Editing Pierre Louis Dulong

{{Short description|French scientist (1785–1838)}}
{{Infobox scientist
| name              = Pierre Louis Dulong
| image             = Pierre Louis Dulong.jpg
| birth_date        = {{Birth date|1785|2|12|df=yes}}
| birth_place       = [[Rouen]], France
| death_date        = {{Death date and age|1838|7|19|1785|2|12|df=yes}}
| death_place       = Paris, France
| fields            = [[Chemistry]]<br>[[Physics]]
| workplaces        = [[École polytechnique (France)|École polytechnique]]
| alma_mater        = [[École polytechnique (France)|École polytechnique]]
| known_for         = [[Dulong–Petit law]]
}}

'''Pierre Louis Dulong''' [[Royal Society of London|FRS]] [[FRSE]] ({{IPAc-en|d|uː|ˈ|l|ɒ|ŋ|,_|-|ˈ|l|oʊ|ŋ}}; {{IPA|fr|dylɔ̃|lang}}; 12 February 1785 &ndash; 19 July 1838) was a French [[physicist]] and [[chemist]]. He is remembered today largely for the [[law of Dulong and Petit]], although he was much-lauded by his contemporaries for his studies into the elasticity of steam, conduction of heat, and specific heats of gases. He worked most extensively on the [[specific heat capacity]] and the expansion and [[Refractive index|refractive indices]] of gases. He collaborated the co-discoverer of the [[Dulong–Petit law]].

== Early life and education ==
Dulong was born in [[Rouen]], [[France]].

An only child, he was orphaned at the age of 4, he was brought up by his aunt in [[Auxerre]].  He gained his secondary education in Auxerre and the [[Lycée Pierre Corneille (Rouen)|Lycée Pierre Corneille]] in Rouen<ref name="LyCo6">[http://lgcorneille-lyc.spip.ac-rouen.fr/spip.php?article6 Lycée Pierre Corneille de Rouen - History]</ref> before entering the [[École Polytechnique|École polytechnique]], [[Paris]] in 1801, only for his studies to be impeded by poor health.<ref name=":2">{{Cite journal|last=Fox|first=Robert|date=1968|title=The Background to the Discovery of Dulong and Petit's Law|jstor=4024983|journal=The British Journal for the History of Science|volume=4|issue=1|pages=1–22|doi=10.1017/s0007087400003150|s2cid=145055644}}</ref> He began studying medicine, but gave this up, possibly because of a lack of financial means,<ref name=":2" /> to concentrate on science, working under the direction of [[Louis Jacques Thénard]].

== Career ==
In chemistry, he contributed to knowledge on:
* the double decomposition of salts (1811)
* [[nitrous acid]] (1815)
* the [[oxide]]s of [[phosphorus]] (1816)
* the oxides of [[nitrogen]]
* [[catalysis]] by metals (1823, with Thénard).

Dulong also discovered the dangerously sensitive [[nitrogen trichloride]] in 1811, losing three fingers and an eye in the process.<ref>{{cite journal|year=1813|title=Report on the work of Pierre Louis Dulong|journal=[[Annales de Chimie et de Physique]]|volume=86|issue=6|pages=37&ndash;43|author=Thénard J. L.|author2=Berthollet C. L.|author-link2=Claude Louis Berthollet|author-link=Louis Jacques Thénard}}</ref> The fact that Dulong kept the accident a secret meant that [[Humphry Davy]]'s investigation of the compound had the same unfortunate consequence, although Davy's injuries were less severe.<ref>{{Cite journal|last=Hale|first=William|date=April 1888|title=Formation of the Explosive Chloride of Nitrogen by Electrolysis|jstor=1764740|journal=Science|volume=11|issue=273|pages=206|bibcode=1888Sci....11..206H|doi=10.1126/science.ns-11.273.206.a|pmid=17806755|s2cid=239564780 |url=https://zenodo.org/record/1448313}}</ref>

In addition to his accomplishments in chemistry, Dulong has been hailed as an interdisciplinary expert. His contemporaries in the [[Royal Society|Royal Society of London]] acknowledged his "command of almost every department of physical science".<ref name=":3">{{Cite book|url=https://play.google.com/books/reader?printsec=frontcover&output=reader&id=gw9LAQAAMAAJ&pg=GBS.RA2-PA97|title=Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London|last=Britain)|first=Royal Society (Great|date=1837-01-01|publisher=Richard Taylor|language=en}}</ref>

In 1815, Dulong collaborated for the first time with [[Alexis Thérèse Petit]], in publishing a paper on heat expansion.<ref name=":0">{{Cite journal|last=Lemay|first=Pierre|date=1948|title=Pierre Louis Dulong, His Life and Work|jstor=27757122|journal=Chymia|volume=1|pages=171–190|doi=10.2307/27757122}}</ref> The two would continue to collaborate, researching the specific heats of metals. In 1819, Dulong and Petit showed that the mass heat capacity of [[metal]]lic [[Chemical element|elements]] are inversely proportional to their [[atomic mass]]es, this being now known as the [[Dulong–Petit law]].<ref name=":4">{{cite journal|year=2006|title=Dulong and Petit's Law: We Should Not Ignore Its Importance|journal=Journal of Chemical Education|volume=83|issue=10|pages=1499&ndash;1504|bibcode=2006JChEd..83.1499L|doi=10.1021/ed083p1499|author=Laing, Mary|author2=Laing, Michael}}</ref> For this discovery  Dulong was honored by the [[Académie française|French Academy]] in 1818. This law helped develop the periodic table and, more broadly, the examination of atomic masses.<ref name=":4" />

In 1820, Dulong succeeded Petit, who retired due to poor health,<ref name=":0" /> as professor of physics at [[École Polytechnique|École polytechnique]]. Dulong studied the elasticity of steam, the measurement of temperatures, and the behavior of elastic fluids. He studied how metals enabled the combinations of certain gases.<ref name=":1">{{Cite encyclopedia |title=Pierre-Louis Dulong {{!}} French scientist |encyclopedia=Encyclopedia Britannica |url=https://www.britannica.com/biography/Pierre-Louis-Dulong |access-date=2017-05-05 |language=en}}</ref> He made the first precise comparison of the mercury- and air-temperature scales. In 1830, he was elected a foreign member of the [[Royal Swedish Academy of Sciences]].

He died of stomach cancer in [[Paris]]. At the time of his death, he was working on the development of precise methods in [[calorimetry]]. His last paper, published the year of his death, examined the heat released from chemical reactions.<ref name=":1" />

== Personality ==
[[File:Tour clovis h4.jpg|thumb|The modern-day [[Abbey of St Genevieve|Tour Clovis]] at the Abbey of St. Genevieve, the tower Dulong climbed to conduct his experiments on steam.]]
Socially, Dulong was often dismissed as a dry, standoffish individual. His few friends disagreed with this view, viewing his personality as subdued rather than dull.<ref name=":0" />According to a fellow physicist who compared Dulong and Petit:<ref name="2018-07-06_Piazza">{{cite arXiv |last=Piazza |first=Roberto |title=The strange case of Dr. Petit and Mr. Dulong |date=2018 |class=physics.hist-ph |eprint=1807.02270}}</ref>

{{Quote2|Petit had a lively intelligence, an elegant and easy speech, he seduced with an amiable look, got easily attached, and surrendered himself to his tendencies rather than governing them. He was credited with an instinctive scientific intuition, a power of premature invention, certain presages of an assured future that everyone foresaw and even desired, so great was the benevolence which he inspired. Dulong was the opposite: His language was thoughtful, his attitude serious and his appearance cold[. . . ] He worked slowly but with certainty, with a continuity and a power of will that nothing stopped, I should say with a courage that no danger could push back. In the absence of that vivacity of the mind which invents easily, but likes to rest, he had the sense of scientific exactness, the gusto for precision experiments, the talent of combining them, the patience of completing them, and the art, unknown before him, to carry them to the limits of accuracy[. . . ] Petit had more mathematical tendency, Dulong was more experimental; the first carried in the work more brilliant easiness, the second more continuity; One represented imagination, the other reason, which moderates and contains it.|[[Jules Jamin]] (1855)}}Dulong was noted both for his devotion to science and the stolid, almost casual, bravery he displayed in prosecuting his experiments. One such experiment involved the construction of a glass tubular apparatus atop the tower at the [[Abbey of Saint Genevieve]]. The tower was unsteady enough that an explosion of the experimental materials, considerably likely considering their volatility, could easily have toppled the tower and killed the researching physicists, including Dulong. The experiment though "full of danger and difficulty", was completed under Dulong's leadership.<ref>{{cite EB1911|wstitle=Dulong, Pierre Louis|volume=08}}</ref>

Another example of Dulong's indifference to danger amid scientific pursuit came about in his studies into [[nitrogen trichloride]]. Despite losing two fingers and one eye in his initial experiments, Dulong continued to research the unknown substance. His inquiry led to more injuries, after which he turned over the results of his studies to Humphry Davy.<ref name=":0" />

== Personal life ==
He was married to Emelie Augustine Riviere in 1803.<ref>{{cite book|url=https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf|title=Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002|date=July 2006|publisher=The Royal Society of Edinburgh|isbn=0-902-198-84-X|access-date=2016-03-16|archive-date=2013-01-24|archive-url=https://web.archive.org/web/20130124115814/http://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf|url-status=dead}}</ref>

== Burial and honors ==
In life, Dulong poured the bulk of his finances into his scientific experiments. He was often destitute. As a result, he died without leaving his family any significant inheritance.<ref name=":0" />

He is buried in [[Père Lachaise Cemetery]]. His monument was paid for by his scientific peers.<ref name=":0" />

His is one of the [[List of the 72 names on the Eiffel Tower|names of 72 scientists]] inscribed on the [[Eiffel Tower]].

==See also==
*[[Hypophosphorous acid]]
*[[Phosphorus pentachloride]]

== References ==
<references />

== Further reading ==
* {{cite journal|year=1819|title=Recherches sur quelques points importants de la Théorie de la Chaleur|journal=[[Annales de Chimie et de Physique]]|language=fr|volume=10|pages=395&ndash;413|author=Petit, Alexis-Thérèse|author2=Dulong, Pierre-Louis}} English translation:  "Research on some important aspects of the theory of heat" from ''[[Annals of Philosophy]]'' 14, 189 &ndash; 198 (1819).

== External links ==
* {{Cite EB1911|wstitle=Dulong, Pierre Louis}}
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{{DEFAULTSORT:Dulong, Pierre Louis}}
[[Category:1785 births]]
[[Category:1838 deaths]]
[[Category:Scientists from Rouen]]
[[Category:Burials at Père Lachaise Cemetery]]
[[Category:19th-century French physicists]]
[[Category:19th-century French chemists]]
[[Category:École Polytechnique alumni]]
[[Category:Members of the French Academy of Sciences]]
[[Category:Members of the Royal Swedish Academy of Sciences]]
[[Category:Foreign members of the Royal Society]]
[[Category:Lycée Pierre-Corneille alumni]]