The chemical used to test for the presence of starch is iodine solution (iodine in potassium iodide solution).

Quick Scoop

  • A few drops of iodine solution are added to the sample.
  • If starch is present, the sample turns blue‑black or purple‑black.
  • If there is no starch, the iodine stays yellow‑brown.

Tiny example

If you drop iodine solution on a piece of potato or bread, the area with starch will quickly turn blue‑black, showing a positive test for starch.

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