L-(+)-lactic acid

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Findings are supported by published information and general physicochemical texts on the relationship between viscosity of aqueous solutions and crystallization of such solutions.

Principles of method if other than guideline:

Determination of solubility of lactic acid in water; determination of viscosity of lactic acid solution at different temperatures; observation of physical state at those temperatures.

GLP compliance:

no

Type of method:

method to determine freezing temperature

Specific details on test material used for the study:

93% aqueous solution of L-lactic acid

Key result

Melting / freezing pt.:

< -80 °C

Atm. press.:

ca. 1 atm

Remarks on result:

other: VIscous solutions do not solidify

Conclusions:

93% solutions of lactic acid do not solidify

Executive summary:

93% solutions of lactic acid do not solidify.

Reference 2

Endpoint:

melting point/freezing point

Type of information:

other: handbook data

Adequacy of study:

weight of evidence

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

Specific details on test material used for the study:

pure crystalline L(+)-lactic acid

Melting / freezing pt.:

>= 52.7 - <= 52.8 °C

Conclusions:

The melting point of L-lactic acid is 53 °C.

Executive summary:

According to Holten, L-lactic acid has a melting point of 53 °C.

Reference 3

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2002-01-15 to 2002-05-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods 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

Key result

Melting / freezing pt.:

53 °C

Table 1: melting point of the mixtures of lactic acid

Melting point of the mixtures of lactic acid
Mixtures	R/S 50 % / 50 %	RS 45 % / 55 %	RS 40 % / 60 %	RS 30 % / 70 %	RS 20 % / 80 %	RS 10 % / 90 %	RS 0 % / 100 %
Melting point (°C)	18.0	22.5	27.5	35.0	41.5	47.0	53.0

Conclusions:

Melting point of L-lactic acid = 53 °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 a eutectic point at a 50:50 mixture at 18 °C.

Reference 4

Endpoint:

melting point/freezing point

Type of information:

other: expert statement

Adequacy of study:

weight of evidence

Study period:

2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Principles of method if other than guideline:

Crystallization and remelting of lactic acid under careful control of temperature; observational.

GLP compliance:

no

Type of method:

thermal analysis

Specific details on test material used for the study:

Pure crystalline L(+)-lactic acid

Melting / freezing pt.:

53 °C

Conclusions:

The melting point of L-lactic acid is 53 °C.

Executive summary:

The melting point of L-lactic acid has been determined in dependence of the percentage of (R)-lactic acid and (S)-lactic acid in the mixture. The melting point of L-lactic acid has been determined to 53 °C.

Description of key information

The melting point of crystalline lactic acid is 53 °C.
Concentrated aqueous solutions of lactic acid do not solidify.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

53 °C

Additional information

Commercial manufacture of lactic acid does not result in solid (crystalline) material. Lactic acid is produced as an aqueous solution at concentrations of up to 93%. Due to the high viscosity of these solutions they do not solidify upon cooling. Also see additional information under "viscosity".