Hydrochloric

Hydrochloric is an adjective used mainly in chemistry to describe hydrogen chloride (HCl) or hydrochloric acid, the aqueous solution of hydrogen chloride. It may refer to the gas HCl or to compounds formed from hydrogen chloride, and is encountered in the term hydrochloride for acid salts.

Hydrogen chloride is a diatomic molecule. In water it forms hydrochloric acid, a strong monoprotic acid that fully dissociates to H+ and Cl−. Concentrated hydrochloric acid is typically around 32–38% by weight, highly corrosive and miscible with water. The solution is acidic across a wide range of concentrations.

Industrial production: HCl is produced mainly as a byproduct of chlorine production from salt; it can also be generated by direct synthesis of hydrogen and chlorine. In plants, HCl gas is absorbed in water to yield aqueous hydrochloric acid.

Occurrence: Hydrochloric acid occurs naturally in stomach juice, where it aids digestion, and is widely used in laboratory and industry.

Uses: It is used for metal cleaning and pickling, pH control, generation of chlorides, and as a reagent in organic synthesis, including production of vinyl chloride monomer. Its salts, chlorides, are common in inorganic and organic chemistry.

Safety: Hydrochloric acid is highly corrosive to skin and eyes; inhalation of fumes irritates the respiratory tract. It reacts with many metals to form metal chlorides and hydrogen gas. Handling requires ventilation, protective equipment, and proper storage.

Derivatives: The term hydrochloride is used for acid salt forms of many compounds, notably in pharmaceuticals (for example, lidocaine hydrochloride), where HCl is combined with the base to form a salt.