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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Administrative data

Link to relevant study record(s)

Description of key information

The pKa of the test material has been measured as 3.4

Key value for chemical safety assessment

pKa at 20°C:

Additional information

In a GLP study conducted according to OECD Guideline 112, the dissociation constant (pKa) of the test material was determined by a spectrophotometric method. The value was checked against that obtained from a simple titration of the potassium salt with dilute hydrochloric acid. For the spectrophotometric method, solutions of the test material in formate buffer (approx. 20 mg/mL) were scanned and the concentration of the ionised and neutral (unionised) fraction determined.

The mean pKa value of 3.4 was calculated from 4 spectrophotometric determinations at pH values between 3.11 and 3.82. Using the titration method, the pKa was found to be between 3.2 and 4.2, supporting the spectrophotometric value of 3.4.