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According to IUCLID Section 5.1.2 (hydrolysis), similar to all coordination complexes of boron trifluoride with organic and inorganic species (like alcohols, ethers, amines, sulfuric acid, sulfuric dioxide, etc) the complex of boron trifluoride and phosphoric acid is extremely water sensitive and reacts even with moist air. In the instantaneous reaction with water as a first step phosphoric acid and boron trifluoride dihydrates are formed. For this reason, the adsorption-desorption behavior of boron trifluoride phosphoric acid complex was assessed in view of these two constituents.

When released in the atmosphere boron trifluoride (BF3) molecules in contact with atmospheric moisture form a complex: dihydrated boron trifluoride (BF3, 2H2O). On the opposite if BF3 is directly brought into contact with water, it reacts violently. That is the reason why the assessment of environmental fate and pathways is based on the properties of the more stable dihydrated form of boron trifluoride.

Measurement of fluoride ion production over a range of pH values (1.2 to 9), using both ion chromatography and an ion-selective electrode, indicated a hydrolytic half-life time of less than 30 minutes for boron trifluoride. Subsequent analysis of boric acid by titration confirmed the rapidity of the reaction. Consequently, the risk associated to dehydrated boron trifluoride when release into water and so in contact with sediments can be assessed based upon the hazards of its breakdown products in water: boric acid and fluoboric acid So, BF3 2H2O formed in moisture air transfers into soil via dry and/or wet deposition, where in turn, in high moistured soils, it could hydrolyse in pore water. In addition, the sorption potential of boron on soils was widely described and assessed as low (European Risk Assessment of Boric acid, 2007).

No experimental data addressing the adsorption/desorption properties of orthophosphoric acid are available. According to Annex XI, Section 2 of Regulation (EC) No 1907/2006 (REACH) testing for a specific endpoint may be omitted if it is technically not possible to conduct the study as a consequence of the properties of the substance itself.

- A screening study according to OECD Guideline 121 is not technically possible as the test method is not validated for inorganic substances.

- A batch equilibrium study according to OECD Guideline 106 was deemed to be not applicable for orthophosphoric acid for the following reasons:

Firstly, phosphates are natural constituents of soils and as such analysis of the test material may not be possible due to interference from the soil extracts that may leach into the aqueous media during the test. This would prevent quantification of the test material. In addition, the mobility of the test item would be dependent on the anion exchange capacity of the soils as the main component of the test material is an anion. This absorption relationship would not be anticipated to correlate with the organic carbon content of the soils and is considered to be beyond the scope of the OECD 106 method.

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