User:Ragesoss/Joseph Priestley and science

Joseph Priestley (March 13, 1733 (old style)–February 8, 1804) was a British polymath best known for his role in the chemical revolution: he discovered, simultaneously with Antoine Lavoisier, oxygen gas. Priestley was a prominent natural philosopher as well as a widely known political and theological controversialist; his science was never divorced from his religion and he consistently tried "to combine Enlightenment principles with a modernized Christian theism." His contemporary scientific reputation rested on his invention of soda water, his writings on electricity and his discovery of several "airs" (gases), the most famous being what Priestley named "dephlogisticated air" (oxygen). But Priestley's determination to reject Lavoisier's "new chemistry" and to cling to phlogiston theory left him isolated within the scientific community.

Priestley's role in the isolation and characterization of oxygen has been used frequently by historians and philosophers of science as a case study on the nature of scientific "discovery". The discovery of oxygen, and the shift from phlogiston theory to Lavoisier's oxygen theory of combustion, is one of Thomas Kuhn's central examples of a paradigm shift in his influential The Structure of Scientific Revolutions.

Scientific training

Though Priestley initially planned to enter the ministry, he gave this up after a serious illness—and an accompanying theological shift from Calvinism to Arminianism—around 1749. Instead, he prepared to join a relative in trade in Lisbon; he studied languages and, under the tutelage of Rev. George Haggerstone, higher mathematics, natural philosophy, logic and metaphysics through the works of Isaac Watts, Willem 's Gravesande and John Locke, among others. However, by the time he was ready to enter higher education, he was once again pursuing ministry.

Priestley entered Daventry, a Dissenting academy, where he was allowed to skip the first two years of coursework, on account his extensive reading. His intensive study and the liberal atmosphere at Daventry resulted in a further leftward theological shift in his thinking, from Arminianism to Arianism and determinism. Priestley later wrote that the book which taught him more than any other (save the Bible) was David Hartley's Observations on Man (1749), a long psychological, philosophical and theological treatise that, based on the earlier work of John Locke and Isaac Newton (two other thinkers Priestley greatly admired), postulated a material theory of mind. Hartley "sought to develop a Christian apologetic in which religious and moral 'facts' were demonstrated to be as tangible and scientific as physical facts." This same goal would occupy Priestley for his entire life.

Early scientific work

Though his early ministry work after leaving Daventry was unpopular (due to his highly heterodox teachings), he some success giving popular science lectures at Needham Market. The proceeds from an astronomy and geography lecture series on the "Use of the Globes" provided enough revenue to pay for the demonstration apparatus he used.

History of Electricity

Priestley's electrical machine, illustrated in the first edition of his Familiar Introduction to Electricity (1768)

Priestley became increasingly interested in natural philosophy while in the intellectually stimulating atmosphere of Warrington, dubbed the "Athens of the north." He gave lectures on anatomy and, along with his friend Seddon, performed some experiments regarding temperature. He also urged the school to purchase more scientific equipment for its teachers and students. Despite his busy teaching schedule, Priestley decided to write a history of electricity. He obtained introductions to the major British experimenters—John Canton, William Watson, and Benjamin Franklin; they encouraged him to perform the experiments he was writing about. Priestley was thus led from replicating others' work to designing and undertaking his own experiments. (Impressed with his work on this history and his Charts, Canton, Franklin, Watson and Richard Price nominated him for a fellowship in the Royal Society—he was accepted in 1766.)

In 1767, the 700-page The History and Present State of Electricity was published to positive reviews. The book went through multiple editions and became the standard history of electricity for over a century; Alessandro Volta, William Herschel and Henry Cavendish all relied upon it. The first half of the text is a history of the study of electricity up until 1766; the second and more influential half is a description of contemporary theories regarding electricity and suggestions for future research. Priestley reported some of his own discoveries in this second section, such as the conductivity of charcoal; this discovery overturned what he termed "one of the earliest and universally received maxims of electricity," that only water and metals could conduct electricity. Such experiments demonstrate that Priestley was interested in the relationship between chemistry and electricity from the beginning of his scientific career. In one of his more speculative moments, he "provided a mathematical quasi-demonstration of the inverse-square force law for electrical charges. It was the first respectable claim for that law, out of which came the development of a mathematical theory of static electricity." Priestley's strength as a natural philosopher was qualitative rather than quantitative experiments and his observation of "a current of real air" between two electrified points would later interest Michael Faraday, James Clerk Maxwell and Svante Arrhenius. Priestley wrote a popular version of the History of Electricity for the general public titled A Familiar Introduction to the Study of Electricity (1768). Like many other middle-class Dissenters at the time, Priestley engaged in commercial endeavors; he and his brother Timothy designed and marketed an "electrical machine" for other budding experimenters, but sales were not brisk and they eventually had to abandon the project.

Natural philosopher: Electricity, Optics, and soda water

Although Priestley claimed that natural philosophy was only a hobby for him, it was one that he took seriously. He believed that science could increase human happiness; in his History of Electricity he describes the scientist as a person who promotes the "security and happiness of mankind" and who is "a good citizen and a useful member of society." For Priestley, science was linked to a "middle-class disdain for the past, for history, and for custom;" he believed that it could and should be used to reinvent the world. Priestley's science was thus always eminently practical and rarely concerned with theoretical questions; his model was Benjamin Franklin. Priestley continued his electrical and chemical experiments (the latter aided by a steady supply of carbon dioxide from a next-door brewery) when he moved to Leeds. Between 1767 and 1770, he presented five papers to the Royal Society out of this initial electrical work; the first four explored coronal discharges and other phenomena related to electrical discharge, while the fifth reported on the conductivity of charcoals from different sources. His subsequent experimental work would increasingly focus on chemistry and pneumatics.

Priestley published the first volume of his projected history of experimental philosophy, The History and Present State of Discoveries Relating to Vision, Light and Colours, in 1772. Unlike his History of Electricity, it was not popular and had only one edition, although it was the only English history of optics for 150 years. Priestley paid careful attention to the history of optics and his explanations of the early experiments (which did not rely on mathematics) were excellent, but he did not understand much advanced mathematics, causing him to dismiss important theories. Furthermore, he did not include any of the practical sections that had made his History of Electricity so useful to practicing natural philosophers. The text was hastily written and it sold poorly; the cost of researching, writing and publishing the Optics caused Priestley to abandon his history of experimental philosophy.

After the dual financial disasters of the Optics and the Theological Repository, Priestley was looking for ways to stabilize his finances. When offered the position of astronomer on James Cook's second voyage to the South Seas, he eagerly accepted and even informed his congregation at Mill Hill that he would be absent for several years. But the offer was suddenly rescinded. Priestley claimed that he was denied the position because he was a Dissenter, but as Schofield explains, the organizing committee replaced him with a more qualified candidate. Schofield attributes the entire disaster to Joseph Banks' highhandedness in nominating Priestley for the position in the first place.

Priestley did still contribute in a small way to the Cook voyage—he provided the crew with a method for making soda water, which he speculated might be a cure for scurvy (it is not). He then published a pamphlet with Directions for Impregnating Water with Fixed Air (1772) for the public. More interested in discovery than business ventures, Priestley did not bother to exploit any potential profits of soda water, but others such as J. J. Schweppe did.

Priestley's friends wished that they could find a more comfortable position for him and in 1772, prompted by Richard Price and Benjamin Franklin, Lord Shelburne delicately wrote to Priestley asking him to direct the education of his children and to act as a general companion and assistant to himself. Priestley debated earnestly about whether to sacrifice his ministry and accept the position. Franklin advised him to calculate the pluses and minuses using "prudential algebra." After intense soul-searching, Priestley resigned from Mill Hill Chapel on 20 December 1772 and preached his last sermon on 16 May 1773.

Natural philosopher of air

Priestley's experiments during his years in Calne were almost entirely confined to "airs" and it was during these years that he published his most important scientific works: the six volumes of Experiments and Observations on Different Kinds of Air (1774–86). These experiments, some of which were performed before he moved to Calne and some after, helped repudiate the last vestiges of the idea that all things were composed of four elements and "taken collectively, did more than those of any one of his contemporaries to uproot and destroy the only generalisation by which his immediate predecessors had sought to group and connect the phenomena of chemistry, but he was wholly unable to perceive this fact." The volumes were not only a scientific enterprise for Priestley; he also argued in them that science could destroy all "undue and usurped authority," writing that the government has "reason to tremble even at an air pump or an electrical machine."

Priestley's work on "airs" is not easily classified. As historian of science Simon Schaffer points out, it "has been seen as a branch of physics, or chemistry, or natural philosophy, or some highly idiosyncratic version of Priestley's own invention." In 1773 Priestley received the Copley Medal from the Royal Society for his achievements in natural philosophy.

Title page from the second edition of Experiments and Observations on Different Kinds of Air

Priestley's first volume of Experiments and Observations on Different Kinds of Air outlined several important discoveries: experiments that would eventually lead to the discovery of photosynthesis, the invention of the nitrous air test (eudiometry), and the discovery of several airs: nitrous air (nitric oxide), vapor of spirit of salt (later called acid air or marine acid air; anhydrous hydrochloric acid), "alkaline air" (ammonia, NH₃), "diminished" or "dephlogisticated nitrous air" (nitrous oxide, N₂O) and "deplogisticated air" (oxygen, O₂). Always the historian, Priestley also included a small history of the study of airs before presenting his own experiments. By clearly explaining his experiments, freely admitting his confusions and asking many questions, Priestley ensured that his work would make a positive impression on the scientific community. He also invented cheap and easily-assembled experimental equipment, which he also described. His colleagues therefore believed that they could easily reproduce Priestley's experiments in order to verify them or to answer the questions that had puzzled him. The work also "begins with one of those prefaces that had become characteristic of Priestley's scientific volumes, with their curious mixture of theology, politics, ontology, epistemology, and personal commentary;" his writing style was open and sincere: "whatever he knows or thinks he tells: doubts, perplexities, blunders are set down with the most refreshing candour."

Although many of Priestley's results puzzled him, he believed that phlogiston theory would help resolve the difficulties; unfortunately, "his experiments, with their phlogistic explanations, led him to believe that the only distinct species of air were the fixed, alkaline, and acid." Priestley ignored the burgeoning chemistry of his day and indeed dismissed it in these volumes on "air." Instead, he focused on gases and the "changes in their sensible properties" as had natural philosophers before him. He isolated carbon monoxide (CO) but seems not to have realized that it was a separate "air" from the others that he had discovered.

Discovery of oxygen

See also: Wikisource:The Mouse's Petition

After the publication of the first volume of Experiments and Observations, Priestley undertook another set of experiments. In August of 1774 he isolated an "air" that appeared to be completely new but did not have a chance to pursue the matter because he was about to tour Europe with Shelburne. While in Paris, Priestley replicated the experiment for others working in the field, including Antoine Lavoisier. After returning to Britain in January 1775, he continued his experiments; he discovered vitriolic acid air (sulfur dioxide, SO₂) and in March he wrote to several people regarding the new "air" that he had discovered back in 1774 (one of these letters was read aloud in the Royal Society). A paper was even published in Philosophical Transactions titled "An Account of further Discoveries in Air." The version of this paper published in Experiments and Observations begins with a description of Priestley's investigative method:

The contents of this section will furnish a very striking illustration of the truth of a remark which I have more than once made in my [natural] philosophical writings, and which can hardly be too often repeated, as it tends greatly to encourage philosophical investigations, viz., that more is owing to what we call chance—that is, philosophically speaking, to the observations of events rising from unknown causes than to any proper design or preconceived theory in this business. . . . For my own part, I will frankly acknowledge that at the commencement of my experiments recited in this section I was so far from having formed any hypothesis that led to the discoveries I made in pursuing them that they would have appeared very improbable to me had I been told of them; and when the decisive facts did at length obtrude themselves upon my notice it was very slowly, and with great hesitation, that I yielded to the evidence of my senses. [emphasis Priestley's]

Priestley called the new substance he discovered "dephlogisticated air" and described it as "five or six times better than common air for the purpose of respiration, inflammation, and, I believe, every other use of common atmospherical air." He had discovered oxygen gas (O₂). After testing the air on a mouse and finding, surprisingly, that it lived after breathing the new air, Priestley tried it on himself and recorded:

The feeling of it to 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.

Priestley assembled his oxygen paper and several others into a second volume of Experiments and Observations on Air and published it in 1776. In it, he does not emphasize his discovery of "dephlogisticated air" but instead argues in the preface how important such discoveries are to rational religion. It is not until the third section of the volume that he explains his discovery of "dephlogisticated air;" his paper narrates the discovery chronologically, relating the long delays between experiments and his initial puzzlements. Thus, it is difficult to determine when exactly Priestley "discovered" oxygen. Since both Lavoisier and Carl Wilhelm Scheele also claimed to have discovered oxygen, such dating is significant.

William Petty, 2nd Earl of Shelburne

Priestley also connected oxygen to respiration. In his paper "Observations on Respiration and the Use of the Blood" he was the first person to suggest that there was a connection between blood and air, although of course he did so through phlogiston theory. In typical Priestley fashion, he prefaced the paper with a history of respiration. A year later, clearly influenced by Priestley, Lavoisier was also talking about respiration at the Académie des sciences. But he saw what Priestley did not and his work began the long train of discoveries that led both to a series of oxygen–respiration papers and, eventually, the overthrow of phlogiston.

Chemical revolution

Many of the friends that Priestley made over the years in Birmingham were members of the Lunar Society, a group of manufacturers, inventors, and natural philosophers who assembled once a month to discuss their work. Matthew Boulton (an early manufacturer), Erasmus Darwin (naturalist, physician, poet and grandfather to Charles Darwin), James Keir (chemist and geologist), James Watt (inventor and engineer), Josiah Wedgwood (manufacturer) and William Withering (botanist, chemist, and geologist) formed the core of the group. Priestley was asked to join this unique society and contributed much to the work of its members. In this stimulating intellectual environment, he published several important scientific papers. One of the most significant was "Experiments relating to Phlogiston, and the seeming Conversion of Water into Air" (1783). The first part of the paper attempts to refute Lavoisier's challenges to his work; the second part describes how the steam that results from heated water is "converted" into air. After several variations of the experiment, with different substances as the fuel for the fire and several different collecting apparatuses which produced different results, he concluded that air could travel through more substances than previously surmised, a conclusion "contrary to all the known principles of hydrostatics." This discovery, along with his earlier work on what would later be recognized as gaseous diffusion, would eventually lead John Dalton and Thomas Graham to formulate the kinetic theory of gases.

Antoine Lavoisier and his wife by Jacques-Louis David

In Réflexions sur le Phlogistique pour servir de Dévelopement à la Théorie de la Combustion et de Respiration (1777) Antoine Lavoisier published his first sustained attack on phlogiston theory; it was against these attacks that Priestley responded in 1783. While Priestley accepted parts of Lavoisier's theory, he was unprepared to subscribe to the major revolutions Lavoisier proposed—the overthrow of phlogiston, an entirely new way of thinking about chemistry based on elements and compounds, and the establishment of an entirely new chemical nomenclature. This new system came to be called the "new chemistry" and with it Lavoisier introduced many of the fundamental concepts of modern chemistry. It was Priestley's original experiments on "dephlogisticated air" (oxygen), combustion and water that provided Lavoisier with the data he needed to construct much of his system, but Priestley never accepted Lavoisier's new theories and continued to cling to phlogiston theory for the rest of his life. Lavoisier's system was based largely on the weight of substances and Priestley was uninterested in these measurements; he preferred to observe changes in heat, color, and particularly volume. His experiments tested "airs" for "their solubility in water, their power of supporting or extinguishing flame, whether they were respirable, how they behaved with acid and alkaline air, and with nitric oxide and inflammable air, and lastly how they were affected by the electric spark."

By 1789 when Lavoisier published his Traité élémentaire de chimie (Elementary Treatise on Chemistry) and founded the Annales de Chimie, the new chemistry had come into its own. Priestley published several more scientific papers in Birmingham, almost all attempting to refute Lavoisier; Priestley and other Lunar Society members argued that the new French system was too expensive, too difficult to test and unnecessarily complex. Priestley's refusal to accept Lavoisier's "new chemistry" and his continued adherence to a theory not borne out by experimental evidence has confused many scholars. Schofield explains it thus: "Priestley was never a chemist; in a modern, and even a Lavoisian, sense, he was never a scientist. He was a natural philosopher, concerned with the economy of nature and obsessed with an idea of unity, in theology and in nature. He attempted, prematurely, to conflate phenomena and give reasons for the reactions he observed." Priestley himself claimed in the last volume of Experiments and Observations that his most valuable works were his theological works because they were "superior [in] dignity and importance." Priestley, unlike his friends in the Lunar Society, would continue the war over phlogiston until he died.

Priestley tried to continue his scientific investigations in America with the support of the American Philosophical Association, but he rarely received news from Europe; unaware of the latest scientific developments, he was no longer on the forefront of discovery. Although most of his published work focused on defending phlogiston theory, he also did some original work on spontaneous generation and dreams. Despite Priestley's lack of real scientific output at this time, his very presence in America stimulated an interest in chemistry in the young country.

By 1801, Priestley had become so ill that he could no longer write or perform experiments and on the morning of 6 February 1804, he died. The American Philosophical Society had a memorial service in his honor; later in April, the members of New Meeting in Birmingham agreed to wear mourning for two months in honor of Priestley and at Mill Hill Chapel in Leeds, the minister preached a funeral sermon on the text "he was a burning and a shining light; and ye were willing for a season to rejoice in his light."

Legacy

When he died in 1804, Priestley had been made a member of every major scientific society in the world and he had discovered numerous substances. In his eulogy of Priestley, the French historian of science George Cuvier, praising his discoveries while at the same time lamenting his refusal to abandon phlogiston theory, called him "the father of modern chemistry (who) never acknowledged his daughter." Priestley published over 150 works on topics ranging from political philosophy to education to theology to natural philosophy, leading James Boswell to describe him as the "literary Jack-of-all Trades." He had been the leader and inspiration for British radicals in the 1790s, including Samuel Taylor Coleridge, William Wordsworth, Charles Lamb, William Hazlitt, William Godwin, Mary Wollstonecraft, Jeremy Bentham and James Mill. He had helped found Unitarianism.

Immanuel Kant praised Priestley in his Critique of Pure Reason (1781), writing that he "knew how to combine his paradoxical teaching with the interests of religion." Indeed, it was Priestley's aim to "put the most 'advanced' Enlightenment ideas into the service of a rationalized thought heterodox Christianity, under the guidance of the basic principles of scientific method." Hazlitt wrote in "The Late Dr. Priestley" (1829) that he "was certainly the best controversialist of his day, and one of the best in the language," adding "in boldness of inquiry, quickness and elasticity of mind, and ease in making himself understood, he had no superior." Upon his election to the Presidency, Jefferson wrote to Priestley "yours is one of the few lives precious to mankind for the continuance of which every thinking man is solicitous." In honor of his many scientific achievements, the American Chemical Society named its highest honor, the Priestley Medal, after him.

Yet, considering Priestley's influence, scholars have not written a great deal on him or his works. In his review of the scholarship on Priestley, historian of science Simon Schaffer describes the two dominant portraits of Priestley: the first depicts him as "a playful innocent" who stumbled across his discoveries; the second portrays him as innocent as well as "warped" for not better understanding the implications of his discoveries. Assessing Priestley's works as a totality has been difficult for scholars as well; his scientific discoveries have usually been divorced from his theological and metaphysical publications in order to make an analysis of his life and writings easier, but this approach has recently been challenged by scholars such as John McEvoy and Robert Schofield. While early Priestley scholarship claimed that his theological and metaphysical works were "distractions" and "obstacles" to his scientific work, recent scholarship has maintained that Priestley's works constitute a unified theory. But as Schaffer explains, no convincing explanation of what this synthesis might be has yet been set forth. Scholars therefore still tend to assess Priestley's accomplishments within modern-day disciplinary frameworks.