In many ways, ¹²⁹I is similar to ³⁶Cl. It is a soluble halogen, fairly non-reactive, exists mainly as a non-sorbing anion, and is produced by cosmogenic, thermonuclear, and in-situ reactions. In hydrologic studies, ¹²⁹I concentrations are usu ally reported as the ratio of ¹²⁹I to total I (which is virtually all ¹²⁷I). As is the case with ³⁶Cl/Cl, ¹²⁹I/I ratios in nature are quite small, 10⁻¹⁴ to 10⁻¹⁰ (peak thermonuclear ¹²⁹I/I during the 1960s and 1970s reached about 10⁻⁷

Ammonium iodide is the chemical compound NH₄I. It is used in photographic chemicals and some medications.^[1] It can be prepared by the action of hydroiodic acid on ammonia. It is easily soluble in water, from which it crystallizes in cubes. It is also soluble in ethanol. It gradually turns yellow on standing in moist air, owing to decomposition with liberation of iodine

Copper(I) iodide is the chemical compound with the formula CuI; it is also known as cuprous iodide. It is useful in a variety of applications ranging from organic synthesis to cloud seeding.

Copper(I) iodide is white, but samples are often tan or even, when found in nature as mineral marshite, reddish brown, but such color is due to impurities.^[1] It is common for iodides to become discolored because of the easy oxidation of the iodide anion to iodine.

Diphosphorus tetraiodide is used in organic chemistry for converting carboxylic acids to nitriles^[3], for deprotecting acetals and ketals to aldehydes and ketones, and for converting epoxides into alkenes and aldoximes into nitriles. It can also cyclize 2-aminoalcohols to aziridines^[4] and to convert α,β-unsaturated carboxylic acids to α,β-unsaturated bromides[