Potassium iodide (KI) crystals are a white salt and the most commercially important compound of iodine. Potassium iodide is commonly used as a dietary source of iodine in animal feed and iodized salt. Potassium iodide can eventually oxidize to iodine and may also be used to isolate pure iodine crystals in the laboratory.
Instructions
1. Weigh 2g of potassium iodide on the scale and pour it into a test tube. Add 1.5 mL of distilled water to the test tube and dissolve the potassium iodide crystals by swirling the solution.
2. Add 1.5 mL concentrated hydrochloric acid to the test tube and mix by swirling. Add 10 mL of a 3 percent solution of hydrogen peroxide. This will immediately cause the iodine to oxidize and precipitate out of the solution as a solid.
3. Fold a piece of filter paper and place it in a funnel. Pour the solution through the funnel to collect the iodine crystals. Pour distilled water through the filter paper and allow it to drain. Repeat this procedure several times to thoroughly rinse the iodine crystals.
4. Remove the filter paper from the funnel and spread it open on a watch glass. Allow the crystals to dry thoroughly, but don't leave them exposed to air longer than necessary, as they will eventually sublimate into a gas.
5. Transfer the dry crystals to storage bottle or vial and seal the container. This procedure should produce about 1g of pure iodine crystals.
Tags: filter paper, iodine crystals, test tube, distilled water, iodide crystals, Potassium iodide, pure iodine