 
Hydrochloric acid, or muriatic acid, has the chemical formula HCl. Molecules are composed of one hydrogen and one chlorine atom. Hydrochloric acid is a strong acid that is used in many industries. It is a solution of hydrogen chloride in water that's colourless and has a pungent odour. It is corrosive to skin, eyes, and mucous membranes, and can cause severe chemical burns and blindness if it gets into the eyes.
Humans and most other animals secrete hydrochloric acid in the digestive system. HCl creates an acidic environment in the stomach with a pH of about 1.5 to 3.5. The stomach's glands produce hydrochloric acid along with digestive enzymes and other substances that make up gastric juice. The body produces about 3 to 4 liters of gastric juice each day. HCl breaks down proteins and activates pepsinogen into pepsin, an enzyme that starts protein digestion. HCl also kills bacteria and other pathogens that may be ingested with food or water. HCl in the stomach also helps the body absorb minerals like calcium, iron, and phosphate. Conditions, medications, and lifestyle factors can cause fluctuations in stomach acid levels. Low stomach acid, also known as hypochlorhydria, can make it difficult to digest food, especially protein. High stomach acid can cause symptoms like heartburn, nausea, ulcers, and vomiting. Hydrochloric acid has many commercial applications. It is used to produce inorganic compounds, refine metals, and regulate pH. It is used in electroplating, gasoline refining, and the production of fertilizers. Of the common strong acids, it is one of the least hazardous to handle, least expensive, and easiest to store. The food industry uses hydrochloric acid to process a variety of food products, such as corn syrups used in soft drinks, cookies, crackers, ketchup and cereals. Hydrochloric acid is also used as an acidifier in sauces, vegetable juices and canned goods, to help enhance flavor and reduce spoilage. |