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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 23 october 2020 to 27 october 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Qualifier:
according to guideline
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
GLP compliance:
yes (incl. QA statement)
Type of method:
differential scanning calorimetry
Key result
Decomposition:
yes
Decomp. temp.:
ca. 275 °C

REFERENCE ITEMS


Melting point by DSC method (EC A.1. method)
Identification: Indium wire
Last validation of the test: 31 July 2020
Periodicity of validation (in months): 12
Results: 157.1 °C ± 0.5 °C
Theoretical value: 156.6 °C ± 0.5 °C
Conformity: Yes



Identification: Tin wire
Last validation of the test: 30 July 2020
Periodicity of validation (in months): 12
Results: 231.9 °C ± 0.5 °C
Theoretical value: 231.9 °C ± 0.5 °C
Conformity: Yes



Identification: Zinc wire
Last validation of the test: 30 July 2020
Periodicity of validation (in months): 12
Results: 420.3 °C ± 0.5 °C
Theoretical value: 419.5 °C ± 2.0 °C
Conformity: Yes


 


AMENDMENTS: No amendment to the study plan was requested.


 


DEVIATIONS: No incident, which could have affected the quality or the interpretation of the results obtained, was observed.


 


DATA RECORDING AND ARCHIVING: All observations were immediately recorded in a paginated laboratory notebook.
The original documents, including the final report and all raw data, are archived at
DEFITRACES for 10 years after completion of the study.


 


MELTING POINT BY DSC METHOD (EC A.1. method)


1. Test objective
The test item is heated within a nitrogen atmosphere, at the atmospheric pressure, using the Differential Scanning Calorimetry method (DSC). Therefore, the determination of the temperature at which the test item changes from the solid state to the liquid state is determined.


 


2. Principle
The test item sample and reference material are both maintained at the temperature predetermined by the program even during a thermal event in the sample. The amount of energy which has to be supplied to the sample to maintain zero temperature differential between the test item sample and the reference material is the experimental parameter displayed as the ordinate of the thermal analysis curve. The rate of energy absorption by the sample is proportional to the specific heat of the sample.
Any transition accompanied by a change in specific heat produces a discontinuity in the power signal.
Melting of the test item is characterised by an endothermic enthalpy change that gives a peak whose area is proportional to the total enthalpy change. By contrast, decomposition is characterised by an exothermic peak.


 


3. Method
3.1. Apparatus
Analyser DSC 131: Connected to a computer using the Setsoft 2000 program
Balance Accuracy: ± 0.01 mg Mettler AB 265 S
Barometer
Crucibles
Gas cylinder of nitrogen


 


3.2. Experimental procedure
An aliquot of test item was placed in a crucible. A lid was fitted and the crucible was placed in the DSC analyser. The heating procedure was performed from room temperature to 600 °C. The other assays were performed up to the temperature necessary to obtain the melting peak.


 


3.3. Expression of the results
Several heating procedures were performed until two values for the melting point
were in the range of the estimated accuracy of the method: ± 0.5 °C up to 326.9 °C and ± 2.0 °C above 326.9 °C.
The melting point was calculated automatically using the Setsoft program by linear
integration of the curves obtained: “Heat flow as a function of the temperature”.
If the test item decomposes or sublimes before the melting point is reached, in this case the temperature at which the effect is observed shall be reported.


 


4. Results
4.1. Introduction
Three assays were performed during the test but no melting point was observed. A
decomposition of the test item was observed. These assays are presented in the following pages.



4.2. Assay No. 1
Gas used: Nitrogen
Ventilation: Yes
Crucible used: Aluminium, 120 μL, with lid
Mass of test item: 8.64 mg
Program


Phase 1: Isotherm at 25 °C for 5 min
Heating phase from 25 °C to 600 °C at 10 °C/min
Phase 2: Cooling phase from about 600 °C to 25 °C
Isotherm at about 25 °C for 20 min


 


4.3. Assay No. 2
Gas used: Nitrogen
Ventilation: Yes
Crucible used: Aluminium, 120 μL, with lid
Mass of test item: 11.25 mg
Program


Phase 1: Isotherm at 25 °C for 5 min
Heating phase from 25 °C to 600 °C at 10 °C/min
Phase 2: Cooling phase from about 600 °C to 25 °C
Isotherm at about 25 °C for 20 min


 


4.4. Assay No. 3
Gas used: Nitrogen
Ventilation: Yes
Crucible used: Aluminium, 120 μL, with lid
Mass of test item: 4.46 mg
Program


Phase 1: Isotherm at 25 °C for 5 min
Heating phase from 25 °C to 600 °C at 10 °C/min
Phase 2: Cooling phase from about 600 °C to 25 °C
Isotherm at about 25 °C for 20 min


 


4.5. Discussion
At the start of the assays, the test item was a white powder. At the end, we obtained black residue on the wall of crucible. At about 275 °C decomposition was observed however no endothermic peak was detected.


 


5. Conclusion
Decomposition was observed at about 275 °C.

Conclusions:
Decomposition was observed at about 275 °C.
Executive summary:

MELTING POINT BY DSC METHOD
In compliance with Regulation (EC) No. 1907/2006, Council Regulation (EC) No. 440/2008 and EC A.1. method (2008) and OECD Guideline No. 102 (1995)


Decomposition was observed at about 275 °C.

Description of key information

Decomposition was observed at about 275 °C.

Key value for chemical safety assessment

Additional information