1833 – UK
‘Under the same conditions, the rate of diffusion of a gas is inversely proportional to the square root of its density’
For example, hydrogen diffuses four times as fast as oxygen under the same conditions of temperature and pressure.
Gases have no fixed volume; they expand to fill the entire volume of their container. This spreading of gas particles is called diffusion. The lightest gases diffuse most rapidly.
Graham is referred to as the father of colloid chemistry. In 1854 he invented the process of dialysis, which is based on the principle that some material will diffuse across a semi-permeable membrane and some material will not.