Saturday, July 26, 2008

Aniline Dyes- Unintended Consequences Extraordinaire

Jack Dini
Livermore, CA

(From a series on unintended consequences)

Aniline dyes are perhaps some of the best examples showing how many divergent paths can lead to unintended consequences. Painting a wooden fence with coal tar to keep dogs from a yard led to what was the first of a multitude of unexpected discoveries. In another case, instead of finding quinine, one researcher essentially founded the synthetic dye industry. Another dye, indigo, was synthesized because a thermometer broke and the spilled mercury catalyzed a reaction that caused collapse of the Indian indigo industry. (1) In another example, some dye accidentally spilled on a bacteria culture dish led to the new science of bacteriology. (2) Noting that some dyes killed certain parasites, one scientist developed the concept of chemotherapy. (3) Work on distilling fractions of coal tar also led to the discovery of carbolic acid, used first in antisepsis by surgeons like Lister in Edinburgh, who developed methods of spraying the liquid. (2) The study of dyes also helped launch the “French Impressionist” painting movement.

One could also argue the case that dyes were responsible for Germany developing into a power that could dominate World War I. By the time the war came along, some leading German companies had made such profits from the dye industry that they were able to branch out into pharmaceuticals and explosives. (4) In the United States prior to World War I, job opportunities for chemists were extremely limited since dyes and drugs were imported from Germany. As a result, the typical American research chemist, among the lower paid professions in the country, studied soils for the US Department of Agriculture. (5)

James Burke sums all this up well, “Aniline dyes are a particularly good example of the interactive and unforseen way scientific and technological discovery is triggered.” (2) In this essay we’ll concentrate on the early beginnings of the synthetic dye industry; some others dye-related activities are covered in subsequent articles. First, an answer to the question—what are aniline dyes? They are artificial dyes derived from coal tar, which was the messy residue left after lighting gas from coal or after obtaining coke (for iron making) from coal. Since there was so much of the stuff around, folks were trying to find uses for it. Most likely, the earliest event came when Friedlieb Ferdinand Runge (1794-1867) tried to keep the neighborhood dogs out of his garden. He erected a wooden fence which he painted with coal tar (creosote) as a preservative. As an added inducement to keep the dogs from lifting their legs against his fence he scattered calcium hypochlorite all around to present a chlorine odor. When he inspected the fence the next day there were blue streaks on the white powder, obviously from the trajectories from dog urine jets. Runge discovered that the blue color was the result of oxidation of the hypochlorite by some constituent of the coal tar. He called the blue substance Kymol. Years later, Professor August Wilhelm Hofmann showed that the parent compound in the coal tar was aminobenzene, or aniline, and Kymol was the first synthetic prototype of a dye. (1)

However, the really pioneering event in this field is attributed to William Henry Perkin (1838-1907), a student at the royal College of Chemistry in London. At age seventeen he was trying to derive quinine from coal tar chemicals. The reason for this was that many English in the tropics were dying from malaria and the curative, quinine, wasn’t available in England’s colonies. (2) Perkin’s professor, August Wilhelm Hofmann, a German chemist who came to London at the personal invitation of Queen Victoria (the same Hoffmann mentioned above when discussing Runge), suspected that perhaps quinine could be derived form coal tar. (6)

An ambitious sort, Perkin had his own laboratory at home. During an Easter, break he mixed some aniline with potassium bichromate and ended up with a messy substance. Perkin noted, however, that this material had a purple tinge. He added alcohol to this concoction and a beautiful purple color appeared. It was a synthetic dye. He called it Tyrain purple, later it was called mauve. He realized that this would be a good dye for textiles. (7)

Perkin patented his process for the preparation of the dye and financed by his father, started a dye factory near London. This was the beginning of the synthetic dye industry. It was monumental in that it rescued the poor and middle classes from the age old austerity of hues. For the first time in history, inexpensive dyes became available and people, other than the rich, no longer had to live their lives in untreated drab and dingy fibers. (8) Although the new industry had started in Britain, it operated mainly in Germany up to World War I.

But Perkin did more than just find a synthetic dye. He essentially was responsible for a new way of doing scientific research. Sharon Bertsch McGrayne notes, “Perkin’s mauve spawned the world’s dye and pharmaceutical industries. His synthetic dye was the first in a cascade of colors that institutionalized scientific research, professionalized chemists, changed the economies of vast regions, and helped make turn of the century Germany the world’s leading industrial power. Perkin was an adolescent college dropout, but his work dramatized the technological power of science and ushered in our uniquely science-oriented epoch. The discovery of mauve by Perkin has been credited with starting the tremendous development of organic chemistry in the latter half of the nineteenth century, especially in Germany. With the possible exception of Apple creators Steven Jobs and Steven Wozniak, college dropouts who developed the first ready-made computer in their teens and twenties, it is difficult to imagine a young person’s invention that has started such an enormous revolution.” (9)

There’s more as James Burke notes, “German expertise with color lead to discoveries in apparently unrelated fields, such as that of medicine: the investigation of the chemistry of color led to systematic thinking about the structure and effects of chemicals, and this led directly to drugs like aspirin and to techniques for staining tissue for diagnosis. It was this use of tissue staining to identify potential sufferers from syphilis that led to the disease being treated successfully with the stain chemical itself. The new drug was called Salvarsan.” (10)

While on the subject of color, here’s one last item of note. French chemist M. E. Chevreul, working with dyes, invented an extraordinary new color tool. By taking the three primary colors, red, blue and green and interspersing them with twenty-three color mixtures, he got a chromatic circle of seventy-two colors, his ‘law of simultaneous contrast.’ Then he toned each color by adding a black or white, thereby creating 15,000, the tone-chromatic circle used by all dyers ever since. (11) In addition, as Burke also points out, “Chevreuls’s placement of color for effect did much more then help the textile industry. It also changed the world of art by triggering the French ‘scientific’ impressionist movement. Painters like Seurat, Signac, and Pissaro used Chevreul’s new law of contrast in their work. They placed spots of different colors next to each other to create the impression of a third color, and in doing so achieved the distinctive shimmering effect for which impressionism is famous. (11)

So Perkin, in looking for a cure for quinine, started us down the road to many and varied unintended consequences. And concluding with Perkin, by the age of twenty-three he was rich and famous and by age 35, already a millionaire, he left manufacturing to return to the scientific research he had loved in his youth. In his private laboratory he synthesized coumarin, the first perfume from coal tar, and prepared cinnamic acid by a method so generally useful that it became known as the Perkin reaction. (12)

1.Walter Gratzer, Eurekas and Euphorias, (Oxford, Oxford University Press, 2002), 45

2.James Burke and Robert Ornstein, Axemaker’s Gift, (New York, G. P. Putnam’s Son’s, 1995), 197

3.James Burke, The Pinball Effect, (New York, Little, Brown and Company, 1996), 155

4.Stephen Van Dulken, Inventing The 19th Century, (Washington Square, New York, New York University Press, 2000), 188

5.Sharon Bertsch McGrayne, Prometheans in the Lab, (New York, McGraw-Hill, 2001), 111

6.Sharon Bertsch MeGrayne, Prometheans in the Lab, 15

7.Alexander Kohn, Fortune or Failure, (Cambridge, MA, Basil Blackwell, 1989), 46

8.Sharon Bertsch McGrayne, Prometheans in the Lab, 9

9.Sharon Bertsch McGrayne, Prometheans in the Lab, 10

10.James Burke, Connections, (Boston, Little, Brown and Company, 1978), 204

11.James Burke, The Pinball Effect, 93

12.Royston M. Roberts, Serendipity, (New York, John Wiley & Sons, 1989), 70

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