* As a mordant when performing a Gram stain. It is applied for 1 minute after staining with crystal violet, but before ethanol to ensure that gram positive organisms' peptidoglycan remains stained, easily identifying it as a gram positive in microscopy.
* This solution is used as an indicator test for the presence of starches in organic compounds, with which it reacts by turning a dark-blue/black. Elemental iodine solutions like Lugols will stain starches due to iodines interaction with the coil structure of the polysaccharide. Starches include the plant starches amylose and amylopectin and glycogen in animal cells. Lugol's solution will not detect simple sugars such as glucose or fructose. In the pathologic condition amyloidosis, amyloid deposits (i.e., deposits that stain like starch, but are not) can be so abundant that affected organs will also stain grossly positive for the Lugol reaction for starch.
* It can be used as a cell stain, making the cell nuclei more visible and for preserving phytoplankton samples.
* Lugol's solution can also be used in various experiments to observe how a cell membrane uses osmosis and diffusion.
* Lugols solution is also used in the marine aquarium industry. Lugols solution provides a strong source of free iodine and iodide to reef inhabitants and macroalgae. Although the solution is thought to be effective when used with stony corals, systems containing xenia and soft corals are assumed to be particularly benefited by the use of Lugols solution. Used as a dip for stony and soft or leather corals, Lugols may help rid the animals of unwanted parasites and harmful bacteria. The solution is thought to foster improved coloration and possibly prevent bleaching of corals due to changes in light intensity, and to enhance coral polyp expansion. The blue colors of Acropora spp. are thought to be intensified by the use of potassium iodide. Specially packaged supplements of the product intended for aquarium use can be purchased at specialty stores and online.