The Physical Laws Relating to Gas. Graham's Law of Diffusion - Part 1

                                                            Graham’s Law of Diffusion

This law is named after Thomas Graham (1805–1869), who discovered that gases will mix with one another quite readily due to the continuous movement of the molecules. However, the rate at which they mix depends on the specific gravity or density of the gases. Graham made a container, consisting of two separate compartments with a small hole in their dividing wall. He placed a different gas in each of the compartments, one having a higher specific gravity than the other. He found that more faster, lighter molecules of the lighter gas passed through the hole rather than the slower, heavier molecules of the heavier gas. After many experiments he discovered that the rates of diffusion, or mixing, varied inversely to the square root of the density of the gas. Thus:

Diffusion rate ∝ 1 ÷

√

Density

Which basically means that a light gas will diffuse twice as fast as a gas four times its density.