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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:
04 May to 17 August 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, with experiments conducted according to appropriate and valid guidelines and conducted under GLP conditions.
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
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7200 (Melting Point / Melting Range)
Deviations:
no
GLP compliance:
yes
Type of method:
differential scanning calorimetry
Key result
Melting / freezing pt.:
107 °C
Atm. press.:
1 012 hPa
Remarks on result:
other: atm ± 3 pHa; decomposition or sublimation were not noted.

An endothermic peak between 100°C and 130 °C was observed in experiment 1. The extrapolated onset temperature of the peak was 107.50°C.

To investigate the melting peak between 100°C and 130°C a repeated heating cycle was applied in the experiment 2. With the first heating the extrapolated onset temperature of the melting peak was 107.53°C. The similar value indicated that melting of the test material was the reason for the effect.

During cooling an exothermic peak was observed between 90°C and 110°C. The effect was obtained due to crystallization of the test material. With the second heating an extrapolated onset temperature of 107.36°C was obtained. The results demonstrated that the endothermic effect was due to melting of the test materail. After the experiment it was observed that the test materail had evaporated from the sample container.

 

Experiment 4 was performed to determine the duplicate melting temperature of the test material. The temperature program was similar as the program of experiment 1. Similar results as with experiment 1 were obtained. The extrapolated onset of the melting peak was 107.44°C. Another endothermic peak was observed between 210°C and 250°C. After the experiment it was observed that the test material had evaporated from the sample container.

Conclusions:
Under the conditions of the test, the melting point of the test material was determined to be 107 ºC at an atmospheric pressure of 1012 ± 3hPa.
Executive summary:

The melting point of the test material was determined in a differential scanning calorimetry study performed in accordance with GLP and to the standardised guidelines OECD 102, EU method A.1 and EPA OPPTS 830.7200.

The melting temperature was determined three times and under the conditions of the test, an endothermic peak was observed between 100°C and 130°C in all three tests. When extrapolated the peak corresponded to an onset temperature of 107°C.

Description of key information

The melting/freezing point of 3,5-Dimethylpyrazole was determined to be 107 ºC in a key study (Baltussen, 2012) performed to OECD 102, EU method  A.1 and EPA OPPTS 830.7200; seven other reports have been provided as supporting information.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
107 °C

Additional information

The melting/freezing point of the test material has been addressed by providing one key study and seven supporting reports.

Baltussen (2012) has been provided as the key study whereby the melting point was determined by differential scanning calorimetry method. The melting temperature was determined three times and under the conditions of the test, an endothermic peak was observed between 100°C and 130°C in all three tests. When extrapolated the peak corresponded to an onset temperature of 107°C. The study was performed to GLP and standardised guidelines and had thus been assigned a reliability score of 1 using the principles for assessing data quality as set out in Klimisch (1997).

Lide (2010) has been provided as the key literature and it states that the melting/freezing point of the test material is 107.5 ºC. The data originates from a peer reviewed handbook citing physical data as found in the literature, which was assigned a reliability score of 2 using the principles for assessing data quality as set out in Klimisch (1997).

The seven supporting studies consist of one peer reviewed handbook, three material safety data sheets, two internet sources and an experimental result taken from the QSAR EPISuite; Lide (2010), Alfa Aesar MSDS (2007), Sigma Aldrich MSDS (2010), Fisher Scientific (2008), chemBlink (2012), Wacker (2012) and MPBPVP v.1.43 EPISuite (2012). Lide has been assigned a reliability score of 2, whereas the remaining reports were scored 4 according to Klimisch (1997). All sources provided as supporting data report the melting point to be within the range 104 – 109 ºC, the consistency between these sources is sufficient to support the value reported in the key study.

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