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Diss Factsheets

Administrative data

Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The study was conducted between 10 June 2005 and 11 August 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Diammonium phthalate
EC Number:
208-341-9
EC Name:
Diammonium phthalate
Cas Number:
523-24-0
Molecular formula:
C8H6O4.2H3N
IUPAC Name:
diammonium phthalate
Test material form:
solid: crystalline
Specific details on test material used for the study:
Description: white crystalline solid
Lot number: 4172005
Date recieved: 02 June 2005
Storage conditions: room temperature, in the dark

Results and discussion

Dissociating properties:
yes
Dissociation constantopen allclose all
pKa:
5.13
Temp.:
20 °C
Remarks on result:
other: phthalate component
pKa:
2.81
Temp.:
20 °C
Remarks on result:
other: phthalate component
pKa:
9.42
Temp.:
20 °C
Remarks on result:
other: ammonium component

Any other information on results incl. tables

Ammonium component

Preliminary test:

Preliminary testing indicated that the dissociation constant was approximately 9.33.

Definitive test:

Mean of seven middle readings, determination 1: 9.43

Mean of seven middle readings, determination 2: 9.44

Mean of seven middle readings, determination 3: 9.38

Overall mean (pKa): 9.42

Phthalate component

Preliminary test:

Preliminary testing indicated that there were two dissociation constants for the phthalate component of the test material. The results are shown in the following table:

pKa

Result

1

5.12

2

2.85

Definitive test:

Mean of seven middle readings, determination 1, dissociation constant 1: 5.13

Mean of seven middle readings, determination 1, dissociation constant 2 : 2.83

Mean of seven middle readings, determination 2, dissociation constant 1: 5.13

Mean of seven middle readings, determination 2, dissociation constant 2: 2.80

Mean of seven middle readings, determination 3, dissociation constant 1: 5.12

Mean of seven middle readings, determination 3, dissociation constant 2: 2.80

Overall mean, dissociation constant 1 (pKa 1): 5.13

Overall mean, dissociation constant 2 (pKa 2): 2.81

Applicant's summary and conclusion

Conclusions:
The dissociation constants of components of the test material have been detennined. The results are shown below

Component pKa Temperature °C
phthalate 5.13 20.0 ± 0.5
phthalate 2.81 20.0 ± 0.5
ammonium 9.42 20.0 ± 0.5
Executive summary:

The dissociation constants of components of the test material have been determined using Method 112 of the OECD Guidelines for Testing of Chemicals, 12 May 1981. The results are as folows:

Component                pKa             Temperature °C

phthalate                   5.13                 20.0 ± 0.5

phthalate                   2.81                 20.0 ± 0.5

ammonium                 9.42                20.0 ± 0.5