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Sodium hexametaphosphate

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Sodium hexametaphosphate[1]
Identifiers
CAS number 10124-56-8 YesY
Properties
Molecular formula (NaPO3)6
Molar mass 611.77 g/mol
Appearance White, odorless, crystalline powder
Density 2.484 g/cm3
Melting point

550 °C
Boiling point

1500 °C
Solubility in water soluble
Solubility in organic solvents insoluble
Hazards
MSDS External MSDS
EU Index Not listed
Main hazards Irritant
Flash point Non-flammable
LD50 3053 mg/kg
Related compounds
Other anions Trisodium phosphate
Tetrasodium pyrophosphate
Pentasodium triphosphate
Related compounds Sodium trimetaphosphate
 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium hexametaphosphate (SHMP) is a hexamer of composition (NaPO3)6.[2] 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. It is prepared by melting monosodium orthophosphate, followed by rapid cooling. SHMP hydrolyzes in aqueous solution, particularly under acidic conditions, to sodium trimetaphosphate and sodium orthophosphate.

[edit] Uses

SHMP is used as a sequestrant and has applications with in 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. Also used as a dispersing agent to break down clay and other soil types.

One of the lesser-known uses for sodium hexametaphosphate is as a deflocculant in the making of terra sigillata, a ceramic technique using a fine particled slip. The sodium hexametaphosphate causes the heavy particles in the slip to drop to the bottom allowing the fine particles to be siphoned off and applied to a green ware ceramic surface.

Sodium hexametaphosphate is also a whitening ingredient included in some whitening toothpastes and mouthwashes.[3]

It can be prepared from Na2HPO3 and NaH2PO3.[citation needed]

[edit] References

  1. ^ Merck Index, 12th Edition, Sodium polymetaphosphate, 8814
  2. ^ Van Wazer, John R. Phosphorus and its compounds. New York : Interscience Publishers (1958)
  3. ^ Crest Vivid White Toothpaste

[edit] External links