Graham, Thomas (1805-1869)

Scottish chemist who laid the foundations of physical chemistry (the branch of chemistry concerned with changes in energy during a chemical transformation) by his work on the diffusion of gases and liquids. Graham's law (1829) states that the diffusion rate of a gas is inversely proportional to the square root of its density.

His work on colloids (which have larger particles than true solutions) was equally fundamental; he discovered the principle of dialysis, that colloids can be separated from solutions containing smaller molecules by the differing rates at which they pass through a semipermeable membrane. The human kidney uses the same principle to extract nitrogenous waste.

Graham was born in Glasgow and studied at Glasgow and Edinburgh. In 1830, Graham became professor at Anderson's College, Glasgow, moving to University College, London 1837-54. In 1855, he was appointed Master of the Royal Mint.