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Physical & Chemical properties

Melting point / freezing point

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Administrative data

Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018-12-19 - 2019-02-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019
Report date:
2019

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Version / remarks:
dated 27 July 1995
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Version / remarks:
puplished 31 May 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
differential scanning calorimetry

Test material

1
Reference substance name:
Reaction product of Graphite, acid-treated and potassium permanganate
IUPAC Name:
Reaction product of Graphite, acid-treated and potassium permanganate
Test material form:
cream / paste
Specific details on test material used for the study:
After receipt of the item in the Test Facility the test item was inspected and appeared as dark brown modelling clay. Therefore it was decided to perform the pre-test for liquids for the determination of the melting point. Additionally, a pre-test with heating up of the test item was performed.

Regarding the containing water, the sample can be seen as a paste (liquid) or as a powder (if dried). Freeze drying is not possible because it is not possible to remove the whole water. Strong van der Waals forces pull the layers more and more together keeping the water trapped.

Results and discussion

Melting / freezing pointopen allclose all
Key result
Decomposition:
yes
Decomp. temp.:
>= 124 °C
Remarks on result:
not determinable
Melting / freezing pt.:
>= -21.12 - <= -18.34 °C
Remarks on result:
other: see 'Remarks'
Remarks:
It must be clearly admit that the detected freezing/melting point of the brownish paste is caused by the contained water in the test item.

Any other information on results incl. tables

FINDINGS

Pre-Test with cooling down

After evaluation the following values were recorded:

 Room Temperature  4.0 °C  -21.8 °C  -80 °C
 Black soft mass, like dough  Same as at room temperatrue  Hard, not piercable anymore  solid like ice

Pre-test with heating-up

All observations of the Pre-test are presented in the following table

 Observations  Temperature in °C
 Clear, colorless condensate  124 °C
Condensate dropped down on the test item and got black  193 °C
 Condensate evaporated  200 °C
 The test item shot out of the test tube (explosively) completeley, heating plate was turned off  209 °C

Observations (DSC measurement)

   Mass test item [mg]  Mass crucible, before measurement [mg]  Mass crucible, after measurement [mg]  Observations
 First measurement  2.90  35.55  35.48  The crucible was optically unchanged after measurement
 Second measurement  2.96  35.78  35.76
 Third measurement (repetition crucible 2)  2.96  35.76  35.72

Interpretation

Referring to the pre-test the freezing / melting point of the test item (stated as brownish paste) should be between -20 °C and -80 °C.

In all three DSC measurements an exothermic event during the cooling down phase and one flat, broad, endothermic event during the heating up phase were detected.

The exothermic event can be identified as freezing point of the brownish paste.

The melting point of the brownish paste was determined as the endothermic event.

During the cooling down phase in the determinations 1 and 2 also a small exothermic Event after the freezing point was detected.

In the repetition measurement with the second crucible this event could not be detected. This can be explained through the process of freezing and melting of the brownish paste, it became more homogenised.

Both exothermic events and the endothermic event were evaluated with the onset function. Additionally the beginning and ending of the events were evaluated with event marker.

The result of the melting point of the brownish paste will be stated in a range of the Onset values.

DISCUSSION

Determination of the melting point of the sample as determined via DSC (differential scanning calorimetry).

Regarding the containing water the sample can be seen as a paste (liquid) or as a powder (if dried). Therefore two approaches were necessary to assess the melting point: Cooling down the paste component and heating up the powder component. Freeze drying is not possible because it is not possible to remove the whole water. Strong van der Waals forces pull the layers more and more together keeping the water "trapped".

Referring to the pre-test the freezing / melting point of the brownish paste should be between -20 °C and -80 °C.

In all three DSC measurements one exothermic event during the cooling down phase and one flat, broad, endothermic event during the heating up phase were detected.

The exothermic event can be identified as freezing point of the brownish paste (evaluated with the onset and event marker function).

The range of the event was detected with: -18.05°C to -30.27°C (255.10 K to 242.88 K)

In an Onset range of -18.34 °C to -21.12 °C (254.81 K to 252.03 K)

These values represent the mean of three independent determinations.

The melting point of the brownish paste was determined as the endothermic event in a range of -16.86 to -16.24 °C (256.29 to 256.91 K) (evaluated with the onset function). This value represents the mean of three independent determinations.

Freezing and melting of the pasty sample means that the contained water is fully frozen or melted at the mentioned temperature.

During the cooling down phase in the determinations 1 and 2 also a small exothermic Event after the freezing point was detected.

The range of the event was detected with: -27.93°C to -35.32°C (245.22 K to 237.83 K)

In the repetition measurement with the second crucible this event could not be detected. This can be explained through the process of freezing and melting of the brownish paste, it became more homogenised.

Applicant's summary and conclusion

Conclusions:
Freezing and melting of the pasty sample means that the contained water is fully frozen or melted at the mentioned temperature.

The freezing point of the brownish paste was determined as the endothermic event in a range of -16.86 to -16.24 °C (256.29 to 256.91 K) (evaluated with the onset function).

Therefore the paste was heated up to determine the melting point of the dried paste indicated by liquefaction. As the test item decomposed, beginning decomposition was visible at 124 °C before reaching the melting stage; this point could not be detected.
Executive summary:

A GLP-conform study was performed according to OECD guideline 102 and EU method A.1 to determine the melting/freezing behaviour of the test item via DSC.

The sample was used for testing as received by the sponsor. Regarding the containing water the sample can be seen as a paste (liquid) or as a powder (if dried). Therefore two approaches were necessary to assess the melting/freezing point:

Cooling down the test item and heating up.

Referring to the pre-test the freezing point of the test item (stated as brownish paste) should be between -20 °C and -80 °C.

In all three DSC measurements one exothermic event during the cooling down phase and one endothermic event during the heating up phase were detected.

The exothermic event can be identified as the freezing point of the brownish paste.

The freezing point of the brownish paste was determined as the endothermic event in a range of -16.86 to -16.24 °C (256.29 to 256.91 K) (evaluated with the onset function).

This value represents the mean of three independent determinations.

Freezing and melting of the pasty sample means that the contained water is fully frozen or melted at the mentioned temperature.

Therefore the paste was heated up to determine the melting point of the dried paste indicated by liquefaction. As the test item decomposed, beginning decomposition was visible at 124 °C before reaching the melting stage; this point could not be detected.

It must be clearly admit that the detected freezing point of the brownish paste is caused by the contained water in the test item.