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j_sum1
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I dug up this thread because I have some problems with a sep funnel stopcock. I don't want to get rough since it is my only one. I am nervous tapping
and heating because that is precisely the location where stresses can concentrate. I have it soaking in an acid bath. We will see what it is like in
the morning. I am open to suggestions if anyone has any.
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woelen
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Not fun at all, those frozen joints. In that way, I lost a very nice round bottom flask and adapter from my distillation setup. I distilled PBr3 in it
and this requires fairly high temperatures (170 C or so). Liquid crept between the joint of the adapter and the flask and this dried out, and red
phosphorus formed in the joint. After distillation, the adapter and flask literally were united into one piece with a lot of red P between them at the
joint. I tried soaking in bleach (this dissolves red P) and used acid, with dissolved Cl2 in it. Nothing helped, the liquid simply did not reach the
joint. In despair, I carefully used a small wooden hammer to release the joint. At a certain moment, I heard a bright "tick" and that was the end of
both flask and adapter 
Right now, I am very reluctant to distill liquids, from which solid matter can be released (either dissolved or from chemical decomposition), which
gets stuck between two pieces of glassware in a joint.
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Swinfi2
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If your sep funnel is like mine I can see why it would make you nervous.
I think the best bet would be blowtorch and applying consistent twisting just hard enough for it to pop when the heat gets to the right depth.
Or if that doesn't work you could hold the tap with some cork in vice and try a gentle tap out with a mallet? (So the force is confined.)
Best of luck.
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unionised
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There is a simple solution to this issue.
You need two things
A time machine and these
https://www.fishersci.co.uk/gb/en/products/IZ8Q7S29/glass-jo...
You go back in time and then set up the distillation or whatever using the PTFE sleeves.
{Note; no responsibility is, was, or will be accepted for temporal paradoxes}
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SWIM
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I do believe I've got like the worst stuck joint ever.
It's a 45'50 joint, but the outer joint has a vacuum jacket around it so heating is a problem.
can't get to the stuck joint from the inside of the apparatus to try to knock it loose either because there are fragile little glass tubes in the way.
I've wondered about heating the whole thing to 200C or so in the oven and then dipping the end of the stuck joint in cold water, but if it cracks and
doesn't come loose I'll have a useless piece of glassware.
Also, I don't want to take any chance on breaking the vacuum jacket which would not only make it useless, but make a bit of a mess as this vacuum
jacket is a big one.
The stuck inner joint piece is a 45/50 to 24/40 adaptor, so I can use the item (distillation head) as is even though it's less than ideal, but it is
an annoyance. And one that has not yielded to WD-40 treatments.
I've even thought about just cutting the adaptor off flush with the vacuum jacket and grinding the inside of the 45/50 inner joint out so it'll seat a
35/40 inner joint inside it.
Without proper tools that sort of thing takes ages, especially if you expect it to hold vacuum fairly well.
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j_sum1
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Ok. I went back in time and tried these things out. Problem is that they don't work on a stopcock.
I got back and now there's two of me and I am my own grandfather. What do I do now?
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Chemetix
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I've had success (sometimes) removing a stuck adapter by using a long bolt with some sort of flat edge on it. This is inserted inside the stuck joint
and useing the flat edge to sort of hook onto the bottom of the joint. With a tapping motion on the bottom edge the stuck joint is forced up and out.
I'm not sure why it works when everything else has failed but it has worked as a last resort. DMSO has also proved quite beneficial; just a drop on
the top edge and it penetrates and dissolves just about anything. NMP or DMF could be substituted or used in conjunction.
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j_sum1
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Thanks for the tips Chemetix.
An update.
After soaking in acid overnight it was still stuck. But in some subtle way it felt a bit different when I put pressure on the stopcock. I soaked it
in boiling water for a few minutes and after that it loosened easily.
My next course of action was going to be WD40 for a few days followed by freezing and then heating the outer with a hot air gun. And of course more
tapping with a wooden stick.
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outer_limits
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Quote: Originally posted by j_sum1  | | I dug up this thread because I have some problems with a sep funnel stopcock. I don't want to get rough since it is my only one. I am nervous tapping
and heating because that is precisely the location where stresses can concentrate. I have it soaking in an acid bath. We will see what it is like in
the morning. I am open to suggestions if anyone has any. |
Happened to me few times. Glass stopcock was impossible to move and after trying few times I gave up trying using force. Instead, I put some joint
grease on the external part and waited one day. After this time the grease managed to get into the internals and I was able to disassemble.
Now, after those accidents I always use some grease on glass stopcocks after washing. Personally, I think that PTFE ones are much better regarding the
friction and such problems
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Jenks
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I had what must be a common problem - a round bottom flask frozen to a reflux condenser due to exposure to hot base. No amount of heating, cooling or
coaxing would separate the two. After learning about cutting non-borosilicate glass by repeatedly heating and cooling a scratch, I thought I would try
the same with this. Sacrificing the flask, I made a series of scratches along the length of the outer 24/40 joint using a carbide cutting disk meant
for a dremmel, but installed in a regular drill. I did this because the dremmel was too fast, and I wasn't trying to cut the glass, only leave a
decent scratch. Then I heated the flask to a few hundred C (below any redness) in a torch and cooled it in a pan of ice water. The heated glass only
made a slight sizzle in the water. After only a few cycles I noticed cracks in the outer glass joint, though they weren't really along the scratch
marks. After about five heating and cooling cycles, pieces had fallen off and I was able to pry off the remaining pieces and recover my condenser
intact. I hope this success can help other chemists recover something useful from their glassware graveyard.
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teodor
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Last few weeks I had some success separating pieces frozen due to the long keeping of alcoholic base solution inside. It's just several hours of WD-40
around the joint and fast heating with a heat gun set to 650C of the outer surface. WD-40 evaporates inside the joint and the alkali residues at this
temperature become liquid but very-very viscous, so a lot of rotating force is required. Some pieces of glassware which already had internal cracks
didn't survive.
With more experience, I think it is possible to separate pieces with less force. I suspect that the melting temperature of "glass" formed by NaOH/KOH
inside the joint is much lower than that of borosilicate glass.
If you need to make an inner part separated there is no need to cut the outer part, just heat it and then pour some water, it will develop cracks.
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solo
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.....i recently open glass joint of a jar long left ecause unable to open...theni tried putting liquid dish soap ....and suprise !!....it opened up
quite easy....solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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PirateDocBrown
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You only need the tiniest amount of Dow grease for your joints. I have a tube I bought for 20 bucks, I think they are up to maybe 35 now. It has
lasted me my entire career.
You need just enough that you can see the film of grease when the joints are together. Normal soap doesn't take it off, so after your wash your glass
there's likely a bit still in there, so you need even less. It's only when you wash with solvent that you need a full dab.
If you get too much on one joint, use the excess by spreading it around on joints of the opposite gender in your apparatus.
Really, an amount equal to a drop of water ought to be enough for a simple distillation apparatus. Maybe less.
I almost never get stuck joints.
Phlogiston manufacturer/supplier.
For all your phlogiston needs.
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Organikum
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The cheapest thinnest kind of PTFE tape, 10 mm wide usually and 0,1 mm thick and a tiny amount of spit on the finger to make it stick and thats it. No
grease anymore, well very rarely, might not do for very high temps but for the rest it is just fine.
Overlap the tape one mm or two and keep the wrapping flat not to create a easy spiral staircase for stuff to travel, put in socket and give it a
quarter rotation pressing down hard, then leave it alone so possible.
The sleeves are just street robbery.
/ORG
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