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Chemistry and society: An explosive pair
It is the early 19th century, and industrialization in Europe is in full swing. Close collaboration between the chemical industry and research – largely in France to start with, then followed by other European countries – is resulting in rapid advances in both sectors. As the chemical industry grows, chemistry is gaining a higher profile in society. The third and fourth parts of our series on the history of chemistry consider the relationship between chemistry, industry, and society from the 19th century onward.
The chemistry of living organisms
One of the most important chemists of the early 19th century is Jöns Jakob Berzelius (1779–1848). This Swedish scientist improved laboratory techniques and developed methods for elemental analysis. By conducting systematic analyses on a large scale, he determined the molecular formulae of virtually all known inorganic compounds and the atomic masses of the elements that had been discovered at that point. He is also the person we have to thank for element symbols: H for hydrogen, O for oxygen, and so on. The only difference between his notation and what we use today is that Berzelius presented element proportions in molecular formulae as superscript characters rather than the subscript characters we see nowadays (e.g., H2O instead of H2O).
As well as this, he dealt extensively with the chemistry of organisms, something which he dubbed «organic chemistry». Being a proponent of vitalism, Berzelius was convinced that only living organisms were capable of producing organic substances, claiming that «vital force» was necessary for this process. The findings of one of his apprentices, Friedrich Wöhler, would later put a question mark on this hypothesis.
Organic from inorganic – is it possible?
In 1828, Friedrich Wöhler (1800–1882) was the first person who successfully managed to synthesize an organic compound from inorganic reagents: by heating ammonium cyanate, he was able to create its organic isomer, urea. He thus showed that organic substances can be created in a laboratory and that humans are therefore able to imitate and manipulate nature. More and more organic syntheses were made possible as the 19th century progressed.
Wöhler’s synthesis of urea was revolutionary. Today, urea is produced industrially at a rate of 150 million tons per year. Among other things, it is used for dermatological products and in the polymer industry.
Wöhler and Liebig: A fruitful friendship
Wöhler formed a friendship with Justus von Liebig (1803–1873) after they settled a dispute about silver fulminate and silver cyanate in 1825. Both substances share the same molecular formula, but the silver fulminate discovered by Liebig is highly explosive, whereas Wöhler’s silver cyanate is not. They eventually ascertained that the type and number of atoms in a compound alone are not enough to characterize a substance – the arrangement of the atoms must also be considered. As well as a spirit of mutual esteem, Liebig and Wöhler thus discovered isomerism. However, determining the molecular structure was not yet possible at that time.
In 1832, the two researchers worked together to formulate their so-called radical theory, which paved the way for modern organic chemistry. This stated that organic substances are composed of atom groups, which they called radicals. These remain unchanged during chemical reactions and are merely exchanged between the reactants. Although the term «radical» now has a different meaning in chemistry, a very similar principle remains until today: functional groups.
Superphosphate revolutionizes agriculture
Around 1840, Liebig, who had studied at the Sorbonne in Paris under such great names as Gay-Lussac and experienced France’s symbiotic relationship between science and industry, turned his back on fundamental research. Instead, he began studying organic chemistry in physiology and agriculture. He realized that plants extract nutrients needed for growth from the ground – with the exception of carbon dioxide, sourced from the air. From his findings, he deduced practical implications which revolutionized agriculture. Through his work, Liebig was the first to establish the need for fertilizer from a scientific point of view. His research also allowed him to determine which nutrients need to be present in fertilizer. This included simple organic compounds, but also inorganic substances such as salts. Based on this knowledge, Liebig developed the first artificial fertilizer, superphosphate, which led to an enormous increase in agricultural yields.
Liebig’s superphosphate fertilizer is still used today. Thanks to new findings, however, there are now a multitude of fertilizers which can provide the necessary nutrients based on the plants and soil conditions.
Kekulé: dreamer or fibber?
Liebig’s students carried on his legacy through conducting fundamental chemical research. One such example is August Kekulé (1829–1896), who was inspired by Liebig to study chemistry during his time at the University of Giessen instead of becoming an architect as Kekulé’s family had envisaged. In 1858, Kekulé recognized the ability of carbon atoms to bond directly with one another to form chains. This explained how the few elements found in organic matter could form such a diversity of organic substances. In 1865, Kekulé also published findings on the structure of benzene.
According to his own statements, both of Kekulé’s groundbreaking ideas were inspirations from dreams – but the truth behind this is disputed. Kekulé is regarded as an intellectual who disparaged the culture prevailing among chemists and industrialists at the time: a pragmatic, positivistic way of thinking was spreading – it was a blind sense of empiricism which afforded no room for imagination.
Christoph Meinel – a historian of chemical sciences – doubts the truth behind the dream anecdote, first told by Kekulé during a speech at a celebration in his honor. He states: «Kekulé’s ambivalent attitude toward the mentality present during this historical period, known as the ‹Gründerzeit›, and toward the patriarchal views of Berlin society resonates only too clearly in his speech. When Kekulé finishes narrating his vision with the words ‹Let’s learn to dream, gentlemen!›, the irony is very difficult to ignore given the prominent profile of those in attendance, who represented Prussian bureaucracy, Gründerzeit industries, and the elitist universities of the time» [1].
Artificial colors: All thanks to benzene
Regardless of whether Kekulé’s anecdote was based on true events or not, his discovery of the benzene structure and its importance to chemistry cannot be denied. Knowledge of organic and aromatic structures enabled systematic synthesis of the same molecules. The work of chemists was increasingly shifting from the isolation of substances from nature to the synthesis of artificial substances. The colorant industry experienced a boom after the discovery of the benzene structure, as this meant that a multitude of artificial colors could now be produced. Indigo production, for example, became an economically significant industrial process.
Colorant syntheses have not lost relevance since their invention in around 1900 – in fact, quite the opposite case. Colorants have been continuously developed for numerous properties and functions. This makes them inherently more complex than their primitive predecessors.
Check out our final article in this series to learn about the advancements of chemistry around World War II. Click the link below for Part 4.
Reference
[1] Sponsel, R. and Rathsmann-Sponsel, I. Kekulés Traum. Über eine typisch-psychoanalytische Entgleisung Alexander Mitscherlichs über den bedeutenden Naturwissenschaftler und Chemiker August Kekulé (1829-1896), Mitschöpfer der Valenz-, Vollender der Strukturtheorie und Entdecker der Bedeutung des Benzolrings. Alternative Analyse und Deutung aus allgemeiner und integrativer psychologisch-psychotherapeutischer Sicht. http://www.sgipt.org/th_schul/pa/kek/pak_kek0.htm (accessed Aug 15, 2016).
