So this is Mercury. It’s a liquid metal, it is one of the, well,
one liquid metal at this temperature. There are a couple of
liquid metals in a little bit more exotic places in the world like
Spain or perhaps Africa. But mercury is the chemical formula
Hg, the best way to remember the formula for mercury is like
H.G. Wells. Hg, mercury, comes out of a well.
Mercury is one of the few elements that is liquid at room
temperature or is the only metal that is liquid at room
temperature unless you live in a very hot country, it is also
very dense. And it has been known again since very early
times. Mercury is very poisonous.
It is a really fantastic liquid. It was really used for making
scientific instruments like barometers and thermometers, you
know, and it’s really quite a beautiful metal. I really love it,
when I was in school we used to but it on the bench and play
football with it. You know, lots of people don’t like us to do
that anymore, but what I will do is to pour a little bit of the
liquid metal into this beaker so we can see the properties and
you can see that it is really nice. Flows, just like a liquid, it
forms really quite nice balls. And you can see the really quite
high meniscus forming around the mercury.
It can get into the human body particularly in the brain where
it gives signs of madness. It used to be used in the UK for
making hats. I am not quite sure what they did with mercury
to make hats, but this is where the expression, “mad as a
hatter” came from, because the people making hats breathed
in mercury vapour and this caused them to show signs of
madness.
So here we can slosh it around a little bit but we have got to
be very careful that we don’t slosh it too much because it is
extremely dense and heavy and it is very, very easy to go
through the middle or the bottom of the glass bottle itself.
Tell me why you aren’t touching it with your hands?
Well mercury it is associated with toxicity especially for the
salts, so you know we like to try and minimise the contact
with the mercury and the mercury salts as much as possible
really, just so that we could be very careful with our health
and safety.
There was a tragic case in Japan in the 1950s, when mercury
got into the sea from chemical emissions from factories, and
the organisms on the bottom of the sea turned them into,
the mercury metal, into a compound that could be absorbed
by the fish, particularly the shellfish, and then the fishermen
and the people living the round this Minamata Bay, starting
eating these things got large amounts of mercury in their
brain. And I can’t remember the number but several thousand
people got very ill and many of them died, so mercury in the
environment is quite a serious problem. It is also an
interesting point that mercury has been used for making
chlorine by putting electric current thought solutions of salt
and it is gradually being replaced. But unlike chemicals you
can’t get rid of an element, so if you have mercury you can’t
burn it or destroy it in any way. And so, there are problems
now, what to do with the mercury that people no longer
want.
But it is a really beautiful element, really fantastic. It is used
very often in electric chemistry, because you can form very,
very good electrical contact with mercury. And in fact, many
people that may have old telephones or old bells, you know
the door bells which we have on our front door, inside the
‘bing-bong’, is a mercury-activated switch which turns on the
magnet and off the magnet very, very quickly. It is really
beautiful.
Mercury has an interesting property that it will very easily
form alloys which are called amalgams. My teeth and probably
many of your teeth are filled with so called silver amalgam
which is a mixture of mercury and silver which when it is
freshly mixed is like a paste. But when the dentist pushes it
into your tooth it then hardens and, all being well, it does not
come out or at least does not come out for a number of
years. But amalgams are not very strong. And many years
ago when I worked at another university, mercury was being
stolen from the university, from the chemistry department
and nobody knew who was stealing it. Until one day the
window cleaner was walking out of the building and the
bottom fell out of his bucket, because he had been stealing
mercury by pouring it into the bottom…pouring it into his
bucket and hiding it below the dirty water. And the mercury
started to amalgamate with the metal of the bucket, it was a
metal bucket, and eventually, the bucket could no longer hold
the weight of the mercury and it suddenly fell out and the
mercury all came off.