MrHomeScientist
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Barking Dog Reaction
I'm going to do the Barking Dog reaction as part of a chemistry demonstration show I'm working on, but I've had a difficult time finding any concrete
information about it. Does anyone have any experience performing this reaction? I'm going to start out small while I figure this thing out, to
minimize reagents and the risk of shattering the reaction vessel. I'll likely add a Lexan safety shield when I do this demonstration, just in case.
What I'm looking for is the amounts of reactants to use, and a chemical equation for the reaction.
I'll be using nitrous oxide and carbon disulfide, so I think the reaction would be
8 N2O + 4 CS2 --> S8 + 4 CO2 + 8 N2
If that's the case (and if I did my stoichiometry right), that means that for a 500mL container filled with N2O gas, I'll need 0.66mL of CS2. From the
videos I've seen of the experiment, you only need a very small amount of CS2, but that seems tiny so I'm not positive it's correct.
If anyone's done this reaction before and has any practical advice, I'd love to hear it!
If you haven't seen this before, this page has some great videos and an explanation of it.
Edit: Also, anyone have any idea where to get those giant glass tubes everybody uses for this reaction? I haven't found any sources for those either,
and I definitely want to ramp up to that scale eventually.
[Edited on 12-9-2010 by MrHomeScientist]
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ScienceSquirrel
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Mood: Dogs are pets but cats are little furry humans with four feet and self determination! 
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I have actually seen this reaction done on a large scale.
I strongly suspect that the glass tubes are custom made.
Very large glass stock is available and I reckon a competent glass blower could make you a set for a few hundred notes depending on your local
currency and whatever deal you can cut.
The reaction is not an explosion so if the glass is of an appreciable thickness, say a few mm and well annealed there should be no problem.
In the demo I saw chiildren were invited on stage to fire up the dogs.
I think the stoichiometry varies with the proportion of reactants employed with sulphur dioxide and carbon monoxide also being formed. The best idea
is to adapt an existing recipe and / or experiment until you find one that works with your set up.
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woelen
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I have done this experiment myself, one time in a small tube and one time in a fairly big tube.
http://woelen.homescience.net/science/chem/exps/barkingdog/i...
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The WiZard is In
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Quote: Originally posted by MrHomeScientist  | | I'm going to do the Barking Dog reaction as part of a chemistry demonstration show I'm working on, but I've had a difficult time finding any concrete
information about it. Does anyone have any experience performing this reaction? I'm going to start out small while I figure this thing out, to
minimize reagents and the risk of shattering the reaction vessel. I'll likely add a Lexan safety shield when I do this demonstration, just in case.
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Me the analogue guy again... but first this is not the
Barking Dog Reaction which uses CS2 and white P.
The most complete description of the Explosive Reaction of
Nitric Oxide and Carbon Disulphide is in :—
BZ Schakhashiri
Chemical Demonstrations : A Handbook for Teachers of Chemistry
V 1 of 4. P. 117-120.
BZS cites Mellor VIII:232-33 [Incorrect pages - I am still looking.]
suggesting 30% CS2, he suggests 31%.
"The amount of CS2, however, should not vary greatly from that
described because larger amounts of CS2 tent to suppress the
flame and smaller amounts tend to produce more violent
explosions."
Library time!
See also
http://www.chem.leeds.ac.uk/delights/texts/expt_22.html
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MrHomeScientist
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Thanks for all the great advice!
Woelen, your site was very informative. Have you ever shattered a container doing this? The first video in the link in my original post shows one
blowing out the bottom of one of their giant tubes, but I suspect there's very little chance of this happening on small scale. I think I'll still make
a small plexiglass safety screen for it just to make the higher-ups happy 
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The WiZard is In
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This months winner of a two week old dead cat for a
fuzzy reference. BZS!
It is not in volume 8 of Mellor's 16-volume opus it is in —
Volume VIII, Supplement II N (Part II)
"The rate of propagation for the mixture was about 3 m
per sec. at 14 cm. Hg total pressure and the dimensions of
the vessel seemed to have little effect." Ref. 39.
Byda 30-31% CS2 is recommended for maximum light emission.
I agree - use a shield.
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MrHomeScientist
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Well I sucessfully performed the barking dog reaction full-scale, and I thought I'd share the experience here.
The lab I now have access to conveniently had a long glass tube 48" long and 1.5" in diameter, which I was able to use as a reaction vessel. I filled
this with N2O gas and stoppered both ends. This wasn't an exact procedure - since the gas is invisible, I had to just make a guess as to when a
sufficient amount was reached. A better way would be to do this over water of course, but the size of the tube and the restrictions of the show made
this awkward. This was done immediately prior to the demonstration, to reduce gas leakage from the tube.
To this was added 0.75mL of CS2, and the tube was upended and swirled around a bit to volitilize the CS2 and ensure the gases were mixed. Some minor
pressure had to be released because of the buildup of CS2 vapor. The tube was held behind a heavy plexiglass shield, a stopper was removed, and the
mix was ignited with a long grill lighter.
A small blue flame started burning at the top, which slowly sank down the tube. When it was about 1/4 - 1/3 of the way down, it suddenly rushed down
the length of the tube with the characteristic bright blue glow and loud "bark." It left a nice coating of yellow sulfur on the inside of the tube
when finished. I was really pleased at how great it turned out!
I had done this once before in testing using the same procedure, but it was quite windy outside when we tried it and it was difficult to get the
lighter to stay lit. When it finally went off, the reaction went much quicker and sped down the whole tube right away. It also gave off a more reddish
flame. I suspect this was because we had to cap and uncap it over and over while trying to light it, so contamination from the air got in the tube or
the gases became diluted.
There were some pictures taken of the event, and once I get those if I'm able to I'll post them here for your viewing pleasure.
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atomicfire
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I have done this countless times using an approx 3" dia tube approx 4ft long.
We filled the tube with water then N2O was bubbled up into the tube from the bottom displacing all the water inside.
When ready, around 2ml was squirted into the tube and the tube was quickly inverted several times and pressure was released.
The tube was taken into the dark room and ignited and the characteristic blue flame and a loud (the best I can describe it) whoooooomp! Needless to
say the cleanup is horrendus unless you enjoy sulfur.
I also did a similar experiment with white phosphorus but can't remember what all was involved.
Fun times!
ban DHMO
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