13 March 1733, Birstall (United Kingdom) - 6 February 1804, Northumberland (United States)
Joseph Priestley was a scientist, theologian, dissenting clergyman, philosopher, educator, and political theorist who published over 150 works and is known as the originator of carbonated water.
He was born into a family of English dissenters, i.e. Protestants who had separated from the Anglican Church, in this case, Calvinists, in Hacnkey, West Yorkshire. He was the first of six children who, after his mother's death, went to live with his aunt and uncle, who provided him with a good education.
In 1749, Priestley became seriously ill and recovering as a devout Calvinist, he thought that a conversion experience would be necessary for his salvation, yet he doubted that there had ever been one, and this emotional distress finally led him to question his theological education. As a result, the elders of his home church refused to accept him as a full member.
To join the family business in Lisbon, he studied French, Italian, German, Chaldean, and Arabic.
In 1774, he identified a gas that he first called ‘dephlogisticated air’ which, in contact with it, made candles burn and glow brighter. Priestley believed that this was air from which the phlogiston had been removed.
The discovery of this gas was also attributed to the chemist Carl Wilhelm Scheele who called it ‘oxygenic air’ and the chemist, biologist, and economist Antoine-Laurent de Lavoisier who called it ‘oxygen’ and disproved the phlogiston theory in the 18th century.
Lavoisier, known for his studies on the oxidation of bodies and the law of conservation of mass, showed that combustion was the result of a relatively rapid chemical reaction of an exothermic nature. Lavoisier's studies made the phlogiston theory obsolete in the world of science.
In any case, Priestley was one of the first scientists to isolate oxygen in gaseous form and the first to recognise its fundamental role in living organisms.
During his lifetime, Priestley had a considerable scientific reputation for his invention of carbonated water, his compositions on electricity, and his discovery of multiple ‘airs’, the most famous of which is the aforementioned ‘dephlogisticated air’. However, his determination to defend the phlogiston theory and to reject what would become the chemical revolution finally isolated him from the scientific community.
Priestley's science was integrated with his theology, and he constantly tried to merge Enlightenment radicalism with Christinised theism. In his metaphysical texts, he attempted to combine theism with materialism and determinism, a project that was considered bold and original for its time. He believed that a proper understanding of the natural world would enable humans to progress and reach the Christinao Millennium.
Priestley believed strongly in the free and open exchange of ideas, which led him to miss the commercial potential of many of his discoveries, such as carbonated water.
He was also a tireless advocate of religious toleration and demanded equal rights for religious dissenters. His theological views led him to found Unitarianism in England.
The controversial nature of Priestley's publications, combined with his outspoken support first for American independence and later for the French Revolution, aroused public and government suspicion, and he was forced into exile in 1791, first to London and then to the United States until his death after a mob burned his Birmingham home and church.
What is phlogiston?
Phlogiston is the disproved 1667 scientific theory that sought to explain the combustion process and was postulated by the physician and alchemist/chemist George Ernst Sthal in the early 18th century, based on the earlier work of his mentor Johann J. Becher.
Stahl assumed that heat can occur in two different forms: free and in combination. This second form is what he referred to as phlogiston, meaning ‘flammable’ in Greek, which is inherent in all combustible bodies, and therefore combustion would be the transition from this combined form of fire to the free form, where it could be seen by the senses. The resulting remains are incapable of re-burning because they would have used up all the phlogiston in the body. For example, Stahl believed that metal was composed of phlogiston and lime, and upon combustion only the lime remained; but if a substance rich in phlogiston (such as coal) was added, it could be returned to its original state.
