Joseph Priestley and the story of dephlogisticated air…

DOCTER PHLOGISTON, The PRIESTLEY politician or the Political priest. Anonymous caricature, 1791

The facts, as they stand, are these: every creature, when respiring, releases phlogiston. In fact, respiration is simply to be considered a form of combustion. Anything that can burn contains phlogiston. Substances, when burnt, release this weightless, invisible substance — an element of their being, their composition — the phlogiston. The phlogiston is always in need of somewhere to go. Such as, air is best for the phlogiston. Air can absorb it. Taking this mode of thinking to its furthest logical conclusion we can only state that the reason creatures “suffocate” is because there is nowhere for the phlogiston to go. When air was removed from around a living creature then there is nowhere for the phlogiston to go and so respiration would cease and the creature dies.

Every now and again we are reminded that science is trial and error, an ongoing process. A collection of our true best current understandings. Yesterday’s taboo and tomorrow’s cliché. And quite often vice versa. We dismiss the science of old for its slavish and almost religious adherence to dogma, classical and entrenched in superstition.

Alas, this is not a story of when science “gets it wrong” so to speak. This is the story of the accidental discoverer. Joseph Priestley. The man who stuck by his wrong theory, right to the very end.

A mild-mannered chemist by nature, Joseph Priestley goes down in the history books as discovering oxygen. Except that he didn’t, and yet, at the same time he did. The problem was he didn’t realise what he discovered. This new-found discovery he called “dephlogis-ticated air”.

You see, this was a recurring problem in the scientific life of Joseph Priestley.

“It has often been claimed that Priestley was a skillful experimenter who lacked the capacities to analyze his own experiments and bring them to a theoretical closure.”

In other words, Joseph was a man who lacked the ability to connect the dots. In this day and age he would probably be the inventor of many answers in search of a question (the guy who invented Twitter for example). Or perhaps carbonated water. Soda water, something he named “mephitic julep”. His mephitic julep was developed hoping it would be the cure for scurvy. When that didn’t quite work he gladly handed over the recipe to a Mr Schweppes, securing his place in an alternative history where we all drink Priestley bitter lemon with ice. Other examples of the talented Mr Priestley include him being the first to note the electrical conductivity of graphite, as well as the first to describe the use of India rubber to erase pencil marks.

A common trait to all scientists is their stubbornness. Joseph was no different. The phlogiston theory, for lack of a better metaphor, had a lot of holes in it. When something burns its weight increases, and yet if a substance is to lose phlogiston from its being it should lose weight. A simple paradoxical problem to solve — the phlogiston had a negative weight!

For much of the 18th century this was the popular school of thought, until the French — Antoine Lavoisier — rivals to the English and American way of science, saw a different way to look at things and called it oxygen instead.

Joseph championed the colourless, odourless gas he had discovered as phlogiston right until his old age. Even after he had been harassed out of England and fled to America as a result of his incongruous opinions on God and politics. In 1796, eight years before his death, he published a final scientific paper on why the phlogiston theory was still valid, and why the Antiphlogistic theory had got it wrong.

“And yet, not having seen sufficient reason to change my opinion, and knowing that free discussion must always be favourable to the cause of truth, I wish to make one appeal more to the philosophical world on the subject, though I have nothing materially new to advance. For I cannot help thinking that what I have observed in several of my publications has not been duly attended to, or well understood. I shall therefore endeavour to bring into one view what appears to me of the greatest weight, avoiding all extraneous and unimportant matter; and perhaps it may be the means of bringing out something more decisive in point of fact, or of argument, than has hitherto appeared.”

Ironic when you think that Joseph Priestley came to prominence at a time when many still believed, as Aristotle did, that there was but one “air”.

Joseph Priestley was an undoubtedly brilliant man, imprisoned by the four walls of his conviction.

Fara, P. (2010). Joseph Priestley: Docter Phlogiston or Reverend Oxygen? Endeavour, 34 (3), 84-86 DOI: 10.1016/j.endeavour.2010.07.005

Wilkinson, D. (2004). The contributions of Lavoisier, Scheele and Priestley to the early understanding of respiratory physiology in the Eighteenth Century Resuscitation, 61 (3), 249-255 DOI: 10.1016/j.resuscitation.2004.04.007

Basu, P. (2003). Theory-ladenness of evidence: a case study from history of chemistry Studies In History and Philosophy of Science Part A, 34 (2), 351-368 DOI: 10.1016/S0039-3681(03)00022-0

Sternbach, G., & Varon, J. (2005). The discovery and rediscovery of oxygen The Journal of Emergency Medicine, 28 (2), 221-224 DOI: 10.1016/j.jemermed.2004.10.012


9 Responses to “Joseph Priestley and the story of dephlogisticated air…”

  1. 1 carolyn March 23, 2012 at 16:14

    i love this, great details:)

  2. 2 TheCellularScale March 25, 2012 at 21:52

    Great post! Examples like this are always interesting. I like that Golgi claimed that all the cells of the brain were continuous (as in, not separate cells), but the techinque he invented, the ‘Golgi stain’ is exactly what showed neurons to be separate from one another. I wonder what dogmas we scientists are adhering to right now that will be laughed about in the future.

  3. 3 Charles March 26, 2012 at 20:35

    Thanks for the comment. The trouble with all these things is hindsight. And in some way that’s the beauty in science. Seeing how it folds and forms over time.

    The golgi example is a great one I didn’t know about.

  4. 4 nonWHIG March 27, 2012 at 00:07

    rather whiggish, seeing how Lavoisier’s oxygen was crippled without caloric (incidentally a colourless, odourless, weightless substance) o.O

  5. 5 JUDE CHINAHA November 19, 2012 at 21:47

    Many old theories will soon be modied. Let us continue THE WAY OF SCIENCE

  6. 6 February 9, 2013 at 23:18

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  1. 1 5 Great Scientists Who Believed Wildly Unscientific Things | Chib Trackback on April 16, 2012 at 17:43
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