Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoCl2 and sky blue in colour. It is most commonly supplied as the hexahydrate CoCl2·6H2O, which is pink in colour. Concentrated aqueous solutions are red at room temperature but become blue at higher temperatures. CoCl2·6H2O is deliquescent while the anhydrous salt CoCl2 is hygroscopic.
Hydrated cobalt chloride is manufactured from reaction of cobalt(II) hydroxide or cobalt(II) carbonate with hydrochloric acid according to the reactions below:
CoCO3 + 2 HCl + 5 H2O → Co(H2O)6Cl2 + CO2
Upon heating, the hexahydrate dehydrates. Dehydration can also be effected with trimethylsilyl chloride:
CoCl2•6H2O + 12 Me3SiCl → CoCl2 + 6 (Me3Si)2O + 12 HCl
Painting and printing Industry: Used as a catalyst, printing and dyeing mordant.
Chemical Industry: Used as an analytical reagent.