Osmosis experiment. Visking tubing being used to demonstrate osmosis. Osmosis is the movement of solvent molecules (such as water) through a semi-permeable membrane to an area of higher solute concentration, until the concentrations are equal on both sides of the membrane. Visking tubing is an artificial semi-permeable membrane that allows smaller molecules like water and glucose to pass through but blocks larger molecules like starch and sucrose. The tubing is filled with a sucrose (sugar) solution (seen here) and then placed in a beaker of water. As the concentration of water molecules is lower in the beaker, there is a net movement of water molecules, by osmosis, from the beaker into the tubing, causing the liquid level in the tube to