Cobalt(II) chloride

Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoCl
₂. It is a sky blue crystalline solid.

The compound forms several hydrates CoCl
₂•nH
₂O, for n = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed. The dihydrate is purple and hexahydrate is pink. It is usually supplied as the hexahydrate CoCl
₂·6H
₂O, which is one of the most commonly used cobalt compounds in the lab.

Because of the ease of the hydration/dehydration reaction, and the resulting color change, cobalt chloride is used as an indicator for water in desiccants.

Niche uses of cobalt chloride include its role in organic synthesis and electroplating objects with cobalt metal.

Cobalt chloride has been classified as a substance of very high concern by the European Chemicals Agency as it is a suspected carcinogen.