Joseph Priestley Remembered

Attendees couldn't have easily missed hearing about 18th-century chemist Joseph Priestley at last month's American Chemical Society national meeting in Philadelphia. A number of events conspired to keep Priestley in the limelight.

"Working the Frontiers of Chemistry," a symposium honoring winners of the Priestley Medal, ACS's highest honor, was held at the Chemical Heritage Foundation (CHF), a few blocks from the meeting site. A new exhibit, "Joseph Priestley, Radical Thinker," had its grand opening, also at CHF. And a two-day ACS symposium, "Joseph Priestley, Universal Catalyst: A Bicentennial Celebration of His Life," sponsored by the Division of the History of Chemistry and cosponsored by the Division of Chemical Education, was held in one of the regular ACS meeting venues.

A highlight of the latter symposium was a personal appearance by Priestley—as channeled by Ronald C. Blatchley, a retired high school chemistry teacher who has portrayed the chemist for the past 20 years. Blatchley portrays Priestley as a volunteer at Joseph Priestley House, in Northumberland, Pa., an ACS National Historic Chemical Landmark.

Priestley, who lived from 1733 to 1804, is a central figure in the history of chemistry. His portrait is displayed prominently in CHF's lobby—next to that of English physicist and chemist Robert Boyle, who carried out early studies on the physical properties of gases. At the Priestley medalist session, CHF President Arnold Thackray presented each awardee with a miniature of this Priestley portrait.

ONE OF THE founders of modern chemistry, Priestley is best known for his discovery of oxygen. But "airs" (gases) that he discovered also include ammonia, carbon monoxide, three nitrogen oxides, silicon tetrafluoride, and sulfur dioxide. Swedish chemist Carl Wilhelm Scheele actually discovered oxygen before Priestley did, but Priestley tends to get top billing for the finding because he was the first one to report it publicly.

Bowood House, Calne, England, where Priestley's lab was located when he discovered oxygen in 1774, is designated an International Historic Chemical Landmark by ACS and the Royal Society of Chemistry. Despite his discovery of oxygen, the basis for combustion, Priestley continued throughout his life to defend the phlogiston theory, the idea that a substance called phlogiston is liberated in the burning process.

In addition to pursuing chemical research, Priestley wrote more than 200 books, pamphlets, and articles, including a grammar text, a history of electricity, and religious treatises. He also served as a Unitarian minister and teacher; had his house and laboratory in England burned down in a political and religious riot; and in 1796 helped found one of the oldest Unitarian congregations in the U.S., the First Unitarian Church of Philadelphia. Unitarians permit considerable individual decision-making about spiritual matters rather than espousing rigid doctrines.

The CHF exhibit includes narrative descriptions about Priestley's life and relationships with his contemporaries, such as U.S. President Thomas Jefferson, English ceramicist Josiah Wedgwood, French chemist Antoine Lavoisier, and U.S. diplomat and scientist Benjamin Franklin. It also contains many Priestley-associated objects from CHF's own collection and others.

This Priestley exhibit is CHF's second, the first having been presented about 20 years ago, said CHF senior research historian Mary Ellen Bowden at the ACS symposium. In the new exhibit, she said, "we hope to show the importance of Priestley in his own times, highlight several areas in which he made important contributions, and showcase two CHF special collections"—a set of Priestley-related caricatures contributed by emeritus professor of chemistry Derek A. Davenport of Purdue University and books written by and about Priestley from CHF's Roy G. Neville Historical Chemical Library and other institutions. The Neville library recently acquired all of Priestley's scientific works and some of his educational books.

SOME OBJECTS in the exhibit, such as a pneumatic pump on loan from the Franklin Institute, were Priestley's personal property. And "The Doctrine of Phlogiston Established, and that of the Composition of Water Refuted," a book by Priestley displayed at the exhibit, is inscribed in his own hand: "From Dr. Priestley at Northumberland, Feb. 16, 1800." The exhibit, created by a CHF team led by head of collections Rob Lukens, will be at CHF through July 2005.

The Priestley symposium at the ACS meeting had a notable cast, including Priestley Toulmin, a direct descendant of Priestley's, and eminent Priestley scholar Robert E. Schofield. A new book by Schofielfield—"The Enlightened Joseph Priestley: A Study of His Life and Work from 1773 to 1804" (Penn State Press, 2004)—was just published, and Schofield signed copies at the CHF exhibit booth during the ACS meeting. This is the second volume of Schofield's definitive two-volume biography of Priestley, the first of which is "The Enlightenment of Joseph Priestley" (Penn State Press, 1997).

The ACS symposium was coorganized by visiting research scientist James J. Bohning of Lehigh University, Bethlehem, Pa.; emeritus professor of chemistry Roy A. Olofson of Pennsylvania State University, University Park; and chemistry professor Leslie V. Woodcock of the University of Manchester, in England. Olofson recounted chronologically the major events in Priestley's life, noting that in addition to Priestley's discoveries of oxygen and other gases, he also discovered the role of blood in oxygen transport and codiscovered the process of photosynthesis.

In fact, this photosynthesis finding, and not his oxygen discovery, was Priestley's "great moment," Davenport said at the symposium. In describing a key experiment showing that oxygen was generated in photosynthesis, Priestley wrote that he "put a sprig of mint into a glass jar" that had been inverted in a vessel of water. Af ter the mint "continued growing there for some months, I found that the air [in the jar] would neither extinguish a candle nor inconvenience a mouse."

At the symposium, Priestley expressed himself not only through his writing, but also in person, in a sense. Priestley, as portrayed by Blatchley in an 18th-century costume, discussed his life and career in a question-and-answer session with Bohning.

THE SESSION revealed that although Priestley did not discover carbon dioxide, he used the gas to invent "Pyrmont water" (soda water). The beverage was produced, said Blatchley on Priestley's behalf, "by putting a large dish of water above an open brewery vat in Leeds," in England. The gases spewing from the vat carbonated the water in the dish. Priestley believed Pyrmont water might be useful for fighting scurvy, a major health problem of the time, and a human clinical trial of sorts was carried out "on board the Resolution and the Adventure by Captain Cook on his second trip around the world," Blatchley said.

"Did it work?" Bohning asked.

"It's fabulous with a twist of lemon," Blatchley replied.

"The most important gas you discovered is oxygen," Bohning continued.

"You mean dephlogisticated air," Blatchley replied. "I first made that when I was the literary companion to Lord Shelburne at Bowood. On Aug. 1, 1774, I focused sunlight through a great burning glass onto [mercuric oxide]. I did a lot of experiments on this new air. I was able to prove to much of the world that it was ordinary air that had been deprived of its phlogiston."

Blatchley recounted how Priestley tested this dephlogisticated air on himself by breathing it. "The feeling of it to my lungs was not sensibly different from that of common air," Blatchley said. "But I fancied that my breast felt particularly light and easy for some time afterwards." Lavoisier later "changed the name of dephlogisticated air to oxygen," he noted.

Other gases discovered by Priestley, such as ammonia, hydrogen chloride, and the nitrogen oxides, were tested on mice first. Unfortunately, some of the mice "died or passed out," Blatchley said. "I did try some [gases] myself, and most of them were awful. There was one, however-dephlogisticated nitrous air-that I remember made me laugh so hard that I was unable to take any notes."

Woodcock pointed out in his presentation that although Priestley's phlogiston theory might seem today to be a crackpot conception, it was at the time a set of believable views about the nature of reactivity. The theory interpreted combustion as a process in which reaction with air yielded "fixed air" (CO₂) and phlogisticated air. Such a chemical equation is "more or less correct," Woodcock said. "There's nothing stupid about it. The phlogiston theory did a reasonable and understandable job of explaining chemical reactivity before the advent of thermodynamics. Historians of science have overlooked the modern explanation—that phlogiston can simply be identified as the thermodynamic driving force of combustion, which is the Gibbs free energy change for a material's reaction with oxygen. Priestley was on the right track all along."

Nevertheless, after 1775 the theory became less and less popular, and by about 1800, Priestley was one of the last of the phlogistonists. "He conceded that the phlogiston theory had some inconsistencies," Woodcock said. "However, until his dying day, he defended the idea that phlogiston was driving chemical reactions."

Blatchley explained that while living in Birmingham, England, he (Priestley) had "angered both the church and the monarchy to such an extent that they conspired to inflame a mob to destroy both my home and my church, on Bastille Day, July 14, 1791. They demolished my manuscripts, my library, and all my scientific apparatus." Fortunately, an inventory of the lab apparatus survived, said chemistry professor William B. Jensen of the University of Cincinnati, during a talk on Priestley's chemical equipment.

In addition, the CHF exhibit includes "one amazing piece of the Ôtrue cross' [authentic relic]—a key and lock from Priestley's Birmingham house," Bowden said. "We don't know how this was saved."

Asked what he thought about aging, Blatchley qua Priestley didn't recommend it. "I don't have as much energy as I did, and this interferes with my work," he said. He added that he just hoped he would live long enough to "prove unequivocally the existence of phlogiston."

At that point, a portly gentleman, also in 18th-century dress, arose in the back of the symposium room and addressed Priestley.

"I'm pleased you're still here," said Benjamin Franklin, as portrayed by impersonator Ralph Archbold. "But I'm a bit concerned about your mention of aging. I want you to know something. I'm approaching my 300th birthday, on Jan. 17, in the year 2006—which of course means you only have one year and a few months left to shop. I would hope you would stay around long enough to celebrate with me." Blatchley expressed relief to Archbold's Franklin "that the rumors of your death were greatly exaggerated."

Unfortunately, the rumors of Priestley's death two centuries ago, in 1804, are all too true. However, he left a rich legacy of achievements for posterity. In a passage from one of Priestley's books that Davenport shared with symposium attendees, Priestley wrote, "The more we see of the wonderful structure of the world, and of the laws of nature, the more clearly do we comprehend their admirable uses, to make all the percipient creation happy: a sentiment which cannot but fill the heart with unbounded love, gratitude, and joy."