14 g of potassium iodate and 15 g of potassium hydroxide are dissolved in 150 mL of water, which is then poured into a narrow container. A chlorinating apparatus is set up and loaded with 30 g of trichloroisocyanuric acid to generate chlorine gas at a rate of 4 bubbles per second. After the reaction is complete, the mixture is acidified with concentrated hydrochloric acid and it is boiled down gently to 50 mL in volume. The solution is poured into 100 mL of cold water and placed in a refrigerator overnight to precipitate all of the product out. The mixture is then filtered, washed with water and the product is dried in open air.
3 KIO3 + 6 KOH + 2 Cl2 = K4I2O9 + 4 KCl + 3 H2O
K4I2O9 + 2 HCl = 2 KIO4 + 2 KCl + H2
Oxidation of the potassium iodide