Sodium hexametaphosphate (SHMP) is a salt of composition Na6[(PO3)6]. Sodium hexametaphosphate of commerce is typically a mixture of metaphosphates (empirical formula: NaPO3), of which the hexamer is one, and is usually the compound referred to by this name. Such a mixture is more correctly termed sodium polymetaphosphate. They are white solids that dissolve in water.
SHMP is used as a sequestrant and has applications within a wide variety of industries, including as a food additive which 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 toothpaste as an anti-staining and tartar-prevention ingredient.
As a food additive, SHMP is used as an emulsifier. 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 drinks, among other foods, can contain SHMP.
SHMP is used in Diamond Crystal brand Bright & Soft Salt Pellets for water softeners in a concentration of 0.03%. It is the only additive other than sodium chloride.
