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Physical and chemical properties of sodium phosphate

Sodium phosphate classification code GBl5.003, INS451 (I). Chemical structure: This product is a kind of amorphous water-soluble linear poly phosphate, both ends with PO4 Na2 termination, chemical formula O10 Na5P3, relative molecular mass 367.86. Commonly used in food, as water retention agent, quality improvement agent, pH regulator, metal chelating agent.

Physical property

Physical and chemical properties: white powder crystal, better mobility.

Density: type I density is 2.62g/cm3, the density of type II is 2.57g/cm3.

Melting point: 622.

Solubility: soluble in water, and its aqueous solution is alkaline. 20 mL g/100 (20 C).

Chemical property

Hydration property

Sodium tripolyphosphate because of different formation temperature and high temperature type (type I) and low temperature type (type II) of, the difference is that both the bond lengths and angles, type I and type II products after hydration are generating hexahydrate na5p3o10 6H2O, under the same conditions, high heat of hydration of type I is produce, dissolved in water is easy to produce caking phenomenon. This is due to the presence of the sodium ions in the four ligands are type I, the four ligands of water has strong affinity and vice type II in the water is at a very slow speed generation six water.

Sodium phosphate is quite stable at room temperature, in the humid air will slow hydrolysis reaction, the final formation of sodium phosphate, the reaction is as follows:

Na5P3O10+2H2O - 2Na2HPO4+NaH2PO4.

Chelating ability of metal ions

Sodium phosphate and soluble in water Ca2+, Mg2+, Fe3+ and other metal ions have a complex role in the formation of soluble complexes, such as: Na5P3O10+Ca2+, Na3 (CaP3O10) +2Na+.

The complexing ability of sodium phosphate is generally expressed by calcium value, that is, the number of calcium ions in 100g phosphate can be complex, and the theoretical value is 13.4.

Buffer action

Sodium tripolyphosphate solution is weakly alkaline (1% aqueous solution of the pH value of approximately 9.7), it in pH for 4.3 ~ 14 range), suspension (similar to emulsion) role in the formation, namely dispersion. Sodium can also make the liquid, solid particles better soluble in liquid (such as water) in the medium, so that the appearance of the solution is completely transparent, as if the solution is the same, this is the role of solubilization. Because of the unique properties of sodium phosphate, it has become an important raw material in the washing powder.

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