8662. Sodium Phosphate, Tribasic

Nomenclature

CAS number: 7601-54-9
Phosphoric acid sodium salt (1:3); trisodium orthophosphate; trisodium phosphate; TSP; Oakite.
Na3O4P; mol wt 163.94.
Na 42.07%, O 39.04%, P 18.89%.
Na3PO4.

Description and references

Crystallizes with 8 and 12 mols of H2O.

Derivative

Dodecahydrate.

Nomenclature

CAS number: 10101-89-0
Na3O4P.12H2O; mol wt 380.12.
Na 18.14%, O 67.34%, P 8.15%, H 6.36%.

Properties

Colorless or white crystals. When rapidly heated melts at ≈75°. Does not lose the last mol of water even on moderate ignition. d 1.6. Sol in 3.5 parts water, 1 part boiling water; insol in alcohol. The aq soln is strongly alkaline. pH of 0.1% soln: 11.5; of 0.5% soln: 11.7; of 1.0% soln: 11.9. Technical crystals are sometimes made with excess alkali to prevent caking and give more alkaline solutions. LD50 orally in rats: 7.40 g/kg, H. F. Smyth et al., Am. Ind. Hyg. Assoc. J. 30, 470 (1969).

Use

In photographic developers; clarifying sugar; removing boiler scale, softening water; manuf paper; laundering; tanning leather; in detergent mixture; buffer; sequestering agent.