For centuries on end the prevalent notion that existed was that air “is a simple elementary substance, indestructible and unalterable”. When Joseph Priestley wrote this, he also added that there have been only a handful of concepts that “have laid firmer hold upon the mind”. With his work, Priestley made sure that this idea, which mankind held dearly, would finally be dropped as his experiments clearly showed that air is a composition, or mixture, of gases.

Scientist, theologian and political theorist

Born in 1733 at Birstall, England, Priestley was the eldest of six children. After his mother died while he was only nine, his father, a maker of wool cloth, sent him to live with his aunt. It was in his aunt’s home that he was exposed to theological and political discussions, fields in which Priestley would go on to play a stellar role, as in his scientific career.

Attending local schools, Priestley had to drop out during his teenage years with a bout of tuberculosis. He had learnt Greek and Latin by then, had also taught himself a good many languages, including French, German and Italian, and was well-versed with the basics of algebra and geometry.

He enrolled himself at Daventry Academy with the objective of becoming a minister, and it was here that he became engrossed in experimenting and sciences. He became self-sufficient for the rest of his life after graduation, serving indeed as a minister, teaching modern languages and finding himself in places where he could indulge his growing interest in scientific experimentation.

Franklin’s friend

His frequent visits to London brought him in touch with some of the leading minds of science and independent thought. Among them was Benjamin Franklin, one of the Founding Fathers of the United States, who would go on to become Priestley’s lifelong friend.

Franklin egged Priestley on in his research and encouraged him to further investigate electricity. Priestley duly did the same and published some of his findings in “The History and Present State of Electricity”. Not long after, Priestley was elected a Fellow of the Royal Society, in 1766.

As he believed that this book was quite over the top for the majority of the people, he looked to tone it down in order to make it more accessible. When he couldn’t find illustrators to help him with this task, he took to drawing himself, managing, along the way, to discover an early form of eraser.

Blessing in disguise

Priestley’s religious stand, however, came under increasing pressure. He missed out on a chance of being the scientific advisor for Captain James Cook, a British explorer, during his second voyage, but it might well have been a blessing in disguise.

The Earl of Shelburne asked Priestley to serve as his intellectual companion and the estate’s librarian in 1773, a position that afforded Priestley the chance to mingle with the elites, and, more importantly, more time for his research.

Discovers oxygen

On August 1, 1774, Priestley used a lens to focus sunlight and heat a sample of mercuric oxide using a pneumatic trough, a laboratory apparatus. He realised that the resulting gas collected allowed a candle to burn more brightly and supported the life of a mouse placed under a glass filled with it for four times as long as a similar quantity of air.

He decided to call the resulting new “air” as “dephlogisticated air” as he was a staunch advocate of the phlogiston theory. This now defunct theory, the dominant belief in that era, postulated that phlogiston, a fire-like element, is contained in combustible bodies. We now know this gas simply as oxygen.

While there were predecessors to the discovery of oxygen, including Swedish chemist Carl Wilhelm Scheele the previous year, Priestley is often credited with the discovery as he was the first to get his results published in a paper.

In the years that followed, Priestley had to eventually flee England owing to his religious views and his political stands, as he supported the American Revolution and then the French Revolution. Setting sail to America in 1794, Priestley continued his research, with much success, until his death in 1804.


Priestley’s prophecy?

On discovering oxygen, Priestley wrote the following: "The feeling of it in my lungs was not sensibly different from that of common air, but I fancied that my breast felt peculiarly light and easy for some time afterwards. Who can tell but that in time, this pure air may become a fashionable article in luxury. Hitherto only two mice and myself have had the privilege of breathing it."

While only two mice and Priestley himself had, according to him, breathed pure oxygen up until that time, his prediction that it might turn out to be a luxury commodity might as well come true.

What with air purifiers for rooms and living spaces and luxury air and mountain air being sold in cans, we are closer than ever to what Priestley envisioned.

One only hopes that pollution doesn’t drive air quality so low that buying air to breathe becomes the norm in the future!

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