Weâve been blogging and tweeting a lot about the historical inventions in the GREATforImagination campaign, with links to the key patents involved. Unfortunately, most British patents from before 1895 arenât available free online and can only be seen if you come to our building at St Pancras. Weâll be making full blog posts about some of these, to give you some more detailed information than can fit into a Tweet or the Instagram post.
Not every invention is made by people who see a problem and set out to find a solution to it. Curiosity-driven science can produce useful inventions that the scientists involved never anticipated. A classic example of this took place in 1856, when William Perkin tried to make an artificial anti-malarial drug, and instead discovered what would become the first totally human-created molecule to become the centre of a profitable business.
The eighteen-year-old Perkin was a student of the chemist August Wilhelm von Hofmann at the Royal College of Chemistry in London (eventually merged into what would become Imperial College). Hofmann had speculated to Perkin that on the basis of the atomic formulas then assigned to the chemicals, it would be possible to create the drug quinine by somehow combining two molecules of napthylamine with one of water. Perkin decided to try to synthesise quinine by oxidising allyltoluidine with dichromate. It is now known that the complex structures of organic molecules make such a naĂŻve approach based purely on atomic formulas useless. When Perkin failed, he decided to try oxidising aniline with dichromate (it was subsequently discovered that the aniline he used was contaminated with toluidine, with mauveine being created by the oxidation of both together), and discovered that the product obtained was a useful dye. Mauveine, as it became known, was the first cheap and stable purple dye, and when Perkin commercialised it a colour that had been traditionally associated with the richest in society became accessible to all. It was the first of the so-called azo dyes, which were among the first products of the modern chemical industry.
Perkin patented his dye and persuaded his relatives to fund him in creating a factory, near Greenford in west London. He continued to work in chemistry, discovering the âPerkin reactionâ to make cinnamic acid from acetic anhydride and benzaldehyde, and developing a way to commercially synthesise the natural dye alizarin (from the madder plant) from coal tar. Unfortunately, a rival German team simultaneously developed the same process and patented it one day earlier! Perkinâs lasting fame can be gauged by the fact that the Perkin Medal, the most important American prize for organic chemistry, and Perkin Transactions, for many years the British Royal Society of Chemistryâs main scholarly journal on organic chemistry, were both named after him.
Perkinâs mauveine is a mixture of up to twelve different compounds containing N-phenylphenazinium ring systems with additional amine and sometimes methyl groups. The structures of the most important two were not clearly discovered until 1994, because an incorrect structure of unclear origin had been repeatedly cited in the literature and assumed to be right. They are seen in the diagram, with the group "R" being a hydrogen atom in one of them, and a methyl (CH3) group in the other.
Further reading at the British Library:
Perkin, W.H. (1901). The origin of the coal-tar colour industry, and the contributions of Hofmann and his pupils. In Memorial lectures delivered before the Chemical Society 1893-1900 (pp. 596-637). London: Gurney & Barrow. Shelfmark W1/9939 â Perkinâs own description of his famous first synthesis of mauveine, the discussions that provoked the experiment, and his later career in the chemical industry.
Perkin, W.H. (1879). On mauveine and allied colouring matters. Journal of the Chemical Society, Transactions, 35, 717-32. Shelfmark (P) JB 00-E(8) â Perkinâs description of the physical properties and chemical reactions of mauveine.
Perkin, W.H. (1858). On the purple dye obtained from coal-tar. In Report of the twenty-eighth meeting of the British Association for the Advancement of Science. Paper presented at the British Association for the Advancement of Science, Leeds, September 1858 (p.58). London: John Murray. Shelfmark Ac.1181. â Perkinâs first brief scholarly announcement of mauveine.
Perkin, W.H. (1856). Producing a new coloring matter for dyeing with a lilac or purple color stuffs of silk, cotton, wool, or other materials. GB1984/1856. Shelfmark IP Reserve South â Perkinâs patent for the creation of azo dyes and dyeing techniques using them.
Meth-Cohn, O. and Smith, M. (1994). What did W. H. Perkin actually make when he oxidised aniline to obtain mauveine? Journal of the Chemical Society, Perkin Transactions 1, pp. 5-7. Shelfmark (P) JU 00 âE(9), also available in online subscription â the first investigation of Perkinâs preserved original samples of mauveine under modern spectroscopic techniques to determine the exact structures.
Written by Philip Eagle