Pyrophosphoric acid, also known under the name diphosphoric acid, is a syrupy liquid or a viscous off-white solid.[1] Pyrophosphoric acid is colorless, odorless, hygroscopic and is soluble in water, diethyl ether, and ethyl alcohol. It is produced from phosphoric acid by dehydration. Pyrophosphoric acid slowly hydrolyzes in the presence of water into phosphoric acid.