Iodine Potassium Iodite 5% Iodine, also known as Lugol's solution, is a valuable resource in medical and scientific fields. The solution consists of iodine (I2), potassium iodide (KI) and water (H2O). Iodine and potassium iodide react together to form triiodide ions, which are soluble in water and cause the dark brown color of the solution.

In histology, Lugol's solution is commonly used to stain cell structures. It is an essential component of Gram staining, a method of distinguishing bacterial species. The solution binds to the cell wall of Gram-positive bacteria and forms larger dye complexes that persist after washing with alcohol.

In addition, Lugol's solution is used to detect starch, chitin and alkaloids. When in contact with starch, the solution forms a blue-black complex, indicating the presence of starch. With chitin and alkaloids, the solution changes color, indicating the presence of these substances.