Sodium hexametaphosphate[1]
Other names	Calgon S; Glassy sodium; Graham's Salt; Hexasodium metaphosphate; Metaphosphoric acid, hexasodium salt
Identifiers
CAS number	10124-56-8 Y
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
Y (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.

[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

• Occupational Health and Safety Agency for Healthcare in British Columbia
• Use of phosphates (including sodium hexametaphosphate) in industry