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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:
March 13, 2018 - April 13, 2018
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:
no
Type of method:
differential scanning calorimetry
Key result
Melting / freezing pt.:
157 °C
Decomposition:
yes
Decomp. temp.:
> 320 °C

Melting point / melting range: DSC measurement

Two DSC measurements with a heating rate of 10 K/min showed two endothermal effects in the temperature range of 80 – 120 °C and 140 – 190 °C. The onset temperature (seeTable1) was derived from the intersection of the tangent line with the highest slope of the endothermal peak with the baseline.

The first DSC measurement additionally showed an exothermal effect starting at approx. 320 °C.

The results of the DSC measurements are summarized in Table 1.

Table1: Melting point (DSC measurements)

Ident No.

Test item /

mg

Starting temperature /

°C

Final test temperature /

°C

Temperature range (endo-thermal) /

°C

Onset / °C

Crucible

Observations after the measurement

36864

10.59

25

500

80 – 120

140 – 190

98.72

157.18

Aluminium with a hole

Black Residue

Mass loss: 46% 

36866

9.04

25

200

90 – 115

145 – 165

98.98

156.91

Aluminium with a hole

Test item was a dark melt

Mass loss: 11%

An additional measurement with the capillary method was performed in order to clarify the melting range.

Melting point / melting range: capillary tube in a metal block

A measurement with the capillary method was performed to clarify the results of the DSC measurements. Since this measurement was performed only as a verifying screening a high heating rate of 10 K/min was chosen and therefore the absolute temperature values derived with the capillary method are not as accurate as the DSC results. The filling height of the test item was approximately 5 mm.

The results are summarized in Table 2.

Table2: Results of the capillary method

No.




Set point /
°C

Heating rate / K/min

End
point /
°C

Remarks

1

80

10

180

Approx. 144 °C: test item showed discolouration

Approx. 151 °C: test item started to melt

Approx. 154 °C: test item was a fully dark melt

Approx. 154 - 180°C: no further change

Under consideration of the results from the DSC measurements and the capillary method it was concluded that the test item melted at 157.0°C (mean onset temperature). Afterwards decomposition started at approx. 320°C. Because of the temperature range of the first endothermal effect (80 – 120 °C) it was concluded that the mass loss of the second DSC measurement was caused by the evaporation of water (water content of the test item: 13.5% (w/w)).

Executive summary:

The test item Disperse Red 91 had a mean melting point of 157.0 °C.

Description of key information

The test item Disperse Red 91 had a mean melting point of 157.0 °C.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
157 °C

Additional information