The blue silica gel desiccant is a small amount of cobalt dichloride CoCl2 added to the silica gel desiccant (this substance is blue). When the silica gel absorbs moisture to a certain extent during the drying process, CoCl2 forms CoCl2·6H2O. The substance is pink. When the blue silica gel desiccant turns to pink, it means that the desiccant has absorbed moisture and has lost its function, but it can be regenerated by heating or by methods such as exposure, roasting, and air drying.

The reaction principle is:

CoCl2 6H2O (pink) = heating = CoCl2 (blue) + 6H2O

The reaction formula of the complex is as follows:

2[Co(H2O)6]Cl2 (pink) = Co[CoCl4](blue + 12H2O

Because blue silica gel contains a small amount of cobalt dichloride CoCl2, it is toxic. Avoid contact with food and inhalation. In case of poisoning, you should seek medical treatment immediately.