Justus von Liebig

1803-1873

German Chemist

Justus von Liebig was one of the most influential chemists of the nineteenth century. As a scientist, Liebig offered bold theoretical frameworks and trained a generation of students and colleagues who led developments in organic chemistry, pharmaceutical chemistry, physiological chemistry, agricultural chemistry, and industrial chemistry for decades. As a popularizer of science, Liebig explained to academics, bureaucrats, farmers, and monarchs chemistry's utility as the basis for modernization, improvements in public health and nutrition, and greater international cooperation. As an entrepreneur, Liebig demonstrated the commercial potential of applied chemistry through enterprises that manufactured fertilizers, mirrors, baking powders, infant formulas, and meat extract.

Liebig was born in Darmstadt in 1803, where his parents operated a small shop that sold hardware and useful chemicals like paints and varnishes. Unable to complete a formal secondary education for financial reasons, Liebig moved to nearby Heppenheim to apprentice as a pharmacist, then the most important step for someone with a career interest in chemistry. Liebig went on to study chemistry at the University of Bonn and the University of Erlangen, where he received a doctorate with little more than the promise to do research on the topic of plant chemistry. He then earned a grant that allowed him to study in Paris under some of the leading chemists of the day, especially Joseph-Louis Gay-Lussac (1778-1850).

In 1824, as part of the grand duchy's broader initiative to modernize its infrastructure, Liebig received an appointment at the small University of Giessen in his home state of Hessen-Darmstadt. Liebig soon transformed Giessen into a center for chemical education that earned an international reputation for its innovative teaching methods and successful graduates. Liebig's approach stressed the development of laboratory skills. Through use of standardized techniques and equipment like the "potash bulp apparatus" and the "Liebig condensor," students learned how to efficiently perform routine analyses. As their skills developed, students tackled independent research projects that led to the synthesis and identification of countless new compounds and reactions. Liebig's own research focused on organic chemistry theory, during a crucial period in its development. In particular, he refined the theory that certain groups of organic compounds, called radicals, remain unchanged through a series of reactions that produce related compounds. Liebig also edited Annalen der Pharmacie und Chemie, which became the most influential journal in the field.

In 1840 Liebig published two works that established his reputation as an influential commentator on the major scientific issues of his day. The first, an article sharply critical of the quality of chemical instruction offered in Prussia, prompted many European governments to revamp their approach to scientific education. The second, Organic Chemistry and Its Applications to Agriculture and Physiology, laid the foundation for a generation of research in the agricultural sciences. Liebig argued that farmers should be cognizant of the role that chemical compounds play in every aspect of farm operations. Illustrating that mineral nutrients from the soil leave the farm with every harvest and livestock sale, Liebig clearly outlined a concept of chemical cycles that stressed a balance of chemical inputs and outputs. He also endorsed artificial fertilizers as an appropriate means to maintain soil fertility. In a related book on animal chemistry, published in 1842, Liebig announced his theories on the protein radical, the metabolism of fats, and the relationship between digestion and respiration, laying the groundwork for future research on nutrition and biochemistry.

In the latter half of his career, Liebig distanced himself from laboratory teaching and his own research projects, concentrating instead on efforts to promote and popularize chemistry in the German area and beyond. His Chemical Letters, eventually published in 11 languages, taught the significance of chemistry in a popular language and format. In 1852 he took a post at the University of Munich that required little in the way of teaching or research, allowing him to concentrate on his roles as popular lecturer and public savant. His later career also included efforts to recycle London's sewage for agricultural purposes, to market the byproducts of South American beef as Liebig's Extract of Meat, and to address international issues of science policy and philosophy of science.

Though many of the specific theories that Liebig promoted have since been proven incorrect, his career furthered the emergence of chemistry as a central branch of scientific inquiry.

MARK R. FINLAY