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Author: Subject: Hydrogen in chlorine flame sound
Endimion17
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[*] posted on 21-8-2011 at 15:24
Hydrogen in chlorine flame sound


I've just had a funny and weird experience.
Have you ever noticed a peculiar sound this flame produces? It's rarely quiet.
I've just burned some hydrogen in 1L flask to take some nice photos, and there was this weird WOOOOOOO sound. Kind of the sound of microphonics, but low pitched.

I uploaded the video so check for yourself.
<iframe sandbox width="480" height="390" src="http://www.youtube.com/embed/nUzugUuwFVA" frameborder="0" allowfullscreen></iframe>
(sorry about the crumbled background)

Touching the flask does nothing, so does covering the neck, and the lower the flame is positioned in the flask, the louder the sound. And it can be really, really loud. It got so fun dipping the flame that I forgot it was midnight so I woke up some people on the upper floor, made them come down and use foul language. :D
Putting hand above the neck of the flask (hydrogen chloride mist comes out; well what the heck, you live only once, and I've got some hand lotion to soothe the pain) reveals tingling vibrations of the air column.

What the hell just happened? It's just warm HCl exiting a flask. Mind that this happens in smaller flasks, too.

I think it's some kind of resonance between the flame and the warm gas exiting the flask neck, because as soon the sound is made, the flame gets all messed up. It reminds me of Ruben's tube.

Now I'd like to try this with a much larger container. :D




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hkparker
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[*] posted on 21-8-2011 at 16:30


Very cool! thanks for sharing.



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MrHomeScientist
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[*] posted on 22-8-2011 at 06:42


Neat video. I'm sure it's just resonance - the same as when you blow over the top of a glass bottle (the sound is nearly the same, too). The reaction creates a warm gas, which quickly rises out of the flask and sets up some resonance with it. The tingling sensation you feel is your flesh dissolving in HCl :P
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blogfast25
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[*] posted on 22-8-2011 at 12:46


Quote: Originally posted by Endimion17  
What the hell just happened? It's just warm HCl exiting a flask. Mind that this happens in smaller flasks, too.

I think it's some kind of resonance between the flame and the warm gas exiting the flask neck, because as soon the sound is made, the flame gets all messed up. It reminds me of Ruben's tube.

Now I'd like to try this with a much larger container. :D


If it's resonance (almost certainly true), the pitch should be in accordance with the flask size: small flask, higher pitch, - larger flask, lower pitch.

Looks like you've created a HCl fuelled saxophone! :cool: Sure beats 'whale songs'!

[Edited on 22-8-2011 by blogfast25]




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FrankRizzo
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[*] posted on 22-8-2011 at 12:56


I believe the hydrogen is reacting in an oscillatory manner at the tip of the tube (flashing inside the tube and back out). That oscillation is then resonating the volume of gas inside the flask.
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Endimion17
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[*] posted on 22-8-2011 at 13:24


This should be repeated with oxygen instead of chlorine. Something tells me that chlorine's large density helps with the resonance.
It would be just awesome if the flask cracked...




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Morgan
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[*] posted on 22-8-2011 at 18:38


Here's some 1802-3 vaguely related subject matter, maybe a few crumbs.
http://www-chaos.engr.utk.edu/hst/delarive-philmag-14-iv.htm...
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blogfast25
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[*] posted on 23-8-2011 at 04:50


Quote: Originally posted by Endimion17  
This should be repeated with oxygen instead of chlorine. Something tells me that chlorine's large density helps with the resonance.




http://en.wikipedia.org/wiki/Speed_of_sound

"For different gases, the speed of sound is inversely dependent on square root of the mean molecular weight of the gas, and affected to a lesser extent by the number of ways in which the molecules of the gas can store heat from compression, since sound in gases is a type of compression. Although, in the case of gases only, the speed of sound may be expressed in terms of a ratio of both density and pressure, these quantities are not fully independent of each other, and canceling their common contributions from physical conditions, leads to a velocity expression using the independent variables of temperature, composition, and heat capacity noted above."

But the resonance (standing sound waves) should really only depend on the size of the cavity, I think... :(




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watson.fawkes
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[*] posted on 23-8-2011 at 06:18


Quote: Originally posted by blogfast25  
But the resonance (standing sound waves) should really only depend on the size of the cavity, I think... :(
Characteristic wavelengths depend on the boundary conditions, i.e. the cavity. Speed of sound determined by chemical composition and physical conditions (such as temperature). Combining the two gives you frequency.

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blogfast25
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[*] posted on 23-8-2011 at 08:49


So the pictch, for a given cavity, would depend on the gas used.



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