Joseph Priestley

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Joseph Priestley (* March 13th July / March 24th  1733 greg. In Fieldhead / Birstall near Leeds , England ; † January 25th July / February 6th  1804 greg. In Northumberland County (Pennsylvania) , USA ) was an English -US-American theologian of Unitarianism , philosopher , chemist and physicist . In 1771 Priestley first described the representation and effect of oxygen and in 1772 the laughing gas (N 2 O) he discovered . He discovered ways to represent numerous other gases : nitrogen dioxide , carbon monoxide , hydrogen chloride , ammonia , hydrogen sulfide , sulfur dioxide , silicon tetrafluoride .

Portrait of Joseph Priestley, painted by Rembrandt Peale , 1801


Priestley was the son of a draper and was born near the manor Oakwell Hall . His mother died in 1739 and he was adopted by his aunt, Sarah Keighley. Priestley was mostly home-schooled and began studying theology and ancient languages at a nonconformist school in Daventry when he was 19 . His thinking developed from Calvinism to Unitarianism.

From 1755 he was a preacher in a non-conformist church in Needham Market ( Suffolk ). In 1758 Priestley took over a second pastor's position in Nantwich and began with physical experiments (induction machine, air pump). From 1761 he was a teacher at the Warrington Academy in Lancashire , a private business school . He was ordained a year later and married Mary Wilkinson.

Black-and-white drawing of a two-story brick house along a road.
Priestley's birthplace in Fieldhead, Birstall, West Yorkshire (about 10 km southwest of Leeds )

From 1763 he took chemistry courses and from 1765 he regularly spent a few weeks in London , where he met leading scientists. So did Benjamin Franklin , who encouraged him to experiment with electricity. In 1766 he was accepted into the Royal Society of London. In 1767 his book A History of Electricity was published , he received a doctorate in law and became known abroad. The following year he became a priest of the Mill Hill Chapel, Leeds ( Yorkshire ). During this time his interest in chemistry developed, especially research into gases and optics. He authored the book The History and Present State of Discoveries Relating to Vision, Light, and Colors . In 1772 he was employed by William Fitzmaurice-Petty, Earl of Shelbourne, on his family estate Bowood House as a librarian and private tutor; he held this position until 1780. In 1772 he received the Copley Medal from the Royal Society . Between 1774 and 1780 he wrote the five-volume work Experiments and Observations on different kinds of Air . His progressive theological views had already earned him criticism in Needham Market. He increasingly approached anti-Trinitarian positions and finally founded the first Unitarian congregation in London in 1774 together with Theophilus Lindsey in Essex Street Chapel. He is therefore now considered to be one of the founders of British Unitarianism . His turn to radical Reformation Unitarianism led, among other things, to the fact that an invitation to participate as an astronomer in James Cook's second expedition was withdrawn. Priestley remained Unitarian throughout his life and promoted the building of Unitarian churches in both England and North America.

Around 1780 there was also a dispute with Count Shelburne, so he moved to Birmingham . In Birmingham, Priestley met many great scientists from England at the Lunar Society such as James Watt (further developer of the steam engine) and Matthew Boulton , Erasmus Darwin (doctor, naturalist, grandfather of Charles Darwin), William Murdock (inventor of gas lighting), Richard Lovell Edgeworth ( Inventor of a telegraph), Josiah Wedgwood .

Although the conditions in Birmingham were very favorable, his theological views and political activities led to a break with his acquaintances. Priestley stood up for human rights and also supported the ideals of the French Revolution.

One of his books was publicly burned as heretical in 1785 . Because of his advocacy of the French Revolution and several other long-running conflicts over himself and the dissenters , the Priestley Riots in Birmingham, which lasted four days, broke out in 1791 . Priestley lost his house with a laboratory, library and numerous unpublished manuscripts. He went to London from Birmingham and emigrated to the United States in 1794, where he was welcomed as a scientist and as an ardent defender of religious and political freedom. In 1782 he was elected to the American Academy of Arts and Sciences . In Pennsylvania he was offered a chair in chemistry, which he declined; instead he wanted to work as a Unitarian preacher. His close friends included John Adams and Thomas Jefferson . He spent the rest of his life as a writer in Pennsylvania.


In 1767 he published The History and Present State of Electricity , a summary in which he also described his extensive experiments: He had discovered that coal is electrically conductive and further established that there are connections between electricity and chemical processes. This work led him to what he later became best known for: chemistry - especially combustion and breathing . In 1770, the British Edward Nairne discovered that rubber was suitable for removing pencil marks. Joseph Priestley made this discovery public after an observation in the same year and was therefore long considered the inventor of the eraser.

Priestley's special magnifying glass


Priestley became famous because he described a special gas, the element oxygen , in a magazine on August 1, 1774 . When mercury (II) oxide was heated , it received pure mercury and a colorless gas that strongly promotes combustion processes. This gas was insoluble in water, but when it was combined with nitric oxide air, a significant gas reduction occurred - more than with pure air - in connection with water. However, he did not realize that he had discovered a hitherto unknown element ; rather he called his gas dephlogisticated air . Priestley remained a supporter of the phlogiston theory until the end of his life . Later he discovered the production of dephlogisticated air by heating saltpeter (1779).

The Dane Ole Borch had already reported in 1674 that gas was generated when saltpeter was heated, but he had not isolated and examined the gas. Oxygen had been presented by the Swedish pharmacist Carl Wilhelm Scheele at least a year before Priestley, but Scheele's report did not appear until 1777. Like Lavoisier, the Paris chemist and pharmacist Pierre Bayen had already published experiments in February and April 1774 which indicated an increase in the weight of metals indicated a gas from the air. Bayen was able to show that the gas is soluble in water and heavier than air. He was also able to show that pure mercury in this gas turns into mercury oxide again. However, Bayen did not chemically examine the resulting gas and is therefore not considered to be the discoverer of oxygen. The identification as a new element was carried out by Antoine de Lavoisier , who knew the experiments of Priestley and Bayen.

It is questionable why Priestley had not read this article in the French magazine, although this magazine was available in England. Lavoisier invited Lord Shelburne and Priestley to Paris in October to share the discoveries made. The knowledge that this new gas in the air, which promotes combustion, is a single substance, a chemical element, was made public by Lavoisier in a lecture on April 26, 1776 after repeating the experiments of Bayen and Priestley. In a later book, Lavoisier wrote that Priestley and Scheele discovered oxygen almost at the same time as he did. Priestley later wrote that he had discovered oxygen, but had not yet given the discovered substance a name.

In the 18th century it was known that animals could not survive in sealed glass containers. Priestley found that plants could survive well in sealed glass containers. From 1779, Priestley and the Dutchman Jan Ingenhousz investigated gas formation as a function of the light conditions ( photosynthesis ). He also made experiments with the resulting gas, which he called dephlogistic air (oxygen). A mouse survived in this closed gas atmosphere and a burning candle did not go out. He also inhaled the gas himself and felt an improvement in his chest. Priestley recognized the dangers of breathing for many living things on earth and the benefits of plants: "The damage that is constantly being inflicted on the atmosphere by the breathing of such a large number of living things [...] and by the decomposition of plant and animal matter, is made up, at least in part, by plant growth ”.

Other gases

Priestley's experiments paved the way for the subsequent development of chemical research. He started with carbon dioxide - he lived near a brewery - which had been known since 1754. He received the Copley Medal for his invention of soda water . During the six years in Leeds he produced four gaseous compounds: the nitrogen oxides , which he called “nitrous air”, “red nitrous vapor”, “diminished nitrous air” ( laughing gas ), and “marine acid air” ( hydrogen chloride ).

Stephen Hales had already represented nitric oxide in 1727. However, Priestley was able to prove that 20-25% of air can be converted into nitrogen oxide, since the nitrogen oxide can be absorbed from the air by means of lime solution. The remaining gas (air-nitrogen) was neither suitable for combustion nor for breathing.

He developed ingenious devices, in particular a considerably improved trap with which water-soluble gases could also be isolated. Priestley took special care in his investigations. In his famous oxygen experiment, for example, he did not heat the mercury oxide with a flame, but with a burning glass. In this way he avoided contamination with exhaust gases.

In addition to the gases mentioned above, he produced ammonia , nitrogen dioxide , sulfur dioxide , carbon monoxide , hydrogen sulfide , silicon tetrafluoride and also produced artificial mineral water with the gases and described the experiments in a series of six volumes, the Experiments and Observations on Different Kinds of Air .

He also observed that a moist precipitate forms when oxyhydrogen explodes, but has not yet identified it with water ( Henry Cavendish did this when he heard about Priestley's experiment, and Lavoisier). At that time he and Cavendish took the view that hydrogen ( inflammable air according to Cavendish) would be the long-sought phlogiston . In 1782 he found another confirmation of this: he conducted hydrogen over metal limes (metal oxides), and was able to reduce these back to metals, whereby the hydrogen disappeared from the air. According to his interpretation, this happened through the absorption of the phlogiston into the metals from the air.

Teaching and philosophy


  • Priestley believed in the doctrine of the resurrection.
  • He rejected the doctrine of the virgin birth because there were no witnesses. So he came into conflict with the state church.
  • He wrote the book Letters to a Philosophical Unbeliever (1780; German: Letters to a philosophically unbeliever ) to substantiate the Christian faith with arguments.
  • He stood up for human rights and opposed the slave trade.
  • He said that the clergy should only have church duties and no offices in politics.
  • He believed that everyone should have the right to express their own religious beliefs; religious penal laws should be abolished.
  • Church criticism: History of the Corruptions of Christianity (1782) and A General History of the Christian Church (six volumes, 1790–1803) and The Doctrines of Heathen Philosophy Compared with those of Revelation (published posthumously).
  • Priestley saw his scientific work as a minor matter compared to his theological. However, he also believed in the Philosopher's Stone and saw in science a means to improve the lives of mankind.


Priestley was not only active as a preacher and scientist: his textbook of the English language ( Rudiments of English Grammar ) appeared in 1761 , which would remain in use for decades. In the following years he wrote the Theory of Language and Universal Grammar (1762), Essay on a Course of Liberal Education for Civil and Active Life (1765), and Lectures on History and General Policy (1765, 1788). With these writings, contrary to the curricula customary at the time, he promoted the practical education of his students and made the Warrington Academy a training institution with a particularly good reputation.

In 1769 he published his essay on the First Principles of Government, and on the Nature of Political, Civil, and Religious Liberty .

Despite his extremely critical views, Priestley was a pious person throughout his life and felt himself to be a devout Christian.

In the context of biology, the so-called “Priestley experiments” are known: A burning candle is placed in a hermetically sealed container. It goes out after a short time. A burning candle and a living mouse in the same container: the candle goes out in less time, the mouse dies.
If you put a branch in the same container for a while, the next candle can burn again, and a mouse can live again for a short time.
If you keep plants and a mouse in a large, airtight container, both will live longer than a mouse or the plants alone.


Individual evidence

  1. ^ Before 1752 the Julian calendar was used in England . In addition, the year began on March 25th July. , around three months after the turn of the year in continental Europe. Priestley wrote in a letter to Wedgwood dated March 23, 1783, "This day I complete my half century" (see Thorpe, p. 2). Accordingly, it is greg on March 24, 1733 . born.
  2. ^ Wolf-Dieter Müller-Jahncke : Priestley, Joseph. In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , pp. 1183 f .; here: p. 1183 ("* 13.3.1733, Fieldhead near Leeds").
  3. a b c d e f Bennett R. Willeford: The Portrait: Joseph Priestley (1733-1804). In: Chemistry in Our Time. 13, 1979, pp. 111-117, doi : 10.1002 / ciuz.19790130403 .
  4. Schofield, Robert E .: The Enlightenment of Joseph Priestley: A Study of his Life and Work from 1733 to 1773. University Park: Pennsylvania State University Press, 1997. ISBN 0-271-01662-0 , p. 2.
  5. a b c d e f g h i j Georg Lockemann: Joseph Priestley In: Das Buch Der Grossen Chemiker , Verlag Chemie GmbH, Volume 1, Weinheim 1974, p. 263 ff.
  6. ^ Joseph Priestley: The History and Present State of Discoveries Relating to Vision, Light, and Colors . Year = 1772 ( full text in google book search).
  7. ^ Robert E. Schofield: Joseph Priestley: A Study of His Life and Work from 1773 to 1804 . University Park: Pennsylvania State University Press, 2004, ISBN 0-271-02459-3 , pp. 225, 236-38 .
  8. Joseph Priestley: An Account of Further Discoveries in Air. By the Rev. Joseph Priestley, LL.DFRS in Letters to Sir John Pringle, Bart. PRS and the Rev. Dr. Price, FRS Phil. Trans. January 1, 1775 65: 384-394; doi : 10.1098 / rstl.1775.0039 ( full text )
  9. ^ Bennett R. Willeford: The Portrait: Joseph Priestley (1733-1804). In: Chemistry in Our Time. 13, 1979, pp. 111-117, doi : 10.1002 / ciuz.19790130403 , p. 111.
  10. ^ Richard E. Dickerson, Harry B. Gray and Marcetta Y. Darensbourg: Principles of Chemistry . Walter de Gruyter & Co Berlin 1988. p. 28.
  11. Martin Carrier, Cavendishs Version der Phlogistonchemie or: On the empirical success of inaccurate theoretical approaches, in: J. Mittelstraß, Chemie und Geisteswissenschaften, Berlin, Akademie Verlag 1992, pp. 35–52, online

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