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Surface tension

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Description of key information

Surface tension_OECD 115_EU Method A.5: The substance is surface active (CMC of 10 mg/L at 21.5 ± 0.5 °C)

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The surface tension of the Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts was not determined according to EU Method A.5 and OECD Guideline 115 since the critical micelle concentration (CMC) test demonstrated the test item was surface active. Usually, the surface tension test is performed with a solution that is 90% of the water solubility concentration (for solubilities below 1 g/L) by diluting a saturated solution. With surface active materials the loading rate is critical to obtain a specific concentration as any additional material will also disperse within the water. The endpoint can be waived in accordance to REACH, Annex VII, Section 7.6, column 2.

The Critical Micelle Concentration (CMC) of the C20 -24 sodium sulfonate (Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts) was determined using a procedure compatible with EU Method A.5 and OECD Guideline 115 in compliance with GLP (Fox, 2015c). The ring method has been applied. The CMC was calculated from the anti-log of the interception of the two lines of best fit plotted on the surface tension versus log concentration plot, specifically the concentration and non-concentration dependent concentration regions. It approximately amounts to 10 mg/L at 21.5 ± 0.5 °C.