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Physical & Chemical properties

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Typically, the purity of disodium hydrogenorthophosphate 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%.

 

Disodium hydrogenorthophosphate has a melting point of >450°C and is considered to be very soluble (>23.8 %<25% (w/w) at 20°C). The pH of this solution, observed in the water solubility study, was pH 9.2. The water solubility study conducted on disodium hydrogenorthophosphate 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 material sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0001). From this data it could be concluded that the solubility of the test material would increase significantly as the pH decreased over the pH range of 9 to 4 (solubility in the range 50.2% to 52.0% w/w, 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 an alkali solution as formed on dissolution of the test material.

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