6.1 - E - Dialysis Tubing Experiments
Dialysis tubing is a type of semi-permable membrane. Because of its small pores, this type of tubing can be used in separation experiments. Mixtures of substances can be placed inside of the the tubing with the ends tied off.
By using indicators, the movement of molecules can be observed. A common variation of this experiment involves the use of starch, amylase and iodine. When in the presence of starch, iodine turns dark color but maintains a brown color in the presence of glucose.
Since starch is large, it is unable to pass through the dialysis tubing unless amylase is present. So, color changes can be used to determine whether starch is being digested and diffusing through the membrane pores. A typical setup can be seen to the right and the results below.