A medium strength inorganic acid corresponding to the highest degree of oxidation of phosphorus (+5). It is used as a flux for soldering (oxidized copper, ferrous metals, stainless steel) and for research in molecular biology. It is also used to remove rust from metal surfaces. It forms a protective film on the treated surface preventing further corrosion. It is also used as a binder in freons, in industrial freezing units.
Orthophosphoric acid is registered as food additive E338. It is used as an acidity regulator in carbonated beverages