not always suitable to Alchemy.

https://youtu.be/mn-u-7fRQv4

Also you will notice I do not use a claisen adapter, I raise the temperature very slowly.

ghetto alchemist
10-14-2016, 02:14 AM
I find bumping is a big problem with vac distillation, eg the distilling flask boils over and contaminates the receiving flask.


Solution is to use a magnetic stir bar.

Also cooling is more important, if you don't cool enough, you'll have vapours of whatever your distilling condensing in your vacuum pump.
So you fix that by using colder water in your cooling setup, and a longer condenser.

Axismundi000
10-14-2016, 08:27 AM
Yes ghetto alchemist identifies a common problem of not enough cooling and vapours reaching the pump. The MIT video shows the vacuum being established and then the system sealed with a stop valve. I don't do this because I haven't obtained a good enough stop valve so I keep the pump running, I currently use a large reserviour flask and apply cooling (ice cubes) to that as well as pumping water through the sleeve of the Liebig condenser, also I'm now using a 40mm condenser. It is important that the calorific output of the heat source does not exceed the cooling of the condenser. If needed I can add ice cubes to the coolant reserviour for the condenser (a bucket of water), another option would be to make high conc alcohol and put it in the freezer for a few days then pour it into a bucket of frozen cold gel packs. Use this as coolant reserviour. The receiving flask can also have ice cubes around it or even calcium chloride and ice for a low temp ( I haven't tried calcium chloride/ice yet).

Just though to add in case for some it is not obvious, a separate water pump for the condenser and a vacuum pump for partial pressure.

elixirmixer
10-16-2016, 11:24 PM
does this look okay?

http://www.ebay.com.au/itm/66-L-Min-two-Stage-Rotary-Vane-Vacuum-Pump-Refrigeration-/322288541337?hash=item4b09e4de99:g:mCUAAOSw3mpXKVk p

Axismundi000
10-29-2016, 08:56 PM
It needs oil for operation and you can get tubing and adapters to connect to the spur on the distillation train.

Here is a usefull overview on vacuum distillation.

http://pcwww.liv.ac.uk/~jwgaynor/prelab/distillation-vacuum.pdf

Axismundi000
11-13-2016, 05:50 PM
I'm doing some reflux vacuum distillation to see if this reduces the likelyhood of distillate going upstream out of the distillation train. The results seem good I'm using alcohol, it is very cold when it arrives in the receiving flask, condensation quickly forms underneath the flask where the liquid is.

http://i66.tinypic.com/xbea03.jpg

http://i63.tinypic.com/e9wyle.jpg

Edit: Without the vacuum the alcohol does not distil at 220Centigrade but with the vacuum it distils at less than 60 centigrade going over the still head above the reflux condenser. Jacobs ladder!