page_title: Justus von Liebig
section_title: Organic chemistry
hierarchical_section_title: Justus von Liebig / Research and development / Organic chemistry
caption_attribution_description: English: Liebig laboratory at Giessen
context_page_description: Justus Freiherr von Liebig was a German scientist who made major contributions to agricultural and biological chemistry, and is considered one of the principal founders of organic chemistry. 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 greatest chemistry teachers of all time. He has been described as the "father of the fertilizer industry" for his emphasis on nitrogen and trace minerals as essential plant nutrients, and his formulation of the law of the minimum, which described how plant growth relied on the scarcest nutrient resource, rather than the total amount of resources available. He also developed a manufacturing process for beef extracts, and with his consent a company, called Liebig Extract of Meat Company, was founded to exploit the concept; it later introduced the Oxo brand beef bouillon cube. He popularized an earlier invention for condensing vapors, which came to be known as the Liebig condenser.
context_section_description: One of Liebig's frequent collaborators was Friedrich Wöhler. They met in 1826 in Frankfurt, after independently reporting on the preparation of two substances, 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.
  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. Throughout these transformations, "a single compound" (which they named benzoyl) "preserves its nature and composition unchanged in nearly all its associations with other bodies."  Their experiments proved that a group of carbon, hydrogen, and oxygen atoms can behave like an element, take the place of an element, and can be exchanged for elements in chemical compounds. This laid the foundation for the doctrine of compound radicals, which can be seen as an early step in the development of structural chemistry.
  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. 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;
  the study of chlorination and the isolation of chloral (1832);
  the identification of the ethyl radical (1834);
  the oxidation of alcohol and formation of aldehyde (1835);
  the polybasic theory of organic acids (1838);
  and the degradation of urea (1837).
  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.  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:
  "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."
  — [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), and Ludwig Büchner (1824–1899).
caption: Liebig laboratory, Giessen
exif: {}