two days ago I got an email sadly
announcing the death of Neil Bartlet who
is the scientist who's probably done
most for the chemistry of xenon since it
was first discovered at the end of the
19th
century so in the balloon we've got a
sample of xenon now Xenon is one of the
inert gases but it's one of the inert
gases that's right the way down in the
bottom of the period so it's really
really dense so what that means is that
the gas molecules themselves are really
really large really really heavy so in
principle they'll
sink NE
Bartlet discovered that Xenon which
everyone had thought was a completely
inert
element had really could form reactions
and could form compounds something that
nobody thought was possible until then
and this took place in the early
1960s and I've got a picture here of his
um iconic experiment he did his
experiment I think in late
1962 or perhaps early 63 and this was
published just over a year later and
these are two exper pictures this is the
experiment before and after so we've
done an experiment here and we filled
this balloon with Xenon now xenon's very
expensive so there's about 40 worth of
xenon in this balloon right now yeah so
we're going to do this experiment and
we're going to see if it
sinks and and I think you'll agree that
it does sink quite quickly what he did
was he took a glass bulb of a compound
of Platinum Platinum hexafluoride
ptf6 which is a gas now that's quite
unusual to have a metal compound that's
a gas but it's rather A nice bright
orange gas and he put together a piece
of equipment here
where in this tube here there is xenon
gas which is colorless and this is a
magnet which can be lifted up and break
a tiny seal so that the two gases mix
but just to show you how dense it is
we've got a similar balloon but you'll
notice that this balloon is much much
higher fied so it's much much bigger now
this is one that we've just blown up
with air
so now what had happened was before this
experiment was done with
Xenon that one of Neil's students had
discovered that Platinum hexafluoride
reacted with oxygen in air to form a
compound in which one electron had been
removed from the oxygen to make O2 plus
and this was a solid material it was
itself quite a surprising
reaction now what Neil did was that he
looked at the periodic table and
wondered which other elements required
about the same amount of energy as
oxygen to remove one electron and he
came up with Xenon so he tried this
experiment using the apparatus here
they lifted this Magnet or he lifted
this magnet it crashed down the Xenon
rushed in and suddenly this red gas was
turned into a yellow solid in fact it
turned out he was doing this experiment
with his student but the students whose
name I've forgotten had to go home so
Neil did this experiment by himself and
he was very late getting home for his
dinner and his wife according to him on
this video was really very angry but
chemistry had been transformed well this
experiment was voted by um American
chemists as one of the top 10 most
important chemical experiments that had
been done in the 20th century so let's
see if we can compare the rates at which
these two balloons will sink so we can
look at the comparative densities
ready Zenon exists in the air and when
people lick liquify air they first of
all separate the nitrogen and then the
oxygen for and at the end they're left
with the noble gases argon Krypton and
Xenon so it is made from the
air and one of the problems with this
price rise of xenon was that at the same
time as there was a bigger demand for
Xenon there was a downturn in the steel
making
industry which uses a lot of oxygen so
the chemical plants that were or the
refrigeration plants that were making
xen oxygen were switched off so there
was a smaller supply of
xenon
again whoa that'll be the
air this is an old-fashioned Xenon lamp
the Xenon in it its bulb and you put a
large voltage through here and the Xenon
gets very hot and shines out as a very
bright light
um it looks black here because the
electrodes get so hot that the metal has
evaporated but Xenon itself is colorless
this is a more modern Xenon lamp of the
sort of lamp that is used in very
powerful spot lights for example on
tanks to illuminate that's military
tanks to illuminate the Target and the
um window here is made of aluminium
oxide and all the light comes out as a
really very powerful beam