In Our Time - Oxygen

Episode Date: November 15, 2007

Melvyn Bragg discusses the discovery of Oxygen by Joseph Priestley and Antoine Lavoisier. In the late 18th century Chemistry was the prince of the sciences – vital to the economy, it shaped how Europeans fought each other, ate with each other, what they built and the medicine they took. And then, in 1772, the British chemist, Joseph Priestley, stood in front of the Royal Society and reported on his latest discovery: “this air is of exalted nature…A candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour; it lived at two different times, a whole hour, and was taken out quite vigorous.” For the British dissenting preacher, Joseph Priestley, and the French aristocrat, Antoine Lavoisier, Chemistry was full of possibilities and they pursued them for scientific and political ends. But they came to blows over oxygen because they both claimed to have discovered it, provoking a scientific controversy that rattled through the laboratories of France and England until well after their deaths. To understand their disagreement is to understand something about the nature of scientific discovery itself. With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge; Jenny Uglow, Honorary Visiting Professor at the University of Warwick; Hasok Chang, Reader in Philosophy of Science at University College London.

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or wherever you get your pods. Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk forward slash radio four. I hope you enjoy the programme. Hello, in 1772, the British chemist Joseph Priestley stood in front of the Royal Society and reported on his latest discovery. This air is of exalted nature, he said.

A candle burned in this air with an amazing strength of flame. And a bit of red-hot wood crackled and burned with a produce. rapidity. But to complete the proof of the superior quality of this air, I introduce a mouse into it, and in a quantity in which, had it been common air, would have died in about a quarter of an hour. It lived a whole hour, and was taken out quite vigorous. Priestley had discovered oxygen, which he called deflegisticated air, or had he. Soon a brilliant French chemist, Antoine LaVoisier, would name and claim the gas for himself, and so began a dispute between the British and French chemical establishments undertaken as chemistry itself,

was in the process of being rediscovered, even revolutionised. It was a revolutionary time. With me to discuss the discovery of oxygen and Jenny Uglow, honorary of visiting a professor at the University of Warwick. Hasak Chang, reader in philosophy of science at University College London, and Simon Schaffer, professor in history and philosophy of science at the University of Cambridge. Hasak Chan at the moment is in a car, and so I'm with you too, you happy too, Simon Schaffer. This, the end of the 18th century, last third,

was an age when chemistry was preeminent in Europe, it was vital in mining, in medicine, for industry, for war. Why did it become important at that time and in such a way? I think there are two ways in which we can understand the triumph of chemistry during the 18th century. One you've already mentioned, the extraordinary economic and industrial significance of chemical processes and the rapid acceleration of the size, efficiency,

and I think above all precision of chemical analysis, because what chemistry seemed to offer was not just, as it were a universal control over industrially significant processes like extracting metals from ores or valuable medicines from plants and chemicals, but also an exact control.

The weapons that chemists had at their disposal had changed during the 1700s. They now had remarkably precise balances. They had extraordinarily sophisticated ovens and furnaces whose temperatures could be controlled to an unparalleled degree of exactitude, and they had a series of glass instruments, which were really the best in the world.

And that, I think, was part of the chemical revolution, the amazing change in the quality of hardware and the amazingly important significance of chemistry for industry. So we're doing about a technological revolution as well as... It is a revolution in technology and around it as well. The images that survive, and their remarkable ones of 18th century chemistry labs look like some of the first factories.

They're on an unprecedentedly large scale. That's very important to remember. They use devices which are some of the largest scientific instruments then available, for example, burning glasses, some feet in diameter. And I think above all, the status of chemists within national and international markets is extremely high. One reason for that is the thing that Benjamin Franklin said would survive forever tax.

Tax systems in the 18th century are by and large indirect taxation. That's to say their taxes on goods. So states had an interest, to put it mildly, in hiring experts to analyze the components of goods, booze, tobacco, gunpowder, sugar, textiles. And it was the great chemists who were servants. of the state very often, who could tell excise officers exactly how much of these taxable commodities was in each good for sale. Can you tell the list of what you mean when you use the word chemist?

Who is this chemist? What person is he? He isn't necessarily or at all at, mostly. A person who's been to university, for instance. That's absolutely right. And the vast majority of chemists in the later 18th century Europe are what we would now call apothecaries or pharmacists, and some of them extremely wealthy men,

commanding very large laboratories. It's very important to remember that up till at least 1800, if not well beyond then, laboratory means uniquely the place where chemists work. Where you labour. Where you labour. Laborare. And we don't yet have laboratories for many other kinds of scientific endeavour. If we ask, you know, who are these chemists?

They range from a very small group of elite chemical philosophers, very often linked either with the state or with medicine because one should remember the enormous significance of pharmaceuticals and botany, medical botany for the work of the chemist, to, as it were, the large reserve army of pharmacists and apothecaries who, above all, are making the materials with which chemists will proceed. So let's go towards oxygen through the separation of gases. Why did that become such an important pursuit?

One of the most defining characteristics of late 18th century chemistry, I think, is that it puts air at the center of its concerns for several reasons. One, for centuries, if not millennia, Europeans since, say, Hippocrates, had understood air, the airs as one of the defining conditions of human health and disease. diseases carried through the air, hence the word malaria, bad air, malaria. And the human body contains, breathes out, breathes in, enormous amounts of air. So that understanding human health in terms of the circulation of air was very important. And I think finally, remember metallurgy. The process of extracting pure metals from their ores or calxes was absolutely a matter of manipulating air. observing the air emitted by oars and calcise

and then trying to find out what's happening in the process of metallurgy. And can you briefly tell us, good morning. Good morning. Isaac Chang has arrived, thank goodness, I can stop stumbling? Can you briefly tell us why the dominant theory was phlogiston for a while and what that was? Phlogiston literally from the Greek means the matter of fire. And it responds to an intuition, I guess we all have, that when something's burning, it's spitting something out.

So that if you watch a candle burning, what you're watching, as it seems, is something coming out of the wick. That thing that's coming out is called flogiston. When stuff burns, it emits flogiston. And the flogiston theory was that a whole range of processes, for example, the extraction of metal from ore, processes of fermentation,

all involved exchanges of Flodgistan. And Jenny Eugler, into this chemical world, arrived Joseph Priestley, who became very powerfully associated with Flodgaston. Can you give us a brief thumbnail sketch of what sort of man he was and what drew him to chemistry? Well, it's fascinating, listening to Simon,

talking about what chemistry was in Europe in the 18th century with these vast laboratories and terribly complicated instruments and so on. because Priestley came from a completely different tradition. He came from a humble family, not really poor. His father was a cloth dresser. He was the oldest of six children. And his mother having too many children,

they sent him to live with his grandfather until he was seven. Then when his mother died, he went to live with his aunt, who was a, they were all dissenters. And they were very, very keen on education. Descenters at that time couldn't go to, Oxford or Cambridge or something. So Priestley was a sort of prodigy. He learnt not science, as we would call it, but languages.

And then he went to one of the dissenting academies at Davenry, again, set up by nonconformists, outside the normal educational sort of sphere, very keen on new knowledge, very keen on knowledge that would help people in industry, in commerce and so on. And one of the things that they were keen on was natural. philosophy. But Priestley went on, really. He was going to be a preacher. He had a, not a natural philosopher. He had his first little living at a place called Needham Market. Did not go well. He was

already very unorthodox and wild in his views. He had the most, all his life, the most tremendous stutter. So he stutter, stutter, stutter, left Niedem Market, not a success. Went to another area at Nantwich, where he was a great education list. And from there he went to Warrington Academy. And that's the important point, because there he found a place, another non-conformist academy, where everybody was interested in making these experiments. But very informally, unlike the big laboratories you've been talking about,

small groups of people following up these gases, airs. The most exciting thing at that point was what everybody was finding out about electricity, Benjamin Franklin, the hero. and that's when he started making his experiments. And one more thing, when we were talking about the state and as it were, the secrecy and the great furnaces, Priestley's science was always linked to his ideas about theology and to his politics.

Can you develop that a little? Yes. Because I meant to ask Simon that the idea of revolution is in the air in everything, and everything being stripped back revolving to the past where you can start from the beginning again in learning as in politics, as we will see, and so and so forth. So this is very much part of it, and in religion, I presume, with the dissenters.

Absolutely. I mean, they really are linked in a complicated way that's quite hard for us, I think, to understand. For instance, in his theology and his thinking about the relation of God and the world and what the church was and what Christianity was. Priestly is always going back to primitive Christianity, to what is the pure, what are the origins, how can we live simply? And one of the processes that he and many people like him

thought was part of the religious process was actually finding out about the world because this is the world that God created so that the more you found out about the world, the material of the world, the near you were to understanding the laws that governed it, which were in a sense the laws of God and so. And politically, it goes as if it were the institutions of the past,

whether it be the church and the state, have thrived on mystification, on keeping people ignorant and just therefore telling them what to do. So that the more you understand, the more questions you ask, constant questioning that the more and that is a process towards revolution

the more you would change things so to Priestley said that the progress of knowledge it's a really democratic idea the progress of knowledge does not go in a straight line does not come top down

but spreads outwards like the light from the sun or the waves from the sea to everybody and that if this process is free and everybody questions, then we hope that in the fullness of time

it will extirate all terror, oppression and prejudice. So knowledge is actually a political tool, science, religion, politics, all linked together. Thank you. Hasak Chan, congratulations on getting here. Can we go, can we be a little bit more detail at Priestley before we move to France and Lavoisier and how he arrived at the,

the notion, how is early interested in gas was aroused? Yes, as Jenny just mentioned, he was not originally trained as a natural philosopher. He was a priest. The crucial point here is 1767 when he moves to Leeds

to take up position at the Mill Hill Chapel, which still exists, although in a different building. Now, Priestley tells us that it just happened that he moved into a house in Leeds right next door to a brewery. And in the brewery, he would visit and play around. He discovered that in the fermenting vats, was produced this gas, which Joseph Black had identified as fixed air,

what we now call carbon dioxide. And Priestley discovered various things about what this gas does. A candle would be extinguished in it and so on. And then he discovered how to dissolve more of this gas than usual into water by basically swishing water around between two cups. And he discovered by this he could make what we would call carbonated water. He said it was an exceedingly pleasant sparkling water. And everyone was wild about this new drink.

First, because they thought it would cure scurvy at sea. which didn't turn out to be the case, but it did catch on as a European-wide phenomenon. It was what made him famous, wasn't it? Exactly, yes. It's about this work that Lord Shelburne, who would later become his patron, heard about while Shelburne was traveling in Italy. So that's the initial entry of Priestley into pneumatic chemistry. He had done his work on...

He had done his work on electricity just before this. His book on that which was quite renowned was published in that same year of 1767. And then the next stage we see that significant would be 1771, 72. In 71 he gets deeply interested in the power of green plants to revive the quality. of air, right? He's worrying about the fact that the process of respiration as well as combustion fowls up air. And he's worrying, well, what's going to happen to us when we gradually exhaust the air that we can breed? And then he's delighted to discover in one of his experiments that a sprig of mint, to begin with, could make this air better. The quality of air he's

measuring by means of a mouse, as you mentioned in the opening introduction. and he discovers... Which is heard in the car. Yes. Then in the following year, he comes up with this so-called nitrous air test. The mouse being not such a precision instrument, he discovers that this particular type of air, he had also discovered what we now call NO,

would, as we would say, combine with oxygen and the product, NO2, is water-soluble. so the volume of the air would diminish, the more so the better its quality. So that sets him off on this whole programme of chemistry of airs. Can you mention, which we must do, Carl Scheler, the Swedish, who a year or two before Priestley could, as I understand it, lay a fair claim to have been in on this discovery, perhaps the first at it.

Yes, I think if we, We are talking about the pure temper priority of who first made that gas, which we now call oxygen. It was clearly called Wilhelm Scherler working in the middle of Sweden. He didn't publish much. Again, a chemist in a small Swedish provincial town. Small Swedish provincial down of Sherping. It was an apothecary. That's how he made his living.

And he did his chemistry for himself. did phenomenal amount of chemistry actually in his spare time, but he didn't publish very much or very promptly, especially outside Sweden. So Priestley, I believe, had no knowledge of what Sherley had done with oxygen, which Sherle called fire air because of his capacity to promote fire. And there's Priestley discovering what he called the logisticated air and Love was here coming later on, naming it oxygen. So we've paid a proper tribute to Shela,

but actually the point is that Priestley did not know of his work, which had been published only in Swedish, and therefore he's acting independently, which often happens in science and in the arts, all over the points, right? Can I just pin this deflogicated air for our listeners, who, this becomes the battleground. Can you, Simon, can you nail that for us?

Can you nail the air, and then we can move on? Only you can nail the air. I think a very good way of thinking about it. Hassock has already helped us here enormously, is Flogiston is what makes air bad for us. So if you burn a candle in a closed chamber, then the air that's left is very bad. Mice, as it were, go out in that air.

So breathing and combustion fill air with this principle called flogiston. And that principle viciates the air. It makes it impossible to support either combustion or life. The nitrous air test, which Priestley develops, which tests for the Flogistin content of any particular kind of air, is therefore testing what Priestley, I think rather beautifully, calls its virtue.

And you should listen to the pun there. Right? Virtue means the capacity to support animal and human life, but it also, because according to Priestley, we live in a world created and maintained by wise and benevolent God, it's moral virtue as well. Priestley, in fact, rather brilliantly, it seems to me, argues that political corruption and social corruption go along with bad phlogisticated air, e.g. It is no coincidence, he argues. argues that the two great English universities, Oxford and Cambridge, are both built on the top of swamps. I can vouch for this fact. And the corrupt quality of the learning pursued there is highly correlated with the corrupt quality of the air that the scholars have to breathe. Similarly, the nitrous air test, the Flodgiston test, excuse me, allows you... Sorry, bad air. Bad air in the studio, folks. The nitrous air test allows...

you to invigilate the virtue or viciousness of different sites, factories, hospitals. Can I come to you, and I know you're raising your hand, Jennifer. I'm just trying to slightly reorganise this. We must bring in Antoine La Boisier, or there'll be another French Revolution, who is deeply important in this. Can you introduce him? And then I'll go to Hazzok to talk about what his theory was, because he's more of a theorist, isn't he?

But the man himself, Lavasia, could not more, as you say, it couldn't be more different from Priestley. It's scarcely more different from Priestley. LaVoisier is, I think, 13 years younger than Priestley and comes and is the son of a very wealthy Paris lawyer. And he,

so his training and his education and his sort of procedure experiments take place in a very different environment both materially and intellectually. And he's elected to the Academy des Cions very at an early age in his 20s.

And he does have a large laboratory at his disposal. And so his background is completely different, and I think Hasop can explain the theoretical differences as well. Could you do that then, Hassook? What are the theatres? Because he's much more of a theorist, isn't he, than Priestley? The Voisier. From the modern point of,

view, yes. I mean, we may come back to the different ways in which the two men viewed the nature of theory, but to come to the immediate question. So we talked about how Priestley had produced deflogisticated air, and how that was done was by what they call the reduction of calx, right? Calx is what we would now call a metal oxide. So Priestley was working with a red oxide of mercury, which he had figured out how to heat up to a very high degree of heat using a large burning lens, right, with sunlight. And he discovered that if you did this in an enclosed space, it would make the air very good, right? And Priestley interpreted this as the mercury calx, absorbing the phlogiston that was present in the air, therefore making the flogisticated air. And

And Lovewas yet comes along, does the same experiment, which in fact he was shown how to do by Priestley in 1774. He turns around... Which he doesn't acknowledge. He's very bad at acknowledging any help he got from anyone else. But he just turns the conception of Priestley's on his head and says, no, no, no, it's not the absorption of flogistence that's going on here. It's the emission of oxygen.

So he says what you guys call Calx is an oxide. That's the terminology he invents for himself later on. So from the mercury oxide, we are disengaging oxygen by intense heating. Had he got there, though, we're looking at a sort of almost a race. Let's call it a race for the same convenience. Between these two men, Shailers said he's a bit rather too late, and he is no longer on the scene that we are now talking about. but he hasn't really, even though he's called it oxygen gas

and he's turned a flitin on its head, he hasn't really arrived there yet, as I understand it, Simon. I think that's absolutely right. I mean, this is a process that takes several years. In fact, if you follow it through, it takes at least a decade for Lavoisier, and I think this is the fascinating point here, to go back over 10 years' work

and reinterpret it in the light of what he comes to realize must be going on. Now that realization dates to the early 1780s and he's going back over work inaugurated in the early 1770s and rereading it

as a series of experiments that demonstrate that when you heat up calpses like mercuric oxide as he now decides to call it what is happening is that a gas is formed and the gas that is formed.

And the gas that is formed he, excuse me, first of all, calls not oxygen gas, but the air itself entire, or the purest part of the air. In other words, he shares with Priestley enormous numbers of theoretical resources. The two men, as Hassoc said, in fact, meet in Paris in the autumn of 74. That's when Priestley communicates the recipe. At that point, Lavoisier is very, very far indeed, even from using the word oxygen. Then we need to think what the word oxygen means. It means the principle of acidity.

So Lavoisier is making the following claim that when you heat mercury calts, what we call mercury oxide, what is going on is that the mercury calts is spitting out a principle called oxygen, which then combines with another element, and this is the element of heat, which he calls caloric, caloric, and what he sees as oxygen gas is a compound, which it is not, of course, for us. Can I come just briefly to you for a second,

before I go back to Jenny, as I understand it, LaVoisier, two of the things LaVoisier was doing, was bringing to the table in this, was a very acute and refined degree of measurement, of weighing, was extraordinarily important to get these experiments, right? Yes. And secondly, he was thinking about chemistry in terms of elements and compounds.

So can you just confirm what I've said in rather more authoritative language? Well, yes and no. Weight is enormously important for Lavoisier, and posterity does remember him for having put this very crucial emphasis on weight in chemistry. But I think it is a slight mistake to. to say that LaVoisier began that recognition of the importance of either weight itself or precise measurement. So, for example, if we asked the question, who in the late 18th century is the best measurer of things in chemistry? I think we would have to give that title to Henry Cavendish, who was a believer in Flogistin, among other things,

and Cavendish could really make precision measurements better than Lovelliv. I wouldn't submit. So there are two sides of that story as well. But in terms of the elements and compound? Yes. That's the other aspect that we often credit LaVoisier with. The way I see it, Lavoisier is important in promoting that picture of chemical reactions as the association and dissociation of stable building blocks, right? The basic units being, called elements. It's sort of a Lego-like picture of chemistry, but Lavoisier is not entirely into that modern picture. As Simon mentioned, he talks about principles, rather than elements, and thus, old language, which is very important for priestly, because for him,

principles are related to this notion of powers, which is in the end divine. But a principle was an active substance which would combine with more passive stuff and impart these characteristic properties to them. So oxygen would combine with anything and then turn it into an acid. Phlogiston would combine with anything turn it into a combustible or metal. So Lavoisier still had one foot in the old tradition of principle-based chemistry while he was really reaching out into this new chemistry of elements and compounds. I think what's interesting about that is that it shows that all revolutionaries are only partially successful or partially revolutionary.

In Lavoisier's case, for example, there is exactly, as Hassox says, an enormous emphasis on the role of weight and of the chemical balance. But the fact of the matter is that some of the principles that Lavoisier thinks are fundamental to chemical reactions. the principle of heat, caloric, and the principle of light, clearly have no weight. Hot bodies are not heavier, even though they certainly have more heat. So Lavoisier is always being driven by, in a certain sense, the practical logic of his enterprise to find ways of estimating these principles without weighing them directly. I'd like to ask Jen to come back to Chen Yuglan, and two things. First of all, what did Lavoisier get from police?

priestly, do you think? And then secondly, I'd like you to fill us in on the sort of nature of the time, bringing in the word revolutionary, it was revolutionary times. Asak mentioned the Duke of Cavendish and how the chemistry was taken up with rich people having their laboratory. So, first of all, what did Lavoisier do we think got from priestly? And then secondly, if you can bring us back to a sense of the period. Well, Lavoisier, as Hussack and Simon said, got from Priestley a description of a quite precise experiment which had produced this air.

Priestley was at that time under the patronage of the Earl of Shoburn, who took him to Paris. And I just always think it's a very sort of comic scene in a way because Priestley, at this point, though he does become more competitive and anxious, because of his desire to spread the scientific endeavor, talks to everybody about it. He hears that Lavoisier is a chemist and Wattsmore has a superb laboratory. And he has been working on this ash and there at dinner.

In his back room. Yes. Oh, I'm sorry, this is a detail of him, but Priestley works deliberately with a sort of simple equipment because his books, he wants everybody to try them. So he's working with bathtubs and jam jars and candles. And in his books he says everybody can do it. And so his laboratory technique is probably actually more precise

than he says in his books. In his books, he makes everything look accidental, the mint growing on the winter, I just happened. So that if you keep your eyes open, we can all be great discoverers. but he hears that lavoisei has this marvelous equipment he has had this problem at the ash and he actually says

Mr LeVoisier I've got this real problem do you think you can sort of help you know what do you think about it and Lavoisier who is no fool goes mm-hmm very interesting that goes on so he and Levoise is not in exactly the same kind of exchange of information so I don't think that he gets back with his precise measurements but I'd like to come back to Haslock too in a way

because it is, I think, the measuring of the ash or what is given and what is absorbed. It is measurement that is that crucial difference in those first experiments that Lavoisier does that it is going to be vital, isn't it? Oh yes, yeah. Can I come back to that just over you for a moment, Jenny? Two things there.

One thing that, as I understand it, Priestley was of the opinion that to seek individual eminence and recognition for a scientist was not what you were supposed to do. You're supposed to take forward the science. And actually, seeking that sort of thing was detrimental to science, held it back. And so that was his conviction, as he was a man, as you yourself pointed out,

of deep convictions, which he followed through to the rest of his life. I think it would be interesting for our list us to know that we are in revolutionary times here. We're about to approach the revolution, which profoundly affected Lavoisier, he was guillotined and profoundly affected

priestly, he was ruined because both of them got caught up in revolution so if you just give us some picture of the times then, because science was exciting, driven, aristocratic occupation by some of the more intelligent aristocrats

and so on it was very much part of the fashion and the scene and the drive of the time. Yes, well to take it sort of rapidly forward over this next 20 years from the great discoveries takes us to the French Revolution

and things are working in parallel. In Britain, again, going back in time, when the experiments that were done at the Royal Society are taken out into the world, it's when these men are growing up, Cavendish, Priestley, Erasmus Darwin, people like that. Science becomes a form of display. Experiments go out into the provinces,

they show that you can do these. miraculous experiments with electricity or whatever. It's an exciting thing. People have then given the possibility that they, in their small provincial places, can make great experiments. And they communicate with one another and with the Royal Society. And patrons then lend them books. There's a great sort of surge of feeling that all these different people,

doctors have you said, apothecaries, industrialists, priests, people with leisure time, finding out about the nature of the world. What happens because the non-conformists are so involved here is it begins to be allied, this sort of questioning, with an opposition to the established church and to the government. So the non-conformists who are fighting the government for repeal of the laws which keep them out of official positions here,

for repeal of the test and corporation laws, they are seen as it were the experimenters. So experimenters, oh, they're dangerous people. They're working on things like gunpowder. The whole language comes around it. So if Priestley makes a speech, as he did, unwisely, saying the movement in the non-conformist churches such that it will explode the established order, that's immediately linked to actual science and actual explosions.

So he thought that they are in a way actual revolutionaries. Their science is actually revolutionary. Meanwhile... He actually says with a sigh, if there's anything unsound in the English constitution, and of course he thought there was, then it has reason to tremble at an air pump. What he meant was if you could show

that nature doesn't work the way the established church and monarchy claim it does. Our soul is mortal, for example, says priestly, the divine right of kings is a sham, nothing happens in the Eucharist. All of those claims can be undermined by chemists. Yeah. And meanwhile, across the channel, in France, when the revolution actually breaks,

the perception of the solid British church and king people is that that revolution has been caused by this group that they call the Philosoph. And that, elides in, our thinking, with the natural philosophers. So scientists have also been responsible for the revolution in France. So that when Burke is talking against the French Revolution, he uses the language of science. He says the wild gas is let loose. So science, inquiry, non-conformism, all become to seem revolutionary, and dangerous.

Would you like to comment on the way Le Voisier was developing his ideas as the revolution gathered pace, hasn't it? Well, he was very conscious of this dual theme of the political and the scientific revolution, right? He says already in one of his writings

in 1770s that he wants to make a revolution in physics and chemistry, which he does proceed to do. and his textbook, the definitive textbook of the new chemistry, is published in 1789. Which led him to be called the father of chemistry, at least by certain seconds of the world. Which I think was one of the beginning shots of his own revolution,

his own campaign to establish himself as the founder of chemistry. And then in the same year he also found a new journal, the Annal de Chimey because he was not happy about the existing premier journal aside from the academy memoirs, which was the journal de Physique, which wouldn't publish all the papers that he and his colleagues were writing. So he says, all right, I'll just have my own thing. And piece by piece, he's assembling the fabric of the new chemistry, and he's very conscious about doing that.

And he is participating in the political revolution as well. He's a reform-minded person, although he's quite conservative and involved in the tax collection business, which costs him his life. But, you know, he is part of the Committee on Wights and Measures, which brings us the metric system. He's the inspector of gunpowder, which brings him to his residence and lab at the Arsenal. Very convenient. So he's mixed up completely into that political fabric of events. Can you tell us briskly, we're getting to the end of this program, unfortunately, how both of them met their end?

And it's in both cases, sorry, it's a terribly overuse. In both cases, it's ironic, isn't it? Yes, yes. It's deeply ironic. In the case of Lavoisier, he's tried, convicted and guillotined essentially because he's running a privatized tax collection system. And most cultures, I think, take a fairly dim view of privatised tax collectors. Lavoisier, remember, was a fabulously wealthy man.

He was earning more than 150,000 pounds a year from his various tax. Well, no, it's an unimaginable. Which is an unimaginable amount of money, whereas he was only getting only 5,000 pounds a year because he was an academician. So he's an entrepreneur and businessman with major political and economic interests. Priestley, on the other hand, is... The guillotine for being a tax man. It's a nice thing to say. Priestley, on the other hand, whom we might want to see, in my view,

certainly as the more revolutionary figure, has his laboratory and much of his library and most of his equipment destroyed in a Tory-inspired riot in Birmingham in July of 17. essentially encouraged by the local magistrates, at least that's one story, against the industrialists and dissenters in the city, who supported the French Revolution. There were petitions both for and also against him. His effigy was burnt in many British cities, and he had to flee the country eventually, moving to Pennsylvania, to Northumberland County, Pennsylvania, partly under the patronage of the great Thomas Jefferson, where he lived for, more than a decade afterwards. Very much the great prophet in exile.

Young radicals, Samuel Taylor Coleridge is one, William Wordsworth is another, admired him as the great prophet across the sea who'd been expelled from Britain for his radical views and for speaking the truth.

Can you give us some idea of who you think, if it's possible, who deserve most of the credit for discovering oxygen? I think it wouldn't have to be Priestley in both the senses that he did isolate the stuff first. And what's usually said is Lavoisier found the right theoretical understanding of the substance. But I think if we look at it more carefully, Priestley did have already the ideas that we have preserved now,

which is that oxygen supports combustion and respiration and so on. the bits that Lovewasia tecton about oxygen aren't quite what we want, such as that oxygen gas is full of caloric and oxygen is the principle of acidity. You would like that, Ilya, don't you? Yes. Very much. You very much like Bricely.

Well, thank you all very much, and thanks for making it, Adam Chan. Thank you very much, in Euglow. Thank you, Simon Chaffler, who mentioned brilliant Advergesp and Xx program, William Wordsworth, the prelude, the first and still the greatest autobiographical poem in the language

who will be the subject of next week's programme. Thank you for listening. We hope you've enjoyed this Radio 4 podcast. You can find hundreds of other programmes about history, science and philosophy at BBC.com.com.uk forward slash radio 4.