Sodium hydroxide can be made (with chlorine and hydrogen) using the chloralkali process. A solution of sodium chloride is electrolyzed and sodium hydroxide is made around the cathode, where water is reduced to hydrogen gas and hydroxide ion. The hydrogen is released and the hydroxide bonds with the sodium to make sodium hydroxide. Special care is required to prepare a solution of sodium hydroxide or NaOH in water because considerable heat is liberated by the exothermic reaction. The solution may splatter or boil.