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Science's powerful companion: A. W. Hofmann's investigation of aniline red and its derivatives

Published online by Cambridge University Press:  05 January 2009

Anthony S. Travis
Affiliation:
Sidney M. Edelstein Center for the History and Philosophy of Science, Technology and Medicine, The Hebrew Universiry of Jerusalem, Givat Ram, Jerusalem, 91 904, Israel.

Extract

Since the eighteenth century chemistry has been deemed to be useful, yet how it might find widespread application, particularly in the case of its most advanced developments, was generally unclear. The discovery of synthetic dyestuffs has often been considered as the turning point towards much closer linkage between chemistry and the manufacture of useful products. How this occurred can best be seen in the case of August Wilhelm Hofmann, who for two decades after 1845 was director of the Royal College of Chemistry in London. As the teacher of many pioneers of the dye industry, Hofmann can be considered its first scientific leader. Indeed, the compounds he studied from 1860 were products made in the factories of his former students and assistants. They in turn were the first to recognize Hofmann's role in stimulating the practical application of science. Henry Armstrong, the chemist and educator, went so far as to imply that this was germane to Hofmann's pedagogic and research strategies: ‘it is clear that the influence he exercised in introducing scientific method into industry was in no sense accidental, but the considered expression of innate convictions’. These convictions were also encouraged by the need to attract funds from industrial sponsors for the Royal College of Chemistry, and they charged the rhetoric that served to enhance Hofmann's ambition and the discipline of chemistry before international audiences.

Type
Research Article
Copyright
Copyright © British Society for the History of Science 1992

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References

For contributions towards reinterpretation of the role of type formulae, I thank Willem J. Hornix. Henk van den Belt, Robert Bud, Ernst Homburg and Peter J. T. Morris are thanked for helpful discussions. For criticism of an earlier version of this paper I wish to express my gratitude to Seymour H. Mauskopf.

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7 This was quite unlike any of the earlier chemical puzzles concerning natural products from plants. In these, extracted substances, isolated from roots and leaves, or their partial degradation products, were the subjects of investigation. Alizarin, the principal dye of the madder root, for example, gave an empirical formula that suggested it was a derivative of the hydrocarbon naphthalene, and this was accepted from 1850 to 1868. An interesting exception was murexide, a laboratory curiosity examined by Wöhler and Liebig in the 1830s, and which became a commercial purple dye in the 1850s.

8 In 1857, Kekulé had suggested the marsh gas, or methane, type. This led to the beginning of valency theory, and a move towards bonding formulations and modern structures as an alternative to types. Henceforth, it was possible to draw molecular structures for aliphatic compounds. The aromatic compounds, however, were expressed by graphie formulae only after 1865.

9 Travis, A. S., The Rainbow Makers: The Origins of the Synthetic Dyestuffs Industry in Western Europe, Bethlehem, Pennsylvania, 1992.Google Scholar

10 Oxygen was assumed to be present by difference. Gold and platinum salts were also analysed, but they contained no oxygen. (Laboratory notebook, William Henry Perkin, City of London School.) The first dated combustion experiment was 18 July 1856, and similar investigations continued after the last dated entry on 24 November 1856.

11 Hofmann, to Perkin, , 23 10 1856Google Scholar, Kirkpatrick Family Collection, Historical Archives, ICI Specialties, Manchester.

12 Perkin established the formula of mauve in 1863, using crystalline salts. Mauve contained twenty-seven carbon atoms, twenty-four hydrogens and four nitrogens. Perkin, W. H., ‘On mauve or aniline purple’, Proc. Roy. Soc. (18621863), 12, 713–15CrossRefGoogle Scholar. There was some uncertainty over the number of carbon atoms, a matter not resolved until 1879; it was eventually shown that commercial ‘mauve’ consisted of three substances.

13 For instance, in 1864 Nicholson claimed that he had received analytical data concerning the red from Hofmann, in 02 1861Google Scholar, one year prior to its publication. See Chem. News (1864), 10, 316Google Scholar. McLeod provides further corroboration. He was introduced to the red in January 1861 when ‘[t]he doctor gave me a substance which produced a red color when dissolved in alcohol. He said it was produced by the action of CCl4 on aniline’. McLeod Diary, 23 01 1861Google Scholar. McLeod must have been occupied with numerous experiments on this reaction during the following months, for, at the end of May, Hofmann told ‘me [McLeod] to look for the substances I had prepared by the action of CCl4 on aniline but they could not be found. After some time he found some wrapped up in a paper’. Ibid., 29 May 1861.

14 McLeod recorded that ‘a friend of William Hofmann Dr. Clemm’ (Carl or August Clemm, soon to become partners in the forerunner of the Badische Anilin und Soda Fabrik) had been in London to obtain details of ‘Perkin's dye’. Clemm had tried to bribe a workman loyal to Nicholson, and, according to McLeod, was ‘tarred and feathered’ for his troubles. It is surprising that McLeod was unaware of the fact that Simpson, Maule & Nicholson did not manufacture Perkin's dye (mauve), or that they were the largest British manufacturers of aniline red, which was, no doubt, the object of Clemm's attentions. So, if we are to rely on McLeod's diary, Hofmann was not advising Nicholson on aniline dyes before the autumn of 1860, at the earliest. Clemm's nefarious activities do, however, attest to Nicholson's success as a dye-maker. McLeod Diary, 22 09 1860Google Scholar. See also Chem. News (1860), 2, 180.Google Scholar

15 Hofmann, A. W., ‘Notes of researches on the poly-ammonias. – No. XX. On the colouring matters produced from aniline’, Proc. Roy. Soc. (18621863), 12, 213Google Scholar. Since rosaniline had been shown to have the formula of a triamine, three types of salts were to be expected, corresponding for the reactions with hydrochloric acid to: C20H19N3, HCl; C20H19N3, 2HCl; and C20H19N3, 3HCl. However, only the first and last members of this series were obtained, the former showing great stability. As a rule, crystalline salts with one equivalent of acid had ‘the splendid metal-lustrous green of the wings of the rose-beetle’.

16 Referring to rosaniline and leucaniline, Hofmann described them as ‘the prototypes of two series of homologous colouring matters which cannot fail to be obtained from the homologues of aniline. Toluidine appears to yield perfectly similar bases’ (a claim which Hofmann later retracted). He had also subjected both rosaniline and leucaniline to treatment with nitrous acid – Piria's reaction, carried out at higher temperatures than Griess' reaction – ‘new bases being thus generated, the platinum-salts of which are remarkable for their fulminating properties’. Although Piria's and Griess' processes were poorly understood, they would come to feature greatly in the eventual structural elucidation of fuchsine dyes.

17 Persoz, J. F., de Luynes, H. J. V. and Salvetat, L. A., Le rouge d'aniline. Brevets de MM. Renard frères et Franc, Repport, Paris, 1860, 2831.Google Scholar

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31 This was probably around May 1863, since on 1 June, McLeod ‘wrote a paper for the doctor on the isomeric anilines’. McLeod Diary, 1 06 1863.Google Scholar

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33 Hofmann, A. W., ‘Contributions towards the history of the colouring matters derived from coal-tar’, Proc. Roy. Soc. (18621863), 11, 647–8CrossRefGoogle Scholar. Since Hofmann was not a particularly competent experimentalist, some reactions may have been carried out by another of his assistants, perhaps Carl A. Martius, who at the end of 1863 joined Roberts, Dale & Co. in Manchester. However, it is more likely that experiments were undertaken by Nicholson in his factory laboratory.

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37 Ibid., 341–7.

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39 Ibid., 489.

40 Ibid., 490.

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45 See, for example, Watson, David, ‘Notes on a course of lectures on organic chemistry delivered by A. W. Hofmann, Ph.D. (Professer Royal School of Mines) from Jan. to March 1865’Google Scholar, Lecture 30. Imperial College Archives, B/Watson/3.