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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Secondary source cited in US ATSDR review
Qualifier:
according to guideline
Guideline:
other: not reported
Principles of method if other than guideline:
No methodological details are reported
GLP compliance:
no
Type of method:
other: no details
Melting / freezing pt.:
-15.5 °C
Remarks on result:
other: 25% solution

The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 degrees Celsius.

Conclusions:
The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 degrees Celsius.
Executive summary:

The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 degrees Celsius.

Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Modern, proprietary study
Qualifier:
no guideline followed
Principles of method if other than guideline:
The freezing point of the substance was determined by differential scanning calorimetry (DSC).
GLP compliance:
no
Type of method:
other: Differential scanning calorimetry (DSC).
Melting / freezing pt.:
-16.6 °C
Decomposition:
no

Melting began at around -20 °C but the broad nature of the peak produced an extrapolated onset temperature of -8.6 °C with a peak temperature of 0.5 °C. The controlled cooling of the sample showed the sample to solidify sharply at -16.6 °C and was completely solid by -24 °C. The subsequent second heating of the sample produced a similar broad peak to that seen in the first heat with an extrapolated onset temperature of -6.6 °C and a peak temperature of 0.1 °C.

Conclusions:
The freezing point of the sample was -16.6°C.
Executive summary:

The freezing point of a sample of 10% aqueous hexafluorosilicic acid was found to be -16.6°C using differential scanning calorimetry (DSC).

Description of key information

Freezing point of a sample of 10% aqueous hexafluorosilicic acid: -16.6°C

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
-16.6 °C

Additional information

The freezing point of a sample of 10% aqueous hexafluorosilicic acid was found to be -16.6°C using differential scanning calorimetry (DSC).The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 °C.  The freezing point of a 60 -70% aqueous solution of hexafluorosilicic acid is reported to be 19 °C.

Since concentrations above about 30 -35% are not stable, the results from the 10% and 25% solutions are more relevant and will be used for the assessment of the registered substance. The Melting point of the 10% solution was determined using the most sophisticated test design and hence the result from this test will be used as key informaiton, i.e., the melting point is -16.6°C.