Acids are substances that taste sour when diluted with water, combine with bases to form salts, and turn blue litmus paper red. There are two main groups of acids: organic and inorganic or mineral acids. Strong mineral acids have a corrosive action and may cause severe burns if placed on the skin or swallowed. Sometimes they are used as cauterizing agents for the strelization of infected wounds. sulfuric, and hydrochloric acids are the most commonly known mineral acids.
Because of their germicidal and antibacterial effects, many acids, both organic and inorganic, have been used in the preservation of certain foods and in various pharmaceutical preparations, in eye and ear solutions, and in surgical dressings. Boric, acetic, and benzoic acids fall in to this category. Many acids are naturally present in thetissues and secretions of the body and play an important role in growth and othervital processes. The role may be a simple one, such as that of the hvdrochloric acid secreted by the gastric cells of the stomach to aid digestion, or very complex ones, as in the cases of arn ino acids, essential fatty acids, and the nucleic acids.