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Physical & Chemical properties

Melting point / freezing point

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Description of key information

Sodium thiosulfate has no melting in the temperature range of 25-500°C. The test item decomposes during the measurement up to 500°C. 

Key value for chemical safety assessment

Additional information

For the evaluation of this endpoint data from an experimental study were used as key information, supported by data from the CRC handbook. The study was conducted according to GLP and according to OECD guidelines 113 (screening for thermal stability) and 102 (determination of melting point). The test data are considered as reliable without restrictions.

The thermal stability and the determination of the melting point were carried out by DSC analysis. The test item and the standard material (aluminium oxide) were heated up from ambient temperature to the final temperature (400°C and 500°C, respectively.) at a constant heating rate under nitrogen. Closed class crucibles were used as containers for the screening test and aluminium crucibles with a small hole were used as containers for the main test. The quantity of heat absorbed or released was measured and recorded.

Experimental study results indicated that sodium thiosulfate has no melting point in the temperature range of 25 -500°C. The test item decomposes during the measurement up to 500°C.

The decomposition is confirmed by the information obtained from the CRC Handbook of Chemistry and Physics. However, according to handbook data, sodium thiosulfate decomposes at 100 °C.