David Chapman (chemist)

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David Leonard Chapman FRS (6 December 1869 – 17 January 1958) was an English physical chemist known for two important ideas: the Chapman–Jouguet condition in detonation theory and the Gouy–Chapman layer, the arrangement of ions near a charged surface. He spent much of his career at Oxford as a fellow and tutor at Jesus College, where he ran the college’s last laboratory.

Chapman was born in Wells, Norfolk, and moved to Manchester as a child. He attended Manchester Grammar School and then Christ Church, Oxford, earning a chemistry degree in 1893 (first class) and a physics degree in 1894 (second class). He was known as a quiet, highly focused scientist who preferred laboratory work but also took part in college affairs. He married Muriel Holmes in 1918, and they had a daughter, Ruth. He died of cancer in Oxford in 1958.

Career highlights include a spell as a science master at Giggleswick School, after which he joined the University of Manchester. In 1907 he became fellow and tutor in charge of Jesus College’s new teaching and research laboratory, a post he held until his retirement in 1944; the laboratory closed in 1947. He also served as vice-principal of the college from 1926 to 1944.

Chapman’s research covered several areas. In photochemistry, he studied the hydrogen–chlorine reaction and showed that tiny impurities could cause significant effects. He proposed the steady-state hypothesis in 1913. In 1926 he demonstrated that interrupting light with a rotating sector affected the reaction rate, a method used to measure the mean life of a reaction intermediate. He contributed to detonation theory (the Chapman–Jouguet treatment) and to the understanding of how ions distribute near charged surfaces (the Gouy–Chapman layer).