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Author: Subject: stopcock on pressure equalized addition funnel is stuck. Help?
ManyInterests
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[*] posted on 21-6-2023 at 10:36
stopcock on pressure equalized addition funnel is stuck. Help?


Last week I pulled out my brand new pressure equalized addition funnel for a series of ammonia synthesis. My ammonia synthesis was a great success and I ended up with 1000ml of 24% ammonia solution. After I was done with that, I decided to wash out the funnel and I left it to dry.

I was afraid that the stopcock on it was going to be a little too easy to pop out, so I kept it with the rubberband that it came wrapped in. I put it in the open position and washed out the hole, but I didn't roll the stopcock around.

Now I find that it is completely shut. I was told that I need to heat it up with a heat gun to loosen it and give it a few taps with a rubber knife handle. I did that, but it did nothing. I read that potassium hydroxide might be an adhesive...

As of right now, I am going to try to boil the bottom part of my funnel in hot water. Any help?

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[*] posted on 21-6-2023 at 10:40


OK guys, I just fixed it... no need for further action. I just put the end of the funnel in a pot of water and boiled it for a while. After a brief bit of drying, it got loose. It's all fine now.
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[*] posted on 21-6-2023 at 11:26


Quote: Originally posted by ManyInterests  
OK guys, I just fixed it... no need for further action. I just put the end of the funnel in a pot of water and boiled it for a while. After a brief bit of drying, it got loose. It's all fine now.


Exactly what i was just getting ready to suggest!!




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[*] posted on 21-6-2023 at 11:32


It works good for my CO2 generator now. I am bubbling through the left over liquid, as urea and potassium hydroxide can have some potassium carbonate and bicarbonate made as a by product. I am bubbling a huge amount of CO2 (1000g of baking soda and 3l of vinegar), into the left over liquid after dissolving it. I already boiled what was left to near dryness to get rid of whatever bits of ammonia that were left. The CO2 should convert what is left into carbonate.
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Dr.Bob
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[*] posted on 22-6-2023 at 09:18


Glad it worked OK. I have had many stuck stopcocks like that, usually heat or sonication works, but best to take the joint apart when not in use and grease it well. PTFE stopcocks can be better, but they tend to get scratched and leak, as well as not work well with some chemicals.
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[*] posted on 22-6-2023 at 18:04


What chemicals would attack PTFE? I recently ordered a sep funnel and decided on a PTFE stopcock over a glass one because I heard the glass ones could be a headache.



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[*] posted on 22-6-2023 at 20:08


Very few chemicals attack PTFE as far as I know. I got a funnel with a glass stopcock because the Chinese lab glassware company only had that available on their aliexpress store.

Most things will not attack glass, except for hydroflouric acid. But I have no interest in that compound, so I am not worried. I learned now what I need to do in using/maintaining my funnel. When cleaning, remove it to dry and only reinsert it when everything is fully dry again.
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[*] posted on 23-6-2023 at 14:41


Bromine and some strong bases can slowly attack PTFE, among a few others. It is a small number of harsh chemicals. PTFE ones are much easier to use than glass, so only rare occassions need glass. You do need to be gentle on PTFE, leave the stopcock loose when not in use to avoid creating a dimple where the hole is.
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