The Probert Encyclopaedia of Science & Technology

HYDROCHLORIC ACID

Hydrochloric acid (also known as chlorhydric acid, muriatic acid and spirit of salt) is a compound of chlorine and hydrogen that occurs in the human stomach. It was discovered in 1648 by Johann Glauber and first prepared in 1772 by Joseph Priestley, while its constitution as a compound solely of chlorine and hydrogen was determined in 1810 by Humphry Davy. Today the term is restricted to the aqueous solution of hydrogen chloride (which is a gas normally).

Hydrochloric acid is evolved during volcanic eruptions, and is found in the water which collects in the crevices of mountains, as well as in rivers which take their rise in volcanic formations, especially in South America. It is manufactured by decomposing common salt with sulphuric acid. A mixture of equal volumes of hydrogen and chlorine combines slowly in diffused daylight, but explosively in bright sunlight. Hydrochloric acid is colourless, has a pungent odour, and an acid taste. It is quite irrespirable, extinguishes flame, and dissolves very readily in water. Its solution is ordinary hydrochloric acid, and is used for the preparation of chlorine for the bleaching-powder manufacturer. It is also used in the preparation of glue, phosphorus, carbonic acid, artificial waters, etc. In medicine it was formerly used diluted as a tonic and astringent. In a concentrated form it is a powerful caustic.
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