LITMIR.BIZ

       Chapter Three

      Floating in the Air

      Wandered in the town, to the Museum and

      Zoo . . . Reconstructions of Hausa and Sanghay villages – combination of indigo and pale calabash. Hunchback boy with staff and bowl and mauve purple jumper stretched like a landscape over his totally deformed body . . . A restaurant in a garden. I drank a beer on a red spotted cloth-covered table. Mosquitoes bit the hard parts of my fingers.

      Bruce Chatwin in Niger, 1971, from Photographs and Notebooks

      When Perkin left the Royal College every evening and walked along Oxford Street, his journey was illuminated by gas light. London was ablaze with gas: houses, factories and streets had been lit this way since the beginning of the century, and Perkin’s laboratory work had begun to rely on gas for other fiery uses.

      But this demand brought some terrible problems. Gas derived from the distillation of coal, and millions of tons were processed each year to meet demand. The process – which involved the highly combustible method of heating coal in closed vessels without oxygen – also yielded several useless and dangerous by-products: foul-smelling water, various sulphur compounds and a large amount of oily tar.

      For many years these were regarded as waste; the problem was not how to utilise them but how to get rid of them. The sulphur was found to be removable with lime and sawdust, while the gas-water and tar were abandoned in streams, where they poisoned the water and killed the fish. Anyone who requested any of these by-products was given them without charge in huge barrels. Some hopeless experiments were conducted with them, and then they were again thrown away into streams. But gradually, in the years leading up to Perkin’s birth, new uses were uncovered.

      The gas-water was found to be rich in ammonia, and the sulphur compounds would be used in the manufacture of sulphuric acid. In Glasgow in the 1820s, Charles Macintosh found a use for the coal tar, developing a method of waterproofing cloth. He used it to prepare a special solution of rubber, applied it to two pieces of coat fabric, and called it a raincoat, but other people soon began calling it a macintosh. It was also used as a protective coating on timber, and was widely employed on the new railway system. Its combination with creosote also afforded a thick coating for wood and metals, and it was used as a disinfectant in sewage. Some patents from the 1840s even suggested the 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

Скачать книгу