Editing Phlogiston theory (section)

==Challenge and demise==
Eventually, quantitative experiments revealed problems, including the fact that some metals gained weight after they burned, even though they were supposed to have lost phlogiston.
Some phlogiston proponents, like [[Robert Boyle]],<ref>{{Cite book |last=Boyle |first=R. A |title=Discovery of the Perviousness of Glass to Ponderable Parts of Flame |publisher=Essays of Effluvium |year=1673 |location=London |pages=57–85}}</ref> explained this by concluding that phlogiston has negative mass; others, such as [[Louis-Bernard Guyton de Morveau]], gave the more conventional argument that it is lighter than air. However, a more detailed analysis based on [[Archimedes' principle]], the densities of magnesium and its combustion product showed that just being lighter than air could not account for the increase in weight.{{cn|date=January 2023}} Stahl himself did not address the problem of the metals that burn gaining weight, but those who followed his school of thought were the ones that worked on this problem.<ref name="White"/>

During the eighteenth century, as it became clear that metals gained weight after they were oxidized, phlogiston was increasingly regarded as a ''principle'' rather than a material substance.<ref>For a discussion of how the term phlogiston was understood during the eighteenth century, see: James R Partington & Douglas McKie; "Historical studies on the phlogiston theory"; ''Annals of Science'', 1937, '''2''', 361–404; 1938, '''3''', 1–58; and 337–371; 1939, '''5''', 113–149. Reprinted 1981 as {{ISBN|978-0-405-13895-9}}.</ref> By the end of the eighteenth century, for the few chemists who still used the term phlogiston, the concept was linked to [[hydrogen]]. [[Joseph Priestley]], for example, in referring to the reaction of steam on iron, while fully acknowledging that the iron gains weight after it binds with oxygen to form a [[calx]], iron oxide, iron also loses "the basis of inflammable air ([[hydrogen]]), and this is the substance or principle, to which we give the name phlogiston".<ref>{{cite book|first=Joseph |last=Priestley |year=1796 |url=http://web.lemoyne.edu/~giunta/phlogiston.html |title=Experiments and Observations Relating to the Analysis of Atmospherical Air: Also, Farther Experiments Relating to the Generation of Air from Water. ... To which are Added, Considerations on the Doctrine of Phlogiston, and the Decomposition of Water |location=London |publisher=[[Joseph Johnson (publisher)|J. Johnson]] |page=42}}</ref> Following [[Antoine Lavoisier|Lavoisier's]] description of oxygen as the ''oxidizing principle'' (hence its name, from Ancient Greek: {{lang|grc|oksús}}, "sharp"; {{lang|grc|génos}}, "birth" referring to oxygen's supposed role in the formation of acids), Priestley described phlogiston as the ''alkaline principle.''<ref>Joseph Priestley (1794). ''Heads of lectures on a course of experimental philosophy''. London: Joseph Johnson.</ref>

Phlogiston remained the dominant theory until the 1770s when [[Antoine-Laurent de Lavoisier]] showed that combustion requires a gas that has weight (specifically, [[oxygen]]) and could be measured by means of weighing closed vessels.<ref>{{Cite journal|last=Best|first=Nicholas W.|date=1 July 2015|title=Lavoisier's "Reflections on phlogiston" I: against phlogiston theory|url=https://doi.org/10.1007/s10698-015-9220-5|journal=[[Foundations of Chemistry]]|language=en|volume=17|issue=2|pages=137–151|doi=10.1007/s10698-015-9220-5|s2cid=254510272 |issn=1572-8463|url-access=subscription}}</ref> The use of closed vessels by Lavoisier and earlier by the Russian scientist [[Mikhail Lomonosov]] also negated the buoyancy that had disguised the weight of the gases of combustion, and culminated in the [[Conservation of mass|principle of mass conservation]]. These observations solved the mass paradox and set the stage for the new [[Antoine Lavoisier#Oxygen theory of combustion|oxygen theory]] of combustion.<ref name="Ihde"/> The British chemist [[Elizabeth Fulhame]] demonstrated through experiment that many [[Redox|oxidation reactions]] occur only in the presence of water, that they directly involve water, and that water is regenerated and is detectable at the end of the reaction. Based on her experiments, she disagreed with some of the conclusions of Lavoisier as well as with the phlogiston theorists that he critiqued. Her book on the subject appeared in print soon after Lavoisier's execution for [[Ferme générale|Farm-General]] membership during the [[French Revolution]].<ref name="Rayner-Canham">{{cite book|last1=Rayner-Canham|first1=Marelene|last2=Rayner-Canham|first2=Geoffrey|title=Women in chemistry: their changing roles from alchemical times to the mid-twentieth century|date=2001|publisher=Chemical Heritage Foundation|location=Philadelphia|isbn=978-0941901277|pages=28–31|url=https://books.google.com/books?id=S_NJ7AubQIcC&pg=PA276|access-date=2 March 2016}}</ref><ref name="Datta">{{cite book|last1=Datta|first1=N. C.|title=The story of chemistry|date=2005|publisher=Universities Press|location=Hyderabad|isbn=9788173715303|pages=247–250|url=https://books.google.com/books?id=IIZkAvdFJhMC&pg=PA248|access-date=2 March 2016}}</ref>

Experienced chemists who supported Stahl's phlogiston theory attempted to respond to the challenges suggested by Lavoisier and the newer chemists. In doing so, the theory became more complicated and assumed too much, contributing to its overall demise.<ref name="Ihde">{{cite book|last1=Ihde|first1=Aaron|title=The Development of Modern Chemistry|url=https://archive.org/details/developmentofmod00ihde|url-access=registration|date=1964|publisher=Harper & Row|location=New York|page=[https://archive.org/details/developmentofmod00ihde/page/81 81]}}</ref> Many people tried to remodel their theories on phlogiston to have the theory work with what Lavoisier was doing in his experiments. [[Pierre Macquer]] reworded his theory many times, and even though he is said to have thought the theory of phlogiston was doomed, he stood by phlogiston and tried to make the theory work.<ref>{{Cite book|title=Historical Studies on the Phlogiston Theory|last1=Partington|first1=J. R.|last2=McKie|first2=Douglas|publisher=Arno Press|year=1981|isbn=978-0405138508}}</ref>