Phosphoric acid , also known as orthophosphoric acid , is a common inorganic acid, is a strong acid, chemical formula H3PO4 , molecular weight 97.995 . Not volatile , not easy to decompose, almost no oxidation. With the commonness of acid, it is a ternary weak acid, and its acidity is weaker than hydrochloric acid , sulfuric acid , nitric acid, but stronger than acetic acid, boric acid, etc. Phosphoric acid delixes easily in ai r . Heat will lose water to pyrophosphoric acid, and further water loss to metaphosphate.

Phosphoric acid is mainly used in pharmaceutical, food, fertilizer and other industries, including as rust inhibitor, food additive, dental and orthopaedic surgery, EDIC etchant, electrolyte, flux, dispersant, industrial etchant, fertilizer raw materials and components of household cleaning products, and can also be used as chemical reagents.