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Melting point / freezing point

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Reference
Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009-07-30 to 2009-08-26 (2010-01-22)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: 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:
other: OECD 113 (1981) Screening test for thermal stability and stability in air
Deviations:
no
GLP compliance:
no
Type of method:
thermal analysis
Remarks:
differential scanning calorimetry (DSC)
Atm. press.:
1 008 hPa
Decomposition:
yes
Decomp. temp.:
ca. 137 °C
Remarks on result:
other: based on DSC-measurement, performed under nitrogen

Thermal stability:

The DSC-measurement (measured at 1008 hPa) in a closed glass crucible with the test item showed an endothermic effect in the temperature range 430 °C to 440 °C. Directly after the endothermic effect an exothermic effect started at a temperature of 440 °C. The end of the exothermic effect and the energy could not be determined because the measurement was stopped at 450 °C, due to technical reasons.

An optical inspection showed a discoloration of the residue of the test item from violet to black. But the test item was still a solid.

Melting point measurements:

The first measurement in aluminium crucible (measured at 1008 hPa) with a hole very uneven course of the baseline. A major multiple endothermic effect has been observed in the temperature range of 190 – 280°C. An exothermic effect was observed in the temperature range 460 – 600°C with an energy of 213 J/g. After measurement a mass lost of 84 % could be observed. The test item residue was black and still a solid.

Two additional measurements were performed up to a temperature of 150 °C. A minimal endothermic effect has been observed in the temperature range of 130 – 140 °C.

An additional measurement in the capillary method was performed. Due to this, the measurement will only be used as confirmation.

It is assumed that the first endothermic effect in the range of 190 – 280°C was observed amongst others due to the decomposition of the complex. In the further process, it could be assumed that decomposition of 2 -ethylhexanoate (boiling point approx. 228°C) occurred. The second endothermic effect at approx. 450°C may have been observed due to the melting of residues followed by a decomposition reaction. A mass loss of approx. 84% was measured. It can safely be assumed that after decomposition of 2-ethylhexanoate cobalt is reduced (with carbon) to elemental cobalt.

 

In conclusion, the cobalt complex has no melting point under atmospheric pressure and starts decomposition at ca. 137°C.

Conclusions:
The cobalt complex has no melting point under atmospheric pressure and starts decomposition at ca. 137 °C.

Description of key information

No melting point can be stated. Cobalt, borate 2-ethylhexanoate complexes decomposes before melting. Temperature of decomposition: approx. 137 °C.

Key value for chemical safety assessment

Additional information

The melting point of the test substance was determined according to OECD guideline 102 with the differential scanning calorimetry method (DSC). The test item was heated up from ambient to the final temperature (150 °C and 600 °C, respectively) at a constant heating rate (10 K/min) in a defined atmosphere (nitrogen). The quantity of heat absorbed or released was measured and recorded. Aluminium crucibles with a small hole were used as containers for the test item and as empty reference crucible.

A measurement in a capillary tube in a metal block was used to clarify the results from the DSC-measurement. The maximum temperature of this equipment is limited to 400 °C. Set point and maximum temperature were chosen according to the results of the DSC measurements.

The results of the DSC and of the capillary measurements showed that after decomposition of 2 -ethylhexanoate cobalt is reduced (with carbon) to elemental cobalt. In conclusion, the cobalt complex has no melting point under atmospheric pressure and starts decomposition at ca. 137 °C.