Iodine and its compounds are primarily used in medicine, photography, and dyes. Iodine is rare in the solar system and Earth's crust. The iodides are very soluble in water, and the element is concentrated in seawater.

Sublimation of an element or compound is a transition from the solid to gas phase with no intermediate liquid stage. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below the triple point (see phase diagram).