Registration Dossier

Administrative data

Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1997-04-03 to 1997-07-23
Reliability:
2 (reliable with restrictions)
Cross-reference
Reason / purpose:
reference to same study

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1997
Report Date:
1997
Reference Type:
study report
Title:
Unnamed
Year:
1997
Report Date:
1997

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
The test substance is dissolved in water and potentiometrically titrated with hydrochloric acid. The dissociation constant is determined from the inflection point of the titration curve.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- CAS name: 1H-Benzimidazole-4,6-disulfonic acid-2,2´-(1,4-diphenylene) bis, disodium salt
- Molecular formula: C20H12N4O12S4Na2
- Molecular weight: 674g/mol
- physical state: solid

Results and discussion

Dissosciation constantopen allclose all
No.:
#1
pKa:
2.5
Temp.:
20 °C
No.:
#2
pKa:
3.9
Temp.:
20 °C

Applicant's summary and conclusion

Conclusions:
pK1: 2.5 and pK2 3.9 (determined at 20°C)
Executive summary:

At a pH-value lower than 2.5 not only the carboxylic function is protonated, but also the amino functions. At higher pH-values the amino functions are deprotonated, but the same applies to the carboxylic function.