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Physical & Chemical properties

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Typically, the purity of trisodium orthophosphate is > 90% (dry weight, after excluding water). All impurities present at >1% are other inorganic phosphates or other related inorganic substances, similar to the registered substance, and which do not significantly affect its toxicological and ecotoxicological properties. There are no hazardous impurities present within the substance at levels >0.1%.

 

Trisodium orthophosphate has a melting point of >450°C and is considered to be very soluble (>13 %<14.1% (w/w) at 20°C). The pH of this solution, observed in the water solubility study, was pH 12.4 -12.6. The water solubility study conducted on trisodium orthophosphate

made the following observations:

The temperature range 10 to 30°C had a significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test materials disodium hydrogenorthophosphate and sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0004 and 2920/0001 respectively). From this data, it be concluded that the solubility of the test material (trisodium orthophosphate) would increase significantly as the pH decreased over the pH range of 9 to 4 (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2 and in the range 50.2 to 52.0% w/w at 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of a strongly alkali solution as formed on dissolution of the test material.

Trisodium orthophosphate is not considered to possess any of the following hazardous physico-chemical properties: autoflammability and/or self-ignition, flammability, explosiveness and oxidising properties.