9/29/2007

rotate monitor or head ninety degrees to right

I've had a fantastic distraction at work this week: a soxhlet extractor. Since not everyone gets to see these used on a regular basis, I thought I'd take a little video. (Hopefully it's faster for you than it was for me to upload!) Unfortunately, it's...sideways. I don't know why it's sideways. The camerahands are mine, so they're shaky. (The little piece that holds the camera on the tripod broke, and I'm a poor student, so...it's still broken and I don't have a tripod to use at the moment.) But it's a soxhlet in action.

If you've never set one up, well, the stuff you want to flush with solvent goes in the little paper thimble. You have boiling solvent (ether, in my case...yay!) in the bottom that...condenses...in the condenser and drips into the thimble. What's soluble collects until it's pushed into the top of the little siphony loop thing, and at some point there's enough that it can drain back down into the flask at the bottom.

My product here is brickdust (unless it's in DMF or THF), so all the brown-looking stuff is crud I'm trying to get rid of. Soxhlets are extremely useful for things that look like dirt. They're also useful for soil extractions, which is pretty much the only other capacity in which I've seen them used.

Anyway, enjoy the video. Loop for maximum distraction.

video

15 comments:

Wilby said...

There's also a great undergrad experiment where you extract trimyristin (I think) from nutmeg using a soxhlet. Bonus upside is that the lab smells nice afterwards!

Kyle Finchsigmate said...

Soxhlet are great for getting your buckeyballs pure from the other shit in carbon soot.

t said...

Wait ... rotate monitor OR head SAME direction, that can't be right .. unless you want to enjoy the vision of a gravity-defying upside down soxhlet extraction.

Ψ*Ψ said...

t: Hmmm, you're correct. I'm not spatial. If I say anything involving the word "left" or "right" then you should probably do the opposite. ;)

hegemon359 said...

yes! seeing soxhlets in action makes me giddy inside

Ashutosh said...

Forrest Gump?

Liquidcarbon said...

What it that sound?

mevans said...

Stir bar maybe?

Uncle Al said...

The big Pyrex Soxhlet stands more than 6 feet tall assembled and running. Uncle Al had the pleasure of removing bitumen from a few kilos of -40/+60 mesh oil shale on the way to removing the rock from the kerogen. Put a round of filter paper atop the thimble opening to disperse the solvent as it drips/floods in. That way you don't dig a cone and splash the solid out of the thimble.

How 'bout a steel Soxhlet in a plumbed bomb for liquid CO2, NH3, SO2, or Freon-12? Chrome-moly is engineering. Pass on those puppies!

(Really good kerogen spontaneously smolders upon exposure to air. Give management a sealed vial and say nothing as its contents are poured upon a sheet of paper. It's the only way they learn.)

David Eaton said...

I love soxhlets. Before I went to grad school, I worked for a grain and vegetable oil company, and we did a lot of extractions of soybean meal. Ether-licious! I get dizzy just thinking about it.

Ψ*Ψ said...

The height of the whole assembly is what gives me trouble, since I'm really short. Condenser, soxhlet & RB nearly reach the ceiling of my hood. Since the sash is broken, I have to stand on a chair with the 2x4 OF SCIENCE holding it open whenever I have to put the condenser on.

milkshake said...

watching a soxhlet to empty by itself is almost orgasmic. I have to find the perfect soxhlet...

There were two nice synthetic experiments done in soxhlet: One is dimerisation of acetone to aldol dimer. It is thermodynamically shifted to acetone. The soxhlet capsule is filled with Ba(OH)2 hexahydrate which works as a solid catalyst insoluble in acetone. As you reflux if overnight the dimer concentrates on the bottom, without being retro-aldoled by hydroxide.

The other nice one is preparation of MeI from MeOH and red P and I2. You put I2 into the capsule. I2 is only slightly soluble in hot methanol so as you reflux it gradualy extracts itself into the reaction mixture - this prevents a highly exothermic runaway or self-ignition that you could get from loading I2 solid directly into the reaction, you don't have to open the flask etc.

Chemgeek said...

I once drove a pesky esterification reaction run in toluene to completion by putting molecular sieves in the thimble. Reflux overnight = dry as a bone. 99+%

kiwi said...

indeed, i swapped my dean-starks for a selection of sohxlets long ago. i also once tried to drive a transesterification from a methyl ester -> long chain ester using 13X sieves in a sohxlet - less good, but worked.

Milo said...

Kiwi,

That is easy... use a Dean Stark that in on top of a fractionating column. Heat your substrate in the long chain alcohol and fractionate off the methanol works like a charm. A pinch of PTSA helps...