dialysis,  in chemistry, separation of suspended colloidal particles from dissolved ions or molecules of small dimensions (crystalloids) by means of their unequal rates of diffusion through the pores of semipermeable membranes. This process was first employed in 1861 by a British chemist, Thomas Graham. If such a mixture is placed in a sack made of parchment, collodion, or cellophane and suspended in water, the ions and small molecules pass through the membrane, leaving the colloidal particles in the sack. Separation by dialysis is a slow process, depending for its speed on the differences in particle size and diffusion rates between ... (100 of 133 words)

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