Hinshelwood, Sir Cyril Norman
- Keith J. Laidler
Sir Cyril Norman Hinshelwood (1897–1967)
Hinshelwood, Sir Cyril Norman (1897–1967), physical chemist, was born on 19 June 1897 in London, the only child of Norman Macmillan Hinshelwood, chartered accountant, and his wife, Ethel Frances Smith (d. 1959). As a child he was taken by his parents to Canada, and received some schooling in Montreal and Toronto. When his father died in 1904 his mother returned with him to a small flat, 13 Holbein House, Pimlico Road, Chelsea, which was their London home until her death and which he continued to use all his life. He never married.
Hinshelwood attended the Westminster City School, and won a Brackenbury scholarship to Balliol College, Oxford, in 1916. Because of the First World War he deferred his university entrance and was employed as a chemist at the explosives supply factory at Queensferry. There he displayed remarkable ability and was known as ‘the boy wonder’. He was appointed deputy chief chemist at the age of twenty-one.
Chemical research from 1919
Hinshelwood went up to Oxford in January 1919, and while still an undergraduate, tutored by Sir Harold Hartley, published three papers in the Journal of the Chemical Society on the decomposition of solid explosives. After five terms of residence he won distinction in the shortened war degree course, and was elected to a research fellowship at Balliol in 1920. In the following year he was elected a tutorial fellow of Trinity College, which shared with Balliol a number of rather primitive and ill-equipped teaching and research laboratories. Here for the next twenty years Hinshelwood lectured and carried out research with his students. Nearly all of his work was on the kinetics and mechanisms of chemical reactions (including those occurring in biological systems).
From 1921 to 1928 Hinshelwood and his students carried out a comprehensive study of the kinetics of chemical reactions catalysed by surfaces. He took as his starting point the realization by the American chemist Irving Langmuir (1881–1957) that molecules are often strongly attached to surfaces by what is called chemisorption, and that the chemical interaction occurs between the chemisorbed molecules. Hinshelwood carried out carefully designed experimental studies of a number of chemical reactions occurring on various surfaces, and explained the kinetic behaviour in terms of the extent of binding of the reactant molecules at the surface. This work laid a firm foundation for the much more detailed studies that were later carried out with the use of more refined experimental techniques.
In 1926 Hinshelwood began a comprehensive series of investigations of chemical reactions that occur entirely in the gas phase. He made pioneering contributions of particular importance on so-called unimolecular reactions, in which individual molecules split into smaller molecules or change (isomerize) into molecules having a different structure. If collisions between molecules supplied the energy, the rate would be expected to be proportional to the frequency of collisions and therefore to the square of the pressure of the gas; there was some evidence, however, that this was not the case. A solution to the dilemma was suggested in 1921 by F. A. Lindemann in terms of the formation by collisions of an energized molecule with a long enough life that it could be deactivated by collisions before undergoing reactions. Hinshelwood saw that the mathematical equation resulting from this hypothesis was capable of experimental test, and in 1926 and 1927 he and several of his students confirmed the general idea by studying several organic decompositions. Also, in 1927, Hinshelwood made an important theoretical extension to Lindemann's hypothesis by treating, in terms of statistical theory, how the energy randomly distributed in a complicated molecule can become organized in such a way that reaction can occur. The Lindemann–Hinshelwood ideas were used in subsequent theories of unimolecular reactions, and remained valid despite the fact that it was later found that all of the ‘unimolecular’ reactions studied experimentally by Hinshelwood and his students are not really unimolecular, but occur in a much more complicated way.
In 1927 Hinshelwood, with his student H. W. Thompson, began to investigate the kinetics and mechanisms of explosions in gases. They made careful experimental studies of the reaction between hydrogen and oxygen, and in 1929 showed that there is a pressure range within which explosion occurs, and above and below which there is slower reaction. They explained these results in terms of chain reactions involving active intermediates. It had previously been suggested that there may be so-called branching reactions which give rise to a great increase in the number of active species, and therefore to explosion. Hinshelwood explained the upper and lower explosion limits in terms of the way in which the active species are destroyed, either at the surface of the vessel or by collisions with gas molecules. In 1927 the Russian chemist N. N. Semyonov had provided evidence for a lower explosion limit, but Hinshelwood was the first, in 1929, to discover both lower and upper limits, and to provide the general explanation accepted by chemists.
In 1930 Hinshelwood began a series of investigations, also continued for several decades, on reactions of organic substances in solution. At first there was little understanding of the details of how such reactions occur, but his work soon brought about a considerable clarification. By comparing the behaviour in different solvents, Hinshelwood and his students were able to gain understanding of the role of the solvent. Important conclusions were also drawn from comparisons between the reactions of series of organic compounds in which minor structural changes had been made ('substituent effects'). Many of the results were later of great value to physical–organic chemists, especially in the study of ‘correlation analysis’ which continued to be under active investigation for many years.
The new physical chemistry laboratory
In 1937, following the retirement of Frederick Soddy, Hinshelwood was elected as Dr Lee's professor of chemistry at Oxford, with responsibility for both physical and inorganic chemistry. This involved a change of residence from Trinity College to Exeter College, but Hinshelwood delayed the move for a few years, continuing to carry out his research in the Trinity laboratories until 1941. In that year, through the generosity of Lord Nuffield, a physical chemistry laboratory was opened on South Parks Road. Although his professorship included responsibility for the inorganic laboratory, Hinshelwood left the running of it entirely to its senior member; by contrast, he took his administrative responsibilities at the physical chemistry laboratory rather more seriously than was necessary, with little delegation. As a result he was at times overstrained, irritable, and unapproachable. His own research work suffered to some extent, but with the help of capable senior assistants he was able to direct much research.
In the new laboratories Hinshelwood directed an important series of studies on charcoal and other materials for use in respirators; as a result, on D-day in 1944 the army had much improved equipment. Hinshelwood also continued his work on reactions in solution. More of his effort was devoted to the kinetics and mechanisms of reactions of organic substances in the gas phase. Certain evidence had convinced Hinshelwood that such reactions occur partly by a molecular mechanism (involving no intermediates), and partly by a chain mechanism. (In the 1950s most organic reactions occurring in the gas phase were shown convincingly to occur entirely by chain mechanisms, but Hinshelwood was slow to accept this conclusion.)
In 1945 C. J. Danby was appointed as Hinshelwood's assistant and gave much support with research and teaching. In particular he took charge of the mass spectrometers used for the analysis of reaction products in Hinshelwood's research in gas kinetics.
Hinshelwood's main interest in the new laboratories was the chemical kinetics of bacterial growth, which he had begun to investigate in 1937. He was particularly concerned with the adaptation shown by bacteria in accommodating themselves to their environment when their supply of foodstuff is changed. They even gradually adapt to substances initially poisonous to them; this is of crucial importance in the adaptability of hostile organisms to substances that could destroy them. Hinshelwood and his students explained their results in terms of changes in chemical equilibria brought about by the environment, changes that are carried into future generations when the bacterial cells divide. In 1949 Hinshelwood was joined in his bacterial work by Alastair C. R. Dean, who collaborated closely with him until 1967 and helped to direct the work of many students.
During the earlier years of Hinshelwood's investigations of bacteria, his conclusions were strongly criticized by some biologists, who mistakenly thought that he was ignoring the well-established conclusion that mutation and natural selection are important factors in the transmission of characteristics from one generation to another. Remarkable developments in molecular genetics were taking place at that time, and to some biologists Hinshelwood's contributions seemed unsound. Some went so far as to say that he was coming dangerously close to ‘Lamarckism’, the belief in the inheritance of acquired characteristics. In several of his publications, however, Hinshelwood emphasized that he had never denied the importance of mutation and natural selection. Some of his experiments indeed provided evidence for mutation. In some cases his results could not be explained entirely in terms of mutation and natural selection, and this led to his conclusion that the adjustment of chemical equilibria in the bacteria must be an additional factor. Subsequent work by biologists has confirmed the importance of the adaptive changes proposed by Hinshelwood and his associates, and has shown that (for example, in some cases of neoplastic transformation—abnormal tissue growth) they may be the predominant factor. Some later biologists have recognized his bacterial work to have been of pioneering importance.
Writing and teaching
Hinshelwood exerted a great influence on physical chemistry through his books. In 1926 he published his Kinetics of Chemical Change in Gaseous Systems, which lucidly expounded the new ideas about gas reactions. It appeared in two more editions, to be superseded in 1940 by his Kinetics of Chemical Change, which although shorter than the third edition also included his work on reactions in solution. His monograph The Structure of Physical Chemistry appeared in 1951 and explained his personal point of view about the unity and continuity of the subject. This book, of great interest to experts in the field, was criticized by some for including no references to sources and for presenting the subject in the form of theoretical ideas for which no experimental basis was given. Hinshelwood's bacterial work was expounded in two influential books, The Chemical Kinetics of the Bacterial Cell (1946) and Growth, Function and Regulation in Bacterial Cells (1966), the latter in collaboration with Dean.
Hinshelwood was an outstanding college tutor, lecturer, and research supervisor. He was tolerant of his students, gently guiding them toward the important responsibilities that many were to assume later. His meticulously prepared lectures were, like his writings, models of precision and clarity. Particularly in his earlier years—before he became harassed by too much administration—he was able to keep in close and friendly contact with his research students, and was always readily available for consultation.
Humanities and the philosophy of science
Hinshelwood was unusual for the breadth of his interests. He was a painter from his boyhood, and continued to use the small palette he had bought at the age of nine. An exhibition of more than a hundred of his paintings at Goldsmiths' Hall after his death showed his skill with a wide range of subjects, including portraits of colleagues, interiors, a racing eight, and his cat. His fine draughtsmanship, colouring, and sense of composition were all used to striking effect.
Hinshelwood was also a remarkable linguist. He was highly proficient in French, German, Italian, and Spanish, and was able to carry out conversations in Russian and Chinese. With the aid of gramophone records he perfected his pronunciation of some languages; he could pass for a Frenchman. He was well versed in Latin, less well in Greek, and had the unique distinction of serving as president of the Royal Society and of the Classical Association at the same time. In his presidential address to the Classical Association in 1959 he expounded his philosophy of languages, and illustrated their individuality with examples of German genders, Arabic plurals, and the difficulties of translating classical Chinese. One of his more remarkable contributions was a paper on Dante's imagery, in which he quoted many passages from the Divina commedia.
As president of many important societies, Hinshelwood gave a number of memorable addresses, always presented with great style and eloquence. In them he revealed his personal philosophy, his reflections on the place of science in society, and his sound appreciation of the connection between the theoretical and the practical.
Hinshelwood was energetic, and sometimes combative, in his efforts to promote science at Oxford. He was often extremely suspicious of the higher officials of the university, who generally did not have a science background. According to his student Sir Harold Thompson, he 'hated bureaucracy, and developed a distrust in the University Establishment. … He was ever watchful of the Gazette to see what the Registrar was up to' (Memoirs FRS, 381). His administrative relationships were, however, less abrasive in his capacity as a delegate to the Oxford University Press, and the steady growth of its publications, particularly in science, owed much to his advice and initiative. In 1967 the delegates described him as 'the most eminent scientist ever to be a member of the board' (ibid., 386).
Honours and awards
Hinshelwood received many honours, including the Faraday and Longstaff medals of the Chemical Society, and the Copley medal of the Royal Society of which he was elected a fellow in 1929 at the early age of thirty-two. He received many honorary degrees, and was an honorary fellow of Trinity, Balliol, Exeter, and St Catherine's colleges, Oxford. He was an honorary member of many foreign academies, including the US Academy of Sciences and the Academy of Sciences of the USSR. He was president of the Chemical Society (1946–8) for its delayed centenary celebrations in 1947, and of the Royal Society (1955–60) for its tercentenary in 1960, having been its foreign secretary since 1950. In 1964–5 he was president of the British Association. He was knighted in 1948, and was admitted to the Order of Merit in 1960.
In 1956 Hinshelwood shared a Nobel prize in chemistry with N. N. Semyonov. To the surprise of his many admirers, this award was criticized in some quarters. The explanation is twofold. The award was given to him at a time when the mistaken criticism of his bacterial work was at its peak. Also, at the time of the award, Hinshelwood's work was not at its most original. He pointed out in 1957 that there are three stages in the study of a branch of science. The first is one of 'gross oversimplification, reflecting … a too enthusiastic aspiration after elegance of form'. The second stage involves more detailed studies in which 'recalcitrant facts increasingly rebel against conformity'. In the third stage 'a new order emerges, more intricately contrived' (PRS, 243A, 1957, v–xvi). There is no doubt that Hinshelwood excelled in the first of these stages, and was less effective in the others. His earlier work, on reactions on surfaces, unimolecular reactions, and explosions, belonged to the first stage, and merited a Nobel prize; if it had been awarded fifteen years earlier, there would have been few complaints. Chemists who were unaware of the history of their subject and knew only of Hinshelwood's later contributions might well have been critical of his failure to adopt some of the latest experimental techniques such as gas chromatography, and of his tendency to ignore the latest theoretical developments in his field.
In 1964 Hinshelwood retired from his professorship and returned to his Chelsea flat. He became a senior research fellow of Imperial College, London, and continued his studies on bacterial growth; he retained this appointment until his death. Free of administrative duties he became noticeably happier and more relaxed. His help and advice were quickly in demand as a consultant. He entered into fruitful associations with the Arts Council, the British Museum, Queen Elizabeth College, London, the National Gallery, and the Goldsmiths' Company, of which he had become an honorary member in 1952. His connection with the company was one of his great pleasures, and he left a large legacy in support of their charitable work. Hinshelwood died suddenly and unexpectedly of a heart attack, alone at home, on 9 October 1967.
- H. Thompson, Memoirs FRS, 19 (1973), 375–431
- E. J. Bowen, ‘Sir Cyril Hinshelwood, 1897–1967’, Chemistry in Britain, 3 (1967), 534–6
- K. J. Laidler, ‘Chemical kinetics and the Oxford college laboratories’, Archive for History of Exact Sciences, 38 (1988), 197–283
- K. Hutchison, High speed gas: an autobiography (1987)
- R. F. Barrow and C. J. Danby, The Physical Chemistry Laboratory: the first fifty years (privately printed, Oxford, 1991)
- RS, papers
- CAC Cam., corresp. with A. V. Hill
- Rice University, Houston, Texas, corresp. with Sir Julian Huxley
- photograph, 1956 (with Nobel prize winners), Hult. Arch.
- D. H. Anderson, oils, 1958, Physical Chemistry Laboratory, Oxford
- G. Kelly, oils, exh. RA 1960, RS [see illus.]
- E. I. Halliday, oils, 1965, Exeter College, Oxford
- C. N. Hinshelwood, self-portrait, Goldsmiths' Hall
- G. Kelly, oils, Chemical Society
- portraits, RS, library
Wealth at Death
£149,047: probate, 1 Feb 1968, CGPLA Eng. & Wales
- Hinshelwood, Sir Cyril (Norman), (19 June 1897–9 Oct. 1967), Senior Research Felow., Imperial College of Science and Technology, since 1964; Dr Lee’s Professor of Chemistry, University of Oxford, 1937–64; Hon. Fellow of Trinity College, Balliol College, Exeter Colege., and St Catherine’s College; Delegate, Clarendon Press; Nobel laureate, 1956; President, British Association, 1964 in Who Was Who