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 states that the diffusion rate
of two gases varies inversely as the square
root of their densities. 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
semi-permeable membrane (a process he termed
`osmosis'). The human kidney uses the
principle of dialysis to extract nitrogenous
waste.