Discovering the Elements Chemistry: A Volatile History

In 1807, maverick Cornish chemist Humphry Davy

attempted something no one had dared try before.

He harnessed a newly discovered force, electricity,

to rip apart a caustic chemical called potash.

And he discovered a new element.

Vivid, violent potassium.

Davy had found a new way of cracking open the natural world to reveal its building blocks.

This is the story of one of the biggest questions there is.

What is everything in our world made of?

The quest to find out would ultimately lead to an extraordinary insight -

that everything, from the diversity of nature to the complexity of man,

was made from just 92 elements.

'I'm Jim Al-Khalili.

'I've studied physics all my life, but I couldn't have gained my knowledge of the subatomic world

'without the work of the chemists who first unravelled the mysteries of matter.'

Brilliant. That was really beautiful.

Finding and understanding the elements would turn out

to be one of the greatest detective stories in the history of science.

A staggeringly difficult task that would span centuries.

I'm going to retrace the steps of the chemists who risked their lives

to prise secrets from the natural world.

It's instantly disfiguring, instant blindness.

It is really hideously dangerous.

I'll find out how scientists struggled

to crack one of the most important codes in the universe.

And I'll discover how our fascination with the elements led to the making of the modern world

and pushed the human race to the edge of destruction.

EXPLOSION

Our compulsion to seek answers at almost any cost,

and to search for fundamental truths,

has powered scientific endeavour.

And it underpins this story.

Our quest to unravel the mysteries of the elements.

It's hard to imagine what it must have been like

to look around and not have a clue what the world is made of.

Not to know what this contained.

To be mystified by fire, to have no idea that

oxygen is essential to make it burn or that oxygen even existed.

Not to know that hydrogen is a vital ingredient of the ocean

or that sodium and chlorine combine to give its salty taste.

It's only in the last 200 years that we've known what an element is.

It's a substance that can't be broken down into a simpler one by a chemical reaction.

The ancient Greeks already knew of lead, copper, gold, silver,

iron, mercury, tin.

But to them these were just metals.

They were convinced that the whole world was made of earth, air, fire and water.

For more than 1,000 years we had no way

of breaking open the natural world

and no choice but to base our concept of elements on what was visible around us.

By the 16th century, things were starting to change.

Alchemists began to penetrate the substances around them

in their bid to turn base metals into gold.

They kept secret notes of their experiments written in mysterious codes and symbols.

And they dreamed of immortality.

From the Far East, through Europe to London,

the backstreets and cellars were a seething, bubbling hotbed of alchemical research.

It was an alchemist who first challenged the Greek idea

that everything was made from earth, fire, air and water,

in a story which begins in Basel, Switzerland.

It starts with Philippus Theophrastus Aureolus Bombastus von Hohenheim who,

thankfully for me because I'm not saying that again,

adopted the nom de plume Paracelsus.

Paracelsus was not just an alchemist trying to unlock

the mysteries of matter, he was also a physician and surgeon.

And he wasn't afraid to challenge the orthodoxy of the day.

In 1526 the city of Basel was famous for its printing.

And its most sought after printer, Frobenius, had just been told by

his doctors that unless he had his leg amputated he would die.

So Frobenius called for Paracelsus,

who wouldn't accept the medical orthodoxy of the day.

He also wasn't afraid to mix medicine with alchemy

to concoct new potions and remedies.

He created a cure that not only saved Frobenius's life,

but established Paracelsus as a true radical.

He proposed a groundbreaking new idea, suggesting that the world

was actually made of three elements -

salt, sulphur and mercury.

Paracelsus saw these as the core ingredients to make metals and medicines.

He reckoned salts would heal wounds, sulphur was combustible

and mercury, known then as quicksilver, was fluid and volatile.

Now, mercury is an incredible substance.

It's the only metal that's liquid at room temperature.

It's also remarkably heavy.

Just this small amount here feels very, very heavy.

But I've got a much larger amount here.

And if I try and lift it...

That's not stuck to the table, it's 14 times heavier than water.

It's also toxic, so I'm wearing a triple layer of gloves here.

Cos I'm going to do something I've always wanted to do,

which is dunk my hand in mercury.

It feels very, very strange.

It's pushing my hand up.

It's nothing like any liquid that I know of.

It feels very cold as well, even through the three layers of gloves I can feel its coolness.

And just to give you an idea of how weird this stuff is, I've got a steel bolt here.

Let's see what happens if I put it in the mercury.

Mercury is so much denser than steel. It floats.

Mercury - silvery and mirror-like,

it's one of the most beautiful and elusive of all the elements.

It's rarely found in its natural form.

But heating a red rock, cinnabar, will reveal molten mercurial lava hidden within.

The phrase "mad as a hatter" was coined when hat makers

who used it suffered from mercury madness.

In the mines of South America, treasure hunters risked their lives

by using toxic mercury to extract another element - gold.

And floating on mercury gave smooth motion to the revolving light of some Victorian lighthouses.

Paracelsus didn't manage to convince the establishment with his idea of

the three elements, mercury, sulphur and salt.

In fact, he'd enraged them by ignoring their medical texts and creating alchemical cures.

He was too radical for his time.

In a dramatic gesture

to show his contempt for the medical authorities, he burned their books.

He was forced to leave Basel University and fled to Germany,

where he could carry on practising medicine and alchemy.

But he'd paved the way for a new era of questioning,

at a time when many alchemists were more interested in making gold.

They would heat metals in scorching furnaces.

They'd boil, they'd distill.

And it was the pursuit of gold that lead to the first major breakthrough

in the hunt to discover elements.

For the alchemists, gold was like the holy grail.

They believed it possessed spiritual, magical, even medical properties.

It was the stuff of power, the colour of the sun.

It was made into crowns and coins.

It adorned kings, queens, palaces and temples for over thousands of years.

In ancient Egypt, gold was thought to be the skin of the gods.

To the Inca civilisation, gold was the sweat of the sun.

The alchemists didn't yet know what an element was.

But some unwittingly touched on the idea that they could be hidden within other substances

when they suggested that gold might be concealed within the human body.

The relentless pursuit of this obsession led one alchemist

to become the first person credited with the discovery of a new element.

Hennig Brand.

He was searching for a way of extracting gold from the body

when he hit upon what seemed like a smart idea,

a gold coloured liquid in plentiful supply - urine.

It was 1669 and in the dark, smelly basement of his Hamburg House, Brand's expensive

alchemical experiments were rapidly eating through the funds of his wealthy wife, Margeretha.

But now, with his urine brainwave, Brand believed that he was on the threshold of a momentous discovery.

He was about to make his name and restore his family fortune.

All he needed was another fifty buckets of urine.

'Chemist Dr Andrea Sella has been studying Brand's work

'and is going to attempt to find the hidden element.'

If you pass me the urine.

-You're welcome.

-And this is courtesy of myself.

I'm already holding my breath.

Ahh, you know, you know you mustn't over-react.

So what would Brand have done?

What Brand was trying to do was to get to the heart of the matter.

To start boiling it down, to get rid of the unimportant parts.

That, of course, was principally the water.

There is an additional feature and it's not really surprising.

But, you know, have a quick waft of that.

Yeah, it's pretty bad.

Brand must have had some very, very patient neighbours.

I really don't know what his romantic life must have been like, but I can't imagine he was all that popular.

You see, I can understand urine being gold coloured.

But Brand was looking to make gold. What is the connection?

First of all it seems tremendously laughable to us to use something as disgusting a waste product as urine.

One of the alchemical views was that man was really a microcosm of the universe and, therefore,

urine actually carried within it some of that vital force. The life force.

So a sort of metaphysical symbol of life?

Absolutely. And so, really, this was a substance of power.

Brand was determined to persevere with his quest for gold.

He distilled the urine down to a paste,

then heated it at a phenomenal temperature for several days.

Eventually, wisps of smoke revealed tiny fragments that combusted in air.

But what was this fiery substance?

It wasn't golden like the sun, but it burned brighter than any medieval candle.

So this is what Brand isolated from urine.

It's not gold.

This is phosphorus.

Brand had discovered, completely by accident, a new element, never seen by man.

Fiery phosphorus.

He was looking for riches but didn't realise that he'd

unearthed a fundamental notion, that elements could be concealed within a hidden world.

Phosphorus is biologically very, very important.

If you think of our bones they're composed predominantly of calcium hydroxy phosphates.

There's lots of phosphate there.

It's in our DNA, it's in all sorts of our tissues, and

as a result there's always phosphate in the blood and some of it, excess, is transferred into the urine.

A little bit less than about a gram per litre.

This stuff is a complete tiger.

You can see that it starts to smoke very gently in air.

And this is really a warning to us that things are going to happen if we don't deal with it quickly.

So we're going to drop it into this flask.

The flask is actually filled with oxygen.

And so it's sitting in sand

just to keep the heat from attacking the glass.

And now I'm going to touch it with a hot glass rod.

And so there it is.

That's fantastic

and it sort of feels cold. It's not hot.

That's quite beautiful.

Because it shone so vividly,

yet was cold enough to hold, Brand called his discovery "Icy Nocta Luca."

Cold night light.

Phosphorus. It's in every cell in the human body.

It's used in drugs to promote bone growth, treating diseases like osteoporosis.

153 million tonnes of phosphorus are produced every year.

Its phosphate is consumed as a food supplement, and is an ingredient of toothpaste.

But eating just 100 milligrams of pure phosphorous,

enough to coat a finger tip, could be fatal.

And it has an even darker side.

In the Second World War, phosphorus was used in the thousands of bombs dropped on Hamburg.

The city where Brand discovered it.

Brand hoped that phosphorus would make him a fortune,

but his cash ran out and he sold the secret of his discovery for a paltry sum.

Before long phosphorous was being touted round the royal courts of Europe.

And in 1677 it arrived at the court of King Charles II.

Soon after, wealthy alchemist Robert Boyle, witnessed its luminous magic

and determined to investigate its properties.

Dr Andrea Sella and I are going to follow Boyle's own instructions

to attempt one of his most significant experiments on phosphorus.

So I have here extracts from Robert Boyle's book,

New Experiments and Observations Made Upon the Icy Nocte Luca.

Having put together about half a grain of our dry nocte luca matter.

How much is half a grain?

Well, half a grain really isn't very much.

There's 7000 grains to the pound.

So you can work it out.

You're the physicist.

OK, and six times its weight of common flowers of sulphur.

OK, so we'll just put a little piece...

-So that's just sulphur powder, is it?

-Yes, it's essentially finely powdered sulphur.

Right and it says, they were lodged in the fold of a piece of white paper.

He rubbed it with the haft of a knife.

Well, I haven't got a knife but I do have a spatula.

-That'll do.

-So we'll use that. OK. It's beginning to smoke.

-OK.

It's beginning to kindle. We've got a little bit of fire there already.

The main lump of phosphorus...

-Oh, look there it goes.

-Oh, there it goes. There it goes. Whoa!

-Didn't have time to bruise it.

-It didn't need bruising.

-It went up.

So you've basically recreated what is the precursor to the match.

Yes, and I've also got some splendid smoke rings here.

I mean this would really radically transform things because what you had was fire on demand.

Boyle had stumbled upon the essential ingredient of a match.

A huge industry was spawned from this single experiment.

But Boyle wasn't really interested in the money making potential of phosphorus,

just understanding the properties of this element

was reward enough for him.

So phosphorus did have transformational powers after all.

It may not have changed lead into gold, but it turned an alchemist into the first modern chemist.

Boyle had set the stage for future element hunters.

Unlike most alchemists, he shared his methods

and was able to pass on the tools they needed to help unlock the mysteries of matter.

I've come to search the vaults of the Royal Society in London.

What I am looking for was deposited here in 1661, just one year after the Society was formed.

Here it is.

The Sceptical Chemist.

It was written by Robert Boyle, who was one of the founders of the Royal Society.

Dr Anna Marie Roos, a specialist in the history of chemistry, has studied Boyle's writings.

I've got a copy of Boyle's, Sceptical Chemist.

Why was this book so important?

This was really considered to be one of one of the books

that signifies a transition from alchemy to chemistry

and some scholars have thought it's the first book of chemistry.

The fact that book was written in plain English was also quite a new thing.

'You only have to compare Boyle's book to the cryptic writings of another alchemist.'

That great man of science, Isaac Newton, to appreciate its innovation.

And we can see here that it's in Latin and we also can see that

there are several alchemical symbols being used for the chemical elements.

It really does remind me of astrology

-and Egyptian hieroglyphics.

-Absolutely.

And I compare that with Boyle where he says things like, "He took 200 pounds of earth,

"dried in an oven, having put it in an earthen vessel and melted it."

He's describing a chemical process.

Absolutely. What made Boyle a bit different is that he was willing to

divulge some of his chemical secrets for the good of the scientific community.

Boyle was bringing alchemy out of the shadows and into an enlightened, rational age.

He was opening up the scientific method for everyone to see.

The alchemists must have feared he was giving away their secrets.

But he wasn't so much interested in debunking alchemy,

as getting rid of its metaphysical baggage

and replacing it with a more rigorous scientific approach.

A new age of scientific experimentation had begun.

And with a more open exchange of ideas came a rejection of tradition.

It heralded an era in which the ancient Greek doctrines

were re-evaluated and new concepts introduced.

Copernicus challenged the ancient idea that the Earth was at the centre of the universe,

proposing instead that it was just one of a number of planets orbiting around the sun.

Vesalius mapped the human body.

It was an exciting and liberating time in which Europe was being

dragged out of its dark ages and into an age of reason.

But just because people were thinking differently,

didn't necessarily mean that they were getting it right.

And while a new generation of scientists were keen to come up with modern elements to replace the

four ancient ones, their enthusiasm didn't stop them from buying into completely false theories.

And so it was that science went up one of the greatest blind alleys in the history of chemistry.

It was 1667, a year after the Great Fire of London

had razed one of Europe's greatest cities to the ground.

The mysteries of fire were at the forefront of everyone's minds.

But no-one really understood what fire was or how it was created.

German chemist, Johann Becher, proposed that the destructive

power of fire was caused by an ethereal entity named phlogiston.

It was thought to be an odourless, colourless,

tasteless and weightless substance, that causes things to burn, reducing them to their true form.

This burning wood produces ash.

So wood must be made up of ash, pure wood, plus phlogiston.

The notion of phlogiston seemed so credible in the 17th century

that it consumed the scientific community.

It was accepted as a truth, virtually paralysing our ability

to discover more elements and map the contours of the natural world.

One great chemist who experimented with gases even claimed to have isolated it.

On the same day every week for 50 years

a rather peculiar scientist came to the Royal Society Dinner Club

to discuss the latest scientific ideas.

Henry Cavendish has been described as "the richest of the learned, and the most learned of the rich".

He was a major shareholder in the Bank of England, and had royal connections.

But it's remarkable he came to a social gathering at all.

Cavendish was painfully shy and lived in virtual isolation.

At home, he insisted that his servants only communicate with him in writing.

Colleagues at the Dinner Club said that he'd often be found outside,

trying to pluck up the courage to go in.

And when speaking to him it was best to look into the air with vacancy rather than directly at him.

Despite signs of what we might recognise today as autism,

Cavendish made a vital contribution to the discovery of the elements.

I'm going to investigate how Cavendish's experiments with airs

led him to find the first element that's a gas.

Cavendish added a metal, zinc, to an acid.

It was deceptively simple.

And pretty soon...

bubbles began to appear on the surface of the zinc.

Cavendish started to collect this gas, which I'm going to do in this test tube.

It didn't smell of anything, it didn't taste of anything, in fact it was completely invisible.

Cavendish soon realised this was no ordinary gas.

And then...

he set light to it.

POP

Cavendish had no idea he'd discovered a new element,

in fact he thought he'd found a new kind of air, different to the air we breath.

He called it, not surprisingly, "inflammable air".

And he believed his inflammable air had to be the mysterious phlogiston.

It was, odourless, tasteless, colourless and most importantly, it caught fire.

It HAD to be phlogiston.

But he was wrong.

Cavendish didn't realise it but he'd isolated a new element, hydrogen.

He investigated the characteristics of his new air and

calculated that it was eleven times lighter than the air we breathe.

Now, I've got Asma here to help me.

She's pumping hydrogen through into this washing up liquid

and creating bubbles of hydrogen coming up through this funnel.

Because hydrogen is so much lighter than air,

at some point these bubbles will separate and start to float up.

Brilliant, that was really beautiful.

'It was lighter than air and burst into flames.

'You can see why Cavendish thought it was phlogiston.'

Cor, they're getting better!

But this belief meant Cavendish wasn't credited with the discovery of hydrogen during his lifetime.

Nor would he witness its full force.

Hydrogen - produced just after the Big Bang alongside helium and lithium,

it's the most abundant and lightest element in the universe.

The suns energy comes from the nuclear fusion of hydrogen.

The same principle harnessed in the hydrogen bomb.

Hydrogen's highly flammable nature was witnessed

when it ignited the Hindenburg zeppelin airship in 1937, killing 36 people.

'Like so many other element hunters, Cavendish didn't realise the significance of his discovery.

'But he did observe something that would play a crucial role in our understanding of the natural world.'

Each time he set light to the gas,

a dewy liquid began to appear on the surface of the glass.

It was water.

Now this had incredible implications back in the 1700's because back then

they believed in the ancient Greek idea that water was an element.

But if you can make water out of two other constituents,

then it couldn't be an element. In fact, water is a compound.

'This struck right to the heart of the ancient concept of four elements.

'Cavendish's observations could have shaken the foundations of accepted belief.

'But they didn't, because he was thrown off-course by phlogiston.

'He reckoned that the airs must contain a form of water

'modified by the presence of phlogiston.

'It simply didn't occur to him that water was a compound.'

So while he was very close to destroying the temple of the ancient four elements,

he couldn't quite yet disprove them.

The pillars of that temple were now standing on very shaky ground,

and it wouldn't be too long before they'd come crashing down.

But it wasn't Cavendish's water that would finally disprove the ancient theory.

It was air.

'19 of what we now call elements had been found so far,

'but 18th-century scientists were still grappling to work out

'what the world was made of.'

'The Royal Society had commissioned its members

'to investigate the invisible airs.'

By the mid-1700s, there were three known types of air, or gases.

There was the common air, that we breathe, inflammable air,

now known as hydrogen, and fixed air, or carbon dioxide.

And experimenting with these airs was a favourite pastime

of clergyman and amateur chemist Joseph Priestley.

'Priestley lived next to a brewery, and spent rather a lot of time there, especially considering

'he was a Unitarian minister, known for his extreme sermons.'

But he wasn't here for the beer.

Priestley was interested in the gas that's produced in the fermentation process.

He called it brewery gas, but of course it was well known by that time as fixed air.

We know it today as carbon dioxide.

Carbon dioxide is being produced inside this vat,

and because it's heavier than air, it's pouring out and cascading down.

Now we can't see it, but an experiment that Priestley himself

carried out involved seeing what carbon dioxide does to a lit flame.

So if I hold this flame here,

it's not in the path of the gas at the moment, but if I bring it down...

You can see it immediately extinguishes.

You can even see the trail of smoke following the path of the gas.

'Priestley was fascinated by fixed air.

'He mixed it with water, and so invented the first fizzy drink.

'In time it would spawn an industry worth millions,

'but he earned almost nothing from it.

'Instead, Priestley's passion for science

'led to an invitation to Bowood House in Wiltshire,

'to tutor the children of the future Prime Minister, Lord Shelburne.'

Priestley lacked the wealth of earlier chemists like Boyle and Cavendish.

And he made little money from his inventions and his radical writings.

Lord Shelburne was offering him financial stability

and the chance to continue with his scientific experiments, in return for teaching.

He became the first professional, salaried chemist.

And it was here that he continued his experiments with airs.

On 1st August 1774, he performed

one of the most important experiments in chemical history.

'Priestley was gripped by unlocking the elemental secrets of the airs.

'On this occasion he started with a powder he knew as mercuric calx.

'Mercuric oxide.

'He put it in a test tube to collect any gas it might give off when he heated it.'

'Then he filled the test tube with mercury, which would trap the gas.'

So I now place my finger over the top of the tube,

invert it, so that it's submerged into the mercury bath.

I now have the mercuric oxide powder at the very top of the tube.

What Priestley did next was heat up this powder.

The level of the mercury in the tube is dropping.

What's going on is a gas is being produced that is pushing the mercury down.

What in fact is happening is that this mercuric oxide powder

is being broken up into its two components.

I'm now going to see what gas Priestley had made.

If I take this splint and blow it out so I just have a glowing ember,

it bursts back into flame again.

'We now know that Joseph Priestley had found oxygen.

'But because he believed in the idea of phlogiston, he thought the splint

'was introducing phlogiston to the new air and catching fire.

'He concluded that his air must be without phlogiston.

'So he called it dephlogisticated air.'

Priestley's experiments with his new air didn't stop there.

In fact, they got stranger.

He placed a mouse inside a sealed container filled with this new air,

expecting it to live for just 15 minutes.

Instead, he found it alive and well after half an hour.

He then tried breathing it himself and noted...

"I fancy my breast felt particularly light and easy after some time.

"Who can tell but that, in time, this pure air

"may become a fashionable article of luxury.

"Hitherto only two mice and I have had the privilege of breathing it."

'Little did Priestley know that everyone had had the privilege of breathing it.'

'Oxygen is the third most abundant element in the universe

'and makes up over half the weight of a human body.

'At minus 183 degrees Celsius, it condenses to a pale blue liquid.

'Steel smelting uses more than half of the world's commercially produced oxygen.

'It's also used in rocket fuel.'

'Around 21% of air is oxygen.

'A few percent less and we couldn't breathe.

'A few percent more and any organic matter ignited

'would burn out of control.'

'Although Priestley knew he'd found something special,

'he didn't realise he'd isolated an element.'

'He was still hampered by his belief in phlogiston.

'But his path was about to cross with a visionary

'who was also thinking about gases and airs.'

In October 1774, Priestley accompanied

his benefactor Lord Shelburne on a Grand Tour of Europe.

They headed to Paris, where they were invited to

dine with some of the country's most pre-eminent scientists.

It must have been quite an occasion for a down-to-earth Yorkshireman like Priestley.

One of the guests was the stellar French scientist Antoine Laviosier.

By the age of 28 he had already been elected to the French Academy of Sciences.

This guy was incredible. He'd published everything from the mineralogy of the Pyrenees

through to locating the best sites for abattoirs in Paris.

'Lavoisier was not only a member of a newly emerging scientific elite,

'but a tax collector and an extremely wealthy member of the bourgeoisie.

'And he was determined to crack open the mysteries of the natural world.'

When Lavoisier and Priestley met over dinner, they talked chemistry.

And conversation soon turned to Priestley's exciting new discovery of dephlogisticated air.

Lavoisier, intrigued, pressed him for details,

and Priestley clearly found him a very attentive listener

because he told him all about his experiment.

'Lavoisier and Priestley were like chalk and cheese.'

Lavoisier had the best-equipped laboratory in Europe,

with more than 10,000 pieces of precision technology.

Priestley worked in a makeshift lab

with equipment he'd just cobbled together.

Lavoisier weighed, measured, re-weighed and calculated precisely

before and after every reaction.

And he applied this approach to investigate the great mystery of phlogiston.

Lavoisier's breakthrough came when he turned his fanatical attention to detail

to the weight of substances before and after they were heated.

He first weighed a metal very precisely - in this case, tin.

And if I check the reading, it's 150.07 grams.

'Heating tin and then reweighing it

'revealed a nagging problem with the theory of phlogiston.

'If phlogiston is given off when a substance is heated, it should weigh less.'

But here the reading is 153.6 grams.

That's nearly four grams more than before it was heated.

Here's where Lavoisier had his flash of inspiration.

Maybe phlogiston isn't given off when a substance is heated.

Instead, maybe it absorbs some kind of air.

That would explain this increase.

But if that was true, what was it that was being added?

'Fresh from his conversation with Priestley, Lavoisier decided to

'repeat Priestley's experiment, only in reverse.'

He heated some mercury inside a sealed container

until it turned into mercuric oxide, which is the same substance

that Priestley had used in his experiment.

He measured the amount of air that was absorbed by the mercury when it was heated.

He then heated the mercuric oxide

and observed that the amount of air released was exactly the same

as the amount of air that had been absorbed by the mercury when it was heated.

So in a flash of inspiration, he realised that something in the air

had been taken in by the mercury to make the mercuric oxide.

And that same gas had then been released.

He had the courage to conclude that this gas had nothing to do with phlogiston.

In fact, it was a brand new element.

Lavoisier called it oxygen.

So thanks to Priestley's experiment, Lavoisier had exposed the truth

of the red herring that had hampered chemistry for a century.

Finally, Lavoiser had shown that phlogiston simply didn't exist.

'Lavoisier had freed chemistry from the shackles of phlogiston,

'the remnants of the medieval worldview.

'And he'd pioneered a scientific method

'and so could make rapid progress in mapping the elements.

'But to Priestley's anger, Lavoisier claimed HE had discovered oxygen,

'because he recognised it as a new element.'

Trying to resolve who should get the glory proved to be a messy business.

An embittered war of words and reputations broke out between England and France.

Priestley was enraged that Lavoisier had tried to steal his thunder,

and he had a point because Lavoisier's experiments on oxygen

weren't completed until after he'd met Priestley.

'Lavoisier may not have discovered oxygen,

'but he had recognised its significance.

'And it is Lavoisier, not Priestley,

'who is known as the Father of Chemistry.

'The discovery of oxygen had finally crushed any vestiges

'of the Greek concept of the four elements.'

Water was made of hydrogen and oxygen.

Earth and air were a whole hotchpotch of different elements.

And fire, well, that wasn't an element at all.

Chemistry was being hauled into the modern era.

It was an age when chemists were splitting matter,

making great discoveries,

just trying to understand what our world was made of.

But there still didn't seem to be any order,

any logic to their findings,

just random elements dotted around the chemical landscape.

'Lavoisier was the first scientist to define what an element was -

'a substance that could not be decomposed by existing chemical means.'

This is the manuscript.

'And he set about drawing up a definitive list of all the elements.

'Now, 33 replaced the ancient four.'

Wow!

So this is it. This is Lavoisier's original list of elements.

It's in French and it's in his handwriting,

but I can still sort of pick out what it says.

He's divided them up into four groups. Four categories of elements.

There's the gases, the non-metals, metals and earths.

You can see among the gases he's got oxygen and hydrogen.

He didn't get it all right.

I see he lists here arsenic and antimony among his metals.

Today, they're not considered to be metals.

But even more fascinating, he has lumiere, or light,

and calorique, heat, listed among his elements in the gases.

Of course light and heat, we know now to be just pure energy.

But these mistakes apart, this was a huge leap forward in chemistry.

It was an early realisation that perhaps there was some order to the elements.

Some grand pattern to the building blocks of our world.

'And Lavoisier didn't stop there.

'He created a system to classify the discoveries of many other chemists,

'and set out to transform the language of chemistry.'

He began a revolution of scientific vocabulary,

replacing the picturesque and poetic with precision.

So dephlogisticated air became oxygen.

Astringent mars saffron

became iron oxide.

Oil of vitriol became sulphuric acid,

and philosophical wool became zinc oxide.

At last there was a universal language to identify the elements.

Maybe it's a shame that some of these exotic names have been replaced,

but in a way I admire Lavoisier's logic.

He revolutionised chemistry,

but other revolutions were in the air.

'In 1789, the French Revolution would have terrible consequences

'for both Lavoisier and his rival Priestley.

'In England, Priestley's sympathies for the uprising

'gained him unwelcome attention.'

Things came to a head in 1791 when an angry mob,

frightened that revolution would find its way to England,

descended on his new home and burnt it to the ground.

'Thanks to a tip-off, Priestley escaped unharmed,

'but decided to flee to America.'

Lavoisier was not so lucky.

Despised for his government work,

Lavoisier and 28 other tax collectors were tried

and found guilty of conspiring against the people of France.

He was brought here to Le Place de la Revolution that same day - May 8th, 1794.

And in 35 minutes, they were all executed.

The next day the French mathematician Joseph Legrange

commented, "It took them just an instant to cut off that head,

"but another 100 years may pass before another like it is seen."

'Lavoisier left an incredible legacy.

'He had cast out old dogma and replaced it with an empirical approach.'

'There was no going back.'

'Experimentation could now prove or disprove the most radical of ideas.

'But scientists were still convinced that more elements must be out there

'and were desperate to find new ways of revealing them.

'Matter remained fundamentally impenetrable.

'And it would take a powerful and dangerous force

'to find a new way of splitting it apart.'

'Enter Humphry Davy, a wild, charismatic Cornish scientist

'who frequently courted jeopardy.

'He was Professor of Chemistry at the Royal Institution in London.

'On 6th October 1807, Davy was working away in the basement

'where he'd adapted the servants' quarters to make a lab.'

He had been working with some crystalline salts...called potash.

Lavoisier had been unable to break it down,

and reckoned that it was an element.

But Davy wasn't convinced.

He suspected that potash was made up of more than one element.

But no matter how hard people had tried, potash had defeated them.

There didn't seem to be any way that chemistry could break it down.

'Now Davy had a new idea.

'The first electric battery had recently been invented.'

'It was very simple. Rows of metal plates and cardboard,

'soaked in salt water.'

'But it made the world's first continuous current.

'I'm going to use the same principle to try to create electricity.'

I've got a copper coin connected to a zinc washer via a copper wire,

and if I have enough of these linking up these wine glasses

filled only with salt water, then I can create a circuit.

Now if I connect up the copper coin on one side, via a lamp,

with the zinc washer on the other,

I've created electricity. The light's come on.

I've made electricity just from glasses filled with salt water and two different metals.

Most chemists at the time thought that the effect had something to do with the different metals.

But Davy believed there was a deeper reason.

That it was a chemical reaction that was causing the electric current.

'But if that were the case, then perhaps the reverse could be true,

'and an electric current could cause a chemical reaction.

'Davy resolved to find out.

'Chemist Dr Hal Sosabowski and I are going to attempt Davy's experiment

'to find out what Davy actually witnessed.'

-Welcome to the lab.

-Thank you.

Right, so we're going to be splitting potash.

The first thing we are going to have to do is melt the potash.

It's got a relatively low melting point of 360, which means we can

melt it with a Bunsen flame and a blowtorch.

So almost straight away you're seeing that glistening of the liquid forming.

It's melting back into the receptacle.

This, I gather in the melted state is very dangerous, very caustic?

Exceptionally so. If it splashed on to us it would be instantly disfiguring, instant blindness.

In a solid state it's bad enough,

but in the molten state it's really hideously dangerous.

So it's scary then to think what it must have been like in Davy's lab.

People losing fingers and eyes and getting disfigured?

Yes, it was an innocent age in some regards.

He would have been standing there in his tweeds and bow tie, no glasses.

That's the way science was. They were all pioneers.

And don't forget, Davy didn't know what he was looking for.

He didn't know he was looking for a very reactive metal that would actually catch fire in air.

So there was a double danger, if you will.

Over here this is a modern-day lorry battery.

It provides 12 volts. Enough for our experiment.

And we've got carbon electrodes, and some jump leads.

So we're all ready to split our potash.

We just don't know what it's going to do when we put this in.

'The electric currents passing through the melted potash

'is creating an unpredictable and volatile chemical reaction,

'wrenching apart the electrically charged particles in the potash.

'But is it enough to split it?'

It's all changed colour.

The electrodes are being consumed because it's a caustic environment.

-Oh, look, there it is!

-Oh, that pink flash?

Yes - that's where the potassium is being produced. And it's reacting straight away.

That's the potassium on the surface burning quickly in oxygen.

There's another one, look. Yes, it's reacting.

Just like a tiny pink matchstick popping on the surface.

Exactly. And that sort of noise, almost like a match flare, is the potassium flaring off.

And that's what he would have seen. Just there and then.

A beautiful lilac flame.

'Where others had failed, Davy succeeded.

'He'd split potash into its most fundamental ingredients,

'forcing out an element never seen before. Potassium.'

I can't possibly imagine the excitement Davy would have felt.

He was discovering this new element for the very first time.

No-one else in the world had seen it.

His assistant reckoned that Davy did a quick dance around the lab when he made the discovery.

'Potassium.

'It's a soft, silvery metal which can be cut like cheese.

'For a minute it shimmers like steel, then tarnishes in air.

'Potassium is essential to human life.

'Our bodies need a constant supply

'to keep the muscles and kidneys working.

'It also helps to transmit nerve impulses.

'But it's a killer, too.

'A large dose of potassium chloride can result in a fatal heart attack.'

'When potassium touches water, it reacts explosively,

'releasing hydrogen and leaving behind potash.'

'But it's abundant as a salt in seawater.'

'It took Humphry Davy to prise it from nature and make it visible.'

Davy seemed to be able to penetrate further into the seemingly unfathomable world of the elements -

further even than Lavoisier had thought possible.

But potassium was just the beginning.

In time, Davy added six new elements to Lavoisier's list,

and he confirmed that substances like chlorine and iodine were also elements.

He was a maverick in the world of chemistry -

fearless, even reckless in the face of a hazardous experiment.

For him, danger was part of the territory.

And it was probably his inhalations of those chemicals over the course of his life that took their toll.

He died in May 1829, aged 50.

'His quest for knowledge, to delve deeper into the concealed natural world,

'perhaps cost him his life.

'But the step he made for scientific progress is immeasurable.'

By the time of Davy's death, the idea of the elements was firmly established.

55 of our planet's building blocks had been identified.

And the world had a new science - chemistry.

'Next time, I'm going to take up the quest of the chemical pioneers...'

Well, my arm's burning up.

'..as they struggled to make sense of elemental chaos.

'I'll find out how a scientist's dream

was to become one of our most beautiful creations -

'the periodic table.

'And I'll delve into the subatomic world to reveal

'the hidden pattern of the universe, the order of the elements.'

Subtitles by Red Bee Media Ltd

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