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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Reference:
Composition 0
Qualifier:
equivalent or similar to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
GLP compliance:
no
Type of method:
other: heating with visual confirmation of melting
Test material information:
Composition 1
Specific details on test material used for the study:
true racemic mixture
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:
Melting point of racemic mixture of lactic acid: 18°C.
Executive summary:

Chirally pure lactic acid has a melting point of 53°C. Mixtures of R- and S-lactic acid have a decreased melting point, with an 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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reference:
Composition 0
GLP compliance:
no
Test material information:
Composition 1
Key result
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 1971 report 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:
Melting point of lactic acid racemic mixture: 16.8 to 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