Abstract
Part I is an investigation of the "rest time" before coalescence of a water droplet on an anisole/water interface. Water droplets of predetermined size made in a novel way were introduced to the interface in an apparatus designed to inhibit contamination, vibration and temperature fluctuation. It was found that there was an inherent scatter in rest tines for any given experimental conditions. The average rest tine and the scatter were dependent on droplet size and on type and concentration of electrolyte in the aqueous phase. Pure water had the greatest stability. Analysis of the results showed that electrolytes affected coalescence in two distinct ways and some suggestions are made as to the processes involved in coalescence. Calculations of the approach of droplet to interface from hydrodynamic considerations are given, which show that coalescence occurs at separations of at least 100-1000 A. Part II concerns the detection of coalescence in fogs. Two solutions which produce a red colour on nixing are sprayed in such a way that the droplets intermingle under reproducible conditions. The resulting fog is sampled and examined for coloured droplets. The number of droplets coalescing under similar conditions is found to depend on concentration of electrolyte and also on type and concentration of added surface active agent. The results are explained qualitatively in terns of the ion distribution near the surface and some deductions are made in regard to coalescence between droplets of the sane solution. Part III is a theoretical analysis of the effect of coalescence on suspended droplets sedimenting under gravity. With the collection efficiency E as an undefined parameter, equations defining the rate of change in size distribution are derived. Assuming E to be constant, general numerical solutions are made for a specific type of radius distribution.