Detailed Overview on Sodium Trimetaphosphate

What exactly is Sodium Trimetaphosphate?

Sodium Trimetaphosphate also referred to as STMP is a metaphosphate of sodium with a chemical formula of Na₃P₃O9 and an empirical formula of NaPO₃. It is a colorless solid that has special applications in food and construction industries. It is prepared by heating samples of sodium polyphosphate.

Sodium Phosphate

Sodium phosphate is defined as the term given to sodium and phosphate. The phosphate groups for families or condensed ions like di, tri, tetra, and polyphosphates and most of these salts are known in both anhydrous (water-free) and hydrated forms. The hydrate forms of these salts are more common than anhydrous forms.

Properties of Sodium Trimetaphosphate

Here are some of the properties of sodium triphosphate.

Chemical Formula  The chemical formula of sodium Trimetaphosphate is Na₃P₃O9.
Molar Mass The molar mass of sodium trimetaphosphate is 305.885 g/mol.
Appearance  Sodium trimetaphosphate is colorless but sometimes it appears as white crystals just like in sodium pyrophosphate.
Density  The density of sodium trimetaphosphate is 2.49 g/cm3 (anhydrous)

1.786 g/cm3 (hexahydrate)

Melting Point  The melting point of sodium trimetaphosphate is 53 °C (127 °F; 326 K) (hexahydrate, decomposes to anhydrous).
Structure  Sodium trimetaphosphate has a triclinic crystalline structure (hexahydrate).
Solubility in Water  Sodium trimetaphosphate is insoluble in water 
Refractive Index  Sodium trimetaphosphate has a refractive index of 1.433 (hexahydrate).
Solubility  Sodium trimetaphosphate is insoluble in alcohol.


Preparation/ Production of Sodium Trimetaphosphate

Sodium Trimetaphosphate is synthesized from sodium chloride and orthophosphoric acid by the process called one step thermal process at 600°C from the fine powder of sodium chloride. The only by-product gotten from the reaction is hydrochloric acid. The reaction temperature and the volume-mean diameter of sodium chloride strongly influenced the elimination of chloride and selectivity in STMP.

Chemical Structure

The chemical structure of sodium trimetaphosphate is Na₃P₃O9,  which means that there are three atoms of sodium, three atoms of phosphorus and nine atoms of oxygen present in this compound.

Uses of Sodium Trimetaphosphate

The following are some of the uses of sodium trimetaphosphate.

  1. It is used as a biomimetic analog of matrix phosphoproteins for the remineralization of artificial dentin.
  2. Sodium Trimetaphosphate is used in the starch industry because it can enhance the interaction between starch chains and restrain the swelling power.
  3. Sodium Trimetaphosphate is used in the production of toothpaste because of its effective stain removal where its mild properties interfere with the stained pellicle.
  4. Sodium Trimetaphosphate can function as a buffering agent.
  5. Sodium trimetaphosphate is used in the food industry as a juice turbidity preventer, meat binder, dispersant and stabilizer for ice and cheese.
  6. It prevents the discoloration of food and it also prevents the decomposition of vitamin C.
  7. It can be added to gypsum board and used in the production of low density washing powder.
  8. It can also be used in the production of dry bleach and automatic dish washing detergent.

Packaging and Storage of Sodium Trimetaphosphate

Sodium Trimetaphosphate is stored in a cool, dry place and kept away from moisture.

Precautions to Take While Handling Sodium Trimetaphosphate

Sodium Trimetaphosphate does not present any particular risk, provided it is handled properly with good occupational hygiene and also safety practices, and precautions are taken. The following precautions should be taken when handling sodium trimetaphosphate.

  1. Ensure Proper Hygiene Measures
  2. Skin Protection: Ensure you wear protective gloves when handling sodium trimetaphosphate.
  3. If sodium trimetaphosphate comes in contact with your eyes, you are advised to wash immediately with fresh running water.
  4. Ensure Proper Ventilation
  5. Ensure you set up emergency exits and risk elimination areas.

Reactions of Sodium Trimetaphosphate

  • Sweet Potato Test

Sweet Potato Esterified Starch Test

An esterified starch is a type of modified starch that is used in the production of raw materials and is crosslinked using sodium trimetaphosphate, hexametaphosphate, and other phosphates as cross linking agents.

Frequently Asked Questions Concerning Sodium Trimetaphosphate

What is sodium Trimetaphosphate used for?

Sodium trimetaphosphate is used as a crosslinking agent in the sweet potato cross-linked test. It also acts as an intermediate in many food industries. Furthermore, it also serves as corrosion inhibitors, anti-scaling agents, fillers, finishing agents, plating agents and even surface treating agents.

What is the pH of Water-Soluble Sodium Trimetaphosphate 

The pH of water-soluble sodium trimetaphosphate is about 10.5.