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Typically the purity of tetrairon tris(pyrophosphate) is 97 % (dry weight, after excluding water). The substance may contain the following impurities, derived from the production process, each one present at the concentrations indicated below:

Sodium sulphate (EINECS No: 231-820-9)


Iron(III)orthophosphate (EINECS No: 233-149-7)


Tetrasodium pyrophosphate (EINECS No. 231-76-1)


All other 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 additional hazardous impurities present within the substance at levels >0.1%.

An investigation of the particle size indicated that > 99% of particles present were < 100µm and as such tetrairon tris(pyrophosphate) is considered to be inhalable. In an acute inhalation study the Mean Mass Median Aerodynamic Diameter was reported to be 4.22 μm. The inhalable fraction of the test material, % <4 μm, was 48.3%, which would allow the test material to reach upper and lower regions of the respiratory tract of the rat. In addition, this also means that a fraction of the particles will be respirable (i.e. reaching the alveoli) in humans.

Tetrairon tris(pyrophosphate) has a melting point of >450°C and is considered to be of low solubility. The following observations were made in a water solubility study:

The effect of temperature over the range 10 to 30°C has been considered not to have had a significant influence on the solubility of the test material (range 2.99 x 10-4 to 3.67 x 10-4 g/l).

The initial solution pH was shown to significantly influence solubility of the test material. When using an identical initial saturation period of 72 hours, the use of the pH 4 buffer solution significantly increased the resulting equivalent test material concentration dissolved (when compared to unbuffered water) to 0.297 g/l at 20.0 ± 0.5°C (at a final solution of 3.3), whereas the use of the pH 9 buffer solution decreased the resulting equivalent test material concentration to less than 2.52 x 10-4 g/l at 20.0 ± 0.5°C (at a final solution pH of 6.0). Therefore, although the maximum observed solubility was 0.297 g/l (at a final solution pH of 3.3), the water solubility of the test material may increase further in cases where additional buffering capacity exists.

Tetrairon tris(pyrophosphate) is not considered to possess any of the following hazardous physico-chemical properties: autoflammability and/or self-ignition, flammability (including pyrophoricity and flammability with water), explosiveness and oxidising properties.

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