Phosphate product classification

Phosphate product classification

Phosphate can be divided into orthophosphate and condensed phosphate. Salts of pentavalent phosphorus oxyacids, including orthophosphate, pyrophosphate and metaphosphate, usually refer to orthophosphate.

Orthophosphoric acid is a tribasic acid, and there are three kinds of orthophosphate: ① dihydrogen phosphate MH2PO4, also known as first-generation phosphate, all soluble in water; ② hydrogen phosphate MHPO4, also known as second-generation phosphate; ③ orthophosphate M3PO4, Also known as three generations of phosphate. The latter two are generally insoluble in water except sodium, potassium and ammonium salts. In addition to being a monovalent metal, M can also be metals in other valence states. The dihydrogen phosphate and hydrogen salt of ammonium and calcium are all important fertilizer components. Sodium dihydrogen phosphate NaH2PO4 is used to control the hydrogen ion concentration of the solution; disodium hydrogen phosphate Na2HPO4 is used in water treatment as a precipitant for polyvalent metals; trisodium phosphate is used to make soaps and detergents.

Pyrophosphate is a tetrabasic acid, and there are four kinds of pyrophosphate: M2H2P2O7 and M4P2O7 types are common, M3HP2O7 type is less, and MH3P2O7 type is rare. Metaphosphate is usually a ring-shaped compound, the general formula is (MPO3)n, the common ones are dimer metaphosphate (six-membered ring) and tetrameric metaphosphate (eight-membered ring), poly-metaphosphate Does not have a definite crystal structure, also known as phosphate vitreous body. Sodium hexametaphosphate is the most common phosphate glass. It has no fixed melting point and its solubility in water is variable. The pH of the aqueous solution is between 5.5 and 6.4. It is actually a long-chain compound with 20 to 100 PO3 units. Chain phosphate can be used as boiler water treatment agent, pigment dispersant, mud dispersant and metal anti-corrosion agent.

Phosphate ions can generate the characteristic yellow precipitate of ammonium phosphomolybdate, which can be used for analytical verification (see phosphoric acid).