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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 03 Nov 2005 to 18 Apr 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
thermal analysis
Remarks:
and capillary method
Melting / freezing pt.:
57 °C
Decomposition:
no

PRELIMINARY TESTS:

The DSC-curve showed several endothermic heat effects with the first peak starting at 58.2°C. After the experiment, the sample had lost about 58% of its mass and was yellowish and powdery. In the second pre-test using capillary method, the test item started melting at about 54°C.

MAIN TEST:

In both runs of the main test the melting was determined at 57°C. The sample lost about 0.6 and 1.1% of its mass during both tests and became molten and colourless.

Conclusions:
The melting point of cerium trinitrate was determined to be 57°C.
Executive summary:

Melting point was assessed using two methods: thermal analysis and capillary method, according to OECD guideline 102 .

A test item amount of 45.12 mg was heated up from 25°C to 400°C at a rate of 20°C/min during a preliminary test (DSC).

The quantities of heat absorbed or released were measured by Differential Scanning Calorimeter and recorded.

As in the temperature range investigated several peaks were observed that could not be identified clearly, a capillary pre-test was performed by heating up the samples from 25°C to about 400°C at a rate of 20°C/min.

The capillary pre-test showed that the first peak observed in the DSC run corresponds to the melting of the test item. Therefore, further DSC runs were performed in the immediate vicinity of the peak temperature (from 25°C to 100°C) with the temperature rise adjusted to 5°C/min.

In both runs of main test with DSC, the melting was recorded at 57°C.

Description of key information

The melting point of cerium trinitrate was determined in a GLP study to be 57°C following differential scanning calorimetry analysis in accordance with EC test method A.1 (Weissenfeld, 2006). 
Actually, the main test is not really complete as the event at 57°C is concluded to be due to melting. Hence, also the conclusion (melting point = 57 °C) is not correct. On the basis of available information on this substance and other rare earth nitrates, it is assumed that the reaction observed is rather solubilisation in hydration water than melting. It is assumed that the real melting point is > 400 °C.

Key value for chemical safety assessment

Additional information

Visual observations showed that the substance was molten and colourless after the test.