Prepare a solution or suspension of the sample by placing ~0.1 g in 10 ml of water. Two ml of a sample solution is placed in a test tube. Two drops of iodine/potassium iodide solution and one ml of water are added. Solids may be tested by placing the iodine/potassium solution directly on the solid.
A positive test is indicated by:
the formation of a blue-black complex.
a negative test (left) and a positive test (right)
