Loschmidt diffusion tube

The Loschmidt diffusion tube is an apparatus used to measure the diffusion of gases. Diffusion is the process by which molecules spread out to become uniformly distributed. In the context of gases, this means that even in a mixture, molecules will move from areas of high concentration to areas of low concentration until they are evenly spread.1

The Loschmidt diffusion tube was developed by Austrian chemist Joseph Loschmidt, who used a modified version of an apparatus originally devised by Thomas Graham. Loschmidt used this tube in 1870 to conduct accurate measurements of diffusion rates for various gas pairs. The diffusion coefficient, a measure of how quickly a substance diffuses, is typically expressed in square meters per second (m²/s). Gases diffuse much faster than liquids, with gaseous diffusion coefficients being about 100,000 times larger.21