Metzington - 16-10-2013 at 12:02
Had some concern whether or not the vacuum pump I am planning on purchasing would be suitable for a vacuum distillation. This is the pump in question:
http://m.ebay.com/itm?itemId=310745557418
Could this particular pump be used on a fairly standard glass distillation setup? If not what are some reasonable (aka less than $100) alternative
pump systems that would be better suited for the task?
Mailinmypocket - 16-10-2013 at 12:31
Those pumps are not built for having chemical fumes go through them. You would need a cold trap to condense any non condensed vapors before they get
into the pump. The metal insides will corrode and jam up with corrosive fumes like when distilling nitric acid. Other things like solvent fumes will
dissolve and/or interact with the pump oil in a nasty way. Either get a pump with a Teflon diaphragm (pricier), or use a cold trap (needs dry ice,
annoying to keep on hand, price adds up). For physics experiments and other projects it is a good pump though.
For alternatives? Try and get a Teflon pump in working order on eBay used... Won't be easy to find though. Aspirator pumps works pretty good too.
[Edited on 16-10-2013 by Mailinmypocket]
Metzington - 16-10-2013 at 13:55
Funny that you would mention nitric acid synthesis, because that is precisely what I would be using this piece of equipment for. I knew there were
several different types of gas traps / cold traps that could be used to prevent damage to the pump. I was more concerned with wether or not this
particular pump was a type that I could use with those setups. Thanks for your response! I'll search the forums for some ideas for gas trap and cold
trap setups.
bfesser - 16-10-2013 at 14:02
<img src="../scipics/_warn.png" /> Use the search function and read a bit before opening new topics on simple questions. <img
src="../scipics/_warn.png" />
There are a multitude of threads already dedicated to vacuum pump selection and use with nitric acid.
<a href="viewthread.php?tid=19143">The ScienceMadness Guidelines</a>
Welcome to ScienceMadness.
[Edited on 16.10.13 by bfesser]
Metzington - 17-10-2013 at 04:04
Thanks bfesser, that's why I didn't initially specify that it was for nitric acid synth. I just wanted some information about this particular pump. I
believed it was within the guidelines. It doesn't matter now anyway, mailinmypocket was very helpful with answering that particular question and the
rest of the questions I had were answered in other threads.
[Edited on 17-10-2013 by Metzington]
testimento - 17-10-2013 at 09:58
An aspirator-ejector pump is quite a good option. It limits the maximum vacuum to 32mbar at ordinary conditions. I have small, 3600L/h 3.6bar water
pump and 30-liter reservoir, where I circle water through the aspirator and this way I can deal with badass corrosives too. If you do vac
distillations not that often, you could use mains water to drive the ejector, so you will only pay for the ~20 bucks for the ejector pump.
Those vac pumps have also another downfall: they're way too powerful. I bought one cheap pump, which can easily generate so high pressures that water
will freeze and slowly sublimate until it reaches temps under -100C. With ejector I got half a liter of frozen acetone when I used the ejector pump at
full power.