When an electric current is passed through a strong solution of salt in water, electrolysis occurs and three products are formed:
- Chlorine (Cl2)
- Sodium hydroxide (NaOH)
- Hydrogen (H2).
Because hydrogen and chlorine gases form an explosive mixture, it is important to keep them separated. All three products are useful individually and they can also be combined together to make further products. Sodium hydroxide and chlorine combine to form sodium hypochlorite solution which is widely used in the home as domestic bleach. A stronger solution of sodium hypochlorite is used as a dairy and industrial disinfectant.
Under different reaction conditions, sodium hydroxide and chlorine will react to form sodium chlorate. This is produced as white crystals which can be highly explosive or inflammable if mixed with organic matter. Solutions of sodium chlorate are widely used as a herbicide.
When chlorine gas is burned in hydrogen, the two gases react to form hydrogen chloride. The hydrogen chloride dissolves in water to form hydrochloric acid. Hydrochloric acid made in this way is very pure, and can be used safely in the food and pharmaceutical industries.