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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Administrative data

Link to relevant study record(s)

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) 
In addition CaXS (Calcium Xylenesulphonate, CAS 28088-63-3, EC 248-829-9) was evaluated for complete the assessment despite it is not registered under REACH.

No experimental data are existing for the substances of the category. The Henry's law constant has been estimated with HENRYWIN v3.20, Bond method and the results are reported below:

STS, CAS: 657-84-1; 2.83  e-004 Pa-m3/mole, episuite v. 4.1

SXS, CAS: 1300-72-7; 3.12 e-004 Pa-m3/mole, episuite v. 4.1

NH4XS, CAS: 26447-10-9; not estimated

SCS, CAS: 15763-76-5; 4.98  e-004 Pa-m3/mole, episuite v. 4.1

KCS, CAS: 164524-02-1; not estimated

NH4CS, CAS: 37475-88-0; not estimated

The value of STS has been selected as representative of the category for the Chemical safety assessment

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
at the temperature of:
25 °C

Additional information

Henry's Law Constant characterizes the equilibrium of dilute concentrations of volatile, soluble substances between the gas and liquid phases. The aromatic sulphonic hydrotopes are not volatile and therefore a Henry's Law Constant is not feasible or relevant. An indicative value to complete the Chemical safety assessment has been calculated with EPIWIN 4.1. The value 0.000283 has been reported as key value for safety assessment, as conservative case.