Measurement of the variation of interfacial tension with temperature between immiscible liquids of equal density

For the measurement of interfacial tensions between liquids of equal densities, methods like drop weight, Wilhelmy plate etc. fail.A method is developed using a liquid bridge between a glass tip and a freely hanging piece of density higher than that of the fluids.The volume of liquid bridge that can sustain a piece of given weight cannot exceed some maximal value. This maximal volume is determined experimentally.A computer program makes it possible to tabulate the maximal volumes of the liquid bridge as a function of the interfacial tension for a given tip and metal piece.The program uses iteratively the circle segment approximation for the calculation of the meridian curve given by Kelvin.Results are given for the system aqueous ethanol/paraffin oil of equal densities.