early use of tar and coal-tar pitch on road surfaces.
At the opening of the Royal College of Chemistry, coal-tar was already recognised as an immensely complex material. The first students understood that it consisted of the elements carbon, oxygen, hydrogen, nitrogen and a little sulphur, and they knew that from these combinations an inviting list of substances could be formed.
The study of modern chemistry was still in its infancy – it was only in 1788 that Antoine Lavoisier demonstrated that air was a mixture of gases which he called oxygen and nitrogen – and important advances were being made every year. Molecules such as the solvent naphtha had already been isolated in coal-tar in the 1820s, but the great challenge was now to reveal its constituent atoms, and to show how these may be modified to form other compounds. Naphtha was found to contain benzene, and, by a painstaking process of fractional distillation, this in turn was found to contain such materials as toluidine and aniline. The chemists often knew the atomic combination of each molecule – how many elements of carbon, how many of oxygen or hydrogen – but not how they fitted together. Their precise chains and points of attachment – those knobbly bead-and-metal constructions that (in the days before three-dimensional computer software) proud chemists liked to pose beside for photographs – would not be fully understood for several decades.
The research students at the Royal College thus conducted much of the exploratory work without map or compass, and some paid the price. Charles Mansfield, one of Hofmann’s most enterprising students, had been discouraged from setting up dangerous large-scale coal-tar experiments at the Royal College, and yet persevered with his project in a building near King’s Cross railway station. While preparing large quantities of benzene for an international exhibition in 1855, a fire broke out which consumed both him and his assistant.
It was aniline that most fascinated Professor Hofmann. He had spent much of his laboratory time in Germany investigating its possibilities, and continued his researches in Oxford Street. Crucially, he managed to impart this enthusiasm to his students.
‘As a teacher he was singularly interesting and lucid,’ Lord Playfair explained in a memorial lecture given in Hofmann’s honour in 1893, the year after his death. ‘He marshalled his arguments with great care, and as he brought them towards the conclusion, he increased in his persuasiveness and seemed to each individual student to take him into his special confidence.’
Frederick Abel, the joint-inventor of cordite, once asked himself, ‘Who would not work, and even slave, for Hofmann?’ Before he tackled explosives, Abel conducted an analysis of the mineral waters of Cheltenham and researched the effects of various substances on aniline (one of which was the poisonous gas cyanogen, from which his eyes suffered permanent damage). Another of his students established the composition of the air on Mont Blanc.
Strangely for a chemist, Hofmann was a rather clumsy man, once explaining to Abel that when he was younger he could hardly handle a test tube without ‘scrunching’ it. ‘There was an indescribable charm in working with Hofmann,’ Abel remembered, ‘in watching his delight at a new result or his pathetic momentary depression when failure attended the attempt to attain a result which theory indicated. “Another dream is gone,” he would mutter plaintively, with a deep sigh.’
One of Hofmann’s principal talents appeared to be choosing the right student for the right job, and in selecting a huge variety of avenues for research. In his first five years, some thirty-six different projects were undertaken. The Queen and the Prince Consort were frequent visitors to his laboratories, and Hofmann delivered several lectures at Windsor Castle. At the Royal Institution in 1865, Hofmann delighted Prince Albert and other notables with a demonstration involving croquet balls and rods. The royals may have enjoyed his quaint English literal translations from German idioms; they were certainly interested in his students’ work on soil and plants – in fact, they were keen on anything which might lead to practical applications.
William Perkin noted how his mentor used to tour the laboratories several times a day and talk to his students as if each piece of their work was of phenomenal importance. Occasionally their work did indeed carry genuine significance; most often it was mundane and doomed. And almost all the time Hofmann seemed to have done it before by himself. ‘I well remember one day,’ Perkin said, ‘when the work was going on very satisfactorily and several new products had been obtained, he came up and commenced examining a product of the nitration of phenol one of the students had obtained by steam distillation. Taking a little of the substance in a watch glass, he treated it with caustic alkali, and at once obtained a beautiful scarlet salt. Looking up at us in his characteristic and enthusiastic way, he at once exclaimed, Gentlemen, new bodies are floating in the air!’*
Another tour was less fruitful. Once, Hofmann was holding a glass bottle containing a little water, and invited a student to pour sulphuric acid into it. The heat cracked the glass, and the acid splashed from the floor into Hofmann’s eyes. ‘Hofmann was sent home in a cab,’ Perkin remembered, ‘and had to be kept in bed in a dark room during several weeks.’ Despite this hardship, he was so anxious about his work that his students were asked to visit him in his murky bedroom to report progress and receive new instructions.
Predictably, Perkin was a formidably diligent student, and found the preliminary coursework rather easy. He sat near a window overlooking Oxford Street’s horsedrawn carriages, and spent some time sharing common interests with a man called Arthur Church seated opposite him. ‘We were both given to painting and were amateur sketchers,’ Church remembered. ‘I was introduced to his home and we began painting a picture together. This must have been soon after the Royal Academy exhibition of 1854, when I had a picture hung.’
Church had created his own domestic laboratory by converting a small aviary at his home, so was keen to see Perkin’s makeshift chemistry room on the top floor at King David Fort, where he worked in the evenings and at weekends. Perkin liked to take his work home with him, particularly when, after the completion of his basic syllabus in 1855, Hofmann had honoured him by making him his youngest assistant. ‘The students working at research seemed to me to be superior beings,’ Perkin observed.
Perkin’s earliest tasks concerned the formation of organic bases from hydrocarbons, but he was more interested in the results of his next assignment which led to one of his earliest published papers. At the beginning of February 1856 he submitted to the Proceedings of the Royal Society a brief report ‘On some new Colouring Matters’ he had found with Arthur Church. ‘This new body presents some remarkable properties,’ they wrote. That substance, which they named nitrosophenyline, was the result of a experiment with hydrogen and a distillation of benzol. It produced a bright crimson colour, it dissolved in alcohol with an orange-red tint, and it changed to a yellowish-brown when diluted with alkali. They concluded that it had ‘a lustre somewhat similar to that of murexide’, the rich purple originally made from guano.
Although August Hofmann was keen to see his students publish (and had in fact communicated the above findings to the journal himself), he believed the colourful discovery was of little value. In one sense he was right, for Perkin and Church could suggest no practical application for their new colour, and so they resumed other work. But it is significant that the pair, both painters, should be alert to what others might consider merely a pretty coincidence.
Hofmann faced other dilemmas. Many of the wealthier patrons of his college were concerned that chemistry was not producing results that would be beneficial to their well-being. And every landowner who had been excited by Justus Liebig’s crusade was soon disappointed that the institution they supported was not, after all, their salvation. Subscriptions dwindled, and the college was forced to merge with the School of Mines; some students in Perkin’s third year gained entry with the sole aim of improving coal extraction.
Even in 1856, there was much debate, and much disquiet, about the true virtues of pure chemistry. Triumphant practical men simply distrusted men of science.
