Tincture of iodine

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Tincture of iodine is a disinfectant. It has iodine and potassium iodide dissolved in ethanol and water. Normally, iodine does not dissolve in water. But when iodide is added, the iodine can dissolve. Also, ethanol helps iodine dissolve. Tincture of iodine has about equal amounts of iodide and iodine. There are two types of tincture of iodine:

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. The rest is water.

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. The rest is water.

It can be used as a skin disinfectant and as a water disinfectant. Because it has iodine in it, it is toxic in large amounts. Lugol's iodine is an alcohol-free version. It is commonly used in experiments in middle school science labs.