Cobalt it reacts slowly with mineral acids, and very slowly with moist, but not with dry, air. Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 (cobalt(II)). These salts form the pink-colored metal aquo complex [Co(HO)] in water. Addition of chloride gives the intensely blue . In a borax bead flame test, cobalt shows deep blue in both oxidizing and reducing flames. Several oxides of cobalt are known. Green cobalt(II) oxide (CoO) has rocksalt structure. It is readily oxidized
Cobalt boride Cobalt boride nanoparticless in the size range of 18 to 22 nm have also been produced. When used as a catalyst, cobalt boride is prepared by reducing a cobalt salt, such as Cobalt(II) nitrate, with sodium borohydride. Prior to reduction, the surface area of the catalyst is maximized by supporting the salt on another material; often this material is activated carbon. Cobalt boride Cobalt borides are inorganic compounds with the general formula CoB. The two main cobalt borides CoB and CoB. These are refractory materials. Cobalt boride is known to be exceptionally resistant to oxidation, a chemical property which makes