Dysprosium trinitrate

Melting point / freezing point

Link to relevant study record(s)

Reference

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 17 September 2014 to 15 January 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

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

GLP compliance:

yes (incl. QA statement)

Type of method:

differential scanning calorimetry

Key result

Decomposition:

yes

Decomp. temp.:

>= 320 °C

Remarks on result:

other: The test item did not melt in the temperature range tested (-60°C to 600°C). The test item first solubilised in its hydration water (endothermic peaks at 65.5 and 87.9°C) and at temperatures >= 320°C it started to decompose.

Assay No. 1:

Neither significant endothermic peak nor exothermic peak was recorded.

Assay No. 2:

Endothermic peaks were observed at 65.5°C and 87.9°C (at 97 kPa). These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. Indeed, the hydrated rare earth salts, such as the hydrated form of dysprosium trinitrate, lose their water of hydration when heated. As these water molecules are loosely bound and as the amount of water in the substance is significant, the attached water is released and as a result the rare earth salt solubilises in the water.

The endothermic peaks observed from about 320°C to 550°C correspond to the decomposition of dysprosium trinitrate. Indeed, it is known based on literature data [1] that above 300°C, rare earth trinitrate loses NOx group to form rare earth oxynitrate (RareEarth-ONO3). Then, the oxynitrate decomposes in rare earth oxide. The formation of rare earth oxide from rare earth trinitrate (after the different steps described above) is observed at high temperatures: from 500°C up to 800°C.

As a result, it is thus concluded that dysprosium trinitrate did not melt over the temperature range tested.

[1]: Handbook on the Physics and Chemistry of Rare Earths, Volume 8, Elsevier, 1986

Assay No. 3:

In terms of peaks, the results obtained with a steel crucible were similar to those observed in the assay No. 2 with the aluminium crucible: with endothermic peaks below 100°C and two endothermic peaks observed above 320°C. It is concluded that the nature of the crucible material did not have any influence on the DSC results. The endothermic peaks observed at 346.7°C and 457.3°C with the aluminium crucible appear between 500°C and 550°C with the steel crucible. As the pressure was higher than atmospheric pressure in the steel crucible (>> 97.9 kPa), it could explain that the endothermic peaks were recorded at higher temperatures than for the assay No. 2.

Conclusions:

The DSC curve revealed endothermic peaks at 65.5°C and 87.9°C at 97.0 kPa. These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. As a result, dysprosium trinitrate did not melt over the temperature range tested (-60 to 600°C). The endothermic peaks observed from about 320°C to 550°C at 97.0 kPa correspond to the decomposition of dysprosium trinitrate.

Executive summary:

The melting behaviour of dysprosium trinitrate was assessed according to EU A.1 method and OECD test guideline 102 in compliance with GLP using Differential Scanning Calorimetry (DSC). The DSC curve revealed endothermic peaks at 65.5°C and 87.9°C at 97.0 kPa. These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. As a result, dysprosium trinitrate did not melt over the temperature range tested (-60°C to 600°C). The endothermic peaks observed from about 320°C to 550°C at 97.0 kPa correspond to the decomposition of dysprosium trinitrate.

Description of key information

Dysprosium trinitrate did not melt over the temperature range tested (-60°C to 600°C). The hexahydrate was used as test item. Dysprosium trinitrate first solubilised in its hydration water (endothermic events at 65.5 and 87.9°C) and started to decompose from 320°C onwards.

Additional information

An experimental study of reliability 1 according to Klimisch, performed in compliance with GLP and according to EU method A.1 and OECD Guideline 102 by Differential Scanning Calorimetry, was selected as a key study.

 

The DSC curve revealed endothermic peaks at 65.5 and 87.9°C at 97 kPa. Theses endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. No melting behaviour was recorded up to 600°C. The endothermic peaks observed from about 320°C to 550°C at 97 kPa correspond to the decomposition of dysprosium trinitrate in dysprosium oxynitrate.