SI units were used where possible. Unless otherwise stated, standard conditions were used.

General
CAS number	10124-56-8
Chemical formula	(NaPO3)6
Appearance	White, odorless, crystalline powder
Physical
Formula weight	611.77
Melting point	?
Boiling point	?
Density	1.2 g/cm3
Crystal structure	?
Solubility	Easily soluble in water
Safety
Ingestion	?
Inhalation	Irritant
Skin	?
Eyes	Irritant

Sodium hexametaphosphate (SHMP) is correctly speaking a hexamer of composition (NaPO₃)₆. "Sodium hexametaphosphate" of commerce is 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, CAS 50813-16-6. 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. 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.

Other names

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• Calgon S
• glassy sodium
• Graham's Salt
• hexasodium metaphosphate
• hexasodium salt
• metaphosphoric acid

References

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• Merck Index, 'Sodium polymetaphosphate'
• Van Wazer, John R. 1958. Phosphorus and its compounds. Interscience Publishers, Inc., N.Y.

External links

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Sodium compounds | Phosphates | Water Treatment | Scale Inhibitor