Organic chemist. Born in Edinburgh, the son of a clergyman, Crum Brown was educated at the Royal High School and University of Edinburgh. He went on to study in London and in Germany before returning to Edinburgh in 1863. He gained the Chair of Chemistry at the University in 1869 occupying it until his retirement in 1908. This Chair now bears his name. He discovered the carbon double bond in ethylene (1864), which was to have important implications for the modern plastics industry. He devised the system of representing chemical compounds in diagrammatic form, with connecting lines representing bonds. He made significant contributions to pharmacology, but also worked in physiology, phonetics, mathematics and crystallography. In the 1880s, he also developed a method to prevent the forgery of banknotes for the Bank of Scotland, but this was soon defeated.