Zirconium dinitrate oxide

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2014-11-28 until 2015-02-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

GLP compliance:

yes (incl. QA statement)

Type of method:

thermal analysis

Remarks on result:

other: Test substance does not melt. Solubilisation in its hydration water and loss of hydration water was observed during the test.

Test A

Endothermic events:

- Onset T = 88.16°C, heat of decomposition -384.45 J/g

- Onset T = 182.77°C, heat of decomposition -195.20 J/g

- Onset T = 223.69°C, heat of decomposition -15.67 J/g

Test B

Endothermic events:

- Onset T = 91.90°C, heat of decomposition -229.57 J/g

- Onset T = 198.13°C, heat of decomposition -110.14 J/g

- Onset T = 231.62°C, heat of decomposition -39.47 J/g

Test C

Endothermic events:

- Onset T = 111.03°C, heat of decomposition -287.48 J/g

- Onset T = 201.55°C, heat of decomposition -152.31 J/g

- Onset T = 234.62°C, heat of decomposition -70.95 J/g

Test D

Endothermic events:

- Onset T = 114.57°C, heat of decomposition -325.83 J/g

- Onset T = 201.29°C, heat of decomposition -146.26 J/g

- Onset T = 234.26°C, heat of decomposition -102.62 J/g

The endothermic events are believed to be related to successive dehydrations (i.e. passage of hydrated form to another, thus to successive loss of hydration water and to solubilisation of the test item in this hydration water. In Test A and B, no test item remained in the crucible at the end of the test, whereas in Test C and D, 5.3 and 6.6 mg of a white solid remained in the crucible, respectively, at the end of the test. It is believed this difference between tests A-B and C-D could be due to the fact the analyst selected finer particles for tests C-D.

Conclusions:

The test item does not melt. The endothermic peaks observed on DSC curves correspond to successive dehydrations (i.e. passage of a hydrated form to another) of the test item upon heating, thus to the loss of hydration water and the solubilisation of the test item in this water.

Reference 2

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

27 July 2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Principles of method if other than guideline:

The temperature behaviour of dried zirconium oxynitrate was analysed using a thermogravimetric (TG) analyser together with a Differential Thermal (DTA) analysis.

GLP compliance:

not specified

Type of method:

thermal analysis

Remarks on result:

other: Test substance does not melt. Successive endothermic events were observed corresponding to loss of hydration water and anionic species removal.

Continuous weight loss was observed between room temperature and 700°C which corresponds to 4 main thermal events:

1. An endothermic event with an onset at 78°C and a maximum at 110°C corresponds mainly to material dehydration. The LOD measurement carried out in the oven at 110°C/4h indicated a 15.5% loss. 

2. There are two further endotherms with onsets at 191 and 231°C and maximums at 210 and 245°C, respectively, which correspond to anionic species removal.

3. The exotherm with an onset at 440°C and a maximum at 456°C corresponds to material crystallisation.

 

Values of nitrogen and hydrogen after elemental analysis were 7.32% and 2.03% respectively. The calculated N:Zr molar ratio in the final product was 1.2:1. The measured LOI up to 1000°C was 57.5%. The final product was a white powder.

Conclusions:

Based on the TG/DTA scans it was concluded that dried zirconium oxynitrate undergoes a decomposition process when heated from room temperature up to 1000°C. Successive endothermic events with maxima at 110°C and at 210 and 245°C, correspond to dehydration and anionic species removal, respectively. An exothermic event with a maximum at 456°C represents material crystallisation. The material decomposes and does not melt.

Description of key information

A weight of evidence approach was used including two available studies. In both studies (Younis, 2015b, Klimisch 1, and Dvininov, 2017, Klimisch 2), no melting was observed. Instead, several endothermic events were observed, which represent consecutive decomposition steps.

Additional information

In a GLP study performed in accordance with EC test method A.1, the melting point of zirconium dinitrate oxide was investigated applying Differential Scanning Calorimetry (Younis, 2015b). It was concluded that the test item does not melt. The endothermic peaks observed on DSC curves correspond to successive dehydrations (i.e. passage of an hydrated form to another) of the test item upon heating, thus to the loss of hydration water and the solubilisation of the test item in this water. The first endothermic event started between 88.16 and 114.57°C, depending on the experiment, whereas the other events started between 182.77 and 201.55°C and between 223.69 and 234.62°C, respectively, depending on the experiment. This study was considered as reliable (Klimisch 1).

In another study, the melting point of dried zirconium dinitrate oxide was investigated using TG/DTA (Dvininov, 2017). In this study, consecutive endothermic events were also observed. The first event, with an onset at 78°C and a maximum at 110°C, represented further dehydration of the dried test substance. The second and third event, with an onset at 191 and 231°C, and maxima at 210 and 245°C, respectively, represented anionic species removal. Finally, an exothermic event with an onset at 440°C and a maximum at 456°C, represented material crystallisation. From the results of this study it was concluded that the test material is subject to decomposition and does not present melting behaviour. This study was considered reliable with restrictions (Klimisch 2).