In the 19th century, Thomas Graham found that the rate of effusion of a
gas is inversely proportional to the square root of the mass of its
particles. Graham's law of effusion is as follows: Rate of effusion for
gas 1 / Rate of effusion for gas 2 = sq rt. M2 / sq rt. M1,
where M1 and M2 represent the atomic or molecular
weights of the gases as appropiate.