Editing Phlogiston theory (section)

==History==
[[Empedocles]] had formulated the [[Classical elements|classical theory]] that there were four elements—water, earth, fire, and air—and [[Aristotle]] reinforced this idea by characterising them as moist, dry, hot, and cold. Fire was thus thought of as a substance, and burning was seen as a process of [[decomposition]] that applied only to compounds. Experience had shown that burning was not always accompanied by a loss of material, and a better theory was needed to account for this.<ref>{{cite book|last=Ladenburg|first=Dr. A|title=Lectures on the History of Chemistry|page=4|url=https://archive.org/stream/cu31924012386987#page/n22|access-date=26 August 2016|year=1911|publisher=University of Chicago Press}}</ref>

=== ''Terra pinguis''===
In 1667, [[J. J. Becher|Johann Joachim Becher]] published his book {{Lang|la|Physica subterranea}}, which contained the first instance of what would become the phlogiston theory. In his book, Becher eliminated fire and air from the classical element model and replaced them with three forms of the earth: {{Lang|la|terra lapidea}}, {{Lang|la|terra fluida}}, and {{Lang|la|terra pinguis}}.<ref name="morris2">{{cite book|url=https://books.google.com/books?id=-V9jM4FkUacC|title=Making modern science: A historical survey|last=Bowler|first=Peter J|publisher=University of Chicago Press|year=2005|location=Chicago|page=60|isbn=9780226068602}}</ref><ref>Becher, ''[http://gallica.bnf.fr/ark:/12148/bpt6k84226t Physica Subterranea]'' p. 256 ''et seq.''</ref>  {{Lang|la|Terra pinguis}} was the element that imparted oily, [[Sulfur|sulphurous]], or combustible properties.<ref name="brock2">{{cite book|title=The Norton history of chemistry|last=Brock|first=William Hodson|publisher=W. W. Norton|year=1993|isbn=978-0-393-03536-0|edition=1st American|location=New York|url-access=registration|url=https://archive.org/details/nortonhistoryofc00broc}}</ref> Becher believed that {{Lang|la|terra pinguis}} was a key feature of combustion and was released when combustible substances were burned.<ref name="morris2" /> Becher did not have much to do with phlogiston theory as we know it now, but he had a large influence on his student Stahl. Becher's main contribution was the start of the theory itself, however much of it was changed after him.<ref name="White">{{Cite book|title=The History of Phlogiston Theory|last=White|first=John Henry|publisher=AMS Press Inc.|year=1973|isbn=978-0404069308|location=New York}}</ref> Becher's idea was that combustible substances contain an ignitable matter, the {{Lang|la|terra pinguis}}.<ref name="Leicester">{{Cite book|title=A Source Book in Chemistry|last1=Leicester|first1=Henry M.|last2=Klickstein|first2=Herbert S.|publisher=Harvard University Press|year=1965|location=Cambridge, Massachusetts}}</ref>

=== Georg Ernst Stahl ===
[[File:Georg Ernst Stahl. Line engraving, 1715. Wellcome V0005595.jpg|thumb|upright|[[Georg Ernst Stahl]]]]

In 1703, [[Georg Ernst Stahl]], a professor of medicine and chemistry at [[University of Halle|Halle]], proposed a variant of the theory in which he renamed Becher's {{Lang|la|terra pinguis}} to ''phlogiston'', and it was in this form that the theory probably had its greatest influence.<ref name="Mason2">Mason, Stephen F., (1962). ''A History of the Sciences'' (revised edition). New York: Collier Books. Ch. 26.</ref> The term 'phlogiston' itself was not something that Stahl invented. There is evidence that the word was used as early as 1606, and in a way that was very similar to what Stahl was using it for.<ref name="White"/> The term was derived from a Greek word meaning inflame. The following paragraph describes Stahl's view of phlogiston:

{{blockquote|To Stahl, metals were compounds containing phlogiston in combination with metallic oxides (calces); when ignited, the phlogiston was freed from the metal leaving the oxide behind. When the oxide was heated with a substance rich in phlogiston, such as charcoal, the calx again took up phlogiston and regenerated the metal. Phlogiston was a definite substance, the same in all its combinations.<ref name="Leicester" />}}

Stahl's first definition of phlogiston first appeared in his {{Lang|la|Zymotechnia fundamentalis}}, published in 1697. His most quoted definition was found in the treatise on chemistry entitled {{Lang|la|Fundamenta chymiae}} in 1723.<ref name="White" /> According to Stahl, phlogiston was a substance that was not able to be put into a bottle but could be transferred nonetheless. To him, wood was just a combination of ash and phlogiston, and making a metal was as simple as getting a metal [[calx]] and adding phlogiston.<ref name="Leicester" /> [[Soot]] was almost pure phlogiston, which is why heating it with a metallic calx transforms the calx into the metal and Stahl attempted to prove that the phlogiston in soot and [[Sulfur|sulphur]] were identical by converting [[sulphate]]s to [[liver of sulphur]] using [[charcoal]]. He did not account for the increase in weight on combustion of tin and lead that were known at the time.{{sfn|Ladenburg|1911|pp=6–7}}

=== J. H. Pott ===
[[Johann Heinrich Pott]], a student of one of Stahl's students, expanded the theory and attempted to [[Popular science|make it much more understandable to a general audience]]. He compared phlogiston to light or fire, saying that all three were substances whose natures were [[Tacit knowledge|widely understood but not easily defined]]. He thought that phlogiston should not be considered as a particle but as an essence that permeates substances, arguing that in a pound of any substance, one could not simply pick out the particles of phlogiston.<ref name="White"/> Pott also observed the fact that when certain substances are burned they increase in mass instead of losing the mass of the phlogiston as it escapes; according to him, phlogiston was the basic fire principle and could not be obtained by itself. Flames were considered to be a mix of phlogiston and water, while a phlogiston-and-earthy mixture could not burn properly. Phlogiston permeates everything in the universe, it could be released as heat when combined with an acid. Pott proposed the following properties:
# The form of phlogiston consists of a circular movement around its axis.
# When homogeneous it cannot be consumed or dissipated in a fire.
# The reason it causes expansion in most bodies is unknown, but not accidental. It is proportional to the compactness of the texture of the bodies or to the intimacy of their constitution.
# The increase of weight during [[calcination]] is evident only after a long time, and is due either to the fact that the particles of the body become more compact, decrease the volume and hence increase the density as in the case of lead, or those little heavy particles of air become lodged in the substance as in the case of powdered [[zinc oxide]].
# Air attracts the phlogiston of bodies.
# When set in motion, phlogiston is the chief active principle in nature of all inanimate bodies.
# It is the basis of colours.
# It is the principal agent in fermentation.<ref name="White"/>

Pott's formulations proposed little new theory; he merely supplied further details and rendered existing theory more approachable to the common man.

=== Others ===
[[File:Phlogiston symbol.svg|thumb|[[Torbern Bergman]]'s alchemical symbol for phlogiston<ref>"Chemistry", ''Encyclopedia Britannica'', 1911</ref>]]

[[Johann Juncker]] also created a very complete picture of phlogiston. When reading Stahl's work, he assumed that phlogiston was in fact very material. He, therefore, came to the conclusion that phlogiston has the property of levity, or that it makes the compound that it is in much lighter than it would be without the phlogiston. He also showed that air was needed for combustion by putting substances in a sealed flask and trying to burn them.<ref name="White"/>

[[Guillaume-François Rouelle]] brought the theory of phlogiston to France, where he was a very influential scientist and teacher, popularizing the theory very quickly. Many of his students became very influential scientists in their own right, Lavoisier included.<ref name="Leicester" /> The French viewed phlogiston as a very subtle principle that vanishes in all analysis, yet it is in all bodies. Essentially they followed straight from Stahl's theory.<ref name="White"/>

[[Giovanni Antonio Giobert]] introduced Lavoisier's work in Italy. Giobert won a prize competition from the Academy of Letters and Sciences of [[Mantua]] in 1792 for his work refuting phlogiston theory. He presented a paper at the {{Lang|fr|Académie royale des Sciences}} of Turin on 18 March 1792, entitled {{Lang|fr|Examen chimique de la doctrine du phlogistique et de la doctrine des pneumatistes par rapport à la nature de l'eau}} ("Chemical examination of the doctrine of phlogiston and the doctrine of pneumatists in relation to the nature of water"), which is considered the most original defence of Lavoisier's theory of water composition to appear in Italy.<ref name="Abbri">{{cite journal|last1=Abbri|first1=Ferdinando|title=GIOBERT, Giovanni Antonio|journal=Dizionario Biografico degli Italiani |trans-journal=Biographical Dictionary of the Italians|year=2001|volume=55|url=http://www.treccani.it/enciclopedia/giovanni-antonio-giobert_(Dizionario-Biografico)/|access-date=15 September 2017}}</ref>