MEASUREMENT OF DYNAMIC SURFACE-TENSION BY THE OSCILLATING DROPLET METHOD

An optical measuring method has been applied to determine the dynamic surface tension of aqueous solutions of heptanol. The method uses the frequency of an oscillating liquid droplet as an indicator of the surf ace tension of the liquid. Droplets with diameters in the range betwee n 100 and 200 mum are produced by the controlled break-up of a liquid jet. The temporal development of the dynamic surface tension of heptan ol-water solutions is interpreted by a diffusion controlled adsorption mechanism, based on the ''three-layer'' model of Ward and Tordai. Mea sured values of the surface tension of bi-distilled water, and the pur e dynamic and static (asymptotic) surface tensions of the surfactant s olutions are in very good agreement with values obtained by classical methods.