THE DYNAMIC SURFACE-TENSION OF SDS-DODECANOL MIXTURES .1. THE SUBMICELLAR SYSTEMS

Samples of sodium dodecyl sulfate (SDS) are commonly contaminated by dodecanol, as a minor component, which is very surface active and not easily removed. The disappearance of the minimum in the surface tension concentration curve at the critical micelle concentration (CMC) gives no definite criterion about the purity of the sample. The question arises as to what the effect of dodecanol is on the dynamic properties of the surface, having repercussions on the practical behavior of the system. Therefore. we investigated the dynamic surface behavior of SDS solution having a known dodecanol content. First, SDS and dodecanol mixtures were considered at concentrations definitely below the CMC, giving mixed adsorption of SDS and dodecanol. Subsequently, SDS and dodecanol mixtures at SDS concentrations above the CMC were studied; at these concentrations, a part of the dodecanol is solubilized in the micelles of SDS.