Oxygen and Revolution

by Read Listen Learn

The discovery of oxygen is closely connected with revolution in late eighteenth century France and with two scientists, one British and the other French, both of whom are sometimes called the father of chemistry. They are Joseph Priestley and Antoine-Laurent de Lavoisier. However, in actual fact, neither of them was the first to identify the element. That honour goes to a man called Carl Wilhelm Scheele, a Swede of German origin, whom the sci-fi writer Isaac Asimov called “hard luck Scheele”. That was because he discovered several other elements as well as oxygen – barium and manganese in 1774 and tungsten seven years later – but has never been credited with them in the popular imagination.

There were many reasons for this. In the first place, Scheele published in Swedish in fairly obscure academic journals and always many months or even years after he had discovered something. So, his work hardly took the world by storm. Next, he continued to work as an apothecary – or pharmacist, as we now call the profession – rather than devoting himself to research. He could have done so, as he was the man who first made the phosphorous match that all the world used until lighters were invented. Because of Scheele, Sweden has been the biggest manufacturer and exporter of matches ever since.

Another reason for his obscurity was that he had a short life and so was not around to stand up for himself. (He had the unfortunate habit of smelling and tasting the chemicals he discovered and died in 1786 in his early forties from lead and mercury poisoning.) By the way, the name he gave to oxygen was “fire air”. However, having paid lip service to Scheele, we can now move on to an English revolutionary who admired what the French were doing to their ruling class in the late 1780s and early 1790s – killing them – and to a French aristocrat and tax collector who lost his head at the guillotine.

The late eighteenth century witnessed something of a revolution in chemistry. There was an economic impetus for this because of the significance of the subject for industry, mining, medicine and war, but there was also the means, as accurate equipment was available to chemists for the first time, meaning they could achieve precision in chemical processes and measurements through controlling the temperature of ovens and using balances and new glass instruments. In consequence, the social status of apothecaries (who were not university graduates, as degrees in Latin and Greek were the staples of higher education) improved and this led many more aspiring chemists to enter the profession.

For eighteenth century scientists, air was what chemistry was all about. It was essential to metallurgy (and so to the Industrial Revolution) as air was vital to the process of refining pure metals from base ones. It was also pivotal to medicine, as it was universally believed that disease was spread by air. Hence, we get the Latin name ‘malaria’, or ‘bad air’. There was great concern too about the quality of air in industrial towns, as burning material was thought to produce ‘phlogiston’, which was harmful to human health.

When Joseph Priestley announced in 1772 that he had discovered a new gas which caused flames to spark, it was, therefore, a major discovery. He also told his audience that he had put a mouse in a very small space with so little air that it would, under normal circumstances, have died in fifteen minutes but, when released after an hour, was not only alive but “vigorous”. The gas it breathed was ‘dephlogisticated’ air – or oxygen, as it’s now known.

Priestley had been working with gases for several years already when he discovered oxygen. In 1767, he had identified carbon dioxide, or ‘fixed air’, as he called it. This had made him a household name because he was able to use it to make drinks fizzy, a very popular invention as it gave us soda water and livened up beer. But it also had the interesting quality that it extinguished fire.

In the twenty-first century, science is often seen as isolated from our lives unless it produces something that we all use, like the Internet, say. True, we hope that scientific research will find cures for cancer and other diseases, but we see the work that goes into it as objective, neutral and detached from everyday life. Even if we donate money to eradicating these diseases, we don’t keep up with the progress scientists are making to achieve their goals. Anyway, it’s so complicated that most of us couldn’t hope to understand it.

This is a very different situation from that in the eighteenth century, when chemistry in particular was seen as intrinsically involved in social change and its practitioners as men with definite political opinions. When Priestley was working, many intellectuals – especially chemists – were dissatisfied with the social order and were very vocal about it. Somehow, their science got mixed up with their politics not only in the popular imagination but in their own. And Joseph Priestley was the most critical social commentator of an already very critical group. How did this come about?

Priestley was the oldest of six children but was brought up by his grandparents, as his parents could not afford to feed and clothe him. He returned home when he was five, after his mother died, but then moved out again and lived with an aunt and uncle when his father re-married. His family were all ‘Dissenters’ who believed in simple lives and devotion to God. It was this all-important principle that guided Priestley’s entire life. The corruption of the Christian Church and its support of social class and inequality were, for him, the root of all evil.

He tried throughout his life to reduce things to their purest forms. He was sure that the only reason corrupt social institutions like the Church and government survived was that they mystified people. If one lived by God’s laws and understood the workings of His universe, one could better see the nature of God Himself. This led the industrious Priestley to study sciences and to share his knowledge eagerly with others for the good of all. He’d continue to do so throughout his life.

But there was no money for him to attend university or even good schools. The lad educated himself and became a linguist. He was exasperated with traditional grammar books which described English by reference to Latin and, so, wrote his own. This was used for decades in schools and is probably the best book on English grammar written in the eighteenth century. He went on to become a minister of religion, but was never much of an orator – he had a stutter – and was always happier in a laboratory than a pulpit.

Meanwhile, in Paris, Antoine Laurent de Lavoisier, who was just ten years older than Priestley, lived a very different life and held equally different political opinions from his English counterpart. For a start, he was an aristocrat and had been born into a very prosperous family. Apart from his scientific research, which was, in fact, a hobby for him and his thirteen-year-old wife, he worked as a tax collector and sat on several aristocratic committees. These posts made him seriously rich and allowed him to build the best-equipped laboratory in the world in his own home. There he and his wife pursued their interest in chemistry, especially on Sundays, which the couple referred to as their day of pleasure.

Lavoisier’s contribution to the development of chemistry can scarcely be overestimated. He was the first person to give oxygen (1778) and hydrogen (1783) their modern names, as well as many other elements. He also devised the first extensive lists of chemical elements and showed that sulphur was one of these, rather than a compound as had previously been thought. Then, he stressed the importance of precise measurement in experimentation.

As if all that were not enough, he helped to devise the metric system which is almost universally used today. But all this pales into insignificance when compared to his supreme achievement: the law of conservation of matter. It was Lavoisier, always more of a theorist than Priestley, who noticed that even when iron had gone rusty, it weighed the same as before. This led him to the all-important law that matter might change its shape or form (for instance when iron becomes rust or burning paper turns to ash), but it never changes its mass.

But back to oxygen! Priestley once wrote that the “progress of knowledge spreads out like the rays of the sun, so that eventually all oppression and ignorance are banished” forever. In that spirit, he shared his ideas on ‘dephlogisticated air’ with the Frenchman, who was not quite as generous as his idealistic colleague. Instead of appreciating his frankness, Lavoisier repeated Priestley’s experiment and published his own conclusions on its relevance to chemistry without discussing these beforehand with the man who had shown him how to conduct them.

The Englishman had heated mercury oxide and showed how the ‘dephlogisticated air’ it gave off ate up phlogiston, thereby making the air cleaner. Lavoisier got exactly the same result but argued very differently about what it meant. He said that mercury oxide, when heated, gave off oxygen, which made the air cleaner. As was immediately obvious to everyone, phlogiston had lost its central role in chemistry. In short, it did not exist.

Priestley never accepted Lavoisier’s theories – neither his dismissal of phlogiston nor his law of the conservation of matter – and slowly drifted into scientific irrelevance as these theories became more central to chemistry.

But the story does not end there. Priestley was openly supportive of the French Revolution at a time when the English ruling class was more than just a little worried that it might spread across the sea to Britain. His revolutionary statements were not very popular and, encouraged by the local authorities, an angry mob burnt down his house. Priestley and his family were lucky to escape with their lives and continued threats made it impossible for them to remain in the country. Priestley went to America, where he was welcomed with open arms as a genius, and slowly but surely wasted the rest of his academic life trying to refute Lavoisier’s theories.

The same revolutionary events that Priestley was so impressed by, however, meant death for Lavoisier, who went to the guillotine as a tax collecting aristocrat. Shockingly, we don’t actually know what the man looked like, except for some rather amateur sketches. A statue was made of him but it later turned out that the sculptor had used a head for it that he had in his storeroom and made no attempt to make it look like Lavoisier. No matter. It was later melted down anyway to be used as bullets by French soldiers fighting in the First World War.

And so end the stories of two of the pioneering fathers of modern chemistry.