When Perkin washed the black goo out of the test tube, however, he saw something that intrigued him: a bright purple residue on the glass. The color was vivid, and it clung stubbornly to the glass. Even more interestingly, when he treated the gunk with alcohol, its purple color transferred flawlessly to a cotton cloth he used to clean his test tubes. Perkin had stumbled upon the molecular magic of aniline. Benzene, toluene, and other components of coal tar were colorless because they absorbed ultraviolet light undetectable by the human eye. But if those aromatic hydrocarbons were treated with an acid to create aniline or another amine, after some additional steps the newly synthesized molecules very efficiently absorbed light particles from specific wavelengths in the visible spectrum. The young chemist did not know why the resulting color was so vivid; the ability of molecules to absorb photons at specific wavelengths based on the structure of their shared electron bonds would not be worked out for another fifty years. He did not even know exactly what he had created; the precise molecular structure of his new chemical would not be deduced until the 1990s. But Perkin did not need anything more than his own eyes to know that what was at the bottom of his test tube might prove very useful, especially after its color transferred so flawlessly onto the cotton cloth. A few months earlier, Perkin and a fellow student had tried to synthesize a textile dye and failed; now he had somehow succeeded while trying to create a medicine for malaria. As Perkin knew, whoever created the first artificial dye capable of staining silk, cotton, and other fabrics with a beautiful color might get very rich. Perhaps, the teenager thought, his failed experiment might not be a failure after all.
Dyes were a very big business, and always had been. The human impulse to drape our bodies in color is primal; ancient cultures from India to the Americas colored their clothes and skin with dyes extracted from wood, animals, and flowering plants. The most celebrated hue of the ancient world, by far, was Tyrian purple. It could be produced only from the milky mucosal secretions of several species of sea snails, or whelks, especially one in the Eastern Mediterranean known as the spiny dye-murex. The reddish purple dye was prized because it was both dazzling in hue and vanishingly scarce. Each murex typically produced only a few drops of dye—and only when freshly caught. It was a color of legendary origin, supposedly discovered by Heracles (Hercules, to the Romans). According to Greek myth, the great hero saw that his dog’s mouth was stained purple after chewing shells on the Levantine shore. Heracles considered the hue to be so magnificent that he presented a purple robe to the king of Phoenicia, who promptly declared the color to be a symbol of royalty and made Tyre the ancient world’s center of murex dye production. And that is why, on the Ides of March in the year 44 B.C., Julius Caesar was wearing his ceremonial robe of Tyrian purple when he was slain by Brutus in the senate house of Rome. It is also why, thirteen years later at the Battle of Actium, the sails of Cleopatra’s royal barge were dyed vivid purple.
With the decline of the Roman Empire, the elaborate system of murex cultivation and dye production established by the Romans disappeared, and so did the purple hue itself. A millennium of grays, browns, and blacks followed. A new dye industry finally arose in the late Middle Ages, allowing Catholic cardinals to cloak themselves in scarlet drawn from the shells of tiny kermes insects and tapestry makers to weave with vivid reds from dyewood trees native to India and Brazil. There were purples, too, mostly from lichens, but they were pale and faded quickly. The deep reddish purple of Caesar and Heracles, hue of power and wealth, monarch of colors, was no longer in the dye maker’s palette. It was gone, sustained only in legend.