Before the mid-1850’s, the experts in the application and improvement of dyes, all obtained from natural products, were the textile colorists. It was their job to analyze the mainly vegetable-based extracts, such as the blue colorant from indigo and the red extract from the root of the madder plant, and to seek out ways of improving the dyes’ fastness. This required the application of chemistry, based on the organization of chemical elements and compounds according to their properties. The colorists conducted simple chemical analyses of the dyes, the organic, or carbon-containing. vegetable products and of certain metal compounds called mordants. The mordants fixed the dye to the fabric and often enabled the creation of several distinct colors.
While these studies were mainly empirical, they resulted in the accumulation of a vast body of knowledge that was made available in manuals and text books. Sometimes, however, details of new findings concerning dyes and dyeing processes were not revealed because of the tradition of regarding this information, on which the fortunes of dyers relied, as closely guarded trade secrets. Although patents for new chemical inventions, including dyes, were sometimes filed, the patent systems, where they existed, offered little protection to inventors.
Leading chemists carried out research in this field and managed to classify colorants according to their dyeing and other properties even without the benefit of modern equations and formulas. Some chemical investigators even considered the possibility of creating artificial or synthetic colorants or other useful products from readily available raw materials. One such raw material was coal tar. The constituents of the abundant and freely available coal tar were investigated by curious scientists. Distillation of coal tar gave mainly hydrocarbons, such as benzene, an aromatic compound containing six carbon atoms and six hydrogen atoms. Benzene is the simplest member of the aromatic class of compounds. In the 1850’s, chemist August Wilhelm Hofmann who served as head of the Royal College of Chemistry in London suggested that a coal-tar derivative might possibly be converted into artificial quinine.
In 1856, one of Hofmann’s assistants was the teenaged William Henry Perkin (1838-1907). Perkin decided to attempt the synthesis of quinine in his home laboratory during the Easter vacation. Though the experiment failed, Perkin decided to repeat it with a similar compound called aniline, and made in two steps from benzene. He soon found that the product could be transformed into a dye that colored a piece of silk a brilliant and fast purplish color. Perkin realized the significance of his discovery, and a few months later filed a patent in London for the synthetic process and product.
One hundred and fifty yeas ago, in late 1857, in partnership with his father and brother, William Perkin began industrial production of the dye at a factory in northwest London. The novel colorant was a success, though only after Perkin had instructed dyers and printers in its use. Early in 1859, English fashion observers gave the purple dye the name Mauve. Other chemists managed to produce a synthetic red coal-tar, or aniline, dye, which became the intermediate for blue and then violet dyes.
Patent litigation in Britain and France both created and destroyed monopolies; the lack of comprehensive patent systems in Switzerland and Germany enabled British and French inventions to be copied with little fear of litigation. In this way the synthetic dye and modern organic chemical industries were born.
In 1869, Perkin followed up his Mauve with another brilliant invention, a process for commercially producing the dye alizarin, which up until then was obtained from the root of the madder plant. However, by this time, several chemists were doing almost the same thing, particularly Heinrich Caro at the German BASF company. Unlike Perkin, these scientists were drawing chemical structures of the coal-tar derivatives. This was enabled thanks to Kekulé’s 1865 Benzene Ring Theory, according to which the six carbon atoms in benzene are held in a hexagon, with one carbon at each apex.
The BASF alizarin patent was filed in London during June 1869, just one day before William Perkin’s application arrived at the same patent office. The outcome was a Perkin-BASF cartel that divided the international market for this important dye, which was, incidentally, the first natural product of some complexity to be synthesized. With this success, chemical synthesis had, on the one hand, replicated nature in the form of artificial alizarin, and on the other hand, created entirely new products. Chemistry effectively reinvented and replaced traditional items. The first high-tech industry had matured.
In late 1873, Perkin retired from business and left the Germans to refine dye technology and chemistry. In 1874, Caro and the academic chemist Adolf Baeyer published a paper that gave the modern structure of alizarin, an achievement that bound science with industry. This and similar research led to the founding of the first industrial research programs and to the development of modern industrial research laboratories.
The dye industry grew tremendously in Germany, where its pioneers were the forerunners of BASF, Bayer, AGFA, and Hoechst, and also in Switzerland, at the factories of Geigy, CIBA, and Sandoz. German chemists lobbied for a patent system that protected chemical inventions, as introduced in 1877. During the 1870’s and 1880’s many dyes of the azo type, that contain the atomic grouping –N=N-, were discovered. In the late 1880’s, Caro designed the BASF Central Research Laboratory, forerunner of all main research laboratories in science-based industries. In 1897, BASF and Hoechst produced synthetic indigo on an industrial scale.
Dye-making firms diversified by converting dye intermediates into pharmaceuticals, such as Sandoz’s anitipyrin and Bayer’s Aspirin (both introduced in 1899). Dyes were also employed in early biomedical research, particularly by Paul Ehrlich who began work in this field in the 1880’s. Ehrlich used dyes’ color loss and color gain to explain reduction and oxidation processes in living cells, and from this research developed a model of the cellular surface. Dyes also became models for the first synthetic drugs to attack sites of infection within the body.
Ehrlich’s Salvarsan (1909) was an arsenic analog of an azo dye. Using analogies with the chemical structures of dyes, and a theory of color and constitution, Ehrlich drew up a model of drug action. However, the next major success in this field took place only in the mid-1930’s when the first sulfa drug (or wonder drug) was developed. This drug was Prontosil, discovered in 1936 as a result of experiments with a bright red azo dye originally discovered by Caro in the 1860s. No less significant were the studies on fermentation conducted just before World War I by the dye chemist Chaim Weizmann. Weizmann developed the acetone process, which came to be essential in the manufacturing of munitions, and contributed to the birth of modern biotechnology. These developments led some of the early dye firms to engage in biomedicine, biotechnology, and the life sciences, fields in which they are now among the world leaders.
Dr. Anthony S. Travis is Deputy Director of the Sidney M. Edelstein Center for the History and Philosophy of Science, Technology, and Medicine at The Hebrew University of Jerusalem, and Senior Research Fellow at the Leo Baeck Institute, London. He is recipient of the American Chemical Society History of Chemistry Division’s 2007 Edelstein Award.