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Subido el 5 de octubre de 2026 por Alicia Beatriz C.

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Documental historia de la química de la BBC parte 1de 3

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In 1807, maverick Cornish chemist Humphrey Davy 00:00:02
attempted something no-one had dared try before. 00:00:07
He harnessed a newly discovered force, electricity, 00:00:11
to rip apart a caustic chemical called potash. 00:00:15
And he discovered a new element. 00:00:20
Vivid, violent potassium. 00:00:26
Davy had found a new way of cracking open the natural world, to reveal its building blocks. 00:00:32
This is the story of one of the biggest questions there is. 00:00:42
What is everything in our world made of? 00:00:47
The quest to find out would ultimately lead to an extraordinary insight. 00:00:53
that everything from the diversity of nature to the complexity of man 00:00:58
was made from just 92 elements. 00:01:04
I'm Jim Al-Khalili and I've studied physics all my life, 00:01:12
but I couldn't have gained my knowledge of the subatomic world 00:01:16
without the work of the chemists who first unravelled the mysteries of matter. 00:01:20
Brilliant. That was really beautiful. 00:01:25
Finding and understanding the elements would turn out to be one of the greatest detective stories in the history of science. 00:01:27
A staggeringly difficult task that would span centuries. 00:01:35
I'm going to retrace the steps of the chemists who risked their lives to prize secrets from the natural world. 00:01:40
Instantly disfiguring, instant blindness, it's really hideously dangerous. 00:01:48
I'll find out how scientists struggled to crack 00:01:52
one of the most important codes in the universe. 00:01:58
And I'll discover how our fascination with the elements 00:02:03
led to the making of the modern world 00:02:07
and pushed the human race to the edge of destruction. 00:02:10
our compulsion to seek answers at almost any cost and to search for fundamental truths has 00:02:15
powered scientific endeavor and it underpins this story our quest to unravel the mysteries 00:02:27
of the elements it's hard to imagine what it must have been like to look 00:02:35
around and not have a clue what the world is made of not to know what this 00:02:56
contained to be mystified by fire to have no idea that oxygen is essential to 00:03:02
make it burn or the oxygen even existed not to know that hydrogen is a vital 00:03:08
ingredient of the ocean or that sodium and chlorine combine to give it salty taste it's 00:03:15
only in the last 200 years that we've known what an element is it's a substance that can't be 00:03:24
broken down into a simpler one by a chemical reaction the ancient greeks already knew of lead 00:03:31
copper gold silver iron mercury tin but to them these were just metals they were convinced that 00:03:40
the whole world was made of earth, air, fire, and water. 00:03:48
For more than a thousand years, 00:03:55
we had no way of breaking open the natural world, 00:03:56
and no choice but to base our concept of elements 00:04:00
on what was visible around us. 00:04:04
By the 16th century, things were starting to change. 00:04:13
Alchemists began to penetrate the substances around them 00:04:17
in their bid to turn base metals into gold. 00:04:21
They kept secret notes of their experiments 00:04:25
written in mysterious codes and symbols, 00:04:28
and they dreamed of immortality. 00:04:31
From the Far East through Europe to London, 00:04:36
the back streets and cellars were a seething, 00:04:39
bubbling hotbed of alchemical research. 00:04:42
it was an alchemist who first challenged the greek idea that everything was made from earth 00:04:46
fire air and water in a story which begins in baal switzerland it starts with philippus 00:04:57
teofrastus ariolus bombastus von hohenheim who thankfully for me because i'm not saying that 00:05:09
again, adopted the nom de plume Paracelsus. Paracelsus was not just an alchemist trying 00:05:16
to unlock the mysteries of matter. He was also a physician and surgeon, and he wasn't 00:05:26
afraid to challenge the orthodoxy of the day. In 1526, the city of Baal was famous for its 00:05:32
printing, and its most sought-after printer, Frobenius, had just been told by his doctors 00:05:48
that unless he had his leg amputated, he would die. 00:05:54
So Frobenius called for Paracelsus, 00:06:00
who wouldn't accept the medical orthodoxy of the day. 00:06:03
He also wasn't afraid to mix medicine with alchemy, 00:06:07
to concoct new potions and remedies. 00:06:12
He created a cure that not only saved Frobenius' life, 00:06:17
but established Paracelsus as a true radical. 00:06:21
He proposed a groundbreaking new idea, 00:06:26
suggesting that the world was actually made of three elements, 00:06:29
salt, sulphur and mercury. 00:06:33
Paracelsus saw these as the core ingredients to make metals and medicines. 00:06:40
He reckoned salts would heal wounds, 00:06:46
Sulfur was combustible, 00:06:49
and mercury, known then as quicksilver, was fluid and volatile. 00:06:51
Now, mercury is an incredible substance. 00:07:00
It's the only metal that's liquid at room temperature. 00:07:02
It's also remarkably heavy. 00:07:07
I mean, just this small amount here feels very, very heavy, 00:07:09
but I've got a much larger amount here, 00:07:12
and if I try and lift it... 00:07:15
it's not stuck to the table 00:07:19
it's 14 times heavier than water 00:07:23
it's also toxic 00:07:26
so I'm wearing a triple layer of gloves here 00:07:28
because I'm going to do something I've always wanted to do 00:07:31
which is dunk my hand in mercury 00:07:33
it feels very very strange 00:07:35
it's pushing my hand up 00:07:40
it's nothing like any liquid that I know of 00:07:42
it feels very cold as well 00:07:48
even through the three layers of gloves I can feel its coolness and just to give 00:07:52
you an idea of how weird this stuff is I've got a steel bolt here and let's see 00:07:58
what happens if I put it in the mercury mercury is so much denser than steel it 00:08:04
floats mercury silvery and mirror-like it's one of the most beautiful and 00:08:11
and elusive of all the elements. 00:08:24
It's rarely found in its natural form, but heating a red rock, cinnabar, will reveal 00:08:28
molten mercurial lava hidden within. 00:08:34
The phrase mad as a hatter was coined when hat makers who used it suffered from mercury 00:08:41
madness. 00:08:48
In the mines of South America, treasure hunters risked their lives by using toxic mercury 00:08:52
to extract another element, gold. 00:08:59
And floating on mercury gave smooth motion to the revolving light of some Victorian lighthouses. 00:09:03
Paracelsus didn't manage to convince the establishment with his idea of the three elements, 00:09:15
mercury, sulphur and salt. 00:09:21
In fact, he'd enraged them by ignoring their medical texts 00:09:24
and creating alchemical cures. 00:09:28
He was too radical for his time. 00:09:31
In a dramatic gesture to show his contempt for the medical authorities, 00:09:34
he burned their books. 00:09:40
He was forced to leave Baal University and fled to Germany, 00:09:46
where he would carry on practising his medicine and alchemy. 00:09:50
But he'd paved the way for a new era of questioning, 00:09:53
at a time when many alchemists were more interested in making gold. 00:10:04
They would heat metals in scorching furnaces. 00:10:09
They'd boil, they'd distill. 00:10:12
And it was the pursuit of gold that led to the first major breakthrough 00:10:16
in the hunt to discover elements. 00:10:21
For the alchemists, gold was like the Holy Grail. 00:10:25
They believed it possessed spiritual, magical, even medical properties. 00:10:29
It was the stuff of power, the colour of the sun. 00:10:35
It was made into crowns and coins. 00:10:38
It adorned kings, queens, palaces and temples for over thousands of years. 00:10:41
In ancient Egypt, gold was thought to be the skin of the gods. 00:10:48
To the Inca civilisation, gold was the sweat of the sun. 00:10:55
The alchemists didn't yet know what an element was, 00:11:02
but some unwittingly touched on the idea 00:11:09
that they could be hidden within other substances 00:11:12
when they suggested that gold might be concealed within the human body. 00:11:15
The relentless pursuit of this obsession 00:11:25
led one alchemist to become the first person 00:11:27
credited with the discovery of a new element, 00:11:31
Hennig Brandt. 00:11:35
He was searching for a way of extracting gold from the body 00:11:36
when he hit upon what seemed like a smart idea. 00:11:43
A gold-coloured liquid in plentiful supply. 00:11:47
Urine. 00:11:52
It was 1669, and in the dark, smelly basement of his Hamburg house, 00:11:55
Brandt's expensive alchemical experiments 00:12:02
were rapidly eating through the funds of his wealthy wife, Margarita. 00:12:05
But now, with his urine brainwave, 00:12:10
Brandt believed that he was on the threshold of a momentous discovery. 00:12:13
He was about to make his name and restore his family fortune. 00:12:17
All he needed was another 50 buckets of urine. 00:12:20
Chemist Dr Andrea Sella has been studying Brandt's work 00:12:27
and is going to attempt to find the hidden element. 00:12:31
If you pass me the urine... 00:12:34
You're welcome. 00:12:36
..and this is courtesy of myself. 00:12:38
I'm already holding my breath. 00:12:41
This is... Look, you know, you mustn't overreact. 00:12:43
So what would Brandt have done? 00:12:47
Well, what Brandt was trying to do 00:12:49
was really to get to the heart of the matter, 00:12:51
to start boiling it down, 00:12:53
to get rid of the sort of unimportant parts, 00:12:55
and that, of course, was principally the water. 00:12:57
There is an additional feature, and it's not really surprising, 00:13:00
really surprising, but you know, have a quick waft of that, and yeah, it's pretty bad. 00:13:03
I mean, Brandt must have had some very, very patient neighbors, and I really don't know 00:13:11
what his romantic life must have been like, but I can't imagine he was all that popular. 00:13:16
You see, I can understand Jürgen being gold-colored, but Brandt was looking to make gold. 00:13:22
What is the connection? 00:13:28
First of all, it seems tremendously laughable to us 00:13:29
to use something as disgusting a waste product as urine. 00:13:32
One of the alchemical views was that man was really a microcosm of the universe 00:13:36
and therefore urine actually carried within it some of that vital force, the life force. 00:13:40
So sort of a metaphysical symbol of life. 00:13:47
Absolutely. And so really this was a substance of power. 00:13:50
Brandt was determined to persevere with his quest for gold. 00:13:55
He distilled the urine down to a paste, 00:13:59
then heated it at a phenomenal temperature for several days. 00:14:02
Eventually, wisps of smoke revealed tiny fragments that combusted in air. 00:14:07
But what was this fiery substance? 00:14:13
It wasn't golden like the sun, but it burned brighter than any medieval candle. 00:14:16
So this is what Brandt isolated from urine. 00:14:21
It's not gold. 00:14:40
This is phosphorus. 00:14:41
Brandt had discovered, completely by accident, 00:14:44
a new element, never seen by man, 00:14:49
fiery phosphorus. 00:14:52
He was looking for riches, 00:14:55
but didn't realise that he'd unearthed a fundamental notion, 00:14:58
that elements could be concealed within a hidden world. 00:15:02
Phosphorus is biologically very, very important. 00:15:08
If you think of our bones, they're composed predominantly of calcium hydroxyphosphate. 00:15:10
So there's lots of phosphate there. 00:15:15
It's in our DNA. 00:15:17
It's in all sorts of our tissues. 00:15:18
And as a result, there's always phosphate in the blood, and some of it, excess, is transferred into the urine. 00:15:20
A little bit less than about a gram per liter. 00:15:26
This stuff is a complete tiger. 00:15:29
You can immediately see that it starts to smoke very gently in air. 00:15:31
And this is really a warning to us that things are going to happen 00:15:36
if we don't sort of deal with it quickly. 00:15:39
So we're going to drop it into this flask. 00:15:42
The flask is actually filled with oxygen, 00:15:45
and so it's sitting in sand just to keep the heat from attacking the glass. 00:15:47
Now, I'm going to touch it with a hot glass rod. 00:15:54
And so there it is. 00:16:05
That's fantastic. 00:16:09
And it sort of feels cold. 00:16:11
it's not it's not hot that's quite beautiful because it shone so vividly it was cold enough 00:16:13
to hold brant called his discovery icy noctiluca cold night light phosphorus it's in every cell 00:16:19
in the human body it's used in drugs to promote bone growth treating diseases like osteoporosis 00:16:33
153 million tonnes of phosphorus are produced every year. 00:16:40
Its phosphate is consumed as a food supplement 00:16:47
and as an ingredient of toothpaste. 00:16:51
But eating just 100 milligrams of pure phosphorus, 00:16:54
enough to coat a fingertip, could be fatal. 00:16:58
And it has an even darker side. 00:17:04
In the Second World War, 00:17:07
Phosphorus was used in the thousands of bombs dropped on Hamburg, 00:17:09
the city where Brandt discovered it. 00:17:14
Brandt hoped that Phosphorus would make him a fortune, 00:17:17
but his cash ran out 00:17:30
and he sold the secret of his discovery for a paltry sum. 00:17:32
Before long, Phosphorus was being touted round the royal courts of Europe. 00:17:37
And in 1677, it arrived at the court of King Charles II. 00:17:42
Soon after, wealthy alchemist Robert Boyle witnessed its luminous magic 00:17:49
and determined to investigate its properties. 00:17:54
Dr Andrea Sella and I are going to follow Boyle's own instructions 00:17:58
to attempt one of his most significant experiments on phosphorus. 00:18:03
So I have here extracts from Robert Boyle's book, 00:18:08
New experiments and observations made upon the icy Noctiluca. 00:18:12
Having put together about half a grain of our dry Noctiluca matter, 00:18:16
how much is half a grain? 00:18:21
Well, half a grain really isn't very much. 00:18:22
There's 7,000 grains to the pound, so you can work it out. 00:18:26
You're the physicist. 00:18:30
Okay, and six times its weight of common flowers of sulphur. 00:18:32
Okay, so we'll put a little piece... 00:18:37
So that's just sulphur powder, is it? 00:18:39
It's just, yeah, it's essentially sulfur, finely powdered sulfur. 00:18:41
Right, and it says they were lodged in the fold of a piece of white paper. 00:18:44
He said he rubbed it with the haft of a knife. 00:18:48
Well, I haven't got a knife, but I do have a spatula, so I'll use that. 00:18:51
Okay, it's beginning to smoke. There it is. It's beginning to kindle. 00:18:56
We've got a little bit of fire there already. 00:18:59
The main lump of phosphorus hasn't gone. 00:19:01
Oh, there it goes. 00:19:03
There it goes, there it goes. Whoa! 00:19:03
Didn't have time to bruise it. 00:19:07
Didn't have time, you didn't need bruising. 00:19:08
so you've basically recreated what is the precursor to the match yes and i also got 00:19:10
some splendid smoke rings here i mean this would really sort of radically transform things because 00:19:16
what you had was fire on demand boyle had stumbled upon the essential ingredient of a match a huge 00:19:23
industry was spawned from this single experiment but boyle wasn't really interested in the money 00:19:33
making potential of phosphorus just understanding the properties of this element was reward enough 00:19:38
for him so phosphorus did have transformational powers after all it may not have changed lead 00:19:44
into gold but it turned an alchemist into the first modern chemist boyle had set the stage 00:20:04
for future element hunters unlike most alchemists he shared his methods and was able to pass on the 00:20:13
tools they needed to help unlock the mysteries of matter. I've come to search the vaults 00:20:20
of the Royal Society in London. What I'm looking for was deposited here in 1661, just one year 00:20:29
after the Society was formed. Here it is. The Skeptical Chemist. It was written by Robert 00:20:38
Boyle, who was one of the founders of the Royal Society. 00:20:49
Dr Anna-Marie Roos, a specialist in the history of chemistry, has studied Boyle's writings. 00:20:54
I've got a copy of Boyle's Skeptical Chemist. Why was this book so important? 00:21:01
This is really considered to be one of the books that signifies a transition from alchemy to 00:21:06
chemistry. And some scholars have thought it's the first book of chemistry. The fact that that 00:21:13
book was written in plain English was also quite a new thing. You only have to compare Boyle's book 00:21:18
to the cryptic writings of another alchemist, that great man of science Isaac Newton, to appreciate 00:21:24
its innovation. And we can see here that it is in Latin and we also can see that there are several 00:21:31
alchemical symbols being used for the chemical elements. It really does remind me of astrology 00:21:37
and even Egyptian hieroglyphics. 00:21:44
Absolutely. 00:21:46
And I compare that with Boyle, where he says things like, 00:21:47
he took 200 pounds of earth, dried it in an oven, 00:21:52
having put it in an earthen vessel and melted it. 00:21:54
He's describing a chemical process. 00:21:57
Absolutely. 00:22:00
What made Boyle a bit different is that he was willing to divulge 00:22:00
some of his chemical secrets for the good of the scientific community. 00:22:06
Boyle was bringing alchemy out of the shadows. 00:22:13
and into an enlightened, rational age. 00:22:17
He was opening up the scientific method for everyone to see. 00:22:20
The alchemist must have feared he was giving away their secrets, 00:22:25
but he wasn't so much interested in debunking alchemy 00:22:28
as getting rid of its metaphysical baggage 00:22:31
and replacing it with a more rigorous scientific approach. 00:22:34
A new age of scientific experimentation had begun. 00:22:38
And with a more open exchange of ideas came a rejection of tradition. 00:22:52
It heralded an era in which the ancient Greek doctrines were re-evaluated 00:23:00
and new concepts introduced. 00:23:04
Copernicus challenged the ancient idea 00:23:10
that the Earth was at the centre of the universe, 00:23:13
proposing instead that it was just one of a number of planets 00:23:16
orbiting around the sun. 00:23:19
Vesalius mapped the human body. 00:23:22
It was an exciting and liberating time in which Europe was being dragged out of its dark ages 00:23:24
and into an age of reason. But just because people were thinking differently didn't necessarily mean 00:23:30
that they were getting it right. And while a new generation of scientists were keen to come up with 00:23:42
modern elements to replace the four ancient ones, their enthusiasm didn't stop them from buying into 00:23:47
to completely false theories. 00:23:54
And so it was that science went up 00:23:57
one of the greatest blind alleys 00:23:59
in the history of chemistry. 00:24:01
It was 1667, a year after the Great Fire of London 00:24:06
had razed one of Europe's greatest cities to the ground. 00:24:10
The mysteries of fire were at the forefront 00:24:16
of everyone's minds, but no one really understood 00:24:19
what fire was or how it was created. 00:24:22
German chemist Johann Becher proposed that the destructive power of fire 00:24:26
was caused by an ethereal entity named phlogiston. 00:24:31
It was thought to be an odourless, colourless, tasteless 00:24:36
and weightless substance that causes things to burn, 00:24:40
reducing them to their true form. 00:24:44
This burning wood produces ash, 00:24:47
ash. So wood must be made up of ash, pure wood, plus phlogiston. 00:24:51
The notion of phlogiston seemed so credible in the 17th century that it consumed the scientific 00:25:00
community. It was accepted as a truth, virtually paralysing our ability to discover more elements 00:25:06
and map the contours of the natural world. One great chemist who experimented with gases 00:25:14
even claimed to have isolated it. 00:25:20
On the same day, every week, for 50 years, 00:25:24
a rather peculiar scientist came to the Royal Society dinner club 00:25:29
to discuss the latest scientific ideas. 00:25:34
Henry Cavendish has been described as the richest of the learned 00:25:42
and the most learned of the rich. 00:25:46
He was a major shareholder in the Bank of England 00:25:49
and had royal connections but it's remarkable he came to a social gathering at all Cavendish 00:25:52
was painfully shy and lived in virtual isolation at home he insisted that his servants only 00:26:00
communicate with him in writing colleagues at the dinner club said that he'd often be found outside 00:26:08
trying to pluck up the courage to go in and when speaking to him it was best to look into the air 00:26:14
with vacancy rather than directly at him despite signs of what we might recognize 00:26:20
today as autism Cavendish made a vital contribution to the discovery of the 00:26:26
elements I'm going to investigate how Cavendish's experiments with heirs led 00:26:32
him to find the first element that's a gas Cavendish added a metal zinc to an 00:26:41
acid it was deceptively simple and pretty soon bubbles began to appear on 00:26:53
the surface of the zinc Cavendish started to collect this gas which I'm 00:27:01
going to do in this test tube it didn't smell of anything it didn't taste of 00:27:08
anything in fact it was completely invisible Cavendish soon realized this 00:27:13
was no ordinary gas and then he set light to it Cavendish had no idea he'd discovered a new 00:27:18
element in fact he thought he'd found a new kind of air different to the air we breathe he called 00:27:32
it not surprisingly inflammable air and he believed his inflammable air had to be the 00:27:38
mysterious phlogiston it was odorless tasteless colorless and most importantly it caught fire 00:27:45
it had to be phlogiston but he was wrong cavendish didn't realize it but he had isolated a new 00:27:56
element hydrogen he investigated the characteristics of his new air and calculated that it was 11 times 00:28:04
lighter than the air we breathe now i've got asthma here to help me she's pumping 00:28:14
hydrogen through into this washing up liquid and creating bubbles of hydrogen coming up 00:28:22
through this funnel because hydrogen is so much lighter than air at some point these 00:28:27
bubbles will separate and start to float up brilliant that was really beautiful 00:28:31
it was lighter than air and burst into flames you can see why Cavendish thought 00:28:39
it was phlogiston oh they're getting better but this belief meant Cavendish 00:28:47
wasn't credited with the discovery of hydrogen during his lifetime nor would 00:28:55
he witness its full force? Hydrogen, produced just after the Big Bang alongside helium and 00:29:03
lithium, it's the most abundant and lightest element in the universe. The sun's energy 00:29:15
comes from the nuclear fusion of hydrogen, the same principle harnessed in the hydrogen 00:29:24
bomb. Hydrogen's highly flammable nature was witnessed when it ignited the Hindenburg Zeppelin 00:29:32
airship in 1937, killing 36 people. Like so many other element hunters, Cavendish didn't 00:29:43
realise the significance of his discovery, but he did observe something that will play 00:30:04
a crucial role in our understanding of the natural world. 00:30:10
Each time he set light to the gas a dewy liquid began to appear on the surface of the glass. 00:30:17
It was water. Now this had incredible implications back in the 1700s because back then they believed 00:30:25
in the ancient Greek idea that water was an element. But if you can make water out of 00:30:32
two other constituents then it couldn't be an element in fact water is a compound 00:30:38
this struck right to the heart of the ancient concept of four elements 00:30:54
cavendish's observations could have shaken the foundations of accepted belief 00:31:01
but they didn't because he was thrown off course by flogiston he reckoned that the heirs 00:31:06
must contain a form of water modified by the presence of phlogiston it simply didn't occur 00:31:13
to him that water was a compound so while he was very close to destroying the temple of the ancient 00:31:22
four elements he couldn't quite yet disprove them the pillars of that temple were now standing on 00:31:30
very shaky ground and it wouldn't be too long before they'd come crashing down but it wasn't 00:31:37
cavendish's water that would finally disprove the ancient theory it was air 00:31:43
19 of what we now call elements had been found so far but 18th century scientists 00:31:55
were still grappling to work out what the world was made of 00:32:03
the royal society had commissioned its members to investigate the invisible heirs 00:32:09
By the mid-1700s, there were three known types of air, or gases. 00:32:18
There was the common air that we breathe, 00:32:26
inflammable air, now known as hydrogen, 00:32:28
and fixed air, or carbon dioxide. 00:32:31
And experimenting with these airs was a favourite pastime 00:32:34
of clergyman and amateur chemist Joseph Priestley. 00:32:39
Priestley lived next to a brewery 00:32:44
and spent rather a lot of time there, 00:32:47
especially considering he was a Unitarian minister 00:32:50
known for his extreme sermons. 00:32:52
But he wasn't here for the beer. 00:32:56
Priestley was interested in the gas 00:33:01
that's produced in the fermentation process. 00:33:03
He called it brewery gas. 00:33:07
But, of course, it was well known by that time. 00:33:09
It was known as fixed air. 00:33:11
We know it today as carbon dioxide. 00:33:13
Carbon dioxide is being produced inside this vat and is, because it's heavier than air, 00:33:16
pouring out and cascading down. 00:33:22
Now we can't see it, but an experiment that Priestley himself carried out involved seeing 00:33:25
what carbon dioxide does to a lit flame. 00:33:31
So if I hold this flame here, it's not in the path of the gas at the moment, but if 00:33:37
I bring it down, you can see it immediately extinguishes. 00:33:42
You can even see the trail of smoke following the path of the gas. 00:33:47
Priestley was fascinated by fixed air. 00:33:54
He mixed it with water and so invented the first fizzy drink. 00:33:58
In time, it would spawn an industry worth millions, but he earned almost nothing from 00:34:03
it. 00:34:09
Instead, Priestley's passion for science led to an invitation to Bowood House in Wiltshire 00:34:10
to tutor the children of the future Prime Minister, Lord Shelburne. 00:34:17
Priestley lacked the wealth of earlier chemists like Boyle and Cavendish, 00:34:23
and he made little money from his inventions and his radical writings. 00:34:28
Lord Shelburne was offering him financial stability 00:34:33
and the chance to continue with his scientific experiments 00:34:37
in return for teaching. 00:34:40
So he became the first professional salaried chemist. 00:34:42
And it was here that he continued his experiments with airs. 00:34:46
On 1st August 1774, 00:34:55
he performed one of the most important experiments in chemical history. 00:34:58
Priestley was gripped by unlocking the elemental secrets of the airs. 00:35:05
On this occasion, he started with a powder he knew as mercuric calx, 00:35:10
mercuric oxide. 00:35:16
He put it in a test tube to collect any gas it might give off when he heated it. 00:35:18
Then he filled the test tube with mercury, which would trap the gas. 00:35:25
OK, so I now place my finger over the top of the tube, 00:35:31
invert it so that it's submerged into the mercury bath. 00:35:34
I now have the mercuric oxide powder at the very top of the tube. 00:35:38
What Priestley did next was heat up this powder 00:35:44
The level of the mercury in the tube is dropping 00:35:48
What's going on is that a gas is being produced that's pushing the mercury down 00:35:54
What in fact is happening is that this mercuric oxide powder 00:36:00
is being broken up into its two components 00:36:04
I'm now going to see what gas Priestley had made 00:36:07
If I take this splint and blow it out so I just have a glowing ember, 00:36:12
it bursts back into flame again. 00:36:19
We now know that Joseph Priestley had found oxygen. 00:36:23
But because he believed in the idea of phlogiston, 00:36:27
he thought the splint was introducing phlogiston to the new air and catching fire. 00:36:30
He concluded that his air must be without phlogiston. 00:36:37
So he called it dephlogisticated air. 00:36:42
Priestley's experiments with his new air didn't stop there. 00:36:47
In fact, they got stranger. 00:36:51
He placed a mouse inside a sealed container filled with the new air, 00:36:53
expecting it to live for just 15 minutes. 00:36:58
Instead, he found it alive and well after half an hour. 00:37:01
He then tried breathing it himself and noted, 00:37:05
I fancy my breast felt particularly light and easy after some time. 00:37:08
Who can tell but that in time this pure air 00:37:15
may become a fashionable article of luxury. 00:37:18
Hitherto just two mice and I have had the privilege of breathing it. 00:37:23
Little did Priestley know, 00:37:29
but everyone had had the privilege of breathing it. 00:37:31
Oxygen is the third most abundant element in the universe 00:37:34
and makes up over half the weight of a human body. 00:37:42
At minus 183 degrees Celsius, it condenses to a pale blue liquid. 00:37:47
Steel smelting uses more than half the world's commercially produced oxygen. 00:37:55
It's also used in rocket fuel. 00:38:01
Around 21% of air is oxygen, a few percent less and we couldn't breathe, 00:38:05
a few percent more and any organic matter ignited would burn out of control. 00:38:12
Although Priestley knew he'd found something special, he didn't realise he'd isolated an element. 00:38:25
He was still hampered by his belief in Flodgestan, 00:38:32
but his path was about to cross with a visionary 00:38:38
who was also thinking about gases and airs. 00:38:42
In October 1774, Priestley accompanied his benefactor, Lord Shelburne, 00:38:50
on a grand tour of Europe. 00:38:58
They headed to Paris, where they were invited to dine 00:39:05
with some of the country's most pre-eminent scientists. 00:39:09
It must have been quite an occasion for a down-to-earth Yorkshireman like Priestley. 00:39:12
One of the guests there was the stellar French scientist Antoine Lavoisier. 00:39:17
By the age of 28, he'd already been elected to the French Academy of Sciences. 00:39:22
This guy was incredible. 00:39:28
He'd published everything from the mineralogy of the Pyrenees 00:39:29
through to locating the best sites for abattoirs in Paris. 00:39:33
Lavoisier was not only a member of a newly emerging scientific elite, 00:39:44
but a tax collector and an extremely wealthy member of the bourgeoisie. 00:39:50
And he was determined to crack open the mysteries of the natural world. 00:39:55
When Lavoisier and Priestley met over dinner, 00:40:02
they talked chemistry and conversations soon turned to Priestley's exciting new discovery of 00:40:05
deflogisticated air. Lavoisier intrigued pressed him for details and Priestley clearly found him 00:40:12
a very attentive listener because he told him all about his experiment. Lavoisier and Priestley were 00:40:20
were like chalk and cheese. 00:40:31
Lavoisier had the best-equipped laboratory in Europe 00:40:34
with more than 10,000 pieces of precision technology. 00:40:37
Priestley worked in a makeshift lab 00:40:44
with equipment he'd just cobbled together. 00:40:46
Lavoisier weighed, measured, reweighed 00:40:50
and calculated precisely before and after every reaction. 00:40:54
and he applied this approach to investigate the great mystery of phlogiston lavoisier's breakthrough 00:40:58
came when he turned his fanatical attention to detail to the weight of substances before 00:41:07
and after they were heated he first weighed a metal very precisely in this case tin and if i 00:41:13
I check the reading, it's 150.07 grams. 00:41:24
Heating tin and then reweighing it 00:41:31
revealed a nagging problem with the theory of phlogiston. 00:41:33
If phlogiston is given off when a substance is heated, 00:41:37
it should weigh less. 00:41:40
But here the reading is 153.6 grams. 00:41:43
That's nearly four grams more than before it was heated. 00:41:47
Here's where Lavoisier had his flash of inspiration. 00:41:51
Maybe phlogiston isn't given off when a substance is heated. 00:41:54
Instead, maybe it absorbs some kind of air. 00:41:57
That would explain this increase. 00:42:01
But if that was true, what was it that was being added? 00:42:03
Fresh from his conversation with Priestley, 00:42:13
Lavoisier decided to repeat Priestley's experiment, only in reverse. 00:42:16
he heated some mercury inside a sealed container until it turned into mercuric oxide which is the 00:42:21
same substance that priestly had used in his experiment he measured the amount of air that 00:42:33
was absorbed by the mercury when it was heated he then heated the mercuric oxide and observed that 00:42:39
the amount of air released was exactly the same as the amount of air that had been absorbed by 00:42:46
the mercury when it was heated. So in a flash of inspiration he realised that something in the air 00:42:51
had been taken in by the mercury to make the mercuric oxide and that same gas had then been 00:42:58
released. He had the courage to conclude that this gas had nothing to do with phlogiston. In fact it 00:43:04
was a brand new element. Lavoisier called it oxygen. So thanks to Priestley's experiment 00:43:12
Lavoisier had exposed the truth of the red herring 00:43:19
that had hampered chemistry for a century. 00:43:23
Finally, Lavoisier had shown that phlogiston simply didn't exist. 00:43:26
Lavoisier had freed chemistry from the shackles of phlogiston, 00:43:35
the remnant of the medieval world view, 00:43:39
and he'd pioneered a scientific method 00:43:42
and so could make rapid progress in mapping the elements. 00:43:45
But to Priestley's anger, 00:43:49
Lavoisier claimed he had discovered oxygen 00:43:51
because he recognized it as a new element. 00:43:55
Trying to resolve who should get the glory 00:43:59
proved to be a messy business. 00:44:02
An embittered war of words and reputations 00:44:04
broke out between England and France. 00:44:07
Priestley was enraged that Lavoisier 00:44:10
had tried to steal his thunder, 00:44:12
And he had a point, because Lavoisier's experiments on oxygen 00:44:15
weren't completed until after he'd met Priestley. 00:44:19
Lavoisier may not have discovered oxygen, 00:44:24
but he had recognised its significance. 00:44:27
And it is Lavoisier, not Priestley, 00:44:31
who's known as the father of chemistry. 00:44:34
The discovery of oxygen had finally crushed any vestiges 00:44:37
of the Greek concept of the four elements. 00:44:42
Water was made of hydrogen and oxygen. 00:44:46
Earth and air were a whole hodgepodge of different elements. 00:44:50
And fire, well, that wasn't an element at all. 00:44:54
Chemistry was being honed into the modern era. 00:45:04
It was an age when chemists were splitting matter, 00:45:07
making great discoveries, 00:45:11
just trying to understand what our world was made of. 00:45:12
But there still didn't seem to be any order, any logic to their findings, 00:45:15
just random elements dotted around the chemical landscape. 00:45:21
Lavoisier was the first scientist to define what an element was, 00:45:30
a substance that could not be decomposed by existing chemical means. 00:45:36
This is the manuscript. 00:45:41
And he set about drawing up a definitive list of all the elements. 00:45:43
Now 33 replace the ancient form. 00:45:49
So this is it. This is Lavoisier's original list of elements. 00:45:57
It's in French and it's in his handwriting, but I can still sort of pick out what it says. 00:46:03
He's divided them up into four groups, four categories of elements. 00:46:09
there's the gases the non-metals metals and earths you can see among the gases he's got 00:46:13
oxygen and hydrogen he didn't get it all right i see he's he lists here arsenic and antimony 00:46:22
among his metals today they're not considered to be metals but even more fascinating he has 00:46:30
lumière, or light, and calorique, heat, listed among his elements in the gases. Of course, 00:46:37
light and heat we know now to be just pure energy. But these mistakes apart, this was 00:46:45
a huge leap forward in chemistry. It was an early realisation that perhaps there was some 00:46:52
order to the elements, some grand pattern to the building blocks of our world. 00:46:57
And Lavoisier didn't stop there. He created a system to classify the discoveries of many 00:47:02
other chemists and set out to transform the language of chemistry. 00:47:11
He began a revolution of scientific vocabulary, replacing the picturesque and poetic with 00:47:17
precision, so dephlogisticated air became oxygen, astringent Mars saffron became 00:47:25
iron oxide, oil of vitriol became sulfuric acid and philosophical wool 00:47:34
became zinc oxide. At last there was a universal language to identify the 00:47:41
elements. Maybe it's a shame that some of these exotic names have been replaced 00:47:48
But in a way, I admire Lavoisier's logic. 00:47:54
He revolutionised chemistry. 00:47:57
But other revolutions were in the air. 00:48:00
In 1789, the French Revolution would have terrible consequences 00:48:05
for both Lavoisier and his rival Priestley. 00:48:11
In England, Priestley's sympathies for the uprising 00:48:14
gained him unwelcome attention. 00:48:18
Things came to a head in 1791, when an angry mob, 00:48:20
frightened that revolution would find its way to England, 00:48:24
descended on his new home and burnt it to the ground. 00:48:28
Thanks to a tip-off, Priestley escaped unharmed, 00:48:32
but decided to flee to America. 00:48:37
Lavoisier was not so lucky. 00:48:40
Despised for his government work, 00:48:43
Lavoisier and 28 other tax collectors were tried and found. 00:48:46
were tried and found guilty of conspiring against the people of France. 00:48:50
He was brought here to La Place de la Révolution that same day, 00:48:55
May the 8th, 1794, 00:48:59
and in 35 minutes they were all executed. 00:49:02
The next day, the French mathematician Joseph Lagrange commented, 00:49:05
it took them just an instant to cut off that head, 00:49:10
but another 100 years may pass before another like it is seen. 00:49:13
Lavoisier left an incredible legacy. 00:49:17
He'd cast out old dogma and replaced it with an empirical approach. 00:49:23
There was no going back. 00:49:31
Experimentation could now prove or disprove the most radical of ideas. 00:49:35
But scientists were still convinced that more elements must be out there 00:49:40
and were desperate to find new ways of revealing them. 00:49:45
Matter remained fundamentally impenetrable and it would take a powerful and dangerous force to find a new way of splitting it apart. 00:49:48
Enter Humphry Davy, a wild, charismatic Cornish scientist who frequently courted jeopardy. 00:50:02
He was Professor of Chemistry at the Royal Institution in London. 00:50:10
On 6 October 1807, Davy was working away in the basement 00:50:14
where he'd adapted the servants' quarters to make a lab. 00:50:20
He'd been working with some crystalline salts called potash. 00:50:24
Lavoisier had been unable to break it down 00:50:30
and reckoned that it was an element. 00:50:34
But Davy wasn't convinced. 00:50:36
He suspected that potash was made up of more than one element. 00:50:38
But no matter how hard people had tried, potash had defeated them. 00:50:42
There just didn't seem to be any way that chemistry could break it down. 00:50:47
Now Davy had a new idea. 00:50:55
The first electric battery had recently been invented. 00:50:58
It was very simple. Rows of metal plates and cardboard, soaked in salt water. 00:51:03
But it made the world's first continuous current. 00:51:12
I'm going to use the same principle to try to create electricity. 00:51:16
I've got a copper coin connected to a zinc washer via a copper wire. 00:51:24
And if I have enough of these linking up these wine glasses filled only with salt water, then I can create a circuit. 00:51:28
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. 00:51:36
The lights come on. I've made electricity just from glasses filled with salt water and two different metals. 00:51:45
Most chemists at the time thought that the effect had something to do with the different metals. 00:51:52
But Davy believed there was a deeper reason, that it was a chemical reaction that was causing the electric current. 00:51:57
But if that were the case, then perhaps the reverse could be true, and an electric current could cause a chemical reaction. 00:52:05
Davy resolved to find out. 00:52:15
Chemist Dr Hal Sosaboski and I are going to attempt Davy's experiment 00:52:18
to find out what Davy actually witnessed. 00:52:23
Andrew, welcome to the lab. 00:52:27
Thank you. 00:52:28
Right, so we're going to be splitting potash. 00:52:30
First thing we're going to have to do is melt the potash. 00:52:32
And it's got a relatively low melting point of 360, 00:52:35
which means we can melt it with a Bunsen flame and a blowtorch. 00:52:38
So, almost straight away, we're seeing that glistening of the liquid forming, and it's 00:52:44
melting back into the receptacle. 00:52:53
And this, I gather, in the melted state, is very, very dangerous, very caustic. 00:52:56
Exceptionally so. 00:53:01
If it splashed onto us, it'll be instantly disfiguring, instant blindness. 00:53:02
In the solid state, it's bad enough, but in the molten state, it's really hideously dangerous. 00:53:08
scary then to think what it must have been like in Davies lab you know people 00:53:13
must have been losing fingers and eyes and getting disfigured yes it was an 00:53:16
innocent age in some regards he would have been standing there in his tweeds 00:53:20
and his bowtie with no glasses on but that's the way science was they were all 00:53:23
pioneers and don't forget Davy didn't know what he was looking for so he 00:53:27
didn't know that he was looking for a very reactive metal that would actually 00:53:30
catch fire almost in air so there was a double danger if you will over here this 00:53:34
modern day lorry battery provides 12 volts enough for our experiment um and we've got carbon 00:53:41
electrodes and some jump leads so we're all ready to split our potash and we just don't know what 00:53:45
it's going to do when we put this in the electric current passing through the melted potash is 00:53:50
creating an unpredictable and volatile chemical reaction wrenching apart the electrically charged 00:53:57
particles in the potash but is it enough to split it it's all changed color it's gone all 00:54:04
yes the electrodes are being consumed because it's a very caustic environment 00:54:11
oh look there it is oh is that that pink flash the lilac flash that's where the potassium is 00:54:15
being produced and it's reacting straight away that's the potassium on the surface and it's just 00:54:20
burning quickly in in in oxygen there's another one look yes it's reacting just like a tiny 00:54:24
pink matchstick popping on the surface yeah exactly and that sort of that sort of noise 00:54:29
that was like a match flare is the potassium flaring off wow and that's fantastic that's 00:54:34
what you would have seen just there and then beautiful lilac flame where others had failed 00:54:40
davey succeeded he'd split potash into its most fundamental ingredients 00:54:46
forcing out an element never seen before potassium I can't possibly imagine the excitement that Davey 00:54:51
would have felt he was discovering this new element for the very first time no one else 00:55:02
in the world has seen it his assistant reckoned that Davey did a quick dance around the lab for 00:55:07
few minutes when he when he made the discovery potassium it's a soft silvery metal which can 00:55:13
be cut like cheese for a minute it shimmers like steel then tarnishes in air potassium is essential 00:55:23
to human life our bodies need a constant supply to keep the muscles and kidneys working it also 00:55:34
helps to transmit nerve impulses. But it's a killer too. A large dose of potassium chloride 00:55:41
can result in a fatal heart attack. When potassium touches water, it reacts explosively, releasing 00:55:50
hydrogen and leaving behind potash. But it's abundant as a salt in sea water. It took Humphry 00:56:00
Davy to prize it from nature and make it visible. Davy seemed to be able to penetrate further 00:56:12
into the unfathomable world of the elements, further even than Lavoisier had thought possible. 00:56:21
But potassium was just the beginning. In time, Davy added six new elements to Lavoisier's list 00:56:27
and he confirmed that substances like chlorine and iodine 00:56:37
were also elements. 00:56:41
He was a maverick in the world of chemistry, 00:56:43
fearless, even reckless in the face of a hazardous experiment. 00:56:47
For him, danger was part of the territory 00:56:51
and it was probably the inhalation of all those chemicals 00:56:53
over the course of his life that took their toll. 00:56:56
He died in May 1829, aged 50. 00:56:59
his quest for knowledge to delve deeper into the concealed natural world perhaps cost him his life 00:57:04
but the step he made for scientific progress is immeasurable by the time of davy's death 00:57:13
the idea of the elements was firmly established 55 of our planet's building blocks had been 00:57:21
identified. And the world had a new science. Chemistry. 00:57:29
Next time, I'm going to take up the quest of the chemical pioneers. 00:57:40
While my arm's burning up. 00:57:45
As they struggled to make sense of elemental chaos. 00:57:47
I'll find out how a scientist's dream was to become one of our most beautiful creations. 00:57:51
the periodic table. 00:57:57
And I'll delve into the subatomic world 00:58:00
to reveal the hidden pattern of the universe, 00:58:04
the order of the elements. 00:58:07
And the BBC's World of Wonder season continues 00:58:18
with How Earth Made Us, over on BBC Two tomorrow at nine. 00:58:21
Still to come tonight, though, stay with us for Only Connect. 00:58:27
Thank you. 00:58:31
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