Potassium Iodide exist as colourless or white cubic crystals or granules and becomes yellowish when exposed to bright light due to photochemical decomposition to liberate traces of free iodine.
Step 1: Potassium iodide is made by absorption of iodine in potassium hydroxide:
Step 2: Potassium iodate, KIO3 is then separated from the product mixture by crystallization and filtration. The remaining iodates are removed by evaporation of the solution and other processes, such as carbon reduction or thermal decomposition at 600ºC to iodide:
2KIO3 → 2KI + 3O2
Method 2: Treat iron turnings with iodine solution. The product, Fe3I8•16H2O, is boiled with 15 wt% potassium carbonate solution according to the equation below:
Fe3I8•16H2O + 4K2CO3 → 8 KI + 4CO2 + Fe3O4 + 16H2O
Method 3: Potassium iodide can be prepared by reacting hydriodic acid with potassium bicarbonate according to the equation below:
HI + KHCO3 → KI + CO2 + H2O
Agriculture Industry: Used as a fungicide
- Used as a nutritional supplement in animal feeds and food additives for human consumption.
- Used in nuclear medicine scintigraphy for thyroid protection.