A month ago I wrote about  “Witcraft,” a book I continue  to read about the history of English philosophers. It has been tough going, but I am halfway through.  

One of the surprises are the number of pages devoted to Joseph Priestley, who began his career as an early 19th-century minister.

From my early days in chemistry class,  I was aware that he was  the scientist who discovered oxygen and other gases, including nitric oxide, carbon monoxide, carbon dioxide, nitrogen, hydrogen, hydrogen chloride, ammonia and sulfur dioxide and that he found that plants absorb carbon dioxide and release oxygen.


 A plaque marking his historical home in Northumberland, Pa., reads: “Joseph Priestley (1733-1804), Unitarian minister, teacher, author, natural philosopher, discoverer of oxygen and friend of Thomas Jefferson and Benjamin Franklin.”   

As a child, Priestley had been teased for being priestly by nature as well as by name.  His early studies included Latin, Greek, French, Italian and High Dutch. He attended an academy in Daventry, Northhampshire, U.K., where he was introduced to philosophy and learned to debate such issues as freedom of the will, the immaterially of the soul and life after death.

After Daventry, Priestley worked as a minister for five years, but his congregations turned against him, partly because of his speech defect, a disabling stammer. He supported himself, and then his family, by a succession of positions as pastor or school teacher.  

In 1760, he found work at an academy in Chesire, where he pioneered the teaching of natural science through experiments, and developed an extraordinary facility as an author.  

He wrote a new English grammar and a book on liberal education for a civil and active life in which he argued that the traditional syllabus of Latin, rhetoric, logic, metaphysics and divinity should be discarded in favor of useful subjects like history, commerce, law and natural science. Courses, he felt, would help gentlemen serve their country.  

In 1773, he became librarian to the Earl of Shelburne, and tutor for the Earl’s children. This position allowed him to travel, and gave him the leisure to pursue his chemical investigations, and to write prolifically on science and philosophy.  In 1780, he moved to Birmingham where he continued both his theological investigations and scientific experiments.

Scientific Work

Priestley’s first scientific work, “The History of Electricity” (1767), was encouraged by Benjamin Franklin, whom he had met in London. In preparing the publication Priestley began to perform experiments, at first merely to reproduce those reported in the literature but later to answer questions of his own.

He believed that the word “science” referred specifically to experimental inquiry — the cause of “science.” In the 1770s, he began his most famous scientific research on the nature and properties of gases. At that time he was living next to a brewery, which provided him an ample supply of carbon dioxide. His first chemical publication was a description of how to carbonate water, in imitation of some naturally occurring bubbly mineral waters. He thus invented soda water.

Inspired by Stephen Hales’ “Vegetable Staticks” (first edition, 1727), which described the pneumatic trough for gathering gases over water, Priestley began examining all the “airs” that might be released from different substances. Many, following Aristotle’s teachings, still believed there was only one “air.” By clever and ingenious design of apparatus and careful manipulation, Priestley isolated and characterized the gases mentioned earlier — a record not equaled before or since. (Oxygen was actually named by Antoine-Laurent Lavoisier, a French aristocrat and scientist. Lavosier also recognized it as one of the chief components of the atmosphere.)  

During Priestley’s time burning or combustion of an object was accompanied by the release of a substance known as phlogiston, thought to impart flammability to the material. Whereas today’s chemists see the gain in oxygen, phlogiston theorists saw the loss of phlogiston. Priestley prepared a sample of the new gas by using a lens to focus sunlight on mercury oxide, floating on mercury in a glass tube.  

Over the next few months, he found that the gas evolved was insoluble in water and that a candle burned more brightly in this gas than in the atmosphere. In addition, he contributed to the understanding of photosynthesis and respiration.

Emigration To The U.S.

Priestley was a supporter of both the American and French revolutions. He saw the latter as the beginning of the destruction of all earthly regimes that would precede the Kingdom of God, as foretold in the Bible. These freely expressed views were considered seditious by English authorities and many citizens.

In 1791, a mob destroyed his house and laboratory in Birmingham. This episode and subsequent troubles made him decide to emigrate to the United States. With his sons he planned to set up a model community on undeveloped land in Pennsylvania, but like many such dreams, this one did not materialize. He and his wife did, however, build a beautiful home equipped with a laboratory far up the Susquehanna River in Northumberland, Pa.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at  maxsherman339@gmail.com.