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Water solubility

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water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-01-17 to 2012-02-24
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to
EU Method A.6 (Water Solubility)
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Key result
Water solubility:
335 g/L
20 °C
ca. 8.6
Details on results:
The preliminary estimate resulted in an estimated water solubility of 200 - 1000 g/L.
Results of individual flasks: flask 1 and 3: 335.1 g/L, flask 2: 376.9 g/L. Flask 2 was considered to be an outlier, see section 'Any other information on results incl. tables'

Due to the closeness of the results to the amount of test material used for the saturations, the test was repeated using larger quantities of the sample. The saturation stage of the test was therefore repeated using about 34.1 g, 29.9 g and 26.7 g of the test material to saturate 25 mL, 20 mL and 20 mL of water in Flasks 1, 2 and 3 respectively. The three flasks were then shaken and treated under similar conditions as before. The solutions in the flasks were filtered with 0.1 µm syringe filter, as there was suspicion that small particles were still present in the test samples, and then diluted by a factor of 100. Analysis was then performed using the UV spectrophotometer.

A mean solubility of 530.5 g/L was obtained. After careful analysis of the concentration from each of the three flasks, the saturation was found to be time dependent. This suspicion was deduced from the trend in the aqueous solubility as determined from the duration of the saturation, i.e. 24 hours saturation < 48 hours saturation < 72 hours saturation (or Flask 1, < Flask 2 < Flask 3). As a result the flasks were placed in the incubated shaker and then shaken for another 24 hours at 30°C.

From the analysis of the solutions, a solubility of 511.9 g/L was observed. A comparative analysis of the concentrations from the initial saturation and the extended saturation was made by the analyst. The concentration of Flask 1 was found to have increased but that of Flasks 2 and 3 had reduced. Also, the magnitude of the drop in concentration as determined for Flask 3 was extremely high (558.4 g/L to 502.6 g/L).

Temperature was controlled during the analysis (saturation stage, equilibration stage and testing stage) and 0.1 µm syringe filters were applied. The analyst therefore suspected that the increase in solubility with respect to increasing amount of sample employed for the saturation might be due to nucleation (transition between super saturation and crystallisation). Nuclei are usually not stable and can therefore dissolve back into solution. Hence an attempt was made to confirm the impact of the chemistry of the sample on the water solubility analysis.

During that investigation about 24.8 g, 23.1 g and 23.6 g were used to saturate 10 mL of water in each of the three flasks. The flasks were then shaken and treated under similar conditions as before. After saturation, a layer of white crystals were found to have settled at the bottom and in the inner walls of all three flasks. The yellow viscous solutions contained suspensions of undissolved particles and some of the white crystals. Samples of the solutions were carefully filtered with 0.1 µm syringe filter and then diluted by a factor of 100 prior to the UV spectrophotometric analysis.

The mean of the concentrations was obtained as 628.2 g/L. However the suspicion of the analyst that the chemistry of the test material was having an impact on the analysis was confirmed by the formation of white crystals observed.

A quick visual solubility check was conducted using about 9 g of the sample and 27.0 mL of water in a flask. The flask was shaken at the test temperature for about 7 hours. Upon visual inspection, all the material appeared to have gone into solution. Therefore, it was deemed that the first results obtained were the most reliable. The aqueous solubility of the test material, as obtained from Flask 2 was comparatively higher than the concentration from Flask 1 and 3. Although all three concentrations were within 15%, the solubility of the material obtained from Flask 2 was considered an outlier. Due to this, the water solubility of NMMO was reported as 335.1 g/L.

Interpretation of results (migrated information): very soluble (> 10000 mg/L)
The water solubility of NMMO was determined to be 335 g/L at 20°C.
Executive summary:

The water solubility of the test item was determined according to EU Method A.6. by applying the flask method. The water solubility of NMMO was determined to be 335 g/L at 20°C.

Description of key information

In a GLP study according to the flask method as specified in test method EC A.6, NMMO was determined to be very soluble in water (335 g/L) at 20°C (Younis, 2012).

Key value for chemical safety assessment

Water solubility:
335 g/L
at the temperature of:
20 °C

Additional information