title: Cobalt(II) carbonate
text: # Cobalt(II) carbonate
  
  Cobalt(II) carbonate is the inorganic compound with the formula $CoCO_3.$ This reddish paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores. It is an inorganic pigment, and a precursor to catalysts. Cobalt(II) carbonate also occurs as the rare red/pink mineral spherocobaltite.
  
  ## Preparation and structure
  
  It is prepared by combining solutions cobaltous sulfate and sodium bicarbonate:
  
      $CoSO_4$ + 2 $NaHCO_3$ → $CoCO_3$ + $Na_2SO_4$ + $H_2O$ + $CO_2$
  
  This reaction is used in the precipitation of cobalt from an extract of its roasted ores.
  
  $CoCO_3$ adopts a structure like calcite, consisting of cobalt in an octahedral coordination geometry.
  
  ## Reactions
  
  Like most transition metal carbonates, cobalt carbonate is insoluble in water, but is readily attacked by mineral acids:
  
      $CoCO_3$ + 2 HCl + 5 $H_2O$ → $[Co(H_2O)_6]Cl_2$ + $CO_2$
  
  It is used to prepare many coordination complexes. The reaction of cobalt(II) carbonate and acetylacetone in the presence of hydrogen peroxide gives tris(acetylacetonato)cobalt(III).
  
  Heating the carbonate proceeds in a typical way for calcining, except that the product becomes partially oxidized:
  
      6 $CoCO_3$ + $O_2$ → 2 $Co_3O_4$ + 6 $CO_2$
  
  The resulting $Co_3O_4$ converts reversibly to CoO at high temperatures.
  
  ## Uses
  
  Cobalt carbonate is a precursor to cobalt carbonyl and various cobalt salts. It is a component of dietary supplements since cobalt is an essential element. It is a precursor to blue pottery glazes, famously in the case of Delftware.
  
  ## Related compounds
  
  At least two cobalt(II) carbonate-hydroxides are known: $Co_2(CO_3)(OH)_2$ and $Co_6(CO_3)_2(OH)_8·H_2O.$
  
  The moderately rare spherocobaltite is a natural form of cobalt carbonate, with good specimens coming especially from the Republic of Congo. "Cobaltocalcite" is a cobaltiferous calcite variety that is quite similar in habit to spherocobaltite.
  
  ## Safety
  
  Toxicity has rarely been observed. Animals, including humans, require trace amounts of cobalt, a component of vitamin B12.
  
  