The German Genius

chemistry across the Rhine. Using new equipment that von Liebig designed himself, which allowed much quicker and more accurate analysis, he and his students analyzed many of the more mysterious natural substances, including quinine, morphine, and strychnine, finding out in the process that their molecules contained relatively large numbers of atoms but not in simple ratios.
    They also discovered the important phenomenon of isomerism, which came about when von Liebig was in Giessen studying the salts of fulminic acid, and Wöhler was in Stockholm, collaborating with Jöns Jakob von Berzelius (1779–1848), the famous Swedish chemist, and examining another acid, cyanic acid. 6 Though completely different in their properties (cyanic acid was not at all explosive, as the fulminates were), Wöhler obtained exactly the same results for his analysis of silver cyanate as von Liebig did for his silver fulminate. How could that be? The two men met in Frankfurt to compare results, and, to everyone’s surprise, decided that they were both right. This meant that two different substances could have the same elemental composition. In this specific case, cyanic acid and fulminic acid each contained carbon, nitrogen, oxygen, and hydrogen in exactly the same proportions. It was Berzelius who coined the term “isomerism” to describe the phenomenon, more and more examples of which would be uncovered in the coming years. 7
    It was a phenomenon slow in being grasped partly because, throughout the eighteenth and nineteenth centuries, organic chemistry, not to mention physiology, were muddied by the concept of “vital force”—the belief that living organisms could not be explained by physical laws alone, that there must be some “special influence” at work. This view was reinforced by the sheer extent and diversity of organic substances which, it was thought, only a deity could have envisaged. As more analyses were completed, and more substances found to be made of carbon, nitrogen, and water only, the mystery deepened. 8
    It was in this intellectual and religious climate that Wöhler performed the experiment for which he will always be remembered. By treating silver cyanate with ammonium chloride he was hoping to derive the ammonium salt of his cyanic acid. However, after he had filtered off the (insoluble) silver chloride and evaporated the residual solution, he found he had “colourless, clear crystals in the form of slender four-sided dull-pointed prisms.” To his astonishment, they resembled nothing so much as urea. “This similarity…induced me to carry out comparative experiments with completely pure urea isolated from urine, from which it was plainly apparent that [urea and] this crystalline substance, of cyanate of ammonia, if one can so call it, are completely identical compounds.” In fact, the two compounds were not identical—they were isomers, but even so Wöhler’s was an iconic experiment: he had manufactured a substance, urea, hitherto the product solely of animals, out of inorganic materials and without any intervention of vital force . “Von Liebig and his successors regarded [this] experiment as [the] beginning of a truly scientific organic chemistry.” 9
    The vital force did not vanish overnight but it did now come under sustained attack, not least from von Liebig, who carried out a raft of experiments on food consumption and heat production in animals. He showed beyond all doubt that the energy that characterizes a living organism is a product of the combustion of food in the tissues, with no need for other mysterious sources such as “electricity” or “nervous energy” or “vital force.” 10
    B ENZENE : A N EW E RA IN C HEMISTRY
     
    Physiological chemistry was one line of biological research. Another, unlikely as it may seem, grew out of gas lighting. By 1816, twenty-six miles of metal piping had been laid in London to carry illuminating gas to factories and for street lighting. * Early gas supplies were made, not from coal tar, as they were later, but from the more obviously organic whale or cod oil, which produced a high residue of liquid waste that would condense out, either at the works or in the pipes themselves. This waste, the so-called gas oil, was produced in sufficient quantities for the owners of the gasworks in London to send a sample to Michael Faraday in 1825 to see what it was and what it might be used for. He experimented for about ten days and found it to be a