Suvarna Garge (Editor)

Sodium hexametaphosphate

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Formula  (NaPO3)6
Density  2.48 g/cm³
Boiling point  1,500 °C
Molar mass  611.77 g/mol
Melting point  628 °C
Appearance  White crystals
Sodium hexametaphosphate httpsuploadwikimediaorgwikipediacommonsthu
Related compounds  Sodium trimetaphosphate

Sodium hexametaphosphate


Sodium hexametaphosphate (SHMP) is a hexamer of composition (NaPO3)6. Sodium hexametaphosphate of commerce is typically a mixture of polymeric metaphosphates, of which the hexamer is one, and is usually the compound referred to by this name. It is more correctly termed sodium polymetaphosphate.

Contents

Sodium hexametaphosphate


Uses

SHMP is used as a sequestrant and has applications within a wide variety of industries, including as a food additive in which it is used under the E number E452i. Sodium carbonate is sometimes added to SHMP to raise the pH to 8.0–8.6, which produces a number of SHMP products used for water softening and detergents.

A significant use for sodium hexametaphosphate is as a deflocculant in the production of clay-based ceramic particles. It is also used as a dispersing agent to break down clay and other soil types for soil texture assessment.

It is used as an active ingredient in toothpastes as an anti-staining and tartar prevention ingredient.

Food additive

Artificial maple syrup, canned milk, cheese powders and dips, imitation cheese, whipped topping, packaged egg whites, roast beef, fish fillets, fruit jelly, frozen desserts, salad dressing, herring, breakfast cereal, ice cream, beer, and bottled beverages, among other foods, can contain sodium hexametaphosphate.

Preparation

SHMP is prepared by heating monosodium orthophosphate to generate sodium acid pyrophosphate:

2 NaH2PO4 → Na2H2P2O7 + H2O

Subsequently, the pyrophosphate is heated to give the corresponding sodium hexametaphosphate:

3 Na2H2P2O7 → (NaPO3)6 + 3 H2O

followed by rapid cooling.

Reactions

SHMP hydrolyzes in aqueous solution, particularly under acidic conditions, to sodium trimetaphosphate and sodium orthophosphate.

References

Sodium hexametaphosphate Wikipedia


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