Anthony Clifford was born in Wanstead, Essex, on 3 November 1938.?Educated at Bristol Grammar School, he entered national service in 1956, where he serviced radar equipment, before he was awarded an open scholarship at Balliol College, Oxford, obtaining a BA and DPhil.

After a postdoctoral period in Minnesota, he was appointed lecturer in physical chemistry at the University of Leeds in 1966, where he remained for the rest of his academic career, eventually retiring as professor of chemical technology in 2001.

He published more than 200 papers, reviews and patents throughout his career, with his very first publication ¨C which suggested a revision of Mendeleev¡¯s periodic table ¨C appearing in Nature.

¡°This clearly showed ambition, even though the paper did not have quite the impact he wished,¡± reflected Chris Rayner, professor of organic chemistry at Leeds, a long-time colleague and collaborator.

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went on to publish research in a broad range of areas, including the oxidation of organic compounds by inorganic salts and the precise measurements of diffusion coefficients and thermal conductivities, the latter of which was subsequently used in collaboration with the National Engineering Laboratory in East Kilbride to make measurements on more than 3,000 molecules. ?

He began a long and productive collaboration with fellow Leeds chemist Keith Bartle in 1984, in which they developed new methods for the use of supercritical fluids ¨C in which normally gaseous substances are cooled to liquid form ¨C for extraction purposes.

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The Bartle-Clifford team were recognised as world-leading by many who knew the area, with Professor Clifford¡¯s 1999 book Fundamentals of Supercritical Fluids viewed as a ¡°must-read¡± for those studying the field.

This work led to the creation of one of Leeds¡¯ first ¡°spin-out¡± companies, Express Separations, of which Professor Clifford was the technical director, and subsequently Critical Processes, where he continued to work after retiring from Leeds.

The companies' work built on much of Clifford¡¯s breakthroughs, including how industry can use superheated water and supercritical fluids to remove chemicals from biomass substances rather than employing more polluting organic solvents.

Many products containing natural extracts pioneered by Professor Clifford can be found on the shelves of major retailers, such as Boots and Marks & Spencer.

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¡°For many, Tony will be remembered as an engaging, generous and entertaining colleague, with a mischievous sense of humour, frequently telling stories over a glass or two of his favourite red wine,¡± said Professor Rayner.

¡°He was held in the highest regard as both an experimentalist and theoretician, and was also noted for his willingness to help fellow researchers, in Leeds and elsewhere,¡± he added.

Professor Clifford, who died on 29 March, is survived by his wife Anna, three children, six grandchildren, two stepchildren and one step-grandchild.

jack.grove@tesglobal.com