Portrait of Sir Cyril Hinshelwood (1897-1967), English chemist and Nobel Laureate. Hinshelwood spent all of his professional life at Oxford, having entered the university on a scholarship in 1919. He devoted his life to the study of reaction mechanisms, particularly explosive 'chain reactions' of gases. He discovered that above a certain temperature, a mixture of oxygen and hydrogen would combine explosively, but below that temperature they would not. This he discovered was due to the mechanism of the reaction, the successive formation of hydrogen and oxygen radicals. It was for this work that he shared the 1956 Nobel Prize for chemistry with Semenov.