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Physical & Chemical properties

Dissociation constant

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Description of key information

Dissociation constant (BHMT-H): BHMT acid has ten ionisable phosphonate groups.

Key value for chemical safety assessment

Additional information

Ten dissociation constants as listed below were obtained for the BHMT acid using an apporpriate estimation method. The result is considered reliable and selected as key study.

BHMT-H was determined to have ten pKa values, of: 
pKa 1 = 1.3

pka 2 = 1.3
pKa 3 = 2.7
pKa 4 = 3.4

pKa 5 = 3.4
pka 6 = 5.9
pKa 7 = 5.9

pKa 8 = 7.0

pKa 9 = >9

pKa 10 = >9

An approximate experimental determination, using stocichiometric titration and pH determination of aqueous solutions, has been conducted. This is considered to provide suitable and practical information, which is fit for purpose in the context of REACH chemical safety assessment. This data is reported in section 4.20.