Iodine Tincture that is 2% Iodine and 47% alcohol can be used to purify water. (This is the typical mixture that you find in drugstores. However, you will want to confirm these ratios before using.) The typical way to do this is to use an eye-dropper. 5 to 10 drops per liter is required. This is a judgment call that you have to make, based on the quality of the water. 10 drops per liter is great, but it does have a bitter taste. After you add the Iodine, wait 30 minutes before drinking. Remember, if you dipped the container that you are purifying, any water you got on the lip can still make you sick. Clean and purify this as well.