A Living Will .net

Priestley’s Scientific Theories And Religious Beliefs

Joseph Priestley was a dissenting Unitarian minister in England at a time when adherence to the established Church of England was of great importance. Preaching was a difficult career for Priestley because his Unitarian views were unpopular and because he spoke with a stammer.  Unitarianism is a Nontrinitarian Christian theology which teaches belief in the single personality of The Almighty, in contrast to the concept of God as three persons.

While the term Unitarianism (with an upper case “U”) customarily refers to a liberal Christian theology, the term unitarian (lower case “u”) is used descriptively to refer to anyone adhering to the teaching of the single personhood of God, a wide-ranging category that also includes many conservative evangelical branches. They generally hold similar beliefs to most other evangelical Christians, apart from their rejection of the Trinity doctrine. This version of unitarianism is more commonly called Nontrinitarianism, rather than Unitarianism. There also are some nontrinitarians who, while holding God to be a single person, perceive Jesus to be God himself, and therefore they do not really fall into the usual unitarian category, which typically rejects the idea of Jesus as Almighty God.

Priestley published widely in a variety of subjects, including theology, education, history, politics, and science. Most often, Priestley is remembered as one of the discoverers of oxygen, but his impact on other lives went much further than this.  Priestley was the first person to isolate a number of gases, including oxygen. His first major scientific publication was The History and Present State of Electricity (1767), which gained him admission to the Royal Society; it was followed by The History and Present State of Discoveries Relating to Vision, Light and Colours (1772). Both light and electricity were regarded as aspects of the Newtonian “imponderable fluid” or “ether.” They were called “imponderable fluids” (or subtle fluids) because they had no detectable weight (no “poundage”), but still had some fluid-like characteristics. Another form of this “ether” was “phlogiston.” Phlogiston was the postulated substance of fire, the active principle of acids, and the driving force behind chemical reactions.

As Priestley expanded his studies in chemistry he became active in the field of pneumatic chemistry, the study of air and gases. Priestley was the first to isolate and characterize a number of gases, including oxygen, nitrogen, hydrogen chloride, ammonia, sulfur dioxide, carbon monoxide, nitric oxide , and nitrous oxide. Priestley’s names for these compounds were different from the modern names, in part because he never adopted the oxygen theory of chemistry. The names he used were in terms of the older “phlogiston theory.” Priestley did this work using very simple apparatuses, such as saucers, glasses, tubes, cylinders, and tubs of water or mercury.

Among the chemical phenomena he investigated was the behavior of a gas or other substance in contact with fire. If fire was the visible escape of phlogiston from a burning substance, then some gases had a greater affinity for phlogiston than ordinary air and encouraged the flame. Other gases had a lesser affinity for phlogiston than ordinary air (or no affinity at all) and would extinguish the flame.

One gas was found to be especially able to support a flame. Priestley called this gas “eminently respirable air.” He later called this same substance “dephlogisticated air,” reasoning that because it had a large affinity for phlogiston, it must be particularly devoid of it, or dephlogisticated. Priestley found that the heating of a sample of “red precipitate” (a calx of mercury) to produce pure mercury generated very pure dephlogisticated air. Priestley’s discovery of the large amount of “air” generated during the heating of red precipitate was similar to Joseph Black’s discovery of “fixed air.” The production of dephlogisticated air also fit Priestley’s belief that a metal is phlogiston compounded with a calc.

The dephlogisticated air liberated from red precipitate also fit well with the observation that when a candle burned out in a closed vessel, the volume of the air was diminished. It was thought that the presence of phlogiston decreased the “springiness” of air. Thus, adding phlogiston to air would cause it to contract, and removing phlogiston from air would cause it to expand. Priestley also found that air saturated with phlogiston could be “revivified” (or dephlogisticated) by green plants in the presence of sunlight. Dephlogisticated air would be renamed “oxygen” by Antoine Lavoisier, who made it the cornerstone of his theory of chemistry.

Priestley resisted the oxygen theory of chemistry to the end of his life. For Priestley, phlogiston was more than just the active principle of fire—it was the active principle of life. Here Priestley’s scientific theory merged with some of his religious beliefs. If phlogiston were the active principle of fire, heat, light, electricity, acids, chemical reactivity, and life, then it might also be the active principle of spirit. This accorded well with his Unitarian belief in one omnipresent active principle in the universe. In his book Disquisition on Matter and Spirit (1777), he asserted that there was only matter and void in the universe—there were no immaterial spiritual influences. Thus, the material existence of phlogiston corresponded well with his religious beliefs.

Priestley also had strong convictions in favor of broad-based democratic reforms and freedom of thought. He advocated wider religious toleration in England. He supported the American colonists in their revolution against the British Crown and supported the French Revolution, even in the face of atrocities such as the Reign of Terror. Priestley made enemies as a result of his political beliefs, and in 1791 his house and laboratory in Birmingham were attacked and burned by a mob. Priestley fled to London and was able to emigrate from there to the United States in 1794. In the United States he was a renowned international figure. When he landed in New York, both the mayor and the governor greeted him. When he arrived in Philadelphia, he was received by President Washington.

In 1794 Priestley declined an offer to be a professor of chemistry at the University of Pennsylvania. He retired from public life in Northumberland, Pennsylvania, and died there in 1804. His home in Northumberland is now preserved as a historical landmark. According to Peter Miller (1993), “A work entitled ‘Joseph Priestley in Context’ would . . . far surpass the competence of any single chronicler.”

There never was a widespread coherent theory of phlogiston. German chemist Johann J. Becher (1635–1682) brought the term “phlogiston” into use among European chemists in the middle 1600s. The word is based upon a Greek word used by Aristotle in his writings on matter. German chemist Georg Stahl (1660–1734) further articulated the phlogiston theory in the early 1700s.  According to the phlogiston theory, a flame was thought to be the visible escape of matter called phlogiston from a burning substance. Another key feature of the theory was that a metal was thought to be composed of phlogiston and earth. Luster, high heat conductivity, malleability, and ductility are all unusual characteristics for metals, but according to the theory, metals share these features because of their postulated phlogiston content. If the phlogiston was removed from a metal, the result was an earth called calc (plural, calx), often the metal’s naturally occurring ore. Under certain conditions, phlogiston might even exhibit a negative weight. This anomaly became problematic after Sir Isaac Newton’s 1687 Law of Universal Gravitation. 

About the Author

Dr. Badruddin Khan teaches Chemistry in the University of Kashmir, Srinagar, India.

136 MAIN STREET SOUTH, Spring City, PA 19475

The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss $3.62 An estimated 10 million Americans have been diagnosed with thyroid disease most of them women and for the majority of them, losing weight is mentioned time and time again as a primary concern and chief frustration a challenge made more difficult due to the metabolic slowdown of a malfunctioning thyroid gland. For these thyroid patients, treatment alone doesn’t seem to resolve weight problems. Furt…