Iodine test

The iodine test is used to test for the presence of starch. When treated with IKI solution—iodine dissolved in an aqueous solution of potassium iodide—the triiodide anion (I₃) complexes with starch, producing an intense blue/purple colour. The colour can be detected visually with concentrations of iodine as low as 2×10 M at 20 °C. However, the intensity of the color decreases with increasing temperature and with the presence of water-miscible organic solvents such as ethanol. The test cannot be performed at very low pH due to the hydrolysis of the starch under these conditions.