Cobalt

About Cobalt

Cobalt is the metal at the center of vitamin B₁₂ — the corrin ring with a Co(III) ion bound to five nitrogens and a sixth axial ligand is the only piece of biochemistry that uses a cobalt-carbon bond, and the rearrangements it catalyzes (methylmalonyl-CoA mutase, methionine synthase) have no good replacement. In the lab, cobalt is the classic teaching system for ligand-field color changes: dissolve CoCl₂·6H₂O in water and you get pink [Co(H₂O)₆]²⁺; add concentrated HCl or just heat it and the tetrahedral [CoCl₄]²⁻ appears as a sharp royal blue, which is why anhydrous cobalt chloride strips were the standard humidity indicator before that use was phased out over toxicity concerns. Industrially the ton-scale demand is for LiCoO₂ cathodes and NMC variants in lithium-ion cells, and for the γ′ phase strengtheners in nickel-cobalt superalloys that hold their creep resistance at the 1000+ °C inside a turbine hot section. About 70% of the world's mined cobalt comes out of the DRC's copper belt as a smelter byproduct.