What is Dialysis?

   Dialysis is a method by which colloidal particles, or large molecules, can be separated from smaller molecules in solution. It makes use of a semi­permeable membrane that prevents the passage of the large molecules. For example, if a mixture of salt solution and glue is placed on one side of a semi­permeable membrane and water is placed on the other side, the salt particles diffuse through the membrane into the water. The colloidal glue particles, however, do not pass through the membrane. If the water into which the salt diffuses is being removed, the salt is carried away as soon as it passes through the mem­brane, and eventually only glue and water will remain on the other side of the membrane. Dialysis should not be confused with osmosis, the passage of solvent through a semipermeable membrane from a less concentrated to a more concentrated solution.