Sodium hexametaphosphate

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Sodium hexametaphosphate

Identifiers
CAS number	[10124-56-8]
Properties
Molecular formula	(NaPO₃)₆
Molar mass	611.77
Appearance	White, odorless, crystalline powder
Density	2.484 g/cm³
Melting point	550.0 °C
Boiling point	1500.0 °C
Solubility in other solvents	Easily soluble in water Insoluble in organic solvents
Hazards
Main hazards	Ingestion: May cause irritation Inhalation: Irritant Skin: May cause irritation Eyes: Irritant
NFPA 704	0 1 0
LD₅₀	3053 mg/kg
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

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. 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. SHMP is used as a sequestrant and has applications 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.

1 Ceramic process
2 Other Uses
3 Health concern
4 Other names
5 References
6 External links

[edit] Ceramic process

One of the lesser-known uses for sodium hexametaphosphate is as a deflocculent 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.

[edit] Other Uses

Sodium hexametaphosphate is also a whitening ingredient included in Crest Pro-Health, Vivid White and Vivid White Night.^[1]

[edit] Health concern

Some individuals may experience an allergic reaction to the ingestion of sodium hexametaphosphate that may produce mild chest pain.^{[citation needed]} One case of this allergic reaction was reported to have been due to trace amounts of sodium hexametaphosphate found in bottled water.^{[citation needed]}

[edit] Other names

Calgon S
Glassy sodium
Graham's Salt
Hexasodium metaphosphate
Hexasodium salt
Metaphosphoric acid

[edit] References

Merck Index, 12th Edition, Sodium polymetaphosphate, 8814
Van Wazer, John R. Phosphorus and its compounds. New York : Interscience Publishers (1958)
Science Lab MSDS Sodium hexametaphosphate MSDS
Crest Website [1]