Phosphoric acid or orthophosphate, is a common inorganic acid, is medium strong acid, chemical formula is H3PO4, molecular weight is 97.994. Not volatile, not easy to decompose, almost no oxidation. Has the common acid, is ternary weak acid, its acidity than hydrochloric acid, sulfuric acid, nitric acid weak, but than acetic acid, boric acid and so on. From phosphorus pentoxide dissolved in hot water can be obtained. Apatite can be obtained by treating apatite with sulfuric acid in orthophosphate industry. Phosphoric acid deliquesces easily in air. Heating will lose water to get pyrophosphate, further loss of water to get metaphosphoric acid. 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 material and component of household cleaning products. Also used as a chemical reagent, phosphate is a nutrient for all life forms.