USP Tincture of Iodine : for every 100 mL , it has 1.8 to 2.2 grams of iodine , 2.1 to 2.6 grams of sodium iodide , and 50mL ethanol . USP Tincture of Iodine is defined in the U.S. National Formulary ( NF ) as containing in each 100 mL , 1.8 to 2.2 grams of elemental iodine , and 2.1 to 2.6 grams of sodium iodide .