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Registration Dossier
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EC number: 233-713-2 | CAS number: 10326-41-7
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- supporting study
- Justification for type of information:
- For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
- Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 3.85
- Temp.:
- 23 °C
- Conclusions:
- At 23 °C, the following values were measured.
Crystalline lactic acid (3-9-1970) Ka 1.42 x 10-4, pKa 3.85 - Executive summary:
The ionization constant was determined by means of potentiometric titration with 0.1 N NaOH and determination of the pH at 50 % neutralization by graphical interpolation. At 23 °C, the following values were measured.
Crystalline lactic acid (3-9-1970) Ka = 1.42 x 10-4, pKa = 3.85.
This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
- Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 3.86
- Temp.:
- 22.5 °C
- Remarks on result:
- other: Acid-base constant: pKa = 3.86
- Conclusions:
- The dissociation constant was determined with 0.0001389 which leads to a pKa of 3.857 at 22.5 ºC.
- Executive summary:
According to Holten, the dissociation constant was determined with 0.0001389 which leads to a pKa of 3.857 at 22.5 ºC.
This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- supporting study
- Justification for type of information:
- For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
- Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 3.85
- Temp.:
- 23 °C
- Conclusions:
- The pKa of L-(+)-lactic acid is generally recognized to be 3.85.
- Executive summary:
The pKa of L-(+)-lactic acid is generally recognized to be 3.85.
This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
Referenceopen allclose all
1. “Holten” data
Paragraph 1.1 of chapter IV of “Holten” is about the dissociation constant of lactic acid.
The results show a broad dispersion. IUPAC have characterised the determination by Martin and Tartar as very reliable. They found that a maximum of dissociation constant (0.0001389) was reached at 22.5 °C. The dissociation constant for lactic acid could be expressed in the following formula: pKa= 3.857 + 5.10-5.(t-22.5)2
The dissociation constant of 0.0001389 leads to a pKa of 3.857 at 22.5 °C.
[ H.Holten: Properties and Chemistry of lactic acid and derivatives. 1971. Paragraph 1.1 of chapter IV (Physical Chemistry). Page 62-67.]
2. PURAC measurements on the dossociation constant of lactic acid.
G.H. Heesen measured the dissociation constant of lactic acid and lactoyl lactic acid in 1970.
At 23 °C he found a Ka for lactic acid of 1.42 x 10-4 and a pKa of 3.85.
[PURAC report: Bepaling van de zuursterkte van melkzuur en lactoylmelkzuur. G.J. Heesen. 15 September 1970]
Description of key information
The pKa of lactic acid is 3.85.
Key value for chemical safety assessment
- pKa at 20°C:
- 3.85
Additional information
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