Peroxydiphosphoric acid
Peroxydiphosphoric acid is an oxyacid of phosphorus. Its salts are known as peroxydiphosphates. It is closely related to peroxymonophosphoric acid. These compounds are in turn related to the peroxydisulfuric acid and peroxysulfuric acid. These compounds are all colorless. In terms of structure, peroxydiphosphoric acid features two tetrahedral phosphorus centers linked by a peroxide group.
Preparation
Both peroxyphosphoric acids were first synthesized and characterized in 1910 by Julius Schmidlin and Paul Massini, where peroxydiphosphoric acid was obtained in poor yields from the reaction between diphosphoric acid and highly-concentrated hydrogen peroxide.Peroxydiphosphoric acid can be prepared by the reaction between phosphoric acid and fluorine, with peroxymonophosphoric acid being a by-product.
The compound is not commercially available and must be prepared as needed. Potassium peroxodiphosphate, which is commercially available, can be obtained by electrolysis of phosphate solutions.