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• Kidney dialysis
• Electrodialysis

Dialysis is a process by which small molecules in a solution are separated from large molecules. Dialysis has a number of important commercial and industrial applications and plays a crucial role in maintaining the health of humans. For some people, in fact, the term dialysis refers to a specific kind of medical treatment in which a machine (the dialysis machine) takes on the functions of a human kidney. Dialysis machines have made possible the survival of thousands of people who would otherwise have died as a result of kidney failure.

Dialysis is a specific example of a more general process known as diffusion. Diffusion was first described by Scottish chemist Thomas Graham (1805–1869) around 1861. Graham studied the movement of molecules of different sizes through a semipermeable membrane. (A semipermeable...