Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive systems of most animal species, including humans. Hydrochloric acid is an important laboratory reagent and industrial chemical.

Johann Rudolf Glauber was a German-Dutch alchemist and chemist. Some historians of science have described him as one of the first chemical engineers. His discovery of sodium sulfate in 1625 led to the compound being named after him: "Glauber's salt".