vacuum distillation?

been trying to understand the whole contraption but i cant get a complete picture of the setup in my mind. so far, from what ive come to understand, the setup should look something like this.. (simple distillation). could anyone help me on how the vacuum part would look?

Well, from an operational standpoint, you would connect the vacuum pump (or water aspirator, if that's what you're using) - via thick-walled rubber tubing, usually - to that "nipple" labeled "vacuum adaptor." Once connected (and assuming all the other joints are tight), the pump/aspirator will lower the air/vapor pressure inside the entire apparatus (essentially by sucking air out of it).

Liquids generally boil at a lower temperature when under lower pressure. The lower the pressure (i.e. stronger the vacuum), the lower the boiling point. So, if you apply a strong enough vacuum, something that normally boils at, say, 150 deg C under normal (atmospheric) pressure can be distilled at, for example, 70 deg C. With a super strong vacuum pump, you could probably lower the pressure enough to distill the same liquid at maybe 50 deg C (or lower).

Usually the reason distillations are done under vacuum is because its safer to distill things off at lower temperatures. Lower temperatures = fewer side-reactions and/or less decomposition than if you were to perform the distillation without applying vacuum. Things can get kinda messy if you heat a flask and its contents to 150-200 deg C for several hours.

Right on mate. I am seriously looking into liquidating some of my silver to buy myself a good set of glassware for a home lab when I move for that college course in the fall.

The word from the supplier I am looking at is willing to give me a stellar deal, throw in a reflux condenser for free, and willing to ship it for free, within the US. Just my luck I am a Canadian. The order is potentially very large, so this guy is probably just laughing. I really want to get a heater/magnetic stirrer combo I saw! I will probably have to get a parcel forwarder from the US, or maybe a general pickup in one of the "Northern states" local post offices.

Anyway, thats exactly what its for. Reducing the amount of energy that needs to be applied to heat a mass. Also there is a bit of a lip that hides the VACK hole from the condensed liquid that should be running down.

Peace

i should have been a lil more specific. i know why we use a vacuum distillation but i dont have a picture of the setup in my mind. you said that you could either use a vacuum pump or a water aspirator, but i have no idea how those 2 things look like in the final setup

JediTangerine said:

thanks. kind of.. +rep anyway. i wonder though.. if a food saver would be a sufficient vacuum that i could connect

Click to expand...

That is a very interesting question. Depends on what you're trying to distill, cause I'm guessing a foodsaver doesn't pull a very strong vacuum, dunno for sure though. If the solvent you're trying to remove has a low enough boiling point, it might be acceptable. Maybe a shop vac would work too. However way you decide to do it, you'll wanna have good seals at the joints of your distillation apparatus if you want any hope of holding a decent vacuum throughout the process.

If you're willing to spend a few bucks, something like this (http://cgi.ebay.com/Rotary-Vacuum-P.../150583347212?pt=BI_Pumps&hash=item230f77880c) or this (http://cgi.ebay.com/BARNANT-VACUUM-PUMP-/270682593891?pt=LH_DefaultDomain_0&hash=item3f05f09a63) would probably work for most common (relatively low boiling) laboratory solvents. For a little more $, you can get this (http://cgi.ebay.com/Thomas-Industri.../120670309623?pt=BI_Pumps&hash=item1c1882ccf7), but the specs aren't much better than the cheaper two. Again, it depends on the the boiling point of whatever you're trying to distill. You can even buy vacuum pumps through amazon these days, lol, I love that site (http://www.amazon.com/FJC-Vacuum-Pump-3-0-CFM/dp/B0017R95DI/ref=pd_sbs_auto_4)

This one (http://cgi.ebay.com/Welch-1399-dist.../220760636295?pt=BI_Pumps&hash=item33665bfb87) could be a real bargain if it actually still works. This is an old school belt-drive type of pump. I used to use this kind in grad school back in the day. At 1/3 hp it would be a lot better than those others which are probably around 1/8 hp.

The least expensive way to go would be a water aspirator...but you would need to have access to a good water line AND it's really wasteful with water, so I would never use one where I live because water isn't cheap here. Basically it requires running water on full blast down the drain for the entire length of the distillation (which can take hours).

Good luck...and don't forget to wear your safety goggles

I dont see what your trying to do ( what are you distilling?) and from what you have drawn up there that wont work at all. please explain to me how you see that working?