7. HYDROCHLORIC ACID

7. HYDROCHLORIC ACID

Hydrochloric acid is a slightly yellow, highly corrosive and poisonous liquid. It is formed by dissolving hydrogen chloride (HCl) gas in water. Commercial, fuming hydrochloric acid contains 37 to 39% (thirty-seven to thirty-nine per cent) hydrogen chloride. Hydrochloric acid is used in the manufacture of a wide variety of substances, e.g. gelatin dyes, pharmaceuticals, etc. It is also used in cleaning metal parts, tanning and etcing.

Hydrogen chloride is prepared by burning hydrogen in an atmosphere of chlorine or by the action of sulphuric acid (H₂SO₄) on common salt (NaCl).

2NaCl + H₂SO₄ = Na₂SO₄ + 2HCl

This reaction takes place at high temperatures only and is used mainly in laboratory. For commercial production of hydrogen chloride the synthetic method is used, that is by burning hydrogen in an atmosphere of chlorine.