Sodium Hexametaphosphate - (NaPO3)6

What is Sodium Hexametaphosphate?

Sodium Hexametaphosphate is also called as Calgon. The formula for Sodium Hexametaphosphate is (NaPO3)6. It is a gathering of sodium polyphosphate polymers based on repeating NaPO3 units. It is a water dissolvable polyphosphate glass that comprises of a circulation of polyphosphate chain lengths. Sodium hexametaphosphate is a complex phosphate glass produced by a thermal process from soda ash and food-grade phosphoric acid.


Sodium Hexametaphosphate


2.48 g/cm³

Molecular Weight/ Molar Mass

611.77 g/mol

Boiling Point

1,500 °C

Melting point

628 °C

Chemical Formula


Sodium Hexametaphosphate Structure – (NaPO3)6

Sodium Hexametaphosphate Structure

Physical Properties of Sodium Hexametaphosphate – (NaPO3)6




White crystals

Refractive index





Soluble in water, insoluble in organic solvents.

Chemical Properties of Sodium Hexametaphosphate – (NaPO3)6

  • When Sodium Hexametaphosphate is added with water normally deposit CaCO3 scale, when made more alkaline or when heated the complex phosphate inhibits precipitation.
  • Sodium Hexametaphosphate is advantageous where the boiler water naturally tends to become too alkaline because this reduces excess of alkalinity by reversion in the boiler to an acid orthophosphate.

Uses of Sodium Hexametaphosphate – (NaPO3)6

  • Used as a surfactant, emulsifier, suspending agent, dispersing agent and as a buffer.
  • Industrial uses include clay processing, drilling fluids and cleaning products which stick together and form clumps.
  • Used in water treatment, when added in to a municipal or industrial water systems it helps to reduce scale formation, corrosion, biofilm formation in pipes and other equipment.
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