Registration Dossier
Registration Dossier
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EC number: 695-022-6 | CAS number: 473278-76-1
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 7 May 2002 - 16 May 2002
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- GLP compliance:
- yes (incl. QA statement)
- Remarks:
- Hess. Ministerium für Umwelt, Landwirtschaft und Forsten, Wiesbaden, Germany
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 3.2
- Temp.:
- 20 °C
Reference
The pKa for each determination was calculated as the average of individual values for which the proportion dissociated are between 10 % and 90 %. Data points outside this range were not used to compute the final result. To calculate the demanded pH range and the percentage ionised of the test substance, the following equations were used:
| value | equation |
| pH range | pH range = pKa ± log 9 |
| %-ionised | %-ionised = 100 / [1 + antilog(pKa - pH)] |
results:
test no. |
temperature [°C] |
pKa | acceptable pH range |
measured pH range (*) |
%-ionised (measured pH range) |
| 1 | 20 | 3.22 | 2.27 - 4.17 | 2.40 - 3.81 | 13.1 - 79.6 |
| 2 | 20 | 3.23 | 2.28 - 4.18 | 2.60 - 3.61 | 19.0 - 70.6 |
| 3 | 20 | 3.25 | 2.30 - 4.20 | 2.40 - 3.20 | 12.4 - 47.1 |
(*) The data inside this range were used to calculate the average pKa.
The overall average pKa-value at 20 °C is pKa = 3.2 .
Description of key information
3.2 at 20 °C (spectrophotometric method, OECD Guideline 112)
Key value for chemical safety assessment
- pKa at 20°C:
- 3.2
Additional information
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