Sodium hexametaphosphate (CAS: 10124-56-8)

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.

Uses

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 softeningand 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

or another deflocculant allows the clay particles of an ordinary slip to remain suspended for an

extended period of time; after 24hrs or more, the slip separates into layers with the larger particles

at the bottom, and the finest particles can be siphoned off and applied to a green ware ceramic surface

. It is also used as a deflocculant or dispersant for the ASTM D422 – 63(2007) Standard Test Method

for Particle-Size Analysis of Soils.

It can be prepared from Na2HPO4 and NaH2PO4.

It is currently used as an active ingredient in Crest Pro-Health as a claimed anti-staining and tartar

prevention ingredient.

Sodium hexmetaphosphate in foods

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.