E451 (Pentasodium triphosphate) is a chemical compound belonging to the condensed phosphate family and is obtained by molecular dehydration of mono- and disodium phosphates.

The name defines the structure of the molecule:

• Pentasodium refers to the presence of five sodium ions in the compound.
• Triphosphate is a type of polyphosphate, a chain of phosphate groups linked by oxygen atoms. In this case, "tri-" indicates that there are three phosphate groups in the chain.

The synthesis process takes place in several stages:

• Formation of phosphoric acid: The first step in the synthesis of pentasodium triphosphate is the production of phosphoric acid with a reaction between phosphate and sulfuric acid.
• Phosphorus pentoxide formation: Phosphoric acid is dehydrated to form phosphorus pentoxide.
• Formation of polyphosphoric acid: Phosphorus pentoxide is hydrated to form polyphosphoric acid.
• Formation of pentasodium triphosphate: Finally, polyphosphoric acid is neutralized with sodium hydroxide to form Pentasodium Triphosphate.

It appears in the form of a white powder.

What it is used for and where

Food

Ingredient on the European food additives list as E451 acting as stabilising agent, emulsifier and bulking agent.

• E451 (i) Penta sodium tri phosphate 
• E451(ii) Penta potassium tri phosphate

Cosmetics

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Chelating agent. It has the function of preventing unstable reactions and improving the bioavailability of chemical components within a product, and removes calcium and magnesium cations that can cause cloudiness in clear liquids.

Other uses

Pentasodium triphosphate is an important component to achieve better cleaning in modern detergents and the optimal dosage is about 1.3 per cent to achieve optimal viscosity.

Sodium Trihosphate studies

• Molecular Formula:  Na₅P₃O₁₀ Na₅O₁₀P₃
• Linear Formula: Na₅O₁₀P₃· nH₂O (n = 0 or 6)
• Molecular Weight: 367.86 g/mol
• UNII: 9SW4PFD2FZ
• CAS: 7758-29-4 
• EC Number: 231-838-7  618-452-8
• PubChem Substance ID 329763729
• MDL number MFCD00003514

Synonyms: 

• Sodium triphosphate
• Sodium tripolyphosphate
• Pentasodium triphosphate
• Sodium triphosphate pentabasic