Ethereal philosopher

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Success was sweet indeed for Victorian chemist A W Williamson. Colin Russell tells his story.

To cram almost all your effective work into a mere five years and then to dominate the chemical scene in your country for another 30 must take some doing. It also needs some explanation. Yet this was the case with the English chemist Alexander Williamson, who died 100 years ago this year.

Alexander William Williamson was born in Wandsworth on 1 May 1824. His father worked for the East India Company as a clerk in India House, though he also appears to have had a private income. Within a few years of Alexander’s birth, the Williamson family moved to Kensington, where their new neighbours included the future philosopher John Stuart Mill, who would later prove to have an influence on the young chemist’s career. Alexander was sent to school in London but by the time he was 15 his father had retired and the whole family removed to France. After a short stay in Paris he became a pupil at the Collège in Dijon.

At his father’s wish the young Williamson then entered the University of Heidelberg in order to study medicine. However, he found the medical lectures extremely dull. Instead he was diverted to chemistry by the lectures of Leopold Gmelin. He imparted to his father the unwelcome, even scandalous, news that he wanted to be a chemist, not a doctor. The aggrieved parent wrote to a relative in England to enquire whether any openings existed for a chemist, the reply to which was ’none at all’. Many a lesser mortal would have been discouraged by this, but Williamson was not to be deflected and, with his mother’s support, persuaded his father to relent.

Williamson left Giessen and went to Paris as a kind of scientific ’finishing school’ and stayed there from 1846 to 1849. Urged on by his childhood neighbour, John Stuart Mill, he took lessons in mathematics from the famous philosopher Auguste Comte. He met many distinguished French chemists of the time such as Dumas, Laurent and Gerhardt, and pursued some investigations of his own in a private laboratory in his house in Rue de Francs Bourgeois. While in Paris he met Thomas Graham, Professor of General Chemistry at University College London. Graham’s colleague George Fownes had recently died, and Williamson was invited to apply for the vacant Chair of Practical Chemistry. Williamson’s application was successful, and he was duly elected in 1849.

His first experiences at University College were rather mixed. An introductory lecture went down like a lead balloon. A usually charitable biographer observed ’the best of it was the title’ - which was ’Development of difference the basis of unity’. It was an amorphous and rambling exposition of some of Comte’s ideas on science and sociology. The best thing that Thomas Graham could find to say was to commend the lecturer for his musical voice.

The ’Williamson synthesis’, as it became universally known, quickly became a standard reaction in the organic chemist’s repertoire. Of more immediate importance, however, was the light that the discovery threw on matters of chemical constitution. At that stage in chemistry the idea of a definite structure still lay in the future. However, it was becoming clear that it was possible to know the empirical formula of a compound, ie the ratio of different atoms in a molecule (though even here not everyone could agree on a common table of atomic or molecular masses). Various ideas had been circulating about alcohol and ether and it was clear that their difference lay in a molecule of water.

Thanks to the influence of the Swedish chemist Berzelius, a widely held belief was that most organic compounds were split into at least two parts, held together by some kind of electrical attraction. Several ways of representing alcohol and ether were being used by the chemical community. While all of these were more or less compatible with the old method of making ether by the dehydration of alcohol, Williamson’s new synthesis was something of a misfit.

In a paper on the constitution of salts in 1851, Williamson went on to extend his ideas to suggest a water type for alkalis and acids. This was a direct attack on the binary system of Berzelius, an attack that was presumably made easier by his experience of chemistry in Paris, where the theories of Berzelius were being questioned.

If, for example, sulphuric acid really were like this it might react in similar ways to other compounds of the water type, like alcohol. Accordingly, Williamson allowed it to react with phosphorus pentachloride to see if a hydrogen atom and an oxygen atom could be replaced by chlorine (later they would be called a hydroxyl group, but not yet). Thus by the successive formation of chlorsulphonic acid and sulphuryl chloride, Williamson had confirmed the nature of sulphuric acid as SO ₂(OH) ₂.

Using his new system of writing out chemical formulae, he could represent these products systematically as: SO ₂(OH) ₂, SO ₂(OH)Cl and SO ₂Cl ₂.

These improved formulae were all very well, but what did they actually mean? French chemists saw them as just ’reaction formulae’, convenient ways of writing down reactants and products so that some relation could be perceived between them. It was how things might be, not how they actually were. The followers of Comte had a horror of metaphysical entities that no one could see, and were extremely reluctant to postulate even atoms, let alone molecular structures. In spite of this, Williamson suggested that formulae ’may be used as an actual image’ of what we think molecules may be like, much as an orrery may be a model of the solar system.

While still in his early years at University College, he looked at the older method for producing ether from alcohol by the action of sulphuric acid. He concluded that ethyl hydrogen sulphate is an essential intermediate, reacting with further alcohol to produce ether. With this conclusion the catalytic action of the sulphuric acid is explained, and Williamson had robbed catalysis of its mysterious power to influence chemical changes without being involved in any of them. This work also led him to propose a dynamical view of chemical equilibrium and this notion that atoms and molecules are in a continual state of dynamic equilibrium was later taken up by Clausius, though with charged particles which Williamson did not mention. The Williamson-Clausius theory was eventually developed by Arrhenius to become the modern theory of electrolytic dissociation.

Williamson made a number of other contributions to organic chemistry. These included the first correct formula for acetone, the discovery of aldehyde and mixed ketone preparation by the pyrolysis of mixed calcium salts of fatty acids. He also predicted the formation of acetic anhydride following his elucidation of the structure of acetic acid.

In 1855 Graham left University College for the Royal Mint, and Williamson was promoted to his chair. By now his short period of experimental research was largely over. He had proceeded bravely until this point with severe physical disabilities: an almost paralysed left arm, and seriously defective eyesight. For the rest of his long career he was prominent for his teaching and role as a guru in the London scientific community.

For many years Williamson’s small room attached to the chemistry laboratory at University College was frequently visited by chemists who were temporarily or permanently in London, among them Kekul?, Odling and Brodie. His influence on all three was considerable, and this influence was greatly extended when he became President of the Chemical Society in 1863 and again in 1869. His second presidential address was on ’The atomic theory’ and modern readers may be astonished that he found it necessary to mount a vigorous defence of a theory that was already 60 years old. In fact the positivism of Comte had profoundly affected - some would say ’poisoned’ - chemistry in France and many Britons were wary about accepting atoms that no one could see. So began a series of atomic debates in which Williamson played a prominent part, deserting his Comteism and advocating atomism. In the end he won but it was a long and wordy battle.

Other activities included the development, with W J Russell, of a modified technique for gas analysis, and an unsuccessful attempt to enter the industrial field of steam boiler manufacture. His father declined to offer financial support to this venture and advised him to concentrate on his academic duties.

Williamson also became President of the British Association in 1869, and Foreign Secretary of the Royal Society in 1873. He retired from his post at University College in 1888, having recently moved to a country house in Hindhead. Despite severe physical disability he maintained vigorous mental activity and was a keen controversialist, if somewhat dogmatic. He was much admired by friends and colleagues, and enjoyed a long and happy marriage to Emma Key, daughter of the headmaster of University College School. This remarkable man died in 1904 leaving behind a legacy that remains with us today. He is remembered as a chemist associated above all with a single group of compounds, the ethers, and one whose philosophical training enabled him to argue and communicate as few others have done.

Acknowledgements

Colin Russell is emeritus professor in the department of history of science at the Open University and affiliated research scholar at the department of history and philosophy of science, University of Cambridge.