Hydrochloric acid (HCl) is a solution of hydrogen chloride gas dissolved in water. A given volume of water can dissolve up to 1,000 times its volume of hydrogen chloride gas. Hydrochloric acid, one of the strongest of all acids, is colorless and very corrosive. It is a clear liquid that may be colored yellow by trace amounts of iron, chlorine or organic matter that occurs in most water sources. It is extremely caustic and can be dangerous. On contact, it causes severe burns that should be flushed immediately with water. In air, the acid gives off strong fumes that irritate the throat and lungs if inhaled. Because it does not contain carbon, hydrochloric acid is categorized as an inorganic acid. It is often referred to by its traditional name, muriatic acid.

Centuries after hydrochloric acid was first prepared, scientists have still not completely explained how the delicate...