Sciencemadness Discussion Board

The Greatest of all solutions to a stuck+broken 24/40 Joint

earpain - 7-4-2021 at 01:06

I don't know if this is some mystical glassblowers' secret society hidden knowledge, or if I missed this somehow in all of my studies, but here's the solution to the all too common problem of joint freezes, apparatus with male joint breaks off, and glass is stuck inside the female joint.

Scenario: 250ml addition funnel in neck #2/2 of 1L RBF. Steam distillation. Water, H2SO4, and then, in the end, drawn out NaOH at high concentration went through the addition funnel, and boiled profusely. When finished, I could not separate the addition funnel from the flask. A very awkward piece of equipment this becomes!
Short tempered, I tried propane torch and pull with welder's mitt, and broke off the addition funnel(under the stopcock, yay!).
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But now the neck of my best flask has a broken mess of a male joint, chemically fused inside of it.

I tried: Heating and pulling, that's how I broke off the addition funnel.
Soaked in WD-40, 2% HF, boiled down 40% H2SO4 to conc. inside the flasks for a few hours, Tea Kettle trick, made a custom tool from a copper pipe, started to dremel and use my glass cutter, and then it hit me.

The glass that remains INSIDE the female 24/40 joint, still has some space of the same taper. Guess what makes a perfect joint seal with that glass?
19/x male!

So what WAS a broken neck on my best 2 neck 1L RBF, is now a free 24/40 -> 19/x reducing adapter

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edit: OK found my proper scientific Standard Taper 19/(the marking has smeared off) glass stopper! Greased, air tight perfect fit.

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[Edited on 7-4-2021 by earpain]

draculic acid69 - 7-4-2021 at 04:14

So nothing worked so you shoved a smaller stopper past the broken fused bit?
At least you figured out a work around.

earpain - 7-4-2021 at 05:42

Quote: Originally posted by draculic acid69  
So nothing worked so you shoved a smaller stopper past the broken fused bit?
At least you figured out a work around.

Oh come on now, surely you see the significance of this. If there's one thing you can never 'shove', it's a ground glass joint connection.
If anything was off, even to the micron, this would not be possible. People pay a lot of money for 24/40 to 19/22 reducing adapters.
I shove silicone, teflon, various rubbers, all the time. even then things aren't air tight on the first try. This fit like a glove. Or better, like a correctly sized ground glass connection.

edit(after thought):
I mean, I think I see what you're imagining. Indeed, all of the ground glass joints are the same taper, and if it weren't for clearance being the limiting barrier, all joints sizes would be compatible with each other.
But the male 19/22 did not go 'past' the broken piece. And the broken piece is still the entire size of the connection surface area. This means that the thickness of the glass, is such that, subtract the space of a 19/22 male, from the negative space of a 24/40 female, and what remains is precisely the wall thickness of this, and likely all devices.

I've already used the flask now for a fractional distillation, just with the stopper. But I wouldn't feel shy about acids, or pulling a vacuum, with the way it is now. Just no more careless caustics!

[Edited on 7-4-2021 by earpain]