9240. Tetrasodium Pyrophosphate

Nomenclature

CAS number: 7722-88-5
TSPP; pyro; sodium pyrophosphate.
Na4O7P2; mol wt 265.90.
Na 34.58%, O 42.12%, P 23.30%.
Na4P2O7.

Description and references

Available alkalinity as Na2O 4.4%, total alkalinity 22.7%. Produced by molecular dehydration of dibasic sodium phosphate at 500°: Bell, Inorg. Synth. 3, 98 (1950).

Properties

Crystals, d 2.534. mp 988°. Soly in water (g/100 ml) at 0°: 2.61; at 25°: 6.70; at 100°: 42.2. pH of a 1% soln = 10.2. Hydrolyzes to orthophosphate in aq soln, but the rate of hydrolysis is much slower than for the more acid pyrophosphate. No noticeable hydrolysis within 60 hrs at 70°: Bell, Ind. Eng. Chem. 39, 136 (1947).

Derivative

Decahydrate.

Properties

Crystals, d 1.82. mp 79.5°. Slight efflorescence in dry air. Soly in water (g/100 ml) at 0°: 3.16; at 20°: 6.23; at 25°: 8.14; at 60°: 21.83; at 80°: 30.04. pH of 1% soln at 25° = 10.2. Insol in alc.

Caution

Potential symptoms of overexposure are irritation of eyes, skin, nose, throat; dermatitis. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 304.

Use

In cleansing compds, oil-well drilling, water treatment, cheese emulsification, as general sequestering agent, to remove rust stains, as ingredient of one-fluid ink eradicators, in electrodeposition of metals.