Tetrasodium pyrophosphate

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Tetrasodium pyrophosphate
Sodium pyrophosphate.png
Identifiers
CAS number 7722-88-5 YesY, 13472-36-1 (decahydrate)
PubChem 24403
EC number 231-767-1
Jmol-3D images Image 1
Properties
Molecular formula Na4O7P2
Molar mass 265.90 g mol−1
Appearance Colorless crystals
Odor odorless
Density 2.534 g/cm3
Melting point 988 °C (1,810 °F; 1,261 K) (anhydrous)
79.5 °C (decahydrate)
Solubility in water 2.61 g/100 mL (0 °C)
6.7 g/100 mL (25 °C)
42.2 g/100 mL (100 °C)
Solubility insoluble in ammonia, alcohol
Refractive index (nD) 1.425
Structure
Crystal structure monoclinic (decahydrate)
Thermochemistry
Specific
heat capacity
C
241 J/mol K
Std molar
entropy
So298
270 J/mol K
Std enthalpy of
formation
ΔfHo298
-3166 kJ/mol
Gibbs free energy ΔG -3001 kJ/mol
Hazards
EU Index Not listed
Flash point Non-flammable
Related compounds
Other anions Trisodium phosphate
Pentasodium triphosphate
Sodium hexametaphosphate
Other cations Tetrapotassium pyrophosphate
Related compounds Disodium pyrophosphate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is a colorless transparent crystalline chemical compound with the formula Na4P2O7. It is a salt composed of pyrophosphate and sodium ions. Toxicity is approximately twice that of table salt when ingested orally.[2] There is also a hydrated form, Na4P2O7 · 10(H2O).[3]

Sodium pyrophosphate is used as a buffering agent, an emulsifier, a dispersing agent, and a thickening agent, and is often used as a food additive. Common foods containing sodium pyrophosphate include chicken nuggets, marshmallows, pudding, crab meat, imitation crab, canned tuna, and soy-based meat alternatives and cat foods and cat treats where it is used as a palatability enhancer. Disodium Dihydrogen Pyrophosphate Na2H2P2O7 was the active ingredient (replacing Potassium Hydrogen Tartrate, Cream of Tartar as the acid component) in Bakewell, a substitute baking powder marketed during shortages in World War II. It is also used in some common baking powders.

In toothpaste and dental floss, sodium pyrophosphate acts as a tartar control agent, serving to remove calcium and magnesium from saliva and thus preventing them from being deposited on teeth. Tetrasodium pyrophosphate is used in commercial dental rinses before brushing to aid in plaque reduction.

Sodium pyrophosphate is sometimes used in household detergents to prevent similar deposition on clothing, but due to its phosphate content it causes eutrophication of water, promoting algae growth.

Calcium pyrophosphate is the crystal deposited in joints in the medical condition pseudogout.[4]

Production[edit]

Tetrasodium pyrophosphate is produced by the reaction of furnace-grade phosphoric acid with sodium carbonate to form disodium phosphate, which is then heated to 450 °C to form tetrasodium pyrophosphate.

References[edit]

  1. ^ CDC - NIOSH Pocket Guide to Chemical Hazards
  2. ^ Handbook of food toxicology, S. S. Deshpande, page 260
  3. ^ D.L. Perry S.L. Phillips (1995) Handbook of inorganic compounds CRC Press ISBN 0-8493-8671-3
  4. ^ Clinical Medicine, Kumar and Clark, 6th Ed., p. 571