[MUSIC PLAYING]
In the year 1792, the Scottish
engineer William Murdoch
presented to the world his
latest invention, an invention
which was to have a huge impact
on society for the next 100
years at least.
He presented the world's first
portable illumination source
using a gas.
And underneath his arm,
which is what I have here,
he had a gas bag.
Now, what I'm going to
talk to you about today
is what this gas is,
where it has come from,
the impact that this
invention had on the world,
and all the side effects.
But before I do so, we must
first of all light our candle.
This is not the
purpose of this gas.
The purpose of the gas is
to actually provide light.
But as you know, flames
also provide heat.
I am now going to ask Andres,
my friend, who is helping me
today, to extinguish the
flame and take the gas
bag from under my arm.
Thank you very much, Andres.
There we are.
We have to take precautions.
And now the gas, of course--
thank you very much.
Can we have the lights.
The gas, of course--
look at that.
The gas that William
Murdoch was burning
was coal gas, a gas which
had been derived from coal.
And which, indeed, people had
already noted some time ago.
But they didn't
recognise what it was.
Now, what I have
to tell you is that
towards the end of
the 18th century
was a great period for
the evolution of science,
where the concept or the idea
of substances which were gases
was very new indeed.
People had for
many, many centuries
talked about different
kinds of air.
But gases as
individual substances,
had been developed by the
English school of chemistry,
especially with
Joseph Priestley, who
was a brilliant
manipulator of gases.
Today, we shall be
manipulating some gases.
Let's go back to coal then, and
how did this situation arise?
Well, coal is one
of the fuels which
mankind has used for many,
many thousands of years.
And I'm just going to hold
up a few pieces of coal.
To prevent my hands
from getting dirty,
obviously I prefer to
get some gloves dirty.
So here we are.
And start off with
a piece of-- this
is the sort of fuel that
for thousands of years
has been known to
humanity to provide
a fantastic source,
above all, of warmth.
But water is coal exactly?
Because it looks like this.
You take a lump
of coal like this.
It's been mined.
And it looks like
a single substance.
That you see is a
great misunderstanding.
It is not actually
a single substance.
It is a very complex mixture.
Coal has been derived from
the compression of vegetable
material, especially trees,
over a period of millions
of millions of
years, dead trees,
during the Carboniferous
period, that's
what it's actually called.
The trees that
grew on this planet
were compressed by layers of
rocks in the absence of air.
And they ended up forming
huge, huge deposits
of this black substance, which,
as I will show you shortly,
burns.
So I've started
off by telling you
that coal is not a
single substance, which
it appears to be.
It is actually a mixture.
I'll very briefly tell you
what it's comprised of.
The main part of coal
is the element carbon.
And I have here a pure sample of
carbon in the form of graphite.
Now, this actually, as you
can see, resembles coal.
But it's considerably shinier.
And it has a shiny
appearance here.
So that is pure carbon, the
main element present in coal.
And I ought to
tell you that there
are several different types
of coal, which, when they burn
and when they react chemically,
produce significantly
different types of results.
And I wanted to say that this
specific type of coal, which
I've got here, is
bituminous coal, which
contains about 85% carbon.
So this is pure carbon.
That's 100% carbon.
This contains about 85% carbon.
Here I have a briquette
of modern smokeless fuel.
This is compressed anthracite.
And this contains
about 95% carbon.
So what are the other
percentages made of?
Well, in bituminous coal,
there are a large number
of substances present.
And the elements are--
rather than telling you what
substances, I'll tell you
which elements are present.
They will be the elements
hydrogen, oxygen, nitrogen,
sulphur, arsenic, tin--
arsenic, lead, for
example and iron.
Those are the principal elements
present in the coal as well.
But rather than going into
the theory, let's first of all
see how a sample of coal burns.
So I am going to set this
sample of coal on fire.
And then we're going
to see how it ignites.
Now, for this
purpose, of course,
I'm going to be
using a little bit
of modern technology like this.
And this is how
people would have
observed coal burning for many,
many, many, many thousands
of years.
And I'm sure you can all
see the first thing you
notice is a foul smoke.
And that, my dear friends,
is, of course, pollution.
You don't get
something for nothing.
There is our coal on fire.
But you see at the same
time a huge cloud of very
unpleasant smoke was produced.
And this, of course, this
very unpleasant coal--
um, smoke is, of
course, pollution.
That is one of the main
problems which people
have been confronted
with in using this fuel.
Now, that pollution
consists of smoke,
which produces soot when
you burn it in a chimney,
for instance.
You burn your-- in
a grate, rather.
The smoke goes up.
And it consists of a
multitude of substances,
which we are going to
very shortly subject
to some simple analysis.
But one of those
substances is soot.
Now, I do have a jar
of soot somewhere here.
Ah, here it is.
Here's my jar.
Just to show you,
this is normal soot
which came out of a chimney.
And I'm just going to
pour a tiny amount.
It's a foul black substance.
There it is.
That's chimney sweep soot.
And you say, well, what is this?
Well, it's a complex mixture
of very, very potentially
hazardous substances,
obviously made up of carbon.
But one of the great
things about human beings
is they're very ingenious.
So I read in a very
recent newspaper article,
just literally a
couple of weeks ago,
that soot can be used to
repel slugs in your garden.
So if you're a chimney
sweep, for instance,
and you have a
huge excess of soot
that you've just collected,
you sprinkle on your garden.
And you can be reassured
that slugs will not
attack your cabbage and your
various other vegetables,
which you're growing.
But the ingenuity
of the human is such
that I can assure you that
scientists will have found
other uses for soot like this.
Now, I am now going
to, therefore,
proceed to the process of
burning some coal and analysing
the products which are produced.
And you see I have an
apparatus set up here.
I am going to very shortly
bring this into action.
And I am going to ask,
first of all, Oscar,
who is my son helping me
today, to come on and start off
our bellows.
First of all, we are going to
be burning the coal in here.
We're going to be burning it by
passing air through it, using
a very, very ancient
type of device,
which is called a bellows.
Bellows have been used
for thousands of years.
And please, when Oscar
pumps the bellows,
I am going to
explain what happens.
He will generate a
flow of air, which will
go across the coal in here.
I will be strongly
heating the coal there.
And the products
of the combustion
will go through three
Drechsel bottles.
These three Drechsel bottles
will contain in turn--
here is lime water, which
detects carbon dioxide.
It turns milky, which
is the main product
of the combustion of coal.
Here I have some--
which I have some universal
indicator dissolved in water,
which will show you
whether the products
are acidic or alkaline.
And here I have some potassium
permanganate solution,
which will tell you
something a little bit more
about the nature of the product.
Now, I want to be
quite frank with you.
The object of this is
to show that acid is
produced when the coal burns.
And the specific
acid we're looking
is sulphur dioxide gas, which
reacts with water to make
a solution of sulphurous acid.
So Oscar, could we first
of all test the pneumatics
and see that air is indeed
going through all three bottles?
So you can see here the
air is bubbling through.
So the system is working.
And I wanted to tell you that
at the same time as I am doing
this experiment, which will
last approximately 10 minutes,
I am going to ask Andres to come
on and do another experiment
by heating coal, which initially
looks to be exactly the same.
So please, look.
Here we have coal powder.
It's going to be heated.
Here we have lumps of coal,
which are also being heated.
But there ends the
similarity because in this--
and they are both going to
undergo a chemical reaction.
But in this particular
case, because we're
passing air over
the coal, the coal
will combine with the oxygen
from the air in a process which
is called combustion.
Here, though, because there
is no air being produced,
et cetera, the coal will
chemically break down
into different substances.
And we have here the
tube, which will be
collecting the product there.
And which will be
collecting a liquid product.
There is some water in there to
help to condense the vapours.
And there will be a gaseous
product coming out of the top
there.
Andres, just one little thing.
We may have a problem in
getting a constant flow of gas
if that's bubbling all the time.
So maybe-- see how it goes.
But if we don't get a constant
flow of gas coming out,
then we will-- and
this gas, by the way,
is going to be the gas I was
burning at the beginning.
It is known today as coal gas.
Then it was called
illuminating gas.
And illuminating gas, as I said,
was a major topic of research
for over a hundred years.
And even today in London, there
are 1,500 gas torch-- gas lamps
burning on our roads.
But the flame is
there, is slightly
different from the
flame that we have
here due to a little
bit of chemical science.
We have improved things.
So I am going to ask Oscar
to turn this-- start pumping.
I will now start
the heating process.
And Andres, if you wouldn't
mind kindly getting this.
Now, this takes about
seven or eight minutes.
So if you could kindly
start heating, Oscar.
I am now-- start pumping, sorry.
Oscar's pumping.
And I am now heating the coal.
And I ask you to
watch carefully.
Notice a little bit of water
vapour condensing there.
Start to look to see, if
you can see any changes
in any of the liquids.
There will be a lot of
smoke produced in this.
And I think we're on fire.
I think we're on fire.
Keep going, Oscar.
We have a flame almost
certainly there.
This will last for at least
five minutes, by the way.
Let's see, we can
take-- that's it.
Keep it going now, Oscar.
Now, the trick is we have
a critical mass of coal
which is burning there.
And that should sustain itself.
Andres, could you kindly
start the process there
of roasting that?
Now, we have here two different
types of chemical process.
This one here, where
the coal is burning--
keep pumping, Oscar-- it
is giving out heat energy.
It's glowing red hot.
And it's giving out heat
energy as it is combining
with the oxygen from the air.
Here, though, we have a
process which is endothermic.
There is no oxygen passing over.
And there is no chance at all
for the coal to catch fire.
There is no air there.
So this is an
endothermic process.
Here, we have an exo.
I'm just going to heat it a
little more, just to make--
please notice the colours
will shortly start to change.
I'm going to-- as
I said, this does
take about five or 10 minutes.
It's not an easy
experiment to do.
Shall we get Clara to help?
Clara, could you come?
My daughter, Clara,
I have asked to keep
the flame going because
it doesn't always
keep itself going.
Keep going, Oscar.
Keep going.
I have to be careful not to
heat too strongly, otherwise
the tube will melt. Are
you OK there, Oscar?
I'm trying to get more coal to
burn in order that we can get
the relevant changes in
the colours of our liquids.
And I hope you can all--
That's better, Oscar.
We've got a roaring
flame in there now.
Not too far, otherwise you'll
set the barn on fire, Oscar.
We have to take care.
Now, please notice.
The colour is going yellow.
This shows an acid being formed.
The colour here we're getting,
clearly is going milky,
showing the formation of carbon.
This is very good, Oscar.
We've now got a
proper fire burning.
I'm going to warm
myself up on this.
Please, excuse me.
Very good, Oscar.
This is a nice glowing fire
by the coal side, et cetera.
But, please note.
Look at the amount of
smoke that it's producing.
And this is the problem.
Not only the smoke, but
please notice this solution,
potassium permanganate
acidified,
is now changing in colour,
from pink to almost colourless.
It will shortly lose its colour.
This solution here--
keep going Oscar.
You're doing very well.
Sorry, I have to keep--
it's very hard work
doing this, by the way.
Oscar has been doing
weight training
to keep himself fit for
this for last three weeks.
You're doing very well, Oscar.
You notice this is
now going yellow.
I might give it-- we now have
loads of carbon dioxide, which
I said obviously is going
to come off because that's
the main product.
Now, we have here
red hot, you notice.
And the flame--
Clara is trying to
keep it sustained.
And it will occasionally burn.
Now, that is illuminating gas.
And I will explain
to you exactly what
that is in a minute.
In here, though,
we have collected--
we have coal tar,
which is collecting,
a few droplets of a
black liquid there.
The idea is to try and keep
it going without it going out.
Now, here you see we've
almost lost our colour there.
And my trick is to try and get
this to go red, by the way.
And the reason is because
sulphurous acid, formed
in this reaction by
the sulphur impurities,
is capable of turning the
universal indicator red.
So I'm just going to give
this a little booster.
I'm just going to give
it a little booster,
to get the fire burning again.
We're aiming for it.
But it does take a while.
Because at the end of the day,
there is not that much sulphur
there, you see.
There is not a great
deal of sulphur there.
And we will hopefully
get it to turn red.
So Oscar, keep going.
We are succeeding there.
I think that one,
though-- oh, we're
about to blow a
hole in this one.
So once we've blown a
hole, that means we've
blown the whole experiment.
So I have to take
great care, great care,
not to overheat locally,
not to overheat locally.
Keep watching to see.
We're getting-- we're
getting close to red now.
We should get-- we're hoping
for colourless on the other one.
As I said, there
is not a great deal
of sulphur present in
the coal, up to 1%.
Now, the next question,
which one may ask,
is how is this coal--
how is this sulphur
present in this coal,
which looks like a single
substance, but is not in fact.
It's a mixture.
So we're continuing to--
keep going, Oscar.
We'll just give it
a little bit more.
It's going red almost now.
And the other one is
almost going colourless.
So we're getting a result.
Oscar is out of breath.
I'm sorry.
OK, still Oscar?
Thank you.
We're very close, Oscar.
Look.
We've almost got the
red, which is caused
by sulphurous acid coming
from the sulphur impurity,
acid rain basically.
And here we've almost
gone colourless.
And that shows that there
is a reducing agent present.
This reaction proves--
Oscar, we're very,
very nearly there.
We have a red colour.
So we've now
definitely acidified
our water, which was there.
And this one has almost
given up the ghost.
Oscar, pump more.
That's it.
Keep-- I'll tell you what.
I am going to block the
end of the other one
with my finger to
get more to go.
There, that's it.
Now, keep going Oscar.
We're very nearly colourless.
Oscar, brilliant.
Thank you.
We'll call it quits there.
Thank you very much, indeed.
Now, we've made--
[APPLAUSE]
We've made a huge amount.
We've made a huge
amount of smoke in here.
We've caused lots of pollution.
And I've warmed my hands up.
But I must say, it's
a heavy price to pay,
all this pollution
we're now sitting in,
in order just to
have a bit of warmth.
And that you see is one-- has
forever been the big problem.
Various laws have
been introduced
for hundreds of
years ago, already
to prohibit the
burning of coal because
of all the unpleasantness.
Now, I wanted to
start off with--
by returning to this
solid lump of coal,
which looks like a single--
so how on earth is
sulphur present?
Well, I'll tell you.
A tiny amount of
this is-- actually
has got this inside it,
which is iron pyrite.
It's iron sulphide.
And I have here a
perfectly grown crystal
because iron sulphide,
when it's pure,
forms beautiful cubic crystals.
And this is some
pure iron sulphide.
And the question which
you may ask, therefore,
if you were to heat this in air,
would it make sulphur dioxide?
The answer is yes.
It will actually chemically
combine with air.
And it will make
sulphur dioxide.
And it will bring about
these two effects.
Potassium permanganate
acidified, going coloured,
and the universal indicator
turning red due to sulphur
dioxide present.
Now, some of the sulphur
is present in the form
of pure sulphur, uncombined.
And huge deposits occur
in the Earth's crust.
And here we have some sulphur
crystals, you see, of--
this is rhombic sulphur here.
And they occur.
We extract the sulphur
by mining, still
on a very, very
large scale today.
The other compounds of sulphur
which are found in coal
are organic compounds, compounds
made of carbon, hydrogen,
sulphur, oxygen, and so forth.
And they are present in here.
So this remarkable substance,
coal, which on the face of it
appears to be one substance,
is actually a mixture.
And you see-- which
was chemists who
devised the supremely useful
way of classifying substances
as elements,
compounds, or mixtures.
And here we have, you
see, the element's carbon,
which is approximately 85%
in this bituminous coal.
Then we have a variety
of other substances.
And this is an example of
a compound, iron sulphide,
pyrite, formula FeS2.
And this inside here is mixed
together with other substances,
mixture, compound, elements.
So these substances I'm showing
you, in a splendid manner
illustrate exactly
what coal is all about.
Now, the next thing
I wanted to show you
is when the coal has burnt
in there-- of course,
it's made these
gaseous products.
But we must not forget that
there is a solid left behind.
And that solid is ash.
And I have some ash here.
And it's horrible stuff.
It comes out.
And know people always
throw it away, et cetera.
And I'm going to show you now
that this ash actually here is
quite an interesting substance.
And as I said, what use
could you make with coal ash?
Not a huge amount comes in.
And I'm going to tell you
that coal ash actually
is made up of principally
three oxides, silicon oxide--
silicon, by the way, I
forgot to mention there--
aluminium oxide, iron
oxide, and calcium oxide.
Now, I'm going to
spoon some into here.
I am going to spoon some
into my philtre paper there.
This is quite a messy
ash from a fireplace.
And I am now going to
show you that if we
pour some universal indicator
through this ash, which I've
got there, then you will see--
hopefully, I'm not sure that
this will definitely work.
But we should see a
slight colour change.
And that will tell us
something about the nature
of the substances.
As I've told you,
made up primarily
of iron oxide, silicon
dioxide, aluminium oxide,
and some calcium oxide.
And we're going to-- this
takes a little while.
Dear, Andres, could I ask you
to just pour that through?
And we'll-- and I'll continue.
If you just carry
on pouring that.
Please note the colour change.
Now, I wanted to turn a little
bit to what I've got in here.
There was water
there to start with.
But there is a black--
dark brown deposit there.
Now, for many years, or when
people started the experiments
with coal, and understanding
the idea of a gas and the liquid
in a solid, the three states
of matter, which also--
those ideas have played a
huge role in our understanding
of the behaviour of matter.
People started-- what
a horrible black mess.
Let's throw it away.
And they did.
It had a foul smell
and a foul appearance.
But this coal--
this tar, which I
have here, which is correctly
called coal tar, obviously,
is a most remarkable
and complex mixture
of several hundreds, if not
thousands, of substances.
And we-- chemists have helped
us to make use of that.
Thank you very much, Andres.
And you will notice as the
universal indicator comes
through, this is not acidic.
But this is a slight alkali.
You should notice the colour,
being a beautiful ultramarine
blue.
Now, the reason for that
is, as I told you earlier,
out of those oxides which
are present in coal ash,
one of them is calcium oxide.
And calcium oxide is alkaline.
It gives the alkaline
reaction with water,
forming calcium hydroxide.
And it's present in tiny
amounts, but sufficiently large
amounts for the indicator, the
universal indicator solution,
to turn from green to blue.
Now, I am going to
return to the ash--
to the coal tar in
just a few seconds.
But I just wanted
to go a little bit
onto this gas which you saw
burning, illuminating gas,
as it was called
by William Murdoch,
and which set off a complete
revolution in the way lighting
is affected.
For thousands of
years, people used
to burn candles,
or oils, et cetera,
to provide a source
of illumination.
And if they wanted
portable illumination,
they would have a torch, a torch
with a wick at the end soaked
in oil.
And that would-- then you
could carry this torch around.
But what William Murdoch
showed is the different--
the use of a totally
different kind of substance
to provide light.
And that substance,
he called illuminating
gas, which he had made from
the distillation of coal.
Now, this process, which Andres
demonstrated to you here,
this process which
Andres had demonstrated
is technically called the
destructive distillation
or the pyrolysis of coal.
Pyrolysis means heating
in the absence of air.
Destructive distillation
means breaking down molecules
into smaller molecules.
So you have large mixture
of molecules present here.
On heating, they split up.
Now, I'm going to tell you
a little bit about the types
of molecules which are present.
You see the majority--
I hope you understand-- the
majority of the compounds that
we're dealing with carbon--
with coal are
compounds of carbon.
Now, when carbon is
present or when substances
are released from this
distillation, pyrolysis
of coal, the carbon is
frequently mostly combined
with hydrogen, which is
another element which
is present in here.
And I wanted to tell you
that the substance, which
is the most simple compound
of carbon and hydrogen,
is methane.
Methane has the
chemical formula CH4.
And it is the gas which comes
out of all of our gas taps
today.
Natural gas, what we have
burning, out of our gas taps,
is mainly methane gas.
It's 99% methane.
It comes out of the ground
without any treatment.
It simply comes out.
Now, the coal gas, which comes
out here, is a mixture of gas.
It's what you saw burning
there, what Clara was burning.
You saw momentarily
this yellow flame,
with quite a bit of
smoke coming off,
is a mixture of gases, of which
the main component is actually
hydrogen. Hydrogen
gas, about 45%.
And then the second most common
gas there is methane, CH4.
And it's about 30%, 35%.
The coal gas composition does
really vary quite a bit on how
strongly, how high
the temperature is,
what coal you started
with, and how long
you are heating the coal for.
So that's the simplest gas,
with carbon forms with--
and that is natural
gas, methane.
So where does the
illumination bit come from?
Well, in coal gas, which is
a mixture of gases, about 5%
of the gases are actually
slightly more complicated
molecules.
I will just very
briefly explain.
Carbon is the
unique element, out
of all the elements,
that is able to form
more compounds with--
because it can form
long chains of itself--
more compounds with
other elements,
but mainly, very
typically with hydrogen,
than all the other
elements put together.
We are substantially
made of carbon.
We are all made up
of organic molecules,
huge organic molecules.
There is a lot of
carbon in all of us.
So when carbon
combines with hydrogen,
it makes compounds which
are called hydrocarbons.
And methane is the simplest
of these, formula CH4.
Now, the next longest
molecule is C2H6, ethane.
And these two burn
pretty much the same.
But the illuminating
part is produced
by compounds of carbon, which
have double carbon-carbon bonds
in.
And this chemists
have recognised today.
This is a molecule
of ethene, C2H4.
This is a molecule
of ethane, C2H6.
And it's that small percentage
of the illuminant gases,
ethene, acetylene, C2H2, or
ethane, as it's known today,
which give it the luminosity.
I'm going to return
to that later on.
But in the meantime,
I want to return back
to our pollutant, the sulphur.
And I wanted just to show you a
few experiments because we saw
it took about 10 minutes there
to get those colours to change,
or several minutes.
I am, though, going to now, to
actually ignite some sulphur
and make some pure
sulphur dioxide.
And the way I'm going to do
that is by burning some sulphur.
Could we have the
candle over here?
Thank you very much, Andres.
Now, what are we
going to do is this.
I am now-- thank you very much.
If you just put it over here.
I am now going to
ignite some sulphur.
And I am going to burn
it in pure oxygen.
Now, the reason
why I am doing is,
it does actually make a
very, very magnificent flame.
Now, to do this, what I am doing
is, I am simply putting some--
I've got some-- this is
crushed roll sulphur.
And it is sulphur which
has been finally pounded.
You can get flowers
of sulphur, which
have a more loose arrangement.
And I am going to ignite the
sulphur on my candle here.
And then I am going to
lower it into this flask.
Now, this flask is full
of the gas oxygen. Pure
oxygen is in there,
and water, with a bit
of universal indicator.
Please note the colour.
It's green.
What I'm going to do now, I'm
going to set this on fire.
And I will ask for the lights
to be switched off from now on,
please.
So if we could have
the lights off?
Because then you will be able to
see how this reaction proceeds.
So we're going to
now lower our--
we're going to set
the sulphur on fire.
Now, this takes a
couple of minutes.
If we were to use one of
those powerful burners,
then this would happen in the
course of a couple of seconds.
But I do want you to show that
we could use the trusty candle
as a source of light--
as a source of heat, in addition
to a source of-- nowhere,
near ready yet.
Sorry.
I got to just-- thank
you very much, Andres.
Now, what's happening?
The sulphur is now melting.
It's melting into
a brown liquid.
It melts 113 degrees centigrade.
And very shortly,
it will catch fire
and burn with a flame,
which you can barely see.
There it is.
It's just-- but not yet.
We'll just wait, just to see.
You can barely see that flame.
There it is.
Please watch carefully as I
now lower it into pure oxygen.
And you will see the
sulphur now continues
to burn with a brilliant
blue flame in there, you see.
And as it does so, it's giving
off a white sort of smoke.
That is the gas,
sulphur dioxide,
which is the main pollutant.
Which is produced
in tiny amounts,
as you saw before,
when coal burns.
And that has been a source
of a considerable headache
for many, many years.
But chemists have
now championed this.
And when coal is
burnt in industrial--
for instance, generated
in coal plants
for producing electricity,
the sulphur dioxide
is removed by combining it
with alkaline substances,
such as a lime slurry.
Now, by the way,
going back to the ash,
because ash does contain
lime, what is ash used for?
It's used in the
building industry
for making bricks, and
cement, and breeze blocks.
So just-- I will be
slightly hovering
backwards and forwards,
just to keep you posted.
But the honest truth is, we as
humans are terribly inventive.
And we waste nothing.
But it's always a challenge.
And the chemists play
a great role in this.
Can we have the lights
back on, please?
I am now going to swirl
around my water in there.
And you'll notice it has now
turned to the red colour.
Now, that red colour, of
course, shows us the formation
of an acid, not
yet-- not that now.
Now, what I'm
going to do now, is
this acid which I have made in
there is very, very unpleasant.
Sulphur dioxide is an
extremely unpleasant gas.
It's a-- it's an--
it causes asthmatic attacks.
And I'm not too good.
And I'm now going to squirt
ammonia in to neutralise.
Now, ammonia is a strong alkali.
Now, it will neutralise.
It may catch fire as well.
You'll see dense
white smoke going on.
Acid plus alkali
makes salt plus water.
If you see a flame,
don't be surprised.
It doesn't have to be a flame.
The flame would only
happen if there's
any oxygen left in there because
the ammonia will catch fire.
But what I'm doing,
I am essentially
neutralising this most
unpleasant acidic gas
with an alkali, which
is sodium hydroxide.
And once I know I've
got enough in there,
then the universal
indicator will turn back
to green, or even to lilac if
I have an excess of ammonia.
So that then is
the demonstration
for Sulphur dioxide.
Can I ask you to take
this away please, Andres?
Thank you very much, indeed.
The flask gets quite hot.
No, this is not yet.
Now, what I've got here--
what I've got here are two
more jars, just to show you.
Sorry, I have to take
care not to burn myself--
just very carefully.
These gas jars both
contain Sulphur dioxide.
And I will now demonstrate for
you very quickly two reactions,
to show it's a reducing agent.
If we pour in some acidified
dichromate solution--
this is a standard test
for a gaseous reducing
agent or a reducing agent.
Andres, can I ask you to
kindly take off the lid?
And I'm going to ask you to
watch the dramatic colour
change.
It turns from orange.
And I'm sure you'll know what
colour it makes, as I pour it.
Just take it off.
There we are.
And there, just hold it up.
Put the top back on,
thank you very much.
So that's the first change.
And that's showing.
Only Sulphur dioxide will
give you this reaction,
from orange to green.
And this one you've
seen already.
This one here is the
one which took us
about five or six minutes when
we were burning the thing.
But here, we will now do it
with pure Sulphur dioxide.
Now, Sulphur dioxide, as I said,
it's a powerful lung irritant.
It's a very unpleasant-- but
we have fantastic ventilation
here.
So that's why we're able to
do these experiments here
in relative safety.
So pour this in.
And you'll notice, it
goes completely colourless
instantly.
Now, that once again--
both of those experiments
illustrate the fact
that Sulphur dioxide is a
powerful reducing agent.
You may like to know that it
is for this reason that it is
present in many foodstuffs;
for instance, dried apricots,
lots of wines, and
lots-- and also ciders--
are at least, those which I
know-- if you read the label,
they contain sulfites.
The Sulphur dioxide is SO2.
When it dissolves in water, it
forms sulphurous acid, H2SO3.
When you neutralise it, it then
forms sulfites, (SO3) 2 minus.
Having shown you some
experiments, let us now return.
So we've had a brief look
at the products here.
Coal, when it burns, makes ash,
which is a mixture of oxides.
And you see they have a
slightly alkaline character.
We've examined the carbon
dioxide and the Sulphur dioxide
here.
That is the burning of
coal or the combination
of coal with oxygen.
We're now going to
just turn our attention
back to what we have here.
We heated the coal very strongly
in the absence of oxygen,
of air.
And we have a solid
product left in here.
We have a liquid product,
which is left in here,
and a gaseous product,
which is left in here.
Now, all three of these
have contributed hugely
to the benefit of mankind.
The destructive
distillation of coal
is one of the most
useful processes
that human beings have
invented because all three
products play, have
played, and continue
to play a most important
role in our everyday lives,
which we perhaps seldom
stop to think about.
I am going to start off by
showing you this one here.
And I am going to tip out
the solid product here.
And you look at that and
you say, but hang around.
That looks exactly the same
as what you started with.
Don't look at the powder.
It's these lumps.
Now, these lumps
here are essential--
and I have made a few more here.
They are a substance
which is called coke.
Essentially, it's
a smokeless fuel.
And indeed, this here which
is crushed anthracite, which
is about 95%, it's
a high grade carbon
fuel, which makes
very little smoke,
is practically the same as this.
Coke, this is very light.
If any one wants to
come and hold this,
it's certainly much lighter
than the coal I start-- and it
is quite porous.
And the reason is
you've driven off
the tar and the gaseous
product by the action of heat.
Now, coke plays an
enormous role in our lives
because when this
process was first
Developed on an industrial
scale in the latter half
of the 19th century,
coke was started
to be produced in large scale.
And immediately, it was used
on a very large scale for steel
making, for steel making.
And today, indeed, you learn at
schools, in the blast furnace,
one of the three
solid ingredients
is coke, which acts as a
powerful reducing agent.
I will return to coke in just--
I'll tell you
another use of coke
because I am going
to go on to tar next.
Another most
important use of coke
was the manufacture
of calcium carbide.
Now, at the beginning
of the 20th century
we started developing
techniques for making
very high temperatures in
furnaces, electric furnaces.
And what they were able to do
was to-- they realised that
if you roast--
if you roast coke, which
is essentially pretty
pure carbon with just
the ash impurities,
and you roast it with calcium
oxide, what we find here,
but obviously in tiny amounts.
But calcium oxide
is relatively easily
obtained from chalk or
limestone simply by roasting it.
If you heat coke with
limestone, you end up with--
coke with calcium
oxide or quick lime,
you end up with a
substance, which
I am going to pour
on my fingers here,
which is called calcium carbide,
a few lumps of calcium carbide.
Now, calcium carbide looks
fairly innocuous here.
It was used for some time.
It was used for the manufacture
of calcium cyanamide
by reacting it with nitrogen
and then for producing ammonia.
But that was not necessary.
Because ammonia,
believe it or not,
if you-- when you actually do
this coal tar production here,
if I was able to
get to 1,000 degrees
centigrade, which we can't
in these circumstances here,
then one of the
important ingredients
there is actually ammonia gas.
That's made from the
nitrogen components of this.
And that ammonia then
forms what we call
an aqueous layer above the tar.
And that was a main source of
artificial fertilisers, which
were so important for
the feeding of humanity,
the rapidly growing
population, towards the end
of the 19th century.
So coal tar had as one of
the very important products,
ammonium compounds
and ammonia, which
is obtained through the
distillation of bituminous coal
at about 1,000
degrees centigrade.
One of the other extraordinary
things that I have learnt
as I've prepared
for this talk is,
depending on what temperature
you heat the coal at, what type
of coal it is, and
how long you heat it,
you get a remarkable
different range of products.
But the industrially
used temperature
was about 1,000
degrees centigrade.
Because that then not
only gave you that tar,
but it also gave you aqueous
distillate containing ammonia.
Back to our calcium--
to our coke and our
calcium carbide.
Now, calcium carbide
is a very interesting--
a very interesting
substance because it
links inorganic chemistry
with organic chemistry.
Organic chemistry
being the chemistry
of carbon and its compounds.
And I wanted to start
off by showing you
the chemical equation.
I think it's very important
that during a chemistry lecture,
we should see at least
one chemical equation.
So could we have it please
just up on the slide.
There it is.
Now, there it is.
And children, you should--
if there's one equation I want
you to learn, that's there.
First, we start with
a word equation.
Calcium oxide plus carbon
makes calcium carbide
plus carbon monoxide, which
is a colourless toxic gas.
And then we have the
balanced chemical equation,
which I've written below.
Now, what's slightly
unusual about this,
is when you learn
your reactivity series
at school about the
relative reactivities
of different metals--
of different elements,
normally oxygen
is far more reactive
than carbon.
But when you do this reaction
at 2,000 degrees centigrade,
the whole process is reversed.
The carbon becomes more
reactive than the oxygen,
stealing the oxygen, as
we say, from the calcium
and leaving behind
calcium carbide.
Now, calcium carbide was
to play a fundamental--
and it was a
blockbuster invention
because this put a new light
altogether on illuminate gases.
I am going to ask Oscar to
make some calcium carbide now
by reacting it with water.
I have here some
calcium carbide.
And I'm going to ask
Andres in the meantime
to put into action two lamps,
because calcium carbide was
used for illumination
purposes, as I've said.
And this was a
significant step up.
Oscar could we get-- go.
We're doing these
two experiments
simultaneously in order that
we can show what's here.
So please focus on both.
Now, there are your things.
Oscar is now--
what's Oscar doing?
He's adding water, pure
water, tap water, very gently
onto some--
and you will notice bubbling
in our pneumatic trough.
There we are.
Very gently, Oscar,
one drop at a time.
It's quite difficult to
control this, by the way,
because the reaction is
very, very rapid, indeed.
And there we have--
there we are.
So bubbling now.
Oscar, could we test the gas?
First test it just to see
that it's pure acetylene.
Acetylene burns with a
very bright yellow flame,
producing clouds of soot.
So don't be put off by this.
The soot is pure car--
Just test it first.
There it is.
Just a little more.
It's coming off pretty
violently, Oscar.
Perhaps we could just turn
the tap down a little bit.
We haven't had much
practise at this.
But Oscar does like
fire, like myself.
So I'm sorry about that.
We are pyromaniacs on the--
Now, Oscar, if we could
collect the gas please.
Collect the gas by passing over.
In the meantime,
what Andres has done,
he's set up two acetylene lamps.
Now, one of these
acetylene lamps
was used by miners for
illuminating under the--
one, they were deep
underground, which
is a most curious habit, as
I will very shortly explain.
And the other type--
the other type of
lamp which I have here
is, in fact, a lamp that
was used by cyclists.
And these, both
of them, give out
very, very beautiful
flames, indeed,
as I hope you will shortly see.
We have not practised these
experiments a great deal.
And I am hoping that--
it takes a little while.
But I think Andres has more
experience of these than I do.
So Oscar is now
going to just-- he's
collecting a couple of
gas jars of the acetylene.
And then he will
set fire to them.
Now, what's important
for you to understand,
that he will be
igniting pure acetylene.
There is no air
mixed in with it.
And when we ignite
pure hydrocarbon gases,
then we have a phenomenon
called incomplete combustion.
The gases burn, but with a smoky
flame, a yellow smoky flame.
So here you have a candle
burning with a yellow flame.
It's not giving off a
great deal of smoke.
But nevertheless,
that's a process
of incomplete combustion
because some soot
is produced, as you know.
Oscar, could we now
kindly try and see--
I hope you've turned
that off already.
If you haven't--
thank you very much.
So we're now-- and now,
could you just ignite
a couple of jars, the two jars.
So we-- here we have more--
Oscar is-- here we
have-- this is now--
can we have all
lights off, please?
This is very beautiful.
I want you to see this
magnificent cycling lamp,
you see, headlamp.
Now, I tested this recently.
And it burns for several
hours, three or four hours.
It's a magnificent light.
I am just going to show--
Oscar, could you just--
I want you to show-- can you
see the green spot there?
Can you see that?
They're little-- there are
beautiful little jewels there.
And on the side, you can see--
so as your cycling
along the road,
people can see the
bicycle, with its--
with its-- and these things
are wind proof as well.
As you're cycling along,
you can imagine this
as draughts, et cetera.
They're draft proof,
very, very beautiful.
And it's quite a
powerful light as well.
And this lasts
for several hours.
So if you run out
of electricity,
you have one of these
at home, you see.
And all your
batteries fail, this
will keep your illumination.
This is a significant
stage up from--
I'm sure you'll all agree--
from the illuminating
gases of earlier.
Have we got the
miner's lamp going?
Ah, the miner's lamp as well.
Now, this is the miner's lamp.
Also a fantastic source
of flame, et cetera.
Now, I'll come on
to the miner's lamp.
It's not such a brilliant idea.
And I'll explain why in
the mean-- for the miners.
And I think-- I am
hoping that some of you
will know and anticipate.
We can leave these
two here for a while.
And Oscar, could you
now in the darkness,
set fire to one-- could you
separate them apart slightly,
Oscar?
Thank you very much.
One of the safety
hazards always--
when you ignite something
which is flammable,
make sure that other
flammables are far away.
So just set-- No, the other one,
further from the candle, Oscar.
That's it.
So watch.
And watch the flame.
Now, that's-- notice the
huge amounts of smoke.
For the second one,
we'll have the lights on.
You can see the flame
there, but not the smoke.
But the second one,
we'll look at the smoke.
Now, I do have to say, can
you move it away a bit further
from the candle, Oscar?
Thank you very much, indeed.
This is purely for
the visual effect.
Thank you, Oscar.
There we are.
And now look at the black smoke.
Now that you see--
acetylene, it's a carbon-carbon,
with triple bonds in it.
And that is what is
unbelievably smoky.
So you're safe.
We're burning acetylene here
with incomplete combustion.
But these lamps don't
produce any smoke at all.
They are quite all
minimal amounts of smoke.
Why is that?
Because they have brilliantly
designed jets inside,
which allow air to go in.
Just as all the gas
cookers at home,
they burn with a blue flame.
Why?
Because the engineers have
designed brilliantly-- oh!
That's OK.
We'll just-- it's--
it's no deal.
We'll just put it off.
I think the flame--
what-- as I said, we haven't
practised with these.
The point is that we
should turn the top down
once you've got the flame.
It's of no concern, as you
see everything is in order.
And we can-- and we
should turn it off.
And we will continue to burn.
So if you're cycling
along, you see,
and suddenly-- you get extra
illumination, free of charge,
extra illumination
free of charge.
And a rapid response, and
we're back to square one.
So thank you very much.
So we continue.
We continue to do these things.
Now, as I was saying then,
the, ah-- the-- why is--
why do we get this fantastic
flame with no smoke?
And the reason is
because the jets, which--
I looked under a
microscope recently.
There are tiny
little holes in them.
And they allow air to go in.
And that then gives you a
flame of maximum luminosity,
but with minimum smoke.
They've been carefully designed.
It's not just someone
messing around.
It is careful engineer-- and
science put into practise.
Now, the next thing I wanted to
tell you-- and this is-- we're
now leading onto something
much more serious.
And that is working in mines.
And the mining--
and the mining--
the history of mining.
The mine-- coal has
been mined, as you know,
for a very long time.
And then I wanted to show
the next slide please
because I'm hoping it shows--
I wanted to tell you something
about miners in general.
And the fact is that
mining is definitely
one of the most dangerous of
activities, the most dangerous
job you can possibly have.
If some of you noticed some
magnificent music of a choir
singing at the
beginning of this,
and you wondered have I
turned up to the right place,
am I in the right department?
Yes, you have.
You had one of the world's
greatest choirs singing,
which was Welsh miners' choirs.
The Welsh miners had a fantastic
tradition of choral music.
And they were among
the best in the world.
Mining has a very long history--
a history.
It's the most dangerous
job in the world.
During the first half
of the 19th century,
a thousand people died
annually working in coal mines.
In the history of mining,
children as young as five
have worked in coal
mines, whole families.
A whole community, the
structure of society,
was built around coal mines.
And that tradition continues
today in many countries
around the world.
People often take
their coal for granted.
I remember when I grew up in
Shepherd's Bush in the 1950s,
every week the coal man
used to come around.
We used to have coal, used
to put it in the coal cellar.
But it's thanks to that--
and I wanted to say,
it's the coal
mining industry that
was the backbone of society.
Thanks to coal miners, we had
the Industrial Revolution.
I am not going to go anymore.
May I warmly recommend-- and the
visit to one of our coal mining
museums.
I personally visited National
Coal Mining Museum in Wetherby,
in Yorkshire,
phenomenal experience.
You will be amazed how much
you can learn and to recognise.
I just wanted to
quote the great--
the great wartime
leader, Churchill,
who was addressing miners
on October 31, 1942.
We've shown-- this
is in the war,
at a time when
things were very bad.
Morale was low.
But things were beginning
to change in the favour
of the Allies.
We shall not fail.
And then someday, when
children ask, what did you
do to win this
inheritance for us
and to make our name
so respected among men,
one will say, I was
a fighter pilot.
Another will say, I was
in the submarine service.
Another, I marched
with the 8th Army.
A fourth will say,
none of you could
have lived without the convoys
and the merchant seamen.
And you, in your turn,
will say, with equal pride
and with equal right,
we cut the coal.
So I am just making the
case that this industry
and the history of mining is
one of the most noble histories
in the whole of the human race.
It gave rise to
communities, et cetera.
Back to acetylene.
Now, the dangers of working in
coal mines, apart from the fact
that the mines could collapse
on top of you, were explosions.
And so far we have just
seen gases burning,
with no explosions at all.
But I now wanted to show
you a couple of examples
of explosions.
Now, when do explosions occur
and why do explosions occur?
Well, it is because the
gas which you are burning
has been premixed
with oxygen. That
is the simple rule as that.
So if you premix your fuel
with air or with oxygen,
it will burn
completely differently.
Now, we have an example
of this every day
in all internal
combustion engines.
When we drive our
motor car, there
are miniature
explosions all the time
going on inside the
cylinders of our engine.
Andres is now going to
demonstrate two explosions.
And one of them is where
we have coal gas-- which
is-- where's the one?
Here, this-- you see, this
here is filled with methane.
Methane, this is not coal gas.
This is methane, natural gas.
And that is the gas which
was dreaded by the miners.
This gas was called fire damp.
And it wreaked havoc
among the miners.
So that when it burns on
its own, it's not a problem.
When you mix it with air, it
can make the most almighty bang
you have ever heard.
So Andres is going
to light this.
Let me explain it.
This is full of pure
methane, pure coal gas--
pure natural gas.
There is a small hole at the top
and a big hole at the bottom.
When he lights it at the
top, it will burn with--
you'll just see a flame coming
out, like pure gas burning.
But, as the flame burns, air
will creep in at the bottom.
And as air creeps
in at the bottom,
there will eventually
be formed a mixture,
which is an explosive mixture.
And that explosive mixture
will make quite a loud bang.
Now, I will tell you when to
put your hands over your ears
because this takes
about five minutes.
So we know from experience--
is that right, Andres?
Thanks.
If you could start that one off.
And then is this one primed yet?
Not yet.
We'll get this one
going first of all.
Now, I will very quickly talk
about coal tar in the meantime.
And coal tar, this magnificent
mixture of substances.
And that is now burning.
Now, please watch.
This here is pure--
this here is pure
methane burning.
But as it burns, air is
being drawn in through the--
she said, that's nothing.
That's just like a candle thing.
Yes, it is.
But the mixture is changing.
The mixture of the gas
in there is changing.
Gradually that flame is going
to get smaller and smaller.
And then it will
almost disappear.
It will go inside.
And then, suddenly
you'll the effect of it.
So tell us Andres,
tell me when we
should get the children to
put their hands over their--
it's not bad.
But it's fairly loud bang.
And you can observe
what happens.
Once you don't see the flame.
OK, as soon as you
don't see the flame,
children, put your hands over
your ears, like this, OK.
So that's one there.
Now, here we have a toy cannon.
This is called a carbide cannon.
And it's where--
it's the exact--
but this is acetylene
mixed with it.
Here, it's methane mixed
with air, here acetylene.
So the rule is, for
making an explosion,
you need a mixture of a fuel
with oxygen premixed, premixed.
If you don't premix
them, they won't explode.
Now, I think we're getting
pretty close to that.
I think-- from the moment
you don't see the flame,
it's still a couple of minutes.
Are we ready to go
with this, Andres?
Are we ready to go with this?
Now, I'm then going
to turn onto--
once this is happening,
I wanted to turn onto--
while this is all
happening, I think you--
I'm going to carry
on talking because I
don't want to carry on.
And are we ready for Oscar
to come and fire the cannon?
Now, this too makes
a bit of a bang.
Now, let me see--
let's just explain.
In here, in this cannon,
Andres has put a small quantity
of calcium carbide.
And there is some water present.
And that is reacting to make
a tiny amount of acetylene.
It's a very small,
0.1 of a gramme.
You can barely see it.
But by gum, when
that's mixed with air,
it does make a little bang.
So children, hands over ears.
Oscar will now-- will set this
off by impacting the plunger.
Yeah.
Hit it with your fist.
[BANG]
Hard.
There it was.
Well, it wasn't
that loud a bang.
Could we try again maybe?
Maybe we waited-- I
don't know what happened.
So we'll-- it doesn't matter.
But this one will.
And I think we're
getting fairly close.
We're getting fairly close.
And we'll just have
another quick go at that.
Now, in the meantime, while
we're waiting for this--
[BANG]
I'll get-- there it was.
There we are.
[APPLAUSE]
Well held, sir.
I think-- I think this for--
for a cricket's team.
I think I must apply
to be a cricketer.
Now, please-- now, are we--
tell us when we're ready.
I will--
Can we have the
next slide, please?
The next slide, please.
Now, the next slide,
tell us a little bit
about the substances
made from coal tar.
The substances
made from coal tar
can be briefly divided
into primaries,
which are those listed there.
Now, benzene, toluene,
naphthalene, anthracite,
and phenol.
Are we ready to go?
Oscar is going to
have another go.
Hopefully, we'll get a
louder bang this time.
[BANG]
Ah.
We've done before--
this, by the way,
we accept no responsibility.
We didn't invent-- this
is a commercial toy.
So Andres, I think we know what
to do with this commercial toy.
But it has always worked
in the past, I have to say.
So it's a little disappointing.
Not to worry, we did have
one successful one here.
Now, on the subject
then of the substances
which you get out of coal tar.
And this is the clever bit.
From crude oil and modern
hydrocarbon sources,
we get primarily aliphatics,
substances which contain
single carbon-carbon bonds.
But out of coal tar,
we have substances
which are primarily aromatic.
This is a molecule of benzene.
I'm not going to go into
detail of the chemistry.
But the pink and the purple
represent chemical bonds.
The important thing--
which represent
delocalized orbitals
and all the rest.
But from a children's point
of view, the formula for this
is C6H12, six black ones, and 12
hydrogens, which are the white.
And every carbon has four bonds.
Here, it's a flat molecule.
And this is a
molecule of benzene.
You may be interested to
know that benzene was first
discovered in this
precise building
by the great Michael Faraday,
who was examining incidentally,
you've guessed it,
illuminate gases.
They were-- they did all
sorts of experiments.
Michael Faraday distilled
whale oil, believe it or not,
which they were investigating.
He separated the product
by fractional distillation.
And using combustion analysis,
discovered the substance
which he called bicarburet
of hydrogen, by the way,
had a formula C6H6.
And that sample is
present in this building.
You may like to go
and look for it.
But this type of compound-- and
opened up a totally new branch
of chemistry, hitherto unknown.
And it all comes from that
horrible black mess in there,
which is coal tar.
So when you distill
coal tar, you
get those which are
called the primaries,
and benzene, toluene,
naphthalene, anthracene,
and phenol.
Now, the first four
are hydrocarbons.
And they all contain
a benzene ring.
The last one, phenol,
contains an OH group, C6H50.
Have you heard of coal tar
soap, used as a antiseptic?
Today, still used.
Coal tar, that word, has
survived to this day.
And through intermediates,
those have been manufactured.
A remarkable range of
substances, as you see,
which are listed up there.
Thanks.
And there are loads of
other substances as well.
There are whole
books and volumes
written on the remarkable
substances obtained
from coal tar.
Could we, Andres, just
have a look at the--
Andres has got a
sample of anthracene,
which is fluorescent.
It would help if we
had the lights off.
This glows in the dark,
if you shine a torch.
So we'll just have a look.
It's a fluorescent substance.
And there you see it fluorescing
in the dark, as a torch.
And that is just one of
the many, many properties
discovered from the
substances which
are extracted from the
fractional distillation of coal
tar.
But now, I am going to
move on to dyestuffs.
Dyestuffs, by the
way, were first
discovered by a
remarkable accident.
William Perkin, a brilliant
young chemist, only 18,
by the way.
So listen, at the age of
18, he was investigating.
And he was trying to
use quinine, I believe.
And he was oxidising it, in an
attempt to make something else.
But, in fact, he ended up
with a fantastically coloured
substances, which subsequently
became his Perkins mauve.
That was 1856.
That totally revolutionised
the dyestuffs industry.
So in other words, dyes which
until then had been obtained
from plants and
from animals, now
they were being able to
make them synthetically.
This here is aniline blue.
That's a dye made from coal tar.
This here we have
is aniline yellow.
And this here is rose aniline,
which is a beautiful purple
colour.
Now, rather than
showing you samples,
allow me to show you the
remarkable collection.
Could we have the nice--
next slide, please?
Look at all of these dyes.
Now, this is a wonderful range
of colours derived from coal
tar.
This is, by the way,
reproduced by kind permission
of Dr. Alexandra Loske,
the curator of the Royal
Pavilion in Brighton,
because she actually
collects these diagrams.
And they are very--
and you can just see all
those coloured dots, children.
Don't bother with
the chemistry below.
Just look at-- and all
those colours, from here.
That's the remarkable fact,
which I wanted to alert you to.
Now, we're turning to the
final topic of the day.
And that is photography.
And I am going to
show you-- could
we start bringing
on the equipment
please, for the photographs now?
And I'm going to show
you-- to tell you
the photographic chemicals.
And you saw
perfumes, explosives.
That would require five
or six separate talks
to explain all of this.
But such were the
remarkable achievements
of organic chemists
in the latter half
of the 19th century, that
synthetic organic chemistry,
combined with
analytical chemistry,
enabled us first to--
separation, first of all,
by fractional distillation,
identification by
combustion analysis.
And then synthetic roots,
making a whole new range
of substances.
And synthetic organic
chemistry continues to this day
to make remarkable products.
By the way, one of the
ways of protecting yourself
while they're setting up there--
this, of course, is the
famous miner's safety lamp
invented by Sir Humphrey
Davy in no other place
than this building.
This, of course, is one
of the things that he did.
He was a remarkable
man, gave lectures here,
and all the rest.
One of the greatest
scientists of all times,
together with Faraday,
in this building.
Now, the safety lamp essentially
works on the principle--
I'm not going to ignite it now.
You burn a flame inside.
And if you go into an area
which is potentially explosive,
then the wire gauze here
allows the air to go through,
but not the heat to go out.
So the flame will turn colour.
The miner will then be warned
that there is methane around,
or fire there.
And they will be able to
move away from the area.
This, of course,
thousands and hundreds--
hundreds of thousands
of these were produced.
If you go to the National Coal
Mining Museum in Wetherby,
you'll see whole
cupboards full of them.
And this is the
point I am coming to.
Isn't it extraordinary
that the miners
used this to protect you
from flames and the flame
to give you light.
Such was the life of the
miner, hovering between success
of getting the coal
and fatality of getting
killed in the process.
So that's why it
has been described
as one of the most
dangerous jobs of all time.
Now, coming to
photography one of the--
the greatest crazes or
the greatest discoveries,
which set off a craze in the
19th century, was photography.
And this photography
stemmed from the fact
that for hundreds
of years people
had noted that
certain substances are
sensitive to light,
especially silver compounds.
And it was Nicephore
Niepce, a Frenchman,
who produced the world's first
ever permanent photographic
image in 1822.
Now, what I'm going
to do now is I'm
going to use the chemistry of
Niepce and the silver bromide
or reducing silver bromide
chemistry to actually
try and take a photograph
in here, in this room.
It's a huge challenge.
I am going to be using
a traditional plate
camera from the Victorian era.
I am going to be using a--
let me just have my photographic
plate, first of all.
Sorry.
I am going to use a photographic
plate, which I have in here.
And I will explain very
briefly the process.
Normally, when we
take-- when we used
to make a photographs
traditionally,
used to make them
on-- on negatives.
So this was first metal plates,
then glass plates, and then
a plastic negative, like this.
Now this coats a gelatinous--
this is gelatin on here,
on this plastic.
And it's sensitised
with silver bromide.
And all I want to tell
you is this obviously
is no longer usable because you
have to store it in a darkroom.
But during exposure to
light, the silver chloride,
silver bromide, gets
converted to metallic silver.
I don't know anymore
about the chemistry of it,
apart from the fact
that one of the greatest
challenges of chemistry
with photography
was to reduce silver
ions to silver
in the process of developing.
And for that process, coal
tar came to the rescue.
There was a compound called--
today, it's called hydroquinone.
Today, it's called
1,3-dihydroxybenzene
hydroquinone, which to this day
serves as the reducing agent
to reduce silver ions to
silver during the development
of a photographic plate.
So I am going to now take--
I'm going to ask the young--
the young-- it's a young lady
who has been asked to cut
come forward and
sit in the chair.
And we're going to
take a photograph.
And after that Andres
will do the final,
the final demonstration.
If you can kindly start
with-- as soon as we can.
So please sit here, my dear.
Thank you, very much indeed.
And what's your name?
Benedicta.
Benedicta.
We're deeply honoured.
Benedicta is putting,
I have to tell you,
slightly herself
at risk you see.
She's going to be exposed
to a bright magnesium flash.
We are using traditional
Victorian technology here.
So none of this computer
nonsense, et cetera.
We're simply-- we're simply
doing basic chemistry
and physics.
Now, I-- what I've got
to do first of all,
I've got to set up the camera
and focus on Benedicta.
Now, this will take
a little while.
We're going to shine a torch.
If we can have--
just for a second, I've
got to shine a torch.
And I've got to focus.
I have prefocused it.
But I'm prefocused
it on my daughter.
And my daughter was just
a little higher, you see.
So we're going to now
lower it for Benedicta.
Please watch carefully.
I have here, a Gandolfi
tripod for those of you who
are interested in photography.
This is a very, very, very--
no, right close up.
Can you just sign on Benedicta's
face, please, very close up.
So the reason why I'm
doing this is I need to--
I need to be able to have a
spot on-- no, it's much closer.
Andres, from the front.
That's it.
That's it.
That's-- a bit more like that.
It's-- now this we have to have
as the technique for focusing
on her, so that I can get the
images pin-sharp as I can.
This does not
guarantee, by the way--
I'm not going to make
a great photograph.
It is the idea of
doing the process,
undertaking the process,
and seeing that.
Thank you very much.
That's it.
She's in focus as much
as I can get it now.
Now, what we do is this.
We now stop the lens down to
give it a greater-- excuse me.
And I'm going to walk in.
Don't move.
Don't move.
You mustn't move, my dear.
Otherwise, we'll
go out of focus.
Now, this-- this is
Victorian photography.
Thank you very much.
We're stopping it now to F8, to
give a greater depth of focus.
We're going to set off the
magnesium flash powder here,
which I'm going
to shortly mix up
using a traditional
Victorian technique.
Let's just have this-- sorry.
Thank you very much.
I'm going to mix
these up together.
Now, this is-- literally,
it's a tiny, tiny amount.
It's a tiny, tiny amount.
It's 1 gramme of
magnesium powder,
with 0.3 grammes of
potassium chloride.
Now, this is a flash powder.
It's used in fireworks.
And I can assure you, they
use much greater quantities
in fireworks.
But, on the other hand,
you're much further away.
So for this range, we think
this should be satisfactory.
Now, can I call Clara to
bring our reflective umbrella,
please.
We need to-- we're
using a full--
we're reproducing a full
Victorian photographic studio
in this here.
And I'd say the chances of
it working are not very high.
But I believe it's
very important
that we should give it a go.
So what I've done, I've
mixed my flash powder here.
I'm going to move it a
bit closer to Benedicta,
who will get a blinding
white flash in her face.
But she'll be looking
there, of course.
And we've given her safety--
Now, is this about
the right distance?
I hope so.
Clara, you're going
to be holding here.
Now, we're going to be using
a hot wire technique, which
the Victorians used as well.
So you don't flap around with
burning splints, et cetera.
But I tried this
out this morning.
And I had to try a few attempts.
It didn't work.
So if this doesn't
work, I will then use--
we will then use
something-- we will then
use-- we will then
have to resort
to the traditional way of
heating it with a lighted
splint.
But this does make
quite a bright flash.
It's not that--
I'm going to be--
I'm going to put
the plate in now.
Now, this is the clever bit.
In here, you see,
I have a plate.
And it-- this is a seal.
This is called a plate holder.
And in here I have a
sheet of positive paper.
So this is photographic paper.
So obviously, when
we have this--
this exposed-- now,
there should be-- where's
the lens cap to the camera?
Excuse me.
We're just -- did I have it?
Thank you very much, Dave.
Thank you very much.
We have a lens cap.
The only exposure here
will be made by the flash,
you see, of the magnesium.
I don't guarantee it will work.
And I will ask
you to operate it.
That's to say it
wasn't my fault.
Now, what we're going
to do is I now have
to put in-- so I focused it.
We now slide our plates
in at the back here.
We now side our plates
in at the back here.
And then we undo
the latch, which
prevents me from accidentally
exposing the plate.
And now we're going-- so now
we've got the lens cap on.
So that means even
though I'm opening the--
even though I'm
exposing the paper--
this is positive
papers, I say, which
has got silver bromide on it--
even though I'm exposing
that to the camera,
there's no light getting
through the camera
because we haven't
set anything off.
So I'm now pulling
the plate out.
By the way, if any of you
have seen school photograph,
they're still using this
technique for school,
for very large photographs now.
So we've now exposed the thing.
I will now ask for the
lights to be turned off.
And we're going to blow
the candle out, obviously.
Now, you'll notice that even
with the lights turned off,
there is a surprisingly large
amount of background light.
But we did-- that's fine, Oscar.
That's fine.
Thank you very much for helping.
So the thing we do now is I'm
going to take the lens cap off.
And we'll see whether-- the--
press now, hard.
Don't look at it anyone.
Fingers crossed.
If not, we'll do it--
Ah, there.
So there it is.
Thank you very much.
Now, we quickly put
the lens cap on.
I now close this off.
I have now closed this off.
Thank you very much, Andres.
And now we go to develop it.
Now, Dave has set up a special--
thank you very much, Benedicta.
I do not guarantee a result. No.
No.
[APPLAUSE]
I think Benedicta, yes, for
bravery, award for bravery.
Now, what we're going to do is
on red light here, which is--
we're going-- now,
which is the developer?
This one.
That's the developer.
Thank you, Dave.
We're now going to
push in our film--
our film in a special darkroom,
which Dave has created here,
which-- we'll
shove it in and see
whether we can get an image.
So have we got the
tongs, the tweezers?
Very many thanks, Dave.
So we keep our fingers crossed.
We keep our fingers
crossed for a result.
So thank you very much.
I can barely see.
I don't know whether I've even
got the right sheet of paper
in, I have to tell
you the truth,
so useless am I. This
is positive paper.
I'll see whether it's this one
or maybe it was the other side.
I can't tell.
Oh, no.
It was-- this is the right one.
Whether we've got an image--
is it-- is it--
Yeah, yeah, yeah, it's
in the right, where--
Yes, we see.
Something is appearing.
We can see some dark glasses.
We can see some dark.
We can see a nice smile.
We can see a nice smile.
Let's just have a look.
It's slightly out of focus.
And there is a slight
amount of fuzziness.
But I think no one will doubt
that that is an image, that
is an image, you
see, which resembles
the very nice, young Benedicta.
You'll have this as a
souvenir to take home.
I'm putting it in
fixer now, the way.
I've finished with the
coal tar derivative.
I now want a fixer,
which is basically
ammonium thiosulphate.
But we'll leave that there.
And we'll now go to the
last experiment of the day.
So photography in action,
thanks to coal tar.
That's the point
I'm trying to make.
Now, for the very
final experiment,
for the very final experiment,
we're back to illumination,
back to illumination.
Now, what I wanted to say,
what I wanted to say--
thank you-- before my--
is a few concluding comments,
a few concluding comments.
And these are as follows.
We owe-- we owe--
today's world, we
owe a great deal
to the energy and
the chemistry, which
has, for thousands of years,
been provided by coal.
In the future,
though, we will be
grateful to other-- for
other sources of energy,
other sources of chemicals.
Coal is not eternal.
And there is a limited
supply in our ground.
The people who are going to
be involved in that science
and technology of energy
and supplies for the future
are among you here
today, children.
You are the future.
And you are-- to you, we
shall be looking forward.
Those among you interested
in science and technology,
you will have this
fantastic role
to play in society of
helping the whole of humanity
to survive with energy and
with chemical resources.
For our final experiment,
which is to do with light,
let me allow-- we're now
back to illumination.
And we have here the gas,
which is the most common gas
in coal gas, which is what we
started with, illuminating gas.
And that is hydrogen.
And what we have is a
balloon filled with hydrogen.
It is the lightest
gas in the universe.
You may be interested to know
that hydrogen was formally
recognised by the great
English chemist Henry Cavendish
in 1766.
Notice the late
'70s, that's when
gas, the chemistry and
the physics of gases,
was being investigated.
So what I'm going to do is this.
I am going-- I have
here a fuse, a fuse
which is made up of
nitrocellulose, which
will burn rapidly down there.
And it will then go
up the light, up the--
thank you very much
indeed, Andres.
So we're going to ask for
lights to be switched off,
as they were at the beginning.
But this time, hands
over ears, children.
This doesn't make
such a loud bang.
But I think it's well worth
protecting yourself, just
in case.
It's going to be a bright yellow
flash, going along the gutter,
and then up the wire, and this.
So let there be light.
[YELLS]
[POP]
So there it is.
Thank you very much, indeed.
Thank you very much, indeed.
[APPLAUSE]
Thank you very much indeed
for your kind attention.
Thank you very much indeed
for your kind attention.
Thank you so much, indeed.
And I hope you learned.
