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Physical & Chemical properties

Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-01-15 to 2002-05-31
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
GLP compliance:
no
Type of method:
other: heating with visual confirmation of melting
Specific details on test material used for the study:
true racemic mixture
Key result
Melting / freezing pt.:
18 °C
Atm. press.:
1 013.15 hPa

Lactic acid

(S/(R+S)*100)

Lactic acid

(R/(R+S)*100)

Melting point

(°C)

 

50

45

40

30

20

10

0

50

55

60

70

80

90

100

18.0

22.5

27.5

35.0

41.5

47.0

53.0

Conclusions:
The melting point of a racemic mixture of lactic acid is 18 °C.
Executive summary:

In a non-GLP study, similar to EU Method A.1, the melting point of lactic acid has been investigated. In the course of this study, it became apparent that there is a strong correlation between the melting point and the content of each enantiomer in the racemic lactic acid. Chiral pure lactic acid has a melting point of 53 °C. Mixtures of R- and S-lactic acid have a decreased melting point, with a eutectic point at a 50:50 mixture at 18 °C.

Endpoint:
melting point/freezing point
Type of information:
other: Handbook data
Adequacy of study:
supporting study
Study period:
1971
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline available
Guideline:
other: handbook data
GLP compliance:
no
Melting / freezing pt.:
>= 16.8 - <= 33 °C
Atm. press.:
1 013.15 hPa

The melting point of lactid acid is influenced by the amount of lactic esters in the mixtures. Vacuum destillation is used to free the substance from ester impurities.

Holten reports the following melting points for the racemic mixture of lactic acid: 16.8 °C, 28 - 33 °C.

When one of the optically active isomers is present in excess, the melting point is higher.

Conclusions:
The melting point of lactic acid racemic mixture is between 16.8 °C and 33 °C.
Executive summary:

According to Holten, the melting point of lactic acid racemic mixture is between 16.8 °C and 33 °C.

Description of key information

The melting point of crystalline lactic acid (racemic mixture) is about 18 °C.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
18 °C

Additional information

In a non-GLP study, similar to EU Method A.1, the melting point of lactic acid has been investigated. In the course of this study, it became apparent that there is a strong correlation between the melting point and the content of each enantiomer in the racemic lactic acid. Chiral pure lactic acid has a melting point of 53 °C. Mixtures of R- and S-lactic acid have a decreased melting point, with a eutectic point at a 50:50 mixture at 18 °C.