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Author: Subject: Help! Frozen joint. I think due to NaOH crystals.
alking
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[*] posted on 19-3-2016 at 21:28
Help! Frozen joint. I think due to NaOH crystals.


So I added some NaOH into a flask, some crystals got stuck around the edge, and I thought I cleaned them off, but apparently not. Now I have a 400mm reflux condenser stuck to it : /. I've tried twisting as hard as possible, banging on it rather hard with a plastic bottle, heating the outer joint with a torch, spraying 70% alcohol around the joint and waiting an hour or two, and I've cussed at it very loudly, but so far no go. The only other thing I can think of is putting it into the freezer but because the condenser is so big it will not fit. Maybe letting it sit overnight with solvent, or even days, but I am kind of beginning to think I'm going to have to break my flask. Does anyone have any advice? I really hoping this isn't lost.
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[*] posted on 19-3-2016 at 21:44


One technique for fixing stuck joints which has been quite successful for me is WD-40. Make sure the joint is affixed vertically, spray some WD40 around the joint then let it sit for 30-60 minutes. That's worked for me every time, though I don't believe I have ever chemically bound them, as you may have in this case (silicates are quote strong adhesives!). It's worth a shot though. If that doesn't work, heating and cooling the outer joint several times might help to weaken the bond and eventually allow the joint to separate.



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[*] posted on 20-3-2016 at 06:40


Ok, well I was able to get my condesor off finally by twisting at the kneck while smashing at the base and then I got my stir bar out of the flask by throwing it against the cement floor. I'll have to remember this trick for the future. After smashing it into pieces the damn joints were still frozen together too, I don't think there was any hope. That condensor was quite possibly my most expensive piece of glass at that : /. Not having a great day so far.
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[*] posted on 20-3-2016 at 08:25


Heat the ground glass joint directly but gently using a gas flame. Every so often twist the joint firmly and see if it will move. The differential expansion of the glass caused by the outer/inner temperature difference works well in helping to unfreeze it. Has worked every time for us, especially with alkali 'freezes' which are apparently quite typical.



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[*] posted on 20-3-2016 at 09:03


I had tried that numerous times and it wouldn't budge. It's broken now anyway. Even once broken I couldn't remove the fused joints though. I have only had stuck joints a couple of times in the past and they were nothing compared to this, though I do believe this was my first chemically fused joint as opposed to simple thermal expansion and contraction.

Do strong alkali solutions typically cause this or is it likely due to how I loaded the flask (adding crystals instead of solution)? If so are there any steps I can take in the future to avoid this?
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[*] posted on 20-3-2016 at 13:04


Quote: Originally posted by alking  


Do strong alkali solutions typically cause this


Yes, notoriously.
You can use Teflon sleeves to prevent it.
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[*] posted on 20-3-2016 at 14:03


Yeah, I was reading about those earlier, I'll have to pick some up.
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[*] posted on 20-3-2016 at 14:13


funny. Today i thought i had my first ever frozen joint.

500ml RBF and the stopper - it would not twist or be pulled out.

I'd put the stopper in while the contents were hot, and this was 30 mins later.

Suspected that the air etc inside had contracted causing a vacuum.

I just heated it up a little and the stopper popped out, yet other glass-destroying scenarios did pop into mind.

Edit:

Second frozen joint. First was a burette which had NaOH in it overnight (lazy/stupid) : the valve stuck so hard that the glass broke whilst trying to free it with a hammer. That was glass/teflon, so beware NaOH in all cases, not just glass-on-glass.

[Edited on 20-3-2016 by aga]
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[*] posted on 20-3-2016 at 15:05


Man, now I'm scared. How much glassware am I going to lose over time?!
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[*] posted on 20-3-2016 at 21:18


I have had this same thing happen to me years ago by adding sodium hydroxide to a hot flask and the joints freezing together. They are pretty solidly stuck and I still have not got them apart to this day. I have tried most of the thing listed in the above post apart from smashing them but nothing worked.
It's never happened again so I wouldn't be too worried, just make sure the joints are always greased especially when sodium hydroxide will be put in apparatus.




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[*] posted on 21-3-2016 at 07:57


I've been lucky so far and have avoided any frozen joint mishaps. Just remember to disassemble your apparatus as soon as you can, and grease your joints.


I now have a feeling of dread that I will return to this thread some day soon with an entirely different story.
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[*] posted on 21-3-2016 at 08:47


All glassware can be safely kept forever - just don't use it, ever !

You got to be brave to get anything done.

Try not to be too stupid and it'll all be fine for years.

I've lost most glassware during cleaning rather than actually using it.
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[*] posted on 21-3-2016 at 16:21


I'm hanging on to a condenser that has a broken joint inside the female 24/40 end. I can't get a purchase on it due to the way it broke and subsequent attempts to get the male 24/40 part out. I have tried sonication (this is a word), WD 40, vegetable oil, NaOH solution, MeOH, acetone, ligroine, naptha, etc. I am afraid to heat the joint too much. I want to recover the condenser as it is of a type normally provided in chem class kits. It has bumps above the bottom joint to hold packing material and I have used it as a column. I have longer better columns but I dislike losing glassware. One nice thing about is it can be warmed with water circulation directly from a faucet that mixes hot and cold. My last resort is the glassblower. One other possibility would be to find a rod narrow enough to pass the bumps but stiff enough to whack the rim of the stuck inner joint. I haven't found one yet.



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[*] posted on 23-3-2016 at 06:51


I have always had luck with a blow drier / heat gun. It can take a few minutes but it eventually has worked the few times I need it to. But you guys are probably doing slightly more "hardcore" stuff then me. Still in simple distillations but even i have learned to grease and disassemble when possible so frozen joint must be at least somewhat common.



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[*] posted on 23-3-2016 at 18:17


I once left sodium benzoate solution in a separatory funnel with a stopper for months. It would not budge. I had to leave it in water for a day and it came off.

While working with calcium hypochlorite, it etched my glassware where the crystals were stuck on the glass and slowly dissolving. The concentrated Ca(OH)2 must have done it.

A RBF 1 L, I dissolved some NaOH in water. The bottom area where the NaOH was sitting got etched. Nasty stuff!




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[*] posted on 23-3-2016 at 19:12


Hahaha. I did the same thing with the same flask. Oh well. I didn't pay much for the RBF and they are available and cheap. Besides, if it's truly etched where's the problem?



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[*] posted on 24-3-2016 at 14:32


Soak it in Viniger solution, to dissolve the hydroxide, the bubbles keep the water moving and excreting the resultant salts.

Takes time but patience is a virtue in all that sort of stuff.
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[*] posted on 3-4-2016 at 16:55


Had that happen to today. A simple heatgun fixed it. I will now buy some lubricant for it.
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