Calcium iodide

Overview
Calcium iodide (CaI2) is an ionic compound of calcium and iodine. It is highly soluble in water and it is deliquescent. It is a salt that is solid at room temperature, and it behaves as a typical ionic halide. Because of its hygroscopic nature, it must be kept in tightly-sealed containers. It is similar to calcium chloride in many respects. It is used in photography.

Reactions
Henri Moissan first isolated pure calcium metal by reducing calcium iodide with pure sodium metal :
 * CaI2 + 2Na → 2NaI + Ca

Calcium iodide can be formed by reacting calcium carbonate with hydroiodic acid :
 * CaCO3 + 2HI → CaI2 + H2O + CO2

Calcium iodide slowly reacts with oxygen and carbon dioxide in the air, giving free iodine.