Sodium hexametaphosphate

Sodium hexametaphosphate

Names
Other names Calgon S Glassy sodium Graham's salt Hexasodium metaphosphate Metaphosphoric acid, hexasodium salt
Identifiers
3D model (Jmol)	Interactive image
ChemSpider	23340 N
ECHA InfoCard	100.030.299
EC Number	233-343-1
MeSH	sodium+polymetaphosphate
PubChem CID	24968
InChI InChI=1S/6Na.H6O18P6/c;;;;;;1-19(2)13-20(3,4)15-22(7,8)17-24(11,12)18-23(9,10)16-21(5,6)14-19/h;;;;;;(H,1,2)(H,3,4)(H,5,6)(H,7,8)(H,9,10)(H,11,12)/q6*+1;/p-6 N Key: GCLGEJMYGQKIIW-UHFFFAOYSA-H N
SMILES [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1
Properties
Chemical formula	Na 6P 6O 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
Refractive index (nD)	1.482
Hazards
Main hazards	Irritant
Safety data sheet	hazard.com
S-phrases	S24/25
Lethal dose or concentration (LD, LC):
LD50 (median dose)	3.053 g kg−1
Related compounds
Other anions	Trisodium phosphate Tetrasodium pyrophosphate Pentasodium triphosphate
Related compounds	Sodium trimetaphosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Glassy sodium
Graham's salt
Hexasodium metaphosphate

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.

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 particles. It is also used as a dispersing agent to break down clay and other soil types for soil texture assessment.

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

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.

SHMP is prepared by heating monosodium orthophosphate to generate sodium acid pyrophosphate:

Subsequently, the pyrophosphate is heated to give the corresponding sodium hexametaphosphate:

followed by rapid cooling.

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