During the 18th century, scientists understood fire and combustion to be the result of a mysterious substance called phlogiston. Although this theory had great explanatory power and was widely accepted among scientists for approximately 100 years, it nevertheless fell eventually (and its fall, once it occurred, happened very quickly). Phlogiston teaches us that just because a theory is widely accepted among scientists, is believed to explain all the evidence, and reigns supreme for a long time, does not mean that it is true. Indeed, phlogiston was in many ways a stronger theory than is evolution today; however, since evolution allows mankind to shake his fist at his Creator, it is not subjected to the same standard of proof as other, more empirical theories such as phlogiston.
What is fire? What happens when something burns? The search for the answers to these questions lasted for centuries, involved many people, and also has much to teach us today as Christians.
Robert Boyle (1627–1691), a devout Christian who is often called ‘the father of chemistry’,1 was very much interested in combustion and made many contributions in this area. Many of his experiments used an air pump invented around 1658 by his assistant Robert Hooke. Boyle had heard of the air pump invented by Guericke2 in 1647, and instructed Hooke to construct a similar device: one that would allow Boyle to evacuate air from a large glass vessel, accessible through a hole in the top. Although crude by today’s standards, this apparatus allowed Boyle to perform and observe experiments in a near vacuum.
Boyle discovered that candles, glowing coals, and sulfur would not burn without air. He also found that flies, bees, butterflies, mice, and birds would ‘swoon’ and then die in a vacuum. Obviously there was some similarity between respiration and combustion. Also, before dying, the mice and birds would first produce vapors—‘steams’3 —that would condense inside the glass first. Boyle surmised that they died because they were poisoning their own air. (He wrote about ‘recrementitious steams that are separated from the mass of blood in its passage through the lungs’3 —he understood that some sort of waste was removed during respiration, but didn’t understand as well that air supplied anything necessary for life.)
Subsequently, German chemist Georg Ernst Stahl (1659–1734) popularized4 an idea called phlogiston. Like most scientists of his time, Stahl was heavily influenced by Greek philosophy and the idea that there were certain ‘essences’ which made up all physical matter. The phlogiston theory was that all material was made up of three basic components: the pure form of the material, the essence of fire (called phlogiston, after the Greek word phlogistos, meaning ‘burning’), and finally any impurities that also happened to be present. Combustion was merely a process by which the inherent phlogiston of a material, its essential fire, was released into the air. As the phlogiston escaped, it produced a whirling motion in the air—the flame.
Stahl’s theory made sense. After all, when a piece of wood burns, the ash that’s left over was obviously much less substantial than the wood itself had been. Something must have left, and that something was phlogiston. The leftover ash was therefore the essence of the wood (plus any contaminants). Different materials varied in their amount of phlogiston. Rock had almost none—thus it wouldn’t burn. Conversely, lampblack was perhaps pure phlogiston, since it burned readily and left very little residue.
The new theory explained past observations very well. For example, it had been known for centuries that the heating of most metals in open air resulted in the formation of a powder. This powder was called a calx (and the process calcination). Now it was understood that the calx was the pure essence of the metal after the phlogiston was removed. The transformation was quite often reversible—many calces could be smelted with charcoal (a source of phlogiston) and be transformed into the metal again.
The phlogiston theory required that air be present during combustion to absorb the phlogiston. Of course, the experiments of Boyle and others had already shown that combustion couldn’t occur in a vacuum. Neither could respiration, which was consistent since respiration was thought to be a form of combustion. However, scientists also realized that a given amount of air can only absorb so much phlogiston. Creatures or flames placed into airtight spaces lived for a while, then died. Obviously, the air would only accept phlogiston until it was saturated, then combustion would cease. Air that was saturated with phlogiston became known as ‘phlogisticated air’.
British chemist Joseph Priestley (1733–1804) even discovered5 that he could manipulate the amount of phlogiston in the air. He heated mercury in air, which turned it into a reddish substance that he called the precipitate per se. Then, when the precipitate per se was heated again to a different temperature, it not only turned back into mercury but also produced a new kind of air. This new air allowed mice to live longer, and wood burned more brightly in it. Obviously this new kind of air could accept more phlogiston than normal air—that must mean it started out with less phlogiston in the first place. Therefore, Priestley named it ‘dephlogisticated air’.
The phlogiston idea was applied to a wide variety of phenomena. Left to its own devices, iron will slowly produce its calx (rust). Therefore, the rusting process was also a (slow) form of combustion. Fermentation, the interactions of acids and alkalis, and the formation of salts, were all explained using phlogiston. Some investigators even suspected that phlogiston itself could be isolated. English scientist Henry Cavendish (1731–1810) dissolved metals in acids and produced ‘inflammable air’, so named because it burned so easily. Cavendish thought it to be pure phlogiston.6
Phlogiston was widely accepted, but it did have some problems. For example, wood ash obviously weighed much less than the wood itself had weighed, and so the phlogiston that had been released must have accounted for at least some of that weight that was lost. However, it had been known for some time that metals gained weight when they were calcified. For example, Boyle had heated tin in a sealed flask. When he opened the flask and weighed the tin afterwards, he found that it had gained weight. (He attributed this to ‘particles of fire’ being absorbed by the metal.) Others had examined this question as well. Louis Bernard Guyton de Morveau (1737–1816) published his Dissertation sur le phlogistique in 1772. He had investigated all of the calcinable metals, and ‘had confirmed in experiments of exceptional precision and care that metals increased in weight when they were roasted in air’ (emphasis in original).7 He proposed that in this case phlogiston had a ‘levity’; thus, when the metals gave up their phlogiston, they became heavier.
French scientist Antoine-Laurent Lavoisier (1743–1794) became skeptical of phlogiston, at least partly because of dissatisfaction with Guyton de Morveau’s ‘absurd’8 explanations. He reperformed many of the classic experiments himself, although being more precise in his measurements and more exact in his overall approach than the original experimenters had been. In 1775 he read the first9 of a series of papers before the French Academy of Sciences, developing a new hypothesis: ‘dephlogisticated air’ was itself responsible for combustion, and there was no such thing as phlogiston. He was very clear that his theory was revolutionary; it was ‘directly contrary to the theory of Stahl’10 and ‘the system of Stahl will be found to be shaken to its foundations’.10
Today we know ‘dephlogisticated air’ as oxygen, and of course we accept his idea as true. Oxygen is of course required for both combustion and respiration, and heated metals absorb it (Priestley’s precipitate per se is today known as mercuric oxide). Rust, also known as iron oxide, is similarly understood today as being the result of the iron being ‘oxidized’ (combined with oxygen). ‘Inflammable air’ is now known as hydrogen. Today we understand combustion in general to be a process whereby oxygen combines with other elements in the material, sometimes producing various gases and other times solids, several forms of energy.
Lavoisier did not stop until he had completely overturned the foundations of chemistry in his day. Among other things, his Traîte elementaire de chimie, published in 1789, replaced the four ancient ‘elements’ with 33.11 Also, ‘The language of chemistry’, Lavoisier now felt, had to be transformed to go with his new theory, and he undertook a revolution in nomenclature, too, replacing the old, picturesque but uninformative terms—like butter of antimony, jovial bezoar, blue vitriol, sugar of lead, fuming liquor of Libavius, flowers of zinc—with precise, analytic, self-explanatory ones. If an element was compounded with nitrogen, phosphorus, or sulfur, it became a nitride, a phosphide, a sulfide. If acids were formed, through the addition of oxygen, one might speak of nitric acid, phosphoric acid, sulfuric acid; and of the salts of these as nitrates, phosphates, and sulfates. If smaller amounts of oxygen were present, one might speak of nitrites or phosphites instead of nitrates and phosphates, and so on. Every substance, elementary or compound, would have its true name, denoting its composition and chemical character, and such names, manipulated as in an algebra, would instantly indicate how they might interact or behave in different circumstances’.12 Laviosier’s insights were so powerful that the old paradigm of phlogiston was completely swept away.
Lavoisier’s new hypothesis was not immediately embraced by all of his peers. The phlogiston theory had been the dominant paradigm for almost 100 years, and it was based on philosophical views that had been in place for over a millenium. But his challenges to the phlogiston theory were substantial, and he pointed out that the advocates of the phlogiston theory (known as ‘Phlogistians’) had many inconsistencies in their explanations: for example, how could wood lose weight when phlogiston was lost, but metal gain weight when phlogiston was lost? In his Mémoires de Chimiel (believed to have been written in 1792 and published posthumously in 1805) he complained:
Lavoisier had much better explanations. For example, he had reperformed Boyle’s tin heating experiment, but unlike Boyle, he weighed the tin and the flask together, before and after the heating. He observed that, even after the heating, the combined weight had not changed. Once he opened the flask, air rushed in, and then the tin gained weight. Therefore, he concluded, the tin was absorbing oxygen from the air, and this accounted for the weight gain. Many of Lavoisier’s contributions to science were due to his insistence on precise quantitative measurements—this emphasis was unusual until that time, and lent great empirical weight to his arguments.
The Phlogistians did not give up easily to the Antiphlogistians, and they pointed out problems with Lavoisier’s ideas as well. However, Lavoisier refined and corrected his hypothesis over time, and the Antiphlogistian case became stronger. As the debate progressed, more and more Phlogistians became Antiphlogistians. Eventually, the Antiphlogistians won, with Priestley (a Phlogistian to the end) mourning in 1796:14
So how is this relevant to us today? The phlogiston theory lasted for over 100 years. For most of that time, all the prominent scientists believed it. It seemed to explain so much. But it was wrong. Although many today would laugh at the phlogiston theory as being hopelessly naive, nevertheless it is in many ways better than the ruling paradigm of our time: evolution. Let’s compare the two:
Phlogiston, although obsolete as a scientific idea, nevertheless has much to teach us today. We see that just because an idea seems to explain a lot of things, and is believed by all the prominent scientists of the day, who all proclaim it to be the ultimate explanation of how things work, does not necessarily mean that this idea won’t be thrown onto the garbage heap later.
There’s no reason why this shouldn’t be as true of today’s evolutionary theories as it was of phlogiston. As creationists, we are often mocked because ‘the majority of scientists believe in evolution.’ Even if that is true, it’s irrelevant. As a paradigm, phlogiston was perceived to be just as powerful then as evolution is today, yet it was completely uprooted and destroyed in a few short years.
(We even see that evolution is actually on shakier ground than phlogiston was. Why then has it not been overthrown yet? Because, unlike phlogiston, the creation/evolution issue is a spiritual battle as well as a scientific one. A godless society will fight tooth and nail to reject any possibility of responsibility towards a creator. If alternative explanations don’t match the evidence, then so be it—anything is preferable to the truth.)
Phlogiston teaches us to resist trusting the majority’s opinions, just because they are held by the majority. We see that those opinions can change in an instant. On the other hand, the Bible is the Word of the Creator of Heaven and Earth. It has been the same from the beginning, and its truth remains … today and forever.
Why then has [evolution] not been overthrown yet? Because, unlike phlogiston, the creation/evolution issue is a spiritual battle as well as a scientific one. A godless society will fight tooth and nail to reject any possibility of responsibility towards a creator.Phlogiston only explained why things burn, whereas evolution explains the much bigger issue of why we are here and where we came from. Most people—including highly educated professionals—believe what they want to believe regardless of the evidence.