Gadolinium 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 22 September 2014 to 23 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.:

>= 350 °C

Remarks on result:

other: The test item did not melt in the temperature range tested (-80°C to 600°C). The test item first solubilised in its hydration water (endothermic peaks at 82.0 and 95.5°C) and at temperatures >= 350°C it started to decompose.

Assay No. 1 (heating ramp: -80°C to 25°C at 10°C/min, crucible: aluminium with lid):

Neither significant endothermic peak nor exothermic peak was recorded. The assays No. 2 and 3 were not reported. They were made to confirm the assay No. 1 and effectively gave the same results.

Assay No. 4 (heating ramp: 25°C to 600°C/min at 10°C/min, crucible: steel with crimped lid):

An assay was done in a steel crucible fitted with a crimped lid to determine the impact of the metal used for the crucible. The results obtained were similar to the ones observed in the Assay N°5 below. It is concluded that the nature of the crucible material does not have any influence on the DSC results.

Assay No. 5 (heating ramp: 25°C to 600°C at 10°C/min, crucible: aluminium with pierced lid):

Endothermic peaks were observed at 82.0 °C and 95.5 °C. 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 gadolinium trinitrate, loose 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 water. The endothermic peaks observed from about 350 °C to 575 °C correspond to the decomposition of gadolinium 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.

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

Conclusions:

The DSC curve revealed endothermic peaks at 82.0 °C and 95.5 °C at 97.5 kPa. These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. As a result, gadolinium trinitrate did not melt over the temperature range tested (-80°C to 600°C). The endothermic peaks observed from about 350 °C to 575 °C at 97.5 kPa correspond to the decomposition of gadolinium trinitrate.

Executive summary:

The melting behaviour of gadolinium 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 82.0 °C and 95.5 °C at 97.5 kPa. These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. As a result, gadolinium trinitrate did not melt over the temperature range tested (-80°C to 600°C). The endothermic peaks observed from about 350 °C to 575 °C at 97.5 kPa correspond to the decomposition of gadolinium trinitrate.

Description of key information

Gadolinium trinitrate did not melt over the temperature range tested (-80°C to 600°C). The hexahydrate was used as test item. Gadolinium trinitrate first solubilised in its hydration water (endothermic events at 82.0 and 95.5°C) and started to decompose from 350°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 82.0 °C and 95.5 °C at 97.5 kPa. These endothermic events reflected the fact that the rare earth salt solubilised in its hydration water. No melting behavior was recorded up to 600°C. The endothermic peaks observed from about 350 °C to 575 °C at 97.5 kPa correspond to the decomposition of gadolinium trinitrate into gadolinium oxynitrate.