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Physical & Chemical properties

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:
Testing was conducted between 30 September 2009 and 13 October 2009.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Date of GLP inspection: 2008-8-19 Date of Signature on GLP certificate: 2009-3-04
Type of method:
thermal analysis
Remarks:
Differential scanning calorimetry (DSC)
Melting / freezing pt.:
> 723 K
Remarks on result:
other: .

Screening test

Result: two significant endotherm events to investigate at approximately 340°C and 430°C. The section of thermogram in brackets (approximately 20 to 40°C) indicates an invalid data region where the instrument response had not yet stabilised and originates from the specific heat capacity of the sample.

Definitive test:

Overall result: Melting temperature greater than 450°C (>723 K). The test material underwent dehydration from approximately 602 K and a reversible, possible crystal form transition at approximately 682 K (during heating), but neither thermal event was associated with a phase transition (i.e. melting) of the test material.

Please see attached “Results 2920 -0004” as this information contains tables and graphs and it would be rendered less comprehensible separated within this section.

Conclusions:
The test material was determined to have a melting temperature greater than 723 K, by differential scanning calorimetry, using ASTM E537-86, Method A1 Melting/Freezing Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008. Although the test material was identified as undergoing dehydration from approximately 602 K and a reversible, possible crystal form transition at approximately 682 K (during heating); neither thermal event was associated with a phase transition (i.e. melting) of the test material.
This study is conducted according to an appropriate guideline and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a key study for this endpoint.
Executive summary:

Melting/Freezing Temperature. 

The test material was determined to have a melting temperature greater than 723 K, by differential scanning caloritry, using ASTM E537-86, Method A1 Melting/Freezing Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008. Although the test material was identified as undergoing dehydration from approximately 602 K and a reversible, possible crystal form transition at approximately 682 K (during heating); neither thermal event was associated with a phase transition (i.e. melting) of the test material.

Conclusion

The test material was determined to have a melting temperature greater than 723 K. Although the test material was identified as undergoing dehydration from approximately 602 K and a reversible, possible crystal form transition at approximately 682 K (during heating); neither thermal event was associated with a phase transition (i.e. melting) of the test material.

Description of key information

The melting point of disodium hydrogenorthophosphate was determined according to EU Method A.1 (Melting / Freezing Temperature) and under the conditions of GLP. 

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
450 °C

Additional information

The test material was determined to have a melting temperature greater than 723 K, by differential scanning calorimetry, using ASTM E537-86, Method A1 Melting/Freezing Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008. Although the test material was identified as undergoing dehydration from approximately 602 K and a reversible, possible crystal form transition at approximately 682 K (during heating); neither thermal event was associated with a phase transition (i.e. melting) of the test material.