Registration Dossier
Registration Dossier
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EC number: 410-070-8 | CAS number: 141880-36-6 ACID RED HT 3728; ERIONYL RED HT 3728
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:
- 10 June 1992 to 02 October 1992
- 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:
- not specified
- GLP compliance:
- yes (incl. QA statement)
- Specific details on test material used for the study:
- Product Designation: FAT 45155/B, (Erionyl Rot KT 3728)
Identification: Vers. Nr. TV 1 - Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 8.02
- Temp.:
- 20 °C
- Remarks on result:
- other: acidic
- No.:
- #2
- pKa:
- 11.97
- Temp.:
- 20 °C
- Remarks on result:
- other: acidic
- No.:
- #3
- pKa:
- > -3 - < -2.5
- Temp.:
- 20 °C
- Remarks on result:
- other: acidic (estimated)
- Conclusions:
- Dissociation constant of FAT 45155/B is pKa1: 8.02; pKa2: 11.97.
- Executive summary:
A GLP-compliant study with FAT 45155/B was carried out according to OECD guideline 112. Based on the test results, the dissociation constants of the test material were determined to be pKa1 as 8.02 and pKa2 as 11.97.
Reference
As the test substance has extremely high pK value, it was not possible to obtain the adsorbance of the fully dissociated compound. The endpoints of titration was obtained by iteration using a LOTUS 123 speadsheet. The best estimation of the endpoint is then reached, when the pK values calculated form the individual measured points show the smallest deviation from each other.
The high measured pK value of 11.97 suggests that in the range pH>8 the compound is in the hydrazo form instead of the azo form.
Description of key information
A GLP-compliant study with FAT 45155/B was carried out according to OECD guideline 112. Based on the test results, the dissociation constant of the test material were determined to be pKa1 as 8.02 and pKa2 as 11.97.
Key value for chemical safety assessment
- pKa at 20°C:
- 8.02
Additional information
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