“Unveiling the Secrets of William Perkin’s Mauveine Dye: A Pioneer of the Victorian Chemical Industry”

In the mid-19th century, a young chemist named William Perkin accidentally created a dye from coal-tar extracts that would revolutionize the chemical industry of the Victorian era. This dye, known as aniline mauve or mauveine, not only transformed the textile industry but also set Perkin on a path to become one of the most celebrated chemists of his time. However, recent analyses suggest that we may have underestimated Perkin’s genius.

John Plater, an organic chemist from the University of Aberdeen, UK, has been studying Perkin’s mauveine dyes found in Victorian stamps and textiles. His findings suggest that Perkin may have had a greater understanding and control over the chemistry of the manufacturing process than previously thought. “Far from the accidental chemist, he really was a true pioneer of his time,” says Plater.

Perkin’s mauve dye, derived from aniline produced from the benzene in coal tar, is a complex substance. The dye contains several distinct chromophore molecules, which were produced in the factory-based manufacturing process by Perkin and later competitors. The aniline used in the process contained isomers of toluidine, which also contributed to the final product.

The exact mixture of different forms of mauveine in surviving samples can act as a fingerprint of its provenance and method of synthesis, showing where and how it was made. The different mixtures also give slightly different shades, and Perkin himself spoke of a ‘red shade’ – which was considered more attractive – and a ‘blue shade’.

Plater has conducted careful detective work to determine the compositions of mauve dyes from different sources. Samples of the bottled dye, allegedly from 1856, and mauveine-dyed fabrics are kept in several museums, including London’s Science Museum, the Manchester Museum of Science and Industry and the Chandler Museum of Columbia University in New York.

However, a more accessible source is Victorian stamps: Perkin’s mauve was used for the lilac-coloured six-penny stamps throughout the latter half of the 19th century, of which many still exist. Plater has used liquid chromatography–mass spectrometry to identify the forms of mauveine in several of these stamps, as well as from a sample of the dye in the Manchester museum.

Interestingly, while all of these mauves, traceable to the manufacturing plant Perkin set up with his father and brother, have a similar composition, they are different from the mauveine that results from the method Perkin actually patented in 1856.

“The difference between museum-housed mauveine and that made by Perkin’s patented method is striking,” says Plater. “I tried many times to make the former using Perkin’s patented method, by adjusting the composition of the amines oxidised, but it never works and always gives a different type of mix of chromophores.”

Plater concludes that this was deliberate. The method in the patent gives a mixture of four types of mauveine chromophore, but the stamps and museum samples have only two key ones, and has the more desirable ‘red shade’. By reconstructing the chemistry, Plater believes the latter dye was deliberately made by incorporating a chemically modified form of toluidine in the mixture. This, he says, improves the yield and simplifies the mix of products. It seems that Perkin knew this, but never revealed it.

“I think he saw this reaction as a major leap in the production process and he wanted it kept secret to stop the French and Germans taking it over,” says Plater. “It seems to me that he never fully revealed what he did to scale-up the production of his famous dye.”

“Mauveine is a wonderful detective story,” says Henry Rzepa of Imperial College London in the UK, who has collaborated with Plater on the synthesis and analysis of mauveines. “Perkin’s public descriptions of its manufacture held only part of the truth. John has deepened the story by combining both syntheses in the lab and analysis of original samples.”

“Perkin was probably the first to realise that R&D would be needed to out-compete rivals in the fine chemicals industry,” Rzepa adds. “Ironically, the German synthetic organic chemistry industry invested far more heavily in it than Perkin had the resources to do.”

This revelation not only sheds new light on Perkin’s genius but also underscores the importance of research and development in the competitive world of fine chemicals. It seems that even in the Victorian era, the race for innovation was as fierce as it is today.