What is the Difference Between Sodium Hexametaphosphate and Sodium Polyphosphate

The key difference between sodium hexametaphosphate and sodium polyphosphate is that sodium hexametaphosphate is a specific six-chain length form of sodium metaphosphate, whereas sodium polyphosphate is an umbrella term used to name all the sodium phosphate units with four or more phosphate units.

The terms sodium hexametaphosphate and sodium polyphosphate refer to substances derived from sodium phosphate salts. These are usually large molecules with complicated chemical formulas.

What is Sodium Hexametaphosphate?

Sodium hexametaphosphate is an inorganic salt having the chemical formula Na₆[(PO₃)₆]. Commercially, it typically occurs as a mixture of metaphosphates having a hexamer form. More precisely, this type of mixture can be named a sodium polymetaphosphate. This substance occurs as a white solid that dissolves in water.

Figure 01: The Chemical Structure of Sodium Hexametaphosphate

The other names that we can use to name this substance include Calgon S, glassy sodium, Graham’s salt, metaphosphoric acid, etc. The molar mass of this compound is 611.77 g/mol. It appears as white crystals, and it is odorless. Although it is water-soluble, insoluble in organic solvents.

There are different uses of sodium hexametaphosphate, which include using it as a sequestrant, as a food additive in the food industry, as a water softening agent, and as a detergent. Another important use of this substance is using it as a deflocculant in the production of clay-based ceramic particles. Moreover, we can use it as a dispersing agent for the breakdown of clay and other soil types in soil texture assessments.

This substance can be prepared by heating monosodium orthophosphate for the formation of sodium acid pyrophosphate, which is subsequently heated to get the corresponding sodium hexametaphosphate.

Sodium Hexametaphosphate

What is Sodium Polyphosphate?

Sodium polyphosphate is a type of sodium phosphate and a salt of sodium ion and phosphate. This type of salt is formed upon heating mixtures of NaH2PO4 and Na2HPO4. This induces a condensation reaction. Thereafter, the specific polyphosphate is generated depending on the details of the heating and annealing.

A common derivative of sodium polyphosphates is Glassy Graham’s salt. It is a linear polyphosphate substance having the chemical formula NaO(NaPO₃)Na₂. There are some crystalline high molecular weight polyphosphates, including Kurrol’s salt and Maddrell’s salt.

What is the Difference Between Sodium Hexametaphosphate and Sodium Polyphosphate?

Sodium hexametaphosphate and sodium polyphosphate are substances derived from sodium phosphate salts. These are usually large molecules with complicated chemical formulas. The key difference between sodium hexametaphosphate and sodium polyphosphate is that sodium hexametaphosphate is a specific six-chain length form of sodium metaphosphate, whereas sodium polyphosphate is an umbrella term used to name all the sodium phosphate units with four or more phosphate units.

Below is a summary of the difference between sodium hexametaphosphate and sodium polyphosphate in tabular form for side by side comparison.

Summary – Sodium Hexametaphosphate vs Sodium Polyphosphate

Sodium hexametaphosphate is an inorganic salt having the chemical formula Na₆[(PO₃)₆]. Sodium polyphosphate is a type of sodium phosphate and a salt of sodium ion and phosphate. The key difference between sodium hexametaphosphate and sodium polyphosphate is that sodium hexametaphosphate is a specific six-chain length form of sodium metaphosphate, whereas sodium polyphosphate is an umbrella term used to name all the sodium phosphate units with four or more phosphate units.