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Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
according to guideline
Guideline:
other: no guideline available (publication data)
Principles of method if other than guideline:
The thermogravimetric measurements were performed with a TA Instruments Model 951 2000 (temperature range, ambient to 1200°C). The evolved gases were examined by a Fisons-VG Thermolab MS and a Bruker FTIR IFS 48, both coupled
with a TGA unit. The FTIR has a resolution of 8 cm- 1. DSC analysis was carried out by heating the obtained solids in a DSC 910-2000 analyser at 10°C min- ~ from roomtemperature up to 600°C.
GLP compliance:
no
Type of method:
thermal analysis
Key result
Decomposition:
yes
Remarks:
First, loss of water at 169 °C then at 420°C, formation of strontium carbonate.
Decomp. temp.:
169 °C
Sublimation:
no
Remarks on result:
not determinable

The following steps describe the decomposition of the strontium .

First Step : The mass spectrometer results indicate that the primary fragment for the first mass loss corresponds with m/e = 18 (loss of coordinated water). By DSC an endothermic peak indicates the dehydratation takes place in two steps (169 and 190°C). From FTIR results, it is also shown that water is the only gas evolved.

In a second step, the percentage mass loss between 420 and 590°C correponds to the formation of strontium carbonate from anhydrous strontium oxalate by the evolution of CO. The mass spectrometer, detected CO2 (m/e = 44) concurrent with CO loss (m/e = 28) in an inert atmosphere

The FTIR spectrum corresponding with this temperature interval also shows peaks due to both CO and CO2 vibrations.

After DSC measurements, traces of black carbon are seen on the cooled residue, confirming that carbon is formed.

Conclusions:
The melting point can not be measured because the substance decomposes from 169 °C -loss of water) to 420-590°C (loss of CO and CO2).
Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
according to guideline
Guideline:
other: no guideline available (publication data)
GLP compliance:
not specified
Type of method:
thermal analysis
Decomposition:
yes
Decomp. temp.:
140 °C
Sublimation:
no
Remarks on result:
not determinable

The first endothermic peak in the temperature range 413–473 K (140°C-200°C) corresponds to loss of adsorbed water.

The decomposition of anhydrous strontium oxalate starts at a temperature of 723 K (450°C), with total mass loss of 14.10 % corresponding to loss of one CO molecule per molecule of oxalate.

The third step in the decomposition, which starts at a temperature of 973 K (700 °C), is due to decomposition of strontium carbonate formed in the second step. The mass loss in this step of Thermogravimetry analysis is 24.26 % which suggests evolution of carbon dioxide.

Conclusions:
140°C : The first endothermic peak in the temperature range 413–473 K (140°C-200°C) corresponds to loss of adsorbed water.
450°C : The decomposition of anhydrous strontium oxalate starts at a temperature of 723 K (450°C) corresponding to loss of one CO molecule per molecule of oxalate.
700°C : The third step in the decomposition is due to decomposition of strontium carbonate formed in the second step with loss of carbon dioxide.

Description of key information

The melting point can not be measured because the substance decomposes from 169°C-250°C (loss of water) to 420-590°C (loss of CO and CO2).

Key value for chemical safety assessment

Additional information