Phorsphorsäure

Phosphoric acid (German: Phosphorsäure) is a mineral acid with the chemical formula H₃PO₄. It is a colorless, odorless, viscous liquid that is highly soluble in water. The acid consists of a phosphorus atom bonded to four oxygen atoms, three of which are protonated. As a triprotic acid, it has three dissociation constants (pK_a1 = 2.15, pK_a2 = 7.20, pK_a3 = 12.32), giving it amphoteric behavior and making it a good buffer in neutral to basic solutions.

Commercial phosphoric acid is produced mainly by treating phosphate rock with sulfuric acid, a process known as wet or acid route. The resulting solution can be concentrated by evaporation or crystallized as orthophosphoric acid for further processing. Alternative production routes, such as the dry or white phosphorus route, involve the oxidation of white phosphorus with oxygen, followed by hydrolysis.

Phosphoric acid is widely used in industry. It serves as a key ingredient in the manufacture of phosphate fertilizers, where it reacts with ammonium salts to form ammonium dihydrogen phosphate or monoammonium phosphate. In food technology it is employed as a flavoring agent (E338), acidity regulator, and as a stabilizer for carbonated beverages. It also finds applications in the production of detergents, electronic cleaners, and as a phosphor source in the synthesis of inorganic compounds. In laboratory settings, phosphoric acid is used as a buffer and as a reagent in various assays.

The acid is corrosive and can cause severe burns upon contact with skin or eyes. Inhalation of its vapors may irritate the respiratory tract. Proper protective equipment, adequate ventilation, and compliance with safety data sheets are necessary when handling. Environmental exposure can lower pH in aquatic ecosystems, affecting flora and fauna, and therefore phosphoric acid must be disposed of according to local regulations.