Priestley,Joseph (1733-1804)

was one of 1) most original thinkers of the English-speakers world in the 1700's.
Priestley made fundamental contributions to science. He discovered ygen and about 10 other gases. He discover basic principles of photosynthesis and con ducted early experiments in electricity. Priestley was a freethinker in religion and a sup-porter of popular government, that is, government by the people.
Priestley's most famous achievement is his discovery of oxygen in 1774. (Actually, a Swedish chemist, Carl Scheele, discovered oxygen at about the same time as Priestley. Today, both scientists are given the credit.) Priestle called the substance "de-phlogisticated air" took this name from a theory that was then current, but later proved false-the phlogiston theory. This theory stated that all flammable materials (those that will burn) contain a substance called phlogiston. (The phl letter group in phlogiston is pronounced like fl) When a substance burns, it gives up its phlogiston to the air. Friestley knew that substances burn the presence of oxygen. He therefore assumed that oxygen readily absorbs the phlogiston given oft by the burning substances. According to his thinking, the oxygen originally contained no phlogiston. It was "dephlogisticated" At about the same time, the great French chemist Antoine Lavoisier was conducting similar experiments. Priestley met Lavoisier France in 1775. He gave Lavoisier detailed accounts of his experiments with the "dephlogisticated" air. Lavoisier repeated Priestley's experiments. He recognized the true nature of the gas-that it was a basic chemical element-and gave it the name oxygen. He also discovered that oxygen combines chemically with other substances during combustion.
Priestley was a great experimenter who had talent for designing new laboratory devices when experiments required them. He was able to isolate, identify, and study a number of gases. These included nitrogen, nitrous oxide, nitrogen dioxide, nitrous oxide (laughing gas), hydrogen chloride, ammonia, sulfur dioxide silicon tetrafluoride, and carbon monoxide ( gas we know today as part of car exhaust fumes).
Priestley studied carbonation in liquids. He went to a beer factory and observed the bubbles of carbon dioxide that develop in a fermenting liquid. Later Priestley developed a method for carbonating water. His work made possible the soda-water industry. (We use carbonated water today in products such as soft drinks and soda water.)
Priestley made some of the first important discoveries on plant photosynthesis. In photosynthesis, green plants use the sun's energy to change water and carbon dioxide into sugar, a basic food. Priestley discovered that green plants give off oxygen. He also noted that green plants need sunlight Scientists studying photosynthesis in the late 1 700's used these observations in their research.
Near the beginning of his scientific career, Priestley conducted experiments in electricity. He observed a relationship between electricity and chemical changes. Later, Priestley used an electric spark to decompose (break down) ammonia. This process is called e/ectrolysis. Although Priestley is not credited with discovering electrolysis, his work paved the way for later discoveries. With the help of his friend, Benjamin Franklin, Priestley published in 1767 an important book on electricity. Entitled The History and Present state of Electricity this book summed up the knowledge about electricity at that time and reported some of Priestley's own experiments. Very successful and popular, the book went into five editions. Priestley also conducted experiments in optics, the study of light and vision. In 1772 he published his experimental findings and theories in a book called History and Present state of Discoveries Relating to Vision, Light and Colours.
Joseph Priestley was born in Yorkshire (northeastern England) in 1733. His parents were dissenters, people who did not belong to the Church of England. Although England allowed some religious freedom at this time, dissenters were barred from many professions, schools, and universities. Young Joseph Priestley entered Northampton Academy, a school run by dissenters, in 1752. There he received an excellent education. He trained to be a teacher and a minister. Priestley was appointed a teacher at a dissenting academy in Warrington. While there he put many new ideas of education into practice. The dissenting schools had great freedom to develop curriculum (the course of study in a school) because the state church and the government were not involved. Priestley developed a new approach to leaching English grammar. He based his method on current English usage rather than models provided by the ancient classical languages (such as Greek and Latin). He also molded the school's curriculum to prepare students for careers in science, industry, the arts, and commerce. Under Priestley's influence, his academy became per haps the best dissenting school in England. In a recognition of his educational work, Priestley received an honorary doctoral degree from the University of Edinburgh, Scotland, in 1765. During the 1760's, Priestley became friends with Benjamin Franklin, who was then serving in London. At about this time Priestley began serious scientific experimentation. In 1766 Priestley was elected to the Royal Society of London. Priestley's scientific career received a boost In 1772 when the Earl of Shelburn, a wealthy nobleman, became his patron In return for tutoring the earl's children, Priestley received a salary and plenty of free time in which to experiment. In 1779 Priestley left Shelburn's household to become minister to a dissenting congregation in Birmingham, England. During this penod, Priestley wrote many theological works. He became more and more radical, rejecting many traditional Christian doctrines. He earned a controversial reputation as a freethinker for his religious and political opinions. When the French Revolution broke out in 1789, Priestley vocally supported it. Many locale people became angry with Priestley because of his radical ideas. On July 14, 1791, a mobbroke into Priestley's house, destroying everything, including his library and laboratory. Priestley and his family escaped Birmingham. Eventually, they immigrated to the United States. In 1794 Priestley and his wife settled in Northumberland, Pennsylvania. Their Priestley continued to write religious and political works. He became friends with John Adams and Thomas Jefferson. Both of these men admired Priestley's free spirit and intellect and agreed with many of his ideas. Joseph Priestley died in 1804.