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Physical & Chemical properties

Melting point / freezing point

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Description of key 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 60 -70% aqueous solution of hexafluorosilicic acid is reported to be 19 degrees Celsius.  The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 degrees Celsius.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
292 K

Additional information

The freezing point of a sample of 10% aqueous hexafluorosilicic acid was found to be -16.6°C using differential scanning calorimetry (Reach Centre, 2010).

The freezing point of a 60 -70% aqueous solution of hexafluorosilicic acid is reported to be 19 degrees Celsius (Hollemann et al, 1995), with the formation of the crystalline dihydrate (Merck Index). The freezing point of a 25% solution of hexafluorosilicic acid is reported to be -15.5 degrees Celsius (ATSDR, 2001).