Preparation of phosphoric acid

The raw materials of phosphoric acid are mainly phosphate ore (the main component is calcium fluorophosphate Ca10F2(PO4)6) and inorganic acid mainly sulfuric acid.

Laboratory method: the laboratory can be used to prepare phosphoric acid with strong acid + phosphate.　　

3H+ + PO43- ==== H3PO4 (principle: strong acid system weak acid)

Wet method: industry commonly used concentrated sulfuric acid and calcium phosphate, phosphate rock reaction to produce phosphoric acid, filtered off slightly soluble in water calcium sulfate precipitate, the resulting filtrate is a solution of phosphoric acid. Or let the white phosphorus and nitric acid, can get pure phosphoric acid solution.

3P4 + 20HNO3 + 8H2O ==== 12H3PO4 + 20NO↑

Thermal method: white phosphorus burned in the air to generate phosphorus pentoxide, and then made by hydration. Note that hot water must be used because phosphorus pentoxide will react with cold water to form highly toxic metaphosphoric acid.

Polyphosphoric acid production: Polyphosphoric acid is produced by dehydrating orthophosphoric acid under appropriate conditions.

Recrystallization method: industrial phosphoric acid is dissolved in distilled water, the solution is purified to remove impurities such as arsenic and heavy metals, filtered, so that the filtrate meets the requirements of the food grade, concentrated, to produce a finished product of edible phosphoric acid.