SHMP

Sodium hexametaphosphate (SHMP) is a hexamer of composition (NaPO3)6. Sodiumhexametaphosphate of commerce is typically a mixture of polymeric metaphosphates, of which thehexamer is one, and is usually the compound referred to by this name. It is more correctly termedsodium polymetaphosphate. It is prepared by melting monosodium orthophosphate, followed byrapid cooling. SHMP hydrolyzes in aqueous solution, particularly under acidic conditions, tosodiumtrimetaphosphate and sodiumorthophosphate.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 issometimes added to SHMP to raise the pHto 8.0-8.6, which produces a number of SHMP productsused for water softening and detergents. Also used as a dispersing agent to break down clay andother soil types.

One of the lesser-known uses for sodium hexametaphosphate is as a deflocculant in themaking of Terra sigillata, a ceramic technique using a fine particled slip. The sodiumhexametaphosphate causes the heavy particles in the slip to drop to the bottom allowing the fineparticles to be siphoned off and applied to a green ware ceramic surface.Sodium hexametaphosphate is also a whitening ingredient included in some whiteningtoothpastes and mouthwashes. It can be prepared fromNa2HPO3 and NaH2PO3.