silver iodide

A chemical compound used in cloud seeding both to produce artificial rain and to inhibit the formation of hail. This silver salt - technically a halide (AgI) - has a crystalline structure very similar to that of ordinary ice, which is why its crystals act as freezing nuclei. When silver iodide is introduced into a cloud, ice tends to accumulate directly on the crystals of this salt through the sublimation of water vapor, which can alter the natural processes that give rise to precipitation and affect the formation of raindrops, snowflakes, and hailstones.