Dialysis tubing

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Dialysis Tubing (Or more generically referred to as Visking Tubing) is a type of semi or partially permeable membrane tubing made from regenerated cellulose or cellophane. It is used for diffusion, or more accurately osmosis, and only allows the passage of small molecules, as explained below. It is used in clinical circumstances to ensure a filtered flow of molecules, preventing the flow of larger solute molecules. The term Visking refers to a company of the same name, which has now become a subsidiary of Medicell International. Despite the fact that the majority of partially, or semi-permeable tubing is now manufactured by a multitude of companies, many still refer to the phase as a generic term.

In terms of education, dialysis tubing is used in experiments, which demonstrate osmosis or diffusion similar to that used by the cell membrane in plant and animal cells. Typically, a solution containing several types of molecules, usually glucose and starch, is placed into a semipermeable dialysis bag, such as a cellulose membrane with pores, and the bag is sealed. The sealed dialysis bag is placed in a container of a different solution, or distilled water. Molecules small enough to pass through the tubing (often distilled water, salts, monosaccharides, and other small molecules) tend to move into or out of the dialysis bag, in the direction of decreasing concentration, therefore displaying diffusion. Larger molecules (often proteins, or polysaccharides) that have dimensions significantly greater than the pore diameter are retained inside the dialysis bag. ==