you probably noticed that we're very
enthusiastic almost obsessed with the
barking dog experiment this is the
reaction of carbon disulfide cs2 with n2
o nitrous oxide makes sulphur and co2
we've done it in tubes of different size
most recently a really long tube nearly
10 feet long while we were doing the
more recent experiments I thought it'd
be really fun to do it in YouTube for
one reason I wasn't quite sure what
would happen would the flame go round
and also I have to admit the idea of a
u-tube on YouTube was quite fun so the
first thing was to persuade Neil that we
could actually make a youtube because
bending fat glass tube is very difficult
and in fact he assembled it from pieces
glued together we thought once we got it
it would all be quite easy but we had
quite a few unsuccessful attempts the
first one we had water in the tube and
the flame went down to the water and
stopped even though there was a big gap
above the water in the horizontal part
of the YouTube why was there water in
the jus because we traditionally use
water to slosh around to help mix the
carbon disulphide in the end - oh we
then tried an experiment without water
and the flame almost started going
around the bend and didn't but then when
we lit the other arm the one that hadn't
gone off it did go round the bend but it
couldn't go any further because we burnt
all the fuel on the other side
so you have to realize this was spread
over several weeks because each time
Neel had spent peps an hour or more
cleaning the YouTube we only had one and
then yesterday we tried it again didn't
work
so Neil scrub the thing and left it full
of mixture overnight to try and get as
good and mixing as possible this morning
we were all sitting there arguing is it
going to work isn't it
it's going to work that's a bold call I
think it's not going to work I wasn't
quite sure but we lit it and it worked
really well
but like all experiments it turned out
to be more exciting than we thought
the flame went down the first arm with a
satisfying flush the dark
you
and then the flame continued silently
and rather slower around the bend
and then did a second inverted bark
going upwards
and interestingly the second arm
appeared much more yellow perhaps
because the sulfur was deposited in a
slightly different way so it was really
nice I think it demonstrated very well
how the flame accelerates down the tube
to produce the bark and then if you slow
it down it becomes silent but then when
it has a chance to accelerate up again
out comes the noise but of course like
every experiment we think of lots more
to do
upside down YouTube horizontal YouTube
and the real problem is persuading Neil
that any of this is scientifically
worthwhile it can be drawn out it could
be roof or sometimes it goes much
quicker not very much come disulfide so
the mixture was rich in oxidant so the
reaction always had enough n2o
to go as fast as it could