my colleague Sam wanted to show you a
really interesting reaction the so
called belousov shall Burtynsky reaction
which oscillates the color changes on
and off sadly she's lost her voice so
she's done the experiment but you stuck
with me to tell you what's happening
very fortunately I have a particularly
appropriate tie it's actually a Russian
tie which is good because it's a Russian
reaction and it has the two key elements
of this reaction manganese here and
bromine there this is a reaction which
has quite a complicated mixture of
materials
it begins quite easily with a beaker of
water and concentrated sulfuric acid and
when you begin stirring it you get
really nice patterns so-called clear and
patterns when you mix two fluids of
slightly different refractive index
which just the fluids mixing together
then you start pouring in all sorts of
ingredients there is malonic acid which
is an organic acid manganese sulfate and
potassium bromate bromate is a salt of
the anion BR for bromine oh three - so
it's bromine with oxygens Randy now what
happens in this reaction is the bromate
reacts with the malonate catalyzed by
the manganese and generates bromine
bromine is orange and so the solution
goes Orange but when the concentration
of bromine gets quite high
suddenly a reaction starts and the
bromine reacts fairly quickly with the
malonate to make bromo malonate and so
it all disappears and the solution gives
color it lists again then slowly more
bromine builds up in the solution and it
goes Orange and then because the rate of
reaction accelerates as you get more and
more
I mean suddenly push it reacts again and
the reaction so oscillates between
orange and colorless this reaction was
first described I think in the late 60s
or early 70s in a Russian publication
and sadly nobody in the West believed it
when they first heard about it they
thought it was quite impossible for a
reaction to oscillate backwards and
forwards but you can see for yourself it
happens and once people saw it they got
really excited because this looked a bit
like a living thing so oscillating
backwards and forwards and suddenly
people started suggesting that
oscillating reactions might be quite
important as a basis of life and like
many things in science once they had
worked through the equations for the
rates of reactions they saw it was quite
possible to have color changes in fact
if you have a slightly more complicated
chemical mix you can change between two
colors instead of being colorless and
it's a really fascinating reaction
because you feel it shouldn't happen but
it's not conjuring it really is there of
course when you see something on video
you always think something may be
cheating but I was in the lab and I saw
it happening so it's okay the reaction
stops eventually partly because the
bromate has all reacted and also because
the manganese catalyst starts reacting
with the malonate the organic compound
which sort of binds onto the manganese
and stops it acting as a catalyst so by
the end of the reaction
everything is spent if you have the
right relative quantities it will go for
20 cycles or so which is long enough to
keep going to your board