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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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
The solid-liquid equilibria of H2O-Y(NO3)3 systems are studied using conductimetry and controlled thermal flux analysis. The solid phase was studied using X-ray diffraction, thermogravimetry and chemical analysis such as calcination and Inductively Coupled Plasma-Atomic Emission Spectrometry.
GLP compliance:
no
Type of method:
differential scanning calorimetry
Key result
Decomposition:
yes
Decomp. temp.:
ca. 300 °C
Remarks on result:
other: The atmospheric pressure was not reported.

The metastable melting point of the tetra-, penta- and hexahydrate was determined to be 120.4, 77.8 and 51.8°C, respectively. The phase transitions could probably best be described as solubilisation of Y(NO)3 in hydration water. Further release of water results in the anhydrous form at approximately 235°C.

Above 300°C and up to 500°C further conversion to YONO3, Y4O3(NO3)3 and finally Y2O3 is observed. As a result, yttrium trinitrate did not melt over the temperature range tested.

Conclusions:
When heating Y(NO3)3 hexahydrate, phase transitions are observed at 51.8°C, 77.8°C (pentahydrate) and 120.4°C (tetrahydrate), which best can be described as solubilisation of Y(NO3)3 in its hydration water. Above 300°C and up to 500°C further conversion to YONO3, Y4O3(NO3)3 and finally Y2O3 is observed.

Description of key information

In a published study, decomposition of yttrium trinitrate was noted from a DSC scan to start from approximately 300°C (Bouchet et al., 1994). As a result, yttrium trinitrate did not melt over the temperature range tested.

Key value for chemical safety assessment

Additional information

A literature study was identified which has been assigned key study status for this endpoint (Bouchet et al., 1994; Klimisch 2). In this study, when heating Y(NO3)3 hexahydrate, phase transitions were observed at 51.8°C, 77.8°C (pentahydrate) and 120.4°C (tetrahydrate), which can best be described as solubilisation of Y(NO3)3 in its hydration water. Above 300°C and up to 500°C, conversion of Y(NO3)3 to YONO3, Y4O3(NO3)3 and finally Y2O3 is observed. Yttrium trinitrate is concluded to decompose starting from approximately 300°C. Yttrium trinitrate did not melt over the temperature range tested in this study.