Justus von Liebig
Justus Freiherr von Liebig was a German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biological chemistry; he 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 most outstanding chemistry teachers of all time. He has been described as the "father of the fertilizer industry" for his emphasis on nitrogen and minerals as essential plant nutrients, 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. 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.
Early life and education
Justus Liebig was born in Darmstadt into the middle-class family of Johann Georg Liebig and Maria Caroline Möser in early May 1803. His father was a drysalter and hardware merchant who compounded and sold paints, varnishes, and pigments, which he developed in his own workshop. 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. 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".
Liebig attended grammar school at the Ludwig-Georgs-Gymnasium in Darmstadt, from the ages of 8 to 14. Leaving without a certificate of completion, he was apprenticed for several months to the apothecary Gottfried Pirsch in Heppenheim before returning home, possibly because his father could not afford to pay his indentures. He worked with his father for the next two years, 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.
Liebig left Erlangen in March 1822, in part because of his involvement with the radical Korps Rhenania, but also because of his hopes for more advanced chemical studies. The circumstances are clouded by possible scandal. 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 Hessian government. He worked in the private laboratory of Joseph Louis Gay-Lussac and was also befriended by Alexander von Humboldt and Georges Cuvier. 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.
Research and development
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. 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.The presence of existing faculty complicated his situation: Professor Wilhelm Zimmermann 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 chair in chemistry on 7 December 1825, receiving a considerably increased salary and a laboratory allowance.
Liebig married Henriette "Jettchen" Moldenhauer, the daughter of a state official, in May 1826. They had five children: Georg, Agnes, Hermann, Johanna, and Marie. 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.
Transforming chemistry education
Liebig and several associates proposed to create an institute for pharmacy and manufacturing within the university. The Senate, however, uncompromisingly rejected their idea, stating that training "apothecaries, soapmakers, beer-brewers, dyers and vinegar-distillers" was not the university's task. 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. Liebig's institute was widely advertised in pharmaceutical journals and opened in 1826. 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 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.
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. 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. It was also significant for its emphasis on applying discoveries in fundamental research to the development of specific chemical processes and products.
In 1833, Liebig convinced chancellor Justin von Linde to include the institute within the university. In 1839, he obtained government funds to build a lecture theatre and two separate laboratories designed by architect Paul Hofmann. The new chemistry laboratory featured innovative glass-fronted fume cupboards and venting chimneys. By 1852, when he left Giessen for Munich, more than 700 students of chemistry and pharmacy had studied with Liebig.
Instrumentation
A significant challenge facing 19th-century 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 was used for the combustion. Weighing carbon and hydrogen directly, rather than estimating them volumetrically, significantly increased the method's accuracy of measurement. Liebig's assistant, Carl Ettling, perfected glass-blowing techniques for producing the Kaliapparat and demonstrated them to visitors. Liebig's kaliapparat simplified the method of quantitative organic analysis and rendered it routine. 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. His method of combustion analysis was used pharmaceutically, and certainly made possible many contributions to organic, agricultural and biological chemistry.Liebig also popularized the use of a counter-current water-cooling system for distillation, still referred to as a Liebig condenser. 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 chemist Johan Gadolin in 1791.
Although it was not widely adopted until after Liebig's death, when safety legislation finally prohibited the use of mercury in making mirrors, 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. 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.