Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoCl2. It is a sky blue crystalline solid.
The compound forms several hydrates CoCl2•nH2O, 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 CoCl2·6H2O, 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.