Cobalt chloride (CoCl₂) is an inorganic compound found mainly in the form of blue crystalline powders. It is highly hygroscopic and rapidly converts to red cobalt dichloride hexahydrate when exposed to moist air. Cobalt chloride is stable at room temperature, but when heated, it loses its crystal water and turns blue, and can turn red again in moist air. Its aqueous solution turns blue when heated or when concentrated hydrochloric acid, chloride or organic solvents are added. It begins to weathered and turbidity at 30~45 °C, becomes tetrahydrate when heated at 45~50 °C for 4 hours, and becomes anhydrous when heated to 110 °C.

Cobalt chloride is a multi-purpose compound whose main uses include:

1. Analytical reagents and ammonia absorbents: Cobalt chloride is widely used as an analytical reagent, especially in ammonia absorption.

2. Instrument manufacturing: Cobalt chloride is a very important component in the manufacture of barometers, hydrometers, wet and dry indicators, etc.

3. Ceramics and coatings industry: used as a colorant in the ceramic industry, and at the same time in the coatings industry for the manufacture of paint driers.

4. Animal husbandry: Cobalt chloride is used in the formulation of compound feeds to support the trace element needs of animals.

5. Brewing industry: Cobalt chloride is used as a beer foam stabilizer to help maintain the durability of beer foam.

6. Defense industry: Cobalt chloride is used in the defense industry to make poison gas hoods.

7. Chemical Reaction Catalyst: In chemical reactions, cobalt chloride is used as a catalyst to facilitate the progress of a specific reaction.

8. Analytical chemistry: In analytical chemistry, cobalt chloride is used for drip analysis of zinc, haplotype, etc.

9. Other uses: Cobalt chloride is also used in the manufacture of hidden inks, cobalt chloride test strips, color-changing silica gel, etc., as well as as ammonia absorbents, colorants and chemical reagents for glass and ceramics.