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EC number: 206-076-3 | CAS number: 299-29-6
Dissociation constant
Administrative data
Link to relevant study record(s)
- 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
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- Deviations:
- no
- GLP compliance:
- yes
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- ca. 6.28
- Temp.:
- 25 °C
- No.:
- #2
- pKa:
- ca. 8.13
- Temp.:
- 25 °C
- Conclusions:
- Results are presented below for the two pKa values determined by potentiometric titration following the OCED test method 112 (12-05-81) protocol.
pKa 1 = 6.28
pKa 2 = 8.13
Results are presented below for the two pKa values determined by potentiometric titration following the OCED test method 112 (12-05-81) protocol.
pKa 1 = 6.28
pKa 2 = 8.13
pKa values are plotted against sample weight and extrapolated back to zero weight to determine the ideal pKa values. All of the individual pKa measurements met the test guideline for suggested repeatability quality criteria of ± 0.1 pKa units of the mean.
Reference
The electrode was calibrated with pH 4, 7, and 10 traceable buffer solutions and a calibration slope of 99.0% was obtained. The room temperature was recorded as 25°C.
The iron gluconate test material was determined to be acidic and subsequently titrated with 0.1 N NaOH to produce titration curves of pH versus volume of titrant added. Table 1 provides a summary of the titration data. The pKa values acquired for each endpoint were plotted on separate graphs against sample weight and extrapolated back to zero weight to determine the ideal pKa value.
Table 1. Summary of Titration Results for Iron Gluconate
| Weighing Number | Wt. of test substance (g) | EnpointNumber | Endpoint Vol (mL) | Half-Point pH (pKa) | Half-pointVol (mL) | Deviation from Mean pKa |
| 1 | 0.0764 | 1 | 1.47 | 6.21 | 0.74 | -0.02 |
| 2 | 3.24 | 8.11 | 2.36 | -0.01 | ||
| 2 | 0.1402 | 1 | 1.44 | 6.24 | 0.72 | -0.06 |
| 2 | 5.23 | 8.12 | 3.33 | -0.01 | ||
| 3 | 0.2493 | 1 | 1.49 | 6.11 | 0.74 | 0.08 |
| 2 | 9.18 | 8.10 | 5.33 | 0.01 |
Description of key information
Results are presented below for the two pKa values determined by potentiometric titration following the OCED test method 112 (12-05-81) protocol.
pKa 1 = 6.28
pKa 2 = 8.13
pKa values are plotted against sample weight and extrapolated back to zero weight to determine the ideal pKa values. All of the individual pKa measurements met the test guideline for suggested repeatability quality criteria of ± 0.1 pKa units of the mean.
Key value for chemical safety assessment
- pKa at 20°C:
- 6.28
Additional information
The above value was recorded at 25*C
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