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Dornier 335A
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A bit higher up on the page was a suggestion that water/peroxide/organics mixtures with energy content of more than 0.8 kcal/g can be initiated with a
detonator. This corresponds to 54% peroxide according to my calculations with EtOH as fuel.
Mixtures inside the explosive range but insensitive to impact are said to have an energy content of less than 1.2 kcal/g. This corresponds to 72%
hydrogen peroxide, again in combination with ethanol. So this means that the foam experiment is safe to conduct, at least with respect to the
plausible detonation of the liquid phase.
EDIT:
Zyklonb, cellolose forms a gel with high concentration H2O2 which can be detonated by a blasting cap but not by
heat or flame.
[Edited on 26-5-2014 by Dornier 335A]
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deltaH
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Thanks Dornier for your most excellent input as always shedding light on the sensitivity of the liquid phase, no doubt of great
importance!
Thanks unionised for being safety conscious, I respect that very much!
If anyone makes a youtube clip of this, please do post a link here!
[Edited on 26-5-2014 by deltaH]
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bismuthate
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Well I believe the subject of calcium carbide and hydrogen peroxide has been brought up before here. Perhaps KI and CaC2 with H2O2 in some proportions
could yield explosive foam (if done with detergent).
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deltaH
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Interesting idea bismuthate, thanks. Oxy-acetylene foam 
Might be difficult to time the production correctly, what I mean to say, the peroxide decomposition is fast, the acetylene production is not as fast?
Perhaps the two won't be mixed properly/uniformly.
If you exclude the catalyst, there is probaby enough impurities in crude industrial CaC2 to catalyse the peroxide decomposition.
I have no idea if one wouldn't also form calcium peroxide, but presumably, this would decompose?
[Edited on 26-5-2014 by deltaH]
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Zyklon-A
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Yes, that's very useful info Dornier.
I went ahead and tried acetone.
About 5 mL of 20% hydrogen peroxide, 5 mL of acetone, several grams of manganese dioxide (and soap) were paced in a beaker. It was ignited with a
fuse. Or at least that was the idea. Due to acetone's volatility, it was initiated by my lighter before the fuse even caught!
The "BANG!" was massive It certainly didn't detonate, [see below, the gasses may have detonated] but my ears were
ringing for a couple minutes.
[Edited on 27-5-2014 by Zyklonb]
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deltaH
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It sounds like the gas phase did detonate, no? We might have a good alternative for the exploding hydrogen balloon experiment...
[Edited on 26-5-2014 by deltaH]
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Zyklon-A
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Yeah, I guess.
I didn't think much of it was gaseous. I lit it within 10 seconds after adding it to the foam.
It was pretty cool, much louder than I expected.
[Edited on 26-5-2014 by Zyklonb]
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deltaH
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I wonder what the foam detonation looks like in slo-mo? Could be pretty neat!
I also wonder if the foam could possibly be facilitating a deflageration to detonation transition in the gas phase? Then again, I might just be
tripping 
[Edited on 26-5-2014 by deltaH]
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Zyklon-A
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For real! I wish I had a camera with a high speed option.
Dornier 335A could you do a video on it?
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Dornier 335A
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240 frames per second is not enough in this case, sadly. And I don't have any hydrogen peroxide.
Gas detonations usually propagate at around 2000 m/s, so not even Periodic Videos' high speed footage of an oxygen hydrogen balloon shows any delay at
all. http://youtu.be/qOTgeeTB_kA?t=3m54s
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deltaH
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Also, sound travels faster through liquids than gas, so perhaps the foam detonation is faster than a purely gaseous one? Then again, the foam might
have a retarding effect, we simply don't know as of yet. My money is on an enhancement 
[Edited on 26-5-2014 by deltaH]
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Zyklon-A
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A high speed video, even if it doesn't capture the the wave will certainly look better than seeing a pile if foam, touching a flame to it, hearing a
bang, and the pile of foam's gone.
I'll email periodic table of videos and ask if they can make a video on it. They've asked for video suggestions several times.
[edit] I'm not sure whether foam would help or not, it'd be rather hard to find out.
[Edited on 26-5-2014 by Zyklonb]
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deltaH
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That would be great Zyklonb, thanks.
[Edited on 27-5-2014 by deltaH]
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Zyklon-A
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OK, I sent the email. Can't say I expect them to make a video, but hopefully they do.
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The Volatile Chemist
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That'd be nice. What's their email?
As a side note, you might show them this post, to proove there is interest in the subject.
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woelen
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I read this thread with pleasure, but I also have concerns about safety. The toothpaste demo usually is done at quite a large scale with a lot of
foam. If foam with pure oxygen/fuel mix is ignited at such large quantities, then you might get really nasty accidents (e.g. blowing out windows, or
blowing out your ear drums). Glass may be shattered and the fire ball may become so large that it engulves the person who ignited the massive amount
of foam.
I would say, keep on thinking and experimenting, but use your common sense and stay safe. I think Zyklonb's experience with a small amount of acetone
demonstrates what can happen with large amounts.
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deltaH
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Thank you woelen, I have added a warning to the opening post emphasising these points for users who may read it for the first time.
Please feel free to modify it if you feel I have left out something important.
As always, safety first people please!
[Edited on 27-5-2014 by deltaH]
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The Volatile Chemist
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Being at a lack of resources, would MnO2 and H2O2 work for foaming? I've never really done it with more than a few mL
of peroxide, would it 'foam' enough?
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deltaH
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Zyklonb did it using MnO2, so should be fine, but one needs a tiny amount of liquid soap to get it to foam.
[Edited on 27-5-2014 by deltaH]
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The Volatile Chemist
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Quote: Originally posted by deltaH  | Zyklonb did it using MnO2, so should be fine, but one needs a tiny amount of liquid soap to get it to foam.
[Edited on 27-5-2014 by deltaH] |
Great! I'll be trying a small amount in the near future, gotta get some peroxide.
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Zyklon-A
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Yes, I included a link to this thread. I'll post the email in a few hours, I'm on my phone now and it's a pain in the @$$ to find stuff, ect. Or I
might just forward it to whoever asks.
[EDIT] Here it is:
| Quote: |
Hello, periodic videos.
I'm not sure if you guys are still doing high speed videos or not.
Me and several members on the chemistry forum sciencemadness, where discussing variations of the classic "elephant toothpaste" demonstration. The
idea is, rather than just using hydrogen peroxide, liquid soap (to produce foam) and a catalyst (generally potassium iodide) we added a volatile
liquid fuel as well. The pillar of foam is then ignited. The reaction is quite impressive.
Depending on several factors, it might burn with "whoosh" or a loud "bang!"
I was able to get the fastest reaction using acetone, but methanol, ethanol and isopropanol all gave great results too.
With the acetone, I believe the gas phase did indeed detonate.
I used 20% hydrogen peroxide, but 30-40% would surely be even better.
I think it would make a great video, to show the reaction in high speed. I tried several other ideas too, like bubbling hydrogen through the foam,
acetylene would probably be even better.
Here is the thread were it is being discussed:http://www.sciencemadness.org/talk/viewthread.php?tid=30447
...
Anyway, I hope to here back from you guys.
Regards, Amos Backstrom. |
[Edited on 27-5-2014 by Zyklonb]
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deltaH
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Looks good Zyklonb, thank you.
I'm started to think of some interesting things one might do with such exploding foams that could facilitate learning / be good for demo's, taking
advantage of the fact that working with these foams allows one to hold a combustable gas mix in the open temporarily.
Something that has come to mind is preparing a small amount of foam and loading tens of foam millilitres into a small rolled paper cone that
has its pointed end cut off so to make a second smaller hole there, then lighting it through the narrow end with a match tied to a wooden rod, the
idea being to make a little mini vortex cannon using the foam.
When directed at light stacked objects some short distance away from the larger opening (say 0.5 - 1m away), perhaps this could collapse them, for
example maybe a stack of light-weight inverted polystyrene cups.
I think so long as one keeps the size small and works with paper and such and wears eye and ear protection, this could be reasonably safe.
I would use alcohol not acetone to tone it down a bit.
I'm reasonably sure the paper cone should be afixed to something with some duct tape.
Does this sound too dangerous / stupid thing to do?
[Edited on 27-5-2014 by deltaH]
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Zyklon-A
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No, that sounds fun, I'd like to try that sometime.
I'm not entirely sure what kind of setup you're talking about though, could you upload a picture from "Paint'' or something?
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deltaH
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Something like this...
Maybe someday this...
https://www.youtube.com/watch?v=2VpLRpcL9CA
Sorry, too lazy to draw the foam, but basically you'd scoop some foam into the open cone vertically, then tape it down with some duct tape so that the
cone lies on its side and will naturally point upwards at a slight angle.
[Edited on 27-5-2014 by deltaH]
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Zyklon-A
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Ah, I see. It took a while, but it makes sense now.
I wish I had a better fuel, almost out of isopropanol, don't have any more methanol, and my ethanol is too dilute.
Maybe if I diluted acetone it would be safer?
Anyway, it's something I want to try when I get home, I've never made a vortex cannon before, but it sure would be fun.
[EDIT] The "cone" would have to be quite strong right? Based on how loud the explosion was. And that was un-confined
[Edited on 27-5-2014 by Zyklonb]
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