yeah
yep The Barking Dog experiment is one of
our favorites we do it very frequently
well let a
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match it is a reaction of n2o carbon
disulfide and when you ignite them you
get a blue flame and a great
V and when we recorded it in slow motion
we realized we didn't understand the
reaction as well as we thought we did so
now we've decided to explore it a bit
further and the first thing we decided
to do was instead of having the tube
vertically to have it horizontally well
I have never seen the experiment done
anyway except vertically so this may be
a real first
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the first thing that's interesting is
that the gas lights long before the
flame actually gets to the edge of the
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tube the second thing was that we
noticed something that we've seen before
the flame shoots along the tube and then
suddenly stops and bounces and goes
rather more slowly but
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oscillating now up till now we had
assumed and it may be the right
explanation that the experiment produces
a shock wave that hits the bottom of the
test tube or the big tube and comes back
again so the flame going this way meets
the shock wave coming back which stops
it for a minute like being thumped so we
did another experiment with a tube with
a rubber buang at the end instead of
being a closed big test tube what we
thought might happen the bung might
shoot away like a cannon
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as before the flame started
bouncing but if there was a shock wave
it wasn't enough to remove the bun and
if you think about it it's really quite
a heavy bum and Neil being a tough guy
had pushed it in quite hard
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so then we thought let's do the
experiment with a tube open at the
bottom as far as I know nobody has ever
tried such an experiment or at least
they may have tried it but I've never
seen it now we were really interested
what sort of noise it would make and it
made a different noise but the
technician who pulled out the bung was
so startled he kicked over some glass
wear that was nearby so all you can hear
is a sort of mixture of whoosh and
breaking
glass but the really interesting thing
was that if you watch it in high speed
the flame doesn't bounce anymore so the
explanation of the shock wave seems
really quite sensible
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but what is also interesting is that the
flame accelerates as it goes down the
tube so what I think is happening is
that the flame front as it goes
compresses the gas just in front of it
and raises the temperature so the gas is
getting hotter and hotter so the
reaction goes faster and faster and then
you get quite a spectacular
Fireball coming out at the end which is
actually giving out blue light and the
blue light is the emission of the
excited electrons partly from sulfur and
partly from sulfur
dioxide so it's really quite an exciting
experiment but it hasn't answered all
our questions so it's really quite
exciting it shows if you do more
experiments you learn more things but of
course it's given us lots more ideas is
so in a video or two's time there'll be
some more excitement from The Barking
Dog subscribe to our Channel and you'll
see some more barking dogs in
interesting
positions but actually what this video
footage has shown us is that it actually
goes in stages it sort of
goes it sort of chugs its way to the
bottom of the tube