ORGANIC DROPLETS AT AN ELECTRIFIED INTERFACE - CRITICAL POTENTIALS OFWETTING MEASURED BY POLAROGRAPHY

Critical wetting potentials of a dropping mercury electrode immersed i n aqueous dispersions of organic liquids represent well-defined and ch aracteristic values, that might offer predictions of interpolative nat ure for interactions of organic particles in the aquatic environment a nd a framework for investigation of fast wetting transients. The polar ographic method is based on measurement of charging current caused by displacement of surface charge due to attachment and spreading of orga nic droplets (micrometer size range) at the aqueous-mercury interface. Dispersion of hexadecane in 0.1 M NaF aqueous solution was used as a model system. Excellent agreement was obtained between critical interf acial tension of wetting (418.2 mJ m-2 at negatively and 418.9 mJ m-2 at positively charged electrodes) determined from critical potentials and prediction based on the Good-Girifalco-Fowkes equation for the mer cury-water-hexadecane system (418.26 mJ m-2). Experimental values for unsaturated hydrocarbons were significantly lower: 414 mJ m-2 for 1-oc tadecene and 400 mJ m-2 for squalene.