Investigations of Charged Water Drops

Charged water drops were suspended in a nonuniform a.c. field and observed through the microscope visually and by high-speed photography. The initial drop size was approximately 100µ. The drop shrank by evaporation and became unstable at approximately 40µ. The evaporation of stable drops and the behavior of unstable drops were studied. The rates of changes of mass and charge were determined at various temperatures, and the activation energy for the evaporation was determined. The evidence indicates that ions are ejected from an unstable drop, and that a burst of ions occurs in the evaporation of a stable drop under these conditions. The removal of water molecules from the evaporating drop is not rate-determining under these conditions. The drop evaporated rapidly at −26°C. and became unstable repeatedly without freezing.