 Thomas Graham is known for his studies on the behaviour of gases, which resulted in his formulation of two relationships, both since becoming known as "Graham's Laws," the first regarding gas diffusion, and the second regarding gas effusion.In the former case, Graham deduced that when measured repeatedly under the same conditions of pressure and temperature, the rate of diffusive mixing of a gas is inversely proportional to the square root of its density, and given the relationship between density and molar mass, also inversely proportional to the square root of its molar mass.In the same way, in the latter case, regarding effusion of a gas through a pin hole in to a vacuum, Graham deduced that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.