Cobalt hydroxide precipitate. Cobalt hydroxide (Co(OH)2) is formed by adding sodium hydroxide (NaOH, clear) to a solution containing cobalt ions, in this case cobalt chloride solution (CoCl2.6H2O, pink). This reaction produces sodium chloride (NaCl) solution and cobalt hydroxide, which is precipitated out of solution as a dark blue solid. Addition of sodium hydroxide is used as a test for positive metal ions in solution, in this case hydrated transition metal ions.
Model release not required. Property release not required.