Sodium hexametaphosphate

Sodium hexametaphosphate[1]
Identifiers
CAS number 10124-56-8 Y
PubChem 24968
ChemSpider 23340 N
EC number 233-343-1
MeSH sodium+polymetaphosphate
Jmol-3D images Image 1
Properties
Molecular formula Na6P6O18
Molar mass 611.7704 g mol-1
Exact mass 611.689650318 g mol-1
Appearance White crystals
Odor Odourless
Density 2.484 g cm-3
Melting point

550 °C, 823 K, 1022 °F

Boiling point

1500 °C, 1773 K, 2732 °F

Refractive index (nD) 1.482
Hazards
MSDS hazard.com
S-phrases S24/25
Main hazards Irritant
LD50 3.053 g kg-1
Related compounds
Other anions Trisodium phosphate
Tetrasodium pyrophosphate
Pentasodium triphosphate
Related compounds Sodium trimetaphosphate
 N (verify) (what is: Y/N?)
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.

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. It is also used as a dispersant for the ASTM D422 - 63(2007) Standard Test Method for Particle-Size Analysis of Soils.

It can be prepared from Na2HPO4 and NaH2PO4.

References

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

External links