View source for Justus von Liebig

{{Short description|German chemist (1803–1873)}}
{{Redirect2|Liebig|von Liebig}}
{{Use dmy dates|date=September 2024}}
{{Infobox scientist
| name              = Justus von Liebig
| honorific_suffix  = ForMemRS
| image             = Justus von Liebig NIH.jpg
| image_size        =
| caption           = Liebig {{c.|1866}}
| birth_date        = {{birth date|df=y|1803|5|12}}
| birth_place       = [[Darmstadt]], Landgraviate of Hesse-Darmstadt
| death_date        = {{death date and age|df=y|1873|4|18|1803|5|12}}
| death_place       = [[Munich]], Kingdom of Bavaria, German Empire
| field             = [[Chemistry]]
| work_institutions = {{ubl|[[University of Giessen]]|[[University of Munich]]}}
| education         = {{ubl|[[University of Bonn]]|[[University of Erlangen]]}}
| doctoral_advisor  = [[Karl Wilhelm Gottlob Kastner]]
| doctoral_students = {{collapsible list|title={{nobold|''See list''}}|{{ubl|item_style={{longitem}}|[[Carl Schmidt (chemist)|Carl Schmidt]]|[[Nikolay Zinin]]|[[Henri Victor Regnault|Victor Regnault]]|[[Carl von Voit]]|[[Hermann von Fehling]]|[[Hermann Franz Moritz Kopp]]|[[August Wilhelm von Hofmann|August von Hofmann]]|[[Lyon Playfair, 1st Baron Playfair|Lyon Playfair]]|[[Emil Erlenmeyer]]|[[Heinrich Ritthausen]]|[[Moritz Traube]]|[[Adolph Strecker]]|[[Wilhelm Henneberg]]}}}}
| notable_students  = {{collapsible list|title={{nobold|''See list''}}|{{ubl|item_style={{longitem}}|[[August Kekulé]]|[[Sir Benjamin Collins Brodie, 2nd Baronet]]|[[Augustus Voelcker]]<ref name=Kumar>{{cite book|last1=Kumar|first1=Prakash|title=Indigo plantations and science in colonial India|date=2012|publisher=Cambridge University Press|location=Cambridge|isbn=978-1-107-02325-3|page=124|url=https://books.google.com/books?id=OldjkdRrKXAC&pg=PA124|access-date=4 November 2014}}</ref>|[[Julius Eugen Schlossberger]]|[[Carl Vogt]]|[[Max Joseph von Pettenkofer]]}}}}
| known_for         = {{collapsible list|title={{nobold|''See list''}}|{{ubl|item_style={{longitem}}|[[Agricultural chemistry]]|[[Analytical chemistry]]|[[Biochemistry]]|[[Organic chemistry]]|[[Benzilic acid rearrangement]]|[[Benzoin condensation]]|[[Barking dog reaction]]|[[Chloral]]|[[Combustion analysis]]|[[Fermentation theory]]|[[Infant formula]]|[[Isocyanic acid]]|[[Kynurenic acid]]|[[Liebig condenser]]|[[Calcium chlorate#production|Liebig process]]|[[Liebig's law of the minimum]]|[[Acid–base reaction#Liebig's hydrogen theory of acids|Liebig's theory of acids]]|[[Liebig–Pasteur dispute]]|[[Kaliapparat]]|[[Marmite]]|[[Meat extract]]|[[Melamine]]|[[Organocatalysis]]|[[Plant nutrition]]|[[Sarcosine]]|[[Silvering]]|[[Tyrosine]]|[[Yeast extract]]}}}}
| prizes     = [[Albert Medal (Royal Society of Arts)|Albert Medal]] (1869)<br/>[[List of recipients of the Pour le Mérite for Sciences and Arts|Pour le Mérite]] (1851)<br/>[[Legion of Honour|Légion d'honneur]] (1850)<br/>[[Copley Medal]] (1840)
}}

'''Justus ''Freiherr'' von Liebig'''{{efn|{{IPA|de|ˈjʊstʊs fɔn ˈliːbɪç|small=no}}, {{IPA|de-AT|- ˈliːbɪɡ|label=[[southern German]]:|small=no}}.}} (12 May 1803 – 18 April 1873<!--PLEASE LEAVE PLACES OF BIRTH AND DEATH IN THE BODYTEXT AS PER MOS:DOB-->)<ref>{{NDB|14|497|501|Liebig, Justus Freiherr von|Priesner, Claus|118572741}}</ref> was a German [[scientist]] who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and [[biology|biological]] [[chemistry]]; he is considered one of the principal founders of [[organic chemistry]].<ref name=RoyalSocietyObit>{{cite journal|last1=Royal Society of London|title=Obituary Notices of Fellows Deceased|journal=Proceedings of the Royal Society of London|date=1 January 1875|volume=24|pages=xxvii–xxxvii|bibcode=1875RSPS...24D...1. |url=https://archive.org/stream/philtrans06902924/06902924#page/n25/mode/2up/search/Liebig|access-date=5 November 2014}}</ref> As a professor at the [[University of Giessen]], he devised the modern laboratory-oriented teaching method, and for such innovations, he is regarded as one of the most outstanding chemistry teachers of all time.<ref name="Americana">{{Cite Americana|wstitle=Liebig, Justus, Baron von}}</ref> He has been described as the "father of the [[fertilizer]] industry" for his emphasis on [[nitrogen]] and [[mineral]]s as essential plant [[nutrient]]s, and his popularization of the [[law of the minimum]], which states that plant growth is limited by the scarcest nutrient resource, rather than the total amount of resources available.<ref name=UNIDO>{{cite book|last1=(UNIDO)|first1=International Fertilizer Development Center (IFDC), United Nations Industrial Development Organization|title=Fertilizer manual|date=1998|publisher=Kluwer Academic|location=Boston|isbn=978-0-7923-5011-8|page=46|edition=3rd|url=https://books.google.com/books?id=qPkoOU4BvEsC&pg=PA46|access-date=6 November 2014}}</ref> He also developed a manufacturing process for [[Meat extract|beef extracts]],<ref>{{cite book|last=Judel|first=Günther Klaus|url=http://geb.uni-giessen.de/geb/volltexte/2013/9259/pdf/GU_36_2003.pdf#page=41|title=Justus Liebig, Georg Giebert und der Fleischextrakt |year=2003|publisher=[[University of Giessen]]|language=de}}</ref> and with his consent a company, called [[Liebig Extract of Meat Company]], was founded to exploit the concept; it later introduced the [[Oxo (food)|Oxo]] brand beef [[bouillon cube]]. He popularized an earlier invention for condensing vapors, which came to be known as the [[Liebig condenser]].<ref name=Cansler />

==Early life and education==
[[Image:Young-Justus-Liebig.jpg|thumb|right|The young Liebig: 1843 lithograph after an 1821 painting (Liebighaus)]]

Justus Liebig was born in [[Darmstadt]] into the [[Middle class|middle-class]] family of Johann Georg Liebig and Maria Caroline Möser in early May 1803.<ref name=Brock/>{{rp|1–3}} His father was a [[drysalter]] and hardware merchant who compounded and sold paints, varnishes, and [[pigment]]s, which he developed in his own workshop.<ref name=Brock>{{cite book
|last1=Brock
|first1=William H.
|title=Justus von Liebig : the chemical gatekeeper
|date=1997
|publisher=Cambridge University Press
|location=Cambridge, UK
|isbn=9780521562249
|edition=1st
}}</ref>{{rp|1}} From childhood, Justus was fascinated with [[chemistry]].

At the age of 13, Liebig lived through [[the year without a summer]], when the majority of food crops in the [[Northern Hemisphere]] were destroyed by a [[volcanic winter]].<ref name=Evans2002>{{cite journal|last1=Evans|first1=Robert|title=Blast from the Past|journal=Smithsonian Magazine|date=July 2002|volume=415 |issue=6875 |page=943 |bibcode=2002Natur.415Q.943. |url=https://www.smithsonianmag.com/history/blast-from-the-past-65102374/}}</ref> [[Germany]] was among the hardest-hit nations in the global famine that ensued, and the experience is said to have shaped Liebig's later work. Due in part to Liebig's innovations in fertilizers and agriculture, the 1816 famine became known as "the last great [[subsistence crisis]] in the Western world".<ref name=Post1977>{{cite book|last1=Post|first1=John D.|title=The last great subsistence crisis in the Western World|date=1977|publisher=Johns Hopkins University Press|location=Baltimore|isbn=9780801818509}}</ref>

Liebig attended grammar school at the Ludwig-Georgs-Gymnasium in Darmstadt, from the ages of 8 to 14.<ref name=Brock/>{{rp|5–7}} Leaving without a certificate of completion, he was apprenticed for several months to the [[apothecary]] Gottfried Pirsch (1792–1870) in [[Heppenheim]] before returning home, possibly because his father could not afford to pay his [[indentures]] (a legal [[contract]] that reflects or covers a debt or purchase obligation). He worked with his father for the next two years,<ref name=Brock/>{{rp|7–8}} then attended the [[University of Bonn]], studying under [[Karl Wilhelm Gottlob Kastner]], his father's business associate. When Kastner moved to the [[University of Erlangen]], Liebig followed him.<ref name=Brock/>{{rp|13}}

Liebig left [[Erlangen]] in March 1822, in part because of his involvement with the radical [[Corps Rhenania Heidelberg|Korps Rhenania]] (a nationalist student organization), but also because of his hopes for more advanced chemical studies. The circumstances are clouded by possible scandal.<ref name=Brock/>{{rp|19–28}} Some scholars argue that he fled to Paris because of his involvement in radical student groups. In late October 1822, Liebig went to Paris to study on a grant obtained for him by Kastner from the [[Hesse|Hessian]] government. He worked in the private laboratory of [[Joseph Louis Gay-Lussac]] and was also befriended by [[Alexander von Humboldt]] and [[Georges Cuvier]] (1769–1832). Liebig's doctorate from Erlangen was conferred on 23 June 1823, a considerable time after he left, as a result of Kastner's intervention on his behalf. Kastner pleaded that the requirement of a dissertation be waived and the degree granted ''in absentia''.<ref name=Brock/>{{rp|33–34}}

==Research and development==
[[File:Justus von Liebig by Trautschold.jpg|thumb|right|upright|Justus von Liebig, by [[Wilhelm Trautschold]], ''circa'' 1846]]

Liebig left Paris to return to Darmstadt in April 1824. On 26 May 1824, at the age of 21 and with Humboldt's recommendation, Liebig became a professor ''extraordinarius'' at the [[University of Giessen]].<ref name=Brock/>{{rp|35}} Liebig's appointment was part of an attempt to modernize the University of Giessen and attract more students. He received a small stipend, without laboratory funding or access to facilities.<ref name=Brock/>{{rp|38–41}}

The presence of existing faculty complicated his situation: Professor Wilhelm Zimmermann (1780–1825) taught general chemistry as part of the philosophy faculty, leaving medical chemistry and pharmacy to Professor Philipp Vogt in the medical faculty. Vogt was happy to support a reorganization in which pharmacy was taught by Liebig and became the responsibility of the faculty of arts, rather than the faculty of medicine. Zimmermann found himself competing unsuccessfully with Liebig for students and their lecture fees.  He refused to allow Liebig to use existing space and equipment and finally committed [[suicide]] on 19 July 1825.  The deaths of Zimmermann and Professor Blumhof, who taught technology and mining, opened the way for Liebig to apply for a full professorship. Liebig was appointed to the ''[[ordentlicher Professor|Ordentlicher]]'' chair in chemistry on 7 December 1825, receiving a considerably increased salary and a laboratory allowance.<ref name=Brock/>{{rp|38–41}}

Liebig married Henriette "Jettchen" Moldenhauer (1807–1881), the daughter of a state official, in May 1826. They had five children: Georg (1827–1903), Agnes (1828–1862), Hermann (1831–1894), Johanna (1836–1925), and Marie (1845–1920). Although Liebig was Lutheran and Jettchen Catholic, their differences in religion appear to have been resolved amicably by bringing their sons up in the Lutheran faith and their daughters as Catholics.<ref name=Brock/>{{rp|44}}

===Transforming chemistry education===
[[File:Justus von Liebigs Labor, 1840.jpg|thumb|right|Liebig's laboratory at Giessen, by Wilhelm Trautschold]]
[[File:Liebig Company Trading Card Ad 01.12.006 front.tif| thumb| right|Liebig's laboratory, Chimistes Celebres, [[Liebig's Extract of Meat Company]] Trading Card, 1929]]

Liebig and several associates proposed to create an institute for pharmacy and manufacturing within the university.<ref name=Brock/>{{rp|42}} The Senate, however, uncompromisingly rejected their idea, stating that training "apothecaries, soapmakers, beer-brewers, dyers and vinegar-distillers" was not the university's task.<ref name=Brock/>{{rp|43}} As of 17 December 1825, they ruled that any such institution would have to be a private venture.  This decision worked to Liebig's advantage.  As an independent venture, he could ignore university rules and accept matriculated and unmatriculated students.<ref name=Brock/>{{rp|42–43}} Liebig's institute was widely advertised in pharmaceutical journals and opened in 1826.<ref name=Brock/>{{rp|44–45}} Its classes in practical chemistry and laboratory procedures for chemical analysis were taught in addition to Liebig's formal courses at the university.

From 1825 to 1835, the laboratory was housed in the guardroom of a disused barracks on the edge of town. The main laboratory space was about {{convert|38|m2|abbr=on}} in size and included a small lecture room, a storage closet, and a main room with ovens and work tables.  An open colonnade outside could be used for dangerous reactions. Liebig could work there with eight or nine students at a time.  He lived in a cramped apartment with his wife and children on the floor above.<ref name=Brock/>{{rp|47}}

Liebig was one of the first chemists to organize a laboratory in its present form, engaging with students in empirical research on a large scale through a combination of research and teaching.<ref name=JLU>{{cite web|last1=Felschow|first1=Eva-Marie|title=Justus Liebig (our Eponym)|url=http://www.uni-giessen.de/cms/about/jlu/justusliebig|publisher=Justus Liebig University|access-date=5 November 2014}}</ref> His methods of organic analysis enabled him to direct the analytical work of many graduate students.  Liebig's students were from many of the German states, as well as Britain and the United States. They helped create an international reputation for their ''Doktorvater.''  His laboratory became renowned as a model institution for the teaching of practical chemistry.<ref name=Brock/>{{rp|47}} It was also significant for its emphasis on applying discoveries in fundamental research to the development of specific chemical processes and products.<ref name=Peppas>{{cite journal|last1=Peppas|first1=Nicholas A.|title=The First Century of Chemical Engineering|journal=Chemical Heritage Magazine|year=2008|volume=26|issue=3|pages=26–29|url=https://www.sciencehistory.org/distillations/article/first-century-chemical-engineering|access-date=20 March 2018}}</ref>

In 1833, Liebig convinced chancellor [[Justin von Linde]] to include the institute within the university.<ref name=Brock/>{{rp|47}} In 1839, he obtained government funds to build a lecture theatre and two separate laboratories designed by architect [[Paul Hofmann (architect)|Paul Hofmann]].  The new chemistry laboratory featured innovative glass-fronted [[fume cupboards]] and venting chimneys.<ref name=Brock/>{{rp|58}} By 1852, when he left Giessen for Munich, more than 700 students of chemistry and pharmacy had studied with Liebig.<ref name=Brock/>{{rp|57}}

===Instrumentation===
[[File:Liebig Manuel 1838 RGNb10348372.03.planche II.tif|thumb|right|Drawing of apparatus from Liebig's ''Manuel pour l'analyse des substances organiques'', 1848, ''Kaliapparat'' in lower right]]
[[File:Fünfkugelapparat.jpg|thumb|right|Modern reproduction of the ''Kaliapparat'' apparatus]]
[[File:Liebig condensers-two 1.jpg|thumb|right|Modern Liebig condenser (left) and West condenser (right)]]

A significant challenge facing 19th-century [[Organic chemistry|organic chemists]] was the lack of instruments and methods of analysis to support accurate, replicable analyses of organic materials.  Many chemists worked on the problem of organic analysis, including French [[Joseph Louis Gay-Lussac]] and Swedish [[Jöns Jacob Berzelius]], before Liebig developed his version of an apparatus for determining the carbon, hydrogen, and oxygen content of organic substances in 1830.  It involved an array of five glass bulbs, called a [[Kaliapparat]], to trap the oxidation product of the carbon in the sample following its combustion. Before reaching the Kaliapparat, the combustion gases were conducted through a tube containing hygroscopic [[calcium chloride]], which absorbed and retained the oxidation product of the hydrogen of the sample, namely water vapor.  Next, in the Kaliapparat, [[carbon dioxide]] was absorbed in a [[potassium hydroxide]] solution in the three lower bulbs and used to measure the weight of carbon in the sample.  For any substance consisting only of carbon, hydrogen, and oxygen, the percentage of oxygen was found by subtracting the carbon and hydrogen percentages from 100%; the remainder must be the percentage of oxygen. A charcoal furnace (a sheet steel tray in which the combustion tube was laid) was used for the combustion.<ref>{{Citation | last=Liebig |first=J. | title = Ueber einen neuen Apparat zur Analyse organischer Körper, und über die Zusammensetzung einiger organischen Substanzen | journal = Annalen der Physik | year = 1831 | volume = 21 |issue=1 | pages = 1–47 | doi=10.1002/andp.18310970102 |bibcode = 1831AnP....97....1L | url = https://zenodo.org/record/1423542 }}</ref> Weighing carbon and hydrogen directly, rather than estimating them volumetrically, significantly increased the method's accuracy of measurement.<ref name=Brock/>{{rp|48–51}}  Liebig's assistant, Carl Ettling, perfected glass-blowing techniques for producing the Kaliapparat and demonstrated them to visitors.<ref name=Brock/>{{rp|50}} Liebig's kaliapparat simplified the method of quantitative organic analysis and rendered it routine.<ref name=Jackson>{{cite journal|last1=Jackson|first1=Catherine M.|title=Synthetical Experiments and Alkaloid Analogues: Liebig, Hofmann, and the Origins of Organic Synthesis|journal=Historical Studies in the Natural Sciences|date=September 2014|volume=44|issue=4|pages=319–363|doi=10.1525/hsns.2014.44.4.319|jstor=10.1525/hsns.2014.44.4.319}}</ref> Brock suggests that the availability of a superior technical apparatus was one reason why Liebig was able to attract so many students to his laboratory.<ref name=Brock/>{{rp|50}} His method of [[combustion analysis]] was used pharmaceutically, and certainly made possible many contributions to organic, agricultural and biological chemistry.<ref name=Brock/>{{rp|76–77}}<ref name=Rochelle>{{cite web|last1=Forrester|first1=Rochelle|title=Organic chemistry in the nineteenth century|url=http://www.rochelleforrester.ac.nz/organic-chemistry.html|access-date=6 November 2014}}</ref>

Liebig also popularized the use of a counter-current water-cooling system for distillation, still referred to as a [[Liebig condenser]].<ref name=Brock/>{{rp|84}}  Liebig himself attributed the vapor condensation device to German pharmacist [[Johann Friedrich August Gottling]], who had made improvements in 1794 to a design discovered independently by German chemist [[Christian Ehrenfried Weigel]] in 1771, by French scientist [[P. J. Poisonnier]] in 1779, and by [[Finnish people|Finnish]] chemist [[Johan Gadolin]] in 1791.<ref name=Jensen>{{citation|author1-link=William B. Jensen |last=Jensen |first=William B. |title=The Origin of the Liebig Condenser |journal=[[J. Chem. Educ.]] |year=2006 |volume=2006 |issue=83 |page=23 |doi=10.1021/ed083p23 |bibcode = 2006JChEd..83...23J }}</ref>

Although it was not widely adopted until after Liebig's death, when safety legislation finally prohibited the use of [[Mercury (element)|mercury]] in making [[mirror]]s, Liebig proposed a process for [[silvering]] that eventually became the basis of modern mirror-making. In 1835, he reported that [[aldehydes]] reduce [[silver salts]] to metallic silver. After working with other scientists, [[Carl August von Steinheil]] approached Liebig in 1856 to see if he could develop a silvering technique capable of producing high-quality optical mirrors for use in [[reflecting telescopes]]. Liebig developed blemish-free mirrors by adding copper to ammoniated silver nitrate and sugar. An attempt to commercialize the process and "drive out mercury mirror-making and its injurious influence on workers' health" was unsuccessful.<ref name=Brock/>{{rp|136–139}} Liebig's mirrors struggled commercially due to poor glass, which produced an off-color, greenish-yellow reflection. Rudely, Liebig commented that Frenchwomen especially hated his mirrors because Frenchwomen already looked yellow and sickly, and the mirrors just reminded them how ugly they were.<ref>{{Cite web |last=Gebelein |first=Helmut |title=Justus Liebig: Life and Work |url=https://bibliotekanauki.pl/articles/896195.pdf}}</ref>

=== Organic chemistry ===
[[File:PSM V74 D619 Liebig laboratory at giessen.png|thumb|right|Liebig laboratory, Giessen]]
[[File:Gießen, Liebig-Museum, the pharmaceutical laboratory.JPG|thumb|right|Liebig-Museum, the pharmaceutical laboratory, Giessen]]
One of Liebig's frequent collaborators was [[Friedrich Wöhler]]. They met in 1826 in Frankfurt, after independently reporting on the preparation of two substances, [[Isocyanic acid|cyanic acid]] and [[fulminic acid]], that apparently had the same composition, but very different characteristics. The [[silver fulminate]] investigated by Liebig was explosive, whereas the [[silver cyanate]] found by Wöhler was not. After reviewing the disputed analyses together, they agreed that both were valid. The discovery of these and other substances led [[Jöns Jacob Berzelius]] to suggest the idea of [[isomers]], substances that are defined not simply by the number and kind of atoms in the molecule, but also by the arrangement of those atoms.<ref name=Brock/>{{rp|72}}<ref name=LWControversy>{{cite journal|last1=Esteban|first1=Soledad|title=Liebig–Wöhler Controversy and the Concept of Isomerism|journal=Journal of Chemical Education|date=September 2008|volume=85|issue=9|pages=1201|doi=10.1021/ed085p1201|bibcode=2008JChEd..85.1201E}}<!--|access-date=6 November 2014--></ref><ref name=LWCHF/>

In 1832, Liebig and Friedrich Wöhler published an investigation of the oil of bitter almonds. They transformed pure oil into several halogenated compounds, which were further transformed in other reactions.<ref>{{cite journal | last1 = Wöhler | last2 = Liebig | year = 1832 | title = Untersuchungen über das Radikal der Benzoesäure |trans-title=Investigations of the radical of benzoic acid | url = https://books.google.com/books?id=z-VAAAAAYAAJ&pg=249| journal = Annalen der Pharmacie | volume = 3 | issue = 3| pages = 249–282 | doi=10.1002/jlac.18320030302| hdl = 2027/hvd.hxdg3f| hdl-access = free }}</ref> Throughout these transformations, "a single compound" (which they named [[benzoyl]]) "preserves its nature and composition unchanged in nearly all its associations with other bodies."<ref name=Brock/>{{rp|79}}  Their experiments proved that a group of carbon, hydrogen, and oxygen atoms could behave like an element, take the place of an element, and can be exchanged for elements in [[chemical compound]]s. This laid the foundation for the doctrine of [[Radical theory|compound radicals]], which can be seen as an early step in the development of structural chemistry.<ref name=LWCHF>{{cite web | url = https://www.sciencehistory.org/historical-profile/justus-von-liebig-and-friedrich-w%C3%B6hler | title = Justus von Liebig and Friedrich Wöhler | publisher = Science History Institute | date = June 2016 | access-date = 21 March 2018 | archive-date = 20 June 2018 | archive-url = https://web.archive.org/web/20180620232155/https://www.sciencehistory.org/historical-profile/justus-von-liebig-and-friedrich-w%C3%B6hler | url-status = dead }}</ref>

The 1830s were a period of intense investigation of organic compounds by Liebig and his students, and of vigorous debate about the theoretical implications of their results. Liebig published on a wide variety of topics, personally averaging 30 papers per year between 1830 and 1840.<ref name=Brock/>{{rp|76}} Liebig not only isolated individual substances, but also studied their interrelationships and the ways in which they degraded and metamorphosed into other substances, looking for clues to the understanding of both chemical composition and physiological function.  Other significant contributions by Liebig during this time include his examination of
the nitrogen content of bases;<ref name=Brock/>{{rp|77}}
the study of chlorination and the isolation of [[chloral]] (1832);<ref name=Brock/>{{rp|83}}
the identification of the [[ethyl radical]] (1834);<ref name=Brock/>{{rp|82}}
the oxidation of alcohol and formation of [[aldehyde]] (1835);<ref name=Brock/>{{rp|84}}
the polybasic theory of organic acids (1838);<ref name=Brock/>{{rp|86–87}}
and the degradation of [[urea]] (1837).<ref name=Brock/>{{rp|88–89}}

Writing about the analysis of urine, a complex organic product, he made a declaration that reveals both the changes that were occurring in chemistry over a short time and the impact of his own work.<ref name=Brock/>{{rp|89}}  At a time when many chemists such as [[Jöns Jakob Berzelius]] still insisted on a hard and fast separation between the organic and inorganic, Liebig asserted:

{{Blockquote|text="The production of all organic substances no longer belongs just to living organisms.  It must be seen as not only probable, but as certain, that we shall be able to produce them in our laboratories.  Sugar, salicin, and morphine will be artificially produced.  Of course, we do not yet know how to do this, because we do not yet know the precursors from which these compounds arise, but we shall come to know them." |source=[Liebig and Woehler (1838)]}}

Liebig's arguments against any chemical distinction between living (physiological) and dead chemical processes proved a great inspiration to several of his students and others who were interested in [[materialism]]. Though Liebig distanced himself from the direct political implications of materialism, he tacitly supported the work of [[Carl Vogt]] (1817–1895), [[Jacob Moleschott]] (1822–1893),<ref>{{Cite thesis |last=Meneghello |first=Laura |title=Jacob Moleschott and the conception of science in the 19th century |date=2010 |degree=PhD |url=https://studenttheses.uu.nl/bitstream/handle/20.500.12932/4982/MasterThesisLauraMeneghello.pdf?sequence=1&isAllowed=y}}</ref> and [[Ludwig Büchner]] (1824–1899).<ref>{{Cite journal |last=Munday |first=Pat |date=1998 |title=Politics by Other Means: Justus von Liebig and the German Translation of John Stuart Mill's "Logic" |url=https://www.jstor.org/stable/4027874 |journal=The British Journal for the History of Science |volume=31 |issue=4 |pages=403–418 |doi=10.1017/S0007087498003379 |jstor=4027874 |issn=0007-0874|url-access=subscription }}</ref>

===Plant nutrition===
By the 1840s, Liebig was attempting to apply theoretical knowledge from organic chemistry to real-world problems of food availability.  His book ''Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie'' (''Organic Chemistry in its Application to Agriculture and Physiology'') (1840) promoted the idea that chemistry could revolutionize agricultural practice, increasing yields and lowering costs. It was widely translated, vociferously critiqued, and highly influential.<ref name=Brock/>

Liebig's book discussed chemical transformations within living systems, both plant and animal, outlining a theoretical approach to agricultural chemistry. The book's first part focused on plant nutrition; the second was on chemical mechanisms of putrefaction and decay.<ref name=Brock/>{{rp|148}} Liebig's awareness of both synthesis and degradation led him to become an early advocate of [[Conservation (ethic)|conservation]], promoting ideas such as the recycling of [[sewage]].<ref name=Brock/>{{rp|250–270}}

Liebig argued against prevalent theories about role of [[humus]] in plant nutrition, which held that decayed plant matter was the primary source of carbon for plant nutrition. Fertilizers were believed to act by breaking down humus, making it easier for plants to absorb. Associated with such ideas was the belief that some sort of "vital force" distinguished reactions involving organic as opposed to inorganic materials.<ref name=Hill>{{cite book|author-last1=Hill|author-first1=Jane F.|chapter=Translator's Introduction|author-last2=de Saussure|author-first2=Theodore|title=Chemical research on plant growth|date=2012|publisher=Springer|location=New York|isbn=978-1-4614-4136-6|chapter-url=https://books.google.com/books?id=cVVJAAAAQBAJ&pg=PR15|access-date=7 November 2014}}</ref>

Early studies of photosynthesis had identified carbon, hydrogen, oxygen, and nitrogen as important, but disagreed over their sources and mechanisms of action. Carbon dioxide was known to be taken in and oxygen released during photosynthesis, but researchers suggested that oxygen was obtained from carbon dioxide, rather than from water. Hydrogen was believed to come primarily from water. Researchers disagreed about whether sources of carbon and nitrogen were atmospheric or soil-based.<ref name=Hill/>{{rp|xv–xxi}} [[Nicolas-Théodore de Saussure]]'s experiments, reported in ''Recherches Chimiques sur la Végétation'' (1804), suggested that carbon was obtained from atmospheric rather than soil-based sources. It also indicated that water was a likely source of hydrogen. He also studied the absorption of minerals by plants, and observed that mineral concentrations in plants tended to reflect their presence in the soil in which the plants were grown. However, the implications of De Saussure's results for theories of plant nutrition were neither clearly discussed nor easily understood.<ref name=Hill/>{{rp|xxii–xxvii}}

Liebig reaffirmed the importance of De Saussure's findings, and used them to critique humus theories, while regretting the limitations of De Saussure's experimental techniques. Using more precise methods of measurement as a basis for estimation, he pointed out contradictions such as the inability of existing soil humus to provide enough carbon to support the plants growing in it.<ref name=Hill/>{{rp|xxix}} By the late 1830s, researchers such as [[Karl Sprengel]] were using Liebig's methods of combustion analysis to assess manures, concluding that their value could be attributed to their constituent minerals.<ref name=Brock/>{{rp|106}} Liebig synthesized ideas about the mineral theory of plant nutrition and added his own conviction that inorganic materials could provide nutrients as effectively as organic sources.<ref name=Brock/>{{rp|148}}

In his theory of mineral nutrients, Liebig identified the chemical elements of nitrogen (N), phosphorus (P), and potassium (K) as essential to plant growth. He reported that plants acquire carbon (C) and hydrogen (H) from the atmosphere and from water (H<sub>2</sub>O). In addition to emphasizing the importance of minerals in the soil, he argued that plants feed on nitrogen compounds derived from the air. This assertion was a source of contention for many years, and turned out to be true for legumes, but not for other plants.<ref name=Brock/>{{rp|181}}

[[File:Minimum-Tonne.svg|thumb|right|Liebig's barrel]]
Liebig also popularized Carl Sprengel's "theorem of minimum" (known as the [[Liebig's Law of the Minimum|law of the minimum]]), stating that plant growth is not determined by the total resources available, but by the scarcest available resource.  A plant's development is limited by the one essential mineral that is in the relatively shortest supply.  This concept of limitation can be visualized as "Liebig's barrel", a metaphorical barrel in which each stave represents a different element. A nutrient stave that is shorter than the others will cause the liquid contained in the barrel to spill out at that level. This is a qualitative version of the principles used for determining the application of fertilizer in modern agriculture.

''Organic Chemistry'' was not intended as a guide to practical agriculture. Liebig's lack of experience in practical applications, and differences between editions of the book, fueled considerable criticism. Nonetheless, Liebig's writings had a profound impact on agriculture, spurring experiment and theoretical debate in Germany, England, and France.<ref name=Brock/>{{rp|165}}

One of his most recognized accomplishments is the development of [[nitrogen]]-based [[fertilizer]]. In the first two editions of his book (1840, 1842), Liebig reported that the atmosphere contained insufficient nitrogen, and argued that nitrogen-based fertilizer was needed to grow the healthiest possible crops.<ref name=Brock/>{{rp|120}} Liebig believed that nitrogen could be supplied in the form of [[ammonia]], and recognized the possibility of substituting chemical fertilizers for natural ones (animal dung, etc.)

He later became convinced that nitrogen was sufficiently supplied by precipitation of ammonia from the atmosphere, and argued vehemently against the use of nitrogen-based fertilizers for many years. An early commercial attempt to produce his own fertilizers was unsuccessful, due to lack of nitrogen in the mixtures.<ref name=Brock/>{{rp|121–124}} When tested in a farmer's field, Liebig's manure was found to have no appreciable effect.<ref>Matter-of-Fact (July 1847) [https://babel.hathitrust.org/cgi/pt?id=hvd.32044048680383&view=1up&seq=214 Liebig's System of Manuring], [[The Cultivator]] series 2, volume 4, page 208 via [[HathiTrust]]</ref>

Liebig's difficulties in reconciling theory and practice reflected that the real world of agriculture was more complex than was at first realized. By the publication of the seventh German edition of ''Agricultural Chemistry'' he had moderated some of his views, admitting some mistakes and returning to the position that nitrogen-based fertilizers were beneficial or even necessary.<ref name=Brock/>{{rp|179}}He was instrumental in the use of [[guano]] for nitrogen.<ref>Charles Mann (2011) [https://archive.org/details/1493uncoveringne00mann 1493: Uncovering the New World Columbus Created], p. 214, Knopf</ref> In 1863 he published the book "Es ist ja die Spitze meines lebens" in which he revised his early perceptions, now appreciating soil life and in particular the biological [[nitrogen fixation]].<ref>Jan Diek von Mansvelt (2017) [https://vanmansvelt.nl/home/historic-and-actual-awareness-of-soil-fertility-in-agriculture-russia-western-europe-usa-draft-of-a-survey/ Historic and actual awareness of soil fertility in agriculture – Russia, Europe, U.S.A.]</ref> Nitrogen fertilizers are now widely used throughout the world, and their production is a substantial segment of the chemical industry.<ref name=Travis2013>{{cite journal|last1=Travis|first1=Anthony S.|title=Dirty Business|journal=Chemical Heritage Magazine|date=Spring 2013|volume=31|issue=1|page=7|url=https://www.sciencehistory.org/distillations/magazine/dirty-business|access-date=20 March 2018}}</ref>

===Plant and animal physiology===
Liebig's work on applying chemistry to plant and animal physiology was especially influential. By 1842, he had published ''Chimie organique appliquée à la physiologie animale et à la pathologie'', published in English as '' Animal Chemistry, or, Organic Chemistry in its Applications to Physiology and Pathology'', presenting a chemical theory of metabolism.<ref name=Brock/>{{rp|185}} The experimental techniques used by Liebig and others often involved controlling and measuring diet, and monitoring and analyzing the products of animal metabolism, as indicators of internal metabolic processes.  Liebig saw similarities between plant and animal metabolism, and suggested that nitrogenous animal matter was similar to, and derived from, plant matter.  He categorized foodstuffs into two groups, nitrogenous materials which he believed were used to build animal tissue, and non-nitrogenous materials which he believed were involved in separate processes of respiration and generation of heat.<ref name=Brock/>{{rp|184}}

French researchers such as [[Jean-Baptiste Dumas]] and [[Jean-Baptiste Boussingault]] believed that animals assimilated sugars, proteins, and fats from plant materials and that animals could not synthesize complex molecules. Liebig's work suggested a common ability of plants and animals to synthesize complex molecules from simpler ones. His experiments on fat metabolism convinced him that animals must be able to synthesize fats from sugars and starches.<ref name=Brock/>{{rp|187}} Other researchers built upon his work, confirming the abilities of animals to synthesize sugar and build fat.<ref name=Brock/>{{rp|189–190}}

Liebig also studied respiration, at one point measuring the "ingesta and excreta" of 855 soldiers, a bodyguard of the Grand Duke of Hessen-Darmstadt, for an entire month.<ref name=Brock/>{{rp|191}}  He outlined an extremely speculative model of equations in which he attempted to explain how protein degradation might balance within a healthy body and result in pathological imbalances in cases of illness or inappropriate nutrition.<ref name=Brock/>{{rp|191–193}} This proposed model was justifiably criticized. Berzelius stingingly stated that "this facile kind of physiological chemistry is created at the writing table".<ref name=Brock/>{{rp|194}} Some of the ideas that Liebig had enthusiastically incorporated were not supported by further research.  The third and last edition of ''Animal Chemistry'' (1846) was substantially revised and did not include the equations.<ref name=Brock/>{{rp|195–197}}

The third area discussed in ''Animal Chemistry'' was fermentation and putrefaction. Liebig proposed chemical explanations for processes such as [[Decomposition|eremacausis]] (organic decomposition), describing the rearrangement of atoms as a result of unstable "affinities" reacting to external causes such as air or already decaying substances.<ref name=Brock/>{{rp|205}}  Liebig identified the blood as the site of the body's "chemical factory", where he believed processes of synthesis and degradation took place. He presented a view of disease in terms of chemical process, in which healthy blood could be attacked by external contagia; secreting organs sought to transform and excrete such substances; and failure to do so could lead to their elimination through the skin, lungs, and other organs, potentially spreading contagion. Again, although the world was much more complicated than his theory, and many of his individual ideas were later proved wrong, Liebig managed to synthesize existing knowledge in a way that had implications for doctors, sanitarians, and social reformers. The English medical journal ''[[The Lancet]]'' reviewed Liebig's work and translated his chemical lectures as part of its mission to establish a new era of medicine.<ref name=Brock/>{{rp|207}} Liebig's ideas stimulated medical research, led to the development of better techniques for testing experimental models of metabolism, and pointed to chemistry as fundamental to the understanding of health and disease.<ref name=Brock/>{{rp|214}}

In 1850, Liebig investigated [[spontaneous human combustion]], dismissing the simplistic explanations based on [[ethanol]] due to alcoholism.<ref name=Ford2012>{{cite journal|last1=Ford|first1=Brian J.|title=Solving the Mystery of Spontaneous Human Combustion|journal=The Microscope|year=2012|volume=60|issue=2|pages=63–72|url=http://www.mcri.org/CMSuploads/Brian%20J.%20Ford%20-%20Solving%20the%20Mystery%20of%20Spontaneous%20Human%20Combustion-85047.pdf|access-date=4 November 2014|url-status=dead|archive-url=https://web.archive.org/web/20130510231220/http://www.mcri.org/CMSuploads/Brian%20J.%20Ford%20-%20Solving%20the%20Mystery%20of%20Spontaneous%20Human%20Combustion-85047.pdf|archive-date=10 May 2013}}</ref>

===Liebig and the chemistry of food===

====Methods of cookery====
Liebig drew upon his work in plant nutrition and plant and animal metabolism to develop a theory of nutrition, which had implications for cookery. In his ''Researches on the Chemistry of Food'' (1847) Liebig argued that eating not only meat fibre, but also meat juices, which contained various inorganic chemicals, was important. These vital ingredients would be lost during conventional boiling or roasting in which cooking liquids were discarded.  For optimum nutritional quality, Liebig advised that cooks should either sear the meat initially to retain fluids, or retain and use cooking liquids (as in soups or stews).<ref name=Brock/>{{rp|217–218}}

Liebig was acclaimed in ''The Lancet'' for revealing "the true principles of cookery", and physicians promoted "rational diets" based on his ideas. Well-known British cookery writer [[Eliza Acton]] responded to Liebig by modifying the cookery techniques in the third edition of her ''Modern Cookery for Private Families'', and subtitling the edition accordingly.<ref name=Brock/>{{rp|218–219}}  Liebig's idea that "[[searing]] meat seals in the juices", though still widely believed, is not true.<ref name=McGee2004>{{cite book |chapter=The Searing Question | last=McGee |first=Harold | title=On Food and Cooking | publisher=Scribner | year=2004 | isbn=0-684-80001-2|page=161| edition=Revised }}</ref>

====Liebig's Extract of Meat Company====
[[File:Liebig Company Memorial Trading Card 01.12.001 front.tif|thumb|right|upright|Memorial tradecard commemorating Justus Liebig, from [[Liebig's Extract of Meat Company]] ]]
[[File:Liebig-Muenchen.jpg|thumb|right|upright|Justus Liebig statue, [[Munich]], Germany]]

{{Main|Liebig's Extract of Meat Company}}

Building on his theories of the nutritional value of meat fluids, and seeking an inexpensive nutrition source for Europe's poor, Liebig developed a formula for producing beef extract.  The details were published in 1847 so that "the benefit of it should ... be placed at the command of as large a number of persons as possible by the extension of the manufacture, and consequently a reduction in the cost".<ref name=Quinologist>{{cite book|editor-last1=Mattison|editor-first1=Richard V.|title=The Quinologist|year=1883|publisher=s.n.|location=Philadelphia|pages=55–58|volume=VI|number=1 |url=https://books.google.com/books?id=_NADAAAAYAAJ&pg=PA55|access-date=4 November 2014}}</ref>

Production was not economically feasible in Europe, where meat was expensive, but in [[Uruguay]] and [[New South Wales]], meat was an inexpensive byproduct of the leather industry. In 1865, Liebig partnered with Belgian engineer [[George Christian Giebert]],<ref>{{cite web|url=https://negocios.elpais.com.uy/noticias/multinacional-liebig-fray-bentos.html |title=Liebig's in Fray Bentos|date=2 July 2018|work=[[El País (Uruguay)|El País]]|language=es}}</ref> and was named scientific director of [[Liebig's Extract of Meat Company]], located in [[Fray Bentos]] in Uruguay.<ref name=Cansler/><ref name=NickSkye>{{cite web|last1=Skye|first1=Nick|title=The Liebig chromolithographs, origins of bouillon, Marmite, Oxo and Campbell's soups|url=http://nickyskye.blogspot.com/2012/06/liebig-chromolithographs-part-1-origins.html|website=nickyskye meanderings|access-date=11 November 2014|date=25 June 2012}}</ref>

Other companies also attempted to market meat extracts under the name "Liebig's Extract of Meat".  In Britain, a competitor's right to use the name was successfully defended on the grounds that the name had fallen into general use and become a [[generic term]] before the creation of any particular company.<ref name=Quinologist/> The judge asserted that "Purchasers must use their eyes", and considered the presentation of the products to be sufficiently different to enable the discriminating consumer to determine which of the products bore Liebig's signature and was supported by Liebig himself.<ref name=Quinologist2>{{cite book|editor-last1=Mattison|editor-first1=Richard V.|title=The Quinologist|year=1883|publisher=s.n.|location=Philadelphia|pages=184–186|volume=VI|number=1 |url=https://books.google.com/books?id=_NADAAAAYAAJ&pg=PA184|access-date=4 November 2014}}</ref>

Liebig's company initially promoted their "meat tea" for its curative powers and nutritional value as a cheap, nutritious alternative to real meat. But such claims did not hold up to scrutiny. In 1868 the German physiologist [https://www.jstor.org/stable/44442675 Edward Kemmerich] ran an experiment involving feeding the extract to dogs, every one of which died. After claims of its nutritional value were questioned, the company emphasized its convenience and flavor, marketing it as a comfort food.<ref name=Cansler>{{cite journal|last1=Cansler|first1=Clay|title=Where's the Beef?|journal=Chemical Heritage Magazine|date=Fall 2013|volume=31|issue=3|url=https://www.sciencehistory.org/distillations/article/where%E2%80%99s-beef|access-date=20 March 2018|archive-date=20 November 2018|archive-url=https://web.archive.org/web/20181120095538/https://www.sciencehistory.org/distillations/article/where%E2%80%99s-beef|url-status=dead}}</ref>

The Liebig company worked with popular cookery writers in various countries to popularize their products. German cookery writer [[Henriette Davidis]] wrote recipes for ''Improved and Economic Cookery'' and other cookbooks.   [[Katharina Prato]] wrote an Austro-Hungarian recipe book, ''Die Praktische Verwerthung Kochrecepte'' (1879). [[Hannah M. Young]] was commissioned in England to write ''Practical Cookery Book'' for the Liebig Company. In the United States, [[Maria Parloa]] extolled the benefits of Liebig's extract. Colorful calendars and trading cards were also marketed to popularize the product.<ref name="Brock" />{{rp|234–237}}

The company also worked with British chemist [[Henry Enfield Roscoe]] to develop a related product, which it registered some years after Liebig's death, under the "[[Oxo (food)|Oxo]]" trademark. Oxo was trademarked worldwide in 1899 and in the United Kingdom in 1900. Originally a liquid, Oxo was released in cubed solid form in 1911.<ref name="Brock"/>{{rp|230}}

====Marmite====
Liebig studied other foods, as well. He promoted the use of baking powder to make lighter bread, studied the chemistry of coffee-making and [[oatmeal]].<ref name="Brock"/><ref>{{Cite book|url=https://books.google.com/books?id=p4o9AQAAIAAJ|title=Scientific American, "Oatmeal"|date=1878|publisher=Munn & Company|pages=25|language=en}}</ref>{{rp|238–248}} He is considered to have made possible the invention of [[Marmite]], because of his discovery that yeast could be concentrated to form [[yeast extract]].<ref name=Boulton>{{cite book|editor-last1=Boulton|editor-first1=Chris|title=Encyclopedia of brewing|date=2012|publisher=Wiley|location=Weinheim|isbn=978-1-4051-6744-4|page=394|url=https://books.google.com/books?id=uWXcajHd3W0C&pg=PA394|access-date=4 November 2014}}</ref>

'''Infant Formula'''

Liebig produced some of the world's first [[infant formula]], a [[Breast milk|breast-milk]] substitute for babies who could not breast-feed.<ref>{{Cite journal |url=https://academic.oup.com/jhmas/article-abstract/79/1/1/7223089?redirectedFrom=fulltext |access-date=4 March 2024 |title="They Perished in the Cause of Science": Justus von Liebig's Food for Infants |journal=Journal of the History of Medicine and Allied Sciences |doi=10.1093/jhmas/jrad035 |volume=79 |date=12 July 2023 |issue=1 |first=Caroline |last=Lieffers |pages=1–22|pmid=37435903 |url-access=subscription }}</ref> However, the product proved controversial, even though Liebig did not make any royalties off it. Liebig first came up with the idea based on the struggles of his favorite daughter, Johanna, who struggled to breastfeed her daughter, Carolina, who was born in 1864.<ref>{{Cite web |title=Family tree of Johanna von Liebig |url=https://gw.geneanet.org/cvpolier?lang=en&n=von+liebig&p=johanna |access-date=4 March 2024 |website=Geneanet |language=en}}</ref> (Johanna did not want to seek a [[Wet nurse|wet-nurse]], a common but controversial practice at the time.) Carolina, according to Liebig, thrived on the formula. But other scientists were skeptical. One of them, a French doctor in Paris named Jean-Anne-Henri Depaul<!--Q61943621-->, decided to test his formula on four infants whose mothers could not suckle.

Liebig himself prepared the first batches of formula. Depaul first gave it to a set of [[twin]]s, who were born somewhat [[Preterm birth|premature]] and weighed 2.24 [[kilogram]]s (4.93 [[Pound (mass)|pounds]]) and 2.64&nbsp;kg (5.82&nbsp;lbs.). Both died within two days. Depaul tried it on a third baby, born full-term at 3.37&nbsp;kg (7.43&nbsp;lbs.); it soon began passing green "[https://www.atlchildrens.com/diarrhea-breastfed-infants starvation stools]" and died within three days. A fourth child, weighing 2.76&nbsp;kg, also developed green stools and died within four days. At this point, Depaul stopped the experiment.

At first, Depaul kept the experiment to himself. But he attended a meeting of the [[Académie Nationale de Médecine|French Academy of Medicine]]. And while didn't want to say anything at first, he felt he had to after another member of the Academy rose to speak, a [[pharmacist]] named [[Nicolas-Jean-Baptiste-Gaston Guibourt|Nicholas-Jean-Baptiste-Gaston Guibourt]]. Guibourt had grave doubts about Liebig's artificial [[milk]], calling it "fake milk" (in [[French language|French]], "lait factice"). As historian [https://www.kingsu.ca/about-us/staff-directory/contact_id/5790 Caroline Lieffers] has written, "He [i.e., Guibourt] worried that the substance would either spoil in liquid form or lose its nutritive quality and convenience in solid form." Upon hearing Guibourt speak, Depaul felt it incumbent upon him to speak as well, and mentioned his experiments with Liebig's formula.

Many [[Ethics|ethical]] questions were quickly raised. Publications in France generally supported Depaul, while German publications rallied to Liebig's defense.

== Major works ==
{{Library resources box|by=yes|onlinebooksby=yes|viaf=51763678 }}

Liebig founded the journal ''[[Liebigs Annalen|Annalen der Chemie]]'', which he edited from 1832. Originally titled ''Annalen der Pharmacie'', it became ''Annalen der Chemie und Pharmacie'' to more accurately reflect its content.<ref name=RoyalSocietyObit/> It became the leading journal of organic chemistry,<ref name=Gratzer>{{cite book|last1=Gratzer|first1=Walter|title=Terrors of the table the curious history of nutrition|date=2006|publisher=Oxford University Press|location=Oxford|isbn=0199205639|url=https://books.google.com/books?id=W2g8vHsjpjwC&pg=PT90|access-date=12 November 2014}}</ref> and still exists, albeit under the name ''[[European Journal of Organic Chemistry]]'' after several mergers with other journals.<ref>{{Cite web |last1=Engberts |first1=Jan B. F. N. |last2=Hafner |first2=Klaus |last3=Hopf |first3=Henning |date=20 September 1997 |editor-last=Temme |editor-first=Robert |title=What is going to become of ''Chemische Berichte/Recueil'' and ''Liebigs Annalen/Recueil''? |url=https://tuprints.ulb.tu-darmstadt.de/22433/1/Liebigs%20Annalen%20-%20September%2022%20%201997%20-%20%20-%20Editorial.pdf |website=Jahrgang}}</ref> The volumes from his lifetime are often referenced just as ''Liebigs Annalen''; following his death the title was officially changed to ''Justus Liebig's Annalen der Chemie''.<ref name=Leicester>{{cite book|last1=Leicester|first1=Henry Marshall|title=The historical background of chemistry|date=1971|publisher=Dover Publications|location=New York|isbn=0486610535|page=214|url=https://books.google.com/books?id=aJZVQnqcwv4C&pg=PA214|access-date=12 November 2014}}</ref>

Liebig published widely in ''Liebigs Annalen'' and elsewhere, in newspapers and journals.<ref name=Hyle>{{cite journal|last1=Blondel-Mégrelis|first1=Marika|title=Liebig or How to Popularize Chemistry|journal=Hyle: International Journal for Philosophy of Chemistry|year=2007|volume=13|issue=1|pages=43–54|url=http://www.hyle.org/journal/issues/13-1/blondel.pdf|access-date=17 November 2014}}</ref> Most of his books were published concurrently in both German and English, and many were translated into other languages, as well. Some of his most influential titles include:
* ''Ueber das Studium der Naturwissenschaften und über den Zustand der Chemie in Preußen'' (1840) Digital edition by the [[University and State Library Düsseldorf]]
* ''Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie''; in English, ''Organic Chemistry in its Application to Agriculture and Physiology'' (1840)
* ''Chimie organique appliquée à la physiologie animale et à la pathologie''; in English, '' Animal chemistry, or, Organic chemistry in its applications to physiology and pathology'' (1842)
* ''Familiar letters on chemistry and its relation to commerce, physiology and agriculture'' (1843)
* ''Chemische Briefe'' (1844) Digital edition (1865) by the [[University and State Library Düsseldorf]]

In addition to books and articles, he wrote thousands of letters, most of them to other scientists.<ref name=Brock/>{{rp|273}}

Liebig also directly influenced the German publication of [[John Stuart Mill]]'s ''Logic.'' Liebig had a close friendship with the Vieweg family publishing house. He arranged for his former student [[Jacob Schiel]] (1813–1889) to translate Mill's important work for German publication. Liebig liked Mill's ''Logic'' in part because it promoted science as a means to social and political progress, but also because Mill featured several examples of Liebig's research as an ideal for the scientific method. In this way, he sought to reform politics in the German states.<ref name=Brock/>{{rp|298–299}}<ref name=Schmidgen>{{cite journal|last1=Schmidgen|first1=H.|title=Wundt as chemist? A fresh look at his practice and theory of experimentation|journal=American Journal of Psychology|year=2003 |volume=116|issue=3|pages=469–476|doi=10.2307/1423504|pmid=14503396|jstor=1423504}}</ref>

==Later life==
[[File:Justus von Liebig.jpg|thumb|right|upright|Liebig was president of the [[Bavarian Academy of Sciences and Humanities|Bavarian Academy of Science]].]]

In 1852, after asking [[Hermann Franz Moritz Kopp|Hermann Kopp]] to take over management of the ''Annalen der Chemie'',<ref name=":0">{{Cite journal |last=Van Klooster |first=H. S. |date=January 1957 |title=The story of Liebig's Annalen der Chemie |url=https://pubs.acs.org/doi/abs/10.1021/ed034p27 |journal=Journal of Chemical Education |language=en |volume=34 |issue=1 |pages=27 |doi=10.1021/ed034p27 |bibcode=1957JChEd..34...27V |issn=0021-9584|url-access=subscription }}</ref> Liebig accepted an appointment from [[King Maximilian II of Bavaria]] to the [[Ludwig Maximilian University of Munich]]. He also became the Royal scientific advisor to King Maximilian II, who hoped to transform the University of Munich into a center for scientific research and development.<ref name=Brock/>{{rp|315}} In part, Liebig accepted the post because, at age 50, he was finding supervision of large numbers of laboratory students increasingly difficult. His new accommodations in Munich reflected this shift in focus.  They included a comfortable house suitable for extensive entertaining, a small laboratory, and a newly built lecture theatre capable of holding 300 people with a demonstration laboratory at the front.  There, he gave lectures to the university and fortnightly to the public.  In his position as a promoter of science, Liebig was appointed president of the [[Bavarian Academy of Sciences and Humanities]], becoming perpetual president of the Royal Bavarian Academy of Sciences in 1858.<ref name=Brock/>{{rp|291–297}}

In the 1850s, Liebig moved next door to the noted [[classics]] scholar and [[Philology|philologist]] [[Friedrich Thiersch|Friederich Thiersch]] in the city of [[Munich]].<ref>{{Cite book |last=Phillips |first=Denise |url=https://books.google.com/books?id=QiFXGKLGVxUC&q=liebig+neighbor |title=Acolytes of Nature: Defining Natural Science in Germany, 1770-1850 |date=4 June 2012 |publisher=University of Chicago Press |isbn=978-0-226-66737-9 |language=en}}</ref> Liebig had previously scorned philologists like Thiersch in articles. (Liebig promoted science over supposedly impractical fields like the classics.) But Liebig's most beloved daughter, Johanna, fell in love with Thiersch's second son, Karl, who had studied medicine in several cities, including Berlin and Vienna. Johanna and Karl reportedly had a happy marriage, producing six children: four daughters and two sons. It was fairly common for the sons and daughters of academics to marry in Germany then.<ref>{{Cite book |last=Phillips |first=Denise |url=https://books.google.com/books?id=QiFXGKLGVxUC&q=liebig+neighbor |title=Acolytes of Nature: Defining Natural Science in Germany, 1770-1850 |date=4 June 2012 |publisher=University of Chicago Press |isbn=978-0-226-66737-9 |language=en}}</ref>

Liebig enjoyed a personal friendship with Maximilian II, who died on 10 March 1864.  After Maximilian's death, Liebig and other liberal Protestant scientists in Bavaria were increasingly opposed by [[ultramontane]] Catholics.<ref name=Brock/>{{rp|319}}

Liebig died in [[Munich]] in 1873, and is buried in the [[Alter Südfriedhof]] in Munich.

==Awards and honors==
[[Image:DBP 1953 166 Liebig.jpg|thumb|right|upright|German stamp picturing Justus von Liebig, 1953]]
[[File:Grab von Justus von Liebig.jpg|thumb|right|upright|Justus von Liebig grave, Munich, Germany]]
Liebig was elected a member of the [[Royal Swedish Academy of Sciences]] in 1837.

He became a first-class member of the [[Ludwig Order]], founded by [[Louis I, Grand Duke of Hesse|Ludwig I]], and awarded by [[Louis II, Grand Duke of Hesse|Ludwig II]] on 24 July 1837.<ref name=Brock/>{{rp|106}}

In 1838, he became a correspondent of the Royal Institute of the Netherlands; when that became the [[Royal Netherlands Academy of Arts and Sciences]] in 1851, he joined as a foreign member.<ref>{{cite web |url=http://www.dwc.knaw.nl/biografie/pmknaw/?pagetype=authorDetail&aId=PE00001583 |title=J. von Liebig (1803–1873) |publisher=Royal Netherlands Academy of Arts and Sciences |access-date=26 July 2015}}</ref>

The British [[Royal Society]] awarded him the [[Copley Medal]] "for his discoveries in organic chemistry, and particularly for his development of the composition and theory of organic radicals" in 1840.<ref name=Brock/>{{rp|96}}<ref name=Adjudication>{{cite journal|last1=Bowyer|first1=W.|last2=Nichols|first2=J.|title=Adjudication of the Medals of the Royal Society for the year 1840 by the President and Council|journal=Philosophical Transactions of the Royal Society of London|year=1840|url=https://books.google.com/books?id=0I05AQAAMAAJ&pg=PA226|access-date=6 November 2014}}</ref>

In 1841, botanist [[Stephan Friedrich Ladislaus Endlicher]] (1804–1849) published a genus of [[flowering plant]]s from [[Malesia]], belonging to the family [[Gesneriaceae]], as ''[[Liebigia]]'' in his honour.<ref>{{cite web |title=''Liebigia'' Endl. {{!}} Plants of the World Online {{!}} Kew Science |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:17092-1 |website=Plants of the World Online |access-date=16 May 2021 |language=en}}</ref>

[[Ludwig II of Bavaria|King Ludwig II of Bavaria]] ennobled Liebig on 29 December 1845, conferring on him the hereditary title of ''[[Freiherr]]'' [[von]] Liebig. In English, the closest translation is [[Baron]] von Liebig.<ref name=Brock/>{{rp|106}}

In 1850, he received the French ''[[Légion d'honneur]]'', presented by chemist [[Jean-Baptiste Dumas]], the French trade minister.<ref name=Tous>{{cite web|title=Justus von Liebig |url=http://tous-les-faits.fr/justus_von_liebig |website=Tous Les Faits |access-date=6 November 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141106032032/http://tous-les-faits.fr/justus_von_liebig |archive-date= 6 November 2014 }}</ref>

He was honored with the Prussian Order of Merit for Science by [[Frederick William IV of Prussia|Friedrich Wilhelm IV of Prussia]] in 1851.<ref name=OrderMerite>{{cite web|title=Civilian or Peace Class Order pour le Merite for Arts and Science|url=http://www.pourlemerite.org/peace/peace.php|publisher=Gretchen Winkler and Kurt M. von Tiedemann|access-date=6 November 2014|archive-url=https://web.archive.org/web/20120716232443/http://www.pourlemerite.org/peace/peace.php|archive-date=16 July 2012|url-status=dead}}</ref>

He was elected as a member of the [[American Philosophical Society]] in 1862.<ref>{{Cite web|title=APS Member History|url=https://search.amphilsoc.org/memhist/search?year=1862;year-max=1862;smode=advanced;startDoc=1|access-date=20 April 2021|website=search.amphilsoc.org}}</ref>

In 1869, Liebig was awarded the [[Albert Medal (Royal Society of Arts)|Albert Medal]] by the [[Royal Society of Arts]], "for his numerous valuable researches and writings, which have contributed most importantly to the development of food-economy and agriculture, to the advancement of chemical science, and to the benefits derived from that science by Arts, Manufactures, and Commerce."<ref name=SocietyArts>{{cite journal|title=Announcements by the Council: Albert Medal|journal=Journal of the Society of Arts|date=26 April 1872|page=491|url=https://books.google.com/books?id=NS4FAAAAQAAJ&pg=PA491|access-date=6 November 2014}}</ref>

===Posthumous honors===
Liebig's portrait appeared on the {{Reichsmark|100|link=yes}} banknote issued by the [[Reichsbank]] from 1935 until 1945.<ref>{{Cite web|url=http://banknote.ws/COLLECTION/countries/EUR/GER/GER0183.htm|title = P-183}}</ref> Printing ceased in 1945 but the note remained in circulation until the issue of the [[Deutsche Mark]] on 21 June 1948.

In 1946, after the end of World War II, the University of Giessen was officially renamed after him, ''"Justus-Liebig-Universität Giessen"''.<ref name=JLU/>

In 1953, the West German [[Deutsche Bundespost|post office]] issued a stamp in his honor.<ref>Germany No. 695, ''[[Scott catalogue]]''</ref>

In 1953, the third General Assembly of the International Scientific Centre of Fertilizers (CIEC), founded in 1932, was organized in Darmstadt to honor Justus von Liebig on the 150th anniversary of his birth.<ref name=OpeningAddress/>

A portrait of Liebig hangs in the [[Burlington House]] headquarters of the [[Royal Society of Chemistry]]. It was presented to the society's forerunner, the [[Chemical Society]], by his god-daughter, [[Ethel Brilliana Tweedie|Mrs Alex Tweedie]], née Harley, daughter of Emma Muspratt.<ref>Label on frame</ref>

===Liebig medals===
Some organizations have granted medals in honor of Liebig. In 1871, the Versammlung deutscher Land- und Forstwirte (Assembly of German Farmers and Foresters) was first awarded a Liebig Gold Medal, given to Theodor Reuning. The image was struck from a portrait commissioned in 1869 from Friedrich Brehmer.<ref name=Brock/>{{rp|327–328}}<ref name=Forrer>{{cite book|last1=Forrer|first1=Leonard|title=Biographical dictionary of medallists : coin-, gem-, and seal-engravers, mint-masters, &c., ancient and modern, with references to their works : B.C. 500-A.D. 1900|date=1904|publisher=Spink and Son|location=London|isbn=0906919037|page=[https://archive.org/details/biographicaldict06forriala/page/271 271]|edition=Reprinted.|url=https://archive.org/details/biographicaldict06forriala}}</ref>

For several years, the Liebig Trust Fund, established by Baron Liebig, was administered by the [[Bavarian Academy of Sciences and Humanities|Royal Bavarian Academy of Sciences]] at Munich and members of the Liebig family. They were empowered to award gold and silver Liebig Medals to deserving German scientists "for the purpose of encouraging research in agricultural science". Silver medals could be awarded to scientists from other countries.<ref name=Pacific1893>{{cite news|title=Honors to Californian|url=http://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=PRP18931014.2.3|access-date=12 November 2014|work=Pacific Rural Press|agency=California Digital Newspaper Collection|volume=46|issue=16|date=14 October 1893}}</ref> Some of those who received medals include:
<!--  Samuel William Johnson of Yale : unverified -->
* 1893, silver, [[John Bennet Lawes|Sir John Lawes]] and [[Joseph Henry Gilbert]], England<ref name=Gilbert1895>{{cite book|last1=Gilbert|first1=Sir Joseph Henry|title=Agricultural investigations at Rothamsted, England, during a period of fifty years: Six lectures delivered under the provisions of the Lawes agricultural trust|date=1895|publisher=Government Printing Office|location=Washington|page=[https://archive.org/details/agriculturalinve22gilb/page/7 7]|url=https://archive.org/details/agriculturalinve22gilb|access-date=12 November 2014}}</ref>
* 1894, silver, Professor [[Eugene Woldemar Hilgard]], United States, "for meritorious work in the investigation of the physical and chemical properties of soils."<ref name=Pacific1893/><ref name=Hinsdale>{{cite book|last1=Hinsdale|first1=B. A. (Burke Aaron)|editor-last=Demmon|editor-first=Isaac Newton|title=History of the University of Michigan, by the late Burke A. Hinsdale, with biographical sketches of the regents and members of the university Senate from 1837 to 1906|date=1906|publisher=Published by the University|location=Ann Arbor|url=http://umhistory.dc.umich.edu/history/Faculty_History/H/Hilgard,_Eugene_Woldemar.html|access-date=12 November 2014|archive-date=2 August 2020|archive-url=https://web.archive.org/web/20200802184827/http://umhistory.dc.umich.edu/history/Faculty_History/H/Hilgard,_Eugene_Woldemar.html|url-status=dead}}</ref>
* 1896, gold, Professor [[Friedrich Stohmann]], professor of agricultural chemistry in [[Leipzig University]].<ref name=Nature1896>{{cite news|title=Notes|url=https://books.google.com/books?id=uiQ6AQAAMAAJ&pg=PA32|access-date=12 November 2014|work=Nature|date=14 May 1896|last1 = Lockyer|first1 = Sir Norman}}</ref>
* 1899, gold, Albert Schultz-Lupitz, Germany<ref name=Killy>{{cite book|last1=Killy|first1=Walther|last2=Vierhaus|first2=Rudolf|title=Schmidt-Theyer|date=2005|publisher=K.G. Saur|location=München|isbn=3110966298|pages=196–197|url=https://books.google.com/books?id=0-hrRQvGV7sC&pg=PA197|access-date=12 November 2014}}</ref>
* 1908, gold, [[Max Rubner]], Germany<ref name=Science1908>{{cite journal|title=Scientific Notes and News|journal=Science|date=24 July 1908|page=115|url=https://books.google.com/books?id=yVk9AQAAMAAJ&pg=PA115|access-date=12 November 2014|doi=10.1126/science.28.708.114-a|volume=28|issue=708|url-access=subscription}}</ref>

In 1903, the [[Gesellschaft Deutscher Chemiker|Verein deutscher Chemiker]] (Association of German Chemists) also had a medal struck using Brehmer's portrait.<ref name=Brock/>{{rp|329}}  Their [[Liebig Medal]] was first awarded in 1903 to [[Adolf von Baeyer]], and in 1904 to Dr. [[Rudolf Knietsch]] of the Badische Anilin- und Soda-Fabrik.<ref name=Dighton>{{cite news|title=Medal for Chemist|url=https://www.newspapers.com/newspage/67423412/|access-date=11 November 2014|work=The Dighton Herald|publisher=Dighton, Kansas|date=1 September 1904}}</ref> {{as of | 2024}}, it continues to be awarded.<ref>{{Cite web| url=https://en.gdch.de/gdch/prizes-and-awards/gdch-awards/liebig-commemorative-medal.html | title=Liebig commemorative medal | language=en |date= 15 May 2024 |website=Gesellschaft Deutscher Chemiker |access-date=17 June 2024}}</ref>

At the third World Congress of CIEC, held at Heidelberg in 1957, the "Sprengel-Liebig Medal" was awarded to Dr. E. Feisst, president of CIEC, for outstanding contributions in agricultural chemistry.<ref name=OpeningAddress>{{cite web|last1=Hera|first1=Cristian|title=80 years dedicated to enhancing soil fertility and crop productivity|publisher=International Scientific Centre of Fertilizers Centre International des Engrais Chimiques (CIEC)|url=http://www.ciec-network.org/fileadmin/dam_uploads/Projektordner/General/CIEC%20History%2012%20sept%202013.pdf|access-date=11 November 2014|url-status=dead|archive-url=https://web.archive.org/web/20141112003010/http://www.ciec-network.org/fileadmin/dam_uploads/Projektordner/General/CIEC%20History%2012%20sept%202013.pdf|archive-date=12 November 2014}}</ref>

==See also==
* [[History of soil science]]
* [[List of chemists]]

==Notes==
{{Notelist}}

==References==
{{Reflist}}

==Sources==
* {{Citation
|pmid = 13187963
|last=Berghoff
|first=E.
|publication-date=11 June 1954
|year=1954
|title=Justus von Liebig, founder of physiological chemistry
|volume=66
|issue=23
|periodical=Wien. Klin. Wochenschr.
|pages=401–2
}}
* {{cite book
|last1=Brock
|first1=William H.
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|date=1997
|publisher=Cambridge University Press
|location=Cambridge, U.K.
|isbn=9780521562249
|edition=1st
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* {{Citation
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|title=The Liebig-Mulder controversy. On the methodology of physiological chemistry
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* {{Citation
|pmid = 11614053
|last=Guggenheim
|first=K. Y.
|publication-date=1985
|year=1985
|title=Johannes Müller and Justus Liebig on nutrition.
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* {{Citation
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* {{Citation
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|pages=3–24
|doi=10.1179/000269803790220066
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* {{Citation
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* {{Citation
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 | author-last = Liebig
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* {{Citation
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|last=Rosenfeld
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|periodical=Clin. Chem.
|pages=1696–707
|doi = 10.1373/49.10.1696
|doi-access=free
}}
* [[Margaret Rossiter|Rossiter, Margaret]] (1975) {{cite book|title=The Emergence of Agricultural Science: Justus Liebig and the Americans, 1840-1880|year=1975|publisher=[[Yale University Press]]|location=New Haven|isbn=978-0-300-01721-2}}
* {{Citation
|pmid = 13088290
|last=Schmidt
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|publication-date=May 1953
|year=1953
|title=To Justus von Liebig on his 150th birthday, 12 May 1953
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|periodical=Pharmazie
|pages=445–6
}}
* {{Citation
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|year=1953
|title=Justus von Liebig and the [[Archiv der Pharmazie]]; in memory of Liebig's birthday, 12 May 1803
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|issue=4
|periodical=[[Archiv der Pharmazie | Archiv der Pharmazie und Berichte der Deutschen Pharmazeutischen Gesellschaft]]
|pages=165–72
|doi=10.1002/ardp.19532860402
|s2cid=98065788
}}
* {{Citation
|pmid = 11615416
|last=Sonntag
|first=O.
|publication-date=September 1974
|year=1974
|title=Liebig on Francis Bacon and the utility of science
|volume=31
|issue=5
|periodical=Annals of Science
|pages=373–86
|doi = 10.1080/00033797400200331
}}
* {{Citation
|pmid = 11610495
|last=Sonntag
|first=O.
|publication-date=November 1977
|year=1977
|title=Religion and science in the thought of Liebig
|volume=24
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|pages=159–69
|doi=10.1179/amb.1977.24.3.159
}}
* {{Citation
|pmid = 11621581
|last=Thomas
|first=U.
|publication-date=1988
|year=1988
|title=Philipp Lorenz Geiger and Justus Liebig.
|volume=35
|issue=2
|periodical=Ambix
|pages=77–90
|doi=10.1179/amb.1988.35.2.77
}}
* {{Citation
 | title = Zur Erinnerung an Justus von Liebig
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 | volume = 8
 | issue = 1
 | pages = 428–458
 | year = 1873
 | doi = 10.1002/prac.18740080148
 | postscript = .    }}

==External links==

{{Commons category}}
{{Wikiquote}}
* {{Gutenberg author |id=1492}}
* {{Internet Archive author |sname=Justus von Liebig}}
* {{Librivox author |id=4307}}
* {{OL author|155483A}}
* [http://www.1902encyclopedia.com/L/LIE/justus-liebig.html Justus Liebig, German chemist (1803–73)] {{Webarchive|url=https://web.archive.org/web/20081121023538/http://www.1902encyclopedia.com/L/LIE/justus-liebig.html |date=21 November 2008 }} from the Encyclopædia Britannica, 10th Edition (1902).
* [https://web.archive.org/web/20110927174315/http://aghalloffame.com/hall/liebig.aspx The National Agricultural Center and Hall of Fame]
* {{HessBib PPN|118196782}}
* {{PM20|FID=pe/011419}}
* {{Wikisource-inline|list=
** "[[s:The Chemical News/Justus Liebig (obituary)|Justus Liebig]]," ''[[s:The Chemical News|The Chemical News]]'', 1873
** {{Cite EB9 |last=Brown |first=A. Crum |author-link=Alexander Crum Brown |wstitle=Liebig, Justus|volume=14|short=x |noicon=x}}
** {{Cite PSM|wstitle=Justus von Liebig|month-and-year=March 1892|volume=40 |noicon=x}}
** {{Cite NIE|wstitle=Liebig, Justus von|year=1905 |short=x |noicon=x}}
** {{Cite Nuttall|wstitle=Liebig, Baron von |short=x |noicon=x}}
** {{Cite EB1911|wstitle=Liebig, Justus von |short=x |noicon=x}}
** "[[s:Biographies of Scientific Men/Liebig|Liebig]]," in [[s:Biographies of Scientific Men|''Biographies of Scientific Men'']] (1912)
** {{Cite Americana|wstitle=Liebig, Justus, Baron von |short=x |noicon=x}}
** {{Cite Collier's|wstitle=Liebig, Justus, Baron von |short=x |noicon=x}}
}}

{{Copley Medallists 1801-1850}}
{{Authority control}}

{{DEFAULTSORT:Liebig, Justus Von}}
[[Category:Justus von Liebig| ]]
[[Category:1803 births]]
[[Category:1873 deaths]]
[[Category:19th-century German chemists]]
[[Category:19th-century German inventors]]
[[Category:German soil scientists]]
[[Category:Scientists from Darmstadt]]
[[Category:People from the Grand Duchy of Hesse]]
[[Category:German barons]]
[[Category:University of Bonn alumni]]
[[Category:University of Erlangen–Nuremberg alumni]]
[[Category:Academic staff of the University of Giessen]]
[[Category:Academic staff of the Ludwig Maximilian University of Munich]]
[[Category:Recipients of the Copley Medal]]
[[Category:Recipients of the Pour le Mérite (civil class)]]
[[Category:Members of the Royal Netherlands Academy of Arts and Sciences]]
[[Category:Members of the Royal Swedish Academy of Sciences]]
[[Category:Foreign members of the Royal Society]]
[[Category:Foreign associates of the National Academy of Sciences]]
[[Category:Corresponding members of the Saint Petersburg Academy of Sciences]]
[[Category:Burials at the Alter Südfriedhof]]
[[Category:Members of the Bavarian Academy of Sciences]]
[[Category:International members of the American Philosophical Society]]