Graham’s Law

Graham’s Law

In 1829, Graham published a paper on the diffusion of gases. Most of the observations on this subject were made by Johann Dobereiner and Joseph Priestley, but Graham formulated the law of diffusion. Graham compared the different rates at which various gases diffuse through some porous pots. He also compared the rate of effusion via a tiny aperture. He concluded that the rate of effusion or diffusion of a gas at a constant temperature is simply inversely proportional to square-root of its density. This is popularly known as the Graham’s Law.

Diffusion of Liquids

In 1860, Graham examined liquids. He noted that colored sugar solution placed at the bottom most part of a glass of water gradually extends its color upward. This process was called diffusion. He also noted substances like gelatin, glue, albumen and starch diffuse slowly. He classified substances into two types: crystalloids, substances that diffuse quickly, and colloids, substances that diffuse slowly.

Other works by Thomas Graham includes research into phosphorous acids, absorption of hydrogen by palladium and the water of crystallization in hydrated salts.

Graham died September 16th, 1869 at the age of 63.