| Synonyms | Sodium phosphate |
| Tribasic sodium phosphate |
| Trisodium orthophosphate |
| Definition | Trisodium phosphate is obtained from aqueous solutions and crystallises in the anhydrous form and with 1/2, 1, 6, 8 or 12 H2O. The dodecahydrate always crystallises from aqueous solutions with an excess of sodium hydroxide. It contains 1/4 molecule of NaOH |
| Chemical name | Trisodium monophosphate |
| Trisodium phosphate |
| Trisodium orthophosphate |
| Einecs | 231-509-8 |
| Chemical formula | Anhydrous: Na3PO4 |
| Hydrated: Na3PO4 · nH2O (n = 1/2, 1, 6, 8, or 12) |
| Molecular weight | 163,94 (anhydrous) |
| Assay | Sodium phosphate anhydrous and the hydrated forms, with the exception of the dodecahydrate, contain not less than 97,0 % of Na3PO4 calculated on the dried basis. Sodium phosphate dodecahydrate contains not less than 92,0 % of Na3PO4 calculated on the ignited basis |
| P2O5 content | Between 40,5 % and 43,5 % on the anhydrous basis |
| Description | White odourless crystals, granules or crystalline powder |
| Identification | |
A.Positive tests for sodium and for phosphate | |
B.Solubility | Freely soluble in water. Insoluble in ethanol |
C.pH of a 1 % solution | Between 11,5 and 12,5 |
| Purity | |
| Loss on ignition | When dried at 120 oC for two hours and then ignited at about 800 oC for 30 minutes, the losses in weight are as follows: anhydrous not more than 2,0 %, monohydrate not more than 11,0 %, dodecahydrate: between 45,0 % and 58,0 % |
| Water insoluble substances | Not more than 0,2 % on the anhydrous basis |
| Fluoride | Not more than 10 mg/kg (expressed as fluorine) |
| Arsenic | Not more than 3 mg/kg |
| Cadmium | Not more than 1 mg/kg |
| Lead | Not more than 4 mg/kg |
| Mercury | Not more than 1 mg/kg |