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Physical & Chemical properties

Melting point / freezing point

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Reference
Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
July 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
GLP compliance:
yes
Type of method:
thermal analysis
Remarks:
differential scanning calorimetry (DSC)
Decomposition:
yes
Decomp. temp.:
ca. 135 °C
Remarks on result:
not determinable

The determination of the melting point and the screening test for explosive properties by DSC, Mettler-Toledo TA8000, were carried out in closed glass pan and in aluminium pan.

The measurement in a closed glass pan does not show any endothermic effect prior a decomposition of the test substance in the range 140-370 °C, with a decomposition energy of 470 J/g. In an aluminium pan the diagram shows a broad endothermal effect in the range 80­210 °C, which can be explained by drying of the test substance. This was further investigated in a separate experment described below. An exothermal decomposition was observed in the range 210-390 °C, with a decomposition energy of 308 J/g.

In an aluminium pan the diagram shows a broad endothermal effect in the range 80-210 °C, which can be explained by drying of the test substance. This result should be verified with the dried substance. For purifying of the test substance the water content was removed by treating the sample at 50 °C ± 5 °C under vacuum for 20 hours. The determination of the melting point / melting range is carried out by differential scanning calorimetry (DSC) (EG-Guideline 92/69/EEC A.1.).

Additionally the result for the thermal decomposition energy in a closed glass pan was verified with the dried test substance.

The test substance was dried at 50 °C under vacuum for 20 hours, the mass loss after this procedure was 9.4 % (the analyzed water content was 9.3 ± 0.1 %, so all water was removed.

The DSC of the dried test substance in a closed aluminium pan shows an exothermal reaction beginning at 145 °C with a strong break at 180 - 185 °C, which can be seen as an opening of the closed aluminium pan caused by inner pressure; possibly a gas evolution coupled with an exothermal decomposition of the test substance had occurred. After this break the exothermal decomposition continued with a similar shape as with the non-dried substance. After the DSC measuring the substance was still a fine powder similar the dried test substance before the DSC measuring, so the result is: The dried test substance has no melting point.

To verify the DSC measuring in a closed glass pan for a decomposition energy to be below 500 J/g, a DSC in a closed glass pan was performed with the dried test substance. Now the decomposition energy amounts 456 J/g i.e. it is still below 500 J/g, so the tests on explosive properties still have not to be performed. The decomposition of the test substance in the closed glass pan begins at 135 °C due to a heating rate of 3 K/min; this has to be compared with the beginning of the decomposition shown in the closed aluminium pan at 145 °C (heating rate: 10 K/min).

Conclusions:
The test substance has no melting point between up to 390°C; exothermic decomposition starting at 135 °C was observed.
Executive summary:

The determination of the melting point and the screening test for explosive properties by DSC, Mettler-Toledo TA8000, were carried out in closed glass pan and in aluminium pan.

The measurement in a closed glass pan does not show any endothermic effect prior a decomposition of the test substance in the range 140-370 °C, with a decomposition energy of 470 J/g. In an aluminium pan the diagram shows a broad endothermal effect in the range 80­210 °C, which can be explained by drying of the test substance. This was further investigated in a separate experment described below. An exothermal decomposition was observed in the range 210-390 °C, with a decomposition energy of 308 J/g.

In an aluminium pan the diagram shows a broad endothermal effect in the range 80-210 °C, which can be explained by drying of the test substance. This result should be verified with the dried substance. For purifying of the test substance the water content was removed by treating the sample at 50 °C ± 5 °C under vacuum for 20 hours.The determination of the melting point / melting range is carried out by differential scanning calorimetry (DSC) (EG-Guideline 92/69/EEC A.1.).

Additionally the result for the thermal decomposition energy in a closed glass pan was verified with the dried test substance.

The test substance was dried at 50 °C under vacuum for 20 hours, the mass loss after this procedure was 9.4 % (the analyzed water content was 9.3 ± 0.1 %, so all water was removed.

The DSC of the dried test substance in a closed aluminium pan shows an exothermal reaction beginning at 145 °C with a strong break at 180 - 185 °C, which can be seen as an opening of the closed aluminium pan caused by inner pressure; possibly a gas evolution coupled with an exothermal decomposition of the test substance had occurred. After this break the exothermal decomposition continued with a similar shape as with the non-dried substance. After the DSC measuring the substance was still a fine powder similar the dried test substance before the DSC measuring, so theresultis: The dried test substance hasno melting point.

To verify the DSC measuring in a closed glass pan for a decomposition energy to be below 500 J/g,a DSC in a closed glass pan was performed with the dried test substance. Now the decomposition energy amounts 456 J/g i.e. it is still below 500 J/g, so the tests on explosive properties still have not to be performed. The decomposition of the test substance in the closed glass pan begins at 135 °C due to a heating rate of 3 K/min; this has to be compared with the beginning of the decomposition shown in the closed aluminium pan at 145 °C (heating rate: 10 K/min).

Description of key information

The melting point was examined following EU method A.1 in compliance with GLP.

The test item decomposes before melting (starting at 135 °C).

Key value for chemical safety assessment

Additional information

The test item has no melting point between 25–3900 °C, only exothermic decomposition beginning at 135 °C was observed.