4
$\begingroup$

I have a fractional distillation setup. I would like to purify a small mixture ($\pu{\approx 100-150 mL}$) of high boiling point compounds (between $200$ and $\pu{300^\circ C}$). The one that interests me has a b.p. of $80\rm~^\circ C$ at $\pu{13 mmHg}$. I don't know what this mixture is composed of.

Now the tricky part and the one that give me the most headaches is the vacuum pump. I need one that has enough vacuum power to be able to distill at $\pu{13 mmHg}$ and one that is not expensive too.

I also need a system to be able to monitor and control the vacuum pressure too, so the vacuum pressure remains constant.

I figured that a diaphragm pump is not suitable since the ones that have that kind of vacuum power are way more expensive than rotatory vane pumps. Can anyone help?

Improve this question
$\endgroup$
3
  • 2
    $\begingroup$ Could you correct your orthography? Also I suggest not to thank in questions, but in comments. $\endgroup$
    – Mithoron
    Feb 10, 2016 at 23:39
  • $\begingroup$ Have you tried if a water aspirator works? It can go as low as 10mmHg (I think) and should be OK for the scale you want $\endgroup$
    – K_P
    Feb 11, 2016 at 8:42
  • $\begingroup$ Thank K_P i have thought about a water aspirator but the water temperature would need to be a very low to reach 13 mmHg, i have thought about using a water pump connected to a water aspirator, the water pump would use a precooled water in a container and then put it back there, but i assume i need i strong water pump but how much strength do i need ? $\endgroup$
    – klaus
    Feb 11, 2016 at 11:56

2 Answers 2

Reset to default
2
$\begingroup$

If you are keeping your hands on you can't beat a water aspirator for cost, simplicity, and chemical compatibility.

Here is an aspirator assembly with a gauge and valves I put together for about $50. Connecting it to a standard hose bib it can pull up to 27mmHg. The water valve controls the vacuum rate, and if you have a closed system once you reach the desired vacuum you can shut one of the other valves to hold it.

Water Aspirator assembly

Note: This was inspired by Lysander's answer to my similar question last year, which has additional useful details.

Improve this answer
$\endgroup$
0
$\begingroup$

I dont know what materials you'll be working with, but Ace usually has a pretty cheap 1.5 cfm two phase pump. They work alright. It pulls too fast in my opinion and not a very deep vacuum. It still hits -29.5 inHg (at the altitude im at), but you can regulate the pressure easily with a second cheap valve already placed on the pump itself. You can also add a inlet and exhaust trap for pretty cheap.

If your pretty good with tools, spend an extra 200USD and buy a deep vacuum off Ebay. Something that just requires an added belt drive motor and you can build yourself a pretty diesel, multi thousand dollar rotary vane pump for about $200 dollars.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.