Sodium tripolyphosphate (Na5P3O10) structure, properties, uses, impact

The sodium tripolyphosphate is an inorganic compound formed by five sodium Na ions⁺ and a tripolyphosphate ion P₃OR₁₀^5-. Its chemical formula is Na₅P₃OR₁₀. The tripolyphosphate ion contains three phosphate units bound together and is what is called a condensed phosphate.

The tripolyphosphate anion P₃OR₁₀^5- has the ability to trap ions such as calcium Ca^two+ and magnesium Mg^two+, Therefore, sodium tripolyphosphate is used as an aid in detergents so that they work better in certain types of water..

Sodium tripolyphosphate is also used as a source of phosphorus in the diet of grazing animals and in the treatment of some ailments of other types of animals. It is also used to thicken and give texture to some processed foods such as creams, puddings and cheeses..

In the agricultural industry it is used in granular fertilizers to prevent them from sticking together and remaining loose..

Although there have been discussions about the environmental impact of sodium tripolyphosphate added to detergents, it is currently estimated that it does not contribute appreciably to damage the environment, at least through detergents..

Article index

• 1 Chemical structure
• 2 Nomenclature
• 3 Properties
  • 3.1 Physical state
  • 3.2 Molecular weight
  • 3.3 Melting point
  • 3.4 Density
  • 3.5 Solubility
  • 3.6 pH
  • 3.7 Chemical properties
  • 3.8 Other properties
• 4 Obtaining
• 5 Uses
  • 5.1 In detergents
  • 5.2 For veterinary use
  • 5.3 In medicine
  • 5.4 In the food industry
  • 5.5 Other uses
• 6 Environmental impact
• 7 Risks
• 8 References

Chemical structure

Sodium tripolyphosphate is one of the so-called condensed phosphates because it consists of several phosphate units linked together. In this case, the tripolyphosphate ion is a linear condensed phosphate as it has a linear chain-like structure, with phosphorus-oxygen-phosphorus bonds (P-O-P).

Nomenclature

- Sodium tripolyphosphate

- Sodium triphosphate

- Pentasodium triphosphate

- STPP (acronym of the English Sodium TriPolyPhosphate)

Properties

Physical state

Colorless to white crystalline solid.

Molecular weight

367.86 g / mol.

Melting point

622 ° C.

Density

2.52 g / cm³

Solubility

Soluble in water: 20 g / 100 mL at 25 ° C and 86.5 g / 100 mL at 100 ° C.

pH

A 1% solution of sodium tripolyphosphate has a pH of 9.7-9.8.

Chemical properties

It is an ion sequestering agent, that is, it can trap ions and stay attached to them. Forms complexes with many metals.

If a solution of sodium tripolyphosphate is heated for a long time it tends to convert to sodium Na orthophosphate.₃PO₄.

Other properties

It is slightly hygroscopic. It forms stable hydrates, that is, compounds that have water molecules attached (without having reacted with it) of the formula Na₅P₃OR₁₀.nH_twoOr where n can be between 1 and 6.

According to some sources, an amount of 20 mg of sodium tripolyphosphate in one liter of water does not affect the odor, taste or pH of said water..

Obtaining

Sodium tripolyphosphate is prepared by dehydrating orthophosphates (such as monosodium phosphate NaH_twoPO₄ and disodium phosphate Na_twoHPO₄) at very high temperatures (300-1200 ° C):

NaH_twoPO₄ + 2 Na_twoHPO₄ → Na₅P₃OR₁₀ + 2 h_twoOR

It can also be obtained by controlled calcination (means heating at a very high temperature) of sodium Na orthophosphate.₃PO₄ with sodium carbonate Na_twoCO₃ and phosphoric acid H₃PO₄.

Applications

In detergents

Sodium tripolyphosphate has the property of forming compounds with certain ions, retaining them. It also has dispersant properties for dirt particles and keeps them in suspension..

For this reason, it is widely used in detergent formulations to trap and immobilize calcium Ca ions.^two+ and magnesium Mg^two+ water (so-called hard water) and to keep the dirt suspended in the water.

The mentioned ions interfere with the cleaning action. By trapping them, the tripolyphosphate prevents these ions from precipitating together with the cleaning agent or sticking the dirt on the fabric, preventing the stain from detaching from it..

Sodium tripolyphosphate is said in this case to "soften" the water. Because of this, it is used in laundry detergents and automatic dishwasher detergents..

Since it forms stable hydrates, the detergents that have it in their formulation can be dried instantly by spraying (very fine spray) forming dry powders..

For veterinary use

Sodium tripolyphosphate is used as a supplement in liquid solutions as a source of phosphorus for livestock.

It is also used to prevent kidney stones in cats, for which it is given orally to these animals. However, attention should be paid to the dosage as it can cause diarrhea..

In medicine

Sodium tripolyphosphate has been used in the preparation of nanoparticles for the proper transport and delivery of cancer chemotherapy drugs. It has also been used in nanoparticles to treat fungal infections in the lungs..

In the food industry

Used in dairy products such as puddings, whipped cream, sour cream, and cheese.

In other foods it is used as an ion sequestrant, to give texture, as a thickener and as a preservative.

Other uses

- As a peroxide stabilizer

- In oil well drilling fluids it works as an emulsifier and dispersant to control mud viscosity.

- In agriculture it is used as an anti-caking agent for certain fertilizers or agricultural products, this means that it prevents them from sticking together and the fertilizer can be easily distributed. It is also used in pesticide formulas applied to growing crops.

Environmental impact

The use of phosphate products has been identified as one of the contributors to the eutrophication of water on the planet.

Eutrophication is the exaggerated and accelerated growth of algae and aquatic plant species that lead to a sharp decrease in available oxygen in the water, leading to the destruction of the affected ecosystem (death of most animal species in it).

Controversy arose in the 1980s that the use of sodium tripolyphosphate in detergents was contributing to eutrophication.

Today it is known that limiting the use of detergents with sodium tripolyphosphate would contribute very little to eliminating eutrophication, since phosphates come in greater amounts from other agricultural and industrial sources.

In fact, there are countries that consider sodium tripolyphosphate as an environmentally friendly component of detergents and promote its use.

Risks

Sodium Tripolyphosphate is a skin and eye irritant. Contact with the eyes can cause damage to the eyes. Prolonged contact with the skin can cause dermatitis.

If ingested in large quantities, it can cause nausea, vomiting and diarrhea, also generating a serious reduction in the calcium ion in the blood. In animals it has caused a decrease in calcium in the bones.

It is considered a safe compound as long as the manufacturing standards of the product in which it is used are followed..

References

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2. U.S. National Library of Medicine. (2019). Sodium tripolyphosphate. National Center for Biotechnology Information. Recovered from pubchem.ncbi.nlm.nih.gov.
3. Mukherjee, B. et al. (2017). Pulmonary Administration of Biodegradable Drug Nanocarriers for More Efficacious Treatment of Fungal Infections in Lungs: Insights Based on Recent Findings. In Multifunctional Systems for Combined Delivery, Biosensing and Diagnostics. Recovered from sciencedirect.com.
4. Kirk-Othmer. (1991). Encyclopedia of Chemical Technology. 4^th New York, John Wiley and Sons.
5. Burckett St. Laurent, J. et al. (2007). Laundry Cleaning of Textiles. In Handbook for Cleaning / Decontamination of Surfaces. Recovered from sciencedirect.com.
6. Budavari, S. (Editor). (nineteen ninety six). The Merck Index. NJ: Merck and Co., Inc.
7. Salahuddin, N. and Galal, A. (2017). Improving chemotherapy drug delivery by nanoprecision tools. In Nanostructures for Cancer Therapy. Recovered from sciencedirect.com.