[toddwick]

First if, this is in the wrong section feel free to move.  It involves organic chemistry but is basically a lab technique issue.

So I was taking something off the high vac.  The ground glass joint was frozen so I was twisting and pulling, but was too vigorous and the portion attached to the vacuum tubing broke off in the tube leaving a rather sharp edge.  I tried heating the female joint while holding the other with enough paper towels, but this wouldn't work.  I couldn't heat with a flame because my pdt was still in the flask and needed to be moved onto to the next step immediately (within the next 15-20 minutes, pretty sensitive sequence).  I opted to do the one thing I wish I didnt need to do and that was to break the rest of the adapter.  I was hoping that cracking it with a hammer/mallet that the rest that was stuck would crack as well, but no dice.  I have a smooth lip to the flask, but the rest of the adapter is still stuck with nothing left to grab.  Thankfully nothing came of the disturbance and subsequent reaction were fine even though I took a lot longer to move forward than wished, but my only problem is;  how do i get this glass out?

There is still solvent stuck between the joints so i dont want to use a propane torch.  I've also tried chipping the glass carefully, but its pyrex and obviously sturdy.  I've tried using a glass cutter to make small cracks that I could possibly lengthen with heat from a heat gun but this hasn't produced and results. 

I'm hoping that someone out there has had this problem before and knows of a solution that will allow me to salvage my flask.  1L flasks are scarce in my lab and expensive...

thanks for any suggestions!

[nj_bartel]

It's probably a very minimal amount of solvent, and it doesn't have ready exposure to any accelerant.  I'd heat it with a heat gun to drive off as much as possible, let it cool completely, then try to heat to remove with the torch (if you're still worried about solvent catching, work behind the hood glass).  If that doesn't work, my next attempt would be piranha solution bath overnight.  If that doesn't work, you could try the sonicator overnight if you have one.  My last bet would be sulfochromic acid soak.  I hate that crap though and would really avoid if possible.

[ardbeg]

sounds silly but good hard taps of the joint against a hard surface often help by putting shockwaves through the joints.  also, try freezing the join in liquid N2 - sometimes loosens the joint or freezes the solvent, making it easier to crack away. either that or heat the crap out of it, or give it to your glass blower.

[democanarchis]

sounds silly but good hard taps of the joint against a hard surface often help by putting shockwaves through the joints.  also, try freezing the join in liquid N2 - sometimes loosens the joint or freezes the solvent, making it easier to crack away. either that or heat the crap out of it, or give it to your glass blower.

Yep, tapping the joint against the corner of a bench is my technique of choice also

[toddwick]

Thank you for the suggestions.  I'll let you know how it goes.

[Babcock_Hall]

I am having the same problem with a reaction run in DMF.  It was put on high vacuum to remove the last DMF, and now the the hose adapter is frozen.  The joint is 14/20.  I have not yet tried a heat gun or liquid nitrogen.  Any other ideas?  Thanks.

[PhDoc]

I'll give you a suggestion, however must also provide a word of caution. I've seen some really bad wounds inflicted by struggling to do exactly what you're doing. Be careful.

When you run into this problem, soak the joint in water if possible. If the flask is too big, then place a water-soaked paper towel around the neck of the joint. Be certain the water seeps into the joint. Then take a propane torch, apply heat, and use insulated gloves (both hands!) to unfreeze the joint.

This trick works so long as you don't have any gummy residue in the joint. Sometimes you have to tap the hot joint with the wooden portion of a hammer. I kept a wooden stick in the lab just for these occasions.

Good luck!

[Babcock_Hall]

Unfortunately, the contents of the flask are still inside and are obviously somewhat valuable.

[synthon]

Heat gun plus light tapping has always been the most effective for me.  Could it be that a small amount of your compound has gotten in the joint and frozen it?  I've had that happen after reflux on occasion.  Sometimes heating underwater can be helpful (submerge in the rotovap bath).

In the future, a teflon sleeve can help to prevent joints sticking, but in my experience it happens infrequently enough that I don't usually bother.

[fledarmus]

My first attempt at opening a frozen glass joint is with a heat gun. Clamp the hose adapter so that the round bottom is suspended about 1/2" above a pad of paper towel, so if it drops off it won't break. Then heat the joint with the heat gun and tap the top rim of the roundbottom joint as you heat. You should see a change in the way the light shines through the joint as the joint heats up. Something heavy and wooden is best for tapping, but since I rarely have something like that, I use the back end of a large pair of forceps - gives nice accurate taps. If you see the joint change transparency but it still doesn't drop off after you've tapped it a while, you can pick it up using your insulated gloves (you are wearing insulated gloves, aren't you?) and try to twist it off. Don't put pressure on the bent end of the hose adaptor, or you may snap that off and have some nice jagged glass to deal with.

If that doesn't work, allow it to cool until you can hold it with your bare hands, then put some heptane or hexane on the top of the joint and let it soak in. Some light tapping here might also help. Then repeat the heat gun.

If all else fails, go to the torch, but you might want to remove your material from the flask first. A long needle on a syringe will allow you to add solvent to dissolve your product, and remove it from the flask through the hose adapter.

Good luck - I hate to say it, but practice really does help in disassembling frozen joints. You can expect to break a few during the process - think about how you will protect your product when your joint breaks (not "if" - "when").

[Babcock_Hall]

The heat gun worked.  Thank you.

[PhDoc]

Buy some teflon sleeves from Aldrich or VWR so you don't have to experience this again. Just a suggestion.