"...it's always good for a scientist to be proven wrong..."

January 11, 2013 4:37 AM

Professor Martyn Poliakoff of Periodic Table Videos fame learns something about burning balloons full of hydrogen via high speed camera footage.
posted by loquacious (34 comments total)

That was really interesting, and super fun to watch. Thanks for posting it!
posted by Superplin at 5:11 AM on January 11 [5 favorites]

Oh yes it was, but he didn't provide the answer to the question he posed - why the burning hydrogen emits light contrary to its usual behavior, even when mixed with oxygen in stoichiometric proportions? He has initially proposed a hypothesis (because the heat produced by the reaction excites the gas) and kinda sorta proved it, but not really, because without a spectrum we don't know what exactly is producing the light. On the other hand, this hypothesis sounds sort of obvious because that's why any kind of burning produces light...

The vision of two professors exchanging amazing news of the exploding balloons over lunch was truly hilarious - it's as if they never watched YouTube videos while work waits to be done. And I felt a pang of envy, because I wish I had a work that exciting.
posted by hat_eater at 5:25 AM on January 11 [5 favorites]

Related: Reports of the Hindenburg disaster mention yellow-red flames at the beginning of the fire.
posted by beagle at 5:41 AM on January 11

I was wondering that as well, hat_eater. He seemed so satisfied by his experiment, but I was left wondering why there was light at all. It did seem like the balloon might be burning with the hydrogen/oxygen mixture, perhaps that's part of it.
posted by mollweide at 5:52 AM on January 11

No discussion of the rapid combustion of everyday objects can be complete without a reference to Ig Nobel Prize winner George Goble, who liked to accelerate his backyard charcoal fires with liquid oxygen.
posted by ubiquity at 6:01 AM on January 11 [5 favorites]

I do hope that the good Prof hasn't been trolled by a Brown's Gas conspiracy theorist.
posted by scruss at 6:09 AM on January 11

I don't think that the balloon is burning at all. Even with the stochiometric mixture you can see pieces of rubber flying away.
My feeling is that what is burning is the air around the balloon. More specifically, the hydrogen+oxygen reaction is so exothermic that it raises the temperature of the surrounding air to the point that the nitrogen and oxygen in the air react to form nitrogen oxides (NOx), as in a lean-burning engine. Or maybe it's just the colour of the heated-up air around the flame: the discharge spectrum of nitrogen has plenty of yellow and red.
posted by Skeptic at 6:14 AM on January 11 [6 favorites]

The phenomenon of the person lighting a match causing a gas explosion ending up pretty much ok but in a crater of destruction should be known as the Yosemite Sam Effect.
posted by unsupervised at 6:25 AM on January 11 [17 favorites]

I propose that the orange/red is the powder (maybe/likely cornstarch) that is used to keep the rubber of the balloons from sticking together pre-inflation. A handful of balloons has a powdery feeling unlike the feeling of a washed balloon. I propose trying the experiment with the hydrogen/oxygen mix in a thin glass vessel with some remote ignition source to see if there's till that bright flash.
posted by zengargoyle at 6:26 AM on January 11 [4 favorites]

Given the source of the video, it's perhaps more appropriate to refer to Professor John Salthouse, who was a colleague of Professor Poliakoff, and who pays tribute to him in this video.

I made an earlier comment on the blue about Salthouse here.
posted by daveje at 6:27 AM on January 11

Ha, thats awesome!

MetaBugs and I once did something similar on MetaFilter proper a while ago at the tail end of a thread, it starts here.
posted by Blasdelb at 6:41 AM on January 11

To back up Skeptic's thinking, here is a short video of a hydrogen/oxygen mixture burning out of a plastic bottle with an invisible flame. The flame becomes visible only when the bottle is squeezed, forcing the burning mixture to interact with the surrounding air. However, in the extended comments on that video, there is mention (reliability unknown) that nitrogen is actually rather non-reactive.

And: Here is a scientific paper about the luminosity of hydrogen flames. "The common misconception that hydrogen flames are not visible is examined. Examples are presented of clearly visible emissions from typical hydrogen flames....Tests were performed to show that this emission does not arise from carbon or nitrogen chemistry resulting from carbon-containing impurities (hydrocarbons) in the hydrogen fuel or from CO2 or N2 entrainment from the surrounding air." Some nice pix and graphs but no access to full article.
posted by beagle at 6:48 AM on January 11 [1 favorite]

nitrogen is actually rather non-reactive

It does get frisky with oxygen, if given adequate motivation (read: very high temperatures). Otherwise, smog wouldn't be such a problem.
posted by Skeptic at 6:59 AM on January 11

Balloons of hydrogen are for wimps. The right way to do it is to use acetylene.
posted by Chocolate Pickle at 7:02 AM on January 11

There's also a difference between an explosion and a controlled flame. The fact that a bunsen burner with hydrogen gives almost no visible flame isn't necessarily relevant to what is happening in this video.
posted by Ickster at 7:03 AM on January 11

The Yosemite Sam Effect is the most interesting part of this to me. Does this apply to other "explosions" (say, an atom bomb) or just combusting gas?
posted by swift at 7:18 AM on January 11

These videos have wastedenhanced my work day.
posted by plinth at 7:20 AM on January 11

If you watch the frame-by-frame of the O2+H balloon, you can see light from the explosion happening inside the top of the balloon before it pops so I don't think it's reacting with the air that causes the light.
posted by VTX at 7:34 AM on January 11 [1 favorite]

I think the part he omitted from "Paul's" explanation is that atomic hydrogen atoms emit red light as part of the Balmer Series. This could be checked by examining the spectrum of the emitted light and seeing if it matches the proper wavelength (656.3 nm).
posted by Didymium at 7:40 AM on January 11

Came for the 'splosions, stuck around for the related REAL PLUTONIUM video.
posted by the painkiller at 7:45 AM on January 11 [1 favorite]

I'm not sure I'm buying that that plastic bottle contains hydrogen and oxygen. If you put a mixture of hydrogen and oxygen in a heavy glass bottle, which you've wrapped with about a half mile of strapping tape, uncork it, and hold the mouth near a flame, the resulting reaction takes about a tenth of a second and sounds like a cannon going off.

The sawtooth effect in the graphs that Beagle links to are probably from various spin states of water. Not nearly as exciting as when you spin iodine vapor with a very powerful holds little finger to mouth laser.
posted by Kid Charlemagne at 8:10 AM on January 11

The thing that bothers me about this video is that he says he was wrong, and I think that's not a good habit to be in. Wrong is when you have data that runs contrary to your assumption, but you're going to continue with your assumption anyway. So there!

Science is like trap shooting. Scientific wild ass guesses (you may have heard these described as hypotheses somewhere) is like making clay pigeons - the sport is in the shooting them down. Shooting them down with clever analysis of old data is like a trick shot.
posted by Kid Charlemagne at 8:40 AM on January 11 [1 favorite]

I was in an engineering club in college [shut up] that sometimes had meetings at the Professor Advisor's house. At one of the meetings or parties we had a contest to use a grab-bag of assorted objects to create a plane that would move up a string to a target point. There were prizes for most creative, fastest, etc.

The team I was on took the soda bottle and balloon in the grab bag as key components. We used a few easily obtained household materials and chemicals [in other words, we secretly raided the Professor's cabinets] to create Hydrogen in the soda bottle with the balloon attached.

This was a long time ago, and I can't remember whether we won or lost any of the contest categories. I can't even remember if our plane ever moved up that string. What I do remember, vividly, is that at the end of the meeting we moved outside, tied a tail of tissue paper or some such to the balloon, lit that tail on fire, and let the balloon full of Hydrogen go.

In short order, there was an impressive ball of fire in the sky directly over the Professor's house.

The Professor was not amused.
posted by It's Raining Florence Henderson at 9:43 AM on January 11 [1 favorite]

I wonder if the explosion might separate into two smaller parts because the hydrogen and the oxygen might not fully mix, die to their differing densities.
posted by Pronoiac at 10:40 AM on January 11

We used a few easily obtained household materials and chemicals [in other words, we secretly raided the Professor's cabinets] to create Hydrogen in the soda bottle with the balloon attached.

Lye (Drano) + Aluminum foil and a little bit of water.

You should note that if you do it wrong you end up with lye in your eyes.

Drano power actually has a few little bits of aluminum in it which is part of the heat reaction that helps liquify coagulated grease.
posted by JackFlash at 10:58 AM on January 11

The bits of aluminium are there to protect the aluminium pipes, should the user choose to ignore the warnings.
posted by hat_eater at 11:02 AM on January 11

hydrogen atoms emit red light as part of the Balmer Series

emission, emission, emission, emission, emission, emission, emission, emission.
posted by smidgen at 11:05 AM on January 11

The Yosemite Sam Effect is the most interesting part of this to me. Does this apply to other "explosions" (say, an atom bomb) or just combusting gas?

Poliakoff explains that, noting that the shock waves spreading out from the center of the blast cause the damage, and that a person positioned at the blast center might escape. And there have been some remarkable instances of ground zero buildings surviving atomic blasts (see here for some examples). But though it happens occasionally, the effect is not guaranteed by any means, nor even likely, and even if you DID survive at ground zero of an atomic bomb, you'd be a goner from the radiation. So please, don't try this at home.
posted by ubiquity at 12:24 PM on January 11 [1 favorite]

Now you tell me!
posted by It's Raining Florence Henderson at 12:29 PM on January 11

The right way to do it is to use acetylene.

Huh? This isn't common knowledge? My junior high school had acetylene gaslight fixtures in every room.
posted by charlie don't surf at 12:32 PM on January 11

I wonder if the explosion might separate into two smaller parts because the hydrogen and the oxygen might not fully mix, die to their differing densities.

Pretty unlikely; for the purposes of the video the oxygen and hydrogen gases can be assumed to be evenly mixed throughout the balloon. Inside that balloon the difference between the force applied by gravity over the 12 inch height of the balloon on the those O2 and H2 molecules is very very small compared to the average kinetic energy of those molecules. Off the cuff, I'd guess the force of gravity pulling the heavier molecules down in the balloon is thousands, if not many tens of thousands times weaker than the kinetic energy of those molecules that has them bouncing up and down and all about inside that balloon.

In ordinary conditions, like this balloon, gases mix homogeneously and each gas in the mixture acts as if it is the only gas present (fills the container fully). This is predicted by the ideal gas law and commonly observed in the air we breathe: why gases mix.

These assumptions do break down in some conditions, like with huge quantities of gases (such as our atmosphere and the systems that creates our weather), large differences in temperature and/or density (such as a CO2 based fire extinguisher releasing a large amount of cold, dense gas to displace the O2 feeding a fire), or a lack of mixing either through a short period of time or physical barriers separating the gasses.

Your hunch that two gases won't completely mix in a confined area is pretty common; I think this comes from the very effective high school chemistry demonstration of an excess of CO2 being added to a confined space with a burning candle. I wish there was a part two that that demonstration when the candle is easily lit again after letting the system sit undisturbed for five minutes to show that gases will indeed mix homogeneously, if left alone and the candle will burn again.

Liquids mix in the same way that gases mix, but you'd be hard pressed to convince anybody that thinks they could buy a bottle of 80 proof vodka, let it sit undisturbed for a short time, then siphon off the top 60% of the volume to remove all the water leaving behind 100% of the heavier ethanol that settled to the bottom of the bottle. We intuitively know that liquids don't behave this way because we can see the denser caramel coloring of Coke doesn't settle under the less dense soda while sitting on the shelf. Gases mix like liquids, only more easily so.
posted by peeedro at 2:34 PM on January 11 [2 favorites]

After he said it, I learned something else we didn't know: it's pronounced "stoy-kee-om-i-tree'.
posted by Twang at 2:43 PM on January 11

It is interesting that he was so distracted by the fact that the rubber wasn't burning that he lost sight of his original question: why is the flame reddish in colour? I suspect Skeptic is on to something.
posted by Decani at 3:36 PM on January 11

Wasn't it implied that the flame was red because of the gas outright glowing from the heat? It would be red because that's the lowest visible wavelength, not because of the inate property of the gas burning releasing those colors.

IANA chemist or physicist, but there are two ways light can be given off by hot things. The release of energy from combustion, and electromagnetic radiation given off by the glow of rapidly-vibrating, sufficently hot molecules. Burning hydrogen doesn't produce visible light, but glowing hydrogen does.
posted by JHarris at 3:44 PM on January 11