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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
GLP compliance:
not specified
Type of method:
thermal analysis
Decomposition:
yes
Decomp. temp.:
ca. 630 °C
Remarks on result:
other: results obtained in nitrogen
Decomposition:
yes
Decomp. temp.:
ca. 700 °C
Remarks on result:
other: results obtained in air

During the melting test the studied neutral leach residue sample the exothermic peaks in the curve are at the temperature range 689 – 700 °C and 830 - 842 °C. These peaks indicate reactions with nitrogen. 

The endothermic peak in the curve is at the temperature 730 – 751 °C, which indicate sulphate decomposition.

The mass of the sample decreases step by step all the time, which indicates dehydration.

During the oxidation test of the studied neutral leach residue sample no endothermic or exothermic peaks in the curve were found. The mass of the sample decreases step by step all the time, which indicates dehydration and sulphate decomposition.

Conclusions:
test done according to standard protocol, useful to assess the characteristic of the substance
Executive summary:

The melting point of the substance was determined by thermo gravimetrical (TGA) measurements.

Sulfate decomposition starts in nitrogen at ca. 630°C and in air at ca. 700°C.

Description of key information

Sulfate decomposition starts in nitrogen at ca. 630°C and in air at ca. 700°C (Outotec, 2010).

Key value for chemical safety assessment

Additional information

Various types of leach residues were analyzed. They display differences in phys-chem. properties depending on their chemical composition. The most representative leach residue was used.