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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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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dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
no guideline followed
Principles of method if other than guideline:
Values for the acid dissociation constant of the ammonium ion based on concentration standards in a series of aqueous ammonium bromide, sodium perchlorate solutions, all of unit ionic strength were determined at 25°C.
A stock solution of ammonium bromide was prepared by neutralisation of a standardised ammonia solution with hydrobromic acid solution. The degree of neutralisation was checked using Bjerrums method. For the temperature and for the salt medium in question, four solutions of different ammonia concentration (0.005 pka = pH + log (C NH3 + [H+] - [OH-}/C NH4+ - [H+] + [OH-]).
Each value is the mean of the four measurements. Standard deviations range from 0.001 and 0.004. Standard errors of estimate on the parameters in the two dimensional interpolation formula were 0.003 on the intercept and 0.005 on the coefficients.
GLP compliance:
Dissociating properties:
25 °C
Remarks on result:
other: 1.00 M solution
The substance will dissociate with a pKa of 9.384 at 25°C

Description of key information

The substance will dissociate with a pKa of 9.384 at 25°C 

Key value for chemical safety assessment

pKa at 20°C:

Additional information

The substance will dissociate with a pKa of 9.384 at 25°C