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Typically the purity of tripotassium orthophosphate is ca. 93% (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. Tripotassium orthophosphate may contain the following typical impurities derived from the production process:


Typical content (%w/w)

Dipotassium orthophosphate, EINECS: 231-834-5

< 5 %

Dipotassium carbonate, EINECS: 209-529-3

< 5 %

Tetrapotassium pyrophosphate, EINECS: 230-785-7

< 2 %

Tripotassium orthophosphate is considered to be very soluble (62.4 - 65.0% w/w at 20.0 ± 0.5°C).The pH of this solution, observed in the water solubility study, was pH >14.

 The results are shown in the following table:

Test temperature

Water solubility

Typical solution pH


In the range 65.0 % w/w to 67.5 % w/w



In the range 62.4 % w/w to 65.0 % w/w



In the range 62.7 % w/w to 65.6 % w/w


Overall, the effect of temperature over the range 10 to 30°C has been considered not to have had a significant influence on the observed solubility of the test material.

Additionally, an assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 indicated observed solubilities and final solution pH’s similar to those obtained using unbuffered water. Thus, it can be anticipated that the water solubility of the test material over the pH range 4 to 9 would be constant, essentially due to the low buffering activities seen in the environment.

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