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(II) nitrate or one of its oxides, hydroxides, or carbonate with nitric acid: Cobalt(II) nitrate Cobalt Nitrate is the Inorganic compound with the formula Co(NO3)xHO. It is cobalt(II) salt. The most common form is the hexahydrate Co(NO)·6HO, which is a red-brown deliquescent salt that is soluble in water and other polar solvents. As well as the anhydrous compound Co(NO), several hydrates of cobalt(II) nitrate exist. These hydrates have the chemical formula Co(NO)·"n"HO, where "n" = 0, 2, 4, 6. Anhydrous cobalt(II) nitrate adopts a three-dimensional polymeric network structure, with each cobalt(II) atom approximately octahedrally coordinated by six oxygen atoms, each from a