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This shows a picture of a recessed plastic tile used to test small quantities of starch - either as a sol or as a solid. The test reagent used here is a solution of iodine (in potassium iodide).
The 3 drops on the top row show (from left to right):
iodine solution on its own
iodine solution mixed with starch sol (positive result)
iodine mixed with colourless liquid (negative result)
The bottom row shows rice grains, before and after adding iodine solution.
