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Physical & Chemical properties

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Cryolite is an inorganic clear or white to yellowish, sometimes reddish or black crystalline solid. It has a melting point of 1009-1012˚C (Ullmann's Encyclopedia of Industrial Chemistry, 2002). As the substance is a solid with a melting point well above 300 ˚C, in accordance with Column 2 of REACH Annex VII, studies on boiling point study and vapour pressure do not need to be conducted. The relative density of cryolite is 2.97 at 20 ˚C (Ullmann's Encyclopedia of Industrial Chemistry, 2002). The water solubility of cryolite is 0.602 g/L at 20 ˚C and pH = 5.5-7 and 0.217 g/L at 20 ˚C and pH = 8.5-9 (Safepharm Laboratories Ltd., 2008). The studies on octanol/water partition coefficient, flash point study 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. Cryolite is hydrolytically unstable. As cryolite 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. 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 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 cryolite based on the experience in handling the substance. 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 cryolite is an inorganic salt, it is expected to dissociate fully into the respective cation and anion in aqueous solution. Possible dissociation of hexafluoroaluminate moiety, although it may occur upon dissolution, is considered to be irrelevant for this endpoint.

The following results regarding the particle distribution were obtained (results of laser diffraction determination) for cryolite: D10 = 1.73μm; D50 = 9.78μm; D90 = 20.97μm (Solvay Fluor GmbH, 2009).