why is iodine solution used to test for starch
Iodine test The iodine test is used to test for the presence of starch. Starch turns an intense "blue-black" colour upon addition of aqueous solutions of the triiodide anion, due to the formation of an intermolecular charge-transfer complex. In the absence of starch, the brown colour of the aqueous solution remains. This interaction between starch and triiodide is also the basis for iodometry.