Hydrochloric acid consists of hydrogen chloride dissolved in water. It has no color and is highly corrosive when concentrated. This strong acid is used for industrial purposes, including cleaning metal surfaces and manufacturing other chemicals, and it occurs naturally in the human digestive system.
The oxyntic cells in the lining of the human stomach produce hydrochloric acid, one of the substances in gastric juice. The acid plays an important role in the digestive process, and it kills some microorganisms in food. Hydrochloric acid also assists in converting pepsinogen to pepsin, an enzyme which is essential to the digestion of proteins.