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The chemical hydrochloric acid is a highly acidic aqueous solution of hydrogen chloride (HCl). It is highly corrosive liquid (at room temperature and pressure) and should be handled only with appropriate precautions. Hydrochloric acid is a commonly used chemical reagent and is one of the strong acids that ionize completely in an aqueous solution. Concentrated hydrochloric acid has a pH of less than -1 (See item 13 in this link [1] (http://www.okstate.edu/jgelder/acidPage27.html)).
Hydrochloric acid was discovered around A.D. 800 by Islamic alchemist Jabir Ibn Hayyam (Geber), by distilling common salt (NaCl) with sulphuric acid (H2SO4). It was known to European alchemists as spirit of salt or acidum salis. Gaseous HCl was called marine acid air. The old (pre-systematic) muriatic acid has the same origin (muriatic means "pertaining to brine or salt"). Hydrochloric acid is still sold under that name at industrial suppliers and hardware stores, for removing mortar stains and film from brickwork, masonry, and stonework.
Aqua regia is a mixture of hydrochloric and nitric acids.
Human digestive fluids consist of a mixture of hydrochloric acid and various enzymes which help break down proteins present in food.
Hydrochloric acid is now manufactured by combustion of chlorine gas in hydrogen to make hydrogen chloride gas followed by dissolution of the gas in water.
Hydrochloric acid is generally purchased in a concentrated form and is diluted in a fume cupboard, also known as a fume hood (see making up solutions).
Unlike other strong acids, hydrochloric acid does not cause rapid damage to healthy skin; it is possible to wash it off before damage occurs.
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