[3] 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.

[8]: 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).

[8]: 13 Liebig left Erlangen in March 1822, in part because of his involvement with the radical Korps Rhenania (a nationalist student organization), but also because of his hopes for more advanced chemical studies.

[8]: 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.

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.

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.

Other significant contributions by Liebig during this time include his examination of the nitrogen content of bases;[8]: 77 the study of chlorination and the isolation of chloral (1832);[8]: 83 the identification of the ethyl radical (1834);[8]: 82 the oxidation of alcohol and formation of aldehyde (1835);[8]: 84 the polybasic theory of organic acids (1838);[8]: 86–87 and the degradation of urea (1837).

[8]: 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.

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),[21] and Ludwig Büchner (1824–1899).

[8] Liebig's book discussed chemical transformations within living systems, both plant and animal, outlining a theoretical approach to agricultural chemistry.

[23]: 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.

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.

[23]: 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.

[8]: 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.

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.

[8]: 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.)

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.

[25] 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 N fixation.

[8]: 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.

[8]: 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.

Liebig proposed chemical explanations for processes such as 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.

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.

[8]: 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.

[8]: 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" trademark.

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.

[8]: 96 [46] In 1841, botanist Stephan Friedrich Ladislaus Endlicher (1804–1849) published a genus of flowering plants from Malesia, belonging to the family Gesneriaceae, as Liebigia in his honour.

[53] 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.

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.

They were empowered to award gold and silver Liebig Medals to deserving German scientists "for the purpose of encouraging research in agricultural science".