Phosphoric acid (English: Phosphoric acid), or phosphoric acid (orthophosphoric acid), chemical formula H3PO4, is a common inorganic acid, which is non-volatile, non-decomposable, and has almost no oxidation. It is a medium and strong acid, which is weaker than hydrochloric acid, sulfuric acid and nitric acid, but stronger than acetic acid and boric acid. It is obtained by dissolving phosphorus pentoxide in hot water. Apatite is treated with sulfuric acid in phosphoric acid industry. Pure phosphoric acid can be obtained by oxidizing phosphorus with nitric acid. Generally 83%-98% thick solution, if re - concentration, you can get a colorless crystal. Phosphoric acid is readily deliriable in air; Heat will gradually lose water to produce pyrophosphoric acid, and further loss of water to produce metaphosphate. Phosphoric acid is likely to bind themselves into a variety of compounds, such as pyrophosphoric acid or triphosphoric acid. In addition to being used as a chemical reagent, phosphoric acid can also be mainly used in medicine, rust converting agent, food additives, solvents, electrolytes, fertilizers, metallurgy, feed, etc. It is also used in medical cosmetology and dentistry. Phosphoric acid is ternary and three hydrogen ions can be dissociated, thus three different acid groups can be formed, namely, dihydrogen phosphate H2PO− 4, hydrogen phosphate HPO2− 4 and phosphate PO3− 4.