Potassium tetrafluoroaluminate

Endpoint summary

Additional information

For appearance, melting point, relative density and granulometry no data were available on potassium tetrafluoroaluminate. Therefore the lacking data were derived by read-across from its analogue multiconstituent aluminium potassium fluoride. Multiconstituent aluminium potassium fluoride is a multiconstituent substance containing ca. 70% of KAlF4and ca. 30% of salts of higher homological penta- and hexafluoroaluminic acids, K2AlF5 and K3AlF6. The properties of all three potassium homological salts KAlF4, K2AlF5 and K3AlF6 are expected to be very similar and thus read across is considered to be acceptable.

Based on the read-across from multiconstituent aluminium potassium tetrafluoride, potassium tetrafluoroaluminate is an inorganic white crystalline solid with a melting point above at least 300 °C. The relative density of potassium tetrafluoroaluminate is expected to ca. 2.9 at 20 ˚C.

The water solubility of potassium tetrafluoroaluminate is ca. 2.5 g/L (HOESCH Metallurgie Laboratory, 2011). From data on multiconstituent aluminium potassium fluoride particle size distribution is determined to be: D10 = 0.92μm, D50 = 3.01μm, D90 = 11.63μm.

Based on the melting point of above 300 ºC, studies on the boiling point and vapour pressure of potassium tetrafluroaluminate are not required in accordance with Column 2 of REACH Annex VII. The studies on the octanol/water partition coefficient, the flash point and the stability in organic solvents do not need to be conducted as the substance is inorganic. Surface activity is not predicted based on the substance structure; neither is it a desired substance property. As potassium tetrafluoroaluminate is a solid, viscosity is not a relevant property. The substance is not expected to be explosive as it does not contain chemical groups which are associated with explosive properties. The performance of the tests on auto-ignition temperature and flammability is considered to be scientifically unjustified in accordance with Annex XI of REACH, as the substance is incapable of reaction with oxygen due to the fact that metal ions are already present in the highest possible oxidation state, and fluorine, being the most electronegative element, cannot be oxidised by oxygen. Water reactivity and pyrophoric properties are not expected for potassium tetrafluoroaluminate based on the experience in handling the substance. In addition, as the substance is considered to be incapable of reacting exothermically with combustible materials based on its chemical structure, oxidising properties are not expected.

The performance of the study on dissociation constant is considered to be scientifically unjustified in accordance with REACH Annex XI, as, according to Chapter R.7.1.17 of REACH Guidance on information requirements and chemical safety assessment, this property is important for ionisable organic substances. As potassium tetrafluoroaluminate is an inorganic salt, it is expected to dissociate fully into the respective cation and anion in aqueous solution. Possible dissociation of fluoroaluminate moiety, although it may occur upon dissolution, is considered to be irrelevant for this endpoint.