[Co(NH3)5Cl]Cl2 + 3NaOH + 4H2O → CoO(OH) + 3NaCl + 5(NH3•H2O)
Chloridopentaamminecobalt(III) chloride react with sodium hydroxide and water to produce metacobalt(III) hydroxide, sodium chloride and ammonium hydroxide. Sodium hydroxide - concentrated cold solution.