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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:
from 2017-03-22 to 2017-04-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
differential scanning calorimetry
Key result
Melting / freezing pt.:
180.24 °C
Atm. press.:
1 013.25 hPa
Decomposition:
yes
Decomp. temp.:
245.79 °C
Sublimation:
no

Pre-test for melting range

The capillary tube containing the test item was set into the block at 20.2 °C. The block was heated until melting started. The temperature was noted at which the first signs of melting of the test item were observed. When the substance was completely melted, the temperature was noted again.

Melting point/range: begin 181.8 °C; end 186.1 °C

Observations: The test item melted to a clear slightly brownish solution. After cooling down, the test item was solidified to a slightly brown mass.

Security pre-test for DSC instrument

The crucible was found visually unchanged after reaching a temperature of 220 °C. The weight was recorded at 49.13 mg. After heating the crucible was opened, the test item was red-brown solid and bonded together. The test item decomposed.

Calibration

For calibration indium and zinc were used. The measurement of indium after calibration met the validity criteria.

DSC measurement of test item

In order to have more information for the evaluation three more determinations with temperatures from 15 – 250 °C (second determination), from 15 – 300 °C (third determination) and from 15 – 400 °C (fourth determination), respectively, were performed. Note: As the deviation between the first and the second determination was > 0.5 °C a third determination was performed. The fourth determination was performed in order to confirm results of the second and the third determination.

Final results

Observations

Table 1: Values and observations from all DSC measurements

Mass test
item
Mass crucible
(before
measurement):
Mass crucible
(after
measurement):
Observations
First
Measurement
1.39 mg 46.91 mg 46.93 mg After the test the crucible was visually unchanged. The crucible was opened, the white solid mass test item was
observed.
Second
Measurement
1.45 mg 47.13 mg 47.09 mg After the test the crucible was visually unchanged. The crucible was opened, the orange solid mass test item was
observed.
Third
Measurement
1.38 mg 47.61 mg 46.99 mg After the test the crucible was visually unchanged. The crucible was opened, the brown-black test item was observed.
Fourth
Measurement
1.79 mg 47.72 mg 46.21 mg After the test the crucible was visually unchanged.

Interpretation of the measurements

Based on the observations of the pre-test the first event (endotherm) was indicated as melting point and the second event was indicated as decomposition of the test item evaluated with event marker function.

Presentation of results

For the calculation of the values of the mean and the standard deviation, the first determination was not taken into account for the melting point.

Table 2: Determination of melting point

Melting point in °C in K
1. Determination 181.91 455.06
2. Determination 180.48 453.63
3. Determination 180.22 453.37
4. Determination 180.02 453.17
First determination was not used for evaluation.    
Mean 180.24 453.39
Standard deviation 0.23 0.23

Table 3: Determination of decomposition

Decomposition in °C in K
3. Determination 247.45 520.60
4. Determination 245.79 518.94
Decomposition begins 245.79 518.94

As the difference between the three evaluated determinations was below 0.5 K the result of the melting point can be considered valid.

Conclusions:
The melting point (first event) was determined to be 180.24 ± 0.23 °C (453.39 ± 0.23 K). These values are the means of three independent determinations.
The decomposition point (second event) was determine to be 245.79 °C (518.94 K), which is the mean of two determinations.
Executive summary:

A study was conducted according to OECD TG 102 and Regulation (EC) No. 440/2008, method A.1 in order to determine the melting point of the test item by using DSC method (differential scanning calorimetry). In the pre-test for melting range the test item melted to a clear slightly brownish solution (range of 181.8 and 186.1 °C. After cooling down, the test item was solidified to a slightly brown mass.

Referring to the pre-test, the melting point was determined as the first event (endothermic) with: 180.24 ± 0.23 °C (453.39 ± 0.23 K). These values are the means of three independent determinations. The second event evaluated with the event marker function of the DSC software was indicated as beginning of decomposition with: 245.79 °C (518.94 K). No observations were made which might cause doubts on the validity of the study outcome (difference between determinations was below 0.5 K). Therefore, the result of the study is considered valid.

Description of key information

The melting point (first event) was determined to be 180.24 ± 0.23 °C (453.39 ± 0.23 K). These values are the means of three independent determinations.

The decomposition point (second event) was determine to be 245.79 °C (518.94 K), which is the mean of two determinations.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
180.24 °C

Additional information

A study was conducted according to OECD TG 102 and Regulation (EC) No. 440/2008, method A.1 in order to determine the melting point of the test item by using DSC method (differential scanning calorimetry). In the pre-test for melting range the test item melted to a clear slightly brownish solution (range of 181.8 and 186.1 °C. After cooling down, the test item was solidified to a slightly brown mass. Referring to the pre-test, the melting point was determined as the first event (endothermic) with: 180.24 ± 0.23 °C (453.39 ± 0.23 K). These values are the means of three independent determinations. The second event evaluated with the event marker function of the DSC software was indicated as beginning of decomposition with: 245.79 °C (518.94 K). No observations were made which might cause doubts on the validity of the study outcome (difference between determinations was below 0.5 K). Therefore, the result of the study is considered valid (reference 4.2 -1).