Thomas Graham (1805-1869), the Scottish physical chemist. Ignoring his father's wish that he should enter the church, Graham began a career in science which led to professorships in Glasgow and London. He was a founder of physical chemistry and the first president of the Chemical Society of London. He investigated the mixing of gases separated by a porous barrier (diffusion), or allowed to mix by passing through a small hole (effusion). He also studied phosphorus and its oxyacids, and examined the behaviour of hydrogen gas with metals of the iron group. His work on dialysis began the effective study of colloidal chemistry.