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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Peer-reviewed public domain data provided the three dissociation constants for phosphoric acid in the range of pKa1= 2.1 - 2.2, pKa2=7.1 - 7.2 and pKa3=12.3 - 12.4. Temperature of measurement (where reported) was 25 deg C.

Key value for chemical safety assessment

Additional information

As the reported pKa values are in a close range, the mean rounded-up values were taken. Temperature of measurement was either 25°C or not reported. It is anticipated that the calculated rounded-up values are applicable at a temperature of 20°C. Value used for CSA: pKa1 = 2.1, pKa2 = 7.2, pKa3 = 12.3 at 20°C