Sciencemadness Discussion Board

Hydrogen and the flying stopper

gardul - 1-12-2014 at 23:11

So I was trying to make a video just now on the production of hydrogen.

Seems simple enough right?

150ml of HCL
2g of aluminium.

The stopper had two holes. one had a glass tube and the other was for safety measures. Just in case pressure got to much there was still another way for the gas to escape.

When I put the flame near the glass tube... it ignited.......... But it did something I didn't expect. it hurled the stopper at my face. Luckily i was wearing safety glasses.

So what I did learn you may ask?

HST stoppers are rather loose. And further inspection I notice that gas was leaking from the sides as well.

While I don't mind HST glassware for the most basic of things. Their stoppers ARE NOT SAFE for anything under pressure.

Just figured I would share a dumb ass moment.

[Edited on 2-12-2014 by gardul]

Jylliana - 1-12-2014 at 23:16

As gas heats up, it expands.

I'm not whether the heating up or the actual combustion was the cause of the sudden increase in volume, but that's what I first thought of.

gardul - 1-12-2014 at 23:23

Yes. I am sure that what caused it no doubt. But just take it as a lesson learned. Loose stoppers are a HUGE NO NO. But I actually Learned a lot from this little experiment even if I failed it.

I would also like to note that I was producing WAY TO much Hydrogen for the experiment. and next time I will use less.

[Edited on 2-12-2014 by gardul]

Jylliana - 2-12-2014 at 00:44

Loose stoppers aren't always a no-go. I'd rather have a stopper blow out(away from my face), than a glass tube shatter in my face.

In fact, I use this feature to demonstrate gas expansion by heating a flask with a lighter and then let the stopper blow towards the ceiling.

[Edited on 2-12-2014 by Jylliana]

forgottenpassword - 2-12-2014 at 01:05

Be very careful that all of the air is removed from the flask before you ignite it. If there is some oxygen inside the flask then it will result in an explosion. It sounds like you DID produce a small explosion -- thankfully you had purged MOST of the oxygen beforehand. Overkill with purging air/oxygen from glass containers of hydrogen is never a bad idea.

gardul - 2-12-2014 at 01:05

Quote: Originally posted by Jylliana  
Loose stoppers aren't always a no-go. I'd rather have a stopper blow out(away from my face), than a glass tube shatter in my face.


That's true. And I guess it might have been a good thing in this case? But from what I caught on film, the hold flask didn't ignite inside. I Just think there might have been to much pressure at the top of the flask which caused the blow out.

I guess I could have worded it better. In this experiment I didnt want loose stoppers. On video, I can see the gas escape the sides and when it ignites, it travels between the stopper and gas and the extra hole in the stopper. So I figure I won't be trying this again as of yet until I can fiure out what exactly went wrong.

The next time I do try, I need figure out when to ignite it. I also think my timing might have had to do with the issue as well. Time will tell.

be safe everyone.
Quote: Originally posted by forgottenpassword  
Be very careful that all of the air is removed from the flask before you ignite it. If there is some oxygen inside the flask then it will result in an explosion. It sounds like you DID produce a small explosion -- thankfully you had purged MOST of the oxygen beforehand. Overkill with purging air/oxygen from glass containers of hydrogen is never a bad idea.


Thank you. I will make sure of this next time. do you have any recommendations on how to do this?

[Edited on 2-12-2014 by gardul]

forgottenpassword - 2-12-2014 at 01:13

Simply time. Hydrogen is a good purging gas, so if it was left purging slowly for half an hour then that wouldn't be a bad idea. I can't give specific recommendations because I don't know, to be honest -- I've never tried it. I once had a near-runaway* dissolving sodium in boiling IPA on a 5 litre scale, which scared me enough not to want to mess with hydrogen for fun!

Using a 2-stoppered flask was a good idea, though. Maybe it saved you from exploding glassware in this case!

*Well, maybe it wasn't. The hydrogen was carrying the IPA vapour up and past the condenser at a faster rate than it could condense it.

[Edited on 2-12-2014 by forgottenpassword]

gardul - 2-12-2014 at 01:17

I try to do everything on a smallish scale first. in case some thing like this happens, the damage isn't to bad. and I always where safety gear.

Praxichys - 2-12-2014 at 05:27

Keep in mind that the lower/upper explosive limit for hydrogen in air is is 4% and 75%, respectively. A concentration anywhere between those values can burn in a closed container.

Based on that data, unless you are sure you have purged at least 96% of the air from the flask, there is an explosion risk. It might be a good idea to purge with CO2 first, from a separate gas generator.

https://www.mathesongas.com/pdfs/products/Lower-%28LEL%29-&a...

Amos - 2-12-2014 at 07:09

I've ignited confined hydrogen in thick-walled apothecary jars, and they stand up to it quite nicely. But I wouldn't expect the same from thin lab glass, especially not something like a test tube.

Zyklon-A - 2-12-2014 at 11:12

No Tears Only Dreams Now What concentration of hydrogen-oxygen/air did you use?

gardul - 2-12-2014 at 11:20

Quote: Originally posted by Praxichys  
Keep in mind that the lower/upper explosive limit for hydrogen in air is is 4% and 75%, respectively. A concentration anywhere between those values can burn in a closed container.

Based on that data, unless you are sure you have purged at least 96% of the air from the flask, there is an explosion risk. It might be a good idea to purge with CO2 first, from a separate gas generator.

https://www.mathesongas.com/pdfs/products/Lower-%28LEL%29-&a...


That you very much for that link.

I will have to rethink this and figure out how I can get most of the air out.