Micellar aggregation numbers of short-chained ionic surfactants through viscosity measurements

Abstract

Micellar aggregation numbers (n) have been determined for short-chained surfactants through viscosity measurements at 20ºC by simple application of the Guth-Simha relationship assuming spherical micelles and neglecting the electroviscous effect. Values of n obtained were: sodium heptyl sulfate 23 (40°C), sodium octyl sulfate 29, sodium decyl sulfate 32, sodium octanoate 16,hexylammonium chloride 20 and octylammonium chloride 25 in agreement with literature values where known. This approximate method appears to be satisfactory for surfactant chain length of six to ten carbon atoms.