Electrification associated with droplet production from liquid jets

Abstract

In the first part, a theoretical model is proposed for the charging of droplets separating from the tip of liquid jets or filaments, based on a previous hypothesis by Iribarne and Mason. The charging is attributed to a shearing of the electrical double layer at the liquid-air interface. Order-of-magnitude estimates are presented, for different jet diameters and conductivities.

In the second part experiments are described, in which jets of water and aqueous solutions were produced from capillaries and made to break regularly into droplets. By eliminating the streaming current from the capillary, it was possible to measure the electrical charge separation occurring when the drops break off from the jet. With a jet 0.26 mm in diameter, the charges are in the order of 10^–5 to 10^–4 e.s.u. per droplet, the sign depending on the breakup mode, with little dependence on the conductivity of the liquid above 10^–3Ω^–1 m^–1. Both sign and order of magnitude are consistent with theoretical predictions.