Phlogiston

Phlogiston (pronounced floh-jis-ton or floh-jis-tuhn)

In chemistry, a hypothetical colorless, odorless, weightless substance once believed to be the combustible part of all flammable substances and given off as flame during burning; sometimes styled poetically as the “fiery principle”.

1610-1620: From the New Latin phlogiston, from the Ancient Greek φλογιστόν (phlogistón), neuter of φλογιστός (phlogistós), (burnt up, inflammable), from φλογίζω (phlogízō), (to set fire to), from φλόξ (phlóx) (flame).  The most familiar Greek forms were phlogizein (to set alight) and phlegein (to burn).  Root was the primitive Indo-European bhel (to shine, flash, burn (also “shining white)).  Bhel proved most productive, used especially when forming words for bright colors and was part of beluga; Beltane; black; blancmange; blanch; blank; blanket; blaze (as in "bright flame, fire)" bleach; bleak; blemish; blench; blende; blend; blind; blindfold; blitzkrieg; blond; blue; blush; conflagration; deflagration; effulgence; effulgent; flagrant; flambe; flambeau; flamboyant; flame; flamingo; flammable; Flavian; Flavius; fulgent; fulminate; inflame; inflammable; phlegm; phlegmatic; phlogiston; phlox; purblind; refulgent & riboflavin.  As well as the Ancient Greek phlegein (to burn), the word was apparently related to the Sanskrit bhrajate (shines), the Latin flamma (flame), fulmen (lightning), fulgere (to shine, flash) & flagrare (to burn, blaze, glow), the Old Church Slavonic belu (white) and the Lithuanian balnas (pale).  The related forms were phlogistic, phlogisticating, phlogistication & phlogisticated and the scientific necessity of the age also demanded the creation of the verb dephlogisticate (deprive of phlogiston), thus also dephlogisticated, dephlogisticating & dephlogistication.

Alchemy & Chemistry

As the surgeons emerged from the barber’s shop the chemists were once alchemists.  Chemistry began as alchemy, once a respectable branch of learning concerned, inter alia, with the study and purification of materials, the dubious reputation it now suffers because of the fixation in popular culture on its work in developing the chemical process chrysopoeia, the transmutation of “base metals” such as lead into "noble metals", especially gold.  That particular notion of molecular re-arrangement proved a cul-de-sac but some of the laboratory techniques and experimental models developed in medieval alchemy remain in use today.

One pioneer of modern chemistry was German chemist & physician Georg Stahl (1660–1734) who devoted much attention to the fundamental nature of combustion: What happens when stuff burns?  Developing an idea first proposed in 1667 by German physician & alchemist Joachim Becher (1635–1682), in 1702, Stahl proposed that all inflammable objects contained a material substance he called “phlogiston”, from the Greek word meaning “to set on fire”.  When something burned, it liberated its content of phlogiston into the air and Stahl believed it to be chemically inert.  Stahl’s phlogiston theory would dominate scientific thinking for a century.

Phlogiston theory for a while survived even the odd inconvenient truth.  When experiments revealed that burning (oxidizing) a piece of metal resulted in it weighing more rather than less (contrary to phlogiston theory which suggested it would be lighter by the weight of the evacuated phlogiston), the inconsistency was resolved by postulating that phlogiston was either (1) an immaterial principle rather than a material substance (2), phlogiston had a negative weight or (3), phlogiston was lighter than air.  So much did the theory become scientific orthodoxy that when chemists isolated hydrogen, it was celebrated as pure phlogiston.

The execution of Lavoisier, woodcut by unknown artist.  Antoine-Laurent de Lavoisier (1743-1794) was a nobleman and a tax collector, neither quality likely much to appeal to the mob which prevailed after the French Revolution.  In 1794 he and twenty-seven other tax-farmers were executed by guillotine in Paris at the Place de la Révolution (now the Place de la Concorde).  A fellow scientist at the time lamented: "It took them only an instant to cut off that head, and one hundred years might not be sufficient to produce another like it.”

It would be decades before those with doubts, and there were a few, systemized their objections into an alternative theory.  In 1775, French chemist Antoine-Laurent de Lavoisier delivered a paper he called Memoir on the nature of the principle which combines with metals during their calcination [oxidation] and which increases their weight to a meeting of the French Royal Academy of Sciences.  Subsequently it was published in 1778.  Lavoisier named the combustible part of air principe oxigine (acidifying principle) from the Ancient Greek, the construct being ὀξύς (oxús) (sharp) + γένος (génos) (birth), referring to his erroneous belief that oxygen was a vital component of all acids, this his choice of “acid producing”.  The French adopted the variant principe oxygène and in English it became oxygen.  The fraction of air that does not support combustion he called azote, (no life) from the Ancient Greek, the construct being ἀ- (a-) (without) + ζωή (zōḗ) (life), the idea being the substance was incapable of sustaining life.  Azote is now called “nitrogen”, from the French nitrogène, the construct being the nitro- (from the Ancient Greek νίτρον (nítron) (sodium carbonate) +‎ the French gène (producing).  From this paper, which eventually laid to rest phlogiston theory, emerged the foundations for the understanding of chemical reactions as combinations of elements which form new materials; the birth of modern chemistry.  Lavoisier’s model was convincingly elegant but there were those in the scientific establishment with reputations vested in phlogiston theory and some would prove recalcitrant.  Even when the existence of oxygen and nitrogen had become widely accepted, some remained so inculcated they felt compelled to integrate the old with the new, oxygen and nitrogen a filter with which to view phlogiston; a construction of reality which in the post-Trumpian world would be called “alternative facts”. 

Most famous was the eminent English chemist Joseph Priestley (1733-1804) who, even after personally identifying oxygen and well after Lavoisier's paper had persuaded nearly all others, insisted oxygen was but “dephlogisticated air” and in his 1796 paper Considerations on the doctrine of phlogiston and the decomposition of water, he labeled Lavoisier's devotees as “Antiphlogistians”, objecting to the idea of some “theory so new” and based on “so very narrow and precarious a foundation” suddenly overturning “the best established chemistry”.  Two centuries later, a similarly doomed rearguard action would be fought by the “steady-staters” against the big-bang theory explaining the origins of the universe.  Until his dying day, Priestley never accepted the invalidation of phlogiston theory but the increasingly complicated modifications he, and a dwindling few others, bolted-on to make it conform with the undeniable implications of Lavoisier’s model were unconvincing and by the turn of the nineteenth century, phlogiston’s days were over.