Measurement of surfactant properties using a circular capillary wave field

Measurements of the decay coefficient are presented for three different surfactants as a function of surface concentration. These measurements were obtained using a circular field of capillary waves. Data was purposely obtained close to the center of the tank, where the wave amplitude is large, and meniscus effects are expected to be small. The theory for linear, standing waves in a circular geometry is developed, without the usual assumption \ kr \ >> 1. The surfactants investigated were: stearic acid, oleyl alcohol and hemicyanine. Measurements of the decay coefficient for hemicyanine have not been obtained heretofore. Several intrinsic benefits of the circular geometry are noted. The potential for improved accuracy in the measurement of surfactant properties using this geometry is suggested.