Sodium hexametaphosphate

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Sodium hexametaphosphate[1]
Skeletal formula of sodium hexametaphosphate
Identifiers
CAS number 10124-56-8 YesY
PubChem 24968
ChemSpider 23340 N
EC number 233-343-1
MeSH sodium+polymetaphosphate
Jmol-3D images Image 1
Properties
Molecular formula Na
6
P
6
O
18
Molar mass 611.7704 g mol−1
Appearance White crystals
Odor odorless
Density 2.484 g/cm3
Melting point 628 °C (1,162 °F; 901 K)
Boiling point 1,500 °C (2,730 °F; 1,770 K)
Solubility in water soluble
Solubility insoluble in organic solvents
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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.

Uses[edit]

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 articles.[3][4][5][6] It is also used as a dispersing agent to break down clay and other soil types.[7]

It is used as an active ingredient in toothpastes as an anti-staining and tartar prevention ingredient.[8]

Food additive[edit]

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. [9][unreliable source?]

Preparation[edit]

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[edit]

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

References[edit]

  1. ^ Merck Index, 12th Edition, Sodium polymetaphosphate, 8814
  2. ^ Van Wazer, John R. Phosphorus and its compounds. New York : Interscience Publishers (1958)
  3. ^ The Role Of Sodium Hexametaphosphate In The Dissolution Process Of Kaolinite And KaolinF. Andreola; E.Castellini; T.Manfredini; M.Romagnoli. Journal Of The European Ceramic Society, Volume 24, Number 7, June 2004.
  4. ^ Impact Of Dispersants On The Mechanical Strength Development Of Alumina-Spinel Self-Flowing Refractory Castables. Sasan Otroj, Mohammad Reza Nilforushan, Arash Daghighi, Reza Marzban. Ceramics – Silikáty 54 (3) 284-289 (2010)
  5. ^ Effect Of Adding Sodium Hexametaphosphate Liquefier On Basic Properties Of Calcium Phosphate Cements. S. Hesaraki; A. Zamanian; F. Moztarzadeh. Journal of Biomedical Materials Research Part A. Vol. 88A, No. 2, 2009
  6. ^ Study Of Clay’s Mineralogy Effect On Rheological Behavior Of Ceramic Suspensions Using An Experimental Design. Afef Jmal Ayadi; Julien Soro; Amel Kamoun; Samir Baklouti. International Journal of Recent Research and Applied Studies 14 (2). February 2013.
  7. ^ ASTM D422 - 63(2007) Standard Test Method for Particle-Size Analysis of Soils.
  8. ^ Crest Pro-Health Frequently Asked Questions
  9. ^ http://www.befoodsmart.com/ingredients/sodium-hexametaphosphate.php

External links[edit]