USP Strong Iodine Tincture : for every 100 mL , it has 6.8 to 7.5 grams of iodine , 4.7 to 5.5 grams of potassium iodide , and 50 mL ethanol . USP Strong Iodine Tincture is defined in the NF as containing in each 100 mL , 6.8 to 7.5 gram of iodine , and 4.7 to 5.5 gram of potassium iodide . Purified water is 50 mL and the balance is alcohol .