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EC number: 617-769-9 | CAS number: 858956-08-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
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:
- 2007-10-17
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- EPA OPPTS 830.7370 (Dissociation constants in water)
- Version / remarks:
- 1996
- GLP compliance:
- yes (incl. QA statement)
- Remarks:
- Bundesinstitut für Risikobewertung, Berlin, Germany / Food and Consumer Product Safety Authority, Den Haag, The Netherlands / National GLP Compliance Monitoring Authority, New Delhi, India
- Dissociating properties:
- yes
- pKa:
- 4.65
- Temp.:
- 20 °C
- Conclusions:
- The dissociation constant (pKa) of the substance at ca. 20 °C was determined to be 4.65 ± 0.04 (OPPTS 830.7370)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 2009-09-16 to 2009-09-18
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- GLP compliance:
- yes (incl. QA statement)
- Remarks:
- Bundesinstitut für Risikobewertung, Berlin, Germany
- Dissociating properties:
- yes
- pKa:
- 4.63
- Temp.:
- 20 °C
- Conclusions:
- The dissociation constant (pKa) of the test item at ca. 20 °C was determined to be 4.63 ± 0.14 (OECD Guideline 112, Spectrophotometric method)
Referenceopen allclose all
The concentration of sodium hydroxide solution used in the titration was found to be 0.0096 M.
The results of the dissociation constants of the test item in water are given in the tables reported below. The mean dissociation constants of the test item in water for replications R1, R2 and R3 were determined to be 4.61 ± 0.53, 4.69 ± 0.59 and 4.66 ± 0.60, respectively, with an overall mean of 4.65 ± 0.04.
The maximum and minimum temperature during the experimental period was 20.2 and 19.8 °C, respectively.
Dissociation constant of the test item (replication R1)
[L] volume of base (titrant) added (mL) |
[P] total volume after adding L (mL) |
pH |
[X] moles of Base
(K * L) / 1000 |
[B] undissociated test item
(N - X) * 1000 / P |
[BH+] dissociated test item
(X * 1000) / P |
log ([B] / [BH+]) |
pKa |
2.5 |
202.5 |
4.27 |
0.00002400 |
0.0003438 |
0.0001185 |
0.4626 |
3.807 |
3.0 |
203.0 |
4.33 |
0.00002880 |
0.0003193 |
0.0001419 |
0.3522 |
3.978 |
3.5 |
203.5 |
4.47 |
0.00003360 |
0.0002949 |
0.0001651 |
0.2519 |
4.218 |
4.0 |
204.0 |
4.54 |
0.00003840 |
0.0002707 |
0.0001882 |
0.1579 |
4.382 |
4.5 |
204.5 |
4.62 |
0.00004320 |
0.0002466 |
0.0002112 |
0.0673 |
4.553 |
5.0 |
205.0 |
4.66 |
0.00004800 |
0.0002225 |
0.0002341 |
-0.0221 |
4.682 |
5.5 |
205.5 |
4.72 |
0.00005280 |
0.0001986 |
0.0002569 |
-0.1118 |
4.832 |
6.0 |
206.0 |
4.80 |
0.00005760 |
0.0001749 |
0.0002796 |
-0.2037 |
5.004 |
6.5 |
206.5 |
4.89 |
0.00006240 |
0.0001515 |
0.0003022 |
-0.3007 |
5.191 |
7.0 |
207.0 |
5.04 |
0.00006720 |
0.0001276 |
0.0003246 |
-0.4055 |
5.446 |
Mean ± S.D. |
4.61 ± 0.53 |
K = Concentration of base used in titration = 0.0096M
Weight of test item taken: 0.0250 g
Volume made up: 250 mL
Aliquot taken for titration (A): 200 mL
Molecular weight of test item: 213.623
Concentration of test item (C) = (0.0250 * 1000) / (213.623 x 250 (mL)) = 0.0004681
Total No. of moles of test item in 200 mL solution taken for titration (N) = 0.0004681 x 200 / 1000 = 0.00009362
Max. and Min. Temp. during the period: 20.2 and 20.0 °C, respectively
Dissociation constant of the test item (replication R2)
[L] volume of base (titrant) added (mL) |
[P] total volume after adding L (mL) |
pH |
[X] moles of Base
(K * L) / 1000 |
[B] undissociated test item
(N - X) * 1000 / P |
[BH+] dissociated test item
(X * 1000) / P |
log ([B] / [BH+]) |
pKa |
2.5 |
202.5 |
4.25 |
0.0002400 |
0.0003476 |
0.0001185 |
0.4614 |
3.783 |
3.0 |
203.0 |
4.35 |
0.0002880 |
0.0003231 |
0.0001419 |
0.3574 |
3.993 |
3.5 |
203.5 |
4.50 |
0.0003360 |
0.0002987 |
0.0001651 |
0.2575 |
4.243 |
4.0 |
204.0 |
4.58 |
0.0003840 |
0.0002744 |
0.0001882 |
0.1638 |
4.416 |
4.5 |
204.5 |
4.68 |
0.0004320 |
0.0002503 |
0.0002112 |
0.0738 |
4.606 |
5.0 |
205.0 |
4.76 |
0.0004800 |
0.0002262 |
0.0002341 |
-0.0149 |
4.775 |
5.5 |
205.5 |
4.85 |
0.0005280 |
0.0002023 |
0.0002569 |
0.1038 |
4.954 |
6.0 |
206.0 |
4.96 |
0.0005760 |
0.0001785 |
0.0002796 |
-0.1949 |
5.155 |
6.5 |
206.5 |
5.06 |
0.0006240 |
0.0001549 |
0.0003022 |
-0.2902 |
5.350 |
7.0 |
207.0 |
5.19 |
0.0006720 |
0.0001313 |
0.0003246 |
-0.3931 |
5.583 |
Mean ± S.D. |
4.69 ± 0.59 |
K = Concentration of base used in titration = 0.0096M
Weight of test item taken: 0.0252 g
Volume made up: 250 mL
Aliquot taken for titration (A): 200 mL
Molecular weight of test item: 213.623
Concentration of test item (C) = (0.0252 * 1000) / (213.623 x 250 (mL)) = 0.0004719
Total No. of moles of test item in 200 mL solution taken for titration (N) = 0.0004719 x 200 / 1000 = 0.00009438
Max. and Min. Temp. during the period: 20.1 and 20.0 °C, respectively
Dissociation constant of the test item (replication R2)
[L] volume of base (titrant) added (mL) |
[P] total volume after adding L (mL) |
pH |
[X] moles of Base
(K * L) / 1000 |
[B] undissociated test item
(N - X) * 1000 / P |
[BH+] dissociated test item
(X * 1000) / P |
log ([B] / [BH+]) |
pKa |
2.5 |
202.5 |
4.23 |
0.00002400 |
0.0003493 |
0.0001185 |
0.4695 |
3.761 |
3.0 |
203.0 |
4.33 |
0.00002880 |
0.0003248 |
0.0001419 |
0.3596 |
3.970 |
3.5 |
203.5 |
4.45 |
0.00003360 |
0.0003004 |
0.0001651 |
0.2600 |
4.190 |
4.0 |
204.0 |
4.56 |
0.00003840 |
0.0002762 |
0.0001882 |
0.1666 |
4.393 |
4.5 |
204.5 |
4.64 |
0.00004320 |
0.0002520 |
0.0002112 |
0.0767 |
4.563 |
5.0 |
205.0 |
4.70 |
0.00004800 |
0.0002280 |
0.0002341 |
-0. 0115 |
4.712 |
5.5 |
205.5 |
4.83 |
0.00005280 |
0.0002041 |
0.0002569 |
-0.0999 |
4.930 |
6.0 |
206.0 |
4.95 |
0.00005760 |
0.0001803 |
0.0002796 |
-0.1905 |
5.141 |
6.5 |
206.5 |
5.04 |
0.00005240 |
0.0001566 |
0.0002538 |
-0.2855 |
5.326 |
7.0 |
207.0 |
5.21 |
0.00006720 |
0.0001330 |
0.0003246 |
-0.3875 |
5.598 |
Mean ± S.D. |
4.66 ± 0.60 |
K = Concentration of base used in titration = 0.0096M
Weight of test item taken: 0.0253 g
Volume made up: 250 mL
Aliquot taken for titration (A): 200 mL
Molecular weight of test item: 213.623
Concentration of test item (C) = (0.0253 * 1000) / (213.623 x 250 (mL)) = 0.0004737
Total No. of moles of test item in 200 mL solution taken for titration (N) = 0.0004737 x 200 / 1000 = 0.00009474
Max. and Min. Temp. during the period: 20.0 and 19.8 °C, respectively
Dissociation constant of the test item (mean)
Replication |
Mean pKa |
R1 |
4.61 |
R2 |
4.69 |
R3 |
4.66 |
Mean ± S.D. |
4.65 ± 0.04 |
Verification of Spectrophotometer Performance
On all occasions of use, the instrument passed all internal calibration checks.
Preliminary test
The absorbance of the test item was measured by adding an aliquot of an aqueous solution of test item to buffers solutions with pH from <1.96 to pH >12.1. Results shown significant difference in the absorbance value measured in the pH range between 1.96 to 12.1. The time gap between adding an aliquot of an aqueous solution of test item and capture of the UV spectrum was 2 to 7 minutes. From the preliminary test result it was observed that the dissociation constant of the test item was to be 4.63 ± 0.17.
The test was used to determine the pH range and optimize the wavelength at which the dissociation constant of the test substance was determined.
Definitive Test
The absorbance of the test item was measured by adding an aliquot of an aqueous solution of the test item to buffers solutions with pH from <2.02 to pH >11.85. The results are presented in Table 1.
Results shown significant difference in the absorbance value of the test item measured in the pH range between 2.02 to 11.85. The time gap between adding an aliquot of an aqueous solution of the test item and capture of the UV spectrum was 2 to 7 minutes. The time measurements are presented in Table 2. Thus, it is concluded, the compound is undergoing dissociation as a function of change in pH. From the test result it was observed that the dissociation constant of the test item is 4.63 ± 0.14.
Table 1: Calculation of dissociation constant - definitive test
pH of the buffer only solution |
pH of solution after addition of test item |
abs @ 260 nm |
mean |
pKa |
2.02 |
2.02 |
0.368 |
0.3690 |
N/C |
0.369 |
N/C |
|||
0.370 |
N/C |
|||
2.65 |
2.65 |
0.361 |
0.3630 |
N/C |
0.363 |
N/C |
|||
0.365 |
N/C |
|||
3.06 |
3.07 |
0.382 |
0.3777 |
N/C |
0.384 |
N/C |
|||
0.367 |
N/C |
|||
3.71 |
3.72 |
0.321 |
0.3307 |
4.459 |
0.342 |
4.902 |
|||
0.329 |
4.590 |
|||
4.24 |
4.28 |
0.289 |
0.2787 |
4.658 |
0.276 |
4.544 |
|||
0.271 |
4.503 |
|||
4.59 |
4.63 |
0.250 |
0.2543 |
4.687 |
0.250 |
4.687 |
|||
0.263 |
4.789 |
|||
4.88 |
4.98 |
0.196 |
0.1860 |
4.602 |
0.178 |
4.420 |
|||
0.184 |
4.485 |
|||
5.31 |
5.42 |
0.169 |
0.1577 |
4.750 |
0.151 |
4.451 |
|||
0.153 |
4.493 |
|||
5.91 |
5.98 |
0.135 |
0.1373 |
4.414 |
0.138 |
4.596 |
|||
0.139 |
4.644 |
|||
6.48 |
6.56 |
0.132 |
0.1320 |
4.687 |
0.132 |
4.687 |
|||
0.132 |
4.687 |
|||
6.96 |
7.01 |
0.130 |
0.1303 |
4.656 |
0.131 |
4.959 |
|||
0.130 |
4.656 |
|||
7.41 |
7.46 |
0.125 |
0.1257 |
N/C |
0.127 |
N/C |
|||
0.125 |
N/C |
|||
7.98 |
8.04 |
0.132 |
0.1300 |
N/C |
0.129 |
N/C |
|||
0.129 |
N/C |
|||
8.41 |
8.44 |
0.124 |
0.1253 |
N/C |
0.126 |
N/C |
|||
0.126 |
N/C |
|||
8.86 |
8.9 |
0.125 |
0.1253 |
N/C |
0.125 |
N/C |
|||
0.126 |
N/C |
|||
9.54 |
9.54 |
0.125 |
0.1260 |
N/C |
0.126 |
N/C |
|||
0.127 |
N/C |
|||
10.01 |
10.03 |
0.120 |
0.1207 |
N/C |
0.119 |
N/C |
|||
0.123 |
N/C |
|||
10.54 |
10.58 |
0.113 |
0.1117 |
N/C |
0.112 |
N/C |
|||
0.110 |
N/C |
|||
10.93 |
10.93 |
0.124 |
0.1223 |
N/C |
0.124 |
N/C |
|||
0.119 |
N/C |
|||
11.49 |
11.49 |
0.131 |
0.1297 |
N/C |
0.130 |
N/C |
|||
0.128 |
N/C |
|||
11.85 |
11.85 |
0.127 |
0.1277 |
N/C |
0.129 |
N/C |
|||
0.127 |
N/C |
|||
AVERAGE |
4.625 |
|||
STANDARD DEVIATION |
0.141 |
|||
RSD% |
3.055% |
Table 2: Time duration between addition of test item and analysis
pH |
Spiked time in hours |
Analysis time in hours |
Time gap in minutes |
11.85 |
10.45 |
10.47 |
2.0 |
10.45 |
10.49 |
4.0 |
|
10.45 |
10.51 |
6.0 |
|
11.49 |
10.53 |
10.56 |
3.0 |
10.53 |
10.59 |
6.0 |
|
10.53 |
11.00 |
7.0 |
|
10.93 |
11.04 |
11.06 |
2.0 |
11.04 |
11.08 |
4.0 |
|
11.05 |
11.10 |
5.0 |
|
10.58 |
11.13 |
11.15 |
2.0 |
11.13 |
11.18 |
5.0 |
|
11.14 |
11.20 |
6.0 |
|
10.03 |
11.27 |
11.29 |
2.0 |
11.27 |
11.31 |
4.0 |
|
11.27 |
11.33 |
6.0 |
|
9.54 |
11.36 |
11.38 |
2.0 |
11.37 |
11.40 |
3.0 |
|
11.37 |
11.42 |
5.0 |
|
8.90 |
11.49 |
11.51 |
2.0 |
11.50 |
11.53 |
3.0 |
|
11.50 |
11.54 |
4.0 |
|
8.44 |
11.58 |
12.01 |
3.0 |
11.58 |
12.03 |
5.0 |
|
11.58 |
12.05 |
7.0 |
|
8.04 |
12.12 |
12.16 |
4.0 |
12.12 |
12.17 |
5.0 |
|
12.12 |
12.18 |
6.0 |
|
7.46 |
12.21 |
12.23 |
2.0 |
12.21 |
12.24 |
3.0 |
|
12.21 |
12.26 |
5.0 |
|
7.01 |
12.28 |
12.30 |
2.0 |
12.31 |
12.34 |
3.0 |
|
12.36 |
12.41 |
5.0 |
|
6.56 |
12.51 |
12.57 |
6.0 |
12.51 |
12.58 |
7.0 |
|
12.59 |
13.03 |
4.0 |
|
5.98 |
13.54 |
13.56 |
2.0 |
13.58 |
14.01 |
3.0 |
|
13.58 |
14.03 |
5.0 |
|
5.42 |
14.10 |
14.13 |
3.0 |
14.10 |
14.15 |
5.0 |
|
14.10 |
14.16 |
6.0 |
|
4.98 |
14.19 |
14.21 |
2.0 |
14.19 |
14.22 |
3.0 |
|
14.19 |
14.24 |
5.0 |
|
4.63 |
14.25 |
14.28 |
3.0 |
14.25 |
14.30 |
5.0 |
|
14.25 |
14.32 |
7.0 |
|
4.28 |
14.34 |
14.36 |
2.0 |
14.34 |
14.38 |
4.0 |
|
14.34 |
14.40 |
6.0 |
|
3.72 |
14.42 |
14.44 |
2.0 |
14.45 |
14.48 |
3.0 |
|
14.45 |
14.52 |
7.0 |
|
3.07 |
14.53 |
14.56 |
3.0 |
14.53 |
14.58 |
5.0 |
|
14.53 |
15.00 |
7.0 |
|
2.65 |
15.06 |
15.10 |
4.0 |
15.06 |
15.09 |
3.0 |
|
15.06 |
15.11 |
5.0 |
|
2.02 |
15.20 |
15.24 |
4.0 |
15.20 |
15.25 |
5.0 |
|
15.20 |
15.27 |
7.0 |
Conclusions
The dissociation constant of the test item is 4.63 ± 0.14 when conducting the measurements within 2 to 7 minutes after the addition of test item in to the respective buffer solutions. This dissociation constant value compares favourably with the dissociation constant for technical grade in water, which was determined to be 4.65 ± 0.04 at 20 ± 1 °C (see study M-539985-02-1).
Description of key information
4.65 at 20 °C (EPA OPPTS 830.7370, titration method)
Key value for chemical safety assessment
- pKa at 20°C:
- 4.65
Additional information
In another study performed using spectrophotometric method (OECD Guideline 112) a pKa of 4.63 at 20 °C was measured starting from a soluble concentrate of the test item.
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