Used as a visual indicator in analytical chemistry to detect the presence of oxidizing agents, particularly free halogens like chlorine and bromine in solution. When exposed to an oxidizing substance, the iodide ions are oxidized to iodine, which then complexes with the starch to produce a distinct blue-black color. The addition of zinc improves the stability and shelf life of the solution, making it more reliable for field testing and laboratory use. Commonly applied in water quality testing to confirm the absence of residual oxidants after dechlorination processes, and in educational demonstrations of redox reactions. Its sensitivity and clear color change make it ideal for qualitative analysis in environmental, industrial, and academic settings.