Sciencemadness Discussion Board

Sugestions for a first EASY SAFE Vacuum distilation

Little_Ghost_again - 25-9-2014 at 12:04

I would like to do a vacuum distillation, Although my vacuum gauge is broken! I can sort something out. The requirements are...... Anything you think a beginner should be able to do with his brain removed :D.

I got the pump today and boiled solvent in the vacuum chamber at room temperature :D was really cool, the beauty of this old pump is although its fairly slow is does pull down to a good vacuum, and the oil part is separate. the oil itself is thicker than the other pump and very easy to change, it looks identical to compressor oil or the thick type hydraulic fluid (we got loads of that).
So not over bothered about oil getting contaminated :D but I will build a trap for when I dont use the chamber

Pyro - 25-9-2014 at 13:19

water... my first was xylene.
as long as its not too volatile, toxic or flammable, you are in the green

JefferyH - 25-9-2014 at 15:31

You don't want solvents escaping through your vacuum, it can cause some problems in the vacuum. Also you need to know what the maximum pressure of your vacuum is. My vacuum pump, starts to smoke if I leave it on for more than 30 minutes straight. It can reach a full vacuum in much less of a time, but I can't vacuum distill most things on a full vacuum (0.02mmHg for my pump) because many compounds at that pressure would be a vapor even below 0 degrees, making a normal condenser useless in that application. The only way I could use my vacuum for long distillations is to use a gauge with a shut off valve, and close off the system when my vacuum brought it down to the needed pressure.

If you have a vacuum that's not as strong, or even a water aspirator, you will have much better luck, but keep the above things in mind before you just go vacuum distilling something. Know what your vacuum is capable of and don't leave it on for very long periods or it could very well overheat or blow up on you.

Little_Ghost_again - 25-9-2014 at 23:29

lucky enough its a constant rated type, it has a valve to adjust how much pressure it will pull at maximum. Having said that I intend to also have an escape valve so I can let some air seep in keeping it in balance.
It dosnt shift much air per min but pulls down to 30Hg (my gauge only goes that far), I had it on the Vacuum chamber messing with chili peppers last night and it ran 3-4 hours no problem.
My mums has more power but you cant run it continuous :D, I will also get some traps sorted for it.

arkoma - 26-9-2014 at 04:05

no gauge? well then, time to make a manometer!!

Little_Ghost_again - 26-9-2014 at 05:17

Quote: Originally posted by arkoma  
no gauge? well then, time to make a manometer!!

I got a job lot of stuff from a school, there is bound to be something in there I can use! No mercury but I guess I can convert whatever it is to mercury inch's.
I did have a gauge (mums), but it appears that the pump she has can pull far more than the gauge could handle :D.

I am going to do a simple distillation first, it also gives me a chance to try out my silicone bungs (should be ready to cast and use by tomorrow).
I am pretty sure the pump can go pretty low pressure wise even if its a bit slow. controlling the pressure is the harder part.

vmelkon - 27-9-2014 at 13:03

Why do you need to control the pressure?

Also, there is probably an equation that relates boiling point to pressure. Probably in physics textbooks.

aga - 27-9-2014 at 14:47

A good Safety thing when You're new to it, and so is the Glassware and Pump, is to have some sort of Shield between You and the apparatus.

A sheet of Perspex would be good.

If it Implodes and subsequently sprays Glass Shards everywhere, no big deal.
Unlikely to happen, yet best be aware that it Can, and Does happen.

Here's a youtube flick of an implosion of a silly sized vaccum chamber with cheapo glass :

[Edited on 27-9-2014 by aga]