Dialysis is a method used for separating lower molecular weight components from macromolecules. A thin membrane in the form of a tube is used in this method. The solution to be separated is filled inside the thin membrane. They porosity (Pore size) of the membrane allows the diffusion of small molecules (amino acids, salts) while the larger molecules (nucleic acids, proteins) cannot pass though and are retained inside the dialysis tube.
This principle of Dialysis is used to filter out waste products and purify blood in individual where the kidneys are no longer functional. Thus, the Dialysis tube performs the function of an Artificial Kidney.