We have heard of the colour "Imperial Purple" since Roman times. Only royalty and the wealthy could afford it as it was made from rare sea snails.
Then one day, quite by accident a young chemist, William Henry Perkin, discovered how to make the colour mauveine or mauve quite by accident.
He was, in fact, looking for a cure for malaria as explained in the clip above. He didn't find a cure for malaria - he found a colour! Later he found others.
Queen Victoria wore a mauve dress to her daughter's wedding and an instant fashion statement was made. Everyone wanted it.Dresses back then required a lot of fabric so Perkin was actually able to combine science with the fashion industry and go into producing mauve or purple garments for the masses.
Textiles have evolved greatly over the years, in quality, variety and methods of production. Similarly, the dyes that make these fabrics so valuable have also undergone enormous changes. It has only been in the past 150 years that true progress has been made, with the invention of synthetic dyes. However, these dyes could never have evolved without the important discoveries that dominated the world of science in the eighteenth and nineteenth centuries: in 1774, Antoine Lavoisier disproved the widely accepted theory of phlogiston, the concept of an inflammable substance that is present in all living things; twenty years later, Jons Jakob Berzelius developed the beginnings of the periodic table; in 1803, John Dalton revolutionized our view of the world with the introduction of the modern atomic theory.
Perhaps the most important innovation in science, for the dye industry, was made by German chemist Friedrich Wohler, in 1828. He discovered that he could convert ammonium cyanate- an inorganic substance- into urea- an organic substance. This was the first evidence that the fabled "life force" wasn't necessary for creation of organic substances, or substances containing carbon. With the first artificial production of a natural substance, this discovery provided the necessary base to begin searching for synthetic substitutes for natural dyes.
Up until the 1850s, dyes were either vegetable, mineral or animal based. The whole process was both costly and impractical. Dyes couldn't be made in large quantities consistently, and they had to be shipped over large distances. The industrial textile revolution in Europe called for a cheaper synthetic dye that could be produced in mass quantities. The most common and valuable dyes were Madder- a red mauve, Indigo- a deep blue, and Saffron yellow. These three dyes were both difficult to produce and expensive.
Madder was distilled from Rubia tinctorum, a plant found in Turkey and the British West Indies. Its main coloring component was alizarin, and it was used to dye cellulose products. It had excellent fastness when combined with an alum-tannin-alum mordant, an insoluble red metal complex found in fiber. Mordants were used to help seal the color into the fabric and preventing fading. However, Madder was an economic disaster for two reasons: using the complicated process, called "Turkey Red", it could take up to one month to complete a bolt of cloth, and the dye had to be shipped from Turkey or the British West Indies to Europe.
Indigo is a blue colorant of vegetable origin that was obtained from Indigofera tinctoria in India. The plant contains indoxyl, which oxidizes with the air when it's fermented to produce the dye. Indigo is insoluble in water, which made for excellent fastness. Indigo could also be obtained from certain snails, such as the murex. Before the introduction of Indigo, Europe had previously used woad to produce blue dye.
The third dye, Saffron, was first used in ancient Minoan civilizations as early as 1900 B.C. They obtained the saffron lily from the hillsides of Crete. When the stamens were simmered, they produced an orange broth which dyed wool bright yellow. To prevent the dye from washing out, an alum mordant had to be used to seal the color fastness into the cloth. The whole process was lengthy and produced mediocre fastness compared to the vat dying technique employed for Indigo and Madder. Just as with Indigo and Madder, a new source of dye needed to be found.
The research began in earnest in 1771, when Woulfe discovered picric acid by combining indigo and nitric acid. He found that this caused silk to turn a greenish yellow. This new dye was unsuccessful due to its poor light-fastness, but it was still used to turn Indigo to bright green. Later, in 1818, Prout experienced similar problems with Murexide. He had created it by combining uric acid, nitric acid, and ammonia. Once again, the dye proved unsuccessful due to poor fastness, which part two of the paper will discuss. The failure to produce a practical synthetic dye was mostly due to the lack of scientific knowledge of organic chemistry. Despite the failure, these men had taken important strides in introducing the possibility of synthetic dyes.
In 1826, it seemed that the dye research for reproducing Indigo had taken a favorable turn with Unverdoben's discovery of aniline through distillation, or heating the indigo at a high temperature. Aniline is an important dye intermediate of indigo that can be reproduced artificially from coal tar. However, aniline remained rare until 1845, when British chemist and physicist Michael Faraday discovered benzene and Mansfield determined that benzene was provided by coal tar, a highly available resource. From there, Zinin and German chemist August Wilhelm von Hofmann deduced a way to nitrate benzene to produce aniline with some regularity. However, the ball of progress stopped rolling until 1856 when William Henry Perkins stepped on the scene.
William Henry Perkins, who attended the Royal College of Chemistry of England, discovered a purple dye almost by accident. He had experimented on the dichromate oxidation of aniline and found that it formed a black solid. From this solid, he isolated a dye that colored silk purple. Perkins demonstrated that his purple dye was actually composed of two dyes. After consulting with a prominent commercial dyer, Robert Pullar of Perth, it was determined that the dye was favorable, in that it had excellent light and washing color fastness. Perkins obtained a patent for the dye and set up a company to commercially process the dye.
The work on the factory began in 1857 and was fraught with technical problems. The large scale nitration and reduction of benzene was difficult to maintain and produced a poor yield of aniline. It wasn't until 1864 that Perkins was able to offer a solid dye on the market.
Aniline spawned an entire new angle of research: triphenylmethane dyes. In 1856, Natanson created magenta. Verguin managed to produce the magenta by oxidizing crude aniline with stannic chloride, a tanning solution, in 1859. At the same time, Hofmann determined that the principal components of magenta were homorosaniline, rosaniline, and toluidine. Magenta quickly became more popular than Aniline Purple and was manufactured all over Britain. Hofmann later developed a violet in 1853, which was followed by Girard Violet Imperial in 1860. The next milestone in dye research was attained by Nicholson and Gilbee in 1862, when they sulfonated N-phenyl derivatives of Magenta to produce dyes with better solubility. These became the first acid dyes for wool, which part two will discuss in more detail.
The only other research that was done up until 1865 involved azo, a non-triphenylmethane dye. The difference is strictly structural: azo dyes contain at least one set of two nitrogens double bonded to each other whereas triphenylmethane dyes don't contain any azo groups. Martius discovered it in 1863, by coupling diazonium ions and amines. Bismarck Brown, the name of the first azo dye, lead to an entirely new class of azo dyes, which were developed by Greiss. In 1865, when German chemists began to assert themselves in the dye industry, they began a new era in innovative synthetic dye research and quickly cornered the commercial dye market.
The year 1865 brought about significant changes in synthetic dye research. The focus of investigation made the switch from empirical research to a deductive approach. Friedrich August Kekulé von Stradonitz, a German chemist, formulated the cyclohexatiene form of benzene, which explained the aromatic character of benzene in terms of oscillating bonds. This revelation gave scientists everywhere a greater understanding of dye structure.
Madder, the natural mauve dye, was created synthetically in the form of alizarin by Graebe and Liebermann in 1868. Unfortunately, their method of synthesis included a high cost process, making their dye economically unstable. Luckily, in 1869, Perkins and his partner, Heinrich Caro developed a favorable method of synthesis by using substances that had been fused with sulfur. Perkins had no other competition in Britain and was able to make a profit for five years until his business failed due to German competition. Perkins' company wasn't the only casualty; Madder was the first natural dye to be lost entirely to synthetics.
The invention of synthetic dyes revolutionized the textile industry. It created a cheaper, readily- available option to the costly, rare natural dyes. The scientific mindset that permeated the culture provided an excellent springboard from which to jump into the newest age of textile dyes. However, the period wasn't without its casualties: the same dyes that were an art, a revered process, were lost to science and technology as society pushed to advance. Synthetic dyes launched a new age of fast-paced commercialized production that continues even now, driving inventors, researchers, and scientists to create, learn, and discover new innovations.
By Meredith Dorner
With thanks to Silk Circa 1840
This picture from Wiki
Top Picture credit:RSC
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