Sir Cyril Norman Hinshelwood

The English chemist Sir Cyril Norman Hinshelwood (1897-1967) was noted for his contributions to reaction kinetics.

Cyril Hinshelwood was born in London on June 19, 1897, the only child of an accountant who died in 1904. The boy was brought up by his mother. Hinshelwood won a scholarship to Oxford but was unable to accept it because of World War I. He became a chemist at an explosives factory at Queensferry, Scotland, and 2 years later he was appointed assistant chief laboratory chemist. In 1919 he entered Balliol College, Oxford, for the shortened postwar degree course. So sure was his grasp of chemical principles that his tutor, Sir Harold Hartley, recommended Hinshelwood for a fellowship at Balliol in 1920. A year later he was made a fellow of Trinity College, Oxford. He remained there until 1937, when he was named Dr. Lee's professor of chemistry at Oxford, a post he held until his retirement in 1964. He then became senior research fellow at Imperial College, London.

Hinshelwood's lifelong preoccupation with the energetics and rates of chemical reactions may be traced to his work of testing explosives at Queensferry. Early work included studies of the decomposition of solid potassium permanganate, reactions between gases on hot filaments, and reactions taking place in solution. Before long, however, he turned to the kinetics of homogeneous gas reactions. By studying the effects of pressure changes on these reactions, Hinshelwood inferred that in some circumstances molecules might gain the necessary energy to react (activation energy) by mutual collision, but in other circumstances deactivation might occur by this process.

Among the gas phase reactions studied at this time was the deceptively simple reaction between hydrogen and oxygen to form water. By studying the way in which the rate of reaction was affected by temperature and pressure changes and by examining the conditions needed for explosion, Hinshelwood was led to propose a branching chain mechanism. By observing the effect of the wall surface, and especially the ability of nitric oxide to inhibit the reaction, he concluded that free radicals played a key role, postulating as active participants H, O, OH, and HO2.

In the late 1930s Hinshelwood turned to a new field of activity. Recognizing that the growth of bacteria was essentially a complex of chemical reactions, he began to apply kinetic studies to the bacterial cell. He examined the effect of additives such as phosphorus and the alkali metals and concluded that bacteria could adapt to their new environment by a shift in the enzyme balance of their cells. He was able to systematize his results in terms of a "principle of total integration" and give them mathematical expression in his "network theorem."

Hinshelwood played an important part in the consolidation and organization of physical chemistry at Oxford for many years. He was a highly articulate scientist with deep insight into the philosophical implications of his subject, and his lectures were tinged with dry humor and delivered with great clarity. His international reputation was widened by his books. The Kinetics of Chemical Change (1926) was his masterpiece; the successive editions reveal the progressive sophistication that came to his views on his own special subject. The Structure of Physical Chemistry (1951) is a magisterial survey of the whole field from his particular viewpoint. In bacteriology, his early work, The Kinetics of the Bacterial Cell (1946), was followed by Growth, Function and Regulation in Bacterial Cells (1966).

Hinshelwood was knighted in 1948. From the Chemical Society he received the Longstaff and Faraday medals and from the Royal Society the Davy, Copley, Royal, and Leverhume medals. He became president of the Royal Society in 1955. He shared the Nobel Prize in chemistry and was admitted to the Order of Merit in 1956. He had the unique distinction of being simultaneously president of the Royal Society and of the Classical Association.

A man of many parts, Hinshelwood was a very accomplished linguist and had an expert knowledge of subjects as diverse as classical music, Chinese porcelain, and Persian carpets. He died in London on Oct. 9, 1967.

Further Reading on Sir Cyril Norman Hinshelwood

Biographical information on Hinshelwood is in Eduard Farber, Nobel Prize Winners in Chemistry, 1901-1961 (rev. ed. 1963), and Nobel Foundation, Chemistry: Including Presentation Speeches and Laureates' Biographies, vol. 3 (1964). For background see Aaron J. Ihde, The Development of Modern Chemistry (1964).