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EC number: 245-740-7 | CAS number: 23564-05-8
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:
- 1990
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- Deviations:
- no
- GLP compliance:
- yes
- Dissociating properties:
- no
- pKa:
- 7.28
- Temp.:
- 25 °C
- Conclusions:
- The dissociation constant of the test item was determined to be 7.28 at 25 °C.
- Executive summary:
A study according to OECD 112 was performed to determine the dissociation constant of the test item. Using a conductometric method, test item solutions with different concentrations were analysed. The conductivity of these solutions was measured and based on it the dissociation constant of the test item at 25 °C was determined to be 7.28.
Reference
Table 1. Equivalent conditions at various concentration of sodium salt of the test item
C (10-2 mol/m3) |
√C (mol1/2m-3/2) |
Conductivity (10-4 S/m) |
Λ (10-4 m2S/mol) |
1/λ (m-2S-1mol) |
3.020 |
0.1734 |
3.42 |
113 |
88.3 |
1.510 |
0.1229 |
2.13 |
141 |
70.9 |
0.755 |
0.0869 |
1.21 |
160 |
62.4 |
0.378 |
0.0615 |
0.67 |
177 |
56.4 |
0.189 |
0.0435 |
0.40 |
212 |
47.3 |
Table 2. Calculation of pKa from conductivity of the test item
C (M) |
Conductivity (10-4 S/m) |
Λi (10-4 S/m) |
α |
Ka |
pKa |
30.20E-6 |
0.70 |
23.2 |
0.0401 |
5.06E-8 |
7.30 |
15.10E-6 |
0.51 |
33.8 |
0.0584 |
5.47E-8 |
7.26 |
7.55E-6 |
0.35 |
46.5 |
0.0802 |
5.28E-8 |
7.28 |
pKa = 7.28 (mean) ± 0.02 (S.D.)
Description of key information
The dissociation constant of the test item was determined to be 7.28 at 25 °C.
Key value for chemical safety assessment
- pKa at 20°C:
- 7.28
Additional information
A study according to OECD 112 was performed to determine the dissociation constant of the test item. Using a conductometric method, test item solutions with different concentrations were analysed. The conductivity of these solutions was measured and based on it the dissociation constant of the test item at 25 °C was determined to be 7.28.
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