Billy Perkin : The Boy Who Dyed

Billy Perkin : The Boy Who Dyed

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William Henry Perkin was born this day, in London, 180 years ago. His accidental invention revolutionised the fashion and textile industry and, in what is infinitely more important, ensured that another Nil Darpan may never need be written. Also, he probably saved a lot of innocent snails from slaughter. As Google honours Perkin with a doodle (header image), the Nerd Druid delves into the life and times of Billy Perkin [Note:BPerkin], the father of the synthetic dye.


Indigo.

A simple word, six letters, three syllables. Nowadays, in India, it is most associated with a certain brand of budget airline. So much so, that a google search this morning yielded a full first page of IndiGo (the airline) results, and none whatsoever of either the colour or the dye, both of which have seen their fair share of history.

Indigo, historical dye collection of the Technical University of Dresden, Germany

Indigo, as a dye, has ancient origins. According to Pliny the Elder, the Harappans extracted the dye from a certain plant (Indigofera tinctoria) that grew in the Indus valley. The Ancient Greek term for the dye was Ἰνδικὸν φάρμακον (Indikon farmakon). This later became indicum in Latin and later indigo in Portuguese. The Silk Route brought indigo to Europe, when Marco Polo reported about it in 1289. However, a further three centuries went by before the European textile landscape realised the potential of the dye, and started large-scale manufacture. The process was not easy, for indigo is a tricky dye, and tends to oxidise easily on contact with air. Once oxidised, it takes its familiar dark blue hue, is insoluble in water, and is then quite permanent. As such, before use, it needs to be reduced to its leuco or white form, and kept in this form, unoxidised, until it is ready to be used. Medieval European technology did ultimately figure out how to tame it, but it was still a laborious and often dangerous process to extract it. Wordsworth has written many a worthy word about the plight of indigo farmers in England [Note:Wordsworth], as has Dinabandhu Mitra about their Indian cousins.

About the time Nil Darpan was being written, that is, about the latter half of the 1850s, a young, talented and precocious chemist was hard at work at his ramshackle hut-lab in London, trying hard to extract quinine from aniline.

Malaria is one of the greatest human killers in history. Each year, more than 200 million people are infected worldwide, of whom more than 700,000 do not make it. Malaria is endemic in many areas of Africa and Asia, and is a primary cause of poverty and a major hindrance to economic development. Malaria has been around since the time agriculture began, ten thousand years ago. While never as singularly destructive as the Black Death, the American smallpox epidemics or the Spanish flu epidemic of 1918, malaria has always been around, whether in civilised urban centres (ancient Rome) or in battlefields (medieval Europe).

19th-century illustration of Cinchona calisaya

The Quechua were the first to find an effective remedy for malaria. Indigenous to Peru, Bolivia and Ecuador, the Quechua would prepare and use a tincture of the bark of the cinchona tree to control the fever to a large extent. Jesuit monks brought the treatment to Europe in the middle of the seventeenth century. In 1820, French chemists Pelletier and Caventou extracted the active ingredient from cinchona bark and named it quinine. For more than a century hence, quinine would prove to be the most miraculous drug human beings had come across.

In spite of its great usefulness, there remained, in the middle of the nineteenth century, no sure way of synthesising quinine in the laboratory. The only source of quinine was the bark of the cinchona tree. In the early nineteenth century, in an attempt to maintain their monopoly over cinchona bark, Peru and adjoining countries began preventing the export of cinchona saplings and seeds. Although the Dutch did manage to smuggle seeds outside South America and grow cinchona in Indonesia, the need for synthetic quinine was acutely felt. This is where August Wilhelm Hofmann, later von Hofmann, came in.

August Wilhelm von Hofmann (1818 – 1892), German chemist

Hofmann was an exceedingly talented German chemist who, at the young age of 28, had been appointed the first director of the Royal College of Chemistry in London. The year was 1845. The appointment was not without merit. Just two years previously, Hofmann had shown that the substances crystallin, kyanol (or cyanol), benzidam, and oil of anil, synthesized independently from different sources, were all actually the same substance. Crystallin had been synthesised by Unverdorben in 1826 when he carried out destructive distillation of a certain naturally occurring dye. Fourteen years later, in 1840, Fritzsche had treated the same dye with caustic potash (potassium hydroxide, KOH) and obtained oil of anil. Six years earlier, in 1834, Runge had obtained the beautiful blue coloured substance kyanol by treating an isolate of coal tar with chloride of lime (Calcium hypochlorite, Ca(ClO)2). Finally, in 1842, Zinin had obtained benzidam by reducing nitrobenzene. After Hofmann’s affirmation, this substance came to be known as aniline.

And the dye used by Unverdorben and Fritzsche?

Indigo.

Hofmann and Perkin were a good match. Both were young, highly talented, and had a tendency to think outside the box. Perkin’s father, himself a builder, wanted him to be an architect. Billy Perkin point-blank refused to join the family business and instead, in 1853 at the age of fifteen, joined the Royal College of Chemistry, under Hofmann. In two years he had impressed his boss enough to be made assistant. Given the desperate need to synthesize quinine, and based on his own hypothesis, Hofmann had the perfect project for his precocious assistant : synthesize quinine from aniline.

2D structure of aniline

Aniline is a rather simple organic molecule, and can be thought of as the organic equivalent of ammonia, with one hydrogen atom replaced by a benzene ring (C6H5NH2). Quinine, on the other hand, is rather more complicated (C20H24N2O2). It was Easter, Hofmann had gone home, leaving Perkin to muck about in his own ramshackle lab. Following Hofmann’s idea, Perkin decided to attack the problem by dissolving aniline in sulphuric acid and then oxidising it with potassium dichromate (K2Cr2O7). What he got instead was a black precipitate. Thinking he had failed, he tried washing it out with alcohol.

Scientific discoveries are often serendipitous. While detailed planned experiments do often bear fruit, a very large and recent example being the detection of the Higgs boson by the LHC and the detection of gravitational waves by LIGO, accidental discoveries tend to be…miraculous.

What Perkin (probably) did not know was that the dichromate he used was impure. In it was mixed isomers of toluidine (C6H5NH2CH3) [Note:Toluidine] which reacted with the aniline and the alcohol to form a beautiful purple compound. Perkin had an interest in painting and photography, and his expert eye soon told him that he had something amazing in his hand.

While extracting indigo dye was complicated and laborious, extracting purple dye was far more so. In Perkin’s time, purple one of the rarest and most expensive dyes in the world. Extraction and manufacture of Tyrian purple was a lengthy and expensive process, involving glandular secretions of murex sea-snails, a rare species of molluscs [Note:TyrianPurple]. Which is why it was deemed a royal colour, fit for personages such as Alexander and Justinian I

Byzantine Emperor Justinian I clad in Tyrian purple, 6th-century mosaic at Basilica of San Vitale

Perkin’s mauveine made Tyrian purple, and its naturally occurring cousins, obsolete. Not only did mauveine have a rich and vibrant purple colour, tests on silk and other fabrics showed that it was quite durable too. Perkin sent off a sample to the dye works in Perth, Scotland, and received very favourable replies. In August of that year, Perkin, still 18, filed for a patent for the dye mauveine. With capital from his reluctant father and on-field help from his brothers, Perkin slowly built up his business. The Industrial Revolution helped him, and so did the adoption of purple dresses by Empresses Victoria of England and Eugénie of France. It became both a fashion statement and a matter of prestige to own purple dresses, especially crinolines (hooped skirts). Perkin’s Mauve provided a cheap way to own purple. Thus, with a little help from history, hard work, and sometimes luck, William Henry Perkin built the first synthetic dyeing industry in the world.

Sir William Henry Perkin (1838 – 1907), English chemist

And in doing so, he saved the lives not only of humans labouring in dyeing factories, but also of the uncountable number of murex sea-snails that would no longer have to be sacrificed for Tyrian purple.

Footnotes

Note:BPerkin The Nerd Druid is not certain that Sir William Henry Perkin was actually ever referred to as Hey Billy Perkin/There’s snot in yer muffin. However, within the field of probabilities and plausibilities, one might not be, presumably, too far off the mark herein should one deign to, er, presume certain presumptuous presumptions about young Billy. I mean Sir William.

Note:Wordsworth In his autobiographical poem The Prelude, William Wordsworth speaks of the plight of the indigo dye workers in his hometown of Cockermouth thus

Doubtless, I should have then made common cause

With some who perished; haply perished too

A poor mistaken and bewildered offering

Unknown to those bare souls of miller blue

Note:Toluidine Toluidine (C6H5NH2CH3) is basically aniline plus a methyl (CH3) group. Depending upon the position of the methyl group with respect to the amine group, toluidine has three isomers : o-toluidine, m-toluidine, and p-toluidine. In the ortho-isomer, the amine and methyl groups sit next to each other (2-methylaniline); in the meta-isomer, they are one space apart (3-methylaniline); while in the para-isomer, they are two spaces apart (4-methylaniline). Perkin’s dichromate had the ortho and para varieties, the former being a dye itself. 

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Caption : 2D structures of the three isomers of toluidine

Note:TyrianPurple The following passage has been taken directly from Wikipedia :

The process of making the dye was long, difficult and expensive. Thousands of the tiny snails had to be found, their shells cracked, the snail removed. Mountains of empty shells have been found at the ancient sites of Sidon and Tyre. The snails were left to soak, then a tiny gland was removed and the juice extracted and put in a basin, which was placed in the sunlight. There a remarkable transformation took place. In the sunlight the juice turned white, then yellow-green, then green, then violet, then a red which turned darker and darker. The process had to be stopped at exactly the right time to obtain the desired color, which could range from a bright crimson to a dark purple, the color of dried blood. Then either wool, linen or silk would be dyed. The exact hue varied between crimson and violet, but it was always rich, bright and lasting.

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