This Cobalt (II) chloride A.R. is an inorganic compound with the chemical formula CoCl2. It has an CAS number of 7646-79-9. It is commonly used in analytical chemistry as a reagent for the determination of water content in various materials. It can also be used in the manufacture of pigments and dyes. Its molecular weight is 134.87 g/mol and it is a yellow-green solid that is highly hygroscopic.