Registration Dossier

Physical & Chemical properties

Dissociation constant

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
GLP compliance:
yes (incl. certificate)
Dissociating properties:
yes
No.:
#1
pKa:
7.1
Temp.:
20 °C

Full test results:

Base: If absorbance of d ion is > absorbance of d molecule

 pH  d  pKa
6.46  2.70  7.749
6.29  2.73  7.698
6.05   2.77  7.687
5.85  2.28  6.434
5.66   2.52  6.540
5.48   2.59  6.484

pH: 5.83

Wavelength: 195.5 nm

d (ion): 2.83

d (molecule): 0.17

Executive summary:

Result: pKa = 7.10 ± 1.0

Generally pKa of seven solutions (partially dissociated) of test sample is determined. However at the selected wavelength of 195.5 nm, absorbance of the ion in the partially dissociated solutions become greater than that of the fully dissociated ion at pH units lower than 5.48 or higher than 6.46. Therefore the mean of six solutions was obtained for the pKa determination.

Description of key information

Key value for chemical safety assessment

pKa at 20°C:
7.1

Additional information