ManyInterests
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mild crack on 2L boiling flask, still safe?
A bit of a background. A few days ago I had some stoner friends of mine come for a short stay. One of them is a bit of a chemist themselves, albeit is
a tad bit of a 'cook' as SM would say (though it is all the legal THC stuff. No meth.
I decided to demonstrate to them how to properly clean and concentrate sulfuric acid from drain cleaner, and it all worked without a hitch. I had left
the mantle on my balcony as I often do to let everything cool before moving the setup inside. Since it was late at night I wanted to do go to bed. I
had since switched everything off long before thing. But my friend had drop his earphone near the power bar that my mantle was plugged into... and he
accidentally turned it back on.
The result was... amazing. It has spent no less than 8 hours being turned on at full blast before I woke up and realized that the thing was stuff on.
I had switched it on and readied all necessary emergency protocols (large amounts of bicarbonate water, long gloves and other PPEs, etc) And what
happened is that the flask was miraculously unharmed, and the inner sleeve on the mantle had acid on the sides that seeped into it.
After recovering my 98% H2SO4 (it HAD to be. I started out with 600ml of drain opener in a 2L flask and ended up with 400ml after all was said and
done) and bottled it away. I had first soaked the mantle's sleeve with large amounts of bicarbonate water before washing it with nearly a half gallon
of distilled water and leaving it upside down to let the water pool away from the insulation. Surprisingly it still works, albeit the power output was
reduced.
I decided to test it to see if it will still boil sulfuric acid. Surprisingly it still did, albeit it took twice the amount of time to complete the
operation. I cleaned and concentrated another 500ml of drain opener to make sure it still works.
I then decided to reboil the same acid to make sure it works. It did take as long for the lopsided bubbling to start again, but then I saw something I
didn't like. Maybe it was because I was boiling pure sulfuric acid this time, or maybe it was because I didn't add enough boiling chips, but there was
a large cloud of acid vapors pluming out. I didn't like it and switched off the heating. I did notice that a few drops of the acid did touch the clamp
holding it. So I gave it a quick spray of bicarbonate water. I also did spray the flask itself to make sure that no acid droplets touched my inner
sleeve.
I am not sure if it was due to my spraying to due to the irregular bumping, but I did see a crack at the back of my 2L flask. I really, REALLY don't
want to lose this mantle due to a stupid accident or have to replace the flask. I want to show you the 2L flask to ask for your opinion to see if it
is still usable. The crack is entirely on the inside and cannot be felt outside.
I figure it would still be safe other than boiling more sulfuric acid. The last thing I want is a flask full of acid cracking on my mantle. What do
you guys think?
I can't keep having this stuff happen. I need to take into consideration other people's possible errors now...
  
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numos
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Trash it or send it to a glassblower. It's not safe to heat anything in a flask with that big of a crack. If you insist on using it - maybe for
aqueous chemistry at rt...?
Honestly, cracks like that are fairly easy for a scientific glassblower to fix, you might be able to get it done for under a hundred bucks, but I
reckon it's a niche field so prices are likely to vary widely.
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ManyInterests
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I'll take your word for it. Also I don't know any scientific glassblowers, and if the prices are what you saying it would be much cheaper for me to
buy another 2L flask than have it repaired.
I have other 1L boiling flasks that I can use in the meantime. I will not be doing anything dangerous like boiling sulfuric acid with this anymore.
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j_sum1
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Probably the thermal shock of spraying caused the cracking.
Time to throw it out. Unless you have a neighbour who is a glass blower and can fix it cheaply and has an annealing oven.
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ManyInterests
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Quote: Originally posted by j_sum1  | Probably the thermal shock of spraying caused the cracking.
Time to throw it out. Unless you have a neighbour who is a glass blower and can fix it cheaply and has an annealing oven. |
That is possible. But if that was the case, why didn't it crack in other places?
Regardless, I'm going to keep the flask since I will need some ground borosilicate glass for other projects. I can get another 2 liter flask. I will
be using my 1 liters in the mean time.
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ManyInterests
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OK I need to write this in here for posterity.
When boiling sulfuric acid, the 1 liter boiling flask is vastly superior to the 2 liter boiling flask. The volume is irrelevant. 500ml boiled in a 1
liter boiling flask with a good deal of boiling chips will boil like water and is far less likely to spew acid all over the place or have sulfuric
acid vapor eruptions. The 2 liter is far more accident prone than the 1 liter.
While I have lost my 2 Liter flask, I won't be shedding any tears. I can get another one in a few months. The good news is, my mantle is fine and I
learned many lessons from this. Ironically if the accident had happened with the 1 liter boiling flask it wouldn't have resulted in the same issue.
[Edited on 8-11-2022 by ManyInterests]
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Texium
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Moral of this story: unplug your heating devices when you are not using them, don’t just turn off the switch!
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ManyInterests
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| Quote: Originally posted by Texium | | Moral of this story: unplug your heating devices when you are not using them, don’t just turn off the switch! |
Amen!
On another note, I should have let last night's sulfuric acid boil go a little longer, while I did end up with around 375ml (from 400ml starting) I
did see shimmering when I added it to the other bottle, meaning that it wasn't as concentrated as the others. But that is fine, it is still extremely
concentrated. Maybe not 98% but at least 95 or 96% Good enough for almost everything.
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