The main fluid that exists in the stomach is gastric acid, which is used to break down food and pass it to the small intestine for nutrient extraction. It is one of the most corrosive acids in existence, consisting of several compounds.
The stomach produces gastric acid as a response to food entering it. Gastric acid consists of hydrochloric acid, potassium chloride and sodium chloride. It has a very low pH that varies from 1 to about 4, enabling it to break down foods quickly. The lining of the stomach is coated with sodium bicarbonate and mucus to protect it against the corrosive effects of gastric acid.