Hydrochloric acid is naturally found in the gastric juices of the stomach. The gastric juices, together referred to as gastric acid, contain mostly potassium chloride, or KCl, and sodium chloride, or NaCl. Because of its highly acidic properties, HCl is able to dissolve many of the foods we eat. The corrosiveness of HCl also aids in fighting off infections and helping the immune system. HCl kills any pathogens, disease-causing particles or organisms that may be on the foods we eat.