What is the tincture of iodine? What is its use?

Hint: We must remember that a tincture of iodine is also known as weak iodine solution or weak alcohol solution. It is usually 2–7% elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of ethanol and water.

Complete step by step answer:
Iodine tincture which is also known as weak alcohol or weak iodine solution is a combination of elemental iodine, sodium iodide or potassium iodide, ethanol, and water.
An iodine tincture is an alcoholic solution that we can prepare by first dissolving \[5{\text{ }}grams\] of potassium iodide or sodium iodide in \[100{\text{ }}ml\] of pure alcohol and then by adding of iodine crystals or elemental iodine. This preparation makes 2% of iodine tincture. Sodium iodide or potassium iodide are needed to first dissolve in ethanol as this mixture only will aid in dissolving elemental iodine which is insoluble in water.
It is a disinfectant or antiseptic.
Following are uses of Iodine tincture:
Tincture of iodine is commonly found in emergency survival kits as it is applicable when we get cuts and scratches. Remember iodine tincture is applicable only on minor wounds.
It is mostly used to clean the skin surface to prevent bacterial or microbial infections.
Iodine tincture is also used in water treatment plants as disinfectant. Five drops of 2% of iodine tincture solution is generally added to 1 liter of water.

Note:
Tincture of Iodine has been defined by the U.S. National Formulary as a solution where each 100 ml contains 1.8 to 2.2 grams of elemental iodine or iodine crystals, 2.1 to 2.6 grams of sodium iodide, 50 ml of pure alcohol and balanced water.
Also we can use it to sanitize water, it does not provide protection against some protozoans like Cryptosporidium and Giardia.
Iodine tincture is not a recommended to use as a nutritional source of iodine.