THE MICELLAR DISSOCIATION CONCENTRATION OF IMPURE SODIUM DODECYL-SULFATE SYSTEMS IN WATER

This paper discusses the subject of the critical micellar concentration (c.m.c.) when it is applied to impure surfactant systems. Sodium dodecyl sulfate (SDS) solutions containing polar and non-polar impurities were used in the experiments. Turbidity and surface tension were measured as a function of the SDS concentration. A turbidity maximum and a surface tension minimum were found in the measured curves. The curves are too complicated for c.m.c. determination according to the general rule. However, it is possible for one to determine a micellar dissociation concentration (m.d.c.). The m.d.c. values obtained from the measured curves were compared with the c.m.c. values taken from the literature for pure SDS samples. It is more practical to determine m.d.c. than c.m.c. for impure surfactant systems. © 1990.