Chronic overexposure can have adverse effects on the thyroid. Potassium iodide is a possible teratogen. Industrial uses KI is used with silver nitrate to make silver iodide (AgI), an important chemical in film photography. KI is a component in some disinfectants and hair treatment chemicals. KI is also used as a fluorescence quenching agent in biomedical research, an application that takes advantage of collisional quenching of fluorescent substances by the iodide ion. However, for several fluorophores addition of KI in μM-mM concentrations results in increase of fluorescence intensity, and iodide acts as fluorescence enhancer. Potassium iodide is a component in the electrolyte of dye sensitised solar cells (DSSC) along with iodine. Potassium iodide finds its most important applications in organic synthesis mainly in the preparation of aryl iodides in the Sandmeyer reaction, starting from aryl amines. Aryl iodides are in turn used to attach aryl groups to other organics by nucleophilic substitution, with iodide ion as the leaving group. Chemistry Potassium iodide is an ionic compound which is made of the following ions: . It crystallises in the sodium chloride structure. It is produced industrially by treating KOH with iodine. It is a white salt, which is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It absorbs water less readily than sodium iodide, making it easier to work with. Aged and impure samples are yellow because of the slow oxidation of the salt to potassium carbonate and elemental iodine. 4 KI + 2 CO2 + O2 -> 2 K2CO3 + 2 I2 Inorganic chemistry Since the iodide ion is a mild reducing agent, is easily oxidised to iodine () by powerful oxidising agents such as chlorine: 2 KI_{(aq)}{} + Cl2_{(aq)} -> 2 KCl_{(aq)}{} + I2_{(aq)} This reaction is employed in the isolation of iodine from natural sources. Air will oxidize iodide, as evidenced by the observation of a purple extract when aged samples of KI are rinsed with dichloromethane. As formed under acidic conditions, hydriodic acid (HI) is a stronger reducing agent. Like other iodide salts, forms triiodide () when combined with elemental iodine. KI_{(aq)}{} + I2_{(s)} -> KI3_{(aq)} Unlike , salts can be highly water-soluble. Through this reaction, iodine is used in redox titrations. Aqueous , "Lugol's solution", is used as a disinfectant and as an etchant for gold surfaces. Potassium iodide and silver nitrate are used to make silver(I) iodide, which is used