A student investigated the diffusion of substances through Viking tubing, an artificial membrane
which has some of the properties of cell membranes.
The student made a bag of Visking tubing as shown in Fig. 4.1. The student added some iodine solution to the water in the test-tube
After 30 minutes at room temperature, the contents of the Viking bag were stained blue-black, but
the water outside remained a yellow colour