Registration Dossier

Administrative data

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Company data with limited reporting

Data source

Referenceopen allclose all

Reference Type:
other company data
Title:
Unnamed
Year:
2007
Reference Type:
other company data
Title:
Unnamed
Year:
1993
Reference Type:
other company data
Title:
Unnamed
Year:
2008

Materials and methods

Principles of method if other than guideline:
Generating saturated solutions at a range of temperatures, and measuring the resultant dissolved concentration.
GLP compliance:
no
Type of method:
flask method

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
IUCLID4 Test substance: other TS: pure lactic acid

Results and discussion

Water solubilityopen allclose all
Water solubility:
86.1 other: % w/w
Temp.:
20 °C
pH:
>= 0 - <= 14
Remarks on result:
other: Lactic acid is soluble in water in all ratios. Solubility is not dependent on pH. pH of the solution will depend on the concentration, but at higher concentrations an ever larger fraction of the lactic acid will form oligomers.
Water solubility:
93 other: % w/w
Temp.:
35 °C
pH:
>= 0 - <= 14
Remarks on result:
other: Lactic acid is soluble in water in all ratios. Solubility is not dependent on pH. pH of the solution will depend on the concentration, but at higher concentrations an ever larger fraction of the lactic acid will form oligomers.
Details on results:
Stable: yes
pKa: 3.85 at 25 °C
Temperature effects: Solubility 76.0% at 0 °C; 81.3% at 10 °C; 95.1% at 40 °C.
Degradation products: no

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): other: highly soluble, up to a viscosity/saturation limit which is a function of temperature
Aqueous olubility of lactic acid is 86% w/w at 20°C. At 35°C, solubility is 93%. Apparently the viscosity of the solution is such that upon cooling, no lactic acid crystallizes from a 93% solution, but all lactic acid remains in a supercooled solution state.
Executive summary:

In order to get more knowledge about L(+)-lactic acid and the crystallization of it, the phase diagram of the system water/lactic acid was constructed. Due to practic al problems the diagram was not complete, but the missing part will be extrapolated by the Development Modelling section. The eutectic point of lactic acid/water is at ca. 62% lactic acid and ca.-28°C.

The solubility of L(+)-lactic acid in water was determined by dissolving freshly centrifuged crystalline lactic acid in water. A jacketed glass vessel of 150ml was used together with a magnetic stirrer and a temperature-controlled water/alcohol bath. The mixture with an excess of crystals was stirred at fixed temperature for at least 1 hr. Samples at 35 and 40°C were only 0.5 hr at temperature, in order to prevent influence of dimerization. Samples were taken an analyzed on the total and free acid contents. In most cases these values should be almost the same regarding the kinetics of lactoylactic acid formation. The results agreed with this hypo- thesis. Comparing these new data with former data (JvK, 4/91), shows that most likely the old data were not completely correct. The new data set is better.

The freezing point depression of water by lactic acid was determined by freezing samples of different concentrations at -21°C, heating them up to the desired temperature (±4 hr at temperature underd regulary swirling) and analysis of the motherliquor on lactic acid content.