Professor Kenneth Denbigh

Kenneth George Denbigh, chemical engineer and philosopher of science: born Luton, Bedfordshire 30 May 1911; chemist, Imperial Chemical Industries 1934-38, 1945-48; Lecturer, Southampton University 1938-41; staff, Ministry of Supply (Explosives) 1941-45; Lecturer, Chemical Engineering Department, Cambridge University 1948-55; Professor of Chemical Technology, Edinburgh University and Heriot-Watt University 1955-60; Professor of Chemical Engineering Science, Imperial College, London 1960-61, Courtaulds Professor 1961-66 (Emeritus 1977); FRS 1965; Principal, Queen Elizabeth College, London 1966-77; Director, Council for Science and Society 1977-83; married 1935 Kathleen Enoch (two sons); died London 23 January 2004

Kenneth Denbigh was trained as a chemist; he became a chemical engineer during the Second World War, and in the last phase of his career was distinguished also for his writings on the metaphysical problems of "time" and its relation to thermodynamics.

He was born in 1911 of Yorkshire farming and industrial stock. His father, George Denbigh, was the manager and later a director of Brothertons, a chemical works in Wakefield. It was Kenneth's early experience of these works that led him to chemistry. He graduated with first class honours at Leeds in 1932 and in two further years completed a PhD with Robert Whytlaw-Gray. Few academic posts were then available and he went to the Billingham Division of ICI until, in 1938, he became a lecturer in chemistry at Southampton.

The war, however, took him back into industry as head of the laboratories at the Royal Ordnance Factory at Bridgwater in Somerset. This move determined the course of his future career, for he found that he had to cope there with engineering problems as well as purely chemical ones and also that he had to consider seriously the role of time in governing the operations. These considerations led him to the field of thermodynamics and to its application to problems of the rate of change of processes of all kinds.

In 1948 he was invited to a lectureship in the Chemical Engineering Department at Cambridge, from which he moved successively to a chair in Chemical Technology at Edinburgh in 1955 and, five years later, to Imperial College where he became the Courtaulds Professor of Chemical Engineering. His last move, in 1966, was to the post of Principal of Queen Elizabeth College, now amalgamated with King's College London.

Denbigh's interests and the evolution of his thought can be followed in the many books that he wrote. The first was the short The Thermodynamics of the Steady State (1951). There came next a more conventional exposition of thermodynamics for students, The Principles of Chemical Equilibrium (1955, three later editions, and many translations). This was followed by the equally successful textbook, Chemical Reactor Theory (1965).

His interests were by then broadening away from purely technical and expository texts to wider social and metaphysical issues. In 1963 he enlarged his inaugural lecture at Edinburgh to produce Science, Industry and Social Policy in which he pointed out how depressing many of the last manifestations of the industrial revolution had been with their legacy of monotonous jobs and the environmental disasters that our manufacturing cities had become. His remedy, based in part on his reading in French sociology, was that of social sensitivity to factors less measurable than money.

He had been a member of the British Society for the Philosophy of Science since its foundation in 1950 and wrote about "Thermodynamics and the Sense of Time" for its journal in 1953. His first book in this field was An Inventive Universe (1975) where he argued, among other things, that the personal sense of time was as valid a measure of its sense, from past to future, as any provided by the physical sciences.

He returned to this field with his more tightly argued Three Concepts of Time in 1981. These were the usually reversible time of theoretical physics, and the irreversible times of thermodynamics and of human consciousness.

His fellow workers in the field of thermodynamics are probably most appreciative of his last book, written in collaboration with his elder son, Jonathan, a mathematician, Entropy in Relation to Incomplete Knowledge (1985). Here they discuss that most slippery concept, entropy, and whether it should be considered to be a fully objective entity or whether it is subjective, and dependent on one's personal knowledge. The subjective view has a long history going back to James Clerk Maxwell in the 19th century and was reinforced by the parallel use of entropy in the field of information theory in the second half of the 20th century. They argue, successfully I believe, that nevertheless its objectivity can be adequately defended.

Few scientists or engineers tackle as wide a range of intellectually challenging problems as Denbigh did. His books are clear, well argued and a delight to read. They are a lasting legacy of a man who thought deeply about some of the hardest problems of our time and who showed always kindness and courtesy in his discussion of them with his colleagues.

J. S. Rowlinson

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