Cobalt(II) Hydroxide or Cobaltous Hydroxide is a highly water insoluble crystalline Cobalt source. It is a inorganic compound with the formula Co(OH)2, consisting of divalent cobalt cations Co2+and hydroxide anions HO−. Cobaltous hydroxide appears as rose-red powder, is soluble in acids and ammonium salt solutions, insoluble in water and alkalies.