Investigating the Permeability of Dialysis Tubing Using Potassium Iodine in an Aqueous Starch Solution.

Biology 1492 Section 202
Introduction: In order to determine whether potassium iodine or starch will move across a semipermeable artificial membrane. We used a piece of dialysis tubing to serve as the artificial semipermeable membrane, the tubing allows some molecules or ions to pass through, but not others, the rate at which it will pass through depended on the temperature of the solutions used. The expected results were that when the potassium iodine combined with the starch it would turn the solution a dark purple/black color. In previous tests the color of the solution containing starch along with potassium iodine were determined to be true. The results we possible because of osmosis when the water combined with the potassium iodine had the ability to pass through the semipermeable membrane causing the two solutions to combine.
Materials Used: * 1 piece of dialysis tubing (wet) * 2 Clamps * 1 250 mL beaker * 1% soluble starch solution * 20 drops of potassium iodine reagent * 1 Disposable pipette
Methods: First we obtained all the materials needed and set up the experiment. We then filled a 250mL glass beaker with a 125mL of deionized water. Clamped one end of an approximately 6 inch dialysis tube, using the disposable pipette we opened the dialysis tube, then placed 59.8 degree Celsius 1% soluble starch solution inside tubing still using a disposable pipette until tube was approximately half way filled then clamped closed. Rinsed the tube thoroughly with deionized water, and placed tubing into beaker with deionized water and placed twenty drops of potassium iodine into the water. We lightly agitated contents of beaker until the potassium iodine was evenly dispersed. Finally we recorded the temperature of the beaker