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Physical & Chemical properties

Melting point / freezing point

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Description of key information

The HYDROTOPES Category comprises the following 6 substances:
STS - Sodium toluene 4-sulphonate (CAS 657-84-1, EC 211-522-5)
SXS - Sodium (xylenes and 4-ethylbenzene) sulphonate (EC 701-037-1)
NH4XS - Ammonium (xylenes and 4-ethylbenzene) sulphonate (EC 943-024-5)
SCS - Sodium p-cumenesulphonate (CAS 15763-76-5, EC 239-854-6)
KCS - Potassium p-cumenesulphonate (CAS 164524-02-1, EC 629-764-9)
NH4CS - Ammonium p-cumenesulphonate (CAS 680972-33-2, EC 811-484-5) 


The substances have the following melting point:


STS > 400 °C


SXS > 300 °C


NH4XS = 198 °C (Estimated)


SCS = 350 °C


KCS = 400 °C


NH4CS = 315 °C


For sake of completeness, the estimated melting point for the other Hydrotropes substances are:


STS = 228 °C


SXS = 233 °C


SCS = 236 °C


KCS = 236 °C


NH4CS = 200 °C


It needs to be considered that the hydrotropes experimental melting point values are higher than the estimated ones and it seems reasonable to consider the value of 300 °C as the key value for the chemical safety assessment.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
300 °C

Additional information

The minimun value resulting from an experimental test was taken for the risk assessment.