Registration Dossier
Registration Dossier
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EC number: 232-051-1 | CAS number: 7784-18-1
Dissociation constant
Administrative data
Link to relevant study record(s)
Description of key information
In aqueous media, the substance can form a number of different species involving Al(3+), F(-) and OH(-), depending on both pH and F(-) concentration. The substance is expected to be present in one charged form or another throughout the environmentally relevant range of pH 5-9.
Key value for chemical safety assessment
Additional information
Information regarding dissociation constants was sourced from a literature article reporting computer-aided QSAR estimates of the speciation of the substance in aqueous media utilizing SOLGASWATER (version Win SGW) model. The author concluded that the substance would dissociate to release fluoride ions and/or exchange fluoride for hydroxide, depending on both the pH and the fluoride concentration. Low pH (i.e. < pH ~6) and higher fluoride concentrations would favour more highly fluorinated/less highly hydroxylated species, and higher pH (i.e. > pH ~6) and lower fluoride concentrations would favour less highly fluorinated/more highly hydroxylated species.
The author goes on to state that the pKa values defined according to the reactions
Al(OH)mFn(3 -m-n)++ H2O = Al(OH)m+1Fn(2 -m-n)++ H+
seem to fall within the range 5.5 to 7.
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